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class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Applications"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Applications</span> </div> </a> <ul id="toc-Applications-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Principles" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Principles"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Principles</span> </div> </a> <button aria-controls="toc-Principles-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Principles subsection</span> </button> <ul id="toc-Principles-sublist" class="vector-toc-list"> <li id="toc-Radar_signal" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Radar_signal"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Radar signal</span> </div> </a> <ul id="toc-Radar_signal-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Illumination" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Illumination"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>Illumination</span> </div> </a> <ul id="toc-Illumination-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Reflection" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Reflection"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.3</span> <span>Reflection</span> </div> </a> <ul id="toc-Reflection-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Radar_range_equation" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Radar_range_equation"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.4</span> <span>Radar range equation</span> </div> </a> <ul id="toc-Radar_range_equation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Doppler_effect" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Doppler_effect"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.5</span> <span>Doppler effect</span> </div> </a> <ul id="toc-Doppler_effect-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Polarization" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Polarization"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.6</span> <span>Polarization</span> </div> </a> <ul id="toc-Polarization-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Limiting_factors" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Limiting_factors"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.7</span> <span>Limiting factors</span> </div> </a> <ul id="toc-Limiting_factors-sublist" class="vector-toc-list"> <li id="toc-Beam_path_and_range" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Beam_path_and_range"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.7.1</span> <span>Beam path and range</span> </div> </a> <ul id="toc-Beam_path_and_range-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Noise" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Noise"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.7.2</span> <span>Noise</span> </div> </a> <ul id="toc-Noise-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Interference" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Interference"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.7.3</span> <span>Interference</span> </div> </a> <ul id="toc-Interference-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Clutter" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Clutter"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.7.4</span> <span>Clutter</span> </div> </a> <ul id="toc-Clutter-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Jamming" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Jamming"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.7.5</span> <span>Jamming</span> </div> </a> <ul id="toc-Jamming-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> </ul> </li> <li id="toc-Signal_processing" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Signal_processing"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Signal processing</span> </div> </a> <button aria-controls="toc-Signal_processing-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Signal processing subsection</span> </button> <ul id="toc-Signal_processing-sublist" class="vector-toc-list"> <li id="toc-Distance_measurement" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Distance_measurement"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.1</span> <span>Distance measurement</span> </div> </a> <ul id="toc-Distance_measurement-sublist" class="vector-toc-list"> <li id="toc-Transit_time" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Transit_time"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.1.1</span> <span>Transit time</span> </div> </a> <ul id="toc-Transit_time-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Frequency_modulation" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Frequency_modulation"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.1.2</span> <span>Frequency modulation</span> </div> </a> <ul id="toc-Frequency_modulation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Pulse_compression" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Pulse_compression"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.1.3</span> <span>Pulse compression</span> </div> </a> <ul id="toc-Pulse_compression-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Speed_measurement" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Speed_measurement"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.2</span> <span>Speed measurement</span> </div> </a> <ul id="toc-Speed_measurement-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Pulse-Doppler_signal_processing" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Pulse-Doppler_signal_processing"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.3</span> <span>Pulse-Doppler signal processing</span> </div> </a> <ul id="toc-Pulse-Doppler_signal_processing-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Reduction_of_interference_effects" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Reduction_of_interference_effects"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.4</span> <span>Reduction of interference effects</span> </div> </a> <ul id="toc-Reduction_of_interference_effects-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Plot_and_track_extraction" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Plot_and_track_extraction"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.5</span> <span>Plot and track extraction</span> </div> </a> <ul id="toc-Plot_and_track_extraction-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Engineering" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Engineering"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Engineering</span> </div> </a> <button aria-controls="toc-Engineering-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Engineering subsection</span> </button> <ul id="toc-Engineering-sublist" class="vector-toc-list"> <li id="toc-Antenna_design" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Antenna_design"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1</span> <span>Antenna design</span> </div> </a> <ul id="toc-Antenna_design-sublist" class="vector-toc-list"> <li id="toc-Parabolic_reflector" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Parabolic_reflector"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1.1</span> <span>Parabolic reflector</span> </div> </a> <ul id="toc-Parabolic_reflector-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Types_of_scan" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Types_of_scan"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1.2</span> <span>Types of scan</span> </div> </a> <ul id="toc-Types_of_scan-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Slotted_waveguide" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Slotted_waveguide"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1.3</span> <span>Slotted waveguide</span> </div> </a> <ul id="toc-Slotted_waveguide-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Phased_array" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Phased_array"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1.4</span> <span>Phased array</span> </div> </a> <ul id="toc-Phased_array-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Frequency_bands" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Frequency_bands"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.2</span> <span>Frequency bands</span> </div> </a> <ul id="toc-Frequency_bands-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Modulators" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Modulators"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.3</span> <span>Modulators</span> </div> </a> <ul id="toc-Modulators-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Coolant" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Coolant"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.4</span> <span>Coolant</span> </div> </a> <ul id="toc-Coolant-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Regulations" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Regulations"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>Regulations</span> </div> </a> <ul id="toc-Regulations-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Configurations" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Configurations"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>Configurations</span> </div> </a> <ul id="toc-Configurations-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Notes_and_references" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Notes_and_references"> <div class="vector-toc-text"> <span class="vector-toc-numb">9</span> <span>Notes and references</span> </div> </a> <ul id="toc-Notes_and_references-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Bibliography" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Bibliography"> <div class="vector-toc-text"> <span class="vector-toc-numb">10</span> <span>Bibliography</span> </div> </a> <button aria-controls="toc-Bibliography-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Bibliography subsection</span> </button> <ul id="toc-Bibliography-sublist" class="vector-toc-list"> <li id="toc-References" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">10.1</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-General" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#General"> <div class="vector-toc-text"> <span class="vector-toc-numb">10.2</span> <span>General</span> </div> </a> <ul id="toc-General-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Technical_reading" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Technical_reading"> <div class="vector-toc-text"> <span class="vector-toc-numb">10.3</span> <span>Technical reading</span> </div> </a> <ul id="toc-Technical_reading-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">11</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" title="Table of Contents" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Radar</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 103 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-103" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">103 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-af mw-list-item"><a href="https://af.wikipedia.org/wiki/Radar" title="Radar – Afrikaans" lang="af" hreflang="af" data-title="Radar" data-language-autonym="Afrikaans" data-language-local-name="Afrikaans" class="interlanguage-link-target"><span>Afrikaans</span></a></li><li class="interlanguage-link interwiki-als mw-list-item"><a href="https://als.wikipedia.org/wiki/Radar" title="Radar – Alemannic" lang="gsw" hreflang="gsw" data-title="Radar" data-language-autonym="Alemannisch" data-language-local-name="Alemannic" class="interlanguage-link-target"><span>Alemannisch</span></a></li><li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D8%B1%D8%A7%D8%AF%D8%A7%D8%B1" title="رادار – Arabic" lang="ar" hreflang="ar" data-title="رادار" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-an mw-list-item"><a href="https://an.wikipedia.org/wiki/Radar" title="Radar – Aragonese" lang="an" hreflang="an" data-title="Radar" data-language-autonym="Aragonés" data-language-local-name="Aragonese" class="interlanguage-link-target"><span>Aragonés</span></a></li><li class="interlanguage-link interwiki-as mw-list-item"><a href="https://as.wikipedia.org/wiki/%E0%A7%B0%E0%A6%BE%E0%A6%A1%E0%A6%BE%E0%A7%B0" title="ৰাডাৰ – Assamese" lang="as" hreflang="as" data-title="ৰাডাৰ" data-language-autonym="অসমীয়া" data-language-local-name="Assamese" class="interlanguage-link-target"><span>অসমীয়া</span></a></li><li class="interlanguage-link interwiki-ast mw-list-item"><a href="https://ast.wikipedia.org/wiki/Radar" title="Radar – Asturian" lang="ast" hreflang="ast" data-title="Radar" data-language-autonym="Asturianu" data-language-local-name="Asturian" class="interlanguage-link-target"><span>Asturianu</span></a></li><li class="interlanguage-link interwiki-az mw-list-item"><a href="https://az.wikipedia.org/wiki/Radar" title="Radar – Azerbaijani" lang="az" hreflang="az" data-title="Radar" data-language-autonym="Azərbaycanca" data-language-local-name="Azerbaijani" class="interlanguage-link-target"><span>Azərbaycanca</span></a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%B0%E0%A6%BE%E0%A6%A1%E0%A6%BE%E0%A6%B0" title="রাডার – Bangla" lang="bn" hreflang="bn" data-title="রাডার" data-language-autonym="বাংলা" data-language-local-name="Bangla" class="interlanguage-link-target"><span>বাংলা</span></a></li><li class="interlanguage-link interwiki-zh-min-nan mw-list-item"><a href="https://zh-min-nan.wikipedia.org/wiki/L%C3%BBi-ta%CC%8Dt" title="Lûi-ta̍t – Minnan" lang="nan" hreflang="nan" data-title="Lûi-ta̍t" data-language-autonym="閩南語 / Bân-lâm-gú" data-language-local-name="Minnan" class="interlanguage-link-target"><span>閩南語 / Bân-lâm-gú</span></a></li><li class="interlanguage-link interwiki-be mw-list-item"><a href="https://be.wikipedia.org/wiki/%D0%A0%D0%B0%D0%B4%D0%B0%D1%80" title="Радар – Belarusian" lang="be" hreflang="be" data-title="Радар" data-language-autonym="Беларуская" data-language-local-name="Belarusian" class="interlanguage-link-target"><span>Беларуская</span></a></li><li class="interlanguage-link interwiki-be-x-old mw-list-item"><a href="https://be-tarask.wikipedia.org/wiki/%D0%A0%D0%B0%D0%B4%D1%8B%D1%91%D0%BB%D1%8F%D0%BA%D0%B0%D1%86%D1%8B%D0%B9%D0%BD%D0%B0%D1%8F_%D1%81%D1%82%D0%B0%D0%BD%D1%86%D1%8B%D1%8F" title="Радыёлякацыйная станцыя – Belarusian (Taraškievica orthography)" lang="be-tarask" hreflang="be-tarask" data-title="Радыёлякацыйная станцыя" data-language-autonym="Беларуская (тарашкевіца)" data-language-local-name="Belarusian (Taraškievica orthography)" class="interlanguage-link-target"><span>Беларуская (тарашкевіца)</span></a></li><li class="interlanguage-link interwiki-bh mw-list-item"><a href="https://bh.wikipedia.org/wiki/%E0%A4%B0%E0%A4%BE%E0%A4%A1%E0%A4%BE%E0%A4%B0" title="राडार – Bhojpuri" lang="bh" hreflang="bh" data-title="राडार" data-language-autonym="भोजपुरी" data-language-local-name="Bhojpuri" class="interlanguage-link-target"><span>भोजपुरी</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%A0%D0%B0%D0%B4%D0%B8%D0%BE%D0%BB%D0%BE%D0%BA%D0%B0%D1%82%D0%BE%D1%80" title="Радиолокатор – Bulgarian" lang="bg" hreflang="bg" data-title="Радиолокатор" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target"><span>Български</span></a></li><li class="interlanguage-link interwiki-bs mw-list-item"><a href="https://bs.wikipedia.org/wiki/Radar" title="Radar – Bosnian" lang="bs" hreflang="bs" data-title="Radar" data-language-autonym="Bosanski" data-language-local-name="Bosnian" class="interlanguage-link-target"><span>Bosanski</span></a></li><li class="interlanguage-link interwiki-br mw-list-item"><a href="https://br.wikipedia.org/wiki/Radar" title="Radar – Breton" lang="br" hreflang="br" data-title="Radar" data-language-autonym="Brezhoneg" data-language-local-name="Breton" class="interlanguage-link-target"><span>Brezhoneg</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Radar" title="Radar – Catalan" lang="ca" hreflang="ca" data-title="Radar" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Radar" title="Radar – Czech" lang="cs" hreflang="cs" data-title="Radar" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-cy mw-list-item"><a href="https://cy.wikipedia.org/wiki/Radar" title="Radar – Welsh" lang="cy" hreflang="cy" data-title="Radar" data-language-autonym="Cymraeg" data-language-local-name="Welsh" class="interlanguage-link-target"><span>Cymraeg</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Radar" title="Radar – Danish" lang="da" hreflang="da" data-title="Radar" data-language-autonym="Dansk" data-language-local-name="Danish" class="interlanguage-link-target"><span>Dansk</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Radar" title="Radar – German" lang="de" hreflang="de" data-title="Radar" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/Radar" title="Radar – Estonian" lang="et" hreflang="et" data-title="Radar" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-el mw-list-item"><a href="https://el.wikipedia.org/wiki/%CE%A1%CE%B1%CE%BD%CF%84%CE%AC%CF%81" title="Ραντάρ – Greek" lang="el" hreflang="el" data-title="Ραντάρ" data-language-autonym="Ελληνικά" data-language-local-name="Greek" class="interlanguage-link-target"><span>Ελληνικά</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Radar" title="Radar – Spanish" lang="es" hreflang="es" data-title="Radar" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/Radaro" title="Radaro – Esperanto" lang="eo" hreflang="eo" data-title="Radaro" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target"><span>Esperanto</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Radar" title="Radar – Basque" lang="eu" hreflang="eu" data-title="Radar" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D8%B1%D8%A7%D8%AF%D8%A7%D8%B1" title="رادار – Persian" lang="fa" hreflang="fa" data-title="رادار" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Radar" title="Radar – French" lang="fr" hreflang="fr" data-title="Radar" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-fy mw-list-item"><a href="https://fy.wikipedia.org/wiki/Radar" title="Radar – Western Frisian" lang="fy" hreflang="fy" data-title="Radar" data-language-autonym="Frysk" data-language-local-name="Western Frisian" class="interlanguage-link-target"><span>Frysk</span></a></li><li class="interlanguage-link interwiki-ga mw-list-item"><a href="https://ga.wikipedia.org/wiki/Radar" title="Radar – Irish" lang="ga" hreflang="ga" data-title="Radar" data-language-autonym="Gaeilge" data-language-local-name="Irish" class="interlanguage-link-target"><span>Gaeilge</span></a></li><li class="interlanguage-link interwiki-gl mw-list-item"><a href="https://gl.wikipedia.org/wiki/Radar" title="Radar – Galician" lang="gl" hreflang="gl" data-title="Radar" data-language-autonym="Galego" data-language-local-name="Galician" class="interlanguage-link-target"><span>Galego</span></a></li><li class="interlanguage-link interwiki-gan mw-list-item"><a href="https://gan.wikipedia.org/wiki/%E9%9B%B7%E9%81%94" title="雷達 – Gan" lang="gan" hreflang="gan" data-title="雷達" data-language-autonym="贛語" data-language-local-name="Gan" class="interlanguage-link-target"><span>贛語</span></a></li><li class="interlanguage-link interwiki-gom mw-list-item"><a href="https://gom.wikipedia.org/wiki/%E0%A4%B0%E0%A4%A1%E0%A4%BE%E0%A4%B0" title="रडार – Goan Konkani" lang="gom" hreflang="gom" data-title="रडार" data-language-autonym="गोंयची कोंकणी / Gõychi Konknni" data-language-local-name="Goan Konkani" class="interlanguage-link-target"><span>गोंयची कोंकणी / Gõychi Konknni</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EB%A0%88%EC%9D%B4%EB%8D%94" title="레이더 – Korean" lang="ko" hreflang="ko" data-title="레이더" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-ha mw-list-item"><a href="https://ha.wikipedia.org/wiki/Radar" title="Radar – Hausa" lang="ha" hreflang="ha" data-title="Radar" data-language-autonym="Hausa" data-language-local-name="Hausa" class="interlanguage-link-target"><span>Hausa</span></a></li><li class="interlanguage-link interwiki-hy mw-list-item"><a href="https://hy.wikipedia.org/wiki/%D5%8C%D5%A1%D5%A4%D5%AB%D5%B8%D5%AC%D5%B8%D5%AF%D5%A1%D6%81%D5%AB%D5%B8%D5%B6_%D5%AF%D5%A1%D5%B5%D5%A1%D5%B6" title="Ռադիոլոկացիոն կայան – Armenian" lang="hy" hreflang="hy" data-title="Ռադիոլոկացիոն կայան" data-language-autonym="Հայերեն" data-language-local-name="Armenian" class="interlanguage-link-target"><span>Հայերեն</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%B0%E0%A4%A1%E0%A4%BE%E0%A4%B0" title="रडार – Hindi" lang="hi" hreflang="hi" data-title="रडार" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Radar" title="Radar – Croatian" lang="hr" hreflang="hr" data-title="Radar" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Radar" title="Radar – Indonesian" lang="id" hreflang="id" data-title="Radar" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-ia mw-list-item"><a href="https://ia.wikipedia.org/wiki/Radar" title="Radar – Interlingua" lang="ia" hreflang="ia" data-title="Radar" data-language-autonym="Interlingua" data-language-local-name="Interlingua" class="interlanguage-link-target"><span>Interlingua</span></a></li><li class="interlanguage-link interwiki-is mw-list-item"><a href="https://is.wikipedia.org/wiki/Ratsj%C3%A1" title="Ratsjá – Icelandic" lang="is" hreflang="is" data-title="Ratsjá" data-language-autonym="Íslenska" data-language-local-name="Icelandic" class="interlanguage-link-target"><span>Íslenska</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Radar" title="Radar – Italian" lang="it" hreflang="it" data-title="Radar" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%9E%D7%9B%22%D7%9D" title="מכ"ם – Hebrew" lang="he" hreflang="he" data-title="מכ"ם" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-kn mw-list-item"><a href="https://kn.wikipedia.org/wiki/%E0%B2%B0%E0%B3%87%E0%B2%A1%E0%B2%BE%E0%B2%B0%E0%B3%8D" title="ರೇಡಾರ್ – Kannada" lang="kn" hreflang="kn" data-title="ರೇಡಾರ್" data-language-autonym="ಕನ್ನಡ" data-language-local-name="Kannada" class="interlanguage-link-target"><span>ಕನ್ನಡ</span></a></li><li class="interlanguage-link interwiki-ka mw-list-item"><a href="https://ka.wikipedia.org/wiki/%E1%83%A0%E1%83%90%E1%83%93%E1%83%90%E1%83%A0%E1%83%98" title="რადარი – Georgian" lang="ka" hreflang="ka" data-title="რადარი" data-language-autonym="ქართული" data-language-local-name="Georgian" class="interlanguage-link-target"><span>ქართული</span></a></li><li class="interlanguage-link interwiki-kk mw-list-item"><a href="https://kk.wikipedia.org/wiki/%D0%A0%D0%B0%D0%B4%D0%B0%D1%80" title="Радар – Kazakh" lang="kk" hreflang="kk" data-title="Радар" data-language-autonym="Қазақша" data-language-local-name="Kazakh" class="interlanguage-link-target"><span>Қазақша</span></a></li><li class="interlanguage-link interwiki-sw mw-list-item"><a href="https://sw.wikipedia.org/wiki/Rada" title="Rada – Swahili" lang="sw" hreflang="sw" data-title="Rada" data-language-autonym="Kiswahili" data-language-local-name="Swahili" class="interlanguage-link-target"><span>Kiswahili</span></a></li><li class="interlanguage-link interwiki-gcr mw-list-item"><a href="https://gcr.wikipedia.org/wiki/Radar" title="Radar – Guianan Creole" lang="gcr" hreflang="gcr" data-title="Radar" data-language-autonym="Kriyòl gwiyannen" data-language-local-name="Guianan Creole" class="interlanguage-link-target"><span>Kriyòl gwiyannen</span></a></li><li class="interlanguage-link interwiki-ku mw-list-item"><a href="https://ku.wikipedia.org/wiki/Radar" title="Radar – Kurdish" lang="ku" hreflang="ku" data-title="Radar" data-language-autonym="Kurdî" data-language-local-name="Kurdish" class="interlanguage-link-target"><span>Kurdî</span></a></li><li class="interlanguage-link interwiki-lo mw-list-item"><a href="https://lo.wikipedia.org/wiki/%E0%BA%A5%E0%BA%B2%E0%BA%94%E0%BA%B2" title="ລາດາ – Lao" lang="lo" hreflang="lo" data-title="ລາດາ" data-language-autonym="ລາວ" data-language-local-name="Lao" class="interlanguage-link-target"><span>ລາວ</span></a></li><li class="interlanguage-link interwiki-la mw-list-item"><a href="https://la.wikipedia.org/wiki/Radar" title="Radar – Latin" lang="la" hreflang="la" data-title="Radar" data-language-autonym="Latina" data-language-local-name="Latin" class="interlanguage-link-target"><span>Latina</span></a></li><li class="interlanguage-link interwiki-lv mw-list-item"><a href="https://lv.wikipedia.org/wiki/Radars" title="Radars – Latvian" lang="lv" hreflang="lv" data-title="Radars" data-language-autonym="Latviešu" data-language-local-name="Latvian" class="interlanguage-link-target"><span>Latviešu</span></a></li><li class="interlanguage-link interwiki-lb mw-list-item"><a href="https://lb.wikipedia.org/wiki/Radar" title="Radar – Luxembourgish" lang="lb" hreflang="lb" data-title="Radar" data-language-autonym="Lëtzebuergesch" data-language-local-name="Luxembourgish" class="interlanguage-link-target"><span>Lëtzebuergesch</span></a></li><li class="interlanguage-link interwiki-lt mw-list-item"><a href="https://lt.wikipedia.org/wiki/Radaras" title="Radaras – Lithuanian" lang="lt" hreflang="lt" data-title="Radaras" data-language-autonym="Lietuvių" data-language-local-name="Lithuanian" class="interlanguage-link-target"><span>Lietuvių</span></a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/R%C3%A1di%C3%B3lok%C3%A1tor" title="Rádiólokátor – Hungarian" lang="hu" hreflang="hu" data-title="Rádiólokátor" data-language-autonym="Magyar" data-language-local-name="Hungarian" class="interlanguage-link-target"><span>Magyar</span></a></li><li class="interlanguage-link interwiki-ml mw-list-item"><a href="https://ml.wikipedia.org/wiki/%E0%B4%B1%E0%B4%A1%E0%B4%BE%E0%B5%BC" title="റഡാർ – Malayalam" lang="ml" hreflang="ml" data-title="റഡാർ" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target"><span>മലയാളം</span></a></li><li class="interlanguage-link interwiki-mr mw-list-item"><a href="https://mr.wikipedia.org/wiki/%E0%A4%B0%E0%A4%A1%E0%A4%BE%E0%A4%B0_%E0%A4%AF%E0%A4%82%E0%A4%A4%E0%A5%8D%E0%A4%B0%E0%A4%A3%E0%A4%BE" title="रडार यंत्रणा – Marathi" lang="mr" hreflang="mr" data-title="रडार यंत्रणा" data-language-autonym="मराठी" data-language-local-name="Marathi" class="interlanguage-link-target"><span>मराठी</span></a></li><li class="interlanguage-link interwiki-arz mw-list-item"><a href="https://arz.wikipedia.org/wiki/%D8%A7%D9%84%D8%B1%D8%A7%D8%AF%D8%A7%D8%B1" title="الرادار – Egyptian Arabic" lang="arz" hreflang="arz" data-title="الرادار" data-language-autonym="مصرى" data-language-local-name="Egyptian Arabic" class="interlanguage-link-target"><span>مصرى</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Radar" title="Radar – Malay" lang="ms" hreflang="ms" data-title="Radar" data-language-autonym="Bahasa Melayu" data-language-local-name="Malay" class="interlanguage-link-target"><span>Bahasa Melayu</span></a></li><li class="interlanguage-link interwiki-min mw-list-item"><a href="https://min.wikipedia.org/wiki/Radar" title="Radar – Minangkabau" lang="min" hreflang="min" data-title="Radar" data-language-autonym="Minangkabau" data-language-local-name="Minangkabau" class="interlanguage-link-target"><span>Minangkabau</span></a></li><li class="interlanguage-link interwiki-mn mw-list-item"><a href="https://mn.wikipedia.org/wiki/Radar" title="Radar – Mongolian" lang="mn" hreflang="mn" data-title="Radar" data-language-autonym="Монгол" data-language-local-name="Mongolian" class="interlanguage-link-target"><span>Монгол</span></a></li><li class="interlanguage-link interwiki-my mw-list-item"><a href="https://my.wikipedia.org/wiki/%E1%80%9B%E1%80%B1%E1%80%92%E1%80%AB" title="ရေဒါ – Burmese" lang="my" hreflang="my" data-title="ရေဒါ" data-language-autonym="မြန်မာဘာသာ" data-language-local-name="Burmese" class="interlanguage-link-target"><span>မြန်မာဘာသာ</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Radar" title="Radar – Dutch" lang="nl" hreflang="nl" data-title="Radar" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E3%83%AC%E3%83%BC%E3%83%80%E3%83%BC" title="レーダー – Japanese" lang="ja" hreflang="ja" data-title="レーダー" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-frr mw-list-item"><a href="https://frr.wikipedia.org/wiki/Radar" title="Radar – Northern Frisian" lang="frr" hreflang="frr" data-title="Radar" data-language-autonym="Nordfriisk" data-language-local-name="Northern Frisian" class="interlanguage-link-target"><span>Nordfriisk</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Radar" title="Radar – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Radar" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/Radar" title="Radar – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Radar" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target"><span>Norsk nynorsk</span></a></li><li class="interlanguage-link interwiki-oc mw-list-item"><a href="https://oc.wikipedia.org/wiki/Radar" title="Radar – Occitan" lang="oc" hreflang="oc" data-title="Radar" data-language-autonym="Occitan" data-language-local-name="Occitan" class="interlanguage-link-target"><span>Occitan</span></a></li><li class="interlanguage-link interwiki-om mw-list-item"><a href="https://om.wikipedia.org/wiki/Raadaarii" title="Raadaarii – Oromo" lang="om" hreflang="om" data-title="Raadaarii" data-language-autonym="Oromoo" data-language-local-name="Oromo" class="interlanguage-link-target"><span>Oromoo</span></a></li><li class="interlanguage-link interwiki-uz mw-list-item"><a href="https://uz.wikipedia.org/wiki/Radiolokator" title="Radiolokator – Uzbek" lang="uz" hreflang="uz" data-title="Radiolokator" data-language-autonym="Oʻzbekcha / ўзбекча" data-language-local-name="Uzbek" class="interlanguage-link-target"><span>Oʻzbekcha / ўзбекча</span></a></li><li class="interlanguage-link interwiki-pa mw-list-item"><a href="https://pa.wikipedia.org/wiki/%E0%A8%B0%E0%A8%A1%E0%A8%BE%E0%A8%B0" title="ਰਡਾਰ – Punjabi" lang="pa" hreflang="pa" data-title="ਰਡਾਰ" data-language-autonym="ਪੰਜਾਬੀ" data-language-local-name="Punjabi" class="interlanguage-link-target"><span>ਪੰਜਾਬੀ</span></a></li><li class="interlanguage-link interwiki-pnb mw-list-item"><a href="https://pnb.wikipedia.org/wiki/%D8%B1%DB%8C%DA%88%D8%A7%D8%B1" title="ریڈار – Western Punjabi" lang="pnb" hreflang="pnb" data-title="ریڈار" data-language-autonym="پنجابی" data-language-local-name="Western Punjabi" class="interlanguage-link-target"><span>پنجابی</span></a></li><li class="interlanguage-link interwiki-ps mw-list-item"><a href="https://ps.wikipedia.org/wiki/%D8%B1%D8%A7%D8%AF%D8%A7%D8%B1" title="رادار – Pashto" lang="ps" hreflang="ps" data-title="رادار" data-language-autonym="پښتو" data-language-local-name="Pashto" class="interlanguage-link-target"><span>پښتو</span></a></li><li class="interlanguage-link interwiki-jam mw-list-item"><a href="https://jam.wikipedia.org/wiki/Riedaar" title="Riedaar – Jamaican Creole English" lang="jam" hreflang="jam" data-title="Riedaar" data-language-autonym="Patois" data-language-local-name="Jamaican Creole English" class="interlanguage-link-target"><span>Patois</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Radar" title="Radar – Polish" lang="pl" hreflang="pl" data-title="Radar" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Radar" title="Radar – Portuguese" lang="pt" hreflang="pt" data-title="Radar" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-kaa mw-list-item"><a href="https://kaa.wikipedia.org/wiki/Radar" title="Radar – Kara-Kalpak" lang="kaa" hreflang="kaa" data-title="Radar" data-language-autonym="Qaraqalpaqsha" data-language-local-name="Kara-Kalpak" class="interlanguage-link-target"><span>Qaraqalpaqsha</span></a></li><li class="interlanguage-link interwiki-ro mw-list-item"><a href="https://ro.wikipedia.org/wiki/RADAR" title="RADAR – Romanian" lang="ro" hreflang="ro" data-title="RADAR" data-language-autonym="Română" data-language-local-name="Romanian" class="interlanguage-link-target"><span>Română</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%A0%D0%B0%D0%B4%D0%B8%D0%BE%D0%BB%D0%BE%D0%BA%D0%B0%D1%86%D0%B8%D0%BE%D0%BD%D0%BD%D0%B0%D1%8F_%D1%81%D1%82%D0%B0%D0%BD%D1%86%D0%B8%D1%8F" title="Радиолокационная станция – Russian" lang="ru" hreflang="ru" data-title="Радиолокационная станция" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-sq mw-list-item"><a href="https://sq.wikipedia.org/wiki/Radari" title="Radari – Albanian" lang="sq" hreflang="sq" data-title="Radari" data-language-autonym="Shqip" data-language-local-name="Albanian" class="interlanguage-link-target"><span>Shqip</span></a></li><li class="interlanguage-link interwiki-scn mw-list-item"><a href="https://scn.wikipedia.org/wiki/Radar" title="Radar – Sicilian" lang="scn" hreflang="scn" data-title="Radar" data-language-autonym="Sicilianu" data-language-local-name="Sicilian" class="interlanguage-link-target"><span>Sicilianu</span></a></li><li class="interlanguage-link interwiki-si mw-list-item"><a href="https://si.wikipedia.org/wiki/%E0%B6%BB%E0%B7%9A%E0%B6%A9%E0%B7%8F%E0%B6%BB%E0%B7%8A_%E0%B6%8B%E0%B6%B4%E0%B7%8F%E0%B6%82%E0%B6%9C" title="රේඩාර් උපාංග – Sinhala" lang="si" hreflang="si" data-title="රේඩාර් උපාංග" data-language-autonym="සිංහල" data-language-local-name="Sinhala" class="interlanguage-link-target"><span>සිංහල</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Radar" title="Radar – Simple English" lang="en-simple" hreflang="en-simple" data-title="Radar" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Radar" title="Radar – Slovak" lang="sk" hreflang="sk" data-title="Radar" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-sl mw-list-item"><a href="https://sl.wikipedia.org/wiki/Radar" title="Radar – Slovenian" lang="sl" hreflang="sl" data-title="Radar" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" class="interlanguage-link-target"><span>Slovenščina</span></a></li><li class="interlanguage-link interwiki-ckb mw-list-item"><a href="https://ckb.wikipedia.org/wiki/%DA%95%D8%A7%D8%AF%D8%A7%D8%B1" title="ڕادار – Central Kurdish" lang="ckb" hreflang="ckb" data-title="ڕادار" data-language-autonym="کوردی" data-language-local-name="Central Kurdish" class="interlanguage-link-target"><span>کوردی</span></a></li><li class="interlanguage-link interwiki-sr badge-Q17437796 badge-featuredarticle mw-list-item" title="featured article badge"><a href="https://sr.wikipedia.org/wiki/%D0%A0%D0%B0%D0%B4%D0%B0%D1%80" title="Радар – Serbian" lang="sr" hreflang="sr" data-title="Радар" data-language-autonym="Српски / srpski" data-language-local-name="Serbian" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-sh mw-list-item"><a href="https://sh.wikipedia.org/wiki/Radar" title="Radar – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Radar" data-language-autonym="Srpskohrvatski / српскохрватски" data-language-local-name="Serbo-Croatian" class="interlanguage-link-target"><span>Srpskohrvatski / српскохрватски</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Tutka" title="Tutka – Finnish" lang="fi" hreflang="fi" data-title="Tutka" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Radar" title="Radar – Swedish" lang="sv" hreflang="sv" data-title="Radar" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-tl mw-list-item"><a href="https://tl.wikipedia.org/wiki/Radar" title="Radar – Tagalog" lang="tl" hreflang="tl" data-title="Radar" data-language-autonym="Tagalog" data-language-local-name="Tagalog" class="interlanguage-link-target"><span>Tagalog</span></a></li><li class="interlanguage-link interwiki-ta mw-list-item"><a href="https://ta.wikipedia.org/wiki/%E0%AE%95%E0%AE%A4%E0%AE%BF%E0%AE%B0%E0%AE%B2%E0%AF%88%E0%AE%95%E0%AF%8D_%E0%AE%95%E0%AF%81%E0%AE%AE%E0%AF%8D%E0%AE%AA%E0%AE%BE" title="கதிரலைக் கும்பா – Tamil" lang="ta" hreflang="ta" data-title="கதிரலைக் கும்பா" data-language-autonym="தமிழ்" data-language-local-name="Tamil" class="interlanguage-link-target"><span>தமிழ்</span></a></li><li class="interlanguage-link interwiki-te mw-list-item"><a href="https://te.wikipedia.org/wiki/%E0%B0%B0%E0%B0%BE%E0%B0%A1%E0%B0%BE%E0%B0%B0%E0%B1%8D" title="రాడార్ – Telugu" lang="te" hreflang="te" data-title="రాడార్" data-language-autonym="తెలుగు" data-language-local-name="Telugu" class="interlanguage-link-target"><span>తెలుగు</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/%E0%B9%80%E0%B8%A3%E0%B8%94%E0%B8%B2%E0%B8%A3%E0%B9%8C" title="เรดาร์ – Thai" lang="th" hreflang="th" data-title="เรดาร์" data-language-autonym="ไทย" data-language-local-name="Thai" class="interlanguage-link-target"><span>ไทย</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/Radar" title="Radar – Turkish" lang="tr" hreflang="tr" data-title="Radar" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-tk mw-list-item"><a href="https://tk.wikipedia.org/wiki/Radar" title="Radar – Turkmen" lang="tk" hreflang="tk" data-title="Radar" data-language-autonym="Türkmençe" data-language-local-name="Turkmen" class="interlanguage-link-target"><span>Türkmençe</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%A0%D0%B0%D0%B4%D0%B0%D1%80" title="Радар – Ukrainian" lang="uk" hreflang="uk" data-title="Радар" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-ur mw-list-item"><a href="https://ur.wikipedia.org/wiki/%D8%B1%DB%8C%DA%88%D8%A7%D8%B1" title="ریڈار – Urdu" lang="ur" hreflang="ur" data-title="ریڈار" data-language-autonym="اردو" data-language-local-name="Urdu" class="interlanguage-link-target"><span>اردو</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/Radar" title="Radar – Vietnamese" lang="vi" hreflang="vi" data-title="Radar" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link interwiki-wa mw-list-item"><a href="https://wa.wikipedia.org/wiki/Rad%C3%A5r" title="Radår – Walloon" lang="wa" hreflang="wa" data-title="Radår" data-language-autonym="Walon" data-language-local-name="Walloon" class="interlanguage-link-target"><span>Walon</span></a></li><li class="interlanguage-link interwiki-war mw-list-item"><a href="https://war.wikipedia.org/wiki/Radar" title="Radar – Waray" lang="war" hreflang="war" data-title="Radar" data-language-autonym="Winaray" data-language-local-name="Waray" class="interlanguage-link-target"><span>Winaray</span></a></li><li class="interlanguage-link interwiki-wuu mw-list-item"><a href="https://wuu.wikipedia.org/wiki/%E9%9B%B7%E8%BE%BE" title="雷达 – Wu" lang="wuu" hreflang="wuu" data-title="雷达" data-language-autonym="吴语" data-language-local-name="Wu" class="interlanguage-link-target"><span>吴语</span></a></li><li class="interlanguage-link interwiki-zh-yue mw-list-item"><a href="https://zh-yue.wikipedia.org/wiki/%E9%9B%B7%E9%81%94" title="雷達 – Cantonese" lang="yue" hreflang="yue" data-title="雷達" data-language-autonym="粵語" data-language-local-name="Cantonese" class="interlanguage-link-target"><span>粵語</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E9%9B%B7%E8%BE%BE" title="雷达 – Chinese" lang="zh" hreflang="zh" data-title="雷达" data-language-autonym="中文" data-language-local-name="Chinese" class="interlanguage-link-target"><span>中文</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q47528#sitelinks-wikipedia" title="Edit interlanguage links" class="wbc-editpage">Edit links</a></span></div> </div> </div> </div> </header> <div class="vector-page-toolbar"> <div class="vector-page-toolbar-container"> <div id="left-navigation"> <nav aria-label="Namespaces"> <div id="p-associated-pages" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-associated-pages" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-nstab-main" class="selected vector-tab-noicon mw-list-item"><a href="/wiki/Radar" title="View the content page [c]" accesskey="c"><span>Article</span></a></li><li id="ca-talk" class="vector-tab-noicon mw-list-item"><a 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searchaux" style="display:none">Object detection system using radio waves</div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">For other uses, see <a href="/wiki/Radar_(disambiguation)" class="mw-disambig" title="Radar (disambiguation)">Radar (disambiguation)</a>.</div> <p class="mw-empty-elt"> </p> <style data-mw-deduplicate="TemplateStyles:r1273380762/mw-parser-output/.tmulti">.mw-parser-output .tmulti .multiimageinner{display:flex;flex-direction:column}.mw-parser-output .tmulti .trow{display:flex;flex-direction:row;clear:left;flex-wrap:wrap;width:100%;box-sizing:border-box}.mw-parser-output .tmulti .tsingle{margin:1px;float:left}.mw-parser-output .tmulti .theader{clear:both;font-weight:bold;text-align:center;align-self:center;background-color:transparent;width:100%}.mw-parser-output .tmulti .thumbcaption{background-color:transparent}.mw-parser-output .tmulti .text-align-left{text-align:left}.mw-parser-output .tmulti .text-align-right{text-align:right}.mw-parser-output .tmulti .text-align-center{text-align:center}@media all and (max-width:720px){.mw-parser-output .tmulti .thumbinner{width:100%!important;box-sizing:border-box;max-width:none!important;align-items:center}.mw-parser-output .tmulti .trow{justify-content:center}.mw-parser-output .tmulti .tsingle{float:none!important;max-width:100%!important;box-sizing:border-box;text-align:center}.mw-parser-output .tmulti .tsingle .thumbcaption{text-align:left}.mw-parser-output .tmulti .trow>.thumbcaption{text-align:center}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}</style><div class="thumb tmulti tright"><div class="thumbinner multiimageinner" style="width:342px;max-width:342px"><div class="trow"><div class="tsingle" style="width:156px;max-width:156px"><div class="thumbimage" style="height:196px;overflow:hidden"><span typeof="mw:File"><a href="/wiki/File:Radar_antenna.jpg" class="mw-file-description"><img alt="A long-range radar antenna, known as ALTAIR, used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on Kwajalein Atoll." src="//upload.wikimedia.org/wikipedia/commons/thumb/9/90/Radar_antenna.jpg/250px-Radar_antenna.jpg" decoding="async" width="154" height="197" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/90/Radar_antenna.jpg/330px-Radar_antenna.jpg 2x" data-file-width="546" data-file-height="697" /></a></span></div><div class="thumbcaption">Long-range radar <a href="/wiki/Antenna_(electronics)" class="mw-redirect" title="Antenna (electronics)">antenna</a>, used to track space objects and ballistic missiles</div></div><div class="tsingle" style="width:182px;max-width:182px"><div class="thumbimage" style="height:196px;overflow:hidden"><span typeof="mw:File"><a href="/wiki/File:Radar-hatzerim-1-1.jpg" class="mw-file-description"><img alt="Israeli military radar is typical of the type of radar used for air traffic control. The antenna rotates at a steady rate, sweeping the local airspace with a narrow vertical fan-shaped beam, to detect aircraft at all altitudes." src="//upload.wikimedia.org/wikipedia/commons/thumb/6/66/Radar-hatzerim-1-1.jpg/180px-Radar-hatzerim-1-1.jpg" decoding="async" width="180" height="196" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/66/Radar-hatzerim-1-1.jpg/270px-Radar-hatzerim-1-1.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/66/Radar-hatzerim-1-1.jpg/360px-Radar-hatzerim-1-1.jpg 2x" data-file-width="1620" data-file-height="1761" /></a></span></div><div class="thumbcaption">Radar of the type used for detection of aircraft. It rotates steadily, sweeping the airspace with a narrow beam.</div></div></div></div></div> <p><b>Radar</b> is a system that uses <a href="/wiki/Radio_wave" title="Radio wave">radio waves</a> to determine the distance (<i><a href="/wiki/Ranging" class="mw-redirect" title="Ranging">ranging</a></i>), <a href="/wiki/Direction_(geometry)" title="Direction (geometry)">direction</a> (<a href="/wiki/Azimuth" title="Azimuth">azimuth</a> and <a href="/wiki/Elevation_angle" class="mw-redirect" title="Elevation angle">elevation angles</a>), and <a href="/wiki/Radial_velocity" title="Radial velocity">radial velocity</a> of objects relative to the site. It is a <a href="/wiki/Radiodetermination" title="Radiodetermination">radiodetermination</a> method<sup id="cite_ref-ITU-2020_1-0" class="reference"><a href="#cite_note-ITU-2020-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> used to detect and track <a href="/wiki/Aircraft" title="Aircraft">aircraft</a>, <a href="/wiki/Marine_radar" title="Marine radar">ships</a>, <a href="/wiki/Spacecraft" title="Spacecraft">spacecraft</a>, <a href="/wiki/Guided_missiles" class="mw-redirect" title="Guided missiles">guided missiles</a>, <a href="/wiki/Motor_vehicle" title="Motor vehicle">motor vehicles</a>, map <a href="/wiki/Weather_radar" title="Weather radar">weather formations</a>, and <a href="/wiki/Terrain-following_radar" title="Terrain-following radar">terrain</a>. </p><p>A radar system consists of a <a href="/wiki/Transmitter" title="Transmitter">transmitter</a> producing <a href="/wiki/Electromagnetic_wave" class="mw-redirect" title="Electromagnetic wave">electromagnetic waves</a> in the <a href="/wiki/Radio_spectrum" title="Radio spectrum">radio</a> or <a href="/wiki/Microwave" title="Microwave">microwaves</a> domain, a transmitting <a href="/wiki/Antenna_(radio)" title="Antenna (radio)">antenna</a>, a receiving antenna (often the same antenna is used for transmitting and receiving) and a <a href="/wiki/Radio_receiver" title="Radio receiver">receiver</a> and <a href="/wiki/Data_processing_system" class="mw-redirect" title="Data processing system">processor</a> to determine properties of the objects. Radio waves (pulsed or continuous) from the transmitter reflect off the objects and return to the receiver, giving information about the objects' locations and speeds. </p><p>Radar was developed secretly for <a href="/wiki/Military" title="Military">military</a> use by several countries in the period before and during <a href="/wiki/World_War_II" title="World War II">World War II</a>. A key development was the <a href="/wiki/Cavity_magnetron" title="Cavity magnetron">cavity magnetron</a> in the <a href="/wiki/United_Kingdom" title="United Kingdom">United Kingdom</a>, which allowed the creation of relatively small systems with sub-meter resolution. The term <i>RADAR</i> was coined in 1940 by the <a href="/wiki/United_States_Navy" title="United States Navy">United States Navy</a> as an <a href="/wiki/Acronym_and_initialism" class="mw-redirect" title="Acronym and initialism">acronym</a> for "radio detection and ranging".<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> The term <i>radar</i> has since entered English and other languages as an <a href="https://en.wiktionary.org/wiki/anacronym" class="extiw" title="wikt:anacronym">anacronym</a>, a common noun, <a href="/wiki/Acronym#All-caps_style" title="Acronym">losing all capitalization</a>. </p><p>The modern uses of radar are highly diverse, including air and terrestrial traffic control, <a href="/wiki/Radar_astronomy" title="Radar astronomy">radar astronomy</a>, <a href="/wiki/Antiaircraft_warfare" class="mw-redirect" title="Antiaircraft warfare">air-defense systems</a>, <a href="/wiki/Close-in_weapon_system" title="Close-in weapon system">anti-missile systems</a>, <a href="/wiki/Marine_radar" title="Marine radar">marine radars</a> to locate landmarks and other ships, aircraft anti-collision systems, <a href="/wiki/Research_vessel" title="Research vessel">ocean surveillance</a> systems, outer <a href="/wiki/Space_surveillance" class="mw-redirect" title="Space surveillance">space surveillance</a> and <a href="/wiki/Space_rendezvous" title="Space rendezvous">rendezvous</a> systems, <a href="/wiki/Meteorology" title="Meteorology">meteorological</a> <a href="/wiki/Precipitation" title="Precipitation">precipitation</a> monitoring, <a href="/wiki/Radar_remote_sensing" title="Radar remote sensing">radar remote sensing</a>, altimetry and <a href="/wiki/Flight_control_system" class="mw-redirect" title="Flight control system">flight control systems</a>, <a href="/wiki/Precision-guided_munition" title="Precision-guided munition">guided missile</a> target locating systems, <a href="/wiki/Self-driving_car" title="Self-driving car">self-driving cars</a>, and <a href="/wiki/Ground-penetrating_radar" title="Ground-penetrating radar">ground-penetrating radar</a> for geological observations. Modern high tech radar systems use <a href="/wiki/Digital_signal_processing" title="Digital signal processing">digital signal processing</a> and <a href="/wiki/Machine_learning" title="Machine learning">machine learning</a> and are capable of extracting useful information from very high <a href="/wiki/Noise_(electronics)" title="Noise (electronics)">noise</a> levels. </p><p>Other systems which are similar to radar make use of other parts of the <a href="/wiki/Electromagnetic_spectrum" title="Electromagnetic spectrum">electromagnetic spectrum</a>. One example is <a href="/wiki/Lidar" title="Lidar">lidar</a>, which uses predominantly <a href="/wiki/Infrared_light" class="mw-redirect" title="Infrared light">infrared light</a> from <a href="/wiki/Laser" title="Laser">lasers</a> rather than radio waves. With the emergence of driverless vehicles, radar is expected to assist the automated platform to monitor its environment, thus preventing unwanted incidents.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="History">History</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=1" title="Edit section: History"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/History_of_radar" title="History of radar">History of radar</a></div> <div class="mw-heading mw-heading3"><h3 id="First_experiments">First experiments</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=2" title="Edit section: First experiments"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>As early as 1886, German physicist <a href="/wiki/Heinrich_Hertz" title="Heinrich Hertz">Heinrich Hertz</a> showed that radio waves could be reflected from solid objects. In 1895, <a href="/wiki/Alexander_Stepanovich_Popov" class="mw-redirect" title="Alexander Stepanovich Popov">Alexander Popov</a>, a physics instructor at the <a href="/wiki/Imperial_Russian_Navy" title="Imperial Russian Navy">Imperial Russian Navy</a> school in <a href="/wiki/Kronstadt" title="Kronstadt">Kronstadt</a>, developed an apparatus using a <a href="/wiki/Coherer" title="Coherer">coherer</a> tube for detecting distant lightning strikes. The next year, he added a <a href="/wiki/Spark-gap_transmitter" title="Spark-gap transmitter">spark-gap transmitter</a>. In 1897, while testing this equipment for communicating between two ships in the <a href="/wiki/Baltic_Sea" title="Baltic Sea">Baltic Sea</a>, he took note of an <a href="/wiki/Interference_beat" class="mw-redirect" title="Interference beat">interference beat</a> caused by the passage of a third vessel. In his report, Popov wrote that this phenomenon might be used for detecting objects, but he did nothing more with this observation.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p><p>The German inventor <a href="/wiki/Christian_H%C3%BClsmeyer" title="Christian Hülsmeyer">Christian Hülsmeyer</a> was the first to use radio waves to detect "the presence of distant metallic objects". In 1904, he demonstrated the feasibility of detecting a ship in dense fog, but not its distance from the transmitter.<sup id="cite_ref-radarworld.org_9-0" class="reference"><a href="#cite_note-radarworld.org-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> He obtained a patent<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> for his detection device in April 1904 and later a patent<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> for a related amendment for estimating the distance to the ship. He also obtained a British patent on 23 September 1904<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> for a full radar system, that he called a <i>telemobiloscope</i>. It operated on a 50 cm wavelength and the pulsed radar signal was created via a spark-gap. His system already used the classic antenna setup of horn antenna with parabolic reflector and was presented to German military officials in practical tests in <a href="/wiki/Cologne" title="Cologne">Cologne</a> and <a href="/wiki/Rotterdam" title="Rotterdam">Rotterdam</a> harbour but was rejected.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p><p>In 1915, <a href="/wiki/Robert_Watson-Watt" title="Robert Watson-Watt">Robert Watson-Watt</a> used radio technology to provide advance warning of thunderstorms to airmen<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> and during the 1920s went on to lead the U.K. research establishment to make many advances using radio techniques, including the probing of the <a href="/wiki/Ionosphere" title="Ionosphere">ionosphere</a> and the detection of <a href="/wiki/Lightning" title="Lightning">lightning</a> at long distances. Through his lightning experiments, Watson-Watt became an expert on the use of <a href="/wiki/Radio_direction_finding" class="mw-redirect" title="Radio direction finding">radio direction finding</a> before turning his inquiry to <a href="/wiki/Shortwave" class="mw-redirect" title="Shortwave">shortwave</a> transmission. Requiring a suitable receiver for such studies, he told the "new boy" <a href="/wiki/Arnold_Frederic_Wilkins" class="mw-redirect" title="Arnold Frederic Wilkins">Arnold Frederic Wilkins</a> to conduct an extensive review of available shortwave units. Wilkins would select a <a href="/wiki/General_Post_Office" title="General Post Office">General Post Office</a> model after noting its manual's description of a "fading" effect (the common term for interference at the time) when aircraft flew overhead. </p><p>By placing a transmitter and receiver on opposite sides of the <a href="/wiki/Potomac_River" title="Potomac River">Potomac River</a> in 1922, U.S. Navy researchers <a href="/wiki/A._Hoyt_Taylor" class="mw-redirect" title="A. Hoyt Taylor">A. Hoyt Taylor</a> and <a href="/wiki/Leo_C._Young" title="Leo C. Young">Leo C. Young</a> discovered that ships passing through the beam path caused the received signal to fade in and out. Taylor submitted a report, suggesting that this phenomenon might be used to detect the presence of ships in low visibility, but the Navy did not immediately continue the work. Eight years later, <a href="/wiki/Lawrence_A._Hyland" title="Lawrence A. Hyland">Lawrence A. Hyland</a> at the <a href="/wiki/Naval_Research_Laboratory" class="mw-redirect" title="Naval Research Laboratory">Naval Research Laboratory</a> (NRL) observed similar fading effects from passing aircraft; this revelation led to a patent application<sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> as well as a proposal for further intensive research on radio-echo signals from moving targets to take place at NRL, where Taylor and Young were based at the time.<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> </p><p>Similarly, in the UK, L. S. Alder took out a secret provisional patent for Naval radar in 1928.<sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> <a href="/wiki/W._A._S._Butement" title="W. A. S. Butement">W.A.S. Butement</a> and P. E. Pollard developed a <a href="/wiki/Breadboard" title="Breadboard">breadboard</a> test unit, operating at 50 cm (600 MHz) and using pulsed modulation which gave successful laboratory results. In January 1931, a writeup on the apparatus was entered in the <i>Inventions Book</i> maintained by the Royal Engineers. This is the first official record in Great Britain of the technology that was used in coastal defence and was incorporated into <a href="/wiki/Chain_Home" title="Chain Home">Chain Home</a> as <a href="/wiki/Chain_Home_Low" title="Chain Home Low">Chain Home (low)</a>.<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Before_World_War_II">Before World War II</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=3" title="Edit section: Before World War II"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Early_radar_antenna_-_US_Naval_Research_Laboratory_Anacostia.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/5e/Early_radar_antenna_-_US_Naval_Research_Laboratory_Anacostia.jpg/250px-Early_radar_antenna_-_US_Naval_Research_Laboratory_Anacostia.jpg" decoding="async" width="180" height="233" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/5e/Early_radar_antenna_-_US_Naval_Research_Laboratory_Anacostia.jpg/330px-Early_radar_antenna_-_US_Naval_Research_Laboratory_Anacostia.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/5e/Early_radar_antenna_-_US_Naval_Research_Laboratory_Anacostia.jpg/500px-Early_radar_antenna_-_US_Naval_Research_Laboratory_Anacostia.jpg 2x" data-file-width="550" data-file-height="711" /></a><figcaption>Experimental radar antenna, US <a href="/wiki/Naval_Research_Laboratory" class="mw-redirect" title="Naval Research Laboratory">Naval Research Laboratory</a>, Anacostia, D. C., from the late 1930s (photo taken in 1945)</figcaption></figure> <p>Before the <a href="/wiki/Second_World_War" class="mw-redirect" title="Second World War">Second World War</a>, researchers in the United Kingdom, <a href="/wiki/French_Third_Republic" title="French Third Republic">France</a>, <a href="/wiki/Nazi_Germany" title="Nazi Germany">Germany</a>, <a href="/wiki/Kingdom_of_Italy" title="Kingdom of Italy">Italy</a>, <a href="/wiki/Japanese_Empire" class="mw-redirect" title="Japanese Empire">Japan</a>, the <a href="/wiki/Netherlands" title="Netherlands">Netherlands</a>,<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> the <a href="/wiki/Soviet_Union" title="Soviet Union">Soviet Union</a>, and the United States, independently and in great secrecy, developed technologies that led to the modern version of radar. Australia, Canada, New Zealand, and South Africa followed prewar Great Britain's radar development, <a href="/wiki/Regency_of_Hungary" class="mw-redirect" title="Regency of Hungary">Hungary</a> and Sweden generated its radar technology during the war.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (September 2024)">citation needed</span></a></i>]</sup> </p><p>In France in 1934, following systematic studies on the <a href="/wiki/Cavity_Magnetron#Split-anode_magnetron" class="mw-redirect" title="Cavity Magnetron">split-anode magnetron</a>, the research branch of the <a href="/wiki/Compagnie_g%C3%A9n%C3%A9rale_de_la_t%C3%A9l%C3%A9graphie_sans_fil" title="Compagnie générale de la télégraphie sans fil">Compagnie générale de la télégraphie sans fil</a> (CSF) headed by Maurice Ponte with Henri Gutton, Sylvain Berline and M. Hugon, began developing an obstacle-locating radio apparatus, aspects of which were installed on the ocean liner <a href="/wiki/SS_Normandie" title="SS Normandie"><i>Normandie</i></a> in 1935.<sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> </p><p>During the same period, Soviet military engineer <a href="/wiki/Pavel_K._Oshchepkov" class="mw-redirect" title="Pavel K. Oshchepkov">P.K. Oshchepkov</a>, in collaboration with the <a href="/wiki/Saint_Petersburg_State_Electrotechnical_University" class="mw-redirect" title="Saint Petersburg State Electrotechnical University">Leningrad Electrotechnical Institute</a>, produced an experimental apparatus, RAPID, capable of detecting an aircraft within 3 km of a receiver.<sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> The Soviets produced their first mass production radars RUS-1 and RUS-2 Redut in 1939 but further development was slowed following the arrest of Oshchepkov and his subsequent <a href="/wiki/Gulag" title="Gulag">gulag</a> sentence. In total, only 607 Redut stations were produced during the war. The first Russian airborne radar, <a href="/wiki/Gneiss-2" title="Gneiss-2">Gneiss-2</a>, entered into service in June 1943 on <a href="/wiki/Petlyakov_Pe-2" title="Petlyakov Pe-2">Pe-2</a> dive bombers. More than 230 Gneiss-2 stations were produced by the end of 1944.<sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> The French and Soviet systems, however, featured continuous-wave operation that did not provide the full performance ultimately synonymous with modern radar systems. </p><p>Full radar evolved as a pulsed system, and the first such elementary apparatus was demonstrated in December 1934 by the American <a href="/wiki/Robert_Morris_Page" title="Robert Morris Page">Robert M. Page</a>, working at the <a href="/wiki/Naval_Research_Laboratory" class="mw-redirect" title="Naval Research Laboratory">Naval Research Laboratory</a>.<sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> The following year, the <a href="/wiki/United_States_Army" title="United States Army">United States Army</a> successfully tested a primitive surface-to-surface radar to aim <a href="/wiki/Coastal_artillery" title="Coastal artillery">coastal battery</a> <a href="/wiki/Searchlight" title="Searchlight">searchlights</a> at night.<sup id="cite_ref-27" class="reference"><a href="#cite_note-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> This design was followed by a pulsed system demonstrated in May 1935 by <a href="/wiki/Rudolf_K%C3%BChnhold" title="Rudolf Kühnhold">Rudolf Kühnhold</a> and the firm <a href="/w/index.php?title=Gesellschaft_f%C3%BCr_elektroakustische_und_mechanische_Apparate&action=edit&redlink=1" class="new" title="Gesellschaft für elektroakustische und mechanische Apparate (page does not exist)">GEMA</a><span class="noprint" style="font-size:85%; font-style: normal;"> [<a href="https://de.wikipedia.org/wiki/GEMA_(Radar)" class="extiw" title="de:GEMA (Radar)">de</a>]</span> in Germany and then another in June 1935 by an <a href="/wiki/Air_Ministry" title="Air Ministry">Air Ministry</a> team led by <a href="/wiki/Robert_Watson-Watt" title="Robert Watson-Watt">Robert Watson-Watt</a> in Great Britain. </p> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Watson_Radar.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/a/ae/Watson_Radar.jpg/250px-Watson_Radar.jpg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/ae/Watson_Radar.jpg/330px-Watson_Radar.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/a/ae/Watson_Radar.jpg/500px-Watson_Radar.jpg 2x" data-file-width="3264" data-file-height="2448" /></a><figcaption>The first workable unit built by <a href="/wiki/Robert_Watson-Watt" title="Robert Watson-Watt">Robert Watson-Watt</a> and his team</figcaption></figure> <p>In 1935, Watson-Watt was asked to judge recent reports of a German radio-based <a href="/wiki/Death_ray" title="Death ray">death ray</a> and turned the request over to Wilkins. Wilkins returned a set of calculations demonstrating the system was basically impossible. When Watson-Watt then asked what such a system might do, Wilkins recalled the earlier report about aircraft causing radio interference. This revelation led to the <a href="/wiki/Daventry_Experiment" class="mw-redirect" title="Daventry Experiment">Daventry Experiment</a> of 26 February 1935, using a powerful <a href="/wiki/BBC" title="BBC">BBC</a> shortwave transmitter as the source and their GPO receiver setup in a field while a bomber flew around the site. When the plane was clearly detected, <a href="/wiki/Hugh_Dowding" title="Hugh Dowding">Hugh Dowding</a>, the <a href="/wiki/Air_Member_for_Supply_and_Research" class="mw-redirect" title="Air Member for Supply and Research">Air Member for Supply and Research</a>, was very impressed with their system's potential and funds were immediately provided for further operational development.<sup id="cite_ref-Alan_Dower_Blumlein-2002_28-0" class="reference"><a href="#cite_note-Alan_Dower_Blumlein-2002-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> Watson-Watt's team patented the device in patent GB593017.<sup id="cite_ref-BREVET_D'INVENTION-1934_29-0" class="reference"><a href="#cite_note-BREVET_D'INVENTION-1934-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-30" class="reference"><a href="#cite_note-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-31" class="reference"><a href="#cite_note-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Chain_home.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/93/Chain_home.jpg/140px-Chain_home.jpg" decoding="async" width="140" height="259" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/93/Chain_home.jpg/210px-Chain_home.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/9/93/Chain_home.jpg 2x" data-file-width="250" data-file-height="462" /></a><figcaption>A <a href="/wiki/Chain_Home" title="Chain Home">Chain Home</a> tower in Great Baddow, Essex, United Kingdom</figcaption></figure> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Watson_watt_02_fr.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b3/Watson_watt_02_fr.jpg/250px-Watson_watt_02_fr.jpg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b3/Watson_watt_02_fr.jpg/330px-Watson_watt_02_fr.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b3/Watson_watt_02_fr.jpg/500px-Watson_watt_02_fr.jpg 2x" data-file-width="2048" data-file-height="1538" /></a><figcaption>Memorial plaque commemorating Robert Watson-Watt and <a href="/wiki/Arnold_Wilkins" title="Arnold Wilkins">Arnold Wilkins</a></figcaption></figure> <p>Development of radar greatly expanded on 1 September 1936, when Watson-Watt became superintendent of a new establishment under the British <a href="/wiki/Air_Ministry" title="Air Ministry">Air Ministry</a>, Bawdsey Research Station located in <a href="/wiki/Bawdsey_Manor" title="Bawdsey Manor">Bawdsey Manor</a>, near Felixstowe, Suffolk. Work there resulted in the design and installation of aircraft detection and tracking stations called "<a href="/wiki/Chain_Home" title="Chain Home">Chain Home</a>" along the East and South coasts of England in time for the outbreak of World War II in 1939. This system provided the vital advance information that helped the Royal Air Force win the <a href="/wiki/Battle_of_Britain" title="Battle of Britain">Battle of Britain</a>; without it, significant numbers of fighter aircraft, which Great Britain did not have available, would always have needed to be in the air to respond quickly. The radar formed part of the "<a href="/wiki/Dowding_system" title="Dowding system">Dowding system</a>" for collecting reports of enemy aircraft and coordinating the response. </p><p>Given all required funding and development support, the team produced working radar systems in 1935 and began deployment. By 1936, the first five Chain Home (CH) systems were operational and by 1940 stretched across the entire UK including Northern Ireland. Even by standards of the era, CH was crude; instead of broadcasting and receiving from an aimed antenna, CH broadcast a signal floodlighting the entire area in front of it, and then used one of Watson-Watt's own radio direction finders to determine the direction of the returned echoes. This fact meant CH transmitters had to be much more powerful and have better antennas than competing systems but allowed its rapid introduction using existing technologies. </p> <div class="mw-heading mw-heading3"><h3 id="During_World_War_II">During World War II</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=4" title="Edit section: During World War II"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Radar_in_World_War_II" title="Radar in World War II">Radar in World War II</a></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:East_Coast_Chain_Home_radar_station_CH15176.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/03/East_Coast_Chain_Home_radar_station_CH15176.jpg/250px-East_Coast_Chain_Home_radar_station_CH15176.jpg" decoding="async" width="220" height="163" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/03/East_Coast_Chain_Home_radar_station_CH15176.jpg/330px-East_Coast_Chain_Home_radar_station_CH15176.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/03/East_Coast_Chain_Home_radar_station_CH15176.jpg/500px-East_Coast_Chain_Home_radar_station_CH15176.jpg 2x" data-file-width="1300" data-file-height="963" /></a><figcaption>East Coast <a href="/wiki/Chain_Home" title="Chain Home">Chain Home</a> radar operators in England</figcaption></figure> <p>A key development was the <a href="/wiki/Cavity_magnetron" title="Cavity magnetron">cavity magnetron</a> in the UK, which allowed the creation of relatively small systems with sub-meter resolution. Britain shared the technology with the U.S. during the 1940 <a href="/wiki/Tizard_Mission" title="Tizard Mission">Tizard Mission</a>.<sup id="cite_ref-Angela_Hind-2007_32-0" class="reference"><a href="#cite_note-Angela_Hind-2007-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-33" class="reference"><a href="#cite_note-33"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> </p><p>In April 1940, <i><a href="/wiki/Popular_Science" title="Popular Science">Popular Science</a></i> showed an example of a radar unit using the Watson-Watt patent in an article on air defence.<sup id="cite_ref-34" class="reference"><a href="#cite_note-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> Also, in late 1941 <i><a href="/wiki/Popular_Mechanics" title="Popular Mechanics">Popular Mechanics</a></i> had an article in which a U.S. scientist speculated about the British early warning system on the English east coast and came close to what it was and how it worked.<sup id="cite_ref-Popular_Mechanics-1941_35-0" class="reference"><a href="#cite_note-Popular_Mechanics-1941-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> Watson-Watt was sent to the U.S. in 1941 to advise on air defense after Japan's <a href="/wiki/Attack_on_Pearl_Harbor" title="Attack on Pearl Harbor">attack on Pearl Harbor</a>.<sup id="cite_ref-36" class="reference"><a href="#cite_note-36"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Alfred_Lee_Loomis" title="Alfred Lee Loomis">Alfred Lee Loomis</a> organized the secret <a href="/wiki/MIT_Radiation_Laboratory" title="MIT Radiation Laboratory">MIT Radiation Laboratory</a> at <a href="/wiki/Massachusetts_Institute_of_Technology" title="Massachusetts Institute of Technology">Massachusetts Institute of Technology</a>, Cambridge, Massachusetts which developed microwave radar technology in the years 1941–45. Later, in 1943, Page greatly improved radar with the <a href="/wiki/Monopulse_radar" title="Monopulse radar">monopulse technique</a> that was used for many years in most radar applications.<sup id="cite_ref-37" class="reference"><a href="#cite_note-37"><span class="cite-bracket">[</span>37<span class="cite-bracket">]</span></a></sup> </p><p>The war precipitated research to find better resolution, more portability, and more features for radar, including small, lightweight sets to equip <a href="/wiki/Night_fighter" title="Night fighter">night fighters</a> (<a href="/wiki/Aircraft_interception_radar" title="Aircraft interception radar">aircraft interception radar</a>) and <a href="/wiki/Maritime_patrol_aircraft" title="Maritime patrol aircraft">maritime patrol aircraft</a> (<a href="/wiki/Air-to-surface-vessel_radar" title="Air-to-surface-vessel radar">air-to-surface-vessel radar</a>), and complementary navigation systems like <a href="/wiki/Oboe_(navigation)" title="Oboe (navigation)">Oboe</a> used by the <a href="/wiki/Pathfinder_(RAF)" title="Pathfinder (RAF)">RAF's Pathfinder</a>. </p> <div class="mw-heading mw-heading2"><h2 id="Applications">Applications</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=5" title="Edit section: Applications"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Rotating_marine_radar_-_rotating_waveguide_antenna.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/51/Rotating_marine_radar_-_rotating_waveguide_antenna.gif/220px-Rotating_marine_radar_-_rotating_waveguide_antenna.gif" decoding="async" width="220" height="124" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/51/Rotating_marine_radar_-_rotating_waveguide_antenna.gif/330px-Rotating_marine_radar_-_rotating_waveguide_antenna.gif 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/51/Rotating_marine_radar_-_rotating_waveguide_antenna.gif/440px-Rotating_marine_radar_-_rotating_waveguide_antenna.gif 2x" data-file-width="845" data-file-height="475" /></a><figcaption>Commercial marine radar antenna. The rotating antenna radiates a vertical fan-shaped beam.</figcaption></figure> <p>The information provided by radar includes the bearing and range (and therefore position) of the object from the radar scanner. It is thus used in many different fields where the need for such positioning is crucial. The first use of radar was for military purposes: to locate air, ground and sea targets. This evolved in the civilian field into applications for aircraft, ships, and automobiles.<sup id="cite_ref-38" class="reference"><a href="#cite_note-38"><span class="cite-bracket">[</span>38<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-39" class="reference"><a href="#cite_note-39"><span class="cite-bracket">[</span>39<span class="cite-bracket">]</span></a></sup> </p><p>In <a href="/wiki/Aviation" title="Aviation">aviation</a>, aircraft can be equipped with radar devices that warn of aircraft or other obstacles in or approaching their path, display weather information, and give accurate altitude readings. The first commercial device fitted to aircraft was a 1938 Bell Lab unit on some <a href="/wiki/United_Air_Lines" class="mw-redirect" title="United Air Lines">United Air Lines</a> aircraft.<sup id="cite_ref-Popular_Mechanics-1941_35-1" class="reference"><a href="#cite_note-Popular_Mechanics-1941-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> Aircraft can land in fog at airports equipped with radar-assisted <a href="/wiki/Ground-controlled_approach" title="Ground-controlled approach">ground-controlled approach</a> systems in which the plane's position is observed on <a href="/wiki/Precision_approach_radar" title="Precision approach radar">precision approach radar</a> screens by operators who thereby give radio landing instructions to the pilot, maintaining the aircraft on a defined approach path to the runway. Military fighter aircraft are usually fitted with air-to-air targeting radars, to detect and target enemy aircraft. In addition, larger specialized military aircraft carry powerful airborne radars to observe air traffic over a wide region and direct fighter aircraft towards targets.<sup id="cite_ref-40" class="reference"><a href="#cite_note-40"><span class="cite-bracket">[</span>40<span class="cite-bracket">]</span></a></sup> </p><p><a href="/wiki/Marine_radar" title="Marine radar">Marine radars</a> are used to measure the bearing and distance of ships to prevent collision with other ships, to navigate, and to fix their position at sea when within range of shore or other fixed references such as islands, buoys, and lightships. In port or in harbour, <a href="/wiki/Vessel_traffic_service" title="Vessel traffic service">vessel traffic service</a> radar systems are used to monitor and regulate ship movements in busy waters.<sup id="cite_ref-41" class="reference"><a href="#cite_note-41"><span class="cite-bracket">[</span>41<span class="cite-bracket">]</span></a></sup> </p><p>Meteorologists use radar to monitor <a href="/wiki/Precipitation" title="Precipitation">precipitation</a> and wind. It has become the primary tool for short-term <a href="/wiki/Weather_forecast" class="mw-redirect" title="Weather forecast">weather forecasting</a> and watching for <a href="/wiki/Severe_weather" title="Severe weather">severe weather</a> such as <a href="/wiki/Thunderstorm" title="Thunderstorm">thunderstorms</a>, <a href="/wiki/Tornado" title="Tornado">tornadoes</a>, <a href="/wiki/Winter_storm" title="Winter storm">winter storms</a>, precipitation types, etc. <a href="/wiki/Geologist" title="Geologist">Geologists</a> use specialized <a href="/wiki/Ground-penetrating_radar" title="Ground-penetrating radar">ground-penetrating radars</a> to map the composition of <a href="/wiki/Crust_(geology)" title="Crust (geology)">Earth's crust</a>. Police forces use <a href="/wiki/Radar_gun" class="mw-redirect" title="Radar gun">radar guns</a> to monitor vehicle speeds on the roads. Automotive radars are used for adaptive cruise control and emergency braking on vehicles by ignoring stationary roadside objects that could cause incorrect brake application and instead measuring moving objects to prevent collision with other vehicles. As part of <a href="/wiki/Intelligent_Transport_Systems" class="mw-redirect" title="Intelligent Transport Systems">Intelligent Transport Systems</a>, fixed-position stopped vehicle detection (SVD) radars are mounted on the roadside to detect stranded vehicles, obstructions and debris by inverting the automotive radar approach and ignoring moving objects.<sup id="cite_ref-42" class="reference"><a href="#cite_note-42"><span class="cite-bracket">[</span>42<span class="cite-bracket">]</span></a></sup> Smaller radar systems are used to <a href="/wiki/Motion_detector" title="Motion detector">detect human movement</a>. Examples are breathing pattern detection for sleep monitoring<sup id="cite_ref-43" class="reference"><a href="#cite_note-43"><span class="cite-bracket">[</span>43<span class="cite-bracket">]</span></a></sup> and hand and finger <a href="/wiki/Gesture_recognition" title="Gesture recognition">gesture detection</a> for computer interaction.<sup id="cite_ref-44" class="reference"><a href="#cite_note-44"><span class="cite-bracket">[</span>44<span class="cite-bracket">]</span></a></sup> Automatic door opening, light activation and intruder sensing are also common. </p> <div class="mw-heading mw-heading2"><h2 id="Principles">Principles</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=6" title="Edit section: Principles"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Radar_signal">Radar signal</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=7" title="Edit section: Radar signal"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure typeof="mw:File/Thumb"><a href="/wiki/File:3D_Doppler_Radar_Spectrum_showing_a_Barker_Code_of_13.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/73/3D_Doppler_Radar_Spectrum_showing_a_Barker_Code_of_13.jpg/250px-3D_Doppler_Radar_Spectrum_showing_a_Barker_Code_of_13.jpg" decoding="async" width="250" height="199" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/73/3D_Doppler_Radar_Spectrum_showing_a_Barker_Code_of_13.jpg/375px-3D_Doppler_Radar_Spectrum_showing_a_Barker_Code_of_13.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/73/3D_Doppler_Radar_Spectrum_showing_a_Barker_Code_of_13.jpg/500px-3D_Doppler_Radar_Spectrum_showing_a_Barker_Code_of_13.jpg 2x" data-file-width="2246" data-file-height="1788" /></a><figcaption>3D Doppler radar spectrum showing a <a href="/wiki/Barker_code" title="Barker code">Barker code</a> of 13</figcaption></figure> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Further information: <a href="/wiki/Radar_signal_characteristics" title="Radar signal characteristics">Radar signal characteristics</a></div> <p>A radar system has a <a href="/wiki/Transmitter" title="Transmitter">transmitter</a> that emits <a href="/wiki/Radio_wave" title="Radio wave">radio waves</a> known as <i>radar signals</i> in predetermined directions. When these signals contact an object they are usually <a href="/wiki/Reflection_(physics)" title="Reflection (physics)">reflected</a> or <a href="/wiki/Scattering" title="Scattering">scattered</a> in many directions, although some of them will be absorbed and penetrate into the target. Radar signals are reflected especially well by materials of considerable <a href="/wiki/Electrical_conductivity" class="mw-redirect" title="Electrical conductivity">electrical conductivity</a>—such as most metals, <a href="/wiki/Seawater" title="Seawater">seawater</a>, and wet ground. This makes the use of <a href="/wiki/Radar_altimeter" title="Radar altimeter">radar altimeters</a> possible in certain cases. The radar signals that are reflected back towards the radar receiver are the desirable ones that make radar detection work. If the object is <i>moving</i> either toward or away from the transmitter, there will be a slight change in the <a href="/wiki/Frequency" title="Frequency">frequency</a> of the radio waves due to the <a href="/wiki/Doppler_effect" title="Doppler effect">Doppler effect</a>. </p><p>Radar receivers are usually, but not always, in the same location as the transmitter. The reflected radar signals captured by the receiving antenna are usually very weak. They can be strengthened by <a href="/wiki/Amplifier" title="Amplifier">electronic amplifiers</a>. More sophisticated methods of <a href="/wiki/Signal_processing" title="Signal processing">signal processing</a> are also used in order to recover useful radar signals. </p><p>The weak absorption of radio waves by the medium through which they pass is what enables radar sets to detect objects at relatively long ranges—ranges at which other electromagnetic wavelengths, such as <a href="/wiki/Visible_light" class="mw-redirect" title="Visible light">visible light</a>, <a href="/wiki/Infrared_light" class="mw-redirect" title="Infrared light">infrared light</a>, and <a href="/wiki/Ultraviolet_light" class="mw-redirect" title="Ultraviolet light">ultraviolet light</a>, are too strongly attenuated. Weather phenomena, such as fog, clouds, rain, falling snow, and sleet, that block visible light are usually transparent to radio waves. Certain radio frequencies that are absorbed or scattered by water vapour, raindrops, or atmospheric gases (especially oxygen) are avoided when designing radars, except when their detection is intended. </p> <div class="mw-heading mw-heading3"><h3 id="Illumination">Illumination</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=8" title="Edit section: Illumination"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Radar relies on its own transmissions rather than light from the Sun or the Moon, or from <a href="/wiki/Electromagnetic_radiation" title="Electromagnetic radiation">electromagnetic waves</a> emitted by the target objects themselves, such as infrared radiation (heat). This process of directing artificial radio waves towards objects is called <i>illumination</i>, although radio waves are invisible to the human eye as well as optical cameras. </p> <div class="mw-heading mw-heading3"><h3 id="Reflection">Reflection</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=9" title="Edit section: Reflection"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Reflection_(physics)" title="Reflection (physics)">Reflection (physics)</a></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Weather_radar.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/96/Weather_radar.jpg/220px-Weather_radar.jpg" decoding="async" width="220" height="237" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/96/Weather_radar.jpg/330px-Weather_radar.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/96/Weather_radar.jpg/440px-Weather_radar.jpg 2x" data-file-width="1088" data-file-height="1172" /></a><figcaption>Brightness can indicate reflectivity as in this 1960 <a href="/wiki/Weather_radar" title="Weather radar">weather radar</a> image (of <a href="/wiki/Hurricane_Abby_(1960)" title="Hurricane Abby (1960)">Hurricane Abby</a>). The radar's frequency, pulse form, polarization, signal processing, and antenna determine what it can observe.</figcaption></figure> <p>If <a href="/wiki/Electromagnetic_radiation" title="Electromagnetic radiation">electromagnetic waves</a> travelling through one material meet another material, having a different <a href="/wiki/Dielectric_constant" class="mw-redirect" title="Dielectric constant">dielectric constant</a> or <a href="/wiki/Diamagnetism" title="Diamagnetism">diamagnetic constant</a> from the first, the waves will reflect or scatter from the boundary between the materials. This means that a solid object in <a href="/wiki/Earth%27s_atmosphere" class="mw-redirect" title="Earth's atmosphere">air</a> or in a <a href="/wiki/Vacuum" title="Vacuum">vacuum</a>, or a significant change in atomic density between the object and what is surrounding it, will usually scatter radar (radio) waves from its surface. This is particularly true for <a href="/wiki/Electrical_conduction" class="mw-redirect" title="Electrical conduction">electrically conductive</a> materials such as metal and carbon fibre, making radar well-suited to the detection of aircraft and ships. <a href="/wiki/Radar_absorbing_material" class="mw-redirect" title="Radar absorbing material">Radar absorbing material</a>, containing <a href="/wiki/Electrical_resistance" class="mw-redirect" title="Electrical resistance">resistive</a> and sometimes <a href="/wiki/Magnetism" title="Magnetism">magnetic</a> substances, is used on military vehicles to <a href="/wiki/Stealth_technology" title="Stealth technology">reduce radar reflection</a>. This is the radio equivalent of painting something a dark colour so that it cannot be seen by the eye at night. </p><p>Radar waves scatter in a variety of ways depending on the size (wavelength) of the radio wave and the shape of the target. If the wavelength is much shorter than the target's size, the wave will bounce off in a way similar to the way light is reflected by a <a href="/wiki/Mirror" title="Mirror">mirror</a>. If the wavelength is much longer than the size of the target, the target may not be visible because of poor reflection. Low-frequency radar technology is dependent on resonances for detection, but not identification, of targets. This is described by <a href="/wiki/Rayleigh_scattering" title="Rayleigh scattering">Rayleigh scattering</a>, an effect that creates Earth's blue sky and red sunsets. When the two length scales are comparable, there may be <a href="/wiki/Resonance" title="Resonance">resonances</a>. Early radars used very long wavelengths that were larger than the targets and thus received a vague signal, whereas many modern systems use shorter wavelengths (a few centimetres or less) that can image objects as small as a loaf of bread. </p><p>Short radio waves reflect from curves and corners in a way similar to glint from a rounded piece of glass. The most reflective targets for short wavelengths have 90° angles between the <a href="/wiki/Reflection_(physics)" title="Reflection (physics)">reflective surfaces</a>. A <a href="/wiki/Corner_reflector" title="Corner reflector">corner reflector</a> consists of three flat surfaces meeting like the inside corner of a cube. The structure will reflect waves entering its opening directly back to the source. They are commonly used as radar reflectors to make otherwise difficult-to-detect objects easier to detect. Corner reflectors on boats, for example, make them more detectable to avoid collision or during a rescue. For similar reasons, objects intended to avoid detection will not have inside corners or surfaces and edges perpendicular to likely detection directions, which leads to "odd" looking <a href="/wiki/Stealth_aircraft" title="Stealth aircraft">stealth aircraft</a>. These precautions do not totally eliminate reflection because of <a href="/wiki/Diffraction" title="Diffraction">diffraction</a>, especially at longer wavelengths. Half wavelength long wires or strips of conducting material, such as <a href="/wiki/Chaff_(countermeasure)" title="Chaff (countermeasure)">chaff</a>, are very reflective but do not direct the scattered energy back toward the source. The extent to which an object reflects or scatters radio waves is called its <a href="/wiki/Radar_cross-section" class="mw-redirect" title="Radar cross-section">radar cross-section</a>. </p> <div class="mw-heading mw-heading3"><h3 id="Radar_range_equation">Radar range equation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=10" title="Edit section: Radar range equation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The power <i>P<sub>r</sub></i> returning to the receiving antenna is given by the equation: </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle P_{r}={\frac {P_{t}G_{t}A_{r}\sigma F^{4}}{{(4\pi )}^{2}R_{t}^{2}R_{r}^{2}}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>P</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>r</mi> </mrow> </msub> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <msub> <mi>P</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>t</mi> </mrow> </msub> <msub> <mi>G</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>t</mi> </mrow> </msub> <msub> <mi>A</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>r</mi> </mrow> </msub> <mi>σ</mi> <msup> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>4</mn> </mrow> </msup> </mrow> <mrow> <msup> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">(</mo> <mn>4</mn> <mi>π</mi> <mo stretchy="false">)</mo> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> <msubsup> <mi>R</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>t</mi> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msubsup> <msubsup> <mi>R</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>r</mi> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msubsup> </mrow> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle P_{r}={\frac {P_{t}G_{t}A_{r}\sigma F^{4}}{{(4\pi )}^{2}R_{t}^{2}R_{r}^{2}}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/6a3fbe6a73c3441889579120260dbf21e71996e2" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -3.171ex; width:18.287ex; height:7.009ex;" alt="{\displaystyle P_{r}={\frac {P_{t}G_{t}A_{r}\sigma F^{4}}{{(4\pi )}^{2}R_{t}^{2}R_{r}^{2}}}}" /></span></dd></dl> <p>where </p> <ul><li><i>P</i><sub>t</sub> = transmitter power</li> <li><i>G</i><sub>t</sub> = <a href="/wiki/Antenna_gain" class="mw-redirect" title="Antenna gain">gain</a> of the transmitting antenna</li> <li><i>A</i><sub>r</sub> = <a href="/wiki/Effective_aperture" class="mw-redirect" title="Effective aperture">effective aperture</a> (area) of the receiving antenna; this can also be expressed as <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {G_{r}\lambda ^{2}} \over {4\pi }}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msub> <mi>G</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>r</mi> </mrow> </msub> <msup> <mi>λ</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> </mrow> </mstyle> <mrow class="MJX-TeXAtom-ORD"> <mn>4</mn> <mi>π</mi> </mrow> </mfrac> </mrow> <annotation encoding="application/x-tex">{\displaystyle {G_{r}\lambda ^{2}} \over {4\pi }}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/8d43880515f866412d8122505b3003c8440ad700" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:6.046ex; height:5.676ex;" alt="{\displaystyle {G_{r}\lambda ^{2}} \over {4\pi }}" /></span>, where</li></ul> <dl><dd><ul><li><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \lambda }"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>λ</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \lambda }</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/b43d0ea3c9c025af1be9128e62a18fa74bedda2a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.355ex; height:2.176ex;" alt="{\displaystyle \lambda }" /></span> = transmitted wavelength</li> <li><i>G</i><sub>r</sub> = gain of receiving antenna<sup id="cite_ref-45" class="reference"><a href="#cite_note-45"><span class="cite-bracket">[</span>45<span class="cite-bracket">]</span></a></sup></li></ul></dd></dl> <ul><li><i>σ</i> = <a href="/wiki/Radar_cross_section" title="Radar cross section">radar cross section</a>, or scattering coefficient, of the target</li> <li><i>F</i> = pattern propagation factor</li> <li><i>R</i><sub>t</sub> = distance from the transmitter to the target</li> <li><i>R</i><sub>r</sub> = distance from the target to the receiver.</li></ul> <p>In the common case where the transmitter and the receiver are at the same location, <i>R</i><sub>t</sub> = <i>R</i><sub>r</sub> and the term <i>R</i><sub>t</sub>² <i>R</i><sub>r</sub>² can be replaced by <i>R</i><sup>4</sup>, where <i>R</i> is the range. This yields: </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle P_{r}={{P_{t}G_{t}A_{r}\sigma F^{4}} \over {{(4\pi )}^{2}R^{4}}}.}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>P</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>r</mi> </mrow> </msub> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow class="MJX-TeXAtom-ORD"> <msub> <mi>P</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>t</mi> </mrow> </msub> <msub> <mi>G</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>t</mi> </mrow> </msub> <msub> <mi>A</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>r</mi> </mrow> </msub> <mi>σ</mi> <msup> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>4</mn> </mrow> </msup> </mrow> <mrow class="MJX-TeXAtom-ORD"> <msup> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">(</mo> <mn>4</mn> <mi>π</mi> <mo stretchy="false">)</mo> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> <msup> <mi>R</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>4</mn> </mrow> </msup> </mrow> </mfrac> </mrow> <mo>.</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle P_{r}={{P_{t}G_{t}A_{r}\sigma F^{4}} \over {{(4\pi )}^{2}R^{4}}}.}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ba703c3d4dc6e3a07bb253d20903e6dc96457116" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -3.171ex; width:18.934ex; height:7.009ex;" alt="{\displaystyle P_{r}={{P_{t}G_{t}A_{r}\sigma F^{4}} \over {{(4\pi )}^{2}R^{4}}}.}" /></span></dd></dl> <p>This shows that the received power declines as the fourth power of the range, which means that the received power from distant targets is relatively very small. </p><p>Additional filtering and pulse integration modifies the radar equation slightly for <a href="/wiki/Pulse-Doppler_radar#Performance" title="Pulse-Doppler radar">pulse-Doppler radar performance</a>, which can be used to increase detection range and reduce transmit power. </p><p>The equation above with <i>F</i> = 1 is a simplification for transmission in a vacuum without interference. The propagation factor accounts for the effects of <a href="/wiki/Multipath_propagation" title="Multipath propagation">multipath</a> and shadowing and depends on the details of the environment. In a real-world situation, <a href="/wiki/Pathloss" class="mw-redirect" title="Pathloss">pathloss</a> effects are also considered. </p> <div class="mw-heading mw-heading3"><h3 id="Doppler_effect">Doppler effect</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=11" title="Edit section: Doppler effect"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main articles: <a href="/wiki/Doppler_radar" title="Doppler radar">Doppler radar</a> and <a href="/wiki/Pulse-Doppler_radar" title="Pulse-Doppler radar">Pulse-Doppler radar</a></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Doppler_effect_diagrammatic.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/7f/Doppler_effect_diagrammatic.svg/260px-Doppler_effect_diagrammatic.svg.png" decoding="async" width="260" height="83" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/7f/Doppler_effect_diagrammatic.svg/390px-Doppler_effect_diagrammatic.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/7f/Doppler_effect_diagrammatic.svg/520px-Doppler_effect_diagrammatic.svg.png 2x" data-file-width="744" data-file-height="238" /></a><figcaption>Change of <a href="/wiki/Wavelength" title="Wavelength">wavelength</a> caused by motion of the source</figcaption></figure> <p>Frequency shift is caused by motion that changes the number of wavelengths between the reflector and the radar. This can degrade or enhance radar performance depending upon how it affects the detection process. As an example, <a href="/wiki/Moving_target_indication" title="Moving target indication">moving target indication</a> can interact with Doppler to produce signal cancellation at certain radial velocities, which degrades performance. </p><p>Sea-based radar systems, <a href="/wiki/Semi-active_radar_homing" title="Semi-active radar homing">semi-active radar homing</a>, <a href="/wiki/Active_radar_homing" title="Active radar homing">active radar homing</a>, <a href="/wiki/Weather_radar" title="Weather radar">weather radar</a>, military aircraft, and <a href="/wiki/Radar_astronomy" title="Radar astronomy">radar astronomy</a> rely on the Doppler effect to enhance performance. This produces information about target velocity during the detection process. This also allows small objects to be detected in an environment containing much larger nearby slow moving objects. </p><p>Doppler shift depends upon whether the radar configuration is active or passive. Active radar transmits a signal that is reflected back to the receiver. Passive radar depends upon the object sending a signal to the receiver. </p><p>The Doppler frequency shift for active radar is as follows, where <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle F_{D}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>D</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle F_{D}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ac0e98e9397b14b2f9399967a0c2154fa2c14d69" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:3.088ex; height:2.509ex;" alt="{\displaystyle F_{D}}" /></span> is Doppler frequency, <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle F_{T}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>T</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle F_{T}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/a6567533114a4b7bb5bfc03e76f3340754e37424" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.884ex; height:2.509ex;" alt="{\displaystyle F_{T}}" /></span> is transmit frequency, <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle V_{R}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>V</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>R</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle V_{R}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/d3ba1cd5708f2c5230fb763aa5a5ac5f3efbc229" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.835ex; height:2.509ex;" alt="{\displaystyle V_{R}}" /></span> is radial velocity, and <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>C</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle C}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/4fc55753007cd3c18576f7933f6f089196732029" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.766ex; height:2.176ex;" alt="{\displaystyle C}" /></span> is the speed of light:<sup id="cite_ref-46" class="reference"><a href="#cite_note-46"><span class="cite-bracket">[</span>46<span class="cite-bracket">]</span></a></sup> </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle F_{D}=2\times F_{T}\times \left({\frac {V_{R}}{C}}\right)}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>D</mi> </mrow> </msub> <mo>=</mo> <mn>2</mn> <mo>×</mo> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>T</mi> </mrow> </msub> <mo>×</mo> <mrow> <mo>(</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <msub> <mi>V</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>R</mi> </mrow> </msub> <mi>C</mi> </mfrac> </mrow> <mo>)</mo> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle F_{D}=2\times F_{T}\times \left({\frac {V_{R}}{C}}\right)}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/39c53d78bc630ce527edbc25df53bf1bef2262dc" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:23.005ex; height:6.176ex;" alt="{\displaystyle F_{D}=2\times F_{T}\times \left({\frac {V_{R}}{C}}\right)}" /></span>.</dd></dl> <p>Passive radar is applicable to <a href="/wiki/Electronic_countermeasures" class="mw-redirect" title="Electronic countermeasures">electronic countermeasures</a> and <a href="/wiki/Radio_astronomy" title="Radio astronomy">radio astronomy</a> as follows: </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle F_{D}=F_{T}\times \left({\frac {V_{R}}{C}}\right)}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>D</mi> </mrow> </msub> <mo>=</mo> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>T</mi> </mrow> </msub> <mo>×</mo> <mrow> <mo>(</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <msub> <mi>V</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>R</mi> </mrow> </msub> <mi>C</mi> </mfrac> </mrow> <mo>)</mo> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle F_{D}=F_{T}\times \left({\frac {V_{R}}{C}}\right)}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/5d2620bf6c76542688d9195d305046cad8535cbd" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:19.002ex; height:6.176ex;" alt="{\displaystyle F_{D}=F_{T}\times \left({\frac {V_{R}}{C}}\right)}" /></span>.</dd></dl> <p>Only the radial component of the velocity is relevant. When the reflector is moving at right angle to the radar beam, it has no relative velocity. Objects moving parallel to the radar beam produce the maximum Doppler frequency shift. </p><p>When the transmit frequency (<span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle F_{T}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>T</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle F_{T}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/a6567533114a4b7bb5bfc03e76f3340754e37424" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.884ex; height:2.509ex;" alt="{\displaystyle F_{T}}" /></span>) is pulsed, using a pulse repeat frequency of <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle F_{R}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>R</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle F_{R}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/36c396599916ca276daed739acd8df48718641cb" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.974ex; height:2.509ex;" alt="{\displaystyle F_{R}}" /></span>, the resulting frequency spectrum will contain harmonic frequencies above and below <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle F_{T}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>T</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle F_{T}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/a6567533114a4b7bb5bfc03e76f3340754e37424" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.884ex; height:2.509ex;" alt="{\displaystyle F_{T}}" /></span> with a distance of <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle F_{R}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>R</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle F_{R}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/36c396599916ca276daed739acd8df48718641cb" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.974ex; height:2.509ex;" alt="{\displaystyle F_{R}}" /></span>. As a result, the Doppler measurement is only non-ambiguous if the Doppler frequency shift is less than half of <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle F_{R}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>R</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle F_{R}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/36c396599916ca276daed739acd8df48718641cb" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.974ex; height:2.509ex;" alt="{\displaystyle F_{R}}" /></span>, called the <a href="/wiki/Nyquist_frequency" title="Nyquist frequency">Nyquist frequency</a>, since the returned frequency otherwise cannot be distinguished from shifting of a harmonic frequency above or below, thus requiring: </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle |F_{D}|<{\frac {F_{R}}{2}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">|</mo> </mrow> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>D</mi> </mrow> </msub> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">|</mo> </mrow> <mo><</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>R</mi> </mrow> </msub> <mn>2</mn> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle |F_{D}|<{\frac {F_{R}}{2}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/6fa44bc6fe91f976cb0374c9c1eb7221d22631b2" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:11.29ex; height:5.343ex;" alt="{\displaystyle |F_{D}|<{\frac {F_{R}}{2}}}" /></span></dd></dl> <p>Or when substituting with <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle F_{D}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>D</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle F_{D}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ac0e98e9397b14b2f9399967a0c2154fa2c14d69" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:3.088ex; height:2.509ex;" alt="{\displaystyle F_{D}}" /></span>: </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle |V_{R}|<{\frac {F_{R}\times {\frac {C}{F_{T}}}}{4}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">|</mo> </mrow> <msub> <mi>V</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>R</mi> </mrow> </msub> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">|</mo> </mrow> <mo><</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>R</mi> </mrow> </msub> <mo>×</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mi>C</mi> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>T</mi> </mrow> </msub> </mfrac> </mrow> </mrow> <mn>4</mn> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle |V_{R}|<{\frac {F_{R}\times {\frac {C}{F_{T}}}}{4}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/d172f3d1dd8c768df1b4c1fb9bbecd7adff87bf2" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:16.874ex; height:6.843ex;" alt="{\displaystyle |V_{R}|<{\frac {F_{R}\times {\frac {C}{F_{T}}}}{4}}}" /></span></dd></dl> <p>As an example, a Doppler weather radar with a pulse rate of 2 kHz and transmit frequency of 1 GHz can reliably measure weather speed up to at most 150 m/s (340 mph), thus cannot reliably determine radial velocity of aircraft moving 1,000 m/s (2,200 mph). </p> <div class="mw-heading mw-heading3"><h3 id="Polarization">Polarization</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=12" title="Edit section: Polarization"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Further information: <a href="/wiki/Polarization_(waves)" title="Polarization (waves)">Polarization (waves)</a></div> <p>In all <a href="/wiki/Electromagnetic_radiation" title="Electromagnetic radiation">electromagnetic radiation</a>, the electric field is perpendicular to the direction of propagation, and the electric field direction is the <a href="/wiki/Polarization_(waves)" title="Polarization (waves)">polarization</a> of the wave. For a transmitted radar signal, the polarization can be controlled to yield different effects. Radars use horizontal, vertical, linear, and circular polarization to detect different types of reflections. For example, <a href="/wiki/Circular_polarization" title="Circular polarization">circular polarization</a> is used to minimize the interference caused by rain. <a href="/wiki/Linear_polarization" title="Linear polarization">Linear polarization</a> returns usually indicate metal surfaces. Random polarization returns usually indicate a <a href="/wiki/Fractal" title="Fractal">fractal</a> surface, such as rocks or soil, and are used by navigation radars. </p> <div class="mw-heading mw-heading3"><h3 id="Limiting_factors">Limiting factors</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=13" title="Edit section: Limiting factors"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading4"><h4 id="Beam_path_and_range">Beam path and range</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=14" title="Edit section: Beam path and range"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">See also: <a href="/wiki/Beam_forming" class="mw-redirect" title="Beam forming">Beam forming</a> and <a href="/wiki/Over-the-horizon_radar" title="Over-the-horizon radar">Over-the-horizon radar</a></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Radar-hauteur-en.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b9/Radar-hauteur-en.svg/330px-Radar-hauteur-en.svg.png" decoding="async" width="330" height="183" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b9/Radar-hauteur-en.svg/500px-Radar-hauteur-en.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b9/Radar-hauteur-en.svg/660px-Radar-hauteur-en.svg.png 2x" data-file-width="563" data-file-height="313" /></a><figcaption>Echo heights above ground<br /><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle H=\left({\sqrt {r^{2}+(k_{e}a_{e})^{2}+2rk_{e}a_{e}sin(\theta _{e})}}\right)-k_{e}a_{e}+h_{a}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>H</mi> <mo>=</mo> <mrow> <mo>(</mo> <mrow class="MJX-TeXAtom-ORD"> <msqrt> <msup> <mi>r</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> <mo>+</mo> <mo stretchy="false">(</mo> <msub> <mi>k</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>e</mi> </mrow> </msub> <msub> <mi>a</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>e</mi> </mrow> </msub> <msup> <mo stretchy="false">)</mo> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> <mo>+</mo> <mn>2</mn> <mi>r</mi> <msub> <mi>k</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>e</mi> </mrow> </msub> <msub> <mi>a</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>e</mi> </mrow> </msub> <mi>s</mi> <mi>i</mi> <mi>n</mi> <mo stretchy="false">(</mo> <msub> <mi>θ</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>e</mi> </mrow> </msub> <mo stretchy="false">)</mo> </msqrt> </mrow> <mo>)</mo> </mrow> <mo>−</mo> <msub> <mi>k</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>e</mi> </mrow> </msub> <msub> <mi>a</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>e</mi> </mrow> </msub> <mo>+</mo> <msub> <mi>h</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>a</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle H=\left({\sqrt {r^{2}+(k_{e}a_{e})^{2}+2rk_{e}a_{e}sin(\theta _{e})}}\right)-k_{e}a_{e}+h_{a}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/b4e8c2ee9567586e98943596292ca2c8bea16c1d" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:51.741ex; height:5.009ex;" alt="{\displaystyle H=\left({\sqrt {r^{2}+(k_{e}a_{e})^{2}+2rk_{e}a_{e}sin(\theta _{e})}}\right)-k_{e}a_{e}+h_{a}}" /></span> <br />Where : <br />  r : distance radar-target <br />ke : 4/3 <br />ae : Earth radius <br />θe : elevation angle above the radar horizon <br />ha : height of the feedhorn above ground</figcaption></figure> <p>A radar beam follows a linear path in vacuum but follows a somewhat curved path in atmosphere due to variation in the <a href="/wiki/Refractive_index" title="Refractive index">refractive index</a> of air, which is called the <a href="/wiki/Radar_horizon" title="Radar horizon">radar horizon</a>. Even when the beam is emitted parallel to the ground, the beam rises above the ground as the <a href="/wiki/Figure_of_the_Earth" title="Figure of the Earth">curvature of the Earth</a> sinks below the horizon. Furthermore, the signal is attenuated by the medium the beam crosses, and the beam disperses. </p><p>The maximum range of conventional radar can be limited by a number of factors: </p> <ul><li>Line of sight, which depends on the height above the ground. Without a direct line of sight, the path of the beam is blocked.</li> <li>The maximum non-ambiguous range, which is determined by the <a href="/wiki/Pulse_repetition_frequency" class="mw-redirect" title="Pulse repetition frequency">pulse repetition frequency</a>. The maximum non-ambiguous range is the distance the pulse can travel to and return from before the next pulse is emitted.</li> <li>Radar sensitivity and the power of the return signal as computed in the radar equation. This component includes factors such as the environmental conditions and the size (or radar cross section) of the target.</li></ul> <div class="mw-heading mw-heading4"><h4 id="Noise">Noise</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=15" title="Edit section: Noise"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main articles: <a href="/wiki/Noise_(electronics)" title="Noise (electronics)">Noise (electronics)</a> and <a href="/wiki/Noise_(radio)" class="mw-redirect" title="Noise (radio)">Noise (radio)</a></div> <p>Signal noise is an internal source of random variations in the signal, which is generated by all electronic components. </p><p>Reflected signals decline rapidly as distance increases, so noise introduces a radar range limitation. The <a href="/wiki/Noise_floor" title="Noise floor">noise floor</a> and <a href="/wiki/Signal-to-noise_ratio" title="Signal-to-noise ratio">signal-to-noise ratio</a> are two different <a href="/wiki/Test_and_evaluation_master_plan#Measures_of_Performance" title="Test and evaluation master plan">measures of performance</a> that affect range performance. Reflectors that are too far away produce too little signal to exceed the noise floor and cannot be detected. <a href="/wiki/Detection" title="Detection">Detection</a> requires a signal that exceeds the <a href="/wiki/Noise_floor" title="Noise floor">noise floor</a> by at least the signal-to-noise ratio. </p><p>Noise typically appears as random variations superimposed on the desired echo signal received in the radar receiver. The lower the power of the desired signal, the more difficult it is to discern it from the noise. The <a href="/wiki/Noise_figure" title="Noise figure">noise figure</a> is a measure of the noise produced by a receiver compared to an ideal receiver, and this needs to be minimized. </p><p><a href="/wiki/Shot_noise" title="Shot noise">Shot noise</a> is produced by electrons in transit across a discontinuity, which occurs in all detectors. Shot noise is the dominant source in most receivers. There will also be <a href="/wiki/Flicker_noise" title="Flicker noise">flicker noise</a> caused by electron transit through amplification devices, which is reduced using <a href="/wiki/Heterodyne" title="Heterodyne">heterodyne</a> amplification. Another reason for heterodyne processing is that for fixed fractional bandwidth, the instantaneous bandwidth increases linearly in frequency. This allows improved range resolution. The one notable exception to heterodyne (downconversion) radar systems is <a href="/wiki/Ultra-wideband" title="Ultra-wideband">ultra-wideband</a> radar. Here a single cycle, or transient wave, is used similar to UWB communications, see <a href="/wiki/List_of_UWB_channels" title="List of UWB channels">List of UWB channels</a>. </p><p>Noise is also generated by external sources, most importantly the natural thermal radiation of the background surrounding the target of interest. In modern radar systems, the internal noise is typically about equal to or lower than the external noise. An exception is if the radar is aimed upwards at clear sky, where the scene is so "cold" that it generates very little <a href="/wiki/Thermal_noise" class="mw-redirect" title="Thermal noise">thermal noise</a>. The thermal noise is given by <i>k</i><sub>B</sub> <i>T</i> <i>B</i>, where <i>T</i> is temperature, <i>B</i> is bandwidth (post matched filter) and <i>k</i><sub>B</sub> is the <a href="/wiki/Boltzmann_constant" title="Boltzmann constant">Boltzmann constant</a>. There is an appealing intuitive interpretation of this relationship in a radar. Matched filtering allows the entire energy received from a target to be compressed into a single bin (be it a range, Doppler, elevation, or azimuth bin). On the surface it appears that then within a fixed interval of time, perfect, error free, detection could be obtained. This is done by compressing all energy into an infinitesimal time slice. What limits this approach in the real world is that, while time is arbitrarily divisible, current is not. The quantum of electrical energy is an electron, and so the best that can be done is to match filter all energy into a single electron. Since the electron is moving at a certain temperature (<a href="/wiki/Black_body" title="Black body">Planck spectrum</a>) this noise source cannot be further eroded. Ultimately, radar, like all macro-scale entities, is profoundly impacted by quantum theory. </p><p>Noise is random and target signals are not. Signal processing can take advantage of this phenomenon to reduce the noise floor using two strategies. The kind of signal integration used with <a href="/wiki/Moving_target_indication" title="Moving target indication">moving target indication</a> can improve noise up to <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\sqrt {2}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msqrt> <mn>2</mn> </msqrt> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\sqrt {2}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/b4afc1e27d418021bf10898eb44a7f5f315735ff" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:3.098ex; height:3.009ex;" alt="{\displaystyle {\sqrt {2}}}" /></span> for each stage. The signal can also be split among multiple filters for <a href="/wiki/Pulse-Doppler_signal_processing" title="Pulse-Doppler signal processing">pulse-Doppler signal processing</a>, which reduces the noise floor by the number of filters. These improvements depend upon <a href="/wiki/Coherence_(physics)" title="Coherence (physics)">coherence</a>. </p> <div class="mw-heading mw-heading4"><h4 id="Interference">Interference</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=16" title="Edit section: Interference"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Interference_(wave_propagation)" class="mw-redirect" title="Interference (wave propagation)">Interference (wave propagation)</a></div> <p>Radar systems must overcome unwanted signals in order to focus on the targets of interest. These unwanted signals may originate from internal and external sources, both passive and active. The ability of the radar system to overcome these unwanted signals defines its <a href="/wiki/Signal-to-noise_ratio" title="Signal-to-noise ratio">signal-to-noise ratio</a> (SNR). SNR is defined as the ratio of the signal power to the noise power within the desired signal; it compares the level of a desired target signal to the level of background noise (atmospheric noise and noise generated within the receiver). The higher a system's SNR the better it is at discriminating actual targets from noise signals. </p> <div class="mw-heading mw-heading4"><h4 id="Clutter">Clutter</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=17" title="Edit section: Clutter"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Multipath_propagation_diagram_en.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Multipath_propagation_diagram_en.svg/250px-Multipath_propagation_diagram_en.svg.png" decoding="async" width="220" height="156" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Multipath_propagation_diagram_en.svg/330px-Multipath_propagation_diagram_en.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Multipath_propagation_diagram_en.svg/500px-Multipath_propagation_diagram_en.svg.png 2x" data-file-width="1052" data-file-height="744" /></a><figcaption>Radar multipath <a href="/wiki/Light_echo" title="Light echo">echoes</a> from a target cause ghosts to appear</figcaption></figure> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Clutter_(radar)" title="Clutter (radar)">Clutter (radar)</a></div> <p>Clutter refers to radio frequency (RF) echoes returned from targets which are uninteresting to radar operators. Such targets include man-made objects such as buildings and — intentionally — by radar countermeasures such as <a href="/wiki/Chaff_(countermeasure)" title="Chaff (countermeasure)">chaff</a>. Such targets also include natural objects such as ground, sea, and — when not being tasked for meteorological purposes — <a href="/wiki/Precipitation" title="Precipitation">precipitation</a>, <a href="/wiki/Hail_spike" title="Hail spike">hail spike</a>, <a href="/wiki/Dust_storm" title="Dust storm">dust storms</a>, animals (especially birds), turbulence in the <a href="/wiki/Atmospheric_circulation" title="Atmospheric circulation">atmospheric circulation</a>, and <a href="/wiki/Meteoroid" title="Meteoroid">meteor</a> trails. Radar clutter can also be caused by other atmospheric phenomena, such as disturbances in the <a href="/wiki/Ionosphere" title="Ionosphere">ionosphere</a> caused by <a href="/wiki/Geomagnetic_storm" title="Geomagnetic storm">geomagnetic storms</a> or other <a href="/wiki/Space_weather" title="Space weather">space weather</a> events. This phenomenon is especially apparent near the <a href="/wiki/Geomagnetic_pole" title="Geomagnetic pole">geomagnetic poles</a>, where the action of the <a href="/wiki/Solar_wind" title="Solar wind">solar wind</a> on the earth's <a href="/wiki/Magnetosphere" title="Magnetosphere">magnetosphere</a> produces convection patterns in the ionospheric <a href="/wiki/Plasma_(physics)" title="Plasma (physics)">plasma</a>.<sup id="cite_ref-Riddolls-2006_47-0" class="reference"><a href="#cite_note-Riddolls-2006-47"><span class="cite-bracket">[</span>47<span class="cite-bracket">]</span></a></sup> Radar clutter can degrade the ability of <a href="/wiki/Over-the-horizon_radar" title="Over-the-horizon radar">over-the-horizon radar</a> to detect targets.<sup id="cite_ref-Riddolls-2006_47-1" class="reference"><a href="#cite_note-Riddolls-2006-47"><span class="cite-bracket">[</span>47<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Elkins-1980_48-0" class="reference"><a href="#cite_note-Elkins-1980-48"><span class="cite-bracket">[</span>48<span class="cite-bracket">]</span></a></sup> </p><p>Some clutter may also be caused by a long radar <a href="/wiki/Waveguide" title="Waveguide">waveguide</a> between the radar transceiver and the antenna. In a typical <a href="/wiki/Plan_position_indicator" title="Plan position indicator">plan position indicator</a> (PPI) radar with a rotating antenna, this will usually be seen as a "sun" or "sunburst" in the center of the display as the receiver responds to echoes from dust particles and misguided RF in the waveguide. Adjusting the timing between when the transmitter sends a pulse and when the receiver stage is enabled will generally reduce the sunburst without affecting the accuracy of the range since most sunburst is caused by a diffused transmit pulse reflected before it leaves the antenna. Clutter is considered a passive interference source since it only appears in response to radar signals sent by the radar. </p><p>Clutter is detected and neutralized in several ways. Clutter tends to appear static between radar scans; on subsequent scan echoes, desirable targets will appear to move, and all stationary echoes can be eliminated. Sea clutter can be reduced by using horizontal polarization, while rain is reduced with <a href="/wiki/Circular_polarization" title="Circular polarization">circular polarization</a> (meteorological radars wish for the opposite effect, and therefore use <a href="/wiki/Linear_polarization" title="Linear polarization">linear polarization</a> to detect precipitation). Other methods attempt to increase the signal-to-clutter ratio. </p><p>Clutter moves with the wind or is stationary. Two common strategies to improve <a href="/wiki/Test_and_evaluation_master_plan#Performance_evaluation" title="Test and evaluation master plan">measures of performance</a> in a clutter environment are: </p> <dl><dd><ul><li>Moving target indication, which integrates successive pulses</li> <li>Doppler processing, which uses filters to separate clutter from desirable signals</li></ul></dd></dl> <p>The most effective clutter reduction technique is <a href="/wiki/Pulse-Doppler_radar" title="Pulse-Doppler radar">pulse-Doppler radar</a>. Doppler separates clutter from aircraft and spacecraft using a <a href="/wiki/Radar_signal_characteristics#In_the_frequency_domain" title="Radar signal characteristics">frequency spectrum</a>, so individual signals can be separated from multiple reflectors located in the same volume using velocity differences. This requires a coherent transmitter. Another technique uses a <a href="/wiki/Moving_target_indication" title="Moving target indication">moving target indicator</a> that subtracts the received signal from two successive pulses using phase to reduce signals from slow-moving objects. This can be adapted for systems that lack a coherent transmitter, such as <a href="/wiki/Radar_signal_characteristics#Unambiguous_range" title="Radar signal characteristics">time-domain pulse-amplitude radar</a>. </p><p><a href="/wiki/Constant_false_alarm_rate" title="Constant false alarm rate">Constant false alarm rate</a>, a form of <a href="/wiki/Automatic_gain_control" title="Automatic gain control">automatic gain control</a> (AGC), is a method that relies on clutter returns far outnumbering echoes from targets of interest. The receiver's gain is automatically adjusted to maintain a constant level of overall visible clutter. While this does not help detect targets masked by stronger surrounding clutter, it does help to distinguish strong target sources. In the past, radar AGC was electronically controlled and affected the gain of the entire radar receiver. As radars evolved, AGC became computer-software-controlled and affected the gain with greater granularity in specific detection cells. </p><p>Clutter may also originate from multipath echoes from valid targets caused by ground reflection, <a href="/wiki/Atmospheric_duct" title="Atmospheric duct">atmospheric ducting</a> or <a href="/wiki/Skywave" title="Skywave">ionospheric reflection</a>/<a href="/wiki/Refraction" title="Refraction">refraction</a> (e.g., <a href="/wiki/Anomalous_propagation" title="Anomalous propagation">anomalous propagation</a>). This clutter type is especially bothersome since it appears to move and behave like other normal (point) targets of interest. In a typical scenario, an aircraft echo is reflected from the ground below, appearing to the receiver as an identical target below the correct one. The radar may try to unify the targets, reporting the target at an incorrect height, or eliminating it on the basis of <a href="/wiki/Jitter" title="Jitter">jitter</a> or a physical impossibility. Terrain bounce jamming exploits this response by amplifying the radar signal and directing it downward.<sup id="cite_ref-49" class="reference"><a href="#cite_note-49"><span class="cite-bracket">[</span>49<span class="cite-bracket">]</span></a></sup> These problems can be overcome by incorporating a ground map of the radar's surroundings and eliminating all echoes which appear to originate below ground or above a certain height. Monopulse can be improved by altering the elevation algorithm used at low elevation. In newer air traffic control radar equipment, algorithms are used to identify the false targets by comparing the current pulse returns to those adjacent, as well as calculating return improbabilities. </p> <div class="mw-heading mw-heading4"><h4 id="Jamming">Jamming</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=18" title="Edit section: Jamming"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Radar_jamming_and_deception" title="Radar jamming and deception">Radar jamming and deception</a></div> <p>Radar jamming refers to radio frequency signals originating from sources outside the radar, transmitting in the radar's frequency and thereby masking targets of interest. Jamming may be intentional, as with an <a href="/wiki/Electronic_warfare" title="Electronic warfare">electronic warfare</a> tactic, or unintentional, as with friendly forces operating equipment that transmits using the same frequency range. Jamming is considered an active interference source, since it is initiated by elements outside the radar and in general unrelated to the radar signals. </p><p>Jamming is problematic to radar since the jamming signal only needs to travel one way (from the jammer to the radar receiver) whereas the radar echoes travel two ways (radar-target-radar) and are therefore significantly reduced in power by the time they return to the radar receiver in accordance with <a href="/wiki/Inverse-square_law" title="Inverse-square law">inverse-square law</a>. Jammers therefore can be much less powerful than their jammed radars and still effectively mask targets along the <a href="/wiki/Line-of-sight_propagation" title="Line-of-sight propagation">line of sight</a> from the jammer to the radar (<i>mainlobe jamming</i>). Jammers have an added effect of affecting radars along other lines of sight through the radar receiver's <a href="/wiki/Sidelobe" class="mw-redirect" title="Sidelobe">sidelobes</a> (<i>sidelobe jamming</i>). </p><p>Mainlobe jamming can generally only be reduced by narrowing the mainlobe <a href="/wiki/Solid_angle" title="Solid angle">solid angle</a> and cannot fully be eliminated when directly facing a jammer which uses the same frequency and polarization as the radar. Sidelobe jamming can be overcome by reducing receiving sidelobes in the radar antenna design and by using an <a href="/wiki/Omnidirectional_antenna" title="Omnidirectional antenna">omnidirectional antenna</a> to detect and disregard non-mainlobe signals. <a href="/wiki/Electronic_counter-counter-measures" class="mw-redirect" title="Electronic counter-counter-measures">Other anti-jamming techniques</a> are <a href="/wiki/Frequency_hopping" class="mw-redirect" title="Frequency hopping">frequency hopping</a> and <a href="/wiki/Polarization_(waves)" title="Polarization (waves)">polarization</a>. </p> <div class="mw-heading mw-heading2"><h2 id="Signal_processing">Signal processing</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=19" title="Edit section: Signal processing"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Distance_measurement">Distance measurement</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=20" title="Edit section: Distance measurement"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading4"><h4 id="Transit_time">Transit time</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=21" title="Edit section: Transit time"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Further information: <a href="/wiki/Time_of_flight" title="Time of flight">Time of flight</a></div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Radaroperation.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/c/c6/Radaroperation.gif/250px-Radaroperation.gif" decoding="async" width="220" height="91" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/c/c6/Radaroperation.gif/330px-Radaroperation.gif 1.5x, //upload.wikimedia.org/wikipedia/commons/c/c6/Radaroperation.gif 2x" data-file-width="340" data-file-height="140" /></a><figcaption>Pulse radar: The round-trip time for the radar pulse to get to the target and return is measured. The distance is proportional to this time.</figcaption></figure> <p>One way to obtain a <a href="/wiki/Distance_measurement" class="mw-redirect" title="Distance measurement">distance measurement</a> (ranging) is based on the <a href="/wiki/Time-of-flight" class="mw-redirect" title="Time-of-flight">time-of-flight</a>: transmit a short pulse of radio signal (electromagnetic radiation) and measure the time it takes for the reflection to return. The distance is one-half the round trip time multiplied by the speed of the signal. The factor of one-half comes from the fact that the signal has to travel to the object and back again. Since radio waves travel at the <a href="/wiki/Speed_of_light" title="Speed of light">speed of light</a>, accurate distance measurement requires high-speed electronics. In most cases, the receiver does not detect the return while the signal is being transmitted. Through the use of a duplexer, the radar switches between transmitting and receiving at a predetermined rate. A similar effect imposes a maximum range as well. In order to maximize range, longer times between pulses should be used, referred to as a pulse repetition time, or its reciprocal, pulse repetition frequency. </p><p>These two effects tend to be at odds with each other, and it is not easy to combine both good short range and good long range in a single radar. This is because the short pulses needed for a good minimum range broadcast have less total energy, making the returns much smaller and the target harder to detect. This could be offset by using more pulses, but this would shorten the maximum range. So each radar uses a particular type of signal. Long-range radars tend to use long pulses with long delays between them, and short range radars use smaller pulses with less time between them. As electronics have improved many radars now can change their pulse repetition frequency, thereby changing their range. The newest radars fire two pulses during one cell, one for short range (about 10 km (6.2 miles)) and a separate signal for longer ranges (about 100 km (62 miles)). </p><p>Distance may also be measured as a function of time. The <b>radar mile</b> is the time it takes for a radar pulse to travel one <a href="/wiki/Nautical_mile" title="Nautical mile">nautical mile</a>, reflect off a target, and return to the radar antenna. Since a nautical mile is defined as 1,852 m, then dividing this distance by the speed of light (299,792,458 m/s), and then multiplying the result by 2 yields a result of 12.36 μs in duration. </p> <div class="mw-heading mw-heading4"><h4 id="Frequency_modulation">Frequency modulation</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=22" title="Edit section: Frequency modulation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Sonar_Principle_EN.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/07/Sonar_Principle_EN.svg/220px-Sonar_Principle_EN.svg.png" decoding="async" width="220" height="118" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/07/Sonar_Principle_EN.svg/330px-Sonar_Principle_EN.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/07/Sonar_Principle_EN.svg/440px-Sonar_Principle_EN.svg.png 2x" data-file-width="496" data-file-height="266" /></a><figcaption>Continuous wave (CW) radar. Using frequency modulation allows range to be extracted.</figcaption></figure> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Frequency_modulation" title="Frequency modulation">Frequency modulation</a></div> <p>Another form of distance measuring radar is based on frequency modulation. In these systems, the frequency of the transmitted signal is changed over time. Since the signal takes a finite time to travel to and from the target, the received signal is a different frequency than what the transmitter is broadcasting at the time the reflected signal arrives back at the radar. By comparing the frequency of the two signals the difference can be easily measured. This is easily accomplished with very high accuracy even in 1940s electronics. A further advantage is that the radar can operate effectively at relatively low frequencies. This was important in the early development of this type when high-frequency signal generation was difficult or expensive. </p><p>This technique can be used in <a href="/wiki/Continuous_wave_radar" class="mw-redirect" title="Continuous wave radar">continuous wave radar</a> and is often found in aircraft <a href="/wiki/Radar_altimeter" title="Radar altimeter">radar altimeters</a>. In these systems a "carrier" radar signal is frequency modulated in a predictable way, typically varying up and down with a <a href="/wiki/Sine_wave" title="Sine wave">sine wave</a> or sawtooth pattern at audio frequencies. The signal is then sent out from one antenna and received on another, typically located on the bottom of the aircraft, and the signal can be continuously compared using a simple <i>beat frequency</i> modulator that produces an audio frequency tone from the returned signal and a portion of the transmitted signal. </p><p>The <a href="/wiki/Frequency_modulation#Modulation_index" title="Frequency modulation">modulation index</a> riding on the receive signal is proportional to the time delay between the radar and the reflector. The frequency shift becomes greater with greater time delay. The frequency shift is directly proportional to the distance travelled. That distance can be displayed on an instrument, and it may also be available via the <a href="/wiki/Transponder_(aeronautics)" title="Transponder (aeronautics)">transponder</a>. This signal processing is similar to that used in speed detecting Doppler radar. Example systems using this approach are <a href="/wiki/AZUSA" title="AZUSA">AZUSA</a>, <a href="/wiki/MISTRAM" title="MISTRAM">MISTRAM</a>, and <a href="/wiki/UDOP" title="UDOP">UDOP</a>. </p><p>Terrestrial radar uses low-power FM signals that cover a larger frequency range. The multiple reflections are analyzed mathematically for pattern changes with multiple passes creating a computerized synthetic image. Doppler effects are used which allows slow moving objects to be detected as well as largely eliminating "noise" from the surfaces of bodies of water. </p> <div class="mw-heading mw-heading4"><h4 id="Pulse_compression">Pulse compression</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=23" title="Edit section: Pulse compression"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Pulse_compression" title="Pulse compression">Pulse compression</a></div> <p>The two techniques outlined above both have their disadvantages. The pulse timing technique has an inherent tradeoff in that the accuracy of the distance measurement is inversely related to the length of the pulse, while the energy, and thus direction range, is directly related. Increasing power for longer range while maintaining accuracy demands extremely high peak power, with 1960s <a href="/wiki/Early_warning_radar" class="mw-redirect" title="Early warning radar">early warning radars</a> often operating in the tens of megawatts. The continuous wave methods spread this energy out in time and thus require much lower peak power compared to pulse techniques, but requires some method of allowing the sent and received signals to operate at the same time, often demanding two separate antennas. </p><p>The introduction of new electronics in the 1960s allowed the two techniques to be combined. It starts with a longer pulse that is also frequency modulated. Spreading the broadcast energy out in time means lower peak energies can be used, with modern examples typically on the order of tens of kilowatts. On reception, the signal is sent into a system that delays different frequencies by different times. The resulting output is a much shorter pulse that is suitable for accurate distance measurement, while also compressing the received energy into a much higher energy peak and thus improving the signal-to-noise ratio. The technique is largely universal on modern large radars. </p> <div class="mw-heading mw-heading3"><h3 id="Speed_measurement">Speed measurement</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=24" title="Edit section: Speed measurement"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Speed" title="Speed">Speed</a> is the change in distance to an object with respect to time. Thus the existing system for measuring distance, combined with a memory capacity to see where the target last was, is enough to measure speed. At one time the memory consisted of a user making <a href="/wiki/Grease_pencil" title="Grease pencil">grease pencil</a> marks on the radar screen and then calculating the speed using a <a href="/wiki/Slide_rule" title="Slide rule">slide rule</a>. Modern radar systems perform the equivalent operation faster and more accurately using computers. </p><p>If the transmitter's output is coherent (phase synchronized), there is another effect that can be used to make almost instant speed measurements (no memory is required), known as the <a href="/wiki/Doppler_effect" title="Doppler effect">Doppler effect</a>. Most modern radar systems use this principle into <a href="/wiki/Doppler_radar" title="Doppler radar">Doppler radar</a> and <a href="/wiki/Pulse-Doppler_radar" title="Pulse-Doppler radar">pulse-Doppler radar</a> systems (<a href="/wiki/Weather_radar" title="Weather radar">weather radar</a>, military radar). The Doppler effect is only able to determine the relative speed of the target along the line of sight from the radar to the target. Any component of target velocity perpendicular to the line of sight cannot be determined by using the Doppler effect alone, but it can be determined by tracking the target's <a href="/wiki/Azimuth" title="Azimuth">azimuth</a> over time. </p><p>It is possible to make a Doppler radar without any pulsing, known as a <a href="/wiki/Continuous-wave_radar" title="Continuous-wave radar">continuous-wave radar</a> (CW radar), by sending out a very pure signal of a known frequency. CW radar is ideal for determining the radial component of a target's velocity. CW radar is typically used by traffic enforcement to measure vehicle speed quickly and accurately where the range is not important. </p><p>When using a pulsed radar, the variation between the phase of successive returns gives the distance the target has moved between pulses, and thus its speed can be calculated. Other mathematical developments in radar signal processing include <a href="/wiki/Time-frequency_analysis" class="mw-redirect" title="Time-frequency analysis">time-frequency analysis</a> (Weyl Heisenberg or <a href="/wiki/Wavelet" title="Wavelet">wavelet</a>), as well as the <a href="/wiki/Chirplet_transform" title="Chirplet transform">chirplet transform</a> which makes use of the change of frequency of returns from moving targets ("chirp"). </p> <div class="mw-heading mw-heading3"><h3 id="Pulse-Doppler_signal_processing">Pulse-Doppler signal processing</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=25" title="Edit section: Pulse-Doppler signal processing"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Pulse-Doppler_signal_processing" title="Pulse-Doppler signal processing">Pulse-Doppler signal processing</a></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Pulse_doppler_signal_processing.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/a/af/Pulse_doppler_signal_processing.png/220px-Pulse_doppler_signal_processing.png" decoding="async" width="220" height="273" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/af/Pulse_doppler_signal_processing.png/330px-Pulse_doppler_signal_processing.png 1.5x, //upload.wikimedia.org/wikipedia/commons/a/af/Pulse_doppler_signal_processing.png 2x" data-file-width="435" data-file-height="540" /></a><figcaption>Pulse-Doppler signal processing. The <i>Range Sample</i> axis represents individual samples taken in between each transmit pulse. The <i>Range Interval</i> axis represents each successive transmit pulse interval during which samples are taken. The Fast Fourier Transform process converts time-domain samples into frequency domain spectra. This is sometimes called the <i>bed of nails</i>.</figcaption></figure> <p>Pulse-Doppler signal processing includes frequency filtering in the detection process. The space between each transmit pulse is divided into range cells or range gates. Each cell is filtered independently much like the process used by a <a href="/wiki/Spectrum_analyzer" title="Spectrum analyzer">spectrum analyzer</a> to produce the display showing different frequencies. Each different distance produces a different spectrum. These spectra are used to perform the detection process. This is required to achieve acceptable performance in hostile environments involving weather, terrain, and electronic countermeasures. </p><p>The primary purpose is to measure both the amplitude and frequency of the aggregate reflected signal from multiple distances. This is used with <a href="/wiki/Weather_radar" title="Weather radar">weather radar</a> to measure radial wind velocity and precipitation rate in each different volume of air. This is linked with computing systems to produce a real-time electronic weather map. Aircraft safety depends upon continuous access to accurate weather radar information that is used to prevent injuries and accidents. Weather radar uses a <a href="/wiki/Pulse_repetition_frequency#Low_PRF" class="mw-redirect" title="Pulse repetition frequency">low PRF</a>. Coherency requirements are not as strict as those for military systems because individual signals ordinarily do not need to be separated. Less sophisticated filtering is required, and range ambiguity processing is not normally needed with weather radar in comparison with military radar intended to track air vehicles. </p><p>The alternate purpose is "<a href="/wiki/Look-down/shoot-down" title="Look-down/shoot-down">look-down/shoot-down</a>" capability required to improve military air combat survivability. Pulse-Doppler is also used for ground based surveillance radar required to defend personnel and vehicles.<sup id="cite_ref-Syracuse_Research_Corporation;_Massachusetts_Institute_of_Technology_50-0" class="reference"><a href="#cite_note-Syracuse_Research_Corporation;_Massachusetts_Institute_of_Technology-50"><span class="cite-bracket">[</span>50<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-51" class="reference"><a href="#cite_note-51"><span class="cite-bracket">[</span>51<span class="cite-bracket">]</span></a></sup> Pulse-doppler signal processing increases the maximum detection distance using less radiation close to aircraft pilots, shipboard personnel, infantry, and artillery. Reflections from terrain, water, and weather produce signals much larger than aircraft and missiles, which allows fast moving vehicles to hide using <a href="/wiki/Nap-of-the-earth" title="Nap-of-the-earth">nap-of-the-earth</a> flying techniques and <a href="/wiki/Stealth_technology" title="Stealth technology">stealth technology</a> to avoid detection until an attack vehicle is too close to destroy. Pulse-Doppler signal processing incorporates more sophisticated electronic filtering that safely eliminates this kind of weakness. This requires the use of medium pulse-repetition frequency with phase coherent hardware that has a large dynamic range. Military applications require <a href="/wiki/Pulse_repetition_frequency#Medium_PRF" class="mw-redirect" title="Pulse repetition frequency">medium PRF</a> which prevents range from being determined directly, and <a href="/wiki/Range_ambiguity_resolution" title="Range ambiguity resolution">range ambiguity resolution</a> processing is required to identify the true range of all reflected signals. Radial movement is usually linked with Doppler frequency to produce a lock signal that cannot be produced by radar jamming signals. Pulse-Doppler signal processing also produces audible signals that can be used for threat identification.<sup id="cite_ref-Syracuse_Research_Corporation;_Massachusetts_Institute_of_Technology_50-1" class="reference"><a href="#cite_note-Syracuse_Research_Corporation;_Massachusetts_Institute_of_Technology-50"><span class="cite-bracket">[</span>50<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Reduction_of_interference_effects">Reduction of interference effects</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=26" title="Edit section: Reduction of interference effects"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Signal_processing" title="Signal processing">Signal processing</a> is employed in radar systems to reduce the <a href="#Interference">radar interference effects</a>. Signal processing techniques include <a href="/wiki/Moving_target_indication" title="Moving target indication">moving target indication</a>, <a href="/wiki/Pulse-Doppler_signal_processing" title="Pulse-Doppler signal processing">Pulse-Doppler signal processing</a>, moving target detection processors, correlation with <a href="/wiki/Secondary_surveillance_radar" title="Secondary surveillance radar">secondary surveillance radar</a> targets, <a href="/wiki/Space-time_adaptive_processing" title="Space-time adaptive processing">space-time adaptive processing</a>, and <a href="/wiki/Track-before-detect" title="Track-before-detect">track-before-detect</a>. <a href="/wiki/Constant_false_alarm_rate" title="Constant false alarm rate">Constant false alarm rate</a> and <a href="/wiki/Digital_terrain_model" class="mw-redirect" title="Digital terrain model">digital terrain model</a> processing are also used in clutter environments. </p> <div class="mw-heading mw-heading3"><h3 id="Plot_and_track_extraction">Plot and track extraction</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=27" title="Edit section: Plot and track extraction"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main articles: <a href="/wiki/Radar_tracker" title="Radar tracker">Radar tracker</a> and <a href="/wiki/Track_algorithm" title="Track algorithm">Track algorithm</a></div> <p>A track algorithm is a radar performance enhancement strategy. Tracking algorithms provide the ability to predict the future position of multiple moving objects based on the history of the individual positions being reported by sensor systems. </p><p>Historical information is accumulated and used to predict future position for use with air traffic control, threat estimation, combat system doctrine, gun aiming, and missile guidance. Position data is accumulated by radar sensors over the span of a few minutes. </p><p>There are four common track algorithms:<sup id="cite_ref-52" class="reference"><a href="#cite_note-52"><span class="cite-bracket">[</span>52<span class="cite-bracket">]</span></a></sup> </p> <ul><li><a href="/wiki/Nearest_neighbour_algorithm" title="Nearest neighbour algorithm">Nearest neighbour algorithm</a></li> <li><a href="/wiki/Probabilistic_data_association_filter" title="Probabilistic data association filter">Probabilistic Data Association</a></li> <li>Multiple Hypothesis Tracking</li> <li>Interactive Multiple Model (IMM)</li></ul> <p>Radar video returns from aircraft can be subjected to a plot extraction process whereby spurious and interfering signals are discarded. A sequence of target returns can be monitored through a device known as a plot extractor. </p><p>The non-relevant real time returns can be removed from the displayed information and a single plot displayed. In some radar systems, or alternatively in the command and control system to which the radar is connected, a <a href="/wiki/Radar_tracker" title="Radar tracker">radar tracker</a> is used to associate the sequence of plots belonging to individual targets and estimate the targets' headings and speeds. </p> <div class="mw-heading mw-heading2"><h2 id="Engineering">Engineering</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=28" title="Edit section: Engineering"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Radar_engineering_details" class="mw-redirect" title="Radar engineering details">Radar engineering details</a></div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Radar_composantes.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/3/38/Radar_composantes.svg/220px-Radar_composantes.svg.png" decoding="async" width="220" height="178" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/3/38/Radar_composantes.svg/330px-Radar_composantes.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/3/38/Radar_composantes.svg/440px-Radar_composantes.svg.png 2x" data-file-width="843" data-file-height="683" /></a><figcaption>Radar components</figcaption></figure> <p>A radar's components are: </p> <ul><li>A <a href="/wiki/Transmitter" title="Transmitter">transmitter</a> that generates the radio signal with an oscillator such as a <a href="/wiki/Klystron" title="Klystron">klystron</a> or a <a href="/wiki/Magnetron" class="mw-redirect" title="Magnetron">magnetron</a> and controls its duration by a <a href="/wiki/Modulator" class="mw-redirect" title="Modulator">modulator</a>.</li> <li>A <a href="/wiki/Waveguide" title="Waveguide">waveguide</a> that links the transmitter and the antenna.</li> <li>A <a href="/wiki/Duplexer" title="Duplexer">duplexer</a> that serves as a switch between the antenna and the transmitter or the receiver for the signal when the antenna is used in both situations.</li> <li>A <a href="/wiki/Receiver_(radio)" class="mw-redirect" title="Receiver (radio)">receiver</a>. Knowing the shape of the desired received signal (a pulse), an optimal receiver can be designed using a <a href="/wiki/Matched_filter" title="Matched filter">matched filter</a>.</li> <li>A display processor to produce signals for human readable <a href="/wiki/Radar_display" title="Radar display">output devices</a>.</li> <li>An electronic section that controls all those devices and the antenna to perform the radar scan ordered by software.</li> <li>A link to end user devices and displays.</li></ul> <div class="mw-heading mw-heading3"><h3 id="Antenna_design">Antenna design</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=29" title="Edit section: Antenna design"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Antenna_(radio)" title="Antenna (radio)">Antenna (radio)</a></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Electronics_Technician_-_Volume_7_-_Figure_2-48.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/4/48/Electronics_Technician_-_Volume_7_-_Figure_2-48.jpg/220px-Electronics_Technician_-_Volume_7_-_Figure_2-48.jpg" decoding="async" width="220" height="147" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/48/Electronics_Technician_-_Volume_7_-_Figure_2-48.jpg/330px-Electronics_Technician_-_Volume_7_-_Figure_2-48.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/48/Electronics_Technician_-_Volume_7_-_Figure_2-48.jpg/440px-Electronics_Technician_-_Volume_7_-_Figure_2-48.jpg 2x" data-file-width="2040" data-file-height="1365" /></a><figcaption>AS-3263/SPS-49(V) antenna (US Navy)</figcaption></figure> <p>Radio signals broadcast from a single antenna will spread out in all directions, and likewise a single antenna will receive signals equally from all directions. This leaves the radar with the problem of deciding where the target object is located. </p><p>Early systems tended to use <a href="/wiki/Omnidirectional_antenna" title="Omnidirectional antenna">omnidirectional broadcast antennas</a>, with directional receiver antennas which were pointed in various directions. For instance, the first system to be deployed, Chain Home, used two straight antennas at <a href="/wiki/Right_angle" title="Right angle">right angles</a> for reception, each on a different display. The maximum return would be detected with an antenna at right angles to the target, and a minimum with the antenna pointed directly at it (end on). The operator could determine the direction to a target by <a href="/wiki/Rotation" title="Rotation">rotating</a> the antenna so one display showed a maximum while the other showed a minimum. One serious limitation with this type of solution is that the broadcast is sent out in all directions, so the amount of energy in the direction being examined is <a href="/wiki/Inverse-square_law" title="Inverse-square law">a small part</a> of that transmitted. To get a reasonable amount of power on the "target", the transmitting aerial should also be directional. </p> <div class="mw-heading mw-heading4"><h4 id="Parabolic_reflector">Parabolic reflector</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=30" title="Edit section: Parabolic reflector"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:SPS-10_radar_antenna_on_a_Knox_class_frigate.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/10/SPS-10_radar_antenna_on_a_Knox_class_frigate.jpg/220px-SPS-10_radar_antenna_on_a_Knox_class_frigate.jpg" decoding="async" width="220" height="178" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/1/10/SPS-10_radar_antenna_on_a_Knox_class_frigate.jpg 1.5x" data-file-width="236" data-file-height="191" /></a><figcaption>Surveillance radar antenna</figcaption></figure> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Parabolic_antenna" title="Parabolic antenna">Parabolic antenna</a></div> <p>More modern systems use a steerable <a href="/wiki/Parabola" title="Parabola">parabolic</a> "dish" to create a tight broadcast beam, typically using the same dish as the receiver. Such systems often combine two radar frequencies in the same antenna in order to allow automatic steering, or <i>radar lock</i>. </p><p>Parabolic reflectors can be either symmetric parabolas or spoiled parabolas: Symmetric parabolic antennas produce a narrow "pencil" beam in both the X and Y dimensions and consequently have a higher gain. The <a href="/wiki/NEXRAD" title="NEXRAD">NEXRAD</a> <a href="/wiki/Pulse-Doppler" class="mw-redirect" title="Pulse-Doppler">Pulse-Doppler</a> weather radar uses a symmetric antenna to perform detailed volumetric scans of the atmosphere. Spoiled parabolic antennas produce a narrow beam in one dimension and a relatively wide beam in the other. This feature is useful if target detection over a wide range of angles is more important than target location in three dimensions. Most 2D surveillance radars use a spoiled parabolic antenna with a narrow azimuthal beamwidth and wide vertical beamwidth. This beam configuration allows the radar operator to detect an aircraft at a specific azimuth but at an indeterminate height. Conversely, so-called "nodder" height finding radars use a dish with a narrow vertical beamwidth and wide azimuthal beamwidth to detect an aircraft at a specific height but with low azimuthal precision. </p> <div class="mw-heading mw-heading4"><h4 id="Types_of_scan">Types of scan</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=31" title="Edit section: Types of scan"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li>Primary Scan: A scanning technique where the main antenna aerial is moved to produce a scanning beam, examples include circular scan, sector scan, etc.</li> <li>Secondary Scan: A scanning technique where the antenna feed is moved to produce a scanning beam, examples include conical scan, unidirectional sector scan, lobe switching, etc.</li> <li>Palmer Scan: A scanning technique that produces a scanning beam by moving the main antenna and its feed. A Palmer Scan is a combination of a Primary Scan and a Secondary Scan.</li> <li><a href="/wiki/Conical_scanning" title="Conical scanning">Conical scanning</a>: The radar beam is rotated in a small circle around the "boresight" axis, which is pointed at the target.</li></ul> <div class="mw-heading mw-heading4"><h4 id="Slotted_waveguide">Slotted waveguide</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=32" title="Edit section: Slotted waveguide"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Radar_antennas_on_USS_Theodore_Roosevelt_SPS-64.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Radar_antennas_on_USS_Theodore_Roosevelt_SPS-64.jpg/250px-Radar_antennas_on_USS_Theodore_Roosevelt_SPS-64.jpg" decoding="async" width="220" height="232" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Radar_antennas_on_USS_Theodore_Roosevelt_SPS-64.jpg/330px-Radar_antennas_on_USS_Theodore_Roosevelt_SPS-64.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Radar_antennas_on_USS_Theodore_Roosevelt_SPS-64.jpg/500px-Radar_antennas_on_USS_Theodore_Roosevelt_SPS-64.jpg 2x" data-file-width="533" data-file-height="562" /></a><figcaption>Slotted waveguide antenna</figcaption></figure> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Slotted_waveguide" class="mw-redirect" title="Slotted waveguide">Slotted waveguide</a></div> <p>Applied similarly to the parabolic reflector, the slotted waveguide is moved mechanically to scan and is particularly suitable for non-tracking surface scan systems, where the vertical pattern may remain constant. Owing to its lower cost and less wind exposure, shipboard, airport surface, and harbour surveillance radars now use this approach in preference to a parabolic antenna. </p> <div class="mw-heading mw-heading4"><h4 id="Phased_array">Phased array</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=33" title="Edit section: Phased array"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:PAVE_PAWS_Radar_Clear_AFS_Alaska.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/9b/PAVE_PAWS_Radar_Clear_AFS_Alaska.jpg/250px-PAVE_PAWS_Radar_Clear_AFS_Alaska.jpg" decoding="async" width="220" height="193" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/9b/PAVE_PAWS_Radar_Clear_AFS_Alaska.jpg/330px-PAVE_PAWS_Radar_Clear_AFS_Alaska.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/9/9b/PAVE_PAWS_Radar_Clear_AFS_Alaska.jpg 2x" data-file-width="354" data-file-height="311" /></a><figcaption><a href="/wiki/Phased_array" title="Phased array">Phased array</a>: Not all radar antennas must rotate to scan the sky.</figcaption></figure> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Phased_array" title="Phased array">Phased array</a></div> <p>Another method of steering is used in a <a href="/wiki/Phased_array" title="Phased array">phased array</a> radar. </p><p>Phased array antennas are composed of evenly spaced similar antenna elements, such as aerials or rows of slotted waveguide. Each antenna element or group of antenna elements incorporates a discrete phase shift that produces a phase gradient across the array. For example, array elements producing a 5 degree phase shift for each wavelength across the array face will produce a beam pointed 5 degrees away from the centerline perpendicular to the array face. Signals travelling along that beam will be reinforced. Signals offset from that beam will be cancelled. The amount of reinforcement is <a href="/wiki/Antenna_gain" class="mw-redirect" title="Antenna gain">antenna gain</a>. The amount of cancellation is side-lobe suppression.<sup id="cite_ref-53" class="reference"><a href="#cite_note-53"><span class="cite-bracket">[</span>53<span class="cite-bracket">]</span></a></sup> </p><p>Phased array radars have been in use since the earliest years of radar in World War II (<a href="/wiki/Mammut_radar" title="Mammut radar">Mammut radar</a>), but electronic device limitations led to poor performance. Phased array radars were originally used for missile defence (see for example <a href="/wiki/Safeguard_Program" title="Safeguard Program">Safeguard Program</a>). They are the heart of the ship-borne <a href="/wiki/Aegis_Combat_System" title="Aegis Combat System">Aegis Combat System</a> and the <a href="/wiki/MIM-104_Patriot" title="MIM-104 Patriot">Patriot Missile System</a>. The massive redundancy associated with having a large number of array elements increases reliability at the expense of gradual performance degradation that occurs as individual phase elements fail. To a lesser extent, phased array radars have been used in <a href="/wiki/Weather" title="Weather">weather</a> <a href="/wiki/Surveillance" title="Surveillance">surveillance</a>. As of 2017, NOAA plans to implement a national network of multi-function phased array radars throughout the United States within 10 years, for meteorological studies and flight monitoring.<sup id="cite_ref-54" class="reference"><a href="#cite_note-54"><span class="cite-bracket">[</span>54<span class="cite-bracket">]</span></a></sup> </p><p>Phased array antennas can be built to conform to specific shapes, like missiles, infantry support vehicles, ships, and aircraft. </p><p>As the price of electronics has fallen, phased array radars have become more common. Almost all modern military radar systems are based on phased arrays, where the small additional cost is offset by the improved reliability of a system with no moving parts. Traditional moving-antenna designs are still widely used in roles where cost is a significant factor such as air traffic surveillance and similar systems. </p><p>Phased array radars are valued for use in aircraft since they can track multiple targets. The first aircraft to use a phased array radar was the <a href="/wiki/B-1B_Lancer" class="mw-redirect" title="B-1B Lancer">B-1B Lancer</a>. The first fighter aircraft to use phased array radar was the <a href="/wiki/Mikoyan_MiG-31" title="Mikoyan MiG-31">Mikoyan MiG-31</a>. The MiG-31M's SBI-16 <a href="/wiki/Zaslon" title="Zaslon">Zaslon</a> <a href="/wiki/Passive_electronically_scanned_array" title="Passive electronically scanned array">passive electronically scanned array</a> radar was considered to be the world's most powerful fighter radar,<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (January 2023)">citation needed</span></a></i>]</sup> until the <a href="/wiki/AN/APG-77" title="AN/APG-77">AN/APG-77</a> <a href="/wiki/Active_electronically_scanned_array" title="Active electronically scanned array">active electronically scanned array</a> was introduced on the <a href="/wiki/Lockheed_Martin_F-22_Raptor" title="Lockheed Martin F-22 Raptor">Lockheed Martin F-22 Raptor</a>. </p><p>Phased-array <a href="/wiki/Interferometry" title="Interferometry">interferometry</a> or <a href="/wiki/Aperture_synthesis" title="Aperture synthesis">aperture synthesis</a> techniques, using an array of separate dishes that are phased into a single effective aperture, are not typical for radar applications, although they are widely used in <a href="/wiki/Radio_astronomy" title="Radio astronomy">radio astronomy</a>. Because of the <a href="/wiki/Thinned_array_curse" class="mw-redirect" title="Thinned array curse">thinned array curse</a>, such multiple aperture arrays, when used in transmitters, result in narrow beams at the expense of reducing the total power transmitted to the target. In principle, such techniques could increase spatial resolution, but the lower power means that this is generally not effective. </p><p><a href="/wiki/Synthetic_aperture_radar" class="mw-redirect" title="Synthetic aperture radar">Aperture synthesis</a> by post-processing motion data from a single moving source, on the other hand, is widely used in space and <a href="/wiki/Airborne_radar_system" class="mw-redirect" title="Airborne radar system">airborne radar systems</a>. </p> <div class="mw-heading mw-heading3"><h3 id="Frequency_bands">Frequency bands</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=34" title="Edit section: Frequency bands"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Radio_spectrum#IEEE" title="Radio spectrum">Radio spectrum § IEEE</a></div> <p>Antennas generally have to be sized similar to the wavelength of the operational frequency, normally within an <a href="/wiki/Order_of_magnitude" title="Order of magnitude">order of magnitude</a>. This provides a strong incentive to use shorter wavelengths as this will result in smaller antennas. Shorter wavelengths also result in higher resolution due to diffraction, meaning the shaped reflector seen on most radars can also be made smaller for any desired beamwidth. </p><p>Opposing the move to smaller wavelengths are a number of practical issues. For one, the electronics needed to produce high power very short wavelengths were generally more complex and expensive than the electronics needed for longer wavelengths or did not exist at all. Another issue is that the <a href="/wiki/Radar_equation" class="mw-redirect" title="Radar equation">radar equation</a>'s effective aperture figure means that for any given antenna (or reflector) size will be more efficient at longer wavelengths. Additionally, shorter wavelengths may interact with molecules or raindrops in the air, scattering the signal. Very long wavelengths also have additional diffraction effects that make them suitable for <a href="/wiki/Over_the_horizon_radar" class="mw-redirect" title="Over the horizon radar">over the horizon radars</a>. For this reason, a wide variety of wavelengths are used in different roles. </p><p>The traditional band names originated as code-names during World War II and are still in military and aviation use throughout the world. They have been adopted in the United States by the <a href="/wiki/Institute_of_Electrical_and_Electronics_Engineers" title="Institute of Electrical and Electronics Engineers">Institute of Electrical and Electronics Engineers</a> and internationally by the <a href="/wiki/International_Telecommunication_Union" title="International Telecommunication Union">International Telecommunication Union</a>. Most countries have additional regulations to control which parts of each band are available for civilian or military use. </p><p>Other users of the radio spectrum, such as the <a href="/wiki/Broadcasting" title="Broadcasting">broadcasting</a> and <a href="/wiki/Electronic_countermeasures" class="mw-redirect" title="Electronic countermeasures">electronic countermeasures</a> industries, have replaced the traditional military designations with their own systems. </p> <table class="wikitable"> <caption><b>Radar frequency bands</b> </caption> <tbody><tr style="background:#ccc;"> <th>Band name</th> <th>Frequency range</th> <th>Wavelength range</th> <th>Notes </th></tr> <tr> <td><a href="/wiki/High_frequency" title="High frequency">HF</a></td> <td>3–30 <a href="/wiki/Hertz" title="Hertz">MHz</a></td> <td>10–100 <a href="/wiki/Metre" title="Metre">m</a></td> <td>Coastal radar systems, <a href="/wiki/Over-the-horizon" class="mw-redirect" title="Over-the-horizon">over-the-horizon</a> (OTH) radars; 'high frequency' </td></tr> <tr> <td><a href="/wiki/VHF" class="mw-redirect" title="VHF">VHF</a></td> <td>30–300 MHz</td> <td>1–10 m</td> <td>Very long range, ground penetrating; 'very high frequency'. Early radar systems generally operated in VHF as suitable electronics had already been developed for broadcast radio. Today this band is heavily congested and no longer suitable for radar due to interference. </td></tr> <tr> <td>P</td> <td>< 300 MHz</td> <td>> 1 m</td> <td>'P' for 'previous', applied retrospectively to early radar systems; essentially HF + VHF. Often used for remote sensing because of good vegetation penetration. </td></tr> <tr> <td><a href="/wiki/UHF" class="mw-redirect" title="UHF">UHF</a></td> <td>300–1000 MHz</td> <td>0.3–1 m</td> <td>Very long range (e.g. <a href="/wiki/Ballistic_Missile_Early_Warning_System" title="Ballistic Missile Early Warning System">ballistic missile early warning</a>), ground penetrating, foliage penetrating; 'ultra high frequency'. Efficiently produced and received at very high energy levels, and also reduces the effects of <a href="/wiki/Nuclear_blackout" title="Nuclear blackout">nuclear blackout</a>, making them useful in the missile detection role. </td></tr> <tr> <td><a href="/wiki/L_band" title="L band">L</a></td> <td>1–2 <a href="/wiki/Hertz" title="Hertz">GHz</a></td> <td>15–30 <a href="/wiki/Centimetre" title="Centimetre">cm</a></td> <td>Long range air traffic control and <a href="/wiki/Surveillance" title="Surveillance">surveillance</a>; 'L' for 'long'. Widely used for long range <a href="/wiki/Early_warning_radar" class="mw-redirect" title="Early warning radar">early warning radars</a> as they combine good reception qualities with reasonable resolution. </td></tr> <tr> <td><a href="/wiki/S_band" title="S band">S</a></td> <td>2–4 GHz</td> <td>7.5–15 cm</td> <td>Moderate range surveillance, Terminal air traffic control, long-range weather, marine radar; 'S' for 'sentimetric', its code-name during WWII. Less efficient than L, but offering higher resolution, making them especially suitable for long-range <a href="/wiki/Ground_controlled_interception" class="mw-redirect" title="Ground controlled interception">ground controlled interception</a> tasks. </td></tr> <tr> <td><a href="/wiki/C_band_(IEEE)" title="C band (IEEE)">C</a></td> <td>4–8 GHz</td> <td>3.75–7.5 cm</td> <td>Satellite transponders; a compromise (hence 'C') between X and S bands; weather; long range tracking </td></tr> <tr> <td><a href="/wiki/X_band" title="X band">X</a></td> <td>8–12 GHz</td> <td>2.5–3.75 cm</td> <td><a href="/wiki/Missile" title="Missile">Missile</a> guidance, <a href="/wiki/Marine_radar" title="Marine radar">marine radar</a>, weather, medium-resolution mapping and ground surveillance; in the United States the narrow range 10.525 GHz ±25 MHz is used for <a href="/wiki/Airport" title="Airport">airport</a> radar; short-range tracking. Named X band because the frequency was a secret during WW2. Diffraction off raindrops during heavy rain limits the range in the detection role and makes this suitable only for short-range roles or those that deliberately detect rain. </td></tr> <tr> <td><a href="/wiki/Ku_band" title="Ku band">K<sub>u</sub></a></td> <td>12–18 GHz</td> <td>1.67–2.5 cm</td> <td>High-resolution, also used for satellite transponders, frequency under K band (hence 'u') </td></tr> <tr> <td><a href="/wiki/K_band_(IEEE)" title="K band (IEEE)">K</a></td> <td>18–24 GHz</td> <td>1.11–1.67 cm</td> <td>From <a href="/wiki/German_language" title="German language">German</a> <i>kurz</i>, meaning 'short'. Limited use due to absorption by <a href="/wiki/Water_vapor" title="Water vapor">water vapor</a> at 22 GHz, so K<sub>u</sub> and K<sub>a</sub> on either side used instead for surveillance. K-band is used for detecting clouds by meteorologists, and by police for detecting speeding motorists. K-band operates at 24.150 ± 0.100 GHz. </td></tr> <tr> <td><a href="/wiki/Ka_band" title="Ka band">K<sub>a</sub></a></td> <td>24–40 GHz</td> <td>0.75–1.11 cm</td> <td>Mapping, short range, airport surveillance; frequency just above K band (hence 'a') Photo radar, used to trigger cameras which take pictures of license plates of cars running red lights, and by police for detecting speeding motorists. Operates at 34.300 ± 0.100 GHz. </td></tr> <tr> <td>mm</td> <td>40–300 GHz</td> <td>1.0–7.5 <a href="/wiki/Millimetre" title="Millimetre">mm</a></td> <td><a href="/wiki/Millimetre_band" class="mw-redirect" title="Millimetre band">Millimetre band</a>, subdivided as below. Oxygen in the air is an extremely effective attenuator around 60 GHz, as are other molecules at other frequencies, leading to the so-called propagation window at 94 GHz. Even in this window the attenuation is higher than that due to water at 22.2 GHz. This makes these frequencies generally useful only for short-range highly specific radars, like <a href="/wiki/Power_line" class="mw-redirect" title="Power line">power line</a> avoidance systems for <a href="/wiki/Helicopter" title="Helicopter">helicopters</a> or use in space where attenuation is not a problem. Multiple letters are assigned to these bands by different groups. These are from Baytron, a now defunct company that made test equipment. </td></tr> <tr> <td><a href="/wiki/V_band" title="V band">V</a></td> <td>40–75 GHz</td> <td>4.0–7.5 mm</td> <td>Very strongly absorbed by atmospheric oxygen, which resonates at 60 GHz. </td></tr> <tr> <td><a href="/wiki/W_band" title="W band">W</a></td> <td>75–110 GHz</td> <td>2.7–4.0 mm</td> <td>Used as a visual sensor for experimental autonomous vehicles, high-resolution meteorological observation, and imaging. </td></tr></tbody></table> <div class="mw-heading mw-heading3"><h3 id="Modulators">Modulators</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=35" title="Edit section: Modulators"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Modulation" class="mw-redirect" title="Modulation">Modulators</a> act to provide the waveform of the RF-pulse. There are two different radar modulator designs: </p> <ul><li>High voltage switch for non-coherent keyed power-oscillators.<sup id="cite_ref-55" class="reference"><a href="#cite_note-55"><span class="cite-bracket">[</span>55<span class="cite-bracket">]</span></a></sup> These modulators consist of a high voltage pulse generator formed from a high voltage supply, a <a href="/wiki/Pulse_forming_network" class="mw-redirect" title="Pulse forming network">pulse forming network</a>, and a high voltage switch such as a <a href="/wiki/Thyratron" title="Thyratron">thyratron</a>. They generate short pulses of power to feed, e.g., the <a href="/wiki/Magnetron" class="mw-redirect" title="Magnetron">magnetron</a>, a special type of vacuum tube that converts DC (usually pulsed) into microwaves. This technology is known as <a href="/wiki/Pulsed_power" title="Pulsed power">pulsed power</a>. In this way, the transmitted pulse of RF radiation is kept to a defined and usually very short duration.</li> <li>Hybrid mixers,<sup id="cite_ref-56" class="reference"><a href="#cite_note-56"><span class="cite-bracket">[</span>56<span class="cite-bracket">]</span></a></sup> fed by a waveform generator and an exciter for a complex but <a href="/wiki/Coherence_(physics)" title="Coherence (physics)">coherent</a> waveform. This waveform can be generated by low power/low-voltage input signals. In this case the radar transmitter must be a power-amplifier, e.g., a <a href="/wiki/Klystron" title="Klystron">klystron</a> or a solid state transmitter. In this way, the transmitted pulse is intrapulse-modulated and the radar receiver must use <a href="/wiki/Pulse_compression" title="Pulse compression">pulse compression</a> techniques.</li></ul> <div class="mw-heading mw-heading3"><h3 id="Coolant">Coolant</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=36" title="Edit section: Coolant"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Coherent microwave amplifiers operating above 1,000 watts microwave output, like <a href="/wiki/Traveling_wave_tube" class="mw-redirect" title="Traveling wave tube">travelling wave tubes</a> and <a href="/wiki/Klystron" title="Klystron">klystrons</a>, require <a href="/wiki/Coolant#Liquids" title="Coolant">liquid coolant</a>. The electron beam must contain 5 to 10 times more power than the microwave output, which can produce enough heat to generate plasma. This plasma flows from the collector toward the cathode. The same magnetic focusing that guides the electron beam forces the plasma into the path of the electron beam but flowing in the opposite direction. This introduces FM modulation which degrades Doppler performance. To prevent this, liquid coolant with minimum pressure and flow rate is required, and deionized water is normally used in most high power surface radar systems that use Doppler processing.<sup id="cite_ref-57" class="reference"><a href="#cite_note-57"><span class="cite-bracket">[</span>57<span class="cite-bracket">]</span></a></sup> </p><p><a href="/wiki/Coolanol" class="mw-redirect" title="Coolanol">Coolanol</a> (<a href="/wiki/Silicate" title="Silicate">silicate</a> <a href="/wiki/Ester" title="Ester">ester</a>) was used in several military radars in the 1970s. However, it is <a href="/wiki/Hygroscopic" class="mw-redirect" title="Hygroscopic">hygroscopic</a>, leading to <a href="/wiki/Hydrolysis" title="Hydrolysis">hydrolysis</a> and formation of highly flammable alcohol. The loss of a U.S. Navy aircraft in 1978 was attributed to a silicate ester fire.<sup id="cite_ref-58" class="reference"><a href="#cite_note-58"><span class="cite-bracket">[</span>58<span class="cite-bracket">]</span></a></sup> Coolanol is also expensive and toxic. The U.S. Navy has instituted a program named <a href="/wiki/Pollution_prevention_in_the_US" class="mw-redirect" title="Pollution prevention in the US">Pollution Prevention</a> (P2) to eliminate or reduce the volume and toxicity of waste, air emissions, and effluent discharges. Because of this, Coolanol is used less often today. </p> <div class="mw-heading mw-heading2"><h2 id="Regulations">Regulations</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=37" title="Edit section: Regulations"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><i>Radar</i> (also: <i>RADAR</i>) is defined by <i>article 1.100</i> of the <a href="/wiki/International_Telecommunication_Union" title="International Telecommunication Union">International Telecommunication Union's</a> (ITU) <a href="/wiki/ITU_Radio_Regulations" title="ITU Radio Regulations">ITU Radio Regulations</a> (RR) as:<sup id="cite_ref-59" class="reference"><a href="#cite_note-59"><span class="cite-bracket">[</span>59<span class="cite-bracket">]</span></a></sup> </p> <style data-mw-deduplicate="TemplateStyles:r1244412712">.mw-parser-output .templatequote{overflow:hidden;margin:1em 0;padding:0 32px}.mw-parser-output .templatequotecite{line-height:1.5em;text-align:left;margin-top:0}@media(min-width:500px){.mw-parser-output .templatequotecite{padding-left:1.6em}}</style><blockquote class="templatequote"><p>A <a href="/wiki/Radiodetermination_service" class="mw-redirect" title="Radiodetermination service">radiodetermination system</a> based on the comparison of reference signals with radio signals reflected, or retransmitted, from the position to be determined. Each <i>radiodetermination system</i> shall be classified by the <i>radiocommunication service</i> in which it operates permanently or temporarily. Typical radar utilizations are <a href="/wiki/Primary_radar" title="Primary radar">primary radar</a> and <a href="/wiki/Secondary_radar" class="mw-redirect" title="Secondary radar">secondary radar</a>, these might operate in the <a href="/wiki/Radiolocation_service" class="mw-redirect" title="Radiolocation service">radiolocation service</a> or the <a href="/wiki/Radiolocation-satellite_service" class="mw-redirect" title="Radiolocation-satellite service">radiolocation-satellite service</a>.</p></blockquote> <div class="mw-heading mw-heading2"><h2 id="Configurations">Configurations</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=38" title="Edit section: Configurations"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Radar come in a variety of configurations in the emitter, the receiver, the antenna, wavelength, scan strategies, etc. </p> <ul><li><a href="/wiki/Bistatic_radar" title="Bistatic radar">Bistatic radar</a></li> <li><a href="/wiki/Continuous-wave_radar" title="Continuous-wave radar">Continuous-wave radar</a></li> <li><a href="/wiki/Doppler_radar" title="Doppler radar">Doppler radar</a></li> <li><a href="/wiki/Fm-cw_radar" class="mw-redirect" title="Fm-cw radar">Fm-cw radar</a></li> <li><a href="/wiki/Monopulse_radar" title="Monopulse radar">Monopulse radar</a></li> <li><a href="/wiki/Passive_radar" title="Passive radar">Passive radar</a></li> <li><a href="/wiki/Planar_array_radar" class="mw-redirect" title="Planar array radar">Planar array radar</a></li> <li><a href="/wiki/Pulse-doppler" class="mw-redirect" title="Pulse-doppler">Pulse-doppler</a></li> <li><a href="/wiki/Synthetic-aperture_radar" title="Synthetic-aperture radar">Synthetic-aperture radar</a> <ul><li><a href="/wiki/Synthetically_thinned_aperture_radar" title="Synthetically thinned aperture radar">Synthetically thinned aperture radar</a></li></ul></li> <li><a href="/wiki/Over-the-horizon_radar" title="Over-the-horizon radar">Over-the-horizon radar</a> with <a href="/wiki/Chirp_transmitter" class="mw-redirect" title="Chirp transmitter">chirp transmitter</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=39" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1266661725">.mw-parser-output .portalbox{padding:0;margin:0.5em 0;display:table;box-sizing:border-box;max-width:175px;list-style:none}.mw-parser-output .portalborder{border:1px solid var(--border-color-base,#a2a9b1);padding:0.1em;background:var(--background-color-neutral-subtle,#f8f9fa)}.mw-parser-output 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href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main listing: <a href="/wiki/List_of_radar_types" title="List of radar types">List of radar types</a></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main category: <a href="/wiki/Category:Radar" title="Category:Radar">Radar</a></div> <ul><li><a href="/wiki/Terrain-following_radar" title="Terrain-following radar">Terrain-following radar</a></li> <li><a href="/wiki/Radar_imaging" class="mw-redirect" title="Radar imaging">Radar imaging</a></li> <li><a href="/wiki/Radar_navigation" title="Radar navigation">Radar navigation</a></li> <li><a href="/wiki/Inverse-square_law" title="Inverse-square law">Inverse-square law</a></li> <li><a href="/wiki/Wave_radar" title="Wave radar">Wave radar</a></li> <li><a href="/wiki/Radar_signal_characteristics" title="Radar signal characteristics">Radar signal characteristics</a></li> <li><a href="/wiki/Pulse_doppler_radar" class="mw-redirect" title="Pulse doppler radar">Pulse doppler radar</a></li> <li><a href="/wiki/Mmwave_sensing" title="Mmwave sensing">Mmwave sensing</a></li> <li><a href="/wiki/Acronyms_and_abbreviations_in_avionics" class="mw-redirect" title="Acronyms and abbreviations in avionics">Acronyms and abbreviations in avionics</a></li></ul> <dl><dt>Definitions</dt></dl> <ul><li><a href="/wiki/Amplitude-comparison_monopulse" title="Amplitude-comparison monopulse">Amplitude-comparison monopulse</a></li> <li><a href="/wiki/Constant_false_alarm_rate" title="Constant false alarm rate">Constant false alarm rate</a></li> <li><a href="/wiki/Sensitivity_time_control" title="Sensitivity time control">Sensitivity time control</a></li></ul> <dl><dt>Application</dt></dl> <ul><li><a href="/wiki/Proximity_fuze" title="Proximity fuze">Proximity fuze</a></li></ul> <dl><dt>Hardware</dt></dl> <ul><li><a href="/wiki/Cavity_magnetron" title="Cavity magnetron">Cavity magnetron</a></li> <li><a href="/wiki/Crossed-field_amplifier" title="Crossed-field amplifier">Crossed-field amplifier</a></li> <li><a href="/wiki/Gallium_arsenide" title="Gallium arsenide">Gallium arsenide</a></li> <li><a href="/wiki/Klystron" title="Klystron">Klystron</a></li> <li><a href="/wiki/Omniview_technology" class="mw-redirect" title="Omniview technology">Omniview technology</a></li> <li><a href="/wiki/Radar_engineering_details" class="mw-redirect" title="Radar engineering details">Radar engineering details</a></li> <li><a href="/wiki/Radar_tower" title="Radar tower">Radar tower</a></li> <li><a href="/wiki/Radio" title="Radio">Radio</a></li> <li><a href="/wiki/Travelling-wave_tube" class="mw-redirect" title="Travelling-wave tube">Travelling-wave tube</a></li></ul> <dl><dt>Similar detection and ranging methods</dt></dl> <ul><li><a href="/wiki/Acoustic_location" title="Acoustic location">Acoustic location</a></li> <li><a href="/wiki/Lidar" title="Lidar">Lidar</a></li> <li><a href="/wiki/LORAN" title="LORAN">LORAN</a></li> <li><a href="/wiki/Sonar" title="Sonar">Sonar</a></li></ul> <dl><dt>Historical radars</dt></dl> <ul><li><a href="/wiki/List_of_radars" title="List of radars">List of radars</a></li> <li><a href="/wiki/Chain_Home" title="Chain Home">Chain Home</a> and <a href="/wiki/Chain_Home_Low" title="Chain Home Low">Chain Home Low</a></li> <li><a href="/wiki/W%C3%BCrzburg_radar" title="Würzburg radar">Würzburg radar</a></li> <li><a href="/wiki/FuG_200_Hohentwiel" title="FuG 200 Hohentwiel">Hohentwiel radar</a></li> <li><a href="/wiki/H2S_(radar)" title="H2S (radar)">H2S radar</a></li> <li><a href="/wiki/SCR-270_radar" class="mw-redirect" title="SCR-270 radar">SCR-270 radar</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="Notes_and_references">Notes and references</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=40" title="Edit section: Notes and references"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output 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(1995). <i>The Origins and Development of Radar in the Royal Navy, 1935–45 with Particular Reference to Decimetric Gunnery Equipments</i>. Springer. pp. <span class="nowrap">5–</span>66. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-349-13457-1" title="Special:BookSources/978-1-349-13457-1"><bdi>978-1-349-13457-1</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Origins+and+Development+of+Radar+in+the+Royal+Navy%2C+1935%E2%80%9345+with+Particular+Reference+to+Decimetric+Gunnery+Equipments&rft.pages=%3Cspan+class%3D%22nowrap%22%3E5-%3C%2Fspan%3E66&rft.pub=Springer&rft.date=1995&rft.isbn=978-1-349-13457-1&rft.aulast=Coales&rft.aufirst=J.F.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></span> </li> <li id="cite_note-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-19">^</a></b></span> <span class="reference-text">Butement, W. A. S., and P. E. Pollard; "Coastal Defence Apparatus", <i>Inventions Book of the Royal Engineers Board</i>, Jan. 1931</span> </li> <li id="cite_note-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-20">^</a></b></span> <span class="reference-text">Swords, S. S.; <i>tech. History of the Beginnings of Radar</i>, Peter Peregrinus, Ltd, 1986, pp. 71–74</span> </li> <li id="cite_note-21"><span class="mw-cite-backlink"><b><a href="#cite_ref-21">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.museumwaalsdorp.nl/en/museum-waalsdorp-2/airacous/air-acoustics-electric-listening-device/">"The "Electric listening device" (1936 – 1941)"</a>. <i>museumwaalsdorp.nl</i><span class="reference-accessdate">. Retrieved <span class="nowrap">10 November</span> 2024</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=museumwaalsdorp.nl&rft.atitle=The+%22Electric+listening+device%22+%281936+%E2%80%93+1941%29&rft_id=https%3A%2F%2Fwww.museumwaalsdorp.nl%2Fen%2Fmuseum-waalsdorp-2%2Fairacous%2Fair-acoustics-electric-listening-device%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></span> </li> <li id="cite_note-22"><span class="mw-cite-backlink"><b><a href="#cite_ref-22">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation magazine cs1"><a rel="nofollow" class="external text" href="https://books.google.com/books?id=x98DAAAAMBAJ&pg=PA844">"Radio Waves Warn Liner of Obstacles in Path"</a>. <i>Popular Mechanics</i>. Hearst Magazines. December 1935. p. 844. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20241007062109/https://books.google.com/books?id=x98DAAAAMBAJ&pg=PA844#v=onepage&q&f=false">Archived</a> from the original on 7 October 2024<span class="reference-accessdate">. Retrieved <span class="nowrap">11 February</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Popular+Mechanics&rft.atitle=Radio+Waves+Warn+Liner+of+Obstacles+in+Path&rft.pages=844&rft.date=1935-12&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3Dx98DAAAAMBAJ%26pg%3DPA844&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></span> </li> <li id="cite_note-23"><span class="mw-cite-backlink"><b><a href="#cite_ref-23">^</a></b></span> <span class="reference-text">Frederick Seitz, Norman G. Einspruch, Electronic Genie: The Tangled History of Silicon – 1998 – page 104</span> </li> <li id="cite_note-24"><span class="mw-cite-backlink"><b><a href="#cite_ref-24">^</a></b></span> <span class="reference-text">John Erickson. Radio-Location and the Air Defence Problem: The Design and Development of Soviet Radar. <i>Science Studies</i>, vol. 2, no. 3 (Jul. 1972), pp. 241–263</span> </li> <li id="cite_note-25"><span class="mw-cite-backlink"><b><a href="#cite_ref-25">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150620161506/http://kret.com/en/news/3657/">"The history of radar, from aircraft radio detectors to airborne radar"</a>. <i>kret.com</i>. 17 February 2015. 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Retrieved <span class="nowrap">28 April</span> 2015</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=kret.com&rft.atitle=The+history+of+radar%2C+from+aircraft+radio+detectors+to+airborne+radar&rft.date=2015-02-17&rft_id=http%3A%2F%2Fkret.com%2Fen%2Fnews%2F3657%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></span> </li> <li id="cite_note-26"><span class="mw-cite-backlink"><b><a href="#cite_ref-26">^</a></b></span> <span class="reference-text">Page, Robert Morris, <i>The Origin of Radar</i>, Doubleday Anchor, New York, 1962, p. 66</span> </li> <li id="cite_note-27"><span class="mw-cite-backlink"><b><a href="#cite_ref-27">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation magazine cs1"><a rel="nofollow" class="external text" href="https://books.google.com/books?id=bygDAAAAMBAJ&pg=PA29">"Mystery Ray Locates 'Enemy'<span class="cs1-kern-right"></span>"</a>. <i>Popular Science</i>. Bonnier Corporation. October 1935. p. 29. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20241007062141/https://books.google.com/books?id=bygDAAAAMBAJ&pg=PA29#v=onepage&q&f=false">Archived</a> from the original on 7 October 2024<span class="reference-accessdate">. Retrieved <span class="nowrap">11 February</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Popular+Science&rft.atitle=Mystery+Ray+Locates+%27Enemy%27&rft.pages=29&rft.date=1935-10&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DbygDAAAAMBAJ%26pg%3DPA29&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></span> </li> <li id="cite_note-Alan_Dower_Blumlein-2002-28"><span class="mw-cite-backlink"><b><a href="#cite_ref-Alan_Dower_Blumlein-2002_28-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFAlan_Dower_Blumlein2002" class="citation web cs1">Alan Dower Blumlein (2002). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110710144447/http://www.doramusic.com/Radar.htm">"The story of RADAR Development"</a>. Archived from <a rel="nofollow" class="external text" href="http://www.doramusic.com/Radar.htm">the original</a> on 10 July 2011<span class="reference-accessdate">. Retrieved <span class="nowrap">6 May</span> 2011</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=The+story+of+RADAR+Development&rft.date=2002&rft.au=Alan+Dower+Blumlein&rft_id=http%3A%2F%2Fwww.doramusic.com%2FRadar.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></span> </li> <li id="cite_note-BREVET_D'INVENTION-1934-29"><span class="mw-cite-backlink"><b><a href="#cite_ref-BREVET_D'INVENTION-1934_29-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1 cs1-prop-foreign-lang-source"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20090116093441/http://www.radar-france.fr/brevet%20radar1934.htm">"Nouveau système de repérage d'obstacles et ses applications"</a> [New obstacle detection system and its applications]. <i>BREVET D'INVENTION</i> (in French). 20 July 1934. Archived from <a rel="nofollow" class="external text" href="http://www.radar-france.fr/brevet%20radar1934.htm">the original</a> on 16 January 2009 – via radar-france.fr.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=BREVET+D%27INVENTION&rft.atitle=Nouveau+syst%C3%A8me+de+rep%C3%A9rage+d%27obstacles+et+ses+applications&rft.date=1934-07-20&rft_id=http%3A%2F%2Fwww.radar-france.fr%2Fbrevet%2520radar1934.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></span> </li> <li id="cite_note-30"><span class="mw-cite-backlink"><b><a href="#cite_ref-30">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation pressrelease cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20060719224405/http://www.patent.gov.uk/media/pressrelease/2001/1009.htm">"British man first to patent radar"</a>. <i>Media Centre</i> (Press release). The Patent Office. 10 September 2001. Archived from <a rel="nofollow" class="external text" href="http://www.patent.gov.uk/media/pressrelease/2001/1009.htm">the original</a> on 19 July 2006.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=British+man+first+to+patent+radar&rft.pub=The+Patent+Office&rft.date=2001-09-10&rft_id=http%3A%2F%2Fwww.patent.gov.uk%2Fmedia%2Fpressrelease%2F2001%2F1009.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></span> </li> <li id="cite_note-31"><span class="mw-cite-backlink"><b><a href="#cite_ref-31">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1041539562" /><span class="citation patent"><a rel="nofollow" class="external text" href="https://worldwide.espacenet.com/textdoc?DB=EPODOC&IDX=GB593017">GB 593017</a></span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Apatent&rft.number=593017&rft.cc=GB&rft.title="><span style="display: none;"> </span></span> <i>Improvements in or relating to wireless systems</i></span> </li> <li id="cite_note-Angela_Hind-2007-32"><span class="mw-cite-backlink"><b><a href="#cite_ref-Angela_Hind-2007_32-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFAngela_Hind2007" class="citation news cs1">Angela Hind (5 February 2007). <a rel="nofollow" class="external text" href="http://news.bbc.co.uk/1/hi/sci/tech/6331897.stm">"Briefcase 'that changed the world'<span class="cs1-kern-right"></span>"</a>. BBC News. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20071115140606/http://news.bbc.co.uk/1/hi/sci/tech/6331897.stm">Archived</a> from the original on 15 November 2007<span class="reference-accessdate">. Retrieved <span class="nowrap">16 August</span> 2007</span>. <q>It not only changed the course of the war by allowing us to develop airborne radar systems, it remains the key piece of technology that lies at the heart of your microwave oven today. The cavity magnetron's invention changed the world.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Briefcase+%27that+changed+the+world%27&rft.date=2007-02-05&rft.au=Angela+Hind&rft_id=http%3A%2F%2Fnews.bbc.co.uk%2F1%2Fhi%2Fsci%2Ftech%2F6331897.stm&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></span> </li> <li id="cite_note-33"><span class="mw-cite-backlink"><b><a href="#cite_ref-33">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFHarford2017" class="citation news cs1">Harford, Tim (9 October 2017). <a rel="nofollow" class="external text" href="https://www.bbc.co.uk/news/business-41188464">"How the search for a 'death ray' led to radar"</a>. <i>BBC World Service</i>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20171009003404/http://www.bbc.co.uk/news/business-41188464">Archived</a> from the original on 9 October 2017<span class="reference-accessdate">. Retrieved <span class="nowrap">9 October</span> 2017</span>. <q>But by 1940, it was the British who had made a spectacular breakthrough: the resonant cavity magnetron, a radar transmitter far more powerful than its predecessors.... The magnetron stunned the Americans. Their research was years off the pace.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=BBC+World+Service&rft.atitle=How+the+search+for+a+%27death+ray%27+led+to+radar&rft.date=2017-10-09&rft.aulast=Harford&rft.aufirst=Tim&rft_id=https%3A%2F%2Fwww.bbc.co.uk%2Fnews%2Fbusiness-41188464&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></span> </li> <li id="cite_note-34"><span class="mw-cite-backlink"><b><a href="#cite_ref-34">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation magazine cs1"><a rel="nofollow" class="external text" href="https://books.google.com/books?id=hCcDAAAAMBAJ&pg=PA56">"Night Watchmen of the Skies"</a>. <i>Popular Science</i>. Bonnier Corporation. December 1941. p. 56. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20241007062141/https://books.google.com/books?id=hCcDAAAAMBAJ&pg=PA56#v=onepage&q&f=false">Archived</a> from the original on 7 October 2024<span class="reference-accessdate">. Retrieved <span class="nowrap">11 February</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Popular+Science&rft.atitle=Night+Watchmen+of+the+Skies&rft.pages=56&rft.date=1941-12&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DhCcDAAAAMBAJ%26pg%3DPA56&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></span> </li> <li id="cite_note-Popular_Mechanics-1941-35"><span class="mw-cite-backlink">^ <a href="#cite_ref-Popular_Mechanics-1941_35-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Popular_Mechanics-1941_35-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation magazine cs1"><a rel="nofollow" class="external text" href="https://archive.org/details/bub_gb_mtkDAAAAMBAJ/page/n67">"Odd-shaped Boats Rescue British Engineers"</a>. <i>Popular Mechanics</i>. 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Retrieved <span class="nowrap">29 November</span> 2015</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=radartutorial.eu&rft.atitle=Radar+Modulator&rft_id=http%3A%2F%2Fwww.radartutorial.eu%2F%2F08.transmitters%2FRadar%2520Modulator.en.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></span> </li> <li id="cite_note-56"><span class="mw-cite-backlink"><b><a href="#cite_ref-56">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.radartutorial.eu//08.transmitters/Fully%20Coherent%20Radar.en.html">"Fully Coherent Radar"</a>. <i>radartutorial.eu</i>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20151208042044/http://www.radartutorial.eu//08.transmitters/Fully%20Coherent%20Radar.en.html">Archived</a> from the original on 8 December 2015<span class="reference-accessdate">. Retrieved <span class="nowrap">29 November</span> 2015</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=radartutorial.eu&rft.atitle=Fully+Coherent+Radar&rft_id=http%3A%2F%2Fwww.radartutorial.eu%2F%2F08.transmitters%2FFully%2520Coherent%2520Radar.en.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></span> </li> <li id="cite_note-57"><span class="mw-cite-backlink"><b><a href="#cite_ref-57">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFJ.L._de_Segovia" class="citation web cs1">J.L. de Segovia. <a rel="nofollow" class="external text" href="http://www.cientificosaficionados.com/libros/CERN/vacio9-CERN.pdf">"Physics of Outgassing"</a> <span class="cs1-format">(PDF)</span>. Madrid, Spain: Instituto de Física Aplicada, CETEF "L. Torres Quevedo", CSIC. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20120105205714/http://cientificosaficionados.com/libros/CERN/vacio9-CERN.pdf">Archived</a> <span class="cs1-format">(PDF)</span> from the original on 5 January 2012<span class="reference-accessdate">. Retrieved <span class="nowrap">12 August</span> 2012</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Physics+of+Outgassing&rft.place=Madrid%2C+Spain&rft.pub=Instituto+de+F%C3%ADsica+Aplicada%2C+CETEF+%22L.+Torres+Quevedo%22%2C+CSIC&rft.au=J.L.+de+Segovia&rft_id=http%3A%2F%2Fwww.cientificosaficionados.com%2Flibros%2FCERN%2Fvacio9-CERN.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></span> </li> <li id="cite_note-58"><span class="mw-cite-backlink"><b><a href="#cite_ref-58">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFStropki,_Michael_A.1992" class="citation web cs1">Stropki, Michael A. (1992). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110605100528/http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA250517&Location=U2&doc=GetTRDoc.pdf">"Polyalphaolefins: A New Improved Cost Effective Aircraft Radar Coolant"</a> <span class="cs1-format">(PDF)</span>. Melbourne, Australia: Aeronautical Research Laboratory, Defense Science and Technology Organisation, Department of Defense. Archived from <a rel="nofollow" class="external text" href="http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA250517&Location=U2&doc=GetTRDoc.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 5 June 2011<span class="reference-accessdate">. Retrieved <span class="nowrap">18 March</span> 2010</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Polyalphaolefins%3A+A+New+Improved+Cost+Effective+Aircraft+Radar+Coolant&rft.place=Melbourne%2C+Australia&rft.pub=Aeronautical+Research+Laboratory%2C+Defense+Science+and+Technology+Organisation%2C+Department+of+Defense&rft.date=1992&rft.au=Stropki%2C+Michael+A.&rft_id=http%3A%2F%2Fwww.dtic.mil%2Fcgi-bin%2FGetTRDoc%3FAD%3DADA250517%26Location%3DU2%26doc%3DGetTRDoc.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></span> </li> <li id="cite_note-59"><span class="mw-cite-backlink"><b><a href="#cite_ref-59">^</a></b></span> <span class="reference-text">ITU Radio Regulations, Section IV. Radio Stations and Systems – Article 1.100, definition: <i>radar / RADAR</i></span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="Bibliography">Bibliography</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=41" title="Edit section: Bibliography"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1251242444">.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output .ambox+link+.ambox,.mw-parser-output .ambox+link+style+.ambox,.mw-parser-output .ambox+link+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+style+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+link+.ambox{margin-top:-1px}html body.mediawiki .mw-parser-output .ambox.mbox-small-left{margin:4px 1em 4px 0;overflow:hidden;width:238px;border-collapse:collapse;font-size:88%;line-height:1.25em}.mw-parser-output .ambox-speedy{border-left:10px solid #b32424;background-color:#fee7e6}.mw-parser-output .ambox-delete{border-left:10px solid #b32424}.mw-parser-output .ambox-content{border-left:10px solid #f28500}.mw-parser-output .ambox-style{border-left:10px solid #fc3}.mw-parser-output .ambox-move{border-left:10px solid #9932cc}.mw-parser-output .ambox-protection{border-left:10px solid #a2a9b1}.mw-parser-output .ambox .mbox-text{border:none;padding:0.25em 0.5em;width:100%}.mw-parser-output .ambox .mbox-image{border:none;padding:2px 0 2px 0.5em;text-align:center}.mw-parser-output .ambox .mbox-imageright{border:none;padding:2px 0.5em 2px 0;text-align:center}.mw-parser-output .ambox .mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox .mbox-image-div{width:52px}@media(min-width:720px){.mw-parser-output .ambox{margin:0 10%}}@media print{body.ns-0 .mw-parser-output .ambox{display:none!important}}</style><table class="box-Further_reading_cleanup plainlinks metadata ambox ambox-style" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/f/f2/Edit-clear.svg/40px-Edit-clear.svg.png" decoding="async" width="40" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/f/f2/Edit-clear.svg/60px-Edit-clear.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/f/f2/Edit-clear.svg/80px-Edit-clear.svg.png 2x" data-file-width="48" data-file-height="48" /></span></span></div></td><td class="mbox-text"><div class="mbox-text-span">This "<a href="/wiki/Wikipedia:Manual_of_Style/Layout#Further_reading" title="Wikipedia:Manual of Style/Layout">Further reading</a>" section <b>may need cleanup</b>.<span class="hide-when-compact"> Please read the <a href="/wiki/Wikipedia:Further_reading" title="Wikipedia:Further reading">editing guide</a> and help improve the section.</span> <span class="date-container"><i>(<span class="date">November 2014</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table> <div class="mw-heading mw-heading3"><h3 id="References">References</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=42" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li>Barrett, Dick, "<i><a rel="nofollow" class="external text" href="http://www.radarpages.co.uk/index.htm">All you ever wanted to know about British air defence radar</a></i>". The Radar Pages. (History and details of various British radar systems)</li> <li>Buderi, "<i><a rel="nofollow" class="external text" href="https://web.archive.org/web/20030803115343/http://privateline.com/TelephoneHistory3/radarhistorybuderi.html">Telephone History: Radar History</a></i>". Privateline.com. (Anecdotal account of the carriage of the world's first high power cavity magnetron from Britain to the US during WW2.)</li> <li>Ekco Radar <a rel="nofollow" class="external text" href="http://www.ekco-radar.co.uk/">WW2 Shadow Factory</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20051212132004/http://www.ekco-radar.co.uk/">Archived</a> 12 December 2005 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a> The secret development of British radar.</li> <li>ES310 <a rel="nofollow" class="external text" href="https://fas.org/man/dod-101/navy/docs/es310/syllabus.htm">"<i>Introduction to Naval Weapons Engineering.</i>". (Radar fundamentals section)</a></li> <li>Hollmann, Martin, "<i><a rel="nofollow" class="external text" href="http://www.radarworld.org/index.html">Radar Family Tree</a></i>". <a rel="nofollow" class="external text" href="http://www.radarworld.org/">Radar World</a>.</li> <li>Penley, Bill, and Jonathan Penley, "<i><a rel="nofollow" class="external text" href="https://web.archive.org/web/20081201090207/http://www.penleyradararchives.org.uk/history/introduction.htm">Early Radar History</a>—an Introduction</i>". 2002.</li> <li>Pub 1310 <i>Radar Navigation and Maneuvering Board Manual</i>, National Imagery and Mapping Agency, Bethesda, MD 2001 (US govt publication '...intended to be used primarily as a manual of instruction in navigation schools and by naval and merchant marine personnel.')</li> <li>Wesley Stout, 1946 <a rel="nofollow" class="external text" href="https://www.web.imperialclub.info/Yr/1945/46Radar/Cover.htm">"<i>Radar – The Great Detective</i>"</a> Early development and production by Chrysler Corp. during WWII.</li> <li>Swords, Seán S., "Technical History of the Beginnings of Radar", <i><a href="/wiki/Institution_of_Electrical_Engineers" title="Institution of Electrical Engineers">IEE</a> History of Technology Series</i>, Vol. 6, London: Peter Peregrinus, 1986</li></ul> <div class="mw-heading mw-heading3"><h3 id="General">General</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=43" title="Edit section: General"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFReg_Batt1991" class="citation book cs1">Reg Batt (1991). <i>The radar army: winning the war of the airwaves</i>. R. Hale. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-7090-4508-3" title="Special:BookSources/978-0-7090-4508-3"><bdi>978-0-7090-4508-3</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+radar+army%3A+winning+the+war+of+the+airwaves&rft.pub=R.+Hale&rft.date=1991&rft.isbn=978-0-7090-4508-3&rft.au=Reg+Batt&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFE.G._Bowen1998" class="citation book cs1">E.G. Bowen (1 January 1998). <i>Radar Days</i>. Taylor & Francis. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-7503-0586-0" title="Special:BookSources/978-0-7503-0586-0"><bdi>978-0-7503-0586-0</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Radar+Days&rft.pub=Taylor+%26+Francis&rft.date=1998-01-01&rft.isbn=978-0-7503-0586-0&rft.au=E.G.+Bowen&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFMichael_Bragg2002" class="citation book cs1">Michael Bragg (1 May 2002). <i>RDF1: The Location of Aircraft by Radio Methods 1935–1945</i>. Twayne Publishers. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-9531544-0-1" title="Special:BookSources/978-0-9531544-0-1"><bdi>978-0-9531544-0-1</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=RDF1%3A+The+Location+of+Aircraft+by+Radio+Methods+1935%E2%80%931945&rft.pub=Twayne+Publishers&rft.date=2002-05-01&rft.isbn=978-0-9531544-0-1&rft.au=Michael+Bragg&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFLouis_Brown1999" class="citation book cs1">Louis Brown (1999). <i>A radar history of World War II: technical and military imperatives</i>. Taylor & Francis. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-7503-0659-1" title="Special:BookSources/978-0-7503-0659-1"><bdi>978-0-7503-0659-1</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=A+radar+history+of+World+War+II%3A+technical+and+military+imperatives&rft.pub=Taylor+%26+Francis&rft.date=1999&rft.isbn=978-0-7503-0659-1&rft.au=Louis+Brown&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFRobert_Buderi1996" class="citation book cs1">Robert Buderi (1996). <i>The invention that changed the world: how a small group of radar pioneers won the Second World War and launched a technological revolution</i>. Simon & Schuster. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-684-81021-8" title="Special:BookSources/978-0-684-81021-8"><bdi>978-0-684-81021-8</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+invention+that+changed+the+world%3A+how+a+small+group+of+radar+pioneers+won+the+Second+World+War+and+launched+a+technological+revolution&rft.pub=Simon+%26+Schuster&rft.date=1996&rft.isbn=978-0-684-81021-8&rft.au=Robert+Buderi&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li>Burch, David F., <i>Radar For Mariners</i>, McGraw Hill, 2005, <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-07-139867-1" title="Special:BookSources/978-0-07-139867-1">978-0-07-139867-1</a>.</li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFIan_Goult2011" class="citation book cs1">Ian Goult (2011). <i>Secret Location: A witness to the Birth of Radar and its Postwar Influence</i>. History Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-7524-5776-5" title="Special:BookSources/978-0-7524-5776-5"><bdi>978-0-7524-5776-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Secret+Location%3A+A+witness+to+the+Birth+of+Radar+and+its+Postwar+Influence&rft.pub=History+Press&rft.date=2011&rft.isbn=978-0-7524-5776-5&rft.au=Ian+Goult&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFPeter_S._Hall1991" class="citation book cs1">Peter S. Hall (March 1991). <i>Radar</i>. Potomac Books Inc. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-08-037711-7" title="Special:BookSources/978-0-08-037711-7"><bdi>978-0-08-037711-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Radar&rft.pub=Potomac+Books+Inc&rft.date=1991-03&rft.isbn=978-0-08-037711-7&rft.au=Peter+S.+Hall&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDerek_HowseNaval_Radar_Trust1993" class="citation book cs1">Derek Howse; Naval Radar Trust (February 1993). <i>Radar at sea: the royal Navy in World War 2</i>. Naval Institute Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-55750-704-4" title="Special:BookSources/978-1-55750-704-4"><bdi>978-1-55750-704-4</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Radar+at+sea%3A+the+royal+Navy+in+World+War+2&rft.pub=Naval+Institute+Press&rft.date=1993-02&rft.isbn=978-1-55750-704-4&rft.au=Derek+Howse&rft.au=Naval+Radar+Trust&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFR.V._Jones1998" class="citation book cs1">R.V. Jones (August 1998). <i>Most Secret War</i>. Wordsworth Editions Ltd. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-85326-699-7" title="Special:BookSources/978-1-85326-699-7"><bdi>978-1-85326-699-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Most+Secret+War&rft.pub=Wordsworth+Editions+Ltd&rft.date=1998-08&rft.isbn=978-1-85326-699-7&rft.au=R.V.+Jones&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li>Kaiser, Gerald, Chapter 10 in "A Friendly Guide to Wavelets", Birkhauser, Boston, 1994.</li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFColin_LathamAnne_Stobbs1997" class="citation book cs1">Colin Latham; Anne Stobbs (January 1997). <i>Radar: A Wartime Miracle</i>. Sutton Pub Ltd. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-7509-1643-1" title="Special:BookSources/978-0-7509-1643-1"><bdi>978-0-7509-1643-1</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Radar%3A+A+Wartime+Miracle&rft.pub=Sutton+Pub+Ltd&rft.date=1997-01&rft.isbn=978-0-7509-1643-1&rft.au=Colin+Latham&rft.au=Anne+Stobbs&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFFrançois_Le_Chevalier2002" class="citation book cs1">François Le Chevalier (2002). <i>Principles of radar and sonar signal processing</i>. Artech House Publishers. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-58053-338-6" title="Special:BookSources/978-1-58053-338-6"><bdi>978-1-58053-338-6</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Principles+of+radar+and+sonar+signal+processing&rft.pub=Artech+House+Publishers&rft.date=2002&rft.isbn=978-1-58053-338-6&rft.au=Fran%C3%A7ois+Le+Chevalier&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDavid_Pritchard1989" class="citation book cs1">David Pritchard (August 1989). <i>The radar war: Germany's pioneering achievement 1904-45</i>. Harpercollins. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-85260-246-8" title="Special:BookSources/978-1-85260-246-8"><bdi>978-1-85260-246-8</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+radar+war%3A+Germany%27s+pioneering+achievement+1904-45&rft.pub=Harpercollins&rft.date=1989-08&rft.isbn=978-1-85260-246-8&rft.au=David+Pritchard&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFMerrill_Ivan_Skolnik1980" class="citation book cs1">Merrill Ivan Skolnik (1 December 1980). <i>Introduction to radar systems</i>. McGraw-Hill. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-07-066572-9" title="Special:BookSources/978-0-07-066572-9"><bdi>978-0-07-066572-9</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Introduction+to+radar+systems&rft.pub=McGraw-Hill&rft.date=1980-12-01&rft.isbn=978-0-07-066572-9&rft.au=Merrill+Ivan+Skolnik&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFMerrill_Ivan_Skolnik1990" class="citation book cs1">Merrill Ivan Skolnik (1990). <i>Radar handbook</i>. McGraw-Hill Professional. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-07-057913-2" title="Special:BookSources/978-0-07-057913-2"><bdi>978-0-07-057913-2</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Radar+handbook&rft.pub=McGraw-Hill+Professional&rft.date=1990&rft.isbn=978-0-07-057913-2&rft.au=Merrill+Ivan+Skolnik&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFGeorge_W._Stimson1998" class="citation book cs1">George W. Stimson (1998). <i>Introduction to airborne radar</i>. SciTech Publishing. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-891121-01-2" title="Special:BookSources/978-1-891121-01-2"><bdi>978-1-891121-01-2</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Introduction+to+airborne+radar&rft.pub=SciTech+Publishing&rft.date=1998&rft.isbn=978-1-891121-01-2&rft.au=George+W.+Stimson&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li>Younghusband, Eileen., <i>Not an Ordinary Life. How Changing Times Brought Historical Events into my Life</i>, Cardiff Centre for Lifelong Learning, Cardiff, 2009., <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-9561156-9-0" title="Special:BookSources/978-0-9561156-9-0">978-0-9561156-9-0</a> (Pages 36–67 contain the experiences of a WAAF radar plotter in WWII.)</li> <li>Younghusband, Eileen. <i>One Woman's War</i>. Cardiff. Candy Jar Books. 2011. <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-9566826-2-8" title="Special:BookSources/978-0-9566826-2-8">978-0-9566826-2-8</a></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDavid_Zimmerman2001" class="citation book cs1">David Zimmerman (February 2001). <i>Britain's shield: radar and the defeat of the Luftwaffe</i>. Sutton Pub Ltd. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-7509-1799-5" title="Special:BookSources/978-0-7509-1799-5"><bdi>978-0-7509-1799-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Britain%27s+shield%3A+radar+and+the+defeat+of+the+Luftwaffe&rft.pub=Sutton+Pub+Ltd&rft.date=2001-02&rft.isbn=978-0-7509-1799-5&rft.au=David+Zimmerman&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li></ul> <div class="mw-heading mw-heading3"><h3 id="Technical_reading">Technical reading</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=44" title="Edit section: Technical reading"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFM_I._Skolnik1970" class="citation book cs1">M I. Skolnik, ed. (1970). <a rel="nofollow" class="external text" href="http://www.geo.uzh.ch/microsite/rsl-documents/research/SARlab/GMTILiterature/PDF/Skolnik90.pdf"><i>Radar Handbook</i></a> <span class="cs1-format">(PDF)</span>. McGraw-Hill. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-07-057913-X" title="Special:BookSources/0-07-057913-X"><bdi>0-07-057913-X</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Radar+Handbook&rft.pub=McGraw-Hill&rft.date=1970&rft.isbn=0-07-057913-X&rft_id=http%3A%2F%2Fwww.geo.uzh.ch%2Fmicrosite%2Frsl-documents%2Fresearch%2FSARlab%2FGMTILiterature%2FPDF%2FSkolnik90.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFNadav_LevanonEli_Mozeson2004" class="citation book cs1">Nadav Levanon; Eli Mozeson (2004). <i>Radar signals</i>. John Wiley & Sons, Inc. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9780471473787" title="Special:BookSources/9780471473787"><bdi>9780471473787</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Radar+signals&rft.pub=John+Wiley+%26+Sons%2C+Inc.&rft.date=2004&rft.isbn=9780471473787&rft.au=Nadav+Levanon&rft.au=Eli+Mozeson&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFHao_HeJian_LiPetre_Stoica2012" class="citation book cs1">Hao He; <a href="/wiki/Jian_Li_(engineer)" title="Jian Li (engineer)">Jian Li</a>; <a href="/wiki/Peter_Stoica" title="Peter Stoica">Petre Stoica</a> (2012). <a rel="nofollow" class="external text" href="http://www.sal.ufl.edu/book/"><i>Waveform design for active sensing systems: a computational approach</i></a>. Cambridge University Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-107-01969-0" title="Special:BookSources/978-1-107-01969-0"><bdi>978-1-107-01969-0</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Waveform+design+for+active+sensing+systems%3A+a+computational+approach&rft.pub=Cambridge+University+Press&rft.date=2012&rft.isbn=978-1-107-01969-0&rft.au=Hao+He&rft.au=Jian+Li&rft.au=Petre+Stoica&rft_id=http%3A%2F%2Fwww.sal.ufl.edu%2Fbook%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFSolomon_W._GolombGuang_Gong2005" class="citation book cs1">Solomon W. Golomb; <a href="/wiki/Guang_Gong" title="Guang Gong">Guang Gong</a> (2005). <a rel="nofollow" class="external text" href="http://www.cambridge.org/us/academic/subjects/computer-science/cryptography-cryptology-and-coding/signal-design-good-correlation-wireless-communication-cryptography-and-radar"><i>Signal design for good correlation: for wireless communication, cryptography, and radar</i></a>. Cambridge University Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0521821049" title="Special:BookSources/978-0521821049"><bdi>978-0521821049</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Signal+design+for+good+correlation%3A+for+wireless+communication%2C+cryptography%2C+and+radar&rft.pub=Cambridge+University+Press&rft.date=2005&rft.isbn=978-0521821049&rft.au=Solomon+W.+Golomb&rft.au=Guang+Gong&rft_id=http%3A%2F%2Fwww.cambridge.org%2Fus%2Facademic%2Fsubjects%2Fcomputer-science%2Fcryptography-cryptology-and-coding%2Fsignal-design-good-correlation-wireless-communication-cryptography-and-radar&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFM._Soltanalian2014" class="citation book cs1">M. Soltanalian (2014). <a rel="nofollow" class="external text" href="http://theses.eurasip.org/theses/573/signal-design-for-active-sensing-and/download/"><i>Signal Design for Active Sensing and Communications</i></a>. Elanders Sverige AB. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-91-554-9017-1" title="Special:BookSources/978-91-554-9017-1"><bdi>978-91-554-9017-1</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Signal+Design+for+Active+Sensing+and+Communications&rft.pub=Elanders+Sverige+AB&rft.date=2014&rft.isbn=978-91-554-9017-1&rft.au=M.+Soltanalian&rft_id=http%3A%2F%2Ftheses.eurasip.org%2Ftheses%2F573%2Fsignal-design-for-active-sensing-and%2Fdownload%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span> <span class="cs1-visible-error citation-comment"><code class="cs1-code">{{<a href="/wiki/Template:Cite_book" title="Template:Cite book">cite book</a>}}</code>: </span><span class="cs1-visible-error citation-comment"><code class="cs1-code">|work=</code> ignored (<a href="/wiki/Help:CS1_errors#periodical_ignored" title="Help:CS1 errors">help</a>)</span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFFulvio_GiniAntonio_De_MaioLee_Patton2012" class="citation book cs1">Fulvio Gini; Antonio De Maio; Lee Patton, eds. (2012). <i>Waveform design and diversity for advanced radar systems</i>. London: The Institution of Engineering and Technology. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1849192651" title="Special:BookSources/978-1849192651"><bdi>978-1849192651</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Waveform+design+and+diversity+for+advanced+radar+systems&rft.place=London&rft.pub=The+Institution+of+Engineering+and+Technology&rft.date=2012&rft.isbn=978-1849192651&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFE._FishlerA._HaimovichR._BlumD._Chizhik2004" class="citation conference cs1">E. Fishler; A. Haimovich; R. Blum; D. Chizhik; L. Cimini; R. Valenzuela (2004). <i>MIMO radar: an idea whose time has come</i>. IEEE Radar Conference.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=conference&rft.btitle=MIMO+radar%3A+an+idea+whose+time+has+come&rft.date=2004&rft.au=E.+Fishler&rft.au=A.+Haimovich&rft.au=R.+Blum&rft.au=D.+Chizhik&rft.au=L.+Cimini&rft.au=R.+Valenzuela&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFMark_R._Bell1993" class="citation journal cs1">Mark R. Bell (1993). "Information theory and radar waveform design". <i>IEEE Transactions on Information Theory</i>. <b>39</b> (5): <span class="nowrap">1578–</span>1597. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1109%2F18.259642">10.1109/18.259642</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=IEEE+Transactions+on+Information+Theory&rft.atitle=Information+theory+and+radar+waveform+design.&rft.volume=39&rft.issue=5&rft.pages=%3Cspan+class%3D%22nowrap%22%3E1578-%3C%2Fspan%3E1597&rft.date=1993&rft_id=info%3Adoi%2F10.1109%2F18.259642&rft.au=Mark+R.+Bell&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFRobert_CalderbankS._HowardBill_Moran2009" class="citation journal cs1">Robert Calderbank; S. Howard; Bill Moran (2009). "Waveform diversity in radar signal processing". <i>IEEE Signal Processing Magazine</i>. <b>26</b> (1): <span class="nowrap">32–</span>41. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2009ISPM...26...32C">2009ISPM...26...32C</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1109%2FMSP.2008.930414">10.1109/MSP.2008.930414</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:16437755">16437755</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=IEEE+Signal+Processing+Magazine&rft.atitle=Waveform+diversity+in+radar+signal+processing&rft.volume=26&rft.issue=1&rft.pages=%3Cspan+class%3D%22nowrap%22%3E32-%3C%2Fspan%3E41&rft.date=2009&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A16437755%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1109%2FMSP.2008.930414&rft_id=info%3Abibcode%2F2009ISPM...26...32C&rft.au=Robert+Calderbank&rft.au=S.+Howard&rft.au=Bill+Moran&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFMark_A._RichardsJames_A._ScheerWilliam_A._Holm2010" class="citation book cs1">Mark A. Richards; James A. Scheer; William A. Holm (2010). <i>Principles of Modern Radar: Basic Principles</i>. SciTech Publishing. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1891121-52-4" title="Special:BookSources/978-1891121-52-4"><bdi>978-1891121-52-4</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Principles+of+Modern+Radar%3A+Basic+Principles&rft.pub=SciTech+Publishing&rft.date=2010&rft.isbn=978-1891121-52-4&rft.au=Mark+A.+Richards&rft.au=James+A.+Scheer&rft.au=William+A.+Holm&rfr_id=info%3Asid%2Fen.wikipedia.org%3ARadar" class="Z3988"></span></li></ul> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Radar&action=edit&section=45" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style 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class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/99/Wiktionary-logo-en-v2.svg/60px-Wiktionary-logo-en-v2.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/99/Wiktionary-logo-en-v2.svg/120px-Wiktionary-logo-en-v2.svg.png 2x" data-file-width="512" data-file-height="512" /></a></span></div> <div class="side-box-text plainlist">Look up <i><b><a href="https://en.wiktionary.org/wiki/Special:Search/radar" class="extiw" title="wiktionary:Special:Search/radar">radar</a></b></i> in Wiktionary, the free dictionary.</div></div> </div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1235681985" /><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1237033735" /><div class="side-box side-box-right plainlinks sistersitebox"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409" /> <div class="side-box-flex"> <div class="side-box-image"><span class="noviewer" typeof="mw:File"><a href="/wiki/File:Commons-logo.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/40px-Commons-logo.svg.png" decoding="async" width="30" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/60px-Commons-logo.svg.png 1.5x" data-file-width="1024" data-file-height="1376" /></a></span></div> <div class="side-box-text plainlist">Wikimedia Commons has media related to <a href="https://commons.wikimedia.org/wiki/Radar" class="extiw" title="commons:Radar"><span style="font-style:italic; font-weight:bold;">Radar</span></a>.</div></div> </div> <ul><li><a rel="nofollow" class="external text" href="http://ocw.mit.edu/resources/res-ll-001-introduction-to-radar-systems-spring-2007/">MIT Video Course: Introduction to Radar Systems</a> A set of 10 video lectures developed at Lincoln Laboratory to develop an understanding of radar systems and technologies.</li> <li><a rel="nofollow" class="external text" href="https://www.radartutorial.eu/html/video.en.html">A set of educational videos created for air traffic control (ATC) staff.</a></li> <li><a rel="nofollow" class="external text" href="https://cambridgepixel.com/support/radar-terminology/">Glossary of radar terminology</a></li></ul> <p><br /> </p> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist ul 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.navbox-abovebelow,.mw-parser-output .navbox-group,.mw-parser-output .navbox-subgroup .navbox-title{background-color:#ddf}.mw-parser-output .navbox-subgroup .navbox-group,.mw-parser-output .navbox-subgroup .navbox-abovebelow{background-color:#e6e6ff}.mw-parser-output .navbox-even{background-color:#f7f7f7}.mw-parser-output .navbox-odd{background-color:transparent}.mw-parser-output .navbox .hlist td dl,.mw-parser-output .navbox .hlist td ol,.mw-parser-output .navbox .hlist td ul,.mw-parser-output .navbox td.hlist dl,.mw-parser-output .navbox td.hlist ol,.mw-parser-output .navbox td.hlist ul{padding:0.125em 0}.mw-parser-output .navbox .navbar{display:block;font-size:100%}.mw-parser-output .navbox-title .navbar{float:left;text-align:left;margin-right:0.5em}body.skin--responsive .mw-parser-output .navbox-image img{max-width:none!important}@media print{body.ns-0 .mw-parser-output .navbox{display:none!important}}</style></div><div role="navigation" class="navbox" aria-labelledby="NATO_naval_weapons_systems62" style="padding:3px"><table class="nowraplinks hlist mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374" /><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Naval_weapons_systems" title="Template:Naval weapons systems"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Naval_weapons_systems" title="Template talk:Naval weapons systems"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Naval_weapons_systems" title="Special:EditPage/Template:Naval weapons systems"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="NATO_naval_weapons_systems62" style="font-size:114%;margin:0 4em">NATO naval weapons systems</div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">General</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Naval_warfare" title="Naval warfare">Naval warfare</a></li> <li><a href="/wiki/Fire-control_system" title="Fire-control system">Fire-control system</a></li> <li><a href="/wiki/Fire-control_radar" title="Fire-control radar">Fire-control radar</a></li> <li><a href="/wiki/Director_(military)" title="Director (military)">Director (military)</a></li> <li><a href="/wiki/Combat_information_center" title="Combat information center">Combat information center</a></li> <li><a href="/wiki/Sonar" title="Sonar">Sonar</a></li> <li><a class="mw-selflink selflink">Radar</a></li> <li><i>Historical:</i></li> <li><a href="/wiki/Ship_gun_fire-control_system" title="Ship gun fire-control system">Ship gun fire-control system</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Weapons</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Naval_artillery" title="Naval artillery">Naval artillery</a></li> <li><a href="/wiki/Guided_missiles" class="mw-redirect" title="Guided missiles">Guided missiles</a></li> <li><a href="/wiki/Torpedoes" class="mw-redirect" title="Torpedoes">Torpedoes</a></li> <li><a href="/wiki/Depth_charges" class="mw-redirect" title="Depth charges">Depth charges</a></li> <li><a href="/wiki/Close-in_weapon_system" title="Close-in weapon system">Close-in weapon system</a></li> <li><a href="/wiki/Naval_mines" class="mw-redirect" title="Naval mines">Naval mines</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Specific systems</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Aegis_Combat_System" title="Aegis Combat System">Aegis Combat System</a></li> <li><a href="/wiki/Aegis_Ballistic_Missile_Defense_System" title="Aegis Ballistic Missile Defense System">Aegis Ballistic Missile Defense System</a></li> <li><a href="/wiki/Active_electronically_scanned_array" title="Active electronically scanned array">Active electronically scanned array</a></li> <li><a href="/wiki/Joint_Tactical_Information_Distribution_System" title="Joint Tactical Information Distribution System">Joint Tactical Information Distribution System</a></li> <li><i>Historical systems:</i></li> <li><a href="/wiki/Nike_Zeus" title="Nike Zeus">Nike Zeus</a></li> <li><i>Lists:</i></li> <li><a href="/wiki/List_of_radars" title="List of radars">List of radars</a></li> <li><a href="/wiki/List_of_radar_types" title="List of radar types">List of radar types</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Sensors</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th id="Radar5" scope="row" class="navbox-group" style="width:1%">Radar</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/OPS-24" title="OPS-24">OPS-24</a></li> <li><a href="/wiki/AN/SPY-1" title="AN/SPY-1">AN/SPY-1</a></li> <li><a href="/wiki/AN/SPY-3" title="AN/SPY-3">AN/SPY-3</a></li> <li><a href="/wiki/AN/SPY-6" title="AN/SPY-6">AN/SPY-6 Air and Missile Defense Radar (AMDR)</a></li> <li><a href="/wiki/Sea-based_X-band_radar" title="Sea-based X-band radar">Sea-based X-band radar (SBX-1)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Optical</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Space-Based_Infrared_System" title="Space-Based Infrared System">Space-Based Infrared System (SBIRS)</a></li> <li><a href="/wiki/Space_Tracking_and_Surveillance_System" title="Space Tracking and Surveillance System">Space Tracking and Surveillance System (STSS)</a></li> <li><a href="/wiki/Space_Surveillance_Telescope" title="Space Surveillance Telescope">Space Surveillance Telescope (SST)</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Naval missiles</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Harpoon_missile" class="mw-redirect" title="Harpoon missile">Harpoon missile</a></li> <li><a href="/wiki/RIM-67_Standard" title="RIM-67 Standard">RIM-67 Standard (SM-2)</a></li> <li><a href="/wiki/MIM-104#MIM-104F_(PAC-3)" class="mw-redirect" title="MIM-104">MIM-104F (PAC-3)</a></li> <li><a href="/wiki/RIM-161_Standard_Missile_3" title="RIM-161 Standard Missile 3">RIM-161 Standard Missile 3 (SM-3)</a></li> <li><a href="/wiki/RIM-174_Standard_ERAM" title="RIM-174 Standard ERAM">RIM-174 Standard Extended Range Active Missile (SM-6)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Historical</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Radar_in_World_War_II" title="Radar in World War II">Radar in World War II</a></li> <li><a href="/wiki/Rangekeeper" title="Rangekeeper">Rangekeeper</a></li> <li><a href="/wiki/Torpedo_Data_Computer" title="Torpedo Data Computer">Torpedo Data Computer</a></li> <li><i>Ship systems:</i></li> <li><a href="/wiki/Naval_Tactical_Data_System" title="Naval Tactical Data System">Naval Tactical Data System</a></li> <li><a href="/wiki/Comprehensive_Display_System" title="Comprehensive Display System">Comprehensive Display System</a></li> <li><a href="/wiki/Sonar#ASDIC" title="Sonar">ASDIC</a></li> <li><i>Specific equipment:</i></li> <li><a href="/wiki/Mark_I_Fire_Control_Computer" title="Mark I Fire Control Computer">Mark I Fire Control Computer</a></li> <li><a href="/wiki/Mark_8_Fire_Control_Computer" title="Mark 8 Fire Control Computer">Mark 8 Fire Control Computer</a></li> <li><i>Navboxes:</i></li> <li><span class="nowrap">{{</span><a href="/wiki/Template:USN_early_guided_weapons" title="Template:USN early guided weapons">USN early guided weapons</a><span class="nowrap">}}</span></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><i>Ground-based systems:</i></li> <li><a href="/wiki/Gun_data_computer" title="Gun data computer">Gun data computer</a></li> <li><a href="/wiki/Kerrison_Predictor" title="Kerrison Predictor">Kerrison Predictor</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><a href="/wiki/Navy" title="Navy">Navy</a></li> <li><a href="/wiki/Naval_combat" class="mw-redirect" title="Naval combat">Naval combat</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374" /><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235" /><style data-mw-deduplicate="TemplateStyles:r1038841319">.mw-parser-output .tooltip-dotted{border-bottom:1px dotted;cursor:help}</style><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1038841319" /><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1038841319" /><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1038841319" /></div><div role="navigation" class="navbox authority-control" aria-label="Navbox1618" style="padding:3px"><table class="nowraplinks hlist navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Help:Authority_control" title="Help:Authority control">Authority control databases</a>: National <span class="mw-valign-text-top noprint" typeof="mw:File/Frameless"><a href="https://www.wikidata.org/wiki/Q47528#identifiers" title="Edit this at Wikidata"><img alt="Edit this at Wikidata" src="//upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/10px-OOjs_UI_icon_edit-ltr-progressive.svg.png" decoding="async" width="10" height="10" class="mw-file-element" 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href="https://catalogue.bnf.fr/ark:/12148/cb119772298">France</a></span></span></li><li><span class="uid"><span class="rt-commentedText tooltip tooltip-dotted" title="Radar"><a rel="nofollow" class="external text" href="https://data.bnf.fr/ark:/12148/cb119772298">BnF data</a></span></span></li><li><span class="uid"><span class="rt-commentedText tooltip tooltip-dotted" title="radary"><a rel="nofollow" class="external text" href="https://aleph.nkp.cz/F/?func=find-c&local_base=aut&ccl_term=ica=ph124969&CON_LNG=ENG">Czech Republic</a></span></span></li><li><span class="uid"><a rel="nofollow" class="external text" href="https://kopkatalogs.lv/F?func=direct&local_base=lnc10&doc_number=000067195&P_CON_LNG=ENG">Latvia</a></span></li><li><span class="uid"><a rel="nofollow" class="external text" href="https://www.nli.org.il/en/authorities/987007555988905171">Israel</a></span></li></ul></div></td></tr></tbody></table></div>    </div><noscript><img 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