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class="vector-toc-link" href="#Continuous_waves"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Continuous waves</span> </div> </a> <ul id="toc-Continuous_waves-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Early_technologies" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Early_technologies"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>Early technologies</span> </div> </a> <ul id="toc-Early_technologies-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Vacuum_tubes" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Vacuum_tubes"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.3</span> <span>Vacuum tubes</span> </div> </a> <ul id="toc-Vacuum_tubes-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Single-sideband" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Single-sideband"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.4</span> <span>Single-sideband</span> </div> </a> <ul id="toc-Single-sideband-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Analysis" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Analysis"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Analysis</span> </div> </a> <ul id="toc-Analysis-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Spectrum" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Spectrum"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Spectrum</span> </div> </a> <ul id="toc-Spectrum-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Power_and_spectrum_efficiency" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Power_and_spectrum_efficiency"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>Power and spectrum efficiency</span> </div> </a> <ul id="toc-Power_and_spectrum_efficiency-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Modulation_index" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Modulation_index"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>Modulation index</span> </div> </a> <ul id="toc-Modulation_index-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Modulation_methods" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Modulation_methods"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>Modulation methods</span> </div> </a> <button aria-controls="toc-Modulation_methods-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 Modulation methods subsection</span> </button> <ul id="toc-Modulation_methods-sublist" class="vector-toc-list"> <li id="toc-Low-level_generation" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Low-level_generation"> <div class="vector-toc-text"> <span class="vector-toc-numb">8.1</span> <span>Low-level generation</span> </div> </a> <ul id="toc-Low-level_generation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-High-level_generation" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#High-level_generation"> <div class="vector-toc-text"> <span class="vector-toc-numb">8.2</span> <span>High-level generation</span> </div> </a> <ul id="toc-High-level_generation-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Demodulation_methods" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Demodulation_methods"> <div class="vector-toc-text"> <span class="vector-toc-numb">9</span> <span>Demodulation methods</span> </div> </a> <ul id="toc-Demodulation_methods-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">10</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">11</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Bibliography" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Bibliography"> <div class="vector-toc-text"> <span class="vector-toc-numb">12</span> <span>Bibliography</span> </div> </a> <ul id="toc-Bibliography-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">13</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" > <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">Amplitude modulation</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 55 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-55" 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">55 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-am mw-list-item"><a href="https://am.wikipedia.org/wiki/%E1%89%81%E1%88%98%E1%89%B5_%E1%88%98%E1%8A%A8%E1%88%AD%E1%8A%A8%E1%88%9D" title="ቁመት መከርከም – Amharic" lang="am" hreflang="am" data-title="ቁመት መከርከም" data-language-autonym="አማርኛ" data-language-local-name="Amharic" class="interlanguage-link-target"><span>አማርኛ</span></a></li><li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D8%AA%D8%B6%D9%85%D9%8A%D9%86_%D8%A7%D9%84%D8%B3%D8%B9%D8%A9" title="تضمين السعة – Arabic" lang="ar" hreflang="ar" data-title="تضمين السعة" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-az mw-list-item"><a href="https://az.wikipedia.org/wiki/Amplitud_modulyasiyas%C4%B1" title="Amplitud modulyasiyası – Azerbaijani" lang="az" hreflang="az" data-title="Amplitud modulyasiyası" data-language-autonym="Azərbaycanca" data-language-local-name="Azerbaijani" class="interlanguage-link-target"><span>Azərbaycanca</span></a></li><li class="interlanguage-link interwiki-be mw-list-item"><a href="https://be.wikipedia.org/wiki/%D0%90%D0%BC%D0%BF%D0%BB%D1%96%D1%82%D1%83%D0%B4%D0%BD%D0%B0%D1%8F_%D0%BC%D0%B0%D0%B4%D1%83%D0%BB%D1%8F%D1%86%D1%8B%D1%8F" title="Амплітудная мадуляцыя – Belarusian" lang="be" hreflang="be" data-title="Амплітудная мадуляцыя" data-language-autonym="Беларуская" data-language-local-name="Belarusian" class="interlanguage-link-target"><span>Беларуская</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%90%D0%BC%D0%BF%D0%BB%D0%B8%D1%82%D1%83%D0%B4%D0%BD%D0%B0_%D0%BC%D0%BE%D0%B4%D1%83%D0%BB%D0%B0%D1%86%D0%B8%D1%8F" title="Амплитудна модулация – Bulgarian" lang="bg" hreflang="bg" data-title="Амплитудна модулация" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target"><span>Български</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Amplitud_modulada" title="Amplitud modulada – Catalan" lang="ca" hreflang="ca" data-title="Amplitud modulada" 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/Amplitudov%C3%A1_modulace" title="Amplitudová modulace – Czech" lang="cs" hreflang="cs" data-title="Amplitudová modulace" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Amplitudemodulation" title="Amplitudemodulation – Danish" lang="da" hreflang="da" data-title="Amplitudemodulation" 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/Amplitudenmodulation" title="Amplitudenmodulation – German" lang="de" hreflang="de" data-title="Amplitudenmodulation" 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/Amplituudmodulatsioon" title="Amplituudmodulatsioon – Estonian" lang="et" hreflang="et" data-title="Amplituudmodulatsioon" 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%94%CE%B9%CE%B1%CE%BC%CF%8C%CF%81%CF%86%CF%89%CF%83%CE%B7_%CF%80%CE%BB%CE%AC%CF%84%CE%BF%CF%85%CF%82" title="Διαμόρφωση πλάτους – Greek" lang="el" hreflang="el" data-title="Διαμόρφωση πλάτους" 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/Amplitud_modulada" title="Amplitud modulada – Spanish" lang="es" hreflang="es" data-title="Amplitud modulada" 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/Amplitudmodulado" title="Amplitudmodulado – Esperanto" lang="eo" hreflang="eo" data-title="Amplitudmodulado" 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/Anplitude_Modulatu" title="Anplitude Modulatu – Basque" lang="eu" hreflang="eu" data-title="Anplitude Modulatu" 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/%D9%85%D8%AF%D9%88%D9%84%D9%87%E2%80%8C%D8%B3%D8%A7%D8%B2%DB%8C_%D8%AF%D8%A7%D9%85%D9%86%D9%87" title="مدوله‌سازی دامنه – Persian" lang="fa" hreflang="fa" data-title="مدوله‌سازی دامنه" 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/Modulation_d%27amplitude" title="Modulation d'amplitude – French" lang="fr" hreflang="fr" data-title="Modulation d'amplitude" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ga mw-list-item"><a href="https://ga.wikipedia.org/wiki/Modhn%C3%BA_aimpliti%C3%BAide" title="Modhnú aimplitiúide – Irish" lang="ga" hreflang="ga" data-title="Modhnú aimplitiúide" data-language-autonym="Gaeilge" data-language-local-name="Irish" class="interlanguage-link-target"><span>Gaeilge</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EC%A7%84%ED%8F%AD_%EB%B3%80%EC%A1%B0" title="진폭 변조 – Korean" lang="ko" hreflang="ko" data-title="진폭 변조" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hy mw-list-item"><a href="https://hy.wikipedia.org/wiki/%D4%B1%D5%B4%D5%BA%D5%AC%D5%AB%D5%BF%D5%B8%D6%82%D5%A4%D5%A1%D5%B5%D5%AB%D5%B6_%D5%B4%D5%B8%D5%A4%D5%B8%D6%82%D5%AC%D5%A1%D6%81%D5%AB%D5%A1" title="Ամպլիտուդային մոդուլացիա – Armenian" lang="hy" hreflang="hy" data-title="Ամպլիտուդային մոդուլացիա" data-language-autonym="Հայերեն" data-language-local-name="Armenian" class="interlanguage-link-target"><span>Հայերեն</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Amplitudna_modulacija" title="Amplitudna modulacija – Croatian" lang="hr" hreflang="hr" data-title="Amplitudna modulacija" 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/Modulasi_amplitudo" title="Modulasi amplitudo – Indonesian" lang="id" hreflang="id" data-title="Modulasi amplitudo" 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-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Modulazione_di_ampiezza" title="Modulazione di ampiezza – Italian" lang="it" hreflang="it" data-title="Modulazione di ampiezza" 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%90%D7%A4%D7%A0%D7%95%D7%9F_%D7%9E%D7%A9%D7%A8%D7%A2%D7%AA" title="אפנון משרעת – Hebrew" lang="he" hreflang="he" data-title="אפנון משרעת" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-kk mw-list-item"><a href="https://kk.wikipedia.org/wiki/%D0%90%D0%BC%D0%BF%D0%BB%D0%B8%D1%82%D1%83%D0%B4%D0%B0%D0%BB%D1%8B%D2%9B_%D0%BC%D0%BE%D0%B4%D1%83%D0%BB%D1%8F%D1%86%D0%B8%D1%8F" title="Амплитудалық модуляция – Kazakh" lang="kk" hreflang="kk" data-title="Амплитудалық модуляция" data-language-autonym="Қазақша" data-language-local-name="Kazakh" class="interlanguage-link-target"><span>Қазақша</span></a></li><li class="interlanguage-link interwiki-lv mw-list-item"><a href="https://lv.wikipedia.org/wiki/Amplit%C5%ABdas_modul%C4%81cija" title="Amplitūdas modulācija – Latvian" lang="lv" hreflang="lv" data-title="Amplitūdas modulācija" data-language-autonym="Latviešu" data-language-local-name="Latvian" class="interlanguage-link-target"><span>Latviešu</span></a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/Amplit%C3%BAd%C3%B3modul%C3%A1ci%C3%B3" title="Amplitúdómoduláció – Hungarian" lang="hu" hreflang="hu" data-title="Amplitúdómoduláció" data-language-autonym="Magyar" data-language-local-name="Hungarian" class="interlanguage-link-target"><span>Magyar</span></a></li><li class="interlanguage-link interwiki-mk mw-list-item"><a href="https://mk.wikipedia.org/wiki/%D0%97%D0%B0%D0%BC%D0%B0%D0%B2%D0%BD%D0%B0_%D0%BC%D0%BE%D0%B4%D1%83%D0%BB%D0%B0%D1%86%D0%B8%D1%98%D0%B0" title="Замавна модулација – Macedonian" lang="mk" hreflang="mk" data-title="Замавна модулација" data-language-autonym="Македонски" data-language-local-name="Macedonian" class="interlanguage-link-target"><span>Македонски</span></a></li><li class="interlanguage-link interwiki-ml mw-list-item"><a href="https://ml.wikipedia.org/wiki/%E0%B4%86%E0%B4%82%E0%B4%AA%E0%B5%8D%E0%B4%B2%E0%B4%BF%E0%B4%B1%E0%B5%8D%E0%B4%B1%E0%B5%8D%E0%B4%AF%E0%B5%82%E0%B4%A1%E0%B5%8D_%E0%B4%AE%E0%B5%8B%E0%B4%A1%E0%B5%81%E0%B4%B2%E0%B5%87%E0%B4%B7%E0%B5%BB" title="ആംപ്ലിറ്റ്യൂഡ് മോഡുലേഷൻ – Malayalam" lang="ml" hreflang="ml" data-title="ആംപ്ലിറ്റ്യൂഡ് മോഡുലേഷൻ" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target"><span>മലയാളം</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Modulasi_amplitud" title="Modulasi amplitud – Malay" lang="ms" hreflang="ms" data-title="Modulasi amplitud" 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-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Amplitudemodulatie" title="Amplitudemodulatie – Dutch" lang="nl" hreflang="nl" data-title="Amplitudemodulatie" 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/%E6%8C%AF%E5%B9%85%E5%A4%89%E8%AA%BF" title="振幅変調 – Japanese" lang="ja" hreflang="ja" data-title="振幅変調" 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-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Amplitudemodulasjon" title="Amplitudemodulasjon – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Amplitudemodulasjon" 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/Amplitudemodulasjon" title="Amplitudemodulasjon – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Amplitudemodulasjon" 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-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Modulacja_amplitudy" title="Modulacja amplitudy – Polish" lang="pl" hreflang="pl" data-title="Modulacja amplitudy" 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/Modula%C3%A7%C3%A3o_em_amplitude" title="Modulação em amplitude – Portuguese" lang="pt" hreflang="pt" data-title="Modulação em amplitude" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ro mw-list-item"><a href="https://ro.wikipedia.org/wiki/Modula%C8%9Bie_de_amplitudine" title="Modulație de amplitudine – Romanian" lang="ro" hreflang="ro" data-title="Modulație de amplitudine" 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%90%D0%BC%D0%BF%D0%BB%D0%B8%D1%82%D1%83%D0%B4%D0%BD%D0%B0%D1%8F_%D0%BC%D0%BE%D0%B4%D1%83%D0%BB%D1%8F%D1%86%D0%B8%D1%8F" title="Амплитудная модуляция – Russian" lang="ru" hreflang="ru" data-title="Амплитудная модуляция" 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/Modulimi_i_amplitud%C3%ABs" title="Modulimi i amplitudës – Albanian" lang="sq" hreflang="sq" data-title="Modulimi i amplitudës" data-language-autonym="Shqip" data-language-local-name="Albanian" class="interlanguage-link-target"><span>Shqip</span></a></li><li class="interlanguage-link interwiki-si mw-list-item"><a href="https://si.wikipedia.org/wiki/%E0%B7%80%E0%B7%92%E0%B7%83%E0%B7%8A%E0%B6%AD%E0%B7%8F%E0%B6%BB_%E0%B6%B8%E0%B7%96%E0%B6%BB%E0%B7%8A%E0%B6%A2%E0%B6%B1%E0%B6%BA" title="විස්තාර මූර්ජනය – Sinhala" lang="si" hreflang="si" data-title="විස්තාර මූර්ජනය" 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/Amplitude_modulation" title="Amplitude modulation – Simple English" lang="en-simple" hreflang="en-simple" data-title="Amplitude modulation" 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-sd mw-list-item"><a href="https://sd.wikipedia.org/wiki/%D8%A7%D9%8A%D9%85%D9%BE%D9%84%D9%8A%D9%BD%D9%8A%D9%88%DA%8A_%D9%85%D8%A7%DA%8A%D9%8A%D9%88%D9%84%D9%8A%D8%B4%D9%86" title="ايمپليٽيوڊ ماڊيوليشن – Sindhi" lang="sd" hreflang="sd" data-title="ايمپليٽيوڊ ماڊيوليشن" data-language-autonym="سنڌي" data-language-local-name="Sindhi" class="interlanguage-link-target"><span>سنڌي</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Amplit%C3%BAdov%C3%A1_modul%C3%A1cia" title="Amplitúdová modulácia – Slovak" lang="sk" hreflang="sk" data-title="Amplitúdová modulácia" 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/Amplitudna_modulacija" title="Amplitudna modulacija – Slovenian" lang="sl" hreflang="sl" data-title="Amplitudna modulacija" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" class="interlanguage-link-target"><span>Slovenščina</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/%D0%90%D0%BC%D0%BF%D0%BB%D0%B8%D1%82%D1%83%D0%B4%D1%81%D0%BA%D0%B0_%D0%BC%D0%BE%D0%B4%D1%83%D0%BB%D0%B0%D1%86%D0%B8%D1%98%D0%B0" title="Амплитудска модулација – Serbian" lang="sr" hreflang="sr" data-title="Амплитудска модулација" 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/Amplitudska_modulacija" title="Amplitudska modulacija – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Amplitudska modulacija" 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-su mw-list-item"><a href="https://su.wikipedia.org/wiki/Modulasi_amplitudo" title="Modulasi amplitudo – Sundanese" lang="su" hreflang="su" data-title="Modulasi amplitudo" data-language-autonym="Sunda" data-language-local-name="Sundanese" class="interlanguage-link-target"><span>Sunda</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Amplitudimodulaatio" title="Amplitudimodulaatio – Finnish" lang="fi" hreflang="fi" data-title="Amplitudimodulaatio" 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/Amplitudmodulering" title="Amplitudmodulering – Swedish" lang="sv" hreflang="sv" data-title="Amplitudmodulering" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-ta badge-Q17437798 badge-goodarticle mw-list-item" title="good article badge"><a href="https://ta.wikipedia.org/wiki/%E0%AE%B5%E0%AF%80%E0%AE%9A%E0%AF%8D%E0%AE%9A%E0%AF%81%E0%AE%AA%E0%AF%8D_%E0%AE%AA%E0%AE%A3%E0%AF%8D%E0%AE%AA%E0%AF%87%E0%AE%B1%E0%AF%8D%E0%AE%B1%E0%AE%AE%E0%AF%8D" title="வீச்சுப் பண்பேற்றம் – Tamil" lang="ta" hreflang="ta" data-title="வீச்சுப் பண்பேற்றம்" data-language-autonym="தமிழ்" data-language-local-name="Tamil" class="interlanguage-link-target"><span>தமிழ்</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/%E0%B8%81%E0%B8%B2%E0%B8%A3%E0%B8%81%E0%B8%A5%E0%B9%89%E0%B8%B3%E0%B9%81%E0%B8%AD%E0%B8%A1%E0%B8%9E%E0%B8%A5%E0%B8%B4%E0%B8%88%E0%B8%B9%E0%B8%94" title="การกล้ำแอมพลิจูด – Thai" lang="th" hreflang="th" data-title="การกล้ำแอมพลิจูด" 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/Genlik_mod%C3%BClasyonu" title="Genlik modülasyonu – Turkish" lang="tr" hreflang="tr" data-title="Genlik modülasyonu" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%90%D0%BC%D0%BF%D0%BB%D1%96%D1%82%D1%83%D0%B4%D0%BD%D0%B0_%D0%BC%D0%BE%D0%B4%D1%83%D0%BB%D1%8F%D1%86%D1%96%D1%8F" title="Амплітудна модуляція – Ukrainian" lang="uk" hreflang="uk" data-title="Амплітудна модуляція" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/%C4%90i%E1%BB%81u_ch%E1%BA%BF_bi%C3%AAn_%C4%91%E1%BB%99" title="Điều chế biên độ – Vietnamese" lang="vi" hreflang="vi" data-title="Điều chế biên độ" 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-wuu mw-list-item"><a href="https://wuu.wikipedia.org/wiki/%E5%B9%85%E5%BA%A6%E8%B0%83%E5%88%B6" title="幅度调制 – Wu" lang="wuu" hreflang="wuu" data-title="幅度调制" 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 mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E6%8C%AF%E5%B9%85%E8%AA%BF%E8%AE%8A" title="振幅調變 – Chinese" lang="zh" hreflang="zh" data-title="振幅調變" 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 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id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Radio modulation via wave amplitude</div> <p class="mw-empty-elt"> </p> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Amfm3-en-de.gif" class="mw-file-description"><img alt="Animation of audio, AM and FM modulated carriers." src="//upload.wikimedia.org/wikipedia/commons/thumb/a/a4/Amfm3-en-de.gif/250px-Amfm3-en-de.gif" decoding="async" width="250" height="195" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/a/a4/Amfm3-en-de.gif 1.5x" data-file-width="256" data-file-height="200" /></a><figcaption>Figure 1: An audio signal (top) may be carried by a <a href="/wiki/Carrier_signal" class="mw-redirect" title="Carrier signal">carrier signal</a> using AM or FM methods.</figcaption></figure> <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 ol,.mw-parser-output .hlist ul ul{display:inline}.mw-parser-output .hlist .mw-empty-li{display:none}.mw-parser-output .hlist dt::after{content:": "}.mw-parser-output .hlist dd::after,.mw-parser-output .hlist li::after{content:" · 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.sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media print{body.ns-0 .mw-parser-output .sidebar{display:none!important}}</style><table class="sidebar nomobile nowraplinks"><tbody><tr><th class="sidebar-title" style="background-color: #bdb"><a href="/wiki/Passband" title="Passband">Passband</a> <a href="/wiki/Modulation" title="Modulation">modulation</a></th></tr><tr><td class="sidebar-image"><span typeof="mw:File"><a href="/wiki/File:Modulation_categorization.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e7/Modulation_categorization.svg/300px-Modulation_categorization.svg.png" decoding="async" width="300" height="72" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e7/Modulation_categorization.svg/450px-Modulation_categorization.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e7/Modulation_categorization.svg/600px-Modulation_categorization.svg.png 2x" data-file-width="1565" data-file-height="374" /></a></span></td></tr><tr><th class="sidebar-heading" style="background-color: #cfc"> <a href="/wiki/Modulation#Analog_modulation_methods" title="Modulation">Analog modulation</a></th></tr><tr><td class="sidebar-content hlist"> <ul><li><a class="mw-selflink selflink">AM</a></li> <li><a href="/wiki/Frequency_modulation" title="Frequency modulation">FM</a></li> <li><a href="/wiki/Phase_modulation" title="Phase modulation">PM</a></li> <li><a href="/wiki/Quadrature_amplitude_modulation" title="Quadrature amplitude modulation">QAM</a></li> <li><a href="/wiki/Space_modulation" title="Space modulation">SM</a></li> <li><a href="/wiki/Single-sideband_modulation" title="Single-sideband modulation">SSB</a></li></ul></td> </tr><tr><th class="sidebar-heading" style="background-color: #cfc"> <a href="/wiki/Modulation#Digital_modulation_methods" title="Modulation">Digital modulation</a></th></tr><tr><td class="sidebar-content hlist"> <ul><li><a href="/wiki/Amplitude-shift_keying" title="Amplitude-shift keying">ASK</a></li> <li><a href="/wiki/Amplitude_and_phase-shift_keying" title="Amplitude and phase-shift keying">APSK</a></li> <li><a href="/wiki/Continuous_phase_modulation" title="Continuous phase modulation">CPM</a></li> <li><a href="/wiki/Frequency-shift_keying" title="Frequency-shift keying">FSK</a></li> <li><a href="/wiki/Multiple_frequency-shift_keying" title="Multiple frequency-shift keying">MFSK</a></li> <li><a href="/wiki/Minimum-shift_keying" title="Minimum-shift keying">MSK</a></li> <li><a href="/wiki/On%E2%80%93off_keying" title="On–off keying">OOK</a></li> <li><a href="/wiki/Pulse-position_modulation" title="Pulse-position modulation">PPM</a></li> <li><a href="/wiki/Phase-shift_keying" title="Phase-shift keying">PSK</a></li> <li><a href="/wiki/Quadrature_amplitude_modulation" title="Quadrature amplitude modulation">QAM</a></li> <li><a href="/wiki/Single-carrier_FDMA" title="Single-carrier FDMA">SC-FDE</a></li> <li><a href="/wiki/Trellis_coded_modulation" title="Trellis coded modulation">TCM</a></li> <li><a href="/wiki/TC-PAM" title="TC-PAM">TC-PAM</a></li> <li><a href="/wiki/Wavelet_modulation" title="Wavelet modulation">WDM</a></li></ul></td> </tr><tr><th class="sidebar-heading" style="background-color: #cfc"> <a href="/wiki/Hierarchical_modulation" title="Hierarchical modulation">Hierarchical modulation</a></th></tr><tr><td class="sidebar-content hlist"> <ul><li><a href="/wiki/Quadrature_amplitude_modulation" title="Quadrature amplitude modulation">QAM</a></li> <li><a href="/wiki/Wavelet_modulation" title="Wavelet modulation">WDM</a></li></ul></td> </tr><tr><th class="sidebar-heading" style="background-color: #cfc"> <a href="/wiki/Spread_spectrum" title="Spread spectrum">Spread spectrum</a></th></tr><tr><td class="sidebar-content hlist"> <ul><li><a href="/wiki/Chirp_spread_spectrum" title="Chirp spread spectrum">CSS</a></li> <li><a href="/wiki/Direct-sequence_spread_spectrum" title="Direct-sequence spread spectrum">DSSS</a></li> <li><a href="/wiki/Frequency-hopping_spread_spectrum" title="Frequency-hopping spread spectrum">FHSS</a></li> <li><a href="/wiki/Time-hopping" title="Time-hopping">THSS</a></li></ul></td> </tr><tr><th class="sidebar-heading" style="background-color: #cfc"> See also</th></tr><tr><td class="sidebar-content hlist"> <ul><li><a href="/wiki/Category:Capacity-approaching_codes" title="Category:Capacity-approaching codes">Capacity-approaching codes</a></li> <li><a href="/wiki/Demodulation" title="Demodulation">Demodulation</a></li> <li><a href="/wiki/Line_code" title="Line code">Line coding</a></li> <li><a href="/wiki/Modem" title="Modem">Modem</a></li> <li><a href="/wiki/Angle_modulation" title="Angle modulation">AnM</a></li> <li><a href="/wiki/Polar_modulation" title="Polar modulation">PoM</a></li> <li><a href="/wiki/Pulse-amplitude_modulation" title="Pulse-amplitude modulation">PAM</a></li> <li><a href="/wiki/Pulse-code_modulation" title="Pulse-code modulation">PCM</a></li> <li><a href="/wiki/Pulse-density_modulation" title="Pulse-density modulation">PDM</a></li> <li><a href="/wiki/Pulse-width_modulation" title="Pulse-width modulation">PWM</a></li> <li><a href="/wiki/Delta-sigma_modulation" title="Delta-sigma modulation">ΔΣM</a></li> <li><a href="/wiki/Orthogonal_frequency-division_multiplexing" title="Orthogonal frequency-division multiplexing">OFDM</a></li> <li><a href="/wiki/Frequency-division_multiplexing" title="Frequency-division multiplexing">FDM</a></li> <li><a href="/wiki/Multiplexing" title="Multiplexing">Multiplexing</a></li></ul></td> </tr><tr><td class="sidebar-navbar"><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:Modulation_techniques" title="Template:Modulation techniques"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Modulation_techniques" title="Template talk:Modulation techniques"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Modulation_techniques" title="Special:EditPage/Template:Modulation techniques"><abbr title="Edit this template">e</abbr></a></li></ul></div></td></tr></tbody></table> <p><b>Amplitude modulation</b> (<b>AM</b>) is a <a href="/wiki/Modulation" title="Modulation">modulation</a> technique used in electronic communication, most commonly for transmitting messages with a <a href="/wiki/Radio_wave" title="Radio wave">radio wave</a>. In amplitude modulation, the <a href="/wiki/Amplitude" title="Amplitude">amplitude</a> (signal strength) of the wave is varied in proportion to that of the message signal, such as an <a href="/wiki/Audio_signal" title="Audio signal">audio signal</a>. This technique contrasts with <a href="/wiki/Angle_modulation" title="Angle modulation">angle modulation</a>, in which either the <a href="/wiki/Frequency" title="Frequency">frequency</a> of the carrier wave is varied, as in <a href="/wiki/Frequency_modulation" title="Frequency modulation">frequency modulation</a>, or its <a href="/wiki/Phase_(waves)" title="Phase (waves)">phase</a>, as in <a href="/wiki/Phase_modulation" title="Phase modulation">phase modulation</a>. </p><p>AM was the earliest modulation method used for transmitting audio in radio broadcasting. It was developed during the first quarter of the 20th century beginning with <a href="/wiki/Roberto_Landell_de_Moura" title="Roberto Landell de Moura">Roberto Landell de Moura</a> and <a href="/wiki/Reginald_Fessenden" title="Reginald Fessenden">Reginald Fessenden</a>'s <a href="/wiki/Radiotelephone" title="Radiotelephone">radiotelephone</a> experiments in 1900.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> This original form of AM is sometimes called <b>double-sideband amplitude modulation</b> (<b>DSBAM</b>), because the standard method produces sidebands on either side of the carrier frequency. <a href="/wiki/Single-sideband_modulation" title="Single-sideband modulation">Single-sideband modulation</a> uses bandpass filters to eliminate one of the sidebands and possibly the carrier signal, which improves the ratio of message power to total transmission <a href="/wiki/Power_(physics)" title="Power (physics)">power</a>, reduces power handling requirements of line repeaters, and permits better bandwidth utilization of the transmission medium. </p><p>AM remains in use in many forms of communication in addition to <a href="/wiki/AM_broadcasting" title="AM broadcasting">AM broadcasting</a>: <a href="/wiki/Shortwave_radio" title="Shortwave radio">shortwave radio</a>, <a href="/wiki/Amateur_radio" title="Amateur radio">amateur radio</a>, <a href="/wiki/Two-way_radio" title="Two-way radio">two-way radios</a>, <a href="/wiki/Airband" title="Airband">VHF aircraft radio</a>, <a href="/wiki/Citizens_band_radio" title="Citizens band radio">citizens band radio</a>, and in computer <a href="/wiki/Modem" title="Modem">modems</a> in the form of <a href="/wiki/QAM" class="mw-redirect" title="QAM">QAM</a>. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Foundation">Foundation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Amplitude_modulation&action=edit&section=1" title="Edit section: Foundation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In <a href="/wiki/Electronics" title="Electronics">electronics</a>, <a href="/wiki/Telecommunications" title="Telecommunications">telecommunications</a> and <a href="/wiki/Mechanic" title="Mechanic">mechanics</a>, <a href="/wiki/Modulation" title="Modulation">modulation</a> means varying some aspect of a <a href="/wiki/Continuous_wave" title="Continuous wave">continuous wave</a> <a href="/wiki/Carrier_signal" class="mw-redirect" title="Carrier signal">carrier signal</a> with an information-bearing modulation waveform, such as an <a href="/wiki/Audio_signal" title="Audio signal">audio signal</a> which represents sound, or a <a href="/wiki/Video_signal" class="mw-redirect" title="Video signal">video signal</a> which represents images. In this sense, the carrier wave, which has a much higher frequency than the message signal, <i>carries</i> the information. At the receiving station, the message signal is extracted from the modulated carrier by <a href="/wiki/Demodulation" title="Demodulation">demodulation</a>. </p><p>In general form, a modulation process of a <a href="/wiki/Sine_wave" title="Sine wave">sinusoidal carrier wave</a> may be described by the following equation:<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> </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 m(t)=A(t)\cdot \cos(\omega t+\phi (t))\,}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>m</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> <mo>=</mo> <mi>A</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> <mo>⋅</mo> <mi>cos</mi> <mo>⁡</mo> <mo stretchy="false">(</mo> <mi>ω</mi> <mi>t</mi> <mo>+</mo> <mi>ϕ</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> <mo stretchy="false">)</mo> <mspace width="thinmathspace" /> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle m(t)=A(t)\cdot \cos(\omega t+\phi (t))\,}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/4f38fe6082bce01427f31f0cdc6aec25b3221df8" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:28.327ex; height:2.843ex;" alt="{\displaystyle m(t)=A(t)\cdot \cos(\omega t+\phi (t))\,}"></span>.</dd></dl> <p><i>A(t)</i> represents the time-varying amplitude of the sinusoidal carrier wave and the cosine-term is the carrier at its <a href="/wiki/Angular_frequency" title="Angular frequency">angular frequency</a> <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 \omega }"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>ω</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \omega }</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/48eff443f9de7a985bb94ca3bde20813ea737be8" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.446ex; height:1.676ex;" alt="{\displaystyle \omega }"></span>, and the instantaneous phase deviation <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 \phi (t)}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>ϕ</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \phi (t)}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/23781b983d21d78467b65e7e32b9e7bc05d625f8" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:4.034ex; height:2.843ex;" alt="{\displaystyle \phi (t)}"></span>. This description directly provides the two major groups of modulation, amplitude modulation and <a href="/wiki/Angle_modulation" title="Angle modulation">angle modulation</a>. In angle modulation, the term <i>A</i>(<i>t</i>) is constant and the second term of the equation has a functional relationship to the modulating message signal. Angle modulation provides two methods of modulation, <a href="/wiki/Frequency_modulation" title="Frequency modulation">frequency modulation</a> and <a href="/wiki/Phase_modulation" title="Phase modulation">phase modulation</a>. </p><p>In amplitude modulation, the angle term is held constant and the first term, <i>A</i>(<i>t</i>), of the equation has a functional relationship to the modulating message signal. </p><p>The modulating message signal may be analog in nature, or it may be a digital signal, in which case the technique is generally called <a href="/wiki/Amplitude-shift_keying" title="Amplitude-shift keying">amplitude-shift keying</a>. </p><p>For example, in AM radio communication, a continuous wave radio-frequency signal has its amplitude modulated by an audio waveform before transmission. The message signal determines the <i><a href="/wiki/Envelope_(waves)" title="Envelope (waves)">envelope</a></i> of the transmitted waveform. In the <a href="/wiki/Frequency_domain" title="Frequency domain">frequency domain</a>, amplitude modulation produces a signal with power concentrated at the <a href="/wiki/Carrier_frequency" class="mw-redirect" title="Carrier frequency">carrier frequency</a> and two adjacent <a href="/wiki/Sideband" title="Sideband">sidebands</a>. Each sideband is equal in <a href="/wiki/Bandwidth_(signal_processing)" title="Bandwidth (signal processing)">bandwidth</a> to that of the modulating signal, and is a mirror image of the other. Standard AM is thus sometimes called "double-sideband amplitude modulation" (DSBAM). </p><p>A disadvantage of all amplitude modulation techniques, not only standard AM, is that the receiver amplifies and detects <a href="/wiki/Noise_(radio)" class="mw-redirect" title="Noise (radio)">noise</a> and <a href="/wiki/Electromagnetic_interference" title="Electromagnetic interference">electromagnetic interference</a> in equal proportion to the signal. Increasing the received <a href="/wiki/Signal-to-noise_ratio" title="Signal-to-noise ratio">signal-to-noise ratio</a>, say, by a factor of 10 (a 10 <a href="/wiki/Decibel" title="Decibel">decibel</a> improvement), thus would require increasing the transmitter power by a factor of 10. This is in contrast to <a href="/wiki/Frequency_modulation" title="Frequency modulation">frequency modulation</a> (FM) and <a href="/wiki/Digital_radio" title="Digital radio">digital radio</a> where the effect of such noise following demodulation is strongly reduced so long as the received signal is well above the threshold for reception. For this reason AM broadcast is not favored for music and <a href="/wiki/High_fidelity" title="High fidelity">high fidelity</a> broadcasting, but rather for voice communications and broadcasts (sports, news, <a href="/wiki/Talk_radio" title="Talk radio">talk radio</a> etc.). </p><p>AM is also inefficient in power usage; at least two-thirds of the power is concentrated in the carrier signal. The carrier signal contains none of the original information being transmitted (voice, video, data, etc.). However its presence provides a simple means of demodulation using <a href="/wiki/Envelope_detector" title="Envelope detector">envelope detection</a>, providing a frequency and phase reference to extract the modulation from the sidebands. In some modulation systems based on AM, a lower transmitter power is required through partial or total elimination of the carrier component, however receivers for these signals are more complex because they must provide a precise carrier frequency reference signal (usually as shifted to the <a href="/wiki/Intermediate_frequency" title="Intermediate frequency">intermediate frequency</a>) from a greatly reduced "pilot" carrier (in <a href="/wiki/Reduced-carrier_transmission" title="Reduced-carrier transmission">reduced-carrier transmission</a> or DSB-RC) to use in the demodulation process. Even with the carrier eliminated in <a href="/wiki/Double-sideband_suppressed-carrier_transmission" title="Double-sideband suppressed-carrier transmission">double-sideband suppressed-carrier transmission</a>, carrier regeneration is possible using a <a href="/wiki/Costas_loop" title="Costas loop">Costas phase-locked loop</a>. This does not work for <a href="/wiki/Single-sideband_suppressed-carrier_transmission" class="mw-redirect" title="Single-sideband suppressed-carrier transmission">single-sideband suppressed-carrier transmission</a> (SSB-SC), leading to the characteristic "Donald Duck" sound from such receivers when slightly detuned. Single-sideband AM is nevertheless used widely in <a href="/wiki/Amateur_radio" title="Amateur radio">amateur radio</a> and other voice communications because it has power and bandwidth efficiency (cutting the RF bandwidth in half compared to standard AM). On the other hand, in <a href="/wiki/Medium_wave" title="Medium wave">medium wave</a> and <a href="/wiki/Short_wave" class="mw-redirect" title="Short wave">short wave</a> broadcasting, standard AM with the full carrier allows for reception using inexpensive receivers. The broadcaster absorbs the extra power cost to greatly increase potential audience. </p> <div class="mw-heading mw-heading3"><h3 id="Shift_keying">Shift keying</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Amplitude_modulation&action=edit&section=2" title="Edit section: Shift keying"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A simple form of digital amplitude modulation which can be used for transmitting <a href="/wiki/Digital_data" title="Digital data">binary data</a> is <a href="/wiki/On%E2%80%93off_keying" title="On–off keying">on–off keying</a>, the simplest form of amplitude-shift keying, in which <a href="/wiki/Binary_numeral_system" class="mw-redirect" title="Binary numeral system">ones and zeros</a> are represented by the presence or absence of a carrier. On–off keying is likewise used by radio amateurs to transmit <a href="/wiki/Morse_code" title="Morse code">Morse code</a> where it is known as continuous wave (CW) operation, even though the transmission is not strictly "continuous". A more complex form of AM, <a href="/wiki/QAM" class="mw-redirect" title="QAM">quadrature amplitude modulation</a> is now more commonly used with digital data, while making more efficient use of the available bandwidth. </p> <div class="mw-heading mw-heading3"><h3 id="Analog_telephony">Analog telephony</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Amplitude_modulation&action=edit&section=3" title="Edit section: Analog telephony"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A simple form of amplitude modulation is the transmission of speech signals from a traditional analog telephone set using a common battery local loop.<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> The direct current provided by the central office battery is a carrier with a frequency of 0 Hz. It is modulated by a microphone (<i>transmitter</i>) in the telephone set according to the acoustic signal from the speaker. The result is a varying amplitude direct current, whose AC-component is the speech signal extracted at the central office for transmission to another subscriber. </p> <div class="mw-heading mw-heading3"><h3 id="Amplitude_reference">Amplitude reference</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Amplitude_modulation&action=edit&section=4" title="Edit section: Amplitude reference"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>An additional function provided by the carrier in standard AM, but which is lost in either single or double-sideband suppressed-carrier transmission, is that it provides an amplitude reference. In the receiver, the <a href="/wiki/Automatic_gain_control" title="Automatic gain control">automatic gain control</a> (AGC) responds to the carrier so that the reproduced audio level stays in a fixed proportion to the original modulation. On the other hand, with suppressed-carrier transmissions there is <i>no</i> transmitted power during pauses in the modulation, so the AGC must respond to peaks of the transmitted power during peaks in the modulation. This typically involves a so-called <i>fast attack, slow decay</i> circuit which holds the AGC level for a second or more following such peaks, in between syllables or short pauses in the program. This is very acceptable for communications radios, where <a href="/wiki/Dynamic_range_compression" title="Dynamic range compression">compression</a> of the audio aids intelligibility. However it is absolutely undesired for music or normal broadcast programming, where a faithful reproduction of the original program, including its varying modulation levels, is expected. </p> <div class="mw-heading mw-heading2"><h2 id="ITU_type_designations">ITU type designations</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Amplitude_modulation&action=edit&section=5" title="Edit section: ITU type designations"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In 1982, the <a href="/wiki/International_Telecommunication_Union" title="International Telecommunication Union">International Telecommunication Union</a> (ITU) designated the types of amplitude modulation: </p> <table class="wikitable"> <tbody><tr> <th>Designation</th> <th>Description </th></tr> <tr> <td>A3E</td> <td><a href="/wiki/Double_sideband" class="mw-redirect" title="Double sideband">double-sideband</a> a full-carrier – the basic amplitude modulation scheme </td></tr> <tr> <td>R3E</td> <td><a href="/wiki/Single-sideband_modulation" title="Single-sideband modulation">single-sideband</a> <a href="/wiki/Reduced-carrier_transmission" title="Reduced-carrier transmission">reduced-carrier</a> </td></tr> <tr> <td>H3E</td> <td><a href="/wiki/Single-sideband_modulation" title="Single-sideband modulation">single-sideband</a> full-carrier </td></tr> <tr> <td>J3E</td> <td><a href="/wiki/Single-sideband_suppressed-carrier_transmission" class="mw-redirect" title="Single-sideband suppressed-carrier transmission">single-sideband suppressed-carrier</a> </td></tr> <tr> <td>B8E</td> <td><a href="/wiki/Independent_sideband" title="Independent sideband">independent-sideband</a> emission </td></tr> <tr> <td>C3F</td> <td><a href="/wiki/Vestigal_sideband" class="mw-redirect" title="Vestigal sideband">vestigial-sideband</a> </td></tr> <tr> <td>Lincompex</td> <td>linked <a href="/wiki/Compander" class="mw-redirect" title="Compander">compressor and expander</a> (a submode of any of the above ITU Emission Modes) </td></tr></tbody></table> <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=Amplitude_modulation&action=edit&section=6" title="Edit section: History"><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:Telefunken_arc_radiotelephone.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/4/4e/Telefunken_arc_radiotelephone.jpg/220px-Telefunken_arc_radiotelephone.jpg" decoding="async" width="220" height="429" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/4e/Telefunken_arc_radiotelephone.jpg/330px-Telefunken_arc_radiotelephone.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/4e/Telefunken_arc_radiotelephone.jpg/440px-Telefunken_arc_radiotelephone.jpg 2x" data-file-width="1095" data-file-height="2135" /></a><figcaption>One of the crude pre-vacuum tube AM transmitters, a Telefunken <a href="/wiki/Arc_converter" title="Arc converter">arc transmitter</a> from 1906. The carrier wave is generated by 6 electric arcs in the vertical tubes, connected to a <a href="/wiki/Tuned_circuit" class="mw-redirect" title="Tuned circuit">tuned circuit</a>. Modulation is done by the large carbon microphone <i>(cone shape)</i> in the antenna lead. </figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Meissner_radiotelephone_transmitter.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/1f/Meissner_radiotelephone_transmitter.jpg/220px-Meissner_radiotelephone_transmitter.jpg" decoding="async" width="220" height="278" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/1f/Meissner_radiotelephone_transmitter.jpg/330px-Meissner_radiotelephone_transmitter.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/1f/Meissner_radiotelephone_transmitter.jpg/440px-Meissner_radiotelephone_transmitter.jpg 2x" data-file-width="811" data-file-height="1026" /></a><figcaption>One of the first <a href="/wiki/Vacuum_tube" title="Vacuum tube">vacuum tube</a> AM radio transmitters, built by Meissner in 1913 with an early triode tube by Robert von Lieben. He used it in a historic 36 km (24 mi) voice transmission from Berlin to Nauen, Germany. Compare its small size with the arc transmitter above. </figcaption></figure> <p>Amplitude modulation was used in experiments of multiplex telegraph and telephone transmission in the late 1800s.<sup id="cite_ref-Bray_4-0" class="reference"><a href="#cite_note-Bray-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> However, the practical development of this technology is identified with the period between 1900 and 1920 of <a href="/wiki/Radiotelephone" title="Radiotelephone">radiotelephone</a> transmission, that is, the effort to send audio signals by radio waves. The first radio transmitters, called <a href="/wiki/Spark_gap_transmitter" class="mw-redirect" title="Spark gap transmitter">spark gap transmitters</a>, transmitted information by <a href="/wiki/Wireless_telegraphy" title="Wireless telegraphy">wireless telegraphy</a>, using pulses of the carrier wave to spell out text messages in <a href="/wiki/Morse_code" title="Morse code">Morse code</a>. They could not transmit audio because the carrier consisted of strings of <a href="/wiki/Damped_wave" class="mw-redirect" title="Damped wave">damped waves</a>, pulses of radio waves that declined to zero, and sounded like a buzz in receivers. In effect they were already amplitude modulated. </p> <div class="mw-heading mw-heading3"><h3 id="Continuous_waves">Continuous waves</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Amplitude_modulation&action=edit&section=7" title="Edit section: Continuous waves"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The first AM transmission was made by Canadian-born American researcher <a href="/wiki/Reginald_Fessenden" title="Reginald Fessenden">Reginald Fessenden</a> on 23 December 1900 using a spark gap transmitter with a specially designed high frequency 10 kHz <a href="/wiki/Induction_coil" title="Induction coil">interrupter</a>, over a distance of one mile (1.6 km) at Cobb Island, Maryland, US. His first transmitted words were, "Hello. One, two, three, four. Is it snowing where you are, Mr. Thiessen?". The words were barely intelligible above the background buzz of the spark.<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. (December 2022)">citation needed</span></a></i>]</sup> </p><p>Fessenden was a significant figure in the development of AM radio. He was one of the first researchers to realize, from experiments like the above, that the existing technology for producing radio waves, the spark transmitter, was not usable for amplitude modulation, and that a new kind of transmitter, one that produced <a href="/wiki/Sinusoidal" class="mw-redirect" title="Sinusoidal">sinusoidal</a> <i><a href="/wiki/Continuous_wave" title="Continuous wave">continuous waves</a></i>, was needed. This was a radical idea at the time, because experts believed the impulsive spark was necessary to produce radio frequency waves, and Fessenden was ridiculed. He invented and helped develop one of the first continuous wave transmitters – the <a href="/wiki/Alexanderson_alternator" title="Alexanderson alternator">Alexanderson alternator</a>, with which he made what is considered the first AM public entertainment broadcast on Christmas Eve, 1906. He also discovered the principle on which AM is based, <a href="/wiki/Heterodyne" title="Heterodyne">heterodyning</a>, and invented one of the first <a href="/wiki/Detector_(radio)" title="Detector (radio)">detectors</a> able to <a href="/wiki/Rectifier" title="Rectifier">rectify</a> and receive AM, the <a href="/wiki/Electrolytic_detector" title="Electrolytic detector">electrolytic detector</a> or "liquid baretter", in 1902. Other radio detectors invented for wireless telegraphy, such as the <a href="/wiki/Fleming_valve" title="Fleming valve">Fleming valve</a> (1904) and the <a href="/wiki/Crystal_detector" title="Crystal detector">crystal detector</a> (1906) also proved able to rectify AM signals, so the technological hurdle was generating AM waves; receiving them was not a problem. </p> <div class="mw-heading mw-heading3"><h3 id="Early_technologies">Early technologies</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Amplitude_modulation&action=edit&section=8" title="Edit section: Early technologies"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Early experiments in AM radio transmission, conducted by Fessenden, <a href="/wiki/Valdemar_Poulsen" title="Valdemar Poulsen">Valdemar Poulsen</a>, <a href="/wiki/Ernst_Ruhmer" title="Ernst Ruhmer">Ernst Ruhmer</a>, <a href="/wiki/Quirino_Majorana" title="Quirino Majorana">Quirino Majorana</a>, <a href="/wiki/Charles_Herrold" title="Charles Herrold">Charles Herrold</a>, and <a href="/wiki/Lee_de_Forest" title="Lee de Forest">Lee de Forest</a>, were hampered by the lack of a technology for <a href="/wiki/Amplifier" title="Amplifier">amplification</a>. The first practical continuous wave AM <a href="/wiki/Transmitter" title="Transmitter">transmitters</a> were based on either the huge, expensive <a href="/wiki/Alexanderson_alternator" title="Alexanderson alternator">Alexanderson alternator</a>, developed 1906–1910, or versions of the <a href="/wiki/Poulsen_arc" class="mw-redirect" title="Poulsen arc">Poulsen arc</a> transmitter (arc converter), invented in 1903. The modifications necessary to transmit AM were clumsy and resulted in very low quality audio. Modulation was usually accomplished by a <a href="/wiki/Carbon_microphone" title="Carbon microphone">carbon microphone</a> inserted directly in the antenna or ground wire; its varying resistance varied the current to the antenna. The limited power handling ability of the microphone severely limited the power of the first radiotelephones; many of the microphones were water-cooled. </p> <div class="mw-heading mw-heading3"><h3 id="Vacuum_tubes">Vacuum tubes</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Amplitude_modulation&action=edit&section=9" title="Edit section: Vacuum tubes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The 1912 discovery of the amplifying ability of the <a href="/wiki/Audion_tube" class="mw-redirect" title="Audion tube">Audion tube</a>, invented in 1906 by <a href="/wiki/Lee_de_Forest" title="Lee de Forest">Lee de Forest</a>, solved these problems. The vacuum tube <a href="/wiki/Feedback_oscillator" class="mw-redirect" title="Feedback oscillator">feedback oscillator</a>, invented in 1912 by <a href="/wiki/Edwin_Armstrong" class="mw-redirect" title="Edwin Armstrong">Edwin Armstrong</a> and <a href="/wiki/Alexander_Meissner" title="Alexander Meissner">Alexander Meissner</a>, was a cheap source of <a href="/wiki/Continuous_wave" title="Continuous wave">continuous waves</a> and could be easily <a href="/wiki/Modulation" title="Modulation">modulated</a> to make an AM transmitter. Modulation did not have to be done at the output but could be applied to the signal before the final amplifier tube, so the microphone or other audio source didn't have to modulate a high-power radio signal. Wartime research greatly advanced the art of AM modulation, and after the war the availability of cheap tubes sparked a great increase in the number of radio stations experimenting with AM transmission of news or music. The vacuum tube was responsible for the rise of <a href="/wiki/AM_broadcasting" title="AM broadcasting">AM broadcasting</a> around 1920, the first electronic <a href="/wiki/Mass_communication" title="Mass communication">mass communication</a> medium. Amplitude modulation was virtually the only type used for <a href="/wiki/Radio_broadcasting" title="Radio broadcasting">radio broadcasting</a> until <a href="/wiki/FM_broadcasting" title="FM broadcasting">FM broadcasting</a> began after World War II. </p><p>At the same time as AM radio began, <a href="/wiki/Telephone_company" class="mw-redirect" title="Telephone company">telephone companies</a> such as <a href="/wiki/AT%26T_Corporation" title="AT&T Corporation">AT&T</a> were developing the other large application for AM: sending multiple telephone calls through a single wire by modulating them on separate <a href="/wiki/Carrier_signal" class="mw-redirect" title="Carrier signal">carrier</a> frequencies, called <i><a href="/wiki/Frequency_division_multiplexing" class="mw-redirect" title="Frequency division multiplexing">frequency division multiplexing</a></i>.<sup id="cite_ref-Bray_4-1" class="reference"><a href="#cite_note-Bray-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Single-sideband">Single-sideband</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Amplitude_modulation&action=edit&section=10" title="Edit section: Single-sideband"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In 1915, <a href="/wiki/John_Renshaw_Carson" title="John Renshaw Carson">John Renshaw Carson</a> formulated the first mathematical description of amplitude modulation, showing that a signal and carrier frequency combined in a nonlinear device creates a sideband on both sides of the carrier frequency. Passing the modulated signal through another nonlinear device can extract the original baseband signal.<sup id="cite_ref-Bray_4-2" class="reference"><a href="#cite_note-Bray-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> His analysis also showed that only one sideband was necessary to transmit the audio signal, and Carson patented <a href="/wiki/Single-sideband_modulation" title="Single-sideband modulation">single-sideband modulation</a> (SSB) on 1 December 1915.<sup id="cite_ref-Bray_4-3" class="reference"><a href="#cite_note-Bray-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> This advanced variant of amplitude modulation was adopted by AT&T for <a href="/wiki/Longwave" title="Longwave">longwave</a> transatlantic telephone service beginning 7 January 1927. After WW-II, it was developed for military aircraft communication. </p> <div class="mw-heading mw-heading2"><h2 id="Analysis">Analysis</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Amplitude_modulation&action=edit&section=11" title="Edit section: Analysis"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Illustration_of_Amplitude_Modulation.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/8d/Illustration_of_Amplitude_Modulation.png/391px-Illustration_of_Amplitude_Modulation.png" decoding="async" width="391" height="152" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/8d/Illustration_of_Amplitude_Modulation.png/587px-Illustration_of_Amplitude_Modulation.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/8d/Illustration_of_Amplitude_Modulation.png/782px-Illustration_of_Amplitude_Modulation.png 2x" data-file-width="797" data-file-height="310" /></a><figcaption>Illustration of amplitude modulation</figcaption></figure> <p>The carrier wave (<a href="/wiki/Sine_wave" title="Sine wave">sine wave</a>) of frequency <i>f<sub>c</sub></i> and amplitude <i>A</i> is expressed by </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 c(t)=A\sin(2\pi f_{c}t)\,}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>c</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> <mo>=</mo> <mi>A</mi> <mi>sin</mi> <mo>⁡</mo> <mo stretchy="false">(</mo> <mn>2</mn> <mi>π</mi> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>c</mi> </mrow> </msub> <mi>t</mi> <mo stretchy="false">)</mo> <mspace width="thinmathspace" /> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle c(t)=A\sin(2\pi f_{c}t)\,}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/d73ad956fbd9068f974b313e29b0427ca3e3d3f1" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:19.354ex; height:2.843ex;" alt="{\displaystyle c(t)=A\sin(2\pi f_{c}t)\,}"></span>.</dd></dl> <p>The message signal, such as an audio signal that is used for modulating the carrier, is <i>m</i>(<i>t</i>), and has a frequency <i>f<sub>m</sub></i>, much lower than <i>f<sub>c</sub></i>: </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 m(t)=M\cos \left(2\pi f_{m}t+\phi \right)=Am\cos \left(2\pi f_{m}t+\phi \right)\,}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>m</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> <mo>=</mo> <mi>M</mi> <mi>cos</mi> <mo>⁡</mo> <mrow> <mo>(</mo> <mrow> <mn>2</mn> <mi>π</mi> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>m</mi> </mrow> </msub> <mi>t</mi> <mo>+</mo> <mi>ϕ</mi> </mrow> <mo>)</mo> </mrow> <mo>=</mo> <mi>A</mi> <mi>m</mi> <mi>cos</mi> <mo>⁡</mo> <mrow> <mo>(</mo> <mrow> <mn>2</mn> <mi>π</mi> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>m</mi> </mrow> </msub> <mi>t</mi> <mo>+</mo> <mi>ϕ</mi> </mrow> <mo>)</mo> </mrow> <mspace width="thinmathspace" /> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle m(t)=M\cos \left(2\pi f_{m}t+\phi \right)=Am\cos \left(2\pi f_{m}t+\phi \right)\,}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/b3166c0549cdcfca829e5b9e97acae7672812c5b" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:48.862ex; height:2.843ex;" alt="{\displaystyle m(t)=M\cos \left(2\pi f_{m}t+\phi \right)=Am\cos \left(2\pi f_{m}t+\phi \right)\,}"></span>,</dd></dl> <p>where <i>m</i> is the amplitude sensitivity, <i>M</i> is the amplitude of modulation. If <i>m</i> < 1, <i>(1 + m(t)/A)</i> is always positive for undermodulation. If <i>m</i> > 1 then overmodulation occurs and reconstruction of message signal from the transmitted signal would lead in loss of original signal. Amplitude modulation results when the carrier <i>c(t)</i> is multiplied by the positive quantity <i>(1 + m(t)/A)</i>: </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 {\begin{aligned}y(t)&=\left[1+{\frac {m(t)}{A}}\right]c(t)\\&=\left[1+m\cos \left(2\pi f_{m}t+\phi \right)\right]A\sin \left(2\pi f_{c}t\right)\end{aligned}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mtable columnalign="right left right left right left right left right left right left" rowspacing="3pt" columnspacing="0em 2em 0em 2em 0em 2em 0em 2em 0em 2em 0em" displaystyle="true"> <mtr> <mtd> <mi>y</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> </mtd> <mtd> <mi></mi> <mo>=</mo> <mrow> <mo>[</mo> <mrow> <mn>1</mn> <mo>+</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mi>m</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> </mrow> <mi>A</mi> </mfrac> </mrow> </mrow> <mo>]</mo> </mrow> <mi>c</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> </mtd> </mtr> <mtr> <mtd /> <mtd> <mi></mi> <mo>=</mo> <mrow> <mo>[</mo> <mrow> <mn>1</mn> <mo>+</mo> <mi>m</mi> <mi>cos</mi> <mo>⁡</mo> <mrow> <mo>(</mo> <mrow> <mn>2</mn> <mi>π</mi> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>m</mi> </mrow> </msub> <mi>t</mi> <mo>+</mo> <mi>ϕ</mi> </mrow> <mo>)</mo> </mrow> </mrow> <mo>]</mo> </mrow> <mi>A</mi> <mi>sin</mi> <mo>⁡</mo> <mrow> <mo>(</mo> <mrow> <mn>2</mn> <mi>π</mi> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>c</mi> </mrow> </msub> <mi>t</mi> </mrow> <mo>)</mo> </mrow> </mtd> </mtr> </mtable> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\begin{aligned}y(t)&=\left[1+{\frac {m(t)}{A}}\right]c(t)\\&=\left[1+m\cos \left(2\pi f_{m}t+\phi \right)\right]A\sin \left(2\pi f_{c}t\right)\end{aligned}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/637cd857e4f781d6d7bbdb570fa8c227d64d4298" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -4.171ex; width:43.273ex; height:9.509ex;" alt="{\displaystyle {\begin{aligned}y(t)&=\left[1+{\frac {m(t)}{A}}\right]c(t)\\&=\left[1+m\cos \left(2\pi f_{m}t+\phi \right)\right]A\sin \left(2\pi f_{c}t\right)\end{aligned}}}"></span></dd></dl> <p>In this simple case <i>m</i> is identical to the <a href="#Modulation_index">modulation index</a>, discussed below. With <i>m</i> = 0.5 the amplitude modulated signal <i>y</i>(<i>t</i>) thus corresponds to the top graph (labelled "50% Modulation") in figure 4. </p><p>Using <a href="/wiki/Prosthaphaeresis#The_identities" title="Prosthaphaeresis">prosthaphaeresis identities</a>, <i>y</i>(<i>t</i>) can be shown to be the sum of three sine waves: </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 y(t)=A\sin(2\pi f_{c}t)+{\frac {1}{2}}Am\left[\sin \left(2\pi \left[f_{c}+f_{m}\right]t+\phi \right)+\sin \left(2\pi \left[f_{c}-f_{m}\right]t-\phi \right)\right].\,}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>y</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> <mo>=</mo> <mi>A</mi> <mi>sin</mi> <mo>⁡</mo> <mo stretchy="false">(</mo> <mn>2</mn> <mi>π</mi> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>c</mi> </mrow> </msub> <mi>t</mi> <mo stretchy="false">)</mo> <mo>+</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> </mrow> <mi>A</mi> <mi>m</mi> <mrow> <mo>[</mo> <mrow> <mi>sin</mi> <mo>⁡</mo> <mrow> <mo>(</mo> <mrow> <mn>2</mn> <mi>π</mi> <mrow> <mo>[</mo> <mrow> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>c</mi> </mrow> </msub> <mo>+</mo> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>m</mi> </mrow> </msub> </mrow> <mo>]</mo> </mrow> <mi>t</mi> <mo>+</mo> <mi>ϕ</mi> </mrow> <mo>)</mo> </mrow> <mo>+</mo> <mi>sin</mi> <mo>⁡</mo> <mrow> <mo>(</mo> <mrow> <mn>2</mn> <mi>π</mi> <mrow> <mo>[</mo> <mrow> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>c</mi> </mrow> </msub> <mo>−</mo> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>m</mi> </mrow> </msub> </mrow> <mo>]</mo> </mrow> <mi>t</mi> <mo>−</mo> <mi>ϕ</mi> </mrow> <mo>)</mo> </mrow> </mrow> <mo>]</mo> </mrow> <mo>.</mo> <mspace width="thinmathspace" /> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle y(t)=A\sin(2\pi f_{c}t)+{\frac {1}{2}}Am\left[\sin \left(2\pi \left[f_{c}+f_{m}\right]t+\phi \right)+\sin \left(2\pi \left[f_{c}-f_{m}\right]t-\phi \right)\right].\,}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/e6540130eb862ec3332481d4f1730806e8352ba0" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:77.742ex; height:5.176ex;" alt="{\displaystyle y(t)=A\sin(2\pi f_{c}t)+{\frac {1}{2}}Am\left[\sin \left(2\pi \left[f_{c}+f_{m}\right]t+\phi \right)+\sin \left(2\pi \left[f_{c}-f_{m}\right]t-\phi \right)\right].\,}"></span></dd></dl> <p>Therefore, the modulated signal has three components: the carrier wave <i>c(t)</i> which is unchanged in frequency, and two <a href="/wiki/Sideband" title="Sideband">sidebands</a> with frequencies slightly above and below the carrier frequency <i>f<sub>c</sub></i>. </p> <div class="mw-heading mw-heading2"><h2 id="Spectrum">Spectrum</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Amplitude_modulation&action=edit&section=12" title="Edit section: Spectrum"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure typeof="mw:File/Thumb"><a href="/wiki/File:AM_spectrum.svg" class="mw-file-description"><img alt="Diagrams of an AM signal, with formulas" src="//upload.wikimedia.org/wikipedia/commons/thumb/a/ae/AM_spectrum.svg/400px-AM_spectrum.svg.png" decoding="async" width="400" height="197" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/ae/AM_spectrum.svg/600px-AM_spectrum.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/a/ae/AM_spectrum.svg/800px-AM_spectrum.svg.png 2x" data-file-width="746" data-file-height="367" /></a><figcaption>Figure 2: Double-sided spectra of baseband and AM signals.</figcaption></figure> <p>A useful modulation signal <i>m(t)</i> is usually more complex than a single sine wave, as treated above. However, by the principle of <a href="/wiki/Fourier_decomposition" class="mw-redirect" title="Fourier decomposition">Fourier decomposition</a>, <i>m(t)</i> can be expressed as the sum of a set of sine waves of various frequencies, amplitudes, and phases. Carrying out the multiplication of <i>1 + m(t)</i> with <i>c(t)</i> as above, the result consists of a sum of sine waves. Again, the carrier <i>c(t)</i> is present unchanged, but each frequency component of <i>m</i> at <i>f<sub>i</sub></i> has two sidebands at frequencies <i>f<sub>c</sub> + f<sub>i</sub></i> and <i>f<sub>c</sub> – f<sub>i</sub></i>. The collection of the former frequencies above the carrier frequency is known as the upper sideband, and those below constitute the lower sideband. The modulation <i>m(t)</i> may be considered to consist of an equal mix of positive and negative frequency components, as shown in the top of figure 2. One can view the sidebands as that modulation <i>m(t)</i> having simply been shifted in frequency by <i>f<sub>c</sub></i> as depicted at the bottom right of figure 2. </p> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:AM_signal.jpg" class="mw-file-description"><img alt="Sonogram of an AM signal, showing the carrier and both sidebands vertically" src="//upload.wikimedia.org/wikipedia/commons/thumb/5/5d/AM_signal.jpg/200px-AM_signal.jpg" decoding="async" width="200" height="160" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/5d/AM_signal.jpg/300px-AM_signal.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/5d/AM_signal.jpg/400px-AM_signal.jpg 2x" data-file-width="640" data-file-height="513" /></a><figcaption>Figure 3: The <a href="/wiki/Spectrogram" title="Spectrogram">spectrogram</a> of an AM voice broadcast shows the two sidebands (green) on either side of the carrier (red) with time proceeding in the vertical direction.</figcaption></figure> <p>The short-term spectrum of modulation, changing as it would for a human voice for instance, the frequency content (horizontal axis) may be plotted as a function of time (vertical axis), as in figure 3. It can again be seen that as the modulation frequency content varies, an upper sideband is generated according to those frequencies shifted <i>above</i> the carrier frequency, and the same content mirror-imaged in the lower sideband below the carrier frequency. At all times, the carrier itself remains constant, and of greater power than the total sideband power. </p> <div class="mw-heading mw-heading2"><h2 id="Power_and_spectrum_efficiency">Power and spectrum efficiency</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Amplitude_modulation&action=edit&section=13" title="Edit section: Power and spectrum efficiency"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The RF bandwidth of an AM transmission (refer to figure 2, but only considering positive frequencies) is twice the bandwidth of the modulating (or "<a href="/wiki/Baseband" title="Baseband">baseband</a>") signal, since the upper and lower sidebands around the carrier frequency each have a bandwidth as wide as the highest modulating frequency. Although the bandwidth of an AM signal is narrower than one using <a href="/wiki/Frequency_modulation" title="Frequency modulation">frequency modulation</a> (FM), it is twice as wide as <a href="/wiki/Single-sideband" class="mw-redirect" title="Single-sideband">single-sideband</a> techniques; it thus may be viewed as spectrally inefficient. Within a frequency band, only half as many transmissions (or "channels") can thus be accommodated. For this reason analog television employs a variant of single-sideband (known as <a href="/wiki/Vestigial_sideband" class="mw-redirect" title="Vestigial sideband">vestigial sideband</a>, somewhat of a compromise in terms of bandwidth) in order to reduce the required channel spacing. </p><p>Another improvement over standard AM is obtained through reduction or suppression of the carrier component of the modulated spectrum. In figure 2 this is the spike in between the sidebands; even with full (100%) sine wave modulation, the power in the carrier component is twice that in the sidebands, yet it carries no unique information. Thus there is a great advantage in efficiency in reducing or totally suppressing the carrier, either in conjunction with elimination of one sideband (<a href="/wiki/Single-sideband_suppressed-carrier_transmission" class="mw-redirect" title="Single-sideband suppressed-carrier transmission">single-sideband suppressed-carrier transmission</a>) or with both sidebands remaining (<a href="/wiki/Double_sideband_suppressed_carrier" class="mw-redirect" title="Double sideband suppressed carrier">double sideband suppressed carrier</a>). While these suppressed carrier transmissions are efficient in terms of transmitter power, they require more sophisticated receivers employing <a href="/wiki/Product_detector" title="Product detector">synchronous detection</a> and regeneration of the carrier frequency. For that reason, standard AM continues to be widely used, especially in broadcast transmission, to allow for the use of inexpensive receivers using <a href="/wiki/Envelope_detector" title="Envelope detector">envelope detection</a>. Even (analog) television, with a (largely) suppressed lower sideband, includes sufficient carrier power for use of envelope detection. But for communications systems where both transmitters and receivers can be optimized, suppression of both one sideband and the carrier represent a net advantage and are frequently employed. </p><p>A technique used widely in broadcast AM transmitters is an application of the Hapburg carrier, first proposed in the 1930s but impractical with the technology then available. During periods of low modulation the carrier power would be <a href="/wiki/Dynamic_carrier_control" title="Dynamic carrier control">reduced</a> and would return to full power during periods of high modulation levels. This has the effect of reducing the overall power demand of the transmitter and is most effective on speech type programmes. Various trade names are used for its implementation by the transmitter manufacturers from the late 80's onwards. </p> <div class="mw-heading mw-heading2"><h2 id="Modulation_index">Modulation index</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Amplitude_modulation&action=edit&section=14" title="Edit section: Modulation index"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The AM modulation index is a measure based on the ratio of the modulation excursions of the RF signal to the level of the unmodulated carrier. It is thus defined as: </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 m={\frac {\mathrm {peak\ value\ of\ } m(t)}{A}}={\frac {M}{A}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>m</mi> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">p</mi> <mi mathvariant="normal">e</mi> <mi mathvariant="normal">a</mi> <mi mathvariant="normal">k</mi> <mtext> </mtext> <mi mathvariant="normal">v</mi> <mi mathvariant="normal">a</mi> <mi mathvariant="normal">l</mi> <mi mathvariant="normal">u</mi> <mi mathvariant="normal">e</mi> <mtext> </mtext> <mi mathvariant="normal">o</mi> <mi mathvariant="normal">f</mi> <mtext> </mtext> </mrow> <mi>m</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> </mrow> <mi>A</mi> </mfrac> </mrow> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mi>M</mi> <mi>A</mi> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle m={\frac {\mathrm {peak\ value\ of\ } m(t)}{A}}={\frac {M}{A}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/5ba8b9a233e81cdb4b223c6948d42e868b51f109" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.005ex; width:30.887ex; height:5.843ex;" alt="{\displaystyle m={\frac {\mathrm {peak\ value\ of\ } m(t)}{A}}={\frac {M}{A}}}"></span></dd></dl> <p>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 M\,}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>M</mi> <mspace width="thinmathspace" /> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle M\,}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/aa66ea8156203e93f2dca12aca24538c2bdce761" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.829ex; height:2.176ex;" alt="{\displaystyle M\,}"></span> 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 A\,}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>A</mi> <mspace width="thinmathspace" /> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle A\,}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/c6aaf5ce10d6add44b973e28fb3d95f37abf3721" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.13ex; height:2.176ex;" alt="{\displaystyle A\,}"></span> are the modulation amplitude and carrier amplitude, respectively; the modulation amplitude is the peak (positive or negative) change in the RF amplitude from its unmodulated value. Modulation index is normally expressed as a percentage, and may be displayed on a meter connected to an AM transmitter. </p><p>So if <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 m=0.5}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>m</mi> <mo>=</mo> <mn>0.5</mn> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle m=0.5}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7aaaaa1dda30437bbd9e157a0a33749d4099e475" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:8.111ex; height:2.176ex;" alt="{\displaystyle m=0.5}"></span>, carrier amplitude varies by 50% above (and below) its unmodulated level, as is shown in the first waveform, below. For <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 m=1.0}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>m</mi> <mo>=</mo> <mn>1.0</mn> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle m=1.0}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/07b8149c8408051f551c031a5c45176b1fe304af" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:8.111ex; height:2.176ex;" alt="{\displaystyle m=1.0}"></span>, it varies by 100% as shown in the illustration below it. With 100% modulation the wave amplitude sometimes reaches zero, and this represents full modulation using standard AM and is often a target (in order to obtain the highest possible <a href="/wiki/Signal-to-noise_ratio" title="Signal-to-noise ratio">signal-to-noise ratio</a>) but mustn't be exceeded. Increasing the modulating signal beyond that point, known as <a href="/wiki/Overmodulation" title="Overmodulation">overmodulation</a>, causes a standard AM modulator (see below) to fail, as the negative excursions of the wave envelope cannot become less than zero, resulting in <a href="/wiki/Distortion" title="Distortion">distortion</a> ("clipping") of the received modulation. Transmitters typically incorporate a <a href="/wiki/Limiter" title="Limiter">limiter</a> circuit to avoid overmodulation, and/or a <a href="/wiki/Dynamic_range_compression" title="Dynamic range compression">compressor</a> circuit (especially for voice communications) in order to still approach 100% modulation for maximum intelligibility above the noise. Such circuits are sometimes referred to as a <a href="/wiki/Vogad" class="mw-redirect" title="Vogad">vogad</a>. </p><p>However it is possible to talk about a modulation index exceeding 100%, without introducing distortion, in the case of <a href="/wiki/Double-sideband_reduced-carrier_transmission" title="Double-sideband reduced-carrier transmission">double-sideband reduced-carrier transmission</a>. In that case, negative excursions beyond zero entail a reversal of the carrier phase, as shown in the third waveform below. This cannot be produced using the efficient high-level (output stage) modulation techniques (see below) which are widely used especially in high power <a href="/wiki/Broadcast" class="mw-redirect" title="Broadcast">broadcast</a> transmitters. Rather, a special modulator produces such a waveform at a low level followed by a <a href="/wiki/Linear_amplifier" title="Linear amplifier">linear amplifier</a>. What's more, a standard AM receiver using an <a href="/wiki/Envelope_detector" title="Envelope detector">envelope detector</a> is incapable of properly demodulating such a signal. Rather, synchronous detection is required. Thus double-sideband transmission is generally <i>not</i> referred to as "AM" even though it generates an identical RF waveform as standard AM as long as the modulation index is below 100%. Such systems more often attempt a radical reduction of the carrier level compared to the sidebands (where the useful information is present) to the point of <a href="/wiki/Double-sideband_suppressed-carrier_transmission" title="Double-sideband suppressed-carrier transmission">double-sideband suppressed-carrier transmission</a> where the carrier is (ideally) reduced to zero. In all such cases the term "modulation index" loses its value as it refers to the ratio of the modulation amplitude to a rather small (or zero) remaining carrier amplitude. </p> <figure class="mw-halign-center" typeof="mw:File/Thumb"><a href="/wiki/File:Amplitude_Modulated_Wave-hm-64.svg" class="mw-file-description"><img alt="Graphs illustrating how signal intelligibility increases with modulation index, but only up to 100% using standard AM." src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b0/Amplitude_Modulated_Wave-hm-64.svg/400px-Amplitude_Modulated_Wave-hm-64.svg.png" decoding="async" width="400" height="553" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b0/Amplitude_Modulated_Wave-hm-64.svg/600px-Amplitude_Modulated_Wave-hm-64.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b0/Amplitude_Modulated_Wave-hm-64.svg/800px-Amplitude_Modulated_Wave-hm-64.svg.png 2x" data-file-width="512" data-file-height="708" /></a><figcaption>Figure 4: Modulation depth. In the diagram, the unmodulated carrier has an amplitude of 1.</figcaption></figure> <div class="mw-heading mw-heading2"><h2 id="Modulation_methods"><span class="anchor" id="AM_modulation_methods"></span>Modulation methods</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Amplitude_modulation&action=edit&section=15" title="Edit section: Modulation methods"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Ammodstage.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/b/bb/Ammodstage.png/300px-Ammodstage.png" decoding="async" width="300" height="232" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/bb/Ammodstage.png/450px-Ammodstage.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/bb/Ammodstage.png/600px-Ammodstage.png 2x" data-file-width="611" data-file-height="473" /></a><figcaption>Anode (plate) modulation. A tetrode's plate and screen grid voltage is modulated via an audio transformer. The resistor R1 sets the grid bias; both the input and output are tuned circuits with inductive coupling.</figcaption></figure> <p>Modulation circuit designs may be classified as low- or high-level (depending on whether they modulate in a low-power domain—followed by amplification for transmission—or in the high-power domain of the transmitted signal).<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> </p> <div class="mw-heading mw-heading3"><h3 id="Low-level_generation">Low-level generation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Amplitude_modulation&action=edit&section=16" title="Edit section: Low-level generation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In modern radio systems, modulated signals are generated via <a href="/wiki/Digital_signal_processing" title="Digital signal processing">digital signal processing</a> (DSP). With DSP many types of AM are possible with software control (including DSB with carrier, SSB suppressed-carrier and independent sideband, or ISB). Calculated digital samples are converted to voltages with a <a href="/wiki/Digital-to-analog_converter" title="Digital-to-analog converter">digital-to-analog converter</a>, typically at a frequency less than the desired RF-output frequency. The analog signal must then be shifted in frequency and <a href="/wiki/Linear_amplifier" title="Linear amplifier">linearly amplified</a> to the desired frequency and power level (linear amplification must be used to prevent modulation distortion).<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> This low-level method for AM is used in many Amateur Radio transceivers.<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><p>AM may also be generated at a low level, using analog methods described in the next section. </p> <div class="mw-heading mw-heading3"><h3 id="High-level_generation">High-level generation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Amplitude_modulation&action=edit&section=17" title="Edit section: High-level generation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>High-power AM <a href="/wiki/Transmitter" title="Transmitter">transmitters</a> (such as those used for <a href="/wiki/AM_broadcasting" title="AM broadcasting">AM broadcasting</a>) are based on high-efficiency <a href="/wiki/Class-D_amplifier" title="Class-D amplifier">class-D</a> and class-E <a href="/wiki/Electronic_amplifier" class="mw-redirect" title="Electronic amplifier">power amplifier</a> stages, modulated by varying the supply voltage.<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>Older designs (for broadcast and amateur radio) also generate AM by controlling the gain of the transmitter's final amplifier (generally class-C, for efficiency). The following types are for vacuum tube transmitters (but similar options are available with transistors):<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup><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> </p> <dl><dt>Plate modulation</dt> <dd>In plate modulation, the plate voltage of the RF amplifier is modulated with the audio signal. The audio power requirement is 50 percent of the RF-carrier power.</dd> <dt>Heising (constant-current) modulation</dt> <dd>RF amplifier plate voltage is fed through a <a href="/wiki/Choke_(electronics)" title="Choke (electronics)">choke</a> (high-value inductor). The AM modulation tube plate is fed through the same inductor, so the modulator tube diverts current from the RF amplifier. The choke acts as a constant current source in the audio range. This system has a low power efficiency.</dd> <dt>Control grid modulation</dt> <dd>The operating bias and gain of the final RF amplifier can be controlled by varying the voltage of the control grid. This method requires little audio power, but care must be taken to reduce distortion.</dd> <dt>Clamp tube (screen grid) modulation</dt> <dd>The screen-grid bias may be controlled through a <i>clamp tube</i>, which reduces voltage according to the modulation signal. It is difficult to approach 100-percent modulation while maintaining low distortion with this system.</dd> <dt><a href="/wiki/Doherty_amplifier" title="Doherty amplifier">Doherty modulation</a></dt> <dd>One tube provides the power under carrier conditions and another operates only for positive modulation peaks. Overall efficiency is good, and distortion is low.</dd> <dt><a href="/wiki/Ampliphase" title="Ampliphase">Outphasing modulation</a></dt> <dd>Two tubes are operated in parallel, but partially out of phase with each other. As they are differentially phase modulated their combined amplitude is greater or smaller. Efficiency is good and distortion low when properly adjusted.</dd> <dt><a href="/wiki/Pulse-width_modulation" title="Pulse-width modulation">Pulse-width modulation (PWM) or pulse-duration modulation (PDM)</a></dt> <dd>A highly efficient high voltage power supply is applied to the tube plate. The output voltage of this supply is varied at an audio rate to follow the program. This system was pioneered by <a href="/wiki/Hilmer_Swanson" title="Hilmer Swanson">Hilmer Swanson</a> and has a number of variations, all of which achieve high efficiency and sound quality.</dd> <dt>Digital methods</dt> <dd>The <a href="/wiki/Harris_Corporation" title="Harris Corporation">Harris Corporation</a> obtained a patent for synthesizing a modulated high-power carrier wave from a set of digitally selected low-power amplifiers, running in phase at the same carrier frequency.<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><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. (May 2021)">citation needed</span></a></i>]</sup> The input signal is sampled by a conventional audio analog-to-digital converter (ADC), and fed to a digital exciter, which modulates overall transmitter output power by switching a series of low-power solid-state RF amplifiers on and off. The combined output drives the antenna system.</dd></dl> <div class="mw-heading mw-heading2"><h2 id="Demodulation_methods"><span class="anchor" id="AM_demodulation_methods"></span>Demodulation methods</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Amplitude_modulation&action=edit&section=18" title="Edit section: Demodulation methods"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The simplest form of AM demodulator consists of a <a href="/wiki/Diode" title="Diode">diode</a> which is configured to act as <a href="/wiki/Envelope_detector" title="Envelope detector">envelope detector</a>. Another type of demodulator, the <a href="/wiki/Product_detector" title="Product detector">product detector</a>, can provide better-quality demodulation with additional circuit complexity. </p> <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=Amplitude_modulation&action=edit&section=19" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/AM_stereo" title="AM stereo">AM stereo</a></li> <li><a href="/wiki/Shortwave_radio" title="Shortwave radio">Shortwave radio</a></li> <li><a href="/wiki/Amplitude_modulation_signalling_system" title="Amplitude modulation signalling system">Amplitude modulation signalling system</a> (AMSS)</li> <li><a href="/wiki/Modulation_sphere" title="Modulation sphere">Modulation sphere</a></li> <li><a href="/wiki/Types_of_radio_emissions" title="Types of radio emissions">Types of radio emissions</a></li> <li><a href="/wiki/Airband" title="Airband">Airband</a></li> <li><a href="/wiki/Double-sideband_suppressed-carrier_transmission" title="Double-sideband suppressed-carrier transmission">DSB-SC</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Amplitude_modulation&action=edit&section=20" title="Edit section: 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 .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.aminharadio.com/radio/files/Artigo-Revista-PCP-USA.pdf">"Father Landell de Moura : Radio Broadcasting Pioneer : FABIO S. FLOSI : UNICAMP – University of Campinas, State of São Paulo"</a> <span class="cs1-format">(PDF)</span>. <i>Aminharadio.com</i>. <a rel="nofollow" class="external text" href="https://ghostarchive.org/archive/20221009/http://www.aminharadio.com/radio/files/Artigo-Revista-PCP-USA.pdf">Archived</a> <span class="cs1-format">(PDF)</span> from the original on 9 October 2022<span class="reference-accessdate">. Retrieved <span class="nowrap">15 July</span> 2018</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Aminharadio.com&rft.atitle=Father+Landell+de+Moura+%3A+Radio+Broadcasting+Pioneer+%3A+FABIO+S.+FLOSI+%3A+UNICAMP+%E2%80%93+University+of+Campinas%2C+State+of+S%C3%A3o+Paulo&rft_id=http%3A%2F%2Fwww.aminharadio.com%2Fradio%2Ffiles%2FArtigo-Revista-PCP-USA.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAmplitude+modulation" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text">AT&T, <i>Telecommunication Transmission Engineering</i>, Volume 1—<i>Principles</i>, 2nd Edition, Bell Center for Technical Education (1977)</span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text">AT&T, <i>Engineering and Operations in the Bell System</i> (1984) p.211</span> </li> <li id="cite_note-Bray-4"><span class="mw-cite-backlink">^ <a href="#cite_ref-Bray_4-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Bray_4-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Bray_4-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Bray_4-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBray2002" class="citation book cs1">Bray, John (2002). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=3h7R36Y0yFUC&pg=PA61"><i>Innovation and the Communications Revolution: From the Victorian Pioneers to Broadband Internet</i></a>. Inst. of Electrical Engineers. pp. 59, 61–62. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0852962185" title="Special:BookSources/0852962185"><bdi>0852962185</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Innovation+and+the+Communications+Revolution%3A+From+the+Victorian+Pioneers+to+Broadband+Internet&rft.pages=59%2C+61-62&rft.pub=Inst.+of+Electrical+Engineers&rft.date=2002&rft.isbn=0852962185&rft.aulast=Bray&rft.aufirst=John&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3D3h7R36Y0yFUC%26pg%3DPA61&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAmplitude+modulation" class="Z3988"></span></span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFAtul_P._GodseU._A._Bakshi2009" class="citation book cs1">Atul P. Godse; U. A. Bakshi (2009). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=coQ6ac-fh6QC&pg=PA36"><i>Communication Engineering</i></a>. Technical Publications. p. 36. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-81-8431-089-4" title="Special:BookSources/978-81-8431-089-4"><bdi>978-81-8431-089-4</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Communication+Engineering&rft.pages=36&rft.pub=Technical+Publications&rft.date=2009&rft.isbn=978-81-8431-089-4&rft.au=Atul+P.+Godse&rft.au=U.+A.+Bakshi&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DcoQ6ac-fh6QC%26pg%3DPA36&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAmplitude+modulation" class="Z3988"></span></span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSilver2011" class="citation book cs1">Silver, Ward, ed. (2011). "Ch. 15 DSP and Software Radio Design". <i>The ARRL Handbook for Radio Communications</i> (Eighty-eighth ed.). American Radio Relay League. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-87259-096-0" title="Special:BookSources/978-0-87259-096-0"><bdi>978-0-87259-096-0</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Ch.+15+DSP+and+Software+Radio+Design&rft.btitle=The+ARRL+Handbook+for+Radio+Communications&rft.edition=Eighty-eighth&rft.pub=American+Radio+Relay+League&rft.date=2011&rft.isbn=978-0-87259-096-0&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAmplitude+modulation" class="Z3988"></span></span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSilver2011" class="citation book cs1">Silver, Ward, ed. (2011). "Ch. 14 Transceivers". <i>The ARRL Handbook for Radio Communications</i> (Eighty-eighth ed.). American Radio Relay League. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-87259-096-0" title="Special:BookSources/978-0-87259-096-0"><bdi>978-0-87259-096-0</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Ch.+14+Transceivers&rft.btitle=The+ARRL+Handbook+for+Radio+Communications&rft.edition=Eighty-eighth&rft.pub=American+Radio+Relay+League&rft.date=2011&rft.isbn=978-0-87259-096-0&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAmplitude+modulation" class="Z3988"></span></span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFFrederick_H._Raab2003" class="citation journal cs1">Frederick H. Raab; et al. (May 2003). <a rel="nofollow" class="external text" href="https://www.scribd.com/doc/8616046/RF-Power-Amplifier-and-Transmitter-Technologies-Part2">"RF and Microwave Power Amplifier and Transmitter Technologies – Part 2"</a>. <i>High Frequency Design</i>: 22ff. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20160306164053/https://www.scribd.com/doc/8616046/RF-Power-Amplifier-and-Transmitter-Technologies-Part2">Archived</a> from the original on 6 March 2016<span class="reference-accessdate">. Retrieved <span class="nowrap">8 September</span> 2017</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=High+Frequency+Design&rft.atitle=RF+and+Microwave+Power+Amplifier+and+Transmitter+Technologies+%E2%80%93+Part+2&rft.pages=22ff&rft.date=2003-05&rft.au=Frederick+H.+Raab&rft_id=https%3A%2F%2Fwww.scribd.com%2Fdoc%2F8616046%2FRF-Power-Amplifier-and-Transmitter-Technologies-Part2&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAmplitude+modulation" class="Z3988"></span></span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLaurence_Gray_and_Richard_Graham1961" class="citation book cs1">Laurence Gray and Richard Graham (1961). <i>Radio Transmitters</i>. McGraw-Hill. pp. 141ff.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Radio+Transmitters&rft.pages=141ff&rft.pub=McGraw-Hill&rft.date=1961&rft.au=Laurence+Gray+and+Richard+Graham&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAmplitude+modulation" class="Z3988"></span></span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCavell,_Garrison_C._Ed.2018" class="citation book cs1">Cavell, Garrison C. Ed. (2018). <i>National Association of Broadcasters Engineering Handbook, 11th Ed</i>. Routledge. pp. 1099ff.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=National+Association+of+Broadcasters+Engineering+Handbook%2C+11th+Ed.&rft.pages=1099ff&rft.pub=Routledge&rft.date=2018&rft.au=Cavell%2C+Garrison+C.+Ed.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAmplitude+modulation" class="Z3988"></span></span> </li> <li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1041539562">.mw-parser-output .citation{word-wrap:break-word}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}</style><span class="citation patent" id="CITEREFSwanson1986"><a rel="nofollow" class="external text" href="https://worldwide.espacenet.com/textdoc?DB=EPODOC&IDX=US4580111">US 4580111</a>, <a href="/wiki/Hilmer_Swanson" title="Hilmer Swanson">Swanson, Hilmer</a>, "Amplitude modulation using digitally selected carrier amplifiers", published 1986-04-01,  assigned to <a href="/wiki/Harris_Corp" class="mw-redirect" title="Harris Corp">Harris Corp</a></span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Apatent&rft.number=4580111&rft.cc=US&rft.title=Amplitude+modulation+using+digitally+selected+carrier+amplifiers&rft.inventor=Swanson&rft.assignee=%5B%5BHarris+Corp%5D%5D&rft.appldate=1981-12-24&rft.pubdate=1986-04-01"><span style="display: none;"> </span></span></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=Amplitude_modulation&action=edit&section=21" title="Edit section: Bibliography"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li>Newkirk, David and Karlquist, Rick (2004). Mixers, modulators and demodulators. In D. G. Reed (ed.), <i>The ARRL Handbook for Radio Communications</i> (81st ed.), pp. 15.1–15.36. Newington: ARRL. <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/0-87259-196-4" title="Special:BookSources/0-87259-196-4">0-87259-196-4</a>.</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=Amplitude_modulation&action=edit&section=22" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><i><a rel="nofollow" class="external text" href="https://web.archive.org/web/20090728105917/http://demonstrations.wolfram.com/AmplitudeModulation/">Amplitude Modulation</a></i> by Jakub Serych, <a href="/wiki/Wolfram_Demonstrations_Project" title="Wolfram Demonstrations Project">Wolfram Demonstrations Project</a>.</li> <li><a rel="nofollow" class="external text" href="http://robotics.eecs.berkeley.edu/~sastry/ee20/modulation/node3.html">Amplitude Modulation</a>, by S Sastry.</li> <li><a rel="nofollow" class="external text" href="https://fas.org/man/dod-101/navy/docs/es310/AM.htm">Amplitude Modulation</a>, an introduction by <a href="/wiki/Federation_of_American_Scientists" title="Federation of American Scientists">Federation of American Scientists</a>.</li> <li><a rel="nofollow" class="external text" href="https://www.electronics-notes.com/articles/radio/modulation/amplitude-modulation-am.php">Amplitude Modulation tutorial</a> including related topics of modulators, demodulators, etc...</li> <li><a rel="nofollow" class="external text" href="https://colab.research.google.com/drive/14Ws9gX1hPzBkE7P1sBepVuoz-uo2f-Be?usp=sharing">Analog Modulation online interactive demonstration</a> using Python in <a rel="nofollow" class="external text" href="https://colab.research.google.com">Google Colab Platform</a>, by C Foh.</li></ul> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1236075235">.mw-parser-output .navbox{box-sizing:border-box;border:1px solid #a2a9b1;width:100%;clear:both;font-size:88%;text-align:center;padding:1px;margin:1em auto 0}.mw-parser-output .navbox .navbox{margin-top:0}.mw-parser-output .navbox+.navbox,.mw-parser-output .navbox+.navbox-styles+.navbox{margin-top:-1px}.mw-parser-output .navbox-inner,.mw-parser-output .navbox-subgroup{width:100%}.mw-parser-output .navbox-group,.mw-parser-output .navbox-title,.mw-parser-output .navbox-abovebelow{padding:0.25em 1em;line-height:1.5em;text-align:center}.mw-parser-output .navbox-group{white-space:nowrap;text-align:right}.mw-parser-output .navbox,.mw-parser-output .navbox-subgroup{background-color:#fdfdfd}.mw-parser-output .navbox-list{line-height:1.5em;border-color:#fdfdfd}.mw-parser-output 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scope="row" class="navbox-group" style="width:1%">Pioneers</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/Nasir_Ahmed_(engineer)" title="Nasir Ahmed (engineer)">Nasir Ahmed</a></li> <li><a href="/wiki/Edwin_Howard_Armstrong" title="Edwin Howard Armstrong">Edwin Howard Armstrong</a></li> <li><a href="/wiki/Mohamed_M._Atalla" title="Mohamed M. Atalla">Mohamed M. Atalla</a></li> <li><a href="/wiki/John_Logie_Baird" title="John Logie Baird">John Logie Baird</a></li> <li><a href="/wiki/Paul_Baran" title="Paul Baran">Paul Baran</a></li> <li><a href="/wiki/John_Bardeen" title="John Bardeen">John Bardeen</a></li> <li><a href="/wiki/Alexander_Graham_Bell" title="Alexander Graham Bell">Alexander Graham Bell</a></li> <li><a href="/wiki/Emile_Berliner" title="Emile Berliner">Emile Berliner</a></li> <li><a href="/wiki/Tim_Berners-Lee" title="Tim Berners-Lee">Tim Berners-Lee</a></li> <li><a href="/wiki/Francis_Blake_(inventor)" title="Francis Blake (inventor)">Francis Blake</a></li> <li><a href="/wiki/Jagadish_Chandra_Bose" title="Jagadish Chandra Bose">Jagadish Chandra Bose</a></li> <li><a href="/wiki/Charles_Bourseul" title="Charles Bourseul">Charles Bourseul</a></li> <li><a href="/wiki/Walter_Houser_Brattain" title="Walter Houser Brattain">Walter Houser Brattain</a></li> <li><a href="/wiki/Vint_Cerf" title="Vint Cerf">Vint Cerf</a></li> <li><a href="/wiki/Claude_Chappe" title="Claude Chappe">Claude Chappe</a></li> <li><a href="/wiki/Yogen_Dalal" class="mw-redirect" title="Yogen Dalal">Yogen Dalal</a></li> <li><a href="/wiki/Daniel_Davis_Jr." title="Daniel Davis Jr.">Daniel Davis Jr.</a></li> <li><a href="/wiki/Donald_Davies" title="Donald Davies">Donald Davies</a></li> <li><a href="/wiki/Amos_Dolbear" title="Amos Dolbear">Amos Dolbear</a></li> <li><a href="/wiki/Thomas_Edison" title="Thomas Edison">Thomas Edison</a></li> <li><a href="/wiki/Lee_de_Forest" title="Lee de Forest">Lee de Forest</a></li> <li><a href="/wiki/Philo_Farnsworth" title="Philo Farnsworth">Philo Farnsworth</a></li> <li><a href="/wiki/Reginald_Fessenden" title="Reginald Fessenden">Reginald Fessenden</a></li> <li><a href="/wiki/Elisha_Gray" title="Elisha Gray">Elisha Gray</a></li> <li><a href="/wiki/Oliver_Heaviside" title="Oliver Heaviside">Oliver Heaviside</a></li> <li><a href="/wiki/Robert_Hooke" title="Robert Hooke">Robert Hooke</a></li> <li><a href="/wiki/Erna_Schneider_Hoover" title="Erna Schneider Hoover">Erna Schneider Hoover</a></li> <li><a href="/wiki/Harold_Hopkins_(physicist)" title="Harold Hopkins (physicist)">Harold Hopkins</a></li> <li><a href="/wiki/Gardiner_Greene_Hubbard" title="Gardiner Greene Hubbard">Gardiner Greene Hubbard</a></li> <li><a href="/wiki/List_of_Internet_pioneers" title="List of Internet pioneers">Internet pioneers</a></li> <li><a href="/wiki/Bob_Kahn" class="mw-redirect" title="Bob Kahn">Bob Kahn</a></li> <li><a href="/wiki/Dawon_Kahng" title="Dawon Kahng">Dawon Kahng</a></li> <li><a href="/wiki/Charles_K._Kao" title="Charles K. Kao">Charles K. Kao</a></li> <li><a href="/wiki/Narinder_Singh_Kapany" title="Narinder Singh Kapany">Narinder Singh Kapany</a></li> <li><a href="/wiki/Hedy_Lamarr" title="Hedy Lamarr">Hedy Lamarr</a></li> <li><a href="/wiki/Roberto_Landell_de_Moura" title="Roberto Landell de Moura">Roberto Landell de Moura</a></li> <li><a href="/wiki/Innocenzo_Manzetti" title="Innocenzo Manzetti">Innocenzo Manzetti</a></li> <li><a href="/wiki/Guglielmo_Marconi" title="Guglielmo Marconi">Guglielmo Marconi</a></li> <li><a href="/wiki/Robert_Metcalfe" title="Robert Metcalfe">Robert Metcalfe</a></li> <li><a href="/wiki/Antonio_Meucci" title="Antonio Meucci">Antonio Meucci</a></li> <li><a href="/wiki/Samuel_Morse" title="Samuel Morse">Samuel Morse</a></li> <li><a href="/wiki/Jun-ichi_Nishizawa" title="Jun-ichi Nishizawa">Jun-ichi Nishizawa</a></li> <li><a href="/wiki/Charles_Grafton_Page" title="Charles Grafton Page">Charles Grafton Page</a></li> <li><a href="/wiki/Radia_Perlman" title="Radia Perlman">Radia Perlman</a></li> <li><a href="/wiki/Alexander_Stepanovich_Popov" class="mw-redirect" title="Alexander Stepanovich Popov">Alexander Stepanovich Popov</a></li> <li><a href="/wiki/Tivadar_Pusk%C3%A1s" title="Tivadar Puskás">Tivadar Puskás</a></li> <li><a href="/wiki/Johann_Philipp_Reis" title="Johann Philipp Reis">Johann Philipp Reis</a></li> <li><a href="/wiki/Claude_Shannon" title="Claude Shannon">Claude Shannon</a></li> <li><a href="/wiki/Almon_Brown_Strowger" title="Almon Brown Strowger">Almon Brown Strowger</a></li> <li><a href="/wiki/Henry_Sutton_(inventor)" title="Henry Sutton (inventor)">Henry Sutton</a></li> <li><a href="/wiki/Charles_Sumner_Tainter" title="Charles Sumner Tainter">Charles Sumner Tainter</a></li> <li><a href="/wiki/Nikola_Tesla" title="Nikola Tesla">Nikola Tesla</a></li> <li><a href="/wiki/Camille_Tissot" title="Camille Tissot">Camille Tissot</a></li> <li><a href="/wiki/Alfred_Vail" title="Alfred Vail">Alfred Vail</a></li> <li><a href="/wiki/Thomas_A._Watson" title="Thomas A. Watson">Thomas A. Watson</a></li> <li><a href="/wiki/Charles_Wheatstone" title="Charles Wheatstone">Charles Wheatstone</a></li> <li><a href="/wiki/Vladimir_K._Zworykin" title="Vladimir K. Zworykin">Vladimir K. Zworykin</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Transmission_medium" title="Transmission medium">Transmission<br />media</a></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/Coaxial_cable" title="Coaxial cable">Coaxial cable</a></li> <li><a href="/wiki/Fiber-optic_communication" title="Fiber-optic communication">Fiber-optic communication</a> <ul><li><a href="/wiki/Optical_fiber" title="Optical fiber">optical fiber</a></li></ul></li> <li><a href="/wiki/Free-space_optical_communication" title="Free-space optical communication">Free-space optical communication</a></li> <li><a href="/wiki/Molecular_communication" title="Molecular communication">Molecular communication</a></li> <li><a href="/wiki/Radio_wave" title="Radio wave">Radio waves</a> <ul><li><a href="/wiki/Wireless" title="Wireless">wireless</a></li></ul></li> <li><a href="/wiki/Transmission_line" title="Transmission line">Transmission line</a> <ul><li><a href="/wiki/Telecommunication_circuit" title="Telecommunication circuit">telecommunication circuit</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Network_topology" title="Network topology">Network topology</a><br />and switching</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/Bandwidth_(computing)" title="Bandwidth (computing)">Bandwidth</a></li> <li><a href="/wiki/Telecommunications_link" title="Telecommunications link">Links</a></li> <li><a href="/wiki/Node_(networking)" title="Node (networking)">Nodes</a> <ul><li><a href="/wiki/Terminal_(telecommunication)" title="Terminal (telecommunication)">terminal</a></li></ul></li> <li><a href="/wiki/Network_switch" title="Network switch">Network switching</a> <ul><li><a href="/wiki/Circuit_switching" title="Circuit switching">circuit</a></li> <li><a href="/wiki/Packet_switching" title="Packet switching">packet</a></li></ul></li> <li><a href="/wiki/Telephone_exchange" title="Telephone exchange">Telephone exchange</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Multiplexing" title="Multiplexing">Multiplexing</a></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-division_multiple_access" title="Space-division multiple access">Space-division</a></li> <li><a href="/wiki/Frequency-division_multiplexing" title="Frequency-division multiplexing">Frequency-division</a></li> <li><a href="/wiki/Time-division_multiplexing" title="Time-division multiplexing">Time-division</a></li> <li><a href="/wiki/Polarization-division_multiplexing" title="Polarization-division multiplexing">Polarization-division</a></li> <li><a href="/wiki/Orbital_angular_momentum_multiplexing" title="Orbital angular momentum multiplexing">Orbital angular-momentum</a></li> <li><a href="/wiki/Code-division_multiple_access" title="Code-division multiple access">Code-division</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Concepts</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/Communication_protocol" title="Communication protocol">Communication protocol</a></li> <li><a href="/wiki/Computer_network" title="Computer network">Computer network</a></li> <li><a href="/wiki/Data_communication" title="Data communication">Data transmission</a></li> <li><a href="/wiki/Store_and_forward" title="Store and forward">Store and forward</a></li> <li><a href="/wiki/Telecommunications_equipment" title="Telecommunications equipment">Telecommunications equipment</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Telecommunications_network" title="Telecommunications network">Types of network</a></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/Cellular_network" title="Cellular network">Cellular network</a></li> <li><a href="/wiki/Ethernet" title="Ethernet">Ethernet</a></li> <li><a href="/wiki/Integrated_Services_Digital_Network" class="mw-redirect" title="Integrated Services Digital Network">ISDN</a></li> <li><a href="/wiki/Local_area_network" title="Local area network">LAN</a></li> <li><a href="/wiki/Mobile_telephony" title="Mobile telephony">Mobile</a></li> <li><a href="/wiki/Next-generation_network" title="Next-generation network">NGN</a></li> <li><a href="/wiki/Public_switched_telephone_network" title="Public switched telephone network">Public Switched Telephone</a></li> <li><a href="/wiki/Radio_network" title="Radio network">Radio</a></li> <li><a href="/wiki/Television_broadcasting" class="mw-redirect" title="Television broadcasting">Television</a></li> <li><a href="/wiki/Telex" title="Telex">Telex</a></li> <li><a href="/wiki/UUCP" title="UUCP">UUCP</a></li> <li><a href="/wiki/Wide_area_network" title="Wide area network">WAN</a></li> <li><a href="/wiki/Wireless_network" title="Wireless network">Wireless network</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Telecommunications_network" title="Telecommunications network">Notable networks</a></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/ARPANET" title="ARPANET">ARPANET</a></li> <li><a href="/wiki/BITNET" title="BITNET">BITNET</a></li> <li><a href="/wiki/CYCLADES" title="CYCLADES">CYCLADES</a></li> <li><a href="/wiki/FidoNet" title="FidoNet">FidoNet</a></li> <li><a href="/wiki/Internet" title="Internet">Internet</a></li> <li><a href="/wiki/Internet2" title="Internet2">Internet2</a></li> <li><a href="/wiki/JANET" title="JANET">JANET</a></li> <li><a href="/wiki/NPL_network" title="NPL network">NPL network</a></li> <li><a href="/wiki/Toasternet" title="Toasternet">Toasternet</a></li> <li><a href="/wiki/Usenet" title="Usenet">Usenet</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Locations</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/Category:Telecommunications_in_Africa" title="Category:Telecommunications in Africa">Africa</a></li> <li>Americas <ul><li><a href="/wiki/Category:Telecommunications_in_North_America" title="Category:Telecommunications in North America">North</a></li> <li><a href="/wiki/Category:Telecommunications_in_South_America" title="Category:Telecommunications in South America">South</a></li></ul></li> <li><a href="/wiki/Category:Communications_in_Antarctica" title="Category:Communications in Antarctica">Antarctica</a></li> <li><a href="/wiki/Category:Telecommunications_in_Asia" title="Category:Telecommunications in Asia">Asia</a></li> <li><a href="/wiki/Category:Telecommunications_in_Europe" title="Category:Telecommunications in Europe">Europe</a></li> <li><a href="/wiki/Category:Telecommunications_in_Oceania" title="Category:Telecommunications in Oceania">Oceania</a></li> <li>(<a href="/wiki/List_of_telecommunications_regulatory_bodies" title="List of telecommunications regulatory bodies">Global telecommunications regulation bodies</a>)</li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><span class="nowrap"><span class="noviewer" typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/4/4e/Telecom-icon.svg/16px-Telecom-icon.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/4e/Telecom-icon.svg/24px-Telecom-icon.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/4e/Telecom-icon.svg/32px-Telecom-icon.svg.png 2x" data-file-width="500" data-file-height="500" /></span></span> </span><a href="/wiki/Portal:Telecommunication" title="Portal:Telecommunication">Telecommunication portal</a></li> <li><span class="noviewer" typeof="mw:File"><span title="Category"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/23px-Symbol_category_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/31px-Symbol_category_class.svg.png 2x" data-file-width="180" data-file-height="185" /></span></span> <a href="/wiki/Category:Telecommunications" title="Category:Telecommunications">Category</a></li> <li><span class="noviewer" typeof="mw:File"><span title="List-Class article"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/d/db/Symbol_list_class.svg/16px-Symbol_list_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/d/db/Symbol_list_class.svg/23px-Symbol_list_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/d/db/Symbol_list_class.svg/31px-Symbol_list_class.svg.png 2x" data-file-width="180" data-file-height="185" /></span></span> <a href="/wiki/Outline_of_telecommunication" title="Outline of telecommunication">Outline</a></li> <li><span class="noviewer" typeof="mw:File"><span title="Commons page"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/12px-Commons-logo.svg.png" decoding="async" width="12" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/18px-Commons-logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/24px-Commons-logo.svg.png 2x" data-file-width="1024" data-file-height="1376" /></span></span> <a href="https://commons.wikimedia.org/wiki/Category:Telecommunications" class="extiw" title="commons:Category:Telecommunications">Commons</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"></div><div role="navigation" class="navbox" aria-labelledby="Analog_and_digital_audio_broadcasting" 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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Audio_broadcasting" title="Template:Audio broadcasting"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Audio_broadcasting" title="Template talk:Audio broadcasting"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Audio_broadcasting" title="Special:EditPage/Template:Audio broadcasting"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Analog_and_digital_audio_broadcasting" style="font-size:114%;margin:0 4em"><a href="/wiki/Analog_recording" title="Analog recording">Analog</a> and <a href="/wiki/Digital_audio" title="Digital audio">digital audio</a> <a href="/wiki/Broadcasting" title="Broadcasting">broadcasting</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Terrestrial</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 scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Radio" title="Radio">Radio</a> <a href="/wiki/Modulation" title="Modulation">modulation</a></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 class="mw-selflink selflink">AM</a></li> <li><a href="/wiki/Frequency_modulation" title="Frequency modulation">FM</a></li> <li><a href="/wiki/Orthogonal_frequency-division_multiplexing" title="Orthogonal frequency-division multiplexing">COFDM</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Frequency_allocation" title="Frequency allocation">Frequency allocations</a></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/Longwave" title="Longwave">LW</a> (<a href="/wiki/Low_frequency" title="Low frequency">LF</a>)</li> <li><a href="/wiki/Medium_wave" title="Medium wave">MW</a> (<a href="/wiki/Medium_frequency" title="Medium frequency">MF</a>)</li> <li><a href="/wiki/Shortwave_radio" title="Shortwave radio">SW</a> (<a href="/wiki/High_frequency" title="High frequency">HF</a>)</li> <li><a href="/wiki/Very_high_frequency" title="Very high frequency">VHF</a> (<a href="/wiki/Band_I" title="Band I">low</a> / <a href="/wiki/Band_II" title="Band II">mid</a> / <a href="/wiki/Band_III" title="Band III">high</a>)</li> <li><a href="/wiki/L_band" title="L band">L band</a> (<a href="/wiki/Ultra_high_frequency" title="Ultra high frequency">UHF</a>)</li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Digital 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/CAM-D" title="CAM-D">CAM-D</a></li> <li><a href="/wiki/Digital_Audio_Broadcasting" title="Digital Audio Broadcasting">DAB/DAB+</a></li> <li><a href="/wiki/Digital_Radio_Mondiale" title="Digital Radio Mondiale">DRM/DRM+</a></li> <li><a href="/wiki/ISDB-T#ISDB-Tsb" class="mw-redirect" title="ISDB-T">ISDB-Tsb</a></li> <li><a href="/wiki/FMeXtra" title="FMeXtra">FMeXtra</a></li> <li><a href="/wiki/HD_Radio" title="HD Radio">HD Radio</a></li> <li>CDR</li> <li><a href="/wiki/DVB-T2" title="DVB-T2">DVB-T2 Lite</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Satellite</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 scope="row" class="navbox-group" style="width:1%">Frequency allocations</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/C_band_(IEEE)" title="C band (IEEE)">C band</a></li> <li><a href="/wiki/Ku_band" title="Ku band">K<sub>u</sub> band</a></li> <li><a href="/wiki/L_band" title="L band">L band</a></li> <li><a href="/wiki/S_band" title="S band">S band</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Digital 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/Astra_Digital_Radio" title="Astra Digital Radio">ADR</a></li> <li><a href="/wiki/Digital_audio_broadcasting" class="mw-redirect" title="Digital audio broadcasting">DAB-S</a></li> <li><a href="/wiki/DVB-SH" title="DVB-SH">DVB-SH</a></li> <li><a href="/wiki/S-DMB" title="S-DMB">S-DMB</a></li> <li><a href="/wiki/ETSI_Satellite_Digital_Radio" title="ETSI Satellite Digital Radio">SDR</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Commercial_broadcasting" title="Commercial broadcasting">Commercial radio</a> providers</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/Sirius_XM" title="Sirius XM">Sirius XM</a> <ul><li><a href="/wiki/Sirius_XM_Canada" title="Sirius XM Canada">Canada</a></li></ul></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Audio_codec" title="Audio codec">Codecs</a></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/Advanced_Audio_Coding" title="Advanced Audio Coding">AAC</a></li> <li><a href="/wiki/Extended_Adaptive_Multi-Rate_%E2%80%93_Wideband" title="Extended Adaptive Multi-Rate – Wideband">AMR-WB+</a></li> <li><a href="/wiki/High-Definition_Coding" title="High-Definition Coding">HDC</a></li> <li><a href="/wiki/High-Efficiency_Advanced_Audio_Coding" title="High-Efficiency Advanced Audio Coding">HE-AAC</a></li> <li><a href="/wiki/MPEG-1_Audio_Layer_II" title="MPEG-1 Audio Layer II">MPEG-1 Audio Layer II</a></li> <li><a href="/wiki/Dynamic_Resolution_Adaptation" title="Dynamic Resolution Adaptation">DRA+</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Subcarrier" title="Subcarrier">Subcarrier</a> signals</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/Amplitude_modulation_signalling_system" title="Amplitude modulation signalling system">AMSS</a></li> <li><a href="/wiki/DirectBand" title="DirectBand">DirectBand</a></li> <li><a href="/wiki/Program-associated_data" title="Program-associated data">PAD</a></li> <li><a href="/wiki/Radio_Data_System" title="Radio Data System">RDS/RBDS</a></li> <li><a href="/wiki/Subsidiary_communications_authority" title="Subsidiary communications authority">SCA/SCMO</a></li> <li><a href="/wiki/Data_Radio_Channel" title="Data Radio Channel">DARC</a></li></ul> </div></td></tr><tr><td colspan="2" class="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 scope="col" class="navbox-title" colspan="2"><div id="Related_topics" style="font-size:114%;margin:0 4em">Related topics</div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Technical (audio)</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/Audio_data_compression" class="mw-redirect" title="Audio data compression">Audio data compression</a></li> <li><a href="/wiki/Audio_signal_processing" title="Audio signal processing">Audio signal processing</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Technical (<a href="/wiki/AM_stereo" title="AM stereo">AM stereo</a> formats)</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/AM_stereo#Belar_System" title="AM stereo">Belar</a></li> <li><a href="/wiki/C-QUAM" title="C-QUAM">C-QUAM</a></li> <li><a href="/wiki/AM_stereo#Harris_System" title="AM stereo">Harris</a></li> <li><a href="/wiki/AM_stereo#Kahn-Hazeltine" title="AM stereo">Kahn-Hazeltine</a></li> <li><a href="/wiki/AM_stereo#Magnavox_System" title="AM stereo">Magnavox</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Technical (emission)</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/AM_broadcasting" title="AM broadcasting">AM broadcasting</a></li> <li><a href="/wiki/AM_expanded_band" title="AM expanded band">AM expanded band</a></li> <li><a href="/wiki/Cable_radio" title="Cable radio">Cable radio</a></li> <li><a href="/wiki/Digital_radio" title="Digital radio">Digital radio</a></li> <li><a href="/wiki/Error_detection_and_correction" title="Error detection and correction">Error detection and correction</a></li> <li><a href="/wiki/FM_broadcast_band" title="FM broadcast band">FM broadcast band</a></li> <li><a href="/wiki/FM_broadcasting" title="FM broadcasting">FM broadcasting</a></li> <li><a href="/wiki/FM_extended_band_in_Brazil" title="FM extended band in Brazil">FM extended band in Brazil</a></li> <li><a href="/wiki/Multipath_propagation" title="Multipath propagation">Multipath propagation</a></li> <li><a href="/wiki/Shortwave_relay_station" title="Shortwave relay station">Shortwave relay station</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Cultural</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/History_of_radio" title="History of radio">History of radio</a></li> <li><a href="/wiki/International_broadcasting" title="International broadcasting">International broadcasting</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><b><span class="nowrap"><span class="noviewer" typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/commons/1/1d/Radio_icon.png" decoding="async" width="32" height="23" class="mw-file-element" data-file-width="30" data-file-height="22" /></span></span> </span><a href="/wiki/Portal:Radio" title="Portal:Radio">Radio portal</a></b></li> <li><a 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