{"id":4591,"date":"2025-03-28T12:00:57","date_gmt":"2025-03-28T06:30:57","guid":{"rendered":"https:\/\/study.madeeasy.in\/?p=4591"},"modified":"2025-07-29T17:27:18","modified_gmt":"2025-07-29T11:57:18","slug":"fourier-transform","status":"publish","type":"post","link":"https:\/\/www.madeeasy.in\/study\/ee\/lti-systems\/fourier-transform","title":{"rendered":"Fourier Transform"},"content":{"rendered":"<h2 style=\"text-align: justify;\">INTRODUCTION<\/h2>\n<p style=\"text-align: justify;\">In the previous chapter, we saw that Fourier series can be generalized only for periodic signals not for aperiodic one i.e. any periodic signal is represented as linear combination of hormonally related complex exponentials.<\/p>\n<p style=\"text-align: justify;\">This limitation is overcome through Fourier transform which is applicable for both aperiodic and periodic signals. The Fourier transform gives a frequency domain description of time domain signal. An aperiodic signal is one which is periodic with an infinite period. As the period increases the fundamental frequency decreases which makes aperiodic signal infinitesimally close in frequency and the representation in terms of linear combination takes the form of an integral rather than sum. The resulting spectrum is called Fourier transform. Thus Fourier transform is extension of Fourier series for aperiodic signals.<\/p>\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_79_1 ez-toc-wrap-left counter-hierarchy ez-toc-counter ez-toc-light-blue ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.madeeasy.in\/study\/ee\/lti-systems\/fourier-transform\/#THE-DEFINITION\" >THE DEFINITION<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.madeeasy.in\/study\/ee\/lti-systems\/fourier-transform\/#Conditions-for-existence-of-Fourier-Transform\" >Conditions for existence of Fourier Transform<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.madeeasy.in\/study\/ee\/lti-systems\/fourier-transform\/#FOURIER-TRANSFORM-OF-SOME-BASIC-SIGNALS\" >FOURIER TRANSFORM OF SOME BASIC SIGNALS<\/a><\/li><\/ul><\/nav><\/div>\n<h3 style=\"text-align: justify;\"><span class=\"ez-toc-section\" id=\"THE-DEFINITION\"><\/span>THE DEFINITION<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\">Consider a continuous time signal x(t). Its Fourier transform is defined as<\/p>\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-4592 size-full\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2025\/03\/fourier.jpg\" alt=\"Fourier\" width=\"664\" height=\"314\" srcset=\"https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2025\/03\/fourier.jpg 664w, https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2025\/03\/fourier-300x142.jpg 300w\" sizes=\"auto, (max-width: 664px) 100vw, 664px\" \/><\/p>\n<h3 style=\"text-align: justify;\"><span class=\"ez-toc-section\" id=\"Conditions-for-existence-of-Fourier-Transform\"><\/span>Conditions for existence of Fourier Transform<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\">(i) Signal x(t) should be absolutely integrable. i.e.,<\/p>\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-4593 size-full\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2025\/03\/fourier-transform.jpg\" alt=\" Fourier Transform\" width=\"225\" height=\"74\" \/><\/p>\n<p style=\"text-align: justify;\">(ii) Signal x(t) should be deterministic over any finite interval.<\/p>\n<p style=\"text-align: justify;\">(a) It should have finite number maxima and minima over a finite interval.<br \/>\n(b) It should have finite number of finite size discontinuities over finite interval.<br \/>\nThe conditions are sufficient not necessary. It means that there is class of signals that violate either one or both conditions, possess Fourier transform.<br \/>\ne.g. power signal, periodic signals. etc.<\/p>\n<h3 style=\"text-align: justify;\"><span class=\"ez-toc-section\" id=\"FOURIER-TRANSFORM-OF-SOME-BASIC-SIGNALS\"><\/span>FOURIER TRANSFORM OF SOME BASIC SIGNALS<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-4594 size-full\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2025\/03\/fourier-spectra.jpg\" alt=\"Fourier spectra \" width=\"485\" height=\"522\" srcset=\"https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2025\/03\/fourier-spectra.jpg 485w, https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2025\/03\/fourier-spectra-279x300.jpg 279w\" sizes=\"auto, (max-width: 485px) 100vw, 485px\" \/><\/p>\n<p style=\"text-align: justify;\">Observing |X (\u03c9)| and \u2220X (\u03c9), we see magnitude spectrum |X (\u03c9)| is even function of \u03c9 and phase spectrum \u2220X (\u03c9) is an odd function of \u03c9.<\/p>\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-4595 size-full\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2025\/03\/Fourier-spectra-1.jpg\" alt=\"Fourier spectra \" width=\"604\" height=\"629\" srcset=\"https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2025\/03\/Fourier-spectra-1.jpg 604w, https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2025\/03\/Fourier-spectra-1-288x300.jpg 288w\" sizes=\"auto, (max-width: 604px) 100vw, 604px\" \/><\/p>\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-4596 size-full\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2025\/03\/gate-pulse.jpg\" alt=\"Gate Pulse \" width=\"692\" height=\"876\" srcset=\"https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2025\/03\/gate-pulse.jpg 692w, https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2025\/03\/gate-pulse-237x300.jpg 237w\" sizes=\"auto, (max-width: 692px) 100vw, 692px\" \/><\/p>\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-4597 size-full aligncenter\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2025\/03\/magnitude.jpg\" alt=\"Magnitude\" width=\"740\" height=\"921\" srcset=\"https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2025\/03\/magnitude.jpg 740w, https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2025\/03\/magnitude-241x300.jpg 241w\" sizes=\"auto, (max-width: 740px) 100vw, 740px\" \/><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-4600 size-full\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2025\/03\/rationalizing.jpg\" alt=\"Rationalizing\" width=\"560\" height=\"537\" srcset=\"https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2025\/03\/rationalizing.jpg 560w, https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2025\/03\/rationalizing-300x288.jpg 300w\" sizes=\"auto, (max-width: 560px) 100vw, 560px\" \/><\/p>\n","protected":false},"excerpt":{"rendered":"<p>INTRODUCTION In the previous chapter, we saw that Fourier series can be generalized only for periodic signals not for aperiodic<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1351,5],"tags":[1360,1361,1359],"class_list":["post-4591","post","type-post","status-publish","format-standard","hentry","category-lti-systems","category-ee","tag-aperiodic-continuous","tag-complex-exponentials","tag-fourier-spectra"],"_links":{"self":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts\/4591","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/comments?post=4591"}],"version-history":[{"count":0,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts\/4591\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/media?parent=4591"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/categories?post=4591"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/tags?post=4591"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}