{"id":1063,"date":"2015-11-30T00:06:00","date_gmt":"2015-11-29T13:06:00","guid":{"rendered":"https:\/\/www.homebrewradio.us\/blog\/2015\/11\/30\/a-very-unusual-explanation-of-am-and-ssb-what-do-you-think-2\/"},"modified":"2015-11-30T00:06:00","modified_gmt":"2015-11-29T13:06:00","slug":"a-very-unusual-explanation-of-am-and-ssb-what-do-you-think-2","status":"publish","type":"post","link":"https:\/\/www.homebrewradio.us\/blog\/2015\/11\/30\/a-very-unusual-explanation-of-am-and-ssb-what-do-you-think-2\/","title":{"rendered":"A Very Unusual Explanation of AM and SSB — What Do You Think?"},"content":{"rendered":"

Wow, I’ve never seen it presented this way. Am I losing it or is this just completely wrong? This comes from this web site: <\/strong>

<\/strong> http:\/\/www.dsprelated.com\/showarticle\/176.php<\/a><\/strong>

<\/strong>
<\/span><\/strong> TRANSMITTED SSB SIGNALS<\/span><\/strong>
Before we illustrate SSB demodulation, it’s useful to quickly review the nature of standard double-sideband amplitude modulation (AM) commercial broadcast transmissions that your car radio is designed to receive. In standard AM communication systems, an analog real-valued baseband input signal may have a spectral magnitude, for example, like that shown in Figure 2(a). Such a signal might well be a 4 kHz-wide audio output of a microphone having no spectral energy at DC (zero Hz). This baseband audio signal is multiplied, in the time domain, by a pure-tone carrier to generate what’s called the modulated signal whose spectral magnitude content is given in Figure 2(b).
In this example the carrier frequency is 80 kHz, thus the transmitted AM signal contains pure-tone carrier spectral energy at \u00b180 kHz. The purpose of a remote AM receiver, then, is to demodulate that transmitted DSB AM signal and generate the baseband signal given in Figure 2(c). The analog demodulated audio signal could then be amplified and routed to a loudspeaker. We note at this point that the two transmitted sidebands, on either side of \u00b180 kHz, each contain the same audio information. <\/p>\n

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In an SSB communication system the baseband audio signal modulates a carrier, in what’s called the “upper sideband” (USB) mode of transmission, such that the transmitted analog signal would have the spectrum shown in Figure 3(b). Notice in this scenario, the lower (upper) frequency edge of the baseband signal\u2019s USB (LSB) has been translated in frequency so that it\u2019s located at 80 kHz (-80 kHz). (The phasing method of SSB radio frequency (RF) generation is given in Appendix A.)<\/div>\n
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The purpose of a remote SSB receiver is to demodulate that transmitted SSB signal, generating the baseband audio signal given in Figure 3(c). The analog demodulated baseband signal can then be amplified and drive a loudspeaker.<\/div>\n
In a “lower sideband” (LSB) mode of SSB transmission, the transmitted analog signal would have the spectrum shown in Figure 4(b). In this case, the upper (lower) frequency edge of the baseband signal\u2019s LSB (USB) has been translated in frequency so that it\u2019s located at 80 kHz (-80 kHz). The baseband signal in Figure 4(a) is real-valued, so the positive-frequency portion of its spectrum is the complex conjugate of the negative-frequency portion. Both sidebands contain the same information, and that’s why LSB transmission and USB transmission communicate identical information.<\/div>\n
And again, in the LSB mode of transmission, the remote receiver must demodulate that transmitted LSB SSB signal and generate the baseband audio signal given in Figure 4(c).<\/div>\n
\"\"<\/b><\/i><\/u><\/sub><\/sup><\/strike><\/div>\n","protected":false},"excerpt":{"rendered":"

Wow, I’ve never seen it presented this way. Am I losing it or is this just completely wrong? This comes from this web site: http:\/\/www.dsprelated.com\/showarticle\/176.php TRANSMITTED SSB SIGNALS Before we illustrate SSB demodulation, it’s useful to quickly review the nature of standard double-sideband amplitude modulation (AM) commercial broadcast transmissions that your car radio is designed … Continue reading “A Very Unusual Explanation of AM and SSB — What Do You Think?”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-1063","post","type-post","status-publish","format-standard","hentry","category-uncategorised"],"_links":{"self":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/1063","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/comments?post=1063"}],"version-history":[{"count":0,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/1063\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media?parent=1063"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/categories?post=1063"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/tags?post=1063"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}