Carrier and Sidebands ```Name: Scot Status: student Age: 40s Location: N/A Country: N/A Date: 1999 ``` Question: Why does amplitude modulation of a carrier signal produce both an upper and a lower sideband? Replies: When you amplitude modulate a carrier, you are mixing a radio-frequency wave with an audio-frequency wave (the audio signal). The mixing of two frequencies produces both the sum and difference of the frequencies, for the simple reason that: cos(w1 t) cos(w2 t) = 0.5 ( cos[(w1+w2)t] + cos[(w1-w2)t] ) w1 is the carrier frequency, w2 is the audio frequency. You see the two sidebands (w1+w2 and w1-w2) right there. Typically most of the power goes into the original carrier (w1) because the mixing isn't very efficient. So you get three signals. Grayce Click here to return to the Physics Archives

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