The spectrum of an ASK signal can easily be determined if the spectrum of
the baseband data symbol stream is known, by viewing the ASK modulation process as a
mixing or multiplication of the baseband symbol stream with the carrier component. |
If we consider for the moment a single frequency component, cos wmt, from within the baseband spectrum, and perform
the mathematical multiplication with the carrier, cos wct,
the modulated signal becomes: cos wmt x cos wct = 0.5 cos (wc wm)t + 0.5 cos (wc + wm)t The modulated spectrum for this sample component becomes two identical components spaced symmetrically either side of the carrier frequency. |
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