Good question. An ideal AM modulator (e.g. a multiplier as DSB modulator) obviously causes no signal distortion as long it keeps the integrity of the baseband signal, in other words satisfies the Nyquist criterion. The same applies to a synchronous demodulator which also does a simple frequency shift and mirroring but doesn't create intermodudation products or harmonics. But how about an envelope detector as demodulator? I modeled it as ideal full wave rectifier and it looks like that it also doesn't distort the baseband signal. My conclusion is that there are no additional restrictions to an AM demodulator than Nyquist.I think there probably is, but do not personally know, some relation between AC signal fidelity and "Nyquist*2^Nbits" for a desired bit-count-fidelity on an analog signal. Or SNR, driven by the per-carrier-cycle "error residue" from too coarse a "sampling".
For effective demodulation of signal from amplitude modulated wave, is there a ratio to be maintained between carrier and signal frequency?. For eg: if carrier is say 10KHz, what can be the maximum signal frequency that will ensure perfect demodulation at the other end? can it be 1KHz?
I also don't see a reference to suppressed carrier in the original question, but I agree, it's unclear in this point.
Then Kerim's fine example of DSB-SC AM sub on FM carrier using a ratio of fc=32768 Hz, Fs 0 to 5000 Hz for a minimum ratio of 6.4 is doable with synchronous demodulation.
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