Demodulation
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Demodulation is the act of removing the modulation from an analog signal.
To demodulate an AM signal, pass it through a dioderectifier. The amplitude variation will integrate into the original modulating signal.
There are several ways to demodulate an FM signal. The most common is to use a discriminator. This is composed of an electronic filter which decreases the amplitude of some frequencies relative to others, followed by an AM demodulator. If the filter response changes linearly with frequency, the final analog output will be proportional to the input frequency, as desired. Another one is to use two AM demodulators, one tuned to the high end of the band and the other to the low end, and feed the outputs into a difference amp. Another is to feed the signal into a phase-locked loop and use the error signal as the demodulated signal.