chapter  3
2 Modulation and demodulation
Pages 1

Modulation is the name given to the process of

changing a particular property of the carrier wave

in sympathy with the instantaneous voltage (or

current) signal.

The most commonly used methods of

modulation are amplitude modulation (AM) and

frequency modulation (FM). In the former case,

the carrier amplitude (its peak voltage) varies

according to the voltage, at any instant, of the

modulating signal. In the latter case, the carrier

frequency is varied in accordance with the

voltage, at any instant, of the modulating signal.