The changing of the frequency
of a “carrier
” in response to a “modulating
, usually an audio waveform
. As the modulating signal voltage
) varies up and down the frequency of the carrier varies up and down from its nominal unmodulated value.
is a form of frequency modulation
because it is a periodic variation in frequency (pitch
In FM broadcasting the audio signal is used to modulate a high frequency carrier that is then transmitted. At the receiving end a special circuit called a FM detector, or “discriminator” is used to recover the audio from the modulated signal. FM is considered a better (than AM
— amplitude modulation
) method of transmitting radio and TV signals because the FM signal is not as sensitive to amplitude variations caused by atmospheric interference.
FM is also used as a sound synthesis technique (see FM Synthesis