Frequency Modulation

alteration of the frequency of transmitting waves to reduce static in the transmitted sound or image

In telecommunications, frequency modulation (FM) conveys information over a carrier wave by varying its frequency (contrast this with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant). In analog applications, the instantaneous frequency of the carrier is directly proportional to the instantaneous value of the input signal.  Digital data can be sent by shifting the carrier's frequency among a set of discrete values, a technique known as frequency-shift keying.
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Noun
1. modulation of the frequency of the (radio) carrier wave
(synonym) FM
(hypernym) modulation

Modulation in which the instantaneous frequency of a sine wave carrier is caused to depart from the center frequency by an amount proportional to the instantaneous value of the modulating signal. (188 ) Note 1: In FM, the carrier frequency is called the center frequency. Note 2: FM is a form of angle modulation. Note 3: In optical communications, even if the electrical baseband signal is used to frequency-modulate an electrical carrier (an "FM" optical communications system), it is still the intensity of the lightwave that is varied (modulated) by the electrical FM carrier. In this case, the "information,"as far as the lightwave is concerned, is the electrical FM carrier. The lightwave is varied in intensity at an instantaneous rate corresponding to the instantaneous frequency of the electrical FM carrier. [After FAA]

<communications> (FM) A method of encoding data by varying the frequency of a constant amplitude carrier signal.
Contrast Amplitude Modulation.
(2001-04-02)