In telecommunications and signal processing, frequency modulation ( FM ) is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave. A major advantage of FM in a communications circuit, compared for example with AM , is the possibility of improved Signal-to-noise ratio
(SNR). Compared with an optimum AM
scheme, FM typically has poorer SNR below a certain signal level called the noise threshold, but above a higher level – the full improvement or full quieting threshold – the SNR is much improved over AM.
