FM (frequency modulation) modulation – also known as frequency FM modulation, is a type of analog modulation in which the information signal controls the frequency of the carrier wave. In this form of modulation, the frequency of the transmitter’s carrier changes in accordance with the informational (modulating) signal, while the amplitude remains constant. Compared to AM and SSB, an FM signal is much less susceptible to interference. This is due to the fact that interference typically affects only the amplitude of the signal, and an FM detector is insensitive to amplitude variations and therefore does not detect them.
Frequency modulation is used for transmitting audio (low-frequency) signals in radio broadcasting (in the VHF band) and for the audio accompaniment of television programs. In radio communications, narrowband FM with a small carrier frequency deviation is applied.
Advantages of Frequency Modulation
1. FM systems provide superior sound quality. This is due to the wide frequency bandwidth of the FM signal, which encompasses a significantly greater number of harmonics.
2. FM transmission achieves a very low noise level. Noise refers to unwanted signals that usually appear at the output as changes in the amplitude of the carrier. In an FM system, such signals are easily eliminated by bilateral limitation of the carrier’s amplitude. The information carried by the varying frequency remains completely intact.
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