Frequency modulation

The encoding of a carrier wave by variation of its frequency in accordance with an input signal.

The harmonic distribution of a simple sine wave signal modulated by another sine wave signal can be represented with Bessel functions - this provides a basis for a mathematical understanding of frequency modulation in the frequency domain.

A [rule of thumb]?, Carson's rule states that nearly all the power of a frequency modulated signal lies within a bandwidth of

2(Δf + f_m)

where Δf is the peak instantaneous deviation of the carrier from the centre frequency and f_m is the highest modulating frequency.

See also:

• amplitude modulation
• phase modulation