Frequency modulation is the encoding of information into 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 + fm)
where Δf is the peak instantaneous deviation of the carrier from the centre frequency and fm is the highest modulating frequency.
See also: