Frequency modulation requires a wider bandwidth than amplitude modulation by an equivalent modulating signal, but this also makes the signal more robust against interference. Frequency modulation is also more robust against simple signal amplitude fading phenomena. As a result, FM was chosen as the modulation standard for high frequency, high-fidelity radio transmission: hence the term "[FM radio]?".
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
where Δf is the peak instantaneous deviation of the carrier from the centre frequency and fm is the highest modulating frequency.
See also:
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