Modulation index of FM
Calculate the modulation index in an FM signal when fm (modulating frequency) is 250Hz and Δf (frequency deviation) is 5KHz.
Correct Answer: a) 20
Modulation index is the measure of how much the modulation parameter changes from its un modulated value. The modulation index of FM is given by
μ = frequency deviation/ modulating frequency
= Δf/ fm
Where Δf is the peak frequency deviation i.e. the deviation in the instantaneous value of the frequency with modulating signal.
fm is the value of modulating frequency