I would like to produce a frequency spectrum plot like this:
(from All About Circuits)
I know that one can take the modulation frequency and multiply it by a given order and scale by the modulation depth to get a similar graph with infinitely sharp peaks, but I am interested in the fact that this spectrum shows some spreading of the frequency around each modulation order. Is there an equation that produces something like this plot, with a variable that influences the frequency spread (I guess caused by phase noise or jitter)?
I'm not interested in the time domain signal, just a means of plotting a signal in the frequency domain with some assumption about frequency spread and modulation depth.