spectrum of PWM

[jh.]

> Perhaps this has some info
>
> http://www.musicsynthesizer.com/Circuitry/probability.htm

Thanks for the link. That's the easy stuff (static pulse wave,
or slow modulation).

But I am looking for the *general* case, as in audio rate PWM.

Maybe there is no analytic function for the spectrum.
I mean you already need Bessel functios for ordinary FM. I was
hoping for something similar for PWM.

JH.