Finding the Bandwidth of PSK Signal

[dimensionless]

I've got a signal and I would like to find the 3 dB bandwidth. The signal has a center frequency of $$f_{c}$$ and a has a bandwidth shaping filter applied to it (ie, a root raised cosine filter).

The problem with finding the bandwidth, is that I have no equation for representing a PSK signal. For this reason, I can't take the Fourier transform to get the spectrum. If I could take the Fourier transform, then I could find the bandwidth, but this seems to be a necessary step that I'm unable to take.

 

[anorlunda]

ping @analogdesign