short pulse fft and comprssion

Hello,

I have a code that should take an initial pulse of FWHM gaussian in how i define it and add some phase to it in the spectrum domain and than bring me back the result in time. But for some reason if i define the phase to be zero it doesn't work and i see different FWHM than the initial one. (PhT=0) I think i have some issue with the fft but could you please take a look?

Example of calling the code: pulsecompress([20 55])

Thanks.