extracting phase from ifft on fft of a signal

Hello,

I'm trying to extract a phase ifft function. But i'm getting something not logical (a triangle) In order to complicate the message here, I'm attaching the code. You should open pulsecompress_original.m file. I'm looking at

phi_p_t=unwrap(angle(fout))

this is the part of the code that's relevant to this question:

Fin_w = fftshift(fft(gaussian)); % fft of E field
Fout=Fin_w.*exp(-1i*PhT);
fout=ifft(Fout);
N=sqrt(sum(abs(fout).^2)*dt);
fout=fout/N;
phi_p_t=unwrap(angle(fout));

I need this phi_p_t and than to make differential to it according to time. It should provide me the relevant frequencies around 815nm (this is needed to check that till this point the code is ok)

You can call the function

pulsecompress_original([20 55])

Thanks