Find spectrum of a Varible

Hi ,

I have the follwing Varible :

m=a(0)*p(t-phi)+a(1)*p(t-T-phi)+a(2)*p(t-2T-phi)+...

a=[-1 1 1 -1] %random vector with -1 or 1 varibles phi ~ Uniform(0,T) p(t) = rasined cosine filter in time domain

how can I find Smm = spectrum of m(t) signal (not fft)