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From: Mikael on 3 Aug 2010 02:26
Due to Wiener-Khinchins theorem the power spectrum of a signal is the fourier transform of its autocorrelation function.

furthermore, the convolution theorem says that convolution in time domain is multiplication in frequency domain and that convolution in frequency domain is multiplication in time domain.

I have a power spectrum vector p1 and a frequency vector f=-125:1/200:125;
I also have p3=p1(*)p1(*)p1 , the threefolded convolution of p1.
then rx=ifft(p1); should be the autocorrelation and these two plots should show the same due to the convolution theorem:

plot(f,fft(rx.^3))
plot(f,p3)

.... but they don't. The latter one's values is much larger with a factor in every point.
What am I doing wrong?

Thank you for your time!

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