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Math Forum » Discussions » Software » comp.soft-sys.matlab

Topic: Phase versus Time from an FFT
Replies: 11   Last Post: Mar 2, 2013 6:33 PM

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Robert Ahrens

Posts: 5
Registered: 9/30/10
Phase versus Time from an FFT
Posted: Sep 30, 2010 1:31 PM
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I am trying to obtain phase versus time information from a discrete time sampled signal. As an example: suppose I have a signal F = sin(w*t + phi) where the value of w is constant, but the value of phi is a function of time. So, if I aquire the signal at some sampling rate, I can perform FFT(F) resulting in amplitude and phase information. Since the value of phi is a function of time, the resulting FFT amplitude spectrum will indicate a spread in frequency values located somewhere around w, with a range of phase values also around w.

My question is this: How can I extract the phase versus frequency values such that I can determine the values of phi (in signal F) as a function of time? I don't believe that performing an IFFT(phase) will result in phi(t).

Thanks
Bob

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