MATLAB and Simulink resources for Arduino, LEGO, and Raspberry Pi
Learn moreOpportunities for recent engineering grads.
Apply TodayMATLAB Central > MATLAB Newsreader > Phase versus Time from an FFT 

Subject: Phase versus Time from an FFT From: Robert Ahrens Date: 30 Sep, 2010 17:31:22 Message: 1 of 12 
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. 
Subject: Phase versus Time from an FFT From: Greg Heath Date: 30 Sep, 2010 17:58:00 Message: 2 of 12 
On Sep 30, 1:31 pm, "Robert Ahrens" <no.re...@none.com> wrote: 
Subject: Phase versus Time from an FFT From: Jim Rockford Date: 30 Sep, 2010 18:32:01 Message: 3 of 12 
On Sep 30, 1:31 pm, "Robert Ahrens" <no.re...@none.com> wrote: 
On Oct 1, 6:31 am, "Robert Ahrens" <no.re...@none.com> wrote: 
Subject: Phase versus Time from an FFT From: Robert Ahrens Date: 30 Sep, 2010 19:29:07 Message: 5 of 12 
Thanks for the information regarding the Hilbert transform... I am going to look into it. 
Subject: Phase versus Time from an FFT From: Jim Rockford Date: 30 Sep, 2010 22:01:42 Message: 6 of 12 
On Sep 30, 3:29 pm, "Robert Ahrens" <no.re...@none.com> wrote: 
Subject: Phase versus Time from an FFT From: Greg Heath Date: 30 Sep, 2010 23:11:09 Message: 7 of 12 
On Sep 30, 1:58 pm, Greg Heath <he...@alumni.brown.edu> wrote: 
Subject: Phase versus Time from an FFT From: Robert Ahrens Date: 30 Sep, 2010 23:12:04 Message: 8 of 12 
Jim, 
On Sep 30, 10:31 am, "Robert Ahrens" <no.re...@none.com> wrote: 
Dear Bob, 
Subject: Phase versus Time from an FFT From: Robert Ahrens Date: 5 Feb, 2013 15:42:11 Message: 11 of 12 
"Nezaket" wrote in message <keqf80$sj0$1@newscl01ah.mathworks.com>... 
Very, nice and exactly what I needed to find the instantaneous phase difference between two noisy oscillating signals (not sinusoids, but the outputs of a dynamical system). Some notes that might be helpful to others: 
A tag is like a keyword or category label associated with each thread. Tags make it easier for you to find threads of interest.
Anyone can tag a thread. Tags are public and visible to everyone.