At 09:36 +0100 02/04/2004, Gerd Rech wrote: >What about this: >1. Cut the long waveform stream into a number of (overlapping) pieces. >2. Use the FFT vi for each piece, which will produce amplitudes and phases >for each frequency bin. >3. Average apmlitude and phase for each frequency bin separately. > >Would this create meaningful phase? >I would guess yes, as all pieces were acquired in a consistant stream of >data originally. I would guess not. Because the phase for each piece is referenced to the time of starting for each piece there is effectively a phase difference applied to each fft. So to do this over the whole data set you would have to off set the phase for each frequency bin by the starting time* frequency of that bin. That would make all the phases referenced to the same starting time. Then you could average them.
Otherwise each frequency bin will have a different phase offset added to it for each segment esstially causing it to be averaged to zero. -Scott
