Re: Finding the phase of unknown signals in data

On Jun 17, 3:32 pm, Jerry Avins <j...@xxxxxxxx> wrote:
cs_post...@xxxxxxxxxxx wrote:
On Jun 17, 2:23 pm, "browny254" <browny...@xxxxxxxxx> wrote:

I have already found their amplitudes and frequencies using a FFT, but Im
not sure how to determine the phase of each, any help or prods in the right
direction to look would be appreciated.

You determined the amplitude from the magnitude of the complex vector
result of the FFT in a given bin (you took the square root of the sum
of squares of its real and imaginary components).

The phase is simply the angle of that complex vector. You'll probably
need to rotate it to the first quadrant based on the signs of the
components and then feed the ratio of imaginary/real to an inverse
tangent function.

Yes, but phase relative to what reference? Also, keep in mind that the
phase of signals at different frequencies can't be compared.

If the frequencies are rationally related, the phase delay of
various waveform relationships (zero crossings, intersections,
etc.) will be a finite set with a pattern. One could always
compare phase(s) relative to some predetermined point in the
repeating pattern set.

..


IMHO. YMMV.
--
rhn A.T nicholson d.0.t C-o-M
.

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