How to determine phase of a sine wave using FFT
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Dear MATLAB experts,
For a small project that I want to do, I need to compute the phase of a sine wave. However, I was unable to obtain a correct result. I have posted my code with this message (please see attachment) for your review and comments. If anyone could help me with this, I would greatly appreciate it.
Thank you!
Fuh
Accepted Answer
Star Strider
on 25 Mar 2016
Edited: Star Strider
on 25 Mar 2016
The code hasn’t posted. Use the angle function on the output of the fft function:
t = [...]; % Time Vector
s = [...]; % Signal Vector
Ts = mean(diff(t)); % Sampling Time
Fs = 1/Ts; % Sampling Frequency
Fn = Fs/2; % Nyquist Frequency
L = length(s);
fts = fft(s)/L; % Normalised Fourier Transform
Fv = linspace(0, 1, fix(L/2)+1)*Fn; % Frequency Vector
Iv = 1:length(Fv); % Index Vector
amp_fts = abs(fts(Iv))*2; % Spectrum Amplitude
phs_fts = angle(fts(Iv)); % Spectrum Phase
Note — This is obviously UNTESTED CODE but it should work.
6 Comments
H S
on 6 Jan 2018
Dear Star Strider,
I think for the zero frequency (DC), your code after "amp_fts = abs(fts(Iv))*2;" should be corrected as follows:
amp_fts(1)=amp_fts(1)/2;
More Answers (1)
Fuh-Cherng
on 27 Mar 2016
1 Comment
Star Strider
on 27 Mar 2016
As always, my pleasure.
I would appreciate it then if you would Accept my Answer.
You can do that by deleting your Answer and then Accepting mine. (No one gets any credit for Accepting their own Answer, anyway.)
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