# How can i determine phase in FFT?

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Hi everyone, right now im trying to calculate signal phases using angle(x) from FFT Function im Matlab. Noted that i've coded the program like below :

%%Plotting Grafik

%create a time vector 't', containing integers from 1 to n(summary of data)

count= length(data);

Ts=mean(diff(times1));

Fs=1/Ts;

NFFT=2^nextpow2(count);

y=fft(data,NFFT)/count;

f=Fs/2*linspace(0,1,NFFT/2+1);

figure(2)

plot(f,2*abs(y(1:NFFT/2+1)));

grid on

title('Single-Sided Amplitude Spectrum of y(t)');

xlabel('Frequency(Hz)');

ylabel('|Y(f)|');

phase=angle(y);

But i'm not really sure with the phase function. Does anyone ever has the same experience?

Thanks before for your answer.

##### 0 Comments

### Accepted Answer

Star Strider
on 24 Oct 2016

Edited: Star Strider
on 24 Oct 2016

Your code appears to me to be correct, including the ‘phase’ assignment. Note that the units of ‘phase’ are in radians. Convert them to degrees (if desired) by multiplying them by 180/pi.

I’m not certain what you want, so also consider the unwrap function. Use it on the radian units, and convert to degrees later if necessary.

EDIT — If you want to plot it, the easiest way is to use the subplot function. Your plotting code changes to:

phase=angle(y);

figure(2)

subplot(2,1,1)

plot(f,2*abs(y(1:NFFT/2+1)));

grid on

title('Single-Sided Spectrum of y(t)');

ylabel('|Y(f)|');

subplot(2,1,2)

plot(f,phase)

grid on

xlabel('Frequency(Hz)');

ylabel('Phase (rad)')

I did not test that, but it should work.

### More Answers (1)

karinkan
on 1 Jun 2018

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