fft phase accuracy

Marco

2012 2 14

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Hello,

I have a problem with my fft analysis, it seems to work for the amplitudes, the spectrum ist the same as in the test function, but the phase ist different. If i change the frequency of the test function it works better, but there's still a difference. Later I want to use the file to analyze a signal from simulink.

Here my test fft:

yout.time=linspace(0,1.6384,16384);
yout.signals.values = sin(2*pi*36*yout.time) +  3*sin(2*pi*18*yout.time+(pi/2))+5; 
Fs = 10000;                    % Sampling frequency
T = 1/Fs;                     % Sample time
L = length(yout.time);% Length of signal
NFFT = 2^nextpow2(L); % Next power of 2 from length of y
fsignal=yout.signals.values-mean(yout.signals.values);
ha=hann(L);
fsignal=2*fsignal(:).*ha;
Y = fft(fsignal,NFFT)/L;
f = Fs/2*linspace(0,1,NFFT/2+1);
phase = angle(Y);