I'm trying to compare a time-series FFT to a transfer function frequency response. For this, I'm using the commands "abs" and "phase" to colect magnitude and phase, respectively, from the data and from the transfer function (using freqresp( ) command). However, when I plot the both graphs, the magnitude is ok, but phase response is not. It's returning to zero phase at the Nyquist Frequency (this frequency is the last one of my frequency vector).
See my code bellow :
Ryu_fft = fft(Ryu)/Ryu_length; %Obtainnig the FFT of my time-series data
Ryu_fft_dB = 20*log10(abs(Ryu_fft(1:NFFT/2+1))); %Evaluating the magnitude response
Ryu_fft_phase = phase(Ryu_fft(1:NFFT/2+1))*180/pi; %Evaluating Phase response in degrees
f = linspace(0,1,NFFT/2+1)
Now, see my semilogx() plot of this:
How could I fix this problem?
I suspect it is only a code problem once the magnitude is ok.