CODEWITHSUNDEEP
matlab
JPV
JPV

Reputation: 1079

Power Spectra density and FFT

I know it may be a basic question but I am having trouble with the limits when applying the fft function in Matlab. I have a time series from this specifications:

bdf=0.005;
fHighCut=0.2;
maxTime=600;
freq=1/maxTime:df:fHighCut;
w=2*pi*freq;
time=linspace(0,600,length(freq)*10);

My time series lloks like: enter image description here

The length of it is 400s. I want to create the PSD from it but it appears that I am obtaining the symetric as well like:enter image description here

with this commands:

timestepFFT=1/time(end);
freqFFT=(1:length(time))*1/time(end);
amplitudeEtaSeries=abs(fft(etaSeries)/length(time));
powerSpectrumEtaSeries=amplitudeEtaSeries.^2/timestepFFT;
powerSpectrumEtaSeries(1)=0;

Can you please help me? THanks

Upvotes: 1

Views: 5390

Answers (1)

User1551892
User1551892

Reputation: 3384

Please read this article. power spectral density calculation by using fft always produce the symmetric PSD. So ignore second half of fft output and details can be found here: http://www.mathworks.se/help/signal/ug/psd-estimate-using-fft.html

Upvotes: 1

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