How to extract phase and amplitude information from FFT?

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Mayank Lakhani 2015-6-26

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https://ww2.mathworks.cn/matlabcentral/answers/225440-how-to-extract-phase-and-amplitude-information-from-fft

评论： Adam 2017-7-14

I am doing signal processing of radar data. I applied butturworth bandpass filter and applied fft to the radar data.I want to know how to extract the phase and amplitude information of radar data so i can add it to my ideal radar simualation and make it non ideal :D . Thanks

load('fb2040'); % loading the data

x = fb2040(3,:);

y_filt = filter(b,a,x); % filtering the received signal

nfft = length(y_filt);

res = fft(y_filt,nfft)/ nfft; % normalizing the fft

f = fs/2*linspace(0,1,nfft/2+1); % choosing correct frequency axes

res = res(1:nfft/2+1);

figure, plot(f,abs(res));

xlabel('Frequency in MHz');ylabel('Amplitude');

return

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Answer 1

Adam 2015-6-26

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https://ww2.mathworks.cn/matlabcentral/answers/225440-how-to-extract-phase-and-amplitude-information-from-fft#answer_184105

在 MATLAB Online 中打开

If you want the phase and amplitude for different frequencies then these are just:

angle( res );
real( res );

or

abs( res );

if you want the magnitude rather than amplitude.

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Peter Mbamaluikem 2017-7-13

Hi, Adam what if there are several frequencies and one is to extract the magnitude of one say 60Hz. what will the code be?

Adam 2017-7-14

'res' in the above code is a vector of results corresponding to the frequencies in 'f' in the original code in the question so just find the 'f' that is closest to 60Hz and take the magnitude of that value rather than the whole vector.

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