I forget to tell that in frequency domain i am muting some y values corresponding to some frequencies, so when i calculate real(ifft(X,NFFT)) i do not get back the signal but if i dont mute those very few values then i recover the signal. The thing is i have muted only 12 values out of more than 1/2 million.
time signal to fft and back ifft
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Hi there
I am using a time series and calculating fft using example provided by MATLAB
L = length(b);
NFFT = 2^nextpow2(L);
y = fft(b, NFFT)/L;
f= Fs/2*linspace(0,1,NFFT/2);
But when i use inverse fourier transform ifft, i do not get real values, i get complex values and the result is not same as the original signal b. I am using y_source = ifft(X,NFFT);
y_source is not same as original signal b.
Could anyone please answer this. Thanks
댓글 수: 2
Daniel Shub
2012년 5월 2일
You need to be careful that you keep symmetry. You haven't shown us how you "mute" the values.
답변 (3개)
Wayne King
2013년 6월 4일
Note sure why you're dividing by the length of the signal and padding the DFT AND expecting to get the signal back.
t = 0:0.001:1-0.001;
x = cos(2*pi*100*t);
xdft = fft(x);
xhat = ifft(xdft);
max(abs(x-xhat))
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ANDRIAMANANTENA Laza
2013년 6월 4일
Hello, I have the same problem with my handling and it blocks the rest of my code.
my y signal is
y=sin(2*pi*500*t) with t=linspace(0,5/Fs,5) Fs=44100
When I proceed with fft like
YF= fft(y,NFFT)/length(y)
and try to recover my original signal with
y2=ifft(YF,NFFT,'symmetric')
I don't have the original signal
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