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
2 Comments
Daniel Shub
on 2 May 2012
You need to be careful that you keep symmetry. You haven't shown us how you "mute" the values.
Answers (3)
Wayne King
on 4 Jun 2013
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))
0 Comments
ANDRIAMANANTENA Laza
on 4 Jun 2013
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
0 Comments
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