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Inverse Fourier Transform ignores oscillations

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Steven
Steven on 18 Oct 2019
Edited: Steven on 22 Oct 2019
Hi. I am doing some time and freq analysis. So lets say I have some x-t data, I use fft to take them in freq domain, do some calculations and finally do ifft to return them back into the time domain. But after getting the ifft, I get the red plot, while the blue plot is obtained from another source (which appranely should be true).
I am not sure which one is correct? How come the ifft is ignoring the oscilaltions?
Thanks in advance.

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Walter Roberson
Walter Roberson on 18 Oct 2019
If you wanted to force that kind of result, you could perhaps boost the high frequencies (the ones near the middle of the vector.) It would take some experimenting to work it out. But I do not think this is the right situation for you -- I do not expect that ti would be justifiable for your purposes.
Sorry, I do not know anything about converting between sides of spectra.
Walter Roberson
Walter Roberson on 20 Oct 2019
fftshift() to convert fft representations.
Bjorn Gustavsson
Bjorn Gustavsson on 20 Oct 2019
Based on your question and comments it is clear (this will come off as a bit abrasive) that you should read up on what you do when Fourier-transforming data and what happens with the Fourier-transform when you do operations on it (what multiplication in the Fourier-domain corresponds to in the time-domain etc).

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