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Altera_Forum's avatar
Altera_Forum
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15 years ago

wrong data through IFFT, FFT

Hi everyone, I use altera fft ip core 9.0, and let my data go through 1024 ifft - GI - GI_remover - 1024 fft, but i did not get the origin data back(not the scaling problem, the data is totall...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

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Sure, ill give you an example. If your signal is lets say, sin(2*pi*t) and you define t = -0.512 : .001 : 0.511, you should configure the FFT's input data as (-N/2 to N/2). However, if you are processing your FFT's out "offline" with MatLab or some other tool, you can do a FFTSHIFT operation that will properly center the output. But if not, you should change the FFT to (-N/2 to N/2).

If that parameter is not set properly, the next component may misinterpret the frequency (or time) values.

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Thanks you again, but I do not quite get you...

The attached file is my input, two column show I, Q for real and imag. Is there any problem if I use fft ip core to process that?