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Observer
Observer
3,878 Views
Registered: ‎08-30-2011

FFT7.1

Hy!

I´m trying to build a FFT7.1-core with system Generator. My biggest problem is that the spectrum looks other than I thought it must be.

I give a 1Hz sine-wave to the real-input and sample at 8Hz. Ithought that at a 8-Point FFT there must be one peak at the 2nd Point in spectrum and at the 7th Point.I get a Point at 5th and at the 8th. I have no Idea what is happening there.

Hope somebody can help me!

My .mdl-File is in the appendix.

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3 Replies
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Teacher
Teacher
3,874 Views
Registered: ‎08-14-2007

Hi,

not sure, but may it be that the outputs of the FFT come out in a shuffled order caused by the butterfly structure and need to be reordered?

 

Have a nice simulation

  Eilert

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Xilinx Employee
Xilinx Employee
3,867 Views
Registered: ‎11-28-2007

Like eilert said, try changing the output order from "Bit reversed order to to "Natural Order".

Cheers,
Jim
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Observer
Observer
3,861 Views
Registered: ‎08-30-2011

It works!!! I have some new problems now, but I think I can handle this. Thank you!

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