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mohamed.shfat
Observer
Observer
3,142 Views
Registered: ‎10-16-2016

FFT's problems

Hello everyone 

I'm trying here to take an FFT but it looks that there is a problem at the output of the FFT core !

I'm taking an FFT with 1024 points , real time , pipelined streaming I/O , fixed point and scaled , my input is a sin wave with 200khz and the sampling freq of the XADC is about 427 ksps . The output data that i'm getting from the core is shown in the pic . i can't understand why i have many peaks there . i know that the data comes in reversed order because when i set the natural order for the core it gives me nothing just empty window with no peaks as it shown in the 2nd graph  . 

Can some one help me please to find what's wrong for my design ? 

wrong !.jpg
wrong 2.jpg
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3 Replies
balkris
Xilinx Employee
Xilinx Employee
3,134 Views
Registered: ‎08-01-2008

please verify the core with standard signals like impulse , ramp, step and sinusoidal. This may be expected result based on your inputs
Thanks and Regards
Balkrishan
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mohamed.shfat
Observer
Observer
3,130 Views
Registered: ‎10-16-2016

My input is already a sinusoidal wave , i'm just wondering why in Bit/digit reversed order i'm getting a results , but in the natural order there is nothing ! 

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balkris
Xilinx Employee
Xilinx Employee
3,119 Views
Registered: ‎08-01-2008

check core configuration . it provides both option for output ordering bit rev/natural
Thanks and Regards
Balkrishan
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