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alvink74

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07-26-2017 12:12 PM

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Registered:
07-10-2017

Hi all,

I'm running the testbench supplied by Vivado and am having some trouble understanding the output.

Here's both of the input and the output.

My question is, I don't see m_axis_data_tdata showing what I expect to be the fourier transform of the input signal.

Here is what I expect the output to look like when I run it on matlab, where the top is the input signal and the bottom the fourier transform.

I know that in order to see the correct FFT waveform you need to take the absolute value, so I saved the input/output data points to a textfile so I could run it in matlab. Here's the results with the input unchanged on the top and the absolute value of the output on the bottom.

The results still don't match what I expect, as I don't see the correct FFT output at any point. I've also tried saving the imaginary and real parts of the output separately, and then taking the magnitude that way and graphing but it still did not work.

Any ideas of how to get the correct output? As the testbench is essentially running a series of FFTs and IFFTs on the same input signal and the signal appears to get recreated correctly, it seems like the core is working as it should, but I just don't see how to view the output of the FFT in the m_axis_data_tdata field.

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alvink74

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07-27-2017 11:49 AM

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Registered:
07-10-2017

Solved, had to make sure that I was doing natural order output.

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alvink74

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07-27-2017 11:49 AM

2,325 Views

Registered:
07-10-2017

Solved, had to make sure that I was doing natural order output.

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appu1

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05-08-2018 11:40 PM

660 Views

Registered:
03-17-2018

Re: FFT Testbench unexpected output

I am implementing fft .

I want to check fft output via logic analyzer as it working fine or not, I am not getting idea how to use logic analyzer to check my fft output.

2 nd

I implemented adc, echo server, ram etc can please help me put all component in right manner for proper fft interfacing.