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Altera_Forum

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05-22-2014
09:26 AM

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A problem about FFT Megacore Function

I generated a FFT Megacore Function by Megawizard. The transform length is 2048 and streaming architecture is used.

Then I did the function simulation with Modelsim SE 6.5 and this Megacore Function seems working normally: the source_error signal is always zero and other output flows are also correct. But when I checked the detail values of source_real and source_imag, I found a problem: for a same block of input data with length of 2048, when it is transfered to the FFT function as the first input block, a different transform results are gotten compared with the transform results gotten when the same input data block is transfered to the FFT function as the second input block. I am very sure I used a same block of input data, and just the input order was changed, then different transform results were gotten, although the difference is not large. By the way, the transform results are more closer to the results calculated in MATLAB when the input data block is transfered to the FFT function as the first input block. I totally have no idea about this problem, can anyone help me? Thanks!! TigreLink Copied

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Altera_Forum

Honored Contributor I

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05-22-2014
12:28 PM

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Altera_Forum

Honored Contributor I

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05-23-2014
12:52 AM

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Altera_Forum

Honored Contributor I

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05-23-2014
10:22 AM

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Altera_Forum

Honored Contributor I

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05-23-2014
10:39 AM

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