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Altera_Forum's avatar
Altera_Forum
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17 years ago

Question regarding FFT IP core

Hi all,

I am using the OpenCore FFT IP to come up with a power spectrum using a 512-pt transform. I was successful in creating a fft module. However I notice a few irregularities. One of them is that my data input is a 16bit signal and my output is a 28bit signal. How is this possible? Isn't my output the same size as my input.

input [15:0] sink_real;

input [15:0] sink_imag;

....

output [27:0] source_real;

output [27:0] source_imag;

Any ideas?

Thanks.

fpga_beginner

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    17 years ago

    for variable streaming that is correct, there are 2.5 bits of growth per FFT radix 2^2 stage. you can see that on page 34 of the user guide.

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    17 years ago

    Thank you! I read that section previously but I was unable to comprehend it.

    Really appreciate the help!