Quartus FFT IP problem

Discussion in 'VHDL' started by patrick.melet@dmradiocom.fr, Feb 6, 2007.

  1. Guest

    Hi everybody,

    I'm trying to use the FFT IP core from Quartus 6.0...

    I would like to know what are the representation of the mantissa (2's
    complement or other ...) and where is the sign bit ?

    My problem is : when I send a 1 MHz sine with 10 MHz sampling
    frequency to the real part input of the FFT, I obtain peaks at 1 MHz
    at the output and at 9 MHz, that's good but my peaks (if I represent
    the mantissa in 2's complement) have one part positive and one part
    negative !!! not a pure negative or positive peak... whats' happen...

    Sure If I take FFT_real ^ 2 + FFT_imag ^2 then my peaks are all
    positives...

    Thanks
     
    , Feb 6, 2007
    #1
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