Matlab FFT Vs. DSP Builder FFT

Honored Contributor

17 years ago

Hi again,

in those days I tried to adjust last things and also to recreate the input signal with an IFFT.

On the file I posted some time ago, I tried to adjust the FFT amplitude that was less then the Matlab one.

I found some trouble with the exponent value again. I will post the text where it speaks about the FFT scaling.

" the exponent records the number of left or right shifts used to perform the scaling. as

a result, the output magnitude relative to the input level is:

output*2-exponent

for example, if exponent = –3, the input samples are shifted right by

three bits, and hence the magnitude of the output is output*2^3 "

To scale I shifted the real and imaginary output. I found a negative exp so a made a right shift as the example. But...

The result is that everything turns really good when I not scale the real and imaginary output. It seem to be futile to scale it!

Also when I try to recreate the input signal with the IFFT everything is good without the scaling....

..mmm i missed something?

I will post the new scheme that bypass the scaling.

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