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Altera_Forum
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17 years ago

Altera FFT Vs Matlab FFT. Strange Results

Hi, I’m testing some FFT Altera Core using those parameters: 1)Single Streaming or Burst 16K length FFT 2)12-14-16 bits input REAL data (pseudorandom code {-1,1}) 3)same bits for twiddle...
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Altera_Forum
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16 years ago

Hi,

I am trying to use FFT Megacore function and got a different result from MATLAB

Following is my code 


t=0:0.001:0.127; 
y=2*sin(2*pi*8*t);
Yfft=fft(y);
stem(abs(Yfft)/128); 
 = MegacoreFFT_VHDL_model(y,128,0);
ymega_change=abs(ymega)*2^2/128; %exponent = -2 and I normalize to 128
stem(ymega_change);
Here are the 2 graphs: 1st one is MATLAB FFT, 2nd is MegaFFT

Am I making any mistakes ?

http://i111.photobucket.com/albums/n126/leejongfan/FFT.jpg

http://i111.photobucket.com/albums/n126/leejongfan/MegaFFT.jpg