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Scalling FFT Magnitude

Expert 2370 points

Hi,

I am working with C6713 DSK, I have computed FFT of real time sine wave with amplitude 1 Vp_p and frequency of 1000 Hz by modifying dsk_app.c project. I used DSPLIB function to compute FFT. I calculated the FFT magnitude but it has very high peak values that can be seen from the attached plot.

http://i35.tinypic.com/2psgakw.jpg

I am calculating magnitude in the following way.

x1[i] = sqrt(samples[i].real*samples[i].real + samples[i].imag*samples[i].imag)/32;

I want to scale the FFT output to get the exact amplitude as of the input signal. Can you please tell me how to do it ?

Thanks.