Hi,
i'm trying to do this:
acquire a signal from codec aic3204 (using C5515 eZdsp) at sampling rate 192KHz: this is successfull.
then i want to FFT the signal with 1024 point FFT (using rom routines) and shift my spectrum of K hertz, then IFFT it and have the modified signal.
I have done this:
say S(w) is my FFT output. I perform on the spectrum the frequency shift by doing (this is like S(w)*exp(j*2*pi*Foffset/Fs))
real = Re(S)*cos(u) - Im(S)*sin(u)
imag = Re(S)*sin(u) + Im(S)*cos(u)
where Re(S), Im(S), real and imag are Int16 arrays. u = 2*pi*Foffset/Fs. sin(u) and cos(u) are Int16 in Q15 format. real and imag are used as input od IFFT.
Whee i IFFT the signal, the output on my scope is a lot of garbage without any useful meaning. I take obviously only the real part of the IFFT output.
What I should do?
Every suggestion in very appreciated.
Regards,
Paolo
