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Discussion Groups | Matlab DSP | FFT vs freqz
Technical discussion about Matlab and issues related to Digital Signal Processing.
FFT vs freqz - divya_8910 - Aug 27 19:18:00 2004
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hi, i have a low pass filter and i plotted the frequency response using freqz and fft and got diff plots... b=remez(102,[0 0.5 0.6 1],[1 1 0 0]); B = fft(b,1024); P = B.*conj(B); t=(pi/512)*[0:511]; figure(1); semilogy(t,P(1:512),'Color',[1 0 0.4975]); hold on; [h,w]=freqz(b,1,1024); semilogy(w,abs(h)); hold off; can anyone tell me why tht happens..i thought freqz uses the fft algorithm thx divya |
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RE: FFT vs freqz - Egler, Mark - Aug 31 17:35:00 2004
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Divya, You probably figured this out by now, but they are the same, except that you squared the fft output but not the freqz output. Try plotting sqrt(P(1:512)) and abs(h). Mark -----Original Message----- From: divya_8910 [mailto:] Sent: Friday, August 27, 2004 3:18 PM To: Subject: [matlab] FFT vs freqz hi, i have a low pass filter and i plotted the frequency response using freqz and fft and got diff plots... b=remez(102,[0 0.5 0.6 1],[1 1 0 0]); B = fft(b,1024); P = B.*conj(B); t=(pi/512)*[0:511]; figure(1); semilogy(t,P(1:512),'Color',[1 0 0.4975]); hold on; [h,w]=freqz(b,1,1024); semilogy(w,abs(h)); hold off; can anyone tell me why tht happens..i thought freqz uses the fft algorithm thx divya _____________________________________ /groups.php3 Yahoo! Groups Links |
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