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Noisy fft
Posted:
Jan 30, 2013 11:41 PM
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Hi,
I create a signal x, let it through an FIR filter to create y. Then I
divide the spectra and I should obtain the frequency response of the
filter. However, what I get is very/noo noisy:
http://snag.gy/7Quwn.jpg
The code is:
N = 1000;
h_orig = [1 0.75 0.5];
H_orig = fft([h_orig.' ; zeros(N-length(h_orig), 1)]);
x = randn(N, 1);
y = filter(h_orig, 1, x);
H = fft(y) ./ fft(x);
plot(abs([H_orig, H]));
Can someone explain this?
Thanks,
Peter
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