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Noisy fft
Posted:
Jan 30, 2013 11:41 PM


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(Nlength(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



