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From: | Matthias Brennwald |
Subject: | Re: Why is my Butterworth filter so noisy? |
Date: | Wed, 24 Sep 2008 06:37:50 +0200 |
On 23.09.2008, at 21:05, Julius Smith wrote:
The "noise" in the original post is due to missing frequencies in the input signal, resulting in spurious numerical failures in the spectral ratio Y./X. If you replace the line x = 2*randn(1,N)-1; % fake time series (original data) by x = [1,zeros(1,N-1)]; % impulse then the response looks fine. To use noise as an input, it is necessary to do a lot more averaging over time (see the topic of system identification, for example). - jos
Thanks for this! That explains a lot... Matthias
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