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From: | Quentin Spencer |
Subject: | Re: Frequencies in fir1, etc. |
Date: | Fri, 09 Jan 2004 16:15:12 -0600 |
User-agent: | Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.6b) Gecko/20031205 Thunderbird/0.4 |
Joe Koski wrote:
The numbers are in the range [0,1], where 1 represents the Nyquist frequency, or half the sample rate. In my code, I usually do something like this:For those of us who took our digital signal processing class 20+ years ago, is there a simple way to relate w in the call b = fir1(n,w) to an actual cutoff frequency (omega sub c or f sub c) based on parameters like point spacing (T), n, pi, etc.? Apparently w is between 0 and 1 (at least for a low or high pass filter). The conversion must be so trivial that it isn't needed, but for me, at least, this conversion would be a useful addition to the help files. My 1975 edition of Oppenheim and Schafer isn't too clear on this conversion either. Thanks. Joe Koski
f_samp = ( put your sample rate here); f_nyquist = f_samp/2; b = fir1(N,[freq_1, freq_2]/f_nyquist); -Quentin ------------------------------------------------------------- Octave is freely available under the terms of the GNU GPL. Octave's home on the web: http://www.octave.org How to fund new projects: http://www.octave.org/funding.html Subscription information: http://www.octave.org/archive.html -------------------------------------------------------------
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