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annotate m-toolbox/classes/@pz/cp2iir.m @ 43:bc767aaa99a8

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CVS Update
author Daniele Nicolodi <nicolodi@science.unitn.it>
date Tue, 06 Dec 2011 11:09:25 +0100
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Daniele Nicolodi <nicolodi@science.unitn.it>
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1 % CP2IIR Return a,b IIR filter coefficients for a complex pole designed using the bilinear transform.
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2 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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3 %
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4 % DESCRIPTION: CP2IIR Return a,b IIR filter coefficients for a complex pole
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5 % designed using the bilinear transform.
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6 %
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7 % CALL: [a,b] = cp2iir(p, fs)
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8 %
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9 % REMARK: This is just a helper function. This function should only be
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10 % called from class functions.
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11 %
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12 % INPUT: p - pole object
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13 % fs - the sample rate for the filter
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14 %
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15 % VERSION: $Id: cp2iir.m,v 1.7 2011/02/18 16:48:54 ingo Exp $
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16 %
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17 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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18
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19 function varargout = cp2iir(varargin)
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20
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21 p = varargin{1};
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22 fs = varargin{2};
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23
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24 f0 = p.f;
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25 q = p.q;
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26
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27 w0 = f0*2*pi;
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28 w02 = w0^2;
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29
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30 k = (q*w02 + 4*q*fs*fs + 2*w0*fs) / (q*w02);
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31 b(1) = 1;
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32 b(2) = (2*w02-8*fs*fs) / (k*w02);
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33 b(3) = (q*w02 + 4*q*fs*fs - 2*w0*fs) / (k*q*w02);
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34
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35 a(1) = 1/k;
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36 a(2) = -2/k;
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37 a(3) = -1/k;
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38 a = a*-2;
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39
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40 varargout{1} = a;
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41 varargout{2} = b;
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42 end
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