


CZ2IIR return a,b IIR filter coefficients for a complex zero designed using the bilinear transform.
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DESCRIPTION: CZ2IIR return a,b IIR filter coefficients for a complex zero
designed using the bilinear transform.
CALL: [a,b] = cz2iir(z, fs)
REMARK: This is just a helper function. This function should only be
called from class functions.
INPUTS: z - zero object
fs - the sample rate for the filter
VERSION: $Id: cz2iir.m,v 1.4 2008/01/11 13:42:41 ingo Exp $
HISTORY: 03-04-2007 Hewitson
Creation
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0001 function [a,b] = cz2iir(z, fs) 0002 % CZ2IIR return a,b IIR filter coefficients for a complex zero designed using the bilinear transform. 0003 % 0004 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 0005 % 0006 % DESCRIPTION: CZ2IIR return a,b IIR filter coefficients for a complex zero 0007 % designed using the bilinear transform. 0008 % 0009 % CALL: [a,b] = cz2iir(z, fs) 0010 % 0011 % REMARK: This is just a helper function. This function should only be 0012 % called from class functions. 0013 % 0014 % INPUTS: z - zero object 0015 % fs - the sample rate for the filter 0016 % 0017 % VERSION: $Id: cz2iir.m,v 1.4 2008/01/11 13:42:41 ingo Exp $ 0018 % 0019 % HISTORY: 03-04-2007 Hewitson 0020 % Creation 0021 % 0022 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 0023 0024 VERSION = '$Id: cz2iir.m,v 1.4 2008/01/11 13:42:41 ingo Exp $'; 0025 0026 %%%%% 'Params' && 'Version' Call %%%%% 0027 if nargin == 2 0028 if isa(z, 'zero') && ischar(fs) 0029 in = fs; 0030 if strcmp(in, 'Params') 0031 a = plist(); 0032 return 0033 elseif strcmp(in, 'Version') 0034 a = VERSION; 0035 return 0036 end 0037 end 0038 end 0039 0040 f0 = get(z, 'f'); 0041 q = get(z, 'q'); 0042 0043 w0 = f0*2*pi; 0044 w02 = w0^2; 0045 0046 a(1) = (-q*w02/2 - 2*q*fs*fs - w0*fs) / (q*w02); 0047 a(2) = (-w02+4*fs*fs) / w02; 0048 a(3) = (-q*w02/2 - 2*q*fs*fs + w0*fs) / (q*w02); 0049 0050 b(1) = 1; 0051 b(2) = -2; 0052 b(3) = -1; 0053 0054 % END