--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/m-toolbox/classes/@pz/cz2iir.m	Wed Nov 23 19:22:13 2011 +0100
@@ -0,0 +1,41 @@
+% CZ2IIR return a,b IIR filter coefficients for a complex zero designed using the bilinear transform.
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%
+% 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 1.7 2011/02/18 16:48:54 ingo Exp $
+%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+function varargout = cz2iir(varargin)
+
+  z  = varargin{1};
+  fs = varargin{2};
+
+  f0 = z.f;
+  q  = z.q;
+
+  w0  = f0*2*pi;
+  w02 = w0^2;
+
+  a(1) = (-q*w02/2 - 2*q*fs*fs - w0*fs) / (q*w02);
+  a(2) = (-w02+4*fs*fs) / w02;
+  a(3) = (-q*w02/2 - 2*q*fs*fs + w0*fs) / (q*w02);
+
+  b(1) =  1;
+  b(2) = -2;
+  b(3) = -1;
+
+  varargout{1} = a;
+  varargout{2} = b;
+end
+