--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/m-toolbox/classes/@pz/cp2iir.m	Wed Nov 23 19:22:13 2011 +0100
@@ -0,0 +1,43 @@
+% CP2IIR Return a,b IIR filter coefficients for a complex pole designed using the bilinear transform.
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%
+% DESCRIPTION: CP2IIR Return a,b IIR filter coefficients for a complex pole
+%              designed using the bilinear transform.
+%
+% CALL:        [a,b] = cp2iir(p, fs)
+%
+% REMARK:      This is just a helper function. This function should only be
+%              called from class functions.
+%
+% INPUT:       p  - pole object
+%              fs - the sample rate for the filter
+%
+% VERSION:     $Id: cp2iir.m,v 1.7 2011/02/18 16:48:54 ingo Exp $
+%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+function varargout = cp2iir(varargin)
+
+  p  = varargin{1};
+  fs = varargin{2};
+
+  f0 = p.f;
+  q  = p.q;
+
+  w0  = f0*2*pi;
+  w02 = w0^2;
+
+  k    = (q*w02 + 4*q*fs*fs + 2*w0*fs) / (q*w02);
+  b(1) =  1;
+  b(2) = (2*w02-8*fs*fs) / (k*w02);
+  b(3) = (q*w02 + 4*q*fs*fs - 2*w0*fs) / (k*q*w02);
+
+  a(1) =  1/k;
+  a(2) = -2/k;
+  a(3) = -1/k;
+  a    =  a*-2;
+
+  varargout{1} = a;
+  varargout{2} = b;
+end
+