--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/m-toolbox/classes/@pzmodel/abcascade.m	Wed Nov 23 19:22:13 2011 +0100
@@ -0,0 +1,31 @@
+% ABCASCADE Cascade two filters together to get a new filter.
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%
+% DESCRIPTION: ABCASCADE Cascade two filters together to get a new filter.
+%
+% CALL:        [a,b] = abcascade(a1,b1,a2,b2)
+%
+% VERSION:     $Id: abcascade.m,v 1.3 2010/10/29 16:09:15 ingo Exp $
+%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+function [ao,bo] = abcascade(a1,b1,a2,b2)
+
+  n = length(a1);
+  m = length(a2);
+  N = m+n-1;
+
+  alpha = zeros(1, N);
+  beta = zeros(1, N);
+
+  for i=0:n-1
+    for j=0:m-1
+      alpha(i+j+1) = alpha(i+j+1) + a1(i+1)*a2(j+1);
+      beta(i+j+1) = beta(i+j+1) + b1(i+1)*b2(j+1);
+    end
+  end
+
+  ao = alpha;
+  bo = beta;
+end
+