cconv

 cconv.m

 Circular convolution.
 Usage : y = cconv(x,h,k)
 x - input signal
 h - filter
 k - output hole in filter (k=0 if the filter is causal)

 Written by : Justin Romberg
 Created : 2/16/98, Revised : 5/1/2001

0001 % cconv.m
0002 %
0003 % Circular convolution.
0004 % Usage : y = cconv(x,h,k)
0005 % x - input signal
0006 % h - filter
0007 % k - output hole in filter (k=0 if the filter is causal)
0008 %
0009 % Written by : Justin Romberg
0010 % Created : 2/16/98, Revised : 5/1/2001
0011 
0012 function y = cconv(x,h,k)
0013 
0014 if (nargin == 2), k = 0; end
0015 
0016 N = length(x);
0017 M = length(h);
0018 inds = mod([1:N 1:M-1]-1, N) + 1;
0019 y = cshift(conv2(x(inds), h, 'valid'),M-k-1,'r');
0020 
0021 % old code
0022 %
0023 %inds = mod([N-M+2+k:N 1:N 1:k]-1, N) + 1;
0024 %y = conv2(x(inds), h, 'valid');