convolve.m

matlab算法集 matlab算法集

function z = convolve (x,y)
%-----------------------------------------------------------------------
% Usage:       z = convolve (x,y)
%
% Description: Compute the convolution of two discrete-time signals.
%
% Inputs:      x = n by 1 vector containing samples of first signal
%              y = m by 1 vector containing samples of second signal
%                  with m <= n.  If m < n, y is padded with n-m zeros. 
%
% Outputs:     z = n by 1 vector containing convolution of x with y.
%-----------------------------------------------------------------------
   
   chkvec (x,1,'convolve');
   chkvec (y,2,'convolve');
   n = length(x);
   m = length(y);
   if m > n
      disp ('Argument 2 of convolve can not be longer than argument 1');
      return
   end;

% Compute DFTs of x(k) and y(k), pad y with (n-m) zeros     
   
   Y = zeros(n,1);
   Y(1:m) = y;
   X = dft (x,1);
   Y = dft (Y,1);

% Compute inverse DFT of X(m)Y(m) 

   X = X .* Y;
   z = real(dft (X,-1));
%-----------------------------------------------------------------------