tconv.m

Matlab时频分析工具箱,希望能对大家有所帮助啊

function h=tconv(f,g)
%TCONV  Twisted convolution
%   Usage:  h=tconv(f,g);
%
%   TCONV(f,g) computes the twisted convolution of the square matrices
%   f and g.
%
%
%   Let h=tconv(f,g) for f,g being LxL matrices. Then h is given by
% 
%                   L-1 L-1
%      h(m+1,n+1) = sum sum f(k+1,l+1)*g(m-k+1,n-l+1)*exp(2*pi*i*(m-k)*l/L);
%                   l=0 k=0
% 
%   where m-k is compute module M and n-l is computed modulo N.
%
%   The routine SPREADINV can be used to calculate an inverse convolution.
%   Define h and r by
% 
%     h=tconv(f,g);
%     r=tconv(spreadinv(f),h);
% 
%   then r is equal to g.
%
%   SEE ALSO:  SPREADOP, SPREADFUN, SPREADINV

% This program is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
% 
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.
% 
% You should have received a copy of the GNU General Public License
% along with this program.  If not, see <http://www.gnu.org/licenses/>.


% AUTHOR: Peter Soendergaard

error(nargchk(2,2,nargin));

M=size(f,1);
N=size(f,2);

if nargin==2
  L=M;
  a=1;
else
  L=N*a; 
end;

if any(size(f)~=size(g))
  error('Input matrices must be same size.');
end;

if a==1
  if M~=N
    error('Input matrices must be square.');
  end;
end;

b=L/M;

f=fft(f);
g=fft(g);

Tf=zeros(L);
Tg=zeros(L);
for ii=0:L-1
  for jj=0:L-1
    Tf(ii+1,jj+1)=f(ii+1,mod(ii-jj,L)+1);
    Tg(ii+1,jj+1)=g(ii+1,mod(ii-jj,L)+1);
  end;
end;

Th=Tf*Tg;

h=zeros(L);
for ii=0:L-1
  for jj=0:L-1
    h(ii+1,jj+1)=Th(ii+1,mod(ii-jj,L)+1);
  end;
end;

h=ifft(h);