spreadinv.m

Matlab时频分析工具箱,希望能对大家有所帮助啊

function out=spreadinv(p1,p2);
%SPREADINV  Symbol of inverse spreading operator.
%   Usage: h=spreadinv(f,c);
%
%   SPREADINV(c) will compute the symbol of the inverse of the spreading
%   operator with symbol c.
%
%   SPREADINV(f,c) will apply the inverse of the spreading with symbol c
%   to the input signal f.
%
%   SEE ALSO: SPREADFUN, TCONV, SPREADFUN, SPREADADJ

% 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/>.

error(nargchk(1,2,nargin));

if nargin==1
  coef=p1;
else
  f=p1;
  coef=p2;
end;

if ndims(coef)>2 || size(coef,1)~=size(coef,2)
    error('Input symbol T must be a square matrix.');
end;

L=size(coef,1);

coef=fft(coef);

% Create a matrix representation of the operator.
T=zeros(L);
for ii=0:L-1
  for jj=0:L-1
    T(ii+1,jj+1)=coef(ii+1,mod(ii-jj,L)+1);
  end;
end;

if nargin==1
  
  % Calculate the inverse symbol.
  Ti=inv(T);
  
  cinv=zeros(L);
  for ii=0:L-1
    for jj=0:L-1
      cinv(ii+1,jj+1)=Ti(ii+1,mod(ii-jj,L)+1);
    end;
  end;

  out=ifft(cinv);
  
else

  out=T\f;
  
end;