zak.m

时间序列的时频分析工具箱

function dzt=zak(sig,N,M)
%ZAK 	Zak transform.
%	DZT=ZAK(SIG,N,M) computes the Zak transform of signal SIG.
%
%	SIG : Signal to be analysed (length(X)=N1).
%	N   : number of Zak coefficients in time (N1 must be a multiple
%	      of N)          (default : closest integer towards sqrt(N1)). 
%	M   : number of Zak coefficients in frequency (N1 must be a
%	      multiple of M) (default : M=N1/N).
%	DZT : Output matrix (N,M) containing the discrete Zak transform.
%
%	Example : 
%	 sig=fmlin(256); DZT=zak(sig);
%	 imagesc(DZT);
%
%	See also IZAK, TFRGABOR.

%	O. Lemoine - February 1996.
%	Copyright (c) 1996 by CNRS (France).
%
%	------------------- CONFIDENTIAL PROGRAM -------------------- 
%	This program can not be used without the authorization of its
%	author(s). For any comment or bug report, please send e-mail to 
%	[e-mail] 

N1=length(sig);

if N1<=2,
  error('SIG must have at least 3 elements');
elseif nargin<1,
  error('The number of parameters must be at least one');
elseif nargin==1,
  [N,M]=divider(N1);
elseif nargin==2,
  N=N1/M;
elseif M<=1|N<=1|M>=N1|N>=N1,
  error('M and N must be between 2 and N1-1');
elseif rem(N1,M)~=0|rem(N1,N)~=0,
  error('M and N must be such that N1 is a multiple of M and N');
end

Msig=zeros(M,N);
dzt=zeros(N,M);

Msig=reshape(sig,M,N);

dzt=fft(Msig.')/sqrt(N);