www.pudn.com > tftb2002toolbox.rar > mexhat.m

function  h = mexhat(nu) ;
%MEXHAT	Mexican hat wavelet in time domain.
%	H=MEXHAT(NU) returns the mexican hat wavelet with central 
%	frequency NU (NU is a normalized frequency in Hz). 
%
%	NU : any real between 0 and 0.5		(default : 0.05).
%	H  : time vector containing the mexhat samples. 
%		length(H)=2*ceil(1.5/NU)+1.
%
%	Example : 
%	 plot(mexhat);
%
%	See also KLAUDER.

%	P. Goncalves, October 95
%	Copyright (c) 1995 Rice University
%
%	------------------- 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 
%	f.auger@ieee.org 

if nargin==0,
 nu=0.05;
elseif nargin>1,
 error('Too many input parameters');
end

if nu>0.5 | nu<0,
 disp('Warning : NU should be between 0 and 0.5');
end

N = 1.5 ;
alpha = pi^2*nu^2 ;
n = ceil(N/nu) ; 
t = -n:n ;
h = nu*sqrt(pi)/2*exp(-alpha*t.^2).*(1-2*alpha*t.^2) ;