shah.m

Matlab时频分析工具箱,希望能对大家有所帮助啊

function f=shah(L,a);
%SHAH  Discrete Shah-distribution
%  Usage: f=shah(L,a);
%
%  SHAH(L,a) computes the discrete, normalized Shah-distribution of
%  length L with a distance of a between the spikes. The Shah
%  distribution is defined by f(n*a+1)=1/sqrt(L/a) for integer n,
%  otherwise f is zero.
%
%  This is also known as a pulse train or as the comb function, because
%  the shape of the function resembles a comb. It is the sum of unit
%  impulses ('diracs') with the distance a.
%
%  The DFT of SHAH(L,a) is SHAH(L,L/a).
%
%  The Shah function has an extremely bad time-frequency localization.
%  It does not generate a Gabor frame for any L and a.
%  
%  SEE ALSO:  PGAUSS 

% 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/>.
if nargin~=2
  error('Wrong number of input parameters.');
end;

if mod(L,a)~=0
  error('a must divide L.');
end;

f=zeros(L,1);

f(1:a:L)=1/sqrt(L/a);