www.gusucode.com > 线性时频分析工具箱 - ltfat-1.0.1源码程序 > 线性时频分析工具箱 - LTFAT\fourier\shah.m
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. % % If a divides L, then 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. % Copyright (C) 2005-2011 Peter L. Soendergaard. % This file is part of LTFAT version 1.0.1 % 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 % TESTING: OK % REFERENCE: OK 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);