anastep.m

用于信号处理里面的时频分析

function y=anastep(N,ti);
%ANASTEP Analytic projection of unit step signal.
%	Y=ANASTEP(N,TI) generates the analytic projection of a
%	unit step signal.
%	
%	N  : number of points.
%	TI : starting position of the unit step.
%	
%	Examples :
%	 signal=anastep(256,128);plot(real(signal));
%	 signal=-2.5*anastep(512,301);plot(real(signal));
%
%	See also ANASING, ANAFSK, ANABPSK, ANAQPSK, ANAASK.

%	O. Lemoine - June 1995, F. Auger, August 1995.
%	Copyright (c) 1996 by CNRS (France).
%
%  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 2 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, write to the Free Software
%  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

if (nargin==0),
 error('at least one parameter required');
elseif (nargin==1),
 ti=round(N/2);
end;

if (N<=0),
 error('N must be greater than zero');
else
 t=(1:N)';
 y=hilbert(t>=ti);
end;