analytic.m

来自「很多matlab的源代码」· M 代码 · 共 34 行

function y = analytic(x)
%ANALYTIC Analytic signal for a real function
%
%	y=ANALYTIC(x): Analytic signal y=x+j*H(x) of a real vector x 
%	where H(x) is the Hilbert transform of x.
%
%	ANALYTIC (with no input arguments) invokes the following example:
%
%	Find and plot the analytic signal for xx=sin(2*pi*t)
%	t=0:.01:0.99;xx=sin(2*pi*t);yy=analytic(xx);plot(t,[real(yy);imag(yy)])


% ADSP Toolbox: Version 2.0 
% For use with "Analog and Digital Signal Processing", 2nd Ed.
% Published by PWS Publishing Co.
%
% Ashok Ambardar, EE Dept. MTU, Houghton, MI 49931, USA
% http://www.ee.mtu/faculty/akambard.html
% e-mail: [e-mail]
% Copyright (c) 1998


if nargin==0,help analytic,disp('Strike a key to see results of the example')
pause,t=0:.01:0.99;xx=sin(2*pi*t);yy=analytic(xx);
plot(t,real(yy),'r',t,imag(yy),'g'),grid
title('Real (r) and imag (g) part of analytic signal'),return,end


j=sqrt(-1);
n=length(x);if n==1,y=x+j*x;return,end      % Trivial case
y=fft(x);                                   % X(f)
y(:)=-j*[0;sign(n/2-(1:n-1)')].*y(:);       % -j*sgn(f)*X(f)
y = x+j*real(ifft(y));                      % Analytic signal