alias.m

很多matlab的源代码

function [fa,fd] = alias(f,fs)
% ALIAS Compuation of aliased frequencies.
%
%	[FA,FD] = ALIAS(F,FS) Computes aliased frequencies 
%	F = frequency array in HERTZ, FS = sampling frequency in HERTZ. 
%       FA = aliased frequencies, FD = aliased DIGITAL frequencies (FD < 0.5) 
%
%       ALIAS (with no input arguments) invokes the following example:
%
%	% Find the aliased frequencies if a signal with [100 200 300 400]Hz 
%	% is sampled at 120Hz
%       >>[fn,fnd] = alias([100,200;300,400],120)


% 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 alias,disp('Strike a key to see results of the example')
pause,[fn,fnd]=alias([100,200;300,400],120),return,end

if fs<=0, error('Sampling frequency must be positive'),return,end
fa=rem(f,fs);i=find(abs(fa)>0.5*fs);
if ~isempty(i),fa(i)=fa(i)-sign(fa(i))*fs;end
fd=fa/fs;