sinc_art.m

matlab中噪声模型

function x=sinc_art(N,wd)
% y = sinc_art(N, wd);
% N  = length of pulse (in samples)
% wd = approx percentage of pulse that central lobe occupies
% (e.g. for N=256, a one second window of ECG sampled at 256Hz, wd=10 
%  gives a central lobe of approx 0.14 seconds (35 samples) )
% 
% uses SINC Sin(pi*x)/(pi*x) function to generate artificial muscle-like
% artefacts on ECG. 
% 
% see PULSTRAN for generating a continuous time series of this output 
% (but remember that artefacts are not periodic!!!!)
%
%   See also: SINC SQUARE, SIN, COS, CHIRP, DIRIC, GAUSPULS, 
%             PULSTRAN, RECTPULS and TRIPULS  

%   Author: G. Clifford, 15-1-03
%   Copyright 2003 Oxford University

if nargin <2
    wd = 10;    
end

% how long is half a window
len=round(N/2);
% for indexes into array
y=ones(1,len);
i=find(y);
% 'normalise' period
ii = i/length(y);
% calculate one half of sinc function
y(i)=sin(pi*ii(i)*100/wd)./(pi*ii(i));
% reflect in origin
z(len+1-i)=y(i);
% concatonate two vectors to form whole sinc fn
x=[z y];
% normalise amplitude
x = x/max(x);