repmat() introduces an unnecessary phase shift
1 Ansicht (letzte 30 Tage)
Ältere Kommentare anzeigen
Hi, I used repmat command to create a periodic waveform.
However I noticed repmat() introduces a phase shift of one element in the array in each repetition.
I compared the analytical waveform (plotted in Green) with the repmat generated signal
Pls give some advice to correct.
Code:
clc;
clear all;
fc=4; %control waveform
T=1/fc;
t1=0:.001:T/6;
t2=T/6:.001:2*T/6;
t3=2*T/6:.001:3*T/6;
t4=3*T/6:.001:4*T/6;
t5=4*T/6:.001:5*T/6;
t6=5*T/6:.001:6*T/6;
%Positive limit
Ap=sqrt(3) + sin(2*pi*t1*fc - 2*pi/3);
Bp=sin(2*pi*t2*fc);
Cp=sqrt(3) + sin(2*pi*t3*fc + 2*pi/3);
Dp=sin(2*pi*t4*fc - 2*pi/3);
Ep=sqrt(3) + sin(2*pi*t5*fc + 2*pi);
Fp=sin(2*pi*t6*fc + 2*pi/3);
%Negative Limit
An=sin(2*pi*t1*fc - 2*pi/3);
Bn=-sqrt(3) + sin(2*pi*t2*fc);
Cn=sin(2*pi*t3*fc + 2*pi/3 );
Dn=-sqrt(3) + sin(2*pi*t4*fc + 4*pi/3);
En=sin(2*pi*t5*fc );
Fn=-sqrt(3) + sin(2*pi*t6*fc + 2*pi/3);
t=[t1 t2 t3 t4 t5 t6];
yp=[Ap,Bp,Cp,Dp,Ep,Fp];
yn=[An,Bn,Cn,Dn,En,Fn];
%plot(t,yp,t,yn)
m=3 ; % Repetition
n=numel(t);
tt=0:0.001:n*m*0.001-0.001;
yy_p=repmat(yp,1,m);
yy_n=repmat(yn,1,m);
max_shoothru=[yy_p;yy_n];
% analytical wave
Y1p=((1-0.5*sqrt(3)))*sin(3*4*2*pi*tt +pi) + sqrt(3)/2;
Y1n=((1-0.5*sqrt(3)))*sin(3*4*2*pi*tt +pi ) - sqrt(3)/2;
analytical=[Y1p;Y1n];
%3 phase voltage waveforms
A_ph=sin(2*pi*tt*fc);B_ph=sin((2*pi*tt*fc)+ 2*pi/3);C_ph=sin((2*pi*tt*fc)- 2*pi/3);
waves=[A_ph;B_ph;C_ph];
plot(tt,max_shoothru,tt,waves,'r',tt,analytical,'g');
grid on;
0 Kommentare
Antworten (1)
Walter Roberson
am 10 Dez. 2013
Suppose you create a periodic waveform over 0 to 1. Then when you repmat it, you get [0...1 0...1 0...1]. Note that the second 1 is not at the position that would correspond to 2, and is instead one sample later.
To correct this, what you need to repeat is the samples over 0 to 1 without the 1 itself. e.g.,
W = linspace(0, 1, 1000);
W25 = repmat(W(1:end-1), 1, 25);
If you want a final return to beginning you can,
W25 = [repmat(W(1:end-1), 1, 25), W(end)];
0 Kommentare
Siehe auch
Kategorien
Mehr zu Matrices and Arrays finden Sie in Help Center und File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!