spll.m

该程序包含一般数字PLL仿真maltab程序和数字COSTAS环程序

%software PLL
clear all;clc;close all;

fs=100;
ts=1/fs;
t=0:ts:2;
n=length(t);
bs_signal=(-1).^floor(t*2);
% figure;stairs(bs_signal)


fin=5;
vin=bs_signal.*sin(2*pi*fin.*t);
figure;plot(t,vin);grid;

floc=5;
vout=cos(2*pi*floc.*t);

zeta=0.7;
omiga=2*pi*10;%关于自然谐振频率
uf=zeros(1,n);
mix=zeros(1,n);
vd=zeros(1,n);
Thetao=zeros(1,n);

w1=0;w2=0;
for i=2:n-1
    mix(i)=vin(i).*vout(i);
    
    in=mix(i);%混频后进行低通滤波
    w1=in+w2;
    w2=in+w1;
    out=w1/2/fs;
    vd(i)=out;
    
    
    uf(i)=uf(i-1)+(2*zeta/omiga+ts/2)*vd(i)-(2*zeta/omiga-ts/2)*vd(i-1);%环路滤波器
    
    Thetao(i+1)=Thetao(i)+omiga^2*ts/2*(uf(i)+uf(i-1));%VCO积分
    
    vout(i+1)=cos(2*pi*floc.*t(i+1)+Thetao(i+1));
end
figure;plot(t,mix,t,vd,'r:',t,uf,'g.-')
figure;plot(t,vin,t,vout,'r:');grid