[PLL][PM]锁相环模拟相位解调

%锁相环测试
%模拟相位解调

clear
close all
clc

fs=1000;	%采样率
tend=100;
t=0:1/fs:tend;
t(end)=[];
fc=1;		%载波频偏
fb=100;		%PM调制信号频率
gain=0.2;	%锁相环输入增益
EbN0=20;

[b,a]=cheby2(3,30,0.2);	%切比雪甫滤波器
num=gain*b;
den=conv([1 -1],a)+[num,0];
pole=roots(den);
abs(pole)		%计算系统稳定性
fvtool(b,a);
lb=length(b);
la=length(a)-1;
bb=zeros(1,lb);
aa=zeros(1,la);

cio=cos(2*pi*fc*t+cos(2*pi*fb*t));
cqo=sin(2*pi*fc*t+cos(2*pi*fb*t));
ci=awgn(cio,EbN0,'measured');
cq=awgn(cqo,EbN0,'measured');
cout=complex(zeros(size(ci)),zeros(size(cq)));
phase_out=zeros(size(ci));
phase=0;

for k=1:length(cout)
	cout(k)=exp(1i*phase);
	err=complex(ci(k),cq(k))*exp(-1i*phase);
	phase_out(k)=angle(err);
	err=phase_out(k)*gain;
	bb=[err,bb(1:lb-1)];
	err=sum(bb.*b)-sum(aa.*a(2:end));
	aa=[err,aa(1:la-1)];
	phase=phase+err;
	if phase>pi, phase=phase-2*pi;
	elseif phase<-pi, phase=phase+2*pi;end
end

CO=fft(cio);
CO=abs(CO)/length(CO);
CR=fft(real(cout));
CR=abs(CR)/length(CR);
F=linspace(0,fs,length(CR));
N=ceil(length(F)/2);
plot(F(1:N),CO(1:N),'r');
hold on
plot(F(1:N),CR(1:N),'b');
figure
plot(t,phase_out);
PO=fft(phase_out);
PO=abs(PO)/length(PO);
figure
plot(F(1:N),PO(1:N));