加载中…载波恢复之初级数字锁相环
(2014-12-18 23:36:36)
标签：
股票 |
分类： InformationAndSignalProcess |
求差值时需要使用到正交相位和同相相位，才可以估计的比较准，整个的简单思路如下图：
仿真实验图：
%频偏：-60Hz
%相偏：在0－2*pi内随机分布
%程序及结果如下：
clear all;
close all;
%定义锁相环的工作模式：单载波为“1”、BPSK调制为“2”、QPSK调制为“3”
PLL_Mode = 3;
%仿真数据长度
Simulation_Length=1000;
%基带信号
if PLL_Mode == 1
I_Data=ones(Simulation_Length,1);
Q_Data=I_Data;
else if PLL_Mode == 2
I_Data=randint(Simulation_Length,1)*2-1;
Q_Data=zeros(Simulation_Length,1);
% Q_Data=randint(Simulation_Length,1)*2-1;
else
I_Data=randint(Simulation_Length,1)*2-1;
Q_Data=randint(Simulation_Length,1)*2-1;
end
end
Signal_Source=I_Data + j*Q_Data;
%载波信号
Freq_Sample=2400;%采样率，Hz
Delta_Freq=-60; %频偏，Hz
Time_Sample=1/Freq_Sample;
Delta_Phase=rand(1)*2*pi; %随机初相，Rad
Carrier=exp(j*(Delta_Freq/Freq_Sample*(1:Simulation_Length)+Delta_Phase));
%只是显示了差分的部分，也就是相位的差别部分，载波并没有加
%调制处理
Signal_Channel=Signal_Source.*Carrier';
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%以下为锁相环处理过程
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%参数清零
Signal_PLL=zeros(Simulation_Length,1);
NCO_Phase = zeros(Simulation_Length,1);
Discriminator_Out=zeros(Simulation_Length,1);
Freq_Control=zeros(Simulation_Length,1);
PLL_Phase_Part=zeros(Simulation_Length,1);
PLL_Freq_Part=zeros(Simulation_Length,1);
%环路处理
C1=0.22013;
C2=0.0024722;
for i=2:Simulation_Length
Signal_PLL(i)=Signal_Channel(i)*exp(-j*mod(NCO_Phase(i-1),2*pi));
I_PLL(i)=real(Signal_PLL(i));
Q_PLL(i)=imag(Signal_PLL(i));
if PLL_Mode == 1
Discriminator_Out(i)=atan2(Q_PLL(i),I_PLL(i));
else if PLL_Mode == 2
Discriminator_Out(i)=sign(I_PLL(i))*Q_PLL(i)/abs(Signal_PLL(i));
else
Discriminator_Out(i)=(sign(I_PLL(i))*Q_PLL(i)-sign(Q_PLL(i))*I_PLL(i))...
/(sqrt(2)*abs(Signal_PLL(i)));
end
end
%后续是如何估计出最后的差别，总而进行纠正，主要是滤波过程
PLL_Phase_Part(i)=Discriminator_Out(i)*C1;
Freq_Control(i)=PLL_Phase_Part(i)+PLL_Freq_Part(i-1);
PLL_Freq_Part(i)=Discriminator_Out(i)*C2+PLL_Freq_Part(i-1);
NCO_Phase(i)=NCO_Phase(i-1)+Freq_Control(i);
end
%画图显示结果
figure
subplot(2,2,1)
plot(-PLL_Freq_Part(2:Simulation_Length)*Freq_Sample);
grid on;
title('锁相环频率响应曲线');
axis([1 Simulation_Length -100 100]);
subplot(2,2,2)
plot(PLL_Phase_Part(2:Simulation_Length)*180/pi);
title('锁相环相位响应曲线');
axis([1 Simulation_Length -2 2]);
grid on;
%设定显示范围
Show_D=300; %起始位置
Show_U=900; %终止位置
Show_Length=Show_U-Show_D;
subplot(2,2,3)
plot(Signal_Channel(Show_D:Show_U),'*');
title('进入锁相环的数据星座图');
axis([-2 2 -2 2]);
grid on;
hold on;
subplot(2,2,3)
plot(Signal_PLL(Show_D:Show_U),'r*');
grid on;
subplot(2,2,4)
plot(Signal_PLL(Show_D:Show_U),'r*');
title('锁相环锁定及稳定后的数据星座图');
axis([-2 2 -2 2]);
grid on;
figure
%设定显示范围
Show_D=300; %起始位置
Show_U=350; %终止位置
Show_Length=Show_U-Show_D;
subplot(2,2,1)
plot(I_Data(Show_D:Show_U));
grid on;
title('I路信息数据');
axis([1 Show_Length -2 2]);
subplot(2,2,2)
plot(Q_Data(Show_D:Show_U));
grid on;
title('Q路信息数据');
axis([1 Show_Length -2 2]);
subplot(2,2,3)
plot(I_PLL(Show_D:Show_U));
grid on;
title('锁相环输出I路信息数据');
axis([1 Show_Length -2 2]);
subplot(2,2,4)
plot(Q_PLL(Show_D:Show_U));
grid on;
title('锁相环输出Q路信息数据');
axis([1 Show_Length -2 2]);
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