94 lines
2.7 KiB
Matlab
Executable File
94 lines
2.7 KiB
Matlab
Executable File
function [time_error,iq] = rx_timing_recovery(signal)
|
||
|
||
N=ceil((length(signal))/4);
|
||
Ns=4*N; %总的采样点数
|
||
|
||
bt=2e-2/1.3;
|
||
c1=8/3*bt;
|
||
c2=32/9*bt*bt;
|
||
w=[0.5,zeros(1,N-1)]; %环路滤波器输出寄存器，初值设为0.5
|
||
n=[0.9,zeros(1,Ns-1)]; %NCO寄存器，初值设为0.9
|
||
n_temp=[n(1),zeros(1,Ns-1)];
|
||
u=[0.6,zeros(1,2*N-1)]; %NCO输出的定时分数间隔寄存器，初值设为0.6
|
||
out_signal_I=zeros(1,2*N); %I路内插后的输出数据
|
||
out_signal_Q=zeros(1,2*N); %Q路内插后的输出数据
|
||
time_error=zeros(1,N); %Gardner提取的时钟误差寄存器
|
||
|
||
ik=time_error;
|
||
qk=time_error;
|
||
|
||
k=1; %用来表示Ti时间序号,指示u,yI,yQ
|
||
ms=1; %用来指示T的时间序号,用来指示a,b以及w
|
||
strobe=zeros(1,Ns);
|
||
aI=real(signal);
|
||
bQ=imag(signal);
|
||
ns=length(aI)-1;
|
||
i=1;
|
||
while(i<ns)
|
||
n_temp(i+1)=n(i)-w(ms);
|
||
if(n_temp(i+1)>0)
|
||
n(i+1)=n_temp(i+1);
|
||
else
|
||
n(i+1)=mod(n_temp(i+1),1);
|
||
%内插滤波器模块
|
||
FI1=0.5*aI(i+2)-0.5*aI(i+1)-0.5*aI(i)+0.5*aI(i-1);
|
||
FI2=1.5*aI(i+1)-0.5*aI(i+2)-0.5*aI(i)-0.5*aI(i-1);
|
||
FI3=aI(i);
|
||
out_signal_I(k)=(FI1*u(k)+FI2)*u(k)+FI3;
|
||
|
||
FQ1=0.5*bQ(i+2)-0.5*bQ(i+1)-0.5*bQ(i)+0.5*bQ(i-1);
|
||
FQ2=1.5*bQ(i+1)-0.5*bQ(i+2)-0.5*bQ(i)-0.5*bQ(i-1);
|
||
FQ3=bQ(i);
|
||
out_signal_Q(k)=(FQ1*u(k)+FQ2)*u(k)+FQ3;
|
||
|
||
strobe(k)=mod(k,2);
|
||
%时钟误差提取模块，采用的是Gardner算法
|
||
if(strobe(k)==0)
|
||
%取出插值数据
|
||
ik(ms)=out_signal_I(k);
|
||
qk(ms)=out_signal_Q(k);
|
||
%每个数据符号计算一次时钟误差
|
||
if(k>2)
|
||
Ia=(out_signal_I(k)+out_signal_I(k-2))/2;
|
||
Qa=(out_signal_Q(k)+out_signal_Q(k-2))/2;
|
||
time_error(ms)=[out_signal_I(k-1)-Ia]*(out_signal_I(k)-out_signal_I(k-2))+[out_signal_Q(k-1)-Qa]*(out_signal_Q(k)-out_signal_Q(k-2));
|
||
else
|
||
time_error(ms)=(out_signal_I(k-1)*out_signal_I(k)+out_signal_Q(k-1)*out_signal_Q(k));
|
||
end
|
||
%环路滤波器,每个数据符号计算一次环路滤波器输出
|
||
if(ms>1)
|
||
w(ms+1)=w(ms)+c1*(time_error(ms)-time_error(ms-1))+c2*time_error(ms-1);
|
||
else
|
||
w(ms+1)=w(ms)+c1*time_error(ms)+c2*time_error(ms);
|
||
end
|
||
ms=ms+1;
|
||
end
|
||
k=k+1;
|
||
u(k)=n(i)/w(ms);
|
||
end
|
||
i=i+1;
|
||
end
|
||
|
||
iq=ik+1i*qk;
|
||
c1=max([abs(real(iq)),abs(imag(iq))]);
|
||
iq=iq ./c1;
|
||
|
||
|
||
% figure(1);
|
||
% subplot(311);
|
||
% plot(u);
|
||
% xlabel('运算点数');
|
||
% ylabel('分数间隔');
|
||
% grid on;
|
||
% subplot(312);
|
||
% plot(time_error);
|
||
% xlabel('运算点数');
|
||
% ylabel('定时误差');
|
||
% grid on;
|
||
% subplot(313);
|
||
% plot(w);
|
||
% xlabel('运算点数');
|
||
% ylabel('环路滤波器输出');
|
||
% grid on;
|
||
|
||
end |