clear all
close all
i=10;
j=5000;
fc=4;%载波频率
fm=i/5;%码元速率
B=2*fm;
t=linspace(0,5,j);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%产生基带信号
a=round(rand(1,i));%随机序列,基带信号
st1=t;
for n=1:10
if a(n)<1;
for m=j/i*(n-1)+1:j/i*n
st1(m)=0;
end
else
for m=j/i*(n-1)+1:j/i*n
st1(m)=1;
end
end
end
figure(1);
subplot(511);
plot(t,st1);
title('基带信号');
axis([0,5,-1,2]);
%%%%%%%%%%%&&&&&&%%%%%%%%%%%%%%%%%产生双极性基带信号
st2=t;
for k=1:j;
if st1(k)>=1;
st2(k)=0;
else
st2(k)=1;
end
end;
st3=st1-st2;%双极性基带信号
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%载波信号
s1=sin(2*pi*fc*t);
subplot(512);
plot(s1);
title('载波信号');
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%调制
psk=st3.*s1;
subplot(513);
plot(t,psk);
title('2PSK信号');
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%相干解调
psk=psk.*s1;%与载波相乘
[f,af] = T2F(t,psk);%%%%%%%%%%%通过低通滤波器
[t,psk] = lpf(f,af,B);
subplot(514);
plot(t,psk);
title('低通滤波后波形');
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%抽样判决
for m=0:i-1;
if psk(1,m*500+250)<0;
for j=m*500+1:(m+1)*500;
psk(1,j)=0;
end
else
for j=m*500+1:(m+1)*500;
psk(1,j)=1;
end
end
end
subplot(515);
plot(t,psk);
axis([0,5,-1,2]);
title('抽样判决后波形')