clear all
close all
i=10;
j=5000;
fc=4;
fm=i/5;
B=2*fm;
t=linspace(0,5,j);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%產(chǎn)生基帶信號
a=round(rand(1,i));
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
subplot(321);
plot(t,st1);
title('基帶信號');
axis([0,5,-1,2]);
st2=t;   %基帶信號求反
for k=1:j;
    if st1(k)>=1;
        st2(k)=0;
    else
        st2(k)=1;
    end
end;
subplot(322);
plot(t,st2);
title('基帶信號反碼');
axis([0,5,-1,2]);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%載波信號
s1=sin(2*pi*fc*t);
s2=sin(2*pi*fc*t+pi);
subplot(323);
plot(s1);
title('載波信號');
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%調(diào)制
p1=st1.*s1;
p2=st2.*s2;
subplot(324);
plot(t,p1);
title('st1*s1');
subplot(325);
plot(t,p2);
title('st2*s2');
e_psk=p1+p2;
subplot(326);
plot(t,e_psk);
title('e_2psk');
noise=rand(1,j);
psk=e_psk+noise;%加入噪聲
figure(2);
subplot(411);
plot(t,psk);
title('加噪后波形');
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%相干解調(diào)
psk=psk.*s1;%與載波相乘
subplot(412);
plot(t,psk);
title('與載波相乘后波');
[f,af] = T2F(t,psk);%通過低通濾波器
[t,psk] = lpf(f,af,B);
subplot(413);
plot(t,psk);
title('通過低通濾波器波形');
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%抽樣判決
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(414);
plot(t,psk);
axis([0,5,-1,2]);
title('抽樣判決后波形')