qpsk2_made.m

QPSK调制解调

clear all;
Rb=2400;   %信息速率
fc=10;  %载波速率
fs=16*10;%采样率
T=0.005;   %时间
s=randsrc(1,0.5*T*Rb,[1,2,3,4]);%信源序列
for i=1:length(s)
    switch(s(i)-1)
        case(0)
            s1(i)=-1;
            s2(i)=-1;
         case(1)
            s1(i)=-1;
            s2(i)=1;
          case(2)
            s1(i)=1;
            s2(i)=-1;
        otherwise
            s1(i)=1;
            s2(i)=1;
    end
end
st=zeros(1,0.5*T*Rb*fs);
for k=1:length(s)
      for t=1:fs
        st((k-1)*fs+t)=s1(k)*cos(2*pi*0.0125*t)+s2(k)*sin(2*pi*0.0125*t);
     end
end
subplot(2,1,1);
plot(st);ylim([-2,2]);
title('未加噪声QPSK信号');
sout=AWGN(st,9);      %加9db的噪声
subplot(2,1,2);
plot(sout);ylim([-2,2]);
title('加噪声后的QPSK信号');
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%  为便于观测图中选取参数：Rb=2400;   %信息速率 fc=10;  %载波速率 fs=8*10;%采样率