四相移相键控(QPSK)调制及解调实验

dos_f_mag=abs(dos_f); dos_f_ang=angle(dos_f); for i=51:1:149

dos_f_mag(1,i)=dos_f_mag(1,i)/3; end

Q_j=dos_f_mag.*exp(j*dos_f_ang); Qa_j1=ifft(Q_j); Qa_j1=2*real(Qa_j1);

for i=1:50 sum=0; for n=1:4;

sum=sum+Qa_j1(1,4*(i-1)+n); end sum=sum/4; if sum>=mq G(1,4*i-3)=1; G(1,4*i-2)=1; G(1,4*i-1)=1; G(1,4*i)=1; else

if sum<=-mq G(1,4*i-3)=-1; G(1,4*i-2)=-1; G(1,4*i-1)=-1; G(1,4*i)=-1; else

G(1,4*i-3)=0; G(1,4*i-2)=0; G(1,4*i-1)=0; G(1,4*i)=0; end end end Qa_j=G;

for i=1:50

if Ia_j(1,4*i-2)==1&&Qa_j(1,4*i-2)==0 data2_out(1,2*i-1)=0; data2_out(1,2*i)=0; else

if Ia_j(1,4*i-2)==0&&Qa_j(1,4*i-2)==1 data2_out(1,2*i-1)=1;

data2_out(1,2*i)=0; else

if Ia_j(1,4*i-2)==-1&&Qa_j(1,4*i-2)==0 data2_out(1,2*i-1)=1; data2_out(1,2*i)=1; else

if Ia_j(1,4*i-2)==0&&Qa_j(1,4*i-2)==-1 data2_out(1,2*i-1)=0; data2_out(1,2*i)=1; end end end end end

for i=1:100

if data2(1,i)~=data2_out(1,i); error_m=error_m+1; end end end

error_rate(1,x+1)=error_m/10000; end

subplot(5,1,3);plot(1:200,Ia_j); subplot(5,1,4);plot(1:200,Qa_j);

subplot(5,1,5);semilogy(0:0.2:9.8,error_rate);

5. 实验结果

I,Q,误码率曲线图