正交幅度调制(QAM)及解调Matlab仿真分解

1、正交幅度调制(QAM)及解调Matlab仿真实验目的：1 .掌握QAM及解调原理与特性；2 ,了解星座图的原理及用途。实验内容：1 .编写MATLAB程序仿真QAM及相干解调;NRZ码上网关系;2 .观察I、Q两路基带信号的特征及与输入3 .观察I、Q调制过程中信号的变化；4 .观察星座图在不同噪声环境下的变化；5 .分析仿真中观察的数据，撰写实验报告。仿真代码：functionproject(N,p)%N为待仿真序列的长度%p为产生1的概率%=%首先产生随机二进制序列N=input(,输入二进制序列的长度：N=');p=input('输入产生1的概率：,);source=ra

2、ndsrc(1,N,1,0;p,1-p);figure(1);stem(source);axis(1N-12);%对产生的二进制序列进行QAM调制source1,source2=Qam_modulation(source);%=%画出星座图figure(2);plot_astrology(source1,source2);%=%两路信号进行插值(8倍过采样)sig_insert1=insert_value(source1,8);sig_insert2=insert_value(source2,8);%=%画出两路信号的波形图figure(3);plot_2way(sig_insert1,sig

3、_insert2,length(sig_insert1),0.5);title('两路信号波形,);%=%通过低通滤波器sig_rcos1,sig_rcos2=rise_cos(sig_insert1,sig_insert2,0.25,2);%=%画出两路信号信号波形图figure(4);plot_2way(sig_rcos2,sig_rcos2,length(sig_rcos1)/4,0.5);title(,通过低通滤波器后两路信号波形图,)holdonstem_2way(sig_insert1,sig_insert2,3,0.25,2,length(sig_rcos1)/4);%=

4、%将基带信号调制到高频上t,sig_modulate=modulate_to_high(sig_rcos1,sig_rcos2,0.25,2.5);figure(5);plot(t(1:500),sig_modulate(1:500);title('载波调制信号图,);%=%将滤波后的信号加入高斯噪声snr=10;x1,x2=generate_noise(sig_rcos1,sig_rcos2,snr);sig_noise1=x1'sig_noise2=x2'figure(6);plot_2way(sig_noise1,sig_noise2,length(sig_noi

5、se1)/4,0.5);title(,加入高斯白噪声后的两路信号波形,);%=%经过匹配滤波器sig_match1,sig_match2=rise_cos(sig_noise1,sig_noise2,0.25,2);figure(7);plot_2way(sig_match1,sig_match2,length(sig_match1)/4,0.5);title('经过匹配滤波器后,);%=%采样x1,x2=pick_sig(sig_match1,sig_match2,8);sig_pick1=x1;sig_pick2=x2;%画出星座图figure(8)plot_astrology(s

6、ig_pick1,sig_pick2);%=%解调signal=demodulate_sig(sig_pick1,sig_pick2);r=signal;%画出解调后的信号figure(9);stem(r);axis(1N-12);demodulate_sigfunctiony=demodulate_sig(x1,x2)%解调xx1(find(x1>=2)=3;xx1(find(x1<2)&(x1>=0)=1;xx1(find(x1>=-2)&(x1<0)=-1;xx1(find(x1<-2)=-3;xx2(find(x2>=2)=3;

7、xx2(find(x2<2)&(x2>=0)=1;xx2(find(x2>=-2)&(x2<0)=-1;xx2(find(x2<-2)=-3;temp1=zeros(1,length(xx1)*2);temp1(find(xx1=-1)*2)=1;temp1(find(xx1=1)*2-1)=1;temp1(find(xx1=1)*2)=1;temp1(find(xx1=3)*2-1)=1;temp2=zeros(1,length(xx2)*2);temp2(find(xx2=-1)*2)=1;temp2(find(xx2=1)*2-1)=1;te

8、mp2(find(xx2=1)*2)=1;temp2(find(xx2=3)*2-1)=1;n=length(temp1);fori=1:2:2*n-1y(i)=temp1(i+1)/2);y(i+1)=temp2(i+1)/2);endgenerate_noisefunctiony1,y2=generate_noise(x1,x2,snr)snr1=snr+10*log10(4);ss=var(x1+i*x2,1);y=awgn(x1+j*x2,snr1+10*log10(ss/10),'measured');y1=real(y);y2=imag(y);insert_valu

9、efunctiony=insert_value(x,ratio)%对两路信号进行插值y=zeros(1,ratio*length(x);a=1:ratio:length(y);y(a)=x;modulate_to_highfunctiont,y=modulate_to_high(x1,x2,f,hf)yo1=zeros(1,length(x1)*hf/f*10);yo2=zeros(1,length(x1)*hf/f*10);n=1:length(yo1);yo1(n)=x1(floor(n-1)/(hf/f*10)+1);yo2(n)=x1(floor(n-1)/(hf/f*10)+1);t

10、=(1:length(yo1)/hf*f/10;y=yo1.*cos(2*pi*hf*t)-yo2.*sin(2*pi*hf*t);pick_sigfunctiony1,y2=pick_sig(x1,x2,ratio)%采样y1=x1(ratio*3*2+1:ratio:(length(x1)-ratio*3*2);y2=x2(ratio*3*2+1:ratio:(length(x2)-ratio*3*2);plot_2wayfunctionplot_2way(x1,x2,len,t)%绘制正交信号图subplot(2,1,2);plot(1:len)*t,x2(1:len);axis(0le

11、n*t-44);holdon;plot(1:len)*t,x2(1:len)，','Color','red');holdoff;xlabel('虚部信号)；subplot(2,1,1);plot(1:len)*t,x1(1:len);axis(0len*t-44);holdonplot(1:len)*t,x1(1:len)，','Color','red');xlabel('实部信号)；holdoffplot_astrologyfunctionplot_astrology(a,b)%画出星座图subp

12、lot(1,1,1);plot(a,b,'+');axis(-55-55);line(-5,5,0,0,'LineWidth'3'Color','red');line(0,0,-5,5,'LineWidth'3'Color','red');title('QAM星座图');Qam_modulationfunctionyy1,yy2=Qam_modulation(x)N=length(x);a=1:2:N;y1=x(a);y2=x(a+1);a=1:2:N/2;temp1

13、1=y1(a);temp12=y1(a+1);y11=temp11*2+temp12;temp21=y2(a);temp22=y2(a+1);y22=temp21*2+temp22;yy1(find(y11=0)=-3;yy1(find(y11=1)=-1;yy1(find(y11=3)=1;yy1(find(y11=2)=3;yy2(find(y22=0)=-3;yy2(find(y22=1)=-1;yy2(find(y22=3)=1;yy2(find(y22=2)=3;endrise_cosfunctiony1,y2=rise_cos(x1,x2,fd,fs)%升余弦滤波yf,tf=rco

14、sine(fd,fs,'fir/sqrt');yo1,to1=rcosflt(x1,fd,fs,'filter/Fs',yf);yo2,to2=rcosflt(x2,fd,fs,'filter/Fs',yf);y1=yo1;y2=yo2;stem_2wayfunctionstem_2way(x1,x2,delay,fd,fs,len)subplot(2,1,1)holdonstem(1:len)+fs/fd*3)/fs,x1(1:len);subplot(2,1,2)holdonstem(1:len)+fs/fd*3)/fs,x2(1:len);实验结果：>>project输入二进制序列的长度：N=200输入产生1的概率：0.8QAM星座图43210