QPSK.zip_QPSK_QPSK 识别_qpsk识别_信噪比_调制识别

close all;clc;clear; fc=2.5e6; % 载波频率为2.5MHZ len=10000; % 取1万个数 Fs=10e6; % 采样率是10MHZ % 基带信号的产生 %% 产生输入序列 data0 = randi([0,1],len,1); figure; subplot(2,1,1);stairs(data0(1:len)),axis([0 250 -0.2 1.2]),title('基带信号');grid on; subplot(2,1,2);plot(20*log(abs(fft(data0(1:len))))),axis([0 len -100 200]),title('基带信号的频谱'); grid on; %% 串并转换，将奇偶位数据分开 I = kron((data0(1:2:len,:)*2-1)',[1,1]); Q = kron((data0(2:2:len,:)*2-1)',[1,1]); figure; subplot(2,2,1);stairs(I),axis([0 250 -1.2 1.2]),title('I路信号');grid on; subplot(2,2,2);plot(20*log(abs(fft(I)))),axis([0 len -150 200]),title('I路信号的频谱'); grid on; subplot(2,2,3);stairs(Q),axis([0 250 -1.2 1.2]),title('Q路信号');grid on; subplot(2,2,4);plot(20*log(abs(fft(Q)))),axis([0 len -150 200]),title('Q路信号的频谱'); grid on; %% 插0 1万个数个数变成了4万个 zero_interval = 4; I0=zeros(1,zero_interval*len); Q0=zeros(1,zero_interval*len); I0(1:zero_interval:zero_interval*len) = I; Q0(1:zero_interval:zero_interval*len) = Q; figure; subplot(2,2,1);stairs(I0),axis([0 250 -1.2 1.2]),title('内插0后的I路信号');grid on; subplot(2,2,2);plot(20*log(abs(fft(I0)))),axis([0 zero_interval*len -700 250]),title('内插0后I路信号的频谱'); grid on; subplot(2,2,3);stairs(Q0),axis([0 250 -1.2 1.2]),title('内插0后的Q路信号');grid on; subplot(2,2,4);plot(20*log(abs(fft(Q0)))),axis([0 zero_interval*len -700 250]),title('内插0后Q路信号的频谱'); grid on; %平方根升余弦滤波器 NT = 16; %滤波器阶数 num=2*zero_interval*NT;%128 rf = 0.1; %滚降系数 Fs=10e6;% 采样率是101HZ psf=rcosfir(rf,NT,zero_interval,Fs,'sqrt'); Ipulse = conv(I0,psf); Qpulse = conv(Q0,psf); figure(4); subplot(2,2,1);plot(psf),axis([0 130 -0.2 0.6]),title('成形滤波器的时域波形');grid on; subplot(2,2,2);plot(20*log(abs(fft(psf)))),axis([0 130 -250 50]),title('成形滤波器的频谱'); grid on; subplot(2,2,3);plot(Ipulse),axis([0 500 -1.2 1.2]),title('成形滤波后的I路信号');grid on; subplot(2,2,4);plot(Qpulse),axis([0 500 -1.2 1.2]),title('成形滤波后的Q路信号');grid on; %% QPSK信号的调制 fc=2.5e6; %载波频率为2.51hz t = (0:1:zero_interval*len+num-1)/(fc*zero_interval); idata1 = Ipulse.*sqrt(2).*cos(2*pi*fc*t); qdata1 = Qpulse.*-sqrt(2).*sin(2*pi*fc*t); s1 = idata1 + qdata1; figure(5); subplot(2,1,1);plot(idata1),axis([num/2 400 -1.2 1.2]),title('调制后的I路信号');grid on; subplot(2,1,2);plot(qdata1),axis([num/2 400 -1.2 1.2]),title('调制后的Q路信号');grid on; figure(6); subplot(2,1,1);plot(s1),axis([num/2 400 -1.2 1.2]),title('调制信号');grid on; subplot(2,1,2);plot(20*log(abs(fft(s1)))),axis([0 zero_interval*len -550 300]),title('调制信号的频谱'); grid on; %% 添加高斯白噪声 SNR=10; % 信噪比 s2=awgn(s1,SNR); figure(7) subplot(2,1,1);plot(s2),axis([num/2 400 -1.2 1.2]),title('添加噪声后信号后的调制信号');grid on; subplot(2,1,2);plot(20*log(abs(fft(s2)))),title('添加噪声后信号的频谱');grid on; %% ----------------------------- QPSK 解调部分 %% 解调部分 idata2 = s2*sqrt(2).*cos(2*pi*fc*t); qdata2 = -s2*sqrt(2).*sin(2*pi*fc*t); % 匹配滤波 mtf= rcosfir(rf,NT,zero_interval,Fs,'sqrt'); idata3= conv(idata2,mtf); qdata3= conv(qdata2,mtf); figure(8); subplot(2,2,1);plot(idata3),axis([num 400+num/2 -1.7 1.7]),title('匹配滤波后I路信号的波形');grid on; subplot(2,2,2);plot(qdata3),axis([num 400+num/2 -1.7 1.7]),title('匹配滤波后Q路信号的波形');grid on; %% 抽样判决的过程，与0作比较，data>=0,则置1，否则置-1 %数据选择 Isel=zeros(1,zero_interval*len); Qsel=zeros(1,zero_interval*len); for jj = 1:zero_interval*len Isel(:,jj) = idata3(:,jj+num); Qsel(:,jj) = qdata3(:,jj+num); end %提取码元 idata4=zeros(1,len); qdata4=zeros(1,len); for jj = 1:len idata4(:,jj) = Isel(:,(jj-1)*zero_interval+1); qdata4(:,jj) = Qsel(:,(jj-1)*zero_interval+1); end subplot(2,2,3);plot(idata4(1,:)),axis([0 250 -1.7 1.7]),title('抽取后I路信号的波形');grid on; subplot(2,2,4);plot(qdata4(1,:)),axis([0 250 -1.7 1.7]),title('抽取后Q路信号的波形');grid on; %判决 idata5=zeros(1,len); qdata5=zeros(1,len); threshold = 0; for jj = 1:len if idata4(jj)>=threshold idata5(jj) = 1; else idata5(jj) = 0; end if qdata4(jj)>=threshold qdata5(jj) = 1; else qdata5(jj) = 0; end end figure(9); subplot(2,1,1);stairs(idata5),axis([0 250 -1.2 1.2]),title('判决后I路信号的波形');grid on; subplot(2,1,2);stairs(qdata5),axis([0 250 -1.2 1.2]),title('判决后Q路信号的波形');grid on; %% 将判决之后的数据存放进数组 s4=zeros(1,len); s4(1:2:len) = idata5(1:2:len); s4(2:2:len) = qdata5(1:2:len); figure(10); subplot(2,1,1);stairs(data0(1:len)),axis([0 250 -0.2 1.2]),title('基带信号');grid on; subplot(2,1,2);stairs(s4(1,:)),axis([0 250 -0.2 1.2]),title('判决后波形');grid on; %% 眼图和星座图 figure(11); plot(I, Q,'r+');xlabel('I路');ylabel('Q路');title('QPSK星座图');hold on; plot(idata4(1,:), qdata4(1,:),'*');grid on;axis([-2 2 -2 2]); legend('发射端的值','实际接收端的值'); A=zeros(1,zero_interval*len);A=Ipulse(1,num/2:zero_interval*len+num/2)+j*Qpulse(1,num/2:zero_interval*len+num/2);eyediagram(A,20); B=zeros(1,zero_interval*len);B=idata3(1,num:zero_interval*len+num)+j*qdata3(1,num:zero_interval*len+num);eyediagram(B,20); % eyediagram(Ipulse,200);title('成型滤波后I路眼图');grid on; % eyediagram(Qpulse,200);title('成型滤波后Q路眼图');grid on; % eyediagram(idata3(1,:),200);title('匹配滤波后I路眼图');grid on; % eyediagram(qdata3(1,:),200);title('匹配滤波后Q路眼图');grid on; % eyediagram(idata5(1,:),5);title('判决后I路眼图');grid on; % eyediagram(qdata5(1,:),5);title('判决后Q路眼图');grid on; %% 累计误码数 % abs(s4-data0)求接收端和发射端 % 数据差的绝对值，累计之后就是误码个数 Awgn_num_BER=sum(abs(s4(1,:)-data0(1:len)'))/len