四分之piQPSK解调部分滤波

1、% pi/4-QPSK系统仿真clear;% -初始化数据-T=1; % 码元周期fc=1/T; % 载波频率ml=2; % 调制阶数 nb=100; % 传输比特数samp_T=T/100; % 抽样间隔fs=1/samp_T; % 抽样频率SNR=8; % 信噪比t=0:samp_T:nb*T-samp_T;N=length(t); % 码元个数 % -产生随机信号-data=randint(1,nb,0 1); datanrz=data.*2-1; % 转换成双极性非归零码data1=zeros(1,nb/samp_T); for q=1:nb data1(q-1)/samp_T/2+1

2、:q/samp_T/2)=datanrz(q);end % 传输信号 % -pi/4-QPSK调制-idata=datanrz(1:ml: (nb-1); % 串/并转换qdata=datanrz(2:ml:nb);idata1=zeros(1,nb/2/samp_T);qdata1=zeros(1,nb/2/samp_T);for q=1:nb/2 idata1(q-1)/samp_T+1:q/samp_T)=idata(q); qdata1(q-1)/samp_T+1:q/samp_T)=qdata(q);endidata2(1)=-1;qdata2(1)=0;for i=1:nb/2 %

3、 映射逻辑 if (idata(i)=0) & (qdata(i)=0) angl=-3*pi/4; elseif (idata(i)=0) & (qdata(i)=1) angl=3*pi/4; elseif (idata(i)=1) & (qdata(i)=0) angl=-pi/4; else angl=pi/4; endidata2(i+1)=idata2(i)*cos(angl)-qdata2(i)*sin(angl);qdata2(i+1)=idata2(i)*sin(angl)+qdata2(i)*cos(angl);endich=zeros(1,nb/2

4、/samp_T);for i=1:nb/2 ich(i-1)/samp_T+1:i/samp_T)=idata2(i);endfor ii=1:N/2 a(ii)=cos(2*pi*fc*t(ii);endidata3=ich.*a; % I支路调制qch=zeros(1,nb/2/samp_T);for j=1:nb/2 qch(j-1)/samp_T+1:j/samp_T)=qdata2(j);endfor jj=1:N/2 b(jj)=sin(2*pi*fc*t(jj);endqdata3=qch.*b; % Q支路调制s=idata3+qdata3; % pi/4-QPSK已调信号%-

5、pi/4-QPSK解调-ich1=s.*a; % 相乘载波qch1=s.*b;b=fir1(300,0.5); % 低通滤波ich2=filter(b,1,ich1);qch2=filter(b,1,qch1);for i=1:nb/2/samp_T-1 % 基带差分变换ich3(i+1)=ich2(i+1)*ich2(i)+qch2(i+1)*qch2(i);qch3(i+1)=qch2(i+1)*ich2(i)-ich2(i+1)*qch2(i);ich3(i)=ich3(i+1);qch3(i)=qch3(i+1);endich4=zeros(1,nb/2);qch4=zeros(1,n

6、b/2);for n=1:nb/2 % 判决输出 ichsum(n)=sum(ich3(n-1)/samp_T+1:n/samp_T)*samp_T; if ichsum(n)>=0 ich4(n)=1; else ich4(n)=0; end qchsum(n)=sum(qch3(n-1)/samp_T+1:n/samp_T)*samp_T; if qchsum(n)>=0 qch4(n)=1; else qch4(n)=0; endendich4=ich4.*2-1;qch4=qch4.*2-1;idata4=zeros(1,nb/samp_T/2); qdata4=zeros

7、(1,nb/samp_T/2);for q=1:nb/2 idata4(q-1)/samp_T+1:q/samp_T)=ich4(q); qdata4(q-1)/samp_T+1:q/samp_T)=qch4(q);end demodata=zeros(1,nb); % 并/串转换demodata(1:ml: (nb-1)=ich4;demodata(2:ml:nb)=qch4;demodata1=zeros(1,nb/samp_T); for q=1:nb demodata1(q-1)/samp_T/2+1:q/samp_T/2)=demodata(q);end画图部分figure(1)su

8、bplot(311);plot(data1);axis(0 1e3 -2 2);title('基带信号');grid onsubplot(312);plot(idata1);axis(0 1e3 -2 2);title('I支路信号');grid onsubplot(313);plot(qdata1);axis(0 1e3 -2 2);title('Q支路信号');grid onfigure(2)subplot(211);plot(ich);axis(0 3e3 -2 2);title('I支路映射后信号');grid onsub

9、plot(212);plot(qch);axis(0 3e3 -2 2);title('Q支路映射后信号');grid onfigure(3)subplot(311);plot(idata3);axis(0 3e3 -2 2);title('I支路载波调制后信号');grid onsubplot(312);plot(qdata3);axis(0 3e3 -2 2);title('Q支路载波调制后信号');grid onsubplot(313);plot(s);axis(0 3e3 -2 2);title('pi/4-QPSK已调信号');grid onfigure(4)subplot(211);plot(ich1);axis(0 3e3 -2 2);title('相乘载波后I支路信号');grid onsubplot(212);plot(qch1);axis(0 3e3 -2 2);title('相乘载波后Q支路信号');grid onfigure(5)s