(完整word版)QPSK調(diào)制與解調(diào)在MATLAB平臺(tái)上的實(shí)現(xiàn)

1、QPSK 調(diào)制與解調(diào)在 MATLAB 平臺(tái)上的實(shí)現(xiàn)QPSK 即四進(jìn)制移向鍵控(Quaternary Phase Shift Keyi ng,它利用載波的四種不 同相位來(lái)表示數(shù)字信息，由于每一種載波相位代表兩個(gè)比特信息，因此每個(gè)四進(jìn)制碼元可以用兩個(gè)二進(jìn)制碼元的組合來(lái)表示。兩個(gè)二進(jìn)制碼元中的前一個(gè)碼元用a 表示，后一個(gè)碼元用 b 表示。QPSK 信號(hào)可以看作兩個(gè)載波正交 2PSK 信號(hào)的合成，下圖表示 QPSK 正交 調(diào)制器。sinr-X - b由 QPSK 信號(hào)的調(diào)制可知，對(duì)它的解調(diào)可以采用與 2PSK 信號(hào)類似的解調(diào)方 法進(jìn)行解調(diào)。解調(diào)原理圖如下所示，同相支路和正交支路分別采用相干解調(diào)方式解調(diào)

2、，得到l(t)和Q(t)，經(jīng)過(guò)抽樣判決和并/串交換器，將上下支路得到的并行 數(shù)據(jù)恢復(fù)成串行數(shù)據(jù)。%調(diào)相法clear all輸入串串/ /并并變換變換載波載波振蕩振蕩輸入帯通帯通濾波器濾波器低通低通. .濾波器濾波器抽樣抽樣 A判決判決位定時(shí)位定時(shí)shi %廣、* X -低通低通一一抽樣抽樣輸出變換變換3b恢復(fù)恢復(fù)2close all t=-1:0.01:7-0.01;tt=le ngth(t);x1=o nes(1,800);for i=1:ttif (t(i)=-1 & t(i)=5& t(i)=0 & t1(i)=4 & t1(i)0 data_recove

3、r_a(i:i+19)=1; bit_recover=bit_recover 1;elsedata_recover_a(i:i+19)=-1; bit_recover=bit_recover -1;endenderror=0;dd = -2*bit_i n+1;ddd=dd;ddd1=repmat(ddd,20,1);for i=1:2e4ddd2(i)=ddd1(i);endfor i=1:1e3if bit_recover(i)=ddd(i) error=error+1;endendp=error/1000;figure(1) subplot(2,1,1);plot(t2,ddd2);ax

4、is(0 100 -2 2);title( 原序列); subplot(2,1,2);plot(t2,data_recover_a);axis(0 100 -2 2);title(效果圖:解調(diào)后序列);6原序列原序列解調(diào)后序列解調(diào)后序列%設(shè)定 T=1,不加噪聲clear all7close all %調(diào)制bit_in = randin t(1e3, 1, 0 1);bit=bit_i n(1:2:1e3);bit_Q = bit_i n(2:2:1e3);data_I = -2*bit_l+1;data_Q = -2*bit_Q+1;data_I1=repmat(data_I,20,1);da

5、ta_Q 仁 repmat(data_Q,20,1);for i=1:1e4data_I2(i)=data_I1(i);data_Q2(i)=data_Q1(i); en d;t=0:0.1:1e3-0.1;f=0:0.1:1;xrc=0.5+0.5*cos(pi*f);data_I2_rc=c on v(data_I2,xrc)/5.5;data_Q2_rc=co nv(data_Q2,xrc)/5.5;f1=1;t1=0:0.1:1e3+0.9;I_rc=data_I2_rc.*cos(2*pi*f1*t1);Q_rc=data_Q2_rc.*si n(2*pi*f1*t1);QPSK_r

6、c=(sqrt(1/2).*l_rc+sqrt(1/2).*Q_rc);%解調(diào)I_demo=QPSK_rc.*cos(2*pi*f1*t1);Q_demo=QPSK_rc.*si n(2*pi*f1*t1);I_recover=c on v(I_demo,xrc);Q_recover=c on v(Q_demo,xrc);I=I_recover(11:10010);Q=Q_recover(11:10010);t2=0:0.05:1e3-0.05;t3=0:0.1:1e3-0.1;dafalrecove衛(wèi)一八for耳20=0000dafalrecove衛(wèi)daQrlrecover-(s+19) Q

7、(z+19)rend 八dddH 2*brn+l八ddchHrepmasdd二03-forIi=e4ddd2(illddd二三endfiguressubpof(411)八p-ofsDaxisao2006一)八subpof(4L2)八pof(Q)oi.s(o2006一)八解調(diào)后奇位解調(diào)后奇位解調(diào)后偶位解調(diào)后偶位解調(diào)后序列解調(diào)后序列匣匣始序列始序列%QPSK1?SNRindBu02E9SNRi ndB2=0:0.1:10;for i=1:le ngth(SNRi ndB1)pb,ps=cm_sm32(SNR in dB1(i);smld_bit_err_prb(i)=pb;smld_symbol_

8、err_prb(i)=ps;en d;for i=1:le ngth(SNR in dB2)SNR=exp(SNRi ndB2(i)*log(10)/10);theo_err_prb(i)=Qfu nct(sqrt(2*SNR); en d;title(QPSK 誤碼率分析);semilogy(SNRi ndB1,smld_bit_err_prb,*);axis(0 10 10e-8 1);hold on;% semilogy(SNRi ndB1,smld_symbol_err_prb,o);semilogy(SNR in dB2,theo_err_prb);legend(仿真比特誤碼率,理論

9、比特誤碼率); hold off;fun ctio ny=Qfu nct(x) y=(1/2)*erfc(x/sqrt(2);fun ctio n pb,ps=cm_sm32(SNRi ndB) N=10000;E=1;SNR=10A(SNRi ndB/10);sgma=sqrt(E/SNR)/2;s00=1 0;sO 仁0 1;si 仁-1 0;s10=0 -1;for i=1:Ntemp=ra nd;if (temp0.25)dsource1(i)=0;dsource2(i)=0;elseif (temp0.5)dsource1(i)=0;dsource2(i)=1;elseif (tem

10、p0.75) dsource1(i)=1;dsource2(i)=0;10elsedsource1(i)=1;dsource2(i)=1;en d;en d;numo fsymbolerror=0;num ofbiterror=0;for i=1:Nn=sgma*ra ndn( size(sOO);if(dsource1(i)=0)&(dsource2(i)=0)r=sOO+n;elseif(dsource1(i)=0)&(dsource2(i)=1)r=s01+ n;elseif(dsource1(i)=1)&(dsource2(i)=0)r=s10+n;elser=

11、s11+ n;en d;cOO=dot(r,sOO);cO 仁 dot(r,s01);c10=dot(r,s10);c11=dot(r,s11);c_max=max(c00 c01 c10 c11);if (c00=c_max)decis 仁 0 ;decis2=0;elseif(c01=c_max)decis 仁 0 ;decis2=1;elseif(c10=c_max)decis 仁 1;decis2=0;elsedecis1=1;decis2=1;en d;symbolerror=0;if(decis1=dsource1(i)num ofbiterror= num ofbiterror+1;symbolerror=1;en d;if(decis2=dsource