QPSK的matlab仿真.rar

%QPSK调制解调仿真 %Author：张宗卫 %date：2018.3.10 clc clear all fc=30; fs=1000; % fcu=200; t=1/fs:1/fs:0.8; L=length(t); %四元符号产生 code4=zeros(1,L); for i=1:L/8 code4(i)=0; end for i=L/8+1:L/8*2 code4(i)=3; end for i=L/8*2+1:L/8*3 code4(i)=1; end for i=L/8*3+1:L/8*4 code4(i)=2; end for i=L/8*4+1:L/8*5 code4(i)=1; end for i=L/8*5+1:L/8*6 code4(i)=0; end for i=L/8*6+1:L/8*7 code4(i)=2; end for i=L/8*7+1:L code4(i)=3; end figure(1) plot(t,code4) title('4进制码元') %串并转换 比特对 bIn=zeros(1,L); bQn=zeros(1,L); for i=1:L switch code4(i) case 0 bIn(i)=0; bQn(i)=0; case 1 bIn(i)=0; bQn(i)=1; case 2 bIn(i)=1; bQn(i)=1; case 3 bIn(i)=1; bQn(i)=0; end end figure(2) subplot(211),plot(t,bIn),title('正交支路bIn') subplot(212),plot(t,bQn),title('同相支路bQn') %比特对双极性形成 aIn=zeros(1,L); aQn=zeros(1,L); for i=1:L if bIn(i)==0 aIn(i)=-1; else aIn(i)=1; end if bQn(i)==0 aQn(i)=-1; else aQn(i)=1; end end figure(3) subplot(211),plot(t,aIn),title('双极性正交支路aIn') subplot(212),plot(t,aQn),title('双极性同相支路aQn') %QPSK信号调制 ISC=cos(2*pi*fc*t); QSC=sin(2*pi*fc*t); QPSK=aIn.*ISC+aQn.*QSC; figure(4) subplot(311),plot(t,ISC),title('正交支路2PSK') subplot(312),plot(t,QSC),title('同相支路2PSK') subplot(313),plot(t,QPSK),title('QPSK信号') %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %QPSK解调 ILo=cos(2*pi*fc*t); QLo=sin(2*pi*fc*t); %step1 混频 RecQt=QPSK.*QLo; RecIt=QPSK.*ILo; figure(5) subplot(211) plot(t,RecQt),title('接收同相支路混频') subplot(212) plot(t,RecIt),title('接收正交支路混频') %step2 过LPF b=[0.00226675464588304,0.00136504505246622,0.00175878104612964,0.00221153432901494,0.00272748466037607,0.00330780022766749,0.00395363565442280,0.00466597851131189,0.00544450028376728,0.00628773584107796,0.00719347499703571,0.00815843398510817,0.00917825631157910,0.0102478237985242,0.0113612748511266,0.0125115706154483,0.0136904482156869,0.0148889062085348,0.0160976629650599,0.0173071380635749,0.0185071499666179,0.0196867585367558,0.0208345741081722,0.0219395410846265,0.0229913842469065,0.0239801230256774,0.0248953112618121,0.0257266964838253,0.0264657446472916,0.0271057988938512,0.0276400460627811,0.0280609918741315,0.0283640711472088,0.0285498939514168,0.0286089914329785,0.0285498939514168,0.0283640711472088,0.0280609918741315,0.0276400460627811,0.0271057988938512,0.0264657446472916,0.0257266964838253,0.0248953112618121,0.0239801230256774,0.0229913842469065,0.0219395410846265,0.0208345741081722,0.0196867585367558,0.0185071499666179,0.0173071380635749,0.0160976629650599,0.0148889062085348,0.0136904482156869,0.0125115706154483,0.0113612748511266,0.0102478237985242,0.00917825631157910,0.00815843398510817,0.00719347499703571,0.00628773584107796,0.00544450028376728,0.00466597851131189,0.00395363565442280,0.00330780022766749,0.00272748466037607,0.00221153432901494,0.00175878104612964,0.00136504505246622,0.00226675464588304]; a=1; RecQtPassLPF=filter(b,a,RecQt); RecItPassLPF=filter(b,a,RecIt); RecQtPassLPF=round(2*RecQtPassLPF); RecItPassLPF=round(2*RecItPassLPF); figure(6) subplot(211) plot(t,RecQtPassLPF);title('接收同相支路混频过LPF') subplot(212) plot(t,RecItPassLPF);title('正交同相支路混频过LPF') %step3 采样判决 RecbIn=zeros(1,L); RecbQn=zeros(1,L); for i=1:L if RecQtPassLPF(i) ==1 RecbQn(i)=1; else RecbQn(i)=0; end if RecItPassLPF(i) ==1 RecbIn(i)=1; else RecbIn(i)=0; end end %step4 串转并 RecCode4=zeros(1,L); for i=1:L if RecbIn(i)==0 && RecbQn(i)==0 RecCode4(i)=0; elseif RecbIn(i)==0 && RecbQn(i)==1 RecCode4(i)=1; elseif RecbIn(i)==1 && RecbQn(i)==1 RecCode4(i)=2; else RecCode4(i)=3; end end figure(7) subplot(211) plot(t,RecCode4);title('解调后的4元符号序列') subplot(212) plot(t,code4);title('调制前的4元符号序列')