BPSK系統(tǒng)仿真—MATLAB

1、程序代碼：主程序：%基帶信號(hào)s(t)clearallcloseallclcnum=10;%碼元個(gè)數(shù)tnum=200;%碼元長(zhǎng)度N=num*tnum;a=randint(1,num,2);%產(chǎn)生1行num列的矩陣，矩陣內(nèi)0和1隨機(jī)出現(xiàn)fc=0.1;%載波頻率t=0:0.05:9.99;s=;c=;fori=1:numif(a(i)=0)A=zeros(1,tnum);elseA=ones(1,tnum);ends=sA;cs=sin(2*pi*fc*t);c=ccs;%產(chǎn)生載波信號(hào)endfigure(1);subplot(4,1,1);plot(s);gridon;xlabel(基帶信號(hào)s(t)

2、;axis(0N-22);%BPSK已調(diào)信號(hào)。采用模擬調(diào)制方法s_NRZ=;fori=1:numif(a(i)=0)A=ones(1,tnum);elseA=-1*ones(1,tnum);ends_NRZ=s_NRZ,A;ende=s_NRZ.*c;figure(1);subplot(4,1,2);plot(e);gridon;xlabel(BPSK調(diào)制信號(hào));axis(0N-22);%加高斯噪聲am=0.7;%輸入信號(hào)經(jīng)信道后振幅由1衰減為0.7SNR=5;snr=10人(SNR/10);N0=(am*am)/2/snr;%計(jì)算噪聲功率N0_db=10*log10(N0);%將噪聲功率轉(zhuǎn)換

3、為dBWni=wgn(1,N,N0_db);%產(chǎn)生1行N列的高斯噪聲yi=e+ni;%BSK已調(diào)信號(hào)中加入白噪聲，輸入信噪比為SNRfigure(1);subplot(4,1,3);plot(yi);gridon;xlabel(加入高斯白噪聲的已調(diào)信號(hào)yi(t);%帶通濾波器b1,a1=BUTTER(3,2*pi*0.0001,2*pi*0.01);%計(jì)算帶通濾波器的H(z)系數(shù)y=filter(b1,a1,yi);%對(duì)信號(hào)yi進(jìn)行濾波，得到信號(hào)yfigure(1);subplot(4,1,4);plot(y);gridon;xlabel(經(jīng)帶通濾波器后信號(hào))；%與恢復(fù)載波相乘x1=2*c.*

4、y;figure(2);subplot(4,1,1);plot(x1);gridonxlabel(與恢復(fù)載波相乘后的信號(hào)x1(t);%低通濾波器b2,a2=butter(2,0.005);%計(jì)算H系數(shù)，頻率為(1/200)x=filter(b2,a2,x1);%對(duì)信號(hào)x1濾波，得到信號(hào)xfigure(2);subplot(4,1,2);plot(x);gridonaxis(0N-22);xlabel(經(jīng)低通濾波器后信號(hào)波形)x=fun_panjue(x);%調(diào)用函數(shù)，進(jìn)行抽樣判決figure(2);subplot(4,1,3);plot(x);gridon;xlabel(加噪后解調(diào)信號(hào)x(t)

5、;axis(0N-22);x=fun_yanc(x);%調(diào)用函數(shù)，進(jìn)行消除延遲figure(2);subplot(4,1,4);plot(x);gridon;xlabel(加噪后去掉延遲的解調(diào)信號(hào)x(t);axis(0N-22);%誤碼率計(jì)算Err1=length(find(x=s)%計(jì)算解調(diào)信號(hào)中錯(cuò)誤碼元個(gè)數(shù)Pe_test1=Err1/N%計(jì)算實(shí)際誤碼率Pe1=(1/2)*erfc(sqrt(snr)%計(jì)算系統(tǒng)理論誤碼率%理論誤碼率曲線Pe=;forSNR=1:10am=0.7;%輸入信號(hào)經(jīng)信道后振幅由1衰減為0.7E=am*am/2;snr=10人(SNR/10);N0=(am*am)/(

6、2*snr);no=N0/(2*200);%計(jì)算噪聲功率N0_db=10*log10(N0);%將噪聲功率轉(zhuǎn)換為dBWni=wgn(1,N,N0_db);%產(chǎn)生1行N列的高斯噪聲yi=e+ni;%BSK已調(diào)信號(hào)中加入白噪聲，輸入信噪比為SNRy=filter(b1,a1,yi);%對(duì)yi進(jìn)行濾波(帶通濾波器)，得到信號(hào)yx1=2*c.*y;%與恢復(fù)載波相乘xx=filter(b2,a2,x1);%經(jīng)低通濾波器濾波xx=fun_panjue(xx);%抽樣判決xx=fun_yanc(xx);%消除延遲snr=10A(SNR/10);Pe=Pe,(1/2)*erfc(sqrt(snr);%計(jì)算理論

7、誤碼率endPe;figure;SNR=1:10;semilogy(SNR,Pe,b-);holdon%以log10(Pe)為縱坐標(biāo)畫(huà)圖gridon子程序一：抽樣判決(由于存在“倒pi”現(xiàn)象，故以0為基準(zhǔn)進(jìn)行判決，大于0,判為0;小于0,判為1)functionw=fun_panjue(w)N=length(w);ifw(100)0w(1:100)=0;elsew(1:100)=1;endfori=101:Nifw(i)0;w(i)=0;elsew(i)=1;endend子函數(shù)二：消除延遲(由于抽樣判決后會(huì)產(chǎn)生延遲，故認(rèn)為對(duì)解調(diào)信號(hào)進(jìn)行時(shí)移，以減小甚至消除延遲，便于與基帶信號(hào)進(jìn)行比較，計(jì)算實(shí)際

8、誤碼率)functionm=fun_yanc(m)N=length(m);leng=0;ifm(1)=0fori=1:Nifm(i)=1leng=i;break;endendelsefori=1:Nifm(i)=0leng=i;break;endendendleng1=leng-(floor(leng/200)*200;fori=1:(N-leng1)m(i)=m(i+leng1);endfori=(N-leng1):Nm(i)=m(N-200+10);end運(yùn)行結(jié)果：輸入信噪比為5dB時(shí)，計(jì)算的錯(cuò)誤碼元，實(shí)際誤碼率，理論誤碼率Err1=15Pe_test1=0.0075Pe1=0.0060各波形圖如下所示FileEditViewInsertToolsDesktopWindow旦即口Qa|fl|B|s5廠|ii|it0_giiiiiiiiiTOC o 1-5 h z0200400600800100012001400160018002000與恢復(fù)載減相乘后的信號(hào)id(t)_2iiiiiiiii0200400600800100012001400150018002000經(jīng)低通濾波器后信號(hào)波形_2iiiiiiii