數(shù)字通信作業(yè)(2)

1、作業(yè)2.1.1 匹配濾波器的性能(方波脈沖信號)源代碼：% 程序功能：畫出誤比特曲線clear all;close all;clcN = 1000;SNRindB = 0:6;% 理論曲線echo on;for i=1:length(SNRindB), SNR=exp(SNRindB(i)*log(10)/10); theo_err_awgn(i)=0.5*erfc(sqrt(SNR); echo off;end % 高斯信道 echo on;for i=1:length(SNRindB) smld_bit_awgn_err(i)=(y(N,i)/N; echo off;end;figure(

2、5)semilogy(SNRindB,theo_err_awgn,'r'),title('誤碼率曲線');hold on;semilogy(SNRindB,smld_bit_awgn_err,'r*');hold on;xlabel('Eb/No');ylabel('BER');legend('理論AWGN','仿真AWGN');% 程序功能：產(chǎn)生基帶信號、發(fā)送機、接收機function Awgn_num = y(N,SNR) %N = 100;M = 4;Tb = 1;Ts = 2

3、*Tb;m = log2(M);dt = Tb/32;fs = 1/dt;t = 0:dt:N-dt;fc = 1; %基帶信號的產(chǎn)生data = sign(randn(1,N);nrz = zeros(1,length(data)/dt);for i = 1:N if(data(i)=1) nrz(i-1)/dt+1:i/dt) = 1; else nrz(i-1)/dt+1:i/dt) = -1; endend %串并變換idata = data(1:m:(N-1);qdata = data(2:m:N);j = 1;for i = 1:N/2 inrz(j-1)/dt+1:(j+1)/d

4、t) = idata(i); qnrz(j-1)/dt+1:(j+1)/dt) = qdata(i); j = j+2;end %QPSK調(diào)制si = zeros(1,N/dt);sq = zeros(1,N/dt);s = zeros(1,N/dt);j = 1;for i = 1:N/2 si(j-1)/dt+1:(j+1)/dt) = idata(i)*cos(2*pi*fc*(j-1)/dt+1:(j+1)/dt)*dt); sq(j-1)/dt+1:(j+1)/dt) = qdata(i)*sin(2*pi*fc*(j-1)/dt+1:(j+1)/dt)*dt); s(j-1)/dt

5、+1:(j+1)/dt) = si(j-1)/dt+1:(j+1)/dt) + sq(j-1)/dt+1:(j+1)/dt); j = j+2;end %高斯信道s_w = channelAWGN(s,SNR); %解調(diào)部分idata_1 = s_w.*cos(2*pi*fc*t(1:length(t);qdata_1 = s_w.*sin(2*pi*fc*t(1:length(t); %匹配濾波imatch_filter = zeros(N/2);qmatch_filter = zeros(N/2);j = 1;for i = 1:N/2 imatch_filter(i) = sum(ida

6、ta_1(j-1)/dt+1:(j+1)/dt); qmatch_filter(i) = sum(qdata_1(j-1)/dt+1:(j+1)/dt); j = j+2;endimatch_filter = imatch_filter/max(abs(imatch_filter);qmatch_filter = qmatch_filter/max(abs(qmatch_filter); %抽樣判決idata_3 = zeros(1,N/2);qdata_3 = zeros(1,N/2);for i = 1:N/2 if(imatch_filter(i)>0) idata_3(i) =

7、1; else idata_3(i) = -1; end if(qmatch_filter(i)>0) qdata_3(i) = 1; else qdata_3(i) = -1; endendj = 1;for i = 1:N/2 idata_3_1(j-1)/dt+1:(j+1)/dt) = idata_3(i); qdata_3_1(j-1)/dt+1:(j+1)/dt) = qdata_3(i); j = j+2;end %并串轉(zhuǎn)換demodata = zeros(1,N);for i = 1:N if(mod(i,2)=1) data_3(i-1)/dt+1:i/dt) = id

8、ata_3_1(i/dt); demodata(i) = idata_3_1(i/dt); else data_3(i-1)/dt+1:i/dt) = qdata_3_1(i/dt); demodata(i) = qdata_3_1(i/dt); endend %累計誤碼個數(shù)Awgn_num = 0;for i = 1:N if(demodata(i)=data(i) Awgn_num = Awgn_num+1; endend %Drawfigure(1)subplot(311)plot(t,nrz(1,:);axis(0 N -1.5 1.5);title('基帶信號');s

9、ubplot(312)plot(t,inrz(1,:);axis(0 N -1.5 1.5);title('I支路信號');subplot(313)plot(t,qnrz(1,:);axis(0 N -1.5 1.5);title('Q支路信號'); figure(2)subplot(311)plot(t,s(1,:);axis(0 N -1.5 1.5);title('QPSK已調(diào)信號');subplot(312)plot(t,si(1,:);axis(0 N -1.5 1.5);title('I路載波調(diào)制后的信號');subp

10、lot(313)plot(t,sq(1,:);title('Q路載波調(diào)制后的信號');axis(0 N -1.5 1.5); figure(3)subplot(211)plot(t,s(1,:);axis(0 N -1.5 1.5);title('QPSK已調(diào)信號');subplot(212)plot(t,s_w(1,:);title('經(jīng)過高斯信道后的信號'); figure(4)subplot(211)plot(t,nrz(1,:);axis(0 N -1.5 1.5);title('原始發(fā)送信號');subplot(212)

11、plot(t,data_3(1,:);axis(0 N -1.5 1.5);title('解調(diào)后的信號');% 程序功能：加入高斯白噪聲function signal_awgn=channelAWGN(signal,snr)snr_lin =10(snr/10);%計算信號功率和噪聲功率signal_power=sum(signal.2)/length(signal);noise_power=signal_power/snr_lin;noise_std=sqrt(noise_power);noise=noise_std*randn(1,length(signal);signal

12、_awgn=signal+noise; 仿真波形：當(dāng)N=10，SNR = 0時，調(diào)制解調(diào)波形作業(yè)2.1.2 接收端使用巴特沃斯低通濾波器的性能源代碼與2.1.1不同的地方：%巴特沃斯低通濾波n,Wn = buttord(0.001,1/8,2,20);b,a = butter(n,Wn);ilow_filter = filter(b,a,idata_1);qlow_filter = filter(b,a,qdata_1);實驗結(jié)果：結(jié)論：綜合兩種實驗結(jié)果得出，匹配濾波器可以得到最佳性能。2.1.3匹配濾波器的性能(三角脈沖信號)源代碼與2.1.1不同的地方：%基帶信號的產(chǎn)生data = sig

13、n(randn(1,N);nrz = zeros(1,length(data)/dt);for i = 1:N if(data(i)=1) nrz(i-1)/dt+1:(i-0.5)/dt)= 2*dt*(i-1)/dt+1:(i-0.5)/dt)-2*(i-1); nrz(i-0.5)/dt+1:i/dt) = -2*dt*(i-0.5)/dt+1:i/dt)+2*i; else nrz(i-1)/dt+1:(i-0.5)/dt) = -2*dt*(i-1)/dt+1:(i-0.5)/dt)+2*(i-1); nrz(i-0.5)/dt+1:i/dt) = 2*dt*(i-0.5)/dt+1

14、:i/dt)-2*i; endend %串并變換idata = data(1:m:(N-1);qdata = data(2:m:N);j = 1;for i = 1:N/2 if(idata(i)=1) inrz(j-1)/dt+1:j/dt) = dt*(j-1)/dt+1:j/dt)-(j-1); inrz(j/dt+1:(j+1)/dt) = -dt*(j/dt+1:(j+1)/dt)+j+1; else inrz(j-1)/dt+1:j/dt) = -dt*(j-1)/dt+1:j/dt)+(j-1); inrz(j/dt+1:(j+1)/dt) = dt*(j/dt+1:(j+1)/

15、dt)-j-1; end if(qdata(i)=1) qnrz(j-1)/dt+1:j/dt) = dt*(j-1)/dt+1:j/dt)-(j-1); qnrz(j/dt+1:(j+1)/dt) = -dt*(j/dt+1:(j+1)/dt)+j+1; else qnrz(j-1)/dt+1:j/dt) = -dt*(j-1)/dt+1:j/dt)+(j-1); qnrz(j/dt+1:(j+1)/dt) = dt*(j/dt+1:(j+1)/dt)-j-1; end j = j+2;end當(dāng)N=10，SNR = 0時，調(diào)制解調(diào)波形結(jié)論：由仿真結(jié)果得出，脈沖信號波形對匹配濾波器的性能是沒有

16、影響的。作業(yè)2.2源代碼：clear allclose allclc%Fc=10; %載頻Fs=40; %系統(tǒng)采樣頻率Fd=1; %碼速率N=Fs/Fd;df=10;numSymb=25;%進行仿真的信息代碼個數(shù)M=4; %進制數(shù)SNRpBit=60;%信噪比SNR=SNRpBit/log2(M);seed=12345 54321;numPlot=15;%產(chǎn)生25個二進制隨機碼x=randsrc(numSymb,1,0:M-1);%產(chǎn)生25個二進制隨機碼figure(1)stem(0:numPlot-1,x(1:numPlot),'bx');title('二進制隨機序列

17、')xlabel('Time');ylabel('Amplitude');%調(diào)制y=dmod(x,Fc,Fd,Fs,'fsk',M,df);numModPlot=numPlot*Fs;t=0:numModPlot-1./Fs;figure(2)plot(t,y(1:length(t),'b-');axis(min(t) max(t) -1.5 1.5);title('調(diào)制后的信號')%在已調(diào)信號中加入高斯白噪聲randn('state',seed(2);y=awgn(y,SNR-10*log

18、10(0.5)-10*log10(N),'measured','dB');%在已調(diào)信號中加入高斯白噪聲figure(3)plot(t,y(1:length(t),'b-');%畫出經(jīng)過信道的實際信號axis(min(t) max(t) -1.5 1.5);title('加入高斯白噪聲后的已調(diào)信號')%相干解調(diào)figure(4)z1=ddemod(y,Fc,Fd,Fs,'fsk/eye',M,df);title('相干解調(diào)后的信號的眼圖')%帶輸出波形的相干M元頻移鍵控解調(diào)figure(5)stem(0:numPlot-1,x(1:numPlot),'bx');hold on;stem(0:numPlot-1,z1(1:numPlot),'ro');hold off;axis(0 numPlot -0.5 2);title(