基于MATLAB的数字调制

1、2ASK、2FSK、2PSK数字调制系统的Matlab实现及性能分析与比较引言：数字带通传输系统为了进行长距离传输，克服传输失真，传输损耗，同时保证带内特性。必须对数字信号进行载波调制，将信号频谱搬移到高频段才能在信道中传输，因而现代通信系统采取数字调制技术。通过数字基带信号对载波某些参量进行控制，使之随机带信号的变化而变化。根据控制载波参量大的不同，数字调制有调幅（ASK），调频(FSK)，调相(PSK) 三种基本形式。Matlab用于仿真，分析和修改，还可以应用图形界面功能GUI能为仿真系统生成一个人机交互界面，便于仿真系统的操作，因此采用matlab对数字系统进行仿真。通过对系统的仿真，

2、我们可以更加直观的了解数字调制系统的性能（）及影响性能的因素，从而便于改进系统，获得更佳的传输性能。 关键词： 数字 . 系统. 性能. ASK. FSK. PSK. Matlab. 仿真.一 .数字调制与解调原理1.1 2ASK（1）2ASK2ASK就是把频率、相位作为常量，而把振幅作为变量，信息比特是通过载波的幅度来传递的。由于调制信号只有0或1两个电平，相乘的结果相当于将载频或者关断，或者接通，它的实际意义是当调制的数字信号"1时，传输载波；当调制的数字信号为"0"时，不传输载波。公式为：1.2 2FSK2FSK可以看做是2个不同频率的2ASK的叠加，其调制

3、与解调方法与2ASK差不多，主要频率F1和F2，不同的组合产生所要求的2FSK调制信号。公式如下：1.3 2PSK2PSK以载波的相位变化为基准，载波的相位随数字基带序列信号的1或者0而改变，通常用已经调制完的载波的0或者表示数据1或者0，每种相位与之一一对应。二数字调制技术的仿真实现本课程设计需要借助MATLAB的M文件编程功能，对2ASK.2PSK.2FSK进行调制与解调的设计，并绘制出调制与解调后的波形，误码率的情况分析，软件仿真可在已有平台上实现。1.2ASK代码主函数close allclear alln=16;fc=1000000; bitRate=1000000;N=50;%no

4、ise=ti;noise=10;signal=source(n,N); %生成二进制代码transmittedSignal=askModu(signal,bitRate,fc,N);%调制后信号signal1=gussian(transmittedSignal,noise);%加噪声configueSignal=demoASK(signal1,bitRate,fc,n,N);source代码function sendSignal=source(n,N) sendSignal=randint(1,n) bit=; for i=1:length(sendSignal) if sendSignal(

5、i)=0 bit1=zeros(1,N); else bit1=ones(1,N); end bit=bit,bit1; end figure(1) plot(1:length(bit),bit),title('transmitting of binary'),grid on; axis(0,N*length(sendSignal),-2,2);endaskModu代码function transmittedSignal=askModu(signal,bitRate,fc,N)%signal为输入信号，bitrate为bit速率，fc调制信号频率，N %signal=0 0 1

6、 0 1 1 0 1;% bitRate=1000000;% fc=1000000;% N=32; t=linspace(0,1/bitRate,N); c=sin(2*pi*t*fc); transmittedSignal=; for i=1:length(signal) transmittedSignal=transmittedSignal,signal(i)*c; endfigure(2) %画调制图plot(1:length(transmittedSignal),transmittedSignal);title('Modulation of ASK');grid on;

7、figure(3)%画频谱实部m=0:length(transmittedSignal)-1;F=fft(transmittedSignal);plot(m,abs(real(F),title('ASK_frequency-domain analysis real');grid on;%figure(4) 画频谱虚部%plot(m,imag(F);title('ASK_frequency-domain analysis imag');%grid on;endCheckRatePe代码function PeWrong=CheckRatePe(signal1,sig

8、nal2,s)rights=0;wrongs=0;for ki=1:s-2 if(signal1(ki)=signal2(ki) rights=rights+1; else wrongs=wrongs+1; endendPeWrong=wrongs/(wrongs+rights);enddemoASK代码function bitstream=demoASK(receivedSignal,bitRate,fc,n,N) load num signal1=receivedSignal; signal2=abs(signal1); %ÕûÁ÷ signal3=

9、filter(num1,1,signal2); %LPF,°üÂç¼ì²¨ IN=fix(length(num1)/2); %ÑÓ³Ùʱ¼ä bitstream=; LL=fc/bitRate*N; i=IN+LL/2; while (i<=length(signal3) %Åоö bitstream=bitstream,signal3(i)>=0.5; i=i+LL; end f

10、igure(6) subplot(3,1,1); %接收波形 plot(1:length(signal1),signal1);title('Wave of receiving terminal(including noise)');grid on; subplot(3,1,2);%接收整流后波形 plot(1:length(signal2),signal2);title('Wave of commutate');grid on; subplot(3,1,3);%包络检波波形 plot(1:length(signal3),signal3);title('W

11、ave of LPF');grid on; bit=; for i=1:length(bitstream) if bitstream(i)=0 bit1=zeros(1,N); else bit1=ones(1,N); end bit=bit,bit1; end figure(7)%解调后的二进制波形 plot(bit),title('binary of receiving terminal'),grid on; axis(0,N*length(bitstream),-2.5,2.5);endgussian代码 %加高斯白噪声function signal=gussia

12、n(transmittedSignal,noise) signal=sqrt(2)*transmittedSignal; signal=awgn(signal,noise); figure(5) plot(1:length(signal),signal); title('Wave including noise'),grid on;end/ fsk主函数代码close allclear alln=16;%二进制代码长度f1=18000000;%频率1f2=6000000;%频率2bitRate=1000000;%bit速率N=50;%码元宽度%noise=ti;noise=10

13、;%家性噪声大小signal=source(n,N);%产生二进制代码transmittedSignal=fskModu(signal,bitRate,f1,f2,N);%调制signal1=gussian(transmittedSignal,noise);%加噪声configueSignal=demoFSK(signal1,bitRate,f1,f2,N);%解调source代码%二进制信号产生函数function sendSignal=source(n,N) sendSignal=randint(1,n) bit=; for i=1:length(sendSignal) if sendSi

14、gnal(i)=0 bit1=zeros(1,N); else bit1=ones(1,N); end bit=bit,bit1; end figure(1) plot(bit),title('transmitting of binary'),grid on; axis(0,N*length(sendSignal),-2.5,2.5);endfskModu代码%频率调制函数function transmittedSignal=fskModu(signal,bitRate,f1,f2,N) t=linspace(0,1/bitRate,N); c1=sin(2*pi*t*f1);

15、%调制信号1 c2=sin(2*pi*t*f2);%调制信号2 transmittedSignal=; for i=1:length(signal)%调制 if signal(i)=1 transmittedSignal=transmittedSignal,c1; else transmittedSignal=transmittedSignal,c2; end endfigure(2) %画调制后波形图 plot(1:length(transmittedSignal),transmittedSignal);title('Modulation of FSK');grid on;f

16、igure(3) %画调制后频谱图m=0:length(transmittedSignal)-1;F=fft(transmittedSignal);plot(m,abs(real(F),title('ASK_frequency-domain analysis real');grid on;enddemoFSK代码function bitstream=demoFSK(receivedSignal,bitRate,f1,f2,N) load num signal1=receivedSignal; signal2=filter(gaotong,1,signal1); %通过HPF，得

17、到高通分量 signal3=abs(signal2); %整流 signal3=filter(lowpass,1,signal3); %通过低通，形成包络 bitstream=; IN1=fix(length(lowpass)/2)+fix(length(gaotong)/2); %延迟时间 bitstream1=; LL=N; %每个bit的抽样点数 i=IN1 +LL/2; while (i<=length(signal3) %判决 bitstream1=bitstream1,signal3(i)>=0.5; i=i+LL; end bitstream1 figure(5) s

18、ubplot(3,1,1); plot(1:length(signal1),signal1);title('Wave of receiving terminal(including noise)');grid on; subplot(3,1,2); plot(1:length(signal2),signal2);title('After Passing HPF');grid on; subplot(3,1,3); plot(1:length(signal3),signal3);title('After Passing LPF');grid on;

19、 signal4=filter(daitong,1,signal1); %通过BPF得到低频分量 signal5=abs(signal4); %整流 signal5=filter(lowpass,1,signal5); %通过LPF，形成包络 IN2=fix(length(lowpass)/2)+fix(length(daitong)/2); %延迟时间 bitstream2=; LL=N; %每个bit的的抽样点数 i=IN2 +LL/2; while (i<=length(signal5) %判决 bitstream2=bitstream2,signal5(i)>=0.5; i

20、=i+LL; end bitstream2 figure(6) subplot(3,1,1); plot(1:length(signal1),signal1);title('Wave of receiving terminal(including noise)');grid on; subplot(3,1,2); plot(1:length(signal4),signal4);title('After Passing BPF');grid on; subplot(3,1,3); plot(1:length(signal5),signal5);title('

21、;After Passing LPF');grid on; for i=1:min(length(bitstream1),length(bitstream2) %判决 if(bitstream1(i)>bitstream2(i) bitstream(i)=1; else bitstream(i)=0; end end bitstream bit=; %接收端波形 for i=1:length(bitstream) if bitstream(i)=0 bit1=zeros(1,N); else bit1=ones(1,N); end bit=bit,bit1; end figure

22、(7) plot(bit),title('binary of receiving terminal'),grid on; axis(0,N*length(bitstream),-2.5,2.5); end CheckRatePe代码function PeWrong=CheckRatePe(signal1,signal2,s)rights=0;wrongs=0;for ki=1:s-2 if(signal1(ki)=signal2(ki) rights=rights+1; else wrongs=wrongs+1; endendPeWrong=wrongs/(wrongs+rig

23、hts);endgussian代码function signal=gussian(transmittedSignal,noise) signal=sqrt(2)*transmittedSignal; signal=awgn(signal,noise); figure(4) plot(1:length(signal),signal),title('Adding Noise'); grid on;end2psk主函数代码close allclear alln=16;%二进制码长fc=1000000;%载波频率bitRate=1000000;%信息频率N=50;%码宽noise=10

24、;%信道加性噪声大小signal=source(n,N);%生成二进制代码transmittedSignal=bpskModu(signal,bitRate,fc,N);%对信号进行调制并进行频%谱分析signal1=gussian(transmittedSignal,noise)%加信道噪声configueSignal=demoBPSK(signal1,bitRate,fc,n,N);%信号解调source代码function sendSignal=source(n,N) sendSignal=randint(1,n) bit=; for i=1:length(sendSignal) if

25、sendSignal(i)=0 bit1=zeros(1,N); else bit1=ones(1,N); end bit=bit,bit1; end figure(1) plot(bit),title('transmitting of binary'),grid on; axis(0,N*length(sendSignal),-2.5,2.5);endbpskModu代码function transmittedSignal=bpskModu(signal,bitRate,fc,N) t=linspace(0,1/bitRate,N); c1=sin(2*pi*t*fc); c

26、2=sin(2*pi*t*fc + pi); transmittedSignal=; for i=1:length(signal) if signal(i)=1 transmittedSignal=transmittedSignal,c1; else transmittedSignal=transmittedSignal,c2; end endfigure(2) % 画调制图plot(1:length(transmittedSignal),transmittedSignal);title('Modulation of BPSK');grid on;figure(3)%画频谱图m

27、=0:length(transmittedSignal)-1;F=fft(transmittedSignal);plot(m,abs(real(F),title('BPSK_frequency-domain analysis real');grid on;endCheckRatePe代码function PeWrong=CheckRatePe(signal1,signal2,s)rights=0;wrongs=0;for ki=1:s-2 if(signal1(ki)=signal2(ki) rights=rights+1; else wrongs=wrongs+1; ende

28、ndPeWrong=wrongs/(wrongs+rights);enddemoBPSK代码function bitstream=demoBPSK(receivedSignal,bitRate,fc,n,N) load num %读取num存储的低通滤波用的数据 signal1=receivedSignal; t=linspace(0,1/bitRate,N); c=sin(2*pi*t*fc); signal=; for i=1:n signal=signal,c; end signal2=signal1.*signal; %乘同频同相sin signal3=filter(num1,1,si

29、gnal2); %LPF,包络检波3 IN=fix(length(num1)/2); %Ñ延迟时间 bitstream=; LL=fc/bitRate*N; i=IN+LL/2; while (i<=length(signal3) %判决 bitstream=bitstream,signal3(i)>=0; i=i+LL; end figure(5) subplot(3,1,1);%画接收的包含噪声的波形 plot(1:length(signal1),signal1);title('Wave of receiving terminal(including nois

30、e)');grid on; subplot(3,1,2);%相干解调波形 plot(1:length(signal2),signal2);title('After Multipling sin Fuction');grid on; subplot(3,1,3);%包络检波波形 plot(1:length(signal3),signal3);title('Wave of LPF');grid on; bit=; for i=1:length(bitstream) if bitstream(i)=0 bit1=zeros(1,N); else bit1=on

31、es(1,N); end bit=bit,bit1; end figure(6)二进制接收信号波形 plot(bit);title('binary of receiving terminal');grid on; axis(0,N*length(bitstream),-2.5,2.5);endgussian代码function signal=gussian(transmittedSignal,noise) signal=sqrt(2)*transmittedSignal; signal=awgn(signal,noise); figure(4) plot(1:length(si

32、gnal),signal),grid on; title('Adding noise')end三种调制方式的性能比较:load PeRate;load PeRatep;%补偿误差fpeask(15)=1e-3;fpefsk(9)=1e-3;fpepsk(24)=0.002;fpepsk(26)=1e-3;figure(1)semilogy(-6:length(fpeask)-7,fpeask,-6:length(fpefsk)-7,fpefsk,-30:length(fpepsk)-31,fpepsk),grid on;title('Analysis Of Bit Er

33、ror Rate');legend('ASK','FSK','PSK');xlabel('r/dB');ylabel('Pe'); figure(2)semilogy(-6:length(fpefsk)-7,fpeask);grid on;title('Bit Error Rate Of ASK');xlabel('r/dB');ylabel('PeASK');figure(3)semilogy(-6:length(fpefsk)-7,fpefsk);grid on;title('Bit Error Rate Of FSK');xlabel('r/dB');ylabel('PeFSK');figure(4)semilogy(-16:length(fpepsk)-17,fpepsk);grid on;title('Bit Error