基于MATLAB的数字调制

1、word文档整理分享2ASK2FSK2PSK数字调制系统的Matlab实现及性能分析与比较参考资料引言：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

2、数字系统进行仿真。通过对系 统的仿真，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.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。Acos ct,S2ASK(t)当ak当ak公式为： TJ*a 至摊器亠 怪通遽翌基

3、予 抽样判决 解话部汨抑E11.2 2FSK2FSK可以看做是2个不同频率的2ASK勺叠加，其调制与解调方法与 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。Acos 1t, 当k 1公式如下：S2FSK（t）Acos 2t，当ak 0word文档整理分享 1汗5心点过西辱泗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n表示数据1或者0,每种相位与之一 一对应。参考资料二.数字调制技术的仿真实现本课程设计需要借助 MATLAB勺M文件编程功能，对2ASK.2PSK.2FSK进行

4、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 all n=16;fc=1OOOOOO; bitRate=1OOOOOO;N=50; %no ise=ti;no ise=10;sig na匸source( n,N); %生成二进制代码tran smittedSig na匸askModu(sig nal,bitRate,fc,N);%调制后信号sig nal1=gussia n(tra nsmittedSig nal, no ise); %加噪声con figueSig nal=demoASK(s

5、ig nal1,bitRate,fc ,n, N);source代码fun cti onsen dSig na匸source( n,N)sen dSig na匸ra ndin t(1, n) bit=;for i=1:length(sendSignal) if sendSignal(i)=0 bit 1=zeros(1,N);elsebit1=o nes(1,N);endbit=bit,bit1; endfigureplot(1:le ngth(bit),bit),title(tra nsmitt ing of bin ary),grid on;axis(0,N*le ngth(se ndSi

6、g nal),-2,2);endaskModu 代码bitrate 为);gridfun cti on tra nsmittedSig nal=askModu(sig nal,bitRate,fc,N)%sig nal为输入信号，bit速率，fc调制信号频率，N%signal=0 0 1 0 1 1 0 1;% bitRate=1000000;% fc=1OOOOOO;% N=32;t=li nspace(0,1/bitRate,N);c=si n(2*pi*t*fc);tra nsmittedSig nal=;for i=1:length(signal)tra nsmittedSig nal

7、=tra nsmittedSig nal,sig nal(i)*c;endfigure(2) %画调制图plot(1:le ngth(tra nsmittedSig nal),tra nsmittedSig nal);title(Modulation of ASKon;figure (3)% 画频谱实部m=0:le ngth(tra nsmittedSig nal)-1;F=fft(tra nsmittedSig nal);plot(m,abs(real(F),title(ASK_freque ncy-domai n an alysis rea l);grid on;%figure(4) 画频

8、谱虚部%plot(m,imag(F);title(ASK_freque ncy-domai n an alysis imag);%grid on;endCheckRatePe 代码fun cti onPeWr on g=CheckRatePe(sig nal1,sig nal2,s)rights=0;wron gs=0;for ki=1:s-2if (signal1(ki)=signal2(ki)rights=rights+1;elsewron gs=wro ngs+1;endendPeWr on g=wr on gs/(wro ngs+rights);enddemoASK 弋码fun cti

9、 on bitstream=demoASK(receivedSig nal,bitRate,fc, n,N)load numsig nal1=receivedSig nal;sig nal2=abs(sig nal1);sig nal3=filter (n um1,1,sig nal2);IN=fix(le ngth( num1)/2);%?石+%LPF； u ?i 2 %?o 3ue ?bitstream=;LL=fc/bitRate*N;i=IN+LL/2;while (i=0.5;i=i+LL;%?D?endfigure(6)subplot(3,1,1); %接收波形plot(1:le

10、ngth(sig nal1),sig nal1);title(no ise);grid on;subplot(3,1,2);%接收整流后波形plot(1:le ngth(sig nal2),sig nal2);title( subplot(3,1,3);%包络检波波形plot(1:le ngth(sig nal3),sig nal3);title(Wave of receiv ing term in al( in clud ingWave of commutate);gridon;Wave of LPF );gridon;bit=;for i=1:length(bitstream) if bi

11、tstream(i)=0 bit 1=zeros(1,N);elsebit1=o nes(1,N);endbit=bit,bit1;endfigure (7)%解调后的二进制波形),grid on;plot(bit),title(bi nary of receiv ing termi nalaxis(0,N*le ngth(bitstream),-2.5,2.5);endgussian代码加高斯白噪声fun cti onsig nal=gussia n( tra nsmittedSig nal, no ise)sig nal=sqrt(2)*tra nsmittedSig nal;sig na

12、l=awg n( sig nal, no ise);figure(5)plot(1:le ngth(sig nal),sig nal);title( Wave in clud ing no ise),grid on;end/fsk主函数close allclear alln=16;%二进制代码长度f1=18000000;% 频率 1f2=6000000;% 频率 2bitRate=1OOOOOO;%bit 速率N=50;%码元宽度%no ise=ti;noise=10;%家性噪声大小sign al=source( n,N);%产生二进制代码tran smittedSig nal=fskModu

13、(sig nal,bitRate,f1,f2,N);%调制sig nal1=gussia n(tra nsmittedSig nal, no ise); %加噪声con figueSig nal=demoFSK(sig nal1,bitRate,f1,f2,N);%解调source代码二进制信号产生函数fun cti onsen dSig nal=source( n,N)sen dSig nal=ra ndin t(1, n) bit=;for i=1:length(sendSignal) if sendSignal(i)=0 bit 1=zeros(1,N);elsebit 1=on es(

14、1,N); end bit=bit,bit1;endfigure),grid on;plot(bit),title(tra nsmitt ing of binaryaxis(0,N*le ngth(se ndSig nal),-2.5,2.5);endfskModu代码频率调制函数fun cti ontra nsmittedSig nal=fskModu(sig nal,bitRate,f1,f2,N)t=li nspace(0,1/bitRate,N);c1=si n(2*pi*t*f1);%调制信号 1c2=sin(2*pi*t*f2);%调制信号 2tra nsmittedSig nal

15、=;for i=1:length(signal)% 调制if signal(i)=1tra nsmittedSig nal=tra nsmittedSig nal,c1;elsetra nsmittedSig nal=tra nsmittedSig nal,c2;endendfigure (2) %画调制后波形图);gridplot(1:le ngth(tra nsmittedSig nal),tra nsmittedSig nal);title(Modulation of FSKon;figure(3) %画调制后频谱图m=0:le ngth(tra nsmittedSig nal)-1;F

16、=fft(tra nsmittedSig nal);plot(m,abs(real(F),title(ASK_freque ncy-domai n an alysis rea l);grid on;enddemoFSI代 码fun cti on bitstream=demoFSK(receivedSig nal,bitRate,f1,f2,N)load numsig nal1=receivedSig nal;signal2=filter(gaotong,1,signail);%通过 HPF,得到高通分量sig nal3=abs(sig nal2);%整流sig nal3=filter(lowp

17、ass,1,sig nal3);%通过低通，形成包络bitstream=;涎迟时间IN1=fix(le ngth(lowpass)/2)+fix(le ngth(gaoto ng)/2);bitstream1=;LL=N;i=IN1 +LL/2;while (i=0.5; i=i+LL;endbitstream1figure(5)subplot(3,1,1);plot(1:le ngth(sig nal1),sig nal1);title(no ise) );grid on;subplot(3,1,2);plot(1:le ngth(sig nal2),sig nal2);title( sub

18、plot(3,1,3);plot(1:le ngth(sig nal3),sig nal3);title(%每个bit的抽样点数%判决Wave of receiv ing term in al( in clud ingAfter Passi ng HPF);gridon;After Passi ng LPF);gridon;sig nal4=filter(daito ng,1,sig nal1);sig nal5=abs(sig nal4);sig nal5=filter(lowpass,1,sig nal5);%通过BPF得到低频分量 流%通过LPF，形成包络IN2=fix(le ngth(

19、lowpass)/2)+fix(le ngth(daiton g)/2);涎迟时间bitstream2=;LL=N;i=IN2 +LL/2;while (i=0.5; i=i+LL;endbitstream2figure(6)subplot(3,1,1);plot(1:le ngth(sig nal1),sig nal1);title(no ise) );grid on;subplot(3,1,2);plot(1:le ngth(sig nal4),sig nal4);title( subplot(3,1,3);plot(1:le ngth(sig nal5),sig nal5);title(

20、%每个bit的的抽样点数%判决Wave of receiv ing term in al( in clud ingAfter Passi ng BPF);gridon;After Passi ng LPF);gridon;for i=1:min(length(bitstream1),length(bitstream2) if (bitstream1(i)bitstream2(i) bitstream(i)=1;elsebitstream(i)=0;endendbitstreambit=;%收端波形for i=1:length(bitstream)if bitstream(i)=0bit 1=z

21、eros(1,N);elsebit1=o nes(1,N);endbit=bit,bit1;endfigure(7)plot(bit),title(binary of receiv ing term inal),gridaxis(0,N*le ngth(bitstream),-2.5,2.5);end%判决on;CheckRatePe代码fun cti onPeWr on g=CheckRatePe(sig nal1,sig nal2,s)rights=0;wron gs=0;for ki=1:s-2if (signal1(ki)=signal2(ki)rights=rights+1;else

22、wron gs=wro ngs+1;endendPeWr on g=wr on gs/(wro ngs+rights);endgussian 代码fun cti onsig nal=gussia n( tra nsmittedSig nal, no ise)sig nal=sqrt(2)*tra nsmittedSig nal;sig nal=awg n( sig nal, no ise);figure(4)plot(1:le ngth(sig nal),sig nal),title(Addi ng Noise );grid on;end2psk主函数代码close allclear alln

23、=16;%二进制码长fc=1OOOOOO%载波频率bitRate=1OOOOOO;% 信息频率N=50;%码宽noise=10;%信道加性噪声大小sign al=source( n,N);%生成二进制代码tran smittedSig nal=bpskModu(sig nal,bitRate,fc,N);%对信号进行调制并进行频%谱分析sig nal1=gussia n(tra nsmittedSig nal, no ise)%力廿信道噪声con figueSig nal=demoBPSK(sig nal1,bitRate,fc, n,N);%信号解调source代码fun cti on se

24、n dSig nal=source( n,N)sen dSig nal=ra ndin t(1, n)bit=;for i=1:length(sendSignal)if sendSignal(i)=0bit 1=zeros(1,N);elsebit1=o nes(1,N);endbit=bit,bit1;endfigure(1)plot(bit),title(tra nsmitt ing of bin ary),grid on;axis(0,N*le ngth(se ndSig nal),-2.5,2.5);endbpskModu代 码fun cti ontra nsmittedSig nal

25、=bpskModu(sig nal,bitRate,fc,N)t=li nspace(0,1/bitRate,N);c1=si n( 2*pi*t*fc);c2=si n(2*pi*t*fc + pi);tra nsmittedSig nal=;for i=1:length(signal)if signal(i)=1tra nsmittedSig nal=tra nsmittedSig nal,c1;elsetra nsmittedSig nal=tra nsmittedSig nal,c2;endendfigure (2) %画调制图plot(1:length(transmittedSign

26、al),transmittedSignal);title(Modulation of BPSK);gridon;figure (3) % 画频谱图m=0:le ngth(tra nsmittedSig nal)-1;F=fft(tra nsmittedSig nal);plot(m,abs(real(F),title(BPSK_freque ncy-domai n an alysis rea l);grid on;endCheckRatePe代 码fun cti on PeWr on g=CheckRatePe(sig nal1,sig nal2,s)rights=0;wron gs=0;fo

27、r ki=1:s-2if (signal1(ki)=signal2(ki)rights=rights+1;elsewron gs=wro ngs+1;endendPeWr on g=wr on gs/(wro ngs+rights);enddemoBPSI代码fun cti on bitstream=demoBPSK(receivedSig nal,bitRate,fc, n,N) loadnum %卖取num存储的低通滤波用的数据sig nal1=receivedSig nal;t=li nspace(0,1/bitRate,N);c=si n(2*pi*t*fc);sig nal=;for

28、 i=1: nsig nal=sig nal,c;endsignal2=signal1.*signal;%乘同频同相 sinsignal3=filter(num1,1,signal2);%LPF，包络检波 3IN=fix(le ngth( num1)/2);%延迟时间bitstream=;LL=fc/bitRate*N;i=IN+LL/2;while (i=0;i=i+LL;endon;figure(5)subplot(3,1,1);%画接收的包含噪声的波形plot(1:le ngth(sig nal1),sig nal1);title(no ise);grid on;subplot(3,1,

29、2);%相干解调波形plot(1:le ngth(sig nal2),sig nal2);title(subplot(3,1,3);%包络检波波形plot(1:le ngth(sig nal3),sig nal3);title(Wave of receiv ing term in al( in clud ingAfter Multipli ng sin Fuctio n);gridWave of LPF );grid on;bit=;for i=1:length(bitstream)if bitstream(i)=0bit 1=zeros(1,N);elsebit1=o nes(1,N);en

30、dbit=bit,bit1;endfigure(6) 二进制接收信号波形);grid on;plot(bit);title(bi nary of receiv ing termi nalaxis(0,N*le ngth(bitstream),-2.5,2.5);endgussian 代码fun cti onsig nal=gussia n( tra nsmittedSig nal, no ise)sig nal=sqrt(2)*tra nsmittedSig nal;sig nal=awg n( sig nal, no ise);on;figure(4)plot(1:le ngth(sig n

31、al),sig nal),grid title( Add ing no ise)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:le ngth(fpeask)-7,fpeask,-6:le ngth(fpefsk)-7,fpefsk,-30:le ngth(fpepsk)-31,fpepsk),grid on;ti tle(An alysis Of Bit Error Rate);le

32、gend( ASK，FSK，PSK);xlabel( r/dB);ylabel(卩e);figure(2)semilogy(-6:le ngth(fpefsk)-7,fpeask);gridon;ti tle(Bit Error Rate Of ASK );xlabel( r/dB);ylabel( PeASK);figure(3)semilogy(-6:le ngth(fpefsk)-7,fpefsk);gridon;ti tle(Bit Error Rate Of FSK );xlabel( r/dB);ylabel( PeFSK);figure(4)semilogy(-16:le ngth(fpepsk)-17,fpepsk);gridon;title( Bit Error Rate Of PSK );axis(-1