通信原理实验结果11

PAGEPAGE2AMcloseall;clearall;dt=0.001;fm=1;fc=10;T=5;t=0:dt:T;mt=sqrt(2)*cos(2*pi*fm*t);%NO=0.01;%AMmodulationA=2;s_am=(A+mt).*cos(2*pi*fc*t);B=2*fm;figure(1)subplot(311)plot(t,s_am);holdon;plot(t,A+mt,'r--');title('AM调制信号及其包络');xlabel('t');%AMdemodulationrt=s_am.*cos(2*pi*fc*t);rt=rt-mean(rt);[f,rf]=T2F(t,rt);rt=lpf(f,rf,2*fm);subplot(312)plot(t,rt);holdon;plot(t,mt/2,'r--');title('相干解调后的信号波形与输入信号的比较');xlabel('t');subplot(313)[f,sf]=T2F(t,s_am);psf=(abs(sf).^2)/T;plot(f,psf);axis([-2*fc2*fc0max(psf)]);title('AM信号功率谱密度');xlabel('f');f2t—lpft2fF2T.mfunction[t,st]=F2T(f,sf)df=f(2)-f(1);Fmx=(f(end)-f(1)+df);dt=1/Fmx;N=length(sf);T=dt*N;t=0:dt:T-dt;sff=fftshift(sf);st=Fmx*ifft(sff);LPF.mfunctionst=lpf(f,sf,B)df=f(2)-f(1);T=1/df;hf=zeros(1,length(f));bf=[-floor(B/df):floor(B/df)]+floor(length(f)/2);hf(bf)=1;yf=hf.*sf;[t,st]=f2t(f,yf);st=real(st);T2F.mfunction[f,sf]=T2F(t,st)dt=t(2)-t(1);T=t(end);df=1/T;N=length(st);f=-N/2*df:df:N/2*df-df;sf=fft(st);sf=T/N*fftshift(sf);AMINO.1NO.2%本程序中时间单位是ms，频率单位是kHz，码元速率单位是kbit/sclearallcloseallN=2^13;L=32;M=N/L;Rb=2;Ts=1/Rb;fs=L/Ts;Bs=fs/2;T=N/fs;t=-T/2+[0:N-1]/fs;f=-Bs+[0:N-1]/T;EP=zeros(1,N);forloop=1:1000%产生数据序列a=(rand(1,M)>0.5);%AMI编码tmp1=1-2*a;tmp2=cumprod(tmp1);b=-a.*tmp2;%产生AMI码波形s=[ones(L/2,1)*b;zeros(L/2,M)];s=s(:)';S=t2f(s,fs);%样本信号的功率谱密度P=abs(S).^2/T;%随机过程的功率谱密度是各个样本的功率谱密度的数学期望EP=EP*(1-1/loop)+P/loop;endfigure(1)plot(t,s)xlabel('t(ms)')ylabel('s(t)(v)')axis([-4,4,-2,+2])figure(2)plot(f,EP)%xlabel('f(kHz)')%ylabel('功率谱(W/kHz)')%axis([-4,4,-2,+2])f2t.mfunctions=f2t(S,fs)N=length(S);T=N/fst=[-(T/2):1/fs:(T/2-1/fs)];tmp1=fft(S)/T;tmp2=N*ifft(S)/T;s(1:N/2)=tmp1(N/2+1:-1:2);s(N/2+1:N)=tmp2(1:N/2);s=s.*exp(-j*pi*t*fs);endt2f.mfunctionS=t2f(s,fs)%s为输入信号，S为s的频谱，fs为采样率；N=length(s);T=1/fs*N;f=[-N/2:(N/2-1)]/T;tmp1=fft(s)/fs;tmp2=N*ifft(s)/fs;S(1:N/2)=tmp2(N/2+1:-1:2);S(N/2+1:N)=tmp1(1:N/2);S=S.*exp(j*pi*f*T);endFMFM.m%FMmodulationanddemodulation,mfm.mclearall;closeall;Kf=5;fc=10;T=5;dt=0.001;t=0:dt:T;%信源fm=1;%mt=cos(2*pi*fm*t)+1.5*sin(2*pi*0.3*fm*t);%信源信号mt=cos(2*pi*fm*t);%信源信号%FM调制A=sqrt(2);%mti=1/2/pi/fm*sin(2*pi*fm*t)-3/4/pi/0.3/fm*cos(2*pi*0.3*fm*t);%mt的积分函数mti=1/2/pi/fm*sin(2*pi*fm*t);%mt的积分函数st=A*cos(2*pi*fc*t+2*pi*Kf*mti);figure(1)subplot(311);plot(t,st);holdon;plot(t,mt,'r--');xlabel('t');ylabel('调频信号')subplot(312)[f,sf]=T2F(t,st);pst=(abs(sf).^2)/T;plot(f,pst);axis([-25250max(abs(sf).^2)])xlabel('f');ylabel('调频信号幅度谱');%FM解调fork=1:length(st)-1rt(k)=(st(k+1)-st(k))/dt;endrt(length(st))=0;subplot(313)plot(t,rt);holdon;plot(t,A*2*pi*Kf*mt+A*2*pi*fc,'r--');xlabel('t');ylabel('调频信号微分后包络')f2t,t2fF2T.mfunction[t,st]=F2T(f,sf)df=f(2)-f(1);Fmx=(f(end)-f(1)+df);dt=1/Fmx;N=length(sf);T=dt*N;t=0:dt:T-dt;sff=fftshift(sf);st=Fmx*ifft(sff);T2F.mfunction[f,sf]=T2F(t,st)dt=t(2)-t(1);T=t(end);df=1/T;N=length(st);f=-N/2*df:df:N/2*df-df;sf=fft(st);sf=T/N*fftshift(sf);带通调制daitong1NO.1NO.2Daitong1.a%OOK,2PSK,文件名binarymod.mclearall;closeall;A=1;fc=2;%2HzN_sample=8;N=500;%码元数Ts=1;%1Buad/sdt=Ts/fc/N_sample;%波形采样间隔t=0:dt:N*Ts-dt;Lt=length(t);T=t(end);%产生二进制信源d=sign(randn(1,N));dd=sigexpand((d+1)/2,fc*N_sample);gt=ones(1,fc*N_sample);%NRZ波形figure(1);subplot(221);%输入NRZ信号波形（单极性）d_RNZ=conv(dd,gt);plot(t,d_RNZ(1:length(t)));axis([01001.2]);ylabel('输入信号');subplot(222);%输入NRZ频谱[f,d_RNZf]=T2F(t,d_RNZ(1:length(t)));plot(f,10*log10(abs(d_RNZf).^2/T));axis([-22-5010]);ylabel('输入功率频谱密度(dB/Hz)');%ook信号ht=A*cos(2*pi*fc*t);s_2ask=d_RNZ(1:Lt).*ht;subplot(223);plot(t,s_2ask);axis([010-1.21.2]);ylabel('ook');[f,s_2ask]=T2F(t,s_2ask);subplot(224);plot(f,10*log10(abs(s_2ask).^2/T));axis([-fc-4fc+4-5010]);ylabel('ook功率谱密度(dB/Hz)');figure(2);%2psk信号d_2psk=2*d_RNZ-1;s_2psk=d_2psk(1:Lt).*ht;subplot(221);plot(t,s_2psk);axis([010-1.21.2]);ylabel('2psk');subplot(222);[f,s_2psk]=T2F(t,s_2psk);plot(f,10*log10(abs(s_2psk).^2/T));axis([-fc-4fc+4-5010]);ylabel('2psk功率频谱密度(dB/Hz)');%2FSK%s_2fsk=Acos(2*pi*fc*t+int(2*d_RNZ-1));sd_2fsk=2*d_RNZ-1;s_2fsk=A*cos(2*pi*fc*t+2*pi*sd_2fsk(1:length(t)).*t);subplot(223);plot(t,s_2fsk);axis([010-1.21.2]);xlabel('t');ylabel('2fsk');subplot(224);[f,s_2fsk]=T2F(t,s_2fsk);plot(f,10*log10(abs(s_2fsk).^2/T));axis([-fc-4fc+4-5010]);xlabel('f');ylabel('2FSK功率频谱密度(dB/Hz)');F2T.mfunction[t,st]=F2T(f,sf)df=f(2)-f(1);Fmx=(f(end)-f(1)+df);dt=1/Fmx;N=length(sf);T=dt*N;t=0:dt:T-dt;sff=fftshift(sf);st=Fmx*ifft(sff);sigexpand.mfunction[out]=sigexpand(d,M)%将输入的系列扩展成间隔为N-1个0的系列N=length(d);out=zeros(M,N);out(1,:)=d;out=reshape(out,1,M*N);T2F.mfunction[f,sf]=T2F(t,st)dt=t(2)-t(1);T=t(end);df=1/T;N=length(st);f=-N/2*df:df:N/2*df-df;sf=fft(st);sf=T/N*fftshift(sf);抽样定理Chouyanbg1.m%低通抽样定理，filename:dtchy.mclearall;closeall;dt=0.01;t=0:dt:10;xt=0.1*cos(0.15*pi*t)+1.5*sin(2.5*pi*t)+0.5*cos(4*pi*t);[f,xf]=T2F(t,xt);%抽样信号，抽样速率为4Hzfs=4;sdt=1/fs;t1=0:sdt:10;st=0.1*cos(0.15*pi*t1)+1.5*sin(2.5*pi*t1)+0.5*cos(4*pi*t1);[f1,s1]=T2F(t1,st);%恢复原始信号t2=-50:dt:50;gt=sinc(fs*2);stt=sigexpand(st,sdt/dt);xt_t=conv(stt,gt);figure(1);subplot(311);plot(t,xt);title('原始信号');subplot(312);plot(t1,st);title('抽样信号');subplot(313);t3=-50:dt:60+sdt-dt;stem(t1,st,'*');title('抽样信号恢复');axis([010-44])[F2T.mT2F.m函数见实验一附录]FDMFDM.mclearall;t=0:0