3种基带传输常用编码与解码方法

3种基带传输常用编码与解码方法AMI编码functiony=AMI(x,samp)last_one=-1;fori=1:length(x)ifx(i)==1forj=1:samp/2y((2*i-2)*samp/2+j)=-last_one;y((2*i-1)*samp/2+j)=0;endlast_one=-last_one;elseforj=1:sampy((i-1)*samp+j)=0;endendendy=[y,x(i)];NRZ编码functionx=NRZ(y,samp)num=0;N=length(y)/samp;fori=1:Nforj=1:sampify((i-1)*samp+j)==1num=num+1;endendifnum>=samp/2x(i)=1;elsex(i)=0;endnum=0;endHDB3编码functiony=HDB3(x,samp)last_V=-1;last_one=-1;num=0;fori=1:length(x)ifx(i)==1forj=1:samp/2y((2*i-2)*samp/2+j)=-last_one;%遇1则极性反转y((2*i-1)*samp/2+j)=0;endlast_one=-last_one;num=0;elsenum=num+1;ifnum==4num=0;temp=-last_V;%遇4连零则置为V,相邻的V极性反转forj=1:samp/2y((2*i-2)*samp/2+j)=temp;y((2*i-1)*samp/2+j)=0;endlast_V=temp;iftemp*last_one==-1%V与前一个非0符号必须同极性forj=1:samp/2y((2*(i-3)-2)*samp/2+j)=temp;%否则置By((2*(i-3)-1)*samp/2+j)=0;endendlast_one=temp;endendendy=[y,x(i)];主程序：clearall;samp=300;%x=randint(1,N);x=[10110000000110000001];N=length(x);t=0:1/samp:N;y1=AMI(x,samp);y2=NRZ(x,samp);y3=HDB3(x,samp);figure(1);subplot(3,1,1);plot(t,y1);axis([0,N,-0.2,1.2]);grid;title('AMI码')；subplot(3,1,2);plot(t,y2);axis([0,N,-1.2,1.2]);grid;title('单极性非归零码')；subplot(3,1,3);plot(t,y3);axis([0,N,-1.2,1.2]);grid;title('HDB3码')；%gtext('基带传输常用码的编码');最后输出结果：

解码程序：AMI解码：>>y=[+10-100+100-10+1-100+10-1000+1-1];>>N=length(y);>>samp=500;>>t=0:1/samp:N;>>x=deAMI(y,samp);>>plot(t,x);>>axis([0,N,-1.2,1.2]);>>grid;>>title('AMI解码');子函数：functionx=deAMI(y,samp)fori=1:length(y)ify(i)==1forj=1:sampx((i-1)*samp+j)=1;endelseify(i)==-1forj=1:sampx((i-1)*samp+j)=1;endelseforj=1:sampx((i-1)*samp+j)=0;endendendendx=[x,y(i)];AMI解码>>t=0:1/samp:N;246810121416182022>>x=deNRZ(y,samp);>>plot(t,x);>>axis([0,N,-1.2,1.2]);>>grid;>>title('NRZ解码');子函数：functionx=deNRZ(y,samp)fori=1:length(y)ify(i)==1forj=1:sampx((i-1)*samp+j)=1;endelseforj=1:sampx((i-1)*samp+j)=0;endendendx=[x,y(i)];NRZ解码ify(i)==0forj=1:sampx((i-1)*samp+j)=0;endelsefirst=y(i);forj=1:sampx((i-1)*samp+j)=1;endendendfori=4:length(y)ify(i)==0forj=1:sampx((i-1)*samp+j)=0;endelseify(i)*first==1forj=1:sampx((i-1)*samp+j)=0;x((i-2)*samp+j)=0;x((i-3)*samp+j)=0;x((i-4)*samp+j)=0;first=y(i);endelsefirst=y(i);forj=1:sampx((i-1)*samp+j)=1;endendendendx=[x,y(i)];主函数：y=[+10-100+100-10+1-100+10-1000-1+1]>>N=length(y);>>samp=500;>>t=0:1/samp:N;>>x=deHDB3(y,samp);>>plot(t,x);>>axis([0,N,-1.2,1.2]);>>grid;>>title('HDB3解码');

10.80.60.40.20-0.2-0.4-0.6-0.8-1HD日3解码024681012141618HD日3解码用窗函数设计FIR数字滤波器滤波器的设计程序：b=1;clearall;i=0;while(b);temp=menu(’选择窗函数长度N',’N=10',’N=15',’N=20',’N=25',’N=30’，‘N=33‘,’N=35‘,’N=40‘,’N=45‘,’N=50‘,’N=55‘,’N=60‘,’N=64‘)；menu1=[10,15,20,25,30,33,35,40,45,50,55,60,64];N=menu1(temp);temp=menu(’选择逼近理想低通滤波器截止频率Wc',‘Wc=pi/4’，'Wc=pi/2’，'Wc=3*pi/4’，‘Wc=pi’，‘Wc=0.5’，‘Wc=1.0’，‘Wc=1.5’，‘Wc=2.0’，‘Wc=2.5’，‘Wc=3.0’)；menu2=[pi/4,pi/2,3*pi/4,pi,0.5,1,1.5,2,2.5,3];w=menu2(temp);n=[0:(N-1)];hd=ideal(w,N);%得到理想低通滤波器，k=menu(’请选择窗口类型：‘，’boxcar‘，’hamming‘,’hanning‘,’blackman‘)；Ifk==1B=boxcar(N);String=[‘Boxcar’，‘N=’，num2str(N)];elseifk==2B=hamming(N);String=[‘hamming’，‘N=’，num2str(N)];elseifk==3B=hanning(N);String=[‘hanning’，‘N=’，num2str(N)];elseifk==4B=blackman(N);String=[‘blackman’，‘N=’，num2str(N)];endendendendh=hd.*(B)‘；％得到FIR数字滤波器[H,m]=freqz(h,[1],1024,’whole‘)；％求其频率响应mag=abs(H)；%得到幅值db=20*log10((mag+eps)/max(mag));pha=angle(H);%得到相位i=i+1;figure(i)subplot(2,2,1);n=0:N-1;stem(n,h,’。‘)；axis([0,N-1,-0.1,0.3]);holdon;n=0:N-1;x=zeros(N);plot(n,x,‘一’)；xlabel(‘n’);ylabel(‘h(n)’);title(‘实际低通滤波器的h(n)’)；text((0.3*N),0.27,string);holdoff;subplot(2,2,2);plot(m/pi,db);axis([0,1,-100,0]);xlabel(‘w/pi’);ylabel(‘db’);title(‘衰减特性(db)’)；grid;subplot(2,2,3);plot(m,pha);holdon;n=0:7;x=zeros(8);plot(n,x,‘-’)；title(‘相频特性’)；xlabel(‘频率(rad)’);ylabel(‘相位(rad)’);axis([0,3.15,-4,4]);subplot(2,2,4);plot(m,mag);title(‘频率特性’)xlabel(‘频率W(rad)’);ylabel(‘幅值’)；axis([0,3.15,0,1.5]);text(0.9,1.2,string)；b=menu(‘DOyouwanttocontinue?’，‘Yes’，‘No’);Ifb==2b=0;endendtemp=menu(‘Closeallfigure?’，‘Yes’，‘No’);Iftemp==1closeallEnd程序中用到的子函数：产生理想低通滤波器单位响应hd(n)functionhd=ideal(w,N);alpha=(N-1)/2;n=[0:(N-1)];m=n-alpha+eps;hd=sin(w*m)./(pi*m)最后的输出结果：当选择输出矩形窗，N=33，Wc=pi/4。S回区］•JFigureNo.2FileEditVie