【程序代码】
figure
subplot(3,1,1) plot(x_t(1:20*8))
axis([1,20*8,-1.5,1.5]); title('initial code')
subplot(3,1,2)
plot(y_AMI(1:20*8)) axis([1,20*8,-1.5,1.5]); title('AMI code')
subplot(3,1,3)
plot(y_HDB3(1:20*8)) axis([1,20*8,-1.5,1.5]); title('HDB3 code')
figure
plot_spectrum(x_t,'b'); hold on
plot_spectrum(y_AMI,'r');
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plot_spectrum(y_HDB3,'g');
title('Power spectrum of NRZ,AMI and HDB3 Code') legend('NRZ','AMI','HDB3')
%Code.m N=1000; fs=8;
x=ceil(rand(1,N)-0.8); AMI=AMI_Code(x); HDB3=HDB3_Code(x); Miller=Miller_Code(x);
y=zeros(1,N*fs); x_t=zeros(1,N*fs); y_AMI=zeros(1,N*fs); y_HDB3=zeros(1,N*fs); y_Miller=zeros(1,N*fs); for i=1:N*fs
if(mod(i-1,8)<=5 & mod(i-1,8)>=2) y(i)=1; else
y(i)=0; end
%分别给画图序列赋值 y_AMI(i)=y(i)*AMI(ceil(i/8)); y_HDB3(i)=y(i)*HDB3(ceil(i/8)); y_Miller(i)=Miller(ceil(i/4)); x_t(i)=x(ceil(i/8)); end
%AMI_Code.m
function AMI=AMI_Code(x) m=length(x);
%初始化AMI编码 AMI=zeros(1,m); %反转标志初始化 f=0; for i=1:m
%若原码为0，直接将AMI码置0 if x(i)==0
AMI(i)=0;
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%否则，使得AMI码交替为＋1，－1 else
f=XOR(f,1); AMI(i)=2*f-1; end end return;
%HDB3.m
function HDB3=HDB3_Code(x) m=length(x);
%初始化HDB3编码 HDB3=zeros(1,m);
%初始化信息“1”标志B和连0数标志V B=-1; V=-1; i=1;
while (i<=m-3)
%若原码为1，交替为＋1，－1 if(x(i)==1)
HDB3(i)=-1*B; B=HDB3(i); i=i+1; else
%原码只有一个0 if(x(i+1)==1) HDB3(i)=0;
HDB3(i+1)=-1*B; B=HDB3(i+1); i=i+2; else
%原码有两个连续0 if(x(i+2)==1) HDB3(i)=0; HDB3(i+1)=0; HDB3(i+2)=-1*B; B=HDB3(i+2); i=i+3; else
%原码有三个连续0 if(x(i+2)==1) HDB3(i)=0; HDB3(i+1)=0; HDB3(i+2)=0; HDB3(i+3)=-1*B;
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B=HDB3(i+3); i=i+4;
%原码出现了四个连续0 else
%原始B、V标志不相同 if(Xor(B,V))
HDB3(i)=01; HDB3(i+1)=0; HDB3(i+2)=0; HDB3(i+3)=B; V=B;i=i+4;
%B、V标志相同 else
HDB3(i)=-1*B; HDB3(i+1)=0; HDB3(i+2)=0; HDB3(i+3)=-1*B; B=-1*B;V=B;i=i+4; end end end end end end for j=i:m
if (x(j)==1)
HDB3(j)=-1*B; B=HDB3(j); else
HDB3(j)=0; end end return;
%plot_spectrum.m
function plot_spectrum(x,str)
P=spectrum(x,8000,0,hanning(300)); plot(10*log10(P(:,1)),str);
return; function plot_spectrum(x,str) P=spectrum(x,8000,0,hanning(300)); plot(10*log10(P(:,1)),str); return;
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