global dt df t f N%全局變量
close all
k=input('取樣樣點=2^k,k>=[14]')
if k==[],k=14;end
g1=[1,0,0,0,0,1,1;0,1,0,0,1,0,1;0,0,1,0,1,1,1;0,0,0,1,1,1,0]%線組分組碼生成矩陣
g2
N=2^k;				%采樣點數
L=64;					%每碼元的采樣點數
M=N/L;				%碼元數
Rb=2;					%碼速率是2Mb/s
Ts=1/Rb;				%碼元間隔
dt=Ts/L;				%時域采樣間隔
df=1/(N*dt);		%頻域采樣間隔
T=N*dt;				%截短時間
Bs=N*df/2;			%系統帶寬
t=[-T/2+dt/2:dt:T/2];%時域橫坐標
f=[-Bs+df/2:df:Bs];		%頻域橫坐標
EP=zeros(size(f));
for jj=1:100
a=round(rand(1,M));	%碼元矢量
s=zeros(1,N);
s1=zeros(1,N/4*7);
for qq=
for ii=1:L
   s(ii+[0:M-1]*L)=a;
end						%產生NRZ碼
S=t2f(s);
P=S.*conj(S)/T;		%功率譜
EP=(EP*(ii-1)+P)/ii; %累計平均
aa=30+10*log10(EP+eps);	%加eps以避免除以零
end

figure(1)
set (1,'position',[10,50,300,200]);%設定窗口位置及大小
figure(2)
set(2,'position',[350,50,300,200]);%設定窗口位置及大小
figure (1)
plot(f,aa,'g');
grid
axis([-10,+10,-50,+50])
xlabel('f(MHZ)')
ylabel('Ps(f)(MHZ)')
figure(2)
plot(t,s,'r')
grid
axis([-10,+10,-1,+2])
xlabel('t(us)')
ylabel('s(t)(V)')