%時(shí)間單位 us 頻率單位 MHz 碼元速率 Mb/s
clear all
close all
clc
%k=input('取樣點(diǎn)數(shù)=2^k,k=[14]');
%if isempty(k),
	k=14;
%end
N=2^k;	%采樣點(diǎn)數(shù)
L=64;	%每碼元采樣點(diǎn)數(shù)
M=N/L;	%碼元數(shù)
Rb=2;	%碼元速率
Ts=1/Rb;	%碼元間隔
dt=Ts/L;	%時(shí)域取樣間隔
df=1/(N*dt);	%頻域取樣間隔
T=N*dt;	%時(shí)域截短時(shí)間
Bs=N*df/2;	%頻域系統(tǒng)帶寬
t=[0+dt/2:dt:T];	%時(shí)域橫坐標(biāo)
f=[-Bs+df/2:df:Bs];		%頻域橫坐標(biāo)  
%Rt=input('占空比=0--1,Rt=0.5');
%if isempty(Rt),
	Rt=0.5;
%end
Ep=zeros(size(f));
for ii=1:50
    a=(round(rand(1,M))-0.5)*2;  %產(chǎn)生雙極性隨機(jī)序列
    rz=zeros(1,N);
    for tt=1:Rt*L
        rz(tt+[0:M-1]*L)=a;
    end
    RZ=t2f(rz,dt);   %傅立葉變換
    P=RZ.*conj(RZ)/T;   %功率譜密度
    Ep=(Ep*(ii-1)+P)/ii;    
end
figure(1)   %畫功率譜密度圖形
set(1,'position',[10,50,300,200])
aa=30+10*log10(Ep+eps);   %將幅度轉(zhuǎn)化成dB值
plot(f,aa,'r')
grid on
axis([-10,+10,-50,50])
xlabel('f(MHz)')
ylabel('Ps(f)(dBm/MHz)')
figure(2)   %畫雙極性歸零碼時(shí)域圖形
set(2,'position',[350,50,300,200])
plot(t,rz,'b')
grid on
axis([0,10,-1.5,1.5])
xlabel('t(us)')
ylabel('s(t)(V)')