%信源為雙極性不歸零碼（NRZ），取樣點數(shù)自己定義 。。。。。QPSK


global dt df t f N T %定義全局變量
close all  %關閉以前的應用窗口
clear Eb_N0 Pe

k=input('取樣點數(shù)＝2^k, k=[13]'); %采樣點數(shù)自定義，默認為2^13 
if k==[], k=13; end

N=2^k;    %總的取樣點數(shù)
L=32;		%L為每個碼元的取樣點數(shù)
M=N/L;		%M碼元總數(shù)	
Rb=2;		%碼元速率Rb=2Mb/s
Ts=1/Rb;		%碼元寬度Ts
dt=Ts/L;	%時域取樣間隔
df=1/(N*dt);%頻域取樣間隔
T=N*dt;     %時間截斷長度
Bs=N*df/2;  %帶寬
Na=2;      %示波器掃描寬度為2個碼元
alpha=0;   %升余弦滾降系數(shù)

t=linspace(-T/2,T/2,N); %頻域橫坐標
f=linspace(-Bs,Bs,N)+eps;%時域橫坐標

%升余弦
hr1=sin(pi*t/Ts)./(pi*t/Ts);
hr2=cos(alpha*pi*t/Ts)./(1-(2*alpha*t/Ts).^2);
hr=hr1.*hr2;
HR=abs(t2f(hr));
GT=sqrt(HR);
GR=GT;

figure(1)
 set(1,'Position',[10,250,500,400])
                %設定窗口位置及大小 
figure(2)
 set(2,'Position',[515,250,500,400])
                %設定窗口位置及大小 
                
figure(3)
 set(3,'Position',[200,10,500,400])
                %設定窗口位置及大小 
%。。。。。。。。。。。。。。兩個載波
A=1;
fc=5/Ts;
m=A*cos(2*pi*fc*t);
n=-A*sin(2*pi*fc*t);  

EP=zeros(size(f));      %發(fā)送功率譜
EPa=zeros(size(f)); 
EPt=zeros(size(f));  
for loop1=1:15    %誤碼率曲線
 Eb_N0(loop1)=2*(loop1-1);  %Eb/N0 in dB
 eb_n0(loop1)=10^(Eb_N0(loop1)/10);
 Eb=0.25;	
 n0=Eb/(eb_n0(loop1)); %信道的噪聲譜密度   
 sita=n0*Bs; %信道中噪聲功率
 n_err=0;     %誤碼計數(shù)

 for loop2=1:5  
 a=sign(randn(1,M));   %產(chǎn)生隨機碼
 i=zeros(1,M);         %串并轉(zhuǎn)換
 q=zeros(1,M);         
y0=zeros(1,M);
s=zeros(1,N);
I=zeros(1,N);
Q=zeros(1,N);
y=zeros(1,N);
for nn=1:M/2          
    i(2*nn-1)=a(2*nn);
    q(2*nn-1)=a(2*nn-1);
    i(2*nn)=i(2*nn-1);
    q(2*nn)=q(2*nn-1);
end;   
for ii=1:Ts/dt;   
s(ii+[0:M-1]*L)=a;   %將信源變成不歸零碼
I(ii+[0:M-1]*L)=i;
Q(ii+[0:M-1]*L)=q;
end

S=t2f(s);           %信源信號的傅式變換
P=S.*conj(S)/T;     
EP=(EP*(loop1-1)+P)/loop1; %發(fā)送功率譜

Ia=I.*m;    %兩路分別調(diào)制
Qa=Q.*n;

st=Ia+Qa;  %并串轉(zhuǎn)換
ST=t2f(st);           %信源信號的傅式變換
PT=ST.*conj(ST)/T;     
EPt=(EPt*(loop1-1)+PT)/loop1; %發(fā)送功率譜
n_ch=sqrt(sita)*randn(size(t));  %信道噪聲

st=st+n_ch; %加噪聲
Iaa=st.*m;  %對兩路信號分別解調(diào)
Qaa=st.*n;

Ir=real(f2t(t2f(Iaa).*GR)); %分別通過濾波器
Qr=real(f2t(t2f(Qaa).*GR)); 

%sr=Ir+Qr;
yi=Ir(L/2:L:N);  %抽樣判決
yq=Qr(L/2:L:N);
yi=sign(yi);
yq=sign(yq);
bc=ones(1,L);        %定義復制的次數(shù)
yii=yi(bc,:);           %將a的第一行復制L次，生成L*M矩陣
ei=reshape(yii,1,L*M);  %將c重排成1*L*M數(shù)組
yqq=yq(bc,:);           %將a的第一行復制L次，生成L*M矩陣
eq=reshape(yqq,1,L*M);  %將c重排成1*L*M數(shù)組
for nn=1:M/2      %并串轉(zhuǎn)換
    y0(2*nn)=yi(2*nn);
    y0(2*nn-1)=yq(2*nn-1);
end; 
for ii=1:L;  
                   
y(ii+[0:M-1]*L)=y0;  %變成不歸零碼

end
n_err=n_err+length(find(y0~=a));  
end
Pe(loop1)=n_err/(M*loop2);
Y=t2f(y);           %信源信號的傅式變換
Pa=Y.*conj(Y)/T;      %發(fā)送功率譜
EPa=(EPa*(loop1-1)+Pa)/loop1;
end

figure(1)
 subplot(2,2,1)
 plot(t,s,'r');
 axis([-T/16,T/16,min(s)-0.5,max(s)+0.5])
 xlabel('t (ms)');
 ylabel('s  (V/KHz)');
 title('雙極性不歸零碼信號波形');
 
 subplot(2,2,2)
 bb=30+10*log10(EP+eps);
 plot(f,bb,'g')
 axis([-20,20,-20,max(bb)+0.5])
 grid
 xlabel('f(Mhz)');
 ylabel('Ps(f) (dBm/MHz)');
 title('信源功率譜密度圖形');
 
 subplot(2,2,3)
 plot(t,y,'b');
 axis([-T/16,T/16,min(y)-0.5,max(y)+0.5])
 xlabel('t (ms)');
 ylabel('y  (V/KHz)');
 title('輸出信號波形');
 
 subplot(2,2,4)
 bb=30+10*log10(EPa+eps);
 plot(f,bb,'g')
 axis([-20,20,-20,max(bb)+0.5])
 grid
 xlabel('f(Mhz)');
 ylabel('Pa(f) (dBm/MHz)');
 title('輸出功率譜密度圖形');
 
 figure(2)
 subplot(2,3,1)
 plot(t,Ia,'b');
 axis([-T/256,T/256,min(Ia)-0.5,max(Ia)+0.5])
 xlabel('t (ms)');
 ylabel('Ia  (V/KHz)');
 title('并聯(lián)調(diào)制信號波形(I)路');
 
 subplot(2,3,2)
 plot(t,Ir,'b');
 axis([-T/16,T/16,min(Ir)-0.5,max(Ir)+0.5])
 xlabel('t (ms)');
 ylabel('Ir  (V/KHz)');
 title('解調(diào)信號波形(I)路');
 
 subplot(2,3,3)
  tt=[0:dt:Na*L*dt];
  hold on
  for jj=1:Na*L:N-Na*L
    plot(tt,Ir(jj:jj+Na*L)); 
  end
  title('解調(diào)信號波形眼圖(I)路');

 subplot(2,3,4)
 plot(t,Qa,'b');
 axis([-T/256,T/256,min(Qa)-0.5,max(Qa)+0.5])
 xlabel('t (ms)');
 ylabel('Qa  (V/KHz)');
 title('并聯(lián)調(diào)制信號波形(Q)路');
 
 subplot(2,3,5)
 plot(t,Qr,'b');
 axis([-T/16,T/16,min(Qr)-0.5,max(Qr)+0.5])
 xlabel('t (ms)');
 ylabel('Qr  (V/KHz)');
 title('解調(diào)信號波形(Q)路');
 
 subplot(2,3,6)
  tt=[0:dt:Na*L*dt];
  hold on
  for jj=1:Na*L:N-Na*L
    plot(tt,Qr(jj:jj+Na*L)); 
  end
  title('解調(diào)信號波形眼圖(Q)路');
  
  figure(3)
 subplot(2,2,1)
 plot(t,st,'b');
 axis([-T/256,T/256,min(st)-0.5,max(st)+0.5])
 xlabel('t (ms)');
 ylabel('st  (V/KHz)');
 title('調(diào)制信號波形');

 subplot(2,2,2)
 plot(t,ei,'b');
 axis([-T/16,T/16,min(ei)-0.5,max(ei)+0.5])
 xlabel('t (ms)');
 ylabel('ei  (V/KHz)');
 title('判決輸出信號波形');
 
 subplot(2,2,3)
 bb=30+10*log10(EPt+eps);
 plot(f,bb,'g')
 axis([-20,20,-20,max(bb)+0.5])
 grid
 xlabel('f(Mhz)');
 ylabel('Pt(f) (dBm/MHz)');
 title('調(diào)制信號功率譜密度圖形');
  
  subplot(2,2,4)
  semilogy(Eb_N0,Pe,'g');
  eb_n0=10.^(Eb_N0/10);
  hold on
  plot(Eb_N0,0.5*erfc(sqrt(eb_n0)));
  axis([0,14,1e-4,1])
  xlabel('Eb/N0')
  ylabel('Pe')
  title('誤碼率曲線')