qpsk.txt

源码中包括了QPSK的调制与解调

clear all 
close all 
x=[1 1 -1 -1 -1 1 1 1]; 
x1=x(1:2:8); 
x2=x(2:2:8); 

t=[-1:0.01:7-0.01]; 
tt=length(t); 
xx1=ones(1,800); 
for i=1:tt 
if (t(i)>=-1 &amt; t(i)<=1) | (t(i)>=5&amt; t(i)<=7); 
xx1(i)=1; 

else xx1(i)=-1; 
end 
end 

t1=[0:0.01:8-0.01]; 
t2=0:0.01:7-0.01; 
t3=-1:0.01:7.1-0.01; 
t4=0:0.01:8.1-0.01; 

tt1=length(t1); 
xx2=ones(1,800); 
for i=1:tt1 
if (t1(i)>=0 &amt; t1(i)<=2) | (t1(i)>=4&amt; t1(i)<=8); 
xx2(i)=1; 

else xx2(i)=-1; 
end 
end 


> ddd=fft(xx1); 
> ddd0=fft(xx2); 
> subplot(2,1,1);plot(t1,ddd); 
> subplot(2,1,2);plot(t1,ddd0); 

f=0:0.1:1; 
xrc=0.5+0.5*cos(pi*f); 

y1=conv(xx1,xrc)/5.5; 
y2=conv(xx2,xrc)/5.5; 

> ddd1=fft(y1); 
> ddd2=fft(y2); 
> figure 
> subplot(2,1,1);plot(t2,ddd1); 
> subplot(2,1,2);plot(t2,ddd2); 


n0=randn(size(t2)); 

f1=1; 
i=xx1.*cos(2*pi*f1*t); 
q=xx2.*sin(2*pi*f1*t1); 

I=i(101:800); 
Q=q(1:700); 

OQPSK=sqrt(1/2).*I+sqrt(1/2).*Q; 

OQPSK_n=(sqrt(1/2).*I+sqrt(1/2).*Q)+n0; 


n1=randn(size(t2)); 
i_rc=y1.*cos(2*pi*f1*t3); 
q_rc=y2.*sin(2*pi*f1*t4); 

I_rc=i(101:800); 
Q_rc=q(1:700); 
OQPSK_rc=(sqrt(1/2).*I_rc+sqrt(1/2).*Q_rc); 
OQPSK_rc_n1=(sqrt(1/2).*I_rc+sqrt(1/2).*Q_rc)+n1; 

figure(1) 
subplot(6,1,1);plot(t3,i_rc);axis([-1 8 -1 1]); 
subplot(6,1,2);plot(t4,q_rc);axis([-1 8 -1 1]); 
subplot(6,1,3);plot(t2,OQPSK);axis([-1 8 -1 1]); 
subplot(6,1,4);plot(t2,OQPSK_rc);axis([-1 8 -1 1]); 
subplot(6,1,5);plot(t2,OQPSK_rc);axis([-1 8 -1 1]); 
subplot(6,1,6);plot(t2,OQPSK_rc_n1);axis([-1 8 -1 1]); 


> I_demo=OQPSK_rc_n1.*cos(2*pi*f1*t2); 
> Q_demo=OQPSK_rc_n1.*sin(2*pi*f1*t2); 
> 
> y1_demo=conv(I_demo,xrc); 
> y2_demo=conv(Q_demo,xrc); 
> 
> 
> 
> x1_recove=ones(1,900); 
> x2_recove=ones(1,900); 
> 
> for i=1:100:900 
> if sum(y1_demo(i:i+99))>100 
> x1_recove(i:i+99)=1; 
> elseif sum(y1_demo(i:i+99))<-100 
> x1_recove(i:i+99)=-1; 
> else x1_recove(i:i+99)=0; 
> end 
> end 
> 
> for i=1:100:900 
> if sum(y2_demo(i:i+99))>100 
> x2_recove(i:i+99)=1; 
> elseif sum(y2_demo(i:i+99))<-100 
> x2_recove(i:i+99)=-1; 
> else x2_recove(i:i+99)=0; 
> end 
> end 




>subplot(2,1,1);plot(t,x1_recove); 
>subplot(2,1,2);plot(t,x2_recove); 
>figure 
>subplot(2,1,1);plot(y1_demo); 
>subplot(2,1,2);plot(y2_demo);