qpskd.m

几个常用通信和雷达信号的matlab仿真

function qpsk=qpskd(g,f) 
%Modulation  QPSK  
%Example: 
%qpskd([1 0 1 1 0 0],2) 

t=0:2*pi/99:2*pi; 
cp=[];sp=[]; 
mod=[];mod1=[];bit=[]; 
for n=1:2:length(g); 
    if g(n)==0 & g(n+1)==1; 
        die=sqrt(2)/2*ones(1,100); 
        die1=-sqrt(2)/2*ones(1,100); 
        se=[zeros(1,50) ones(1,50)]; 
    elseif g(n)==0 & g(n+1)==0; 
        die=-sqrt(2)/2*ones(1,100); 
        die1=-sqrt(2)/2*ones(1,100); 
        se=[zeros(1,50) zeros(1,50)]; 
    elseif g(n)==1 & g(n+1)==0; 
        die=-sqrt(2)/2*ones(1,100); 
        die1=sqrt(2)/2*ones(1,100); 
        se=[ones(1,50) zeros(1,50)]; 
    elseif g(n)==1 & g(n+1)==1; 
        die=sqrt(2)/2*ones(1,100); 
        die1=sqrt(2)/2*ones(1,100); 
        se=[ones(1,50) ones(1,50)]; 
    end 
    c=cos(f*t); 
    s=sin(f*t); 
    cp=[cp die];    %Amplitude cosino 
    sp=[sp die1];   %Amplitude sino 
    mod=[mod c];    %cosino carrier (Q) 
    mod1=[mod1 s];  %sino carrier   (I) 
    bit=[bit se]; 
end 
qpsk=cp.*mod+sp.*mod1; 
subplot(2,1,1);plot(bit,'LineWidth',1.5);grid on; 
title('Binary Signal') 
axis([0 50*length(g) -1.5 1.5]); 
 
subplot(2,1,2);plot(qpsk,'LineWidth',1.5);grid on; 
title('QPSK modulation') 
axis([0 50*length(g) -1.5 1.5]);