quad.m

f=1000000;
len=length(b);
t=0:1/999:1;
qcar=[];icar=[];  %initialize in-phase and quadrature carriers
ic=[];qc=[];   %initialize in-phase and quadrature components;
for n=1:2:len
    if b(n)==0 & b(n+1)==0;
    temp=-1/sqrt(2)*ones(1,1000); 
    temp1=-1/sqrt(2)*ones(1,1000);
    elseif b(n)==0 & b(n+1)==1;
    temp=-1/sqrt(2)*ones(1,1000);
    temp1=1/sqrt(2)*ones(1,1000);
    elseif b(n)==1 & b(n+1)==0;
    temp=1/sqrt(2)*ones(1,1000);
    temp1=-1/sqrt(2)*ones(1,1000);
    elseif b(n)==1 & b(n+1)==1;
    temp=1/sqrt(2)*ones(1,1000);
    temp1=1/sqrt(2)*ones(1,1000);
end
i=cos(2*pi*f*t);
q=sin(2*pi*f*t);
ic=[ic temp];
qc=[qc temp1];
icar=[icar i];
qcar=[qcar q];
end
qpsk=ic.*icar+qc.*qcar
plot(qpsk);