function ration=doppler(dop,k,N)
for u=1:N-1
    for l=1:N-1
        x2(l)=(N-l)*besselj(0,dop*l);
        x3(l)=x2(l)*cos(2*pi*l*(u-k)/N);
    end
    x4(u)=N+2*sum(x3);
end
x5=N+2*sum(x2);
pow1=sum(x4);
pow2=x5;
ration=(pow1-pow2)/pow2;