gain of traveling-wave antenna of length L
[g,th,c,th0] = vee(L,Nth);
length in units of lambda
Nth+1 equally-spaced polar angles in [0,pi] = (0:Nth)*pi/Nth
g(th)=c*[sin(th)*sin(pi*L*(1-cos(th)))/(1-cos(th))]^2
unity-max normalization constant
acos(1 - 0.371/L) = direction of main lobe in degrees.
vee(L, alpha, Nth) computes gain of traveling-wave antenna of length L.
add sample pgm