A PROLATE SPHEROIDAL UNIFORM ISOTROPIC DIELECTRIC LENS FEEDING A CIRCULAR COAX

In launching the TEM mode on a coaxial circular cylindrical transmissi on line at high frequencies, one can use coaxial circular cones as a w ave launcher. Characteristic impedances are matched at the boundary of the conical waveguide and the cylindrical waveguide, and in the usual lens sense rays on the conical structure travel with equal time to an aperture plane perpendicular to the axis of the system. To accomplish this the conical region is filled with a uniform, isotropic, dielectr ic with frequency-independent dielectric constant (lossless and disper sionless). While the lens is not perfect in that there are small refle ctions at the lens surface, the high-frequency performance can be quit e good for a large range of lens parameters.