A Prolate Spheroidal Uniform Isotropic Dielectric Lens Feeding A Circular Coax

ABSTRACT

In launching the TEM mode on a coaxial circular cylindrical transmission line at high frequencies, one can use coaxial circular cones as a wave 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, dielectric with frequency-independent dielectric constant (lossless and dispersionless). While the lens is not perfect in that there are small reflections at the lens surface, the high-frequency performance can be quite good for a large range of lens parameters.