Polarization Properties of Planar Dielectric Lenses

Composite planar dielectric structures used for increasing the directivity of a point source, have been investigated for many years. In earlier works, the effects of a superstrate with high permittivity, placed on a substrate with very low permittivity, have been studied. This substrate/superstrate structure was demonstrated to establish a resonance condition, which maximizes antenna gain, radiation resistance, and radiation efficiency. Particular attention has been given to the physical interpretation of this resonance gain effect, which can be described in terms of leaky waves (LW) excited in the structure. Under certain resonance conditions, a pair of weakly attenuated TE/TM leaky waves become the dominant contributions to the antenna aperture field. Although the demonstrated interest in such type of configurations, the polarization characteristics of the structure has not been investigated, yet. The aim of this paper is to rigorously demonstrate that the conventional choice of the stratification, not only ensures a large aperture field, but the same field is also well polarized when excited by any linearly polarized point source