A Study on Scattering Performance of Reflectarray Element Covered by Dielectric Superstrate

Abstract

In this paper, effect of a dielectric superstrate on scattering performance of reflectarray elements is clarified. At first, analytical electric field expressions of an infinite line current backed by a ground plane with the dielectric superstrate and so-called resonance conditions derived by Sugio et al., are reviewed. According to the electric field expressions and reciprocity, enhancement of the scattering field strength by the dielectric superstrate under the resonance conditions is expressed analytically. Since the scatterers are illuminated by the incident wave arriving from outside of the scatterers, the effect of its incident angle θi on the scattering field strength is also studied. Based on inequalities that are derived from the electric field expressions, range of θi for enhancing the scattering field strength by the dielectric superstrate under the resonance conditions is found. As a result, it is found that the range of θi is independent of εr when εr ≫ 1, where εr is relative permittivity of the dielectric superstrate. Numerical simulation is performed and it is demonstrated that the analytical fomulae derived here are useful for predicting the effect of the dielectric superstrate on practical reflect array elements such as dipole, patch and loop elements. Results and theories demonstrated in this paper give quantitative guidelines on designing the reflectarray elements covered by the superstrate from the viewpoints of angle dependance, geometry, and permittivity of the superstrate.

Analytical Study of Scattering Performance of Scatterers Covered by Dielectric Slab

“…Numerical simulation is performed and it is demonstrated that the predictions work for practical scatterers. This paper is enhancement of our previous work [4].…”