A patch antenna with a top dielectric layer

The paper presents a technique of enhancing the gain of a patch antenna. The enhancement is realized by putting a dielectric layer on top of the patch. The analysis is performed using the finite-difference time domain method, where Yee\´s rectangular mesh is used with Liao\´s second order absorbing boundary condition (Taflove, A. "Computational electrodynamics", Artech House, 1995). The assumptions used in the analysis are as follows: the bottom (substrate) and top dielectric layers are lossless; the ground plane is of infinite extent; the patch is infinitesimally thin. As the top dielectric layer thickness, B_top, increases, the input impedance shows oscillatory variations, with a period slightly larger than one-half of the guided-wave length of a plane wave propagating in an unbounded dielectric material. It is also found that, as B_top increases, the radiation pattern becomes narrower and the gain reaches a maximum value. However, as B_top further increases, the gain decreases due to rising side-lobe levels. A gain increase of 7.2 dB is obtained at B_top=1.48λ₈ for ε_r=2.07.