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/sub 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/sub top/ increases, the radiation pattern becomes narrower and the gain reaches a maximum value. However, as B/sub top/ further increases, the gain decreases due to rising side-lobe levels. A gain increase of 7.2 dB is obtained at B/sub top/=1.48/spl lambda//sub 8/ for /spl epsiv//sub r/=2.07.