Realization of high directivity enhancement by using an array of microstrip patch antennas (MPAs) covered by a dielectric superstrate

In this paper we present a Fabry-Perot type of design, involving a microstrip array covered by a 14¿₀ × 14¿₀ superstrate that realizes a directivity of 32 dB when excited by an array of 25 microstrip patches. We show that the directivity of the array can be enhanced by an additional 2 dB by using a two-layer superstrate. We present the radiation patterns for the two cases to show that the sidelobe level for the two-layer case is lower than that for the one-layer version. We also carry out a parametric study of the superstrates layers and the distance between the lower superstrate and the ground plane, and examine how the separation distance between the two superstrate layers affects the resonant frequency of the composite structure.