Compact circularly-polarized microstrip patch antenna on Reactive Impedance Substrates

A reduced-size wideband single-feed circularly polarized microstrip patch antenna is presented for telemetry applications in S-band around 2.4 GHz. In this paper we compare the performance of microstrip patch antenna designed over two layer conventional substrate with different relative permittivity and different height and over a Reactive Impedance Substrate with slot, both of them being constituted with the same substrate layers. In particular we optimize the feeding position and number of reactive elements upon the antenna bandwidth and axial ratio. The proposed structure consists of a slot-loaded patch antenna printed over an optimized metamaterial-inspired reactive impedance substrate (RIS). We demonstrate, step by step, the main role of each antenna element by comparing numerically the performance of various antenna configurations, antenna over a single layer substrate or dual-layer substrate, patch without slot or slot-loaded patch, antenna with or without RIS. The final optimized structure exhibits an axial-ratio bandwidth of about 15% and an impedance bandwidth better than 10%, which is much wider than the conventional printed antenna on the same materials. The return loss pattern of different microstrip patch antenna with and without RIS arrangement is also compared using HFSS simulation software.