Triple-band circularly polarized antenna on a two-layered high impedance surface with two in-phase reflection bands

Abstract

This paper presents a novel two-layered dual-band high impedance surface (HIS) and its applications to enhance the performance of a triple-band circularly polarized (TBCP) antenna. The proposed HIS consists of periodically arranged 6×6 nested concentric square patches on the top layer of the substrate to produce two in-phase reflection bands. The bottom layer is printed with periodic square patches to achieve miniaturization. The antenna comprises of a square patch radiator with four T-shaped slits around the edges and a narrow diagonal slot at the center. The antenna element is placed at a height of 0.8 mm over the HIS and two simultaneous operating modes of the metasurface are studied. By using the HIS in its inductive region as a reactive impedance surface (RIS), significant reduction in the resonant frequencies up to 32.86% and 20.27% are observed in the lower and upper operating bands of the antenna, respectively. When used in HIS mode, the front-to-back ratio in the mid-frequency band of the antenna is greater than 20 dB and the broadside gain is 3.96 dBi. The antenna radiates CP waves in all the three bands with stable radiation patterns and the overlapped impedance and axial ratio bandwidths are 7.69% (2.02–2.18 GHz), 3.17% (4.35–4.49 GHz) and 1.2% (8.32–8.42 GHz), respectively. The overall design (TBCP antenna on HIS) maintains a very low profile (0.002λ 0 ).