Bandwidth and Gain Improvement of an L-Shaped Slot Antenna With Metamaterial Loading

Abstract

A metamaterial-based wideband and high-gain circularly polarized (CP) mushroom antenna is proposed and analyzed in this letter. The proposed antenna consists of a $4 \times 4$ mushroom-cells array and an L-shaped slot coupling-fed layer. The metamaterial-based mushroom cells are adopted to adjust the axial ratio (AR) to realize wideband CP and high gain. With the optimization, the proposed dielectric-filled mushroom antenna is with a low profile of $0.08{\lambda _0}$ ( ${\lambda _0}$ is the operating wavelength in free space) while covering an area of $60\,{\text{mm}} \times 60\,{\text{mm}}$ only. The measured impedance bandwidth of the proposed antenna is 48.2% (5.2–8.5 GHz), and the measured 3 dB AR bandwidths are 35.5% (5.8–8.3 GHz). Moreover, the antenna performed a stable high gain which is better than 10.5 dBic from 6 to 7.5 GHz across the CP region.