Low-profile, Broadband, and High-gain Circularly Polarized Metasurface Antenna using Characteristic Mode Analysis

In this paper, a low-profile broadband and high-gain circularly polarized (CP) metasurface antenna (MSA) is proposed. The characteristic mode analysis is employed to select the valuable modes for the 4×4 square metasurface elements printed on the top of the single-layer dielectric slab. The coplanar waveguide feeding structure combines a horizontal aperture and two slots rotated in a counter-clockwise direction is utilized to excite the CP radiation of the MSA. The proposed CP MSA is fabricated and measured, which achieves a -10 dB impedance bandwidth ranging from 4.83 GHz to 6.35 GHz, with a fractional bandwidth of 27.2%, the overlapped 3 dB axial ratio (AR) bandwidth is 20.1% (covers from 4.83 GHz to 5.91 GHz). Furthermore, the peak boresight gain measured at 5.2 GHz reaches 9.88 dBic. The average gain consistently maintains 8.94 dBic throughout the overlapped AR bandwidth, while the 3 dB gain bandwidth fully encompasses the entirety of the 3 dB overlapped AR bandwidth showing good performance for 5G Wi-Fi band utilization.