Low-Profile Broadband Circularly Polarized Patch Antenna Using Metasurface

A low-profile single-feed circularly polarized (CP) patch antenna using metasurface is proposed for broadband operation. The antenna is comprised of a truncated corner square patch sandwiched between a lattice of 4 × 4 periodic metal plates and the ground plane. Surface waves propagating on the metasurface are excited in the proposed structure. This phenomenon generates additional resonances and minimum axial ratio (AR) points for the radiating structure, consequently broadening the impedance-matching and AR bandwidths of the antenna. The final prototype, with an overall size of 32 mm × 32 mm × 3 mm (0.58λ_o × 0.58λ_o × 0.056λ_o at 5.5 GHz), was fabricated and tested. The measurements resulted in a IS₁₁I<;-10 dB bandwidth of 4.70-7.48 GHz (45.6%) and a 3-dB AR bandwidth of 4.9-6.2 GHz (23.4%). In addition, the antenna yielded a good broadside left-hand CP radiation with a small gain variation (7.0-7.6 dBic) and a high radiation efficiency (>90%) within the operational bandwidth.