A Low-Profile Broadband Dual-Circularly-Polarized Metasurface Antenna

A low-profile broadband dual-circularly-polarized metasurface antenna is proposed. The antenna consists of a modified cross-slot coupling antenna with a lattice of 4 × 4 square metallic patches. A characteristic mode analysis is used to investigate the operating mechanism of the metasurface antenna. Then, the desired modes are chosen and excited by the modified slots. The modified slot introduces a new resonance to achieve broadband characteristic. Two orthogonally placed microstrip lines are used to achieve both right-hand circular polarization and left-hand circular polarization in the same frequency band. The final prototype, with an overall size of 100 mm × 100 mm × 6 mm (0.71 λ ₀ × 0.71 λ ₀ × 0.04 λ ₀ at 2.15 GHz) is measured. The measured results show that the proposed antenna has an axial-ratio bandwidth of 31.3% and an impedance bandwidth of 52.5%.