Miniaturized circularly polarized metasurface antenna based on characteristic mode analysis

Abstract

A miniaturized circularly polarized (CP) metasurface (MTS) antenna is investigated based on characteristic mode theory (CMT). The 4 × 4 square patch structure was used as the initial structure for characteristic mode analysis (CMA) and improvement using CMT to guide the evolution of antenna structures. The square ring is bent and the capacitive strips are introduced to obtain the final miniaturized MTS. Comparing the proposed MTS with traditional MTS, the proposed antenna size is significantly reduced. To give the proposed antenna a CP, a feeding structure with a 90° phase difference is designed to excite a pair of orthogonal target patterns. The final antenna structure has a reduced overall size and has circular polarization characteristics. For verification, the proposed CP MTS antenna is fabricated and measured. The measured results show an impedance bandwidth of 2.9–3.65 GHz and 3 dB axial ratio bandwidth of 3.1–3.57 GHz, and a stable gain in the operating frequency band.