Dual-Band Dual-Circularly Polarized Fabry-Pérot Cavity MIMO Antenna Using CMM-Based Polarization Converter and MMA for Vehicular Satellite Communications

A 2 × 2 dual-band dual-circularly polarized (CP) Fabry-Pérot cavity (FPC) multiple input multiple output (MIMO) antenna is proposed in this paper. It is formed by arranging four identical FPC antenna elements with 90° rotation. The FPC antenna element is composed of a single linearly polarized (LP) feeder and a chiral metamaterial (CMM)-based partially reflective surface (PRS), which acts as a polarization converter. The feeder is with a hybrid structure of a slot radiator operating in the low band and a patch radiator in the high band. As the orthogonal currents on the end and center arms of the H-shaped patch break the degeneracy of two CP waves at different frequencies, the PRS simultaneously realizes left-hand CP (LHCP) and right-hand CP (RHCP) features at two different bands, respectively. To enhance the port isolation between two adjacent antenna elements, a broadband, wide-angle, polarization-independent metamaterial absorber (MMA) is introduced to suppress the space wave coupling. To verify the design concept, the proposed MIMO antenna prototype is fabricated and measured. The measured bandwidth with a voltage standing wave ratio (VSWR) of less than 2 covers 3.32–3.42 GHz and 6.23–6.93 GHz, and the LHCP pattern and RHCP pattern are realized at 3.33-3.42 GHz (2.7%) and 6.59–6.75 GHz (2.4%), respectively. A maximum gain enhancement is up to 5.31 dBi in the low band and up to 4.3 dBi in the high band. In addition, the port isolation is better than 42 dB, and the ECC is less than −40 dB. With these performances, the proposed MIMO antenna is suitable for vehicular satellite communication applications.