Projeto e análise de propagação de antenas MIMO com diversidade de polarização para 5G

Abstract

This work presents the design of two four-port MIMO antennas with circular polarization diversity, operating at 3.5 and 26 GHz, and the evaluation of their performance in propagation scenarios. The antennas employ concentric rectangular slots, with right-hand or left-hand circular polarization defined by the feeding port, allowing the simultaneous excitation of two ports, one from each cell, with equal or opposite polarizations. The 3.5 GHz antenna was fabricated and experimentally characterized on FR-4 substrate, presenting a bandwidth of 596 MHz (3.25–3.85 GHz), an axial-ratio bandwidth of 473 MHz (3.27–3.74 GHz), and a gain of 3.88 dB. The 26 GHz antenna, designed on Rogers RO4003C substrate, presented, according to simulations, a bandwidth of 6.65 GHz (23.6–30.3 GHz), an axial-ratio bandwidth of 570 MHz (25.91–26.48 GHz), and a gain of 8.16 dB. Both antennas exhibited good port isolation and satisfactory performance in the evaluated MIMO metrics. Additionally, the circularly polarized antennas were simulated in different propagation scenarios and compared with a linearly polarized dipole. The results showed that, under transmitter–receiver misalignment conditions, circular polarization provided higher received power, demonstrating its contribution to link stability under variations in propagation conditions.