Miniaturized Broadband Dual-Polarized MIMO Antenna Array With Stable Radiation Pattern for Base-Station Application

A wideband dual-polarized MIMO antenna array having small size and stable radiation performance for base-station applications is introduced. The antenna element, which is formed by four folded dipole antennas arranged in a small square aperture, is introduced to obtain excellent impedance matching and steady radiation pattern within a broad bandwidth of 36.7% (0.69–1 GHz) with low profile. Based on the high-performance element, a compact broadband dual-polarized MIMO array for mobile communications is then designed. To stabilize the radiation pattern of the MIMO array, a new method of element-shared scheme and 90° phase compensation is introduced to design the MIMO array to obtain stable half power beamwidth (HPBW) of around 64° for desired 120° sector coverage of cellular mobile communications. A special feed network with good performance is designed to excite the MIMO array. The MIMO array introduces a broad bandwidth of 43.7% (0.68–1.06 GHz) for reflection coefficient $< -15$ dB, as well as good isolation of more than 25 dB between all the ports. Steady radiation pattern with an HPBW of 64 ± 7° and low sidelobe level of below −15 dB is observed, which is desirable for modern mobile communications.