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 degrees phase compensation is introduced to design the MIMO array to obtain stable half power beamwidth (HPBW) of around 64 degrees for desired 120 degrees 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 degrees and low sidelobe level of below -15 dB is observed, which is desirable for modern mobile communications.