A Compact Base Station MIMO Antenna Array With Miniaturized Antenna Elements

Multiple-input and multiple-output (MIMO) antenna arrays have become a key component for 5G wireless network. In this brief, a compact base station MIMO antenna array is constructed with a novel miniaturized antenna element. The novelty of the miniaturized antenna design lies in the meander-line radiation arm designs for size miniaturization, and a ring director placed over the aperture for achieving wide impedance bandwidth and stable radiation patterns. The size of the miniaturized antenna element is only 40 mm $\times 40$ mm ( $0.22{\lambda }_{L}\times 0.22{\lambda }_{L}$ ), where ${\lambda }_{L}$ is the wavelength at the lowest frequency of the 1.7-2.7 GHz operating frequency band. The miniaturized antenna enables densely antenna placement with an 80 mm $\times 80$ mm square lattice, while simultaneously offering high port isolation, mutual coupling suppression, and non-distorted antenna radiation patterns in such a crowding array environment. Experimental validation of an array prototype confirms the high port isolation (28 dB), stable realized gain (8±0.3 dB), stable 3 dB beamwidth ( $70^{\circ }\pm 1^{\circ }$ ), and stable 10 dB beamwidth $127^{\circ }\pm 2^{\circ }$ over a 45.5% bandwidth (1.7-2.7 GHz).