A Large-scale Compact Base Station Antenna Array with Improved Radiation Performance

This work presents a large-scale compact base station antenna array with improved radiation patterns, realized gains and high port isolation. The compact 6 × 4 antenna array, which is in uniform configuration, has a small spacing between two columns of antennas(every column of antenna is a subarray) that is only 0.36λ (λ is the free space wavelength at center frequency, 1.95GHz) and it is well known that the small spacing leads to severe distortion of radiation patterns of antenna array and decrease of realized gains, which critically deteriorates the beamforming ability of base station antenna array. A method is proposed to effectively improve the radiation performance of large-scale compact dual-polarized antenna array. At first, the metal baffles are used to improve the distorted radiation patterns of the compact antenna array. The baffles are placed between every two subarrays to concentrate the radiation energy of antennas so that the distortion of radiation patterns are improved. Furthermore, a nonuniform metasurface is proposed and placed above the array to enhance the realized gains of the antenna array. The metasurface consists of periodic metal patches and substrates. The periodic structures above two edge subarrays and four other subarrays are different because of the difference of radiation characteristics of subarrays at different positions, which realizes highest enhancement of the realized gains. This array is simulated by Ansys HFSS software and the simulated results show that in the operating frequency band, 1.71GHz–2.17GHz, the reflection coefficients of all ports are below −17dB and the mutual couplings between every two ports are below −22dB. The realized gain of central subarray is enhanced from 9.15±1.05dBi to 10.4±0.6dBi and smooth radiation patterns are realized, which contribute to accurate beamforming of the antenna array. This work provides a valid method to improve radiation performance of large-scale compact antenna array and the proposed array is a good candidate for application in compact 2G/3G/4G/5G integration base station antenna array.