MIMO Antenna for Indoor Low-Band 5G Base Stations

A broadband high efficiency cavity-backed antenna with independent beams is presented. The design is milled in a metallic box and capacitively fed by 4 coaxial cables. Matching is accomplished with the use of an impedance transformer created by the extension of the coaxial inner conductor. This antenna is a compact, and low-cost solution which can be easily manufactured to be mounted as a 5G indoor base station antenna providing MIMO behaviour due to its four independent beams. The operating frequency band ranges from 3 GHz to 5 GHz (50%), covering the early deployment 5G low band. The results of the simulations show a total efficiency greater than 67%. By properly feeding the ports, the antenna can be configured to radiate with horizontal polarization, vertical polarization or circular polarization. The overall dimensions of the antenna are λ
_c
×λ
_c
×0.25λ
_c
, where λ
_c
the wavelength at the central frequency (4 GHz).