Design of convex and concave dual bent array for 5G lens antenna system

Abstract

Previous research on the multi-beam system for the fifth generation (5G) application has shown that the number of feed elements of a lens antenna system at the mobile base station is increasing due to the massive MIMO requirements. The design of the array circuits of the 5G lens antenna systems will be more complicated due to the feeding structure, which consists of the power dividers and phase shifters, thus contributing to higher feeding losses. The antenna fabrication process also becomes more complicated. Besides that, the conventional array feed also produces a single radiation beam only. Thus, a large space is needed, where array feed antennas should be arranged to perform wide-angle beam scanning for 5G massive MIMO operation. Therefore, to overcome these issues, this paper uses a bent array configuration as the lens antenna feed to produce bifurcated beam radiation and has a wide beam angle from the feed radiator to the lens edge. Multiple bent arrays are arranged on the lens axis to generate a multi-beam by cylindrical lens antenna. This paper shows a comparison of the bent array in convex and concave configurations. This process investigates the mutual coupling when more than one bent array is arranged as feed radiators. By comparing the arrays in convex and concave structures, it is observed that the convex structure produces a better-bifurcated beam with a smaller middle lobe. The antenna also produces the same bifurcated beam shifting angle, θs for both ports, when s = 4λ is used. It is verified as the optimum spacing value between two bent array structures by the optimization process.