Butler-Matrices-Based Omnidirectional Beamforming of Circular/Cylindrical Arrays

The tendency of customized communication has inspired the fifth-generation (5G) and above technologies, characterized by multi-node and localization. Therefore, high requirements are raised of the omni-directional beamforming of base stations. An omnidirectional subarray beamforming scheme is proposed, based on Butler matrix fed array. For this purpose, two array configurations are provided, using circular and cylindrical structures, and fed by multiple Butler matrices, so as to flexibly select sub arrays as excitation. Combined with practical application, the general solution of the connection form of multiple overlapping Butler matrix is derived, based on the circular symmetry. The vertical and azimuth beamforming performance of the proposed array structure is numerically calculated, and the feasibility and superiority of the proposed scheme are verified.