Multi-beam multiplexing design for arbitrary directions based on the interleaved subarray architecture

Through a common set of analogue coefficients and a simple digital coding scheme in the form of ones and minus ones, a previous technique can only multiplex two beams whose directions satisfy a fixed relationship. In this work, two novel designs are proposed, which together with the corresponding inter-subarray coding schemes, can achieve multi-beam multiplexing for arbitrary directions to serve corresponding users. In the first design, based on the relationship of directions between the two required beams, the adjacent antenna spacing is regarded as a variable to be determined, while in the second design, the adjacent antenna spacing is fixed and an alternate optimisation procedure is proposed to solve the problem based on a least-square formulation. Designed examples based on uniform linear arrays and uniform planar arrays are provided to demonstrate the effectiveness of the proposed methods.