Folded C-Type SIW Butler Matrix

This work presents a novel miniaturized 4×4 Butler Matrix (BM) base on Folded C-Type substrate integrated waveguide (FCSIW), operating from 28 to 32GHz. In theory, the size of FCSIW can be reduced by nearly 50% compared with the substrate integrated waveguide (SIW) with similar propagation and cut-off characteristics. However, this excellent size reduction characteristic has not been widely used in millimeter wave equipment. Therefore, a modified BM multi-beam forming network based on FCSIW is proposed. The multibeam forming network is composed of directional coupler, crossover and phase shifter. The overall dimension of the novel BM is 1.04λ0 ×5.54λ0, which is half smaller than the traditional single-layer BM size. The compact BM will be an attractive candidate for future 5G terminal applications.