A Miniaturized Double-Stage 3dB Broadband Branch-Line Hybrid Coupler Using Distributed Capacitors

A miniaturized double-stage 3dB branch-line hybrid coupler using distributed capacitors in the inner area is proposed in this paper. It is composed of high impedance transmission lines with reduced length and distributed capacitors. Compared to a conventional double-stage branch-line hybrid coupler, which is typically used to obtain wider bandwidth than a single-stage approach can provide, the proposed topology allows for considerable size reduction, while maintaining similar electrical performance. For experimental validation, a conventional single-stage 3dB hybrid coupler, a conventional double-stage, and a miniaturized double-stage hybrid couplers are designed and fabricated. The size of the proposed miniaturized double-stage 3dB broadband branch-line hybrid coupler is reduced by 39.04% and 68.32% compared to a single-stage and a conventional double-stage branch-line hybrid coupler, respectively.