A compact 180° hybrid for mode-based beamforming networks

In this work, a compact cascadable 180deg hybrid is proposed for use in the mode-based beamforming networks described. It utilizes a pair of broadside-coupled asymmetric coplanar stripline (ACPS) to achieve strong coupling required by the lambda/4 coupled-line section, and at the same time, to facilitate a cascadable realization. While presenting the fundamental principles for the device, some layout issues are also addressed. An experimental verification is provided to validate the proposed concept.