Ridge waveguide branch-line directional couplers for wideband applications and LTCC technology

A new branch-line directional coupler is proposed for achieving wide bandwidth. The device is implemented in ridge waveguide to exploit its wide monomode band. It can be physically realized either in empty ridge waveguide or in LTCC for integration in a chip module. Two prototypes of two and five branches are designed following a systematic procedure. An appropriate equivalent circuit provides initial dimensions and the desired optimum response is obtained by means of a final full-wave optimization based on the rigorous and efficient Mode-Matching method. The results are verified with the Finite Element Method of the HFSS software and a prototype will be manufactured for testing.