A compact patch coupler with an arbitrary phase difference for millimeter-wave applications

This paper presents a millimeter-wave 3 dB coupler configuration to provide an arbitrary phase difference between two output ports. The property can be easily achieved by adjusting the separation angle between ports located on the contour of patch, resulting in a simple design procedure. To verify the feasibility of the proposed configuration, the 60° and 135° patch 3 dB couplers operating at 30 GHz are designed, fabricated and measured. Excellent performance is achieved with a significant size reduction of 84% compared to the conventional substrate integrated waveguide cruciform directional couplers.