Novel uniplanar 180/spl deg/ hybrid-ring couplers with spiral-type phase inverters

Novel uniplanar 180/spl deg/ hybrid-ring couplers consisting of coplanar-waveguide (CPW) rings and spiral-type phase inverters are proposed. In this study, CPW phase inverters with single-spiral and twin-spiral type slotline short stubs are utilized to design the hybrid-ring couplers. Specifically, two hybrid-ring couplers with 33% (single-spiral type) and 40% (twin-spiral type) bandwidths are implemented and examined, theoretically and experimentally.