Planar 180° hybrid coupler with non-interspersed ports for millimeter-wave applications

Abstract

AbstractThis paper presents a simple topology of 180° hybrid coupler with non-interspersed inputs and outputs, as opposed to the conventional rat-race topology. Such hybrid coupler topologies with inputs located on one side and outputs at the opposite side simplify the design of signal routings and module packaging when integrated with other circuits and components. It also relaxes the necessity of using auxiliary compensating components such as tapers, jumpers, and crossovers. The proposed coupler topology is theoretically analyzed through a T-matrix approach. The analysis comes up with design equations and diagrams that help choose the structural parameters for the desired specification. The simplicity and also the immunity against intrinsic parasitic effects within the proposed topology make it an excellent candidate for operation over any RF and millimeter-wave frequency bands, for applications such as automotive radar or E-band backhaul radio. To this end, a coupler based on the proposed scheme is realized for operation over 77 GHz and assessed through on-wafer measurements. Good agreement of the measured results with the simulated and analytical counterparts demonstrates the superior performance of the proposed 180° hybrid coupler.