Miniaturized couplers using multi-mode star-junction

This paper proposes a novel multi-mode star junction, which consists of eight three-conductor structures connected in a star configuration. It also proposes its equivalent circuit model and its application in the design of compact size 90ᵒ hybrid and rat-race couplers. The areas of the proposed designs are 50% and 20% of the conventional ones, respectively, without degrading the electrical characteristics. The couplers are fabricated and characterized. Measurements, which are in a very good agreement with the EM simulations, confirm the theoretical predictions.