Dual-band rat-race hybrid design with considering of junction reactance

The design of rat-race hybrid that can operate at two widely separated frequency bands is presented. The junction reactance is considered in the design process. The final circuit has an asymmetrical structure. The proposed circuit features high isolation, wide bandwidth (lager than 300MHz at low operating frequency band and 250MHz at high operating frequency band). For validation, both simulated and measured performances of a microstrip rat-race coupler operating at 2.45/5.8 GHz are shown.