4-port Microstrip Ferrite Coupled-Line Circulator

A 4-port microstrip Ferrite Coupled-Line (FCL) circulator is designed at 11.4 GHz by cascading a longitudinally-magnetized FCL structure with a 180° hybrid coupler. A broadband 180° hybrid ring with a bandwidth of approximately 7 GHz is realised by employing stepped impedance sections on the hybrid coupler. The simulated results of the respective sections are presented in this paper. The scattering matrix of the cascaded 4-port microstrip FCL circulator is predicted using a power flow diagram.