LAUSR

A compact substrate integrated waveguide (SIW) three-state diplexer (TSD) is proposed in this Letter for the first time. Basically, the TSD operating in three frequency bands integrates three diplexers in three different states on a single circuit. Meanwhile, TE102, TE201 and TE103 modes, investigated in the cavity, are employed to implement and control the three frequency bands. Each state utilises two of them as duplexing channels as well as excites one port as input to implement relevant functions. Owing to the modal orthogonality, high isolation among these channels could be achieved. To further improve design flexibility, a +-shaped slot, etched on the SIW middle metal surface, is used to control the resonant frequencies independently. To verify, an example SIW TSD has been fabricated and measured, showing good consistency with simulated results.