Design of Multistate Cavity Diplexers Based on Coaxial Resonators

Abstract

The design approach for multistate diplexers based on coaxial resonators is presented for the first time in this letter. By partitioning a large cylindrical cavity into multiple sections, a wide range of frequency channels is established, enabling the formation of different states for the diplexer through the selection of specific frequency channels. By introducing cross coupling in the resonators, a transmission zero is achieved within each channel, resulting in sharp out-of-band rejection skirts. The proposed multistate diplexers exhibit improved performance along with compact structures. A third-order four-state diplexer (FSD) is designed and presented, and the same methodology can be applied to create the mth-order and n-state diplexers. To validate this concept, the FSD is fabricated and measured, with the measurement results exhibiting good agreement with the simulation results.