Dielectric TM-Mode Y-Shaped Doublet Structure

Abstract

This paper discusses dielectric TM-mode filters based on high permittivity Y-shaped ceramics. It is shown that this type of ceramic operates as a dual-mode resonator and therefore contributes two reflection zeros as well as one transmission zero (TZ) to the filter response. Hence, it can be interpreted as a doublet structure and used for the realization of quasi-elliptical filter responses of different order. The dual-mode resonator can be used in multiple different filter set-ups: On the one hand, a combination with classical TM$_{010}$-mode resonators is possible to allow the realization of TZs in an in-line filter configuration without using cross-coupling apertures. Therefore, negative or diagonal cross-couplings, which are often difficult to realize and handle, can be avoided. On the other hand, several Y-shaped ceramics can be coupled directly with each other to increase the number of TZs to $n_{fz}=n/2$, where $n$ is the order of the filter. Finally, it is shown that even a combination with extracted pole elements is realizable. Prototypes based on modular segments are manufactured as proof of concept.

Keywords

• Doublet
• dual-Mode
• extracted pole
• TM-mode
• Y-shaped ceramic