Differential Dielectric Resonator Filters

This paper presents a detailed investigation of the differential bandpass filters with high performance using the popular TE
_01δ
-mode ring-shaped dielectric resonator (DR). According to the field distribution of the TE
_01δ
mode, the design principle for differentially exciting it is constructed, i.e., a pair of feeding probes should be face-to-face. Under this feeding scheme, it can be found that the resonant modes of the DR cavity can be divided into two kinds of responses, i.e., differential-mode and common-mode responses. Furthermore, the differential feeding scheme is flexible, and then two modified differentially fed structures by changing the positions of differential port pair are introduced to improve the filter selectivity by incorporating an additional transmission zero or to enable the filter to meet the requirement of integration with other differential devices. To validate the proposed idea, several design examples of the differential DR filters are presented, and their simulated and measured results are given.