Inline Quasi-Elliptic Dielectric Resonator Filters With Mixed Coupling Using Dielectric Junction

The conventional implementation of a quasi-elliptic dielectric resonator (DR) filter with electric coupling usually leads to high manufacturing and performance costs due to the need for additional accessories, such as capacitive probes and fixtures. To address this issue, this article proposes a new electric coupling structure using a dielectric junction. The junction is connected between two coupled rectangular DRs and enables electric coupling when it is parallel to the electric components of TE
$_{11\delta }$
mode. Two stretched holes are introduced to improve spurious-free window while enhancing electric coupling strength. Furthermore, the dielectric junction can cooperate with the inductive iris of the enclosure to enable mixed electric and magnetic coupling. This allows the construction of an Nth-order quasi-elliptic filter using inline topology with up to N
$-$
1 transmission zeros (TZs). For demonstration, six filters with different filter orders and TZs requirements are designed. For validation, one of them is fabricated and measured. Reasonable agreement can be observed between the simulated and measured results. Compared to the traditional method, the proposed one offers several advantages, including fewer accessories, lower manufacturing cost, better spurious performance, and higher quality factor.