Analysis, design and applications of the triple-mode conductor-loaded cavity filter

This study presents the analysis and design of a new triple-mode filter that employs the recently proposed triple mode conductor-loaded cavity resonator. The resonator consists of a cubic-shaped metallic structure suspended in a metallic enclosure. The resonator is mounted in the cavity through a low-loss low-dielectric-constant support structure. The triple-mode conductor-loaded cavity resonator is considerably cheaper, easier to design and manufacture, and offers a significantly wider spurious-free response in comparison with the triple-mode dielectric resonator. A six-pole filter is designed using Ansoft HFSS employing the proposed triple mode conductor-loaded cavity resonator. The analysis shows that introducing asymmetry into the structure of the resonator in the form of chamfers or corner cuts creates the necessary perturbation to achieve the required coupling between the degenerate modes inside each block to realise the desired filter response. The six-pole triple-mode conductor-loaded cavity filter is fabricated and tested. Finally, two applications of the proposed concept are identified. The triple mode conductor-loaded cavity resonator is combined with higher Q-factor triple-mode ceramic resonators to realise a small size, high Q-factor filter with wide spurious-free response. Also, a direct-coupled band-stop filter is proposed employing the triple-mode conductor-loaded cavity filter.