Reconfigurable Cavity Bandpass Filters Using Fluid Dielectric

Rui-Sen Chen,Yin Li,Sai-Wai Wong,Lei Zhu,Long Zhang,Jing-Yu Lin,Yejun He,Yang Yang

doi:10.1109/tie.2020.3009566

Abstract

A novel method for the development of a reconfigurable cavity bandpass filter using fluid dielectric is proposed. Dielectric material can produce an effective permittivity ε eff of the resonant mode when it is loaded into the cavity. Thus, a tube filled with fluid dielectric, e.g., distilled water, can achieve controlled and reversible ε eff by adjusting the amount of water in the tube. The same manner of resonant frequency can be achieved as the resonant frequency is related to ε eff , and then frequency tuning is realized. The fluid property can realize easier and faster tuning mechanism than conventional solid dielectric. As ε eff is affected by the loaded dielectric parallel to the electric field, a triple-mode resonator with resonant modes TE 101 , TE 011 , and TM 110 , which have orthogonal electric fields, is investigated to realize tri-band reconfiguration. The ε eff , as well as the resonant frequencies, corresponding to each mode can be individually controlled by adjusting their related water posts. Then, reconfigurable single-band and tri-band bandpass filters are designed. A reconfigurable tri-band cavity filter using a triple-mode cavity resonator and fluid dielectric with individual and continuous frequency tuning is reported for the first time. Finally, the reconfigurable tri-band filter is fabricated and measured to validate the concept.

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