Reconfigurable TM-Mode Dielectric Bandpass Filter Using Liquid Metals

This paper reports on an octave-tunable miniaturized TM
010
-mode dielectric bandpass filter based on pneumatically-actuated liquid metals. The resonant frequency is tuned with the movement of the liquid metal which functions as a movable metallic post inside the inner hole of the dielectric resonators. Compared with the conventional screw-based tuning, the proposed technique features faster and more stable tuning process because of the assured excellent electrical contact, continuously for all tuning states. For verification, a second-order TM
010
-mode dielectric bandpass filter is designed, fabricated, and tuned using a non-toxic liquid metal alloy commercially known as “Galinstan”. The measured responses exhibit high tuning capabilities with octave tuning ratio of 1:2.22 over a broad window of 1.51 GHz from 1.24 GHz to 2.75 GHz. Further, the presented filter has many desirable merits as the high quality-factor, miniaturized structure, and simple configuration.