Continuously Tunable 3-D Printed Helical Resonators and Bandpass Filters Using Actuated Liquid Metals

Abstract

This letter reports on a new class of agile helical resonators and bandpass filters (BPFs) with continuously-tunable center frequency. RF tuning is achieved by altering the liquid metal (LM) volume within an additively-manufactured plastic tube that has the shape of a helix and forms the inner conductor of the helical resonator. A low-cost and versatile integration scheme using 3-D printing and pneumatically-actuated Galinstan is proposed. For proof-of-concept validation purposes, a helical resonator with center frequency tuning between 1 and 1.5 GHz, and unloaded quality factor between 131 and 145 was manufactured and measured. Two BPF porotypes namely: 1) two-pole BPF with center frequency tuning between 1.16 and 1.49 GHz and insertion loss (IL) < 2 dB and 2) three-pole BPF with center frequency tuning between 1.18 and 1.49 GHz, and IL < 2.1 dB, were manufactured and tested at L-band.

Wireless Reading and Localization of Additively Manufactured Galinstan-Based Sensor Using a Polarimetric Millimeter-Wave Radar Imaging Technique

“…The combined use of Galinstan with an electromagnetic cavity is often motivated to design tunable devices such as bandpass filters [34], [35], [36], [37], [38], resonators [39], or phase-shifters [40], [41], [42]. In this work, the cavity acts as a temperature sensor.…”