Tunable whispering gallery mode resonance structure for millimeter-wave/sub-THz applications

This paper presents a novel approach to realize a low-cost wide tunable Whispering Gallery Mode (WGM) resonance-based structure at Millimeter-wave and sub-THz range of frequencies. The tunability is achieved by moving a metallic structure over the WGM resonator using a micro-positioner. Perturbing the WGM resonance causes shift in the resonance frequency and the coupling. Two types of perturbation are tested for two different structures: grounded Alumina-based WGM resonance structure and Silicon-On-Glass (SOG) WGM resonance structure, operating in D-band (110-170 GHz) and G-band (140-220 GHz), respectively. The experimental results reveal the SOG-based resonator has tuning range of 4.5 GHz at 154 GHz and resonance depth better than -20 dB over the tuning range.