Electrically Tunable Open-Stub Bandpass Filters Based on Nematic Liquid Crystals

Tunable filters are crucial in networks for microwave signal processing, but are being stymied for millimeter-wave applications, due to a lack of materials with suitable properties. This study presents liquid-crystal-based filters with tunable passband resonances at 30, 50, and 85 GHz. These filter devices additionally provide an interesting method to characterize the dielectric properties of liquid crystals (and solids and liquids in general) in the 1--1000 GHz frequency range. Such a method promotes better engineering of planar microwave devices, and the scientific investigation of materials, in this frequency range.