Improvement of decay time in nematic-liquid-crystal-loaded coplanar-waveguide-type microwave phase shifter by polymer stabilizing method

Abstract

Polymer stabilization by UV light irradiation in nematic liquid crystals is proposed to improve the decay time of coplanar-waveguide-type microwave phase shifters. The effect of polymer concentration on the decay time of polymer-stabilized nematic liquid crystals is confirmed by a dielectric experiment on a liquid-crystal-sandwiched indium–tin-oxide (ITO) glass cell before loading into a coplanar-waveguide-type microwave phase shifter. The decay time, phase shift value, and insertion loss of microwave phase shifters with different polymer concentrations are measured. The decay time of polymer-stabilized nematic liquid crystals in the microwave phase shifter markedly decreases compared with that of pure nematic liquid crystals. It is confirmed that the use of polymer-stabilized nematic liquid crystals is effective to improve the response time of microwave phase shifters.

Graphene-Augmented Polymer Stabilization: Drastically Reduced and Temperature-Independent Threshold and Improved Contrast Liquid Crystal Device

“…However, the reduction in V th between the non-CNT and CNT systems was only about 20%, in contrast to a factor of 7 diminution seen in the current studies for the graphene-incorporated system. In fact, such a large reduction in V th is unprecedented in the PSLC/PDLC systems, wherein nanostructures of various kinds have been incorporated, ,− especially so considering that the concentration of the graphene employed here is extremely small (0.01%). The fact that the lowered V th and its thermal invariance have been achieved without any special functionality imposed on the nanostructure (graphene) is attractive and suggests that there is a huge potential for generalization of the methodology, which allows for various nanostructures to be incorporated for strengthening the polymer fibers.…”

Microwave Liquid Crystal Enabling Technology for Electronically Steerable Antennas in SATCOM and 5G Millimeter-Wave Systems

“…To enable faster relaxation of the LC molecules, special classes of LC materials have been investigated such as polymer-stabilized nematic LCs [72,233,234], porous PTFE membranes impregnated with LC [185,235,236], nematic LCs doped with nanoparticles [51,185,[237][238][239][240], ferroelectric LCs [51,241,242], ferroelectric LC mixtures doped with carbon nanotubes [243], BaTiO 3 nanoparticles suspended in a ferroelectric LC mixture [244] and dual-frequency LCs [51,62,186,245]. This can improve the response time by one up to two orders of magnitude compared to pure nematic LCs.…”

Design of liquid crystal based coplanar waveguide tunable phase shifter with no floating electrodes for 60–90 GHz applications

“…However, limited by the current status of LC mm-wave technology in which most of the LC-based devices have been designed for <40 GHz, LC-based tunable phase shifters and other phase components are not well established in the frequency regime of 60-90 GHz. LC-based coplanar waveguide (CPW) variable phase shifters reported [2] [3] were based on tuning in the interlayer between coplanar electrodes and the floating electrode (FE) on top. This has an advantage of relatively fast electrically tuning speed due to the thin LC layer required.…”