Liquid-Crystal-Based Floating-Electrode-Free Coplanar Waveguide Phase Shifter with an Additional Liquid-Crystal Layer for 28-GHz Applications

2021 ◽  
Author(s):  
Junseok Ma ◽  
Jin Young Choi ◽  
Seung-Won Oh ◽  
Wook-Sung Kim
Keyword(s):  
Liquid Crystal ◽  
Phase Shifter ◽  
Coplanar Waveguide ◽  
Characteristic Impedance ◽  
Thickness Variation ◽  
Driving Voltage ◽  
Electrode Thickness ◽  
Electric Flux ◽  
First Time ◽  
Floating Electrode

Abstract A liquid-crystal (LC)-based floating electrode-free (FE-free) coplanar waveguide (CPW) phase shifter with an additional LC layer is demonstrated for the first time. An LC layer is overlain on the electrodes of the original model; this change increases the amount of electric flux that the proposed structure can confine in the tunable region, and thereby greatly increases the figure-of-merit (FoM) while maintaining the benefits of the simple coplanar structure. We simulated the variations in the phase shifter’s FoM, characteristic impedance, and driving voltage while sweeping the additional LC layer thickness up to 300 μm with each electrode condition at 28 GHz. In the case of electrode thickness variation, the FoM increased as electrode thickness increased, regardless of the presence of the additional LC layer. However, in the case of the signal electrode width variation, we obtained an opposite FoM tendency depending on the presence of the additional LC layer. This work shows the possibility of an efficient LC-based FE-free CPW phase shifter design for a given LC layer and electrode conditions.

scholarly journals Response Improvement of Liquid Crystal-Loaded NRD Waveguide Type Terahertz Variable Phase Shifter

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 307 ◽  
Author(s):  
Trong Nghia Lang ◽  
Van Bao Bui ◽  
Yo Inoue ◽  
Hiroshi Moritake
Keyword(s):  
Liquid Crystal ◽  
Response Time ◽  
Phase Change ◽  
Decay Time ◽  
Phase Shifter ◽  
Dielectric Anisotropy ◽  
Driving Voltage ◽  
Crystal Layer ◽  
Liquid Crystal Layer ◽  
Waveguide Type

Liquid crystals, which have high dielectric anisotropy even in the terahertz region and are easily controllable for dielectric permittivity by applying an electric field, have become increasingly attractive in recent years. The non-radiative dielectric (NRD) waveguide has a structure in which a dielectric line is sandwiched between two metal plates and by replacing the dielectric part with liquid crystal, a low loss liquid crystal-loaded NRD waveguide type terahertz phase shifter can be obtained. However, since the thickness of the liquid crystal layer is several hundred micrometers, it has a response time of as long as several hundred seconds when the driving voltage is removed. It is necessary to devise improvements for practical application. By inserting two polyethylene terephthalate (PET) films and reducing the thickness of the liquid crystal layer, the decay time was improved well, but the phase change was significantly reduced. In this study, we report improving both decay time and phase change with aligned nanofiber/liquid crystal complex. In addition, we demonstrate liquid crystal-load phase shifter, which has 360° phase change and the response time below one second.

scholarly journals Liquid Crystal-Based Enclosed Coplanar Waveguide Phase Shifter for 54–66 GHz Applications

Crystals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 650 ◽  
Author(s):  
Jinfeng Li ◽  
Daping Chu
Keyword(s):  
Liquid Crystal ◽  
Phase Shifter ◽  
Coplanar Waveguide ◽  
Time Domain Reflectometry ◽  
Device Fabrication ◽  
Metallic Surface ◽  
Volume Distribution ◽  
60 Ghz ◽  
Phase Tuning ◽  
Tunable Dielectrics

A 0–10 V bias voltage-driven liquid crystal (LC) based 0°–180° continuously variable phase shifter was designed, fabricated, and measured with insertion loss less than −4 dB across the spectrum from 54 GHz to 66 GHz. The phase shifter was structured in an enclosed coplanar waveguide (ECPW) with LC as tunable dielectrics encapsulated by a unified ground plate in the design, which significantly reduced the instability due to floating effects and losses due to stray modes. By competing for spatial volume distribution of the millimeter-wave signal occupying lossy tunable dielectrics versus low-loss but non-tunable dielectrics, the ECPW’s geometry and materials are optimized to minimize the total of dielectric volumetric loss and metallic surface loss for a fixed phase-tuning range. The optimized LC-based ECPW was impedance matched with 1.85 mm connectors by the time domain reflectometry (TDR) method. Device fabrication featured the use of rolled annealed copper foil of lowest surface roughness with nickel-free gold-plating of optimal thickness. Measured from 54 GHz to 66 GHz, the phase shifter prototype presented a tangible improvement in phase shift effectiveness and signal-to-noise ratio, while exhibiting lower insertion and return losses, more ease of control, and high linearity as well as lower-cost fabrication as compared with up-to-date documentations targeting 60 GHz applications.

Design of filtering tunable liquid crystal phase shifter based on coplanar waveguide and split-ring resonators

2019 ◽  
Vol 46 (15) ◽  
pp. 2127-2133
Author(s):  
Chang Ding ◽  
Fan-Yi Meng ◽  
Hui-Lin Mu ◽  
Jian-Qiao Han ◽  
Chuan-Hong Zhao ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Phase Shifter ◽  
Coplanar Waveguide ◽  
Ring Resonators ◽  
Crystal Phase ◽  
Liquid Crystal Phase ◽  
Split Ring ◽  
Split Ring Resonators

scholarly journals Twisted Nematic Liquid-Crystal-Based Terahertz Phase Shifter using Pristine PEDOT: PSS Transparent Conducting Electrodes

2019 ◽  
Vol 9 (4) ◽  
pp. 761 ◽  
Author(s):  
Anup Sahoo ◽  
Chan-Shan Yang ◽  
Chun-Ling Yen ◽  
Hung-Chun Lin ◽  
Yu-Jen Wang ◽  
...  
Keyword(s):  
Thin Films ◽  
Liquid Crystal ◽  
Phase Shifter ◽  
Phase Shifters ◽  
Driving Voltage ◽  
Transparent Conducting ◽  
Twisted Nematic ◽  
Twisted Nematic Liquid Crystal ◽  
Pristine Pedot ◽  
Transparent Conducting Electrodes

For this study, we demonstrated three different types of twisted nematic (TN) liquid crystal (LC) terahertz (THz) phase shifters using pristine poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT: PSS) thin films as transparent conducting electrodes (TCEs). The transmittance of spin-coated pristine PEDOT: PSS thin film was as high as 92% in the frequency range of 0.2–1.2 THz. This is among the highest reported. Several TN-LC cells were constructed in a comparative study, which confirmed the reliability of pristine PEDOT: PSS as a TCE layer for THz phase shifter applications. The highest phase shift, required root-mean-square (RMS) driving voltage, and threshold voltage achieved by devices tested were 95.2° at 1 THz, 7.2 VRMS, and 0.5 VRMS, respectively. The thickness of the LC layer for the phase shifter was 250 µm, approximately half as thick as previous designs. In addition, the pristine PEDOT: PSS-based TN-LC phase shifter exhibited a figure-of-merit (FOM) value of approximately 6.65 degree·dB−1·V−1. This compared favorably with previously reported homogeneously aligned phase shifters with an FOM of 2.19 degree·dB−1·V−1. Our results indicated that a twisted nematic LC cell with pristine PEDOT: PSS thin films as electrodes is a good combination for a THz phase shifter and wave plates as well as other LC-based THz devices.

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