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Open AccessArticle

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

by Jinfeng Li 1,2 and Daping Chu 1,*
1
Centre for Photonic Devices and Sensors, University of Cambridge, Cambridge CB3 0FA, UK
2
Department of Electrical and Electronic Engineering, Imperial College London, London SW7 2AZ, UK
*
Author to whom correspondence should be addressed.
Crystals 2019, 9(12), 650; https://doi.org/10.3390/cryst9120650
Received: 29 October 2019 / Revised: 4 December 2019 / Accepted: 4 December 2019 / Published: 6 December 2019
(This article belongs to the Special Issue Microwave Liquid Crystal Technology)
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. View Full-Text
Keywords: liquid crystal; millimeter-wave; phase shifter; enclosed coplanar waveguide; 60 GHz; tunable circuits and devices; true time delay liquid crystal; millimeter-wave; phase shifter; enclosed coplanar waveguide; 60 GHz; tunable circuits and devices; true time delay
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MDPI and ACS Style

Li, J.; Chu, D. Liquid Crystal-Based Enclosed Coplanar Waveguide Phase Shifter for 54–66 GHz Applications. Crystals 2019, 9, 650.

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