Characterization of Nematic Liquid Crystal Dielectric Properties Using Complementary FSSs Featuring Electrically Small Cell Gaps Across a Wide Sub-THz Range

Liquid crystal (LC) is a valuable material for constructing tunable devices in the sub-terahertz (sub-THz) spectrum, and to utilize it effectively, it is imperative to accurately measure the permittivity of the LC. Frequency-selective surfaces (FSSs) serve as an effective tool for assessing LC permi...

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Bibliographic Details
Published in:IEEE transactions on antennas and propagation 2024-02, Vol.72 (2), p.2019-2024
Main Authors: Kim, Daehyeon, Choi, Jinyoung, Youn, Youngno, Chang, Suho, Lee, Cheonga, Kim, Wooksung, Hong, Wonbin
Format: Article
Language:English
Subjects:
Broadband
Characterization
complementary frequency-selective surface (CFSS)
D-band
Dielectric properties
Electric fields
Extraction procedures
Finite element method
Frequency selective surfaces
liquid crystal (LC)
Liquid crystals
Metals
Nematic crystals
Permittivity
Permittivity measurement
Resonant frequency
Sensitivity
sub-terahertz (sub-THz)
Terahertz frequencies
Transmission line measurements
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Summary:Liquid crystal (LC) is a valuable material for constructing tunable devices in the sub-terahertz (sub-THz) spectrum, and to utilize it effectively, it is imperative to accurately measure the permittivity of the LC. Frequency-selective surfaces (FSSs) serve as an effective tool for assessing LC permittivity in the sub-THz frequencies. However, existing research lacks measurements of the loss tangent and exhibits certain limitations and sources of error. In this communication, we propose a multiloop complementary FSS (CFSS) structure to extract the permittivity of LC at sub-THz. The designed multiloop CFSS exhibits high sensitivity despite featuring an extremely thin LC cell gap of less than 10 \mu \text{m} , the smallest cell gap to be reported in the literature for such applications. The structure can estimate LC permittivity across a broadband range by utilizing multiresonant characteristics. Moreover, we propose a procedure using an averaged inhomogeneous model, thereby enabling accurate calculation of LC permittivity. The proposed method estimates the parallel and perpendicular permittivity and loss tangent of the LC using the measurement results and comparison with the finite element simulation results. The permittivity extraction procedure is experimentally verified in the D-band (110-170 GHz).
ISSN:0018-926X
1558-2221
DOI:10.1109/TAP.2023.3344274