Reconfigurable Design of mmWave Liquid-Crystal Frequency Selective Surface at Ka-Band

• Published in: IEEE transactions on electromagnetic compatibility Vol. 64; no. 5; pp. 1734 - 1741
• Main Authors: Chou, Hsi-Hsir, Ke, Guan-Jhou, Lin, Cheng-Chung, Lin, Guo-Sheng
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.10.2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Anisotropy; Bandpass filter; Dielectrics; Electromagnetic radiation; Extremely high frequencies; Frequency deviation; frequency selective surface (FSS); Frequency selective surfaces; Lighting; Liquid crystals; liquid crystals (LCs); Millimeter waves; Nematic crystals; Permittivity; polarization-insensitivity; Prototypes; Reconfiguration; Resonant frequency; Substrates; Tolerances; Voltage
• ISSN: 0018-9375; 1558-187X
• DOI: 10.1109/TEMC.2022.3193995

A reconfigurable design of frequency selective surface (FSS) using nematic liquid crystal (LC) materials is reported. The proposed LC-FSS resonates at Ka-band frequencies to provide a bandpass nature. The frequency selection was achieved by altering the dielectric anisotropy of LC materials. This study used a low-cost Merck-E7 LC material with dielectric tunability of nearly 0.45 to study the resonance characteristics. Full-wave simulations have achieved a frequency tunability range of 5.06%. An LC-FSS prototype of 7 cm × 7 cm in size was fabricated for experimental evaluation, consisting of 25 × 25 unit cells. The measurement results show that a maximum frequency tunability close to 4.8% has been achieved for a normally incident illumination of electromagnetic waves. Moreover, the maximum frequency deviations were only 4.73% and 4.94% with/without a bias voltage to shift the center frequency. These experimental results have precisely verified the numerical simulations despite the frequency deviations resulting from the fabrication tolerances.