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Potential of Liquid-Crystal Materials for Millimeter-Wave Application

Department of Intelligent Mechatronics, Faculty of Systems Science and Technology, Akita Prefectural University, Yurihonjyo, Akita 015-0055, Japan
Author to whom correspondence should be addressed.
Appl. Sci. 2018, 8(12), 2544;
Received: 31 October 2018 / Revised: 28 November 2018 / Accepted: 3 December 2018 / Published: 8 December 2018
(This article belongs to the Special Issue Liquid Crystal THz Photonics: Materials, Devices and Applications)
In this study, we reviewed three topics regarding the application of liquid-crystal (LC) materials to millimeter-wave (MMW) devices. It is essential to develop useful measurement methods for refractive indices of LC materials in the MMW region. Herein, a novel measurement method using optical short is demonstrated using a Si semiconductor substrate. There are two approaches to develop MMW LC devices. One is the quasi-optical approach, which involves scaling up the optical components, and the other approach involves integrating the LC materials into high-frequency electric circuits. A three-dimensional (3D) printer is used to fabricate the Fresnel lens, which is a typical quasi-optical device useful in the MMW region, where we can develop the tunable lens by introducing LC materials. A planar-type MMW waveguide is advantageous for integrating the LC materials to develop LC MMW devices using the second approach. We investigated a useful microstrip-line-type LC phase shifter by developing a novel conversion circuit to introduce the LC material onto the dielectric substrate surface. A phase shifter is an important MMW component that is used to attain a phased array antenna system, and a minimal twin antenna array is demonstrated using the microstrip-line-type LC phase shifters. View Full-Text
Keywords: liquid crystal; millimeter wave; refractive index; 3D printer; Fresnel lens; phase shifter; phased array; beam steering liquid crystal; millimeter wave; refractive index; 3D printer; Fresnel lens; phase shifter; phased array; beam steering
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Nose, T.; Ito, R.; Honma, M. Potential of Liquid-Crystal Materials for Millimeter-Wave Application. Appl. Sci. 2018, 8, 2544.

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