scholarly journals Design Optimization of Reconfigurable Liquid Crystal Patch Antenna

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 932
Author(s):  
Dowon Kim ◽  
Kitae Kim ◽  
Hogyeong Kim ◽  
Moonyoung Choi ◽  
Jun-Hee Na
Keyword(s):  
Liquid Crystal ◽  
Patch Antenna ◽  
Satellite Communication ◽  
Smart Antenna ◽  
Design Method ◽  
Antenna System ◽  
Dielectric Anisotropy ◽  
Radiation Characteristics ◽  
Liquid Crystal Material ◽  
Tunable Frequency

In various fields such as the 5G antenna system and satellite communication system, there is a growing demand to develop a smart antenna with a frequency selective or beamforming function within a limited space. While antennas utilizing mechanical, electronic, and material characteristics are being studied, a method of having tunable frequency characteristics by applying a liquid crystal material with dielectric anisotropy to a planar patch antenna is proposed. In resonance mode, the design method for using only the minimum amount of expensive liquid crystals is systematically arranged while maximizing the amount of change in the operating frequency of the antenna by considering the electric field distribution on the surface of the patch antenna. Furthermore, to increase the dielectric anisotropy of the liquid crystal, the liquid crystal must be aligned. Simultaneously, in cases where the cell gap of the liquid crystal exceeds 100 μm, the alignment force is weakened. While compensating for this shortcoming, securing the radiation characteristics of the antenna is proposed, and simulations are performed.

scholarly journals MEASUREMENT OF THE DIELECTRIC PROPERTIES OF LIQUID CRYSTAL MATERIAL FOR MICROWAVE APPLICATIONS

2019 ◽  
Author(s):  
Juan R. Sanchez ◽  
Vicente Nova ◽  
Carmen Bachiller ◽  
Belen Villacampa ◽  
Alberto De la Rua ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Dielectric Properties ◽  
Dielectric Permittivity ◽  
Loss Tangent ◽  
Dielectric Material ◽  
Orientational Order ◽  
Dielectric Anisotropy ◽  
Microwave Devices ◽  
Liquid Crystal Material ◽  
Microwave Applications

Liquid Crystal (LC) is an anisotropic liquid material which flows like a liquid, but at the same time its molecules have an orientational order like in the solid state [1]. Thus, LC is a promising dielectric material for designing reconfigurable devices at microwave frequencies. In order to optimize the design of reconfigurable microwave devices, accurate values of the dielectric permittivity and the loss tangent of LCs are needed. However, new LCs are not well characterized at these frequencies because of its recent use for microwave applications. Therefore, the characterization in this frequency range is required for its practical use within microwave components and devices [2].   In this work, the split-cylinder resonator method has been used for the characterization of LCs at two frequency points, i.e. 5 and 11 GHz. The method is based on the measurement of the resonance frequency and quality factor of the two states of the LC molecules for extracting the complex dielectric permittivity [3].   For achieving these two states, no electric or magnetic fields are needed, just the cell must be turned 90º inside the cavity. The dielectric properties (permittivity and loss tangent) of four different LC samples, GT3-23002 from Merck and QYPD193, QYPD142, and QYPD036 from Qingdao QY Liquid Crystal Co, have been obtained. The highest values of the dielectric anisotropy are presented for the samples QYPD036 and QYPD193, together with the highest values of the corresponding loss tangent parameters. Furthermore, it is observed for all the LCs that the loss tangent decreases and the dielectric anisotropy increases at higher frequencies, which must be taken into account in the development of reconfigurable microwave devices.

Electron beam irradiation induced changes in liquid-crystal compound 5CB

2008 ◽  
Vol 16 (4) ◽  
Author(s):  
M. Rath ◽  
S. Sarkar ◽  
V. Wadhawan ◽  
R. Verma ◽  
I. Das ◽  
...  
Keyword(s):  
Electron Beam ◽  
Liquid Crystal ◽  
Electron Beam Irradiation ◽  
Spectroscopic Characterization ◽  
High Energy ◽  
Dielectric Anisotropy ◽  
Beam Irradiation ◽  
Isotropic Liquid ◽  
Time Resolved ◽  
Liquid Crystal Material

AbstractElectron beam irradiation studies on liquid crystal material 5CB have been carried out at a temperature where the compound exists in the isotropic liquid phase. In situ time-resolved spectroscopic characterization was carried out during the irradiation. Three different transients were observed during the 2-μs electron pulse. After about 50 μs, only one transient species was found to be present, which has an absorption peak at 360 nm. Radiolysed sample exhibits a broad absorption at ∼400 nm. The dielectric measurements show that even a low level of irradiation results in a dramatic increase in the component of dielectric permittivity normal to the long axes of the molecules ε⊥′, and a corresponding decrease in the dielectric anisotropy (Δε′=ε∥′−ε⊥′ ). These studies show that 5CB is prone to substantial radiation damage on exposure to the beam of high-energy electrons.

scholarly journals Signal Amplification in an Optical and Dielectric Biosensor Employing Liquid Crystal-Photopolymer Composite as the Sensing Medium

Biosensors ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 81
Author(s):  
Hassanein Shaban ◽  
Shih-Chun Yen ◽  
Mon-Juan Lee ◽  
Wei Lee
Keyword(s):  
Dielectric Constant ◽  
Liquid Crystal ◽  
Uv Irradiation ◽  
Signal Amplification ◽  
Limit Of Detection ◽  
Optical Signal ◽  
Uv Exposure ◽  
Dielectric Anisotropy ◽  
Optical Texture ◽  
Potential Development

An optical and dielectric biosensor based on a liquid crystal (LC)–photopolymer composite was established in this study for the detection and quantitation of bovine serum albumin (BSA). When the nematic LC E7 was doped with 4-wt.% NOA65, a photo-curable prepolymer, and photopolymerized by UV irradiation at 20 mW/cm2 for 300 s, the limit of detection determined by image analysis of the LC optical texture and dielectric spectroscopic measurements was 3400 and 88 pg/mL for BSA, respectively, which were lower than those detected with E7 alone (10 μg/mL BSA). The photopolymerized NOA65, but not the prepolymer prior to UV exposure, contributed to the enhanced optical signal, and UV irradiation of pristine E7 in the absence of NOA65 had no effect on the optical texture. The effective tilt angle θ, calculated from the real-part dielectric constant ε’, decreased with increasing BSA concentration, providing strong evidence for the correlation of photopolymerized NOA65 to the intensified disruption in the vertically oriented LC molecules to enhance the optical and dielectric signals of BSA. The optical and dielectric anisotropy of LCs and the photo-curable dopant facilitate novel quantitative and signal amplification approaches to potential development of LC-based biosensors.

Electro-thermal tuning in a negative dielectric cholesteric liquid crystal material

2008 ◽  
Vol 103 (9) ◽  
pp. 093107 ◽  
Author(s):  
Lalgudi V. Natarajan ◽  
Jeremy M. Wofford ◽  
Vincent P. Tondiglia ◽  
Richard L. Sutherland ◽  
Hilmar Koerner ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Cholesteric Liquid Crystal ◽  
Crystal Material ◽  
Liquid Crystal Material ◽  
Thermal Tuning
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