Liquid crystal microwave dielectric constant measurement sensor based on spoof localized surface plasmon

Liquid crystal materials have good modulation characteristics in the microwave band, and have great potential for application in the field of microwave tunable devices. In this paper, a sensor based on the resonance of spoof localized surface plasmon is proposed for the demand of microwave dielectric constant measurement of liquid crystal materials. The ring resonator structure is designed to form narrow -band resonant peaks in the sub-6 GHz band with localized surface surface plasmon. By applying an applied electric field to the liquid crystals, the modulation of the liquid crystal dielectric constant can be achieved. The corresponding dielectric constant can be obtained by fitting the position of the resonant frequency points, thus realizing the measurement of the dielectric constant of the liquid crystal material in the microwave band. The effects of different liquid crystal layer thicknesses and different liquid crystal dielectric constants on the resonant frequency points of the spoof localized surface plasmon are studied. The resonant frequency points f1 and f2 increase gradually with the increases of the liquid crystal layer thickness or the decreases of the liquid crystal dielectric constant. When the thickness of liquid crystal layer is equal or greater than 0. 5 mm, the resonant frequency points f1 and f2 have good linearity with the change of the liquid crystal dielectric constant. The proposed sensor has a high sensitivity (>400 MHz/ & UDelta;& epsilon;), which is much larger than that based on other forms of dielectric constant sensors reported so far. At the same time, this sensor structure can apply electric field above and below the liquid crystal layer, thus realizing the measurement of microwave dielectric constant of liquid crystal materials under the action of different applied electric fields, which has potential for application in the field of microwave characterization of liquid crystals.