CN-116466141-B - Liquid crystal complex dielectric constant measuring device and measuring method and application thereof

Abstract

The invention discloses a liquid crystal complex dielectric constant measuring device, a measuring method and application thereof, and belongs to the technical field of microwave device engineering. The invention solves the problem that the accurate characterization of the dielectric parameters of the liquid crystal material cannot be realized by the existing measurement mode. The liquid crystal dielectric parameter extraction method provided by the invention is based on a near-zero dielectric constant metamaterial transmission structure, the structure is realized by adopting a dumbbell-shaped rectangular waveguide and mainly comprises two-end wide waveguides and a middle narrow waveguide structure, and the near-zero dielectric constant metamaterial can form a super-coupling channel in a narrow waveguide area, so that an electric field shows extremely strong electric field constraint characteristic and extremely strong directivity in the area, and further, the liquid crystal material filled in the area realizes the perception of electromagnetic characteristic. Meanwhile, a thermal sensor is arranged above the narrow waveguide area, and when a thermal platform is adopted for heating, accurate temperature parameters are obtained, so that accurate characterization of liquid crystal node parameters under different temperature conditions is realized.

Inventors

• DING CHANG
• JI WENLONG
• MU HUILIN
• JIA YUXIANG
• SUI SAI
• ZHU RUICHAO
• WANG JIAFU
• QU SHAOBO

Assignees

• 中国人民解放军空军工程大学

Dates

Publication Date

20260512

Application Date

20230414

Claims (9)

1. 1. A liquid crystal complex dielectric constant measuring device is characterized by comprising a metal shell, a metal bottom plate, an upper medium layer, a lower medium layer, a metal patch and a feed patch, wherein the upper medium layer, the lower medium layer, the metal patch and the feed patch are positioned in a cavity formed by fixing the metal shell and the metal bottom plate through bolts, the lower medium layer is a dumbbell-shaped groove formed in the metal bottom plate, a rectangular through hole is formed in the middle of the lower medium layer, a liquid crystal material to be measured is positioned in the rectangular through hole, the rectangular through hole is covered with the metal patch, the upper end of the metal shell is provided with a U-shaped through groove rectangular cavity, the bottom of the U-shaped through groove is provided with a through hole, the upper medium layer is a dumbbell-shaped structure with two ends high and middle low, the upper medium layer is sleeved in the metal shell, the feed patch is positioned on the upper surface of the upper medium layer, the metal patch is positioned on the lower surface of the upper medium layer, two ends of the metal shell are respectively connected with an SMA joint, and the upper medium layer and the lower medium layer are all nearly zero dielectric constant meta-materials.
2. 2. The liquid crystal complex permittivity measurement device according to claim 1, wherein the upper medium comprises two large cuboids of size l 1 ×h 2 x w, and the two large cuboids are connected into a whole through a small cuboid of size l 2 ×h×w 4 ; When the working frequency is 2GHz, specific structural parameters are as follows: , , , 。
3. 3. The liquid crystal complex permittivity measurement device according to claim 2, wherein a thermal sensor having a radius x is further mounted on the metal case, and the thermal sensor is inserted on opposite side walls of the metal case and is located above the small rectangular parallelepiped.
4. 4. The liquid crystal complex permittivity measurement device according to claim 1, wherein the metal case has a width w 1 and a height h 1 ; When the working frequency is 2GHz, specific structural parameters are as follows: 。
5. 5. the liquid crystal complex permittivity measurement device according to claim 1, wherein the size of the metal patch is A bias line is connected to one side of the metal patch, and penetrates out of the through hole to be connected with the positive electrode of the power supply; When the working frequency is 2GHz, specific structural parameters are as follows: , 。
6. 6. The liquid crystal complex permittivity measurement device according to claim 1, wherein the lower medium comprises two large rectangular plates with a size of l 1 ×h 3 ×w, and the two large rectangular plates are connected into a whole through a small rectangular plate with a size of l 2 ×h 3 ×w 4 ; When the working frequency is 2GHz, specific structural parameters are as follows: , , , 。
7. 7. The liquid crystal complex permittivity measurement device according to claim 6, wherein the rectangular through hole is formed in the middle of the small rectangular plate, and has a size of l 3 ×h 3 ×w 3 , the thickness of the outer edge of the groove of the metal bottom plate and the thickness of the shell of the metal shell are both h 5 , and the depth of the dumbbell-shaped groove is h 4 ; When the working frequency is 2GHz, specific structural parameters are as follows: , , And 。
8. 8. A method for measuring complex dielectric constant of liquid crystal, characterized in that the device according to any one of claims 1 to 7 is used to measure dielectric constant and loss tangent of liquid crystal material at different temperatures by perturbation method.
9. 9. Use of a liquid crystal complex permittivity measurement device according to any one of claims 1 to 7, characterized in that the device is used in a radio frequency circuit, an antenna, a radar or a wireless communication system.

Description

Liquid crystal complex dielectric constant measuring device and measuring method and application thereof Technical Field The invention relates to a liquid crystal complex dielectric constant measuring device, a measuring method and application thereof, and belongs to the technical field of microwave device engineering. Background Liquid crystal is an anisotropic material, and as a uniaxial crystal, the molecular long axis of the material has a specific orientation, and the orientation of the long axis of the liquid crystal molecule is deflected under the action of an applied electric field or magnetic field, so that the macroscopic dielectric constant of the liquid crystal material is changed. Such characteristics make it possible to use it in the design of radio frequency switches. The problem of large electromagnetic interference of the radio frequency switch based on ferrite or ferroelectric materials can be solved because the external driving voltage required by the liquid crystal material is smaller. At present, adjustable microwave devices and antenna technology based on liquid crystal materials are fully developed, and are widely applied in various scenes such as the Internet of things, satellite communication, 5G mobile networks and the like. The liquid crystal adjustable filter, the liquid crystal adjustable phase shifter, the liquid crystal electric control wave beam scanning antenna, the liquid crystal adjustable super surface and other various structural and functional devices are designed and applied to various modern communication scenes, and the liquid crystal adjustable wave beam scanning antenna has important practical application value. However, as a liquid anisotropic material, the node parameters of the liquid anisotropic material are expressed in tensor form, and the dielectric parameters of the liquid anisotropic material are difficult to accurately represent by the traditional dielectric constant calculation method, so that a certain difference exists between the design result and the actual test result of the adjustable microwave device based on the liquid anisotropic material, even the actual sample cannot be used, and the research and development efficiency is severely limited. Therefore, it is necessary to provide a device for measuring the complex dielectric constant of liquid crystal, so as to accurately measure the dielectric properties of the liquid crystal material. Disclosure of Invention Aiming at the problem that the existing measurement mode can not realize accurate characterization of dielectric parameters of liquid crystal materials, the invention provides a liquid crystal complex dielectric constant measurement device, a measurement method and application thereof. The technical method comprises the following steps: The invention aims to provide a liquid crystal complex dielectric constant measuring device which comprises a metal shell 1, a metal bottom plate 2, an upper medium 3, a lower medium 4, a metal patch 6 and a feed patch 7, wherein the upper medium 3, the lower medium 4, the metal patch 6 and the feed patch 7 are positioned in a cavity formed by fixing the metal shell 1 and the metal bottom plate 2 through bolts, the lower medium 4 is a dumbbell-shaped groove formed in the metal bottom plate 2, a rectangular through hole 5 is formed in the middle of the lower medium 4, a liquid crystal material to be measured is positioned in the rectangular through hole 5 during testing, the rectangular through hole 5 is covered with the metal patch 6, the metal shell 1 is a rectangular cavity with a U-shaped through groove at the upper end, a through hole 10 is formed in the bottom of the U-shaped through groove, the upper medium 3 is a dumbbell-shaped cavity with two ends high and a middle low, the upper medium 3 is sleeved in the metal shell 1, the feed patch 7 is positioned on the upper surface of the upper medium 3, the metal patch 6 is positioned on the lower surface of the upper medium 3, two ends of the metal shell 1 are respectively connected with an SMA joint 9, and the upper medium 3 and the lower medium 4 are near-zero dielectric constant materials. Further defined, the upper medium 3 comprises two large cuboids 3-1 with dimensions l 1×h2 ×w, which are connected together by a small cuboid 3-2 with dimensions l 2×h×w4. Still further defined, i 1＝140mm,h2＝18.3mm,l2＝60mm,w4 = 50mm. Further defined, the metal casing 1 is also provided with a thermal sensor 8 with a radius x, and the thermal sensor 8 is inserted on two opposite side walls of the metal casing 1 and is located above the small cuboid 3-1. Further defined is the width w 1 and the height h 1 of the metal housing 1, and the size a 1×b1 of the feeding patch 7. Further defined, w 1＝85mm,h1 = 58.5mm. Further defined, the metal patch 6 has a rectangular structure with a dimension w 2×l4, and a bias line 6-1 is connected to one side of the metal patch 6, and the bias line 6-1 passes through the through hole 10 to