Liquid crystal dielectric constant measuring device based on waveguide resonant cavity structure and application thereof

Abstract

The application discloses a liquid crystal dielectric constant measuring device based on a waveguide resonant cavity structure and application thereof, and belongs to the technical field of microwave device engineering.The application solves the problem that the dielectric parameter characterization of the existing liquid crystal material is not accurate enough.The application is based on a waveguide resonant cavity, an EMNZ metamaterial structure is constructed, and a metal photon doping structure is constructed to effectively stimulate the EMNZ effect, so that electromagnetic response sensing is realized by using the extremely high Q value response characteristics and high sensitivity, accurate characterization of the dielectric characteristics of the liquid crystal material in different states is realized, and the accuracy of the dielectric parameter characterization of the liquid crystal material is improved.

Description

Technical Field

[0001] This invention relates to a liquid crystal dielectric constant measurement device based on a waveguide resonant cavity structure and its application, belonging to the field of microwave device engineering technology. Background Technology

[0002] Liquid crystals are anisotropic materials. As uniaxial crystals, their molecules have a specific orientation along their long axes. Under the influence of an external electric or magnetic field, the orientation of the long axes of liquid crystal molecules will deflect, causing a change in the macroscopic dielectric constant of the liquid crystal material. This characteristic makes it applicable to the design of radio frequency (RF) switches. Because liquid crystal materials require relatively low external driving voltages, the problem of high electromagnetic interference in RF switches based on ferrite or ferroelectric materials can be solved.

[0003] Currently, tunable microwave devices and antenna technologies based on liquid crystal materials have been fully developed and are widely used in various scenarios such as the Internet of Things, satellite communication, and 5G mobile networks. Various structural and functional devices, such as liquid crystal tunable filters, liquid crystal tunable phase shifters, liquid crystal electrically controlled beam scanning antennas, and liquid crystal tunable metasurfaces, have been designed and applied in various modern communication scenarios, demonstrating significant practical application value.

[0004] However, as an anisotropic liquid material, liquid crystals exhibit node parameters in the form of tensors. Traditional methods for calculating dielectric constants struggle to accurately characterize these parameters. This leads to discrepancies between the design results and actual test results of tunable microwave devices based on liquid crystals, sometimes even rendering prototypes unusable and severely limiting research and development efficiency. Therefore, providing a device for measuring the dielectric constant of liquid crystals to achieve accurate measurement of the dielectric properties of liquid crystal materials is essential. Summary of the Invention

[0005] This invention addresses the problem of insufficient accuracy in the characterization of dielectric parameters of existing liquid crystal materials by providing a liquid crystal dielectric constant measurement device, measurement method, and application based on a waveguide resonant cavity structure.

[0006] The technical method of the present invention:

[0007] One objective of this invention is to provide a liquid crystal dielectric constant measurement device based on a waveguide resonant cavity structure. This device includes an upper metal cover plate 1, a lower metal body 2, an intermediate metal structure 3, and a filling medium 4. The intermediate metal structure 3 and the filling medium 4 are located within a cavity formed by bolts fixing the upper metal cover plate 1 and the lower metal body 2. The lower metal body 2 includes a first rectangular cavity and two second rectangular cavities. Both second rectangular cavities communicate with the first rectangular cavity and are arranged perpendicularly to each other on adjacent sidewalls of the first rectangular cavity. The upper part; the second rectangular cavity is filled with filling medium 4; the middle metal structure 3 is a cuboid with a T-shaped through groove, located at the center of the first rectangular cavity, the dielectric plate 5 and the liquid crystal material to be tested are encapsulated in the gap with an opening in the T-shaped through groove; the dielectric plate 5 is a double-layer plate structure, with a metal patch 8 and a feed plate connected to the metal patch through a metal bias line between the two dielectric plates 5, one of the dielectric plates 5 has a test cavity 6, and the liquid crystal material to be tested is located in the test cavity 6; liquid injection holes 7 are opened at the corresponding positions of the middle metal structure 3 and the test cavity 6 of the dielectric plate 5.

[0008] Further specifying, the size of the metal patch 8 is l3×w3.

[0009] Further specifying, an SMA connector 9 is connected to the outside of the lower metal body 2.

[0010] Further, the lower metal body 2 is provided with a flange structure corresponding to its shape at the opening, and the lower metal body 2 is connected to the upper metal cover plate 1 by using the flange structure.

[0011] Further specified, the upper metal cover plate 1 is provided with threaded holes 10.

[0012] Further specifying, the upper metal cover plate 1, the lower metal body 2, and the middle metal structure 3 are made of aluminum alloy 6061.

[0013] Further specifying, the filling medium 4 and the medium plate 5 are made of Rogers 4350B material.

[0014] Further defined, the inner dimensions of the first rectangular cavity are l1×h1×w1, the inner dimensions of the second rectangular cavity are l2×h1×w2, the dimensions of the intermediate metal structure are l4×h1×w4, the dimensions of the dielectric plate are l5×h2×w5, and the length of the cavity to be tested is d2.

[0015] Further specifying the structural parameters when the operating frequency is 7GHz, the specific parameters are as follows: w1 = 38mm, w2 = 10mm, w3 = 3mm, w4 = 8mm, w5 = 3mm, l1 = 38mm, l2 = 50mm, l3 = 22mm, l4 = 10mm, l5 = 0.516mm, h1 = 32mm, h2 = 29mm, d2 = 6.5mm.

[0016] The second objective of this invention is to provide a method for using the above-mentioned liquid crystal dielectric constant measurement device based on a waveguide resonant cavity structure, specifically using the perturbation method to test the dielectric constant and loss tangent of the liquid crystal material.

[0017] Furthermore, the aforementioned liquid crystal dielectric constant measurement device based on waveguide resonant cavity structure can be applied to radio frequency circuits, antennas, radar, or wireless communication systems.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) Based on waveguide resonant cavity, this invention constructs EMNZ metamaterial structure to accurately characterize the dielectric properties of liquid crystal materials under different states, improves the accuracy of dielectric parameter characterization of liquid crystal materials, and solves the problem of low design efficiency of existing tunable microwave devices based on liquid crystal materials.

[0020] (2) This invention achieves effective excitation of the EMNZ effect by constructing a metal photonic doped structure, thereby utilizing its extremely high Q-value response characteristics and high sensitivity to realize electromagnetic response sensing, and further improves the accuracy of dielectric parameter characterization of liquid crystal materials.

[0021] (3) In order to add voltage drive to the liquid crystal material, the present invention covers the liquid crystal layer with a metal patch and connects it to the feed plate structure through a metal bias line, so that the voltage provided by the positive electrode of the power supply can be effectively fed to the liquid crystal region, thereby realizing the characterization of node parameters of liquid crystal molecules in different states.

[0022] (4) The present invention uses the resonance method to measure and extract dielectric properties, so its accuracy has a significant advantage over the transmission line method; and the provided test device can realize flexible control of the liquid crystal material under test in the working frequency band, which has the significant advantages of simple design and high efficiency; at the same time, the device also has the advantage of miniaturization, reducing the preparation cost and making the preparation simple. Attached Figure Description

[0023] Figure 1 A schematic diagram of the liquid crystal dielectric constant measuring device based on a waveguide resonant cavity structure provided by the present invention;

[0024] Figure 2 This is a schematic diagram of the lower metal body structure;

[0025] Figure 3 This is a schematic diagram of the structure of the intermediate metal;

[0026] Figure 4 To test the corresponding transmission response simulation results for different liquid crystal materials;

[0027] Figure 5 This is a comparison between the dielectric constant and loss tangent of the liquid crystal material calculated using the perturbation method and the theoretical values;

[0028] In the figure, 1-upper metal cover plate, 2-lower metal body, 3-middle metal structure, 4-filling medium, 5-medium plate, 6-test chamber, 7-injection hole, 8-metal patch, 9-SMA connector, 10-threaded hole. Detailed Implementation

[0029] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0031] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0032] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] Example 1

[0034] Reference Figure 1 , Figure 2 and Figure 3This embodiment provides a liquid crystal dielectric constant measuring device operating at a frequency of 7 GHz. The device includes an upper metal cover plate 1, a lower metal body 2, an intermediate metal structure 3, and a filling medium 4. The intermediate metal structure 3 and the filling medium 4 are located within a cavity formed by bolts fixing the upper metal cover plate 1 and the lower metal body 2. The lower metal body 2 includes a first rectangular cavity and two second rectangular cavities. The two second rectangular cavities are connected to the first rectangular cavity and are arranged perpendicularly to each other on two adjacent side walls of the first rectangular cavity. The second rectangular cavities are filled with the filling medium 4. The intermediate metal structure 3 is a cuboid with a T-shaped through-slot located at the center of the first rectangular cavity. The dielectric plate 5 and the liquid crystal material to be tested are encapsulated in the gap with an opening in the T-shaped through-slot. A liquid injection hole 7 is opened at the corresponding position of the intermediate metal structure 3 and the liquid crystal material to be tested. An SMA connector 9 is connected to the outside of the lower metal body 2. With this configuration, the first rectangular cavity hollow metal structure with dimensions l1×w1 is used to realize the ENZ effect under the excitation of the metal waveguide structure; the intermediate metal structure 3 with dimensions l4×w4 is used as a metal photonic doping structure, and the dielectric substrate and the liquid crystal material under test are encapsulated in the slit structure of the intermediate metal structure 3. A significant electric field enhancement effect is formed in the slit structure, and the electric field in this region exhibits extremely strong electric field confinement characteristics and extremely strong directionality, thus realizing accurate characterization and sensing of the liquid crystal material under test.

[0035] The dielectric substrate 5 has a double-layer structure, with a metal patch 8 and a feed plate connected to the metal patch via a metal bias line between the two dielectric substrates 5. One of the dielectric substrates 5 has a cavity 6 to be measured. The metal patch 8 has dimensions of l3×w3. This configuration, by adding a l3×w3 metal patch 8 structure between the two dielectric substrates 5 and connecting it to the feed plate structure via a metal bias line, effectively feeds the voltage provided by the positive terminal of the power supply to the liquid crystal region to be measured, applying voltage drive to the liquid crystal molecules and enabling the characterization of node parameters of the liquid crystal molecules in different states.

[0036] The upper metal cover plate 1, lower metal body 2, and intermediate metal structure 3 are made of aluminum alloy 6061. The filling medium 4 and medium plate 5 are made of Rogers 4350B material. The lower metal body 2 has a flange structure with a corresponding shape at its opening, which is used to connect the lower metal body 2 to the upper metal cover plate 1. The inner dimensions of the first rectangular cavity are l1×h1×w1, the inner dimensions of the second rectangular cavity are l2×h1×w2, the dimensions of the intermediate metal structure are l4×h1×w4, the dimensions of the medium plate are l5×h2×w5, and the length of the cavity to be measured is d2. Specifically, w1 = 38mm, w2 = 10mm, w3 = 3mm, w4 = 8mm, w5 = 3mm, l1 = 38mm, l2 = 50mm, l3 = 22mm, l4 = 10mm, l5 = 0.516mm, h1 = 32mm, h2 = 29mm, and d2 = 6.5mm.

[0037] Based on the above structure, different liquid crystal materials were filled into the cavity under test 6, and the corresponding transmission response simulation results are as follows. Figure 4 As shown, by Figure 4 It can be seen that the transmission response S 21 The obvious differences indicate that the above structure can effectively sense the dielectric properties of different test materials, laying the foundation for subsequent extraction of dielectric parameters based on the perturbation method.

[0038] The dielectric constant and loss tangent of the liquid crystal material were calculated using the perturbation method and compared with the theoretical values. The results are as follows: Figure 5 As shown, the results indicate that the dielectric constant of the liquid crystal material extracted using this method is almost consistent with the theoretical value, further verifying the effectiveness of the above-mentioned device.

[0039] Finally, it should be noted that the above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A liquid crystal dielectric constant measuring device based on a waveguide resonant cavity structure, characterized in that, The device comprises an upper metal cover, a lower metal body, an intermediate metal structure, and a filling medium. The intermediate metal structure and filling medium are located within a cavity formed by bolts fixing the upper metal cover and the lower metal body. The lower metal body includes a first rectangular cavity and two second rectangular cavities, both of which communicate with the first rectangular cavity and are arranged perpendicularly to each other on adjacent sidewalls of the first rectangular cavity. The second rectangular cavities are filled with the filling medium. The intermediate metal structure is a cuboid with a T-shaped slot, located at the center of the first rectangular cavity. A dielectric plate and the liquid crystal material to be tested are encapsulated within the opening of the T-shaped slot. The dielectric plate has a double-layer structure, with a metal patch and a feed plate connected to the metal patch via a metal bias line between the two dielectric plates. One dielectric plate has a test cavity, and the liquid crystal material to be tested is located within the test cavity. Injection holes are provided at positions corresponding to the test cavities on the intermediate metal structure and the dielectric plate. The size of the metal patch is: l 3× w 3; The internal dimensions of the first rectangular cavity are l 1× h 1× w 1. The internal dimensions of the second rectangular cavity are: l 2× h 1× w 2. The dimensions of the intermediate metal structure are: l 4× h 1× w 4. The dimensions of the dielectric substrate are: l 5× h 2× w 5. The length of the cavity to be tested is d 2.

2. The measuring device according to claim 1, characterized in that, An SMA connector is attached to the outside of the lower metal body.

3. The measuring device according to claim 1, characterized in that, The lower metal body has a flange structure at its opening, which is used to connect the lower metal body to the upper metal cover plate.

4. The measuring device according to claim 1, characterized in that, The upper metal cover, the lower metal body, and the middle metal structure are made of aluminum alloy 6061.

5. The measuring device according to claim 1, characterized in that, The filler medium and the medium plate are made of Rogers 4350B material.

6. The measuring device according to claim 1, characterized in that, The specific structural parameters of this device when operating at a frequency of 7GHz are as follows: w 1=38mm, w 2 = 10mm w 3 = 3mm, w 4 = 8mm w 5 = 3mm l 1=38mm, l 2=50mm, l 3 = 22mm l 4 = 10mm l 5 = 0.516 mm h 1 = 32mm h 2=29mm, d 2 = 6.5mm.

7. A method for measuring the dielectric constant of liquid crystal, characterized in that, Using the apparatus according to any one of claims 1 to 6, the dielectric constant and loss tangent of the liquid crystal material are tested by the perturbation method.

8. A method for measuring the dielectric constant of a liquid crystal based on a waveguide resonant cavity structure as described in any one of claims 1 to 6, characterized in that, This device is used in radio frequency circuits, antennas, radar, or wireless communication systems.

Images