Liquid crystal complex permittivity measuring device, measuring method and application thereof

Abstract

The application discloses a liquid crystal complex permittivity measuring device and a measuring method and application thereof, and belongs to the technical field of microwave device engineering. The application solves the problem that the existing measuring method cannot realize accurate characterization of the dielectric parameters of liquid crystal materials. The liquid crystal dielectric parameter extraction method provided by the application is based on a near-zero permittivity metamaterial transmission structure, the structure is realized by adopting a dumbbell-shaped rectangular waveguide, mainly comprises a wide waveguide at two ends and a narrow waveguide in the middle, and the near-zero permittivity metamaterial can form a super-coupling channel in the narrow waveguide area, so that the electric field in the area exhibits extremely strong electric field confinement characteristics and extremely strong directivity, and further enables the liquid crystal material filled in the area to realize sensing of electromagnetic characteristics. Meanwhile, a thermal sensor is arranged above the narrow waveguide area, when heating is performed by using a thermal platform, accurate temperature parameters are acquired, and therefore, accurate characterization of liquid crystal node parameters under different temperature conditions is realized.

Description

Technical Field

[0001] This invention relates to a liquid crystal complex permittivity measuring device, its measuring method, 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 a liquid anisotropic material, the node parameters of liquid crystal materials are in the form of tensors. Traditional methods for calculating dielectric constants are difficult to accurately characterize their dielectric parameters. This often leads to discrepancies between the design results and actual test results of tunable microwave devices based on liquid crystal materials, and may even render actual prototypes unusable, severely limiting research and development efficiency.

[0005] Therefore, it is essential to provide a device for measuring the complex dielectric constant of liquid crystals to achieve accurate measurement of the dielectric properties of liquid crystal materials. Summary of the Invention

[0006] This invention addresses the problem that existing measurement methods cannot accurately characterize the dielectric parameters of liquid crystal materials by providing a liquid crystal complex dielectric constant measuring device, its measurement method, and its application.

[0007] The technical method of the present invention:

[0008] One objective of this invention is to provide a liquid crystal complex dielectric constant measuring device. This device includes a metal housing 1, a metal base plate 2, an upper dielectric 3, a lower dielectric 4, a metal patch 6, and a power supply patch 7. The upper dielectric 3, lower dielectric 4, metal patch 6, and power supply patch 7 are located within a cavity formed by bolts fixing the metal housing 1 and the metal base plate 2. The lower dielectric 4 is dumbbell-shaped and located within a dumbbell-shaped groove in the metal base plate 2. A rectangular through-hole 5 is formed in the center of the lower dielectric 4. During testing, the liquid crystal under test... The material is located inside a rectangular through-hole 5, and a metal patch 6 covers the rectangular through-hole 5; the metal housing 1 is a rectangular cavity with a U-shaped through-slot at the top and a through-hole 10 at the bottom of the U-shaped through-slot; the upper dielectric 3 is dumbbell-shaped with high ends and low middle; the upper dielectric 3 is fitted inside the metal housing 1, and the power supply patch 7 is located on the upper surface of the upper dielectric 3, and the metal patch 6 is located on the lower surface of the upper dielectric 3; each end of the metal housing 1 is connected to an SMA connector 9; both the upper dielectric 3 and the lower dielectric 4 are near-zero dielectric constant metamaterials.

[0009] Further defining the upper medium 3, it includes two large cuboids 3-1 with dimensions l1×h2×w, which are connected as one unit by a small cuboid 3-2 with dimensions l2×h×w4.

[0010] Further specifying, l1 = 140mm, h2 = 18.3mm, l2 = 60mm, w4 = 50mm.

[0011] Furthermore, a thermal sensor 8 with a radius of x is also installed on the metal housing 1. The thermal sensor 8 is inserted into two opposite side walls of the metal housing 1 and is located above the small cuboid 3-1.

[0012] Further specified, the width of the metal casing 1 is w1 and the height is h1; the size of the power supply patch 7 is a1×b1.

[0013] Further specifying, w1 = 85mm, h1 = 58.5mm.

[0014] Further defining the dimensions, the metal patch 6 is a rectangular structure with dimensions of w2×l4. 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 and is connected to the positive terminal of the power supply.

[0015] Further specifying, w2 = 35mm, l4 = 52mm.

[0016] Further defining the lower medium 4, it comprises two large rectangular plates with dimensions l1×h3×w, which are connected as one unit by a small rectangular plate with dimensions l2×h3×w4.

[0017] Further specifying, l1 = 140mm, h3 = 0.762mm, l2 = 60mm, h3 = 0.762mm, w4 = 50mm.

[0018] Further specified, the rectangular through hole 5 is opened in the middle of the small rectangular plate, with dimensions of l3×h3×w3; the outer edge thickness of the groove of the metal base plate 2 is h5, and the groove depth is h4.

[0019] Further specifying, l3 = 40mm, h3 = 0.762mm, w3 = 25mm, h5 = 6mm.

[0020] The second objective of this invention is to use the aforementioned liquid crystal complex dielectric constant measuring device to test the dielectric constant and loss tangent of liquid crystal materials at different temperatures, specifically employing the perturbation method.

[0021] Furthermore, the aforementioned liquid crystal complex permittivity measuring device can be applied to radio frequency circuits, antennas, radar, or wireless communication systems.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) The present invention provides a device and method for accurately extracting the dielectric parameters of liquid crystal based on near-zero dielectric constant metamaterials, which improves the defects in the liquid crystal material tunable microwave device technology caused by the inability of existing technology to accurately determine the dielectric parameters of liquid crystal.

[0024] (2) The liquid crystal dielectric parameter extraction method provided by the present invention is based on a near-zero dielectric constant (Epsilon-Near-Zero, ENZ) metamaterial transmission structure. This structure is realized by a dumbbell-shaped rectangular waveguide, mainly composed of wide waveguides at both ends and a narrow waveguide in the middle. The near-zero dielectric constant metamaterial can form a super-coupled channel in the narrow waveguide region, so that the electric field exhibits extremely strong electric field confinement characteristics and extremely strong directionality in this region, further enabling the liquid crystal material filled in this region to realize the sensing of electromagnetic properties.

[0025] (3) In order to add voltage drive to liquid crystal molecules, the present invention covers a metal patch on the liquid crystal layer and reverses the bias line connected to the upper structure through the metal via, so that the voltage provided by the positive terminal of the power supply is effectively fed to the liquid crystal region, thereby realizing the characterization of node parameters of liquid crystal molecules in different states.

[0026] (4) The present invention sets a thermal sensor above the narrow waveguide region. When a thermal platform is used for heating, accurate temperature parameters are obtained, thereby realizing accurate characterization of liquid crystal node parameters under different temperature conditions.

[0027] (5) In addition, 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

[0028] Figure 1 This is a schematic diagram of the liquid crystal complex permittivity measuring device provided by the present invention;

[0029] Figure 2 A longitudinal sectional view of the liquid crystal complex permittivity measuring device provided by the present invention;

[0030] Figure 3 This is a front view of the upper medium.

[0031] Figure 4 This is a top view of the upper medium;

[0032] Figure 5 This is a top view of the metal patch;

[0033] Figure 6 This is a top view of the metal base plate;

[0034] Figure 7 Simulation graphs of dielectric property curves obtained from testing different liquid crystal materials;

[0035] Figure 8 The graph shows the dielectric constant curves obtained by testing liquid crystal materials at different temperatures.

[0036] Figure 9 The loss tangent curves are obtained from testing liquid crystal materials at different temperatures.

[0037] In the diagram, 1-metal housing, 2-metal base plate, 3-upper dielectric, 3-1-large cuboid, 3-2-small cuboid, 4-lower dielectric, 5-rectangular through hole, 6-metal patch, 6-1-bias line, 7-power supply patch, 8-thermal sensor, 9-SMA connector, 10-through hole. Detailed Implementation

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] Example 1

[0043] Reference Figure 1 and 2This embodiment provides a liquid crystal complex dielectric constant measuring device operating at a frequency of 2 GHz. The device includes a metal housing 1, a metal base plate 2, an upper dielectric layer 3, a lower dielectric layer 4, a metal patch 6, and a power supply patch 7. The upper dielectric layer 3, lower dielectric layer 4, metal patch 6, and power supply patch 7 are located within a cavity formed by bolts fixing the metal housing 1 and the metal base plate 2. The lower dielectric layer 4 is dumbbell-shaped and located within a dumbbell-shaped groove in the metal base plate 2. A rectangular through hole 5 is formed in the center of the lower dielectric layer 4. During testing, the liquid crystal material under test is located inside a rectangular through-hole 5, and a metal patch 6 covers the rectangular through-hole 5. The metal housing 1 is a rectangular cavity with a U-shaped through-slot at the top and a through-hole 10 at the bottom of the U-shaped through-slot. The upper dielectric 3 is dumbbell-shaped with high ends and low middle. The upper dielectric 3 is fitted inside the metal housing 1, and the power feeding patch 7 is located on the upper surface of the upper dielectric 3, while the metal patch 6 is located on the lower surface of the upper dielectric 3. An SMA connector 9 is connected to each end of the metal housing 1. Both the upper dielectric 3 and the lower dielectric 4 are near-zero dielectric constant metamaterials. With this configuration, the liquid crystal dielectric parameter extraction method designed in this invention is based on a near-zero dielectric constant (Epsilon-Near-Zero, ENZ) metamaterial transmission structure. This structure is realized using a dumbbell-shaped rectangular waveguide. The structure mainly consists of wide waveguides at both ends (w1×h1), a narrow waveguide in the middle (w4×h4), and SMA feeding structures on both sides. The outer layer is a metal structure with a thickness of h5, and the interior is filled with a dielectric structure, which enables the near-zero dielectric constant metamaterial to form a supercoupled channel in the narrow waveguide region.

[0044] like Figure 3 and Figure 4 As shown, the upper medium 3 includes two large cuboids 3-1 with dimensions l1×h2×w, which are connected as one unit by a small cuboid 3-2 with dimensions l2×h×w4. Wherein, l1=140mm, h2=18.3mm, w=65mm, l2=60mm, w4=50mm, and h=0.7mm.

[0045] A thermal sensor 8 with radius x is also installed on the metal housing 1. The thermal sensor 8 is inserted into two opposite side walls of the metal housing 1 and is located above the small cuboid 3-1.

[0046] The metal casing 1 has a width of w1 and a height of h1; the power supply patch 7 has dimensions a1×b1. Wherein, w1=85mm, h1=58.5mm, a1=1mm, b1=1mm.

[0047] like Figure 5 As shown, the metal patch 6 has a rectangular structure with dimensions w2×l4. A bias wire 6-1 is connected to one side of the metal patch 6, and the bias wire 6-1 passes through the through hole 10 and is connected to the positive terminal of the power supply. Wherein, w2=35mm, l4=52mm.

[0048] The lower medium 4 comprises two large rectangular plates with dimensions l1×h3×w, which are connected as one unit by a smaller rectangular plate with dimensions l2×h3×w4. Wherein, l1=140mm, h3=0.762mm, l2=60mm, h3=0.762mm, and w4=50mm.

[0049] A rectangular through hole 5 is formed in the middle of the small rectangular plate, with dimensions of l3×h3×w3; the outer edge thickness of the groove of the metal base plate 2 and the shell thickness of the metal shell 1 are both h5, and the depth of the dumbbell-shaped groove is h4. Wherein, l3=40mm, h3=0.762mm, w3=25mm, h5=6mm, h3=0.7mm, and h4=0.7mm.

[0050] Based on the above structure, the dielectric properties of different liquid crystal materials were simulated, and the results are as follows: Figure 7 As shown, by Figure 7 As can be seen, the transmission response S changes when different materials are added to the cavity region under test. 21 The results show a clear distinction, demonstrating that the aforementioned structure can effectively sense the dielectric properties of different liquid crystal materials under test, laying the foundation for subsequent extraction of dielectric parameters based on the perturbation method.

[0051] Furthermore, the dielectric constant and loss tangent of the liquid crystal material were measured using the perturbation method at different temperatures, and the results are as follows: Figure 8 and 9 As shown, the liquid crystal material exhibits relatively stable dielectric properties at different temperatures, which further verifies the effectiveness of the temperature control device in the proposed method.

[0052] 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 complex permittivity measuring device, characterized in that, The device comprises a metal housing, a metal base plate, an upper dielectric layer, a lower dielectric layer, a metal patch, and a power feed patch. The upper dielectric layer, lower dielectric layer, metal patch, and power feed patch are located within a cavity formed by bolts fixing the metal housing and the metal base plate. The lower dielectric layer is dumbbell-shaped and located within a dumbbell-shaped groove in the metal base plate. A rectangular through-hole is formed in the center of the lower dielectric layer, and the liquid crystal material under test is located within this rectangular through-hole, which is covered by a metal patch. The metal housing is a rectangular cavity with a U-shaped through-slot at the top and a through-hole at the bottom. The upper dielectric layer is dumbbell-shaped, higher at both ends and lower in the middle, and is fitted inside the metal housing. The power feed patch is located on the upper surface of the upper dielectric layer, and the metal patch is located on the lower surface. An SMA connector is connected to each end of the metal housing. Both the upper and lower dielectric layers are near-zero dielectric constant metamaterials.

2. The liquid crystal complex permittivity measuring device according to claim 1, characterized in that, The upper medium includes two dimensions. l 1× h 2× w A large cuboid, two large cuboids are connected by a dimension of... l 2× h × w The four small cuboids are connected as one unit; When the operating frequency is 2GHz, the specific structural parameters are as follows: , , , .

3. The liquid crystal complex permittivity measuring device according to claim 2, characterized in that, A thermal sensor with radius x is also installed on the metal housing. The thermal sensor is inserted into two opposite side walls of the metal housing and located above the small cuboid.

4. The liquid crystal complex permittivity measuring device according to claim 1, characterized in that, The width of the metal casing is w 1. High is h 1; Power supply patch size a 1× b 1; When the operating frequency is 2GHz, the specific structural parameters are as follows: .

5. The liquid crystal complex permittivity measuring device according to claim 1, characterized in that, The size of the metal patch is The rectangular structure has a bias line connected to one side of the metal patch, and the bias line passes through the through hole and is connected to the positive terminal of the power supply. When the operating frequency is 2GHz, the specific structural parameters are as follows: , .

6. The liquid crystal complex permittivity measuring device according to claim 1, characterized in that, The lower medium includes two layers with dimensions of l 1× h 3× w Two large rectangular panels are connected by a dimension of... l 2× h 3× w The four small rectangular plates are connected as one piece; When the operating frequency is 2GHz, the specific structural parameters are as follows: , , , .

7. The liquid crystal complex permittivity measuring device according to claim 6, characterized in that, A rectangular through hole is made in the middle of the small rectangular plate, with dimensions of [missing information]. l 3× h 3× w 3; The thickness of the outer edge of the groove in the metal base plate is the same as the thickness of the metal shell. h 5. The depth of the dumbbell-shaped groove is h 4; When the operating frequency is 2GHz, the specific structural parameters are as follows: , , and .

8. A method for measuring the complex permittivity of liquid crystal, characterized in that, Using the apparatus described in any one of claims 1 to 7, the dielectric constant and loss tangent of the liquid crystal material at different temperatures were tested using the perturbation method.

9. An application of the liquid crystal complex permittivity measuring device according to any one of claims 1 to 7, characterized in that, This device is used in radio frequency circuits, antennas, radar, or wireless communication systems.

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