Grid film for realizing ultra-wideband wave absorption by regulating and controlling conductivity and dielectric constant

Abstract

The invention provides the grid film for realizing ultra-wideband wave absorption by regulating and controlling the conductivity and the dielectric constant. Wherein the grid film is a porous film with the conductivity of 10 S / m, the relative dielectric constant of 1 and the thickness of 1 mm, and efficient wave absorption in the ultra-wide frequency range from the microwave high frequency band to the terahertz wave low frequency band can be achieved. The grid film provided by the invention can be prepared by adopting various methods, is convenient to use and can be applied to the fields of future 6G communication and the like.

Description

Technical Field

[0001] The present invention relates to the fields of electromagnetic wave absorption, regulation of electromagnetic parameters of composite materials, and preparation of porous films, and particularly relates to a grid film that realizes ultra-wideband wave absorption by regulating conductivity and permittivity. Background Art

[0002] Absorbing materials and absorbing devices have urgent application requirements in both military and civilian fields. Traditional absorbing materials and absorbing devices often cannot well meet the growing requirements for bandwidth, performance, and size. In particular, the operating frequency band of future 6G communication signals can cover the high-frequency gigahertz (GHz) to terahertz (THz) bands, posing higher requirements for ultra-wideband electromagnetic absorbing and shielding materials.

[0003] To achieve broadband and efficient absorption of microwave and / or terahertz waves, artificial electromagnetic materials, such as porous films, frequency selective surfaces, metamaterials, grid films, etc., have played an important role. Typically, for example: using methods such as sol-gel and chemical vapor deposition to fabricate conductive porous films (the conductivity and permittivity of the porous film can be regulated by controlling the proportion of conductive fillers, the number and pore size of air holes, etc.) for wave absorption or electromagnetic shielding; designing metamaterials with dual-band resonance, loading lumped elements on the unit structure, fabricating low-conductivity metamaterials, using resistive films, resistive rings, arranging unit structures in a plane or vertically stacking multiple layers. Among them, the use of resistive materials has received much attention. However, in conductive thin films, frequency selective surfaces, and metamaterials, conductivity has a complex influence on the electrical and magnetic response characteristics and wave absorption performance, which still needs to be further explored. In addition, the type of thin film and the fabrication method also need to be selected according to requirements. The present invention focuses on considering the conductivity of conductive thin films and the influence of eddy currents on the effective permeability and wave absorption performance, and proposes a grid film that realizes ultra-wideband wave absorption by regulating conductivity and permittivity, which can efficiently absorb waves in a wide frequency range from the high-frequency band of microwaves to the low-frequency band of terahertz waves. The grid film is fabricated by screen printing on the basis of modulating a conductive silver paste with appropriate conductivity, and can also be fabricated by etching, 3D printing, etc. Summary of the Invention

[0004] The purpose of the present invention is to provide a grid film that realizes ultra-wideband wave absorption by regulating conductivity and permittivity, so as to achieve efficient wave absorption in a wide frequency range from the high-frequency band of microwaves to the low-frequency band of terahertz waves, and meet the electromagnetic compatibility requirements in aspects such as future 6G communication.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A grid film that achieves ultra-wideband microwave absorption by regulating conductivity and permittivity. The grid film is a thin film with a conductivity of 10 S / m, a relative permittivity of 1, and a thickness of 1 mm, capable of achieving efficient microwave absorption in an ultra-wide frequency range from the high-frequency microwave band to the low-frequency terahertz wave band.

[0007] Furthermore, due to the influence of eddy currents, the effective relative permeability of the conductive film is less than 1. To avoid excessive impedance mismatch, the grid film is prepared by selecting a low-permittivity material, which includes a matrix material and conductive fillers.

[0008] Furthermore, the grid film has a conductivity in the range of 5 S / m to 10 S / m, a relative permittivity of less than 2, and a thickness of 1 mm, and can maintain broadband high-efficiency microwave absorption performance.

[0009] Furthermore, the effective permittivity not related to the conductivity σ is not considered. When (i is the imaginary unit, ω is the angular frequency, ∈ 0 is the vacuum permittivity), the relative permittivity of the grid film is set to 1.

[0010] Furthermore, the side length of the square grid unit of the grid film is less than 0.15 mm (much smaller than the minimum wavelength of the considered electromagnetic wave), and the area ratio of the grid lines is less than 25%, meeting the requirements of a conductivity value in the range of 5 S / m to 10 S / m and a relative effective permittivity of less than 2.

[0011] Furthermore, the preparation method of the grid film is as follows:

[0012] S1. Using epoxy resin as the matrix, adding a curing agent DDM and silver nanowires to prepare a conductive silver paste with a conductivity value in the range of 5 S / m to 10 S / m.

[0013] S2. Using the prepared conductive silver paste and adopting screen printing technology to make the grid film, or other methods such as etching and 3D printing can also be used.

[0014] An application of a grid film that achieves ultra-wideband microwave absorption by regulating conductivity and permittivity. The grid film can be used in future 6G communication systems to enhance electromagnetic compatibility performance.

[0015] Through the technical solution provided by the present invention, there are at least the following technical effects:

[0016] 1. The grid film with ultra-wideband microwave absorption proposed by the present invention has a working frequency covering the high-frequency microwave band and the low-frequency terahertz wave band, and can be applied to fields such as future 6G communication.

[0017] 2. The grid film with ultra-wideband wave absorption proposed by the present invention focuses on regulating the conductivity and dielectric constant, and has a wider working frequency band compared with the reported thin film absorbers and electromagnetic metamaterial absorbers.

[0018] 3. The grid film with ultra-wideband wave absorption proposed by the present invention can be fabricated by methods such as screen printing, etching, 3D printing, etc., and is convenient to use and easy to maintain. Description of the Drawings

[0019] The drawings are used to provide a further understanding of the embodiments of the present invention, and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the embodiments of the present invention, but do not constitute a limitation to the embodiments of the present invention. In the drawings:

[0020] Figure 1 It is a schematic structural diagram of the ultra-wideband wave-absorbing grid film provided by the present invention. On the left: a side view of the thin film with a thickness h = 1 mm. In the middle: a front view of the thin film. On the right: an enlarged front view of the thin film, where the width of the grid line is a and the interval between adjacent lines is b; the side length a + b of the square grid unit of the grid film is < 0.15 mm, which is much smaller than the minimum wavelength of the considered electromagnetic wave. For simplicity, the conductivity and dielectric constant of the grid film are adopted as effective values during calculation;

[0021] Figure 2 It is the ultra-wideband wave-absorbing grid film of Embodiment 1 provided by the present invention, with the relative dielectric constant ideally set to 1 (the effective dielectric constant related to the conductivity σ is not included ), a thickness of 1 mm, and the wave absorption rate curve diagrams at different conductivities;

[0022] Figure 3 It is the ultra-wideband wave-absorbing grid film of Embodiment 1 provided by the present invention, with the relative dielectric constant ideally set to 1 (not including ), a conductivity of 10 S / m, and the wave absorption rate curve diagrams at different thicknesses;

[0023] Figure 4 It is the ultra-wideband wave-absorbing grid film of Embodiment 1 provided by the present invention, with the relative dielectric constant ideally set to 1 (not including ), a conductivity of 10 S / m, a thickness of 1 mm, and the energy loss diagram at different positions along the z-axis under the vertical irradiation of a 150 GHz wave;

[0024] Figure 5 It is the ultra-wideband wave-absorbing grid film of Embodiment 2 provided by the present invention, with a conductivity of 10 S / m, a thickness of 1 mm, and the wave absorption rate curve diagrams at different dielectric constants (not including ). Detailed Description of the Embodiments

[0025] Embodiment 1:

[0026] As shown in the appendix Figure 1 The grid film proposed by the present invention realizes ultra-wideband wave absorption by regulating the conductivity and dielectric constant. The grid film has certain conductivity, a relatively low relative dielectric constant, and a thickness of about 1 mm.

[0027] The main index for measuring the wave absorption performance of the grid film is the wave absorption rate. Using the finite element method in the frequency domain for simulation, the boundary conditions of the grid film are set as periodic boundary conditions along the x and y directions, the lower end of the grid film is set as an electric wall, and a plane wave is vertically incident on the grid film along the -z direction, with its electric field E along the x-axis direction and magnetic field H along the y-axis direction. Through simulation, the scattering coefficient S 11 (where S 12 = 0), and then the wave absorption rate A(ω) = 1 - |S 11 | 2 .

[0028] This Example 1 focuses on showing the influence of the conductivity of the grid film on its wave absorption performance. For simplicity, when not considering the effective dielectric constant related to the conductivity σ, the relative dielectric constant of the grid film is ideally set to 1, and the thickness of the grid film is taken as 1 mm. When the conductivity is taken as 1 S / m, 3 S / m, 5 S / m, 10 S / m, 15 S / m, 25 S / m respectively, the wave absorption rates are as shown in the appendix Figure 2 . It can be seen that when the conductivity is between 5 S / m and 10 S / m, in the frequency range of 50 GHz to 75 GHz, the wave absorption rate is above 80%; in the frequency range of 75 GHz to 300 GHz, the wave absorption rate is above 90%, showing good wave absorption performance.

[0029] The relative dielectric constant of the grid film is set to 1 (not considering ), the conductivity is taken as 10 S / m, when the thickness of the grid film changes, the change of the wave absorption rate is as shown in the appendix Figure 3 . It can be seen that increasing the thickness of the grid film will improve the wave absorption performance in the low-frequency band of microwaves. However, for electromagnetic waves with a frequency near 50 GHz and above, when the thickness of the grid film reaches a certain level and continues to increase, the wave absorption rate may instead decrease. In addition, as the structure thickness increases, the change of the lowest absorption frequency point with an absorption rate above 80% is not very obvious. Therefore, based on the requirements of thin and wide wave absorption of the grid film, a thickness of about 1 mm is more ideal.

[0030] The relative dielectric constant of the grid film is set to 1 (not considering ), the conductivity is taken as 10 S / m, the thickness is 1 mm, when an electromagnetic wave with a frequency of 150 GHz is vertically incident on the grid film, the change of the electromagnetic energy density in the grid film along z is as shown in the appendix Figure 4As shown, it can be seen that the energy density of the electromagnetic wave is the largest near the incident surface. Due to losses, the energy density of the electromagnetic wave rapidly decays with the increase of the incident depth. Near the lower surface of the grid film, the energy density weakens to about 1 / 300 of that on the upper surface.

[0031] Example 2:

[0032] The dielectric constant is a parameter that describes the electrical response characteristics of materials and also has an important impact on the wave absorption performance. Considering that a grid film with a certain thickness is in a changing magnetic field, eddy currents cause the real part of the effective magnetic permeability of the grid film to decrease and the imaginary part to increase. Therefore, the influence of the dielectric constant on the wave absorption performance of the grid film is further investigated.

[0033] Based on Example 1, the conductivity of the grid film is taken as 10 S / m, and the thickness is taken as 1 mm. The variation of the wave absorption rate with the relative dielectric constant is as Figure 5 shown. It can be seen that increasing the dielectric constant value helps to improve the low-frequency wave absorption performance. However, it will cause obvious oscillations in the wave absorption rate curve and the overall wave absorption performance will decline.

[0034] In summary, the present invention proposes to prepare a grid film with a conductivity in the range of 5 S / m to 10 S / m, a relative dielectric constant in the range of 1 to 2, and a thickness of about 1 mm to achieve ultra-wideband and high-efficiency wave absorption. The grid film proposed by the present invention can be prepared by methods such as the sol-gel method and chemical vapor deposition method, is easy to use, and can be applied to future 6G communication and other fields.

Claims

1. A mesh membrane that achieves ultra-wideband wave absorption by regulating conductivity and dielectric constant, characterized in that: The grid membrane is a thin film with a conductivity of 10S / m, a relative dielectric constant of 1, and a thickness of 1 mm. It can achieve efficient wave absorption in an ultra-wide frequency range from the high frequency band of microwaves to the low frequency band of terahertz waves.

2. The grid film for achieving ultra-wideband wave absorption by regulating conductivity and dielectric constant according to claim 1, characterized in that: Due to the influence of eddy currents, the effective relative magnetic permeability of the conductive film is less than 1. To avoid excessive impedance mismatch, the grid film is prepared by selecting low dielectric constant materials, wherein the low dielectric constant materials include a base material and a conductive filler.

3. The grid film for achieving ultra-wideband wave absorption by regulating conductivity and dielectric constant according to claim 1, characterized in that: The electrical conductivity of the grid membrane is in the range of 5S / m to 10S / m, the relative dielectric constant is less than 2, the thickness is 1 mm, and it can maintain broadband and high-efficiency wave absorbing performance.

4. The grid film for achieving ultra-wideband wave absorption by regulating conductivity and dielectric constant according to claim 1, characterized in that: The effective dielectric constant related to the conductivity σ is not taken into account The relative dielectric constant of the mesh membrane is set to 1.

5. The grid film for achieving ultra-wideband wave absorption by regulating conductivity and dielectric constant according to claim 1, characterized in that: The side length of the square grid unit of the grid membrane is less than 0.15 mm, wherein the area of ​​the grid lines accounts for less than 25%, achieving the requirements of a conductivity value in the range of 5S / m to 10S / m and a relative effective dielectric constant of less than 2.

6. The grid film for achieving ultra-wideband wave absorption by regulating conductivity and dielectric constant according to claim 1, characterized in that: The preparation method of the grid membrane is as follows: S1. Using epoxy resin as the matrix, adding curing agent DDM and silver nanowires, and modulating the conductive silver paste with a conductivity value ranging from 5S / m to 10S / m S2. Use the prepared conductive silver paste and adopt screen printing technology to make the grid membrane. It can also be made by etching and 3D printing methods.

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