A composite material with broadband wave absorption and wave transmission functions

Abstract

This invention provides a composite material with both broadband absorption and transmission functions. The material comprises the following layers in sequence: a metal FSS layer, a first subwavelength structural film layer, a first glass fiber reinforced substrate, a first foam layer, a second subwavelength structural film layer, a first glass fiber composite FSS layer, a second foam layer, a third subwavelength structural film layer, a second glass fiber composite FSS layer, a third foam layer, and a second glass fiber reinforced substrate. Adjacent layers are bonded together. The metal FSS layer is located on the outermost side and serves as a bandpass filter and impedance adjustment unit. The first and second glass fiber composite FSS layers are located on the inner side, with different patterns and sheet resistance values. They utilize ohmic loss and electromagnetic resonance of the dielectric layer to dissipate electromagnetic wave energy, achieving efficient transmission in specific frequency bands while exhibiting broadband strong absorption characteristics in out-of-band frequencies. Through the cooperation between the layers, the transmittance can exceed 80% in a specific frequency band of the S-band, and the absorption rate can exceed 80% in the X and Ku bands.

Description

Technical Field

[0001] This invention relates to the field of wireless communication and electromagnetic functional materials technology, and more specifically, to a composite material that combines broadband wave absorption and wave transmission functions. Background Technology

[0002] With the rapid development of modern radar detection, high-speed communication, and electronic countermeasures technologies, high-end civilian platforms have placed stringent demands on the electromagnetic performance of key components, requiring both low detectability and high information transmission efficiency. While traditional radome structures offer mechanical protection and some wave transmission, they lack effective suppression of out-of-band stray scattering. Conversely, conventional absorbing materials, while reducing reflection, significantly hinder the transmission of in-band communication signals. A single absorbing or transmitting structure is insufficient to meet the comprehensive requirements of "high in-band transmission and strong out-of-band absorption" in complex electromagnetic environments.

[0003] Integrated microwave absorption / transmission functional materials are a key technological approach for achieving synergistic design of radio frequency stealth and electromagnetic compatibility. Among them, resistive film metamaterial microwave absorbers, through the patterned design of conductive thin films such as graphene, can achieve flexible control of surface impedance and efficient dissipation of electromagnetic energy, combining the advantages of thinness, flexibility, and high design freedom. However, existing designs largely rely on empirical trial and error and local parameter scanning, making it difficult to achieve a globally optimal match between transmission and absorption performance across multiple structural variables. Furthermore, integrated microwave absorption / transmission functional materials generally exhibit low transmittance and absorption rates. Summary of the Invention

[0004] In view of this, the present invention aims to propose a composite material that combines broadband wave absorption and wave transmission functions, in order to solve the problems of low design efficiency, difficulty in balancing wave absorption and wave transmission performance, low wave transmission rate and wave absorption rate, and insufficient engineering applicability of the existing integrated absorption and transmission materials.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0006] A composite material with both broadband wave absorption and wave transmission functions comprises the following layers in the following stacking order: a metal FSS layer, a first subwavelength structural film layer, a first glass fiber reinforced substrate, a first foam layer, a second subwavelength structural film layer, a first glass fiber composite FSS layer, a second foam layer, a third subwavelength structural film layer, a second glass fiber composite FSS layer, a third foam layer, and a second glass fiber reinforced substrate, with adjacent layers bonded together.

[0007] Furthermore, the patterns and sheet resistance values ​​of the first and second glass fiber composite FSS layers are different.

[0008] Furthermore, the first and second glass fiber composite FSS layers are prepared with graphene conductive ink, and the sheet resistance is 50~350Ω / sq.

[0009] Furthermore, the patterns of the first and second glass fiber composite material FSS layers are 19×19 pixel genetic algorithm optimized array structures, and the corresponding resistive film unit side length is 16mm, with multiple units arranged in a planar periodic manner.

[0010] Furthermore, the metal FSS layer is formed by a periodic arrangement of third units, each third unit including a square ring and a square hole located inside the square ring, with a gap patch disposed between the square ring and the square hole, and the outer side length P of the third unit is 20mm.

[0011] Furthermore, the outer side length of the square ring is L=18~19mm, the slit width is W=0.7~1mm, the length of the slit patch is L1=9~12mm, the width is W1=0.3~0.6mm, and the side length of the square hole is L2=5~6mm.

[0012] Furthermore, the metal FSS layer is a copper thin film with a conductivity of 5.8×107S / m and a thickness of 0.017±0.003mm.

[0013] Furthermore, the first foam layer, the second foam layer, and the third foam layer are made of the same foam material, and the electromagnetic parameters in the range of 2~18GHz satisfy the following: 1.05≤real part of dielectric constant≤1.3, 0≤imaginary part of dielectric constant≤0.01, real part of magnetic permeability is 1, and imaginary part of magnetic permeability is close to 0.

[0014] Furthermore, the real part of the dielectric constant of the first subwavelength structural film, the second subwavelength structural film, and the third subwavelength structural film is 4~4.5, and the thickness is 0.1±0.01mm.

[0015] Furthermore, the total thickness of the composite material is 3~10mm.

[0016] Compared with existing technologies, the composite material with both broadband wave absorption and wave transmission functions described in this invention has the following advantages:

[0017] (1) It has low-frequency high-efficiency wave transmission and high-frequency broadband wave absorption characteristics. The wave transmission rate is higher than 80% in the target frequency band of S-band and the wave absorption rate is higher than 80% in X-band and Ku-band.

[0018] (2) The overall thickness is 3~10mm, and it has good engineering application prospects in the fields of radar stealth, electromagnetic compatibility and radome integration.

[0019] (3) The unit size of the present invention is optimized by a genetic algorithm, and the fitness value of the algorithm is determined based on the joint simulation results of Matlab and CST Studio Suite. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0021] Figure 1 This is a schematic diagram of the composite material of the present invention that combines broadband wave absorption and wave transmission functions;

[0022] Figure 2 for Figure 1 Side view;

[0023] Figure 3 This is a schematic diagram of the structure of the metal FSS layer of the present invention;

[0024] Figure 4 This is a top view of the first glass fiber composite material FSS layer and the second glass fiber composite material FSS layer in Embodiment 1 of the present invention;

[0025] Figure 5 This is a graph of the S-parameters in a simulation experiment of Embodiment 1 of the present invention;

[0026] Figure 6 This is an absorptivity / transmittance curve of Embodiment 1 of the present invention;

[0027] Figure 7 This is a top view of the first glass fiber composite material FSS layer and the second glass fiber composite material FSS layer in Embodiment 2 of the present invention;

[0028] Figure 8 This is a graph of the S-parameters in a simulation experiment of Embodiment 2 of the present invention;

[0029] Figure 9 This is an absorptivity / transmittance curve of Embodiment 2 of the present invention.

[0030] Explanation of reference numerals in the attached figures:

[0031] 1. Metal FSS layer; 2. First subwavelength structure film layer; 3. First glass fiber reinforced substrate; 4. First foam layer; 5. Second subwavelength structure film layer; 6. First glass fiber composite material FSS layer; 7. Second foam layer; 8. Third subwavelength structure film layer; 9. Second glass fiber composite material FSS layer; 10. Third foam layer; 11. Second glass fiber reinforced substrate; 12. Square hole; 13. Gap patch; 14. Square ring. Detailed Implementation

[0032] The present invention will be further described below with reference to specific embodiments. First, it should be noted that the data in the following experimental examples were obtained by the inventors through numerous experiments. Due to space limitations, only a portion of these data is shown in the specification, and those skilled in the art can understand and implement the present invention based on this data. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various modifications or alterations to the invention, and these modifications or alterations also fall within the scope of protection of this application.

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0034] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] like Figures 1-2 As shown, the composite material of the present invention, which combines broadband wave absorption and wave transmission functions, comprises the following layers in the following stacking order:

[0036] The metal FSS layer 1, the first subwavelength structural film layer 2, the first glass fiber reinforced substrate 3, the first foam layer 4, the second subwavelength structural film layer 5, the first glass fiber composite material FSS layer 6, the second foam layer 7, the third subwavelength structural film layer 8, the second glass fiber composite material FSS layer 9, the third foam layer 10, and the second glass fiber reinforced substrate 11 are bonded together with each other.

[0037] This invention, composed of stacked layers, boasts a simple structure and a mature, reliable manufacturing process, facilitating large-scale industrial production. The outermost metal FSS layer 1 serves as a bandpass filter and impedance adjustment unit. The first glass fiber composite FSS layer 6 and the second glass fiber composite FSS layer 9 are located on the inner side of the composite material. They utilize ohmic loss and electromagnetic resonance of the dielectric layer to dissipate electromagnetic wave energy, achieving high-efficiency wave transmission in specific frequency bands while exhibiting broadband strong absorption characteristics in out-of-band frequencies. Through the interplay between the layers, a transmittance greater than 80% can be achieved in a specific frequency band of the S-band, and an absorption rate greater than 80% in the X and Ku bands.

[0038] Specifically, the metallic FSS layer 1 allows specific frequency bands to pass through efficiently, while reflecting electromagnetic waves outside this band. For S-band electromagnetic waves, the metallic FSS layer 1 can pass through efficiently, achieving wave transmission with minimal reflection and absorption losses.

[0039] The first glass fiber composite material FSS layer 6 and the second glass fiber composite material FSS layer 9 have specific resistances. When encountering electromagnetic waves, they can induce a current on the surface, and the induced current passes through the resistor, converting the energy of the electromagnetic wave into heat energy for dissipation. Each foam layer and the glass fiber composite material FSS layers located above and below it form multiple resonant cavities. When electromagnetic waves propagate within the resonant cavities, they will form a resonance effect due to multiple reflections and interferences, which is beneficial to the ohmic loss of the glass fiber composite material FSS layer. For electromagnetic waves in the X and Ku bands, which are outside the band, they will be directly incident or reflected by the metal FSS layer 1 to the foam layer, exciting electromagnetic resonance. Then, through the first glass fiber composite material FSS layer 6 and the second glass fiber composite material FSS layer 9, the energy is efficiently converted into heat energy for dissipation through ohmic loss, thus achieving the wave absorption function.

[0040] It should be noted that, due to the relatively small thicknesses of the metal FSS layer 1, the first glass fiber composite FSS layer 6, and the second glass fiber composite FSS layer 9, in Figure 2 These three layers are not shown in the image.

[0041] As a preferred example of the present invention, the patterns and sheet resistance values ​​of the first glass fiber composite material FSS layer 6 and the second glass fiber composite material FSS layer 9 are different.

[0042] The patterns of the first glass fiber composite FSS layer 6 and the second glass fiber composite FSS layer 9 correspond to one or more electromagnetic resonant frequencies. Different pattern designs facilitate the achievement of a wider continuous frequency band, thereby realizing broadband absorption. When electromagnetic waves encounter the first glass fiber composite FSS layer 6, the energy in a specific frequency band is first consumed, and the remaining energy reaches the second glass fiber composite FSS layer 9 for supplementary absorption. Glass fiber composite FSS layers with different patterns and sheet resistance values ​​generate resonant losses at different frequency points, thereby broadening the absorption frequency band.

[0043] It should be noted that the present invention is not limited to only two layers of glass fiber composite material FSS. The number of glass fiber composite material FSS layers can be increased accordingly, but the total thickness requirement of the composite material must still be met.

[0044] The first glass fiber composite material FSS layer 6 and the second glass fiber composite material FSS layer 9 are made of graphene conductive ink with a sheet resistance of 50~350Ω / sq.

[0045] The first glass fiber composite material FSS layer 6 is formed by periodically arranging square first units along a plane. The resistive film pattern corresponding to the first unit is a 19×19 pixel genetic algorithm optimized array structure, and the unit side length of the resistive film corresponding to the first unit is 16mm. The side length of the first unit is 20mm.

[0046] The second glass fiber composite material FSS layer 9 is formed by periodically arranging square second units along a plane. The resistive film pattern corresponding to the second unit is a 19×19 pixel genetic algorithm optimized array structure, and the unit side length of the resistive film corresponding to the second unit is 16mm. The side length of the second unit is 20mm.

[0047] like Figure 3 As shown, the metal FSS layer 1 is formed by a periodic arrangement of third units. Each third unit includes a square ring 14 and a square hole 12 located inside the square ring 14. A gap patch 13 is provided between the square ring 14 and the square hole 12. The outer side length of the third unit is P=20mm.

[0048] The outer side length of the square ring 14 is L=18~19mm, the slit width is W=0.9~1mm, the length of the slit patch 13 is L1=10~11mm, the width is W1=0.3~0.5mm, and the side length of the square hole 12 is L2=5~6mm.

[0049] Specifically, the metal FSS layer 1 is a copper thin film with a conductivity of 5.8 × 10⁻⁶. 7 S / m, thickness is 0.017±0.003mm.

[0050] The first foam layer 4, the second foam layer 7, and the third foam layer 10 are made of the same foam material, and their electromagnetic parameters in the range of 2~18GHz satisfy the following: 1.05≤real part of dielectric constant≤1.3, 0≤imaginary part of dielectric constant≤0.01, real part of magnetic permeability is 1, and imaginary part of magnetic permeability is close to 0.

[0051] Specifically, the first foam layer 4, the second foam layer 7, and the third foam layer 10 can be made of PMI (polymethacrylimide foam), which not only has low dielectric constant and low loss properties, but is also lightweight. It does not affect the absorption and reflection of electromagnetic waves, and as a filler layer, it can support adjacent layers and give the composite material the appropriate thickness.

[0052] The real part of the dielectric constant of the first subwavelength structural film layer 2, the second subwavelength structural film layer 5, and the third subwavelength structural film layer 8 is 4~4.5, and the thickness is 0.1±0.01mm.

[0053] The first subwavelength structural film layer 2, the second subwavelength structural film layer 5, and the third subwavelength structural film layer 8 can be used to support the metal FSS layer 1 and each glass fiber composite FSS layer. Specifically, the first subwavelength structural film layer 2, the second subwavelength structural film layer 5, and the third subwavelength structural film layer 8 can be made of ceramic matrix composite materials or modified epoxy resin. A specific epoxy resin system, after curing, can form a thin layer with the required dielectric constant and thickness.

[0054] The first glass fiber reinforced substrate 3 and the second glass fiber reinforced substrate 11 serve to provide support and act as mounting sites for other layers. Glass fiber reinforced composite materials based on cyanate ester or bismaleimide resin systems can be used.

[0055] The cell size of the present invention is optimized by a genetic algorithm, and the fitness value of the algorithm is determined based on the joint simulation results of Matlab and CSTStudio Suite.

[0056] The total thickness of the composite material of the present invention is 3~10mm, and it has good engineering application prospects in the fields of radar stealth, electromagnetic compatibility and radome integration.

[0057] Example 1

[0058] This embodiment presents a composite material with both broadband wave absorption and transmission functions, comprising the following layers in the following order: a metal FSS layer 1, a first subwavelength structural film layer 2, a first glass fiber reinforced substrate 3, a first foam layer 4, a second subwavelength structural film layer 5, a first glass fiber composite FSS layer 6, a second foam layer 7, a third subwavelength structural film layer 8, a second glass fiber composite FSS layer 9, a third foam layer 10, and a second glass fiber reinforced substrate 11. Adjacent layers are bonded together with adhesive.

[0059] The thickness of the first foam layer 4 is h1=1.8mm, the thickness of the second foam layer 7 is h2=1.9mm, and the thickness of the third foam layer 10 is h3=2.1mm. All foam layers use PMI foam. The thickness hr of the first subwavelength structural film layer 2, the second subwavelength structural film layer 5, and the third subwavelength structural film layer 8 is 0.1mm. The thickness hm of the first glass fiber reinforced substrate 3 is 0.4mm, the thickness hmm of the second glass fiber reinforced substrate 11 is 0.4mm, the metal FSS layer is a copper film with a thickness of 0.017mm, and the overall thickness of the composite material is 6.917mm.

[0060] The metal FSS layer 1 is formed by a periodic arrangement of third units on a plane. Each third unit includes a square ring 14 and a square hole 12 located inside the square ring 14. A slot patch 13 is disposed between the square ring 14 and the square hole 12. The outer side length of the third unit is P = 20 mm, the outer side length of the square ring 14 is L = 19 mm, and the slot width is W = 1 mm. The length of the slot patch 13 is L1 = 11 mm, and the width is W1 = 0.5 mm. The side length of the square hole 12 is L2 = 6 mm.

[0061] like Figure 4As shown, the first glass fiber composite material FSS layer 6 is formed by the periodic arrangement of first units on a plane. The side length L3 of the resistive film corresponding to the first unit is 16mm. The first unit includes multiple cells, using 19×19 encoding, and the side length of each cell is a=0.8mm. The sheet resistance of the first glass fiber composite material FSS layer 6 is 160Ω / sq.

[0062] The second glass fiber composite FSS layer 9 is formed by periodically arranging second units on a plane. The side length L3 of the resistive film corresponding to the second unit is 16 mm. The second unit includes multiple cells, encoded in 19×19, with each cell having a side length a = 0.8 mm. The sheet resistance of the second glass fiber composite FSS layer 9 is 140 Ω / sq. The patterns of the first glass fiber composite FSS layer 6 and the second glass fiber composite FSS layer 9 are optimized using a genetic algorithm. The fitness value of this algorithm is determined based on the joint simulation results of Matlab and CSTStudio Suite.

[0063] After modeling and simulation in this embodiment, the S11 and S21 curves for perpendicular incidence are as follows: Figure 5 As shown, the absorptivity / transmittance curve is as follows: Figure 6 As shown, the embodiment of the present invention achieves a transmittance of 84% at a frequency of 2.6 GHz, an absorption rate of over 80% in the range of 7.7~18 GHz, and an overall thickness of only 6.9 mm, exhibiting the characteristics of high-efficiency transmission at low frequencies and broadband absorption at high frequencies.

[0064] Performance simulation was performed using CST Studio Suite 2025 simulation software. Specific simulation settings included:

[0065] Boundary conditions:

[0066] X / Y direction unit cell;

[0067] Zmin Open (add space), Zmax Open (add space);

[0068] Port: One Floquet port, port impedance 377Ω, port mode TE (E-field / / Y);

[0069] Frequency band: 2~18 GHz, using Frequency Domain Solver's adaptive wideband sampling, Minimum samples = 15, actual output of 1001 frequency point data;

[0070] Mesh settings: Tetrahedral mesh, maximum cell size (Cells per max model box egds) = model 10, background 1; minimum cell size (Absolute value) = 0; adaptive mesh iterations 3-8 times, convergence condition |S11|, |S21| change < 1e-3.

[0071] Example 2

[0072] This embodiment presents a composite material with both broadband wave absorption and transmission functions, comprising the following layers in the following order: a metal FSS layer 1, a first subwavelength structural film layer 2, a first glass fiber reinforced substrate 3, a first foam layer 4, a second subwavelength structural film layer 5, a first glass fiber composite FSS layer 6, a second foam layer 7, a third subwavelength structural film layer 8, a second glass fiber composite FSS layer 9, a third foam layer 10, and a second glass fiber reinforced substrate 11. Adjacent layers are bonded together with adhesive.

[0073] The thickness of the first foam layer 4 is h1=2.0mm, the thickness of the second foam layer 7 is h2=1.0mm, and the thickness of the third foam layer 10 is h3=3.0mm. All foam layers use PMI foam. The thickness hr of the first subwavelength structural film layer 2, the second subwavelength structural film layer 5, and the third subwavelength structural film layer 8 is 0.1mm. The thickness hm of the first glass fiber reinforced substrate 3 is 0.2mm, the thickness hmm of the second glass fiber reinforced substrate 11 is 0.6mm, the metal FSS layer 1 is a copper film with a thickness of 0.017mm, and the overall thickness of the composite material is 7.017mm.

[0074] The metal FSS layer 1 is formed by a periodic arrangement of third units on a plane. Each third unit includes a square ring 14 and a square hole 12 located inside the square ring 14. A slot patch 13 is disposed between the square ring 14 and the square hole 12. The outer side length of the third unit is P = 20 mm, the outer side length of the square ring 14 is L = 19 mm, and the slot width is W = 0.9 mm. The length of the slot patch 13 is L1 = 10 mm, and the width is W1 = 0.4 mm. The side length of the square hole 12 is L2 = 6 mm.

[0075] like Figure 7 As shown, the first glass fiber composite material FSS layer 6 is formed by the periodic arrangement of first units on a plane. The side length L3 of the resistive film corresponding to the first unit is 16mm. The first unit includes multiple cells, using 19×19 encoding, and the side length of each cell is a=0.8mm. The sheet resistance of the first glass fiber composite material FSS layer 6 is 120Ω / sq.

[0076] The second glass fiber composite FSS layer 9 is formed by periodically arranging second units on a plane. The side length L3 of the resistive film corresponding to the second unit is 16 mm. The second unit includes multiple cells, encoded in 19×19, with each cell having a side length a = 0.8 mm. The sheet resistance of the second glass fiber composite FSS layer 9 is 100 Ω / sq. The patterns of the first glass fiber composite FSS layer 6 and the second glass fiber composite FSS layer 9 are optimized using a genetic algorithm. The fitness value of this algorithm is determined based on the joint simulation results of Matlab and CSTStudio Suite.

[0077] After modeling and simulation in this embodiment, the S11 and S21 curves for perpendicular incidence are as follows: Figure 8 As shown, the absorptivity / transmittance curve is as follows: Figure 9 As shown, the embodiment of the present invention achieves a transmittance of 88% at a frequency of 2.55 GHz, and an absorption rate of more than 80% in the ranges of 7.85~14.58 GHz and 15.16~18 GHz. The overall thickness is only 6.9 mm, exhibiting the characteristics of high-efficiency transmission at low frequencies and broadband absorption at high frequencies.

[0078] The simulation conditions used in Example 2 and Example 1 are the same.

[0079] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A composite material that combines broadband wave absorption and wave transmission functions, characterized in that, The layers are stacked in the following order: metal FSS layer (1), first subwavelength structural film layer (2), first glass fiber reinforced substrate (3), first foam layer (4), second subwavelength structural film layer (5), first glass fiber composite material FSS layer (6), second foam layer (7), third subwavelength structural film layer (8), second glass fiber composite material FSS layer (9), third foam layer (10), and second glass fiber reinforced substrate (11), with adjacent layers bonded together.

2. The composite material according to claim 1, characterized in that, The patterns and sheet resistance values ​​of the first glass fiber composite material FSS layer (6) and the second glass fiber composite material FSS layer (9) are different.

3. The composite material according to claim 1, characterized in that, The first glass fiber composite material FSS layer (6) and the second glass fiber composite material FSS layer (9) are made of graphene conductive ink with a sheet resistance of 50~350Ω / sq.

4. The composite material according to claim 1, characterized in that, The pattern of the first glass fiber composite material FSS layer (6) and the second glass fiber composite material FSS layer (9) is a 19×19 pixel genetic algorithm optimized array structure, and the corresponding resistance film unit has a side length of 16mm, with multiple units arranged in a planar periodic manner.

5. The composite material according to claim 1, characterized in that, The metal FSS layer (1) is formed by a periodic arrangement of third units. Each third unit includes a square ring (14) and a square hole (12) located inside the square ring (14). A gap patch (13) is provided between the square ring (14) and the square hole (12). The outer side length of the third unit is P=20mm.

6. The composite material according to claim 5, characterized in that, The outer side length of the square ring (14) is L=18~19mm, the slit width is W=0.7~1mm, the length of the slit patch (13) is L1=9~12mm, the width is W1=0.3~0.6mm, and the side length of the square hole (12) is L2=5~6mm.

7. The composite material according to claim 1, characterized in that, The metal FSS layer (1) is a copper thin film with a conductivity of 5.8×107S / m and a thickness of 0.017±0.003mm.

8. The composite material according to claim 1, characterized in that, The first foam layer (4), the second foam layer (7) and the third foam layer (10) are made of the same foam material, and the electromagnetic parameters in the range of 2~18GHz satisfy: 1.05≤real part of dielectric constant≤1.3, 0≤imaginary part of dielectric constant≤0.01, real part of magnetic permeability is 1, and imaginary part of magnetic permeability is close to 0.

9. The composite material according to claim 1, characterized in that, The real part of the dielectric constant of the first subwavelength structure film (2), the second subwavelength structure film (5) and the third subwavelength structure film (8) is 4~4.5, and the thickness is 0.1±0.01mm.

10. The composite material according to claim 1, characterized in that, The total thickness of the composite material is 3~10mm.

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