Fractal square combined sandwich wave-absorbing structure and preparation method thereof

Abstract

The application discloses a fractal-square combined sandwich wave-absorbing structure and a preparation method thereof, and belongs to the technical field of electromagnetic stealth, and aims to solve the problems of limited wave-absorbing bandwidth and large thickness of a Salisbury screen wave-absorber in the prior art. The sandwich wave-absorbing structure comprises a bottom plate, a first dielectric layer, a square conductive film, a second dielectric layer and a fractal conductive film which are sequentially stacked, and the square resistance of the square conductive film is different from that of the fractal conductive film. The method comprises sequentially forming the first dielectric layer, the square conductive film, the second dielectric layer and the fractal conductive film on the bottom plate to obtain the fractal-square combined sandwich wave-absorbing structure. The application can be used for electromagnetic shielding.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic stealth technology, and particularly relates to a fractal square sandwich absorbing structure and its preparation method. Background Technology

[0002] The application of radio transmission has promoted the generation of electromagnetic waves, which has also led to practical problems such as electromagnetic interference, electromagnetic information radiation, and electromagnetic environmental pollution. Absorbers made of microwave absorbing materials (MAMs) that have high efficiency in shielding or eliminating electromagnetic waves can effectively solve these problems.

[0003] The traditional absorber is the Salisbury screen absorber, which consists of a surface resistive layer, a quarter-wavelength dielectric layer, and a metal backplate stacked in sequence. It utilizes the impedance of the surface resistive layer to match the free space, allowing the incident electromagnetic wave to completely enter the dielectric layer, and uses the principle of interference destructive to achieve the purpose of absorbing electromagnetic waves of a specific wavelength.

[0004] However, due to the inherent characteristics of its structure, the absorption bandwidth of the Salisbury screen absorber is limited. To increase the bandwidth, multiple layers of resistive and dielectric layers are arranged alternately, which leads to an increase in thickness. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a sandwich absorbing structure combining fractal and square elements and its preparation method, in order to solve the problems of limited absorbing bandwidth and large thickness of the Salisbury screen absorber in the prior art.

[0006] The objective of this invention is mainly achieved through the following technical solutions.

[0007] The present invention provides a sandwich absorbing structure combining fractal and square elements, comprising a base plate, a first dielectric layer, a square conductive film, a second dielectric layer, and a fractal conductive film stacked sequentially, wherein the square conductive film and the fractal conductive film have different sheet resistances.

[0008] Furthermore, the sheet resistance of the fractal conductive film is 380–400 Ω / sq.

[0009] Furthermore, the sheet resistance of the square conductive film is 75–80 Ω / sq.

[0010] Furthermore, the base plate is a carbon fiber plate; and / or, the first dielectric layer and the second dielectric layer are high-temperature resistant dielectric plates; and / or, the square conductive film and the fractal conductive film are high-temperature resistant resistive films.

[0011] Furthermore, the first dielectric layer and the second dielectric layer are alumina ceramic plates, silicon carbide plates, or SiCN ceramic plates; the square conductive film and the fractal conductive film are graphene films or ruthenium-based resistive films.

[0012] Furthermore, the base plate has a thickness of 0.4 to 0.5 mm.

[0013] Furthermore, the relative permittivity of the first dielectric layer and the second dielectric layer is 9 to 10, the thickness of the first dielectric layer is 2.5 to 3.0 mm, and the thickness of the second dielectric layer is 2.3 to 2.5 mm.

[0014] Furthermore, the sandwich absorbing structure also includes an adhesive layer, which connects the base plate to the first dielectric layer and the first dielectric layer to the second dielectric layer.

[0015] Furthermore, the sandwich absorbing structure also includes a first carrier layer and a second carrier layer, with a square conductive film formed on the first carrier layer and a fractal conductive film formed on the second carrier layer.

[0016] The present invention also provides a method for fabricating a fractal-square combined sandwich absorbing structure, which is used to fabricate the above-mentioned fractal-square combined sandwich absorbing structure. The fabrication method includes the following steps:

[0017] Provide a base plate;

[0018] A first dielectric layer, a square conductive film, a second dielectric layer, and a fractal conductive film are sequentially formed on the substrate to obtain a sandwich absorbing structure combining fractal and square elements.

[0019] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0020] A) The sandwich absorbing structure combining fractal and square structures provided by this invention combines square and fractal structures. The fractal conductive film has self-similarity and exhibits resonant characteristics in multiple frequency bands, enabling effective absorption. At the same time, square and fractal conductive films with different sheet resistances are used, and each layer is optimized for different frequency bands. When electromagnetic waves are incident on the sandwich absorbing structure proposed in this invention, multiple electromagnetic wave reflections will occur in the two conductive films with different sheet resistances, so that the absorption effects of each layer are superimposed. This not only matches the free space impedance to produce an ultra-wideband high absorption effect, but also effectively reduces the thickness of the sandwich absorbing structure, making it more practical.

[0021] B) The fractal-square combined sandwich absorbing structure provided by the present invention, wherein the base plate, the first dielectric layer and the second dielectric layer are used to realize the interlayer coupling of electromagnetic waves, so that the impedance in the sandwich absorbing structure is matched with the impedance of free space, thereby achieving a better absorption effect.

[0022] C) The fractal-square combined sandwich absorbing structure provided by this invention uses high-temperature resistant materials for each layer, thereby greatly improving the high-temperature resistance of the fractal-square combined sandwich absorbing structure, maintaining stable energy dissipation and oxidation resistance, and achieving high-performance absorption at high temperatures. Furthermore, because the materials used in each layer are lightweight and thin, the overall thickness and weight of the fractal-square combined sandwich absorbing structure can be further reduced while ensuring broadband absorption effect and high absorption rate.

[0023] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained through the embodiments described and the accompanying drawings, which are particularly pointed out. Attached Figure Description

[0024] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0025] Figure 1 A schematic diagram of the fractal-square combined sandwich absorbing structure provided by the present invention;

[0026] Figure 2 A longitudinal cross-sectional schematic diagram of the fractal-square combined sandwich absorbing structure provided by the present invention;

[0027] Figure 3 A schematic diagram of the fractal conductive film in the sandwich absorbing structure combining fractals and squares provided by the present invention;

[0028] Figure 4 A schematic diagram of the square conductive film in the fractal-square combined sandwich absorbing structure provided by the present invention;

[0029] Figure 5 The simulated curve of the dual-polarization reflection coefficient of the sandwich absorbing structure combining fractal and square elements in Embodiment 1 of the present invention is shown. In this embodiment, TE refers to transverse polarization and TM refers to longitudinal polarization.

[0030] Figure 6 The simulated curve of the dual-polarization reflection coefficient of the sandwich absorbing structure combining fractal and square elements in Embodiment 3 of the present invention is shown. Here, TE refers to transverse polarization and TM refers to longitudinal polarization.

[0031] Figure label:

[0032] 1-Base plate; 2-First dielectric layer; 3-Square conductive film; 4-Second dielectric layer; 5-Fractal conductive film. Detailed Implementation

[0033] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0034] In a first aspect, the present invention provides a sandwich absorbing structure combining fractal and square elements, see [link to previous document]. Figures 1 to 2 It includes a base plate 1, a first dielectric layer 2, a square conductive film 3, a second dielectric layer 4 and a fractal conductive film 5 stacked in sequence, wherein the square conductive film 3 and the fractal conductive film 5 have different sheet resistances.

[0035] Compared with existing technologies, the fractal-square combined sandwich absorbing structure provided by this invention combines a square structure (square conductive film 3) and a fractal structure (fractal conductive film 5). The fractal conductive film 5 has self-similarity and exhibits resonant characteristics in multiple frequency bands, enabling effective absorption. At the same time, by using square conductive films 3 and fractal conductive films 5 with different sheet resistances, each layer is optimized for different frequency bands. When electromagnetic waves are incident on the sandwich absorbing structure proposed in this invention, multiple electromagnetic wave reflections will occur in the two conductive films with different sheet resistances, so that the absorption effects of each layer are superimposed. This not only matches the free space impedance to produce an ultra-wideband high absorption effect, but also effectively reduces the thickness of the sandwich absorbing structure, making it more practical.

[0036] In addition, in the sandwich absorbing structure combining fractal and square elements, the base plate 1, the first dielectric layer 2, and the second dielectric layer 4 are used to achieve interlayer coupling of electromagnetic waves, so that the impedance within the sandwich absorbing structure matches the impedance of free space, thereby achieving a better absorption effect.

[0037] In order to better adjust the bandwidth and enhance the absorption effect, for example, the sheet resistance of the fractal conductive film 5 is 380 to 400 Ω / sq, and the sheet resistance of the square conductive film 3 is 75 to 80 Ω / sq.

[0038] Considering that the microwave absorption performance of existing metal-based materials, ferrite materials, and carbon-based materials decreases with increasing temperature and cannot achieve stable and efficient microwave absorption performance, in order to improve the high-temperature resistance of the above-mentioned fractal-square sandwich microwave absorption structure, for example, the base plate 1 is a carbon fiber plate for reflecting electromagnetic waves; the first dielectric layer 2 and the second dielectric layer 4 are high-temperature resistant dielectric plates, such as alumina ceramic plates, silicon carbide plates, or SiCN ceramic plates; the square conductive film 3 and the fractal conductive film 5 are high-temperature resistant resistive films, such as graphene films or ruthenium-based resistive films.

[0039] In this way, all the above layers are made of high-temperature resistant materials, which greatly improves the high-temperature resistance of the fractal-square sandwich absorbing structure, maintains stable energy dissipation and oxidation resistance, and achieves high-performance absorption at high temperatures. In addition, since the materials used in the above layers are lightweight and thin, the overall thickness and weight of the fractal-square sandwich absorbing structure can be further reduced while ensuring broadband absorption effect and high absorption rate.

[0040] It should be noted that the aforementioned sandwich absorbing structure combining fractal and square elements has the characteristics of high mechanical hardness and good chemical stability, which can ensure stable performance under long-term high-temperature environments and has a longer service life.

[0041] Considering the thickness of each layer, in order to further adjust the bandwidth and absorption rate, the shape of the sandwich absorbing structure combining fractal and square elements is a square with a side length of 25-30 mm. The base plate 1 is a carbon fiber plate with a thickness of 0.4-0.5 mm. The first dielectric layer 2 and the second dielectric layer 4 are alumina ceramic plates with a relative permittivity of 9-10. The thickness of the first dielectric layer 2 is 2.5-3.0 mm, and the thickness of the second dielectric layer 4 is 2.3-2.5 mm.

[0042] For the structure of the fractal conductive thin film 5, see [link to documentation]. Figure 3 The fractal conductive film 5 comprises horizontal and vertical stripes that form a mesh structure. The curves of both horizontal and vertical stripes are sine function curves. Existing technologies typically use complex snowflake shapes as patterns for fractal conductive films. However, snowflake patterns are irregular and the line distribution is uneven, making it complex to adjust parameters such as reflection bandwidth in practical applications. This invention uses sine function curves to construct complex patterns for the fractal conductive film 5. Since the sine function has multiple parameter variables such as A, ω, and T, by changing these parameters and through proper design, various regular shapes of fractal conductive film 5 patterns can be formed, thereby achieving different wave absorption effects.

[0043] After research, considering the absorption effect, the sin function curve y=A×sin(ω×t+φ) is defined as follows: A=0.55~0.60, ω=0.35~0.40π, φ=0, t=12~13.

[0044] For the structure of the square conductive thin film 3, see [link to documentation]. Figure 4 It consists of multiple square rings arranged in a matrix.

[0045] From a structural and layout perspective, there are four square rings, arranged in a 2×2 pattern.

[0046] For example, the outer ring of the square ring has a side length of 12-13 mm, and the inner ring has a side length of 4-5 mm.

[0047] In order to improve the connection stability between the above layers, the above-mentioned fractal square sandwich absorbing structure also includes an adhesive layer. The base plate 1 and the first dielectric layer 2, and the first dielectric layer 2 and the second dielectric layer 4 are connected by an adhesive layer (e.g., POE film), so that the fractal square sandwich absorbing structure forms an integral structure.

[0048] Secondly, the present invention provides a sandwich absorbing structure combining fractal and square elements, the structure of which is basically the same as the sandwich absorbing structure combining fractal and square elements provided in the first aspect, the difference being:

[0049] The aforementioned sandwich absorbing structure combining fractal and square elements also includes a first carrier layer and a second carrier layer. The square conductive film 3 is formed on the first carrier layer, and the fractal conductive film 5 is formed on the second carrier layer. That is, the first carrier layer is disposed between the first dielectric layer 2 and the square conductive film 3, and the second carrier layer is disposed between the second dielectric layer 4 and the fractal conductive film 5.

[0050] To further improve the absorption performance of the aforementioned sandwich absorbing structure combining fractals and squares, the surface of the square conductive film 3 facing the first carrier layer is textured, and the surface of the fractal conductive film 5 facing the second carrier layer is also textured. By textured surfaces of both the square conductive film 3 and the fractal conductive film 5, the surface roughness of both is effectively increased, allowing for greater reflection of electromagnetic waves and further enhancing the absorption effect.

[0051] For example, the first and second carrier layers are polyethylene film (PE film) or polyimide film (PI film).

[0052] Thirdly, the present invention provides a method for fabricating a fractal-square combined sandwich absorbing structure, used for fabricating the fractal-square combined sandwich absorbing structure provided in the first or second aspect, the method comprising the following steps:

[0053] Provide a base plate 1;

[0054] A first dielectric layer 2, a square conductive film 3, a second dielectric layer 4, and a fractal conductive film 5 are sequentially formed on the base plate 1 to obtain a sandwich absorbing structure combining fractal and square elements.

[0055] Compared with the prior art, the beneficial effects of the method for preparing the fractal-square combined sandwich absorbing structure provided by the present invention are basically the same as those of the fractal-square combined sandwich absorbing structure provided in the first or second aspect, and will not be elaborated here.

[0056] For example, the above-mentioned square conductive film 3 can be formed in the following two ways:

[0057] In one method, the square conductive film 3 is formed directly on the first dielectric layer 2. The specific formation method includes the following steps:

[0058] A square conductive film 3 pattern is printed on the surface of the first dielectric layer 2 using thick film screen printing technology to obtain the square conductive film 3.

[0059] In another method, the square conductive film 3 relies on the first carrier layer, and the specific formation method includes the following steps:

[0060] Provide a rigid template with a textured surface;

[0061] A raw material solution (e.g., polyethylene solution or polyimide solution) is coated onto a rigid template to form the first support layer, and the first support layer is obtained after the solvent evaporates.

[0062] The first load-bearing layer is peeled off from the rigid template to form a first load-bearing layer with a textured structure;

[0063] After the first carrier layer is flipped up and down, it is placed on the first dielectric layer 2, with the textured surface facing away from the first dielectric layer 2.

[0064] According to the pattern of the square conductive film 3, the conductive paste is coated on the textured surface of the first carrier layer to form the square conductive film 3.

[0065] In this way, the above-mentioned formation method uses a rigid template as the template for the first carrier layer, transfers the texture structure from the rigid template to the first carrier layer, and then transfers the texture structure to the square conductive film 3 by coating a conductive paste, thereby achieving efficient and high-precision preparation of the square conductive film 3.

[0066] Accordingly, the fractal conductive thin film 5 described above can be formed in the following two ways:

[0067] In one method, the fractal conductive film 5 is formed directly on the second dielectric layer 4. The specific formation method includes the following steps:

[0068] A pattern of fractal conductive film 5 is printed on the surface of the second dielectric layer 4 using thick film screen printing technology to obtain fractal conductive film 5.

[0069] In another method, the fractal conductive film 5 relies on a second carrier layer, and the specific formation method includes the following steps:

[0070] Provide a rigid template with a textured surface;

[0071] A raw material solution (e.g., polyethylene solution or polyimide solution) is coated onto a rigid template to form a second support layer, and the solvent is evaporated to obtain the second support layer.

[0072] The second load-bearing layer is peeled off from the rigid template to form a second load-bearing layer with a textured structure;

[0073] After the second carrier layer is flipped up and down, it is placed on the second medium layer 4, with the textured surface facing away from the second medium layer 4.

[0074] According to the pattern of the fractal conductive film 5, the conductive paste is coated on the textured surface of the second carrier layer to form the fractal conductive film 5.

[0075] In this way, the above-mentioned formation method uses a rigid template as the template for the second carrier layer, transfers the texture structure from the rigid template to the second carrier layer, and then transfers the texture structure to the fractal conductive film 5 by coating with conductive paste, thereby achieving efficient and high-precision preparation of the fractal conductive film 5.

[0076] Example 1

[0077] This embodiment provides a sandwich absorbing structure combining fractal and square elements, comprising a base plate, a first dielectric layer, a square conductive film, a second dielectric layer, and a fractal conductive film stacked sequentially.

[0078] The period of the structural unit is L = 30 mm.

[0079] The outer ring of the ring above the first dielectric layer has a side length of 13 mm, the inner ring of the ring above the first dielectric layer has a side length of 5 mm, and the sheet resistance of the square conductive film on the first dielectric layer is RS2 = 80 Ω / sq.

[0080] The sin function curve of the fractal conductive layer on the second dielectric layer is y = A × sin(ω × t + φ), where A = 0.6, ω = 0.4π, φ = 0, t = 13, and the sheet resistance of the fractal conductive film on the second dielectric layer is RS1 = 400Ω / sq.

[0081] Both the first and second dielectric layers are made of alumina ceramic with a relative permittivity of 9. The thickness of the second dielectric layer is 2.5 mm, and the thickness of the first dielectric layer is 3 mm.

[0082] The base plate is made of carbon fiber plate with a thickness of 0.5mm.

[0083] The reflection coefficient of the sandwich absorbing structure in this embodiment was obtained by simulating it using the electromagnetic simulation software CST Studio Suite, in the range of 2–18 GHz. (See [link to relevant documentation]). Figure 5 .

[0084] from Figure 5It can be seen that the reflection coefficient is less than -10dB within the range of 2 to 15GHz. Simulation results show that the absolute operating bandwidth of this embodiment is greater than 13GHz, the relative bandwidth reaches 153%, the absorption rate within the absorption bandwidth is greater than 90%, and the thickness of the sandwich absorbing structure is only 0.16λ0 (where λ0 is the wavelength corresponding to the absorption center frequency).

[0085] Example 2

[0086] This embodiment provides a sandwich absorbing structure combining fractal and square elements, comprising a base plate, a first dielectric layer, a square conductive film, a second dielectric layer, and a fractal conductive film stacked sequentially.

[0087] The period of the structural unit is L = 25 mm.

[0088] The outer ring of the ring above the first dielectric layer has a side length of 12 mm, the inner ring of the ring above the first dielectric layer has a side length of 4 mm, and the sheet resistance of the square conductive film on the first dielectric layer is RS2 = 75 Ω / sq.

[0089] The sin function curve of the fractal conductive layer on the second dielectric layer is y = A × sin(ω × t + φ), where A = 0.55, ω = 0.35π, φ = 0, t = 12, and the sheet resistance of the fractal conductive film on the second dielectric layer is RS1 = 380Ω / sq.

[0090] Both the first and second dielectric layers are made of alumina ceramic with a relative permittivity of 10. The thickness of the second dielectric layer is 2.3 mm, and the thickness of the first dielectric layer is 2.5 mm.

[0091] The base plate is made of carbon fiber plate with a thickness of 0.4mm.

[0092] Within the 2–14.5 GHz range, the reflection coefficient is less than -10 dB. Simulation results show that the absolute operating bandwidth of this embodiment is greater than 12.5 GHz, the relative bandwidth reaches 151%, the absorption rate within the absorption bandwidth is greater than 90%, and the thickness of the sandwich absorbing structure is only 0.16λ0 (where λ0 is the wavelength corresponding to the absorption center frequency).

[0093] Example 3

[0094] This embodiment provides a sandwich absorbing structure combining fractal and square elements, comprising a base plate, a first dielectric layer, a first carrier layer, a square conductive film, a second dielectric layer, a second carrier layer, and a fractal conductive film stacked sequentially. The contact surface between the first carrier layer and the square conductive film has a textured structure, and the contact surface between the second carrier layer and the square conductive film also has a textured structure.

[0095] The period of the structural unit is L = 30 mm.

[0096] The outer ring of the ring above the first dielectric layer has a side length of 13 mm, the inner ring of the ring above the first dielectric layer has a side length of 5 mm, and the sheet resistance of the square conductive film on the first dielectric layer is RS2 = 80 Ω / sq.

[0097] The sin function curve of the fractal conductive layer on the second dielectric layer is y = A × sin(ω × t + φ), where A = 0.6, ω = 0.4π, φ = 0, t = 13, and the sheet resistance of the fractal conductive film on the second dielectric layer is RS1 = 400Ω / sq.

[0098] Both the first and second dielectric layers are made of alumina ceramic with a relative permittivity of 9. The thickness of the second dielectric layer is 2.5 mm, and the thickness of the first dielectric layer is 3 mm.

[0099] The base plate is made of carbon fiber plate with a thickness of 0.5mm.

[0100] The reflection coefficient of the sandwich absorbing structure in this embodiment was obtained by simulating it using the electromagnetic simulation software CST Studio Suite, in the range of 2–18 GHz. (See [link to relevant documentation]). Figure 6 .

[0101] from Figure 6 It can be seen that the reflection coefficient is less than -10dB within the range of 2 to 16 GHz. Simulation results show that the absolute operating bandwidth of this embodiment is greater than 14 GHz, the relative bandwidth reaches 156%, the absorption rate within the absorption bandwidth is greater than 90%, and the thickness of the sandwich absorbing structure is only 0.17λ0 (where λ0 is the wavelength corresponding to the absorption center frequency).

[0102] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A sandwich-type absorbing structure combining fractal and square elements, characterized in that, It includes a base plate, a first dielectric layer, a square conductive film, a second dielectric layer, and a fractal conductive film stacked in sequence, wherein the square conductive film and the fractal conductive film have different sheet resistances.

2. The sandwich absorbing structure combining fractal and square elements according to claim 1, characterized in that, The sheet resistance of the fractal conductive film is 380–400 Ω / sq.

3. The sandwich absorbing structure combining fractal and square elements according to claim 1, characterized in that, The sheet resistance of the square conductive film is 75–80 Ω / sq.

4. The sandwich absorbing structure combining fractal and square elements according to claim 1, characterized in that, The base plate is a carbon fiber plate; And / or, the first dielectric layer and the second dielectric layer are high-temperature resistant dielectric plates; And / or, the square conductive film and the fractal conductive film are high-temperature resistant resistive films.

5. The sandwich absorbing structure combining fractal and square elements according to claim 4, characterized in that, The first dielectric layer and the second dielectric layer are alumina ceramic plates, silicon carbide plates, or SiCN ceramic plates; The square conductive film and the fractal conductive film are graphene films or ruthenium-based resistive films.

6. The sandwich absorbing structure combining fractal and square elements according to claim 1, characterized in that, The base plate has a thickness of 0.4 to 0.5 mm.

7. The sandwich absorbing structure combining fractal and square elements according to claim 4, characterized in that, The relative permittivity of the first dielectric layer and the second dielectric layer is 9 to 10, the thickness of the first dielectric layer is 2.5 to 3.0 mm, and the thickness of the second dielectric layer is 2.3 to 2.5 mm.

8. The sandwich absorbing structure combining fractal and square elements according to claim 1, characterized in that, The sandwich absorbing structure also includes an adhesive layer, and the base plate is connected to the first dielectric layer and the first dielectric layer and the second dielectric layer through the adhesive layer.

9. The sandwich absorbing structure combining fractal and square elements according to claim 1, characterized in that, The sandwich absorbing structure further includes a first carrier layer and a second carrier layer, with the square conductive film formed on the first carrier layer and the fractal conductive film formed on the second carrier layer.

10. A method for fabricating a sandwich absorbing structure combining fractal and square elements, characterized in that, The fabrication method for the fractal-square combined sandwich absorbing structure as described in any one of claims 1 to 9 comprises the following steps: Provide a base plate; A first dielectric layer, a square conductive film, a second dielectric layer, and a fractal conductive film are sequentially formed on the substrate to obtain a sandwich absorbing structure combining fractal and square elements.

Images