A stacked transparent cloaking superstructure embedded with a patterned resistive film and a preparation method thereof

Abstract

The application discloses a kind of embedded patterned resistive film's laminated transparent stealth superstructure and preparation method, belong to transparent electromagnetic stealth structure technical field.Embedded patterned resistive film's laminated transparent stealth superstructure, including patterned wave-absorbing layer, dielectric layer, frame, frame sealing plate and reflective back plate.Patterned wave-absorbing layer includes N layer patterned conductive film and N layer support substrate.Support substrate is placed below patterned conductive film.Patterned conductive film includes patterned conductive material and substrate.Conductive material is patterned on the surface of substrate.Forming.By customizing N layer optically transparent frequency selective surface conductive film geometric pattern, realize laminated multi-frequency point resonance, adopt multi-layer frequency selective surface laminated interface resonance loss wave absorption.Dielectric layer includes N+1 layer transparent dielectric, by transparent liquid material solidification forming.Preparation method uses embedded patterned resistive film and liquid dielectric layer frame mold solidification manufacturing process, so that transparent stealth superstructure is not easy to delaminate, and mechanical reliability is high.

Description

Technical Field

[0001] This invention relates to an optically transparent ultra-wideband electromagnetic stealth superstructure and its fabrication method, belonging to the technical field of transparent electromagnetic stealth structures. Background Technology

[0002] With the rapid development of modern military and aerospace technologies, stealth technology has become one of the key means to improve the battlefield survivability and penetration capability of equipment. 90% of the radar cross section (RCS) of the cockpit of weapon systems such as fighter jets and ground vehicles originates from electromagnetic scattering by internal instruments; therefore, the electromagnetic stealth design of the cockpit windshield is crucial for reducing its RCS. Transparent electromagnetic stealth structure technology has emerged in this context. This technology combines electromagnetic stealth functionality with the transparency of materials, achieving effective absorption and reflection of electromagnetic waves while maintaining high light transmittance, thus achieving electromagnetic stealth.

[0003] Microwave absorbing materials are crucial for electromagnetic interference suppression and low-detectability technologies, and have become a hot research topic in electromagnetic stealth. Traditional microwave absorbing structures utilize single or multiple layers of additional resistive films to achieve narrow-band or broadband absorption. The Salisbury screen consists of a single layer of uniform resistive film placed in front of a fully conductive ground plane. The Jaumann absorber broadens the absorption bandwidth by increasing the number of resistive films. In recent years, superstructure absorbing materials composed of subwavelength periodic patterns and dielectric substrates have seen rapid development. By fabricating each layer of uniform resistive film into a patterned frequency-selective surface, and employing a resonant loss mechanism to convert electromagnetic waves into internal energy or thermal energy, thinner electromagnetic absorbing structures can be achieved with wider absorption performance. Transparent electromagnetic absorbing structures generally combine transparent dielectrics such as PDMS (polydimethylsiloxane), PMMA (polymethyl methacrylate), and PC (polycarbonate) with transparent conductive materials such as ITO (indium tin oxide), metal nanowires, metal meshes, and graphene two-dimensional materials. However, their absorption mechanisms, such as electromagnetic resonance and phase destructive phase, remain essentially unchanged compared to non-transparent electromagnetic absorbing structures.

[0004] Currently, laminated superstructures composed of patterned transparent conductive layers and transparent dielectrics are the mainstream design for transparent electromagnetic stealth structures. However, related research on the optimization design of transparent electromagnetic stealth performance and actual fabrication schemes is often limited by the unconventional thickness of the dielectric layer material, which makes processing difficult. This results in narrow absorption bandwidth and high frequency concentration in the measured electromagnetic optimization design fabrication results. In addition, traditional simple laminated bonding fabrication methods are prone to structural delamination. Summary of the Invention

[0005] To address the challenges of high-frequency narrowband absorption and the difficulty in fabricating non-integer thicknesses of the dielectric layer in current optically transparent electromagnetic stealth structures, this invention proposes a transparent superstructure with embedded patterned resistive film layers and its fabrication method. This method considers the optimized design of the dielectric layer thickness for any non-integer transparent electromagnetic absorbing structure. Multilayer patterned frequency-selective surface transparent resistive films are embedded in a frame mold, and transparent liquid material is injected into the frame mold and solidified to form the dielectric layer. This achieves a thinner, less prone-to-delamination ultrawideband transparent electromagnetic absorbing superstructure.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] The present invention discloses an embedded patterned resistive film stacked transparent stealth superstructure, comprising a patterned absorbing layer, a dielectric layer, a frame, a frame cover plate, and a reflective back plate.

[0008] The patterned absorbing layer comprises N layers of patterned conductive thin films and N layers of supporting substrate.

[0009] The patterned conductive film comprises a patterned conductive material and a substrate. The conductive material is patterned on the surface of the substrate. Multi-frequency resonance is achieved by customizing the geometry of N layers of optically transparent, frequency-selective surface conductive films. Achieving multi-frequency resonance is key to realizing ultra-wideband microwave absorption in a patterned resistive film stacked transparent stealth superstructure.

[0010] Preferably, the frequency-selective surface conductive pattern is composed of square concentric rings or regular hexagonal concentric rings as basic units, which are inlaid and densely paved.

[0011] The supporting substrate is placed under the patterned conductive film to provide support for the patterned conductive film.

[0012] The dielectric layer comprises N+1 transparent dielectric layers, which are solidified from a transparent liquid material, eliminating the need to consider the processing difficulties associated with specifying the desired dielectric layer thickness. The thickness of the N+1 transparent dielectric layers is a crucial variable for adjusting the surface electromagnetic wave absorption resonant frequency.

[0013] The patterned absorbing layer composite structure consisting of N-layer patterned conductive film and N-layer supporting substrate is alternately placed with N+1 layers of transparent dielectric, that is, a single layer of patterned conductive film and supporting substrate are placed between two layers of transparent dielectric, forming an interface loss type resonant absorbing mode.

[0014] The frame consists of a three-sided connected frame and a single-sided frame, facilitating the embedding of a patterned absorbing layer. The inner wall of the frame is customized with N grooves matching the thickness of the single-layer patterned conductive film in the patterned absorbing layer and the supporting substrate. The spacing between adjacent grooves matches the thickness of the corresponding transparent dielectric in the dielectric layer. Grooves are present on the top and bottom edges of the frame for securing the frame sealing plate.

[0015] Preferably, the frame is made of transparent resin material.

[0016] The frame sealing plate is placed at the corresponding groove positions on the upper and lower edges of the frame, and together with the frame, they form a transparent medium liquid curing molding mold for the medium layer.

[0017] The reflective backplate is positioned outside the electromagnetic wave transmission surface within the frame sealing plate and features low sheet resistance. The low sheet resistance value is less than or equal to 5Ω / sq. Resonant absorption is achieved based on the reflective backplate, ensuring sufficient absorption of electromagnetic waves and reducing electromagnetic wave transmittance.

[0018] The method for fabricating a stacked transparent stealth metastructure with embedded patterned resistive films disclosed in this invention includes the following steps:

[0019] Step 1: Optimization design of a stacked transparent stealth superstructure with embedded patterned resistive films.

[0020] The transparent stealth superstructure is designed using the NSGA-II non-dominated sorting genetic algorithm with an elitist strategy, employing multi-objective optimization. The optimization objectives consider both the absorption bandwidth performance under perpendicular electromagnetic wave incidence and the overall thickness of the transparent absorbing structure. The fitness function f is constructed using the reflectivity curves of electromagnetic waves incident perpendicularly in the 2GHz-18GHz frequency band and the total thickness of the absorbing structure. obj1 and f obj2 .

[0021] Preferably, the fitness function f obj1 The expression is shown in (1), where M is the number of frequency points corresponding to the reflectivity curve, Std is the preset reflectivity to be achieved, and Min is the preset minimum value. The minimum value is less than 1×10⁻⁶. -3 .

[0022]

[0023] The transparent stealth superstructure optimizes the selection of N+1 transparent dielectric layer thickness parameters, N layer frequency selection surface pattern geometric parameters and sheet resistance as optimization variables to jointly control the resonant frequency of the absorbing structure.

[0024] As a preferred option, considering the optical transparency of the overall transparent absorbing structure, a design of three frequency-selective surface absorption layers matched with four layers of alternating transparent dielectric layers is used as a reference. The frequency-selective surface uses a hexagonal ring-shaped tessellation pattern. Therefore, the selected optimization design variables include the height of each transparent dielectric layer, the radius of the circumscribed circle of the periodic unit of the in-plane hexagonal ring-shaped stacked structure, the radius of the circumscribed circle of the inner and outer boundaries of each layer of the concentric hexagonal ring pattern, and the sheet resistance of each layer of the concentric hexagonal ring pattern. The height variable of each transparent dielectric layer includes the thickness of the supporting substrate, which is set to a constant value during the optimization calculation. The reflectivity of the embedded patterned resistive film stacked transparent stealth superstructure at different frequencies along the perpendicular incident direction of electromagnetic waves is calculated using the three-dimensional electromagnetic simulation software CST (CST Studio Suite) with frequency domain algorithms and oblique coordinate system periodic boundary conditions. The NSGA-II algorithm iteratively calculates the fitness values ​​of each generation of the population, comprehensively judges and generates a Pareto front solution set, and selects suitable optimal solutions to determine the values ​​of all variable parameters.

[0025] Step 2: Fabrication of a layered transparent stealth superstructure patterned absorbing layer.

[0026] Based on the frequency selected in step one, the surface pattern is optimized with geometric parameters and sheet resistance to fabricate a corresponding transparent conductive pattern, resulting in N patterned conductive films. The N-layer support substrate is a transparent sheet of the same specified thickness. The N-layer support substrate and the N-layer patterned conductive films are then bonded together with transparent adhesive to obtain N patterned conductive film-support substrate composite structures.

[0027] As a preferred option, indium tin oxide polyester (ITO-PET) transparent conductive films are patterned using magnetron sputtering and chemical etching techniques, with surface patterns selected according to frequency.

[0028] Preferably, the supporting substrate and the patterned conductive film are bonded together using UV-cured photosensitive transparent epoxy resin adhesive.

[0029] Preferably, the supporting substrate is made of transparent polymethyl methacrylate (PMMA) sheet with a thickness of 1 mm to 5 mm.

[0030] Step 3: Fabrication of the mold for the stacked transparent stealth superstructure frame.

[0031] Based on the thickness of the N+1 transparent dielectric layers generated in step one, determine the corresponding groove spacing on the inner wall of the frame. Prepare the frame by dividing it into a three-sided groove component and a single-sided groove component. Prepare two frame sealing plates that match the grooves on the upper and lower edges of the frame. Adhere the two frame sealing plates to the grooves on the upper and lower edges of the three-sided groove component using transparent adhesive to form a single-sided open mold for the injection molding and curing of the dielectric layer.

[0032] Preferably, the three-sided groove component and the single-sided groove component are prepared by photopolymerization 3D printing of transparent photosensitive resin.

[0033] Preferably, the two frame sealing plates and the upper and lower edge grooves of the three-sided groove component are bonded with UV-cured photosensitive transparent epoxy resin adhesive.

[0034] Step 4: Preparation by injection molding and curing of the stacked transparent stealth superstructure dielectric layer.

[0035] The N patterned conductive film-supporting substrate composite structures obtained in step two are sequentially embedded into the mold through the corresponding grooves on the inner wall of the frame from the single-sided opening end of the dielectric layer curing mold obtained in step three, thus fixing the relative positions between the N patterned conductive film-supporting substrate composite structures. Liquid transparent adhesive is injected into the mold through the single-sided opening, a vacuum is drawn, and the single-sided opening end of the mold is sealed using the single-sided groove component in the frame. The transparent resin medium is allowed to cure at room temperature to form N+1 layers of transparent medium, which integrate the absorption layer, frame, and frame sealing plate of the N patterned conductive film-supporting substrate composite structures into one piece.

[0036] Preferably, the liquid transparent adhesive uses a two-component high-transparency epoxy resin adhesive.

[0037] Preferably, the frame sealing plate is made of transparent PMMA sheet with a thickness of 1mm to 5mm.

[0038] Step 5: Integration of the reflective backplate of the stacked transparent stealth superstructure: The reflective backplate is bonded to the outer surface of the composite stacked absorbing structure obtained in Step 4, which is to realize the fabrication of the stacked transparent stealth superstructure with embedded patterned resistive film.

[0039] Preferably, the reflective backplate is prepared using magnetron sputtering technology to produce a patternless ITO-PET film with a sheet resistance value of less than or equal to 5Ω / sq.

[0040] Preferably, the reflective backplate and the outer surface of the composite laminated microwave absorbing structure are bonded with UV-cured photosensitive transparent epoxy resin adhesive.

[0041] Beneficial effects:

[0042] 1. Compared with traditional single-layer frequency-selective surface resonant absorption, the present invention discloses a stacked transparent stealth superstructure with embedded patterned resistive film, which adopts multi-layer frequency-selective surface stacked interface resonant loss absorption, thereby achieving 2GHz-18GHz ultrawideband absorption of the transparent stealth superstructure.

[0043] 2. The present invention discloses a stacked transparent stealth superstructure with embedded patterned resistive film. The dielectric layer is formed by solidifying transparent liquid using a frame-made mold. Compared with traditional dielectric plates with specified integer thickness, the problem of processing difficulties for non-integer thickness dielectric layers does not need to be considered in the optimization design, thereby effectively expanding the optimization design range of transparent absorbing structures.

[0044] 3. The present invention discloses a stacked transparent stealth superstructure with embedded patterned resistive film and its preparation method. The fabrication process adopts an embedded patterned resistive film and a liquid dielectric layer frame mold curing process, which makes the transparent stealth superstructure less prone to delamination and has high mechanical reliability.

[0045] 4. The present invention discloses a stacked transparent stealth superstructure with embedded patterned resistive film and its preparation method. The dielectric layer includes N+1 layers of transparent dielectric, which are solidified and formed by transparent liquid material. There is no need to consider the problem of difficult processing by specifying the value of the dielectric layer thickness optimization design result. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the embedded patterned resistive film stacked transparent superstructure design provided by the present invention;

[0047] Figure 2 The two-component highly transparent epoxy resin adhesive with embedded patterned resistive film stack transparent superstructure dielectric layer provided by the present invention (a) relative permittivity-frequency curve (b) relative permeability-frequency curve;

[0048] Figure 3 Periodic boundary conditions for the finite element electromagnetic simulation model of the embedded patterned resistive film stacked transparent superstructure unit provided by the present invention; Figure 4 The Pareto solution set for the multi-objective optimization design of the embedded patterned resistive film stacked transparent superstructure provided by this invention;

[0049] Figure 5 The first electromagnetic wave absorption structure layer frequency selection surface design diagram provided by the present invention;

[0050] Figure 6 This invention provides a surface design diagram for the frequency selection of the second electromagnetic wave absorption structure layer.

[0051] Figure 7 The surface design diagram for frequency selection of the third electromagnetic wave absorption structure layer provided by the present invention;

[0052] Figure 8 The mold frame for the 3D printing of a transparent superstructure with embedded patterned resistive film stacks and photosensitive resin dielectric layer provided by the present invention.

[0053] Figure 9 This is a schematic diagram illustrating the fabrication process of the embedded patterned resistive film stacked transparent superstructure provided by the present invention;

[0054] Figure 10 Electromagnetic simulation results of the embedded patterned resistive film stacked transparent superstructure provided by the present invention;

[0055] Wherein: 1.1—patterned conductive film, 1.2—supporting substrate, 2—dielectric layer, 3—frame, 4—frame sealing plate, 5—reflective back plate. Detailed Implementation

[0056] Exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0057] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0058] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0059] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0060] The terms “comprising,” “including,” “having,” “containing,” etc., used in this invention are all open-ended terms, meaning that they include but are not limited to.

[0061] The present invention will now be further described in conjunction with the accompanying drawings and embodiments.

[0062] Example

[0063] like Figure 1As shown, a stacked transparent stealth superstructure with embedded patterned resistive films (taking a patterned absorbing layer 1 composed of 3 layers of patterned conductive thin films 1.1 and 3 layers of supporting substrate 1.2 as an example) includes a patterned absorbing layer 1, a dielectric layer 2, a frame 3, a frame sealing plate 4, and a reflective back plate 5.

[0064] The patterned absorbing layer comprises three patterned conductive films and three supporting substrates.

[0065] The patterned conductive film comprises a patterned conductive material and a substrate. The conductive material is patterned on the surface of the substrate. Multi-frequency resonance is achieved by customizing the geometry of three optically transparent frequency-selective surface conductive films.

[0066] The frequency-selective surface conductive pattern is composed of closely spaced hexagonal concentric rings as basic units.

[0067] The supporting substrate is placed under the patterned conductive film to provide support for the patterned conductive film.

[0068] The medium layer comprises four transparent media layers, which are solidified from transparent liquid materials, eliminating the need to consider the processing difficulties caused by specifying the thickness of the medium layer in the optimized design.

[0069] The composite structure of the patterned absorbing layer, consisting of three patterned conductive films and three supporting substrates, is alternately placed with four transparent dielectric layers. That is, a single patterned conductive film and a supporting substrate are placed between two transparent dielectric layers to form an interface loss type resonant absorption mode.

[0070] The frame consists of a three-sided connected frame and a single-sided frame, facilitating the embedding of a patterned absorbing layer. The inner wall of the frame features three grooves matching the thickness of the single-layer patterned conductive film in the patterned absorbing layer and the supporting substrate. The spacing between adjacent grooves matches the thickness of the corresponding transparent dielectric in the dielectric layer. Grooves are present on the top and bottom edges of the frame for securing the frame sealing plate.

[0071] The frame is made of transparent resin material.

[0072] The frame sealing plate is placed at the corresponding groove positions on the upper and lower edges of the frame, and together with the frame, they form a transparent medium liquid curing molding mold for the medium layer.

[0073] The reflective backplate is placed outside the electromagnetic wave transmission surface in the frame sealing plate.

[0074] The method for fabricating a stacked transparent stealth metastructure with embedded patterned resistive films disclosed in this embodiment includes the following steps:

[0075] Step 1: Optimization Design of Stacked Transparent Stealth Superstructure with Embedded Patterned Resistive Film

[0076] The transparent stealth superstructure employs a non-dominated sorting genetic algorithm (NSGA-II) with an elitist strategy for multi-objective optimization design. The optimization objectives consider both the absorption bandwidth performance under perpendicular electromagnetic wave incidence and the overall thickness of the transparent absorbing structure. The fitness function f is constructed using the reflectivity curves of electromagnetic waves incident perpendicularly in the 2GHz-18GHz frequency band and the total thickness of the absorbing structure. obj1 and f obj2 .

[0077] The fitness function f obj1 The expression is shown in (1), where M is the number of frequency points corresponding to the reflectivity curve, which is 95, Std is the preset reflectivity to be achieved, and Min is the preset minimum value. The minimum value is 1×10 -4 .

[0078]

[0079] Considering the optical transparency of the overall transparent absorbing structure, a design with three frequency-selective surface absorption layers and four layers of transparent dielectric layers stacked alternately is used as a reference. The maximum total thickness of the overall transparent absorbing structure is limited to 15mm. The frequency-selective surface adopts a hexagonal concentric ring tessellation pattern design, with the maximum cell surface inscribed circle radius limited to 30mm. The height variable of each transparent dielectric layer includes the 1.2mm thickness of the supporting substrate, and the 1.2mm thickness of the supporting substrate is set to a constant value during the optimization calculation. The relative permittivity and relative permeability measurement results of the two-component high-transparency epoxy resin waveguide method for the dielectric layers of the transparent absorbing structure are as follows: Figure 2 As shown. The relative permittivity of PMMA material is set to 3.4, and the relative permeability is set to 1. The reflectivity of electromagnetic waves at different frequencies along the perpendicular incident direction of the embedded patterned resistive film stacked transparent stealth superstructure is calculated using the three-dimensional electromagnetic simulation software CST Studio Suite (CST) with frequency domain algorithms and oblique coordinate system periodic boundary conditions. For example... Figure 3 As shown, the finite element electromagnetic simulation model of the transparent electromagnetic absorbing structure has periodic boundary conditions. The NSGA-II algorithm iterative calculation is set with a population size of 50, a maximum number of iterations of 30, and a Pareto coefficient of 0.2. Based on the fitness values ​​of each generation of the NSGA-II algorithm, a Pareto front solution set is generated, and suitable optimal solutions are selected to determine the values ​​of all variable parameters. The Pareto solution set for the multi-objective optimization design of the transparent electromagnetic absorbing structure described in this invention is as follows: Figure 4 As shown. Based on the total thickness of the electromagnetic absorbing structure and its electromagnetic absorption performance, the better solutions (marked as pentagrams) are selected from the above solution set.

[0080] The common features of the optimized design results of the three-layer frequency-selective surface ITO transparent conductive pattern include a circumcircle radius L3 of 8.8 mm for the hexagonal tessellation cell, an overall in-plane size of 176 mm × 176 mm for the tessellation pattern, and a PET substrate thickness t of 0.125 mm. The first layer of the frequency-selective surface ITO transparent conductive pattern, such as... Figure 5 As shown, the sheet resistance R1 is 126Ω / sq, and the radius L of the circumcircle of the concentric inner and outer rings of the regular hexagon is... 1_1 and L 1_2 The thicknesses are 3.0mm and 7.8mm respectively. The second layer uses a frequency-selective surface ITO transparent conductive pattern, such as... Figure 6 As shown, the sheet resistance R2 is 165Ω / sq, and the radius L of the circumcircle of the concentric inner and outer rings of the regular hexagon is... 2_1 and L 2_2 The thicknesses are 3.7mm and 8.2mm respectively. The third layer features a frequency-selective surface ITO transparent conductive pattern, such as... Figure 7 As shown, the sheet resistance R3 is 365Ω / sq, and the radius L of the circumcircle of the concentric inner and outer rings of the regular hexagon is... 3_1 and L 3_2 The thicknesses are 1.9 mm and 7.9 mm, respectively. The thicknesses of the four transparent absorbing dielectric layers (h1 / h2 / h3 / h4) are 3.3 mm, 3.2 mm, 3.3 mm and 4.2 mm, respectively.

[0081] Step 2: Fabrication of a layered transparent stealth superstructure patterned absorbing layer

[0082] Based on the frequency selected in step one, the surface pattern is optimized with geometric parameters and sheet resistance to process a corresponding transparent conductive pattern, resulting in three patterned conductive films 1.1. The three supporting substrates 1.2 are transparent sheets of the same specified thickness. The three supporting substrates 1.2 and the three patterned conductive films 1.1 are bonded together with transparent adhesive to obtain a composite structure of three patterned conductive films 1.1 and supporting substrates.

[0083] ITO-PET transparent conductive films are patterned using magnetron sputtering and chemical etching techniques, with surface patterns selected by custom frequency.

[0084] The substrate 1.2 and the patterned conductive film 1.1 are bonded together with UV-curable photosensitive transparent epoxy resin.

[0085] The supporting substrate 1.2 is a transparent PMMA sheet with a thickness of 1 mm.

[0086] Step 3: Fabrication of the mold for the layered transparent stealth superstructure frame

[0087] Based on the thickness of the 4 transparent media layers generated in step one, determine the spacing of the grooves on the inner wall of the corresponding frame 3. Prepare a three-sided groove component and a single-sided groove component for the frame 3. Prepare two frame sealing plates 4 that match the grooves on the upper and lower edges of the frame. Adhere the two frame sealing plates 4 to the grooves on the upper and lower edges of the three-sided groove component using transparent adhesive to form a single-sided opening mold for the injection molding and curing of the media layer. Figure 8 As shown, the edge frame of the 3D printing medium layer forming mold is 180mm×180mm×14mm in length, width and height, the mold frame width is 2mm, the thickness of the electromagnetic absorption layer embedded in the groove edge is 1mm, the height between the reflective back plate and the upper edge of the inner wall of the first groove is 3.3mm, the height between the upper edge of the inner wall of the first groove and the upper edge of the inner wall of the second groove is 3.2mm, and the height between the upper edge of the inner wall of the second groove and the upper edge of the inner wall of the third groove is 3.3mm.

[0088] Both the three-sided groove component and the single-sided groove component were fabricated using a photopolymerization 3D printing method with transparent photosensitive resin.

[0089] The two frame sealing plates 4 are bonded to the upper and lower edge grooves of the three-sided groove component using UV-cured photosensitive transparent epoxy resin adhesive.

[0090] Step 4: Preparation of Layered Transparent Stealth Metastructure Dielectric Layer by Injection Molding and Curing

[0091] A schematic diagram illustrating the fabrication process of a transparent superstructure with embedded patterned resistive film layers, as shown below. Figure 9 As shown, the three patterned conductive film 1.1-support substrate composite structures obtained in step two are sequentially embedded into the mold through the corresponding grooves on the inner wall of the frame from the single-sided opening end of the dielectric layer curing mold obtained in step three, thus fixing the relative positions between the three patterned conductive film 1.1-support substrate composite structures. Liquid transparent adhesive is injected into the mold from the single-sided opening, a vacuum is drawn, and the single-sided groove component in frame 3 is used to seal the single-sided opening end of the mold. The transparent resin medium is left to cure at room temperature to form four layers of transparent medium, which integrate the absorption layer, frame, and frame sealing plate of the three patterned conductive film 1.1-support substrate composite structures into one piece.

[0092] The liquid transparent adhesive is a two-component, highly transparent epoxy resin adhesive with a mass ratio of epoxy resin and curing agent of 2.5:1.

[0093] The frame cover 4 is made of transparent PMMA sheet with a thickness of 1mm.

[0094] Step 5: Integration of the stacked transparent stealth superstructure reflective backplate: The reflective backplate 5 is bonded to the outer surface of the composite stacked microwave absorbing structure obtained in Step 4, through which the electromagnetic wave incident direction passes.

[0095] The reflective backplane is prepared by magnetron sputtering of a patternless ITO-PET film, with sheet resistance and PET substrate thickness of 5Ω / sq and 0.125mm, respectively.

[0096] The reflective backplate 5 is bonded to the outer surface of the composite laminated microwave absorbing structure using UV-cured photosensitive transparent epoxy resin adhesive.

[0097] like Figure 10 The figure shows the electromagnetic simulation results of the transparent superstructure with embedded patterned resistive film stacks of the present invention, which demonstrates a wideband electromagnetic stealth effect of less than -10dB across the entire 2-18GHz frequency band.

[0098] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An embedded patterned resistive film stacked transparent stealth superstructure, characterized in that: It includes a patterned absorbing layer (1), a dielectric layer (2), a frame (3), a frame sealing plate (4), and a reflective back plate (5); The patterned absorbing layer (1) includes N layers of patterned conductive thin films (1.1) and N layers of supporting substrates (1.2); The patterned conductive film (1.1) includes a patterned conductive material and a substrate; Conductive materials are patterned on the substrate surface; multi-frequency resonance is achieved by customizing the geometric pattern of N-layer optically transparent frequency-selective conductive thin films. The supporting substrate (1.2) is placed under the patterned conductive film (1.1) to provide support for the patterned conductive film (1.1); The dielectric layer (2) includes N+1 layers of transparent dielectric, which are solidified from transparent liquid material; the thickness of the N+1 layers of transparent dielectric is an important variable for adjusting the frequency selection of the surface electromagnetic wave absorption resonant frequency; The patterned absorbing layer composite structure consisting of the N-layer patterned conductive film (1.1) and the N-layer support substrate (1.2) is alternately placed with the N+1 layer transparent medium of the dielectric layer (2), that is, a single layer of patterned conductive film (1.1) and support substrate (1.2) are placed between two layers of transparent medium to form an interface loss type resonant absorbing mode. The frame (3) is composed of a three-sided connected frame and a single-sided frame, which facilitates the embedding of the patterned absorbing layer; the inner wall of the frame (3) is customized with N grooves that match the thickness of the single-layer patterned conductive film (1.1) in the patterned absorbing layer and the supporting substrate (1.2), and the spacing between adjacent grooves matches the thickness of the corresponding transparent medium in the dielectric layer (2); the upper and lower edges of the frame (3) have grooves for fixing the frame sealing plate (4); The frame sealing plate (4) is placed at the corresponding groove positions on the upper and lower edges of the frame (3), and together with the frame (3) forms a transparent medium liquid curing molding mold for the medium layer (2); The reflective backplate (5) is placed outside the electromagnetic wave transmission surface in the frame sealing plate (4); based on the reflective backplate, resonant wave absorption is achieved, so that the electromagnetic wave is fully absorbed and the electromagnetic wave transmittance is reduced.

2. The embedded patterned resistive film stacked transparent stealth superstructure as described in claim 1, characterized in that: The frequency-selective surface conductive pattern is composed of square concentric rings or regular hexagonal concentric rings as basic units, which are inlaid and densely tiled.

3. The embedded patterned resistive film stacked transparent stealth superstructure as described in claim 1, characterized in that: The frame (3) is made of transparent resin material.

4. The embedded patterned resistive film stacked transparent stealth superstructure as described in claim 1, characterized in that: The reflective backplate (5) has a low sheet resistance; the low sheet resistance value is less than or equal to 5Ω / sq.

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