A functional and structurally integrated ultrawideband absorbing material

Abstract

This invention discloses an integrated ultra-wideband absorbing material. From top to bottom, the material comprises a first lossy dielectric substrate, multiple lightweight interlayers, five resistive frequency selective surfaces, a metal backplate, and a composite material frame penetrating between the layers. Through slots are formed between the square rings and concentric geometric patterns of each resistive frequency selective surface. The composite material frame is embedded in these slots and continuously arranged along the thickness direction, creating a non-uniform dielectric structure within the material composed of high-dielectric and low-dielectric regions. This structure jointly regulates the resonance conditions and equivalent impedance gradient of the multiple resistive frequency selective surfaces, shifting the low-frequency absorption initiation frequency towards lower frequencies without increasing the thickness, and maintaining stable absorption performance at large oblique incidence angles. Simultaneously, the composite material frame improves the overall structural mechanical stability. This invention achieves thinness, wide bandwidth, and wide-angle absorption characteristics, making it suitable for electromagnetic stealth and electromagnetic compatibility applications.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic wave absorption technology, specifically to an integrated functional and structural ultra-wideband wave absorbing material. Background Technology

[0002] With the widespread use of modern electronic and electrical equipment, the problem of high-density electromagnetic radiation is becoming increasingly prominent. Ultra-wideband absorbing materials can effectively capture electromagnetic energy and convert it into heat energy, showing significant application potential in fields such as radar stealth, electromagnetic interference resistance, and electromagnetic shielding. To adapt to the complex and ever-changing electromagnetic environment, the operating frequency band of absorbing materials needs to cover the commonly used radar operating frequency range.

[0003] Early research proposed Salisbury screens and Jaumann absorber structures, while capable of meeting some millimeter-wave and centimeter-wave absorption requirements, suffered from limited absorption bandwidth and significant dependence on material thickness, making it difficult to balance low-frequency absorption with overall lightweight design. Subsequent developments of resistive frequency selective surfaces (RFS) and circuit-like analog absorbing structures, by constructing multi-scale resonant units within the material and stacking impedance matching networks, theoretically achieved wider operating frequency bands. However, these structures generally rely on multilayer dielectric stacks, often requiring significantly increased thickness for low-frequency absorption. Furthermore, commonly used low-dielectric-constant materials such as air layers and foam interlayers have weak mechanical properties, making them prone to damage under load, pressure, or engineering environmental conditions, leading to degradation of absorption performance or structural failure. On the other hand, achieving wide-angle, wide-band, and thin absorbing structures still faces engineering bottlenecks.

[0004] 1) In the low-frequency band, absorption depends on the structure thickness. Under the condition of satisfying the λ / 4 absorption mechanism, the structure thickness is difficult to be further compressed.

[0005] 2) The mechanical properties of lightweight sandwich layers are insufficient. In order to avoid the overall stability from being reduced due to weak mechanical layers, existing solutions often require additional reinforcement structures, which in turn introduces problems such as increased thickness and increased costs.

[0006] 3) The absorption performance deteriorates significantly under large oblique incident angles. The resistive frequency selective surface structure is prone to impedance mismatch when the angle changes, which significantly reduces the absorption rate.

[0007] In view of this, the present invention proposes an ultra-wideband absorbing material with integrated functional structure. Summary of the Invention

[0008] The purpose of this invention is to provide an integrated ultra-wideband absorbing material that solves the problems of traditional ultra-wideband absorbing materials, such as dependence on large thickness for low-frequency absorption, insufficient mechanical properties of lightweight sandwich layers, and easy deterioration of absorption performance under oblique incidence conditions. It realizes the engineering requirement of simultaneously achieving wideband, high intensity, and wide-angle stable absorption in a thin structure.

[0009] In a first aspect, the present invention provides an integrated ultra-wideband absorbing material with functional structure, comprising, from top to bottom, the following components in a three-dimensional coordinate space, with the Z-axis pointing upwards as the positive direction:

[0010] The material comprises a first lossy dielectric substrate, a first lightweight interlayer, a first resistive frequency selective surface, a second lightweight interlayer, a second resistive frequency selective surface, a third lightweight interlayer, a third resistive frequency selective surface, a fourth lightweight interlayer, a fourth resistive frequency selective surface, a fifth lightweight interlayer, a fifth resistive frequency selective surface, a sixth lightweight interlayer, and a metal backplate.

[0011] Among them, all multilayer resistive frequency selective surfaces have through slots reserved in the gaps between square rings and concentric geometric patterns.

[0012] The composite material frame is inserted into the above-mentioned through slot, and its thickness is consistent with the total thickness of the material, so that the frame forms a rigid through support between the layers; the lateral dimensions of the frame are strictly corresponding to the slot, so that the frame and the resistive frequency selection surface of each layer form a one-to-one embedded coupling interface.

[0013] The dielectric constant of the composite frame is higher than that of each lightweight interlayer, and its cuboid prisms and equilateral right-angled structures are continuously arranged along the thickness direction, so that the equivalent dielectric constant between the layers forms a controllable non-uniform distribution region, thereby forming a low-frequency compensation resonance path inside the material.

[0014] The coupling structure of the slot and the composite material frame changes the equivalent impedance gradient between the multilayer resistive frequency selective surfaces, causing the low-frequency absorption starting frequency to shift towards lower frequencies without increasing the structural thickness; and forming an additional loss path under oblique incidence conditions, which significantly increases the oblique incidence absorption retention angle.

[0015] As a preferred embodiment of the present invention, the first, second, third, fourth, and fifth resistive frequency selective surfaces each form a slotted structure corresponding to the composite material frame at the gap between the outer ring of the square ring and the inner concentric geometric pattern. Each slot is aligned with each other in the thickness direction, so that the composite material frame forms an integral solid support that runs through all resistive frequency selective surfaces after being embedded. This also causes the field distribution between each resistive layer to exhibit multi-order dielectric transition characteristics with fixed boundary perturbations, thereby affecting the resonance conditions of adjacent resistive frequency selective surfaces and generating a smoother impedance gradient compared to the frameless structure.

[0016] As a preferred embodiment of the present invention, the composite material frame includes four equilateral right-angled structures and a central cuboid column. Each structure fits tightly with the grooved boundary of the resistive frequency selective surface in the lateral direction and is made of a high dielectric constant material. This allows the frame to form a continuous high dielectric region in each lightweight interlayer when it passes through the resistive frequency selective surface, so that the equivalent dielectric constant distribution of the overall structure decreases layer by layer from the center outward. Under this arrangement, the standing wave position of the low-frequency electromagnetic wave is closer to the interior of the material than that of the traditional resistive frequency selective surface structure, thereby causing the low-frequency resonance condition to be met earlier and achieving low-frequency absorption broadening.

[0017] As a preferred embodiment of the present invention, the lightweight sandwich layer is composed of PMI foam, PI foam or honeycomb structure material, with a dielectric constant lower than that of the composite material frame, thereby forming an alternating arrangement of high and low dielectrics between the layers and the frame; this arrangement generates periodic dielectric disturbances between the multilayer resistive frequency selective surfaces, causing the resonant points of each resistive frequency selective surface to exhibit different trends with the thickness direction, and forming a wideband absorption range after combining with the sheet resistance of each layer of resistive film; at the same time, the presence of the frame restricts the compression deformation of each lightweight sandwich layer, so that the structure maintains flatness under external force loading.

[0018] As a preferred embodiment of the present invention, the resistive frequency selection surface adopts a square ring structure with cross-arm connections, and different ranges of sheet resistance are selected. The high sheet resistance layer is arranged near the incident surface above to enhance high-frequency absorption capability, while the low sheet resistance layer is arranged near the metal backplate to suppress low-frequency reflection. The above resistive distribution, combined with the dielectric reconstruction of the composite material frame, creates differentiated partitions of high and low frequency absorption paths in the thickness direction, significantly widening the overall absorption bandwidth compared to a frameless structure.

[0019] As a preferred embodiment of the present invention, the composite material frame is continuously interwoven between the resistive frequency selective surfaces, so that the gap process of each layer of resistive frequency selective surfaces remains unchanged; the frame forms a fixed dielectric boundary in the transverse direction, so that the incident electromagnetic wave generates a different refraction path distribution in the material than that of the traditional stacked structure. Especially when the oblique incident angle exceeds 45°, the frame region forms an additional absorption area, which reduces the energy leakage between the resistive frequency selective surfaces, thereby achieving stable maintenance of the absorption rate in the range of 60° to 75° and reducing the fluctuation of the reflection coefficient under large angle conditions.

[0020] As a preferred technical solution of the present invention, the arrangement of the through slots makes the composite material frame form a mechanical continuum in the thickness direction, so that the frame can uniformly transmit the force to the upper and lower sides when subjected to external loads, avoiding warping or interlayer misalignment of the substrate plate (FR4 or F4B) of the resistive frequency selective surface due to local stress concentration; under this support system, the resistive frequency selective surface still maintains the designed geometric dimensions under pressure, so that the resonant frequency is in a stable range and the absorption bandwidth is not affected by mechanical disturbances.

[0021] As a preferred technical solution of the present invention, the composite material frame is formed by 3D printing, carving or molding, so that the geometric error of the frame is kept within the tolerance range of the corresponding slots of the lightweight sandwich and the resistive frequency selection surface. After the insertion structure is installed, the frame forms a symmetrical arrangement along the thickness direction in the stack, so that the dielectric properties inside the frame are maintained between different resistive frequency selection surfaces. During the perpendicular and oblique incidence of electromagnetic waves, the frame generates a stable fixed boundary constraint on the electric field component, so that the reflection path and the absorption path are relatively stable, which helps to reduce the sensitivity of the absorption characteristics to the change of the incident angle.

[0022] As a preferred technical solution of the present invention, the composite material frame forms a through structure between each lightweight interlayer, so that the interior of the material has a composite mode of alternating high dielectric region, low dielectric region and resistive structure; in this composite mode, the local dielectric environment of each resistive frequency selective surface is non-uniform, so that each resistive frequency selective surface forms a different resonant response, so that the multilayer resonant peaks fill the gaps in the frequency domain, and the overall absorption remains continuous in the range of 1.8 to 40 GHz.

[0023] As a preferred technical solution of the present invention, the through-layout of the composite material frame in the thickness direction causes electromagnetic waves to be divided into two paths after entering the material: one path propagates in the lightweight interlayer region and the other path propagates in the frame region; the phase difference between the two paths shifts periodically with the frequency, causing the field distribution between the resistive frequency selective surfaces to exhibit a multi-level coupling state, thereby generating additional absorption peaks at low frequencies and generating multi-order energy attenuation at high frequencies, so that the overall structure can simultaneously satisfy the effects of low-frequency broadening, wide-band coverage and large-angle absorption.

[0024] The technical effects and advantages provided by the present invention in the above technical solution are as follows:

[0025] The proposed multi-layer resistive frequency-selective surface and composite material frame co-design mechanism simultaneously enhances the electromagnetic and structural properties of the absorbing material. The embedded composite material frame effectively improves the overall mechanical strength of the lightweight sandwich layer, avoiding the local instability inherent in traditional foam sandwich layers under pressure or vibration. Furthermore, its adjustment of the equivalent dielectric constant of the spacer layer lowers the starting frequency of low-frequency absorption without increasing thickness, thus significantly broadening the effective absorption bandwidth under perpendicular incidence. Simultaneously, the loss and impedance adjustment of the composite material frame itself compensates for the impedance mismatch caused by electromagnetic path changes under oblique incidence, maintaining high absorption at large angles. Therefore, this invention achieves a comprehensive improvement over traditional broadband absorbing structures in terms of thinness, mechanical enhancement, and stable absorption over wide angles, possessing significant engineering application value. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0027] Figure 1 This is a schematic diagram of the structural unit of the integrated ultra-wideband absorbing material design example of the present invention.

[0028] Figure 2 This is a schematic diagram of a composite material frame, representing an example of the design of an integrated ultra-wideband absorbing material with functional structure according to the present invention.

[0029] Figure 3 This is a schematic diagram of the frequency selection surface of a five-layer resistive film, which is an example of the design of an integrated ultra-wideband absorbing material with functional structure according to the present invention.

[0030] Figure 4 This invention presents an example of a functionally integrated ultra-wideband absorbing material design, showing the reflection coefficients under different oblique incidence angles under TE polarization after removing the composite material frame.

[0031] Figure 5 This invention presents an example of an integrated functional structure ultrawideband absorbing material design, showing the absorption rate under different oblique incident angles under TE polarization after removing the composite material frame.

[0032] Figure 6 This invention presents an example of a functionally integrated ultra-wideband absorbing material design, showing the reflection coefficients under different oblique incidence angles under TM polarization after removing the composite material frame.

[0033] Figure 7This invention presents an example of a functionally integrated ultrawideband absorbing material design, showing the absorption rate under different oblique incident angles in TM polarization after removing the composite material frame.

[0034] Figure 8 This is a design example of an integrated ultra-wideband absorbing material with functional structure according to the present invention, showing the reflection coefficient under different oblique incident angles in TE polarization.

[0035] Figure 9 This is an example of the design of an integrated ultra-wideband absorbing material with functional structure according to the present invention, showing the absorption rate under different oblique incident angles under TE polarization.

[0036] Figure 10 This is a design example of an integrated ultra-wideband absorbing material with functional structure according to the present invention, showing the reflection coefficient under different oblique incident angles in TM polarization.

[0037] Figure 11 This is an example of the design of an integrated ultra-wideband absorbing material with functional structure according to the present invention, showing the absorption rate under different oblique incident angles in TM polarization.

[0038] The components are: 1. First lossy dielectric plate; 2. First lightweight interlayer; 3. First resistive frequency selective surface; 4. Second lightweight interlayer; 5. Second resistive frequency selective surface; 6. Third lightweight interlayer; 7. Third resistive frequency selective surface; 8. Fourth lightweight interlayer; 9. Fourth resistive frequency selective surface; 10. Fifth lightweight interlayer; 11. Fifth resistive frequency selective surface; 12. Sixth lightweight interlayer; 13. Metal backplate; 14. Composite material frame. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings.

[0040] Throughout the accompanying drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. The described embodiments are only a part of the embodiments of this application, not all of them. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0041] Example 1

[0042] Please see Figure 1-3As shown, this embodiment provides a functional and structurally integrated ultra-wideband absorbing material. By embedding a composite material frame 14 in a lightweight sandwich of a multi-layer resistive frequency-selective absorbing structure, the mechanical properties are improved without deteriorating the overall absorbing performance of the composite absorbing material. Furthermore, the low-frequency absorption starting frequency point is broadened downward at the same thickness, and the oblique incident angle of the absorbing material is significantly increased, thus meeting the current application requirements for low-cost functional and structurally integrated absorbing materials.

[0043] Within the XYZ three-dimensional coordinate system, from top to bottom, it includes a first lossy dielectric plate 1, a first lightweight interlayer 2, a first resistive frequency selective surface 3, a second lightweight interlayer 4, a second resistive frequency selective surface 5, a third lightweight interlayer 6, a third resistive frequency selective surface 7, a fourth lightweight interlayer 8, a fourth resistive frequency selective surface 9, a fifth lightweight interlayer 10, a fifth resistive frequency selective surface 11, a metal backplate 13, and a composite material frame 14.

[0044] The aforementioned integrated functional structure ultra-wideband absorbing material is periodically arranged in the XOY plane, with a period size of 18.0~40.0 mm.

[0045] Furthermore, the first lossy dielectric plate 1 is a material with certain dielectric loss or magnetic loss characteristics, such as PLA, PET, Carbon / Glass Fiber Reinforced PLA, PPA-CF / GF, PPS doped with magnetic metal micropowder, glass fiber plate, etc., with a relative permittivity ranging from 1.5 to 15.0 and a relative permeability ranging from 1.0 to 15.0.

[0046] The materials of the first lightweight interlayer 2, the second lightweight interlayer 4, the third lightweight interlayer 6, the fourth lightweight interlayer 8, the fifth lightweight interlayer 10, and the sixth lightweight interlayer 12 can be one or more of the low dielectric constant lightweight materials such as PMI foam, PI foam, and honeycomb panels, with thicknesses of 1.0-3.0mm, 1.5-4.0mm, 2.0-6.0mm, 2.0-6.0mm, 2.0-6.0mm, and 3.0-15.0mm, respectively.

[0047] The first resistive frequency selection surface 3, the second resistive frequency selection surface 5, the third resistive frequency selection surface 7, the fourth resistive frequency selection surface 9, and the fifth resistive frequency selection surface 11 are composed of resistive structural units and a substrate. The preferred resistive structural unit for each resistive frequency selection surface layer is a combination of a square ring connected by cross arms and a concentric geometric pattern. The shapes of the units selected for different resistive frequency selection surface layers can be similar or completely different. The substrate is made of FR4 board, F4B board, or other boards with a certain mechanical strength, and the substrate thickness is 0.1-1.0 mm. The substrate between the two geometric patterns of the frequency selection surface unit is removed to reserve space for the construction of the composite material frame 14. The side length of the outer large square ring is 18.0-40.0 mm, and the side width is 0.2-3.0 mm. The internal geometric pattern can be easily adjusted according to performance requirements.

[0048] Specifically, the first resistive frequency selective surface 3 consists of two parts: a resistive structural unit and a substrate. The resistive structural unit of the first resistive frequency selective surface 3 is a concentric square ring structure with cross-arm connections. The substrate is made of FR4 board, F4B board, or other board materials with a certain mechanical strength. The substrate between the two concentric square rings of the frequency selective surface unit is removed to reserve space for the construction of the composite material frame 14. The outer large square ring has a side length of 20.0-35.0 mm and a side width of 0.5-3.0 mm. The inner small square ring has a side length of 12.5-31.5 mm and a side width of 0.2-3.0 mm. To reduce costs, the geometric unit of the first resistive frequency selective surface 3 adopts the form of a resistive film with a sheet resistance of 800-3000 ohms per square and a substrate thickness of 0.1-1.0 mm.

[0049] Furthermore, the material of the second lightweight interlayer 4 can be a lightweight material with a low dielectric constant, such as PMI foam, PI foam, or honeycomb board, with a thickness of 1.5-4.0mm.

[0050] Furthermore, the second resistive frequency selective surface 5 consists of two parts: a resistive structural unit and a substrate. The resistive structural unit of the second resistive frequency selective surface 5 is a concentric square ring structure with cross-arm connections. The substrate is made of a plate with certain mechanical strength, such as FR4 or F4B board. The substrate between the two concentric square rings of the frequency selective surface unit is removed to reserve space for the construction of the composite material frame 14. The outer large square ring has a side length of 20.0-35.0 mm and a side width of 0.2-3.0 mm. The inner small square ring has a side length of 12.5-31.5 mm and a side width of 0.2-3.0 mm. To reduce costs, the geometric unit of the first resistive frequency selective surface 3 adopts the form of a resistive film with a sheet resistance of 300-1000 ohms per square and a substrate thickness of 0.1-1.0 mm.

[0051] Furthermore, the material of the third lightweight interlayer 6 can be a lightweight material with a low dielectric constant, such as PMI foam, PI foam, or honeycomb board, with a thickness of 2.0-6.0 mm.

[0052] Furthermore, the third resistive frequency selective surface 7 consists of two parts: a resistive structural unit and a substrate. The resistive structural unit of the third resistive frequency selective surface 7 is a concentric square ring structure with cross-arm connections. The substrate is made of FR4 board, F4B board, or other board materials with a certain mechanical strength. The substrate between the two concentric square rings of the frequency selective surface unit is removed to reserve space for the construction of the composite material frame 14. The outer large square ring has a side length of 20.0-35.0 mm and a side width of 0.2-3.0 mm. The inner small square ring has a side length of 12.5-31.5 mm and a side width of 0.2-3.0 mm. To reduce costs, the geometric unit of the first resistive frequency selective surface 3 adopts the form of a resistive film with a sheet resistance of 70-600 ohms per square and a substrate thickness of 0.1-1.0 mm.

[0053] Furthermore, the material of the fourth lightweight interlayer 8 can be a lightweight material with a low dielectric constant, such as PMI foam, PI foam, or honeycomb board, with a thickness of 2.0-6.0mm.

[0054] Furthermore, the fourth resistive frequency selective surface 9 consists of two parts: a resistive structural unit and a substrate. The resistive structural unit of the fourth resistive frequency selective surface 9 is a concentric square ring structure with cross-arm connections. The substrate is made of FR4 board, F4B board, or other board materials with certain mechanical strength. The substrate between the two concentric square rings of the frequency selective surface unit is removed to reserve space for the construction of the composite material frame 14. The outer large square ring has a side length of 20.0-35.0 mm and a side width of 0.2-3.0 mm. The inner small square ring has a side length of 12.5-31.5 mm and a side width of 0.2-3.0 mm. To reduce costs, the geometric unit of the first resistive frequency selective surface 3 adopts the form of a resistive film with a sheet resistance of 50-400 ohms per square and a substrate thickness of 0.1-1.0 mm.

[0055] Furthermore, the material of the fifth lightweight interlayer 10 can be a lightweight material with a low dielectric constant, such as PMI foam, PI foam, or honeycomb board, with a thickness of 2.0-6.0 mm.

[0056] Furthermore, the fifth resistive frequency selective surface 11 consists of two parts: a resistive structural unit and a substrate. The resistive structural unit of the fifth resistive frequency selective surface 11 is a concentric square ring structure with cross-arm connections. The substrate is made of FR4 board, F4B board, or other board materials with certain mechanical strength. The substrate between the two concentric square rings of the frequency selective surface unit is removed to reserve space for the construction of the composite material frame 14. The outer large square ring has a side length of 20.0-35.0 mm and a side width of 0.2-3.0 mm. The inner small square ring has a side length of 12.5-31.5 mm and a side width of 0.2-3.0 mm. To reduce costs, the geometric unit of the first resistive frequency selective surface 3 adopts the form of a resistive film with a sheet resistance of 20-300 ohms per square and a substrate thickness of 0.1-1.0 mm.

[0057] Furthermore, the material of the sixth lightweight interlayer 12 can be a lightweight material with a low dielectric constant, such as PMI foam, PI foam, or honeycomb board, with a thickness of 5.0-13.0 mm.

[0058] Furthermore, the composite material frame 14 is composed of four equilateral right angles and a central cuboid column. The width of the two equal sides is less than or equal to the width of the gap between the two square rings, the length is less than or equal to the length of the gap between the two square rings, and the thickness is equal to the overall thickness of the composite material. The material is epoxy resin cured with glass fiber, carbon fiber reinforced PLA, and other materials with good mechanical properties.

[0059] The composite material frame 14 of the functional and structurally integrated ultra-wideband absorbing material of the present invention can be prepared by 3D printing or by processes such as engraving and molding. The design principle is as follows:

[0060] a. The broadband absorption performance of the integrated functional structure ultra-wideband absorbing material is mainly obtained by impedance matching design through the layer-by-layer superposition of two-dimensional resistive frequency selective surfaces. The fifth resistive frequency selective surface 11 is the most important strong absorption layer, the fourth resistive frequency selective surface 9 and the third resistive frequency selective surface 7 are strong absorption compensation layers, and the second resistive frequency selective surface 5, the first resistive frequency selective surface 3 and the first lossy dielectric plate 1 are weak absorption compensation layers.

[0061] b. The fourth resistive frequency selection surface 9, the third resistive frequency selection surface 7, the second resistive frequency selection surface 5, the first resistive frequency selection surface 3, and the first lossy dielectric plate 1 play the main role in regulating the mid-to-high frequency absorption performance.

[0062] c. The first lossy dielectric plate 1, the first lightweight interlayer 2, the second lightweight interlayer 4, the third lightweight interlayer 6, the fourth lightweight interlayer 8, the fifth lightweight interlayer 10, the sixth lightweight interlayer 12, the substrate of the first resistive frequency selective surface 3, the substrate of the second resistive frequency selective surface 5, the substrate of the third resistive frequency selective surface 7, the substrate of the fourth resistive frequency selective surface 9, the substrate of the fifth resistive frequency selective surface 11, and the composite material frame 14 together determine the mechanical properties of the functional structure integrated ultra-wideband absorbing material. Among them, the composite material frame 14 is the main functional component for enhancing the mechanical properties of the functional structure integrated ultra-wideband absorbing material.

[0063] d. The targeted design of the composite material frame 14 can effectively increase and adjust the equivalent dielectric constant of the integrated ultra-wideband absorbing material spacer layer, achieving near-perfect performance while reducing the thickness of the absorbing material.

[0064] e. The loss characteristics and impedance adjustment characteristics of the composite material frame 14 itself can realize impedance loss compensation and impedance matching adjustment under oblique incidence state, so as to increase the oblique incidence angle.

[0065] Figure 4 This invention presents an example of an integrated ultra-wideband absorbing material design, where the composite material frame 14 is removed. Under TE polarization, the reflection coefficients at different oblique incidence angles are measured. For vertical incidence, the frequency band with a reflection coefficient below -10dB is 2.07-40.0GHz. At an oblique incidence angle of 45°, the frequency band with a reflection coefficient below -10dB is 3.79-40.0GHz. At an oblique incidence angle of 60°, the frequency band with a reflection coefficient below -10dB is 7.77-25.8GHz.

[0066] Figure 5 This invention presents an example of an integrated ultra-wideband absorbing material design, where the composite material frame 14 is removed. Under TE polarization, the absorption rate is measured at different oblique incidence angles. At an oblique incidence angle of 60°, the frequency band with an absorption rate greater than 80% is 4.03-40.00 GHz. At an oblique incidence angle of 75°, the frequency band with an absorption rate greater than 80% is 10.45-29.60 GHz.

[0067] Figure 6 This invention presents an example of an integrated functional structure ultra-wideband absorbing material design. After removing the composite material frame 14, the reflection coefficients under TM polarization at different oblique incidence angles are shown. For vertical incidence, the frequency band with a reflection coefficient below -10dB is 2.07-40.00GHz. At an oblique incidence angle of 45°, the frequency band with a reflection coefficient below -10dB is 2.82-36.46GHz. At an oblique incidence angle of 60°, the frequency bands with a reflection coefficient below -10dB are 4.16-24.39GHz and 28.86-40.00GHz.

[0068] Figure 7 This invention presents an example of an integrated functional and structural ultrawideband absorbing material design. After removing the composite material frame 14, the absorption rate under TM polarization at different oblique incidence angles is measured. At an oblique incidence angle of 60°, the frequency band with an absorption rate greater than 80% is 3.38-40.0 GHz. At an oblique incidence angle of 75°, the frequency bands with an absorption rate greater than 80% are 7.58-20.19 GHz and 23.42-35.43 GHz.

[0069] Figure 8 This is a design example of the integrated ultra-wideband absorbing material of the present invention, showing the reflection coefficient under TE polarization at different oblique incidence angles. For vertical incidence, the frequency band with a reflection coefficient below -10dB is 1.87-40.0GHz. At an oblique incidence angle of 45°, the frequency band with a reflection coefficient below -10dB is 3.70-40.0GHz. At an oblique incidence angle of 60°, the frequency band with a reflection coefficient below -10dB is 7.78-27.11GHz.

[0070] Figure 9 This is a design example of the integrated functional structure ultra-wideband absorbing material of the present invention, showing the absorption rate under TE polarization at different oblique incidence angles. At an oblique incidence angle of 60°, the frequency band with an absorption rate greater than 80% is 4.03-40.00 GHz. At an oblique incidence angle of 75°, the frequency band with an absorption rate greater than 80% is 10.45-24.7 GHz.

[0071] Figure 10 This is a design example of an integrated ultra-wideband absorbing material based on the functional structure of this invention, showing the reflection coefficient under TM polarization at different oblique incidence angles. For vertical incidence, the frequency band with a reflection coefficient below -10dB is 2.07-40.00GHz. At an oblique incidence angle of 45°, the frequency band with a reflection coefficient below -10dB is 2.27-40.00GHz. At an oblique incidence angle of 60°, the frequency band with a reflection coefficient below -10dB is 2.93-40.00GHz.

[0072] Figure 11 This is a design example of an integrated ultra-wideband absorbing material based on the functional structure of this invention, showing the absorption rate under TM polarization at different oblique incidence angles. At an oblique incidence angle of 60°, the frequency band with an absorption rate greater than 80% is 2.32-40.0 GHz. At an oblique incidence angle of 75°, the frequency bands with an absorption rate greater than 80% are 4.21-9.87 GHz and 11.38-40.00 GHz.

[0073] Therefore, a functional-structure integrated ultra-wideband absorbing material is provided. Through layer-by-layer impedance matching design of multi-layer resistive frequency-selective surfaces, adjustment of the equivalent dielectric constant of the spacer layer by the embedded composite material frame 14 in the absorbing structure, and loss compensation of the composite material frame under oblique incidence, ultra-wideband absorption performance is achieved with a relative thickness of about 0.15λL. In particular, the introduction of the composite material frame 14 significantly improves the oblique incidence performance of the absorbing material while reducing the thickness of the absorbing material, which has great value in functional-structure integrated ultra-wideband absorbing materials.

[0074] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A functional structure integrated ultra-wideband wave-absorbing material, characterized in that, In three-dimensional coordinate space, the Z-axis is upward with positive direction, and from top to bottom includes: The first lossy dielectric substrate (1), the first lightweight interlayer (2), the first resistive frequency selective surface (3), the second lightweight interlayer (4), the second resistive frequency selective surface (5), the third lightweight interlayer (6), the third resistive frequency selective surface (7), the fourth lightweight interlayer (8), the fourth resistive frequency selective surface (9), the fifth lightweight interlayer (10), the fifth resistive frequency selective surface (11), the sixth lightweight interlayer (12), and the metal backplate (13); Among them, all multilayer resistive frequency selective surfaces have through slots reserved in the gaps between square rings and concentric geometric patterns. The composite material frame (14) is inserted into the above-mentioned through slot, and its thickness is consistent with the total thickness of the material, so that the frame forms a rigid through support between the layers; the transverse dimension of the frame corresponds strictly to the slot, so that the frame and each layer of resistive frequency selection surface form a one-to-one embedded coupling interface. The dielectric constant of the composite frame (14) is higher than that of each lightweight interlayer, and its cuboid columns and equilateral right-angle structures are continuously arranged along the thickness direction, so that the equivalent dielectric constant between layers forms a controllable non-uniform distribution region, thereby forming a low-frequency compensation resonance path inside the material. The coupling structure of the slot and the composite material frame (14) changes the equivalent impedance gradient between the multilayer resistive frequency selective surfaces, causing the low-frequency absorption starting frequency to move towards the low-frequency direction without increasing the structural thickness, and forming an additional loss path under oblique incidence, thereby increasing the oblique incidence absorption holding angle.

2. The functional structure-integrated ultra-wideband wave-absorbing material according to claim 1, characterized in that, The first resistive frequency selective surface (3), the second resistive frequency selective surface (5), the third resistive frequency selective surface (7), the fourth resistive frequency selective surface (9) and the fifth resistive frequency selective surface (11) all form a slotted structure that is continuously corresponding to the composite material frame (14) at the gap between the outer ring of the square ring and the inner concentric geometric pattern. Each slot is aligned with each other in the thickness direction, so that the composite material frame forms an integral solid support that runs through all resistive frequency selective surfaces after being embedded, and makes the field distribution between each resistive layer exhibit multi-order dielectric transition characteristics with fixed boundary perturbation, thereby affecting the resonance conditions of adjacent resistive frequency selective surfaces and generating a smoother impedance gradient compared to the frameless structure.

3. The functional-structure integrated ultra-wideband absorbing material according to claim 1, characterized in that, The composite material frame (14) includes four equilateral right-angle structures and a central cuboid column. Each structure fits tightly with the grooved boundary of the resistive frequency selective surface in the transverse direction and is made of a high dielectric constant material. When the frame passes through the resistive frequency selective surface, it forms a continuous high dielectric region in each lightweight interlayer (2, 4, 6, 8, 10). The equivalent dielectric constant distribution of the overall structure shows a state of decreasing layer by layer from the center outward. Under this layout, the standing wave position of the low-frequency electromagnetic wave is closer to the interior of the material than the traditional resistive frequency selective surface structure, thereby causing the low-frequency resonance condition to be met in advance and realizing the broadening of low-frequency absorption.

4. The functional-structure integrated ultra-wideband absorbing material according to claim 1, characterized in that, The lightweight interlayer is made of PMI foam, PI foam or honeycomb structure material, with a dielectric constant lower than that of the composite frame (14), thus forming an alternating arrangement of high and low dielectrics between the interlayer and the frame; this arrangement generates periodic dielectric disturbances between the multilayer resistive frequency selective surfaces, causing the resonant points of each resistive frequency selective surface to change with different trends in the thickness direction, and forming a wideband absorption range after combining with the sheet resistance of each layer of resistive film. At the same time, the presence of the frame restricts the compression deformation of each lightweight interlayer, so that the structure maintains flatness under external force loading.

5. The functional-structure integrated ultra-wideband absorbing material according to claim 4, characterized in that, The resistive frequency selection surface adopts a square ring structure with cross arms, and different ranges of sheet resistance are selected respectively, so that the high sheet resistance layer is arranged above the incident surface to enhance the high frequency absorption capability; the low sheet resistance layer is arranged near the metal back plate (13) to suppress low frequency reflection; the above resistive distribution combined with the dielectric reconstruction of the composite material frame (14) creates differentiated partitions of high and low frequency absorption paths in the thickness direction, making the overall absorption bandwidth wider than that of the frameless structure.

6. The integrated functional and structural ultrawideband absorbing material according to claim 5, characterized in that, The composite frame (14) forms a continuous through-hole between resistive frequency selective surfaces, so that the gap process of each layer of resistive frequency selective surfaces remains unchanged; the frame forms a fixed dielectric boundary in the transverse direction, so that the incident electromagnetic wave generates a different refraction path distribution in the material than the traditional stacked structure. When the oblique incident angle exceeds 45°, the frame area forms an additional absorption area, which reduces the energy leakage between resistive frequency selective surfaces, thereby achieving stable maintenance of the absorption rate in the range of 60° to 75° and reducing the fluctuation of the reflection coefficient under large angle conditions.

7. The functional-structure integrated ultra-wideband absorbing material according to claim 6, characterized in that, The arrangement of the through slots makes the composite material frame (14) form a mechanical continuum in the thickness direction, so that the frame can uniformly transmit the force to the upper and lower sides when subjected to external loads, avoiding warping or interlayer misalignment of the substrate of the resistive frequency selection surface due to local stress concentration; under this support system, the resistive frequency selection surface still maintains the designed geometric dimensions under pressure, so that the resonant frequency is in a stable range and the absorption bandwidth is not affected by mechanical disturbances.

8. The functional-structure integrated ultra-wideband absorbing material according to claim 7, characterized in that, The composite material frame (14) is formed by 3D printing, carving or molding, so that the geometric error of the frame is kept within the tolerance range of the slots corresponding to the lightweight sandwich and the resistive frequency selection surface. After the insertion structure, the frame forms a symmetrical arrangement along the thickness direction in the stack, so that the dielectric properties inside the frame are continuous between different resistive frequency selection surfaces. During the vertical and oblique incidence of electromagnetic waves, the frame generates a stable fixed boundary constraint on the electric field component, so that the reflection path and absorption path are relatively stable, which helps to reduce the sensitivity of absorption characteristics to changes with the incident angle.

9. The functional-structure integrated ultra-wideband absorbing material according to claim 8, characterized in that, The composite material frame (14) forms a through structure between each lightweight interlayer, so that the interior of the material has a composite mode with alternating high dielectric region, low dielectric region and resistive structure; under this composite mode, the local dielectric environment of each resistive frequency selective surface is non-uniform, so that each resistive frequency selective surface forms a different resonant response, so that the multilayer resonant peaks fill the gaps in the frequency domain, and the overall absorption remains continuous in the range of 1.8 to 40 GHz.

10. The functional-structure integrated ultra-wideband absorbing material according to claim 1, characterized in that, The through-layout of the composite frame (14) in the thickness direction causes electromagnetic waves to be divided into two paths after entering the material: one propagates in the lightweight interlayer region and the other propagates in the frame region; the phase difference between the two paths is periodically shifted with the frequency, causing the field distribution between the resistive frequency selective surfaces to exhibit a multi-level coupling state, thereby generating additional absorption peaks at low frequencies. The high-frequency generation generates multi-stage energy attenuation, enabling the overall structure to simultaneously achieve the effects of low-frequency widening, wide-band coverage, and large-angle absorption.

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