An omnidirectional matching electromagnetic wave-absorbing structure

Abstract

This invention relates to an omnidirectional matched electromagnetic absorbing structure. By radially arranging a resonant absorption section and an impedance matching section in a ring-shaped absorbing layer, the equivalent relative permittivity of the absorbing layer satisfies the spatial Kramers-Kronig dispersion relation. Combined with the real part of the equivalent relative permittivity approaching 1 at the outer edge of the impedance matching section, electromagnetic waves can smoothly enter the structure without reflection and be dissipated. This effectively solves the technical problem of enhanced reflection and absorption performance failure caused by impedance mismatch when traditional absorbing materials are incident at large angles. Ultimately, it achieves wide-angle impedance matching and omnidirectional non-reflective absorption of multi-directional incident electromagnetic waves in a purely passive structural system.

Description

Technical Field

[0001] This invention belongs to the field of microwave absorbing medium technology, specifically relating to an omnidirectional matching electromagnetic wave absorbing structure. Background Technology

[0002] With the increasing complexity of the electromagnetic environment, electromagnetic wave absorbing structures have fundamental application requirements in fields such as electromagnetic compatibility and stealth. Traditional electromagnetic wave absorbing structures typically rely on specific material compositions or fixed physical configurations to dissipate incident electromagnetic energy. However, in practical applications, because these conventional absorbing structures are often designed to match specific incident angles, polarization methods, or narrow frequency bands, severe impedance mismatch occurs at the interface of the absorbing structure when electromagnetic waves are incident at a large angle, or when the location of the radiation source changes, resulting in a wide-angle distribution of the incident direction. This impedance mismatch causes a large number of electromagnetic waves to undergo strong interface reflection before entering the absorbing structure, preventing the structure's built-in electromagnetic energy dissipation mechanism from functioning effectively, ultimately leading to a significant decrease in overall absorption efficiency.

[0003] To improve impedance matching under large-angle incident conditions, some existing technologies attempt to introduce active devices with gain characteristics or complex energy compensation networks. However, this not only greatly increases the complexity of engineering implementation and manufacturing costs, but also severely limits the operational stability of the absorption structure in passive, complex electromagnetic environments.

[0004] Therefore, there is an urgent need for an omnidirectional matching electromagnetic absorbing structure that can eliminate abrupt changes in structural interface impedance without active gain compensation and achieve non-reflective absorption of electromagnetic waves incident from different directions. Summary of the Invention

[0005] One of the objectives of this invention is to solve at least one or more of the aforementioned problems existing in the prior art. In other words, one of the objectives of this invention is to provide an omnidirectional matching electromagnetic absorbing structure that meets one or more of the aforementioned requirements.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides an omnidirectional matching electromagnetic absorbing structure, comprising: It includes an annular absorbing layer, which radially includes an inner resonant absorption section and an impedance matching section outside the resonant absorption section. The resonant absorption section is composed of several first resonant units arranged in a concentric ring, and the size of the first resonant units is arranged in a radially varying manner. The real part of the equivalent relative permittivity of the impedance matching section decreases radially outward. The variation and decrease make the equivalent relative permittivity of the absorbing layer radially varied, and the real and imaginary parts of the varied distribution satisfy the spatial Kramers-Kronig relationship, and approach 1 at the outer edge of the absorbing layer.

[0007] In a preferred embodiment, the first resonant unit includes a first insulating medium, two metal patterns spaced apart by the first insulating medium, and an interlayer conductive element that penetrates the first insulating medium and is electrically connected at both ends to the two metal patterns respectively. The two metallic shapes, the first insulating medium, and the interlayer conductive elements work together to form an equivalent LC resonant structure.

[0008] In one preferred embodiment, each metal graphic includes multiple metal arms that are bent and connected in sequence; In the same first resonant unit, the two metal patterns are arranged in a 180-degree rotational symmetry on the projection along the thickness direction of the first insulating medium.

[0009] In a preferred embodiment, the dimensions of the first resonant unit are arranged to vary radially, wherein the length or width of at least a portion of the metal arm in each first resonant unit varies radially to change the equivalent capacitance and equivalent inductance of the first resonant unit.

[0010] In a preferred embodiment, the impedance matching section includes a plurality of transition units arranged in a concentric ring.

[0011] In a preferred embodiment, the impedance matching section further includes a plurality of second resonant units arranged in a concentric ring, the second resonant units being located inside the transition unit; The dimensions of the second resonant unit are arranged in a radially decreasing manner, such that at the second resonant unit, the real part of the equivalent relative permittivity of the impedance matching part decreases radially outward.

[0012] In a preferred embodiment, the second resonant unit includes a second insulating medium, two metal patterns spaced apart by the second insulating medium, and an interlayer conductive element that penetrates the second insulating medium and is electrically connected at both ends to the two metal patterns respectively. The two metallic shapes, the second insulating medium, and the interlayer conductive elements work together to form an equivalent LC resonant structure.

[0013] In a preferred embodiment, the transition unit includes a third insulating medium whose axial height decreases radially outward, such that the volume percentage of the third insulating medium in the transition unit decreases radially outward, and exhibits an equivalent relative permittivity approaching 1 when combined with adjacent air on the outermost side.

[0014] In a preferred embodiment, the spacing between the resonant absorption section and the impedance matching section that changes or decreases each time is less than one-tenth of the free space wavelength corresponding to the preset operating frequency band.

[0015] Compared with the prior art, the omnidirectional matching electromagnetic absorbing structure provided by the present invention has the following beneficial effects: This invention addresses the problem of enhanced reflection and absorption performance failure caused by impedance mismatch in traditional absorbing materials at large angles of incidence. By radially arranging a resonant absorption section and an impedance matching section in an annular absorbing layer, the equivalent relative permittivity of the absorbing layer satisfies the spatial Kramers-Kronig dispersion relation. Combined with the real part of the equivalent relative permittivity approaching 1 at the outer edge of the impedance matching section, electromagnetic waves can smoothly enter the structure without reflection and be dissipated. This effectively solves the technical problem of enhanced reflection and absorption performance failure caused by impedance mismatch in traditional absorbing materials at large angles of incidence. Ultimately, it achieves wide-angle impedance matching and omnidirectional non-reflective absorption of multi-directional incident electromagnetic waves in a purely passive structural system. Attached Figure Description

[0016] Figure 1 This is a top view of the omnidirectional matching electromagnetic wave absorbing structure of the present invention; Figure 2 This is a cross-sectional view of the omnidirectional matching electromagnetic wave absorbing structure of the present invention; Figure 3 This is a schematic diagram of the structure of the first metal pattern of the present invention; Figure 4 This is a cross-sectional view of the first resonant unit of the present invention; Figure 5 This is a plan view of the first metal pattern of the present invention; Figure 6 This is a schematic diagram of the structure of the second metal pattern of the present invention; Figure 7 This is a cross-sectional view of the second resonant unit of the present invention; Figure 8 This is a plan view of the second metal pattern of the present invention; Figure 9 This is a schematic diagram of the structure of the third insulating medium of the present invention; Figure 10 This is a schematic diagram of the volume duty cycle of the third insulating medium in air according to the present invention; Figure 11 This is a schematic diagram of the equivalent relative permittivity distribution of the omnidirectional absorbing structure of this invention at three test frequencies: 7.8 GHz, 8.0 GHz, and 8.2 GHz. Figure 12 The equivalent relative permittivity of the first resonant unit in this embodiment of the invention; Figure 13The equivalent relative permittivity of the second resonant unit in this embodiment of the invention; Figure 14 The equivalent relative permittivity of the transition unit in the embodiments of the present invention; Figure 15 The simulation results of this invention using plane waves as excitation at three test frequencies: 7.8 GHz, 8.0 GHz, and 8.2 GHz. Figure 16 The simulation results are obtained by using a line source as the excitation in the embodiments of the present invention at three test frequencies: 7.8 GHz, 8.0 GHz, and 8.2 GHz.

[0017] Reference numerals: First resonant unit - 110, First insulating medium - 111, First metal pattern - 112, First interlayer conductive element - 113, Second resonant unit - 120, Second insulating medium - 121, Second metal pattern - 122, Second interlayer conductive element - 123, Transition unit - 130, Third insulating medium - 131. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0019] The following description provides examples and does not limit the scope, applicability, or examples set forth in the claims. Changes may be made to the function and arrangement of the described elements without departing from the scope of the invention. Various processes or components may be appropriately omitted, substituted, or added to the various examples. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Furthermore, features described with respect to some examples may be combined into other examples.

[0020] Reference Figure 1 and Figure 2 This invention provides an omnidirectional matching electromagnetic absorbing structure, including an annular absorbing layer. The absorbing layer includes a resonant absorption section located on the inner side and an impedance matching section located on the outer side of the resonant absorption section along the radial direction. The resonant absorption section is composed of a plurality of first resonant units 110 arranged concentrically in a ring. The size of the first resonant units 110 is arranged in a radially varying manner. The real part of the equivalent relative permittivity of the impedance matching section decreases radially outward. This variation and decrease result in a radially varying distribution of the equivalent relative permittivity of the absorbing layer, and the real and imaginary parts of the varying distribution satisfy the spatial Kramers-Kronig relation, approaching 1 at the outer edge of the absorbing layer.

[0021] Furthermore, the real and imaginary parts of the varying and decreasing distributions satisfy the following spatial Kramers-Kronig analytical relation model in cylindrical coordinates: .

[0022] Where ξ is the set spatial scale parameter of the profile, and A is the amplitude. This is the radial distance, r0 is the set resonance position parameter, and R0 is the set outer radius parameter of the cylinder. The background permittivity is given, and the permeability is set to 1 (μ=1).

[0023] In this invention, efficient omnidirectional non-reflective absorption of electromagnetic waves in the target frequency band can be achieved through the coordinated configuration of the inner resonant absorption section and the outer impedance matching section. Specifically, the real part of the equivalent relative permittivity of the outermost impedance matching section gradually decreases and approaches 1. When an electromagnetic wave is incident on the absorbing structure of this embodiment, the impedance of the absorbing structure in the outer layer matches that of the free space, which serves as the electromagnetic wave propagation medium. This ensures that electromagnetic waves incident at any angle are almost not reflected and instead smoothly enter the interior of the absorbing layer. As the electromagnetic wave propagates inward, it passes through the equivalent complex permittivity profile constructed by the absorbing layer, which is adjusted to satisfy the spatial Kramers-Kronig relation.

[0024] In the equivalent relative permittivity profile that satisfies this relationship, its continuously changing real part can provide a channel with a smooth refractive index transition for electromagnetic waves, guiding the electromagnetic waves to propagate continuously inward in the non-uniform medium without interface reflection; at the same time, the imaginary part, as a loss term, utilizes the ohmic loss of the conductive material constituting the resonant unit and the dielectric loss of the insulating medium to gradually convert the electromagnetic wave energy propagating along the channel into heat energy and dissipate it completely.

[0025] Unlike traditional solutions that require the introduction of gain characteristic factors or active compensation devices, this embodiment utilizes the aforementioned structure to guide electromagnetic energy to propagate continuously and unidirectionally within a lossy artificial medium, where it is absorbed and dissipated. This fundamentally suppresses scattering into the back half-space, achieving near-reflection-free absorption and mitigating the problem of a sharp drop in absorption efficiency in traditional absorbing materials at large incident angles.

[0026] In one specific embodiment of the present invention, the first resonant unit 110 constituting the resonant absorption section adopts a multilayer solid structure based on an equivalent LC resonant model. Specifically, in conjunction with Figure 3 , Figure 4 , Figure 5 As shown, in a conventional configuration, each first resonant unit 110 uses a first insulating medium 111 as its physical support base, and a first metal pattern 112 made of conductive material is attached to two opposite surfaces of the first insulating medium 111.

[0027] In addition, the first insulating medium 111 may not serve as a physical support foundation. In this case, the overall physical support of the first resonant unit 110 is achieved by additional support components, while the first insulating medium 111 is placed between the two first metal patterns 112, thereby stimulating capacitive coupling effect between the upper and lower first metal patterns 112, thus providing the local coupling capacitance and electrical insulation guarantee required to construct the LC equivalent resonant circuit.

[0028] A first interlayer conductive element 113 is disposed inside the first insulating medium 111, extending through its thickness direction. The two ends of the first interlayer conductive element 113 form a reliable electrical connection with the first metal pattern 112 on the upper and lower surfaces, respectively.

[0029] The first interlayer conductive element 113 breaks the physical isolation between the upper and lower first metal patterns 112, providing a crucial vertical electrical path for constructing LC equivalent resonance, thereby closing and assembling the originally dispersed two-dimensional planar patterns into a complete three-dimensional solid conductive loop in space. When an electromagnetic wave with an electric field direction parallel to the first interlayer conductive element 113 is incident, a high-frequency alternating current is excited on the first interlayer conductive element 113, thus providing crucial distributed inductance for the entire resonant structure.

[0030] In this case, the upper and lower first metal patterns 112 are used to generate distributed capacitance. At the same time, the first interlayer conductive element 113 and the first metal pattern 112 work together to provide distributed inductance. The two cooperate with the first insulating medium 111 to generate strong field resonance and localization effect under the excitation of electromagnetic waves at a specific frequency, thereby forming an equivalent LC resonant structure.

[0031] In one specific embodiment, the first insulating medium 111 can be made of inorganic dielectric material or electrically insulating resin to form a solid substrate; the first metal pattern 112 located on the upper and lower surfaces of the substrate can be formed by a preparation process such as direct mounting, photolithography etching, screen printing, inkjet printing or vacuum coating; correspondingly, the first interlayer conductive element 113 can be manifested as a metal via penetrating the solid substrate.

[0032] The materials of the first insulating dielectric 111 include, but are not limited to, F4B (polytetrafluoroethylene glass cloth copper-clad laminate), FR-4 (epoxy resin glass fiber board), polyimide (PI), and other microwave radio frequency substrate materials with excellent dielectric loss tangent; the materials of the first metal pattern 112 and the first interlayer conductive element 113 can be selected from copper, silver, gold, or highly conductive ink and other metal conductor materials with excellent conductivity.

[0033] In one specific embodiment of the present invention, the first metal pattern 112 in the first resonant unit 110 may specifically include: multiple metal arms that are bent and connected in sequence; in the same first resonant unit 110, the two first metal patterns 112 are arranged in a 180-degree rotational symmetry on the projection along the thickness direction of the first insulating medium 111.

[0034] Figure 3 This is a structural schematic diagram showing the first metal pattern 112 alone, and a complete first resonant unit 110, its side view is as follows. Figure 4 As shown.

[0035] Figure 5 The figure shown is a plan view of the two first metal figures 112 viewed from the same direction. From a geometric topological perspective, the first metal figure 112 mainly includes a central connecting part located in the central region, and multiple metal arms extending from the central connecting part to both sides and formed by multiple right-angle bends. The central connecting part is used in physical space to align and electrically connect to the first interlayer conductive element 113 that penetrates the insulating medium. The multiple metal arms are used to extend the electrical length of the resonant unit.

[0036] pass Figure 5 It can be seen intuitively that in the same first resonant unit 110, the first metal pattern 112 located on the top surface of the insulating medium and the first metal pattern 112 located on the bottom surface maintain a strict 180-degree central rotational symmetry in the projection along the thickness direction.

[0037] The above structure significantly extends the physical path of high-frequency surface current without increasing the overall macroscopic dimensions of the first resonant unit 110. When it is necessary to change the equivalent inductance of the resonant unit to adjust the center resonant frequency in engineering applications, the effective electrical length can be changed simply by adjusting the extension length of one or more end metal arms in the two-dimensional plane, without altering the position of the center via. This gives the above structure an extremely high degree of freedom in frequency tuning.

[0038] In this invention, to achieve the aforementioned spatial Kramers-Kronig relationship in the absorbing layer, the complex permittivity of the absorbing layer needs to exhibit a specific radial gradient distribution. Typically, simply arranging resonant units of the same size uniformly makes it difficult to achieve such a continuously varying permittivity profile. Therefore, in this invention, by giving resonant units located at different radial positions different sizes and adjusting their local resonant frequencies, each resonant unit can exhibit the required equivalent relative permittivity at its corresponding spatial location. This allows for precise alignment and realization of the aforementioned continuously varying theoretical profile.

[0039] Based on the above objectives, in a specific embodiment of the present invention, the radially varying size configuration of the first resonant unit 110 may specifically include: the length or width of at least a portion of the metal arms in each first resonant unit 110 varies radially to change the equivalent capacitance and equivalent inductance of the first resonant unit 110.

[0040] Specifically, for ease of actual engineering manufacturing, the physical length of the first interlayer conductive element 113 penetrating the insulating medium is typically configured as a uniform fixed value throughout the entire resonant absorption section. This fixed length provides a macroscopic distributed inductance reference for all first resonant units 110. Under this reference, in order to meet the requirements of different radial positions for specific resonant frequencies, this embodiment transfers the structural modifications required for frequency modulation to a two-dimensional plane. Based on the radial coordinates of the unit, the effective electrical length through which the high-frequency current flows in the local area is directly changed by selectively adjusting the arm length or width of the bent metal arms in the upper and lower first metal patterns 112 along the radial gradient.

[0041] In each of the first resonant units 110, in response to the change in the length or width of the two-dimensional metal arm, the parameters of the entire equivalent LC resonant structure change, and its center resonant frequency also changes accordingly.

[0042] This implementation takes into account that the target continuous dielectric constant profile needs to be discretized at the microscale. Therefore, by keeping the length of the three-dimensional interlayer conductive parts fixed and only fine-tuning the size of the two-dimensional surface metal arm, it not only effectively avoids the high cost of processing three-dimensional stepped plates of varying thicknesses and ensures the manufacturability of the overall structure of the absorbing layer, but also can accurately approximate the target equivalent capacitance and equivalent inductance required to match each discrete ring at high resolution, thereby achieving the profile that satisfies the spatial Kramers-Kronig relationship.

[0043] In one specific embodiment of the present invention, such as Figure 1 , Figure 2 As shown, the impedance matching part in the above-mentioned omnidirectional matching electromagnetic wave absorbing structure may specifically include: a plurality of transition units 130 arranged in a concentric ring.

[0044] In this specific embodiment, an impedance matching section including a transition unit 130 is provided around the resonant absorption section constructed by the first resonant unit 110. This facilitates the smooth bridging of the equivalent electromagnetic parameters of the inner absorbing structure's outer edge with the external free space. Through this smooth transition of the equivalent electromagnetic parameters, the abrupt change in dielectric constant at the interface between free space and the artificial medium is effectively eliminated. Therefore, the incident electromagnetic wave hardly undergoes physical reflection when it contacts the surface of the absorbing structure, but rather propagates smoothly and efficiently into the interior of the absorbing layer, as if it were continuously propagating in a uniform medium.

[0045] In one specific embodiment of the present invention, the impedance matching section may further include: a plurality of second resonant units 120 arranged in a concentric ring, the second resonant units 120 being located inside the transition unit 130; the size of the second resonant units 120 is arranged in a radially decreasing manner, such that at the second resonant unit 120, the real part of the equivalent relative permittivity of the impedance matching section decreases radially outward.

[0046] To achieve impedance matching with extremely low reflection between the absorbing structure and the external free space where the equivalent dielectric constant approaches 1, this invention places a pure dielectric transition unit 130 on the outermost side of the absorbing layer. This relies solely on the volume gradient of the dielectric substrate towards air to make the real part of its equivalent relative dielectric constant infinitely approach 1. However, a significant dielectric constant span and impedance difference exist between the high dielectric absorption region formed by the first resonant unit 110 and the aforementioned pure dielectric transition unit 130. Their direct proximity easily induces strong reflections. Therefore, this embodiment adds a second resonant unit 120 located inside the transition unit 130 in the impedance matching section. This second resonant unit 120, with its specific metallic configuration, can smoothly reduce the high equivalent dielectric constant inside the absorbing layer to a lower critical range, thereby forming a stable impedance buffer between the first resonant unit 110 and the transition unit 130.

[0047] By combining the transition unit 130 and the second resonant unit 120, this embodiment effectively eliminates impedance abrupt changes, ensuring that electromagnetic waves can smoothly enter the resonant absorption section inside the absorbing layer from free space with almost no reflection.

[0048] In one specific implementation, the second resonant unit 120 adopts a multi-layer solid structure based on the equivalent LC resonant model.

[0049] Combination Figure 6 , Figure 7 , Figure 8 Specifically, the structure of the second resonant unit 120 shown includes a second insulating medium 121 as a physical support foundation, with two spaced-apart second metal patterns 122 attached to opposite surfaces of the second insulating medium 121. Simultaneously, a second interlayer conductive element 123 penetrating the thickness direction is disposed within the second insulating medium 121, with its two ends electrically connected to the second metal patterns 122 on the upper and lower surfaces, providing distributed inductance for the equivalent LC resonant circuit of the second resonant unit 120.

[0050] Figure 6 This is a structural schematic diagram showing the second metal pattern 122 alone, and a complete second resonant unit 120, its side view is as follows. Figure 7 As shown, the bottom view is as follows Figure 8As shown.

[0051] Furthermore, the second insulating medium 121 can also be made of inorganic dielectric materials or electrically insulating resins to form a solid substrate; the second metal pattern 122 located on the upper and lower surfaces of the substrate can be formed by manufacturing processes such as direct mounting, photolithography etching, screen printing, inkjet printing or vacuum coating; correspondingly, the second interlayer conductive element 123 can be manifested as a metal via penetrating the solid substrate.

[0052] The material of the second insulating medium 121 includes, but is not limited to, microwave RF substrate materials with excellent dielectric loss tangents such as F4B (polytetrafluoroethylene glass cloth copper-clad laminate), FR-4 (epoxy resin glass fiber board), and polyimide (PI); the materials of the second metal pattern 122 and the second interlayer conductive element 123 can be selected from metal conductor materials with excellent conductivity such as copper, silver, gold, or high conductivity ink.

[0053] In one specific embodiment of the present invention, the transition unit 130 in the impedance matching section may specifically include: a third insulating medium 131, the axial height of the third insulating medium 131 decreasing radially outward, so that the volume ratio of the third insulating medium 131 in the transition unit 130 decreases radially outward, and the outermost part exhibits an equivalent relative permittivity close to 1 when combined with the adjacent air. This implementation takes into account the boundary conditions where the outermost layer is in direct contact with free space. It adopts a structure in which the physical volume ratio of the pure dielectric layer changes continuously and gradually, so that the real part of the equivalent relative permittivity of the outermost layer approaches the permittivity of air infinitely, ensuring that electromagnetic waves have extremely low reflection and can penetrate without damage.

[0054] Figure 9 A cross-sectional structural schematic diagram of multiple transition units 130 is provided. Specifically, from a geometric perspective, the axial height of the third insulating medium 131 in its radially outward extension direction exhibits a continuous slope-like or discrete step-like decreasing trend, thus forming a wedge-shaped cross-sectional profile. Since the equivalent relative permittivity of the spatial region where the transition unit 130 is located is jointly determined by the intrinsic permittivity of the third insulating medium 131 and the permittivity of the air filling it (approximately 1) according to their respective physical volume duty cycles, the equivalent relative permittivity of this region can be effectively controlled by changing the volume duty cycle of the third insulating medium 131, ultimately achieving a smooth transition with air at the outermost edge.

[0055] To facilitate understanding of the volume duty cycle of the third insulating medium 131, the following is used: Figure 10 The volume duty cycle of the third insulating medium 131 in air is illustrated.

[0056] To ensure the applicability of the equivalent medium theory in the discretized structure, the array arrangement of the resonant absorbing medium section and the impedance matching medium section is specifically set such that the spacing of each change or decrease is less than one-tenth of the free space wavelength corresponding to the preset operating frequency band. Specifically, the free space wavelength corresponding to the preset operating frequency band is λ 0; Set the radial spacing step size of any adjacent annular elements to 0. a Then the structural parameter matrix satisfies the boundary condition constraint relationship: 0 < a < λ 0 / 10.

[0057] To further illustrate the embodiments of the present invention, the following example provides a specific implementation designed for a center operating frequency of 8 GHz.

[0058] Regarding the macroscopic construction of the radial profile, this embodiment sets the target radial complex permittivity distribution based on the spatial Kramers-Kronig relation, wherein the relevant theoretical profile parameters are configured as follows: background permittivity reference value parameters. ε 0=0.7, amplitude characteristic parameter A =5, cross-sectional spatial scale parameter ξ =0.048, resonance position parameter r 0=90mm, and the outer radius of the cylinder is an overparameter. R 0 = 180mm. To avoid potential singularities in the central region, the inner boundary cutoff radius is set to... r 1 = 48mm, outer boundary cutoff radius r 3= R 0=180mm is used to achieve matching with free space.

[0059] Based on the above settings, this embodiment discretizes the continuous radial complex permittivity profile into 59 radial annular layers in space, and wraps the radial strip structure tangentially to form a ring. Figure 11 This is a schematic diagram of the equivalent relative permittivity distribution at three frequency points (7.8GHz, 8.0GHz, and 8.2GHz) in this embodiment. The specific discretization strategy is as follows: The first part consists of layers 1 to 35 corresponding to the resonant absorption section, with a radial range from... r Extending outwards, this region serves as the medium body that satisfies the Lorentz profile, and the radial width of its elements is uniformly set to 3mm.

[0060] The second part consists of layers 36 to 59 corresponding to the impedance matching section, with a radial range from... r 2 to r3. Within this region, layers 36 to 38 maintain a radial width of 3mm; while layers 39 to 59, closest to the outer boundary, have their radial width reduced to 1mm. This segmented width design is based on the consideration that the primary task of the outer boundary region is to smoothly transition the equivalent dielectric constant from the interior and gradually approach free space. ε (≈1) Although this region has lower requirements for the wide tuning capability of the equivalent parameters, it has extremely high requirements for the fineness and smoothness of parameter transitions. Therefore, by introducing a 1mm wide subdivided high-resolution transition segment here, a smoother and gentler impedance matching can be achieved, thereby minimizing high-frequency electromagnetic reflections at the outer boundary.

[0061] Regarding the material and size settings of the first resonant unit 110 and the second resonant unit 120, this embodiment uses the same first resonant unit 110 structure as described in the above embodiment in layers 1 to 35. To ensure that the unit maintains subwavelength scale characteristics at 8 GHz, the radial width of the unit... a Fixed at 3mm to meet the requirements. a < λ 0 / 10, and simultaneously set its tangential period. p =8mm. Regarding the selection of base materials, the first insulating medium 111 uses F4B high-frequency board as the insulating substrate, with a thickness of... h =1.2mm, its relative permittivity ε r =3.5, dielectric loss tangent tan δ =0.003; The first metal pattern 112, set on the two opposite surfaces of the first insulating medium 111, is made of copper, and the copper foil thickness is... t =0.035mm; the diameter d of the metal via penetrating the first insulating medium 111 is 0.4mm. Furthermore, symmetrical thicknesses are left on the outer sides of the upper and lower surfaces of the first insulating medium 111 along the thickness direction. h An air layer of 1 mm.

[0062] The specific geometric parameters of the first metal pattern 112 of the first resonant unit 110 are configured as follows: the line width of the bent metal arms constituting the first metal pattern 112. w 1= w 2 = 0.25mm, line spacing g =0.25mm; the rectangular metal plates connected to both ends of the metal via have widths of... b =1mm, length c =1.5mm; the total arm length and single arm length of the bent metal arm are respectively taken as... L 1 = 1.4 mm L2 = 1.1 mm. Depending on the specific needs of different layers, increasing the metal arm length can enlarge the equivalent electrical dimension of the first resonant unit 110, thereby lowering the resonant frequency; conversely, decreasing it can increase the resonant frequency. This can be achieved by finely adjusting the total arm length. L 1 and single arm length L 2. The absorbing structure in this embodiment can achieve extremely precise frequency tuning steps.

[0063] Figure 12 To calculate the equivalent relative permittivity of a first resonant unit 110 using the equivalent parameter extraction algorithm, the results of the equivalent parameter extraction algorithm show that, under the above parameter configuration, the electric resonant frequency of the first resonant unit 110 is set at around 8.4 GHz. In this embodiment, the strong Lorentz-type dispersion abrupt change characteristics exhibited by the unit near the resonant frequency point are utilized to successfully synthesize a highly matched equivalent complex permittivity as needed near the target 8 GHz.

[0064] In the impedance matching section, i.e., layers 36 to 59, this embodiment sequentially deploys a second resonant unit 120 that serves as the first-stage transition unit and a transition unit 130 that serves as the second-stage transition unit.

[0065] The second resonant unit 120 also adopts p =8mm tangential period, the base dielectric layer remains the same thickness h =1.2mm F4B board material with the top and bottom sides retained h An air layer of 1 mm. Its second metal pattern 122 is composed of two standard rectangular metal strips electrically connected to a metal via penetrating the second insulating medium 121.

[0066] In this design, the length of the metal strip is configured as follows: L a =4mm, the second resonant unit 120 exhibits weak dispersion response characteristics, making its equivalent dielectric constant change gradually around 8GHz. Figure 10 This is the equivalent relative permittivity of the second resonant unit 120 in this embodiment.

[0067] The transition unit 130 is configured as a third insulating medium 131 with a rectangular or trapezoidal cross-section, and the axial length of the third insulating medium 131 is precisely changed. L b This directly changes the volume duty cycle of the third insulating medium 131 in its spatial grid, thereby changing the equivalent dielectric constant of the transition unit 130. Figure 11 This is the equivalent relative permittivity of the transition unit 130 in this embodiment.

[0068] Figure 13To calculate the equivalent relative permittivity of a second resonant unit 120 using an equivalent parameter extraction algorithm, Figure 14 The equivalent relative permittivity of a certain transition unit 130 is calculated using the equivalent parameter extraction algorithm.

[0069] By combining the second resonant unit 120 and the transition unit 130, the equivalent dielectric constant of the impedance matching section successfully transitions continuously from approximately 1.68 to 1.00 (air reference value) within the operating frequency band, supporting impedance matching between the inner resonant absorber and the outer free space. By matching the inverted equivalent dielectric constant with the target value layer by layer at different radial layers, the resonant absorber (layers 1 to 35) constructs a complete physical profile conforming to the spatial Kramers-Kronig relation, and achieves non-reflective incident electromagnetic waves from the external space through the impedance matching section (layers 36 to 59).

[0070] Table 1 provides the specific parameters of the first resonant unit 110 from layer 1 to layer 35, and Table 2 provides the specific parameters of the second resonant unit 120 and transition unit 130 from layer 36 to layer 59.

[0071]

[0072] Table 1

[0073] Table 2 The embodiments with the above specific parameter configurations were verified in a full-wave electromagnetic simulation environment: A transversely polarized (TE) plane wave is used as the excitation, and the electric field direction is along... z The axis, the direction of the magnetic field is located at r - φ In the plane, at the three test frequencies of 7.8 GHz, 8.0 GHz, and 8.2 GHz, the results are as follows: Figure 15 As shown, electromagnetic waves are significantly absorbed at different spatial locations within the Kramers-Kronig medium inside the absorbing structure, and no obvious standing waves or reflections were detected near the structure. Further bistatic RCS distribution data show that the RCS is close to zero in the backscattering half-space range of 90° to 270°, while the energy is mainly concentrated in the forward direction, demonstrating excellent backscattering suppression capability. This exhibits a consistent trend in the 7.8 GHz to 8.2 GHz range, verifying the structure's robustness within the target frequency band.

[0074] To further verify the omnidirectional scattering suppression capability under line source incident conditions, a line source excitation was also set up in the electromagnetic simulation environment for verification, and the results are as follows: Figure 16As shown, the structure exhibits the same strength of backscatter suppression (matched absorption) capability for radiated electromagnetic waves in the rear half-space. The above data fully demonstrates that, utilizing the highly discretized and cascaded integrated spatial Kramers-Kronig configuration architecture provided by this invention, broadband stable absorption and omnidirectional non-reflective modulation of the incident electromagnetic field's intrinsic characteristics can be achieved without the need for external active devices.

[0075] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed in this application can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0076] The foregoing description is merely an exemplary embodiment of this application and should not be construed as limiting the scope of this application. Any equivalent changes and modifications made in accordance with the teachings of this application shall still fall within the scope of this application. Those skilled in the art will readily conceive of other embodiments of this application upon considering the disclosure of the specification and practice. The foregoing disclosure is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary technical means in the art not described in this application. The specification and embodiments are considered exemplary only, and the scope and spirit of this application are defined by the claims.

Claims

1. An omnidirectional matched electromagnetic wave absorber structure, characterized in that, It includes an annular absorbing layer, which radially comprises an inner resonant absorption section and an impedance matching section outside the resonant absorption section; The resonant absorption section is composed of a plurality of first resonant units arranged in a concentric ring, and the size of the first resonant units is arranged in a radially varying manner. The real part of the equivalent relative permittivity of the impedance matching section decreases radially outward. The variation and decrease make the equivalent relative permittivity of the absorbing layer radially varied, and the real and imaginary parts of the varied distribution satisfy the spatial Kramers-Kronig relation, and approach 1 at the outer edge of the absorbing layer.

2. The omnidirectional matched electromagnetic wave absorbing structure according to claim 1, characterized in that, The first resonant unit includes a first insulating medium, two metal patterns spaced apart by the first insulating medium, and an interlayer conductive element that penetrates the first insulating medium and is electrically connected at both ends to the two metal patterns respectively. The two metal patterns, the first insulating medium, and the interlayer conductive element together constitute an equivalent LC resonant structure.

3. The omnidirectional matched electromagnetic wave absorber structure according to claim 2, characterized in that, Each of the metal figures comprises multiple metal arms that are bent and connected in sequence; In the same first resonant unit, the two metal patterns are arranged in a 180-degree rotational symmetry on the projection along the thickness direction of the first insulating medium.

4. The omnidirectional matching electromagnetic absorbing structure according to claim 3, characterized in that, The dimensions of the first resonant unit are arranged to vary radially, wherein at least a portion of the length or width of the metal arm in each of the first resonant units varies radially to change the equivalent capacitance and equivalent inductance of the first resonant unit.

5. The omnidirectional matching electromagnetic absorbing structure according to claim 1, characterized in that, The impedance matching section includes several transition units arranged in a concentric ring.

6. The omnidirectional matching electromagnetic absorbing structure according to claim 5, characterized in that, The impedance matching section further includes several second resonant units arranged in a concentric ring, the second resonant units being located inside the transition unit; The dimensions of the second resonant unit are arranged in a radially decreasing manner, such that at the second resonant unit, the real part of the equivalent relative permittivity of the impedance matching part decreases radially outward.

7. The omnidirectional matching electromagnetic absorbing structure according to claim 6, characterized in that, The second resonant unit includes a second insulating medium, two metal patterns spaced apart by the second insulating medium, and an interlayer conductive element that penetrates the second insulating medium and is electrically connected at both ends to the two metal patterns respectively; The two metal patterns, the second insulating medium, and the interlayer conductive element together constitute an equivalent LC resonant structure.

8. The omnidirectional matching electromagnetic absorbing structure according to claim 6, characterized in that, The transition unit includes a third insulating medium whose axial height decreases radially outward, such that the volume percentage of the third insulating medium in the transition unit decreases radially outward, and exhibits an equivalent relative permittivity approaching 1 when combined with adjacent air on the outermost side.

9. The omnidirectional matching electromagnetic absorbing structure according to claim 1, characterized in that, The spacing between each change or decrease of the resonant absorption section and the impedance matching section is less than one-tenth of the free space wavelength corresponding to the preset operating frequency band.

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