A design method for ultra-wideband composite absorbers based on equivalent circuit models

Abstract

This invention provides an ultra-wideband composite absorber based on an equivalent circuit model and its design method, belonging to the field of electromagnetic absorbing materials technology. The ultra-wideband composite absorber is composed of multiple planar periodically arranged structural units. Each structural unit includes, from bottom to top, a metal base plate, a bottom absorbing dielectric layer, and an n-layer composite structure. The composite structure includes, from bottom to top, an intermediate dielectric layer, a dielectric substrate, and a resistive film square ring. The intermediate dielectric layer is made of pure aramid paper honeycomb, and the bottom absorbing dielectric layer is also made of aramid paper absorbing honeycomb, combining lightweight construction with strong impact resistance. This invention combines the characteristics of absorptive and interferometric absorbing materials, maximizing the absorption bandwidth of the absorbing material within a fixed thickness. It optimizes the ultra-wideband composite absorber using an equivalent circuit model and transmission line theory, considering the non-uniform current distribution within the square ring when extracting the equivalent resistance of the resistive film square ring, thus making the extracted surface impedance more accurate.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic absorbing materials technology, specifically relating to an ultra-wideband composite absorber based on an equivalent circuit model and its design method. Background Technology

[0002] With the continuous development of radar detection technology, low-frequency radar has been widely used. Faced with the dense detection threat of low-frequency radar, the demand for low-frequency ultra-wideband absorbing materials is becoming increasingly urgent. However, traditional absorbing materials mainly operate in the 2-18 GHz range, which cannot meet the requirements for low-frequency stealth.

[0003] Based on their absorption mechanisms, microwave absorbing materials are classified into absorptive and interferometric types. Absorptive materials absorb incident electromagnetic wave energy through their own electrical or magnetic losses. Increasing the material thickness or introducing magnetic materials can produce a certain degree of low-frequency absorption, but increasing the thickness and weight significantly reduces the practicality of the absorbing material. Interferometric absorbing materials utilize the principle of destructive interference to achieve absorption, such as Salisbury screens, Jaumann absorbers, and circuit-simulated absorbers. These periodic structure-based absorbing materials can achieve broadband absorption within a specific frequency band with relatively thin thicknesses by increasing the number of layers and adjusting the structural parameters of the units. Composite absorbers utilize both of these electromagnetic wave loss mechanisms simultaneously, and hold promise for achieving ultra-wideband absorption.

[0004] The traditional design method for composite absorbers involves first estimating a set of initial structural parameters based on the absorption performance requirements within a given frequency band. These parameters are then substituted into electromagnetic simulation software to calculate the frequency response. The results are compared with the given requirements, and the structural parameters are repeatedly adjusted until a solution that meets the requirements is obtained. This traditional design method is only suitable for simple structures with a small number of layers. For complex multi-layer structures, this method is not only inefficient but also struggles to find the optimal solution. To address these issues, this invention employs an equivalent circuit model and transmission line theory to treat any multi-layer composite absorber as an equivalent cascaded circuit, obtaining an analytical expression for reflectivity. This enables accurate and efficient structural design and optimization. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention proposes an ultra-wideband composite absorber based on an equivalent circuit model and its design method. This absorber exhibits superior broadband absorption performance in terms of absorption bandwidth and has advantages such as thinness, high strength, light weight, and flexible and efficient design.

[0006] The technical solution adopted in this invention is as follows:

[0007] An ultra-wideband composite absorber based on an equivalent circuit model is characterized by being composed of multiple planar periodically arranged structural units. Each structural unit includes, from bottom to top, a metal base plate, a bottom absorbing dielectric layer, and an n-layer composite structure. The composite structure includes, from bottom to top, an intermediate dielectric layer, a dielectric substrate, and a resistive film ring. Wherein, n≥1.

[0008] Furthermore, the intermediate dielectric layer is made of pure aramid paper honeycomb with a dielectric constant ε. a The value is 1 to 1.5; the material of the bottom absorbing medium layer is aramid paper absorbing honeycomb, that is, aramid paper honeycomb modified with absorbing material. The present invention does not limit the absorbing material.

[0009] Furthermore, the thickness of the intermediate dielectric layer in each layer of the composite structure may be different or the same, and the thickness h of the intermediate dielectric layer in the k,k=1,...,n layer of the composite structure is... k k = 1, ..., n is 10 to 30 mm.

[0010] Furthermore, the thickness h of the bottom absorbing dielectric layer m It is 10-20mm.

[0011] Furthermore, the resistive film ring is a ring-shaped ITO (indium tin oxide) conductive film.

[0012] Furthermore, the dimensions of the resistive film square rings in each layer of the composite structure are different or the same. Specifically, the period P of the resistive film square rings in the k-th, k=1,...,n-th composite structure is... k k = 1, ..., n is 10 ~ 50 mm, and the ring width s k k = 1, ..., n is 0.5 ~ 5 mm, and the inter-ring gap g between adjacent resistive film square rings is... k k = 1, ..., n is 0.1 to 1 mm, and the thickness of the resistive film square ring is 10 to 200 nm.

[0013] Furthermore, the dielectric substrate is a PET (polyethylene terephthalate) dielectric substrate with a thickness t of 0.1–0.5 mm and a dielectric constant ε. s =3-0.18j.

[0014] Furthermore, the metal base plate is made of materials such as iron, copper, or aluminum.

[0015] This invention also proposes a design method for the ultra-wideband composite absorber based on the equivalent circuit model, specifically including:

[0016] First, based on the structural dimension parameters of the resistive film square ring in each layer of the composite structure, the corresponding equivalent circuit parameters are extracted, and the surface impedance of the resistive film square ring in each layer of the composite structure is derived. Then, based on the equivalent circuit model and transmission line theory, the analytical expression of the reflectivity of the ultra-wideband composite absorber is extracted. Finally, the genetic optimization algorithm is used to optimize the overall structure of the ultra-wideband composite absorber to obtain the ultra-wideband composite absorber with the best absorption performance.

[0017] Furthermore, the process of deriving the surface impedance of the resistive film square ring in each layer of the composite structure specifically includes:

[0018] Based on the structural dimensions of the resistive film square ring in the k-th, k=1,...,n-th layer composite structure, calculate the equivalent resistance R of the resistive film square ring in the k-th, k=1,...,n-th layer composite structure. k k = 1, ..., n:

[0019]

[0020] The equivalent capacitance C between adjacent resistive film square rings due to coupling effect k k = 1, ..., n:

[0021]

[0022] The equivalent inductance L between adjacent resistive film square rings k k = 1, ..., n:

[0023]

[0024] In the formula,

[0025]

[0026]

[0027]

[0028]

[0029] Among them, Rs k Z0 is the sheet resistance of the square ring of the resistive film in the composite structure of the kth, k = 1, ..., nth layer; Z0 is the air impedance; ω = 2πf is the angular frequency corresponding to different frequencies f of the electromagnetic wave; λ is the wavelength of the electromagnetic wave; F(P) k (x, λ) is related to P k The catenary model function related to X and λ; G(P) k ,X,λ) is F(P k The correction factors in (X, λ); A and β are meaningless intermediate variables;

[0030] Since the resistive film ring is attached to the upper surface of the dielectric substrate, the equivalent capacitance C′ after considering the influence of the dielectric substrate is... k k = 1, ..., n and equivalent inductance L′ k k = 1, ..., n are respectively:

[0031] C′ k =ε r,eff,k C k (8)

[0032] L′ k =μ r,eff,k L k (9)

[0033] Where, ε r,eff,k ,k=1,...,n is the equivalent dielectric constant of the resistive film square ring in the k,k=1,...,n-th layer composite structure; μ r,eff,k ,k=1,...,n is the equivalent permeability coefficient of the resistive film square ring in the k,k=1,...,n layer composite structure, with a value of 1;

[0034] The equivalent dielectric constant ε of the resistive film square ring in the nth (top) composite structure r,eff,n for:

[0035]

[0036]

[0037] Where, ε av The average dielectric constant of the dielectric substrate and air: ε s ε represents the dielectric constant of the substrate in each layer of the composite structure; ε represents the equivalent dielectric constant ε of the resistive film ring in the k',k'=1,...,n-1 layer (other layers) of the composite structure. r,eff,k' The values ​​of k' = 1, ..., n-1 are:

[0038]

[0039] Where, ε a h is the dielectric constant of the intermediate dielectric layer 3 in the composite structure. k'+1 The thickness of the intermediate dielectric layer in the (k'+1)th layer of the composite structure;

[0040] Furthermore, the surface impedance Z of the resistive film square ring in the k-th, k=1,...,n-th layer composite structure was calculated. FSSk For k = 1, ..., n:

[0041]

[0042] The beneficial effects of this invention are as follows:

[0043] 1. This invention proposes an ultra-wideband composite absorber based on an equivalent circuit model. Compared with traditional single-type absorbing materials, the ultra-wideband composite absorber combines the broadband absorption advantage of absorptive absorbing materials (bottom absorbing dielectric layer) for high-frequency electromagnetic waves with the flexible design characteristics of interference absorbing materials (resistive film square ring), ultimately maximizing the absorption bandwidth of the absorbing material at a fixed thickness.

[0044] 2. This invention uses pure aramid paper honeycomb and aramid paper absorbing honeycomb as dielectric layer materials, which makes the ultra-wideband composite absorber lighter in weight and also has strong impact resistance.

[0045] 3. This invention employs an equivalent circuit model and transmission line theory to achieve precise and efficient structural design and optimization for any multilayer composite absorber. Furthermore, when extracting the equivalent resistance of the resistive film square ring, the non-uniform current distribution within the ring is taken into account. Therefore, compared with the traditional analytical formula for the surface impedance of the resistive film square ring, the surface impedance extracted by this invention is more accurate, resulting in greater flexibility and feasibility in structural design. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the structural unit of the ultra-wideband composite absorber based on the equivalent circuit model proposed in this invention;

[0047] Figure 2 This is a structural diagram of the resistive film square ring in the ultrawideband composite absorber based on the equivalent circuit model proposed in this invention.

[0048] Figure 3 The equivalent circuit model of the ultra-wideband composite absorber proposed in this invention is shown below.

[0049] Figure 4 This is a comparison chart of the reflectivity calculated by theory and simulated by electromagnetic simulation software for the ultra-wideband composite absorber based on the equivalent circuit model proposed in Example 1.

[0050] Figure 5 This is a comparison chart of the reflectivity of the ultra-wideband composite absorber based on the equivalent circuit model proposed in Example 2, calculated theoretically and simulated by electromagnetic simulation software.

[0051] Figure 6 This is a comparison chart of the reflectivity of the ultra-wideband composite absorber based on the equivalent circuit model proposed in Example 3, between theoretical calculations and electromagnetic simulation software simulations.

[0052] Figure 7 This is a comparison of the reflectivity calculated by the theory and simulated by the electromagnetic simulation software for the ultra-wideband composite absorber based on the equivalent circuit model after optimization by the genetic algorithm proposed in Example 4.

[0053] Figure 8 This is a comparison chart of the reflectivity of the ultra-wideband composite absorber based on the equivalent circuit model optimized by the genetic algorithm proposed in Example 4, using electromagnetic simulation software simulation and experimental testing. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in conjunction with the accompanying drawings.

[0055] This invention proposes an ultra-wideband composite absorber based on an equivalent circuit model, which is composed of multiple planar periodically arranged structural units. The specific structure of the structural units is as follows: Figure 1 As shown, the structure includes a metal base plate 5, a bottom absorbing dielectric layer 4, and an n-layer composite structure from bottom to top. The composite structure includes an intermediate dielectric layer 3, a dielectric substrate 2, and a resistive film ring 1 from bottom to top; wherein, n≥1.

[0056] The design method for ultra-wideband composite absorbers based on equivalent circuit models specifically includes the following steps:

[0057] Step 1: Based on the structural dimensional parameters of the resistive film square ring 1 in each layer of the composite structure, such as... Figure 2 As shown, the corresponding equivalent circuit parameters are extracted, and the surface impedance of the resistive film square ring 1 in each layer of the composite structure is derived, specifically:

[0058] Step 1.1: Based on the structural dimension parameters of the resistive film square ring 1 in the k-th, k=1,...,n-th layer composite structure, calculate the equivalent resistance R of the resistive film square ring 1 in the k-th, k=1,...,n-th layer composite structure. k k = 1, ..., n:

[0059]

[0060] The equivalent capacitance C between adjacent resistive film square rings 1 due to coupling effect k k = 1, ..., n:

[0061]

[0062] The equivalent inductance L between adjacent resistive film square rings 1 k k = 1, ..., n:

[0063]

[0064] In the formula,

[0065]

[0066]

[0067]

[0068]

[0069] Among them, Rs k ,k=1,...,n is the sheet resistance of the resistive film square ring 1 in the kth,k=1,...,n-th composite structure; Z0=377 is the air impedance; ω=2πf is the angular frequency corresponding to different frequencies f of the electromagnetic wave; λ is the wavelength of the electromagnetic wave; F(P k (x, λ) is related to P k The catenary model function related to X and λ; G(P) k ,X,λ) is F(P k The correction factors in (X, λ); A and β are meaningless intermediate variables;

[0070] Step 1.2: Since the resistive film square ring 1 is attached to the upper surface of the dielectric substrate 2, the equivalent capacitance C′ after considering the influence of the dielectric substrate 2 is calculated. k k = 1, ..., n and equivalent inductance L′ k k = 1, ..., n are respectively:

[0071] C′ k =ε r,eff,k C k (8)

[0072] L′ k =μ r,eff,k L k (9)

[0073] Where, ε r,eff,k ,k=1,...,n is the equivalent dielectric constant of the resistive film square ring 1 in the k,k=1,...,n-th layer composite structure; μ r,eff,k ,k=1,...,n is the equivalent permeability coefficient of the resistive film square ring 1 in the k,k=1,...,n layer composite structure, with a value of 1;

[0074] The equivalent dielectric constant ε of the resistive film square ring 1 in the nth (top) composite structure r,eff,n for:

[0075]

[0076]

[0077] Where, ε av The average dielectric constant of dielectric substrate 2 and air: ε s denoted as , where is the dielectric constant of the dielectric substrate 2 in each layer of the composite structure;

[0078] The equivalent dielectric constant ε of the resistive film square ring 1 in the composite structure of the k',k'=1,...,n-1 layers (other layers) r,eff,k' The values ​​of k' = 1, ..., n-1 are:

[0079]

[0080] Where, ε a h is the dielectric constant of the intermediate dielectric layer 3 in the composite structure. k'+1 The thickness of the intermediate dielectric layer 3 in the k'+1th layer composite structure;

[0081] Step 1.3: Calculate the surface impedance Z of the resistive film square ring 1 in the k-th, k=1,...,n-th layer composite structure. FSSk For k = 1, ..., n:

[0082]

[0083] Step 2: Based on the equivalent circuit model and transmission line theory, extract the analytical expression for the reflectivity of the ultra-wideband composite absorber, specifically:

[0084] Step 2.1 Figure 3 The equivalent circuit diagram of the ultra-wideband composite absorber is shown. The metal base plate 5 is equivalent to a grounded terminal. The input admittance Y of the bottom absorbing dielectric layer 4 is calculated. m :

[0085]

[0086]

[0087]

[0088] Where, η m The characteristic admittance of the bottom absorbing dielectric layer 4; β m μ is the propagation constant of the bottom absorbing medium layer 4. m and ε m These are the magnetic permeability and dielectric constant of the bottom absorbing dielectric layer 4, respectively.

[0089] Step 2.2: Based on transmission line theory, calculate the input admittance Y below the intermediate dielectric layer 3 in the k-th, k=1,...,n-th layer composite structure. ak k = 1, ..., n:

[0090]

[0091] The input admittance Y of the dielectric substrate 2 and below in the k-th, k=1,...,n-th layer composite structure sk k = 1, ..., n:

[0092]

[0093] The input admittance Y below the kth, k=1,...,nth layer of the composite structure k k = 1, ..., n:

[0094] Y k =Y sk +Y FSSk (19)

[0095]

[0096] In the above formula,

[0097]

[0098]

[0099]

[0100]

[0101] Where, η a The characteristic admittance of intermediate dielectric layer 3 in the multilayer composite structure; β a η is the propagation constant of the intermediate dielectric layer 3 in the composite structure; s The characteristic admittance of the dielectric substrate 2 in each layer of the composite structure; β s η0 is the propagation constant of the dielectric substrate 2 in each layer of the composite structure; η0 is the air waveguide admittance; c is the speed of light in vacuum; μ a μ represents the permeability of the intermediate dielectric layer 3 in the composite structure. s Y represents the permeability of the dielectric substrate 2 in each layer of the composite structure. FSSk ,k=1,...,n is the input admittance of the resistive film square ring 1 in the k,k=1,...,n-th layer composite structure; when k=1, Y k-1 =Y0=Y m ;

[0102] Step 2.3: Calculate the reflectivity Γ of the ultra-wideband composite absorber when the electromagnetic wave is incident perpendicularly from the top of the absorber.

[0103]

[0104] Where Y0 is the air waveguide admittance, its value is equal to

[0105] Step 3: Optimize the overall structure of the ultra-wideband composite absorber using a genetic optimization algorithm to obtain the ultra-wideband composite absorber with optimal absorption performance. The frequency band selected is 0.1–18 GHz, and the optimization parameters are: the period P of the resistive film square ring 1. k k = 1, ..., n, ring width s k k = 1, ..., n, interring gap g k The sheet resistance Rs of the resistive film square ring 1, k = 1, ..., n, is given. k k = 1, ..., n, where h is the thickness of the bottom absorbing dielectric layer 4. m and the thickness h of the intermediate dielectric layer 3 k ,k=1,...,n;The optimization objective is: to maximize the absorption bandwidth of the ultra-wideband composite absorber with a reflectivity of less than -10dB, while keeping the total thickness of the ultra-wideband composite absorber constant.

[0106] To verify the accuracy of the reflectivity calculated by the equivalent circuit model, the reflectivity of single-layer, double-layer, and triple-layer composite structures in Examples 1-3 was calculated using Matlab, and compared with the simulation results of electromagnetic simulation software in Comparative Examples 1-3.

[0107] Example 1

[0108] This embodiment proposes an ultra-wideband composite absorber based on an equivalent circuit model, which is composed of multiple planar periodically arranged structural units. The structural units include, from bottom to top, a metal base plate 5, a bottom absorbing dielectric layer 4, and a single-layer composite structure. The composite structure includes, from bottom to top, an intermediate dielectric layer 3, a dielectric substrate 2, and a resistive film square ring 1.

[0109] In this embodiment, the sheet resistance Rs1 of the resistive film square ring 1 is 30Ω / sqr, the period P1 is 30mm, the ring width s1 is 1mm, and the inter-ring gap g1 is 0.2mm; the thickness t of the dielectric substrate 2 is 0.125mm, the thickness h1 of the intermediate dielectric layer 3 is 14.875mm, and the thickness h of the bottom absorbing dielectric layer 4 is... m =15mm.

[0110] Compile the equivalent circuit model program of the ultra-wideband composite absorber proposed in this embodiment in Matlab, substitute the specific structural parameters, and calculate the corresponding reflectivity curve; then simulate the ultra-wideband composite absorber proposed in this embodiment using electromagnetic simulation software to obtain the corresponding simulated reflectivity curve. Figure 4 The graph shows a comparison between the theoretical calculation and the electromagnetic simulation results of the ultra-wideband composite absorber proposed in this embodiment. It can be seen that the calculated results and the simulation results are in high agreement within the 0.1 to 10 GHz frequency band, which indicates that the equivalent circuit model of the ultra-wideband composite absorber proposed in this embodiment has high accuracy in the calculation of reflectivity.

[0111] Example 2

[0112] This embodiment proposes an ultra-wideband composite absorber based on an equivalent circuit model, which is composed of multiple planar periodically arranged structural units. The structural units include a metal base plate 5 from bottom to top, a bottom absorbing dielectric layer 4, and a double-layer composite structure. The composite structure includes an intermediate dielectric layer 3 from bottom to top, a dielectric substrate 2, and a resistive film square ring 1.

[0113] In this embodiment, the specific structural parameters of the double-layer composite structure are the same: the sheet resistance of the resistive film square ring 1 is Rs1=Rs2=30Ω / sqr, the period is P1=P2=30mm, the ring width is s1=s2=1mm, and the inter-ring gap is g1=g2=0.2mm; the thickness of the dielectric substrate 2 is t=0.125mm, the thickness of the intermediate dielectric layer 3 is h1=h2=14.875mm, and the thickness of the bottom absorbing dielectric layer 4 is h1=h2=14.875mm. m =15mm.

[0114] Compile the equivalent circuit model program of the ultra-wideband composite absorber proposed in this embodiment in Matlab, substitute the specific structural parameters, and calculate the corresponding reflectivity curve; then simulate the ultra-wideband composite absorber proposed in this embodiment using electromagnetic simulation software to obtain the corresponding simulated reflectivity curve. Figure 5 The graph shows a comparison between the theoretical calculation and the electromagnetic simulation results of the ultra-wideband composite absorber proposed in this embodiment. It can be seen that the calculated results and the simulation results are in high agreement within the 0.1 to 10 GHz frequency band, which indicates that the equivalent circuit model of the ultra-wideband composite absorber proposed in this embodiment has high accuracy in the calculation of reflectivity.

[0115] Example 3

[0116] This embodiment proposes an ultra-wideband composite absorber based on an equivalent circuit model, which is composed of multiple planar periodically arranged structural units. The structural units include a metal base plate 5 from bottom to top, a bottom absorbing dielectric layer 4, and a three-layer composite structure. The composite structure includes an intermediate dielectric layer 3 from bottom to top, a dielectric substrate 2, and a resistive film square ring 1.

[0117] In this embodiment, the specific structural parameters of the three-layer composite structure are the same: the sheet resistance of the resistive film square ring 1 is Rs1=Rs2=Rs3=30Ω / sqr, the period is P1=P2=P3=30mm, the ring width is s1=s2=s3=1mm, and the inter-ring gap is g1=g2=g3=0.2mm; the thickness of the dielectric substrate 2 is t=0.125mm, the thickness of the intermediate dielectric layer 3 is h1=h2=h3=14.875mm, and the thickness of the bottom absorbing dielectric layer 4 is h1=h2=h3=14.875mm. m =15mm.

[0118] Compile the equivalent circuit model program of the ultra-wideband composite absorber proposed in this embodiment in Matlab, substitute the specific structural parameters, and calculate the corresponding reflectivity curve; then simulate the ultra-wideband composite absorber proposed in this embodiment using electromagnetic simulation software to obtain the corresponding simulated reflectivity curve. Figure 6 The graph shows a comparison between the theoretical calculation and the electromagnetic simulation results of the ultra-wideband composite absorber proposed in this embodiment. It can be seen that the calculated results and the simulation results are in high agreement within the 0.1 to 10 GHz frequency band, which indicates that the equivalent circuit model of the ultra-wideband composite absorber proposed in this embodiment has high accuracy in the calculation of reflectivity.

[0119] Example 4

[0120] This embodiment proposes an ultra-wideband composite absorber based on an equivalent circuit model optimized by a genetic algorithm. It consists of multiple planar periodically arranged structural units. The structural units include a metal base plate 5, a bottom absorbing dielectric layer 4, and a double-layer composite structure from bottom to top. The composite structure includes an intermediate dielectric layer 3, a dielectric substrate 2, and a resistive film square ring 1 from bottom to top.

[0121] In this embodiment, the sheet resistance of the resistive film square ring 1 is Rs1 = 15Ω / sqr, Rs2 = 50Ω / sqr; the period is P1 = 25mm, P2 = 25mm; the ring width is s1 = 1mm, s2 = 1.6mm; the inter-ring gap is g1 = 0.4mm, g2 = 0.8mm; the thickness of the dielectric substrate 2 is t = 0.125mm; the thickness of the intermediate dielectric layer 3 is h1 = 9.875mm, h2 = 12.875mm; the thickness of the bottom absorbing dielectric layer 4 is h1 = 9.875mm, h2 = 12.875mm. m =12mm; the overall thickness of the ultra-wideband composite absorber is 35mm.

[0122] Compile the equivalent circuit model program of the ultra-wideband composite absorber proposed in this embodiment in Matlab, substitute the specific structural parameters, and calculate the corresponding reflectivity curve; perform software simulation on the ultra-wideband composite absorber proposed in this embodiment using electromagnetic simulation software to obtain the corresponding simulated reflectivity curve. Figure 7 The image shows a comparison of the reflectivity calculated by the theoretical calculation and the reflectivity simulated by the electromagnetic simulation software for the ultra-wideband composite absorber proposed in this embodiment. It can be seen that the calculation and simulation results are in good agreement within the 0.1 to 10 GHz frequency band. The simulation results show that the reflectivity is less than -10 dB within the 0.82 to 18 GHz frequency band, achieving an absorption of more than 90%. The corresponding relative bandwidth is calculated to be 182%, and the theoretical minimum thickness corresponding to this reflectivity is calculated to be 33.5 mm, while the actual structural thickness is only 4% higher than the theoretical minimum thickness.

[0123] To verify the reliability of the design, the ultra-wideband composite absorber based on the equivalent circuit model optimized by the genetic algorithm proposed in this embodiment was actually fabricated. The reflectivity of electromagnetic waves incident perpendicularly to the ultra-wideband composite absorber was then tested using the bow-shaped reflectivity testing technique, with a test frequency range of 2–18 GHz. The resulting reflectivity curves are shown below. Figure 8 As shown, the results indicate that the test results are in good agreement with the simulation results.

[0124] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A design method for an ultra-wideband composite absorber based on an equivalent circuit model, characterized in that, The ultra-wideband composite absorber based on the equivalent circuit model is composed of multiple planar periodically arranged structural units. Each structural unit includes, from bottom to top, a metal substrate, a bottom absorbing dielectric layer, and an n-layer composite structure. The composite structure includes, from bottom to top, an intermediate dielectric layer, a dielectric substrate, and a resistive film ring. ; The design method specifically includes: First, based on the structural dimension parameters of the resistive film square ring in each layer of the composite structure, the corresponding equivalent circuit parameters are extracted, and the surface impedance of the resistive film square ring in each layer of the composite structure is derived. Then, based on the equivalent circuit model and transmission line theory, the analytical expression of the reflectivity of the ultra-wideband composite absorber is extracted. Finally, the genetic optimization algorithm is used to optimize the overall structure of the ultra-wideband composite absorber to obtain the ultra-wideband composite absorber with the best absorption performance. The process of deriving the surface impedance of the resistive film ring in each layer of the composite structure specifically includes: According to the Calculate the structural dimensional parameters of the resistive film square ring in the layered composite structure. Equivalent resistance of the resistive film square ring in the layered composite structure : （1） The equivalent capacitance generated between adjacent resistive film square rings due to coupling effect : （2） Equivalent inductance between adjacent resistive film square rings : （3） In the formula, （4） （5） （6） （7） in, For the first Sheet resistance of the resistive film square ring in the layered composite structure; For air resistance; f represents the angular frequency of the electromagnetic wave at different frequencies; λ represents the wavelength of the electromagnetic wave. To and , and Relevant catenary model functions; for Correction factor in; and These are meaningless intermediate variables; Since the resistive film ring is bonded to the upper surface of the dielectric substrate, the equivalent capacitance after considering the influence of the dielectric substrate is... and equivalent inductance They are respectively: （8） （9） in, For the first The equivalent dielectric constant of the resistive film square ring in the layered composite structure; For the first The equivalent permeability coefficient of the resistive film square ring in the layered composite structure is taken as 1; No. The equivalent dielectric constant of the resistive film square ring in the layered composite structure for: （10） （11） in, The average dielectric constant of the dielectric substrate and air: is the dielectric constant of the dielectric substrate in each layer of the composite structure; No. The equivalent dielectric constant of the resistive film square ring in the layered composite structure for: （12） in, is the dielectric constant of the intermediate dielectric layer (3) in each composite structure; For the first The thickness of the intermediate dielectric layer in a multilayer composite structure; Then the first one is calculated. Surface impedance of resistive film square ring in layered composite structure for: 。 （13） 2. The design method for an ultra-wideband composite absorber based on an equivalent circuit model according to claim 1, characterized in that, The intermediate dielectric layer is made of pure aramid paper honeycomb material, with a dielectric constant of [missing value]. The value is 1~1.5; the material of the bottom absorbing medium layer is aramid paper absorbing honeycomb.

3. The design method for an ultra-wideband composite absorber based on an equivalent circuit model according to claim 1, characterized in that, No. Thickness of the intermediate dielectric layer in a layered composite structure It is 10~30 mm.

4. The design method of ultra-wideband composite absorber based on equivalent circuit model according to claim 1, characterized in that, The thickness of the bottom absorbing medium layer It is 10~20 mm.

5. The design method for an ultra-wideband composite absorber based on an equivalent circuit model according to claim 1, characterized in that, The resistive film ring is a ring-shaped ITO conductive film.

6. The design method of ultra-wideband composite absorber based on equivalent circuit model according to claim 1, characterized in that, No. Period of the resistive film square ring in the layered composite structure 10~50 mm, ring width The inter-ring gap between adjacent resistive film square rings is 0.5~5 mm. The thickness is 0.1~1 mm, and the thickness of the resistive film square ring is 10~200 nm.

7. The design method for an ultra-wideband composite absorber based on an equivalent circuit model according to claim 1, characterized in that, The dielectric substrate is a PET dielectric substrate with a thickness t of 0.1~0.5 mm and a dielectric constant of .

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