Dual-mode broadband wave-absorbing metasurface structure based on lumped element

Abstract

The utility model discloses a dual-mode broadband wave-absorbing metasurface structure based on a lumped element. The dual-mode broadband wave-absorbing metasurface structure sequentially comprises a pattern layer, a dielectric layer, an air interlayer and a metal backboard from top to bottom. The pattern layer comprises a cross-shaped metal patch, lumped resistors are arranged at the central positions of four support arms of the cross-shaped metal patch, and the tail ends of the four support arms of the cross-shaped metal patch are connected with the middle ends of four transversely arranged resonant coupling microstrip lines respectively; the cross-shaped metal patch is a copper cross-shaped metal patch, the metal backboard is a copper metal backboard, and the dielectric layer is a polyimide dielectric layer. All parameter values of the wave-absorbing metasurface are subjected to simulation optimization and manufacturing test, the wave-absorbing metasurface can respectively have an efficient and stable wave-absorbing function in a wide frequency band range of 5.5-12.5 GHz, two remarkable strong resonance absorption peaks are formed at frequency points of 6.7 GHz and 11.4 GHz, and the absorption rate of the wave-absorbing metasurface can reach 99%.

Description

Technical Field

[0001] The utility model relates to the field of military stealth, in particular to a dual-mode broadband wave-absorbing metasurface structure based on lumped elements. Background Art

[0002] In the military field, radar stealth technology and electromagnetic stealth materials remain at the forefront of modern military warfare development. Currently, stealth technology is primarily achieved through design and materials. However, shape-based stealth technology is susceptible to aerodynamic performance, while electromagnetic stealth materials, which rely on intrinsic stealth properties, can compensate for this deficiency. For example, absorbing materials can achieve low target detectability through energy loss, demonstrating superior applicability in applications such as radar cross-section reduction. Therefore, electromagnetic metasurfaces with wave-absorbing properties have become a key research topic in electromagnetic stealth materials. Electromagnetic metasurfaces are a new type of artificial material composed of periodically arranged subwavelength structures. Typically, an electromagnetic metasurface consists of a metal pattern etched onto a dielectric substrate. Its electromagnetic properties are primarily determined by the structural parameters of the pattern and substrate, rather than the intrinsic properties of the constituent materials. Due to this, electromagnetic metasurfaces, through appropriate structural design, can effectively control the loss characteristics of incident electromagnetic waves, thereby exhibiting "perfect absorption" properties not possessed by traditional materials.

[0003] The first absorbing metasurface structure was proposed by Landy et al. in 2008. Through strong electromagnetic resonance between its upper and lower metal layers, it achieved nearly 100% effective absorption at 11.65 GHz. However, with the increasing complexity of electromagnetic environments, the application scenarios of single-band absorbing metasurfaces have become limited due to their single operating frequency band. Therefore, researchers have systematically investigated the multi-frequency characteristics of absorbing metasurfaces. A common approach to achieving broadband and multi-frequency absorption in absorbers is to combine different resonator models horizontally or vertically. In 2017, Zhang et al. designed a composite absorber composed of circular gold foil coupled with graphene, effectively broadening the absorption bandwidth. However, this absorber was relatively thick, making it unsuitable for stealth systems. In 2018, MC et al. designed an absorber composed of two stacked unit structures, achieving perfect absorption at two frequencies, but this also increased the design complexity. With the continuous advancement of absorber research, new absorbing structures are constantly being proposed. In 2021, Bilal et al. prepared a single-type multimode resonant metasurface based on a fractal pattern, which achieved a relative bandwidth of 29% by utilizing multiple resonant modes generated by the fractal pattern. In 2023, Huang et al. proposed a wave-absorbing metasurface based on a single-type multimode resonator, which obtained four resonant modes by applying slot lines and branch loading technology, thereby achieving a second-order dual-band wave-absorbing response with high sideband selectivity. It can be seen that the design based on a single-type multimode resonator is an effective solution to obtain high-performance wave-absorbing response. However, the wave-absorbing metasurfaces of the existing technology have problems such as large size, complex structure, and absorption rate that does not reach strong absorption (99%).

[0004] Therefore, in response to the above problems, providing a dual-mode broadband absorbing metasurface structure based on lumped elements is a technical problem that needs to be solved urgently in this field. Utility Model Content

[0005] The purpose of the utility model is to overcome the deficiencies of the prior art and provide a dual-mode broadband wave-absorbing metasurface structure based on lumped elements.

[0006] The purpose of this utility model is achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides a dual-mode broadband absorbing metasurface structure based on lumped elements, comprising, from top to bottom, a pattern layer, a dielectric layer, an air barrier layer, and a metal backplane; the pattern layer comprises a cross-shaped metal patch, the center positions of the four arms of the cross-shaped metal patch are each provided with a lumped resistor, and the ends of the four arms of the cross-shaped metal patch are respectively connected to the middle ends of four laterally arranged resonant coupling microstrip lines;

[0008] The cross-shaped metal patch is a copper cross-shaped metal patch, the metal back plate is a copper metal back plate, and the dielectric layer is a polyimide dielectric layer;

[0009] The cross length of the cross-shaped metal patch is 8.4 mm, the cross width of the cross-shaped metal patch is 0.8 mm, the length of the resonant coupled microstrip line is 3 mm, the width of the resonant coupled microstrip line is 0.8 mm, the resistance of the lumped resistor is 75 Ω, the thickness of the dielectric layer is 1 mm, and the thickness of the air spacer is 5 mm.

[0010] Furthermore, the length of the dielectric layer and the metal back plate is 12 mm, and the width of the dielectric layer and the metal back plate is 12 mm.

[0011] Furthermore, the cross-shaped metal patch is arranged in the middle of the dielectric layer, and the cross of the cross-shaped metal patch points to the four corners of the dielectric layer.

[0012] The beneficial effects of the utility model are:

[0013] In an exemplary embodiment of the present invention, the absorbing metasurface structure has only four layers, and the pattern of the pattern layer serving as the impedance surface is simple, which significantly reduces the difficulty of designing and manufacturing the absorber.

[0014] The materials of the pattern layer and the metal backplane of the absorbing metasurface structure are both copper; polyimide (PI) is used as the material of the dielectric layer 2, which is low in cost and flexible. Therefore, the present application has the advantages of simple structure, easy processing and low cost, while also having the advantages of flexibility and easy shaping.

[0015] In addition, the various parameter values ​​of the absorbing metasurface have been optimized through simulation and production testing, and can have efficient and stable absorbing functions in the wide frequency band range of 5.5-12.5GHz, and form two significant strong resonant absorption peaks at the frequency points of 6.7GHz and 11.4GHz, with an absorption rate of up to 99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A side view of a dual-mode broadband absorbing metasurface structure based on lumped elements provided in an exemplary embodiment of the present invention;

[0017] Figure 2 A top view of a dual-mode broadband absorbing metasurface structure based on lumped elements provided in an exemplary embodiment of the present invention;

[0018] Figure 3 This is a schematic diagram of simulation results of a dual-mode broadband absorbing metasurface structure based on lumped elements provided in an exemplary embodiment of the present invention under structural parameters of different air barrier thicknesses;

[0019] Figure 4This is a schematic diagram of simulation results of a dual-mode broadband absorbing metasurface structure based on lumped elements provided in an exemplary embodiment of the present invention under structural parameters of different lumped resistance values;

[0020] Figure 5 This is a schematic diagram of an equivalent circuit model of a dual-mode broadband absorbing metasurface structure based on lumped elements provided in an exemplary embodiment of the present invention;

[0021] Figure 6 This is a reflection coefficient curve diagram in HFSS and ADS of an equivalent circuit model of a dual-mode broadband absorbing metasurface structure based on lumped elements provided in an exemplary embodiment of the present utility model;

[0022] Figure 7 A normalized impedance curve diagram of a dual-mode broadband absorbing metasurface structure based on lumped elements within a key frequency band provided in an exemplary embodiment of the present utility model;

[0023] Figure 8 A graph showing the normalized impedance difference between a dual-mode broadband absorbing metasurface structure based on lumped elements and free space provided in an exemplary embodiment of the present invention;

[0024] Figure 9 A schematic diagram of the surface current of a dual-mode broadband absorbing metasurface structure based on lumped elements provided in an exemplary embodiment of the present utility model;

[0025] Figure 10 A schematic diagram of the power loss density distribution of a dual-mode broadband absorbing metasurface structure based on lumped elements provided in an exemplary embodiment of the present invention;

[0026] Figure 11 A schematic diagram of a physical sample of a dual-mode broadband absorbing metasurface structure based on lumped elements provided in an exemplary embodiment of the present invention;

[0027] Figure 12 A schematic diagram of a testing environment for a physical sample of a dual-mode broadband absorbing metasurface structure based on lumped elements provided in an exemplary embodiment of the present invention;

[0028] Figure 13 A schematic diagram comparing simulation and test results of the reflection coefficient of a dual-mode broadband absorbing metasurface structure based on lumped elements provided in an exemplary embodiment of the present invention;

[0029] Figure 14 This is a schematic diagram comparing the simulation and test results of the absorptivity of a dual-mode broadband absorbing metasurface structure based on lumped elements provided in an exemplary embodiment of the present invention.

[0030] In the figure, 1-pattern layer, 101-cross-shaped metal patch, 10101-support arm, 102-lumped resistor, 103-resonant coupled microstrip line, 2-dielectric layer, 3-air spacer, 4-metal backplane. DETAILED DESCRIPTION

[0031] The following is a clear and complete description of the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0032] In the description of the present invention, it should be noted that the directions or positional relationships indicated by "center", "up", "down", "left", "right", "vertical", "horizontal", "inside" and "outside" are based on the directions or positional relationships described in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0033] In the description of this utility model, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; direct connections, indirect connections through an intermediate medium, and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model in specific contexts.

[0034] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. As used in this application and the appended claims, the singular forms "a," "an," "the," and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0035] It should be understood that although the terms first, second, third, etc. may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein can be interpreted as "at the time of" or "when" or "in response to a determination". In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance.

[0036] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0037] See also Figure 1 and Figure 2 , Figure 1 and Figure 2 The figure shows a side view and a top view of a dual-mode broadband absorbing metasurface structure based on lumped elements provided in an exemplary embodiment of the present invention. The structure comprises, from top to bottom, a pattern layer 1, a dielectric layer 2, an air spacer 3, and a metal backplane 4. The pattern layer 1 includes a cross-shaped metal patch 101. Lumped resistors 102 are provided at the center of each of the four arms 10101 of the cross-shaped metal patch 101. The ends of the four arms 10101 of the cross-shaped metal patch 101 are also connected to the middle ends of four laterally arranged resonant coupling microstrip lines 103.

[0038] The cross-shaped metal patch 101 is a copper cross-shaped metal patch, the metal back plate 4 is a copper metal back plate, and the dielectric layer 2 is a polyimide dielectric layer;

[0039] The cross length of the cross-shaped metal patch 101 is 8.4 mm, the cross width of the cross-shaped metal patch 101 is 0.8 mm, the length of the resonant coupled microstrip line 103 is 3 mm, the width of the resonant coupled microstrip line 103 is 0.8 mm, the resistance of the lumped resistor 102 is 75 Ω, the thickness of the dielectric layer is 1 mm, and the thickness of the air barrier is 5 mm.

[0040] Specifically, in this exemplary embodiment, the absorbing metasurface structure has only four layers, including a pattern layer 1 (impedance surface), a dielectric layer 2 (dielectric substrate), an air spacer 3 and a metal backplane 4 from top to bottom. The pattern of the pattern layer 1 serving as the impedance surface is simple, including only a cross-shaped metal patch 101 and a resonant coupling microstrip line 103, which significantly reduces the difficulty of designing and manufacturing the absorber.

[0041] The material of the pattern layer 1 and the metal back plate 4 of the wave-absorbing metasurface structure is copper (conductivity σ = 5.8 × 10 7S / m); polyimide (PI) is used as the material of the dielectric layer 2, which has a relative dielectric constant εr = 4.4 and a dielectric loss tangent tanδ = 0.02. This material is low-cost and flexible, so the present application has the advantages of simple structure, easy processing and low cost, while also having the advantages of flexibility and easy shaping. In the specific production process, metal copper can be printed on the dielectric layer 2 of polyimide PI through a flexible printed circuit (FPC) process with a thickness of 0.012mm; and a 1mm long and 0.5mm wide SMD 0402 series is used as the lumped resistor 102 and soldered to the corresponding position of the cross-shaped metal patch 101.

[0042] In addition, in order to optimize the various parameter values ​​of the absorbing metasurface, this exemplary embodiment uses the dual-frequency response as the optimization target during the design process, and adopts the control variable method to perform a series of parameter sweeps and impedance matching analysis. The model is modeled and simulated based on the high-frequency structure of the finite element method using Ansoft HFSS simulation software. Among them, the simulation of the lumped resistance is achieved by constructing a rectangular patch and loading the resistance-inductance-capacitance (RLC) boundary conditions. It is particularly noteworthy that the design ignores the parasitic reactance of the lumped resistance during the simulation process to simplify the model structure. An air box is loaded outside the model, and the master-slave boundary conditions and Floquet port excitation are set around and on the top of the simulation structure to simulate the vertical incidence of electromagnetic waves on the infinite periodic surface structure. Figure 3 and Figure 4 Shown are the reflection coefficient curves of the designed structure under different structural parameters:

[0043] from Figure 3 As can be seen from the figure, as the thickness t of the air spacer 3 increases, the two resonant modes gradually move to lower frequencies. In addition, if the value is too small or too large, it will affect the impedance matching level of the two resonant modes, thereby affecting the effective working bandwidth.

[0044] At the same time, the ohmic loss of the lumped resistor 102 is the key to generating wave absorption, so the two resonant modes are also controlled by the resistance value R. Figure 4 As shown, as the resistance R of the lumped resistor 102 increases, the two resonant modes gradually merge into a single mode; conversely, the distance between the two resonant modes increases. Only when the resistance R is set to 75Ω can the operating bandwidth, number of modes, and resonance depth all reach optimal values.

[0045] The same method was used to simulate the influence of the parameters of the cross-shaped metal patch 101 and the resonant coupled microstrip line 103 of the pattern layer 1 (the cross length l1 of the cross-shaped metal patch 101, the length l2 of the resonant coupled microstrip line 103, the cross width w1 of the cross-shaped metal patch 101, and the width w2 of the resonant coupled microstrip line 103) on the reflection coefficient. Finally, the structural parameters of the designed absorbing metasurface unit were obtained: the cross length of the cross-shaped metal patch 101 is 8.4 mm, the cross width of the cross-shaped metal patch 101 is 0.8 mm, the length of the resonant coupled microstrip line 103 is 3 mm, the width of the resonant coupled microstrip line 103 is 0.8 mm, and the resistance of the lumped resistor 102 is 75Ω.

[0046] For field-road collaborative analysis:

[0047] Since the metasurface is a subwavelength periodic structure, its working performance can be analyzed using effective medium theory. The absorption rate AR can be calculated using the following formula:

[0048] AR=1-RR-TR=1-|S 11 | 2 -|S 21 | 2 (1

[0049] Among them, RR and TR are reflectivity and transmittance respectively, S 11 and S 21 are the reflection coefficient and transmission coefficient respectively. Since the bottom layer of the absorbing metasurface is a metal backplane 4 and its thickness is greater than the skin depth of the incident electromagnetic wave, TR is close to zero, so that the absorption rate is only related to the reflection coefficient. When S 11 When it is close to 0, AR is close to 1, which means perfect absorption is achieved. The absorption performance of the designed absorbing metasurface in this exemplary embodiment is as follows: Figures 3-4 The simulation results show that the reflection coefficient in the range of 5.5-12.5 GHz is less than -10 dB, and there are two absorption resonance peaks at 6.7 GHz and 11.4 GHz, with amplitudes of -35 dB and -28 dB respectively.

[0050] According to Figure 1 and Figure 2 The structural diagram of the absorbing metasurface can be obtained as follows Figure 5 The equivalent circuit model shown in Figure 1 is shown in Figure 2. The length is h1 and the dielectric constant is ε. r1 (ε r2) represents the dielectric layer 2 (air), and R, L, and C represent the cross-shaped metal patch 101 loaded with the lumped resistor 102. When the lumped element resonates, the designed metasurface exhibits the characteristics of "absorption-reflection-absorption" in the key frequency band. Then, the model was established and simulated using the Advanced Design System (ADS). After curve fitting, the circuit element values ​​were obtained as follows: R = 263.5Ω, L1 = 10.68nH, C1 = 42.6fF, L2 = 3.3nH, and C2 = 50fF. Figure 6 It can be seen that the "field" and "path" simulation results have similar trends in resonant frequency and reflection intensity. The slight errors mainly come from ignoring the parasitic coupling effects between components in the equivalent circuit. The thickness of the material layer is 1mm, and the thickness of the air barrier is 5mm.

[0051] For the analysis of absorption mechanism:

[0052] For absorbing metasurfaces to achieve efficient and stable absorption, they must meet two conditions: impedance matching and energy loss. Impedance matching aims to allow incident electromagnetic waves to enter the metasurface as non-reflectively as possible, while energy loss aims to convert the electromagnetic waves that enter the metasurface into other forms of energy and dissipate them. For impedance matching, the reflection coefficient S11 is minimized when the normalized impedance of the structure is as close as possible to the normalized impedance of free space (1 + j0). Figure 7 is the normalized impedance curve of the dual-frequency metasurface in the key frequency band. It can be found that the real and imaginary parts of the normalized impedance of the metasurface fluctuate around 1 and 0 respectively in this frequency band. In addition, the normalized impedance difference between the metasurface and free space is close to zero at the resonant frequency and its adjacent frequency bands, as shown in Figure 8 The above simulation results indicate good impedance matching and a small reflection coefficient, which enables the incident electromagnetic wave to enter the metasurface as non-reflective as possible.

[0053] To further explain the working mechanism, Figure 9 and Figure 10 The surface current and power loss density distribution of the designed metasurface at each absorption resonant frequency were simulated. It was found that the surface current is primarily distributed in the lumped resistor and the metal patch nearby, and that energy loss is primarily concentrated in the lumped resistor. Based on this analysis, the designed dual-frequency absorbing metasurface achieves effective absorption primarily through ohmic losses in the lumped resistor, similar to the absorption mechanism of the Salisbury screen.

[0054] In order to verify the accuracy of the simulation results of the dual-frequency absorbing metasurface, a 180*180mm 2 Metasurface samples, such as Figure 11As shown in the figure, the unit period of a single absorber surface structure is set to 12 mm. That is, in the preferred embodiment, the length of the dielectric layer 2 and the metal backplate 4 is 12 mm, and the width of the dielectric layer 2 and the metal backplate 4 is 12 mm. This smaller size and thinner thickness offer a significant size advantage. In another exemplary embodiment, the cross-shaped metal patch 101 is positioned in the middle of the dielectric layer 2, with the cross of the cross-shaped metal patch 101 pointing toward the four corners of the dielectric layer 2. Therefore, the entire sample includes 15*15 absorber surface structures.

[0055] The conductor part of the structure is made by printing metal copper on the polyimide PI layer through the Flexible Printed Circuit (FPC) process. The electrical conductivity of the metal copper is 5.8×10 7 The S / m and thickness are 0.012mm. A 1mm long and 0.5mm wide SMD 0402 series resistor is used as a lumped resistor and soldered to the corresponding position of the metal patch. To improve the mechanical strength of the metasurface structure, a honeycomb layer with a dielectric constant of 1.061 and a loss tangent of 0.0026 is used to replace the air to separate the frequency selective surfaces. According to the national military standard GJB2038A-2011, the bow method is used to measure the sample. The test environment diagram is as follows Figure 12 The measurement setup consists of two antennas (2-18 GHz) and an Agilent vector network analyzer N5230A.

[0056] Figure 13 Comparison curves of simulation and test results for the absorbing metasurface are presented. The measured (simulated) absorbing resonance frequencies are 6.13 and 7.99 GHz, respectively, and the reflection coefficients are less than -10 dB in the 6.43–13.40 GHz and 5.70–9.07 / 11.75–16.00 GHz ranges, respectively. Overall, the simulation and test results are in good agreement, with minor discrepancies likely due to manufacturing tolerances, the limited number of units, and SMD resistors.

[0057] In summary, in this exemplary embodiment, by combining lumped elements and single-type multimode resonators, a dual-frequency wave absorption response of the structure can be achieved based on a simple passive structure. Thanks to good impedance matching, strong electromagnetic resonance and efficient ohmic loss, the designed metasurface can have efficient and stable wave absorption functions in a wide frequency range of 5.5-12.5 GHz, and forms two significant strong resonant absorption peaks at 6.7 GHz and 11.4 GHz, with an absorption rate of up to 99%. The designed single-type multimode metasurface sample was successfully prepared and experimentally verified. The sample was made using the FPC process, and its test results showed good consistency with the simulation results. In summary, the dual-frequency metasurface has good multimode resonance characteristics and is of great significance in anti-electromagnetic interference applications. It realizes a wide-band full-absorption metasurface absorber, which is more widely used in military stealth, such as stealth surfaces on aircraft.

[0058] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. A person skilled in the art will readily be able to make other variations or modifications based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications derived therefrom remain within the scope of protection of the present invention.

Claims

1. A dual-mode broadband absorbing metasurface structure based on lumped elements, characterized by: From top to bottom, it includes a pattern layer, a dielectric layer, an air barrier layer, and a metal backplane. The pattern layer includes a cross-shaped metal patch. The center positions of the four arms of the cross-shaped metal patch are each provided with a lumped resistor. The ends of the four arms of the cross-shaped metal patch are also respectively connected to the middle ends of four laterally arranged resonant coupling microstrip lines. The cross-shaped metal patch is a copper cross-shaped metal patch, the metal back plate is a copper metal back plate, and the dielectric layer is a polyimide dielectric layer; The cross length of the cross-shaped metal patch is 8.4 mm, the cross width of the cross-shaped metal patch is 0.8 mm, the length of the resonant coupled microstrip line is 3 mm, the width of the resonant coupled microstrip line is 0.8 mm, the resistance of the lumped resistor is 75 Ω, the thickness of the dielectric layer is 1 mm, and the thickness of the air spacer is 5 mm.

2. The dual-mode broadband absorbing metasurface structure based on lumped elements according to claim 1, characterized in that: The length of the dielectric layer and the metal back plate is 12 mm, and the width of the dielectric layer and the metal back plate is 12 mm.

3. The dual-mode broadband absorbing metasurface structure based on lumped elements according to claim 2, characterized in that: The cross-shaped metal patch is arranged in the middle of the dielectric layer, and the cross of the cross-shaped metal patch points to the four corners of the dielectric layer.

Images