Electromagnetic camouflage metamaterial structure design method based on abnormal reflection

Abstract

The invention relates to the technical field of electromagnetic shielding, in particular to an electromagnetic camouflage metamaterial structure design method based on abnormal reflection, which comprises the following steps: carrying out structural evolution on the geometric configuration of a unit cell; taking whether a reflection unit is placed at the grid as an optimization variable, and carrying out topological optimization design; calculating a mirror equivalent condition when the electromagnetic wave is reflected in the realizable reflection angle direction through the geometrical relationship; fitting and comparing an actual scattering curve obtained through simulation with a target curve in a domain of definition, and taking the minimum sum of squares of difference values as an optimized target function; topological optimization design is carried out on a metamaterial unit composed of three layers of three-dimensional structures, and the abnormal reflection structure with the multi-angle reflection regulation and control capacity is achieved. The structure can effectively guide scattered waves to deviate from the radar receiving direction, and therefore active control over electromagnetic scattering is achieved, and the purpose of electromagnetic camouflage is achieved.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic shielding technology, and in particular to a method for designing electromagnetic camouflage metamaterial structures based on anomalous reflection. Background Technology

[0002] Traditionally, "camouflage" refers to invisibility to the human eye within the visible light spectrum. However, with the development of detection technology, target observation methods have expanded from the naked eye to multi-dimensional sensing systems including radar, infrared, and acoustic waves. In this context, the connotation of camouflage has also broadened to include the ability to effectively evade, interfere with, and mislead corresponding detection methods. For example, electromagnetic shielding chambers, due to their inherent reflective properties, are easily detected by enemy radar. Therefore, camouflage or camouflage characteristics of the chamber in radar detection are particularly necessary. In this case, the chamber can be considered a camouflage carpet. A camouflage carpet refers to a structure that can effectively guide scattered waves away from the radar's receiving direction, thereby achieving active control of electromagnetic scattering to achieve electromagnetic camouflage. It does not achieve visual camouflage of the target, but rather, by adjusting the direction of the scattered waves, its reflection behavior simulates the specular reflection characteristics similar to the ground, thus concealing the target's true existence in radar detection.

[0003] Therefore, there is a need to provide a "camouflage carpet" structure based on the generalized Snell's theorem that can conceal real objects and simulate the properties of specular reflection. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a design method for an electromagnetic camouflage metamaterial structure based on anomalous reflection. This invention aims to achieve an anomalous reflection structure with multi-angle reflection control capabilities by performing topology optimization design on a metamaterial unit composed of a three-layer three-dimensional structure. This structure utilizes topology optimization methods to evolve the geometric configuration of the unit cell. To obtain a sufficiently rich phase response, the entire design region is divided into three layers from bottom to top. The placement of reflective elements at the grid points is used as an optimization variable for structural layout. The reflection direction of the reflective surface in this structure is consistent with the specular reflection from the ground under radar views; that is, relative to the ground, the reflection and incident angles are equal. However, relative to the reflective surface, the reflection and incident angles are not equal. The relationship between the reflection and incident angles is determined based on the angle between the reflective surface and the ground, making the object "look" like the ground under radar views, thus achieving camouflage in the desired direction.

[0005] The technical means employed in this invention are as follows: A method for designing an electromagnetic camouflage metamaterial structure based on anomalous reflection includes: structural evolution of the geometric configuration of the unit cell; topology optimization design using whether or not reflective elements are placed at the grid as optimization variables; calculation of the mirror equivalence conditions when electromagnetic waves are reflected at achievable reflection angles using geometric relationships; fitting and comparing the actual scattering curve obtained through simulation with the target curve within the defined domain, and taking the minimum sum of squared differences as the optimization objective function; and performing topology optimization design on the metamaterial unit composed of a three-layer three-dimensional structure to achieve an anomalous reflection structure with multi-angle reflection control capability.

[0006] Furthermore, the structural evolution of the geometric configuration of the unit cell specifically includes: dividing the design region with a size of 2L×L into a three-layer structure from bottom to top, with each sub-design region represented by a discretized mesh.

[0007] Furthermore, the topology optimization design, which uses whether or not a reflection unit is placed at the grid as an optimization variable, specifically includes: using a binary encoded sequence X to represent the structural layout, when the first... Bit Encoding When, reflective units are arranged at the corresponding positions; when At this time, the grid is empty; the size of the reflective unit is slightly larger than the grid size to ensure that there is partial overlap between adjacent reflective units, thereby avoiding structural breakage or suspension and meeting the processing feasibility.

[0008] Furthermore, the step of calculating the mirror equivalence condition for electromagnetic waves to be reflected at an achievable reflection angle using geometric relationships specifically includes: determining the achievable reflection angle. And select the angle of incidence. Let the angle between the target camouflage structure and the ground be . The mirror equivalence condition is obtained as follows: the reflection direction is consistent with the ground mirror reflection from the radar perspective; a target normalized RCS function is constructed. In the target direction The normalized RCS is 1, and 0 in the other directions.

[0009] Furthermore, the objective function of minimizing the sum of squared differences specifically includes: when the difference is 0, it indicates that the actual scattering characteristics meet the expected directional camouflage target.

[0010] Furthermore, the topology optimization design of the metamaterial unit composed of a three-layer three-dimensional structure is carried out to realize an abnormal reflection structure with multi-angle reflection control capability. When electromagnetic waves are incident on the metamaterial with a spatially non-uniform metallic structure, the structural unit is excited to generate electromagnetic resonance at a specific frequency, generating a local induced current, which in turn forms a spatially varying phase response on the metamaterial. The phase abrupt change between different structural units can realize precise control of the incident wavefront, thereby causing a deviation in the reflection direction and generating an abnormal reflection phenomenon.

[0011] Compared with the prior art, the present invention has the following advantages: This invention presents the first all-metal electromagnetic camouflage metamaterial structure, proposing a three-layer "camouflage carpet" to achieve unique electromagnetic reflection, effectively simulating the specular reflection behavior of the Earth's surface, thereby achieving the purpose of "hiding" the target's shape from a radar perspective. The metal itself possesses high strength, high hardness, and good plasticity and toughness. This achieves electromagnetic response without compromising the necessary load-bearing characteristics. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram illustrating the camouflage effect of the electromagnetic camouflage metamaterial structure design method based on anomalous reflection in this invention.

[0014] Figure 2 This is a schematic diagram of the single-cell design domain and its supercell in this invention.

[0015] Figure 3 This is a schematic diagram of the camouflage array when the angle with the ground is 10° in an embodiment of the present invention.

[0016] Figure 4 This is a schematic diagram of the topology-optimized camouflage supercell and array structure when the angle with the ground is 10° in an embodiment of the present invention.

[0017] Figure 5 This is a schematic diagram of the reflection characteristics of the camouflage structure when the angle between the camouflage structure and the ground is 10° in an embodiment of the present invention.

[0018] Figure 6 This is a schematic diagram of the camouflage array when the angle with the ground is 15° in an embodiment of the present invention.

[0019] Figure 7 This invention relates to a topology-optimized camouflage supercell and array structure with an angle of 15° to the ground in an embodiment of the invention.

[0020] Figure 8 This is a schematic diagram of the reflection characteristics of the camouflage structure when the angle with the ground is 15° in an embodiment of the present invention. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0024] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0025] like Figure 1As shown, this invention provides a method for designing electromagnetic camouflage metamaterial structures based on anomalous reflection, including: structural evolution of the geometric configuration of the unit cell; specifically, in a preferred embodiment of this invention, a design region of size 2L×L is divided into three layers from bottom to top, and each sub-design region is represented by a discretized mesh, such as... Figure 2 As shown.

[0026] Topology optimization design is performed using whether or not a reflection unit is placed at the grid location as an optimization variable; in a preferred embodiment of the invention, a binary encoding sequence X is used to represent the structural layout, when the... Bit Encoding When, reflective units are arranged at the corresponding positions; when At this time, the grid is empty; the size of the reflective unit is slightly larger than the grid size to ensure that there is partial overlap between adjacent reflective units, thereby avoiding structural breakage or suspension and meeting the processing feasibility.

[0027] The mirror equivalence conditions for electromagnetic waves to be reflected at an achievable reflection angle are calculated using geometric relationships; in a preferred embodiment of the invention, the achievable reflection angle is determined. And select the angle of incidence. Let the angle between the target camouflage structure and the ground be . The mirror equivalence condition is obtained as follows: the reflection direction is consistent with the ground mirror reflection from the radar perspective; a target normalized RCS function is constructed. In the target direction The normalized RCS is 1, and 0 in the other directions.

[0028] The actual scattering curve obtained through simulation is fitted and compared with the target curve within the defined domain, and the minimum sum of squared differences is taken as the optimization objective function. In specific implementation, as a preferred embodiment of the present invention, when the difference is 0, it indicates that the actual scattering characteristics meet the expected direction of the camouflage target.

[0029] A topology optimization design is performed on a metamaterial unit composed of a three-layer three-dimensional structure to achieve an anomalous reflection structure with multi-angle reflection control capability. Specifically, in a preferred embodiment of this invention, when an electromagnetic wave is incident on a metamaterial with a spatially non-uniform metallic structure, the structural unit excites electromagnetic resonance at a specific frequency, generating a local induced current, which in turn forms a spatially varying phase response on the metamaterial. The phase abrupt change between different structural units allows for precise control of the incident wavefront, thereby causing a deviation in the reflection direction and producing an anomalous reflection phenomenon.

[0030] Example 1 Taking a 10GHz incident wave as an example, the design of a specific camouflage structure model is presented. The designed supercell has overall dimensions of 99.2mm × 30.2mm × 10mm, consisting of three layers of structural units arranged from bottom to top. Each layer of unit cell is discretized into 33 × 10 equally spaced grids with heights of 3mm, 4mm, and 3mm, respectively. Each grid corresponds to a potential reflecting unit location. The reflecting unit has a size of 3mm × 3mm and is made of polylactic acid (PLA). A PE boundary is set on the outer side of the entire structure. A 0.2mm overlap area is designed between adjacent reflecting units to improve the structural integrity and electromagnetic continuity.

[0031] When constructing the complete structure, the designed supercells are periodically laid out along the x and y axes to ultimately form a complete camouflage metamaterial array structure. Taking the case where the metamaterial structure forms a 10° angle with the ground as an example, such as... Figure 3 As shown, an incident electromagnetic wave is obliquely incident on the metamaterial at an azimuth angle of -20°, and its target reflection angle is set to 40°. This reflection direction is deflected by 20° compared to the specular reflection direction, thus achieving directional control of the electromagnetic wave's outgoing direction. At this time, the outgoing wave direction is consistent with the direction of specular reflection from the imaginary ground, achieving "reflective camouflage" of the target and realizing the purpose of electromagnetic camouflage. Figure 4 As shown, the topology-optimized supercell structure is periodically replicated along the x-axis and y-axis directions to finally construct a complete camouflage metamaterial array structure. The array consists of 6×3 supercells, and the overall structure size is 297.6mm×181.2mm.

[0032] To verify the performance of the designed camouflage structure, simulation analysis was performed on the structure, such as... Figure 5 As shown in (a), the main lobe of the reflection is clearly concentrated in the 40° direction and has a narrow beamwidth, reflecting good directional accuracy. Figure 5 (b) is the normalized bistatic RCS of the structure in the pitch direction. It can be observed that the scattering intensity reaches its maximum value in the 40° reflection angle direction, which further illustrates that the camouflage structure can effectively concentrate the reflected energy in a specific direction and has good controllability of the reflection direction.

[0033] An analysis was conducted to address different camouflage requirements. For example, when the angle between the metamaterial structure and the ground is 15°, ... Figure 6 As shown, taking the oblique illumination of the metamaterial structure at an incident angle of -20° as an example, its target reflection angle is 50°. To simulate the reflection behavior of the ground plane and achieve camouflage, the emitted wave needs to be deflected by 30° from the original specular reflection direction. For example... Figure 7As shown, the topology-optimized supercell structure was periodically replicated along the x-axis and y-axis to construct a complete camouflage metamaterial array structure. This array consists of 6×3 supercells, with an overall structural size of 207.6 mm × 181.3 mm. Simulation analysis was performed on the designed structure. Figure 8 It is a normalized bistatic RCS and three-dimensional radiation pattern in the elevation direction, with a clear reflected beam in the 50° direction of the target angle.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for designing electromagnetic camouflage metamaterial structures based on anomalous reflection, characterized in that, include: Structural evolution of the geometry of a single cell; Topology optimization design is performed using whether or not a reflective element is placed at the grid location as an optimization variable; The mirror equivalence conditions for electromagnetic waves to be reflected at achievable reflection angles are calculated using geometric relationships. The actual scattering curve obtained through simulation is compared with the target curve within the defined domain, and the minimum sum of squared differences is taken as the optimization objective function. A topology optimization design was carried out on a metamaterial unit composed of a three-layer three-dimensional structure to realize an anomalous reflection structure with multi-angle reflection control capability.

2. The method for designing electromagnetic camouflage metamaterial structures based on anomalous reflection according to claim 1, characterized in that, The structural evolution of the geometric configuration of the unit cell specifically includes: dividing the design region with a size of 2L×L into a three-layer structure from bottom to top, with each sub-design region represented by a discretized grid.

3. The electromagnetic camouflage metamaterial structure design method based on anomalous reflection according to claim 1, characterized in that, The topology optimization design, which uses whether or not a reflection unit is placed at a grid location as an optimization variable, specifically includes: The structural layout is represented by a binary encoded sequence X, when the... Bit Encoding When, reflective units are arranged at the corresponding positions; when At this time, the grid is empty; the size of the reflective unit is slightly larger than the grid size to ensure that there is partial overlap between adjacent reflective units, thereby avoiding structural breakage or suspension and meeting the processing feasibility.

4. The electromagnetic camouflage metamaterial structure design method based on anomalous reflection according to claim 1, characterized in that, The mirror equivalence conditions for calculating electromagnetic waves at achievable reflection angles using geometric relationships specifically include: Determine the achievable reflection angle And select the angle of incidence. Let the angle between the target camouflage structure and the ground be . The mirror equivalence condition is obtained as follows: the reflection direction is consistent with the ground mirror reflection from the radar perspective; a target normalized RCS function is constructed. In the target direction The normalized RCS is 1, and 0 in the other directions.

5. The electromagnetic camouflage metamaterial structure design method based on anomalous reflection according to claim 1, characterized in that, The objective function for minimizing the sum of squared differences specifically includes: When the difference is 0, it means that the actual scattering characteristics meet the expected direction of the camouflage target.

6. The electromagnetic camouflage metamaterial structure design method based on anomalous reflection according to claim 1, characterized in that, The topology optimization design of the metamaterial unit composed of a three-layer three-dimensional structure is carried out to realize an anomalous reflection structure with multi-angle reflection control capability. When electromagnetic waves are incident on the metamaterial with a spatially non-uniform metallic structure, the structural unit is excited to generate electromagnetic resonance at a specific frequency, generating a local induced current, which in turn forms a spatially varying phase response on the metamaterial. The phase abrupt change between different structural units can realize precise control of the incident wavefront, thereby causing a deviation in the reflection direction and generating an anomalous reflection phenomenon.

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