A Mobius-knot-based wide-angle RCS-enhanced metamaterial electromagnetic tag and a preparation method thereof

Abstract

The application belongs to the field of radar target recognition, and particularly relates to application of a Mobius knot as a metamaterial electromagnetic label in wide-angle RCS enhancement. The application can obtain stable RCS scattering enhancement within an angle of -90°-90° at a design frequency point by designing a metamaterial electromagnetic label with Mobius knot units of different sizes and attaching the label on a target to be measured. Compared with a target without the label, average RCS enhancement within an angle of -90°-90° at the design frequency point can reach 10 dB, thereby forming a wide-angle RCS enhancement metamaterial electromagnetic label, which has application prospects in the fields of target recognition, target tracking, article management, traffic monitoring, identity verification and inventory management.

Description

Technical Field

[0001] This invention belongs to the field of radar target recognition, and specifically relates to the application of a Möbius knot in wide-angle RCS enhancement. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] With the development of radio communication systems, radar plays an important role in various scenarios, including military and civilian applications, to identify and track targets. However, changes in the spatial position between dynamic targets and radar can cause changes in the characteristics of the target's radar cross section (RCS), making stable identification and tracking difficult and greatly limiting the effectiveness of radar.

[0004] In recent years, with the development of electromagnetic theory and materials science, researchers have proposed a variety of methods to enhance the stability of RCS signals. For example, they have used highly reflective materials and specific geometric designs to improve signal stability. These methods include coating the target surface with a reflective layer or installing specially designed reflectors (such as Luneburg spheres or corner reflectors) to increase the intensity of reflected signals at specific angles. However, these methods usually face the following problems in practical applications: (1) Angle sensitivity: Traditional RCS enhancement methods mainly focus on optimizing the effect at specific incident angles and cannot provide a consistent enhancement effect over a wide angle range. This means that when the relative position of the target object changes, the RCS signal will still fluctuate significantly, affecting the radar's identification and tracking accuracy; (2) Structural complexity: These methods usually require a large weight and volume, increasing the complexity and cost of the system; (3) Poor adaptability: Traditional methods are poorly adaptable to dynamic environments. When the target object moves rapidly or environmental conditions change, the enhancement effect of the RCS signal is unstable and cannot meet the needs of high-precision detection and identification.

[0005] The inventors discovered in their research that although existing technologies utilize metamaterials to achieve wide-angle RCS enhancement, they can only achieve RCS enhancement in the 9-12 GHz frequency range within the angular domain of -45° to 45°. Although this solves the aforementioned problem to some extent, its angular range greatly limits the widespread application of radar detection technology in variable environments. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide an application of Möbius knots in wide-angle RCS enhancement. By using Möbius knots as structural units in the fabrication of metamaterial electromagnetic tags, the omnidirectionality, accuracy, and reliability of radar target identification are enhanced. This invention achieves stable wide-angle RCS signal enhancement at the designed frequency point by attaching the fabricated metamaterial electromagnetic tag to the object to be identified, thus enabling stable omnidirectional target identification based on the characteristic spectrum of the RCS.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] In a first aspect, the present invention provides an application of a Möbius knot in wide-angle domain RCS enhancement.

[0009] Preferably, the Möbius knots are arranged as structural units into a two-dimensional metamaterial array to obtain a metamaterial electromagnetic tag.

[0010] Preferably, the application includes: a Möbius knot as a metamaterial electromagnetic tag for stable RCS scattering enhancement within an angle range of -90° to 90°.

[0011] Preferably, the Möbius knot is obtained by topological transformation of the classic Möbius strip. The middle part of the Möbius strip is hollowed out, leaving only the edges to form two overlapping edge lines. The edge lines are then replaced with metal wires, which is the Möbius knot.

[0012] Preferably, the Möbius knot has a knot line diameter d of 0.1~3.0 mm, a center circle (auxiliary line) diameter D of 2.0~16.0 mm, and a height of 0.5~2 mm in the z direction.

[0013] Preferably, the Möbius knot is made of metal; more preferably, the metal is selected from one or more of silver, gold, aluminum, iron, tin, copper, and stainless steel.

[0014] Preferably, the processing technology of the Möbius knot is one or more of 3D printing, printed circuit board processing, and machining.

[0015] In a second aspect, the present invention provides a metamaterial electromagnetic tag with wide-angle RCS enhancement, wherein the metamaterial electromagnetic tag is composed of Möbius knots as structural units, and the structural units are arranged in a two-dimensional metamaterial array.

[0016] Preferably, the Möbius knot is obtained by topological transformation of the classic Möbius strip. The middle part of the Möbius strip is hollowed out, leaving only the edges to form two overlapping edge lines. The edge lines are then replaced with metal wires, which is the Möbius knot.

[0017] Preferably, the Möbius knot has a knot line diameter d of 0.1~3.0 mm, a center circle (auxiliary line) diameter D of 2.0~16.0 mm, and a height of 0.5~2 mm in the z direction.

[0018] More preferably, the Möbius knot has a knot line diameter d of 2 mm and a height of 1 mm in the z direction.

[0019] In a third aspect, the present invention provides a method for preparing a metamaterial electromagnetic tag with wide-angle domain RCS enhancement, specifically: using a Möbius knot as a structural unit, arranging them in a square on the xoy plane to form an m×n two-dimensional metamaterial array, thereby obtaining the metamaterial electromagnetic tag.

[0020] Preferably, the distance α between adjacent units of the two-dimensional metamaterial array is 5~40 mm.

[0021] Preferably, in the m×n two-dimensional metamaterial array, the value of m ranges from 5 to 30, and the value of n ranges from 5 to 30.

[0022] In a fourth aspect, the present invention provides an application of the metamaterial electromagnetic tag described in the second aspect in the fields of target identification, target tracking, item management, traffic monitoring, identity verification, and inventory management.

[0023] In a fifth aspect, the present invention provides a target identification method based on a metamaterial electromagnetic tag with wide-angle RCS enhancement, the target identification method comprising the following steps:

[0024] A metamaterial electromagnetic tag with wide-angle RCS enhancement is attached to the surface of a target object;

[0025] The radar emits electromagnetic waves, which are incident on the surface of the target object within an angle range of -90° to 90°.

[0026] The radar receives electromagnetic waves reflected from the surface of a target object and identifies the target object based on the enhanced RCS characteristics of a single station.

[0027] In a sixth aspect, the present invention provides a target tracking method based on a metamaterial electromagnetic tag with wide-angle RCS enhancement, the target tracking method comprising the following steps:

[0028] A metamaterial electromagnetic tag with wide-angle RCS enhancement is attached to the surface of a moving target object;

[0029] The radar emits electromagnetic waves, which are incident on the surface of the target object within an angle range of -90° to 90°.

[0030] The radar receives electromagnetic waves reflected from the surface of a target object and tracks the target object's trajectory based on the enhanced RCS characteristics of a single station.

[0031] The beneficial effects achieved by one or more technical solutions of the present invention are as follows:

[0032] (1) This invention designs metamaterial electromagnetic tags with different topological resonant frequencies by using Möbius knots of different sizes. Simply attaching the tag to the target surface can achieve stable RCS scattering enhancement within an angle of -90° to 90° at the design frequency. Compared with a target without a tag, the average RCS enhancement at the design frequency can reach 10 dB.

[0033] (2) In this invention, the size of the Möbius knot unit corresponds one-to-one with the designed characteristic frequency point, and the characteristic RCS of structural units of different sizes are decoupled from each other. For different targets, tags with different resonant frequencies are designed respectively. By simply superimposing them, different electromagnetic tags can be made with a small number of structural units, which facilitates the differentiation and identification of different targets.

[0034] (3) The present invention identifies target objects and obtains relevant data through radar signals. The identification distance is long and the process is simple. Moreover, based on passive identification of passive devices, the risk of information leakage is low.

[0035] (4) The preparation materials involved in this application can be inexpensive metals such as stainless steel, which are inexpensive, waterproof, corrosion-resistant, high temperature resistant, and have a long service life and are easy to mass-produce. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of an electromagnetic tag;

[0037] Figure 2 This is a schematic diagram of the structure of a Möbius knot obtained by topological transformation of the classic Möbius kink.

[0038] Figure 3 This is a schematic diagram of the structure of a Möbius strip unit, where 1 is the central circle (auxiliary line).

[0039] Figure 4 This is a schematic diagram illustrating the principle of the metamaterial electromagnetic tag prepared in Example 1 of the present invention;

[0040] Figure 5 This is a schematic diagram of the two-dimensional metamaterial array prepared in Example 1 of the present invention;

[0041] Figure 6 This is a photograph of the sample from Embodiment 2 of the present invention;

[0042] Figure 7The results are from Example 2 of this invention, where (a), (b), and (c) are the RCS values ​​as a function of frequency when electromagnetic waves are incident at 0 degrees, 20 degrees, and 40 degrees, respectively, and (d) is the RCS value as a function of the incident angle of electromagnetic waves at the design frequency of 6 GHz.

[0043] Figure 8 This is a photograph of the sample from Embodiment 3 of the present invention;

[0044] Figure 9 The results are from Example 3 of this invention, where (a), (b), and (c) show the RCS values ​​as a function of frequency when electromagnetic waves are incident at 0 degrees, 20 degrees, and 40 degrees, respectively, and (d) shows the RCS values ​​as a function of the incident angle of electromagnetic waves at the design frequency of 3.5 GHz.

[0045] Figure 10 This is a photograph of the sample from Embodiment 4 of the present invention;

[0046] Figure 11 The results are from Example 4 of this invention. (a), (b), and (c) show the RCS values ​​as a function of frequency when electromagnetic waves are incident at 0, 20, and 40 degrees. (d) and (e) show the RCS values ​​as a function of the incident angle of electromagnetic waves at the design frequencies of 3.5 GHz and 6 GHz, respectively. Detailed Implementation

[0047] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0048] In previous research, the inventors designed a Möbius strip with topological resonance characteristics (Metamaterial Design and Electromagnetic Topological Properties Based on Metallic Möbius Strips, Zhang Wenjin, Master's Thesis, Shandong University, May 20, 2021, Chapter 3). This structure exhibits strong robustness, maintaining its electromagnetic scattering parameters at a specific frequency point under incident electromagnetic waves at all angles. Based on this Möbius strip structure, this invention designs a metamaterial electromagnetic tag that provides stable RCS signal enhancement over a wide angle domain at the designed frequency point, simplifying radar identification and tracking processes and reducing costs.

[0049] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0050] Example 1:

[0051] This embodiment provides a metamaterial electromagnetic tag with wide-angle RCS enhancement.

[0052] The metamaterial electromagnetic tag is composed of structural units of Möbius knots, which are arranged into a two-dimensional metamaterial array.

[0053] Among them, the Möbius knot was prepared using the content of Chapter 3 of "Metamaterial Design and Electromagnetic Topological Properties Based on Metallic Möbius Knots · Zhang Wenjin · Shandong University Master's Thesis · May 20, 2021";

[0054] like Figure 2 As shown, the Möbius knot is obtained by topological transformation of the classic Möbius strip. The middle part of the Möbius strip is hollowed out, leaving only the edges to form two overlapping edge lines. The edge lines are then replaced with metal wires, which is the Möbius knot.

[0055] The specific parameters can be set as follows: the diameter d of the Möbius knot is 0.1~3.0 mm, the diameter D of the center circle (auxiliary line) is 2.0~16.0 mm, and the height in the z direction is 0.5~2 mm.

[0056] Example 2:

[0057] This embodiment provides a method for preparing a metamaterial electromagnetic tag and explores its application in wide-angle RCS enhancement, including the following steps:

[0058] by Figure 3 The Möbius knot shown serves as the basic structural unit, with a knot wire diameter of 2 mm, a central circle diameter of 8 mm, a corresponding design frequency of 6 GHz, and a height of 1 mm in the z-direction. It is fabricated using metal 3D printing technology and is made of stainless steel. Figure 5 As shown, the elements are arranged in a square to form a 7×7 two-dimensional array on the xoy plane, with the distance between adjacent elements being 35 mm, and fabricated as shown. Figure 6 Metamaterial electromagnetic tags.

[0059] The prepared sample was placed in a microwave anechoic chamber to test the far-field monostation RCS results, and the label was attached to a metal plate for testing. Figure 7 As obtained from (a)-(c), when the electromagnetic wave is randomly selected to be incident at 0 degrees, 20 degrees, and 40 degrees, the metal plate with the label shows an increase in RCS value to varying degrees compared to the metal plate without the label at the design frequency of 6 GHz.

[0060] To further verify the omnidirectionality and stability of the electromagnetic tag, electromagnetic waves were incident from different angles ranging from -90° to 90°, and the RCS value was extracted every 10°. This result was compared with that of a single metal plate. The results are as follows: Figure 7As shown in (d), when electromagnetic waves are incident at the design frequency of 6 GHz with an angle of -90 to 90°, the average RCS enhancement can reach 10 dB. This wide-angle, stable RCS characteristic signal can be easily read and identified, enabling the recognition and tracking of objects.

[0061] The specific principle is as follows: Figure 4 As shown, under the influence of an incident electromagnetic wave, the Möbius knot will generate two circular currents that oscillate repeatedly along its surface in opposite directions (path A-A' and path B-B'). Each current in each oscillation cycle will produce a geometric phase transition of π. Considering the propagation direction, the geometric phase transition along the A-A' path is π, and along the B-B' path it is -π. Therefore, the quantum geometric phase transition of the current will be half of the geometric phase transition, i.e., π / 2 and -π / 2, with a phase difference of π. The two electromagnetic waves with a phase difference of π will cause coherent cancellation, i.e., complete absorption. However, in the instant immediately after the electromagnetic wave is absorbed, the Möbius knot re-emits the electromagnetic wave omnidirectionally, resulting in an omnidirectional RCS enhancement effect.

[0062] Example 3:

[0063] This embodiment provides a method for preparing a metamaterial electromagnetic tag and explores its application in wide-angle RCS enhancement, including the following steps:

[0064] by Figure 3 The Möbius knot shown is used as the basic structural unit. The knot line has a diameter of 2 mm, the central circle diameter is 12 mm, the corresponding design frequency is 3.5 GHz, and the height of the knot in the z-direction is 1 mm. It is fabricated using metal 3D printing technology and the material is stainless steel. Arranged in a square on the xoy plane to form a 7×7 two-dimensional array, the distance between adjacent units is 35 mm, and the fabrication is as follows. Figure 8 Metamaterial electromagnetic tags.

[0065] The prepared sample was placed in a microwave anechoic chamber to test the far-field monostation RCS results, and the label was attached to a metal object for testing. Figure 9 As shown in Figures (a)-(c), when the electromagnetic wave is randomly selected to be incident at 0 degrees, 20 degrees, and 40 degrees, the metal plate with the label shows a different degree of enhancement in its RCS value at the design frequency of 3.5 GHz compared to the metal plate without the label.

[0066] To further verify the omnidirectionality and stability of the electromagnetic tag, electromagnetic waves were incident from different angles ranging from -90° to 90°, and the RCS value was extracted every 10°. This result was compared with that of a single metal plate. The results are as follows: Figure 9As shown in (d), when electromagnetic waves are incident at the design frequency of 6 GHz with an angle of -90 to 90°, the average RCS enhancement can reach 10 dB. This wide-angle, stable RCS characteristic signal can be easily read and identified, enabling the recognition and tracking of objects.

[0067] Example 4:

[0068] This embodiment provides a method for preparing a metamaterial electromagnetic tag and explores its application in wide-angle RCS enhancement, including the following steps:

[0069] by Figure 3 The Möbius knot shown is used as the basic structural unit. Two different sized structural units are selected, with central circle diameters of 8 mm and 12 mm respectively. The diameter of the knot line is 2 mm for both units, and the height of the knot in the z-direction is 1 mm. The corresponding design frequencies are 3.5 GHz and 6 GHz. It is fabricated using metal 3D printing technology, and the material is stainless steel. The units are arranged in a square on the xoy plane to form a 10×10 two-dimensional array. The two structural units are arranged alternately, with a distance of 25 mm between adjacent units, as shown in the figure. Figure 10 Metamaterial electromagnetic tags.

[0070] The prepared sample was placed in a microwave anechoic chamber to test the far-field monostation RCS results, and the label was attached to a metal object for testing. Figure 11 As shown in Figures (a)-(c), when the electromagnetic wave is randomly selected to be incident at 0 degrees, 20 degrees, and 40 degrees, its RCS value is enhanced to varying degrees at the design frequency points of 3.5 GHz and 6 GHz.

[0071] To further verify the omnidirectionality and stability of the electromagnetic tag, electromagnetic waves were incident from different angles ranging from -90° to 90°, and the RCS value was extracted every 10°. This result was compared with that of a single metal plate. The results are as follows: Figure 11 As shown in (d)-(e), at the design frequencies of 3.5 GHz and 6 GHz, the average RCS enhancement can reach 10 dB when the electromagnetic wave is incident at an angle of -90 to 90°. This wide-angle, stable RCS characteristic signal can be easily read and identified, enabling the recognition and tracking of objects.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A metamaterial electromagnetic tag with wide-angle domain RCS enhancement based on a Möbius knot, characterized in that, The metamaterial electromagnetic tag is composed of Möbius knots as structural units, which are arranged into a two-dimensional metamaterial array; thus, a metamaterial electromagnetic tag is obtained. The Möbius knot is obtained by topological transformation of the classic Möbius strip. The middle part of the Möbius strip is hollowed out, leaving only the edges to form two overlapping edge lines. The edge lines are then replaced with metal wires, which is the Möbius knot. Möbius knots, as metamaterial electromagnetic tags, exhibit stable RCS scattering enhancement within an angle range of -90° to 90°. The Möbius knot has a knot line diameter d of 0.1~3.0 mm and a height of 0.5~2 mm in the z direction; the central circle diameter D is 2.0~16.0 mm. A metamaterial electromagnetic tag with wide-angle RCS enhancement is attached to the surface of a moving target object; The radar emits electromagnetic waves, which are incident on the surface of the target object within an angle range of -90° to 90°. The radar receives electromagnetic waves reflected from the surface of a target object and identifies the target object based on the enhanced RCS characteristics of a single station.

2. The metamaterial electromagnetic tag as described in claim 1, characterized in that, The diameter d of the knot line of the Möbius knot is 2 mm; the height of the Möbius knot in the z direction is 1 mm.

3. The metamaterial electromagnetic tag as described in claim 1, characterized in that, The Möbius knot is made of metal; the metal is selected from one or more of silver, gold, aluminum, iron, tin, copper, and stainless steel.

4. The metamaterial electromagnetic tag as described in claim 1, characterized in that, The processing technology of the Möbius knot is one or more of 3D printing, printed circuit board technology, and machining.

5. A method for fabricating a metamaterial electromagnetic tag with wide-angle RCS enhancement based on a Möbius knot according to claim 1, characterized in that, Specifically, a two-dimensional metamaterial array of m×n is formed by arranging Möbius knots as structural units in a square arrangement on the xoy plane, thus obtaining a metamaterial electromagnetic tag. The distance α between adjacent units of the two-dimensional metamaterial array is 5~40 mm; In the m×n two-dimensional metamaterial array, the value of m ranges from 5 to 30, and the value of n ranges from 5 to 30.

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