Quasi-omnidirectional reverse enhanced RCS device based on metasurface and design method

Abstract

The invention relates to an unmanned aerial vehicle cluster cooperative positioning and navigation technology, and particularly discloses a quasi-omni-directional reverse enhanced RCS device based on a metasurface and a design method of the quasi-omni-directional reverse enhanced RCS device based on the metasurface. The six same three-angle backscattering arrays form a regular hexahedron honeycomb type device; the three-angle backscattering array is formed by alternately arranging first metasurface units and second metasurface units; the reflection phase difference between the first metasurface unit and the second metasurface unit is 180 degrees; the first metasurface unit and the second metasurface unit have the same structure and each comprise a dielectric substrate; a floor is arranged below the dielectric substrate, and a metal resonance layer is arranged above the dielectric substrate. According to the invention, high signal-to-noise ratio millimeter wave echo signals can be generated under a long-distance condition; and zero-power-consumption operation of the passive positioning beacon is realized.

Description

Technical Field

[0001] This invention relates to the field of UAV swarm cooperative positioning and navigation technology, and more specifically to a quasi-omnidirectional reverse RCS enhancement device and design method based on metasurfaces. Background Technology Unmanned aerial vehicle (UAV) swarm cooperative positioning and navigation technology has become a core research direction in the field of unmanned systems, demonstrating irreplaceable value in scenarios such as military reconnaissance, disaster relief, logistics delivery, and large-scale environmental monitoring. Especially in complex electromagnetic environments, GNSS-denied areas (such as indoor spaces, canyons, urban canyons, or battlefields with strong interference), and highly dynamic dense formation scenarios, UAVs within a swarm need to rely on high-precision relative pose perception to achieve cooperative obstacle avoidance, formation maintenance, and task allocation. However, existing technologies struggle to meet millimeter-level positioning accuracy requirements under constraints of low power consumption, low cost, and strong robustness, constituting a key bottleneck restricting swarm autonomy.

[0002] Millimeter-wave radar active detection schemes rely on airborne radar transmit-receive links to achieve target ranging / angle measurement. While providing centimeter-level accuracy, its coverage and accuracy are strongly negatively correlated—increasing transmit power is required to ensure long-range detection, leading to a sharp decrease in the UAV's payload and endurance. Simultaneously, multi-aircraft radar beam interference in high-density clusters causes severe co-channel interference, and dynamic resource allocation algorithms further increase system complexity and latency. Ultra-wideband (UWB) wireless ranging technology achieves relative positioning through time-of-flight measurement. While offering low power consumption, its effective range is typically limited to the hundred-meter range, and it suffers from severe non-line-of-sight errors in urban multipath environments or densely metal areas (such as industrial facilities). More critically, UWB wireless ranging technology requires a fully interconnected communication topology within the cluster. As the number of nodes N increases, the communication overhead required to maintain high refresh rate positioning grows O(N²), resulting in a sharp decrease in system scalability. Intelligent metasurface-assisted positioning, as an emerging solution, enhances positioning signal strength by modulating the electromagnetic properties of the environment. However, existing smart metasurface technologies mostly rely on base station backhaul links or predictive coarse-grained UAV positions to dynamically adjust the phase, making real-time coordinated control difficult to achieve in decentralized clusters. Furthermore, single-sided smart metasurfaces have limited beam coverage (typical half-power beamwidth < 60°), and UAV attitude deflection or position shifts can easily lead to positioning link interruptions, making them unsuitable for the motion characteristics of highly maneuverable clusters.

[0003] Metasurfaces, with their outstanding ability to flexibly control the amplitude and phase of electromagnetic waves at subwavelength scales, have become an electromagnetic control platform of great interest in industry. They show broad application prospects in the microwave / millimeter-wave bands, with typical applications including beam scanning, polarization conversion, and frequency reconfigurable devices. In recent years, reverse metasurfaces, as an emerging research direction, have shown unique value in the field of radar cross section (RCS) enhancement by precisely controlling the backscattering characteristics of electromagnetic waves—especially suitable for enhancing the electromagnetic characteristics of low-observable targets (i.e., targets with extremely low inherent backscattering power).

[0004] While existing technologies have driven the development of swarm positioning in specific scenarios, they are all constrained by the impossible triangle of "coverage-power consumption-cost": millimeter-wave radar's coverage is limited by the strong coupling between its operating range and power consumption; ultra-wideband wireless ranging technology is limited by its effective ranging range in non-line-of-sight environments; and the narrow-beam characteristics of intelligent metasurface technology make it difficult to support full-space coverage. Simultaneously, the high cost of active sensing hardware and the overhead of multi-node deployment severely restrict the large-scale application of swarms, and the sensitivity of existing solutions to the dynamic pose of UAVs further exacerbates system vulnerability. To fundamentally overcome these three constraints, a disruptive passive positioning beacon mechanism is urgently needed—one that simultaneously achieves zero-power operation, omnidirectional spatial coverage, and stable scattering characteristics independent of attitude, thereby providing a highly robust and low-cost cooperative positioning infrastructure for UAV swarms in GNSS-denied environments. Summary of the Invention The purpose of this invention is to provide a quasi-omnidirectional reverse-enhanced RCS device and design method based on metasurfaces to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides a device for quasi-omnidirectional reverse RCS enhancement based on metasurfaces, comprising: The device includes a rectangular triangular backscattering array; six identical triangular backscattering arrays form a hexahedral honeycomb structure; the triangular backscattering arrays are arranged alternately by first and second metasurface units; this design achieves near 360° coverage in the azimuth dimension through multi-panel cooperative scattering, ultimately realizing quasi-omnidirectional RCS enhancement, providing a high-sensitivity positioning beacon with no blind spots for UAV swarms. The reflection phases of the first and second metasurface units differ by 180°.

[0006] Preferably, the three-angle backscatter array is a 40×40 array. This design can simultaneously achieve backscatter enhancement at three azimuth angles of +30°, 0° and -30°, which can meet the positioning and navigation needs in the 60° angular domain.

[0007] Preferably, both the first and second metasurface units include a dielectric substrate that supports the electromagnetic wave phase modulation structure. A ground plane is located beneath the dielectric substrate, providing a total reflection substrate for the metal grounding layer, and a metal resonant layer is located above it. The metal resonant layer includes a square metal patch at the center of the dielectric substrate, and a square metal ring is disposed around the metal patch. By precisely optimizing the size of the rectangular patch and the geometric parameters of the ring patch, active modulation of the incident electromagnetic wave phase can be achieved.

[0008] Preferably, the square metal ring in the metal resonant layer of the first metasurface unit has a width of 0.1 mm and an outer side length of 1.25 mm, and the square metal patch has a side length of 0.85 mm.

[0009] Preferably, the square metal ring in the metal resonant layer of the second metasurface unit has a width of 0.1 mm and an outer side length of 2.3 mm, and the square metal patch has a side length of 1.9 mm.

[0010] A design method for a quasi-omnidirectional reverse-polarity enhanced RCS device based on metasurfaces includes the following steps: S1. Based on the simulation, select the phase difference between adjacent metasurface units; S2. Based on the phase gradient metasurface theory of the generalized Snell's law, establish a mathematical model for three-angle RCS enhancement. Assuming a plane wave of arbitrary direction is incident from air at an angle θ onto an infinitely large metasurface, and the incident surface lies in the XZ plane, then the electric field of the incident wave is:

[0011] In the formula, For the incident wave electric field, The amplitude of the incident wave electric field. Let be the propagation constant. The polarization vector, The angle of incidence; Based on the boundary conditions, the electric field of the reflected wave is:

[0012] In the formula, For the electric field of the reflected wave, The amplitude of the incident wave electric field. Let be the propagation constant. The polarization vector, For the reflection angle, The modulation phase of the metasurface; Since Z=0, and the tangential component of the electric field on the boundary is continuous, the sum of the tangential components of the incident wave and the reflected wave is 0. Therefore: + =0 In the formula, The amplitude of the incident wave electric field. Let be the propagation constant. For the angle of incidence, For the reflection angle, The modulation phase of the metasurface; Based on this, the reflection angle can be derived. and Modulation phase relation of metasurface:

[0013] In the formula, For the angle of incidence, For the reflection angle, Let be the propagation constant. For phase gradient; S3. Based on the model obtained in step S2, adjust the phase gradient to verify the phase difference selected in S1; S4. Construct a three-angle backscattering array based on the selected phase difference; S5. Construct a regular hexahedral honeycomb device using a three-angle metasurface reverse array as the basic unit.

[0014] Preferably, the simulation steps in step S1 include: S101. Alternately arrange metasurface units with the same structure but different sizes to form a one-dimensional three-angle backscattering array with different phase differences; S102. Simulate a three-angle backscattering array with different phase differences and analyze the simulation results. Preferably, the optimal phase difference between the first metasurface unit and the second metasurface unit in step S1 is 180°.

[0015] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects: A hexahedral quasi-omnidirectional anti-array was constructed for collaborative positioning and navigation of UAV swarms, breaking through the spatial coverage limitations of traditional intelligent metasurfaces and achieving omnidirectional electromagnetic response capability; it generates high signal-to-noise ratio millimeter-wave echo signals under long-distance conditions, providing a passive positioning reference with centimeter-level accuracy for UAV swarms; and it eliminates the power consumption constraints of active sensing, realizing zero-power operation of passive positioning beacons. Attached Figure Description

[0016] Figure 1 This is a diagram showing the hexahedral honeycomb device and beam scattering of the present invention; Figure 2 This is a flowchart of the design method of the present invention; Figure 3 This is a structural diagram of the metasurface unit of the present invention; Figure 4 This is a schematic diagram of the metasurface electromagnetic wave reverse enhancement principle of the present invention; Figure 5 This is a structural diagram of the 40×40 triangular backscattering array of the present invention; Figure 6 The simulated phase and amplitude response curves of the metasurface unit of the present invention are shown below. Figure 7 Full-wave simulation of the three-angle reverse metasurface array of the present invention; Figure 8 The data provided are simulation data for the one-dimensional three-angle backscattering array with different phase differences according to the present invention.

[0017] As shown in the figure: 1-Metal resonant layer, 101-Square metal ring, 102-Square metal patch, 2-Dielectric substrate, 3-Ground floor, 4-First metasurface unit, 5-Second metasurface unit, 6-Three-angle backscattering array. Detailed Implementation

[0018] This invention aims to overcome the technical bottleneck caused by the "coverage-power consumption-cost" impossible triangle in UAV swarm cooperative positioning. Specifically, it addresses the following: First, eliminating the power consumption constraints of active sensing: It overcomes the fundamental defect of existing UAV swarm positioning technologies that rely on airborne active transmission links, avoiding the high power consumption generated by the RF front-end, signal processing unit, and beam control module, thus achieving zero-power operation of the passive positioning beacon. Second, breaking through the spatial limitations of angular coverage: It overcomes the coverage blind zone problem caused by the narrow beamwidth of traditional technologies, constructing an all-domain electromagnetic response capability, i.e., maintaining stable scattering characteristics within a 360° azimuth angle range. Third, establishing a high-precision passive positioning reference: For the relative positioning needs of swarms in GNSS-denied environments, it constructs a spatial reference beacon with centimeter-level accuracy. Strong directional echoes are generated through subwavelength phase modulation in the millimeter-wave band (60GHz), allowing UAVs to calculate their precise relative pose (distance, azimuth) with the beacon by receiving this echo signal.

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] Reference Figure 1 As shown, the present invention provides a device for quasi-omnidirectional reverse RCS enhancement based on metasurfaces: The device includes a rectangular triangular backscattering array 6; six identical triangular backscattering arrays 6 form a regular hexahedral honeycomb device; the triangular backscattering array 6 is arranged alternately by a first metasurface unit 4 and a second metasurface unit 5; the reflection phases of the first metasurface unit 4 and the second metasurface unit 5 differ by 180°; the regular hexahedral honeycomb device generates 18 discrete enhancement beams in the azimuth plane, which can achieve RCS back enhancement in the azimuth plane at 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and 330°, ultimately meeting the cooperative positioning and navigation requirements of UAV swarms in the 360° all-space domain.

[0021] According to Figure 3 As shown in the metasurface unit structure diagram, both the first metasurface unit 4 and the second metasurface unit 5 include a dielectric substrate 2; a ground plane 3 is provided below the dielectric substrate 2, and a metal resonant layer 1 is provided above it; The metal resonant layer 1 includes a square metal patch 102 located at the center of the dielectric substrate, and a square metal ring 101 is disposed outside the square metal patch 102.

[0022] according to Figure 6 Simulation curves of the phase and amplitude response of the metasurface unit were obtained. The results show that, in the target millimeter-wave band of 60 GHz, adjusting the size of the rectangular patch can produce a continuously varying emission phase response with a phase coverage of 360°, while maintaining reflection amplitude stability (>-3 dB). This characteristic provides a core physical basis for constructing directional scattering fields.

[0023] In one specific embodiment, the square metal ring 101 in the first metasurface unit 4 has a width of 0.1 mm and an outer side length of 1.25 mm, and the square metal patch 102 has a side length of 0.85 mm.

[0024] In one specific embodiment, the square metal ring 101 in the second metasurface unit 5 has a width of 0.1 mm and an outer side length of 2.3 mm, and the square metal patch 102 has a side length of 1.9 mm.

[0025] Specifically, the three-angle backscattering array 6 is a 40×40 array. For example... Figure 7 Full-wave simulations of the three-angled reverse metasurface array show that this design achieves simultaneous reverse enhancement at three azimuth angles of +30°, 0°, and -30°, with corresponding single-station RCS values ​​of 12.3 dB, 12.18 dB, and 12.3 dB, respectively. Compared to the reference value of a metal ground plane of the same size (17.1 dB), the overall RCS of the array is reduced by approximately 4.9 dB. This directional energy redistribution characteristic significantly improves azimuth resolution while maintaining high scattering intensity (>12 dB) at key angles.

[0026] Specifically, a method for enhancing RCS based on metasurfaces in a quasi-omnidirectional reverse direction includes the following steps: S1. Based on the simulation, select the phase difference between adjacent metasurface units; in step S1, the phase difference between the first metasurface unit and the second metasurface unit is 180°.

[0027] Specifically, according to Figure 8 Simulation data for a one-dimensional three-angle backscattering array with different phase differences are shown.

[0028] S101. Alternately arrange metasurface units with the same structure but different sizes to form a one-dimensional three-angle backscattering array with different phase differences; the specific phase differences include 0°, 90°, 180°, and 270°.

[0029] S102. Simulations were performed on three-angle backscattering arrays with different phase differences. The simulation results were analyzed, and it was found that the angle of the main lobe of the reflection shifted regularly with the phase difference. Based on this conclusion, the phase difference of adjacent metasurface units was selected.

[0030] S2. Based on the phase gradient metasurface theory of the generalized Snell's law, establish a mathematical model for three-angle RCS enhancement. Specifically, according to Figure 4 The principle of metasurface electromagnetic wave inversion enhancement is shown in the illustration, where Let σ be the permittivity and permeability of free space. ∞ indicates that the surface beneath the metasurface is an ideal conductor. The angle of incidence, For the reflection angle, For the incident electric field, For the reflected electric field, For the incident magnetic field, It is for reflecting magnetic fields.

[0031] Assuming a plane wave of arbitrary direction is incident from air at an angle θ onto an infinitely large metasurface, and the incident surface lies in the XZ plane, then the electric field of the incident wave is:

[0032] In the formula, For the incident wave electric field, The amplitude of the incident wave electric field. Let be the propagation constant. The polarization vector, The angle of incidence is denoted as .

[0033] Based on the boundary conditions, the electric field of the reflected wave is:

[0034] In the formula, For the electric field of the reflected wave, The amplitude of the incident wave electric field. Let be the propagation constant. The polarization vector, For the reflection angle, The modulation phase of the metasurface.

[0035] Since Z=0, and the tangential component of the electric field on the boundary is continuous, the sum of the tangential components of the incident wave and the reflected wave is 0. Therefore: + =0 In the formula, The amplitude of the incident wave electric field. Let be the propagation constant. For the angle of incidence, For the reflection angle, The modulation phase of the metasurface.

[0036] Based on this, the reflection angle can be derived. With phase gradient Relationship:

[0037] In the formula, For the angle of incidence, For the reflection angle, Let be the propagation constant. This represents the phase gradient.

[0038] S3. Based on the model obtained in step S2, adjust the phase gradient to verify the phase difference selected in S1; S4. Based on the selected phase difference, construct a three-angle backscattering array 6; S5. Using a three-angle backscatter array 6 as the basic unit, construct a regular hexahedral honeycomb device.

[0039] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A quasi-omnidirectional reverse-polarity enhanced RCS device based on metasurfaces, characterized in that, It includes a rectangular triangular backscattering array (6); six identical triangular backscattering arrays (6) form a regular hexahedral honeycomb device; the triangular backscattering array (6) is arranged alternately by a first metasurface unit (4) and a second metasurface unit (5); the reflection phases of the first metasurface unit (4) and the second metasurface unit (5) are 180° apart; The first metasurface unit (4) and the second metasurface unit (5) have the same structure, both including a dielectric substrate (2); a ground plane (3) is provided below the dielectric substrate (2), and a metal resonant layer (1) is provided above it; The metal resonant layer (1) includes a square metal patch (102) located at the center of the dielectric substrate, and a square metal ring (101) is provided outside the square metal patch (102).

2. The quasi-omnidirectional reverse-polarity enhanced RCS device based on metasurfaces according to claim 1, characterized in that, The square metal ring (101) of the first metasurface unit (4) has a width of 0.1 mm and an outer side length of 1.25 mm, and the square metal patch (102) has a side length of 0.85 mm.

3. The quasi-omnidirectional reverse-polarity enhanced RCS device based on metasurfaces according to claim 1, characterized in that, The square metal ring (101) of the second metasurface unit (5) has a width of 0.1 mm and an outer side length of 2.3 mm, and the square metal patch (102) has a side length of 1.9 mm.

4. The quasi-omnidirectional reverse-polarity enhanced RCS device based on metasurfaces according to claim 1, characterized in that, The three-angle backscatter array (6) is a 40×40 array.

5. A design method for a quasi-omnidirectional reverse-polarity enhanced RCS device based on metasurfaces, characterized in that, For designing the apparatus according to any one of claims 1-4, comprising: S1. Based on the simulation, select the phase difference between adjacent metasurface units; S2. Based on the phase gradient metasurface theory of the generalized Snell's law, establish a mathematical model for three-angle RCS enhancement. S3. Based on the model obtained in step S2, adjust the phase gradient to verify the phase difference selected in S1; S4. Construct a three-angle backscattering array (6) based on the selected phase difference. S5. Using a three-angle backscatter array (6) as the basic unit, construct a regular hexahedral honeycomb device.

6. The design method of a quasi-omnidirectional reverse-polarity enhanced RCS device based on metasurfaces according to claim 5, characterized in that, The mathematical model in step S2 is: In the formula, For the angle of incidence, For the reflection angle, Let be the propagation constant. This represents the phase gradient.

7. The design method of a quasi-omnidirectional reverse-polarity enhanced RCS device based on a metasurface according to claim 5, characterized in that, The simulation steps in step S1 include: S101. Alternately arrange metasurface units with the same structure but different sizes to form a one-dimensional three-angle backscattering array with different phase differences; S102. Simulate a three-angle backscattering array with different phase differences and analyze the simulation results.

8. The design method of a quasi-omnidirectional reverse-polarity enhanced RCS device based on a metasurface according to claim 5, characterized in that, In step S1, the phase difference between adjacent metasurface units is selected to be 180°.

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