Moiré metasurface for dynamic beamforming

Abstract

The present invention discloses a moiré metasurface for realizing dynamic beamforming, comprising two layers of tightly fitted periodic metal patterns, an isolation layer, and a metal backplane; the surface impedance distribution is adjusted by the moiré pattern formed by the relative rotation of the two layers of periodic metal patterns, thereby realizing wavefront control of the incident wave and achieving the purpose of dynamic beamforming; the invention does not require active devices, and the cost is greatly reduced compared to programmable metamaterials, large-scale MIMO and active array antennas using active elements (such as switching diodes, varactor diodes); at the same time, the invention has the advantages of zero static power consumption and zero receiving noise, and is expected to be widely used as an intelligent reflector antenna in 6G mobile communications; in addition, since the present invention has a purely passive characteristic, it can be applied to high-power microwave scenarios such as radar detection and electronic countermeasures.

Description

Technical Field

[0001] The present invention belongs to the intersection of new artificial electromagnetic materials and wireless communication technology, and relates to a passive electromagnetic material capable of realizing dynamic beamforming, and more specifically, to a passive metamaterial that realizes beam scanning and beam shape switching through mechanical rotation. Background Art

[0002] As a new type of dynamic beamforming antenna, programmable metamaterials can achieve highly flexible real-time control of the incident wave by dynamically controlling the reflection / transmission phase of the array with a given bit accuracy, thereby achieving the goal of high-speed scanning and switching of far-field beams. Although the manufacturing cost of programmable metamaterials is greatly reduced compared to phased array antennas, since each metamaterial unit needs to be equipped with an independent switching diode, the cost of large arrays of programmable metamaterials is still high and difficult to use for large-scale commercial deployment. Therefore, the importance of seeking lower-cost programmable metamaterials has gradually become prominent. In recent years, the moiré effect has gradually emerged in the field of topological electronics and metamaterials. This is a low-frequency periodic pattern visible to the naked eye formed by the superposition of two high-frequency spatial periodic texture patterns. It was first discovered by the French researcher Moiré in the 18th century. In 2018, the British journal Nature reported a work on achieving Mott insulators and high-temperature superconductivity through a "magic angle" graphene structure. The researchers found that by stacking two layers of graphene and adjusting the rotation angle between them, the band structure of the material can be effectively changed, making it present physical properties that are completely different from those of single-layer graphene, and for the first time, superconductivity was observed in pure carbon-based two-dimensional materials. The publication of this work quickly attracted widespread attention from scholars in the fields of condensed matter superconductivity and photonics, opening the door to studying topological insulators and metamaterials based on the moiré effect. Summary of the invention

[0003] Technical problem: The purpose of the present invention is to provide a moiré metasurface for realizing dynamic beamforming. Through the close fitting of two layers of high-frequency periodic metal patterns, the superposition process produces a low-frequency moiré pattern, thereby changing the surface equivalent impedance distribution, realizing the wavefront control of the incident wave, and further achieving the purpose of controlling the far-field radiation pattern.

[0004] Technical solution: A moiré metasurface for realizing dynamic beamforming of the present invention comprises a first periodic metal pattern, a second periodic metal pattern, an isolation layer, and a metal backplane which are tightly fitted from top to bottom; two layers of tightly fitted first periodic metal pattern and second periodic metal pattern are superimposed to form a moiré pattern, and the two layers of periodic metal patterns can rotate relative to each other in the fitting plane, thereby realizing a dynamically adjustable metamaterial for beam scanning and beam shape switching through mechanical rotation.

[0005] in,

[0006] The styles of the two-layer periodic metal patterns can be arbitrarily and independently selected from a two-dimensional space group.

[0007] Each layer of the two-layer periodic metal pattern is composed of multiple layers of periodic patterns tightly attached.

[0008] The periodic metal pattern includes a pseudo-periodic pattern having an approximate periodicity.

[0009] The electrical thickness of the periodic metal pattern ranges from 0.0001 wavelength to 0.1 wavelength.

[0010] The periodic metal pattern is processed on a dielectric substrate with any dielectric constant, and the electrical thickness of the dielectric substrate ranges from 0.0001 wavelength to 0.1 wavelength.

[0011] The isolation layer is a dielectric material with arbitrary dielectric constant and dielectric loss.

[0012] The electrical thickness of the isolation layer is from 0.0001 wavelength to 0.1 wavelength.

[0013] The material of the metal back plate has excellent electrical conductivity, and the electrical thickness is greater than 0.0001 wavelength.

[0014] The appearance of the moiré super surface is any shape.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following advantages

[0016] 1. Compared with active antenna arrays such as programmable metamaterials and massive MIMO antennas that use active devices (such as switching diodes and varactor diodes), the present invention eliminates active devices and peripheral circuits. Only by superimposing and rotating two layers of passive metasurfaces, the shape and number of beams can be efficiently controlled, greatly reducing costs.

[0017] 2. Active antenna arrays such as programmable metamaterials and massive MIMO antennas that use active devices (such as switching diodes and varactor diodes) cannot achieve truly continuous scanning angles due to the fixed unit period. The present invention can form a continuously changing Moiré pattern through the continuous rotation of the two-layer pattern, thereby achieving continuous and infinite control of the beam angle.

[0018] 3. Active antenna arrays such as programmable metamaterials and massive MIMO antennas using active devices have certain static power consumption because they contain a large number of switching diodes or varactor diodes and peripheral circuits. The present invention has the unique advantage of zero static power consumption, that is, the state of the beam can be maintained without consuming any electricity.

[0019] 4. Since the present invention does not include active devices such as switching diodes or varactor diodes, it can work in high-power microwave scenarios such as radar detection and electronic countermeasures. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the moiré supersurface structure.

[0021] Figure 2 This is a schematic diagram of the principle of Moiré supersurface.

[0022] Figure 3 It is a checkerboard pattern moiré metasurface.

[0023] Figure 4 is a regular triangle pattern moiré supersurface.

[0024] Figure 5 is the k-space representation of the checkerboard pattern moiré metasurface when the twist angle is 10°.

[0025] Figure 6 is the k-space representation of the checkerboard pattern moiré metasurface when the twist angle is 80°.

[0026] Figure 7 is the k-space representation of the moiré hypersurface with a regular triangle pattern when the twist angle is 10°.

[0027] Figure 8 is the k-space representation of the moiré hypersurface with a regular triangle pattern when the twist angle is 50°.

[0028] Fig. 9 are the moiré component trajectories (a, b) and beam trajectories (c) of the checkerboard-pattern moiré metasurface when pattern 2 is rotated counterclockwise from 0° to 90°.

[0029] Fig.10 are the moiré component trajectories (a, b) and beam trajectories (c) of the equilateral triangle pattern moiré metasurface when pattern 2 is rotated counterclockwise from 0° to 60°.

[0030] Fig.11 The moiré component trajectories (a, b) and beam trajectories (c) of the checkerboard-equilateral triangle hybrid moiré metasurface when pattern 2 is rotated counterclockwise from 0° to 60°.

[0031] Fig.12 The simulation results of the 3D far-field pattern of the checkerboard pattern moiré metasurface when the twist angle ψ = 0.25°, 2°, 4°, 6°, 8°, 10°, 12°, and 14°. The double solid line and single solid line represent the mean and fluctuation range of the normalized intensity of all beams, respectively.

[0032] Fig.13These are the simulation results of the two-dimensional far-field patterns of the checkerboard pattern moiré metasurface when the twist angle ψ = 0.25°, 2°, 4°, 6°, 8°, 10°, 12°, and 14°.

[0033] Fig.14 It is the beam peak angle trajectory and normalized intensity of the checkerboard pattern moiré metasurface when the twist angle is rotated counterclockwise from 0.25° to 14° (step size 0.25°).

[0034] Fig.15 The simulation results of the 3D far-field pattern of the equilateral triangle pattern moiré metasurface when the twist angle ψ = 0.25°, 2°, 4°, 6°, 8°, 10°, 12°, and 13°. The double solid line and single solid line represent the mean and fluctuation range of the normalized intensity of all beams, respectively.

[0035] Fig.16 These are the simulation results of the two-dimensional far-field patterns of the equilateral triangle pattern moiré metasurface when the twist angle ψ = 0.25°, 2°, 4°, 6°, 8°, 10°, 12°, and 13°.

[0036] Fig.17 It is the beam peak angle trajectory and normalized intensity of the equilateral triangle pattern moiré metasurface when the twist angle rotates counterclockwise from 0.25° to 13° (step size 0.25°).

[0037] Fig.18 These are sample photos of the checkerboard pattern moiré metasurface at twist angles of (a) 0.25°, (b) 2°, (c) 4°, (d) 6°, (e) 8°, (f) 10°, (g) 12°, (h) 14°, and (i) 16°.

[0038] Fig.19 These are the measured results of the three-dimensional far-field patterns of the checkerboard-patterned moiré metasurface when the twist angles ψ = 6°, 8°, 10°, and 12°.

[0039] Fig. 20 These are the measured results of the two-dimensional far-field patterns of the checkerboard pattern moiré metasurface when the twist angles ψ = 0.25°, 2°, 4°, 6°, 8°, 10°, 12°, and 14°.

[0040] Fig.21 These are sample photos of the equilateral triangle pattern moiré metasurface at twist angles of (a) 0.25°, (b) 2°, (c) 4°, (d) 6°, (e) 8°, (f) 10°, (g) 12°, (h) 14°, and (i) 16°.

[0041] Fig. 22These are the measured results of the three-dimensional far-field patterns of the equilateral triangle pattern moiré metasurface when the twist angle ψ = 6°, 8°, 10°, and 12°.

[0042] Fig.23 These are the measured results of the two-dimensional far-field patterns of the equilateral triangle pattern moiré metasurface when the twist angle ψ = 0.25°, 2°, 4°, 6°, 8°, 10°, 12°, and 13°.

[0043] Fig.24 These are the (ah) simulation results and (ip) measured results of the two-dimensional far-field directional diagram (logarithmic coordinates) of the checkerboard pattern moiré metasurface when the torsion angle ψ = 0.25°, 2°, 4°, 6°, 8°, 10°, 12°, and 14°.

[0044] Fig.25 These are the (ah) simulation results and (ip) measured results of the two-dimensional far-field directional diagram (logarithmic coordinates) of the equilateral triangle pattern moiré metasurface when the torsion angle ψ = 0.25°, 2°, 4°, 6°, 8°, 10°, 12°, and 13°.

[0045] The figure includes: a first periodic metal pattern 1, a second periodic metal pattern 2, an isolation layer 3, and a metal back plate 4. DETAILED DESCRIPTION

[0046] The moiré metasurface for realizing dynamic beamforming of the present invention is a dynamically adjustable metamaterial that realizes beam scanning and beam morphology switching through mechanical rotation. It produces a low-frequency moiré pattern through the close fitting of two layers of high-frequency periodic metal patterns, and the superposition process thereof produces a low-frequency moiré pattern, thereby changing the surface equivalent impedance distribution, realizing the wavefront control of the incident wave, and then achieving the purpose of controlling the far-field radiation pattern. Through the relative rotation of the two layers of metasurfaces, continuous control of the beam angle can be realized, and the beam efficiency can reach or even exceed that of traditional metasurfaces. More importantly, since the moiré metasurface does not require any active components, it greatly reduces the cost, system complexity and power consumption. It fundamentally solves the disadvantage that the existing programmable metamaterials are expensive due to the use of a large number of RF diodes, and is therefore expected to be widely used as smart reflector antennas in 6G mobile communications.

[0047] Figure 1 An exploded diagram of a moiré metasurface is given, which includes a first periodic metal pattern 1, a second periodic metal pattern 2, an isolation layer 3, and a metal backplane 4 that are tightly fitted from top to bottom; two layers of tightly fitted first periodic metal pattern 1 and second periodic metal pattern 2 are superimposed to form a moiré pattern, and the two layers of periodic metal patterns can rotate relative to each other in the fitting plane, thereby realizing a dynamically adjustable metamaterial that realizes beam scanning and beam shape switching through mechanical rotation.

[0048] The styles of two layers of periodic metal patterns can be arbitrarily and independently selected from a two-dimensional space group; at the same time, each layer of periodic metal pattern can be composed of multiple layers of periodic patterns tightly fitted together; the periodic metal pattern can also be a pseudo-periodic pattern with approximate periodicity; the electrical dimensional thickness of the metal pattern can be from 0.0001 wavelength to 0.1 wavelength; the periodic metal pattern can be processed on a dielectric substrate with any dielectric constant, and the electrical dimensional thickness of the dielectric substrate can be from 0.0001 wavelength to 0.1 wavelength.

[0049] The isolation layer can be a dielectric material with any dielectric constant and dielectric loss, including air, and its electrical dimension thickness can be from 0.0001 wavelength to 0.1 wavelength.

[0050] The appearance of the moiré supersurface can be any shape including a circle.

[0051] Figure 2 The working principle of the moiré metasurface is given. When two layers of tightly fitted periodic (or pseudo-periodic) metal patterns are tightly fitted, a moiré periodic pattern will be formed in the overlapping area, thereby changing the surface impedance distribution of the metasurface, so that the wavefront of the incident wave obtains the expected amplitude and phase distribution, thereby achieving the purpose of arbitrary regulation of the far field. By rotating the two layers of tightly fitted periodic (or pseudo-periodic) metal patterns, the moiré pattern will change continuously, thereby achieving continuous regulation of the far-field pattern and achieving the purpose of dynamic beamforming.

[0052] Figure 3 and Figure 4 Two specific example schematic diagrams of moiré metasurfaces are given, namely, the checkerboard pattern ( Figure 3 ) and the equilateral triangle pattern ( Figure 4 ), where the relative rotation angle of the two layers of the metasurface is ψ = 10°. The moiré pattern formed by the overlapping parts of the patterns can be clearly seen in the figure. It should be emphasized that there are many essential differences between the moiré metasurface and the traditional metasurface in theoretical analysis and design methods. For example, the unit structure with periodic repetition originally used to construct the metasurface no longer exists, and the super subunit used to construct the coding metasurface is also not suitable for the moiré metasurface.

[0053] Since the superposition of two binary images contains their product, the formation of moiré patterns can be studied in k-space. Figure 5The representation of two checkerboard-patterned metasurfaces in k-space and their convolution process are shown. Pattern 1 and Pattern 2 mainly have four second-order diffraction components, which are represented by triangles and circles in the figure, respectively, and are located on the grid points of k-space. The superposition of two metasurface patterns in real space is equivalent to their convolution in k-space and is strictly equivalent to the vector sum of their diffraction components. This process will produce two sets of moiré components, which are represented by five-pointed star-shaped patterns in the figure and named after the diffraction components of the two patterns. The two sets of moiré components are equidistant from the rotation origin and show C4 rotational symmetry about the z-axis (perpendicular to the paper). When the torsion angle ψ = 10°, four of the moiré components are located within the light cone as shown by circles. These moiré components may correspond to actual radiation beams. It should be pointed out that the moiré pattern formed by the superposition of binary patterns has infinite moiré components. Since the amplitude of high-order moiré components is extremely small, they are not considered in the design. As the twist angle continues to increase, the Moiré components within the light cone will gradually move away from the origin, while the Moiré components outside the light cone will gradually approach the origin. When ψ = 80°, the Moiré components marked by the five-pointed star almost exchange positions ( Figure 6 ). It should be noted that the position of the main moiré components determines the shape and size of the moiré periods in real space, while their intensity determines the visibility (clarity) of these moiré periods. Once the periods of the two metasurface patterns and their relative rotation angles are given, we can uniquely determine the positions of the moiré components in k-space, and changing the specific style of the pattern will only affect the intensity of the moiré pulse.

[0054] Figure 7 The convolution result of two equilateral triangle patterns is given. Similar to the checkerboard pattern, two groups of moiré components are also generated (indicated by the star-shaped pattern). Each group contains 6 moiré components, which are equidistant from the origin and maintain C6 rotational symmetry about the origin. Similarly, when the torsion angle continues to increase, the two groups of moiré components will gradually exchange positions ( Figure 8 ).

[0055] Fig. 9 It shows how the moiré components and their corresponding radiation beams move in the reflection space when the pattern 2 is rotated counterclockwise. First, the checkerboard case is introduced, and the period of the pattern is set to: p1 = 12 mm, p2 = 11.4 mm. Fig. 9 (a, b) show the movement trajectories of the two groups of moiré components when the torsion angle increases from 0° to 90°. The trajectories of the two groups of moiré components are mirror-symmetric about the ±45° symmetry line.

[0056] Next, through the coordinate transformation between k-space and angular space,

[0057] Then we can get the radiation beam angle information corresponding to the moiré component, where k x and ky are the normalized wave vectors along the x and y directions, respectively, and θ and φ are the elevation and azimuth angles, respectively. Taking the (+1,+1,-1,-1) moiré component as an example, the elevation and azimuth angles of the radiation beam when a plane wave with a wavelength of λ0 is incident are given below.

[0058]

[0059]

[0060] Fig. 9 (c) shows the beam trajectory of the checkerboard Morse metasurface when the twist angle increases from 0° to 90°. When the twist angle increases from 0° to 15.55°, the pitch angle of one group of beams increases from 11° to the grazing angle, and when the twist angle increases from 74.45° to 90°, the pitch angle of the other group of beams decreases from the grazing angle to 11°. It can be seen from formula (1) that when the periods of the two patterns are equal (p1=p2), the minimum pitch angle corresponding to the twist angle ψ=0° can be reduced to 0°. At the same time, the twist angle required for the beam to reach the grazing angle can be derived from formula (1): This means that the sensitivity of the beam angle to the twist angle can be improved by reducing the period length of the pattern. It should be noted that by rotating the entire moiré metasurface, the beam can be rotated in azimuth, so that the beam covers the entire upper half space.

[0061] Fig.10 (a, b) show the moiré component trajectories of the equilateral triangular moiré metasurface when the torsion angle increases from 0° to 60°, and the period of the pattern is set to: p1 = 11.4mm, p2 = 12mm. As the torsion angle increases, the two sets of moiré component trajectories move in opposite directions, and the moving trajectories are mirror-symmetric about the three high symmetry lines (φ = 30°, 90°, 120°). Fig.10 (c) is the corresponding beam trajectory. When the twist angle increases from 0° to 19.2°, the pitch angle of one group of beams increases from 8.7° to the grazing angle. When the twist angle increases from 40.8° to 60°, the pitch angle of the other group of beams decreases from the grazing angle to 8.7°.

[0062] Due to the symmetry of the two-layer pattern itself, the moiré pattern changes periodically with the twist angle. From the perspective of pattern symmetry, the checkerboard pattern has p4m space group symmetry, so the moiré pattern formed has a periodic rotation angle ψ p =45°, that is, the torsion angle difference is ψ p The two patterns are identical or mirror-symmetric about some high symmetry line; the regular triangle pattern has p3m1 space group symmetry, so the moiré pattern formed has a periodic rotation angle ψ p= 60°. When two layers of patterns independently select any symmetry from the planar space group, many moiré metasurfaces with different beam trajectories can be obtained, which greatly grants the design freedom of beam shape and beam trajectory. For example, Fig.11 The moiré component trajectories and beam trajectories of a checkerboard-equilateral triangle hybrid moiré metasurface consisting of a checkerboard pattern and an equilateral triangle pattern are given, which can generate a pair of dual beams that exhibit C2 rotational symmetry about the origin.

[0063] The k-space based moiré pattern analysis scheme can only provide a prediction of the moiré beam angle, but cannot predict the beam intensity that can be produced by the actual structure. Fig. 9 and Fig.10 The specific performance of the predicted beam radiation is simulated and calculated using the time-domain simulation solver of the full-wave simulation software CST for checkerboard and equilateral triangle moiré metamaterials. Since moiré metasurfaces are usually anisotropic in a rectangular coordinate system, left-handed circularly polarized plane waves are considered as the excitation source. Since lossless reflective metasurfaces are always chirally symmetric, the response of the moiré metasurface to right-handed and left-handed circularly polarized plane waves is symmetrical (only polarization flips). In order to facilitate the comparison of results at different angles, all far-field results are normalized for the backscattering of metal plates of the same size.

[0064] In order to ensure that the patterns can overlap at any rotation angle, the model is designed to be a circle with a diameter of 250mm. The thickness of the isolation layer has a key influence on the radiation characteristics. In the given checkerboard example, d = 3.1mm, and in the equilateral triangle example, d = 2.7mm, which can ensure that the moiré metasurface has excellent beam efficiency at most torsion angles. The isolation layer material is polymethacrylimide (PMI) foam, which has a refractive index close to that of air. The two layers of metasurfaces are processed using conventional printed circuit board (PCB) technology on a 40-micron thick flexible polyimide dielectric layer (dielectric constant is about 3.1). The checkerboard pattern period p and side length L parameters used in simulations and experiments are: p1 = 12mm, p2 = 11.4mm, L1 = 5.25mm, L2 = 4.95mm. The equilateral triangle pattern period p and side length L parameters used in simulations and experiments are: p1 = 11.4mm, p2 = 12mm, L1 = 10.1mm, L2 = 10.7mm. In order to ensure a close fit between the layers, all layers are assembled and fixed by nylon clamps, and the top layer is covered with a 5mm thick foam layer. Under the downward pressure of the clamp, the distance between the two layers of metasurface and the metal backplane is guaranteed to be equal everywhere. As a principle prototype, the experimental sample shown in this example does not include a motor drive device. It should be noted that the structural schematic diagram given in the present invention is only the most important component required to realize the functions described. In order to achieve automated electronic control and mechanical stability, any mechanical and electronic control components added on the basis of the present invention for mechanical fixation, mechanical rotation, electronic control, etc. are considered to be modifications of the present invention and are within the scope of protection of this invention patent.

[0065] Fig.12 The simulation results of the three-dimensional far-field pattern (left-hand circularly polarized component) of the checkerboard Morse metasurface at ψ = 0.25°, 2°, 4°, 6°, 8°, 10°, 12°, and 14° are given. It can be seen from the figure that the four beams at all rotation angles have stable beam intensity. This feature can also be seen from the average value (double solid line) and fluctuation range (single solid line) of the beam intensity at each torsion angle. Here, we define the normalized beam intensity as the beam efficiency. It can be seen that the beam efficiency at all torsion angles is greater than 0.3. It is worth pointing out that this beam efficiency is higher than the beam efficiency of the traditional metasurface.

[0066] Fig.13 The two-dimensional far-field pattern of the beam plane is given. It can be seen that when the twist angle increases from 0.25° to 14°, the beam elevation angle increases from 10° to 63°. Fig.14 The beam trajectory is further shown when the twist angle increases from 0° to 14° (step size 0.25°). Fig. 9 It is highly consistent with the theoretical prediction.

[0067] Fig.15 The simulation results of the 3D far-field pattern (left-hand circular polarization component) of the regular triangle moiré hypersurface at ψ = 0.25°, 2°, 4°, 6°, 8°, 10°, 12°, and 13°. Due to the increase in the number of beams, the beam intensity of the triangular moiré hypersurface is about 25% lower than that of the checkerboard moiré hypersurface. Observe carefully Fig.15 It can be found that when ψ = 10°, the beams change from six beams to three beams. This is because at this twist angle, the surface current distribution caused by the moiré pattern of the moiré metasurface changes suddenly. Fig.16 is the two-dimensional far-field pattern of the beam plane. When the twist angle increases from 0.25° to 14°, the beam elevation angle increases from 10° to 45°. Fig.17 The beam trajectory shown is consistent with the theoretically predicted altitude ( Fig.10 ) are highly consistent.

[0068] In order to experimentally verify the actual dynamic beamforming performance of the moiré metasurface, we processed two samples with checkerboard pattern and regular triangle pattern, such as Fig.18 and Fig.21 As shown, the far-field pattern of the sample is tested in a darkroom. The experimental test environment and scheme are as follows: A pair of dual circularly polarized horn antennas (gain of 20dB) are used as transmitting and receiving antennas, and they are connected to a RF signal generator (Keysight N9040B) and a spectrum analyzer (Keysight E8257D) respectively. The sample and the transmitting antenna are coaxially placed on a wooden board, 1.79 meters apart. By rotating the wooden board as a whole in the horizontal plane (0.1° accuracy), the far-field pattern of the sample in the pitch angle plane can be obtained. In order to be able to measure the far-field pattern of the sample in different azimuth planes, the sample is placed on a rotating table and can be rotated in the vertical plane with an accuracy of 0.2°. Since the sample is not at the center of the rotation circle, the measured far-field pattern produces different degrees of stretching distortion at the pitch angle. The following formula is used to modify the error θ′=cos -1 [(R+Lcosθ0) / (R 2 +L 2 +2RLcosθ0)], where R represents the distance between the sample and the transmitting antenna, L is the distance between the rotation center and the receiving antenna, and θ0 is the rotation angle in the horizontal plane.

[0069] Fig.19 The experimentally measured 3D far-field patterns of the checkerboard moiré hypersurface and the equilateral triangle moiré hypersurface at ψ=6°, 8°, 10°, and 12° are given. The measured beam angles are consistent with the simulation results ( Fig.12 ) are highly consistent. Fig. 20This is the two-dimensional far-field pattern of the checkerboard Morse metasurface when the twist angle increases from 0.25° to 14°. The measured beam efficiency is consistent with the simulation result at small pitch angles, and is slightly lower than the simulation result at large pitch angles. This is because the sample is not at the center of the rotation circle during the test. Fig. 22 The experimentally measured 3D far-field patterns of the checkerboard moiré hypersurface and the equilateral triangle moiré hypersurface at ψ=6°, 8°, 10°, and 12° are given. The measured beam angles are consistent with the simulation results ( Fig.15 ) are highly consistent. Fig.23 The two-dimensional far-field pattern of the chessboard Morse metasurface when the twist angle increases from 0.25° to 13°. The measured beam efficiency is consistent with the simulation at small pitch angles. It can be found that the three-beam phenomenon that originally appeared at ψ=10° in the simulation results shifted to ψ=11° in the measured results. The deviation may be due to the failure of the two layers of the metasurface in the sample to fit tightly and evenly. In order to further compare the simulation and measured results, Fig.24 and 25 The simulation and measured results (logarithmic coordinates) of the two-dimensional far-field patterns of the moiré metasurface with checkerboard pattern and equilateral triangle pattern are given respectively.

[0070] Given the advantages of low cost and low power consumption of the moiré metasurface, it is expected to be widely used as a smart reflective surface (RIS) in the next generation of mobile communications. In indoor scenarios, it can be hidden in the ceiling, furniture surface, wall surface, behind decorative paintings, etc.; in outdoor scenarios, it can be placed on the facade of a building, light boxes, billboards, etc. Since the dynamic control of the beam by the moiré metasurface depends on mechanical rotation, its control speed is not as fast as that of programmable metamaterials loaded with diodes (and similar designs), but it can still be applied to many communication scenarios that only require channel control in seconds and minutes. In addition, the moiré metasurface has a purely passive characteristic, so it does not introduce additional channel noise. In addition to RIS applications, the moiré metasurface can also be used in the field of radar detection, such as realizing a purely planar parabolic antenna, whose ultra-low profile appearance facilitates installation and conformality, and due to its purely passive characteristics, it can be applied to electronic countermeasures equal to high-power scenarios.

[0071] It should be noted that the above is only a preferred embodiment of the present invention. Since the present invention uniquely utilizes two layers of passive materials to form a moiré pattern and thus realizes continuous regulation of the far-field pattern, it has the characteristics of being easy to implement and imitate. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A moiré metasurface for realizing dynamic beamforming, characterized in that The moiré metasurface comprises a first periodic metal pattern (1), a second periodic metal pattern (2), an isolation layer (3), and a metal back plate (4) which are closely fitted in sequence from top to bottom; the two layers of closely fitted first periodic metal pattern (1) and second periodic metal pattern (2) are superimposed to form a moiré pattern, and the fitted planes of the two layers of periodic metal patterns can rotate relative to each other, thereby realizing a dynamically adjustable metamaterial that realizes beam scanning and beam shape switching through mechanical rotation.

2. The moiré metasurface for realizing dynamic beamforming according to claim 1, characterized in that: The styles of the two-layer periodic metal patterns can be independently selected from a two-dimensional space group.

3. The moiré metasurface for realizing dynamic beamforming according to claim 2, characterized in that: Each layer of the two-layer periodic metal pattern is composed of multiple layers of periodic patterns tightly attached.

4. The moiré metasurface for realizing dynamic beamforming according to claim 3, characterized in that: The periodic metal pattern includes a pseudo-periodic pattern having an approximate periodicity.

5. The moiré metasurface for realizing dynamic beamforming according to claim 4, characterized in that: The electrical thickness of the periodic metal pattern ranges from 0.0001 wavelength to 0.1 wavelength.

6. The moiré metasurface for realizing dynamic beamforming according to claim 5, characterized in that: The periodic metal pattern is processed on a dielectric substrate with any dielectric constant, and the electrical thickness of the dielectric substrate ranges from 0.0001 wavelength to 0.1 wavelength.

7. The moiré metasurface for realizing dynamic beamforming according to claim 1, characterized in that: The electrical thickness of the isolation layer is from 0.0001 wavelength to 0.1 wavelength.

8. The moiré metasurface for realizing dynamic beamforming according to claim 1, characterized in that: The material of the metal back plate (4) has excellent electrical conductivity, and the electrical thickness is greater than 0.0001 wavelength.

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