A metasurface-based adjustable orbital angular momentum single-mode antenna and its manufacturing process

Abstract

The present invention proposes a metasurface-based adjustable orbital angular momentum single-mode antenna and a manufacturing process thereof. The metasurface-based adjustable orbital angular momentum single-mode antenna comprises a planar dielectric substrate and a plurality of Y-shaped metal units disposed on the planar dielectric substrate. The three-arm width and rotation angle of each Y-shaped metal unit at a spatial coordinate r satisfy Dirac vortex modulation and angle perturbation, respectively. The manufacturing process of the metasurface-based adjustable orbital angular momentum single-mode antenna comprises the following steps: preparing a mask on the planar dielectric substrate and etching a metal microstructure; welding an SMA interface on the back of the planar dielectric substrate; connecting with a coaxial line; and chemically polishing the front of the planar dielectric substrate and covering it with a protective film. The present invention solves the problems of orbital angular momentum antennas, such as difficulty in flexibly adjusting the orbital angular momentum mode, easy coupling between different orbital angular momentum modes, poor single-mode properties, easy signal interference, the need for precise adjustment of phase control, and complex design.

Description

Technical Field

[0001] The present invention relates to the technical field of metasurface antennas, and in particular to a metasurface-based adjustable orbital angular momentum single-mode antenna and a manufacturing process thereof. Background Art

[0002] An orbital angular momentum antenna is an antenna that utilizes the orbital angular momentum of electromagnetic waves for signal transmission. The spiral phase leading edge of an orbital angular momentum beam enables it to carry multiple independent signal patterns, thereby improving the capacity and efficiency of communication systems within limited spectrum resources.

[0003] Electromagnetic metasurfaces are two-dimensional materials with artificially designed structures that can precisely manipulate the propagation characteristics of electromagnetic waves. They are composed of subwavelength-scale structural units whose shape, size, arrangement, and material properties can be adjusted to control the phase, amplitude, and polarization of electromagnetic waves. Currently, the most mature orbital angular momentum antenna designs are primarily based on spiral phase plates. However, these designs have drawbacks: difficulty in flexibly adjusting the orbital angular momentum mode, easy coupling between different orbital angular momentum modes, poor single-mode properties that can easily lead to signal interference, precise phase control, and complex design. Summary of the Invention

[0004] The present invention aims to provide an adjustable orbital angular momentum single-mode antenna based on a metasurface and a manufacturing process thereof, so as to achieve the effects of the orbital angular momentum antenna being able to flexibly adjust the orbital angular momentum mode, preventing coupling between different orbital angular momentum modes, having good single-mode properties, avoiding signal interference, accurately adjusting phase control, and having a simple design.

[0005] To this end, the technical solution adopted by the present invention is: a metasurface-based adjustable orbital angular momentum single-mode antenna, including an electromagnetic metasurface, the electromagnetic metasurface including a planar dielectric substrate and a plurality of Y-shaped metal units fixedly arranged on the planar dielectric substrate to form an array, a coaxial line is fixedly connected to the center of the bottom end of the planar dielectric substrate, the metal inner core of the coaxial line extends into the planar dielectric substrate, and the end of the coaxial line away from the planar dielectric substrate is connected to an SMA interface, and the three-arm width and rotation angle of each of the Y-shaped metal units at the spatial coordinate r respectively satisfy Dirac vortex modulation and angle perturbation, and the expression of the Dirac vortex modulation is:

[0006] ,

[0007] Where, To adjust the arm width of the rear Y-shaped metal unit, is the initial arm width of the Y-shaped metal unit, is the modulation intensity, is the Kekulé vector, is the position vector of each Y-shaped metal unit in space, Modulate phase for Kekulé;

[0008] The rotation angle calculation formula of the angle perturbation is as follows:

[0009] ,

[0010] Where, is the rotation angle of the angular perturbation, is a constant parameter, is the Kekulé vector, is the position vector of each Y-shaped metal unit in space, For vector angle.

[0011] As a preferred embodiment of the above solution, the planar dielectric substrate is a Rogers RO3003 or Taconic RF-35 planar dielectric substrate.

[0012] More preferably, the planar dielectric substrate has a thickness of 0.254 mm to 0.508 mm and a dielectric constant of 2.2 to 3.5.

[0013] More preferably, the Y-shaped metal unit is made of copper or aluminum.

[0014] A process for manufacturing a metasurface-based adjustable orbital angular momentum single-mode antenna comprises the following steps:

[0015] S1. Using laser direct writing lithography to prepare a mask on the front surface of the planar dielectric substrate, and etching the Y-shaped metal unit array;

[0016] S2, welding an SMA interface on the back side of the planar dielectric substrate;

[0017] S3. Connect the planar dielectric substrate and the SMA interface with the coaxial line to ensure feed port impedance matching;

[0018] S4. Chemically polishing the front surface of the planar dielectric substrate after etching, and covering the front surface of the planar dielectric substrate with a PTFE protective film.

[0019] As a preferred embodiment of the above solution, in step S4, the thickness of the PTFE protective film is 25 μm.

[0020] Beneficial effects of the present invention:

[0021] 1. By performing Dirac vortex modulation and angle perturbation on the Y-shaped metal unit of the antenna, the antenna can radiate orbital angular momentum beams of different orders, thereby achieving flexible adjustment of the orbital angular momentum mode and precise adjustment of the phase control. Only one antenna is required to radiate an orbital angular momentum beam of one order, so that coupling between different orbital angular momentum modes does not occur, the single-mode property is good, signal interference will not occur, and the antenna design of the present invention is simple. The antenna of the present invention can arbitrarily switch the order of the radiated orbital angular momentum beam, supports time division / frequency division multiplexing or hybrid addressing, and multiple data channels can be superimposed and transmitted in the airspace to achieve ultra-large capacity links.

[0022] 2. The antenna of the present invention can achieve high-purity single-mode orbital angular momentum radiation. Relying on the topological protection characteristics of the Dirac vortex cavity, it only produces a single localized mode, significantly reducing the crosstalk and phase distortion of high-order orbital angular momentum beams. Compared with traditional multi-antenna array orbital angular momentum transmission, the antenna of the present invention has significant improvements in radiation field shape, phase distribution, and mode purity. On an economic level, the antenna of the present invention simplifies the manufacturing and maintenance process and saves costs. On a social level, the antenna of the present invention will promote the development of high-frequency, high-speed wireless communications, satellite Internet, national defense communications and other fields, and has extremely high market application value and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of a metasurface-based adjustable orbital angular momentum single-mode antenna in the present invention.

[0024] Figure 2 It is a normalized electric field distribution diagram in the far field of the electromagnetic wave radiated by a metasurface-based adjustable orbital angular momentum single-mode antenna after feeding in the present invention, wherein 2(a) is the far-field electric field distribution diagram of the Dirac vortex when radiating when the θ perturbation is of order 1 in the present invention, 2(b) is the far-field electric field distribution diagram of the Dirac vortex when radiating when the θ perturbation is of order 2 in the present invention, and 2(c) is the far-field electric field distribution diagram of the Dirac vortex when radiating when the θ perturbation is of order 3 in the present invention.

[0025] Figure 3 Schematic diagram of the structure of the unmodulated metasurface, where 3(a) is the structural diagram of the electromagnetic metasurface without Kekulé modulation, and 3(b) is an enlarged schematic diagram of the yellow area in 3(a).

[0026] Figure 4 4( a ) is a schematic diagram of the Dirac vortex modulation and the orbital angular momentum order modulation in the present invention, wherein 4( a ) is a schematic diagram of the Dirac vortex modulation in the present invention, and 4( b ) is a schematic diagram of the angle modulation in the present invention.

[0027] Figure 5Schematic diagram of a sample that generates Dirac vortices without angle modulation and a photograph of the sample, where 5(a) is a schematic diagram of a sample that has undergone Kekulé modulation, and 5(b) is a diagram of a sample actually prepared by the PCB method. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] like Figure 1-5 As shown, a metasurface-based adjustable orbital angular momentum single-mode antenna includes an electromagnetic metasurface, which includes a planar dielectric substrate and a plurality of Y-shaped metal units fixedly arranged on the planar dielectric substrate to form an array. A coaxial line is fixedly connected to the center of the bottom end of the planar dielectric substrate. The metal core of the coaxial line extends into the planar dielectric substrate. The end of the coaxial line away from the planar dielectric substrate is connected to an SMA interface. The three-arm width and rotation angle of each Y-shaped metal unit at the spatial coordinate r respectively satisfy Dirac vortex modulation and angle perturbation. The expression of Dirac vortex modulation is:

[0030] ,

[0031] Where, To adjust the arm width of the rear Y-shaped metal unit, is the initial arm width of the Y-shaped metal unit, is the modulation intensity, is the Kekulé vector, is the position vector of each Y-shaped metal unit in space, Kekulé modulation phase.

[0032] The rotation angle calculation formula of angle perturbation is as follows:

[0033] ,

[0034] Where, is the rotation angle of the angular perturbation, is a constant parameter, is the Kekulé vector, is the position vector of each Y-shaped metal unit in space, For vector angle. The range of determines the order of orbital angular momentum, for example when From 0 to 2π, the order is 1, From 0 to 4π, the order is 2, and so on.

[0035] The width of each Y-shaped metal element in the antenna is designed through Dirac vortex modulation, and the rotation angle of each Y-shaped metal element is designed through angular perturbation, allowing each Y-shaped metal element to rotate slightly around its center point, thereby determining the orientation of the three arms of the Y-shaped metal element. The planar dielectric substrate is then powered via an SMA interface and a coaxial cable, which in turn conducts electricity to the Y-shaped metal elements. The Y-shaped metal element array radiates an orbital angular momentum beam of the corresponding order. The dimensions of the Y-shaped metal element array are roughly matched to several multiples of the operating wavelength, ensuring the desired radiation beam diameter and diffraction angle. The orbital angular momentum beam radiation mechanism is achieved by introducing spatially continuously varying phase vortices on the electromagnetic metasurface, allowing the radiated wavefront to carry an integer order L of orbital angular momentum. The impedance of the coaxial cable is 50 ohms. Dirac vortex modulation and angular perturbation form Kekulé modulation of the antenna. Each Y-shaped metal unit realizes a Dirac vortex cavity mode through Kekulé modulation, which is equivalent to a pair of mutually coupled pseudospin-pseudovalley oscillation states, generating an extremely narrow resonant cavity mode near a specific frequency. While ensuring the local resonance of the Dirac vortex mode, Kekulé modulation of the Y-shaped metal unit can precisely control the vortex phase order, thereby achieving switchable single-mode orbital angular momentum radiation from order L = ±1 to ±N (N is the design upper limit).

[0036] The planar dielectric substrate uses Rogers RO3003 or Taconic RF-35 planar dielectric substrate. The thickness of the planar dielectric substrate ranges from 0.254 mm to 0.508 mm, and the dielectric constant ranges from 2.2 to 3.5.

[0037] The planar dielectric substrate uses Rogers RO3003 or Taconic RF-35, which can further reduce dielectric loss by approximately 30–50% compared to FR-4 planar dielectric substrates in the Ku band and higher frequency bands. The thickness of the planar dielectric substrate ranges from 0.254mm to 0.508mm, ensuring a balanced balance between electromagnetic localization of high-Q modes and board strength, while also facilitating the etching of finer Y-shaped metal elements.

[0038] The material of the Y-shaped metal unit is copper or aluminum.

[0039] When the material of the Y-shaped metal unit is copper, a high-purity copper foil with a thickness of 70μm (≥2N purity) can be used. If necessary, the Y-shaped metal unit can also use an 18-20μm silver-plated metal layer to further reduce conductor loss and improve the resonance quality factor.

[0040] A process for manufacturing a metasurface-based adjustable orbital angular momentum single-mode antenna comprises the following steps:

[0041] S1. Using laser direct write lithography to prepare a mask on the front surface of a planar dielectric substrate, and etching a Y-shaped metal unit array;

[0042] S2. Solder the SMA interface on the back of the planar dielectric substrate;

[0043] S3. Use a coaxial cable to connect the planar dielectric substrate and the SMA interface to ensure feed port impedance matching;

[0044] S4. Chemically polishing the front surface of the etched planar dielectric substrate, and covering the front surface of the planar dielectric substrate with a PTFE protective film.

[0045] In step S4 , the thickness of the PTFE protective film is 25 μm.

[0046] When the orbital angular momentum beam is static and single-order (L=1), the antenna's planar dielectric substrate can be made of Rogers RO3003 high-frequency copper-clad laminate with a thickness of h=0.508mm and dimensions of 150mm×150mm. The front copper layer is 35μm thick and etched into an array of 4000 Y-shaped metal elements. The period of the Y-shaped metal elements is 5mm, and each Y-shaped three-arm structure has an arm width of 1mm and an arm length of 3mm.

[0047] Kekulé modulation is performed on each Y arm to realize that the orbital angular momentum beam is a static single-order vortex phase spiral equal to 1.

[0048] During the simulation, the metal parts were set as perfect conductors, and the air and dielectric boundaries were set as scattering boundary conditions. The solver was set to an eigenmode solver in the electromagnetic wave frequency domain, with a center frequency of 16.9 GHz, and approximately 50 frequencies were solved. The far-field phase distribution exhibited a single-order L=1 vortex at 16.90 GHz, with the far-field phase wrapping around the circumference by 2π, resulting in a nearly complete circular field.

[0049] During the experimental test, in an anechoic chamber, the transmitting end was a commercial calibrated horn antenna (12–18 GHz, gain 16 dBi), and the receiving end was the same horn antenna, with a distance R≈4.5 m (the far-field condition was met). The transmission S was measured using a Keysight N5225B VNA. 21 The results are basically consistent with the simulation: the reflection S 11 ≈–18dB, bandwidth 16.85–16.95GHz. Planar phase distribution was recorded using near-field planar scanning (1mm step), verified using Fourier transform decomposition to be L=1, with a modal purity ≥92%. The measured pattern gain was approximately 11.2dBi, and the radiation efficiency was approximately 78%.

[0050] Figure 2 The effect of the angular momentum order (θ perturbation) modulation achieved in the present invention is demonstrated, wherein Figure 2a to c are the far-field electric field distributions of the Dirac vortex during radiation when the θ perturbation is of order 1 / 2 / 3, respectively. The change in order can be clearly observed.

[0051] Figure 3 a is an electromagnetic metasurface structure without Kekulé modulation. It is a Y-shaped resonant unit array periodically arranged in a honeycomb lattice on a planar dielectric substrate. Its main features are as follows:

[0052] Each unit cell is a three-arm "Y"-shaped metal resonator, with three equal-length and equal-width metal arms converging at the center, angled 120 degrees from each other. The arm length and width together determine the unit's resonant frequency and quality factor. The symmetry at the central intersection ensures the unit's isotropic response to incident waves without introducing additional perturbations. Figure 3 b shows the specific size of each Y-shaped pattern, where = = = = 1 mm, is the initial arm width. Figure 3 A, B, and C in b represent three inequivalent lattice positions, respectively, and l represents the arm length of the Y-shaped metal unit.

[0053] Lattice arrangement, the Y-type metal resonator is arranged according to the two-dimensional triangular Bravais lattice, and two equivalent sub-lattices form a honeycomb structure. Its lattice vector can be taken as , is the lattice constant, and Since the honeycomb lattice has a six-fold rotational symmetry, a typical Dirac cone dispersion will appear near the K / K′ point in its corresponding two-dimensional Brillouin zone. Figure 3 The blue area in (a) represents the initial hexagonal lattice, and the yellow area is the extension of the times the lattice. Figure 3 (b) Figure 3 Schematic enlargement of the yellow area in (a).

[0054] Figure 4 The transparent pattern in is the initial pattern. Figure 5 (a) Schematic diagram of the sample after Kekulé modulation. The inset in the lower right corner shows the distribution of the Kekulé phase on the sample surface. Figure 5 (b) is a picture of the sample actually prepared by the PCB method.

[0055] This invention utilizes a planar, low-cost, single-mode orbital angular momentum antenna structure, comprising a metasurface array based on Dirac vortex modes. This structure achieves high-purity orbital angular momentum beam radiation within the operating frequency band, and the order (L) of the orbital angular momentum beam can be adjusted by adjusting structural parameters. This design offers stable mode purity and low manufacturing cost, overcoming the limitations of traditional orbital angular momentum antenna designs. By designing symmetrical Y-shaped metal units and utilizing Kekulé modulation, the electromagnetic metasurface generates a single orbital angular momentum mode, avoiding multimode interference and crosstalk.

[0056] By fine-tuning the geometry of the Y-shaped metal units (for example, by varying the width of the three Y-shaped arms), the present invention can break the symmetry and thereby adjust the electromagnetic response of the Y-shaped metal units of the electromagnetic metasurface. This modulation method generates a local pseudomass term in each unit, thereby controlling the generation and order of orbital angular momentum beams.

[0057] In the Y-shaped metal unit array of the electromagnetic metasurface, each unit adjusts its phase through a tiny rotation (angular perturbation), further refining the control of the orbital angular momentum beam. This angular perturbation allows the order of the orbital angular momentum beam to be adjusted according to actual needs, thus achieving flexible orbital angular momentum control.

[0058] The proposed antenna structure can switch between orbital angular momentum modes in a pre-set manner. This has important applications in communication systems requiring multiplexing and spatial multiplexing, especially in areas such as 5G / 6G and satellite communications.

[0059] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A metasurface-based single-mode antenna with adjustable orbital angular momentum, comprising an electromagnetic metasurface comprising a planar dielectric substrate and a plurality of Y-shaped metal units fixedly arranged on the planar dielectric substrate to form an array, a coaxial line fixedly connected to the center of the bottom end of the planar dielectric substrate, a metal core of the coaxial line extending into the planar dielectric substrate, and an SMA interface connected to the end of the coaxial line away from the planar dielectric substrate, characterized in that: The three-arm width and rotation angle of each Y-shaped metal unit at the spatial coordinate r respectively satisfy Dirac vortex modulation and angle perturbation. The expression of the Dirac vortex modulation is: ， Where, To adjust the arm width of the rear Y-shaped metal unit, is the initial arm width of the Y-shaped metal unit, is the modulation intensity, is the Kekulé vector, is the position vector of each Y-shaped metal unit in space, Modulate phase for Kekulé; The rotation angle calculation formula of the angle perturbation is as follows: ， Where, is the rotation angle of the angular perturbation, is a constant parameter, is the Kekulé vector, is the position vector of each Y-shaped metal unit in space, For vector angle.

2. The metasurface-based adjustable orbital angular momentum single-mode antenna according to claim 1, characterized in that: The planar dielectric substrate is a Rogers RO3003 or Taconic RF-35 planar dielectric substrate.

3. The metasurface-based adjustable orbital angular momentum single-mode antenna according to claim 1, characterized in that: The thickness of the planar dielectric substrate is 0.254 mm to 0.508 mm, and the dielectric constant is 2.2 to 3.

5.

4. The metasurface-based adjustable orbital angular momentum single-mode antenna according to claim 1, characterized in that: The material of the Y-shaped metal unit is copper or aluminum.

5. A process for manufacturing a metasurface-based adjustable orbital angular momentum single-mode antenna, characterized in that: Using a metasurface-based adjustable orbital angular momentum single-mode antenna according to any one of claims 1 to 4, comprising the following steps: S1. Using laser direct writing lithography to prepare a mask on the front surface of the planar dielectric substrate, and etching the Y-shaped metal unit array; S2, welding an SMA interface on the back side of the planar dielectric substrate; S3. Connect the planar dielectric substrate and the SMA interface with the coaxial line to ensure feed port impedance matching; S4. Chemically polishing the front surface of the planar dielectric substrate after etching, and covering the front surface of the planar dielectric substrate with a PTFE protective film.

6. The process for manufacturing a metasurface-based single-mode antenna with adjustable orbital angular momentum according to claim 5, wherein: In the step S4, the thickness of the PTFE protective film is 25 μm.

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