Holographic metasurface antenna

Abstract

The invention provides a holographic metasurface antenna which adopts a three-layer parallel plate waveguide structure and comprises a dielectric substrate, an upper metal plate and a lower metal plate. A cross slot unit array in matrix arrangement is etched on the upper metal plate, and each unit comprises orthogonal transverse slots and vertical slots to realize circular polarization. The metal through hole array is composed of a plurality of hollow cylindrical through holes and surrounds the gap array layer, and energy leakage is effectively reduced. According to the design, the gain of the antenna is increased by 1.23 dB, the antenna has the characteristics of low profile and small size, and beam forming can be realized without a complex feed network.

Description

Technical Field

[0001] This application belongs to the field of antennas, and in particular relates to a holographic metasurface antenna. Background Technology

[0002] With the rapid development of modern communication technology, traditional linearly polarized antennas, due to their sensitivity to placement and the tendency for even small deviations to significantly reduce reception efficiency, are no longer able to meet the ever-increasing communication demands. In contrast, circularly polarized antennas, with their only two polarization directions (left-hand and right-hand) and their insensitivity to changes in spatial position, have become the preferred choice for modern communication systems.

[0003] However, current technologies for obtaining highly polarized circularly polarized antennas often result in increased antenna profile and size, limiting their application in miniaturized and integrated communication devices.

[0004] Metasurface technology, as an innovative approach, achieves low profile and easy integration characteristics for antennas through the periodic or aperiodic arrangement of subwavelength-sized units, providing a new solution to the miniaturization problem of circularly polarized antennas. Holographic metasurface antennas, an important branch of metasurface technology, utilize the holographic principle of physical optics to generate a holographic surface through the interference of a reference wave and a target wave, thereby deriving the target wave in reverse, simplifying the antenna structure and reducing costs.

[0005] However, traditional holographic metasurface antennas still face challenges in dynamic control and gain enhancement. The proposed dynamically reconfigurable holographic metasurface aperture antenna provides a direction for solving this problem, but the gain of holographic metasurfaces designed using the polarized particle principle is relatively low. Ordinary slot-type radiating elements cannot accommodate RF switching devices such as PIN diodes or varactor diodes, which is not conducive to the subsequent fabrication into reconfigurable metasurface antennas. Summary of the Invention

[0006] The purpose of this application is to overcome the deficiencies in the prior art and provide a holographic metasurface antenna.

[0007] This application provides a holographic metasurface antenna, comprising: a three-layer parallel plate waveguide structure and a metal through-hole array;

[0008] The three-layer parallel plate waveguide structure includes a dielectric substrate, an upper metal plate covering the upper surface of the dielectric substrate, and a lower metal plate covering the lower surface of the dielectric substrate.

[0009] The upper metal plate is etched with a slot array layer, which includes multiple cross-shaped slot units arranged in a matrix.

[0010] Each of the cross-shaped slot units includes horizontal slots and vertical slots;

[0011] The metal via array includes multiple hollow cylindrical vias penetrating the three-layer parallel plate waveguide structure and is arranged around the slot array layer.

[0012] The horizontal seams and the vertical seams are arranged orthogonally in the cross-shaped gap unit.

[0013] Optionally, each of the cross-slot units may also include a metal patch.

[0014] Optionally, the hollow cylindrical through hole includes an annular gap structure formed by the outer wall and the inner wall.

[0015] Optionally, the coaxial power supply interface is located at the geometric center of the lower metal plate.

[0016] Optionally, the upper metal plate forms a discrete unit network structure.

[0017] Optionally, the horizontal and vertical seams form an intersecting structure in the cross-shaped slot unit.

[0018] Optionally, the dielectric substrate is laminated between the upper metal plate and the lower metal plate.

[0019] The beneficial effects of this application are:

[0020] This application provides a holographic metasurface antenna, comprising: a three-layer parallel plate waveguide structure and a metal via array; the three-layer parallel plate waveguide structure includes a dielectric substrate, an upper metal plate covering the upper surface of the dielectric substrate, and a lower metal plate covering the lower surface of the dielectric substrate; the upper metal plate is etched with a slot array layer, the slot array layer including a plurality of matrix-arranged cross-shaped slot elements; each cross-shaped slot element includes a horizontal slot and a vertical slot; the metal via array includes a plurality of hollow cylindrical vias penetrating the three-layer parallel plate waveguide structure and arranged around the slot array layer; the horizontal slots and the vertical slots are orthogonally arranged in the cross-shaped slot elements. This application achieves circular polarization through the three-layer parallel plate waveguide structure and the cross-shaped slot element design, and reduces energy leakage by combining the surrounding metal via array, thereby increasing the antenna gain by 1.23dB, while also possessing the advantages of low profile, small size, and beamforming without the need for a feed network. Attached Figure Description

[0021] Figure 1 This is a schematic diagram illustrating the principle of circularly polarized beam generation.

[0022] Figure 2 A schematic diagram of a holographic metasurface model for loading metal vias;

[0023] Figure 3 This is a schematic diagram of the phase distribution of the reference wave.

[0024] Figure 4 This is a diagram showing the gap distribution of metasurface units;

[0025] Figure 5 The final distribution diagram of the surface units of the designed holographic metasurface;

[0026] Figure 6 For the testing environment and physical images of the circularly polarized holographic metasurface;

[0027] Figure 7 The reflection coefficient of the circularly polarized holographic metasurface obtained after simulation and physical measurement;

[0028] Figure 8 The axial ratio of the circularly polarized holographic metasurface obtained after simulation and physical measurement;

[0029] Figure 9 This is a schematic diagram of the total gain of the circularly polarized holographic metasurface obtained after simulation and physical measurement. Detailed Implementation

[0030] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it will be understood that various forms of implementation of the present disclosure are possible and should not be limited to the embodiments set forth herein. Rather, the embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0031] Please refer to Figures 1 to 8 As shown, Figure 1 (a) X-polarized holographic metasurface model, (b) Y-polarized holographic metasurface model, (c) circularly polarized holographic metasurface model, (d) metasurface unit model; Figure 2 (a) Holographic metasurface antenna model with metal through-hole, (b) Metal through-hole model; Figure 3 (a) X component (Hx), (b) Y component (Hy); Figure 4 (a) Horizontal gap (Mx), (b) Vertical gap (My); Figure 6 (a) Comparison of two holographic metasurface antennas; (b) Test environment; Figure 7 (a) Reflectance of a holographic metasurface antenna without metal vias, (b) Reflectance of a holographic metasurface antenna with metal vias; Figure 8 (a) Axial ratio of a holographic metasurface antenna without metal vias; (b) Axial ratio of a holographic metasurface antenna with metal vias. Figure 9 (a)(b) Total gain of holographic metasurface antenna without metal vias, (c)(d) Total gain of holographic metasurface antenna with metal vias.

[0032] like Figures 1-6As shown, a holographic metasurface antenna includes: a three-layer parallel plate waveguide structure and a metal through-hole array.

[0033] The three-layer parallel plate waveguide structure is the core framework of the holographic metasurface antenna, used to support and guide the propagation of electromagnetic waves. Specifically, it refers to a waveguide structure composed of three parallel plates, where "waveguide" represents a channel capable of confining and transmitting electromagnetic waves. Overall, this structure ensures the effective propagation of the reference wave in the medium and provides the physical basis for the slot array and metal vias.

[0034] The three-layer parallel plate waveguide structure consists of three layers: a middle dielectric substrate, and upper and lower copper plates. The dielectric substrate is Rogers 3003 material with a dielectric constant ε. r =3, loss tangent tanδ = 0.001, height h1 = 1.542 mm. A coaxial feed is inserted at the center of the lower metal plate as the excitation source, while the upper metal plate is discretized to form a unit network. The overall structure is fixed by lamination: the dielectric substrate is tightly pressed between the upper and lower metal plates, forming a stable parallel plate waveguide. This design allows electromagnetic waves to propagate within the dielectric substrate, while the metal plates act as shielding and reflection. For example, at a center frequency of 24 GHz, this structure can support the propagation of a reference wave described by a zero-order Hankel function, reducing energy loss. This waveguide structure is fundamental to antenna radiation because it defines the propagation path and coupling interface of the reference wave, ensuring that the subsequent slot array can effectively couple energy.

[0035] The three-layer parallel plate waveguide structure includes a dielectric substrate, an upper metal plate covering the upper surface of the dielectric substrate, and a lower metal plate covering the lower surface of the dielectric substrate.

[0036] The upper metal plate is a metal layer covering the upper surface of the dielectric substrate, serving as the coupling and radiation interface for electromagnetic waves. The phrase "covers" indicates that the metal plate is physically bonded to the upper surface of the dielectric substrate, forming an upper shield. The lower metal plate is a metal layer covering the lower surface of the dielectric substrate, serving as the mounting base for the power supply interface. The phrase "covers" indicates that it is bonded to the lower surface of the dielectric substrate, providing reflection and support for the lower layer. The dielectric substrate is an insulating layer sandwiched between the two metal plates, serving as the electromagnetic wave propagation medium.

[0037] The dielectric substrate uses Rogers 3003 material with a dielectric constant εr = 3, a loss tangent tanδ = 0.001, and a height h1 = 1.542 mm, ensuring low-loss propagation at a 24 GHz operating frequency. Both the upper and lower metal plates are copper plates, laminated to cover the dielectric substrate. Specifically, the upper metal plate is discretized into a unit network structure, forming a matrix arrangement of 2121 units, each unit being 3.125 mm long. A coaxial feed interface is inserted at the geometric center of the lower metal plate as a monopole feed source to excite the reference wave. For example, when the reference wave propagates in the dielectric substrate, its wavenumber k... g Determined by the properties of the dielectric, this structure achieves tight integration through lamination, ensuring the mechanical stability and electromagnetic performance of the waveguide; the discretization of the upper metal plate facilitates subsequent etching of the slot array, while the center feeding of the lower metal plate enables symmetrical excitation.

[0038] The dielectric substrate is laminated between the upper metal plate and the lower metal plate.

[0039] The lamination is a bonding method between a dielectric substrate and a metal plate, in which the layers are fixed together through a pressing process. "Laminated on" indicates that the dielectric substrate is pressed between the upper and lower metal plates, forming an inseparable sandwich structure.

[0040] In the three-layer parallel plate waveguide structure, the dielectric substrate is laminated between the upper and lower metal plates to form a single parallel plate. For example, a hot-pressing process is used to bond Rogers 3003 sheet metal to a copper plate, ensuring a gapless bond, which reduces interface reflection and energy leakage. The lamination process ensures structural rigidity and optimizes the propagation efficiency of electromagnetic waves in the dielectric.

[0041] The upper metal plate is etched with a slot array layer, which includes multiple cross-shaped slot units arranged in a matrix.

[0042] The slot array layer is a collection of radiating units formed by etching on the upper metal plate, consisting of an array of multiple slots. "Etching" refers to removing material from the surface of the upper metal plate using chemical or mechanical processes to form a slot pattern. The cross-shaped slot unit is the basic unit in the slot array, its name indicating a cross-shaped slot structure. "Matrix arrangement" means that these units are uniformly arranged in a grid pattern, forming a two-dimensional array.

[0043] The upper metal plate is etched with a slit array layer, consisting of a matrix arrangement of 21×21 units. The overall dimensions are calculated based on a unit length of 3.125 mm. Each unit is a cross-shaped slit unit, including horizontal and vertical slits. The horizontal slits are used to couple the x-direction magnetic field component of the reference wave, and the vertical slits are used to couple the y-direction component, achieving circularly polarized beams by introducing a 90° phase difference. For example, at the unit location, the etching process forms a cross structure of horizontal and vertical slits with dimensions of a = 2.63 mm (overall unit width), c = 1.2 mm (slit width), a1 = 1.85 mm (patch size), and c1 = 0.6 mm (slit detail). The matrix arrangement ensures the uniformity of the holographic interference plane, allowing the reference wave to couple to each unit. The cross-shaped slit unit design allows for simultaneous processing of horizontal and vertical components, with the radiation direction controlled by the holographic phase distribution. The slit distribution is calculated based on the holographic interference formula. Where P obj It is the target wave, H * ref It is the complex conjugate of the reference magnetic field. The final distribution of the cross-shaped slot element is as follows: Figure 5 As shown.

[0044] The element distribution state of the horizontal magnetic field component Hx and the vertical magnetic field component Hy collected on the metasurface can be calculated using the formula, which correspond to the horizontal slit (Mx) and the vertical slit (My), respectively. Figure 4 As shown.

[0045] The upper metal plate forms a discrete unit network structure.

[0046] The discrete unit network structure is the organizational form of the upper metal plate, referring to the metal plate being divided into independent unit blocks. Here, "forming" means discretizing the continuous metal plate into a network structure through etching or cutting processes.

[0047] The upper metal plate is divided into 21×21 discrete units, each unit being an independent block measuring 3.125mm×3.125mm, forming a network structure. For example, this network allows for individual etching of slots in each unit, facilitating adjustments to the arrangement of horizontal and vertical slots. Discretization enhances design flexibility, supports holographic phase compensation calculations, and ensures the directivity of the radiated beam.

[0048] Each of the cross-shaped slot units includes horizontal slots and vertical slots.

[0049] The horizontal seam is a horizontal seam in a cross-shaped slot unit, meaning it extends in the horizontal direction. The vertical seam is a vertical seam in a cross-shaped slot unit, meaning it extends in the vertical direction.

[0050] Horizontal slits are used to couple the x-component of the reference wave, and vertical slits are used to couple the y-component; they are arranged orthogonally within the element, forming a cross structure. The dimensions are a = 2.63 mm (element outer frame) and c = 1.2 mm (slit width), with the lengths of the horizontal and vertical slits adjusted based on the element dimensions. For example, where both horizontal and vertical slits need to be placed simultaneously, they are arranged in a cross shape, ensuring that the two components have equal amplitudes and a 90° phase difference, thus fusing to generate a circularly polarized beam.

[0051] The coupling effect between the horizontal and vertical slits is based on the holographic principle: when the reference wave illuminates, the slits couple energy and achieve circular polarization through the phase difference.

[0052] The phase difference is calculated using the following formula:

[0053]

[0054] Where θ r and It is the radiation direction angle, (x,y) is the element position, and φ is the radiation direction angle. r (x0,y0) is the initial phase, and k0 is the free space wavenumber.

[0055] Target wavefield distribution:

[0056]

[0057] Used to calculate interference fields.

[0058] The horizontal and vertical seams form an intersecting structure in the cross-shaped gap unit.

[0059] The intersecting structure refers to the arrangement of horizontal and vertical seams, where they intersect to form a cross shape. An etching process is used to make the horizontal and vertical seams intersect at the center of the unit.

[0060] In the cross-slot element, horizontal and vertical slots intersect at a 90° angle, forming an orthogonal intersection. For example, a dimension c1 = 0.6 mm defines the slot detail. This ensures that the coupling points of the horizontal and vertical components coincide. The intersecting structure optimizes space utilization and provides the physical basis for a 90° phase difference, supporting circularly polarized beam generation. The element model is as follows: Figure 1 As shown in (d).

[0061] Each of the cross-slot units also includes a metal patch.

[0062] The metal patch is an additional element in the cross-shaped slot unit, referring to a small metal block. The patch is added to the slot area to enhance performance.

[0063] The metal patch is implemented as follows: A metal patch with a size a1 = 1.85 mm (patch width) is added to each cross-shaped slot unit. For example, the patch is integrated with the slot through an etching process, improving coupling efficiency and radiation gain. Logically, the metal patch increases the surface current path, optimizing the antenna's radiation characteristics.

[0064] The metal via array includes multiple hollow cylindrical vias penetrating the three-layer parallel plate waveguide structure and is arranged around the slot array layer.

[0065] The metal via array is a structure that reduces energy leakage. The name indicates that it is an array composed of multiple vias. "Through" means that the vias penetrate the entire three-layer structure, and "surround arrangement" means that the vias are arranged around the periphery of the slot array.

[0066] The metal via array consists of multiple hollow cylindrical vias that penetrate the upper metal plate, dielectric substrate, and lower metal plate, surrounding the entire slot array layer to confine energy. The via locations are based on the antenna edge arrangement to reduce reference wave leakage. For example, adding vias to the periphery of a 21×21 element array increases the gain by 1.23 dB. The surrounding arrangement creates a Faraday cage effect, suppressing edge diffraction and optimizing radiation efficiency. The via model is as follows. Figure 2 As shown in (b).

[0067] The hollow cylindrical through hole includes an annular gap structure formed by the outer wall and the inner wall.

[0068] The annular gap structure is an internal feature of a hollow cylindrical through-hole, referring to an annular gap defined by the inner and outer walls.

[0069] Each hollow cylindrical through-hole forms an annular gap with an outer wall radius of Rout = 0.22 mm and an inner wall radius of Rin = 0.2 mm. This gap, for example, reduces material usage and optimizes shielding effectiveness. The annular structure reduces weight while maintaining mechanical strength.

[0070] The horizontal and vertical seams are arranged orthogonally in the cross-shaped gap unit.

[0071] The orthogonal arrangement refers to the relative orientation of the horizontal and vertical slits, meaning they intersect perpendicularly. "Orthogonal arrangement" indicates that the slit directions are perpendicular to each other, forming a 90° angle. Orthogonal arrangement ensures that the horizontal and vertical components of the electric field have equal amplitudes and a 90° phase difference, which is crucial for circularly polarized beams.

[0072] The coaxial power supply interface is located at the geometric center of the lower metal plate.

[0073] The coaxial power supply interface is the excitation source mounting point, and its name refers to the coaxial connector. It is located at the center of the lower metal plate.

[0074] The coaxial feed interface is located at the geometric center of the lower metal plate, serving as a monopole feed. This ensures symmetrical propagation of the reference wave. For example, the feed excites a zero-order Hankel function reference wave:

[0075]

[0076] Where k g Here, r is the wavenumber in the dielectric substrate, and r is the distance from the cell location to the center. It is the azimuth angle. Then, MATLAB software was used to calculate the phase distribution of the reference for different components, as shown below. Figure 3 As shown, H x H y Indicates the x and y directions of the reference wave.

[0077] k g The wavenumber in the dielectric substrate is represented by... Calculate, where f is the frequency; r represents the distance from the discrete aperture position of the upper plate to the coordinates of the center origin; ε r μ is the dielectric constant. r denoted as ρ, where ρ is the relative permeability of the medium.

[0078] The radiation principle of a holographic metasurface antenna states that a reference wave coupled with a designed metasurface element can generate a beam in a desired direction. This requires phase compensation of the reference wave excited at the coaxial port using the designed metasurface antenna. The goal of compensation is to transform the field distribution (H) of the reference wave at all discrete element locations on the metasurface into the desired target beam field distribution (P). Finally, the holographic phase distribution and slot distribution that meet the radiation requirements are calculated using H and P, which is the holographic metasurface to be designed.

[0079] The reference wave is excited by a coaxial feed and uses the Hankel function H. ref Description; Target wave P obj Through formula Define φ r Introducing a 90° phase difference at (x,y); holographic interference field The slot distribution was calculated. The antenna operated at 24 GHz, and testing verified that the reflection coefficient S11 remained <-10 dB in the 23.5-24.5 GHz range, the axial ratio was <3 dB, and the bandwidth was 0.25 GHz, demonstrating the purity of circular polarization. After adding the metal via, the gain increased from 12.76 dB to 13.98 dB, an improvement of 1.23 dB. The test results are as follows. Figure 7 , Figure 8 and Figure 9 As shown.

[0080] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be made to the above embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made to the present invention by those skilled in the art based on the disclosure thereof should be within the scope of protection of the present invention.

Claims

1. A holographic metasurface antenna, characterized in that, include: Three-layer parallel plate waveguide structure and metal through-hole array; The three-layer parallel plate waveguide structure includes a dielectric substrate, an upper metal plate covering the upper surface of the dielectric substrate, and a lower metal plate covering the lower surface of the dielectric substrate. The upper metal plate is etched with a slot array layer, which includes multiple cross-shaped slot units arranged in a matrix. Each of the cross-shaped slot units includes horizontal slots and vertical slots; The metal via array includes multiple hollow cylindrical vias penetrating the three-layer parallel plate waveguide structure and is arranged around the slot array layer. The horizontal seams and the vertical seams are arranged orthogonally in the cross-shaped gap unit.

2. The holographic metasurface antenna according to claim 1, characterized in that, Each of the cross-slot units also includes a metal patch.

3. The holographic metasurface antenna according to claim 1, characterized in that, The hollow cylindrical through hole includes an annular gap structure formed by the outer wall and the inner wall.

4. The holographic metasurface antenna according to claim 1, characterized in that, The coaxial power supply interface is located at the geometric center of the lower metal plate.

5. The holographic metasurface antenna according to claim 1, characterized in that, The upper metal plate forms a discrete unit network structure.

6. The holographic metasurface antenna according to claim 1, characterized in that, The horizontal and vertical seams form an intersecting structure in the cross-shaped gap unit.

7. The holographic metasurface antenna according to claim 1, characterized in that, The dielectric substrate is laminated between the upper metal plate and the lower metal plate.

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