Focusing metasurface lens with anti-shielding function

Abstract

The invention belongs to the technical field of metasurfaces and plane lenses, and particularly relates to a focusing metasurface lens with an anti-shielding function, the lens is composed of 40 * 40 units with the period of 7.5 mm, each unit comprises a top layer metal annular patch, a dielectric layer and a bottom layer metal patch, the relative dielectric constant of a dielectric substrate is 2.65, and the relative dielectric constant of the dielectric substrate is 2.65. The units realize anisotropic response through circumferential notch design, a stable 180-degree phase difference is formed by adopting a mirror image inversion structure, the 1-bit phase modulation requirement is met, the array performs phase coding in the radial direction according to an Airy function, and a hollow annular layout is adopted, so that the self-bending and self-repairing characteristics of Airy beams are effectively utilized, and the phase modulation efficiency is improved. The electromagnetic wave can bypass physical shielding of an axis area, field intensity reconstruction is realized at a set focus, and the design can remarkably improve focusing gain and energy recovery capability of a system in a shielding environment while maintaining high cross polarization conversion efficiency in Ku frequency band application of 13GHz and the like.

Description

Technical Field

[0001] This invention belongs to the field of metasurface and planar lens technology, and specifically relates to a focusing metasurface lens with anti-obstruction function. Background Technology

[0002] In the field of microwave antennas and electromagnetic control, metasurfaces, as two-dimensional planar arrays composed of subwavelength artificial microstructures, have attracted much attention because they can overcome the limitations of traditional materials and achieve flexible control over the phase, amplitude, and polarization state of electromagnetic waves. Especially in Ku-band satellite communication and radar systems, metalenses are gradually replacing traditional bulky and heavy refractive lenses due to their advantages of being ultra-thin, lightweight, and easy to integrate.

[0003] However, traditional transmissive focusing systems generally employ a solid array structure, with their energy contribution concentrated primarily in the central region. In practical installations, however, feed supports, RF front-end components, or protective metal baffles often exist in front of the focal point. These physical obstacles directly block the main propagation path of electromagnetic waves, leading to severe distortion of the energy distribution at the focal point, a sharp drop in gain, and decreased signal transmission reliability. Although some research has been conducted on anti-blocking designs, most rely on complex algorithm optimizations or active devices, making it difficult to effectively recover the blocked field strength while maintaining structural simplicity.

[0004] In recent years, Airy beams, a special type of beam with non-diffraction properties, have offered a new physical approach to solving the aforementioned challenges. Airy beams possess unique self-bending and self-healing properties, enabling them to bypass obstacles and reconstruct their wavefronts during propagation. However, a systematic solution that combines the complex phase distribution of Airy beams with 1-bit (0 / 1) coding technology and achieves efficient cross-polarization conversion and anti-blocking focusing in a hollow ring array configuration still lacks a simple, robust, and applicable solution suitable for the Ku-band. Therefore, developing a 1-bit transmissive metasurface that simplifies manufacturing processes and leverages Airy beam characteristics to achieve focus energy recovery in extreme environments is of significant application value for improving the environmental adaptability of microwave communication systems. Summary of the Invention

[0005] The purpose of this invention is to provide a focusing metasurface lens with anti-obstruction function, which can effectively utilize the self-bending and self-healing characteristics of Airy beams to enable electromagnetic waves to bypass physical obstructions in the axis region and achieve field strength reconstruction at the set focal point. In Ku-band applications such as 13GHz, it can significantly improve the focusing gain and energy recovery capability of the system in obstructed environments while maintaining high cross-polarization conversion efficiency.

[0006] The specific technical solution adopted by this invention is as follows: A focusing metasurface lens with anti-obstruction function includes multiple 1-bit metasurface units, which are arranged in a ring hollow array. The 1-bit metasurface unit includes a top metal patch structure, a dielectric layer, and a bottom patch structure; Both the top metal patch and the bottom metal patch are asymmetric open resonant ring structures with circumferential notches. Furthermore, the angle between the center line of the notch in the top metal patch and the center line of the notch in the bottom metal patch is 90°; The annular hollow array is phase-coded radially according to the sign distribution of the Airy function.

[0007] Furthermore, the center distance between two adjacent 1-bit metasurface units is 7.5 mm.

[0008] Furthermore, the thickness of the dielectric layer is 1.5 mm, and the dielectric layer material is F4B material with a relative permittivity of 2.65.

[0009] Furthermore, the outer diameter of both the top metal patch structure and the bottom patch structure is 3.6 mm, the ring width is 1.1 mm, the notch opening width is 0.9 mm, and the thickness is 0.035 mm. The material of both the top metal patch structure and the bottom patch structure is copper foil.

[0010] The technical effects achieved by this invention are as follows: This invention discloses a focusing metasurface lens with anti-obstruction function, which achieves efficient cross-polarization conversion and phase modulation through a mirror-reversed 1-bit structure. It aims to utilize the unique self-bending and self-healing physical mechanism of circular Airy beams, combined with a hollow ring array layout, to enable electromagnetic wave energy to bypass obstructions on the axis during propagation and achieve effective reconstruction of the field strength at the focal point. This can significantly improve the focusing gain and signal recovery capability of microwave antenna systems in complex engineering environments such as those with feed support or metal component obstructions. When applied in the Ku band (13 to 15 GHz), it reduces technical problems such as severe energy attenuation caused by physical obstruction in the central region, complex multi-bit metasurface structure design, and low processing tolerance. It greatly simplifies the design complexity and manufacturing process of metasurfaces and is suitable for complex electromagnetic environments such as satellite communication and radar systems. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of the 1-bit metasurface unit of the present invention; Figure 1 (a) is a structural diagram of the 1-bit metasurface unit of the present invention; Figure 1 (b) is a structural side view of the 1-bit metasurface unit of the present invention; Figure 1 (c) is a top-layer patch structure diagram of the 1-bit metasurface unit of the present invention; Figure 1 (d) is a diagram of the bottom patch structure of the 1-bit metasurface unit of the present invention; Figure 2 This is the amplitude and phase characteristic of the 1-bit metasurface unit of this invention; Figure 3 This is a diagram showing the control relationship between the array design parameters of this invention and the focal position; Figure 4 This is a schematic diagram of the focusing lens structure with a baffle in this invention; Figure 5(a) is a comparative analysis of the energy recovery efficiency when the baffle radius of the present invention is 45 mm; Figure 5(b) is a comparative analysis of the energy recovery efficiency when the baffle radius of the present invention is 37.5 mm; Figure 5(c) is a comparative analysis of the energy recovery efficiency when the baffle radius of the present invention is 30 mm; Figure 5(d) is a comparative analysis of the energy recovery efficiency when the baffle radius of the present invention is 22.5 mm; Figure 6 This is the Airy lens distribution at 500mm in this invention; Figure 7 is a detailed structural diagram of the 1-bit metasurface unit ring array of the present invention; Figure 7(a) is a top-layer patch distribution diagram of the 1-bit metasurface unit ring array of the present invention; Figure 7(b) is a diagram of the bottom patch structure of the 1-bit metasurface unit ring array of the present invention; Figure 8 This is the full-wave simulation result of the Airy lens of this invention; Figure 9 This invention relates to focal plane energy distribution and full width at half maximum (FWHM). Detailed Implementation

[0012] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of the invention and does not strictly limit the scope of protection specifically claimed by the invention.

[0013] like Figures 1-9 As shown, a focusing metasurface lens with anti-obstruction function includes an array of 40×40 square units with a period of 7.5 mm, wherein the size of the square unit is... ; The grid cells are selectively equipped with 1-bit metasurface units or left empty, so that multiple 1-bit metasurface units achieve a specific annular hollow array arrangement, that is, the array of 1-bit metasurface units is geometrically distributed in a ring, and the central region of the annular hollow array is a physically hollow region, since the size of the grid cells is... The center distance between two adjacent 1-bit metasurface units is 7.5 mm.

[0014] The core of the ring array lies in its phase encoding method: Phase modulation is performed according to the Airy function in any radial direction. This design aims to fully utilize the inherent self-bending and self-healing properties of the Airy beam in the near-field region, thereby ensuring that the lens has the ability to resist physical obstruction.

[0015] Using a circular array instead of a square array has a key advantage: it ensures the consistency of the Airy function's range across all directions. This not only helps achieve greater focal distances but also makes the focused energy more concentrated.

[0016] The hollow ring design is designed to maximize the self-bending characteristics of the Airy beam, enabling electromagnetic waves to effectively bypass obstructions near the axis during propagation. This is the core structural design for achieving anti-obstruction functionality, and the configuration can effectively achieve cross-polarization conversion of linear polarization.

[0017] Among them, such as Figure 1 As shown, it is important to note that the 1-bit metasurface unit includes a top metal patch structure, a dielectric layer, and a bottom patch structure. The dielectric layer serves as a dielectric substrate, with a preferred thickness of 1.5 mm. The dielectric layer is preferably made of a material with a relative permittivity of 2.65, such as F4B material.

[0018] Specifically, the top metal patch structure and the bottom patch structure are fixedly connected to the upper and lower sides of the dielectric layer, respectively. Both the top metal patch structure and the bottom patch structure are ring-shaped metal resonant structures, i.e., resonant rings, and the two resonant rings are concentrically arranged so that the centers of the two resonant rings are opposite each other. Both the top metal patch structure and the bottom patch structure introduce gaps at specific positions in the circumference, so that the original closed loop structure (resonant ring) with rotational symmetry is transformed into an asymmetric open resonant ring structure.

[0019] The outer diameter of both the top-layer metal patch structure and the bottom-layer patch structure is 3.6 mm, the ring width is 1.1 mm, the notch opening width of both the top-layer metal patch structure and the bottom-layer patch structure is 0.9 mm, and the material of both the top-layer metal patch structure and the bottom-layer patch structure is copper foil with a thickness of 0.035 mm.

[0020] It should be noted that the angles of the openings introduced by the top metal patch structure and the bottom patch structure differ by 90°, so that the angle between the center line of the notch of the top metal patch and the center line of the notch of the bottom metal patch is 90°. When the opening directions of the top metal patch structure and the bottom patch structure are vertical and horizontal, respectively, they correspond to X polarization and Y polarization. Under the excitation of external electromagnetic waves, this asymmetric open resonator can form a significant induced current distribution in the circumferential direction, thereby generating a concentrated equivalent capacitance effect at the notch. The circumferential path itself provides equivalent inductance, and the two together determine the resonant characteristics of the unit.

[0021] In a toroidal metallic resonant structure, the inner and outer rings form a composite resonant mode through near-field electromagnetic coupling, the coupling strength of which is controlled by the ring spacing and the size of the notch opening. By rationally designing the geometric parameters of the inner and outer rings, the resonant mode and resonant frequency of the unit can be finely adjusted, thereby changing the phase response of reflected or transmitted electromagnetic waves. Due to the introduction of the circumferentially asymmetric notch, the unit's response to incident electromagnetic waves exhibits obvious anisotropic characteristics, enabling phase abrupt changes or resonance enhancement under specific polarization conditions.

[0022] Furthermore, by mirroring the top metal patch structure or the bottom patch structure of the 1-bit metasurface unit, a stable phase difference of 180° between the top metal patch structure and the bottom patch structure is ensured, which precisely meets the requirements of 1-bit phase modulation.

[0023] This invention introduces a scaling factor Airy function The dimensionless independent variable and the radial coordinates of the lens planar array unit Establish mapping relationship This maps the zero-point distribution of the Airy function to the radial phase modulation structure of the lens surface. The phase modulation of the incident light field by the lens is determined by the sign distribution of the Airy function and is achieved using a binary phase approach, with its phase function expressed as: ; in This represents the phase delay applied by the lens at radial position r. This phase distribution, with the zero point of the Airy function as the phase jump boundary, forms a non-uniformly radially arranged phase region in the lens plane. To enhance the focusing effect, a hollow annular aperture parameter dR is introduced, limiting the effective phase modulation region of the lens to satisfy... This focusing process does not rely on traditional refractive surfaces or continuous phase lenses, but is achieved by a self-bending and phase compensation mechanism driven by the Airy function, making it suitable for ultrathin planar lens systems.

[0024] Phase sampling is performed according to the Airy function and mapped onto the array. 1-bit metasurface units are used for arrangement. The metasurface polarization conversion rate is 73%, the energy transmittance is 91%, the energy on the focal plane is 72% of the incident energy, the total energy within a range of two half-height full width equal to the diameter at the focal point accounts for 44% of the total energy of the entire plane, and the Y-polarization energy accounts for 48% of the total energy of the entire plane.

[0025] like Figure 2 As shown, Figure 2 The electromagnetic response characteristics of a 1-bit metasurface unit from 13 GHz to 15 GHz were demonstrated. The cross-polarization conversion amplitude exhibited high efficiency and low loss, reaching approximately 0.965, which is within the resonant gain plateau of the frequency band. In terms of phase characteristics, the 3dB bandwidth of the 1-bit metasurface unit was 14%. The phase of a set of 1 bits at the 14 GHz frequency corresponded to +78.2° and -101.5°, respectively, forming a precise phase difference of 179.7° (approximately 180°). This quasi-180° phase flip, combined with its high amplitude efficiency, makes it an ideal unit for constructing 1-bit metasurface units. It can effectively achieve dynamic control functions such as destructive interference (RCS reduction) or beam deflection through state switching.

[0026] like Figure 3 As shown, in a ring array configuration with a diameter of 300 mm and a grid cell side length of 7.5 mm, Figure 3 This study demonstrates the sensitivity of the focusing characteristics of the annular Airy function to parameter variations, specifically the synergistic evolution of the focal position with the range of Airy function values ​​and its corresponding hollow radius dR. With the maximum value of the Airy function set to 1, the results show a significant positive correlation between the focal position and the minimum value of the Airy function. As this minimum value gradually increases from -8, the focal position extends from approximately 150 mm to over 500 mm in the far field. Furthermore, after the minimum value exceeds -4.5, the sensitivity of the focal position to parameter variations significantly improves. In addition, the hollow radius dR has a significant modulating effect on the focal position. Within the same value range, a smaller dR (e.g., 7.5 mm) consistently corresponds to a focal position farther than a larger dR (e.g., 45.0 mm), indicating that reducing the hollow radius is beneficial for achieving a greater focusing distance. This chart reveals the feasibility of achieving precise control of the focal position by adjusting the Airy function parameters.

[0027] Figure 4 The model setup shown features a baffle positioned in front of the focal point, on the center line of the array, in front of the focal point, at a distance of 5 / 6 of the focal length from the lens.

[0028] Figures 5(a)-5(d) systematically illustrate the impact of varying baffle positions (dR values ​​of 22.5, 30.0, 37.5, and 45.0) on the energy recovery efficiency at the focal point. By comparing the Airy ring focusing array (represented by solid circles) with the traditional metasurface lens (represented by dashed squares), it is clearly revealed that the Airy array exhibits significantly higher recovery efficiency in all test scenarios. As the baffle position gradually increases from 0 (unobstructed state), although the energy recovery rate of both decreases, the efficiency curve of the traditional lens drops extremely drastically, while the Airy array, thanks to its unique self-healing properties, maintains a smoother attenuation, thus retaining more focal energy under the same obstruction conditions. This phenomenon is highly consistent across different dR parameters, fully verifying that the Airy ring focusing array possesses stronger robustness and energy reconstruction capability compared to traditional metasurface lenses when dealing with central obstruction interference.

[0029] Figure 6 Figure 7 shows the phase distribution and 1-bit metasurface unit distribution of the array with the focal point at 500 mm. The array structure adopts a hollow ring layout based on the phase distribution of the circular Airy beam, which is composed of several 1-bit metasurface units with polarization conversion function at 13 GHz frequency arranged according to a specific radial phase matrix.

[0030] Specifically, the array is spatially presented as a non-fully filled annular aperture. No microstructure units are arranged in the central axis region of the metasurface to form a physical hollow area. Within the outer annular effective control region, 1-bit discretization and quantization mapping is performed based on the continuous phase function of the Airy beam. The "state 0" and "state 1" units, obtained through mirror inversion and possessing a π-phase difference, are precisely arranged on a two-dimensional grid according to the generated binary matrix. This unique array distribution logic ensures that the transmitted electromagnetic waves no longer converge radially along a straight path during propagation. Instead, they strictly follow the inward-curving parabolic trajectory characteristic of the Airy beam, allowing the main energy flow to cleverly bypass paraxial obstructions directly in front of the metasurface. At the preset focal length after crossing the obstacle, a sudden self-focusing effect occurs through field strength coherent interference. This, from the array configuration perspective, ensures the system's energy recovery capability and beam self-healing characteristics under complex electromagnetic environments.

[0031] Figure 8 The full-wave simulation results of the lens phase distribution and array with the focal point at 500mm are presented. The energy recovery efficiency at the designed focal point is 34.25%.

[0032] Figure 9 The full width at half maximum (FWHM) of the focal energy on the focal plane is shown, with a total FWHM of 48.7 mm; the full FWHM of the Y-polarization energy is 51.1 mm.

[0033] In summary, this technical solution achieves efficient cross-polarization conversion and phase modulation through a mirror-reversed 1-bit structure. It aims to utilize the unique self-bending and self-healing physical mechanism of circular Airy beams, combined with a hollow ring array layout, to enable electromagnetic wave energy to bypass obstructions on the axis during propagation and achieve effective reconstruction of the field strength at the focal point. The ultimate goal is to significantly improve the focusing gain and signal recovery capability of microwave antenna systems in complex engineering environments with feed supports or metal components obstructing the signal, while greatly simplifying the design complexity and manufacturing process of metasurfaces.

[0034] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A focusing metasurface lens with anti-obstruction function, characterized in that: It includes multiple 1-bit metasurface units, which are arranged in a ring-shaped hollow array; The 1-bit metasurface unit includes a top metal patch structure, a dielectric layer, and a bottom patch structure; Both the top metal patch and the bottom metal patch are asymmetric open resonant ring structures with circumferential notches. Furthermore, the angle between the center line of the notch in the top metal patch and the center line of the notch in the bottom metal patch is 90°; The annular hollow array is phase-coded radially according to the sign distribution of the Airy function.

2. A focusing metasurface lens with anti-obstruction function according to claim 1, characterized in that: The center distance between two adjacent 1-bit metasurface units is 7.5 mm.

3. A focusing metasurface lens with anti-obstruction function according to claim 1, characterized in that: The thickness of the dielectric layer is 1.5 mm.

4. A focusing metasurface lens with anti-obstruction function according to claim 1, characterized in that: The dielectric layer material is F4B material with a relative permittivity of 2.

65.

5. A focusing metasurface lens with anti-obstruction function according to claim 1, characterized in that: The outer diameter of both the top-layer metal patch structure and the bottom-layer patch structure is 3.6 mm, the ring width is 1.1 mm, the notch width is 0.9 mm, and the thickness is 0.035 mm.

6. A focusing metasurface lens with anti-obstruction function according to claim 1, characterized in that: The top-layer metal patch structure and the bottom-layer patch structure are made of copper foil.

7. A focusing metasurface lens with anti-obstruction function according to claim 1, characterized in that: The annular hollow array is phase-coded radially according to the sign distribution of the Airy function, and the phase function is expressed as: 。 8. A focusing metasurface lens with anti-obstruction function according to claim 1, characterized in that: The diameter of the annular hollow array is 300 mm.

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