A design method for a polarization-selective transmission-reflection quasi-diffraction-free beam generation array based on Huygens metasurface

Abstract

This invention discloses a design method for a polarization-selective transmission-reflection quasi-diffraction-free beamforming array based on Huygens metasurfaces, comprising the following steps: Step 1) Designing a single-layer transmission-reflection unit based on Huygens metasurface theory; Step 2) Using the single-layer transmission-reflection unit as the main transmission surface, and designing a polarization conversion reflection unit and a sub-reflection surface to construct a low-profile quasi-diffraction-free folded transmission-reflection array; wherein, the polarization conversion reflection unit is used to convert the x-polarized wave emitted by the feed source into a y-polarized wave via the sub-reflection surface; the main transmission surface and the sub-reflection surface perform transmission phase modulation on the y-polarized wave to generate a quasi-diffraction-free beam. This invention is not only applicable to quasi-diffraction-free beamforming in MWPT systems, but can also be extended to other scenarios based on electromagnetic wave vector control, such as polarization conversion antennas and dual-polarization beamforming. It is applicable in fields such as wireless power transmission, indoor wireless communication, and small radar, and has strong versatility.

Description

Technical Field

[0001] This invention relates to the field of planar transflective array antennas, specifically a design method for a polarization-selective transflective quasi-diffraction-free beam generation array based on a Huygens metasurface. Background Technology

[0002] With the widespread adoption of smartphones, tablets, smart home devices, and wearable electronics, the demand for wireless power has evolved from "short-range charging of a single device" to "coordinated power supply for multiple devices over medium to long distances." Microwave wireless power transfer (MWPT) technology, with its medium-to-long-distance transmission capabilities, unobstructed environmental adaptability, and ability to power multiple devices simultaneously, has become a core technological solution to the problems of complex wiring and poor device portability associated with wired charging. In indoor scenarios, this technology can simultaneously power multiple devices in the living room, such as smartphones, smart speakers, and robot vacuums, or provide contactless power to small kitchen appliances through a single transmitter, demonstrating enormous market potential. However, in practical applications, microwave wireless power transfer technology still faces two key bottlenecks that restrict its performance improvement and scenario adaptability. The first major bottleneck is the low efficiency of beam modulation. Traditional quasi-diffraction-free beam generation relies on multilayer transmissive metasurface structures. In order to achieve polarization-selective transmission, these structures need to embed additional metal polarization gratings or slotted metal grounds in the metasurface units. These polarization-selective layers introduce significant insertion loss, resulting in electromagnetic wave energy transmittance generally being less than 50% (corresponding to a transmission coefficient <-3dB). At the same time, the discrete phase modulation mode of the multilayer structure will produce a phase error of more than 10°, which degrades the quality of the generated quasi-diffraction-free beam, accelerates the energy diffusion rate during transmission, and significantly reduces the energy transfer efficiency. The second major bottleneck is the low system integration. Traditional quasi-diffraction-free beamforming devices mostly use horn antennas for space feeding. To ensure that the radiation beam of the horn antenna can uniformly cover the entire metasurface array, a large focal length (usually 1-1.5 times the metasurface aperture) is required. Taking a metasurface with an aperture of 480mm as an example, the focal length under traditional feeding schemes needs to reach more than 320mm, resulting in an overall system profile height of more than 400mm. This not only occupies a lot of installation space, but also makes it difficult to integrate with indoor furniture and embedded devices, severely limiting its application in home, office and other scenarios.

[0003] To address these issues, the industry has explored various technological improvement approaches: In terms of transmissive and reflective element design, some solutions have simplified the polarization selection layer structure, such as using thinner metal grids or smaller slot sizes, attempting to reduce losses and manufacturing complexity. However, these solutions still fall under the inherent limitation of a "multi-layered structure," and the transmission coefficient remains difficult to exceed -3dB. Regarding system volume optimization, folded metasurface technology has been proposed. This involves folding the optical path between the metasurface and the feed source to shorten their distance. However, existing folding solutions are mostly designed for simple reflected or planar beams, failing to incorporate the theory of quasi-diffraction-free beamforming. This results in the inability to meet the beam energy focusing requirements of microwave wireless power transmission, and the low integration between the feed source and metasurface necessitates additional support structures for fixation, hindering true miniaturization. Furthermore, most existing technologies treat "polarization selection," "quasi-diffraction-free beamforming," and "system miniaturization" as independent objectives for separate optimization, lacking an integrated design approach. This leads to mutual constraints among performance indicators, making it difficult to simultaneously meet the comprehensive requirements of high power transmission efficiency, small size, and low loss. This has become a key obstacle restricting the large-scale application of microwave wireless power transmission technology. Summary of the Invention

[0004] The purpose of this invention is to provide a design method for a polarization-selective transmission-reflection quasi-diffraction-free beamforming array based on a Huygens metasurface, comprising the following steps:

[0005] Step 1) Based on Huygens' metasurface theory, design a single-layer transmission and reflection unit;

[0006] Step 2) Use a single-layer transmission-reflection unit as the main transmission surface, and design polarization conversion reflection units and sub-reflection surfaces to construct a low-profile quasi-diffraction-free folded transmission-reflection array.

[0007] The polarization conversion reflection unit is used to convert the x-polarized wave emitted by the feed source into a y-polarized wave via the sub-reflector surface.

[0008] The main transmission surface and the sub-reflector surface perform transmission phase modulation on the y-polarized wave to generate a quasi-diffraction-free beam.

[0009] Furthermore, the single-layer transmissive and reflective unit includes a single-layer dielectric substrate and an orthogonally polarized electric resonant structure located on the same side of the single-layer dielectric substrate.

[0010] Furthermore, the orthogonal polarization electric resonant structure includes an I-shaped structure located in the y-polarization direction and a four-opening square ring structure located in the x-polarization direction;

[0011] The I-shaped structure and the four-opening square ring structure are arranged orthogonally to realize the y-polarized transmission and x-polarized reflection functions, respectively.

[0012] Furthermore, the dimensional parameters of the I-shaped structure and the four-opening square ring structure are determined by the application frequency and transmission linearity.

[0013] Furthermore, the single-layer transmissive-reflective unit excites Huygens transmission resonance in the y-polarization direction, achieving high transmission efficiency and 360° full-phase modulation;

[0014] The single-layer transmissive and reflective unit has a transmission coefficient greater than -0.99dB at frequencies of 5.5GHz-6.5GHz.

[0015] Furthermore, the single-layer transmissive-reflective unit excites Huygens reflection resonance in the x-polarization direction to achieve high reflection efficiency;

[0016] The single-layer transmissive and reflective unit has a reflection coefficient greater than -0.83dB and a phase fluctuation of less than 5° at frequencies of 5.3GHz-6GHz.

[0017] Furthermore, the polarization conversion reflection unit includes a single-layer dielectric substrate, a 45° symmetrical double L-shaped metal patch located on the upper surface of the single-layer dielectric substrate, and a metal ground located on the lower surface of the single-layer dielectric substrate.

[0018] Furthermore, the sub-reflective surface is a microstrip patch array;

[0019] The microstrip patch array is integrated with the polarization conversion reflector unit.

[0020] Furthermore, the principal transmission surface compensates the spherical wavefront for a conical wavefront, and the phase distribution of the conical wavefront is shown below:

[0021] (1)

[0022] Where k is the wave number, F is the focal length, and θ is the half-angle of the cone. It is the azimuth angle. For unit The phase distribution.

[0023] The technical advantages of this invention are undeniable. 1. Based on Huygens' metasurface theory, this invention designs an orthogonally polarized (x and y directions) electric resonant structure (I-shaped in the y direction + four-opening square ring in the x direction) on the same side of a single-layer dielectric substrate, and designs identical metal patch structures on both sides of the substrate. This allows for simultaneous excitation of electric and magnetic resonances, achieving independent dual-polarization control and completing the optimized design of a transmission-reflection unit. This unit requires no additional polarization selection layer, has a simple structure, and is symmetrical on both sides, enabling precise control of electromagnetic wave polarization, amplitude, and phase. It achieves full phase coverage from 0° to 360° in the y-polarization direction, with a transmission coefficient better than -0.99dB (energy transmittance > 89%); and a reflection coefficient better than -0.83dB in the x-polarization direction (reflectivity > 82%), with a reflection phase fluctuation of < 5°. Therefore, this method is not only applicable to quasi-diffraction-free beam generation in MWPT systems, but can also be extended to other scenarios based on electromagnetic wave vector control, such as polarization conversion antennas and dual-polarization beamforming. It is applicable in wireless power transmission, indoor wireless communication, and small radar, demonstrating strong versatility. 2. Existing Huygens metasurfaces with both transmission and reflection typically rely on additional polarization layers (such as metal polarization gates or slotted metal grounds) to achieve x / y polarization separation, or on metal vias connecting the upper and lower layers to excite magnetic resonance. This results in complex fabrication processes (requiring multi-layer alignment and via etching) and high transmission loss (generally >3dB). This invention proposes a simplified design: an orthogonal electric resonant structure is integrated on the same side of a single-layer dielectric substrate. By independently adjusting the two polarization parameters (adjusting the length of the I-shaped horizontal bar lcxy and the length of the vertical bar lcy in the y-direction, and fixing the size of the four-opening square ring in the x-direction), multiple sets of magnetic resonances (3 magnetic resonance points + 1 electric resonance point) can be excited by utilizing interlayer structural coupling and the same-side dimension interleaving effect. Furthermore, the structures on both sides of the dielectric substrate are identical, eliminating the need for metal vias and allowing for complementary or anti-symmetrical designs. This design ensures both the full phase control range of y-polarization and the high reflectivity of x-polarization, while reducing transmission loss to less than 1 dB. It also reduces more than 40% of the processing steps (such as polarization layer preparation and multilayer bonding). The structure is simple and easy to implement, significantly reducing processing costs and precision requirements.

[0024] 3. Based on the theory of diffraction-free beamforming and geometric optics, and combined with the optical path characteristics of folded metasurfaces, this invention proposes a method for calculating the phase distribution of quasi-diffraction-free folded transmission and reflection arrays. This method establishes the optical path geometric mapping relationship of "feed-sub-reflector-main-transmitter" based on the equivalent focal length between the feed phase center and the main transmission surface: first, the path difference from the feed spherical wave to the sub-reflector is calculated; then, the path difference from the sub-reflector to the main transmission surface after polarization conversion is superimposed; finally, the free-space wavenumber (k=2π / λ) is introduced to derive the formula for the quasi-diffraction-free phase distribution of the main transmission surface. This strategy, based on full optical path path compensation, can flexibly adapt to design requirements with different focal length ratios (F / D) and cone half-angles (θ). It can not only generate quasi-diffraction-free beams but also extend to other target wavefront forms such as near-field focusing beams and directional high-gain beams, providing a universal phase design scheme for high-performance beam control of low-profile transmission-reflection arrays. 4. Based on the transmission-reflection type unit design method and the folded array phase distribution method, this invention proposes a quasi-diffraction-free folded transmission-reflection array design method that can achieve precise control of the target beam wavefront. This method integrates the "main transmission surface (transmission-reflection unit) + sub-reflection surface (polarization conversion unit + patch antenna)" to fold the focal length of traditional space-fed systems to 1 / 3, reducing the system height from 401mm to 66mm (volume reduction of 83.5%), while maintaining the quasi-diffraction-free beam quality (maximum diffraction-free distance 1361mm, received power increased by 182%). This method not only meets the core requirements of MWPT systems for high efficiency and low profile, but also adapts to the electromagnetic wave control requirements of different frequency bands (such as 2.4GHz and 24GHz) by adjusting the unit period and feed parameters. It has significant application value in integrated electromagnetic systems such as wireless power supply for multiple indoor devices, power transmission for small home appliances, and portable communication terminals. Attached Figure Description

[0025] Figure 1 shows the transmissive and reflective unit structure; (a) three-dimensional view, (b) front view;

[0026] Figure 2 shows the imaginary part of the equivalent impedance of the transmission and reflection unit;

[0027] Figure 3 shows the surface current distribution of the transmissive and reflective elements: (a) frequency f = 4.8 GHz, (b) frequency f = 5.9 GHz, and (c) frequency f = 6.9 GHz.

[0028] Figure 4 shows the structure of a polarization conversion reflective unit cell.

[0029] Figure 5 (a) Front view and (b) Side view of a 2×2 microstrip patch antenna structure.

[0030] Figure 6 The overall structure of the quasi-diffraction-free folded transmission and reflection array;

[0031] Figure 7 shows the integrated design of the sub-reflector unit arrangement and the feed antenna;

[0032] Figure 8 It consists of 12 transmissive and reflective unit structures;

[0033] Figure 9 Transmission-reflection metasurface with quasi-diffraction-free phase distribution: (a) transmission phase distribution; (b) unit structure distribution.

[0034] Figure 10 Radial electric field distribution;

[0035] Figure 11 The results of power reception tests before and after applying the metasurface; Figure 12 This is a schematic diagram of the feed source location. Detailed Implementation

[0036] The present invention will be further described below with reference to embodiments, but it should not be construed that the scope of the present invention is limited to the following embodiments. Various substitutions and modifications made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention should be included within the scope of protection of the present invention.

[0037] Example 1:

[0038] See Figures 1 to 11 A design method for a polarization-selective transmission-reflection quasi-diffraction-free beamforming array based on Huygens metasurfaces includes the following steps:

[0039] Step 1) Based on Huygens' metasurface theory, design a single-layer transmission and reflection unit;

[0040] Step 2) Use a single-layer transmission-reflection unit as the main transmission surface, and design polarization conversion reflection units and sub-reflection surfaces to construct a low-profile quasi-diffraction-free folded transmission-reflection array.

[0041] The polarization conversion reflection unit is used to convert the x-polarized wave emitted by the feed source into a y-polarized wave via the sub-reflector surface.

[0042] The main transmission surface and the sub-reflector surface perform transmission phase modulation on the y-polarized wave to generate a quasi-diffraction-free beam.

[0043] Example 2:

[0044] A design method for a polarization-selective transmission-reflection quasi-diffraction-free beam generation array based on Huygens metasurface, with the same technical content as in Embodiment 1, further comprising a single-layer transmission-reflection unit including a single-layer dielectric substrate and an orthogonal polarization electric resonant structure located on the same side of the single-layer dielectric substrate.

[0045] Example 3:

[0046] A design method for a polarization-selective transmission-reflection quasi-diffraction-free beam generation array based on Huygens metasurface, with the same technical content as any one of Embodiments 1-2. Further, the orthogonal polarization electric resonant structure includes an I-shaped structure located in the y-polarization direction and a four-opening square ring structure located in the x-polarization direction.

[0047] The I-shaped structure and the four-opening square ring structure are arranged orthogonally to realize the y-polarized transmission and x-polarized reflection functions, respectively.

[0048] Example 4:

[0049] A design method for a polarization-selective transmission-reflection quasi-diffraction-free beamforming array based on Huygens metasurfaces, with the same technical content as any one of Examples 1-3, further wherein the dimensional parameters of the I-shaped structure and the four-opening square ring structure are determined by the application frequency and transmission linearity.

[0050] Example 5:

[0051] A design method for a polarization-selective transmission-reflection quasi-diffraction-free beam generation array based on Huygens metasurface, with the same technical content as any one of embodiments 1-4. Further, the single-layer transmission-reflection unit excites Huygens transmission resonance in the y-polarization direction to achieve high transmission efficiency and 360° full phase control.

[0052] The single-layer transmissive and reflective unit has a transmission coefficient greater than -0.99dB at frequencies of 5.5GHz-6.5GHz.

[0053] Example 6:

[0054] A design method for a polarization-selective transmission-reflection quasi-diffraction-free beam generation array based on Huygens metasurface, with the same technical content as any one of embodiments 1-5, further wherein the single-layer transmission-reflection unit excites Huygens reflection resonance in the x-polarization direction to achieve high reflection efficiency;

[0055] The single-layer transmissive and reflective unit has a reflection coefficient greater than -0.83dB and a phase fluctuation of less than 5° at frequencies of 5.3GHz-6GHz.

[0056] Example 7:

[0057] A design method for a polarization-selective transmission-reflection quasi-diffraction-free beam generation array based on Huygens metasurface, with the same technical content as any one of embodiments 1-6, further comprising a polarization conversion reflection unit including a single-layer dielectric substrate, a 45° symmetrical double L-shaped metal patch on the upper surface of the single-layer dielectric substrate, and a metal ground on the lower surface of the single-layer dielectric substrate.

[0058] Example 8:

[0059] A design method for a polarization-selective transmission-reflection quasi-diffraction-free beamforming array based on a Huygens metasurface, with the same technical content as any one of embodiments 1-7, further wherein the sub-reflecting surface is a microstrip patch array;

[0060] The microstrip patch array is integrated with the polarization conversion reflector unit.

[0061] Example 9:

[0062] A design method for a polarization-selective transmission-reflection quasi-diffraction-free beamforming array based on a Huygens metasurface, with the same technical content as any one of Examples 1-8, further wherein the main transmission surface is compensated with a spherical wavefront to form a conical wavefront, and the phase distribution of the conical wavefront is shown below:

[0063] (1)

[0064] Where k is the wave number, F is the focal length, and θ is the half-angle of the cone. It is the azimuth angle. For unit The phase distribution.

[0065] Example 10:

[0066] A design method for a polarization-selective transmission-reflection quasi-diffraction-free beamforming array based on a Huygens metasurface is presented. The technical content is the same as any one of embodiments 1-9. Furthermore, when generating the same diffraction-free beam, if a traditional focusing method is used, the feed source needs to be placed at the focal length F; however, with a transmission-reflection array, the feed source only needs to be placed at 1 / 3 of F. This demonstrates… Figure 12 .

[0067] Example 11:

[0068] A design method for a polarization-selective transmission-reflection quasi-diffraction-free beamforming array based on Huygens metasurfaces is proposed. This method is based on Huygens metasurface theory and involves designing symmetrical "I-shaped + four-opening square ring" composite metal structures on both sides of a single-layer dielectric substrate to independently control the electromagnetic parameters of orthogonal polarization (x-polarization and y-polarization). Huygens transmission resonance is excited in the y-polarization direction to achieve high transmission efficiency and 360° full phase control; Huygens reflection resonance is excited in the x-polarization direction to achieve high reflection efficiency and phase fluctuation of less than 5°. Polarization-selective transmission-reflection functionality can be achieved without an additional polarization selection layer. Based on this, by combining the theory of diffraction-free beam generation and geometric optics, the phase distribution formula of quasi-diffraction-free beams is derived, and a folded array structure of "main transmission surface + sub-reflection surface + integrated feed" is constructed. This reduces the system profile height from 401mm of the traditional transmission array to 66mm (volume reduction of 83.5%). At the same time, within a 1-meter transmission distance, the received power after loading this array can reach up to 3.7 times that of the unloaded array. This solves the problems of complex structure, large system size and low transmission efficiency of traditional transmissive and reflective metasurfaces, and provides design methods and technical support for the miniaturization and high efficiency of microwave wireless power transmission systems.

[0069] The polarization-selective transmissive-reflective quasi-diffraction-free beamforming array proposed in this invention adopts an integrated design with a single-layer dielectric substrate. It directly achieves polarization selection through the electromagnetic resonance characteristics of the composite metal structure, eliminating the need for an additional polarization selection layer. This not only reduces the processing steps by 50% but also avoids alignment errors and additional losses caused by multi-layer structures. The measured transmittance coefficient in the y-polarization direction is better than -0.99dB (energy transmittance exceeds 80%), and the reflectance coefficient in the x-polarization direction is better than -0.83dB (energy reflectance exceeds 85%). The processing cost is reduced by more than 40%, while significantly improving the yield during mass production (from 70% of traditional multi-layer structures to more than 95%). In terms of volume optimization, an innovative folded array structure is adopted. Through the optical path folding design of "main transmission surface + sub-reflection surface", the distance between the feed and the metasurface is reduced from 180mm in the traditional solution to 60mm (only 1 / 3 of the original focal length). The system profile height is finally reduced to 66mm, and the overall volume is reduced by 83.5% compared with the traditional transmission array. It can be easily embedded in narrow spaces such as under the desktop and behind the furniture, and is suitable for various indoor installation scenarios. In terms of energy transmission efficiency, the quasi-diffraction-free beam generated by this array has extremely strong energy focusing characteristics. Within the maximum diffraction-free distance of 1378mm, the energy distribution of the beam cross section is uniform and the diffusion rate is less than 10%. In the microwave wireless power transmission system, when the receiver is at a distance of 700mm, the received power after loading this array can reach up to 3.7 times that of the unloaded version. Even at a distance of 1200mm, the received power can still maintain 2.1 times that of the unloaded version, providing a reliable energy transmission path for simultaneous power supply of multiple devices and stable power transmission over medium and long distances.

[0070] Furthermore, this array possesses exceptional versatility and scalability: by adjusting the metal structure dimensions of the units (such as reducing the size of I-shaped and square rings), it can adapt to different microwave frequency bands such as 2.4GHz and 10GHz, meeting the power transmission requirements in various scenarios; in terms of functional expansion, in addition to microwave wireless power transmission, the highly directional quasi-diffraction-free beam generated by this array can also be used for beamforming in radar systems to reduce energy loss during target detection, or for directional signal transmission in the field of wireless communication to enhance anti-interference capabilities, providing a standardized design paradigm for electromagnetic wave control needs in multiple fields.

[0071] Example 12:

[0072] A design method for a polarization-selective transmission-reflection quasi-diffraction-free beamforming array based on a Huygens metasurface is described below:

[0073] First, based on Huygens' metasurface theory, a single-layer transmission and reflection unit is designed, such as... Figure 1 As shown, an orthogonally polarized (x and y directions) electric resonant structure (I-shaped + four-open square ring) is designed on the same side of the dielectric substrate, and the polarization parameters are independently controlled: the y-polarization direction is controlled by adjusting the length of the I-shaped crossbar (lcx). y ), vertical rod length (lcy) y ) and the width of the square ring opening (d) x The transmission coefficient is better than -0.99dB and 360° full phase coverage is achieved. In the x-polarization direction, the reflection coefficient is better than -0.83dB and the phase fluctuation is <5° by fixing the parameters of the square ring and the I-shaped structure. Then, the main transmission surface (with a quasi-diffraction-free transmission phase distribution) is constructed using this transmission-reflection type unit. A dual L-shaped polarization conversion reflection unit and a 2×2 microstrip patch array integrated feed (sub-reflection surface) are designed so that the x-polarized wave emitted by the feed is converted into a y-polarized wave through the sub-reflection surface, and then transmitted and phase-modulated through the main transmission surface to generate a quasi-diffraction-free beam. By folding the optical path, the distance between the main and sub-reflection surfaces is reduced to 1 / 3 of the traditional focal length, and finally a low-profile quasi-diffraction-free folded transmission-reflection array is formed.

[0074] The specific steps include:

[0075] (1) Design of a single-layer transmission and reflection unit based on Huygens metasurface

[0076] 1) Structural design: A single-layer dielectric substrate (ε) is adopted. r =2.65, thickness h=3mm), symmetrical metal patches (linewidth w0=1mm, unit period P=24mm) are designed on both sides of the substrate; the patches include an "I-shaped" structure in the y-polarization direction and a "four-opening square ring" structure in the x-polarization direction, which are orthogonally arranged to correspond to the y-polarization transmission and x-polarization reflection functions, respectively, without the need for an additional polarization selection layer, see details. Figure 1 .

[0077] 2) Parameter optimization: In high-frequency applications, reduce the length of the I-shaped crossbar (lcx). y =2~10mm), square ring opening width (d) x =4~16mm); in low-frequency applications, the opposite adjustment is made; the metal line width and substrate thickness need to be selected in combination with processing accuracy (≥0.01mm) and transmission linearity to avoid physical deformation affecting performance.

[0078] (2) Electromagnetic resonance analysis and control parameter design of transmissive and reflective unit

[0079] 1) Equivalent impedance calculation: Based on Huygens metasurface theory, the transmission coefficient (T) and reflection coefficient (R) of the unit cell are extracted by simulation, and the equivalent electrical admittance (Y) is calculated using formulas (1) and (2). es ) and equivalent magnetic impedance (Z ms Verification of the electro-magnetic resonance excitation effect:

[0080] (1)

[0081] (2)

[0082] Where η is the free-space wave impedance (≈377Ω). Simulation results are as follows: Figure 2 As shown, the unit has three magnetic resonant points (f) at 5.8 GHz. M1 =4.8GHz, f M2 =5.9GHz, f M3 =6.9GHz) and one electric resonant point (f E1 =5.8GHz), satisfying the Huygens resonance condition.

[0083] 2) Current distribution verification: under y-polarized incident conditions, f M1 / f M3 Reverse currents (equivalent magnetic dipoles) are induced in the upper and lower layers of the I-shaped / square ring structure, f E1 The I-shaped and square rings on the same layer induce currents in the same direction (equivalent to electric dipoles); when x-polarized incident, the current concentrates in the square ring, forming high reflection, verifying the dual-polarization function, specifically as follows: Figure 3 As shown.

[0084] 3) Selection of control parameters: Select d x (Square ring opening width), lcx y (Length of the I-beam crossbar), lcy y (Length of the I-shaped vertical bar) is the core parameter, d x Increasing this value shifts fM1 / fM2 to the right, lcx y Increasing this value shifts fM1 / fM3 to the left, achieving full y-polarization phase coverage and high x-polarization reflection at 5.8 GHz.

[0085] (3) Polarization conversion reflective unit and integrated feed design

[0086] 1) Polarization conversion unit: A single-layer dielectric substrate (h=3mm) is used, with a 45° symmetrical double L-shaped metal patch (P=20mm, R1=18mm, L1=16mm) on the upper side and a metal ground plane on the lower side; the polarization conversion reflection coefficient at 5.8GHz is better than -0.35dB, and the reflection phase fluctuation is <5°, achieving x→y polarization conversion, specifically as follows... Figure 4 As shown.

[0087] 2) Integrated feed source: Integrating a 2×2 microstrip patch array (Sub x =60mm×60mm, gain≈10.98dBi, E / H plane 3dB beamwidth≈52° / 53.3°) integrated with the polarization conversion unit, the feed back-feed is installed on the reserved window of the sub-reflector to avoid obstruction and ensure radiation uniformity, specifically as follows Figure 5 As shown.

[0088] (4) Phase distribution and array arrangement of quasi-diffraction-free folded transmission and reflection array

[0089] 1) Derivation of phase distribution: Based on the theory of diffraction-free beams, the main transmission surface needs to be compensated by the spherical wavefront to become a conical wavefront. The phase distribution formula is shown in (3):

[0090] (3)

[0091] Where k is the wave number, F = 180 mm (focal length), and θ = 10° (half-angle of the cone). (azimuth)

[0092] 2) Array Arrangement: The main transmission surface has an aperture of D = 480mm (20 periodic units of 24mm each). Based on the phase distribution, 12 transmission and reflection units are arranged as shown in Table 1. The distance between the sub-reflecting surface and the main transmission surface is F / 3 = 60mm, forming a folded structure, as detailed below. Figure 6 As shown.

[0093] (5) System assembly and performance verification: The main transmitting surface is installed vertically, and the secondary reflecting surface is coaxially aligned with the integrated feed, with a spacing of 60mm; the quasi-diffraction-free beam (stable axial bright spot channel) is verified by electric field scanning test, and the receiving power enhancement effect is verified by energy transfer experiment, as detailed below. Figure 7 As shown.

[0094] Example 13:

[0095] Verification of a polarization-selective transmission-reflection quasi-diffraction-free beam generation array design method based on Huygens metasurfaces, as follows:

[0096] Taking the design of a transflective array for 5.8GHz microwave wireless power transmission as an example, this array has quasi-diffraction-free beamforming capabilities. The specific implementation of this invention is demonstrated through simulation verification. Firstly, a transflective unit based on a Huygens metasurface is designed, such as... Figure 1 As shown. The transmission unit period is... Dielectric substrate thickness Metal line width These parameters are fixed and identical across each transmission unit. In the y-polarization direction, to achieve phase modulation from 0° to 360° while maintaining high transmission, the y-polarization is adjusted at 5.8 GHz. es and Z ms While maintaining the same purely imaginary numbers, their values ​​vary within a certain range. In the x-polarization direction, to achieve only high-efficiency reflection, at 5.8 GHz, Y... es and Z ms While using the opposite purely imaginary number, ensure that the resulting reflection phase error is within 5°. Ultimately, as... Figure 8 The 12 transmissive and reflective unit structures are numbered to ensure that their transmission phase is uniformly distributed within the range of 0° to 360°. Table 1 lists the detailed control parameters of this unit.

[0097] Table 1. Control parameters and transmission coefficients of the 12 units covering 360°

[0098]

[0099] A 2×2 microstrip patch array (with polarization conversion unit) with a gain of 10.98 dBi was selected as the integrated feed source, according to... Figure 7 To illustrate, the equivalent focal length from the feed phase center to the main transmission surface is selected as F=180mm, and the side length of the main transmission surface is set as D=48mm (20 transmission and reflection units with a period of 24mm), with a quasi-diffraction-free beam conical half-angle. Maximum non-diffraction distance Approximately 1361 mm; according to equation (3), the phase distribution diagram of the main transmission surface is as follows: Figure 9 As shown in (a). Based on the calculated phase distribution and the transmission phase of the transmissive and reflective elements in Table 1, the element distribution of the main transmission surface is designed as follows. Figure 9 As shown in (b). Under the above settings, the radial electric field distribution obtained by electromagnetic simulation software (CSTMicrowaveStudio) is as follows. Figure 10 As shown, the receiving power at a receiver aperture of 143mm × 250mm is as follows Figure 11 As shown, the quasi-diffraction-free folded transmission-reflection array design method proposed in this invention can form high-quality quasi-diffraction-free beams: such as... Figure 10As shown, within the theoretically designed maximum non-diffraction distance, a bright spot channel with a stable width (3dB focal spot radius 50mm) appears at the center of the electric field distribution; Figure 11 The received power was compared between the feed only (patch antenna) and the loaded folded transflector array. As the receiving surface moves further away from the main transmitting surface, the decrease in received power after loading the array slows significantly. Within the range of 500mm to 1300mm, the received power is 1.82 times that without the array. This demonstrates that this method can effectively improve the energy transmission efficiency of the MWPT system while reducing the system height from 401mm to 66mm (a volume reduction of 83.5%), proving its feasibility in low-profile, high-efficiency electromagnetic systems.

Claims

1. A design method for a polarization-selective transmission-reflection quasi-diffraction-free beamforming array based on a Huygens metasurface, characterized in that, Includes the following steps: Step 1) Based on Huygens' metasurface theory, design a single-layer transmission and reflection unit; Step 2) Use a single-layer transmission-reflection unit as the main transmission surface, and design polarization conversion reflection units and sub-reflection surfaces to construct a low-profile quasi-diffraction-free folded transmission-reflection array. The polarization conversion reflection unit is used to convert the x-polarized wave emitted by the feed source into a y-polarized wave via the sub-reflector surface. The main transmission surface and the sub-reflector surface perform transmission phase modulation on the y-polarized wave to generate a quasi-diffraction-free beam.

2. The design method for a polarization-selective transmission-reflection quasi-diffraction-free beamforming array based on a Huygens metasurface according to claim 1, characterized in that, The single-layer transmissive and reflective unit includes a single-layer dielectric substrate and an orthogonally polarized electric resonant structure located on the same side of the single-layer dielectric substrate.

3. The design method for a polarization-selective transmission-reflection quasi-diffraction-free beamforming array based on a Huygens metasurface according to claim 2, characterized in that, Orthogonal polarization electric resonant structures include an I-shaped structure located in the y-polarization direction and a four-opening square ring structure located in the x-polarization direction.

4. The design method for a polarization-selective transmission-reflection quasi-diffraction-free beamforming array based on a Huygens metasurface according to claim 3, characterized in that, The I-shaped structure and the four-opening square ring structure are arranged orthogonally to realize the y-polarized transmission and x-polarized reflection functions, respectively.

5. The design method for a polarization-selective transmission-reflection quasi-diffraction-free beamforming array based on a Huygens metasurface according to claim 3, characterized in that, The dimensional parameters of the I-shaped structure and the four-opening square ring structure are determined by the application frequency and transmission linearity.

6. The design method for a polarization-selective transmission-reflection quasi-diffraction-free beamforming array based on a Huygens metasurface according to claim 1, characterized in that, The single-layer transmissive and reflective unit excites Huygens transmission resonance in the y-polarization direction, achieving high transmission efficiency and 360° full-phase control. The single-layer transmissive and reflective unit has a transmission coefficient greater than -0.99dB at frequencies of 5.5GHz-6.5GHz.

7. The design method for a polarization-selective transmission-reflection quasi-diffraction-free beamforming array based on a Huygens metasurface according to claim 1, characterized in that, The single-layer transmissive and reflective unit excites Huygens reflection resonance in the x-polarization direction to achieve high reflection efficiency; The single-layer transmissive and reflective unit has a reflection coefficient greater than -0.83dB and a phase fluctuation of less than 5° at frequencies of 5.3GHz-6GHz.

8. The design method for a polarization-selective transmission-reflection quasi-diffraction-free beamforming array based on a Huygens metasurface according to claim 1, characterized in that, The polarization conversion reflection unit includes a single-layer dielectric substrate, a 45° symmetrical double L-shaped metal patch on the upper surface of the single-layer dielectric substrate, and a metal ground on the lower surface of the single-layer dielectric substrate.

9. The design method for a polarization-selective transmission-reflection quasi-diffraction-free beamforming array based on a Huygens metasurface according to claim 1, characterized in that, The sub-reflective surface is a microstrip patch array; The microstrip patch array is integrated with the polarization conversion reflector unit.

10. The design method for a polarization-selective transmission-reflection quasi-diffraction-free beamforming array based on a Huygens metasurface according to claim 1, characterized in that, The principal transmission surface compensates the spherical wavefront for a conical wavefront, and the phase distribution of the conical wavefront is shown below: （1） Where k is the wave number, F is the focal length, and θ is the half-angle of the cone. It is the azimuth angle; For unit The phase distribution.

Images