A transmissive metasurface unit, a transmissive metasurface array and a design method

Abstract

The application discloses a kind of transmission metasurface unit, transmission metasurface array and design method, belong to transmission metasurface communication technical field.It includes dielectric substrate, top metal layer being arranged in the first surface of dielectric substrate and bottom metal layer being arranged in the second surface of dielectric substrate, the structure of bottom metal layer is strip-shaped open square ring, strip-shaped open square ring includes four structures same strip-shaped metal sheet being distributed along the symmetry of dielectric substrate four around, and adjacent strip-shaped metal sheet is not closed connection;The structure of top metal layer is angular open square ring, angular open square ring includes four structures same right-angle metal sheet group being distributed along the symmetry of dielectric substrate four around, and adjacent right-angle metal sheet is equipped with same open gap, the length of strip-shaped metal sheet l And the open gap of right-angle metal sheet g Satisfy C Constant. By adjusting a group of length l And open gap g It can realize the continuous accurate control of transmission phase, simple structure, low processing difficulty.

Description

Technical Field

[0001] This invention belongs to the field of transmission metasurface communication technology, and specifically relates to a transmission metasurface unit, a transmission metasurface array, and a design method. Background Technology

[0002] With the development of fifth-generation (5G) and future mobile communication technologies, millimeter wave bands are widely used due to their abundant spectrum resources. However, millimeter wave signals suffer from high path loss and weak diffraction ability during propagation, and are easily blocked by obstacles such as buildings, resulting in poor signal coverage, especially in dense urban environments where there are serious signal blind spots.

[0003] Millimeter-scale transmission metasurfaces are two-dimensional planar structures based on metamaterials. By adjusting the phase, amplitude, and other characteristics of electromagnetic waves, they can control beam pointing and polarization, providing an effective means to solve the aforementioned signal coverage problem. Currently, phase-gradient metasurfaces based on the generalized Snell's law are a common method for achieving beam deflection. These introduce a linear phase gradient at the metasurface interface, causing a fixed-angle deflection of perpendicularly incident electromagnetic waves. While this method has a clear design principle, it typically suffers from the following limitations: First, in order to achieve a wide range of phase modulation, traditional designs often require the use of complex three-dimensional structures or irregularly shaped units with multiple stacked layers, which significantly increases design complexity, processing difficulty and manufacturing cost.

[0004] For example, Chinese patent document CN202511041665.1 discloses a metasurface based on a nanoresonator and a design method for achieving wavelength classification deflection. The metasurface uses a multi-layer square patch structure that requires precise multi-layer alignment processes, resulting in a complex structure and high manufacturing difficulty.

[0005] Chinese patent document CN202411468476.8 discloses a dynamic control device on a terahertz metasurface transmission wave or surface wave wavefront. The metasurface structure disclosed in this document requires a multi-layer configuration of metal substrate-dielectric layer-metal ring-photosensitive material and a complex external spatial light excitation system, resulting in low integration and system complexity.

[0006] Chinese patent document CN202411634360.7 discloses a high-gain, large-angle beam deflection antenna based on a metasurface. The metasurface structure adopts a multi-layer stacked structure and various irregularly shaped patches, and must maintain a precise distance from the antenna, which makes it impossible to use it as a standalone device.

[0007] Secondly, a single phase gradient design can only generate a fixed beam deflection angle. In practical broadband coverage scenarios, this design will produce a deep radiation pattern null (i.e., a "null") at non-target angles, resulting in a narrow signal enhancement range and an inability to achieve uniform broadband coverage. For example, existing technologies (such as patent document CN202511041665.1) can typically only achieve deflection around a single angle, such as 25°-30° or 41°-43°, leaving a large number of signal dead zones in broadband areas such as 20°-70°.

[0008] Furthermore, when attempting to increase the physical size of metasurface arrays to improve gain, the performance of cells located at the array edges often deteriorates at larger incident angles, leading to a decrease in the overall efficiency of large-scale arrays. The paper "Optically Transparent Metasurfaces for Wide-Angle Transmission Enhancement in 5G Millimeter Waves" points out that the transmission amplitude of most cells decreases significantly when the incident angle increases to 20°-40°, which limits the realization of high-performance large-scale arrays.

[0009] In summary, there is an urgent need in this field for a transmission metasurface solution that is simple in structure, easy to fabricate, capable of achieving stability in a wide-angle domain, uniform signal gain response, and has good scalability. Summary of the Invention

[0010] To overcome the aforementioned shortcomings of existing technologies, the main objective of this invention is to provide a novel transmissive metasurface unit, transmissive metasurface array, and design method for transmissive metasurface units. The transmissive metasurface unit provided by this invention solves the problems of high processing difficulty, low yield, and high manufacturing cost caused by the complex multilayer or three-dimensional structures commonly used in existing transmissive metasurfaces to achieve wide-range phase modulation. Furthermore, the transmissive metasurface unit array provided by this invention solves the problems of fixed beam deflection angles and narrow signal enhancement angular domains in traditional metasurfaces based on a single phase gradient, resulting in discontinuous signal coverage and blind zones.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a transmissive metasurface unit, comprising a dielectric substrate, a top metal layer disposed on a first surface of the dielectric substrate, and a bottom metal layer disposed on a second surface of the dielectric substrate; The bottom metal layer has a strip-shaped open square ring structure, comprising four identical strip-shaped metal sheets symmetrically distributed around the perimeter of the dielectric substrate, with adjacent strip-shaped metal sheets not closed connections; the length of each strip-shaped metal sheet is defined as... l ; The top metal layer has a angular open square ring structure, which comprises four identical right-angled metal sheets symmetrically distributed around the perimeter of the dielectric substrate, with adjacent right-angled metal sheets having the same opening gap; the distance between the opening gaps is defined as... g ; The length of the strip metal sheet l The gap between the opening of the right-angled metal sheet g Satisfy the constraints: ;in, C It is a constant.

[0012] Furthermore, the value of the constant C ranges from 4.2 mm to 4.6 mm; the length l The value ranges from 0.1 mm to (C-0.1) mm.

[0013] Furthermore, the dielectric substrate is made of a low-loss microwave dielectric material with a dielectric constant range of 3.0-4.0 and a loss tangent of less than 0.005.

[0014] Furthermore, the top view of the dielectric substrate is a square, the side length of the square is 4.5mm-5.5mm, and the thickness of the dielectric substrate is 1.4mm-1.6mm.

[0015] Secondly, the present invention provides a transmissive metasurface array, comprising a plurality of the aforementioned transmissive metasurface units, wherein the plurality of transmissive metasurface units are arranged in a two-dimensional periodic pattern; the plurality of transmissive metasurface units are divided into at least two sub-array regions along a first direction, wherein the transmissive metasurface units in different sub-array regions have different phase gradient distributions to correspond to different target transmission angles respectively.

[0016] Furthermore, the at least two sub-array regions include a first sub-array, a second sub-array, and a third sub-array; The first subarray, the second subarray, and the third subarray are arranged sequentially along the first direction; The transmissive metasurface units of the first subarray are configured to have a first linear phase gradient, corresponding to a first target transmission angle θ1; The transmissive metasurface units of the second subarray are configured to have a second linear phase gradient, corresponding to the second target transmission angle θ2; The transmissive metasurface units of the third subarray are configured to have a third linear phase gradient, corresponding to a third target transmission angle θ3; wherein the angles θ1, θ2, and θ3 are all different.

[0017] Furthermore, the first target transmission angle θ1 is 30°, the second target transmission angle θ2 is 45°, and the third target transmission angle θ3 is 60°.

[0018] Furthermore, the transmission metasurface array maintains a transmission efficiency of over 90% in the operating frequency band from 24.5 GHz to 27.5 GHz, and the maximum gain of signal enhancement exceeds 20 dB.

[0019] Thirdly, a design method for the aforementioned transmissive metasurface unit is provided, comprising the following steps: Determine the operating frequency band of the transmissive metasurface unit and the parameters of the dielectric substrate; A structural model of a transmission metasurface unit is constructed: a dielectric substrate, a top metal layer disposed on the first surface of the dielectric substrate, and a bottom metal layer disposed on the second surface of the dielectric substrate. The bottom metal layer has a strip-shaped open square ring structure, which includes four identical strip-shaped metal sheets symmetrically distributed around the perimeter of the dielectric substrate, and adjacent strip-shaped metal sheets are not closed connections. The top metal layer has a angular open square ring structure, which includes four identical right-angled metal sheets symmetrically distributed around the perimeter of the dielectric substrate, and adjacent right-angled metal sheets have the same opening gap. The length of the strip metal sheet is defined as follows: l The distance of the opening gap is defined as g ;length l and opening gap g Satisfy the constraints: ;in, C It is a constant; Determine the parameter mapping relationship: while maintaining the constraint relationship Under the condition of changing the length l The parameter values ​​are used to continuously adjust the transmission phase of the structural model of the transmissive metasurface unit in 360°. Based on electromagnetic simulation, the mapping relationship curve between the length l and the transmission phase value of the structural model of the transmissive metasurface unit is obtained under the target operating frequency band. Select structural parameters: Calculate the required phase gradient based on the target transmission angle, and select the corresponding length based on the mapping curve. l The parameters are used to determine the distance of the opening gap based on the stated constraint relationship. g .

[0020] Furthermore, the process of determining the constant C is as follows: A series of candidate values ​​Ci for the constant Ci i ; For each candidate value C i In its corresponding length l Within the scanning range, the transmission metasurface unit structure model was subjected to parameter scanning simulation using electromagnetic simulation software; among which, for lThe parameter scanning range is 0.1 mm to (C). i -0.1) mm; Based on each candidate value C i The corresponding simulation results yield the corresponding candidate value C. i The lengths of different strip metal sheets in the following transmission metasurface unit l The transmission phase curve corresponding to the value; According to the length of the different strip metal sheets l The transmission phase curve corresponding to the value is used to determine the value of each candidate C. i The maximum coverage phase achievable by the following transmissive metasurface unit; Compare each candidate value C i The maximum coverage phase is selected, and C is chosen to make the maximum coverage phase optimal. i value.

[0021] Compared with the prior art, the present invention has the following beneficial effects: 1. The structure of the transmissive metasurface unit of the present invention adopts a single-layer dielectric substrate and a strip-shaped and angular-shaped open square ring with a double-sided asymmetric multi-opening resonant ring metal pattern. This metasurface unit structure is achieved by adjusting a set of structural parameters (length of the strip metal sheet). l The gap between the openings of the right-angled metal sheet g This allows for continuous and precise control of the transmission phase. Compared to existing metasurface structures, the transmission metasurface unit of this invention employs a passive single-layer double-sided metal structure, which eliminates the need for complex feeding networks or integrated antennas, as well as external excitation sources and active materials. Its simple structure simplifies design and fabrication.

[0022] 2. The transmissive metasurface array provided by this invention, based on array factor superposition, integrates multiple subarrays corresponding to different transmission angles (e.g., 30°, 45°, 60°) in space by periodically arranging the transmissive metasurface units with phase gradients. The incoherent superposition of their radiation fields effectively "fills in" the inherent deep nulls of each individual beam. This makes the synthesized radiation pattern of the array smooth in a wide angular range of 20°-70°, eliminating signal blind zones and achieving uniform and stable gain enhancement in this region.

[0023] 3. Based on the above design of the transmissive metasurface unit and array, high-performance large-scale arrays can be realized. Within the 24.5-27.5 GHz frequency band, the array maintains a high transmission efficiency of over 90% while achieving a maximum gain improvement of over 20 dB. This design method ensures that when the array is expanded to a large size such as 15.6 cm × 15.6 cm, its performance will not significantly degrade due to the decrease in efficiency of the edge units, demonstrating good engineering feasibility.

[0024] Other features and effects of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 A schematic diagram of the structure of a transmission metasurface unit according to an embodiment of the present invention is shown; Figure 2 The lengths of different strip metal sheets in the transmission metasurface unit of this invention are shown in the embodiments. l The transmission phase curve corresponding to the value; Figure 3 The reflection characteristic curve of the transmissive metasurface unit according to an embodiment of the present invention is shown; Figure 4 The transmission characteristic curves of the transmission metasurface unit according to an embodiment of the present invention are shown. Figure 5 A schematic diagram of the structure of a transmission metasurface array according to an embodiment of the present invention is shown; Figure 6 The simulation diagram of the transmission characteristics of the transmission metasurface array in dual polarization mode according to an embodiment of the present invention is shown. Figure 7 The simulation comparison diagram of the transmission characteristics of a single 30° transmission array and a transmission metasurface array using a mixed combination of 30°, 45° and 60° transmission angles is shown in the embodiment of the present invention. Figure 8 The simulation comparison diagram of the transmission characteristics of a single 45° transmission array and a transmission metasurface array using a mixed combination of 30°, 45° and 60° transmission angles is shown in the embodiment of the present invention. Figure 9 The simulation comparison diagram of the transmission characteristics of a single 60° transmission array and a transmission metasurface array using a mixed combination of 30°, 45° and 60° transmission angles is shown in the embodiment of the present invention. Figure 10 The simulation comparison diagram of the transmission characteristics of a single 0° transmission array and a transmission metasurface array using a mixed combination of 30°, 45° and 60° transmission angles is shown in the embodiment of the present invention. The above figures include the following reference numerals: 10, dielectric substrate; 11, top metal layer; 12, bottom metal layer; 21, 30° transmission array; 22, 45° transmission array; 23, 60° transmission array. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] To achieve one of the above objectives, a first aspect of the present invention provides a transmissive metasurface unit, such as... Figure 1 As shown, it includes a dielectric substrate 10, a top metal layer 11 disposed on a first surface of the dielectric substrate, and a bottom metal layer 12 disposed on a second surface of the dielectric substrate; The top metal layer 11 has a angular open square ring structure, which comprises four identical right-angled metal sheets symmetrically distributed around the perimeter of the dielectric substrate, with adjacent right-angled metal sheets having the same opening gap; the distance of the opening gap is defined as... g ; The bottom metal layer 12 has a strip-shaped open square ring structure, comprising four identical strip-shaped metal sheets symmetrically distributed around the perimeter of the dielectric substrate, with adjacent strip-shaped metal sheets not closed connections; the length of each strip-shaped metal sheet is defined as... l ; The length of the strip metal sheet l The gap between the opening of the right-angled metal sheet g Satisfy the constraints: ;in, C It is a constant.

[0029] The structure of the transmissive metasurface unit of this invention consists of a single-layer dielectric substrate and strip-shaped and angular-shaped open square rings with a double-sided asymmetric multi-opening resonant ring metal pattern. This metasurface unit structure is achieved by adjusting a set of structural parameters (length of the strip metal sheet). l The gap between the openings of the right-angled metal sheet g This allows for continuous and precise control of the transmission phase. Compared to existing metasurface structures, the transmission metasurface unit of this invention employs a passive single-layer double-sided metal structure, which eliminates the need for complex feeding networks or integrated antennas, as well as external excitation sources and active materials. Its simple structure simplifies design and fabrication.

[0030] Furthermore, the length of the strip metal sheet in the transmission metasurface unit of the present invention l Gap between the openings of the right-angled metal sheet g By satisfying specific constraints, under these constraints, it is possible to continuously adjust the transmission phase while maintaining the stability of the Huygens resonant frequency, i.e., to maintain... l+g The constant C ensures that the sum of the equivalent path lengths of the two-layer structure remains stable when adjusting the parameters, thus preventing drastic drift in the resonant center frequency.

[0031] In this invention, the constant C is not a uniquely determined number, but is determined based on the structural simulation of the transmission metasurface unit using electromagnetic simulation software. The specific determination process is as follows: Electromagnetic simulation software is used to calculate different constants C... i The following parameters l Perform parameter scanning on the values. l The parameter scanning range is from 0.1 mm to (C-0.1) mm (for example, taking C sequentially). i Perform several parameter scans for values ​​such as 4.0, 4.1, 4.2, ..., 4.9, 5.0, etc., for example, C. i When the value is 4.2, the parameter l The scanning range is 0.1mm to 4.1mm; the lengths of different strip-shaped metal sheets in the transmission metasurface unit are obtained from electromagnetic simulation software. l The transmission phase curve corresponding to the value is determined at the corresponding C. i The maximum coverage phase of the transmissive metasurface unit is determined by the value of C; the optimal value of C is selected to achieve the maximum coverage phase. i The value is a definite constant. C Simulation results show that, when the operating frequency band of the transmission metasurface unit is 24.5-27.5 GHz, the preferred range for the C value is 4.2 to 4.6 mm.

[0032] In some preferred embodiments of the present invention, the dielectric substrate is made of a low-loss microwave dielectric material with a dielectric constant in the range of 3.0-4.0 and a loss tangent of less than 0.005.

[0033] In some preferred embodiments of the present invention, the top view of the dielectric substrate is square, the side length p of the square is 4.5mm-5.5mm, and the thickness h of the dielectric substrate is 1.4mm-1.6mm.

[0034] In some preferred embodiments of the present invention, the width w of both the right-angled metal strip and the strip-shaped metal strip is the same. Further, the preferred range for the width w is 0.1 mm to 0.3 mm.

[0035] In some preferred embodiments of the present invention, the side length s of the square ring in the strip-shaped open square ring is the same as that in the square ring in the angular open square ring. Further, the preferred range for the side length s of the square ring is 0.5-1.0 mm.

[0036] For example, refer to Figure 1 This invention provides a transmissive metasurface unit, comprising a dielectric substrate 10, a top metal layer 11 disposed on a first surface of the dielectric substrate, and a bottom metal layer 12 disposed on a second surface of the dielectric substrate. The dielectric substrate 10 is made of Rogers RO 4003 C material, with a dielectric constant of 3.55 and a loss tangent of 0.0027. The thickness h of the dielectric substrate 10 is 1.524 mm, and the top view of the dielectric substrate 10 is square, with a side length p of 5.2 mm.

[0037] The top metal layer 11 is a square ring with an angular opening, composed of four right-angled metal sheets with identical structures symmetrically distributed around the perimeter of the dielectric substrate, and adjacent right-angled metal sheets have the same opening gap. g The bottom metal layer 12 is a strip-shaped open square ring, composed of four identical strip metal sheets symmetrically distributed around the perimeter of the dielectric substrate. Adjacent strip metal sheets are not closed connections. The length of each strip metal sheet is... l The side length s of both the triangular open square ring and the strip open square ring is 4.8 mm, and the width w of both the strip metal sheet and the right-angled metal sheet is 0.2 mm.

[0038] In this embodiment, the length of the strip metal sheet l Gap between the openings of the right-angled metal sheet g satisfy The constraint relationship is mm. This constraint ensures that during adjustment... l When the electromagnetic response is changed, the resonant frequency of the unit remains basically stable, thereby achieving performance with phase modulation as the main feature and small amplitude fluctuation.

[0039] In this embodiment, l Perform parameter scanning within a range of 0.3mm to 4.3mm with a step size of 0.1mm, and evaluate the parameter scanning results. l Plot the lengths of different strip metal sheets used to control the transmission metasurface unit, with the x-axis representing the length and the y-axis representing the phase. l The transmission phase curve corresponding to the value, such as Figure 2 As shown. In lengths ranging from 0.3mm to 4.3mm. l Within this range, the phase can be continuously adjusted from -90° to -396°. Based on this, in the design of transmission metasurface units, when the target transmission phase is within the range of -90° to -396°, the length of the strip metal sheet... lThe phase error is continuously varied within the range of 0.3mm to 4.3mm. For the remaining phase range that cannot be covered by the continuous adjustment range, the 360° periodicity of the electromagnetic wave transmission phase is utilized, employing a "boundary parameter reuse" strategy for compensation. The -396° to -450° phase range is divided into two parts: -396° to -423° and -423° to -450°. When the phase is in the range of -396° to -423°, the upper limit parameter l=4.3mm of the continuous adjustment range is fixed to minimize the phase error. When the phase is in the range of -423° to -450°, according to the phase periodicity, -450° is equivalent to -90°. Therefore, the lower limit parameter l=0.3mm of the continuous adjustment range is fixed to minimize the phase error and achieve 360° periodic phase adjustment.

[0040] like Figure 3 As shown, this represents the length of the strip metal sheet of the transmission metasurface unit in the above embodiment. l The value is 3.4mm, the opening gap of the right-angled metal sheet. g The graph shows the reflection characteristics of a 1.0 mm metasurface unit. This graph clearly demonstrates the reflection characteristics of the transmissive metasurface unit in the 23 GHz to 29 GHz frequency band. Within the operating frequency range of 24.5 GHz to 27.5 GHz, the reflection coefficient remains consistently below -10 dB. Simulation results indicate that this metasurface unit exhibits excellent impedance matching characteristics within the operating frequency band.

[0041] like Figure 4 As shown, this represents the length of the strip metal sheet of the transmission metasurface unit in the above embodiment. l The value is 3.4mm, the opening gap of the right-angled metal sheet. g The graph shows the transmission characteristics of a 1.0 mm metasurface unit. This graph clearly demonstrates the transmission performance of the metasurface unit in the 23 GHz to 29 GHz frequency band. Within the operating frequency range of 24.5 GHz to 27.5 GHz, the transmission coefficient consistently remains above -1 dB. Simulation results show that throughout the entire 3 GHz bandwidth, the transmission coefficient consistently significantly exceeds -1 dB (corresponding to 90% transmission efficiency), exhibiting excellent transmission characteristics.

[0042] To overcome the problem of uneven wide-angle coverage caused by traditional single phase gradient design, a second aspect of the present invention provides a transmissive metasurface array, including a plurality of the aforementioned transmissive metasurface units, wherein the plurality of transmissive metasurface units are arranged in a two-dimensional periodic manner; the plurality of transmissive metasurface units are divided into at least two sub-array regions along a first direction, wherein the transmissive metasurface units in different sub-array regions have different phase gradient distributions to correspond to different target transmission angles respectively.

[0043] This invention adjusts the phase gradient distribution of each subarray by superimposing array factors in different subarray regions, thereby achieving energy redistribution of the transmitted beam in a wide-angle domain. This improves the deep null point problem in the radiation pattern caused by single-angle deflection and enhances the signal within a preset wide-angle range. The method of adjusting the phase gradient distribution of each subarray involves periodically adjusting the length of a set of strip metal sheets within the transmission metasurface unit. l Gap between the openings of the right-angled metal sheet g The size relationship enables the phase gradient distribution.

[0044] In a preferred embodiment of the present invention, the at least two sub-array regions include a first sub-array, a second sub-array, and a third sub-array; The first subarray, the second subarray, and the third subarray are arranged sequentially along the first direction; The transmissive metasurface units of the first subarray are configured to have a first linear phase gradient, corresponding to a first target transmission angle θ1; The transmissive metasurface units of the second subarray are configured to have a second linear phase gradient, corresponding to the second target transmission angle θ2; The transmissive metasurface units of the third subarray are configured to have a third linear phase gradient, corresponding to a third target transmission angle θ3; wherein the angles θ1, θ2, and θ3 are all different.

[0045] In an optional embodiment of the present invention, the first target transmission angle θ1 is 30°, the second target transmission angle θ2 is 45°, and the third target transmission angle θ3 is 60°.

[0046] It should be noted that the target transmission angle of the subarray is not limited to the combination of 30° / 45° / 60°, and can be adjusted to any combination according to the actual base station location and coverage requirements. The number of subarrays can also be increased to 4 or more.

[0047] For example, such as Figure 5 As shown, a transmissive metasurface array is provided, which is composed of 30×30 transmissive metasurface units arranged periodically, with an area of ​​15.6cm×15.6cm. It is divided into three sub-array regions along the X-axis, namely 30° transmissive array 21, 45° transmissive array 22, and 60° transmissive array 23. Each sub-array region is composed of 10×30 transmissive metasurface units with the same phase gradient arranged periodically.

[0048] Among them, the transmissive metasurface units in the 30° transmission array 21, 45° transmission array 22, and 60° transmission array 23 are all made of strip metal sheets with the same length as other structures. lThe aforementioned embodiments are constructed using transmissive metasurface units with different values ​​for the g-value and the gap between the right-angled metal sheet openings. The length of the strip metal sheet in each subarray region of the transmissive metasurface unit is precisely controlled. l The value and the gap g of the right-angled metal sheet opening cause a specific phase gradient between each subarray unit.

[0049] The implementation of each subarray's function depends on the distinct linear phase gradient distributions calculated based on its target deflection angle. The calculation formula is as follows: ,in, The target's transmission angle. The wavelength corresponding to the center frequency of the metasurface unit. Let be the side length of the metasurface unit. This represents the required phase gradient at the target transmission angle.

[0050] In this embodiment, the center frequency of the metasurface unit is 26 GHz. It is 11.54mm. The length is 5.2mm. Using the above formula, the required phase gradients for transmission angles of 30°, 45°, and 60° are calculated to be 81.1°, 114.7°, and 140.5°, respectively. The length of the strip metal is then selected accordingly. l The initial value for each subarray is 0.3 mm (φ = -90.46°). The initial phase φ = -90.46° is continuously reduced by 81.1° (114.7° / 140.5°) to obtain 10 different phase values ​​at a transmission angle of 30° (45° / 60°). When the phase is below -450°, 360° is added to the phase to satisfy the periodic variation. Within the phase period of -90° to -450°, the corresponding transmission angles at 30°, 45°, and 60° are obtained based on different phase values. l The values ​​are shown in the table below.

[0051]

[0052] Note: l 1~ l 10 These figures represent the lengths of the bottom strip metal sheets of 10 transmission metasurface units arranged along the positive x-axis from the origin, all in mm. Along the longitudinal y-axis, the lengths of the bottom strip metal sheets in each column of transmission metasurface units are identical. Figure 5 In the array, 21 is a 30° transmission array, 22 is a 45° transmission array, and 23 is a 60° transmission array.

[0053] like Figure 6As shown, the simulation results of the transmission characteristics of the transmissive metasurface array of the above embodiment at three frequency points of 24.5 GHz, 26 GHz, and 27.5 GHz for two polarization modes: TE (transverse electric wave) and TM (transverse magnetic wave). From the curve distribution above, it can be seen that all combinations achieved signal enhancement in the range of 20° to 70°, with the maximum gain improvement exceeding 20 dB.

[0054] The traditional single 30° transmission array, 45° transmission array, and 60° transmission array (the 30° transmission array is about to be replaced) Figure 5 In the original text, parts 22 and 23 are both changed to 21 (the same applies to the 45° and 60° transmission arrays). The transmission characteristics of the transmissive metasurface array in the TE polarization mode at a center frequency of 26 GHz are simulated and compared with those of the embodiment of this invention using a combination of 30°, 45°, and 60° transmission angles. The results are as follows: Figure 7-9 As shown, Figure 7-9 The effect of array factor superposition on the compensation of zeros in the radiation pattern is clearly demonstrated. The 30° transmission curve exhibits sharp zeros at certain angles, while the hybrid-angle transmission metasurface array of this invention significantly improves these zeros by 13dB, 16dB, 14dB, and 13dB respectively through the incoherent superposition of multi-angle array factors. The 45° transmission curve also exhibits sharp zeros at certain angles, while the hybrid-angle transmission metasurface array of this invention significantly improves these zeros by 22dB, 25dB, 16dB, 15dB, and 9dB respectively through the incoherent superposition of multi-angle array factors. Similarly, the 60° transmission curve shows sharp zeros at certain angles, while the hybrid-angle transmission metasurface array of this invention significantly improves these zeros by 17dB, 15dB, 15dB, 13dB, and 14dB respectively through the incoherent superposition of multi-angle array factors. This compensation mechanism stems from the fact that multi-beam interference disrupts the strict destructive condition of a single angle, resulting in a smoother transition in the radiation pattern within the 30° to 60° range. In addition, a 0° transmission array was designed (without any metal structure, i.e., without the top metal layer corner-shaped opening square ring and the bottom metal layer strip-shaped opening square ring of the present invention, and its array size is similar to...). Figure 5 A simulation comparison of the transmission characteristics of a 15.6cm × 15.6cm dielectric array (of the same size) and a transmission metasurface array using a combination of 30°, 45°, and 60° transmission angles in this invention was performed. Figure 10 As shown, the hybrid-angle transmission metasurface array of the present invention achieves an average signal enhancement of more than 10 dB in the target angle range of 20° to 70° compared to 0° transmission.

[0055] In summary, the transmissive metasurface array unit provided by this invention exhibits excellent performance in the 24.5~27.5GHz operating frequency band: it not only achieves a dual-polarization operating mode with a transmission efficiency consistently above 90%, but also extends the signal enhancement angular domain to 20°~70°, with a maximum gain increase of 20dB. Its area is 15.6cm×15.6cm, and the array size is more than 13×13 times the center frequency wavelength.

[0056] A third aspect of the present invention provides a design method for the aforementioned transmissive metasurface unit, comprising the following steps: Determine the operating frequency band of the transmissive metasurface unit and the parameters of the dielectric substrate; A structural model of a transmission metasurface unit is constructed: a dielectric substrate, a top metal layer disposed on the first surface of the dielectric substrate, and a bottom metal layer disposed on the second surface of the dielectric substrate. The bottom metal layer has a strip-shaped open square ring structure, which includes four identical strip-shaped metal sheets symmetrically distributed around the perimeter of the dielectric substrate, and adjacent strip-shaped metal sheets are not closed connections. The top metal layer has a angular open square ring structure, which includes four identical right-angled metal sheets symmetrically distributed around the perimeter of the dielectric substrate, and adjacent right-angled metal sheets have the same opening gap. The length of the strip metal sheet is defined as follows: l The distance of the opening gap is defined as g ;length l and opening gap g Satisfy the constraints: ;in, C It is a constant; Determine the parameter mapping relationship: while maintaining the constraint relationship Under the condition of changing the length l The parameter values ​​are used to continuously adjust the transmission phase of the structural model of the transmissive metasurface unit in 360°. Based on electromagnetic simulation, the mapping relationship curve between the length l and the transmission phase value of the structural model of the transmissive metasurface unit is obtained under the target operating frequency band. Select structural parameters: Calculate the required phase gradient based on the target transmission angle, and select the corresponding length based on the mapping curve. l The parameters are used to determine the distance of the opening gap based on the stated constraint relationship. g .

[0057] In one specific embodiment of the present invention, the process of determining the constant C is as follows: A series of candidate values ​​Ci for the constant Ci i ; For each candidate value C i In its corresponding lengthl Within the scanning range, the transmission metasurface unit structure model was subjected to parameter scanning simulation using electromagnetic simulation software; among which, for l The parameter scanning range is 0.1 mm to (C). i -0.1) mm; Based on each candidate value C i The corresponding simulation results yield the corresponding candidate value C. i The lengths of different strip metal sheets in the following transmission metasurface unit l The transmission phase curve corresponding to the value; According to the length of the different strip metal sheets l The transmission phase curve corresponding to the value is used to determine the value of each candidate C. i The maximum coverage phase achievable by the metasurface unit described below; Compare each candidate value C i The maximum coverage phase is selected, and C is chosen to achieve the optimal value of the maximum coverage phase. i value.

[0058] In one specific embodiment of the present invention, the formula for calculating the phase gradient based on the target transmission angle is as follows: ; in, The target's transmission angle. The wavelength corresponding to the center frequency of the metasurface unit. Let be the side length of the metasurface unit. This represents the required phase gradient at the target transmission angle.

[0059] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A transmissive metasurface unit, characterized in that, It includes a dielectric substrate, a top metal layer disposed on a first surface of the dielectric substrate, and a bottom metal layer disposed on a second surface of the dielectric substrate; The bottom metal layer has a strip-shaped open square ring structure, comprising four identical strip-shaped metal sheets symmetrically distributed around the perimeter of the dielectric substrate, with adjacent strip-shaped metal sheets not closed connections; the length of each strip-shaped metal sheet is defined as... l ; The top metal layer has a angular open square ring structure, which comprises four identical right-angled metal sheets symmetrically distributed around the perimeter of the dielectric substrate, with adjacent right-angled metal sheets having the same opening gap; the distance between the opening gaps is defined as... g ; The length of the strip metal sheet l The gap between the opening of the right-angled metal sheet g Satisfy the constraints: ;in, C It is a constant.

2. The transmission metasurface unit according to claim 1, characterized in that, The constant C ranges from 4.2 mm to 4.6 mm; the length l The value ranges from 0.1 mm to (C-0.1) mm.

3. The transmission metasurface unit according to claim 1, characterized in that, The dielectric substrate uses a low-loss microwave dielectric material with a dielectric constant range of 3.0-4.0 and a loss tangent of less than 0.

005.

4. The transmission metasurface unit according to any one of claims 1 to 3, characterized in that, The dielectric substrate has a square top view, with a side length of 4.5mm-5.5mm and a thickness of 1.4mm-1.6mm.

5. A transmissive metasurface array, characterized in that, It includes a plurality of transmissive metasurface units as described in any one of claims 1 to 4, wherein the plurality of transmissive metasurface units are arranged in a two-dimensional periodic manner; the plurality of transmissive metasurface units are divided into at least two sub-array regions along a first direction, wherein the transmissive metasurface units in different sub-array regions have different phase gradient distributions to correspond to different target transmission angles respectively.

6. The transmissive metasurface array according to claim 5, characterized in that, The at least two sub-array regions include a first sub-array, a second sub-array, and a third sub-array; The first subarray, the second subarray, and the third subarray are arranged sequentially along the first direction; The transmissive metasurface units of the first subarray are configured to have a first linear phase gradient, corresponding to a first target transmission angle θ1; The transmissive metasurface units of the second subarray are configured to have a second linear phase gradient, corresponding to the second target transmission angle θ2; The transmissive metasurface units of the third subarray are configured to have a third linear phase gradient, corresponding to a third target transmission angle θ3; wherein the angles θ1, θ2, and θ3 are all different.

7. The transmissive metasurface array according to claim 6, characterized in that, The first target has a transmission angle θ1 of 30°, the second target has a transmission angle θ2 of 45°, and the third target has a transmission angle θ3 of 60°.

8. The transmissive metasurface array according to any one of claims 5 to 7, characterized in that, The transmissive metasurface array maintains a transmission efficiency of over 90% in the operating frequency band from 24.5 GHz to 27.5 GHz, and the maximum gain of signal enhancement exceeds 20 dB.

9. A design method for a transmission metasurface unit as described in claim 1, characterized in that, Includes the following steps: Determine the operating frequency band of the transmissive metasurface unit and the parameters of the dielectric substrate; A structural model of a transmission metasurface unit is constructed: a dielectric substrate, a top metal layer disposed on the first surface of the dielectric substrate, and a bottom metal layer disposed on the second surface of the dielectric substrate. The bottom metal layer has a strip-shaped open square ring structure, which includes four identical strip-shaped metal sheets symmetrically distributed around the perimeter of the dielectric substrate, and adjacent strip-shaped metal sheets are not closed connections. The top metal layer has a angular open square ring structure, which includes four identical right-angled metal sheets symmetrically distributed around the perimeter of the dielectric substrate, and adjacent right-angled metal sheets have the same opening gap. The length of the strip metal sheet is defined as follows: l The distance of the opening gap is defined as g ; length l and opening gap g Satisfy the constraints: ;in, C It is a constant; Determine the parameter mapping relationship: while maintaining the constraint relationship Under the condition of changing the length l The parameter values ​​are used to continuously adjust the transmission phase of the structural model of the transmissive metasurface unit in 360°. Based on electromagnetic simulation, the mapping relationship curve between the length l and the transmission phase value of the structural model of the transmissive metasurface unit is obtained under the target operating frequency band. Select structural parameters: Calculate the required phase gradient based on the target transmission angle, and select the corresponding length based on the mapping curve. l The parameters are used to determine the distance of the opening gap based on the stated constraint relationship. g .

10. The design method of the transmission metasurface unit according to claim 9, characterized in that, The process of determining the constant C is as follows: A series of candidate values ​​Ci for the constant Ci i ; For each candidate value C i In its corresponding length l Within the scanning range, the transmission metasurface unit structure model was subjected to parameter scanning simulation using electromagnetic simulation software; among which, for l The parameter scanning range is 0.1 mm to (C). i -0.1) mm; Based on each candidate value C i The corresponding simulation results yield the corresponding candidate value C. i The lengths of different strip metal sheets in the following transmission metasurface unit l The transmission phase curve corresponding to the value; According to the length of the different strip metal sheets l The transmission phase curve corresponding to the value is used to determine the value of each candidate C. i The maximum coverage phase achievable by the following transmissive metasurface unit; Compare each candidate value C i The maximum coverage phase is selected, and C is chosen to make the maximum coverage phase optimal. i value.

Images