A Huygens metasurface unit and planar transmission array antenna

Abstract

The present invention discloses a Huygens metasurface unit and a planar transmission array antenna, relating to the field of Huygens metasurface design. The Huygens metasurface unit comprises: a dielectric substrate, an upper metal structure, and a lower metal structure; the upper and lower metal structures are disposed on the upper and lower surfaces of the dielectric substrate, respectively; the two metal structures are antisymmetric; each metal structure comprises: a first metal layer, a second metal layer perpendicular to the first metal layer, a variable metal layer, and a third metal layer; the first metal layer has two ends connected to the first ends of the second and third metal layers, respectively; the variable metal layer is located between the second and third metal layers, and its first end is connected to the first metal layer; the projection of the upper metal structure on the lower surface of the dielectric substrate overlaps with the lower metal structure; when an incident wave enters the Huygens metasurface unit, the transmission phase changes by adjusting the length of the variable metal layer. The present invention has a simple structure and is easy to design and process.

Description

Technical Field

[0001] The present invention relates to the field of Huygens metasurface design, and in particular to a Huygens metasurface unit and a planar transmission array antenna. Background Art

[0002] Metasurfaces are planar metamaterials that, like traditional three-dimensional metamaterials, possess powerful electromagnetic wave control capabilities. Metasurfaces are generally classified into two types: reflective and transmissive. However, for transmissive metasurfaces, achieving both high transmittance and 360° transmission phase control using single or double-layer metal structures is difficult.

[0003] In order for traditional metasurfaces to achieve 360° transmission phase control while maintaining high transmittance, they require at least three layers of metal structures. However, multi-layer metal transmission structures are complex, the manufacturing process is difficult, and the cost is high, which brings difficulties to the miniaturization and processing of metasurface structures. As a new type of metasurface, the Huygens metasurface has a unit structure composed of an electric resonance part and a magnetic resonance part, which respectively regulate the electric field and the magnetic field, thereby achieving free regulation of electromagnetic waves. The Huygens metasurface greatly expands the degree of freedom of the metasurface to regulate electromagnetic waves, making it possible to simultaneously achieve high transmittance and 360° transmission phase control using only one dielectric plate and two layers of metal structure. Due to the excellent control ability of Huygens metasurfaces on electromagnetic waves, they are widely used in the design of beam deflection, flat lenses, polarization converters, imaging systems, etc., and have therefore attracted widespread attention.

[0004] In recent years, scholars have designed different Huygens metasurface units. For example, the patent document with Chinese patent publication number CN110380222A discloses a Huygens metasurface unit. The unit includes a dielectric substrate, an upper metal layer located on the upper surface of the dielectric substrate, and a lower metal layer located on the lower surface of the dielectric substrate. The upper metal layer and the lower metal layer both include open metal resonant rings, and metal patches are embedded inside the metal resonant rings. The opening positions of the open metal resonant rings of the upper metal layer and the open metal resonant rings of the lower metal layer are antisymmetric. The unit structure operates at 13GHz, and by changing the two structural parameters of the unit at the same time, it can achieve 360° transmission phase control while keeping the transmission loss higher than -2.5dB. The patent document with Chinese patent publication number CN109994836A discloses a Huygens metasurface unit. The metasurface transmission unit consists of two axisymmetric composite metal structures and a dielectric plate. The upper composite metal structure consists of two interconnected concentric arcs, each opening upward. The lower composite metal structure is axisymmetric with the upper one, with the concentric arcs opening downward and the outer arcs overlapping. When operating at 24 GHz, 26 GHz, and 28 GHz, the transmission phase can be adjusted by a total of 405°, 427°, and 481°, respectively, while the transmission loss is consistently above -2.3 dB. However, the unit also requires simultaneous adjustment of two structural parameters.

[0005] The Huygens metasurface units in the aforementioned patent can achieve 360° transmission phase control at high transmittance, but this requires changing two or more structural parameters. This results in significant structural differences between units controlling different transmission phases, making the design and fabrication of the metasurface array complex and cumbersome. Summary of the Invention

[0006] Based on this, an embodiment of the present invention provides a Huygens metasurface unit and a planar transmission array antenna, which have a simple structure and are easy to design and process.

[0007] To achieve the above objectives, the present invention provides the following solutions:

[0008] A Huygens metasurface unit comprises: a dielectric substrate and two identical metal structures; the two metal structures are an upper metal structure and a lower metal structure;

[0009] The upper metal structure is located on the upper surface of the dielectric substrate; the lower metal structure is located on the lower surface of the dielectric substrate; the upper metal structure and the lower metal structure are anti-symmetric with respect to the dielectric substrate;

[0010] The metal structure includes: a first metal layer, a second metal layer perpendicular to the first metal layer, a variable metal layer, and a third metal layer; a first end of the first metal layer is connected to a first end of the second metal layer, a second end of the first metal layer is connected to a first end of the third metal layer; a first end of the variable metal layer is connected to the first metal layer, and the variable metal layer is located between the second metal layer and the third metal layer;

[0011] The projection of the upper metal structure on the lower surface of the dielectric substrate has an overlapping area with the lower metal structure;

[0012] When an incident wave enters a Huygens metasurface unit, the transmission phase changes by adjusting the length of the variable metal layer.

[0013] Optionally, a projection of the second metal layer of the upper metal structure on the lower surface of the dielectric substrate has a first overlapping area with the second metal layer of the lower metal structure; a projection of the third metal layer of the upper metal structure on the lower surface of the dielectric substrate has a second overlapping area with the third metal layer of the lower metal structure;

[0014] The first overlapping area is a section on the second metal layer starting from the second end of the second metal layer; the second overlapping area is a section on the third metal layer starting from the second end of the third metal layer; the lengths of the first overlapping area and the second overlapping area are equal.

[0015] Optionally, the first end of the variable metal layer is connected to the midpoint of the first metal layer;

[0016] The distance between the variable metal layer and the second metal layer is equal to the length of the first non-overlapping area; the first non-overlapping area is the area on the second metal layer except the first overlapping area.

[0017] Optionally, the width of the second metal layer and the third metal layer are both 0.2 mm; the length of the second metal layer and the third metal layer are both 3.4 mm; and the adjustment range of the length of the variable metal layer is 0 mm to 4.4 mm.

[0018] Optionally, the lengths of the first overlapping area and the second overlapping area are both 1.3 mm.

[0019] Optionally, both the upper surface and the lower surface of the dielectric substrate are square.

[0020] Optionally, the side lengths of the upper surface and the lower surface of the dielectric substrate are both 5.2 mm; and the thickness of the dielectric substrate is 1.5 mm.

[0021] Optionally, the dielectric constant of the dielectric substrate is 2.2, and the tangent value of the loss angle of the dielectric substrate is 0.001.

[0022] The present invention also provides a planar transmission array antenna, comprising: a transmission array and a feed horn; the transmission array is connected to the feed horn; the transmission array comprises a plurality of the above-mentioned Huygens metasurface units.

[0023] Optionally, the position and structural parameters of each Huygens metasurface unit in the transmission array are determined by a multi-objective optimization algorithm based on a Gaussian random process proxy model; the structural parameters include: the length of the second metal layer, the length of the variable metal layer and the length of the third metal layer.

[0024] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0025] An embodiment of the present invention proposes a Huygens metasurface unit and a planar transmission array antenna. The Huygens metasurface unit has only a single-layer dielectric base and a two-layer metal structure. It has a simple structure and is a thin metasurface unit. It is easy to miniaturize and has higher transmittance and a larger transmission phase control range. The metal structure of the Huygens metasurface unit is "E"-shaped. Only one structural parameter needs to be changed (that is, the length of the variable metal layer) to achieve a transmission amplitude within -2dB and 360° continuous control of the transmission phase. The Huygens metasurface unit requires few structural parameters to be changed, the structural changes are simple, and it is easier to arrange and process the metasurface. The planar transmission array antenna designed based on the Huygens metasurface unit has a simple structure, low cost, and is easy to design and process. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 A schematic structural diagram of a Huygens metasurface unit provided in an embodiment of the present invention;

[0028] Figure 2 An exploded view of a Huygens metasurface unit provided by an embodiment of the present invention;

[0029] Figure 3 A flowchart of designing a transmission array using a multi-objective optimization algorithm based on a Gaussian random process surrogate model provided in an embodiment of the present invention;

[0030] Figure 4A schematic diagram of the upper surface structure of a Huygens metasurface unit provided in an embodiment of the present invention;

[0031] Figure 5 Transmission amplitude and transmission phase diagram of the Huygens metasurface unit provided in an embodiment of the present invention;

[0032] Figure 6 is the surface current distribution diagram of the Huygens metasurface unit at t = 0 in one cycle when the x-polarized wave is incident vertically;

[0033] Figure 7 is the surface current distribution of the Huygens metasurface unit at t = π / 2 within one cycle when the x-polarized wave is incident vertically;

[0034] Figure 8 is the surface current distribution diagram of the Huygens metasurface unit at t = π in one cycle when the x-polarized wave is incident vertically;

[0035] Figure 9 is the surface current distribution diagram of the Huygens metasurface unit at t = π3 / 2 in one cycle when the x-polarized wave is incident vertically;

[0036] Figure 10 Schematic diagram of the upper surface structure of the transmission array antenna when the scanning angle θ is 0°;

[0037] Figure 11 Schematic diagram of the upper surface structure of the transmission array antenna when the scanning angle θ is 30°;

[0038] Figure 12 Schematic diagram of the upper surface structure of the transmission array antenna when the scanning angle θ is 60°;

[0039] Figure 13 The simulation and measured results of the transmission array antenna working at 20GHz.

[0040] Explanation of symbols:

[0041] Upper metal structure—1, dielectric substrate—2, lower metal structure—3. DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0043] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] See Figure 1 and Figure 2 The Huygens metasurface unit of this embodiment exemplarily includes: a dielectric substrate 2 and two layers of identical metal structures; the two layers of metal structures are an upper metal structure 1 and a lower metal structure 3.

[0045] The upper metal structure 1 is located on the upper surface of the dielectric substrate 2 ; the lower metal structure 3 is located on the lower surface of the dielectric substrate 2 ; the upper metal structure 1 and the lower metal structure 3 are anti-symmetric with respect to the dielectric substrate 2 .

[0046] The metal structure is an "E"-shaped structure. The metal structure exemplarily includes: a first metal layer, a second metal layer perpendicular to the first metal layer, a variable metal layer, and a third metal layer; a first end of the first metal layer is connected to a first end of the second metal layer, and a second end of the first metal layer is connected to a first end of the third metal layer; a first end of the variable metal layer is connected to the first metal layer, and the variable metal layer is located between the second metal layer and the third metal layer.

[0047] The projection of the upper metal structure 1 on the lower surface of the dielectric substrate 2 has an overlapping area with the lower metal structure 3 .

[0048] When the incident wave enters the Huygens metasurface unit, when the induced currents in the overlapping area of ​​the upper and lower metal structures are opposite, an equivalent current loop can be formed, thereby generating a magnetic dipole, and at the same time interacting with the surface current of the "E"-shaped structure itself. When the equilibrium condition between the surface current and the induced magnetic current is met, the Huygens resonance is excited, thereby realizing high-transmittance transmission phase control. In this embodiment, the transmission phase changes by adjusting the length of the variable metal layer. In this way, the Huygens metasurface unit only needs to change one structural parameter to achieve 360° continuous transmission phase control, and the transmission loss is higher than -2dB.

[0049] In one example, the projection of the second metal layer of the upper metal structure 1 on the lower surface of the dielectric substrate 2 has a first overlapping area with the second metal layer of the lower metal structure 3; the projection of the third metal layer of the upper metal structure 1 on the lower surface of the dielectric substrate 2 has a second overlapping area with the third metal layer of the lower metal structure 3.

[0050] The first overlapping area is a section on the second metal layer starting from the second end of the second metal layer; the second overlapping area is a section on the third metal layer starting from the second end of the third metal layer; the lengths of the first overlapping area and the second overlapping area are equal.

[0051] In another example, the first end of the variable metal layer is connected to the midpoint of the first metal layer; the distance between the variable metal layer and the second metal layer is equal to the length of the first non-overlapping area; and the first non-overlapping area is the area on the second metal layer excluding the first overlapping area.

[0052] In yet another example, both the upper surface and the lower surface of the dielectric substrate 2 are square.

[0053] Based on the Huygens metasurface unit of the above embodiment, the present invention also provides a planar transmission array antenna, comprising: a transmission array and a feed horn; the transmission array is connected to the feed horn; the transmission array comprises a plurality of the above-mentioned Huygens metasurface units.

[0054] The positions and structural parameters of each Huygens metasurface unit in the transmission array are determined using a multi-objective optimization algorithm based on a Gaussian random process surrogate model, making the design of the transmission array more convenient and efficient. These structural parameters include the length of the second metal layer, the length of the variable metal layer, and the length of the third metal layer. This planar transmission array antenna can operate at 20 GHz.

[0055] The multi-objective optimization algorithm provides a multi-objective optimization framework and a fast global evolution operator, while the Gaussian random process surrogate model provides an accurate and reliable surrogate model that can accurately predict the transmission amplitude and phase of the unit based on the structural parameters of the Huygens metasurface unit. Figure 3 The specific design steps of the transmission array using the multi-objective optimization algorithm based on the Gaussian random process surrogate model are as follows:

[0056] Step 1: Randomly generate N transmission arrays, that is, initialize the population. Each transmission array is composed of different Huygens metasurface units, and the structural parameters of each metasurface unit are determined.

[0057] Step 2: Use the differential evolution operator to generate N new transmission arrays, that is, generate a new population.

[0058] Step 3: Evaluate the fitness of the transmission array, that is, predict and evaluate the radiation performance of the transmission array. To predict the radiation performance of the transmission array, it is first necessary to evaluate the transmission amplitude and phase of each Huygens metasurface unit on the transmission array. The evaluation of the transmission amplitude and phase of the transmission unit does not rely on software modeling simulation and physical testing, but is completed through a Gaussian random process proxy model. The Gaussian random process proxy model predicts the transmission amplitude and phase of the transmission unit based on the structural parameters of the transmission unit. After calculating the transmission amplitude and phase of each metasurface unit on the transmission array, the radiation performance of the transmission array can be calculated, and then the performance of the transmission array can be evaluated. Finally, it is determined whether the radiation performance of the transmission array meets the target conditions. If the conditions are not met, the differential evolution operator is used to generate a new population. When the conditions are met, the process stops and the structural parameters of the different units on the transmission array are output.

[0059] Step 4: Automated modeling of the transmission array. Use the output structural parameters of different units to create a VB script. This script is then used to automatically model and generate the transmission array in HFSS. This script-based automated modeling saves significant time and improves efficiency, convenience, and accuracy for modeling large-scale arrays.

[0060] A specific design example in practical application is given below, and the effectiveness of the designed Huygens metasurface unit and planar transmission array antenna is verified.

[0061] Still see Figure 1 and Figure 2 The Huygens metasurface unit in this example includes a dielectric substrate and two metal structures. The Huygens metasurface unit is a planar structure and is placed horizontally along the xoy plane. Along the positive z-axis square direction are the lower metal structure 3, the middle dielectric substrate 2, and the upper metal structure 1. The Huygens metasurface unit is a square structure with a side length of l = 8mm. The dielectric substrate is made of F4B sheet material, with a dielectric constant of 2.2 and a loss tangent of 0.001. F4B sheet material has a low cost and low loss among high-frequency sheet materials, which reduces processing costs. The thickness of the dielectric substrate of the Huygens metasurface unit is h = 1.5mm, and the overall dimensions of the dielectric substrate are 5.2mm × 5.2mm × 1.5mm. The upper metal structure 1 and the lower metal structure 3 of the Huygens metasurface unit are both made of copper, and both are 0.018mm thick. The upper metal structure 1 and the lower metal structure 3 are both E-shaped structures. The upper metal structure 1 and the lower metal structure 3 of the Huygens metasurface unit are exactly the same size and are symmetrically etched on both sides of the dielectric substrate. Figure 4 As shown, Figure 4The width w of the upper metal structure 1 is 0.2 mm, the length d of the first non-overlapping region is 2.1 mm, the length of the third metal layer is Lo, and the length of the second metal layer is equal to the length of the third metal layer. The distance between the variable metal layer and the second metal layer is equal to the length d of the first non-overlapping region. The length of the variable metal layer is represented by Li. Adjusting Li is to achieve transmission phase control. In this way, control can be achieved by changing a variable of the upper metal structure 1 and the lower metal structure 3. The adjustment range of the length Li of the variable metal layer is 0 mm to 4.4 mm. The length of the first overlapping region and the second overlapping region is Lo-d = 1.3 mm.

[0062] Figure 5 Shown are simulation results of the transmission amplitude and transmission phase of a single-layer Huygens metasurface unit varying with Li length. Figure 5 The triangle line is the transmission amplitude change curve, and the circular curve is the transmission phase change curve. The Huygens metasurface unit of the present invention works at 20GHz, and the incident wave is an x-polarized wave and is transmitted along the positive direction of the z-axis. Figure 5 It can be seen that under normal x-polarized wave incidence, when Li continuously changes from 0 mm to 4.4 mm, the transmission phase continuously changes from -136° to -500°, achieving a transmission phase coverage of over 360°. This shows that the Huygens metasurface unit in this example only needs to change a single structural parameter to achieve 360° continuous transmission phase control, and the transmission loss is within -2 dB.

[0063] Figures 6 to 9 The surface current distribution of the upper and lower metal structures of the proposed Huygens metasurface unit under x-polarized incident wave conditions when operating at 20 GHz is shown, where the lengths of Li and Lo are both 3.4 mm. Figures 6 to 9 Part (a) corresponds to the surface current distribution of the upper metal structure when it operates at 20 GHz. Figures 6 to 9 Part (b) corresponds to the surface current distribution of the lower metal structure when it operates at 20 GHz. Jsurf represents the surface current in A / m. Figures 6 to 9It can be seen that the direction of the surface current in the overlapping area of ​​the upper metal structure 1 and the lower metal structure 3 is opposite at t = 0 and t = π within one cycle, which means that an equivalent current loop is formed by the overlapping area of ​​the upper metal structure 1 and the lower metal structure 3, which can generate a magnetic dipole. The magnetic dipole also interacts with the surface current of the "E"-shaped metal structure itself. When the equilibrium condition between the surface current and the induced magnetic current is met, the Huygens resonance is excited, thereby achieving high-transmittance transmission phase control. The simulation results show that the single-layer Huygens metasurface unit in this example has a simple structure and can achieve 360° transmission phase coverage at high transmittance. It is an excellent performance transmission metasurface unit that can be widely used in the design of beam deflection, flat lens formation, etc.

[0064] Figures 10 to 12 The top surface structure of the transmission array antenna is shown for scanning angles θ of 0°, 30°, and 60°, respectively. All three transmission arrays are composed of 20×20 Huygens metasurface elements. The structural parameters and location distribution of the different elements in the transmission array are designed using a multi-objective optimization algorithm based on a Gaussian random process surrogate model. The use of a genetic algorithm makes the design of the transmission array more convenient and efficient.

[0065] Figure 13 The simulation and measured results of the transmission array antenna working at 20GHz are shown. The planar transmission array antenna includes a transmission array and a horn feed, which provides excitation for the transmission array. Figure 13 It can be seen that the simulation results are basically consistent with the measured results. The side lobes of the transmission array antenna are less than -15dB, -12dB, and -10dB when the scanning angles θ are 0°, 30°, and 60°, respectively. Therefore, the planar transmission array antenna has the advantage of low side lobes.

[0066] Compared with the traditional transmission metasurface unit, the Huygens metasurface unit of all the above embodiments has only a single-layer dielectric plate and a two-layer metal structure. It is a thin metasurface unit, easy to miniaturize, and has higher transmittance and a larger transmission phase control range. The Huygens metasurface unit only needs to change one structural parameter to achieve a transmission amplitude within -2dB and 360° continuous transmission phase control. The unit needs to change few structural parameters, the structural change is simple, and it is easier to arrange and process the metasurface. The above-mentioned planar transmission array antenna has the advantages of low side lobes, low profile, low cost, easy design and easy processing.

[0067] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0068] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the structure and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A Huygens metasurface unit, characterized in that: include: A dielectric substrate and two identical metal structures; the two metal structures are an upper metal structure and a lower metal structure; The upper metal structure is located on the upper surface of the dielectric substrate; The lower metal structure is located on the lower surface of the dielectric substrate; the upper metal structure and the lower metal structure are anti-symmetric with respect to the dielectric substrate; The metal structure includes: a first metal layer, a second metal layer perpendicular to the first metal layer, a variable metal layer, and a third metal layer; a first end of the first metal layer is connected to a first end of the second metal layer, a second end of the first metal layer is connected to a first end of the third metal layer; a first end of the variable metal layer is connected to the first metal layer, and the variable metal layer is located between the second metal layer and the third metal layer; The projection of the upper metal structure on the lower surface of the dielectric substrate has an overlapping area with the lower metal structure; When an incident wave enters a Huygens metasurface unit, the transmission phase changes by adjusting the length of the variable metal layer.

2. The Huygens metasurface unit according to claim 1, characterized in that The projection of the second metal layer of the upper metal structure on the lower surface of the dielectric substrate has a first overlapping area with the second metal layer of the lower metal structure; the projection of the third metal layer of the upper metal structure on the lower surface of the dielectric substrate has a second overlapping area with the third metal layer of the lower metal structure; The first overlapping area is a section on the second metal layer starting from the second end of the second metal layer; the second overlapping area is a section on the third metal layer starting from the second end of the third metal layer; the lengths of the first overlapping area and the second overlapping area are equal.

3. The Huygens metasurface unit according to claim 2, characterized in that The first end of the variable metal layer is connected to the midpoint of the first metal layer; The distance between the variable metal layer and the second metal layer is equal to the length of the first non-overlapping area; the first non-overlapping area is the area on the second metal layer except the first overlapping area.

4. The Huygens metasurface unit according to claim 1, characterized in that The width of the second metal layer and the third metal layer are both 0.2 mm; the length of the second metal layer and the third metal layer are both 3.4 mm; and the length of the variable metal layer can be adjusted in the range of 0 mm to 4.4 mm.

5. The Huygens metasurface unit according to claim 2, characterized in that: The lengths of the first overlapping area and the second overlapping area are both 1.3 mm.

6. The Huygens metasurface unit according to claim 1, characterized in that: The upper surface and the lower surface of the dielectric substrate are both square.

7. The Huygens metasurface unit according to claim 6, characterized in that: The side lengths of the upper surface and the lower surface of the dielectric substrate are both 5.2 mm; the thickness of the dielectric substrate is 1.5 mm.

8. The Huygens metasurface unit according to claim 1, characterized in that: The dielectric constant of the dielectric substrate is 2.2, and the loss tangent value of the dielectric substrate is 0.

001.

9. A planar transmission array antenna, characterized in that: include: A transmission array and a feed horn; the transmission array is connected to the feed horn; the transmission array comprises a plurality of Huygens metasurface units according to any one of claims 1 to 8.

10. The planar transmission array antenna according to claim 9, characterized in that: The position and structural parameters of each Huygens metasurface unit in the transmission array are determined by a multi-objective optimization algorithm based on a Gaussian random process agent model; the structural parameters include: the length of the second metal layer, the length of the variable metal layer, and the length of the third metal layer.

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