A broadband and high-efficiency Huygens metasurface lens

Abstract

The present invention provides a broadband high-efficiency Huygens metasurface lens, comprising a plurality of lens units arranged in a square array, the lens units having high transmission performance and 360° transmission phase regulation, and the structure thereof comprises, from top to bottom, a first metal layer, a dielectric substrate layer, and a second metal layer; the first metal layer is located on the upper surface of the dielectric substrate, and comprises an outermost C-shaped circular ring, a second outer C-shaped circular ring, four circular arcs intermittently distributed in the middle layer, and a circular patch with a cross-slit structure removed in the inner layer. The second metal layer is located on the lower surface of the dielectric substrate, and comprises a C-shaped circular ring that is centrally symmetrical with the outer layers of the first and second metal layers, and an intermediate layer and an inner layer structure that are mirror-symmetrical with the intermediate layer and inner layer structure of the first metal layer; the Huygens metasurface lens of the present invention solves the shortcomings of a high aperture profile of a traditional plane and the need for a multi-layer structure to achieve full-cycle phase compensation, and has high gain, high efficiency, and a wide working bandwidth.

Description

Technical Field

[0001] The invention relates to a broadband high-efficiency Huygens metasurface lens, and belongs to the field of artificial electromagnetic materials. Background Art

[0002] The electromagnetic metasurface is a new type of two-dimensional metamaterial structure with many advantages such as low profile, electromagnetic wave front control, small size, light weight and low cost. It is widely used in lens antenna design, orbital angular momentum surface, optical instrument manufacturing, electromagnetic stealth materials and 5G communications.

[0003] In order to achieve the wavefront modulation effect of any electromagnetic wave, the metasurface needs to achieve a 360° phase change and a transmission amplitude close to 1. The traditional wavefront control period is based on the spatial phase accumulation of electromagnetic wave propagation in space, and a multi-layer structure is required to achieve 360° phase coverage. Therefore, this method limits the miniaturization of the relevant period in the microwave frequency band. Most of the current metasurface structures only consider the electric resonance effect of the metal structure itself, and do not consider the magnetic resonance effect between metals. Therefore, the pure electric resonance metasurface requires multi-layer dielectrics or thicker air gaps to achieve 360° phase coverage, which increases the profile height of the surface. The Huygens metasurface can arbitrarily control the amplitude, phase, polarization, etc. of electromagnetic waves through the designed subwavelength unit structure. It does not require a complex feeding network and is simple to design. In terms of the bandwidth of the metasurface, most of the Huygens metasurfaces currently studied have a relatively narrow bandwidth. This is due to the close frequency points of the electric resonance and magnetic resonance in the Huygens resonance.

[0004] It can be seen that most of the metasurface units studied currently have a narrow working bandwidth and a thick cross-section. In order to achieve 360° phase coverage, it is necessary to introduce a multi-layer structure or a thicker air gap. These methods make the unit structure design complex, the processing difficult, and the performance unstable. Summary of the invention

[0005] The object of the present invention is to provide a broadband high-efficiency Huygens metasurface lens.

[0006] To achieve the above-mentioned purpose of the invention, the technical solution of the present invention is as follows:

[0007] A broadband high-efficiency Huygens metasurface lens comprises a plurality of lens units arranged periodically in a square array, wherein the lens units at different positions in the square array obtain the required phase shift by adjusting parameters, and the lens units cover a phase control range of 0° to 360°. The square array in which the lens units are arranged has a transmission wave phase that satisfies the function of focusing electromagnetic waves.

[0008] The broadband high-efficiency Huygens metasurface lens is characterized in that the transmission wave phase of the lens unit satisfies:

[0009]

[0010] Where k0 is the phase shift constant in free space, F is the focal length, (i, j) is the coordinate of the lens element, and L i,j is the straight-line distance between the lens unit and the focus at coordinate (i, j), is the phase difference between the lens unit at coordinate (i, j) and the lens unit at the center The difference between.

[0011] The lens unit comprises, from top to bottom, a first metal layer, a dielectric substrate layer, and a second metal layer. The lens unit has high transmission performance and 360° transmission phase regulation, and has a wide working bandwidth.

[0012] The first metal layer (1) of the lens unit is located on the upper surface of the dielectric substrate (2), and the second metal layer (3) is located on the lower surface of the dielectric substrate (2). The first metal layer (1) includes an outermost C-shaped circular ring (101), a second outermost C-shaped circular ring (102), four intermittently distributed circular arcs (103) in the middle layer, and a circular patch (104) in the inner layer without a cross-slit structure. The second metal layer 3 includes an outermost C-shaped circular ring (301), a second outermost C-shaped circular ring (302), four intermittently distributed circular arcs (303) in the middle layer, and a circular patch (304) in the inner layer without a cross-slit structure. The C-shaped circular ring of the first metal layer and the C-shaped circular ring of the second metal ring are centrally symmetrical. The four circular arcs in the middle layer of the first metal layer and the circular patch in the inner layer without a cross-slit structure are mirror-symmetrical to the four circular arcs in the middle layer of the second metal layer and the circular patch in the inner layer without a cross-slit structure.

[0013] As a preferred embodiment, the upper and lower surfaces of the dielectric substrate layer are square, with a side length of p=8.6 mm and a thickness of h=2 mm. The dielectric substrate is made of Rogers 4003C with a relative dielectric constant of 3.0.

[0014] As a preferred embodiment, the inner diameter of the outermost C-shaped ring is r=3.66 mm, and the width is wa=0.55 mm.

[0015] As a preferred embodiment, the inner diameter of the sub-outer C-shaped ring is r1=3.06 mm, and the width is wb=0.3 mm.

[0016] As a preferred embodiment, the inner diameter of the four arcs intermittently distributed in the middle layer is r2=2.66 mm, the width is wc=0.2 mm, the center angle of the arc is α=120°, and the four arcs are distributed in a centrally symmetrical manner.

[0017] As a preferred embodiment, the radius of the inner disk is r3=2.16 mm, the length of the central cross gap is a=2.2 mm, and the width is wd=0.2 mm.

[0018] As a preferred embodiment, the thickness of the first metal layer and the second metal layer is h1 = 0.018 mm.

[0019] As a preferred embodiment, the inner diameter and radius of the C-shaped ring, disk and arc are used to adjust the resonant frequency of the magnetic resonance and the electric resonance.

[0020] Principle of the present invention:

[0021] The passive Huygens metasurface can theoretically realize a passive and lossless metasurface structure. The scattering field of the induced current and magnetic current caused by the metasurface structure can generate an output field by interacting with the incident wave. Its unit structure consists of an electric resonance part and a magnetic resonance part, which regulate the electric field and magnetic field respectively, thereby realizing the free regulation of electromagnetic waves. The electromagnetic characteristics of the Huygens metasurface can be described by the electric surface admittance Yes and the magnetic surface impedance Zms. According to the derivation, the relationship between the electric admittance and the reflection coefficient and the transmission coefficient on the metasurface is:

[0022]

[0023] The relationship between magnetic impedance, reflection coefficient and transmission coefficient is:

[0024]

[0025] Where η is the free space wave impedance, the lower right subscript s represents the surface distribution of this function, the lower right subscript e indicates that the term is related to the surface current of the Huygens surface, and the lower right subscript m indicates that the term is related to the surface magnetic current (or circular current) of the Huygens surface.

[0026] The present invention forms reversely symmetrical upper and lower surface currents through the C-shaped open circular rings in the first metal layer and the second metal layer, synthesizes the circular current in three-dimensional space, and forms a certain magnetic resonance; the metal disks with cross gaps in the first metal layer and the second metal layer form upper and lower surface currents with the same flow direction, forming an electric resonance mode. The four discontinuously distributed arcs introduced between the disk and the C-shaped circular ring can, on the one hand, weaken the unnecessary coupling between the inner layer electric resonance and the outer layer magnetic resonance, so that the electric resonance and the magnetic resonance can be independently regulated respectively, and on the other hand, the four discontinuously distributed arcs can contribute to part of the magnetic resonance response, so that the working bandwidth is further widened and the transmission performance is greatly improved.

[0027] Compared with the prior art, the present invention has the following significant advantages: 1) The lens has a low cross-section, which effectively improves the focusing efficiency of the lens unit on the incident wave; 2) The lens unit can adjust the resonant frequency of the magnetic resonance and the electric resonance by adjusting the inner diameter and radius of the C-shaped ring, the disk and the arc, and realizes a 360° phase control range under the condition that the transmission coefficient is greater than -2dB; 3) The lens unit uses the symmetric mode and the antisymmetric mode of the current to generate multiple electric resonance and magnetic resonance modes, expand the bandwidth, and improve the transmission performance; 4) The lens unit maintains a high gain characteristic within a larger bandwidth.

[0028] The present invention is described in further detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of the structure of a reference metasurface lens of the present invention;

[0030] Figure 2 A schematic diagram showing the positional relationship between the phases of the transmitted waves between the reference metasurface lens units of the present invention;

[0031] Figure 3 The lens unit array arrangement mode of the reference metasurface lens of the present invention and the precise phase shift required for the lens units at each position;

[0032] Figure 4 The lens unit array arrangement mode of the reference metasurface lens of the present invention and the 3-bit quantized phase shift required for the lens units at each position;

[0033] Figure 5 This is a schematic diagram of the decomposition of the reference metasurface lens unit structure of the present invention;

[0034] Figure 6 A top view of a reference supersurface unit of the present invention;

[0035] Figure 7 A bottom view of a reference super surface unit of the present invention;

[0036] Figure 8 A front view of a reference super surface unit of the present invention;

[0037] Fig. 9 The current distribution of the first and second metal layers when the reference metasurface lens unit of the present invention works at 14 GHz;

[0038] Fig.10 is the transmission coefficient (S21) and phase of the metasurface lens unit;

[0039] Fig.11 The normalized electrical admittance and magnetic impedance curves of the reference metasurface lens unit of the present invention;

[0040] Fig.12 The gain variation curve of the metasurface lens unit of the present invention at 14.8 GHz is plotted against the angle;

[0041] Fig.13 This is the curve of the gain of the supersurface lens unit changing with frequency. DETAILED DESCRIPTION

[0042] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0043] The present embodiment provides a broadband and high-efficiency Huygens metasurface lens, comprising a plurality of lens units periodically arranged in a square array, wherein the lens units at different positions in the square array obtain the required phase shift by adjusting parameters, and the lens units cover a phase control range of 0° to 360°. The square array in which the lens units are arranged has a transmission wave phase that satisfies the function of focusing electromagnetic waves.

[0044] The broadband high-efficiency Huygens metasurface lens is characterized in that the transmission wave phase of the lens unit satisfies:

[0045]

[0046] Where k0 is the phase shift constant in free space, F is the focal length, (i, j) is the coordinate of the lens unit, Li, j is the straight-line distance between the lens unit at coordinate (i, j) and the focus, and ψ(i, j) is the phase difference between the lens unit at coordinate (i, j) and the lens unit at the center ψ0.

[0047] The lens unit comprises, from top to bottom, a first metal layer (1), a dielectric substrate layer (2), and a second metal layer (3), wherein the first metal layer (1) is located on the upper surface of the dielectric substrate (2), and the second metal layer (3) is located on the lower surface of the dielectric substrate (2).

[0048] The first metal layer 1 comprises an outermost C-shaped circular ring (101), a second outermost C-shaped circular ring (102), four intermittently distributed circular arcs (103) in the middle layer, and a circular patch (104) in the inner layer with a cross-slit structure removed; the second metal layer (3) comprises an outermost C-shaped circular ring (301), a second outermost C-shaped circular ring (302), four intermittently distributed circular arcs (303) in the middle layer, and a circular patch (304) in the inner layer with a cross-slit structure removed. The outermost C-shaped circular ring (101) and the second outermost C-shaped circular ring (102) of the first metal layer (1) are centrally symmetrical with the outermost C-shaped circular ring (301) and the second outermost C-shaped circular ring (302) of the second metal layer (3), and the directions of the currents on the upper and lower surfaces of the excited lens unit are opposite, synthesizing a circular current in a three-dimensional space to form a certain magnetic resonance. At the same time, the circular patch (104) with the cross-slit structure removed from the inner layer of the first metal layer (1) is mirror-symmetrical to the circular patch (304) with the cross-slit structure removed from the inner layer of the second metal layer (3), and the current directions of the upper and lower surfaces of the excited lens unit are the same, forming electric resonance. The four arcs intermittently distributed in the middle are between the two layers of C-shaped circular rings and the inner disk. On the one hand, the unnecessary coupling between the inner layer electric resonance and the outer layer magnetic resonance can be weakened, so that the electric resonance and the magnetic resonance can be independently regulated respectively. On the other hand, the four arcs intermittently distributed can contribute to part of the magnetic resonance response, so that the working bandwidth is further widened and the transmission performance is greatly improved.

[0049] In a further embodiment, the upper and lower surfaces of the dielectric substrate layer are square, with a side length of p=8.6 mm and a thickness of h=2 mm. The dielectric substrate is made of Rogers 4003C with a relative dielectric constant of 3.0.

[0050] In a further embodiment, the thickness of the first metal layer and the second metal layer are both h1=0.018 mm.

[0051] In a further embodiment, the inner diameter of the outermost C-shaped ring is r=3.66 mm, and the width is wa=0.55 mm.

[0052] In a further embodiment, the inner diameter of the sub-outer C-shaped ring is r1=3.06 mm, and the width is wb=0.3 mm.

[0053] In a further embodiment, the inner diameter of the four arcs intermittently distributed in the middle layer is r2=2.66 mm, the width is wc=0.2 mm, the center angle of the arc is α=120°, and the four arcs are distributed in a centrally symmetrical manner.

[0054] In a further embodiment, the radius of the inner disk is r3=2.16 mm, the length of the central cross gap is a=2.2 mm, and the width is wd=0.2 mm.

[0055] Figure 1A schematic diagram of the structure and function of the reference metasurface lens of the present invention;

[0056] Figure 2 A schematic diagram showing the positional relationship between the phases of the transmitted waves between the reference metasurface lens units of the present invention; Figure 3 , 4 The lens unit array arrangement mode of the reference metasurface lens of the present invention and the precise phase shift and 3-bit quantized phase shift required for the lens units at each position; Figure 5 This is a schematic diagram of the decomposition of the reference metasurface lens unit structure of the present invention; Figure 6 , 7 8 are a top view, a bottom view, and a front view of a reference metasurface unit of the present invention, comprising a first metal layer 1, a dielectric substrate layer 2, and a second metal layer 3; Fig. 9 This is the current distribution of the first and second metal layers when the metasurface unit of the present invention works at 14GHz. It can be seen that the current directions of the C-shaped rings of the first and second metal layers are opposite, forming a current antisymmetric mode, namely, a magnetic resonance mode; the four arcs discontinuously distributed in the middle have a tendency to contribute to magnetic resonance, so the magnetic resonance frequency can be adjusted by adjusting the radius of the C-shaped ring and the middle layer arc; the current directions of the inner disk are the same or the current intensities of the two layers are quite different to form a single layer current, thus forming an electric resonance mode, so the radius of the inner disk can be used to adjust the electric resonance frequency.

[0057] In a further embodiment, the inner diameter and radius of the C-shaped ring, disk and arc are used to adjust the resonant frequency of the magnetic resonance and the electric resonance.

[0058] Fig.10 are the normalized electrical admittance and magnetic impedance of the metasurface lens unit of the present invention. The imaginary parts of the normalized electrical admittance and magnetic impedance are equal near the four resonance points, forming Huygens resonance.

[0059] Fig.11 The transmission coefficient and phase distribution of the metasurface lens unit. The metasurface unit maintains a good transmission coefficient and a wide transmission bandwidth while satisfying the phase control of 0° to 360°.

[0060] Fig.12 This is the curve of the unit gain of the metasurface lens of the present invention changing with the angle at 14.8GHz. The beam width of the transmitted wave of the metasurface lens unit is very small, and a higher pointing accuracy can be obtained, so that the metasurface lens of the present invention has a higher focusing efficiency.

[0061] Fig.13 The gain variation curve and efficiency curve of the metasurface lens unit of the present invention are as a function of frequency. The metasurface lens unit of the present invention maintains high gain characteristics within a larger bandwidth.

[0062] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A broadband high-efficiency Huygens metasurface lens, comprising a plurality of lens units arranged periodically in a square array, wherein the lens units at different positions in the square array obtain the required phase shift by adjusting parameters, and the lens units cover a phase control range of 0° to 360°, and the square array of the lens units has a transmission wave phase that satisfies the function of focusing electromagnetic waves; The lens unit comprises, from top to bottom, a first metal layer (1), a dielectric substrate layer (2), and a second metal layer (3), wherein the first metal layer (1) is located on the upper surface of the dielectric substrate (2), and the second metal layer (3) is located on the lower surface of the dielectric substrate (2); The first metal layer (1) comprises an outermost C-shaped circular ring (101), a second outermost C-shaped circular ring (102), four intermittently distributed circular arcs (103) in the middle layer, and an inner circular patch (104) provided with a cross-slit structure; The second metal layer (3) comprises an outermost C-shaped circular ring (301), a second outermost C-shaped circular ring (302), four intermittently distributed circular arcs (303) in the middle layer, and an inner circular patch (304) provided with a cross-slit structure; The outermost C-shaped circular ring (101) and the second outermost C-shaped circular ring (102) of the first metal layer (1) are centrally symmetrical with the outermost C-shaped circular ring (301) and the second outermost C-shaped circular ring (302) of the second metal layer (3).

2. The broadband high-efficiency Huygens metasurface lens according to claim 1, characterized in that: The phase of the transmitted wave of the lens unit satisfies: Where k0 is the phase shift constant in free space, F is the focal length, (i, j) is the coordinate of the lens element, and L i,j is the straight-line distance between the lens unit and the focus at coordinate (i, j), is the phase difference between the lens unit at coordinate (i, j) and the lens unit at the center The difference between.

3. The broadband high-efficiency Huygens metasurface lens according to claim 1, characterized in that: The four arcs (103) in the middle layer of the first metal layer (1) of the lens unit and the circular patch (104) in the inner layer provided with a cross-slit structure are mirror-symmetrical with the four arcs (303) in the middle layer of the second metal layer (3) of the lens unit and the circular patch (304) in the inner layer provided with a cross-slit structure.

4. The broadband high-efficiency Huygens metasurface lens according to claim 1, characterized in that: The inner diameter of the outermost C-shaped ring of the lens unit is r, the width is wa, and the opening size is 120°. The inner diameter of the second outermost C-shaped ring is r1, the width is wb, and the opening size is 120°.

5. The broadband high-efficiency Huygens metasurface lens according to claim 4, characterized in that: The inner diameter of the four arcs intermittently distributed in the middle layer of the lens unit is r2, the width is wc, the center angle of the arc is α, and the four arcs are distributed in a centrally symmetrical manner.

6. The broadband high-efficiency Huygens metasurface lens according to claim 5, characterized in that: The radius of the inner disk of the lens unit is r3, the length of the central cross gap is a, and the width is wd.

7. The broadband high-efficiency Huygens metasurface lens according to claim 6, characterized in that: The values ​​of r, r1, r2, and r3 satisfy r>r1>r2>r3.

8. The broadband high-efficiency Huygens metasurface lens according to claim 7, characterized in that: The upper and lower surfaces of the dielectric substrate layer of the lens unit are square, with a side length of p, satisfying p≥2*(r+wa), and a thickness of h. The plate material of the dielectric substrate is Rogers 4003C, and the relative dielectric constant is 3.

0.

9. The broadband high-efficiency Huygens metasurface lens according to claim 8, characterized in that: The first metal layer and the second metal layer of the lens unit have a thickness of h1.

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