A type of "bee-head" shaped multi-ring Huygens metasurface phase-shifting unit

Abstract

This invention provides a "bee-head" shaped multi-ring Huygens metasurface phase-shifting unit. This phase-shifting unit possesses ultra-wide bandwidth, high transmittance, and a phase modulation capability exceeding 360°. Its structure, from top to bottom, comprises: a first metal layer, a dielectric substrate layer, and a second metal layer. The first metal layer, located on the upper surface of the dielectric substrate, includes an inner arc group, a first ring of small-angle arcs, a second ring of large-angle arcs, and an outer arc group. The inner arc group includes small arcs, large arcs, and rectangular connecting strips; the outer arc group includes a third ring of large-angle arcs, two outermost small arcs, and two chamfered rectangular connecting strips. The second metal layer, located on the lower surface of the dielectric substrate, has an anti-symmetrical structure with the first metal layer. This "bee-head" shaped multi-ring Huygens metasurface phase-shifting unit solves the problems of narrow bandwidth and poor transmittance of Huygens metasurface units, providing a foundation for phase-shifting units in high-gain lenses, orbital angular momentum surfaces, and holographic imaging surfaces.

Description

Technical Field

[0001] This invention relates to a "bee-head" shaped multi-ring Huygens metasurface phase-shifting unit, belonging to the field of artificial electromagnetic materials. Background Technology

[0002] Electromagnetic metasurfaces are a novel type of two-dimensional metamaterial that have gradually attracted attention due to their low profile, lightweight, low cost, and wide application in electromagnetic wavefront manipulation. These metasurfaces are widely used in lens antenna design, orbital angular momentum surfaces, optical instruments, electromagnetic stealth materials, and 5G communications, and may be extended to sensors and imaging systems in the future, showing great promise, especially in high-frequency and optical frequency bands.

[0003] To achieve wavefront modulation of arbitrary electromagnetic waves, metasurfaces must be able to vary the phase within a 360° range while maintaining a transmission amplitude close to 1. Traditional wavefront modulation methods primarily rely on phase accumulation during electromagnetic wave propagation, typically requiring multilayer structures to achieve 360° phase coverage. This limits miniaturization for microwave-related applications. Currently, most metasurface structures focus primarily on electrical resonance effects, with insufficient consideration for magnetic resonance between metals. Therefore, relying solely on electrical resonance to achieve 360° phase coverage usually necessitates multiple dielectric layers or thick air gaps, increasing the overall structural profile height.

[0004] Huygens metasurfaces, by designing subwavelength-scale unit cell structures, can flexibly control the amplitude, phase, and polarization of electromagnetic waves without requiring complex feeding networks, making their design relatively simple. However, existing Huygens metasurfaces typically have narrow bandwidths, mainly because the resonant frequencies of electric and magnetic resonances are close, leading to bandwidth limitations. To address this challenge, current research focuses on employing novel materials (such as graphene and superconducting materials) and optimizing designs to enhance the bandwidth and phase control capabilities of metasurfaces.

[0005] In general, most metasurface units currently have relatively limited operating bandwidth and generally thick profiles. To achieve 360° phase coverage, multi-layer structures or thick air gaps are often required, which not only complicates the design of the unit structure and increases the difficulty of fabrication, but may also affect the stability of its performance. Therefore, promoting research on the feasibility and efficiency of metasurfaces in practical applications remains of great significance, especially their performance under non-ideal environments, which will be a key area for future development. Summary of the Invention

[0006] The purpose of this invention is to provide a "bee-head" shaped multi-ring Huygens metasurface phase-shifting unit.

[0007] To achieve the above-mentioned objectives, the technical solution of this invention is as follows:

[0008] A "bee-head" shaped multi-ring Huygens metasurface phase-shifting 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 inner arc group (101), a first small-angle arc (102), a second large-angle arc (103), and an outer arc group (104), wherein the inner arc group (101) comprises a small arc (1013), a large arc (1011), and a rectangular connecting strip (1012), and the outer arc group comprises a third large-angle arc (1043), two outermost small arcs (1041, 1045), and two chamfered rectangular connecting strips (1042, 1044); the structure of the second metal layer (3) is anti-symmetrical with that of the first metal layer (1).

[0009] As a preferred embodiment, the upper and lower surfaces of the dielectric substrate layer are rectangular, with the long side length p1 = 5.5 mm and the short side length p = 4.1 mm. The dielectric substrate material is Rogers 4003C with a relative permittivity of 3.0.

[0010] As a preferred embodiment, all the arcs in the inner arc group, the first small-angle arc, the second large-angle arc, and the outer arc group are concentric arcs, and the distance between the center of the concentric circle and the center point of the rectangular dielectric substrate is ee = 0.7 mm.

[0011] As a preferred embodiment, the opening direction of all arcs in the inner arc group, the first small-angle arc, the second large-angle arc, and the outer arc group is the direction of the short side of the rectangular dielectric substrate on the side furthest from all the arcs.

[0012] As a preferred embodiment, the inner arc group, the first small-angle arc, the second large-angle arc, and the outer arc group are axially symmetrical about the long axis of the rectangular dielectric substrate.

[0013] As a preferred embodiment, the inner diameter of the smaller arcs in the inner arc group is r1, the inner diameter of the larger arcs in the inner arc group is r2, the inner diameter of the first small-angle arc is r3, the inner diameter of the second large-angle arc is r4, the inner diameter of the third large-angle arc in the outer arc group is r5, and the inner diameter of the two outermost small arcs in the outer arc group is r6. r, r1, r2, r3, r5, and r6 are used to adjust the resonant frequencies of the magnetic and electrical resonances, and their values ​​satisfy r <r1<r2<r3<r5<r6。

[0014] As a preferred embodiment, the central angle of the small arcs in the inner arc group is θ1 = 116°, the central angle of the large arcs in the inner arc group is θ2 = 124°, the central angle of the first ring of small-angle arcs is θ3 = 120°, and the central angle of the second ring of large-angle arcs and the central angle of the third ring of large-angle arcs in the outer arc group are θ4 = 116°.

[0015] As a preferred embodiment, the width of all arcs in the inner arc group, the first small-angle arc, the second large-angle arc, and the outer arc group is wa = 0.1 mm.

[0016] As a preferred embodiment, the distance between the two outermost small arcs of the outer arc group and the long and wide sides of the rectangular dielectric substrate is q = 0.1 mm.

[0017] As a preferred embodiment, the lengths of the long and short sides of the upper and lower surfaces of the dielectric substrate layer satisfy the following conditions: p1>p, p≥2*(r5+wa), p1≥2*(r5+wa+ee).

[0018] The principle of this invention:

[0019] Passive Huygens metasurfaces are theoretically capable of achieving passive and lossless metasurface structures. The scattered fields of induced current and magnetic current induced by the metasurface structure can generate an output field through interaction with the incident wave. Its unit cell structure consists of an electric resonant section and a magnetic resonant section, which respectively modulate the electric and magnetic fields, thereby achieving free control of electromagnetic waves. The electromagnetic properties of the Huygens metasurface can be described by the electric surface admittance Yes and the magnetic surface impedance Zms. The relationship between the electric admittance and the reflection and transmission coefficients on the metasurface is derived as follows:

[0020]

[0021] The relationship between magnetic impedance and reflection coefficient and transmission coefficient is as follows:

[0022]

[0023] Where η0 is the free space wave impedance, the subscript s represents the surface distribution of this function, the subscript e indicates that the term is related to the surface current of the Huygens surface, and the subscript m indicates that the term is related to the surface magnetic current (or ring current) of the Huygens surface.

[0024] Based on the relationships between admittance, magnetoresistance, reflection coefficient, and transmission coefficient, under ideal conditions (T = 1, R = 0), we can obtain Yes = Zms, meaning the admittance and magnetoresistance are equal, and the Huygens resonance is excited. At this point, the transmission amplitude is close to full transmission. When the transmission coefficient of the Huygens metasurface is 1, the real parts of the normalized admittance Yes*η0 and the normalized magnetoresistance Zms / η0 are 0, and their imaginary parts are equal. Furthermore, as the imaginary parts of the normalized admittance Yes and the normalized magnetoresistance Zms change, the phase of the transmitted electromagnetic wave can achieve a phase coverage from 0° to 360°.

[0025] In this invention, the first metal layer and the second metal layer are two sets of antisymmetric electric dipoles. By antisymmetrically distributing the first metal layer and the second metal layer on both sides of the dielectric substrate, the surface current can be adjusted to form a current loop, generate orthogonal magnetic current, and thus produce the Huygens effect.

[0026] This invention employs multiple methods to broaden the bandwidth of the aforementioned "bee-head" shaped multi-ring Huygens metasurface phase-shifting unit. First, the "bee-head" shaped multi-ring Huygens metasurface phase-shifting unit is a rectangular periodic structure, rather than a square periodic structure. This is to compress the dimensions in the non-dominant polarization direction, thereby expanding the bandwidth. Second, the first and second metal layers consist of multiple arcs, forming a strip coupling structure. Arcs of different lengths generate multimode resonances, producing a total of eight mode resonant frequencies, achieving the effect of expanding the bandwidth. Third, two chamfered rectangular connecting strips in the outer arc group connect the third large-angle arc and the two outermost small arcs, extending their electrical length and increasing the current area of ​​the metal structure. Furthermore, increasing the width of the two chamfered rectangular connecting strips further increases the current area of ​​the metal structure, causing the frequency center to shift towards lower frequencies, expanding the low-frequency bandwidth, and also increasing the phase coverage. Finally, the small arcs in the inner arc group play a role in expanding the high-frequency bandwidth. Through the above methods, the "bee-head" shaped multi-ring Huygens metasurface phase shifting unit of the present invention has an ultra-wideband performance of 24GHz-42GHz, and at the same time has a phase modulation capability of more than 360°.

[0027] In this invention, the central angle of the first small-angle arc is smaller than the central angle of the second large-angle arc. By adjusting the central angle of the first small-angle arc, the transmission performance can be improved, thereby enabling the "bee-head" shaped multi-ring Huygens metasurface phase-shifting unit of this invention to have both ultra-wideband performance and high projection performance.

[0028] Compared with the prior art, the present invention has the following significant advantages: 1) The inner diameters of all the arcs in the inner arc group, the first small-angle arc, the second large-angle arc, and the outer arc group of the phase shift unit can be used to adjust the resonant frequencies of magnetic resonance and electric resonance, achieving a phase control range of more than 360° under the condition that the transmission coefficient is greater than -2dB; 2) The phase shift unit utilizes multiple resonant modes of current to expand the bandwidth and increase the phase control range; 3) The lens unit maintains high transmission characteristics within a large bandwidth.

[0029] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the three-dimensional split structure of the reference metasurface phase-shifting unit of the present invention;

[0031] Figure 2 This is a perspective top view of the reference metasurface phase-shifting unit of the present invention;

[0032] Figure 3 These are two top views and dimension annotations of the reference metasurface phase-shifting unit of the present invention;

[0033] Figure 4 These are two bottom views and dimension annotations of the reference metasurface phase-shifting unit of the present invention;

[0034] Figure 5 This is a front view and dimensioning of the reference metasurface phase-shifting unit of the present invention;

[0035] Figure 6 The transmission coefficient (S21) and phase versus frequency curve of the reference metasurface phase shifting unit of the present invention are shown.

[0036] Figure 7 The normalized electrical admittance and magnetoresistance of the reference metasurface phase-shifting unit of this invention are curves as a function of frequency. Detailed Implementation

[0037] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0038] This embodiment provides a "bee-head" shaped multi-ring Huygens metasurface phase shifting unit, which has ultra-wideband, high transmittance and a phase modulation capability of more than 360°.

[0039] A "bee-head" shaped multi-ring Huygens metasurface phase-shifting 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 inner arc group (101), a first small-angle arc (102), a second large-angle arc (103), and an outer arc group (104), wherein the inner arc group (101) comprises a small arc (1013), a large arc (1011), and a rectangular connecting strip (1012), and the outer arc group comprises a third large-angle arc (1043), two outermost small arcs (1041, 1045), and two chamfered rectangular connecting strips (1042, 1044); the structure of the second metal layer (3) is anti-symmetrical with that of the first metal layer (1).

[0040] In this embodiment, the thickness of the first metal layer and the second metal layer is t = 0.018 mm, and the thickness of the substrate layer is h = 1.3 mm.

[0041] In this embodiment, the upper and lower surfaces of the dielectric substrate layer are rectangular, with a long side length of p1 = 5.5 mm and a short side length of p = 4.1 mm. The dielectric substrate material is Rogers 4003C with a relative permittivity of 3.0.

[0042] In this embodiment, all the arcs in the inner arc group, the first small-angle arc, the second large-angle arc, and the outer arc group are concentric arcs, and the distance between the center of the concentric circle and the center point of the rectangular dielectric substrate is ee = 0.7 mm.

[0043] In this embodiment, the inner diameter of the small arc of the inner arc group is r1 = 0.7 mm, the inner diameter of the large arc of the inner arc group is r2 = 0.9 mm, the inner diameter of the first small-angle arc is r3 = 1.6 mm, the inner diameter of the second large-angle arc is r4 = 1.75 mm, the inner diameter of the third large-angle arc of the outer arc group is r5 = 1.9 mm, and the inner diameter of the two outermost small arcs of the outer arc group is r6 = 2.2 mm.

[0044] In this embodiment, the central angle of the small arcs in the inner arc group is θ1 = 116°, the central angle of the large arcs in the inner arc group is θ2 = 124°, the central angle of the first small-angle arcs is θ3 = 120°, and the central angle of the second large-angle arcs and the central angle of the third large-angle arcs in the outer arc group are θ4 = 116°.

[0045] In this embodiment, the width of all arcs in the inner arc group, the first small-angle arc, the second large-angle arc, and the outer arc group is wa = 0.1 mm.

[0046] In this embodiment, the length and width of the inner arc group rectangular connecting strip are wa = 0.1 mm.

[0047] In this embodiment, the length of the two chamfered rectangular connecting strips of the outer arc group is wb = 0.3 mm and the width is wm = 0.2 mm.

[0048] In this embodiment, the distance between the two outermost small arcs of the outer arc group and the long and wide sides of the rectangular dielectric substrate is q = 0.1 mm.

[0049] Figure 1 This is a schematic diagram of the three-dimensional split structure of the reference metasurface phase-shifting unit of the present invention;

[0050] Figure 2 This is a perspective top view of the reference metasurface phase-shifting unit of the present invention;

[0051] Figure 3 , 4 5 are top view, bottom view and front view of the reference metasurface phase shifting unit of the present invention, including a first metal layer 1, a dielectric substrate layer 2, and a second metal layer 3;

[0052] Figure 6 The transmission coefficient and phase distribution of the reference metasurface phase shifting unit of the present invention are shown. The metasurface phase shifting unit maintains a good transmission coefficient and a wide transmission bandwidth while satisfying phase modulation of more than 360°.

[0053] Figure 7 The normalized electrical admittance and magnetoresistance of the reference metasurface phase-shifting unit of this invention are equal in imaginary parts near the eight resonant points, forming Huygens resonance. It should be noted that two Huygens resonance points are included in the five circles from left to right.

[0054] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can 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 those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A "Bee Head" shaped multi-ring Huygens super surface phase shift unit, comprising a first metal layer (1), a dielectric substrate layer (2), and a second metal layer (3) from top to bottom, 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 inner arc group (101), a first circle of small angle arcs (102), a second circle of large angle arcs (103), and an outer arc group (104), wherein the inner arc group (101) comprises small arcs (1013), large arcs (1011), and rectangular connecting strips (1012), and the outer arc group comprises a third circle of large angle arcs (1043), two outermost circles of small arcs (1041, 1045), and two corner-cut rectangular connecting strips (1042, 1044). The second metal layer (3) is anti-symmetric to the first metal layer (1) in structure.

2. A "Bee's head" shaped multi-looped Huygens super surface phase shifting unit according to claim 1, characterized in that: The thickness of the first metal layer and the second metal layer is t, and the thickness of the dielectric substrate layer is h.

3. A "Bee's head" shaped multi-looped Huygens super surface phase shifting unit according to claim 2, characterized in that: The upper and lower surfaces of the dielectric substrate layer are rectangular, the length of the long side is p1, and the length of the short side is p, and the dielectric substrate is made of Rogers 4003C with a relative dielectric constant of 3.

0.

4. A "Bee's head" shaped multi-looped Huygens super surface phase shifting unit according to claim 3, characterized in that: All the arcs in the inner arc group, the first circle of small angle arcs, the second circle of large angle arcs, and the outer arc group are concentric arcs, and the distance between the concentric circle center and the rectangular dielectric substrate center point is ee.

5. A "Bee's head" shaped multi-looped Huygens super surface phase shifting unit according to claim 4, characterized in that: The inner arc group, the first circle of small angle arcs, the second circle of large angle arcs, and the outer arc group are axially symmetric about the long axis of the rectangular dielectric substrate, and the opening direction of all the arcs is the short side direction of the rectangular dielectric substrate far from all the arcs.

6. A "Bee's head" shaped multi-looped Huygens super surface phase shifting unit according to claim 5, characterized in that: The inner diameter of the small arc of the inner arc group is r1, the inner diameter of the large arc of the inner arc group is r2, the inner diameter of the first circle of small angle arcs is r3, the inner diameter of the second circle of large angle arcs is r4, the inner diameter of the third circle of large angle arcs of the outer arc group is r5, and the inner diameter of the two outermost circles of small arcs of the outer arc group is r6, and the values of r, r1, r2, r3, r5, and r6 satisfy r < r1 < r2 < r3 < r5 < r6.

7. A "Bee's head" shaped multi-looped Huygens super surface phase shifting unit according to claim 6, characterized in that: The central angle of the small arc of the inner arc group is θ1, the central angle of the large arc of the inner arc group is θ2, the central angle of the first circle of small angle arcs is θ3, and the central angle of the second circle of large angle arcs and the third circle of large angle arcs of the outer arc group is θ4.

8. A "Bee's head" shaped multi-looped Huygens super surface phase shifting unit according to claim 7, characterized in that: The width of all the arcs in the inner arc group, the first circle of small angle arcs, the second circle of large angle arcs, and the outer arc group is wa, the length and width of the rectangular connecting strip of the inner arc group is wa, the length of the two corner-cut rectangular connecting strips of the outer arc group is wb, and the width is wm.

9. A "Bee's head" shaped multi-looped Huygens super surface phase shifting unit according to claim 8, characterized in that: The distance between the two outermost circles of small arcs of the outer arc group and the long side and the short side of the rectangular dielectric substrate is q.

10. A "Bee's head" shaped multi-looped Huygens super surface phase shifting unit according to claim 9, characterized in that: The length of the long side and the short side of the upper and lower surfaces of the dielectric substrate layer satisfy p1 > p, p ≥ 2*(r5 + wa), and p1 ≥ 2*(r5 + wa + ee).

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