Metamaterial unit for wireless energy transmission and wireless energy transmission system

Abstract

The utility model discloses a metamaterial unit for wireless energy transmission and a wireless energy transmission system. The metamaterial unit comprises a substrate and two copper foils which are arranged on the substrate and are different in size and same in shape. The copper foil is a regular hexagonal ring-shaped copper foil; an opening is formed in one side of the regular hexagonal ring-shaped copper foil, and a chip capacitor is arranged on the opening; the substrate is in the shape of a regular hexagon. The metamaterial unit is simple in structure, can be widely applied to complex scenes and is high in applicability; in addition, the metamaterial unit has a lower cost and a higher WPT efficiency improvement effect under the condition that the performance improvement of the metamaterial on the WPT system is not influenced.

Description

Technical Field

[0001] The utility model relates to the technical field of wireless energy transmission, and in particular to a metamaterial unit for wireless energy transmission and a wireless energy transmission system. Background Art

[0002] Since wireless power transfer (WPT) can conveniently and wirelessly transmit power, it has been applied to various fields, especially charging smartphones and electric vehicles. Taking smartphone charging as an example, a receiving coil is installed inside the phone, and then the phone is placed on a base with a power transmitting coil. Compared with traditional charging methods, this wireless charging method eliminates the need for charging cables and transmits energy through an alternating electric field. With the deepening of research, some new technologies have been widely used in WPT systems.

[0003] At present, the most commonly used WPT system is the WPT system based on magnetic resonance coupling (MCR), which can transmit efficiently and reliably, and has the advantage of longer transmission distance compared to inductive wireless energy transmission. The focus of MCR wireless energy transmission technology is mainly on efficiency improvement, power improvement, transmission stability and anti-interference performance. Among them, for long-distance WPT systems, without changing the parameters of the coil, the efficiency will drop sharply with the increase of distance. In order to solve the above problems, in the prior art, electromagnetic metamaterials are used to enhance the efficiency of long-distance WPT systems. There are two main types of electromagnetic metamaterials, one is to use a split resonant ring (SSR) as a metamaterial unit, and the other is to use a spiral coil (SR) as a metamaterial unit. However, the existing WPT technology based on electromagnetic metamaterials has the following shortcomings:

[0004] 1. Using split ring resonator (SSR) as the metamaterial unit, the self-resonance frequency and effective permeability are determined by the parameters of the initial split ring design, and cannot be changed at will after the physical design. It is generally used in a single scenario (frequency). For WPT systems with different frequencies, it needs to be redesigned, and cannot be widely used in complex scenarios, with poor applicability.

[0005] 2. Using spiral coils (SR) as metamaterial units has a lower self-resonant frequency than SSR, and can be used in WPT systems with lower frequencies (kHz to MHz). SR can adjust the resonant frequency by adding compensation capacitors. For WPTs with different resonant frequencies, only the appropriate compensation capacitors need to be matched to obtain the effective permeability value required by the metamaterial at a given operating frequency. However, the SR structure is relatively complex, and the parasitic parameters of the SR itself will cause large losses, which reduces the effect of improving WPT. Utility Model Content

[0006] The purpose of the utility model is to overcome the above-mentioned problems and provide a metamaterial unit for wireless energy transmission, which has not only a simple structure, but also can be widely used in complex scenarios and has high applicability; in addition, the metamaterial unit has lower cost and higher WPT efficiency improvement effect without affecting the performance improvement of the WPT system by the metamaterial.

[0007] Another object of the present invention is to provide a wireless energy transmission system including the above-mentioned metamaterial unit.

[0008] The purpose of the utility model is achieved through the following technical solutions:

[0009] A metamaterial unit for wireless energy transmission comprises a substrate and two copper foils of different sizes and the same shape arranged on the substrate; the copper foil is a regular hexagonal ring-shaped copper foil; an opening is arranged on one side of the regular hexagonal ring-shaped copper foil, and a patch capacitor is arranged on the opening; the shape of the substrate is a regular hexagon.

[0010] The working principle of the above metamaterial unit is:

[0011] A regular hexagonal copper foil with an opening constitutes a hexagonal open resonant ring. A patch capacitor is set at the opening of the hexagonal open resonant ring. By adding patch capacitors with different capacitance values, a metamaterial unit for WPT systems of different frequencies is obtained. The shape of the substrate is a regular hexagon, which makes the metamaterial unit have a smaller area and fewer array units when it is arrayed, thereby making the metamaterial unit have a lower cost and a higher wireless energy transmission efficiency improvement effect.

[0012] In a preferred solution of the utility model, the centers of the two copper foils coincide with the center of the substrate, so as to make the structure more compact.

[0013] Preferably, the larger regular hexagonal copper foil is the outer copper foil, and the smaller regular hexagonal copper foil is the inner copper foil; the circumscribed circle radius of the substrate is larger than the circumscribed circle radius of the outer copper foil. By setting the above structure, it is ensured that the copper foil can be completely installed on the substrate.

[0014] Preferably, the capacitances of the two chip capacitors are equal.

[0015] Preferably, the copper foil has a thickness of 1 ounce.

[0016] Preferably, the copper foil is connected to the chip capacitor by welding, so as to ensure the stability of the connection between the chip capacitor and the copper foil.

[0017] Preferably, the substrate is a FR4 substrate.

[0018] A wireless energy transmission system comprises a transmitting coil, a receiving coil and a metamaterial array unit arranged between the transmitting coil and the receiving coil; the metamaterial array unit is formed by a plurality of metamaterial unit arrays.

[0019] The working principle of the above wireless energy transmission system is:

[0020] The alternating current is converted from the transmitting coil into electromagnetic waves and emitted into the air. The metamaterial array unit can converge the electromagnetic waves emitted by the transmitting coil, and the receiving coil receives the electromagnetic waves converged by the metamaterial array unit.

[0021] Preferably, the size of the metamaterial array unit is larger than the size of the transmitting coil and the receiving coil.

[0022] Preferably, the metamaterial array unit is a honeycomb metamaterial array unit or a spherical metamaterial array unit. In the above structure, the honeycomb metamaterial array unit is a unit in which the metamaterial units are arrayed according to a honeycomb structure, which has the advantages of small space area, lower cost and higher strength; the spherical metamaterial array unit is a unit in which the metamaterial units are arrayed according to a football-like space structure, which has the advantages of being more stable in strength and closer to a sphere than quadrilateral materials. By using an array of this structure, a spatial 3D wireless energy transmission system can be formed by reasonably setting the parameters of the metamaterial units and the positions of the metamaterial units.

[0023] Preferably, when the metamaterial array unit is a honeycomb metamaterial array unit, the number of metamaterial units in the honeycomb metamaterial array unit is 7, the 7 metamaterial units are double-layer arrays, the number of metamaterial units in the first layer array is 1, the number of metamaterial units in the second layer array is 6, and the metamaterial units in the second layer array are arrayed along the circumferential direction of the metamaterial units in the first layer array. That is, the metamaterial units in the first layer array are located in the middle of the metamaterial units in the second layer array, and two adjacent metamaterial units are closely connected to each other.

[0024] Compared with the prior art, the utility model has the following beneficial effects:

[0025] 1. The metamaterial unit in the utility model, with an open regular hexagonal ring copper foil, can form a hexagonal open resonant ring. A patch capacitor is arranged at the opening of the hexagonal open resonant ring. The frequency is adjusted by adding an additional patch capacitor according to the required frequency. It has the function of easy on-site adjustment, can be widely used in complex scenes, has high applicability, and a very simple structure.

[0026] 2. The metamaterial unit in the utility model has a substrate arranged in a regular hexagon. Without affecting the performance improvement of the WPT system by the metamaterial unit, it has a smaller area and fewer array units, thereby making the metamaterial unit have a lower cost and a higher wireless energy transmission efficiency improvement effect. Therefore, the metamaterial unit in the utility model can be used in medical implants and other wireless energy transmission scenarios that require a smaller size. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the three-dimensional structure of one specific implementation of a metamaterial unit for wireless energy transmission in the utility model.

[0028] Figure 2 This is a schematic diagram of the three-dimensional structure of the metamaterial unit in the utility model without the chip capacitor.

[0029] Figure 3 It is a top view of the metamaterial unit in the present invention.

[0030] Figure 4 It is a front view of the metamaterial unit in the utility model.

[0031] Figure 5 It is an equivalent circuit diagram of the metamaterial unit in the utility model.

[0032] Figure 6 This is a relationship diagram between the equivalent magnetic permeability and the resonant frequency of the metamaterial unit in the present invention.

[0033] Figure 7 It is a schematic diagram of the three-dimensional structure of a wireless energy transmission system in the utility model.

[0034] Figure 8 It is a front view of the wireless energy transmission system in the present utility model.

[0035] Fig. 9 It is a top view of the metamaterial array unit in the present utility model.

[0036] Fig.10 This is a diagram showing the effect of the wireless energy transmission system in the present invention on the convergence of the magnetic field.

[0037] Fig.11 This is the WPT magnetic field distribution diagram without metamaterial array units.

[0038] Fig.12 This is the WPT magnetic field distribution diagram of the utility model with the metamaterial array unit added.

[0039] Fig.13 Figure 2 is a graph showing the relationship between the transmission distance and efficiency of WPT without metamaterial array units.

[0040] Fig.14 This is the relationship between the transmission distance and efficiency of the WPT with the metamaterial array unit added in the present invention.

[0041] Fig.15 It is a schematic structural diagram of the honeycomb metamaterial array unit in the utility model.

[0042] Fig.16 This is a surface magnetic field distribution diagram of the metamaterial array unit in the present utility model.

[0043] Fig.17 It is a schematic diagram of the structure of the spherical metamaterial array unit in the utility model. DETAILED DESCRIPTION

[0044] In order to enable those skilled in the art to better understand the technical solution of the utility model, the utility model is further described below in conjunction with embodiments and drawings, but the implementation methods of the utility model are not limited thereto.

[0045] Example 1

[0046] See also Figure 1-Figure 4 This embodiment discloses a metamaterial unit for wireless energy transmission, including a substrate 1 and two copper foils 2 of different sizes and the same shape arranged on the substrate 1; the copper foil 2 is a regular hexagonal copper foil; an opening 3 is arranged on one side of the regular hexagonal copper foil, and a patch capacitor 4 is arranged on the opening 3; the shape of the substrate 1 is a regular hexagon. The metamaterial unit in this embodiment has the advantages of simple structure, easy frequency adjustment, and lower cost.

[0047] See also Figure 1-Figure 4 , the centers of the two copper foils 2 coincide with the center of the substrate 1, the larger regular hexagonal copper foil is the outer copper foil, and the smaller regular hexagonal copper foil is the inner copper foil; the inner copper foil is located inside the outer copper foil, the circumscribed circle radius D_sub of the substrate 1 is greater than the circumscribed circle radius D_out of the outer copper foil, and the copper foil 2 and the substrate 1 have the same orientation, that is, the copper foil 2 and the sides of the substrate 1 are neatly arranged. By setting the above structure, it is ensured that the copper foil 2 can be completely installed on the substrate 1, and at the same time, the structure is very compact; D_sub>D_out, but it cannot exceed too much, otherwise it will cause the unit's own loss to increase, and also increase the cost.

[0048] See also Figure 1-Figure 4 , the capacitance values ​​of the two chip capacitors 4 are equal. The two openings 3 are respectively arranged on the opposite sides of the two copper foils 2, that is, the opening 3 on the outer copper foil is arranged on the upper side of the outer copper foil, and the opening 3 on the inner copper foil is arranged on the lower side of the inner copper foil.

[0049] See also Figure 1-Figure 4 The thickness of the copper foil 2 is 1 ounce, ie, 35 μm, the width of the copper foil 2 is w, and the width of the opening 3 is s.

[0050] See also Figure 1-Figure 4 The copper foil 2 is welded to the chip capacitor 4. By welding, the stability of the connection between the chip capacitor 4 and the copper foil 2 is ensured.

[0051] See also Figure 1-Figure 4 The substrate 1 is a FR4 substrate 1.

[0052] Negative magnetic metamaterials are materials with negative magnetic permeability and positive dielectric constant. How to use ordinary metal materials to prepare artificial magnetic materials with negative magnetic permeability characteristics is mainly achieved through the special structure of metal materials. In the design theory of metamaterial units, the structure that can produce negative magnetic permeability is called a magnetic resonator (MR). The structural design of metamaterial units has strong flexibility. The design principle is that the designed structure must be able to generate a circular current, which can generate a magnetic response, thereby achieving negative magnetic permeability. The specific principle is that an electromagnetic wave is incident on the surface of the magnetic resonator. Since the magnetic field component of the electromagnetic wave is alternating and has a high frequency, it can be known from the principle of electromagnetic induction that an induced current will be generated in the magnetic resonator at this time. The geometric structure of the magnetic resonator can usually be equivalent to an LC oscillation circuit. When the frequency of the alternating magnetic field is the same as the resonant frequency of the oscillation circuit, the magnetic resonator resonates. At this time, the induced current generated in the metal structure is the largest. Since the induced current is circular, a magnetic response will be generated, and the characteristics of negative magnetic permeability will appear in the negative region of the resonance.

[0053] See also Figure 1-Figure 5 The equivalent circuit diagram of the metamaterial unit of this embodiment is as follows: Figure 5 As shown, L is the equivalent inductance of the metamaterial unit, R is the equivalent resistance, C 0 is the chip capacitor 4 added at opening 3, C 1 is the equivalent capacitance between the inner and outer copper foils 2. The metamaterial unit forms an LC series resonance, so C 1 The capacitance value is much smaller than the added chip capacitor C 0 To simplify the analysis, we ignore C 1 The resonant frequency value ω of the proposed metamaterial unit is:

[0054]

[0055] After obtaining the resonant frequency of the metamaterial unit, the parameters of the magnetic negative metamaterial can be extracted. In this embodiment, the S parameter inversion method proposed by Smith is used to extract the parameters of the metamaterial unit. The calculation formula of the S parameter inversion method is as follows:

[0056]

[0057]

[0058] ε=n / z (4)

[0059] μ=nz (5)

[0060] Among them, k 0 is the wave number in vacuum, k 0 =2π / λ 0 ,λ 0 is the wavelength in vacuum; S 11 and S 21 is the S parameter, S 21 is the transmission coefficient, representing the transmission capacity; S 11 is the reflection coefficient, representing the loss. The equivalent impedance z of the metamaterial unit is calculated using formula (2). The sign of the equivalent impedance z needs to be considered. The principle of selecting the sign is to ensure that the real part of the calculated z is positive, because the real part of the equivalent impedance represents the loss of the material, similar to the resistance in the circuit, so it is positive. Substituting the scattering parameters into formula (3) to calculate the equivalent refractive index of the metamaterial unit, n refers to the equivalent refractive index of the metamaterial unit, and d is the size of the metamaterial unit measured along the propagation direction of the wave.

[0061] See also Figure 1-Figure 6 After obtaining the equivalent impedance z and the equivalent refractive index n, the equivalent dielectric constant ε and the equivalent magnetic permeability μ of the metamaterial unit are calculated by formulas (4) and (5) respectively; in the wireless power transmission (WPT) system, the equivalent magnetic permeability of the metamaterial unit is a key parameter. For the calculation of the equivalent magnetic permeability, appropriate parameters are selected, with the width of the copper foil 2 w = 3mm, the width of the opening 3 s = 1.5mm, the distance between the inner and outer copper foils 2 gap = 1.0mm, D_out = 20mm, D_sub = 21mm, and the thickness of the substrate 1 sub_h = 1.6mm as typical values, and the external patch capacitor C 0 =2.15nF.

[0062] See also Figure 6 As shown, the real part of the equivalent magnetic permeability (also called effective magnetic permeability) of the metamaterial unit at f = 13.56MHz is -1, and the imaginary part is close to 0, that is, the metamaterial unit using the typical value has a suitable magnetic negative value and a low self-loss at 13.56MHz, thereby providing a magnetic field convergence effect for the WPT system with a resonant frequency of 13.56MHz. For WPT systems with different resonant frequencies, the parameters of the proposed metamaterial unit can be fine-tuned arbitrarily. The main adjustment method is to adjust the external compensation capacitor (chip capacitor 4).

[0063] See also Figure 1-Figure 4, the working principle of the above metamaterial unit is:

[0064] A regular hexagonal ring-shaped copper foil with an opening 3 forms a hexagonal opening 3 resonant ring, and a patch capacitor 4 is arranged at the opening 3 of the hexagonal opening 3 resonant ring. By adding patch capacitors 4 with different capacitances, a metamaterial unit for a WPT system with different frequencies is obtained. The shape of the substrate 1 is a regular hexagon, so that the metamaterial unit has a smaller area and a smaller number of array units when it is arrayed, thereby making the metamaterial unit have a lower cost and a higher wireless energy transmission efficiency improvement effect.

[0065] Example 2

[0066] See also Figure 1 and 7 - Fig.10 This embodiment discloses a wireless energy transmission system, including a transmitting coil 5, a receiving coil 7, and a metamaterial array unit 6 arranged between the transmitting coil 5 and the receiving coil 7; the metamaterial array unit 6 is formed by a plurality of metamaterial unit arrays as described in Example 1.

[0067] See also Figure 1 and 7 - Fig.10 , the working principle of the above wireless energy transmission system is:

[0068] The alternating current is converted from the transmitting coil 5 into electromagnetic waves and emitted into the air. The metamaterial array unit 6 can converge the electromagnetic waves emitted by the transmitting coil 5 , and the receiving coil 7 receives the electromagnetic waves converged by the metamaterial array unit 6 .

[0069] See also Figure 1 and 7 - Fig.10 , the size of the metamaterial array unit 6 is larger than the size of the transmitting coil 5 and the receiving coil 7.

[0070] See also Figure 1 and 7 - Fig.10 In the wireless energy transmission system of this embodiment, after selecting the metamaterial unit parameters to obtain the negative equivalent magnetic permeability value at the required frequency, the metamaterial array unit 6 is added to the wireless energy transmission system (i.e., placed between the transmitting coil 5 and the receiving coil 7). The metamaterial array unit 6 with negative equivalent magnetic permeability placed between the transmitting coil 5 and the receiving coil 7 can converge the magnetic field, thereby reducing the leakage of the magnetic field and improving the transmission efficiency of the wireless energy transmission system. The electromagnetic wave emitted by the transmitting coil 5 undergoes a negative refraction effect through the magnetic negative metamaterial unit, showing the effect of magnetic field convergence. Fig.10It can be seen that in the wireless energy transmission system with the metamaterial array unit 6, the metamaterial array unit 6 converges the magnetic flux lines, while without the metamaterial array unit 6, the magnetic flux lines cannot be converged.

[0071] See also Figure 10-12 , Fig.11 This is a WPT magnetic field distribution diagram without metamaterial array unit 6. In the figure, the transmitting coil 5 transmits electromagnetic waves, generating a high magnetic field intensity around the transmitting coil 5. The electromagnetic waves are coupled to the receiving coil 7 through the air, and the coupling amount is small, which is characterized by low transmission efficiency in wireless energy transmission. Fig.12 This is the WPT magnetic field distribution diagram after adding the metamaterial array unit 6. After adding the metamaterial array unit 6, the magnetic field around the receiving coil 7 is compared. Figure 7 The magnetic field in the WPT system is significantly increased, that is, the transmission efficiency of the WPT system is improved after the metamaterial array unit 6 is added. In addition, after the metamaterial array unit 6 is added, the magnetic field around the transmitting coil 5 is also weakened, reducing electromagnetic leakage. Compared with other structures, such as open three resonant rings (SSR) and spiral coils (SR), the hexagonal metamaterial unit proposed in this embodiment has the same transmission efficiency improvement performance for the WPT system, and has the advantages of smaller size, smaller space occupation area, simple structure, easy frequency adjustment, etc. This embodiment can be applied to WPT systems with tight space and complex scenarios.

[0072] See also Figure 8-Figure 10 and Figure 13-Figure 14 , Fig.13 is the relationship between the transmission distance and efficiency of WPT without metamaterial array unit 6, Fig.14 The relationship between the transmission distance and efficiency of the WPT with the metamaterial array unit 6 added, the transmission distance D in the figure is the distance between the transmitting coil 5 and the receiving coil 7. It can be seen from the figure that the wireless energy transmission system of this embodiment can converge electromagnetic waves, thereby improving the efficiency of the WPT system. Except for 4cm to 5cm, the efficiency of the WPT with the metamaterial array unit 6 added is lower than the efficiency of the WPT without the metamaterial array unit 6. The efficiency of the WPT with the metamaterial array unit 6 added at the remaining transmission distances is higher than the efficiency of the WPT without the metamaterial array unit 6. In particular, at a transmission distance of 10cm, the efficiency of the WPT system without the metamaterial array unit 6 is 9%, while the efficiency of the WPT system with the metamaterial array unit 6 is 70%, and the efficiency is improved by 670%. The wireless energy transmission system of this embodiment has a good efficiency improvement effect.

[0073] See also Figure 8-Figure 9 and Fig.15, the metamaterial array unit 6 is a honeycomb metamaterial array unit. In the above structure, the honeycomb metamaterial array unit is a unit in which the metamaterial units are arrayed according to a honeycomb structure, which has the advantages of small space area, lower cost and higher strength.

[0074] See also Figure 8-Figure 9 , the number of metamaterial units in the honeycomb metamaterial array unit is 7, the 7 metamaterial units are double-layer arrays, the number of metamaterial units in the first layer array is 1, the number of metamaterial units in the second layer array is 6, and the metamaterial units in the second layer array are arrayed along the circumferential direction of the metamaterial units in the first layer array. That is, the metamaterial unit in the first layer array is located in the middle of the metamaterial unit in the second layer array, and two adjacent metamaterial units are closely connected to each other.

[0075] See also Figure 7 and Fig.16 , Fig.16 FIG. 1 is the magnetic field distribution of the metamaterial unit at the resonant frequency. It is obvious that a circular current characterized by an electromagnetic field appears on the metamaterial unit, that is, the metamaterial array unit 6 achieves a negative equivalent magnetic permeability at the resonant frequency.

[0076] Example 3

[0077] See also Fig.17 , the other structures in this embodiment are the same as those in embodiment 2, except that the metamaterial array unit 6 is a spherical metamaterial array unit. In the above structure, the spherical metamaterial array unit is a unit in which the metamaterial units are arrayed in a football-like spatial structure. This structure has the advantages of being more stable and closer to a sphere than a quadrilateral material. By using this array, a spatial 3D wireless energy transmission system can be formed by reasonably setting the parameters of the metamaterial units and the positions of the metamaterial units. In the figure, the white arrows are magnetic lines of force.

[0078] The metamaterial array unit 6 of this embodiment may also be a spider web structure array unit.

[0079] The above is a preferred implementation mode of the present invention, but the implementation mode of the present invention is not limited by the above content. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A metamaterial unit for wireless energy transmission, characterized in that: It comprises a substrate and two copper foils of different sizes and the same shape arranged on the substrate; the copper foil is a regular hexagonal ring copper foil; an opening is arranged on one side of the regular hexagonal ring copper foil, and a chip capacitor is arranged on the opening; the shape of the substrate is a regular hexagon.

2. A metamaterial unit for wireless energy transmission according to claim 1, characterized in that: The centers of the two copper foils coincide with the center of the substrate.

3. A metamaterial unit for wireless energy transmission according to claim 2, characterized in that: The larger regular hexagonal ring copper foil is the outer ring copper foil, and the smaller regular hexagonal ring copper foil is the inner ring copper foil; the circumscribed circle radius of the substrate is greater than the circumscribed circle radius of the outer ring copper foil.

4. A metamaterial unit for wireless energy transmission according to claim 1, characterized in that: The capacitance values ​​of the two chip capacitors are equal.

5. The metamaterial unit for wireless energy transmission according to claim 1, characterized in that: The copper foil has a thickness of 1 ounce.

6. The metamaterial unit for wireless energy transmission according to claim 1, characterized in that: The copper foil is connected to the chip capacitor by welding.

7. A wireless energy transmission system, characterized in that: It comprises a transmitting coil, a receiving coil and a metamaterial array unit arranged between the transmitting coil and the receiving coil; the metamaterial array unit is formed by a plurality of metamaterial unit arrays according to any one of claims 1 to 6.

8. A wireless energy transmission system according to claim 7, characterized in that: The size of the metamaterial array unit is larger than the size of the transmitting coil and the receiving coil.

9. A wireless energy transmission system according to claim 7, characterized in that: The metamaterial array unit is a honeycomb metamaterial array unit or a spherical metamaterial array unit.

10. A wireless energy transmission system according to claim 9, characterized in that: When the metamaterial array unit is a honeycomb metamaterial array unit, the number of metamaterial units in the honeycomb metamaterial array unit is 7, the 7 metamaterial units are a double-layer array, the number of metamaterial units in the first layer array is 1, the number of metamaterial units in the second layer array is 6, and the metamaterial units in the second layer array are arranged along the circumferential direction of the metamaterial units in the first layer array.

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