Composite magnetic shielding metamaterial and preparation method thereof

Abstract

The present invention relates to a composite magnetic shielding metamaterial and a preparation method thereof. The preparation method comprises the following steps: designing a near-zero magnetic permeability metamaterial unit with a non-magnetic substrate as a unit substrate based on the principle of using near-zero magnetic permeability metamaterial for magnetic field shielding; replacing the non-magnetic substrate in the near-zero magnetic permeability metamaterial unit with a magnetic substrate to prepare a composite magnetic shielding metamaterial unit; adjusting the size of the resonant capacitor in the composite magnetic shielding metamaterial unit so that the frequency ω at the near-zero magnetic permeability is MNZ The present invention can effectively shield normal incident waves that traditional metamaterials cannot shield, and greatly improves the shielding effectiveness of composite magnetic shielding metamaterials in a smaller size and volume.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic shielding, and in particular to a composite magnetic shielding metamaterial for near-field frequencies and a preparation method thereof. Background Art

[0002] In recent years, the development of wireless energy transmission methods using magnetic fields, such as magnetic resonance and magnetically coupled wireless energy transmission systems, has led to the generation of strong magnetic field radiation on both sides of the transmitting coil. In practical wireless power transmission applications, only the magnetic field on one side of the coil is required; the magnetic field on the other side remains unavailable to the receiving end. This unused magnetic field can pose a serious threat to the surrounding environment, particularly in power-based wireless devices. It can interfere with the reception of radio, television, and telecommunication signals, disrupt the normal operation of electronic equipment, and potentially cause information errors and control failures. It can also ignite flammable and explosive materials, causing explosions and fires. Furthermore, the strong electromagnetic radiation has a significant impact on human health. Therefore, effective magnetic field shielding for wireless devices has become an unavoidable and important issue in the industry. Furthermore, with the growing trend toward portable electronic devices, miniaturized, lightweight, and efficient magnetic shielding has become a pressing need in these applications.

[0003] Current magnetic shielding methods for frequencies above 5kHz primarily utilize high-permeability materials such as ferrites and conductive metals. However, these shielding methods are limited in their applications. For example, the shielding effectiveness (SE) (dB) of ferrites is related to their thickness. Therefore, achieving a high SE (dB) typically requires ferrite materials with larger mass and volume. While conductive metals offer high SE (dB), they can cause eddy current heating in high-power wireless devices. Recently, David Smith of Duke University proposed a method for magnetic field shielding using mu-near-zero (MNZ) metamaterials. According to effective medium theory, the near-zero permeability region near the localized magnetic resonance generated by the metamaterial can be used to reflect near-field magnetic fields. According to Snell's law, this MNZ metamaterial can only shield obliquely incident waves and cannot shield normally incident magnetic fields. Furthermore, SE (dB) is heavily dependent on the metamaterial's quality factor (Q), meaning that each metamaterial unit requires a large number of conductor turns to provide a high inductance and achieve a high Q. However, a larger number of conductor turns will increase the intrinsic loss of the unit, which is not conducive to improving the unit's Q value. Moreover, this method still cannot effectively solve the problem of transmission of normally incident waves.

[0004] Disadvantages of traditional solutions: 1. Traditional solutions require a thicker thickness to meet the required shielding effectiveness, but the density of ferrite is relatively high. Therefore, when the volume increases, the required ferrite mass becomes thicker, which increases the burden on the system.

[0005] 2. Ferrite is relatively expensive, and relying heavily on ferrite to achieve better shielding effectiveness will increase the shielding cost of the system.

[0006] 3. The disadvantage of traditional metamaterials is that they do not take into account the shielding mechanism of normally incident waves, which will cause part of the normally incident waves to be transmitted, resulting in magnetic leakage. Therefore, under the same volume as the composite magnetic shielding metamaterial, its shielding performance is poor. Summary of the Invention

[0007] In order to solve the above problems, the present invention provides a composite magnetic shielding metamaterial and a preparation method thereof, which can better shield normally incident waves that traditional metamaterials cannot shield, and greatly improve the shielding effectiveness of the composite magnetic shielding metamaterial in a smaller size and volume.

[0008] The present invention is achieved through the following scheme: A method for preparing a composite magnetic shielding metamaterial, comprising the steps of:

[0009] Based on the principle of using near-zero magnetic permeability metamaterials for magnetic field shielding, a near-zero magnetic permeability metamaterial unit is designed with a non-magnetic substrate as the unit substrate;

[0010] Replacing the non-magnetic conductive substrate in the near-zero magnetic permeability metamaterial unit with a magnetic conductive substrate to prepare a composite magnetic shielding metamaterial unit;

[0011] Adjust the size of the resonant capacitor in the composite magnetic shielding metamaterial unit so that the frequency ω at the near-zero magnetic permeability is MNZ Equal to the frequency of the desired shielding.

[0012] A further improvement in the preparation method of the composite magnetic shielding metamaterial of the present invention is that the near-zero magnetic permeability material unit includes the non-magnetic substrate and a first coil and a second coil symmetrically attached to both sides of the non-magnetic substrate, the tail end of the first coil is connected to the center of the second coil, and a resonant capacitor is connected between the center of the first coil and the tail end of the second coil.

[0013] A further improvement of the method for preparing the composite magnetic shielding metamaterial of the present invention is that the step of designing the near-zero magnetic permeability metamaterial unit comprises:

[0014] Set the shielding operating frequency f, and determine the unit side length a according to the operating frequency f, so that the unit side length a satisfies the requirement of being less than the operating wavelength 1 / 10 of

[0015] Let the outer diameters of the non-magnetic substrate, the first coil, and the second coil be equal to the unit side length a;

[0016] The size of the resonant capacitor is determined so that it satisfies the equivalent permeability μ of the near-zero permeability metamaterial unit perpendicular to the direction of the non-magnetic substrate at the operating frequency f. z is zero.

[0017] A further improvement of the method for preparing the composite magnetic shielding metamaterial of the present invention is that the method for adjusting the size of the resonant capacitance in the composite magnetic shielding metamaterial unit comprises the steps of:

[0018] According to the effective medium theory, the equivalent magnetic permeability μ is determined z and frequency ω and resonant frequency ω r Relationship:

[0019]

[0020] Where: F is the filling factor of the metamaterial; when the equivalent magnetic permeability μ z = 0, the resonant frequency ω can be obtained r and the frequency ω at near-zero permeability MNZ Relationship:

[0021]

[0022] According to the resonance frequency formula, the resonance frequency ω can be obtained r Relationship with inductance and capacitance:

[0023]

[0024] Where: L is the sum of the inductance of the first coil and the inductance of the second coil; ΔL is the inductance provided by the magnetic substrate; C is the capacitance of the resonant capacitor in the near-zero permeability metamaterial unit; C+ΔC is the capacitance of the resonant capacitor in the composite shielding metamaterial unit;

[0025] By adjusting the size of ΔC, the resonant frequency ω is adjusted r The size of the frequency ω MNZ Equal to the frequency to be shielded.

[0026] A further improvement of the method for preparing the composite magnetic shielding metamaterial of the present invention is that the setting range of the operating frequency f is 5KHZ to 30GHZ.

[0027] A further improvement of the method for preparing the composite magnetic shielding metamaterial of the present invention is that the magnetic conductive substrate is made of ferrite material.

[0028] The present invention also provides a composite magnetic shielding metamaterial, comprising a composite magnetic shielding metamaterial unit prepared by the above-mentioned composite magnetic shielding metamaterial preparation method.

[0029] A further improvement of the composite magnetic shielding metamaterial of the present invention is that there are multiple composite magnetic shielding metamaterial units, and the multiple composite magnetic shielding metamaterial units are closely arranged in an array.

[0030] Based on the anti-magnetic properties of traditional metamaterials, the present invention uses a magnetic conductive substrate to construct a magnetic conductive magnetic circuit, which can better shield the normal incident waves that traditional metamaterials cannot shield, effectively reduce leakage magnetic flux, and greatly improve the shielding effectiveness of the composite magnetic shielding metamaterial in a smaller size and volume. High-performance magnetic shielding can be achieved by arbitrarily selecting frequencies within the range of 5KHZ to 30GHZ. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A flow chart of a method for preparing a composite magnetic shielding metamaterial according to the present invention is shown.

[0032] Figure 2 A front view of an embodiment of a near-zero permeability metamaterial unit is shown.

[0033] Figure 3 A side view of an embodiment of a near-zero permeability metamaterial cell is shown.

[0034] Figure 4 A front view of an embodiment of a ferrite sheet is shown.

[0035] Figure 5 A side view of an embodiment of a ferrite sheet is shown.

[0036] Figure 6 A front view of an embodiment of a composite shielding metamaterial unit of the present invention is shown.

[0037] Figure 7 A side view of an embodiment of a composite shielding metamaterial unit of the present invention is shown.

[0038] Figure 8 The equivalent circuit diagram of the composite shielding metamaterial unit of the present invention is shown.

[0039] Figure 9 A front view of an embodiment of a composite shielding metamaterial array of the present invention is shown.

[0040] Figure 10 A schematic diagram of an embodiment of shielding a non-resonant wireless energy transmission system using the present invention is shown.

[0041] Figure 11 A schematic diagram showing the shielding effectiveness comparison of a comparison experiment using a near-zero permeability metamaterial, a ferrite sheet, and the composite shielding metamaterial of the present invention is shown. DETAILED DESCRIPTION

[0042] Because traditional ferrite shielding solutions require a relatively thick thickness to achieve the required shielding effectiveness, and ferrite has a high density, as the volume increases, the required ferrite mass increases, increasing the system burden. Ferrite is also relatively expensive, and relying heavily on ferrite to achieve good shielding effectiveness increases the system's shielding cost. Traditional shielding solutions using near-zero permeability metamaterials fail to consider the shielding mechanism for normally incident waves, which can cause some normally incident waves to be transmitted, resulting in magnetic leakage and loss of shielding performance. The present invention combines the magnetic conductivity of magnetic materials such as ferrite with the anti-magnetic properties of near-zero permeability metamaterials to design a high-performance composite magnetic shielding metamaterial with selectable frequencies within the 5 kHz to 30 GHz range. By adding a magnetically conductive material to create a magnetically conductive magnetic circuit, this composite magnetic shielding metamaterial effectively shields normally incident waves, which are not shielded by traditional near-zero permeability metamaterials, thereby significantly improving shielding effectiveness (SE) (dB).

[0043] The composite magnetic shielding metamaterial and its preparation method are further described below with reference to specific embodiments and accompanying drawings.

[0044] See Figure 1 As shown, a method for preparing a composite magnetic shielding metamaterial includes the following steps:

[0045] Step S1: Based on the principle of using near-zero magnetic permeability metamaterials for magnetic field shielding, a near-zero magnetic permeability metamaterial unit is designed with a non-magnetic conductive substrate as a unit substrate.

[0046] First, let's briefly describe the principle of magnetic field shielding by this near-zero permeability metamaterial:

[0047] Under deep subwavelength conditions, according to Snell's law, the boundary conditions of the near-field magnetic field excitation source coil are solved, and the relationship between the transmittance T and the equivalent magnetic permeability can be obtained, that is:

[0048]

[0049] Where: T is the transmission coefficient; k is the wave vector in air (k0 is the wave vector in vacuum, k x and k z are the wave vectors in the air along the x direction and along the z direction respectively); q is the wave vector component passing through the metamaterial along the z direction; δ is the thickness of the metamaterial; μ x and μ z are the magnetic permeabilities of the metamaterial along the x and z directions, ε x is the dielectric constant of the metamaterial along the x direction, μ x , ε x Both are 1.

[0050] When designing the near-zero permeability metamaterial unit, it is only necessary to make the equivalent permeability μ along the z directionz =0.

[0051] According to the effective medium theory, the equivalent magnetic permeability μ can be determined z and frequency ω and resonant frequency ω r The relationship is as follows:

[0052]

[0053] Where: r is the damping, ω r is the resonant frequency of the unit, Q is the quality factor; and F is the filling factor of the metamaterial.

[0054] For near-zero permeability metamaterials, when the equivalent permeability μ z = 0, the resonant frequency ω can be obtained according to formula (3) r and the frequency ω at near-zero permeability MNZ The relationship is as follows:

[0055]

[0056] According to formula (4), the equivalent frequency ω of the near-zero permeability metamaterial can be calculated MNZ According to the LC resonance frequency formula It can be seen that the resonant frequency ω r It is related to the total inductance L and total capacitance C in the LC equivalent circuit. Therefore, the equivalent permeability μ can be adjusted by adjusting the LC resonant circuit. z =0.

[0057] On the structure of unit 4 of near-zero permeability materials: coordination Figure 2 and Figure 3 As shown, the near-zero magnetic permeability material unit 4 includes the non-magnetic substrate 3 (such as an acrylic plate, etc.) and two enameled coils 2 symmetrically attached to both sides of the non-magnetic substrate 3, namely a first coil a and a second coil b. The tail end of the first coil a is connected to the center of the second coil b, and a resonant capacitor 1 is connected between the center of the first coil a and the tail end of the second coil b.

[0058] When designing the near-zero permeability metamaterial unit 4, first, the shielding operating frequency f is set according to the magnetic field conditions of the wireless transmission system to be shielded. The setting range of the operating frequency f can be any value in the range of 5KHZ to 30GHZ. The unit side length a is determined according to the operating frequency f, so that the unit side length a satisfies the requirement of being less than the operating wavelength. 1 / 10 of the value, to ensure that the near-zero permeability metamaterial is under sub-wavelength conditions; then, the outer diameters of the non-magnetic substrate 3, the first coil a, and the second coil b are all equal to the side length a of the unit; finally, the size of the resonant capacitor 1 is determined to satisfy the equivalent permeability of the near-zero permeability metamaterial unit 4 perpendicular to the direction of the non-magnetic substrate at the operating frequency f is zero.

[0059] Step S2: Coordination Figure 6 and Figure 7 As shown, the non-magnetic substrate 3 in the near-zero magnetic permeability metamaterial unit 4 is replaced with a magnetic substrate 10 to prepare a composite magnetic shielding metamaterial unit 11. Preferably, the magnetic substrate 10 is the same size as the non-magnetic substrate 3 and is made of a ferrite material with high magnetic permeability. That is, the structure of the composite magnetic shielding metamaterial unit 11 includes a magnetic substrate 10 that is the same size and thickness as the non-magnetic substrate 3 and two enameled coils 9 symmetrically attached to both sides of the magnetic substrate 10, namely, a first coil a and a second coil b that are the same as those in the near-zero magnetic permeability metamaterial unit, and the tail end of the first coil a is connected to the center of the second coil b, and a resonant capacitor 8 of the same specification is connected between the center of the first coil a and the tail end of the second coil b.

[0060] Since the near-zero permeability metamaterial has the characteristics of near-zero permeability, it behaves as a diamagnetic material. However, due to the near-field manipulation of its wave vector k x ≥k0, when there is normal incidence, that is, the wave vector k x When ≈ k, conventional near-zero permeability metamaterials experience some transmission. To address this issue, a high-permeability ferrite substrate is added in step S2 to replace the non-magnetic substrate 3, providing a magnetic path for the transmitted waves. Therefore, it is necessary to combine the near-zero permeability metamaterial with the high-permeability ferrite substrate to obtain a composite magnetic shielding metamaterial with high shielding effectiveness.

[0061] Step S3, adjusting the size of the resonant capacitor 8 in the composite magnetic shielding metamaterial unit 11 so that the frequency ω at the near-zero magnetic permeability is MNZ Equal to the frequency of the desired shielding.

[0062] Since the equivalent permeability μ of the near-zero permeability metamaterial Z It is related to the frequency, so the addition of ferrite will result in the frequency ω of the near-zero magnetic permeability of the composite magnetic shielding metamaterial MNZ Therefore, step S3 adjusts the frequency ω of the unit's near-zero magnetic permeability by fine-tuning the resonant capacitor. MNZ Adjust to the frequency where shielding is required. The adjustment method is the same as that of near-zero permeability metamaterials. Figure 8 As shown:

[0063] According to formula (3), formula (4) and the following resonance frequency formula (5), adjust the size of ΔC to make ω MNZ Equal to the frequency of the desired shielding:

[0064]

[0065] Wherein: L is the sum of the inductance of the first coil and the inductance of the second coil; ΔL is the inductance provided by the magnetic conductive substrate; C is the capacitance value of the resonant capacitor in the near-zero magnetic permeability metamaterial unit; C+ΔC is the capacitance value of the resonant capacitor in the composite shielding metamaterial unit.

[0066] This solution is unique in that, building on the antimagnetic properties of traditional near-zero permeability metamaterials, the addition of high-permeability ferrites allows for more precise control of the metamaterial's magnetic circuit, effectively reducing magnetic flux leakage and thereby improving shielding effectiveness (SE) (dB). Ultimately, the shielding effectiveness (SE) (dB) of the composite magnetic shielding metamaterial is significantly improved while maintaining a compact size and volume. At frequencies above 5 kHz, the shielding body and the source coil are close in size, and conventional magnetic permeable materials with a thickness of 3 mm only have a shielding effectiveness of 2dB to 4dB. In contrast, a composite magnetic shielding metamaterial of the same size as this ferrite can achieve a shielding effectiveness of 20dB to 25dB. On the other hand, achieving a shielding effectiveness of 20dB to 25dB using ferrites would require a large and heavy ferrite. However, the shielding of this composite magnetic shielding metamaterial is limited to a specific frequency, rather than broadband, and therefore offers frequency tunability. Compared to single metamaterials (such as near-zero permeability metamaterials), the addition of ferrite to this solution significantly improves the inductance of the metamaterial unit, resulting in a higher quality factor (Q). Furthermore, the composite magnetic shielding metamaterial provides a magnetic field path for incident waves at small angles of incidence, effectively preventing the penetration of positive magnetic fields. This effectively shields the positively incident magnetic field, further enhancing shielding effectiveness.

[0067] As a preferred embodiment, it includes a composite magnetic shielding metamaterial unit 11 prepared by the preparation method of the composite magnetic shielding metamaterial. Figure 9 and Figure 10 As shown, there are multiple composite magnetic shielding metamaterial units 11, and the multiple composite magnetic shielding metamaterial units 11 are densely arranged in an array to form a whole shielding structure 12. The shielding structure 12 is arranged between the transmitting coil and the receiving coil to be shielded, and its size is consistent with the two.

[0068] The following comparative experiments are conducted using near-zero permeability metamaterials, high permeability ferrite materials, and the composite magnetic shielding metamaterial of this solution as samples. These three samples are added to a non-resonant wireless energy transmission system to compare the final shielding effectiveness. Specifically:

[0069] Provide near-zero permeability metamaterial samples, refer to Figure 2 and Figure 3 : It includes 49 near-zero magnetic permeability metamaterial units 4, and each near-zero magnetic permeability metamaterial unit 4 is composed of three parts: one is a resonant capacitor 1 for adjusting the lumped parameters, and the resonant capacitor 1 is a metal film polyester capacitor with a capacitance C of 10nF and a withstand voltage of about 1000VDC; the second is two enameled coils 2 for providing inductance, and the two enameled coils 2 provide inductance for the resonant unit, and the inductance L is 0.395uH. The radius of each enameled coil 2 is L1=26.5mm. Specifically, each enameled coil 2 contains two identical enameled coils ab wound in the same direction, wherein the center of coil a is connected to the tail end of coil b, and the tail end of coil a and the center of coil b are connected to the two ends of the resonant capacitor 1. Therefore, the metamaterial unit has a resonant frequency in the near field. The operating frequency is f=72.5kHz, and the quality factor The resistance introduced by the wire is R=1Ω. After fitting, the filling factor is F=0.3 and the damping r=25.1kHz. The third is a square acrylic sheet 3, which plays a fixing role and has a magnetic permeability of 1. The side length L2 of the acrylic sheet 3 is 53mm and the thickness d is 1mm.

[0070] Provide ferrite material samples, refer to Figure 4 and Figure 5 : It includes 49 square ferrite sheets 6. Specifically, the ferrite sheet 6 is MnZn ferrite, and its thickness and area are the same as those of the near-zero magnetic permeability metamaterial unit 4, with a side length L2 = 53 mm and a thickness of 2d = 2 mm. Its initial magnetic permeability μ is about 2800 below 1 MHz at 25°C.

[0071] Provide composite magnetic shielding metamaterial samples, refer to Figure 6 and Figure 7 : It includes 49 composite magnetic shielding metamaterial units 11, and each composite magnetic shielding metamaterial unit 11 is composed of three parts: one is a resonant capacitor 8 for adjusting the lumped parameters, and the resonant capacitor 8 is exactly the same as the resonant capacitor of the near-zero magnetic permeability metamaterial unit; the second is two enameled coils 9 for providing inductance, and the two enameled coils 9 are exactly the same as the enameled coils of the near-zero magnetic permeability metamaterial unit, and the connection method between the two enameled coils 9 and the resonant capacitor 8 is also exactly the same as the near-zero magnetic permeability metamaterial; the third is a square ferrite sheet (i.e., a magnetic conductive substrate 10), with a side length L2 of 53mm and a thickness d of 1mm. The initial magnetic permeability of the magnetic conductive substrate 10 is about 2800 at 25°C below 1MHz. After the enameled coil 9 is compounded with the ferrite sheet, the ferrite provides a certain equivalent inductance, such as Figure 8As shown, the resonant frequency of the composite magnetic shielding metamaterial unit 11 shifts from 80 kHz to 78.5 kHz. According to the resonant frequency formula, the ferrite provides an additional inductance ΔL of approximately 0.016 μH. Therefore, the quality factor Q of the composite magnetic shielding metamaterial unit 11 is 202.72. This quality factor is higher than that of the near-zero permeability metamaterial unit 4. By adjusting the resonant capacitor 8, the shifted frequency is restored to ensure near-zero permeability characteristics.

[0072] Each sample is densely arranged in a 7×7 array to form a corresponding shielding structure, such as Figure 9 form, Figure 9 The shielding structure is formed by a dense array of 49 composite magnetic shielding metamaterial units 11, with a total side length L3 of 371 mm.

[0073] Build a non-resonant wireless transmission system and add the three samples mentioned above into the system. Figure 10 , Figure 10 Taking the composite magnetic shielding metamaterial shielding structure 12 as an example, the transmitting coil Tx and receiving coil Rx of this non-resonant wireless power transmission system are wound with 400 strands of enameled wire, each with a cross-sectional diameter of 0.078 mm. The enameled wire is a polyester-covered wire with a polyurethane enameled wire core. Both coils are 312 mm in diameter and have 10 turns each, forming planar spiral coils. The ends of the metal conductors are heat-treated in a high-temperature tin furnace to form terminal blocks that can be connected to a 50 ohm impedance wiring clamp. The shielding structure 12 is positioned symmetrically with the transmitting coil Tx and the receiving coil Rx at a distance S = 60 mm from the central axis. The distance between the transmitting coil Tx and the receiving coil Rx is set to 2S = 120 mm. The non-resonant transmitting coil Tx and receiving coil Rx are connected to port 1 and port 2 of a network analyzer, respectively, via coaxial cables. The network analyzer has a detection range of 9 kHz to 1.5 GHz. The three samples were added into the non-resonant wireless transmission system in the manner of the shielding structure 12, and the transmission coefficients S of the three shielding states were recorded in the dB mode using a network analyzer. 21样品 , and the transmission coefficient S of the unshielded sample 21系统 Finally, the shielding effectiveness formula (7) is used to calculate the shielding effectiveness SE of the three 样品 (dB) and obtain the shielding effectiveness comparison chart, such as Figure 11 shown.

[0074] SE 样品 (dB) = -10log10 (S 21样品 -S 21系统 ) (7)

[0075] The size of the above-mentioned shielding structure sample is determined according to the system to be shielded. In this embodiment, it is determined according to the size of the transmitting coil Tx. It is required that the size of the shielding structure should not be smaller than the size of the transmitting coil Tx to ensure the shielding effect.

[0076] Depend on Figure 11 It can be seen that under a certain operating frequency, the shielding effectiveness of the composite magnetic shielding metamaterial is the best, and the composite magnetic shielding metamaterial has a smaller size and volume than the ferrite material.

[0077] The present invention has been described in detail above with reference to the embodiments of the accompanying drawings. A person skilled in the art can make various modifications to the present invention based on the above description. Therefore, certain details in the embodiments should not be construed as limiting the present invention. The scope of protection of the present invention shall be determined by the scope defined in the appended claims.

Claims

1. A method for preparing a composite magnetic shielding metamaterial, characterized in that: Including steps: Based on the principle of using near-zero magnetic permeability metamaterials for magnetic field shielding, a near-zero magnetic permeability metamaterial unit is designed with a non-magnetic substrate as the unit substrate; Replacing the non-magnetic conductive substrate in the near-zero magnetic permeability metamaterial unit with a magnetic conductive substrate to prepare a composite magnetic shielding metamaterial unit; Adjust the size of the resonant capacitor in the composite magnetic shielding metamaterial unit so that the frequency at the near-zero magnetic permeability is equal to the frequency of the desired shielding; where, The near-zero magnetic permeability metamaterial unit includes the non-magnetic substrate and a first coil and a second coil symmetrically attached to two sides of the non-magnetic substrate, wherein the tail end of the first coil is connected to the center of the second coil, and a resonant capacitor is connected between the center of the first coil and the tail end of the second coil; The steps of designing the near-zero permeability metamaterial unit include: Set the shielding operating frequency , according to the operating frequency Determine the element side length , so that the unit side length Less than the working wavelength 1 / 10 of Let the outer diameters of the non-magnetic substrate, the first coil and the second coil be equal to the side length of the unit ; Determine the size of the resonant capacitor so that it satisfies the near-zero permeability metamaterial unit at the operating frequency The equivalent magnetic permeability perpendicular to the direction of the non-magnetic substrate is is zero.

2. The method for preparing the composite magnetic shielding metamaterial according to claim 1, wherein: The operating frequency The setting range is 5KHZ~30GHZ.

3. The method for preparing the composite magnetic shielding metamaterial according to claim 1, wherein: The magnetic conductive substrate is made of ferrite material.

4. A composite magnetic shielding metamaterial, characterized in that: It comprises a composite magnetic shielding metamaterial unit prepared by the preparation method of the composite magnetic shielding metamaterial according to any one of claims 1 to 3.

5. The composite magnetic shielding metamaterial according to claim 4, wherein: There are multiple composite magnetic shielding metamaterial units, and the multiple composite magnetic shielding metamaterial units are closely arranged in an array.

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