A design method for small-size shielded electromagnetic metamaterials in the KHz band

Abstract

The present invention discloses a design method for a small-size shielding electromagnetic metamaterial for the KHz band, which relates to the field of metamaterial design technology, including: constructing a double-layer end-to-end spiral coil electromagnetic metamaterial primitive model, simulating the model to obtain inductance parameters and resistance parameters, determining the external lumped capacitance parameters and quality factor; judging whether near-zero permeability may occur; simulating the latest model to obtain a solution for the primitive resonant frequency, and comparing the solution with the resonant frequency required by the design; calculating the model geometric factor; calculating the curve of the complex permeability of the electromagnetic metamaterial; determining the point where the permeability is zero and selecting one's own target near-zero interval; simulating the designed model to observe the shielding effect. The present invention is easy to operate, improves the efficiency and repeatability of the design and manufacturing process, realizes the small size of the metamaterial, can meet the electromagnetic shielding requirements of low frequency bands and high efficiency, and has high practicality and market value.

Description

Technical Field

[0001] The present invention relates to the technical field of metamaterial design, and in particular to a design method for a small-size shielding electromagnetic metamaterial in the KHz band. Background Art

[0002] Wireless charging technology supports load devices to obtain electrical energy in a non-contact manner and has been widely used in the field of power supply for power equipment. Magnetic coupling resonant wireless charging technology has attracted widespread attention due to its advantages of high energy transfer efficiency, large transmission power, long energy transfer distance, and no strict directionality, and has broad prospects for engineering applications. However, since the inductive coupling transmitting coil and receiving coil are separated, a large leakage inductance will be generated, which also brings about a series of problems such as electromagnetic compatibility, electromagnetic radiation and pollution.

[0003] Traditional electromagnetic compatibility means mainly use paramagnetic materials represented by metals for shielding, and use high magnetic materials represented by ferrites to improve the working performance of wireless energy transmission systems. However, this method has shortcomings. Although this technical route can better solve the electromagnetic environment and working performance optimization problems of medium and low frequency magnetic resonance wireless power transmission systems in the frequency band of tens of KHz, as the application scenarios further increase the transmission distance requirements, the efficiency of medium and long distance magnetic resonance wireless power transmission systems will drop sharply. Therefore, it is necessary to increase the operating frequency of the system to increase the coupling between the transceiver coils. However, in the frequency band of around MHz, ferrite cores and ferromagnetic metals will significantly increase the loss of the system as the operating frequency increases. In addition, the shielding body made by this technical route has problems such as difficult to control volume and weight, and a greater impact on the original structure during rectification.

[0004] Electromagnetic metamaterials are subwavelength structures composed of periodically arranged metal and / or dielectric hybrid materials. These hybrid materials are engineered to achieve unique electromagnetic properties that do not exist in natural materials or are difficult to achieve. Under certain circumstances, electromagnetic metamaterials can achieve zero or near-zero magnetic permeability and can achieve complete or partial reflection of magnetic fields. Therefore, the zero magnetic permeability characteristics of shielding electromagnetic metamaterials can be used to make the magnetic field lines freely emitted to the electromagnetic metamaterials produce mirror reflections, so as to increase the magnetic field strength of the transmission channel and reduce the magnetic field strength of the non-transmission channel, thereby achieving the effect of electromagnetic shielding.

[0005] At present, the existing technology mainly focuses on the design of negative magnetic permeability electromagnetic metamaterials. Although it has certain advantages in specific applications such as wireless charging of power equipment, since the design object is negative magnetic permeability metamaterials, it cannot meet the application scenarios with more special shielding effects, especially for the design of electromagnetic metamaterials that require near-zero magnetic permeability. This results in the existing technology being unable to effectively support the design of small-size shielding electromagnetic metamaterials in the KHz frequency band.

[0006] The existing technology adjusts the relative magnetic permeability of electromagnetic metamaterials by adding magnetorheological fluids of different concentrations or magnetorheological fluids of magnetic nanoparticles of different particle sizes, which is complex and difficult to operate. The concentration control of magnetorheological fluids and the precise regulation of particle sizes have a great impact on the actual performance of the material and are not easy to standardize, which makes the existing control methods lack flexibility and repeatability in practical applications.

[0007] Existing technologies generally use a planar spiral coil structure. This design has certain limitations for small-sized, high-frequency electromagnetic metamaterials. The planar structure performs poorly in miniaturization, especially in situations where it is necessary to control volume, improve shielding efficiency, and ensure low loss. It often fails to achieve the expected results.

[0008] The existing technology lacks the precise calculation and optimization of geometric parameters that are closely related to the area, volume, and winding tightness of the metamaterial unit in the design, resulting in a lack of systematicity and scientificity in the design of the metamaterial unit. In practical applications, the influence of geometric parameters is often ignored, which affects the overall performance of the metamaterial, especially in the optimization of parameters such as the resonant frequency and quality factor. Summary of the invention

[0009] The present invention provides a design method for small-size shielding electromagnetic metamaterials in the KHz band, which can solve the above-mentioned technical problems.

[0010] In order to solve the technical problems in the prior art and mentioned above, the technical solution adopted by the present invention is as follows:

[0011] The present invention provides a design method for a small-size shielding electromagnetic metamaterial for the KHz band, comprising the following steps:

[0012] S1. Determine the size and resonant frequency of the electromagnetic metamaterial element according to the parameters of the wireless energy transmission system that are consistent with the actual working conditions;

[0013] S2. Construct the latest double-layer end-to-end spiral coil electromagnetic metamaterial element model according to the size of the electromagnetic metamaterial element and confirm its model parameters.

[0014] S3. Use finite element simulation technology to simulate the double-layer end-to-end spiral coil electromagnetic metamaterial element model to obtain inductance parameters and resistance parameters, and determine the external lumped capacitance parameters and quality factor;

[0015] S4, judging whether near-zero magnetic permeability occurs according to the quality factor, if the quality factor is lower than the quality factor threshold, jumping to step S2, if the quality factor reaches the quality factor threshold, continuing to execute step S5;

[0016] S5, putting the latest double-layer end-to-end spiral coil electromagnetic metamaterial primitive model parameters into the finite element simulation software, simulating to obtain the solution of the primitive resonance frequency, and comparing the solution with the resonance frequency required by the design, if the difference between the two is less than the difference threshold, continue to execute step S6, otherwise jump to step S2;

[0017] S6. Calculate the geometric factors of the double-layer end-to-end spiral coil electromagnetic metamaterial element model based on the volume and inductance parameters of the electromagnetic metamaterial element, the maximum area enclosed by the spiral coils of the electromagnetic metamaterial element on the front side of the double-layer end-to-end spiral coil electromagnetic metamaterial element model, and the maximum area enclosed by the spiral coils of the electromagnetic metamaterial element on the back side of the double-layer end-to-end spiral coil electromagnetic metamaterial element model;

[0018] S7. Based on the geometric factor, inductance parameter, external lumped capacitance parameter, quality factor and resonant frequency, a curve of the complex magnetic permeability of the electromagnetic metamaterial is calculated, where the real part of the complex magnetic permeability of the electromagnetic metamaterial is the equivalent magnetic permeability, and the imaginary part is the metamaterial element loss;

[0019] S8. Determine the point where the magnetic permeability is zero according to the curve of the equivalent magnetic permeability and select the target near-zero interval to obtain the electromagnetic metamaterial model designed this time;

[0020] S9. Establish a wireless energy transmission system that is consistent with the actual working conditions in the electromagnetic simulation software, and add the electromagnetic metamaterial model designed this time. If the magnetic field strength on both sides changes significantly and the field strength meets the design requirements, it proves that this design is valid. Otherwise, jump to step S2.

[0021] Furthermore, the electromagnetic metamaterial primitive is the smallest unit for realizing the function of small-sized shielding electromagnetic metamaterials in the KHz band.

[0022] Furthermore, the structure of the double-layer end-to-end spiral coil electromagnetic metamaterial element model is as follows: square spiral structures with the same structure and the same number of turns but opposite spiral directions are respectively located on the front and back sides of the element substrate, and the beginning part of the spiral coil on the front side and the ending part of the spiral coil on the back side, as well as the ending part of the spiral coil on the front side and the beginning part of the spiral coil on the back side are respectively connected through through holes of the substrate. The model parameters include the outermost circle side length l of the square spiral coil on the electromagnetic metamaterial element, the length a of the electromagnetic metamaterial element, the width b of the electromagnetic metamaterial element, the height h, the number of turns N, the line width W and the line spacing S.

[0023] Furthermore, the calculation formula of the external lumped capacitance parameter C is as follows:

[0024] ;

[0025] The quality factor Q is calculated as follows:

[0026] ;

[0027] Among them, L is the inductance parameter, f0 is the resonant frequency; R is the resistance parameter.

[0028] Furthermore, the calculation formula of the geometric factor F is:

[0029] F= ;

[0030] Among them, 𝜇0 is the magnetic permeability of vacuum, S1 is the maximum area enclosed by the spiral coil on the front side of the magnetic metamaterial element, and S2 is the maximum area enclosed by the spiral coil on the back side; V represents the volume, which is obtained by calculating the length × width × height of the electromagnetic metamaterial element model.

[0031] Furthermore, the calculation formula of the complex magnetic permeability μ of the electromagnetic metamaterial is:

[0032] ;

[0033] Where j is the imaginary unit and f is the frequency.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. Design of small-size shielding electromagnetic metamaterials for KHz frequency band, using a double-layer series spiral coil structure, which can more effectively achieve near-zero magnetic permeability shielding effect compared with the negative magnetic permeability electromagnetic metamaterial design in the prior art, especially in electromagnetic wave shielding in the low-frequency band;

[0036] 2. Unlike the prior art in which the magnetic permeability is adjusted by adjusting the concentration or particle size of the magnetorheological fluid, the present invention adjusts the LC parameters through lumped capacitance. This method is not only easy to operate, but also easy to standardize and accurately control. The lumped capacitance method simplifies the adjustment process and improves the efficiency and repeatability of the design and manufacturing process.

[0037] 3. The present invention innovatively adopts a double-layer series spiral coil structure, which can better achieve miniaturization and high-efficiency performance compared to the traditional planar spiral coil structure. This design not only improves the inductance and quality factor of the metamaterial unit cell, but also performs better in shielding effect, loss control and space occupancy, and can meet the needs of high-frequency and high-efficiency electromagnetic shielding.

[0038] 4. The present invention introduces geometric factors that are closely related to the unit area, volume and winding tightness of electromagnetic metamaterials, and proposes a new calculation formula suitable for double-layer spiral coil structures in the KHz frequency band. By optimizing the geometric factors, the performance of electromagnetic metamaterials can be effectively improved, especially in terms of resonant frequency and quality factor, making the design more accurate and the performance more superior. This innovative design solves the problem of lack of geometric factor considerations in the design process of electromagnetic metamaterial primitives in the prior art, and greatly improves the scientificity and systematicity of the design.

[0039] 5. The electromagnetic metamaterial obtained by the design method of the present invention not only realizes a relatively good near-zero magnetic permeability characteristic in theory, but also shows an excellent shielding effect in practical applications when combined with the simulation analysis of the wireless energy transmission system. This design can not only meet the electromagnetic shielding requirements in wireless charging of power equipment, but also adapt to a wider range of electromagnetic wave shielding application scenarios, and has high practicality and market value. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 It is a front plan view of a small-sized shielding-type electromagnetic metamaterial element in the KHz segment in the embodiment.

[0042] Figure 2 3 is a back plan view of a small-sized shielded electromagnetic metamaterial element in the KHz segment in an embodiment.

[0043] Figure 3 It is a partial top view of the front side of a small-sized shielding electromagnetic metamaterial element in the KHz segment in the embodiment.

[0044] Figure 4 It is a partial top view of the back side of a small-sized shielded electromagnetic metamaterial element in the KHz segment in the embodiment.

[0045] Figure 5 4 is a side view of a small-sized shielded electromagnetic metamaterial element in the KHz range in an embodiment.

[0046] Figure 6 : is the normalized admittance-frequency curve of the RLC equivalent circuit of the metamaterial element at low frequency in the embodiment.

[0047] Figure 7: is the equivalent permeability-frequency theoretical curve of the small-sized shielded electromagnetic metamaterial element in the KHz range in the embodiment.

[0048] Figure 8 This is the theoretical curve of loss-frequency of a small-sized shielded metamaterial element in the KHz range in the embodiment.

[0049] Fig. 9 This is a wireless energy transmission system in the embodiment that is consistent with actual working conditions, in which the designed electromagnetic metamaterial is added.

[0050] Fig.10 for Fig. 9 The magnetic field distribution diagram of the wireless energy transmission system in the XZ plane is shown.

[0051] Fig.11 It is a flow chart of the design method of small-size shielding electromagnetic metamaterial in the KHz range described in the embodiment. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0053] This embodiment provides a design method for a small-sized shielding electromagnetic metamaterial in the KHz range. Fig.11 As shown, the specific steps include:

[0054] S1. Determine the size of the electromagnetic metamaterial element (length, width, and height are a, b, and h, respectively, in mm) and the resonant frequency f0, h according to the parameters of the wireless energy transmission system that are consistent with the actual working conditions. Figure 5 As shown, it is specifically the sum of the thickness of the front coil, the back coil, and the substrate.

[0055] S2. Construct the latest double-layer end-to-end spiral coil electromagnetic metamaterial element model according to the size of the electromagnetic metamaterial element and confirm its model parameters.

[0056] The basic model of the electromagnetic metamaterial with double-layer end-to-end spiral coils is as follows: Figure 1 , Figure 2As shown in FIG. 1 , square spiral structures with the same structure and the same number of turns but opposite spiral directions are located on the front and back sides of the base element, and the beginning of the spiral coil on the front side is connected to the end of the spiral coil on the back side, and the end of the spiral coil on the front side is connected to the beginning of the spiral coil on the back side through the through holes of the base element. The model parameters include the outermost circle length l of the square spiral coil on the electromagnetic metamaterial base element, the length a of the electromagnetic metamaterial base element, the width b of the electromagnetic metamaterial base element, the height h of the electromagnetic metamaterial base element, the number of turns N, the line width W and the line spacing S, respectively, as shown in FIG. Figure 1 , Figure 3 , Figure 4 As shown, and as Figure 1 As shown, the added lumped capacitor is also added on the front side, in series with the square spiral coil.

[0057] S3. Use finite element simulation technology to simulate the double-layer end-to-end spiral coil electromagnetic metamaterial element model to obtain the inductance parameter L and the resistance parameter R, and determine the external lumped capacitance parameter C and the quality factor Q.

[0058] Among them, the calculation formula of the external lumped capacitance parameter C is as follows:

[0059]

[0060] The quality factor Q is calculated as follows:

[0061]

[0062] S4. Preliminarily determine whether near-zero magnetic permeability is likely to occur based on the quality factor Q. If the quality factor Q is too low (Q<15), near-zero magnetic permeability is unlikely to occur, and jump to step S2. If the quality factor Q meets the requirements, continue to execute step S5.

[0063] S5. Put the latest double-layer end-to-end helical coil electromagnetic metamaterial element model parameters into the finite element simulation software, and simulate to obtain the solution of the element resonant frequency. , and compare the solution with the resonant frequency f0 required by the design. If the difference between the two is within 15%, the data is credible and step S6 is executed, otherwise jump to step S2.

[0064] At low frequencies, the normalized admittance of the metamaterial element RLC equivalent circuit (RLC circuit refers to a circuit structure composed of resistance R, inductance L, and capacitance C) is approximately equal to the normalized magnetic susceptibility of the metamaterial obtained by full-wave simulation and S parameter (scattering parameter) inversion. During simulation, the metamaterial element model is placed in the finite element calculation software to solve the normalized admittance curve of the model, as shown in the figure below: Figure 6As shown in , the resonant frequency of the element can be obtained by finite element calculation method, which can be cross-validated with the previous calculation results. Figure 6 As shown in the figure, it is the normalized admittance-frequency curve obtained by the finite element calculation method. The horizontal coordinate corresponding to the frequency point corresponding to the highest point is the resonant frequency calculated by the finite element method. , is 172KHz, and the determined resonant frequency point is 175KHz, the difference between the two is less than 15%, so the data is credible and f0 is taken as the standard.

[0065] S6, based on the volume V of the electromagnetic metamaterial primitive, the inductance parameter L, the front of the double-layer end-to-end spiral coil electromagnetic metamaterial primitive model, and the maximum area S1 enclosed by the spiral coil of the electromagnetic metamaterial primitive, such as Figure 1 As shown. And the maximum area S2 enclosed by the spiral coil on the back of the double-layer end-to-end spiral coil electromagnetic metamaterial element model, as shown Figure 2 The maximum area refers to the area enclosed by the outermost spiral line. The geometric factor F of the double-layer end-to-end spiral coil electromagnetic metamaterial primitive model is calculated using the following formula:

[0066]

[0067] Where f is the frequency; 𝜇0 is the vacuum permeability, which is 4π × 10 −7 𝐻 / 𝑚;

[0068] The volume V is calculated as length × width × height;

[0069] S7. Based on the geometric factor F, inductance parameter L, external lumped capacitance parameter C, quality factor Q and resonant frequency f0, the complex magnetic permeability μ-frequency curve of the electromagnetic metamaterial is calculated. The real part of the complex magnetic permeability μ of the electromagnetic metamaterial is the equivalent magnetic permeability, and the imaginary part is the metamaterial element loss.

[0070] The principle of this step is to use a physical open circuit method to achieve the continuity of current through the inter-turn capacitance, accumulate reverse charges on the outer and inner circles, and use the conservation of electromotive force to obtain the equivalent magnetic permeability of the resonator unit of the square spiral coil. And for the electromagnetic metamaterial with a double-layer end-to-end spiral coil structure, there is currently no very complete calculation formula. The embodiment of the present invention proposes an improved electromagnetic metamaterial equivalent magnetic permeability calculation method suitable for the KHz frequency band based on the calculation formula of the equivalent magnetic permeability of the traditional single-sided structure electromagnetic metamaterial.

[0071] For the double-layer coil structure electromagnetic metamaterial, the spiral coils on both sides will affect the overall parameters; further, the spiral coils on both sides each form a closed area, and each has its own winding tightness. Therefore, the traditional single-sided electromagnetic metamaterial complex permeability calculation formula is no longer applicable to the double-layer coil structure electromagnetic metamaterial.

[0072] In this regard, the calculation formula for the complex magnetic permeability μ of the improved electromagnetic metamaterial proposed in this embodiment is:

[0073]

[0074] in, is the frequency, in Hz; is the resonant frequency of the electromagnetic metamaterial unit; j is an imaginary unit. In the calculation formula for the complex magnetic permeability μ of the improved electromagnetic metamaterial proposed in this embodiment, the real part Re(μ) is the equivalent magnetic permeability, which indicates the change of the magnetic permeability of the unit in electromagnetic fields of different frequencies. Figure 7 As shown; the imaginary part Im(μ) is the metamaterial element loss, which indicates the change of the element dissipation of electromagnetic waves of different frequencies in electromagnetic fields of different frequencies, such as Figure 8 shown.

[0075] S8. Determine the point where the magnetic permeability is zero based on the curve of the equivalent magnetic permeability and select your own target near-zero interval to obtain the electromagnetic metamaterial model designed this time.

[0076] The equation for determining the point where the magnetic permeability is zero based on the equivalent magnetic permeability curve and selecting one's own target near-zero interval is expressed as:

[0077]

[0078] Solving this equation can obtain the frequency point when the equivalent magnetic permeability is zero.

[0079] S9. Establish a wireless energy transmission system that is consistent with the actual working conditions in the electromagnetic simulation software, and add the electromagnetic metamaterial primitives or arrays of the electromagnetic metamaterial model designed this time, such as Fig. 9 As shown in Figure 1, the wireless energy transmission system includes a transmitting coil and a receiving coil. The corresponding field strength diagram is obtained to visually observe the actual shielding effect of the electromagnetic metamaterial, as shown in Figure 1. Fig.10 As shown, different colors correspond to different field intensities. Before and after the electromagnetic wave emitted by the transmitting coil passes through the electromagnetic metamaterial element, the field intensity distribution of the electromagnetic wave changes greatly, and an area with obvious shielding effect on the electromagnetic wave is formed within a certain range of the electromagnetic metamaterial element.

[0080] When it is seen that the magnetic field strength on both sides changes significantly after the electromagnetic metamaterial element or array is added and the field strength meets the design requirements, it proves that the design is effective. Otherwise, jump to step S2 to rebuild the model.

[0081] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A design method for small-size shielded electromagnetic metamaterials in the KHz range, characterized in that: The following steps are involved: S1. Determine the size and resonant frequency of the electromagnetic metamaterial element according to the parameters of the wireless energy transmission system that are consistent with the actual working conditions; S2. construct a double-layer end-to-end spiral coil electromagnetic metamaterial primitive model according to the size of the electromagnetic metamaterial primitive, and confirm the model parameters; S3. Use finite element simulation technology to simulate the double-layer end-to-end spiral coil electromagnetic metamaterial element model to obtain inductance parameters and resistance parameters, and determine the external lumped capacitance parameters and quality factor; S4, judging whether near-zero magnetic permeability occurs according to the quality factor, if the quality factor is lower than the quality factor threshold, jumping to step S2, if the quality factor reaches the quality factor threshold, continuing to execute step S5; S5, putting the latest double-layer end-to-end spiral coil electromagnetic metamaterial primitive model parameters into the finite element simulation software, simulating to obtain the solution of the primitive resonance frequency, and comparing the solution with the resonance frequency required by the design, if the difference between the two is less than the difference threshold, continue to execute step S6, otherwise jump to step S2; S6. Calculate the geometric factor of the double-layer end-to-end spiral coil electromagnetic metamaterial element model based on the volume of the electromagnetic metamaterial element, the inductance parameter, the maximum area enclosed by the spiral coil of the electromagnetic metamaterial element on the front side of the double-layer end-to-end spiral coil electromagnetic metamaterial element model, and the maximum area enclosed by the spiral coil of the electromagnetic metamaterial element on the back side of the double-layer end-to-end spiral coil electromagnetic metamaterial element model; the calculation formula of the geometric factor F is: Wherein, μ0 is the vacuum magnetic permeability, S1 is the maximum area enclosed by the spiral coil on the front side of the magnetic metamaterial unit, and S2 is the maximum area enclosed by the spiral coil on the back side; L is the inductance parameter, and V represents the volume, which is obtained by calculating the length × width × height of the electromagnetic metamaterial unit model; S7. Based on the geometric factor, inductance parameter, external lumped capacitance parameter, quality factor and resonant frequency, a curve of the complex magnetic permeability of the electromagnetic metamaterial is calculated, where the real part of the complex magnetic permeability of the electromagnetic metamaterial is the equivalent magnetic permeability, and the imaginary part is the metamaterial element loss; S8. Determine the point where the magnetic permeability is zero according to the curve of the equivalent magnetic permeability and select the target near-zero interval to obtain the electromagnetic metamaterial model designed this time; S9. Establish a wireless energy transmission system that is consistent with the actual working conditions in the electromagnetic simulation software, and add the electromagnetic metamaterial model designed this time. If the magnetic field strength on both sides changes significantly and the field strength meets the design requirements, it proves that this design is valid. Otherwise, jump to step S2.

2. A design method for small-size shielding electromagnetic metamaterials for KHz band according to claim 1, characterized in that: The electromagnetic metamaterial primitive is the smallest unit for realizing the function of small-sized shielded electromagnetic metamaterials in the KHz band.

3. The design method of a small-size shielding electromagnetic metamaterial for KHz band according to claim 2, characterized in that: The structure of the double-layer end-to-end spiral coil electromagnetic metamaterial element model is as follows: square spiral structures with the same structure and the same number of turns but opposite spiral directions are respectively located on the front and back sides of the element substrate, and the beginning part of the spiral coil on the front side and the ending part of the spiral coil on the back side, as well as the ending part of the spiral coil on the front side and the beginning part of the spiral coil on the back side are respectively connected through through holes of the substrate. The model parameters include the outermost circle side length l of the square spiral coil on the electromagnetic metamaterial element, the length a of the electromagnetic metamaterial element, the width b of the electromagnetic metamaterial element, the height h of the electromagnetic metamaterial element, the number of turns N, the line width W and the line spacing S.

4. The design method of a small-size shielding electromagnetic metamaterial for KHz band according to claim 3 is characterized in that: The calculation formula of the external lumped capacitance parameter C is as follows: The quality factor Q is calculated as follows: Among them, L is the inductance parameter, f0 is the resonant frequency; R is the resistance parameter.

5. The design method of a small-size shielding electromagnetic metamaterial for KHz band according to claim 4, characterized in that: The quality factor threshold is 15.

6. The design method of a small-size shielding electromagnetic metamaterial for KHz band according to claim 4, characterized in that: The difference threshold is 15%.

7. A design method for small-size shielding electromagnetic metamaterials for KHz band according to claim 6, characterized in that: The calculation formula of the complex magnetic permeability μ of the electromagnetic metamaterial is: Where j is the imaginary unit and f is the frequency.

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