Dual-frequency magnetic negative metamaterial array structure and design method

Abstract

The application discloses a dual-frequency magnetic negative metamaterial array structure and a design method, and relates to the technical field of wireless power and information collaborative transmission. The structure comprises a hexagonal epoxy glass fiber copper-clad plate, an external capacitor and a nested hexagonal metal spiral coil, three unit cells form an array, and the size of the external capacitor is changed to realize simultaneous transmission under two frequency bands. The application further provides a design method of the dual-frequency magnetic negative metamaterial array, which comprises the following steps: S1, determining the size of a metamaterial unit cell and the maximum side length of inner and outer spiral coils according to actual requirements of an implantable device; S2, optimizing the turn spacing and line width of the hexagonal coil; S3, calculating the size of the external capacitor and verifying the magnetic negative characteristics of the dual-frequency magnetic negative metamaterial; and S4, arranging three unit cells to form an array and placing the array in the middle of a transmitting coil and a receiving coil. The application provides a dual-frequency magnetic negative metamaterial array structure and a design method which can effectively improve the energy transmission efficiency and information transmission quality.

Description

Technical Field

[0001] This invention relates to the technical field of wireless power and information transmission, specifically to a dual-frequency magnetic negative metamaterial array structure and its design method. Technical Background

[0002] The continuous and stable operation of implantable medical devices (IMDs) relies on reliable power supply and two-way data interaction. However, traditional built-in batteries pose a significant burden and risk to patients due to their limited battery life and the need for surgical replacement. Magnetic-coupled resonant wireless power transfer (MCR-WPT) technology, with its contactless, compatible, and flexible nature, provides an effective way to achieve external wireless power supply for IMDs. As IMDs become more intelligent and complex, they have an equally urgent need for real-time and reliable in-vivo and out-of-body communication, making synchronous wireless power and information transfer systems suitable for implantable scenarios a key research direction. [Cai C, Liang C, Wu S, et al. Simultaneous wireless power and data transfer system with full-duplex mode based on t-type and m-derived filters[J]. IEEE Transactions on Transportation Electrification, 2025, 11(6): 12974-12984.]

[0003] Currently, wireless power and information transmission in IMDs mainly employs near-field inductive coupling or low-frequency magnetic coupling schemes. These schemes offer advantages such as mature technology, high transmission efficiency, and simple circuit structure. However, they also have significant shortcomings in clinical applications, primarily: the external transmitting device is large and heavy, making it inconvenient for patients to carry, affecting their daily lives and appearance; the transmission distance is short, requiring strict alignment and making it difficult to penetrate deep tissues, limiting its application location; unnecessary thermal effects may occur both inside and outside the body during energy transmission, posing a risk of local tissue overheating; simultaneously, its electromagnetic field may cause electromagnetic interference to other surrounding precision medical devices, and it is difficult to achieve stable, high-speed bidirectional data communication in complex biological tissue environments. [Park Y, Hung PD, Youn D, ​​et al. A wireless power and data transfer system for medical implants using a miniaturized inductive link with frequency-splitting enhancement[J]. IEEE Journal of Solid-State Circuits,2025, 60(11): 3966-3984.]

[0004] Ma Hongshuai et al. from North China University proposed adding stacked metamaterials to the power and signal transmission system. By designing central stacking and edge stacking, the two stacked blocks exhibit specific equivalent permeability at different frequencies. Although this improves transmission performance, it introduces additional dielectric losses. They also proposed a metamaterial-inspired absorber based on an open resonant ring. This absorber uses the negative refraction principle of metamaterials to reflect the magnetic field generated at the signal port back to itself, thereby suppressing magnetic field leakage and enhancing port isolation. However, it suffers from poor anti-offset performance and large size. In summary, existing technologies cannot simultaneously achieve the synergistic optimization of high transmission efficiency, strong anti-offset capability, and high information quality. A novel power and signal transmission system scheme is urgently needed. [Ma H, Zhang P, Zhang J, et al. Laminated Hybrid Metamaterial Block for Enhanced Efficiency and SNR in Simultaneous Wireless Power and Signal Transmission System With Dual-Sided LCCL Compensation Networks[J]. IEEE Transactions on PowerElectronics, 2025, 40(7):10077-10094.]

[0005] Chinese invention patent CN202210225527.9 discloses a wireless power supply device based on electromagnetic metamaterials, but it only considers the wireless transmission of electrical energy. Chinese invention patent CN202311015771.3 discloses a dual-band WIFI energy harvesting device based on an electromagnetic metamaterial structure, where both bands are used for signal transmission, resulting in a relatively simple function that cannot meet the integrated requirements of modern devices for simultaneous signal and power transmission. Chinese invention patent CN202310829577.2 discloses a magnetic harmonic power transmission and communication system, which avoids the need for a separate information transmission module in addition to the power transmission module, but it does not consider the problems of low efficiency and poor signal quality during energy transmission.

[0006] Therefore, to improve system transmission efficiency, enhance anti-migration capability, and maintain information transmission rate, a dual-frequency magnetic negative metamaterial array structure and design method are proposed. This structure nests two hexagonal metal spiral coils, corresponding to two operating frequencies respectively. The magnetic negative properties of the metamaterial are used to focus the magnetic field while reducing the distribution of spatial leakage magnetic field. Then, by assembling DB-MNG primitives into an array structure, a certain degree of anti-migration performance is achieved. Summary of the Invention

[0007] The technical problem to be solved by this invention is to address the shortcomings of the prior art by proposing a dual-frequency magnetic negative metamaterial array structure and design method to solve the problems mentioned in the background art.

[0008] On one hand, according to the embodiments of this application, a dual-frequency magnetic negative metamaterial array structure is provided, including an epoxy glass fiber copper-clad laminate (FR-4), an external capacitor, and a nested hexagonal metal spiral coil. The FR-4 substrate is designed as a regular hexagon to reduce the overall metamaterial intervention loss. The nested hexagonal metal spiral coil structure is also designed as a regular hexagon to improve the system's anti-displacement capability. The nested hexagonal metal spiral coil structure includes P1 and P2. P1 is wound around the central region of the FR-4 substrate, and P2 is printed on the surface of the FR-4 substrate and surrounds P1. Both P1 and P2 are connected in series with the external capacitor on the back of the FR-4 substrate through vias, forming an array structure with the three unit elements. Simultaneous transmission of dual frequency bands is achieved by changing the size of the external capacitor.

[0009] On the other hand, this application proposes a design method for a dual-frequency magnetic negative metamaterial array, including the following steps: S1: Select the energy transmission frequency and information transmission frequency reasonably according to the operating frequency requirements of the implantable device's energy and information transmission system; S2: Determine the size of the unit cell of the dual-frequency magnetic negative metamaterial (DB-MNG) and the maximum side lengths of P1 and P2; S3: Optimize the turn spacing and linewidth of the DB-MNG unit element through the control variable method and finite element analysis; S4: Determine the size of the external capacitor based on the permeability of the electromagnetic metamaterial at its operating frequency and verify the negative permeability characteristics of DB-MNG. S5: Based on the designed unit DB-MNG primitive array, place it between the transmitting and receiving coils to achieve high-efficiency energy transmission and high-quality information transmission of the system.

[0010] According to one aspect of the present application, the implantable energy transmission and communication device operates in a wide frequency range in step S1, extending from a low frequency of 9kHz to a high frequency of 2.4GHz. In practical applications, the low frequency band of 9kHz-315kHz and the mid frequency band of 6.78MHz-13.56MHz are often used for short-distance energy transmission and communication. Two frequencies can be selected within this range as the operating frequencies of the implantable energy transmission and communication device, but the interval between the two selected frequencies should be large to reduce interference between frequencies.

[0011] According to one aspect of the present application, the characteristic feature is that, in step S2, the diameter D of the receiving and transmitting coil is determined based on the actual parameters of the implanted device. x The diameter of the DB-MNG unit cell is 34mm. It must be greater than 1 / 3 of the diameter of the receiving / transmitting coil, but not exceed it. Therefore, the maximum side lengths l of P1 and P2 are determined by the side length of the DB-MNG unit cell. p1 and l p2 , l p1 Compared to a 1mm reduction in the edge length of the basic unit, l p2 It increases by 2mm compared to half the side length of the basic element.

[0012] According to the design method of claim 2, the parameter optimization index in step S3 is the quality factor Q, which is achieved by controlling the number of turns N1 and N2 and the thickness t of P1 and P2. c The distance D between the two t For parameters such as s1 and s2, and line widths w1 and w2, the optimal values ​​for the inner and outer coil turns are selected by default. The specific values ​​of these parameters should satisfy the following formula: (1)

[0013] Finally, the optimized P1 and P2 were printed on the FR-4 substrate, ensuring that there was no overlap between P1 and P2.

[0014] According to the design method of claim 2, the effective permeability of DB-MNG is changed by adjusting the size of the external capacitor in step S4. When the permeability is negative, the DB-MNG primitives specifically exhibit that P1 and P2 resonate violently before and after the corresponding operating frequencies, and the surface currents reverse before and after the resonant frequencies.

[0015] According to one aspect of the present application, the optimized three DB-MNG primitives are arranged into an array in step S5. The distance between the two coils is determined to be 20mm according to the actual position of the implanted device in the human body, and the center is aligned in the horizontal direction. The designed DB-MNG array is placed vertically and horizontally at 1 / 2 of the receiving and transmitting coil.

[0016] The beneficial effects of this invention are as follows:

[0017] After incorporating the energy and information transmission system, the magnetic field distribution in both frequency bands of the DB-MNG array structure of this invention is significantly improved compared to the traditional system without metamaterials. Furthermore, the addition of the DB-MNG array effectively reduces the leakage magnetic field, effectively avoids electromagnetic interference to other precision medical equipment in the vicinity, improves the electromagnetic compatibility of the system, and enhances the overall safety of the system.

[0018] The present invention significantly enhances the stability of the energy field as the information carrier in terms of information transmission, fundamentally reducing the bit error rate of signal demodulation; it improves the overall anti-interference capability of the energy-information co-transmission link, ensures the transmission reliability of modulated signals in complex bioelectromagnetic environments, and provides a new solution for building a more efficient and safer wireless energy and information co-transmission system for implantable devices. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the DB-MNG unit structure;

[0020] Figure 2 A schematic diagram of the DB-MNG array;

[0021] Figure 3 This is a graph showing the relationship between the metamaterial quality factor and the pitch and linewidth of the spiral coil turns;

[0022] Figure 4 The equivalent permeability curve of DB-MNG;

[0023] Figure 5 Verification of the negative magnetic characteristics of DB-MNG in two frequency bands;

[0024] Figure 6 To add the DB-MNG array system simulation model diagram;

[0025] Figure 7To illustrate the situation, a comparison of the magnetic field distribution before and after the addition of the dual DB-MNG array system is shown.

[0026] Figure 8 A comparison of the magnetic field distribution before and after the DB-MNG array system is added for the case of a 20mm offset.

[0027] Figure 9 To illustrate the situation, waveform comparison charts before and after the DB-MNG array system were added.

[0028] Figure 10 A waveform comparison chart showing the DB-MNG array system before and after the 20mm offset is added. Detailed Implementation

[0029] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be described in further detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are intended to explain this application only and are not intended to limit this application. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples of this application.

[0030] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0031] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0032] In this application, "multiple" means two or more (including two).

[0033] This invention is applied to wireless power and signal transmission systems for implantable devices, specifically relating to the structure and design method of Litzized magnetic negative metamaterials.

[0034] The following is combined with Figures 1 to 10The structure and design method of the Litzized magnetic negative metamaterial of the present invention will be described in detail according to the embodiments of this application.

[0035] See appendix Figure 1 The DB-MNG basic structure includes a hexagonal FR-4 substrate 0101, nested hexagonal metal spiral coils 0102 and 0103, external capacitors 0111 and 0112, substrate vias 0113, and coil vias 0114 and 0115. When the system is operating, the DB-MNG array focuses the magnetic field in both frequency bands onto the receiving coil, thereby enhancing the coupling between the two coils.

[0036] Specifically, considering the size of the implantable device, in this embodiment, the side length 0104 of the DB-MNG FR-4 substrate is set to 12mm; the outer ring metal spiral coil 0102 has 2 turns, a maximum side length 0106 of 11mm, a line width 0109 of 0.8mm, and a turn spacing 0110 of 0.3mm; the inner ring metal spiral coil 0103 has 4 turns, a maximum side length 0105 of 8mm, a line width 0107 of 1mm, and a turn spacing 0108 of 0.2mm; the inner and outer metal spiral coils are printed on the FR-4 substrate and connected in series with an external capacitor on the back of the substrate through vias, thereby changing the operating frequency corresponding to the inner and outer metal spiral coils by changing the external capacitance values ​​of the inner and outer rings.

[0037] See appendix Figure 2 To further improve the overall anti-offset performance of the system, in this embodiment, the three designed DB-MNG primitives are arranged into an array.

[0038] On one hand, according to the embodiments of this application, a dual-frequency magnetic negative metamaterial array structure is provided, including an epoxy glass fiber copper-clad laminate (FR-4), an external capacitor, and a nested hexagonal metal spiral coil. The FR-4 substrate is designed as a regular hexagon to reduce the overall metamaterial intervention loss. The nested hexagonal metal spiral coil structure is also designed as a regular hexagon to improve the system's anti-offset capability. The nested hexagonal metal spiral coil structure includes an inner hexagonal metal spiral coil P1 and an outer hexagonal metal spiral coil P2. P1 is wound around the central region of the FR-4 substrate, and P2 is printed on the FR-4 surface and surrounds P1. Both P1 and P2 are connected in series with the external capacitor on the back of the FR-4 substrate through vias, forming an array structure with the three unit elements. At this time, no matter which direction the receiving coil is offset, 1-2 unit elements in the array can always adjust the magnetic field to make the receiving coil receive more magnetic lines of force, thereby improving the overall system's anti-offset performance.

[0039] On the other hand, this application proposes a design method for a dual-frequency magnetic negative metamaterial array, including the following steps: S1: Select the energy transmission frequency and information transmission frequency reasonably according to the operating frequency requirements of the implantable device's energy and information transmission system; S2: Determine the size of the DB-MNG unit cell and the maximum side lengths of P1 and P2; S3: Optimize the turn spacing and linewidth of the DB-MNG unit element through the control variable method and finite element analysis; S4: Determine the size of the external capacitor based on the permeability of the electromagnetic metamaterial at its operating frequency and verify the negative permeability characteristics of DB-MNG. S5: Based on the designed unit DB-MNG primitive array, place it between the transmitting and receiving coils to achieve high-efficiency energy transmission and high-quality information transmission of the system.

[0040] According to one aspect of the present application, the characteristic feature is that, in step S1, the operating frequency of the implantable simultaneous communication device is selected as 6.78MHz and 13.56MHz.

[0041] The equivalent inductance and equivalent capacitance of the hexagonal electromagnetic metamaterial can be calculated using formulas (1) and (2). (2) (3)

[0042] Based on the results of the above two equations, the resonant frequency of the metamaterial element can be calculated using formula (3). (4)

[0043] The AC impedance of the coil can be obtained from formula (4). (5)

[0044] The equivalent magnetic permeability of the metamaterial can be obtained from formula (5). (6)

[0045] In the formula Represents the permeability of free space. d represents the fill factor of a metal spiral coil. avg Let be the average diameter of the metal spiral coil, s be the turn spacing of the electromagnetic metamaterial, n be the number of turns of the coil, f be the resonant frequency of the metamaterial element, C0 be the external lumped capacitance, and ρ be the average diameter of the metal spiral coil. c l is the resistivity of a metallic material. c δ is the total length of the coil; F is the skin effect coefficient; F is the area ratio of the metal helical coil on the resonant element; the above formulas establish the relationship between the structural parameters of electromagnetic metamaterials, resonant frequency and negative permeability characteristics of electromagnetic metamaterials, which can provide a basis for the optimized design of electromagnetic metamaterial structures.

[0046] According to one aspect of the embodiments of this application, the diameter D of the receiving and transmitting coil is determined in step S2 based on the actual parameters of the implanted device. x The diameter of the DB-MNG unit cell is 34mm. It is greater than 1 / 3 of the diameter of the receiving / transmitting coil, but does not exceed the diameter of the receiving / transmitting coil. Determine the side length L of the DB-MNG unit cell. a The maximum side lengths of P1 and P2 are 8mm and 11mm respectively, which are determined by the side length of the DB-MNG primitive.

[0047] See appendix Figure 3 Using the controlled variable method and finite element simulation, the number of turns, thickness, and spacing between P1 and P2 are controlled, while other parameters are left at their default optimal values. The quality factor Q is used as the optimization target to optimize the turn spacing and line width of the inner and outer metal spiral coils.

[0048] Specifically, through attachment Figure 3 It can be seen that when the spacing between the inner and outer turns and the line width increase, the quality factor Q shows a trend of first increasing and then decreasing. The optimal values ​​of the spacing between the inner and outer metal spiral coils, s1 and s2, are determined to be 0.2 mm and 0.3 mm, respectively, and the optimal values ​​of the width, w1 and w2, are 1 mm and 0.8 mm, respectively.

[0049] See appendix Figure 4 After determining the DB-MNG basic parameters, the external capacitance of the inner and outer rings can be calculated using fixed operating frequencies of 6.78MHz and 13.56MHz. When the permeability is close to -1, the external capacitance corresponding to the energy operating frequency of 6.78MHz is 740pF, and the external capacitance corresponding to the information operating frequency of 13.56MHz is 167pF. (See attached diagram.) Figure 4 The equivalent permeability curve shown is shown.

[0050] Participate in the attached Figure 5 Adjusting the size of the external capacitor behind the inner and outer metal spiral coils changes the equivalent permeability of the DB-MNG. The negative permeability characteristic of the element is specifically reflected in the reverse current distribution in the element when its operating frequency is around the resonant frequency.

[0051] Specifically, at 6.7 MHz, the current direction in the element of the metamaterial inner ring (0501) is counterclockwise, and at 7 MHz, the current direction is clockwise. At 13.50 MHz, the current direction in the element of the metamaterial outer ring (0503) is counterclockwise, and at 13.66 MHz, the current direction is clockwise, indicating that DB-MNG exhibits negative magnetic characteristics at both resonant frequencies.

[0052] See appendix Figure 6The optimized three DB-MNG primitives are arranged into an array. The distance between the two coils is determined to be 20mm according to the actual placement position of the implanted device in the human body, and the center is aligned in the horizontal direction. The designed DB-MNG array is placed vertically and horizontally at 1 / 2 of the receiving and transmitting coils.

[0053] See appendix Figure 7 The magnetic field distribution of the system before and after adding the DB-MNG array was compared through finite element simulation.

[0054] Specifically, attached Figure 7 The diagram shows the system magnetic field distribution before and after the addition of the DB-MNG array. Before the DB-MNG array was added, the overall magnetic field strength of the system was low and the distribution was relatively dispersed, with most of the magnetic field focused on the transmitting coil. After the DB-MNG array was added, the magnetic field was focused from the metamaterial to the receiving coil, and the magnetic field distribution became more concentrated.

[0055] See appendix Figure 8 The magnetic field distribution of the receiving coil of the system after adding the DB-MNG array was simulated by finite element method to show the magnetic field distribution in three directions offset by 20mm.

[0056] Specifically, Figure 0801 shows the magnetic field distribution of the system receiving coil offset by 20mm along the y-axis before and after the addition of the DB-MNG array. When the DB-MNG array is not added and the offset is 20mm, the magnetic field strength of the system is low. After the DB-MNG array is added, the magnetic field strength increases because the alignment between the receiving coil and the elements above the DB-MNG array increases, which increases the magnetic field lines received by the receiving coil.

[0057] Specifically, Figure 0802 shows the magnetic field distribution of the system receiving coil offset by 20mm along the z-axis before and after the addition of the DB-MNG array. When the DB-MNG array is not added and the offset is 20mm, the magnetic field strength of the system is also low. After the DB-MNG array is added, the magnetic field strength is less than that of the y-axis offset because the alignment between the receiving coil and the elements on the right side of the DB-MNG array increases, but they do not completely overlap.

[0058] Specifically, Figure 0803 shows the magnetic field distribution of the system's receiving coil offset by 20mm along a 45° direction before and after adding the DB-MNG array. When the DB-MNG array is not added and the offset is 20mm, the magnetic field strength of the system is the lowest value under the three offset directions. After adding the DB-MNG array, the improvement of the system is relatively small because the alignment between the receiving coil and the basic elements of the DB-MNG array is completely reduced. In summary, the anti-offset capability of the system is significantly improved after adding the DB-MNG array.

[0059] See appendix Figure 9An experimental system was built to compare the current and voltage waveforms of the receiving coil and the signal demodulation waveform before and after the DB-MNG array was added. After the DB-MNG array was added, the waveform amplitude of the current and voltage of the receiving coil increased, which improved the system transmission efficiency and the information transmission rate reached 0.4 Mkbs.

[0060] See appendix Figure 10 The waveforms were compared by offsetting them by 20mm in three directions. When offset by 20mm in three directions, the transmission performance of the system with the DB-MNG array was improved compared to the system without the metamaterial.

[0061] The above are merely embodiments of this application and are not intended to limit this application. The general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application shall be included within the scope of the claims of this application.

Claims

1. A dual-frequency magnetic negative metamaterial array structure, characterized in that... The system includes an epoxy fiberglass copper-clad laminate (FR-4), an external capacitor, and a nested hexagonal metal spiral coil structure. The FR-4 substrate is designed as a regular hexagon to reduce overall metamaterial interference loss. The nested hexagonal metal spiral coil structure is also designed as a regular hexagon to improve the system's anti-displacement capability. The nested hexagonal metal spiral coil structure includes an inner coil P1 and an outer coil P2. P1 is wound around the central region of the FR-4 substrate, and P2 is printed on the FR-4 surface and surrounds P1. Both P1 and P2 are connected in series with an external capacitor on the back of the FR-4 substrate through vias, forming an array structure with the three unit cells. Simultaneous transmission of dual frequency bands is achieved by changing the size of the external capacitor.

2. A design method for a dual-frequency magnetic negative metamaterial array, comprising the dual-frequency magnetic negative metamaterial array structure as described in claim 1, characterized in that, Includes the following steps: S1: Select the energy transmission frequency and information transmission frequency reasonably according to the operating frequency requirements of the implantable device's energy and information transmission system; S2: Determine the size of the unit cell of the dual-frequency magnetic negative metamaterial (DB-MNG) and the maximum side lengths of P1 and P2; S3: Optimize the turn spacing and linewidth of the DB-MNG unit element through the control variable method and finite element analysis; S4: Determine the size of the external capacitor based on the permeability of the electromagnetic metamaterial at its operating frequency and verify the negative permeability characteristics of DB-MNG. S5: Based on the designed unit DB-MNG primitive array, place it between the transmitting and receiving coils to achieve high-efficiency energy transmission and high-quality information transmission of the system.

3. The design method according to claim 2, characterized in that, In step S1, the operating frequency range of the implantable energy and communication simultaneous transmission device is relatively wide: from a low frequency of 9kHz to a high frequency of 2.4GHz. In practical applications, the low frequency band of 9kHz-315kHz and the mid frequency band of 6.78MHz-13.56MHz are often used for short-distance energy transmission and communication. Two frequencies can be selected within this range as the operating frequencies of the implantable energy and communication simultaneous transmission device, but the interval between the two selected frequencies should be large to reduce interference between frequencies.

4. The design method according to claim 2, characterized in that, In step S2, the diameter D of the receiving and transmitting coil is determined based on the actual parameters of the implanted device. x The diameter of the DB-MNG unit cell is 34mm. It must be greater than 1 / 3 of the diameter of the receiving / transmitting coil, but not exceed it. Therefore, the maximum side lengths l of P1 and P2 are determined by the side length of the DB-MNG unit cell. p1 and l p2 , l p1 Compared to a 1mm reduction in the edge length of the basic unit, l p2 It increases by 2mm compared to half the side length of the basic element.

5. The design method according to claim 2, characterized in that, In step S3, the parameter optimization index is the quality factor Q, which is achieved by controlling the number of turns N1 and N2 and the thickness t of P1 and P2. c The distance D between the two t For parameters such as s1 and s2, and line widths w1 and w2, the optimal values ​​for the inner and outer coil turns are selected by default. The specific values ​​of these parameters should satisfy the following formula: Finally, the optimized P1 and P2 were printed on the FR-4 substrate, ensuring that there was no overlap between P1 and P2.

6. The design method according to claim 2, characterized in that, In step S4, adjusting the size of the external capacitor changes the equivalent permeability of the DB-MNG. When the permeability is negative, the DB-MNG primitives specifically exhibit the following behavior: P1 and P2 resonate violently before and after the corresponding operating frequencies, and the surface currents reverse before and after the resonant frequencies.

7. The design method according to claim 2, characterized in that, In step S5, the optimized three DB-MNG primitives are arranged into an array. The distance between the two coils is determined to be 20mm according to the actual placement position of the implanted device in the human body, and the center is aligned in the horizontal direction. The designed dual-frequency magnetic negative metamaterial array is placed vertically and horizontally at 1 / 2 of the receiving and transmitting coil.

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