A structure of a magnetically negative metamaterial and a design method

Abstract

This invention discloses a Litzized magnetic negative metamaterial structure and design method, relating to the field of wireless power transmission in implantable devices. The structure consists of three square printed circuit boards (PCBs), arranged from top to bottom as a top-layer metal spiral, a middle-layer metal spiral, and a surface-mount capacitor. The top and middle layers are connected by vias, with multiple parallel metal spirals wound sequentially from the inside out in an alternating manner to achieve planar Litzized wiring, reducing AC losses. The bottom layer connects the two ends of the metal coil to the surface-mount capacitor through vias, used to adjust the operating frequency and permeability. A Litzized magnetic negative metamaterial design method is also proposed, including S1: presetting the basic parameters of the receiving and transmitting coils and the metamaterial; S2: optimizing the optimal number of turns; S3: selecting a relatively optimal range of strand counts; and S4: optimizing the number of split strands. This application provides a Litzized magnetic negative metamaterial structure and design method for implantable devices that can effectively reduce metamaterial AC losses and improve magnetic focusing capabilities.

Description

Technical Field

[0001] This invention relates to the field of wireless power transmission in implantable devices, and specifically to a Litzized magnetic negative metamaterial structure and design method. Technical Background

[0002] Traditional implantable medical devices primarily address the issue of wireless power supply, extending the device's operating time within the body. Once implanted, their operational status, battery condition, and treatment effectiveness are difficult to monitor effectively. Adjustments to the implanted device's parameters often require further surgical intervention, resulting in a lack of flexibility and adaptability in treatment. Real-time monitoring of various physiological data within the body provides more accurate treatment guidance in clinical practice. However, implantable medical devices typically use independent links for data communication, increasing the size and power consumption of the implant. The emergence of Wireless Power and Data Transfer (WPDT) technology offers a safer option for transmitting information and energy from implantable medical devices with monitoring capabilities. In practical applications, patient movement makes it difficult to ensure proper alignment of the receiving coil (Tx) and transmitting coil (Rx), leading to significant variations in the coupling coefficient. This reduces power and transmission efficiency. Furthermore, the modulation index (MI) of the data is also affected by changes in mutual inductance, further reducing data transmission reliability. [Karimi MJ, Schmid A,Dehollain C. Wireless power and data transmission for implanted devices viainductive links: A systematic review[J]. IEEE Sensors Journal, 2021, 21(6):7145-7161.]

[0003] Magnetic negative metamaterials are artificial materials with negative magnetic permeability. Their application in wireless power transmission systems and energy-controlled energy-to-infrastructure (WPT) systems can significantly improve mutual inductance, thereby enhancing transmission performance and anti-misalignment capabilities. However, the addition of metamaterials introduces additional ohmic and dielectric losses, affecting or even negating the gain gained through the focusing magnetic field. Furthermore, at high frequencies, the uneven current distribution on the surface of traditional metamaterial metal spiral coils affects their magnetic focusing ability, hindering further improvements in system transmission performance after the addition of metamaterials. [Xia N, Ma H, Yan S, et al. Designof Low‐Loss Electromagnetic Metamaterial with Non‐uniform Linewidth for Magnetic Field Convergence in WPT System[J]. IEEJ Transactions on Electrical and Electronic Engineering, 2024, 19(12): 2033-2043.]

[0004] Therefore, to reduce the impact of metamaterial intervention losses on the system in implantable devices, a Litzized magnetic negative metamaterial structure and design method are proposed. This structure uses a multi-strand wire interleaved winding method wound on a multilayer printed circuit board, eliminating the induced voltage difference between each strand, suppressing the skin effect and proximity effect, reducing AC resistance, and enhancing magnetic focusing capability. This structure can be applied to implantable devices to achieve robust energy and signal transmission. Summary of the Invention

[0005] The core objective of this invention is to provide a Litzized magnetic negative metamaterial structure and design method. By using a wiring method of "periodic interleaving of multiple strands in the top and middle layers + series-connected chip capacitors in the bottom layer", the invention solves the pain points of the prior art.

[0006] On one hand, according to the embodiments of this application, a Litzized magnetic negative metamaterial structure is provided, which is composed of a three-layer PCB, and is arranged from top to bottom as top layer traces, middle layer traces, and bottom layer chip capacitors. The PCB substrate is set as a square. The top layer and middle layer traces are carried by the PCB and are spirally wound from the center of the PCB substrate to the PCB boundary using a planar Litzized wiring structure. The bottom layer chip capacitors connect the top layer and middle layer traces end to end through vias. The operating frequency and permeability can be changed by changing the capacitance value.

[0007] According to one aspect of the embodiments of this application, the top layer trace and the middle layer trace are connected end to end. The top layer trace moves segment by segment from the outside to the inside along a metal spiral winding path within the turn width limit. After each segment of the trace, it is displaced inward by one strand width. When it is displaced to the innermost side of the trace, a via is added to switch the strand to the middle layer. The middle layer trace is wound in the opposite way to the top layer, moving segment by segment from the inside to the outside along a metal spiral winding path. When it is moved to the outermost side, a via is added to switch to the top layer. This cycle realizes a periodically interleaved planar Litzized wiring structure.

[0008] On the other hand, embodiments of this application provide a method for designing a Litzized magnetic negative metamaterial for the above-mentioned structure, comprising the following steps: S1: Preset the size of the receiving and transmitting coils, and preset the inner diameter, turn width, turn gap, and substrate thickness of the Litzized magnetic negative supermaterial; S2: Analyze the trend of transmission efficiency variation in metamaterial systems with unsplit wires and optimize the number of turns of the metal spiral; S3: Calculate the resistance variation trend of Litzized magnetic negative supermaterials under different number of segments, and select the optimal number of segments based on modeling difficulty and preparation cost; S4: Through finite element analysis, the transmission efficiency and magnetic field strength of Litzized magnetic negative metamaterial systems with different number of segments are used to determine the optimal number of strands in the metal spiral.

[0009] According to one aspect of the embodiments of this application, in step S1, a receiving and transmitting coil conforming to the size limit of the Lepu Qinming8631SR pacemaker is selected, and the substrate of the Litzite magnetic negative metamaterial is cubic in shape with an inner radius d. in outer radius d of the substrate out Width of turn w, width of strand w t Turn gap s, coil thickness t c Substrate thickness h, number of turns N, and number of segments N t Should meet (1)

[0010] Where the inner radius d in The distance from the center of the substrate to the metal spiral, and the outer radius d out This is the distance from the center of the substrate to the substrate boundary, which is limited by the size of the implanted device.

[0011] According to one aspect of the embodiments of this application, in step S2, a receiving and transmitting coil is constructed in a finite element simulation, and the transmission distance is set with reference to the implantation location of the heart pacemaker. The undivided metamaterial is placed at the center of the transmission path at the same distance from the transmitting coil and the receiving coil. Starting from 2, the number of turns is increased in steps of 1, and the optimal number of turns is obtained with the highest system transmission efficiency as the condition.

[0012] According to one aspect of the embodiments of this application, in step S3, a homogeneous model of the Litzized magnetic negative metamaterial is constructed using finite element simulation; specifically, a model of length 2*d is established. out The height is h+2t c A cuboid, made of copper, with boundary conditions set as a coil, is used to simulate the current homogenization effect of Litzized winding by using an external current density as excitation. The square of the normalized magnetic field strength of the metamaterial is obtained through volume integral, and combined with the conduction and proximity loss coefficient ϕ. cond ϕ prox,r ϕ prox,z The study calculates the trends of conduction loss, proximity loss, and total loss for Litzized magnetic negative metamaterials with different numbers of segments under ideal conditions. Since the homogenization model does not consider the impact of vias on the metamaterial, and the number of vias increases with the number of segments, introducing additional losses, a range of segment numbers that are easy to manufacture and have low losses needs to be selected for further modeling and analysis, taking into account wiring difficulty and manufacturing cost. Specifically, an odd number of segments facilitates layout; if the metal spiral is polygonal, N segments should be selected. t =k*a+1 strands can ensure the symmetry of the metal spiral and simplify the modeling difficulty. Here, k is a constant that increases by 1 step size starting from 1, and a is the number of sides of the polygon. At the same time, the minimum line width of the trace and the minimum size of the via directly affect the number of strands and the manufacturing cost. In summary, a better range of the number of strands that meets the above conditions is selected.

[0013] According to one aspect of the embodiments of this application, in step S4, Litzized magnetic negative supermaterials with different numbers of strands are modeled, the lumped capacitance value when the permeability is -1 is calculated using the S-parameter inversion method, and the value is placed at the center of the transmission path. The center point of the receiving coil is set as the reference point, and the optimal number of strands is selected with the goal of maximizing the system transmission efficiency and the magnetic field strength at the reference point.

[0014] The beneficial effects of this invention are as follows: The Litzized magnetic negative metamaterial of this invention divides the metal spiral into many parallel traces, providing a larger effective area for current transmission and reducing conduction losses caused by the skin effect; furthermore, the parallel multi-strand wires are wound in an alternating manner between the upper and middle layers of the PCB, ensuring that each wire has the same relative position in the magnetic field, and each parallel conductor can be considered identical, eliminating the induced voltage difference between coils, reducing eddy currents between each wire, and thus reducing the proximity effect. Combined with the chip capacitors at the bottom layer for connecting the two ends of the metal spiral, the metamaterial's own losses can be effectively reduced, the uniformity of current distribution can be improved, and the magnetic focusing ability can be enhanced. Attached Figure Description

[0015] Figure 1 The diagram shows the structure of the Litzized magnetic negative metamaterial, where 01-1 is a three-dimensional schematic diagram of the Litzized magnetic negative metamaterial and 01-2 is a two-dimensional cross-sectional view of the Litzized magnetic negative metamaterial.

[0016] Figure 2 A diagram of the finite element simulation model for optimizing the number of turns;

[0017] Figure 3 The transmission efficiency of the system when the number of turns varies;

[0018] Figure 4 A homogeneous model for Litzized magnetic negative supermaterials;

[0019] Figure 5 The resistance variation trend of the Litzized magnetic negative metamaterial is shown when the number of segments changes, where 05-1 represents the skin resistance and proximity resistance, and 05-2 represents the total resistance.

[0020] Figure 6 Equivalent permeability plot of S-parameter inversion primitives;

[0021] Figure 7 The diagram shows the magnetic field distribution of the system, where 07-1 represents the system without metamaterials, 07-2 represents the system with undivided metamaterials, 07-3 represents the system with 5 strands of Litzized magnetic negative metamaterials, and 07-4 represents the system with 9 strands of Litzized magnetic negative metamaterials.

[0022] Figure 8 The system transmission efficiency and magnetic field strength are given when the receiver is offset, where 08-1 represents the horizontal offset and 08-2 represents the angular offset.

[0023] Figure 9 The waveform of the receiving coil is shown when the image is directly facing the source, where 9-1 represents the waveform without the addition of metamaterial. Figure 9-2 To incorporate Litzized magnetic negative supermaterials;

[0024] Figure 10Let 10⁻¹ represent the system's transmission efficiency, root mean square (RMS) output voltage, and modulation index under receiver offset conditions. Here, 10⁻¹ represents the system's transmission efficiency and RMS output voltage under horizontal offset, 10⁻² represents the system's modulation index under horizontal offset, 10⁻³ represents the system's transmission efficiency and RMS output voltage under angular offset, and 10⁻⁴ represents the system's modulation index under angular offset. Detailed Implementation

[0025] 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.

[0026] 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.

[0027] 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.

[0028] In this application, "multiple" means two or more (including two).

[0029] This invention relates to wireless power transmission systems for implantable devices, specifically to a Litzized magnetic negative metamaterial structure and design method.

[0030] The following is combined with Figures 1 to 10 The present invention provides a detailed description of the structure and design method of a Litzized magnetic negative metamaterial according to the embodiments of this application.

[0031] See appendix Figure 1The Litz-modified magnetic negative supermaterial consists of a top metal spiral 0101, a middle metal spiral 0103, a bottom chip capacitor 0105, and upper and middle dielectric substrates 0102 and lower and middle layers 0104. The top layer trace 0101 moves segment by segment along the winding path of the metal spiral from the outside to the inside. After each segment, it moves inward by one trace width. When it reaches the innermost layer, a via 0106 is added to switch the trace to the middle layer. The winding method of the middle layer trace 0103 is the opposite of that of the top layer. The middle layer trace moves segment by segment along the winding path of the metal spiral from the inner circle to the outer circle. When it reaches the outermost layer, a via 0106 is added to switch it to the top layer. This cycle achieves a planar Litz structure, making the relative position of each trace in the magnetic field the same, thus canceling the induced voltage difference between each trace and reducing the skin loss and conduction loss of the metal spiral coil. The bottom-layer chip capacitor 0105 connects the top and middle layers of the Litzized metal spiral end through via 0107. By changing the capacitance of the chip capacitor 0105, the Litzized metamaterial can exhibit different permeabilities at different frequencies.

[0032] Specifically, refer to the two-dimensional cross-sectional diagram of the Litzized magnetic negative metamaterial in 01-1, where 0108, 0109, 0110, 0111, 0113, 0114, and 0115 represent the inner radius d. in , turn gap s, strand width w t Coil thickness t c , width of turn w, outer radius d out Substrate thickness h, 0.112 is the number of segments N t ,in: (2)

[0033] On the other hand, this application presents a design method for Litzized magnetic negative metamaterials, including the following steps. S1: Preset dimensions of the receiving and transmitting coils and parameters of the Litzized magnetic negative metamaterial: S3: Calculate the resistance variation trend of Litzized magnetic negative supermaterials under different number of segments, and select the optimal number of segments based on wiring difficulty and fabrication cost; S4: By analyzing the transmission efficiency and magnetic field strength at the reference point of Litzized magnetic negative metamaterial systems with different number of segments through finite element simulation, the optimal number of segments in the metal helix is ​​determined.

[0034] According to one aspect of the embodiments of this application, the substrate shape of the pre-set Litzized magnetic negative supermaterial in step S1 is square, with an inner radius of 0.5 mm, a turn width of 3 mm, a turn gap of 0.5 mm, a metal spiral coil thickness of 0.035 mm, and a substrate thickness of 1.2 mm, wherein the top layer is 1 mm from the middle layer and the middle layer is 0.2 mm from the bottom layer.

[0035] See appendix Figure 2 0201 and 0202 are the transmitting and receiving coils, respectively; 0203 is a metamaterial with unsegmented wires; and 0204 is a perfectly matched layer. The transmitting and receiving coils consist of helical coils with an outer diameter of 38 mm, an inner diameter of 10 mm, and a thickness of 0.6 mm, with a spacing of 20 mm between the two coils. The metamaterial is 10 mm away from both coils. The system is constructed within a spherical perfectly matched layer with a diameter of 200 mm and a thickness of 20 mm, and the system operates at a frequency of 6.78 MHz.

[0036] See appendix Figure 3 Using the controlled variable method, the system transmission efficiency was analyzed by varying only the number of turns of the unsegmented conductor metamaterial. The results showed that the transmission efficiency increased with increasing turns, reaching its maximum at 6 turns. However, beyond 6 turns, the transmission efficiency exhibited the opposite downward trend.

[0037] The conduction loss of 6-turn Litzized magnetic negative metamaterials with different number of split strands can be calculated by N. t The resistance value of parallel strands of equal length is calculated as follows: (3)

[0038] In equation (3) l t =2N(l ext +l int ) represents the total length of the metal spiral per strand, l ext Let l be the outer side length of the Litz-MNG metamaterial. int ϕ is the inner side length of the Litz-MNG metamaterial. σ is the electrical conductivity of copper; ϕ cond The geometric correlation coefficient for conduction loss is related to frequency f and strand width w. t and the thickness t of the metal spiral coil c related.

[0039] ϕ cond The solution is as follows: In a two-dimensional finite element simulation, establish the geometric cross-section of a single-strand conductor with different numbers of segments, set the excitation current I0 to 1A, and perform finite element analysis on its electromagnetic loss density. Substituting this into the following formula, ϕ can be obtained. cond : (4)

[0040] In equation (4), P cond.t R is the electromagnetic loss density. cond.t The conduction loss per unit length of a single-strand coil is given. The conduction loss of the Litzized magnetic negative supermaterial for different numbers of turns and strands can be calculated by combining equations (3) and (4). The proximity effect resistance can be calculated using equation (5). (5)

[0041] In equation (5), R prox.r and R prox.z These represent the horizontal and vertical proximity resistances of the Litzized magnetic negative supermaterial, respectively; ϕ prox.r and ϕ prox.z These are the proximity effect coefficients in the horizontal and vertical directions, respectively; and These are the squares of the normalized magnetic field strength in the horizontal and vertical directions of the Litzized magnetic negative supermaterial, respectively.

[0042] See appendix Figure 4 A simplified model of the Litzized magnetic negative metamaterial with 6 turns was established in finite element simulation software. 0401 is a square air domain with a side length of 120 mm; 0402 is a homogenized Litzized magnetic negative metamaterial model with a length equal to the side length of the substrate (46 mm) and a height equal to the sum of the substrate thickness and the thickness of the double-layer metal spiral (1.27 mm). The material is defined as copper, and its boundary conditions are set as coils with a uniform external current density. As an incentive, where I coil =1A,S coil =(Nw+(N-1)s)(h+2t c ) represents the cross-sectional area of ​​the coil. and It can be calculated from equation (6): (6)

[0043] In equation (6), V coil To simplify the modeling of the overall coil volume, due to I coil =1A, so in the simulation, the squares of the magnetic field strength in the horizontal and vertical directions of the uniform model of the Litzized magnetic negative metamaterial are integrally divided by the coil cross-sectional area to obtain the square of the normalized magnetic field strength for the corresponding number of turns. =16670 1 / m, =42821 1 / m.

[0044] Proximity effect loss coefficient ϕ prox.r and ϕ prox.z Solving for the conduction loss coefficient ϕ cond The calculation method is similar. In the two-dimensional finite element simulation, the geometric cross-section of a single-strand conductor with different numbers of segments is established, and the excitation source is set as H. o.r =1A / m external horizontal magnetic field and H o.z A vertical magnetic field of 1 A / m is used to simulate the proximity effect on a frequency of 6.78 MHz and a strand width of w. t Thickness is t cTo determine the electromagnetic loss density of the coil by using the finite element method and substituting it into equation (7), ϕ can be calculated. prox.r and ϕ prox.z : (7)

[0045] (7) P prox.r.t and P prox.z.t These represent the electromagnetic loss densities in the horizontal and vertical directions, respectively. Combining equations (5), (6), and (7), the proximity effect resistance of the Litz-MNG metamaterial can be obtained. At this point, the R0 of the Litz-MNG metamaterial is... t The total loss is: (8)

[0046] See Figure 5 Conduction loss R cond and R prox,z With the number of shares N t R decreases as R increases. prox,r The overall resistance remains essentially unchanged, and the decreasing trend in total resistance gradually weakens as the number of strands increases. It is worth noting that the design of Litzized magnetic negative metamaterials must consider manufacturing factors, such as the minimum spacing between two traces, via size, and minimum linewidth of the metal coil. Additionally, the metal helix is ​​square. Based on the ease of solid simulation modeling, the optimal number of strands for the Litzized magnetic negative metamaterial is N. t The number of shares is compared using the formula =k*a+1, where k is an integer incrementing by 1 starting from 1, and a is the number of outer sides of the metal spiral coil. For a square metal spiral coil, a=4. Considering both the layout and manufacturing difficulty of the metal coil, N is chosen. t Comparison and selection of Litzized magnetic negative supermaterials with N=1, 5, and 9. t The total resistance N = 1 t =5、N t When the number of strands is 9, the resistance decreases by 18.83% and 26.08% respectively. Since the effect of vias on resistance was not considered in the calculation, there will be some deviation in the calculation. Considering the modeling difficulty and manufacturing cost, further simulation analysis was conducted on 1-, 5-, and 9-strand metamaterials. The equivalent impedance of the Litzized magnetic negative metamaterial coil can be calculated by dividing the induced capacitance by the induced current. At this time, the self-inductance of the Liz-modified magnetic negative supermaterial L coil It can be represented as: (9)

[0047] Finite element simulation was performed on the model, and S-parameters were extracted. The relationship between effective permeability and S-parameters is as follows: (10)

[0048] See appendix Figure 6 The real part of the equivalent permeability represents the refractive index to a magnetic field, and the imaginary part represents the degree of loss of the element. When the operating frequency is 6.78 MHz, N... t =1、N t =5、N t The real parts of the effective permeability of the basic element with a permeability of 9 are -1.007, -0.998, and -1.005, which basically meet the design requirements. At this time, the imaginary parts of the effective permeability are 0.286, 0.092, and 0.189, respectively. This is because the increase in the number of strands of the Litzized magnetic negative metamaterial will lead to a multiple increase in the number of vias, thereby affecting the degree of loss of the basic element.

[0049] See appendix Figure 7 To verify the magnetic focusing and low-loss characteristics of the Litzized magnetic negative metamaterial, the magnetic field distribution and transmission efficiency of the system were simulated and compared with those without metamaterial, with the addition of unsplit strands of metamaterial, with the addition of 5 strands of Litzized magnetic negative metamaterial, and with the addition of 9 strands of Litzized magnetic negative metamaterial. Taking the center point of the receiving coil as the reference point, the magnetic field strength at the reference point of the receiving coil in the system without metamaterial was relatively low. After adding the three metamaterials, more magnetic field lines were able to be concentrated near the receiving coil, and the magnetic field strength at the reference point was increased by 7.354 A / m, 7.945 A / m, and 7.698 A / m, respectively. While a single undivided metamaterial can enhance the magnetic field strength at the receiving end, the uneven distribution of the magnetic field on the substrate surface results in a stronger central magnetic focusing ability but a weaker peripheral magnetic focusing ability. Simultaneously, high-frequency skin loss and proximity loss significantly impact system performance. The five-strand and nine-strand Litzized magnetic negative metamaterial substrates show significantly improved surface magnetic field uniformity and enhanced peripheral magnetic focusing ability. However, with the increase in the number of segments, the number of vias also increases, causing the surface magnetic field to concentrate at the vias, introducing more losses. This results in more energy being consumed within the nine-strand Litzized magnetic negative metamaterial substrate without being transmitted to the receiving end. In contrast, the system with five Litzized magnetic negative metamaterials effectively concentrates more energy near the receiving coil, resulting in a significant improvement in system transmission performance. This demonstrates the superiority of the five-strand Litzized magnetic negative metamaterial.

[0050] See appendix Figure 8 Considering the potential for reduced transmission performance due to severe patient movement or horizontal and angular offsets at the receiver during operation, simulations were conducted on systems with and without Litzized magnetic negative metamaterials for horizontal offsets of 0mm-20mm and angular offsets of 0°-40°. The results show that the system with the Litzized magnetic negative metamaterial significantly improves both transmission efficiency and magnetic field strength at the reference point under offset conditions, and its resistance to offset is significantly enhanced.

[0051] The main circuit uses an SP compensation topology and employs an ASK modulation and demodulation circuit for coordinated energy and information transmission. On the primary side, a MOSFET controls the switching of a modulation capacitor connected in parallel across the compensation capacitor, thereby controlling the coil amplitude to transmit binary signals downlink. The drive voltage of the MOSFET is provided by a microcontroller. Since the demodulation circuit is located inside the body, a simple incoherent demodulation structure is used. The "101010" signal segment output by the microcontroller simulates the downlink input data. Experiments were conducted on an energy-information simultaneous transmission system without metamaterials and an energy-information simultaneous transmission system with Litz-MNG metamaterials.

[0052] See appendix Figure 9 Compared to the system without metamaterials, the system with Litzized magnetic negative metamaterials showed a significant increase in the voltage amplitude across the receiving coil and an increase in ASK modulation depth of 0.0201, resulting in a significant improvement in system transmission efficiency.

[0053] See appendix Figure 10 When the receiving coil experiences horizontal and angular offsets, the transmission efficiency, root mean square output voltage, and modulation index are significantly improved when the Litzized magnetic negative supermaterial is added. In summary, the system's energy transmission efficiency and signal transmission robustness are significantly improved.

[0054] The above description is merely an embodiment of the present invention and is not intended to limit the scope of the invention. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive technical essence shall fall within the protection scope of the present invention.

Claims

1. A Litzized magnetic negative metamaterial structure, characterized in that the Litzized magnetic negative metamaterial is composed of three layers of PCB, which are arranged from top to bottom as top layer traces, middle layer traces, and surface mount capacitors; the PCB substrate is square; the top layer and middle layer traces are carried by the PCB and are wound in a square spiral from the center of the PCB substrate to the PCB boundary using a planar Litzized wiring structure; the surface mount capacitor is placed on the bottom layer of the PCB substrate, and the top layer and middle layer traces are connected end to end through vias, and the operating frequency and permeability can be changed by changing the capacitance value.

2. The Litzized magnetic negative metamaterial structure according to claim 1, characterized in that, The planar Litz routing structure is achieved by periodically interleaving the top layer and middle layer traces. The top layer traces are connected end to end. Within the turn width limit, the top layer trace moves segment by segment from the outside of the turn to the inside. After each segment, it moves inward by one strand width. When it moves to the innermost part of the turn, a via is added to switch the strand to the middle layer. The middle layer traces are wound in the opposite way to the top layer. Within the turn width limit, they move segment by segment from the inside of the turn to the outside. When they reach the outermost part, a via is added to switch to the top layer, and this cycle continues.

3. A method for designing a Litzized magnetic negative metamaterial, comprising the Litzized magnetic negative metamaterial structure as described in any one of claims 1-2, characterized by comprising the following steps: S1: Preset dimensions of the receiving and transmitting coils and parameters of the Litzized magnetic negative metamaterial: S2: Analyze the trend of transmission efficiency variation in metamaterial systems with unsplit wires and optimize the number of turns of the metal spiral; S3: Calculate the resistance variation trend of Litzized magnetic negative supermaterials under different number of segments, and select the optimal range of segments based on wiring difficulty and fabrication cost; S4: By analyzing the transmission efficiency and magnetic field strength at the reference point of Litzized magnetic negative metamaterial systems with different numbers of strands through finite element simulation, the optimal number of strands in the metal spiral is determined.

4. The design method according to claim 3, characterized in that, In step S1, referring to the size of the Lepu Qinming8631SR pacemaker, a circular receiving and transmitting coil with a diameter of 38mm is selected. The substrate shape of the Litzs-modified magnetic negative metamaterial is a cube with an inner radius d. in outer radius d of the substrate out Width of turn w, width of strand w t Turn gap s, coil thickness t c Substrate thickness h, number of turns N, and number of segments N t Should meet: Where the inner radius d in The distance from the center of the substrate to the metal spiral, and the outer radius d out This is the distance from the center of the substrate to the substrate boundary, which is limited by the size of the implanted device.

5. The design method according to claim 3, characterized in that, In step S2, a coaxially placed receiving and transmitting coil is constructed in the finite element simulation. The transmission distance is set with reference to the implantation location of the heart pacemaker. The undivided metamaterial is coaxially placed at the center of the transmission path, at the same distance from the transmitting and receiving coils. Starting from 2, the number of turns is increased in steps of 1. The optimal number of turns is obtained with the highest system transmission efficiency as the condition.

6. The design method according to claim 3, characterized in that, In step S3, the trends of conduction loss, proximity loss, and total loss of the Litzized magnetic negative metamaterial with different numbers of segments are calculated under ideal conditions. Considering the increased via loss with increasing number of segments and its impact on intervention loss, under the size constraints of a minimum linewidth of 0.1 mm and a minimum aperture of 0.15 mm, the number of segments is selected as N. t =k*4+1 is the optimal number of shares, where k is an integer starting from 0 and increasing by 1 in increments.

7. The design method according to claim 3, characterized in that, In step S4, the Litzized magnetic negative metamaterial with the optimal number of strands is modeled in the finite element simulation. The lumped capacitance value of the permeability λ⁻¹ is calculated using the S-parameter inversion method and placed at the center of the transmission path. The center point of the receiving coil is set as the reference point. The optimal number of strands is selected with the goal of maximizing the system transmission efficiency and the magnetic field strength at the reference point.

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