Wireless passive micro-magnetic stimulator and multi-channel energy regulation method thereof

Abstract

This invention discloses a Wireless Passive Micro-magnetic Stimulation (WP-μMS) device and its multi-channel energy regulation method. Employing a coordinated control and transmission design, it aims to solve the problems of independent power control and channel decoupling in multi-target neural modulation. The technical solution includes: at the control level, a multi-frequency hybrid sinusoidal pulse width modulation (HWM-SPWM) strategy is used to achieve real-time independent adjustment of multi-target channel power and suppress electromagnetic crosstalk using a single inverter; at the hardware level, the transmitter employs a single inverter cascaded with a multi-frequency resonant compensation (MFRC) network, combined with a receiver-side resonant microcoil operating at different frequencies, to achieve system miniaturization and scalability. A multi-frequency magnetic coupling resonant linear mapping model is established to achieve quantitative control of the magnetic stimulation dose. Experimental prototypes were validated at three frequency points: 0.5MHz, 1MHz, and 1.5MHz. The results show that the system achieves millimeter-level spatial resolution with a channel isolation better than -5.08dB and a magnetic stimulation efficacy of 0.37mT / W. This invention enables independent regulation of multiple targets, providing a highly efficient and integrated system solution for implantable neuromodulation.

Description

Technical Field

[0001] This invention belongs to the field of implantable neuromodulation technology, specifically relating to a wireless passive micromagnetic stimulator based on multi-frequency hybrid waveform sinusoidal pulse width modulation and its multi-channel energy modulation method. Background Technology

[0002] Micro-magnetic stimulation (μMS), as an emerging non-invasive or minimally invasive neuromodulation technique, achieves precise intervention of neuronal electrical activity through a localized high-gradient magnetic field generated by an implanted microcoil. Wireless-powered micro-magnetic stimulation (WP-μMS) systems typically employ magnetic coupling resonance technology to transfer energy from an external transmitting coil to the internal microcoil, avoiding the infection risks and operational inconveniences associated with physical wire connections. However, existing WP-μMS systems still face significant technical challenges in their clinical translation and multi-target synergistic modulation: First, the system architecture suffers from insufficient integration and portability. In 2021, Xia et al. from China University of Mining and Technology proposed a multi-frequency, multi-load magnetically coupled resonant system based on a hybrid modulation wave sinusoidal pulse width modulation (HMW-SPWM) control method. This system achieved independent dual-frequency power supply at 20 kHz and 60 kHz using a single inverter, overcoming the hardware redundancy of traditional systems with multiple inverters. In 2022, Hou et al. designed a dual-frequency, dual-load, multi-relay WPT system, increasing the operating frequency to 347.22 kHz and 446.3 kHz, achieving selective power distribution among different loads. In 2023, Liu et al. proposed a primary-side multi-frequency constant current compensation network, providing constant current output for long-distance, high-power applications. That same year, the team also proposed a dual-frequency three-dimensional wireless power transmission system, utilizing dual H-bridge inverter branches to achieve independent voltage regulation, which was verified at modulation frequencies of 80 kHz and 200 kHz. In 2024, Liu et al. further proposed a multi-load wireless power transmission system based on hybrid frequencies, supporting multiple independently adjustable loads, but its operating frequency was still limited to within 200 kHz. In the field of neural micromagnetic stimulation applications, in 2025, Tian et al. designed a fully integrated WP-μMS system based on H-bridge inverters and hybrid frequency PWM modulation, achieving independent power control and synchronous stimulation of 8 MHz and 10 MHz dual channels, marking a key step towards dynamic modulation and full integration of WP-μMS. However, the above modulation strategies still have three limitations when applied to micromagnetic stimulation: the operating frequency is limited to the kHz band (<200 kHz), making it difficult to meet MHz-level requirements. Even though Tian et al. achieved MHz-level transmission, the high-order harmonics introduced by their PWM modulation easily lead to severe crosstalk between channels and reduce efficiency; the multi-inverter or dual H-bridge architecture leads to hardware complexity, which is not conducive to implantable integration; and multi-frequency resonance depends on specific frequency combinations, lacking flexible adaptation capabilities to stimulation frequencies of different targets, making it difficult to achieve true multi-target independent control. Secondly, achieving both independent power modulation for multiple targets and channel decoupling is challenging. In 2019, Lee et al. proposed an electrostimulator integrating 32-channel recording and 4-channel stimulation, but its single-frequency power supply structure could not achieve independently adjustable power allocation, limiting the ability to individually modulate multiple targets. In 2021, Lee et al. achieved independent addressing of neural particles through time-division communication, but still lacked a precise power adjustment mechanism, making it impossible to achieve personalized stimulation dose control for different neural targets. In 2022, Tian et al. developed a WP-μMS device based on a bilayer WPT structure for isolated hippocampal slices, achieving single-point magnetic stimulation at 920 kHz. In 2023, the team further introduced a multi-carrier resonance compensation (MFRC) network, extending the stimulation channels to three targets in the hippocampus: CA1, CA3, and DG.However, this system still relies on discrete hardware compensation networks for channel selection, and the resolution of stimulation parameters is limited by the hardware component parameters, making it difficult to achieve high-precision quantitative output. In 2024, Liu et al. designed a passive micromagnetic stimulation system for multi-brain region collaborative modulation and verified its efficacy in the hippocampal neural circuit. However, the passive energy coupling architecture of this system results in non-programmable power of the stimulation unit and fixed timing, making it impossible to achieve independent and adjustable quantitative control of multiple channels, which is difficult to meet the adaptive modulation requirements of complex in vivo neural networks. In 2025, Dong et al. designed a wired implantable magnetic stimulation system (using commercially available 0201 inductors) and verified its bioefficacy in vitro and in vivo. However, its global control architecture is difficult to support independent multi-channel modulation, limiting the flexibility of in vivo applications. Furthermore, there is a lack of a quantitative dose-response evaluation system.

[0003] Therefore, this invention proposes a novel WP-based multi-frequency hybrid sinusoidal pulse width modulation (HWM-SPWM) method. The MS system achieves spatial orientation through frequency gating—each channel's receiving coil resonates at different frequencies (0.5 / 1 / 1.5 MHz), with only the energy at the corresponding frequency driving the corresponding target. Simultaneously, precise duty cycle control via SPWM enables independent adjustment of the amplitude of each frequency component, thus achieving multi-channel quantitative magnetic dosing output. This method decouples "frequency gating" from "amplitude control," achieving a stable and programmable magnetic field distribution, providing a flexible and efficient platform for multi-target neuromodulation research. Summary of the Invention

[0004] This invention employs HWM-SPWM modulation technology to achieve multi-channel independent energy transfer for WP-μMS inverters using a single H-bridge inverter. The specific algorithm is as follows: the controller generates an SPWM carrier of a specific frequency according to a frequency command, selects the corresponding resonant channel through frequency matching, and achieves directional energy transfer. Furthermore, by adjusting the modulation ratio of the modulation signal in real time, the fundamental amplitude of the output voltage can be effectively controlled, thereby achieving quantitative adjustment of the transmitted power.

[0005] The invention's technical solution is: The design and implementation of a high-precision neural-modulated wireless passive micromagnetic stimulator based on multi-frequency HWM-SPWM is characterized by the following steps: analytical modeling of a wireless micromagnetic stimulation system, COMSOL modeling and simulation analysis, and the design and implementation of the high-precision neural-modulated wireless passive micromagnetic stimulator based on multi-frequency HWM-SPWM. The method is as follows: (1) Analytical modeling and performance analysis of wireless micromagnetic stimulation system The wireless passive array micromagnetic stimulator (WP-μMS) mainly consists of a transmitter and an array of microcoils, such as... Figure 1As shown. The transmitting end mainly includes a DC source, an HWM-SPWM dynamic control circuit, a high-frequency H-bridge multi-frequency inverter, a multi-frequency resonant compensation network (MFRC), and a transmitting coil. The construction process of the circuit theoretical model is as follows: HMW-SPWM modulation mechanism based on dual Fourier analysis To achieve independent linear control of multi-channel stimulation dose in a single inverter and effectively suppress low-order harmonics, this system adopts HMW-SPWM bipolar modulation, the principle of which is as follows: Figure 2 As shown, the modulated wave It is composed of multiple sinusoidal components with adjustable amplitude and frequency. (1) In the formula, and The first i The modulation index and frequency of the modulated wave. To ensure that the inverter operates in the linear modulation region, the total amplitude of the mixed modulated wave shall not exceed the carrier amplitude.

[0006] To quantitatively analyze the output characteristics of HMW-SPWM, this paper employs a dual Fourier series model to establish its spectral analysis model. This method maps the switching behavior in the time domain to the frequency domain analytical space by constructing a bivariate function of the carrier angular frequency and the fundamental angular frequency. By extracting and solving the fundamental component within the dual integration interval, and neglecting non-ideal factors such as dead time, the effective value of the fundamental frequency of the inverter output voltage is obtained. With adjustment system A linear relationship exists: (2) This formula provides a direct theoretical basis for subsequent quantitative magnetic stimulation, proving that the stimulation intensity of each channel can be independently controlled. The software algorithm achieves precise mapping, thereby overcoming the limitations of nonlinear dose control and mutual interference between channels in traditional modulation methods.

[0007] Modeling and Decoupling Analysis of Multi-Load Systems under MFRC Topology To improve the system's transmission efficiency across multiple target frequencies, an MFRC network is employed in the primary loop. This network can simultaneously construct multiple power transmission channels to power multiple loads, eliminating the need for additional auxiliary equipment such as coils, transformers, and repeaters, thereby effectively reducing power loss in multi-channel wireless power transmission systems. MFRC is key to achieving multi-frequency drive, and its design is intended for multiple discrete frequency points. Simultaneously, impedance compensation of the primary circuit at different frequencies is achieved, enabling the primary circuit to exhibit purely resistive resonance at multiple specified frequencies. The impedance characteristics of this network can be expressed as: (3) Through passive components ( L n , C n ) parameter, making The inverter exhibits a resonant state at the target frequency, thereby reducing its impedance when outputting current at a specific frequency and significantly decreasing switching losses; while maintaining high impedance at non-target frequencies, it suppresses harmonic currents. Indicates the transmitting coil; , ,…and Indicates the compensation coil; , ,…and It is a resonant capacitor; It is the DC resistance of the transmitting coil; It is the current in the transmitting circuit.

[0008] Then, a three-level circuit theoretical model consisting of a transmitting coil, a micro-coil, and a detection coil is established, such as... Figure 1 As shown. Based on the circuit model, we can obtain: (4) in , and The DC resistance of the micro-coil itself. , and For the current in micro-coil circuits with different resonant frequencies, , and respectively transmitting coil The mutual inductance coefficient with each micro-coil. and Representing coils and , and as well as and The mutual inductance coefficients between them; It is the total impedance of the transmitting circuit; , and It is the total impedance of different resonant micro-coil circuits in the array. This indicates that the output frequency of the H-bridge inverter is... The effective value of the voltage component. To achieve frequency addressing, each secondary circuit is tuned to the target frequency through a capacitor, and its impedance expression is: (5) Combining formulas (4) and (5), the current in the transmitting circuit can be obtained. and the current of each receiving circuit , and The parsing, specifically the expression is: (6) From formula (6), it can be seen that when the operating frequency When matched with the resonant frequency of a certain receiving loop (e.g., loop 1), the impedance of that loop is... The imaginary part is zero, and the real part is at its minimum. At this point, formula 6(b) applies. The middle denominator Decrease, making The self-impedance of other non-resonant circuits increases significantly; while the self-impedance of other non-resonant circuits... , Larger, leading to and It is effectively suppressed, thereby enabling multi-channel directional energy transmission.

[0009] The expression for the system input impedance is further derived as follows: (7) Equation (7) shows that the system input impedance consists of self-impedance and reflected impedance. The MFRC network compensates for the imaginary part of the reflected impedance, making the system purely resistive at multiple frequency points and achieving efficient transmission; on the other hand, it also reveals the dynamic influence of the secondary multi-channel load on the total power distribution of the system through mutual inductance coupling.

[0010] Power distribution and magnetic field performance analysis According to the superposition principle, the three operating frequencies ( , , The instantaneous output power generated in the corresponding receiving circuit (micro-coil) can be expressed as follows: (8) in, , and These represent the frequencies at which the system operates. The instantaneous output power generated in receiving circuits 1, 2, and 3 at that time. The total average output power of each receiving circuit over a complete duty cycle is a linear superposition of its corresponding frequency components: (9) in, This represents the total output power obtained from receiving Coil_1, determined by frequency. , and The power component transmitted to the coil , and It is formed by stacking. Similarly, and These are the total output power of receiving coils 2 and 3, respectively, obtained by superimposing the corresponding frequency components.

[0011] Furthermore, the system at a single excitation frequency Total output power This represents the sum of the power of each receiving microcoil at that frequency; the total output power of the system throughout the entire cycle. This is the sum of the power of each frequency component, i.e.: (10) The power loss of the WP-μMS system is mainly caused by the internal resistance of the transmitting and receiving coils. At a single operating frequency... ( i Under the condition (=1,2,3), the power loss components of the system It can be represented as: (11) Total power loss of the system throughout the entire cycle and total input power They are respectively: (12) To evaluate the energy efficiency of the magnetic field generated by the system, this paper defines a core performance indicator—magnetic flux density per unit power. The magnetic flux density generated by each receiving microcoil... Its current Proportional: (13) in For the first n The magnetic field coefficient of a receiving microcoil (unit: mT / A). At frequency Below, the magnetic field vector summation magnetic induction intensity of the three micro-coils .

[0012] (14) Define the magnetic flux density per unit input power at this frequency. Defined as: (15) To comprehensively evaluate multi-frequency performance, the average magnetic flux density per unit input power of the system is defined. The ratio of the total strength of the synthesized magnetic field to the total input power of the system at each frequency. (16) The power analytical model and its core indicators This study reveals the mechanism by which the system achieves independent power allocation and spatial orientation selection through frequency coding. Furthermore, after normalization of the input power, this index can quantify the relationship between magnetic field dose and stimulation efficacy, demonstrating the crucial role of the MFRC topology in reducing losses and improving magnetic stimulation efficiency.

[0013] (2) Simulation analysis A theoretical model of the WP-μMS was established using COMSOL finite element simulation, along with material parameters for the hippocampal slices and artificial cerebrospinal fluid (ACSF). The simulation results determined the minimum induced current (i.e., activation current threshold) required for each microcoil. Based on this current threshold and a three-frequency SPWM modulation method, the key operating parameters of the WP-μMS in multi-frequency operating mode were further optimized and determined, including the primary circuit drive current and the modulation ratio of each channel. This enables precise control of the microcoil induced current in multi-target scenarios, achieving focused magnetic stimulation.

[0014] Figure 3 This study presents the spatial distribution of the electromagnetic field of WP-μMS under different SPWM modulation signals. To simplify the simulation analysis, this study first performs FFT analysis on the SPWM modulation signal to extract the frequency and amplitude of its fundamental component; then, using this fundamental component as an equivalent excitation source, the magnetic field distribution is calculated through COMSOL finite element simulation.

[0015] Figs. 3A-3B show the magnetic field distribution under single-frequency modulation. When the excitation signal is a 0.5MHz SPWM component and the fundamental current is 0.6 A, the magnetic field strength at the microcoil with a resonant frequency of 0.5MHz is 0.5 mT, while the magnetic field strengths of the other two non-resonant microcoils are 0.27 mT and 0.23 mT, respectively. When the excitation signal is a 1MHz SPWM component and the fundamental current is 0.35 A, the magnetic field strength of the 1MHz resonant microcoil is 0.54 mT, and the magnetic field strengths of the non-resonant microcoils are 0.15 mT and 0.21 mT, respectively.

[0016] Figs. 3C-3D show the results of the combined magnetic field distribution under multi-frequency modulation. Since COMSOL cannot directly simulate the effect of multi-frequency superimposed magnetic fields, this study uses a method of independent frequency division simulation and vector superposition: first, the magnetic field under each single-frequency equivalent sinusoidal excitation is simulated independently, and then vector superposition is completed in MATLAB. Fig. 14C shows the superposition distribution of the magnetic fields at 0.5MHz / 0.6A and 1.5MHz / 0.28A, with magnetic field strengths of 0.51mT and 0.6mT for the two resonant microcoils, and 0.21mT for the non-resonant microcoil. Fig. 3D shows the superposition results of the magnetic fields at 0.5MHz / 0.6A, 1MHz / 0.28A, and 1.5MHz / 0.28A, with magnetic field strengths of 0.51mT, 0.61mT, and 0.64mT for the three resonant microcoils, respectively.

[0017] (3) Design of a high-precision neural modulation wireless passive micro magnetic stimulator based on multi-frequency HWM-SPWM The high-precision neural modulation wireless passive micro magnetic stimulator based on multi-frequency HWM-SPWM was designed, specifically as follows: The WP-μMS platform mainly consists of an FPGA controller, a high-speed comparator, a high-frequency H-bridge multi-frequency inverter, an MFRC resonant network, a transmitter coil, and multiple receiving microcoils with different resonant frequencies. The system control core uses a Xilinx ZYNQ 7010 FPGA to generate modulation and triangular wave signals. These signals are compared by a TLV3501 high-speed comparator to generate multiple SPWM drive signals. The primary transmitter coil uses a circular helical coil structure with an inner diameter of 2.5 cm, an outer diameter of 2.7 cm, a coil height of 5.5 mm, 7 turns, a wire diameter of 0.7 mm, and an inductance of 2.27 μH. The receiving microcoil uses a planar square helical coil with dimensions of 3.66 × 3.66 mm, 8 turns, a line width of 110 μm, a line spacing of 70 μm, and an inductance of 1.762 μH. It is fabricated using a 4-layer series flexible circuit board. The microcoils are vacuum-insulated with parylene with a coating thickness of 5 μm to ensure good biocompatibility and water resistance. The resonant capacitor used was a high-frequency capacitor of model RF0402. With excitation signal frequencies of 0.5MHz, 1MHz, and 1.5MHz, the resonant capacitor values ​​were 58.9nF, 14.7nF, and 6.5nF, respectively. The power supply was provided by a ROGIL DP2031 power supply, which drove the transmitting coil via an H-bridge inverter and an MFRC resonant network. Experimental waveforms and data were acquired and recorded using a Tektronix MD03104 oscilloscope, while the current signal was simultaneously measured using a current probe (ETA5520A, ETA).

[0018] (4) Experimental verification a. Experimental verification of single-frequency operating mode Figure 4 This study aims to verify the selective magnetic stimulation experiment in the dual-frequency operating mode of WP-μMS. Figure 4 In section a, the MOSFET supply voltage of the H-bridge is 7V, and it is configured for the first frequency. f 1 = 0.5MHz, modulation ratio a 1=0.9, the experimental result is: setting parameters to make the primary current =1.44A. The experimentally measured induced current of the target micro-coil with a resonant frequency of 0.5 MHz was 1.44A. =31.6mA, reaching the threshold of magnetic stimulation, while the induced current of the non-target coil was significantly suppressed ( =17.3 mA, =17.2 mA).

[0019] Figure 4 In section b, the MOSFETs of the H-bridge are supplied with a voltage of 6V and configured for the second frequency. f 2 = 1MHz, modulation ratio a 2=0.9, the experimental result is: primary current The target coil with an A value of 1.0A and a resonant frequency of 1MHz is effectively activated, generating an induced current. =33mA, the non-target coil current is suppressed to a low level; Figure 4 The MOSFETs in the H-bridge of component c are supplied with a voltage of 9V and are configured for the second frequency. f 2 = 10MHz, first duty cycle a 3=0.9, the experimental result is: primary current =1.0A, the target coil with a resonant frequency of 1.5 MHz was effectively activated, generating an induced current. =37.4mA, and the non-target coil current is deeply suppressed.

[0020] According to the COMSOL theoretical model, a magnetic field greater than 0.5 mT, i.e., reaching the magnetic stimulation threshold, can only be generated in the region when the induced current of a 0.5 MHz resonant single coil is greater than 28 mA, the induced current of a 1 MHz resonant single coil is greater than 29.4 mA, and the induced current of a 1.5 MHz resonant single coil is greater than 30.4 mA. The above experimental results show that the WP-μMS device, in single-frequency operation, can perform directional and quantitative selection of stimulation targets by frequency, while suppressing interference from other cross frequencies.

[0021] b. Experimental verification of dual-frequency operating mode Figure 5 Selective magnetic stimulation experimental verification in dual-frequency operating mode of WP-μMS. The modulation wave frequencies were 0.5MHz and 1.5MHz, and the modulation ratios were respectively... =0.5, =0.7, the supply voltage of the H-bridge is 15V, and the primary circuit current is measured. =2.24A, voltage across the 0.5MHz resonant microcoil The voltage is 640mV, with a 0.5MHz frequency component of 235.7mV (induced current of 35.2 mA) and a 1.5MHz frequency component of 45.5mV (2.7mA). The channel selectivity ratio (current ratio) is approximately 13: 1; Voltage across the 1.5MHz resonant microcoil The voltage is 2.24V, with a 0.5MHz frequency component of 135mV (20 mA) and a 1.5MHz frequency component of 831.6mV (48.6mA), resulting in a selectivity of approximately 2.43. : 1.1MHz resonant microcoil voltage The voltage was 0.76V, with the 0.5MHz frequency component being 124mV (18.5 mA) and the 1.5MHz frequency component being 171.6mV (10 mA), significantly lower than that of the two target channels, and therefore unable to generate effective magnetic stimulation. The experimental results show that WP-μMS, under dual-frequency operating parameters, can transmit energy from two independent channels, achieving simultaneous stimulation of multiple target points.

[0022] c. Experimental verification of the three-frequency operating mode Figure 6 Output performance and dose compliance verification of WP-μMS in tri-frequency operating mode. The modulation wave is composed of superposition of 0.5MHz, 1MHz, and 1.5MHz, with modulation ratios of respectively. =0.35, =0.25 and =0.55, H-bridge supply voltage is 20V. Under this configuration, measure the transmit circuit current. =2.7 A, and the induced voltages across each resonant micro-coil are as follows: =0.6 V, = 1.20V, = 2.04 V, indicating that the system successfully transmitted frequency-selective power synchronously to the three channels. The voltage across the 0.5MHz resonant microcoil is 600mV, of which the 0.5MHz component is 202mV (corresponding to a current of 30 mA), the 1MHz component is 47mV (4mA), and the 1.5MHz component is 25.9mV (1.5mA); the voltage across the 1MHz resonant microcoil is 1.2V, of which the 1MHz component is 361mV (30.6mA), the 0.5MHz component is 132mV (19.7 mA), and the 1.5MHz component is 132mV (7.2mA); the voltage across the 1.5MHz resonant microcoil is 2.04V, of which the 1.5MHz component is 768mV (44.9mA), the 0.5MHz component is 110mV (16.4mA), and the 1MHz component is 207mV (17.5mA).

[0023] Each target microcoil produces a dominant response at its resonant frequency (current > 30). The current value (mA) has reached the effective threshold determined by simulation; while at other frequency components, the current is suppressed to below 20mA, and the corresponding channel crosstalk (CR) is better than -5.08 dB. This result demonstrates that, in tri-frequency operating mode, the system can output an induced current that meets the dosage requirements and has excellent channel isolation.

[0024] Independent power control experimental verification To verify the proposed WP-μMS's multi-channel independent power dynamic regulation capability in dual-frequency and multi-frequency operating modes, this study controls the primary circuit current by adjusting the modulation ratio of different modulation waves. The amplitude of each frequency component in the array is determined, thereby enabling independent power distribution to individual coils with different resonant frequencies in the array microcoils.

[0025] Figure 7 The results show the experimental results of independent power adjustment for different channels of the WP-μMS device in dual-frequency and tri-frequency operating modes. Fig. 7a shows the modulation ratio of the 0.5MHz channel in dual-frequency operating mode. The modulation ratio of the modulated wave is fixed at 0.5 for the 1MHz channel. Adjust from 0.5 to 0.7 in increments of 0.05. The results show: It remained relatively stable at 34mA (fluctuation ≤ ±0.7mA), while along with The increase of approximately 10.4mA indicates that the system is able to independently control the output power of the 1MHz channel without affecting the 0.5MHz channel. Figure 7 b indicates a tri-frequency operating mode, with the modulation ratio of the 0.5MHz and 1MHz channels. , The modulation ratios for the 1.5MHz channel are fixed at 0.35 and 0.25 respectively. With a phase length of 0.5 Adjustment within a range of 0.7. Three resonant circuits were measured ( =0.5MHz =1 MHz and Current (=1.5MHz) , and The results showed that and They remained stable around 30 mA (fluctuation ≤ ±0.8 mA), while along with The increase was from 31.4 mA to 40.3 mA, an increase of approximately 28.3%.

[0026] The above results collectively demonstrate that by independently adjusting the modulation ratio corresponding to the target channel, the system can achieve independent and continuous control of the output power of a specific load without affecting the power transmission of other channels. This verifies the proposed WP-μMS's ability to independently and controllably supply power to multiple loads of different power levels in multi-frequency mode.

[0027] The advantages and positive effects of this invention are: This invention employs a method for a high-precision neural-modulated wireless passive micromagnetic stimulator based on multi-frequency HWM-SPWM. This method uses a multi-frequency hybrid sinusoidal pulse width modulation (HWM-SPWM) algorithm as its control core, achieving independent control of the multi-channel output power by adjusting the amplitude of each frequency component. At the hardware level, a precisely matched multi-frequency resonant compensation network (MFRC) is designed at the transmitter, effectively solving the impedance matching problem in multi-frequency wireless transmission; at the receiver, each micro-coil resonates at the aforementioned frequencies, and channel addressing is achieved through a frequency selection mechanism. Attached Figure Description

[0028] Figure 1 This is the theoretical model of wireless power transmission for WP-μMS devices; Figure 2 It is a theoretical model of a bipolar HMW-SPWM control circuit; Figure 3 It is the spatial distribution of electromagnetic field of WP-μMS under different SPWM modulation signals; Figure 4 This is a waveform diagram of selective stimulation experiment verification in single-frequency operating mode of WP-μMS; Figure 5 This is a selective stimulation experiment verification in the dual-frequency operating mode of WP-μMS; Figure 6 This is a selective stimulation experiment verification under the WP-μMS tri-frequency operating mode; Figure 7 These are experimental results of independent power adjustment of different channels in dual-frequency and tri-frequency operating modes of the WP-μMS device. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] Implementation Method 1: Step 1: Establish a theoretical model of WP-μMS and derive and analyze the primary current based on the theoretical model. i p The factors influencing the ratio of the first, second, and third frequency components provide a theoretical basis for subsequent control methods. Step 2: Based on the above theoretical model, innovative control methods for three working modes, namely single-frequency, dual-frequency, and tri-frequency, are proposed. Step 3: In dual-frequency operating mode, fix the modulation ratio of the first frequency signal. a 1. Adjustment a 3. The energy of the third receiving unit can be directionally adjusted; Step 4: In tri-frequency operating mode, fix the duty cycle of the first and second frequency signals. a 1. a 2. Adjustment a 3. The energy of the third receiving unit can be directionally adjusted; Step 5: Experimental verification of WP-μMS in single-frequency operating mode; Step 6: Experimental verification of WP-μMS in dual-frequency operating mode; Step 7: Experimental verification of WP-μMS in tri-frequency operating mode; Step 8: Experimental verification of WP-μMS independent power control.

Claims

1. A wireless passive micromagnetic stimulator and its multi-channel energy regulation method, characterized in that, Includes the following steps: S1. Construction of multi-frequency hybrid modulation wave: Multi-frequency hybrid modulation wave is constructed through the control unit. The modulated wave is composed of n sinusoidal modulation signal It is formed by linear superposition, and the expression is as follows: (1) in, These are the modulation coefficients for the corresponding channel. The operating frequency of the corresponding channel; S2. SPWM drive signal generation: The multi-frequency hybrid modulation wave The signal is compared with a triangular carrier signal to generate multiple SPWM drive signals, which are then input to the inverter. The fundamental effective value of the inverter's output voltage is... With the modulation coefficient a i satisfy: (2) in, V in The DC power supply voltage for the H-bridge; S3. Multi-frequency resonance compensation and decoupling reception: A multi-frequency resonant compensation network (MFRC) is used in the primary circuit, and parameter matching is employed to make the primary circuit resonate at multiple discrete frequency points. f 1, f 2,….., f n It simultaneously exhibits a purely resistive resonance state; The secondary circuit employs an array of microcoils, with each microcoil matched with a different resonant capacitor to correspond to a specific resonant frequency. f i This enables frequency-selective energy reception and multi-channel decoupling; S4. Evaluation and Quantitative Control of Magnetic Field Efficiency: Based on the induced current generated by each receiving microcoil Determine the magnetic field strength And based on the system's average unit input power magnetic flux density The relationship between quantified magnetic field dosage and stimulation efficacy: (3) in, For the first i The magnetic field vector sum generated by each microcoil The total input power of the system. For the first i Channel output power, For the first i The power loss of the channel system; utilizing the The indicator allows for quantitative adjustment of the stimulus dose.

2. The wireless passive micromagnetic stimulator and its multi-channel energy regulation method according to claim 1, characterized in that: The equivalent impedance of the multi-frequency resonant compensation network (MFRC) Z s ( f It satisfies the following formula: (4) in, L 1 and C 1 represents the basic inductance and capacitance of the primary circuit; L n and C n For the first n The inductance and capacitance parameters in the parallel resonant branch; by configuring the above parameters, the primary circuit is made to operate at the operating frequency. f i The imaginary part of the impedance at that point is zero.

3. A wireless passive micromagnetic stimulator device, characterized in that, The apparatus is used to perform the method as described in claim 1 or 2, and the apparatus comprises: Control unit: Employs an FPGA logic architecture to generate the multi-frequency hybrid modulation wave and triangular carrier signal; Comparison logic circuit: Used to compare the hybrid modulated wave with the triangular carrier wave to generate multiple SPWM drive signals; High-frequency inverter unit: Employs an H-bridge inverter circuit to receive the SPWM drive signal and drive the primary circuit; Primary transmitting coil: Electrically connected to the multi-frequency resonant compensation network (MFRC) for generating a multi-frequency alternating magnetic field; Receiver microcoil array: Contains multiple microcoils with different resonant frequencies to achieve frequency-selective energy reception.

4. The wireless passive micromagnetic stimulator device according to claim 3, characterized in that: The primary transmitting coil adopts a circular spiral coil structure with an inductance range of 2.0-2.5μH, an inner diameter range of 2.4-2.6cm, and an outer diameter range of 2.6-2.8cm. The receiving microcoil adopts a planar square spiral structure and is made of multiple series flexible circuit boards, with a single layer side length ranging from 3.5 to 3.8 mm.

5. The wireless passive micromagnetic stimulator device according to claim 4, characterized in that: The receiving microcoil has an insulating layer formed using a Parylene vacuum coating process, with a coating thickness ranging from 3 to 8 μm, which provides biocompatibility protection and waterproof insulation.

6. The wireless passive micromagnetic stimulator device according to claim 3, characterized in that: The system has a channel isolation better than -5.08dB at three frequency points: 0.5MHz, 1MHz, and 1.5MHz, and a magnetic stimulation efficacy of 0.37mT / W.

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