An adaptive multi-frequency resonant matching system and design method

Abstract

The application belongs to the technical field of electromagnetic detection, and particularly relates to a self-adaptive multi-frequency resonance matching system and a design method, which comprises a magnetic coupling resonance module and a controllable variable impedance unit connected in series, a switch control capacitor comprising a matching capacitor and a control switch connected in parallel, and a switch control inductor comprising a matching inductor and a control switch connected in series; the magnetic coupling resonance module comprises an inductor and a capacitor connected in parallel, and the capacitor connected in series; the application improves the signal strength of a multi-frequency grounded electromagnetic transmitter, and realizes efficient transmission of a multi-frequency excitation signal.

Description

Technical Field

[0001] This application belongs to the field of electromagnetic detection technology, specifically an adaptive multi-frequency resonant matching system and its design method. Background Technology

[0002] With the development of electromagnetic detection technology, the application of electromagnetic detectors has gradually expanded from single-frequency to multi-frequency to improve detection efficiency and reflect more geological information. For multi-frequency electromagnetic transmitters used as excitation sources in field tests, current research mainly focuses on improving the transmitter topology or control strategies to enhance the intensity of the excitation signal, thereby achieving effective excitation. Specifically, existing methods can be summarized as follows:

[0003] 1) Multiple independent transmitters can be cascaded or connected in parallel to operate simultaneously to enhance the signal power of the excitation source. For example, multiple power transmitters can be cascaded to form a multi-stage transmission system with a higher DC supply voltage to increase the excitation current intensity. Alternatively, multiple independent grounded transmitters can be used to achieve vector superposition of the spatial excitation electromagnetic field, but this also introduces inter-source circulating current and interference problems.

[0004] 2) Optimize the layout and configuration of the transmitter coils to constrain the magnetic field shape and increase the field strength. For example, in non-destructive testing (NDT) of buried objects, reverse coil or reverse-loop coil structures are increasingly being used to relatively increase the effective signal strength by suppressing unwanted magnetic fields. Furthermore, researchers have proposed a floating coil design to amplify the magnetic field without introducing power loss. Other studies have shown that using multiple coils and adjusting the coil layout can also enhance the effective magnetic field.

[0005] 3) Utilizing special modes to improve transmitter control strategies. Some studies employ pulse width modulation (PWM) transmission waveform configuration based on data statistics and probability, rationally configuring the functional form of the excitation signal to enhance the transmitted signal power. To further improve the flexibility of spectral amplitude control and optimize the configuration of the main frequency energy, multi-frequency modulation methods can be used, employing modulation wave calculation methods and direct synthesis methods to optimize the transmitter waveform configuration, thereby increasing the intensity of the excitation signal.

[0006] 4) Utilizing impedance matching techniques for inductive loads to enhance power transmission across multiple frequencies. Typically, due to the energy storage characteristics of passive devices, a combination of inductors and capacitors is used to construct a resonant transmission path to reduce impedance and reactive power at specific frequencies. For example, LCL resonant compensators are used for impedance matching of inductive loads, achieving power enhancement when continuously distributing multiple mains frequencies. Researchers have also applied a typical LCC-type multi-frequency resonant circuit to wireless charging scenarios to simultaneously minimize transmission impedance across multiple mains frequencies.

[0007] The above comparison and analysis reveal that the first method is the most direct, but due to limitations in power electronics technology, high-voltage switching devices increase the initial cost of the instrument and create complex heat dissipation analysis and design problems. In field exploration experiments, the second technique undoubtedly increases the complexity and technical difficulty of the exploration work. While the third method requires no additional peripheral hardware, according to Passavar's law, the spectral energy of its transmitted signal is severely limited, and spectral energy allocation alone cannot eliminate the reactive power suppression problem caused by load inductive reactance. Unlike the first three methods, the fourth method, because it fundamentally solves the reactive power consumption problem, is gradually becoming a research hotspot. Under this method, the strength of the transmitted signal can be effectively enhanced without increasing the DC supply voltage and transmitter system capacity; that is, this method can substantially improve the capacity utilization rate and excitation signal strength of the power transmitter.

[0008] Existing impedance matching techniques are widely used in fields such as radio frequency communication, wireless charging, and underwater radar, which involve inductive coil loads. In these applications, structures with fixed coil loads typically have fixed parameters, making the influence of the external environment negligible. Meanwhile, existing research has proposed parameter optimization design methods to address the impact of uncertainties in small-scale loads and improve matching accuracy. However, unlike the aforementioned explicit coil loads, grounded electromagnetic transmission systems in electromagnetic detection instruments operate in outdoor environments, with their transmitting load consisting of a long grounding conductor, grounding electrodes, and the earth's dielectric. The electrical parameters of the earth vary depending on the region, specifically soil type, humidity, temperature, and other factors. Furthermore, the load inductance is typically positively correlated with conductor length, and the length and shape of the conductors deployed for different transmission and reception distances vary, leading to variations in load impedance. These uncertainties result in significant differences in load impedance across different application scenarios.

[0009] Because resonant circuits are highly sensitive to component parameters, changing load parameters in multi-frequency impedance matching systems can cause inherent frequency shifts and mismatches with the transmitted signal frequency. These problems prevent traditional fixed-parameter multi-frequency impedance matching systems from achieving precise load impedance matching.

[0010] In existing electromagnetic transmitter applications, uncompensated strategies are still quite common. Although some impedance matching techniques for fixed coil loads have been directly applied, overall, existing transmitter systems still show significant inadequacy in their compatibility with various grounding conditions with different load parameters. Summary of the Invention

[0011] The technical problem to be solved by this application is to provide an adaptive multi-frequency resonant matching system and design method, which aims to solve the problem that grounded electromagnetic transmitters cannot maintain the stability of the matching frequency and a high excitation signal strength under the environment of load impedance variation.

[0012] An adaptive multi-frequency resonant matching system according to an embodiment of the first aspect of this application includes: a series-connected magnetically coupled resonant module and a controllable variable impedance unit, wherein the switching control capacitor includes a parallel-connected matching capacitor. With control switch The switch control inductor includes a series matching inductor. and control switch The magnetically coupled resonant module includes an inductor. and capacitors ,capacitance Among them, capacitor With inductance After parallel connection with capacitor Series connection.

[0013] Furthermore, the control switch With control switch They have the same structure, both including two reverse-connected series switching transistors, each connected in parallel with a body diode. The forward or reverse transmission channel is formed by the conduction angle of the switching transistors.

[0014] Furthermore, the equivalent capacitance of the switch control capacitor for: ,in, To match the capacitor, This is the conduction angle of the capacitor used for switch control.

[0015] Furthermore, the parameters of the matching capacitor satisfy: ,in, This represents the deviation value of the load impedance. This represents the deviation value of the load inductance. Angular frequency, It is the imaginary unit.

[0016] Furthermore, the equivalent inductance of the switch control inductor for: ,in To match the inductor, The conduction angle of the inductor is controlled by the switch.

[0017] Furthermore, the parameters of the matching inductor satisfy: ,in, This represents the deviation value of the load impedance. This represents the deviation value of the load inductance. Angular frequency, It is the imaginary unit.

[0018] Furthermore, the parameters of the magnetically coupled resonant module are calculated based on the target matching frequency and the multi-frequency impedance matching equation. The multi-frequency impedance matching equation for the two angular frequencies is as follows:

[0019] , and The angular frequencies corresponding to the two principal frequencies contained in the target matching frequency. The imaginary unit, It is the load inductance.

[0020] Furthermore, the system also includes a DSP controller for calculating the conduction angle of the switching transistor. The calculation of the conduction angle of the switching transistor includes:

[0021] Sample the load voltage signal and the load current signal;

[0022] Perform a fast Fourier transform on the load voltage signal and the load current signal to obtain the nth harmonic of the load voltage signal and the nth harmonic of the load current signal;

[0023] The actual load inductance is calculated based on the nth harmonic of the load voltage signal and the nth harmonic of the load current signal.

[0024] Based on the deviation between the actual load inductance and the ideal load impedance, the impedance required for the controllable variable impedance unit to achieve matching is calculated. Combining the equivalent capacitance of the switch control capacitor and the equivalent inductance of the switch control inductor, the conduction angles of the switch control capacitor and the switch control inductor in the controllable variable impedance unit are calculated.

[0025] A design method for an adaptive multi-frequency resonant matching system according to a second aspect embodiment of this application includes:

[0026] The parameters of inductor L1, capacitor C1, and capacitor C2 of the magnetically coupled resonant module are determined based on the target matching frequency and the multi-frequency impedance matching equation.

[0027] Calculate the two boundary impedance values ​​of the controllable variable impedance unit, which correspond to the maximum inductive impedance and the minimum capacitive impedance, respectively;

[0028] Within the range of maximum inductive impedance and minimum capacitive impedance, a matching capacitor C is set. M Matching inductor L M Parameter value range:

[0029] ;

[0030] ;

[0031] in, This represents the deviation value of the load inductance. Angular frequency, This represents the deviation value of the load impedance. Imaginary unit.

[0032] Compared with existing technologies, the advantages of this application are as follows: This application improves the signal strength of the multi-frequency grounded electromagnetic transmitter, achieving efficient transmission of multi-frequency excitation signals. It significantly broadens the range of loads to be matched at the interface. By controlling the controllable variable impedance unit (VIC), it achieves the cancellation of load impedance deviations, thereby ensuring that the matching frequency of the entire multi-frequency resonant matching system remains stable and fully matched with the transmitter frequency. This application enables the grounded electromagnetic transmitter to maintain the stability of the matching frequency and a high excitation signal strength even under varying load impedance conditions. Attached Figure Description

[0033] Figure 1 A load model of a grounded electromagnetic transmitter provided in the embodiments of this application;

[0034] Figure 2 The inductor L accompanying the transmitting antenna provided in the embodiments of this application W and parasitic capacitance C E A graph showing the changing load impedance characteristics;

[0035] Figure 3 A circuit block diagram of a grounded electromagnetic transmitter with an integrated adaptive multi-frequency resonant matching system provided in an embodiment of this application;

[0036] Figure 4 Impedance characteristic curves of conventional multi-frequency resonant matching provided in the embodiments of this application;

[0037] Figure 5 A trend diagram of the main frequency impedance versus load impedance deviation provided in an embodiment of this application;

[0038] Figure 6 The circuit diagram (a) of the switch-controlled capacitor and the circuit diagram (b) of the switch-controlled inductor of the controllable variable impedance unit provided in the embodiments of this application are shown.

[0039] Figure 7 A graph showing the relationship between the equivalent parameters of the switch control capacitor and the switch control inductor and the control signal, provided in the embodiments of this application.

[0040] Figure 8 Impedance diagrams of synthesized controllable variable impedance units with different equivalent inductance and equivalent capacitance parameters provided in the embodiments of this application. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0042] The transmission load connected to the grounded electromagnetic transmitter is an electromagnetic transducer, consisting of a transmitting antenna, grounding electrodes, and the electrical parameters of the ground layer between the electrodes. The transmitting antenna is a long grounding wire connected to the ground through the grounding electrodes, forming a closed loop. The transmitter supplies alternating current to the load to generate an electromagnetic field in space. The transmitter electrode spacing can be configured according to the requirements of the site conditions. Therefore, the length of the grounding wire is determined by the target area, typically ranging from several kilometers to tens of kilometers. Furthermore, the electrical parameters of the grounding electrodes and the ground between them vary significantly depending on the detection area. Considering the large current transmission during transmission, the electrical parameters of the grounding electrodes and the ground layer between them will cause changes in their equivalent impedance. The grounding electrodes are considered as concentrated at a single point, and the influence of distributed parameters is not considered. The main factors considered include the impedance of the grounding electrodes themselves and the contact impedance between the grounding electrodes and the ground. Due to the inherent characteristics of the long grounding wire, the transmitting antenna exhibits both inductive and resistive characteristics. Considering the characteristics of the Debye equivalent model of the ground, the load characteristics of the long grounding wire can be modeled as a combination of two resistors and one capacitor.

[0043] Based on the above considerations, establish as follows Figure 1 The load model of the grounded electromagnetic transmitter shown can be categorized into two cases: 1) inductive at higher probe current frequencies; 2) capacitive at lower probe frequencies. Considering the relatively high frequency requirement (tens of hertz and above) for shallow surface electromagnetic detection, and the parasitic capacitance C... E The effect is negligible. Therefore, the load impedance can be considered inductive, and the mathematical expression for the load impedance in the load model is:

[0044] ,

[0045] in, For load impedance, and These are the equivalent resistance and equivalent reactance of the load, respectively; and These are the resistance and inductance of the transmitting antenna, respectively, and they are connected in series. The resistance of the grounding electrode is the contact gap between the long grounding conductor and the earth. and These are all equivalent resistances to the ground. Typically, 1Ω < <5Ω, 1mH< <4mH, 5Ω< <100Ω, 5Ω< <100Ω, 0.1Ω< <5Ω, and 1×10⁻ 4 μF < <1×10⁻³μF.

[0046] Based on the above analysis and impedance expression, the transmitting load will exhibit different reactance values ​​under different parameter conditions. Figure 2 The inductance L of the transmitting antenna is shown. W and parasitic capacitance C E The load impedance characteristic diagram shows the change. It can be seen that with the parasitic capacitance... and transmitting antenna inductance As the parameter values ​​change, the load impedance will also gradually change, which directly leads to changes in the impedance matching target under different detection environments.

[0047] Based on the above problems, this application proposes an adaptive multi-frequency resonant matching system, see [link to relevant documentation]. Figure 3 As shown, an adaptive multi-frequency resonant matching system of this application includes a magnetically coupled resonant module connected in series and a controllable variable impedance unit. The controllable variable impedance unit includes a switch-controlled capacitor and a switch-controlled inductor connected in parallel. The switch-controlled capacitor includes a matching capacitor connected in parallel. With control switch The switch control inductor includes a series matching inductor. and control switch Control switch and control switch Composed of a pair of MOSFETs with body diodes, the matching capacitor can be adjusted by applying desired control to the control switch. Matching inductor The equivalent value is used to control the total impedance of the magnetically coupled resonant module, thereby achieving effective matching with the load. The magnetically coupled resonant module is composed of passive components, including an inductor. and capacitors ,capacitance Among them, capacitor With inductance After parallel connection with capacitor Series connection. This application uses a second-order fixed magnetically coupled resonant module as an example for illustration. The combination of a higher-order fixed magnetically coupled resonant module and a controllable variable impedance unit is similar in principle. Since the core idea of ​​this application is to improve the adaptability to load changes by introducing a controllable variable impedance unit, the extension of the resonance matching order of the magnetically coupled resonant module is not discussed here.

[0048] A transmitter typically consists of an AC power supply, a rectifier, and an inverter. Since the work site is usually far from mains power, a generator is generally used as the AC power source. The rectifier consists of diodes. ,diode ,diode and diodes Composition, including diodes With diode Series connection, diode With diode Series connection, and parallel connection with the power supply, diode With diode Center tap and diode With diode The center tap serves as the output terminal, connected to both ends of the inverter. Its function is to convert AC power to DC power and supply power to the inverter. This inverter adopts a traditional H-bridge inverter structure, including switching transistors. Switching transistor Switching transistor Switching transistor The bridge circuit consists of two parallel filter capacitors connected at both ends. One output of the H-bridge inverter is connected to one end of the magnetically coupled resonant module, and the other output is connected to one end of the load. The magnetically coupled resonant module is connected in series with a controllable variable impedance unit, the other end of which is connected to the other end of the load. The H-bridge inverter is controlled by a controller and outputs a voltage containing multiple frequency components for use in subsequent circuits. The controller is a digital signal processing (DSP) controller. Figure 3 middle, This is the DC supply voltage at the inverter input terminal.

[0049] In electromagnetic detection, pulse width modulation (PWM) technology is commonly used for inverter control to efficiently generate excitation signal waveforms containing the desired frequency. According to existing research, by configuring the controller's multi-frequency modulated signal waveform as follows, the inverter output containing the main frequency can be controlled. Corresponding multi-frequency voltage signal :

[0050] ,

[0051] in, These represent the modulation amplitudes of each main frequency. It is time. Indicates the first indivual.

[0052] By comparing the signal with a high-frequency triangular carrier wave, the controller processes the signal and outputs control signals to the switching devices in the inverter, thereby causing the inverter to output a multi-frequency excitation voltage signal. Its output voltage waveform can be summarized as follows:

[0053] ;

[0054] This is the inverter output voltage. This represents the i-th dominant frequency. Given the modulation amplitude of the i-th dominant frequency, and considering the load impedance, the actual transmission current can be expressed as:

[0055] ;

[0056] ;

[0057] The amplitude of the transmitted current, The phase angle of the transmitted current. Angular frequency, Let be the equivalent resistance of the load. The equivalent reactance of the load. For inductance, It is a resistor.

[0058] The inductive reactance of the transmission load significantly suppresses the current intensity. Impedance matching is typically necessary to eliminate the effect of inductive impedance and maximize the excitation signal strength.

[0059] To analyze the effectiveness and impact of the proposed magnetically coupled resonant module, it is necessary to model the module. Assuming a fixed load, we first consider using the magnetically coupled resonant module to construct a multi-frequency impedance matching system suitable for multiple required frequencies. A fixed dual-frequency resonant network is designed, where "fixed" means the dominant frequency remains constant. Its equivalent impedance can be obtained as follows: . This is the equivalent impedance of the magnetically coupled resonant module.

[0060] Given the load inductance L0, the total impedance of the transmitter can be determined. The purpose of impedance matching is to reduce the imaginary part of the transmission loop, thereby increasing the effective signal strength of the excitation current. Combining the set main transmission frequencies f1 and f2, and assuming the imaginary part of the impedance is zero, the multi-frequency impedance matching equation can be derived:

[0061] ,

[0062] It is understandable that the main transmission frequency includes not only the main frequencies f1 and f2 listed in the embodiments, and The angular frequencies corresponding to the two principal frequencies contained in the target matching frequency. It is the imaginary unit.

[0063] At this point, the fixed magnetic coupling resonant module can simultaneously achieve zero reactance at multiple main frequencies, maximizing the multi-frequency excitation signal and thus eliminating the energy suppression effect caused by the inductive transmission load. The impedance characteristics of traditional multi-frequency resonant matching are as follows: Figure 4 As shown. By Figure 4 As can be seen, R0 is the load resistance. Comparing the impedance characteristics of unmatched and matched impedances, it can be seen that a transmission path with zero reactance can be established simultaneously at multiple frequencies to reduce the suppression effect of load inductance on the transmission current. However, the above multi-frequency impedance matching equation is based on the assumption of constant load parameters, that is, it only applies to a fixed transmitting coil load. Once the load inductance L0 changes, the corresponding matching frequency will also change, leading to a mismatch with the output voltage signal of the transmitting system. To analyze this problem more intuitively, Figure 5 The graph shows the trend of the main frequency impedance as a function of the load impedance deviation, illustrating the main frequency impedance when the load parameters deviate. It is clear that the main frequency impedance gradually increases with the degree of load parameter deviation. This indicates that changes in grounding parameters lead to a significant mismatch between impedance compensation and transmission frequency, thereby reducing the performance of the impedance matching system.

[0064] As the above analysis shows, the influence of time-varying characteristics on load parameter changes is unavoidable. To offset the adverse effects of load inductive reactance changes, this application employs a controllable variable impedance unit to compensate for the variation in load reactance. The key to this application lies in precisely controlling the equivalent value of the controllable variable impedance unit, making it equal to the deviation between the load impedance and the ideal value. Figure 6 As shown, the proposed controllable variable impedance unit consists of a switch-controlled capacitor and a switch-controlled inductor connected in parallel, which can provide capacitive and inductive matching capabilities to adapt to changes in load parameters.

[0065] Figure 6 The switch control capacitor (SCC) in (a) uses a switching transistor. With switching transistor The entire assembly is connected in reverse series with a matching capacitor C. M Parallel connection. To make the impedance conditions suitable for AC scenarios, the switching transistors... With body diode D C1 Parallel connection forms a forward transmission channel, while the switching transistors With body diode D C2 This forms a reverse transmission channel. During each duty cycle, the switching transistor... It conducts during the positive half-cycle, while the switching transistor... It conducts during the negative half-cycle. This is achieved by controlling the switching transistor during the duty cycle. With switching transistor The switching control capacitor conduction angle The equivalent capacitance value of the adjustable switch-controlled capacitor is denoted as . Follow the following impedance expression: .

[0066] For matching capacitors After initialization, the desired equivalent capacitance can be adjusted using the impedance expression. Similarly, for Figure 6 In (b) of the diagram, the switch control inductor (SCI) and the switching transistor... With switching transistor The entire assembly is connected in reverse series with a matching capacitor C. M Parallel connection. To make the impedance conditions suitable for AC scenarios, the switching transistors... With body diode D L1 Parallel connection forms a forward transmission channel, while the switching transistors With body diode D L2 This forms a reverse transmission channel. During each duty cycle, the switching transistor... It conducts during the positive half-cycle, while the switching transistor... It conducts during the negative half-cycle. The conduction angle of the inductor can be controlled by a switch. Control switch S L1 With the switching transistor S L2 The state.

[0067] Equivalent Inductance The control function can be determined as follows: ;

[0068] Based on the above analysis, the switch-controlled capacitor and the switch-controlled inductor can be equivalent to a variable capacitor and a variable inductor, respectively. Figure 7 The graph shows the relationship between the equivalent parameters of the switch-controlled capacitor and inductor and the control signal, illustrating the impedance corresponding to the equivalent capacitance and inductance values ​​at different control conduction angles. The left vertical axis represents the impedance at the equivalent capacitance value, and the right vertical axis represents the impedance at the equivalent inductance value. It can be seen that by coordinating the on / off states of the switching transistors in the switch-controlled capacitor and inductor, the average current flowing through the passive components in each cycle can be controlled, thereby controlling the total impedance of the controllable variable impedance unit. Furthermore, combining the above-mentioned switch-controlled capacitor and inductor, the total impedance of the controllable variable impedance unit... The following can be calculated: .

[0069] Figure 8 Impedance diagrams of the synthesized controllable variable impedance unit under different equivalent inductance and equivalent capacitance parameters are shown. It can be seen that by reasonably controlling the conduction angle, the synthesized impedance can be continuously varied to adapt to changes in the grounded load.

[0070] In this embodiment, the overall resonance matching function of the adaptive multi-frequency resonance matching system can be represented as follows:

[0071] in, This is the overall impedance.

[0072] Based on the above analysis, by adjusting the control signal of the controllable variable impedance unit, the dynamic grounding load impedance can be effectively matched, thereby ensuring that the proposed adaptive multi-frequency resonant matching system achieves reliable multi-frequency impedance matching at the desired transmission frequency.

[0073] In one embodiment, the DSP controller is used to calculate the conduction angle of the switching transistor. The calculation of the conduction angle of the switching transistor includes:

[0074] The load voltage signal and load current signal are sampled. The load voltage signal and load current signal pass through the voltage and current sensor, AD sampling chip and signal filtering circuit in sequence to complete the sampling and transmit to the DSP controller.

[0075] Performing a Fast Fourier Transform (FFT) on the load voltage and load current signals yields the nth harmonic of the load voltage and load current signals. To achieve load impedance identification, a FFT is required, specifically targeting the load voltage signal. With load current signal The actual sampling results show that the nth harmonic can be expressed as follows:

[0076] ;

[0077] ;

[0078] in, Where N is the harmonic order, and N is the number of sampling points in one operating cycle. Representing the One sampling point, This is the nth harmonic of the load voltage signal. This is the nth harmonic of the load current signal.

[0079] Identify the actual load inductance Based on the Fast Fourier Transform analysis results of the load voltage and load current signals, an impedance-related equation can be established, thereby identifying the actual load inductance parameters as follows:

[0080] ; This represents the actual load impedance.

[0081] The impedance required for matching by the controllable variable impedance unit is calculated based on the deviation between the actual load impedance and the ideal load impedance (set reference value). The conduction angles of the switching control capacitor and the switching control inductor in the controllable variable impedance unit are calculated by combining the equivalent capacitance of the switching control capacitor and the equivalent inductance of the switching control inductor. The actual load impedance is then determined based on the identification results of the actual load parameters. With ideal load impedance The deviation can be used to determine the impedance required for matching by the controllable variable impedance unit, as follows:

[0082] ,

[0083] Combination and The required control signal conduction angle for the switch control capacitor and switch control inductor in the controllable variable impedance unit can be calculated.

[0084] Output control signal. This output signal is used to control the switching transistor of the controllable variable impedance unit, adjusting the deviation of the equivalent impedance of the controllable variable impedance unit to match the actual load, which is also the goal of resonant matching. Therefore, for varying loads, it can maintain the desired stable multi-frequency resonant matching.

[0085] On the other hand, embodiments of this application provide a design method for an adaptive multi-frequency resonant matching system, including:

[0086] The parameter design of the adaptive multi-frequency resonant matching system includes the parameter design of the magnetically coupled resonant module and the parameter design of the controllable variable impedance unit. First, assume the theoretically calculated load inductive reactance is... For the fixed multi-frequency impedance matching section, by combining the target matching frequency and the multi-frequency impedance matching equation, the parameter expressions for the passive components inductor L1, capacitor C1, and capacitor C2 can be determined for specific calculations. The focus of parameter design in this application is on the controllable variable impedance unit. Under extreme operating conditions of the switching transistor, when control switch K1 is off and control switch K2 is on, the external characteristic of the controllable variable impedance unit exhibits maximum capacitive impedance; while when control switch K1 is on and control switch K2 is off, the external characteristic of the controllable variable impedance unit exhibits maximum inductive impedance. Through the coordinated operation of control switches K1 and K2, a wide range of impedance adjustment from capacitive to inductive can be achieved. Therefore, the two boundary impedance values ​​of the controllable variable impedance unit are calculated, corresponding to the maximum inductive impedance and the minimum capacitive impedance, respectively:

[0087] ;

[0088] ;

[0089] Based on the assumed load inductive reactance X L0 The deviation of the actual load impedance is set as ΔX. L The range of load reactance variation is [X]. L(min) X L(max) ], [ [X] represents the impedance variation range of the controllable variable impedance unit, which needs to satisfy the possible variation range of the load inductance [X]. L(min) X L(max) Each impedance value in the [] can be matched. To ensure perfect matching throughout the entire transmission process, within the impedance variation range of the controllable variable impedance unit [] Within this range, the following parameter design relationships must be met to determine the matching capacitor C. M Matching inductor L M The parameter value range is as follows: ;

[0090] ;

[0091] This represents the deviation value of the load inductance. Angular frequency, This represents the deviation value of the load impedance.

[0092] Compared to the uncompensated scenario, traditional fixed compensation methods can only guarantee matching for identified load parameters. In contrast, this application can identify and adaptively match changing load parameters, thus maintaining the matching effect during load switching. This helps improve the adaptability of grounded electromagnetic transmitters to changing loads.

[0093] This application can maintain good resonant matching performance and effective signal transmission even under varying grounding load impedance. It not only improves the signal strength of multi-frequency transmitters, but more importantly, significantly broadens the range of loads to be matched, enabling grounded electromagnetic transmitters to maintain stable matching frequencies and high excitation signal strength even under varying load impedance conditions.

[0094] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An adaptive multi-frequency resonant matching system, characterized in that, include: The system consists of a series-connected magnetically coupled resonant module and a controllable variable impedance unit. The controllable variable impedance unit includes a parallel-connected switching control capacitor and a switching control inductor. The switching control capacitor includes a parallel-connected matching capacitor. With control switch The switch control inductor includes a series matching inductor. and control switch The magnetically coupled resonant module includes an inductor. and capacitors ,capacitance Among them, capacitor With inductance After parallel connection with capacitor Series connection.

2. The adaptive multi-frequency resonant matching system according to claim 1, characterized in that, The control switch With control switch They have the same structure, both including two reverse-connected series switching transistors, each connected in parallel with a body diode. The forward or reverse transmission channel is formed by the conduction angle of the switching transistors.

3. The adaptive multi-frequency resonant matching system according to claim 1, characterized in that, The equivalent capacitance of the switch-controlled capacitor for: ,in, To match the capacitor, This is the conduction angle of the capacitor used for switch control.

4. The adaptive multi-frequency resonant matching system according to claim 3, characterized in that, The parameters of the matching capacitor must satisfy: ,in, This represents the deviation value of the load impedance. This represents the deviation value of the load inductance. Angular frequency, It is the imaginary unit.

5. An adaptive multi-frequency resonant matching system according to claim 1, characterized in that, The equivalent inductance of the switch control inductor for: ,in To match the inductor, The conduction angle of the inductor is controlled by the switch.

6. The adaptive multi-frequency resonant matching system according to claim 5, characterized in that, The parameters of the matching inductor satisfy: ,in, This represents the deviation value of the load impedance. This represents the deviation value of the load inductance. Angular frequency, It is the imaginary unit.

7. The adaptive multi-frequency resonant matching system according to claim 1, characterized in that, The parameters of the magnetically coupled resonant module are calculated based on the target matching frequency and the multi-frequency impedance matching equation. The multi-frequency impedance matching equation for the two angular frequencies is as follows: , and The angular frequencies corresponding to the two principal frequencies contained in the target matching frequency. The imaginary unit, It is the load inductance.

8. An adaptive multi-frequency resonant matching system according to claim 2, characterized in that, The system also includes a DSP controller for calculating the conduction angle of the switching transistor. The calculation of the conduction angle of the switching transistor includes: Sample the load voltage signal and the load current signal; Perform a fast Fourier transform on the load voltage signal and the load current signal to obtain the nth harmonic of the load voltage signal and the nth harmonic of the load current signal; The actual load inductance is calculated based on the nth harmonic of the load voltage signal and the nth harmonic of the load current signal. Based on the deviation between the actual load inductance and the ideal load impedance, the impedance required for the controllable variable impedance unit to achieve matching is calculated. Combining the equivalent capacitance of the switch control capacitor and the equivalent inductance of the switch control inductor, the conduction angles of the switch control capacitor and the switch control inductor in the controllable variable impedance unit are calculated.

9. A design method for an adaptive multi-frequency resonant matching system, used to design the adaptive multi-frequency resonant matching system according to any one of claims 1-8, characterized in that, include: The parameters of inductor L1, capacitor C1, and capacitor C2 of the magnetically coupled resonant module are determined based on the target matching frequency and the multi-frequency impedance matching equation. Calculate the two boundary impedance values ​​of the controllable variable impedance unit, which correspond to the maximum inductive impedance and the minimum capacitive impedance, respectively; Within the range of maximum inductive impedance and minimum capacitive impedance, a matching capacitor C is set. M Matching inductor L M Parameter value range: ； ； in, This represents the deviation value of the load inductance. Angular frequency, This represents the deviation value of the load impedance. Imaginary unit.

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