Method and system for eliminating low-frequency interference magnetic field

Abstract

The invention discloses a low-frequency interference magnetic field elimination method and system, and belongs to the technical field of electromagnetism and control. The device mainly comprises a magnetic sensor module used for collecting interference magnetic field signals, a conversion circuit module used for converting the interference magnetic field signals into analog voltage signals, a characteristic frequency band interference signal selection module, an analog signal phase adjustment module, a multi-path characteristic frequency band interference signal addition module, an output gain adjustable module and a power amplification module. A magnetic field generation module and an elimination effect detection feedback module. According to the low-frequency interference magnetic field elimination system, an analog circuit design method is adopted, low-frequency interference magnetic fields of several different frequency bands can be effectively weakened and eliminated, and the low-frequency interference resistance of devices with high low-frequency interference sensitivity such as ultralow-field magnetic resonance imaging equipment can be improved by adjusting system related parameters; and the equipment availability is enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic interference suppression, and specifically relates to a method and system for eliminating low-frequency interference magnetic fields, which is suitable for scenarios such as medical equipment, precision instruments, and communication systems that are sensitive to low-frequency magnetic fields. Background Art

[0002] The low-frequency interference magnetic field elimination system is a device that cancels out interference at specific frequencies or frequency bands. It includes multiple modules such as signal acquisition sensors, conversion circuits, frequency band processing modules, amplitude and phase calibration modules, gain adjustment, power amplification and output, etc., which constitute the control loop of the entire system.

[0003] The system uses a highly sensitive magnetoresistive sensor to acquire magnetic field signals. By detecting the resistance changes caused by the magnetic field, it converts low-frequency magnetic fields in the environment into a weak voltage signal. A magnetic shielding layer is built into the sensor to suppress high-frequency electromagnetic noise. The sensor can detect a wide range of magnetic field strengths and uses a built-in temperature sensor to calibrate the output signal in real time.

[0004] The magnetic field-to-analog conversion circuit amplifies the microvolt-level voltage output by the sensor and converts it into a standard analog signal. The basic principle is to use a low-noise amplifier combined with an integrator circuit to perform time integration of the magnetic field signal to restore the original magnetic field waveform. Existing technologies still suffer from significant nonlinear errors in the output signal over a wide dynamic range, and some circuits lack bandwidth, necessitating careful design of this component.

[0005] The collected analog signal is filtered through parallel bandpass analog filters to separate the characteristic frequency band signals, including low-pass and bandpass filter designs. Traditional filters often have a fixed frequency and an unadjustable center frequency, making them incompatible with the requirements of 50Hz or 60Hz power frequency switching. For interference signals with a center frequency of approximately 17Hz, the filter's roll-off characteristics are poor, resulting in leakage of signals from adjacent frequency bands. Furthermore, existing technical methods typically only target a single frequency band and lack the ability to collaboratively extract multiple frequency bands, such as 0-10Hz, 17Hz, and 50Hz / 60Hz.

[0006] In low-frequency interference signal elimination systems, a phase-shifting circuit is used to compensate for signal phase. By adjusting the resistance value, a phase shift of + / - 90 degrees can be achieved. The adjustment error accuracy of the phase-shifting circuit should be kept within a small range, while also requiring fast dynamic response.

[0007] The basic principle of the multi-channel characteristic signal addition module is to weightedly superimpose the three phase-calibrated signals to generate a comprehensive cancellation signal. An operational amplifier addition circuit is used, and an isolation resistor is connected in series with each signal input to prevent signal crosstalk.

[0008] The signal amplitude is dynamically adjusted according to the output interference magnetic field elimination effect. The gain adjustable module can be manually adjusted through an external potentiometer, or it can be designed through closed-loop feedback control. After receiving the error signal, the gain is adjusted in real time through feedback control algorithms.

[0009] The power amplifier module of the low-frequency interference magnetic field elimination system amplifies the weak cancellation signal to a current of a certain power to drive the coil to generate a reverse magnetic field. It uses an AB type power amplifier and supports distortion-free amplification in the low-frequency range of 0~100Hz.

[0010] After power amplification, the signal drives the coil to generate a magnetic field with the same amplitude and opposite phase to the original interference magnetic field. The coil is implemented using a Helmholtz coil pair. The distance between the two coils of the circular Helmholtz coil pair is equal to the radius, and the square Helmholtz coil pair adopts an appropriate spacing. The number of winding turns and the input current parameters are determined in combination with the requirements for generating the magnetic field to generate a uniform offsetting magnetic field.

[0011] The effectiveness of the low-frequency interference magnetic field elimination system is detected by the monitoring module. The residual magnetic field strength is detected by the secondary sensor and fed back to the front-end modules to optimize the parameters, mainly including amplitude detection and phase detection, and calculating the RMS value ratio of the original interference and the residual signal and the phase deviation. Summary of the Invention

[0012] The technical problem to be solved by the present invention is to address the deficiencies in the above-mentioned prior art and provide a method and system for eliminating low-frequency interference magnetic fields, which can effectively weaken or eliminate the characteristic low-frequency interference magnetic field to the order of 10nT in a set spatial area, while ensuring that the system can adjust the output elimination effect according to the changes in the interference magnetic field, thereby improving the overall performance of the system, and is used to solve the technical problems of nonlinear distortion in wide dynamic range signal conversion, dynamic accuracy bottleneck in phase compensation, and waveform distortion in power amplification.

[0013] The present invention adopts the following technical solutions: A method for eliminating a low-frequency interference magnetic field comprises the following steps: Collect low-frequency interference magnetic field signals in the target environment and pre-process them to obtain analog electrical signals; Extracting interference signals of preset characteristic frequency bands from the analog signal; and performing phase adjustment on the interference signals of the preset characteristic frequency bands respectively; The phase-adjusted multi-path signals are superimposed to obtain a comprehensive characteristic frequency band interference signal; the amplitude of the comprehensive characteristic frequency band interference signal is adjusted to obtain a characteristic frequency band signal; The characteristic frequency band signal is power amplified to obtain a power amplified voltage; the obtained power amplified voltage is used to drive the coil load, and the driving voltage and the generated magnetic field are calibrated to generate a canceling magnetic field that is opposite to the interference magnetic field, thereby eliminating the original low-frequency interference magnetic field.

[0014] Preferably, preprocessing is performed to obtain an analog electrical signal, specifically: In the first stage circuit, a preamplifier circuit is used, and a low-noise operational amplifier is used to build a common-mode amplifier circuit. The amplification factor is determined by the operational amplifier circuit parameters to enhance the weak signal output by the sensor. In the second stage circuit, an anti-aliasing filter circuit is used, and a second-order active low-pass filter is used to suppress high-frequency noise in the mixed signal, including radio frequency interference and switching noise, to obtain an analog electrical signal.

[0015] Preferably, the interference signals of the preset characteristic frequency bands include frequency band interference signals of 0~10Hz, center frequency of 17Hz, and center frequency of 50Hz / 60Hz. A second-order voltage-controlled low-pass filter is used for 0~10Hz; a second-order active band-pass filter is used for 17Hz and 50Hz / 60Hz.

[0016] Preferably, the phase adjustment is specifically: The analog phase shift circuit is used for adjustment, and the topology is to generate 0~ The first-level integrator produces 0~ A first-stage inverting amplifier is used, and the phase shift amount is adjusted by a variable resistor. In the 50Hz / 60Hz channel, two different power frequency interference bands are switched by jumpers, so that the generated offset magnetic field is opposite to the phase of the original interference signal.

[0017] Preferably, the phase-adjusted multi-path signals are superimposed to obtain a comprehensive characteristic frequency band interference signal, specifically: A multi-input inverting addition circuit is built through high-precision operational amplifiers to support weighted superposition of three independent signals; input signal 1 comes from the phase-shifted signal of characteristic frequency band 1, input signal 2 comes from the phase-shifted signal of characteristic frequency band 2, and input signal 3 comes from the phase-shifted signal of characteristic frequency band 3. Each input is connected in series with a precision adjustable resistor to support dynamic adjustment of the superposition weight.

[0018] Preferably, at the input front end, each signal is isolated by a voltage follower, and the gain of each channel is set by a digital potentiometer. The relationship between the output signal and the input signal is expressed as:

[0019] in, The output voltage of the operational amplifier; It is the feedback resistor of the operational amplifier circuit, connecting the output terminal and the inverting input terminal of the operational amplifier; is the input resistance of the first channel, is the input resistance of the second channel, is the input resistance of the third channel, which controls the gain ratio of each channel respectively; is the input voltage signal of the first channel, is the input voltage signal of the second channel, is the input voltage signal of the third channel.

[0020] Preferably, the amplitude of the comprehensive characteristic frequency band interference signal is adjusted to obtain the characteristic frequency band signal, as follows: The external voltage signal is mapped to the gain range in an analog manner and is compatible with manual adjustment. This is achieved by adjusting the feedback resistor. The input signal comes from the integrated offset signal and is amplified by the operational integrated circuit before output. A voltage follower is set at the input front end for isolation. The gain range is 1 to 100 times and the bandwidth is 0 to 1kHz.

[0021] Preferably, the characteristic frequency band signal is power amplified to obtain a power amplified voltage, specifically: It adopts hierarchical voltage amplification. The front-stage voltage amplification is based on a high-speed operational amplifier with adjustable gain. The rear-stage current drive adopts a class AB power amplifier and directly drives the coil load. After voltage-current conversion, power output is performed, and overcurrent protection and temperature protection modules are set in the circuit.

[0022] Preferably, the obtained power amplified voltage drives the coil load, and the driving voltage and the generated magnetic field are calibrated to generate a canceling magnetic field that is in opposite phase to the interfering magnetic field, specifically: A Helmholtz coil pair is used to generate a canceling magnetic field according to Ampere's loop law. The residual interference signal after cancellation is monitored in real time. Dynamic optimization is achieved through feedback control to ensure that the interference elimination effect is continuously optimized.

[0023] In a second aspect, an embodiment of the present invention provides a low-frequency interference magnetic field elimination system, comprising: The acquisition module collects low-frequency interference magnetic field signals in the target environment and pre-processes them to obtain analog electrical signals; The phase module extracts the interference signal of the preset characteristic frequency band from the analog signal; and adjusts the phase of the interference signal of the preset characteristic frequency band respectively; The adjustment module superimposes the phase-adjusted multi-channel signals to obtain a comprehensive characteristic frequency band interference signal; and adjusts the amplitude of the comprehensive characteristic frequency band interference signal to obtain a characteristic frequency band signal; The elimination module amplifies the characteristic frequency band signal to obtain a power amplification voltage; the obtained power amplification voltage drives the coil load, and the driving voltage and the generated magnetic field are calibrated to generate a canceling magnetic field that is opposite to the interference magnetic field, thereby eliminating the original low-frequency interference magnetic field.

[0024] In a third aspect, a computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned method for eliminating low-frequency interference magnetic fields when executing the computer program.

[0025] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, comprising a computer program, which implements the steps of the above-mentioned method for eliminating low-frequency interference magnetic fields when executed by a processor.

[0026] In a fifth aspect, a chip comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned method for eliminating low-frequency interference magnetic fields when executing the computer program.

[0027] In a sixth aspect, an embodiment of the present invention provides an electronic device, comprising a computer program, which implements the steps of the above-mentioned method for eliminating low-frequency interference magnetic fields when executed by the electronic device.

[0028] Compared with the prior art, the present invention has at least the following beneficial effects: A low-frequency interference magnetic field elimination method constructs a complete control loop from magnetic field detection to reverse cancellation. Interference signals are collected in real time using high-sensitivity magnetoresistive sensors (with detection accuracy reaching 1nT). A closed-loop feedback mechanism is formed through cascade optimization of signal preprocessing, multi-band decomposition, phase compensation, vector superposition, and power amplification modules. This reduces the residual magnetic field strength from 50nT (using traditional methods) to the 10nT level, improving elimination accuracy fivefold and meeting the stringent electromagnetic environment requirements of high-precision scientific research instruments. A second-order voltage-controlled low-pass filter effectively eliminates geomagnetic pulsation interference. A high-Q bandpass filter precisely targets industrial equipment harmonics in the 17Hz characteristic frequency band. Hardware-level jumper switching between the 50Hz and 60Hz power frequency channels adapts to different national grid standards. This system can simultaneously handle complex scenarios such as natural magnetic field fluctuations, industrial equipment harmonics, and grid interference, extending the interference coverage band to more than three times that of traditional systems. A dual closed-loop phase-amplitude adjustment mechanism is employed: the phase compensation module, using a cascaded integrator and inverting amplifier, adapts to changes in interference intensity in real time. When encountering sudden magnetic field interference, the system can complete parameter recalibration within 100ms, achieving a dynamic response speed 10 times faster than traditional manual adjustment systems. Using a Helmholtz coil magnetic field generation model, Ampere's loop law establishes a linear transfer function between drive voltage and offset magnetic field. Combined with a Class AB amplifier and overcurrent protection module, this ensures stable, high-fidelity offset magnetic field output even at a 10A drive current.

[0029] Furthermore, a two-stage pre-processing architecture is adopted, and the signal-to-noise ratio of the preamplifier is improved to 120dB. Combined with the anti-aliasing filter with a -40dB / decade roll-off characteristic, the effective detection rate of microvolt-level signals is increased by 98%, solving the problem of insufficient signal-to-noise ratio of traditional circuits in the frequency band below 1kHz.

[0030] Furthermore, an innovative frequency band separation solution is used to achieve ±0.5dB passband fluctuation in the 0-10Hz range through a second-order voltage-controlled filter. The Q value of the bandpass filter is increased to 20 (17Hz) and 50 (industrial frequency), which is 15dB higher than the out-of-band suppression of traditional designs, effectively preventing frequency band crosstalk.

[0031] Furthermore, the improved phase-shifting network has a phase resolution of 0.1°, supports 50 / 60Hz dual-frequency fast switching (<10ms), and improves phase alignment accuracy by 10 times, ensuring that the phase deviation of the reverse magnetic field is controlled within ±1°.

[0032] Furthermore, the multi-channel weighted superposition circuit uses a combination of 0.1% precision resistors and digital potentiometers to achieve 0.1dB step adjustment of the gain of each channel. Combined with the voltage follower isolation, the crosstalk between channels is reduced to -80dB, significantly improving the vector synthesis accuracy of multi-frequency cancellation.

[0033] Furthermore, the dual-mode gain adjustment supports a 100-fold dynamic range (1-100 times), maintains ±0.2dB linearity within a 1kHz bandwidth, and has a response speed 5 times faster than traditional manual adjustment systems, adapting to millisecond-level magnetic field mutation scenarios.

[0034] Furthermore, the hybrid power amplifier architecture reduces the total harmonic distortion (THD) to less than 1% in the frequency band below 100Hz, and the peak-to-peak driving current reaches 10A. Combined with the dual protection mechanism, it ensures the stability of the system under 4x overload conditions.

[0035] Furthermore, the Helmholtz coil is optimized to make the 0.5m 3 The spatial magnetic field uniformity reaches 95%, and combined with real-time feedback, the residual magnetic field strength is stably controlled to below 8nT RMS, which is 6dB higher than the existing technology.

[0036] It can be understood that the beneficial effects of the second to sixth aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0037] In summary, the present invention constructs a complete closed-loop control system to achieve full-process control from signal acquisition to reverse magnetic field generation. Through multi-technological integration and innovation, it achieves breakthroughs in core indicators such as elimination accuracy, response speed, and frequency band coverage, providing a cost-effective active magnetic compensation solution for precision measurement, biomedicine, industrial automation and other fields.

[0038] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0040] Figure 1 A flow chart of a method for eliminating low-frequency interference magnetic fields provided by an embodiment of the present invention; Figure 2 A structural diagram of a low-frequency interference magnetic field elimination system provided by an embodiment of the present invention; Figure 3 A schematic diagram of the low-pass filter module structure provided by an embodiment of the present invention; Figure 4 A schematic structural diagram of a bandpass filter module provided in an embodiment of the present invention; Figure 5 A schematic diagram of the structure of a phase adjustment module provided in an embodiment of the present invention; Figure 6 A schematic diagram of the structure of a signal addition module provided in an embodiment of the present invention; Figure 7 A schematic diagram of the structure of a gain adjustment module provided in an embodiment of the present invention; Figure 8 A schematic diagram of the structure of a power amplifier module provided in an embodiment of the present invention; Figure 9 A schematic diagram of a load compensation coil module provided in an embodiment of the present invention; Figure 10 A schematic diagram of an elimination effect monitoring module provided in an embodiment of the present invention; Figure 11 A schematic diagram of a computer device provided in accordance with an embodiment of the present invention; Figure 12 A block diagram of an electronic device provided according to an embodiment of the present invention; Figure 13 This is the image obtained by the ultra-low field magnetic resonance imaging device after scanning the test water film when it is subjected to a low-frequency interference magnetic field; Figure 14 The image is obtained after the device scans the test water film after the interference magnetic field is eliminated by the system device provided by the present invention; Figure 15 This is a schematic diagram showing the image and signal-to-noise ratio of the test water film scanned by the ultra-low field magnetic resonance device without external low-frequency interference magnetic field; Figure 16 This is a schematic diagram showing the image and signal-to-noise ratio of the test water film scanned by the ultra-low field magnetic resonance device under the condition of external low-frequency interference magnetic field; Figure 17 This is a schematic diagram showing the image and signal-to-noise ratio of the test water film scanned by the ultra-ultra-low field magnetic resonance equipment after the system device provided by the present invention is running.

[0041] Among them, 60. Computer device; 61. Processor; 62. Memory; 63. Computer program; 600. Electronic device; 610. Processing unit; 620. Storage unit; 6201. Random access memory unit; 6202. Cache memory unit; 6203. Read-only memory unit; 6204. Program / Utility; 6205. Program module; 630. Bus; 640. Display unit; 650. Input / output interface; 660. Network adapter; 700. External device. DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0043] In the description of the present invention, it is to be understood that the terms “include” and “comprise” indicate the presence of the described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0044] It should also be understood that the terms used in the present specification are only for the purpose of describing particular embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0045] It should be further understood that the term "and / or" as used in the present specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0046] It should be understood that although the terms "first," "second," and "third" may be used to describe preset ranges in embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are merely used to distinguish one preset range from another. For example, without departing from the scope of embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0047] The word "if," as used herein, may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to the determination" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)," depending on the context.

[0048] The accompanying drawings illustrate various schematic diagrams of structures according to embodiments disclosed herein. These figures are not drawn to scale; for clarity, some details are exaggerated and some details may be omitted. The shapes of the various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art may design regions / layers with different shapes, sizes, and relative positions as needed.

[0049] The present invention provides a method for eliminating low-frequency interference magnetic field.

[0050] After collecting the mixed interference magnetic field signal in the target environment, it is converted into an analog voltage signal; Convert the collected interference magnetic field signal into an analog signal; Selecting a specific low-frequency interference signal frequency band in the mixed interference magnetic field signal collected by the magnetic signal sensor; The characteristics of the selected and extracted multi-channel low-frequency interference signals are restored, including the signal phase adjustment circuit and the addition circuit module to obtain the control voltage signal for driving the back-end output; Dynamically adjust the gain of the comprehensive offset signal. This module is set to 0~100 times gain adjustable to ensure that the signal has the best amplitude range before power amplification to avoid system overload or insufficient drive; Used to power amplify the control voltage signal, specifically, to amplify it into an AC or DC current with a constant signal phase and adjustable amplitude, so as to drive the load coil to generate an alternating magnetic field or a constant magnetic field; Used to generate a compensation magnetic field with the same characteristics as the output control signal, wherein the compensation coil is a square Helmholtz coil or a circular Helmholtz coil, and the parameters of the coil are determined according to the calibration results of different output drive signals.

[0051] Example 1 The present invention provides a method for eliminating a low-frequency interference magnetic field, comprising the following steps: S1. Collect low-frequency interference magnetic field signals in the target environment using a magnetic signal sensor. The sensor should first be placed in a central location including but not limited to the target area for detection. The basic principle of the magnetic signal sensor for receiving interference magnetic field signals is to identify changes in the magnetic field through built-in micro-Hall elements or other high-precision magnetic signal sensing devices. The above-mentioned devices are arranged in the three-axis directions of space inside the sensor, and the sensor responds to changes in magnetic field signals in different directions by different placement positions, and converts the magnetic field signals in each direction through subsequent conversion circuits.

[0052] S2, preprocessing the signals collected by the sensor; Preprocessing includes electromagnetic signal conversion, amplification and filtering and other functions.

[0053] The raw magnetic field signal collected by the sensor is converted into a stable, processable analog signal as follows: In the first stage circuit, a preamplifier circuit is used, and a low-noise operational amplifier is used to build a common-mode amplifier circuit. The amplification factor is determined by the operational amplifier circuit parameters, which is used to enhance the weak signal output by the sensor. In the second-stage circuit, an anti-aliasing filter circuit is used, and a second-order active low-pass filter design is used to suppress high-frequency noise in the mixed signal, including radio frequency interference, switching noise, etc., to avoid spectrum aliasing when subsequent modules are sampled.

[0054] Through high-precision amplification and filtering, the signal-to-noise ratio of the signal collected by the sensor is improved, providing a high-quality signal source for subsequent frequency band selection and phase adjustment.

[0055] S3, selecting the analog electrical signal generated by preprocessing and extracting the characteristic frequency band signal; Feature frequency band extraction includes the design of low-pass filtering and band-pass filtering channels.

[0056] The target frequency band is separated from the wide-band interference signal, including three independent frequency band interference signals: 0~10Hz, center frequency 17Hz (bandwidth 6Hz), and center frequency 50Hz / 60Hz (bandwidth 10Hz), providing a basis for subsequent targeted processing.

[0057] See also Figure 3 and Figure 4, including three independent filter channels, each channel corresponds to a characteristic frequency band.

[0058] Among them, channel 1 (0~10Hz) adopts a second-order voltage-controlled low-pass filter design, and the design can be expanded on this basis; Channel 2 (center frequency is 17Hz) and channel 3 (center frequency is 50Hz / 60Hz) adopt second-order active bandpass filter design.

[0059] By selecting three independent frequency bands, the required target low-frequency interference signal is obtained and input into the next module for processing.

[0060] The active filter design is used to select the signal channel within the 0~10Hz frequency band, specifically using a second-order voltage-controlled Sallen-Key structure solution, such as Figure 3 As shown in the figure, this is a schematic diagram of the circuit topology, and its transfer function is described as:

[0061] At the same time, it can be set to Butterworth, Chebyshev, Bessel and other forms according to needs. The bandpass filter channel used to select the center frequency 17Hz (bandwidth 6Hz) and center frequency 50 / 60Hz (bandwidth 10Hz) bands can be realized by combining a second-order low-pass filter and a second-order high-pass filter, such as Figure 4 As shown in the figure, it is a schematic diagram of the topological design scheme of the module circuit, in which the transfer function of the second-order low-pass filter can be described as:

[0062] The transfer function of a second-order high-pass filter is described as:

[0063] Combined with the above transfer function, by changing the cutoff frequency and Q value, different center frequencies and frequency band signals can be selected and extracted. Among them, the cutoff frequency of the low-pass or high-pass filter is Expressed as:

[0064] The Q value is:

[0065] The above three signals are completely independent when output, without cross-interference. At the same time, more characteristic frequency bands can be supported by adjusting the filter or adding other sub-modules.

[0066] S4, performing phase adjustment on the extracted characteristic frequency band signals respectively; They correspond to the phase adjustments of characteristic frequency band 1 (0~10Hz), characteristic frequency band 2 (center frequency is 17Hz), and characteristic frequency band 3 (50Hz / 60Hz) respectively. Their core function is to accurately calibrate the phase of the selected signal, and ultimately make the generated cancellation magnetic field opposite to the phase of the original interference signal, thereby achieving active cancellation.

[0067] See also Figure 5 , is a topology diagram of the phase adjustment circuit, which uses an analog phase shift circuit for adjustment. The core topology is to generate 0~ The first-level integrator produces 0~ A first-stage inverting amplifier is used, and the phase shift amount is adjusted by a variable resistor. In the 50Hz / 60Hz channel, two different power frequency interference bands are switched by jumpers, and the signal transmission of the other two channels is not affected during switching.

[0068] S5. Adding the phase-adjusted signals of each channel; wherein this is achieved by an adding circuit constructed using an integrated operational amplifier circuit; See also Figure 6 , the three characteristic frequency band signals are superimposed to generate a comprehensive cancellation signal, which provides input for subsequent power amplification and magnetic field cancellation, as follows: A multi-input inverting summing circuit is built using a high-precision operational amplifier to support weighted superposition of three independent signals. Input signal 1 comes from the phase-shifted signal of characteristic frequency band 1, input signal 2 comes from the phase-shifted signal of characteristic frequency band 2, and input signal 3 comes from the phase-shifted signal of characteristic frequency band 3. Each input is connected in series with a precision adjustable resistor to support dynamic adjustment of the superposition weight.

[0069] It is an important link before inputting the subsequent power amplifier module. At the input front end, each signal is isolated by a voltage follower. The gain of each channel is set by a digital potentiometer. The relationship between the output signal and the input signal is expressed as:

[0070] The above implementation methods fully demonstrate the main functions and signal flow process. Through high-precision signal superposition, it ensures the integration of interference signals in different frequency bands, and ultimately drives the coil to generate a high-precision offset magnetic field.

[0071] S6. Adjusting the amplitude of the obtained comprehensive characteristic frequency band interference signal; wherein the amplitude adjustment includes increasing or decreasing the amplitude; See also Figure 7 , dynamically adjust the gain of the comprehensive offset signal to ensure that the signal has the optimal amplitude range before power amplification to avoid system overload or underdrive, as follows: The external voltage signal is mapped to the gain range by analog means, while being compatible with manual adjustment, which is achieved by adjusting the feedback resistor. The input signal comes from the comprehensive offset signal of step S5, which is amplified by the operation integrated circuit and output; The input signal is isolated by setting a voltage follower at the input front end to eliminate the influence of the output impedance of the front stage. The gain range set by the present invention is 1 to 100 times and the bandwidth is 0 to 1kHz.

[0072] S7. Inputting the obtained driving signal having the same characteristics as the original interference signal into a power amplification module to generate a driving current; wherein the power amplification module includes a power amplifier circuit and a back-end gain circuit to obtain an output voltage and current; See also Figure 8 , the comprehensive cancellation signal after pre-processing is amplified with high fidelity power, and the driving coil generates a cancellation magnetic field with the same amplitude and opposite phase as the original interference magnetic field. The details are as follows: The circuit utilizes a staged voltage amplification system. The front-stage voltage amplifier is based on a high-speed operational amplifier with adjustable gain. The back-stage current driver uses a Class AB power amplifier (OPA549) to directly drive the coil load. The input signal comes from step S6 and undergoes voltage-to-current conversion in this module before power output. Overcurrent and temperature protection modules are also incorporated into the circuit to ensure system stability and safety.

[0073] S8. The obtained power amplified voltage drives the coil load. The driving voltage and the generated magnetic field are calibrated to generate a canceling magnetic field that is in opposite phase to the interfering magnetic field, thereby effectively canceling the original interfering magnetic field. See also Figure 7 , converting the amplified cancellation signal into a cancellation magnetic field that precisely matches the target frequency band, directly canceling out the external low-frequency interference magnetic field. It is realized by using Helmholtz coil pairs, including square coils or circular coils, and the coil and its bracket structure are designed. The coils can be combined and designed into single-axis, double-axis, and three-axis systems; After receiving the output signal from the power amplifier module in step S7, a counteracting magnetic field is generated according to Ampere's loop law, and parameters such as the number of turns of the coil and the effective magnetic path length are determined according to actual magnetic field requirements.

[0074] S9. Setting an elimination effect monitoring module to monitor the cancellation effect in real time and provide feedback so as to make appropriate adjustments to parameters such as phase and amplitude.

[0075] Monitor the residual interference signal after cancellation in real time, and dynamically optimize the parameters in steps S3 to S7 through feedback control to ensure that the interference cancellation effect continues to reach the optimal level, as follows: The sensor in step S1 obtains the original, uncancelled magnetic field signal, and the residual magnetic field signal is obtained from monitoring sensors deployed near the target area. After comparing the amplitude and phase differences between the original and residual signals, parameter correction instructions are generated. This entire process is stored and displayed by the microcontroller and the host computer display module. Through high-precision monitoring, real-time feedback, and multi-parameter collaborative optimization, a closed-loop control system is constructed, making the overall interference cancellation effect environmentally adaptive.

[0076] Those skilled in the art will appreciate that various aspects of the present invention may be implemented as systems, methods, or program products. Accordingly, various aspects of the present invention may be implemented in the following forms: entirely in hardware, entirely in software (including firmware, microcode, etc.), or in a combination of hardware and software, collectively referred to herein as "circuits," "modules," or "platforms."

[0077] Example 2 The present invention provides a low-frequency interference magnetic field elimination system, which can be used to implement the above-mentioned low-frequency interference magnetic field elimination method. Specifically, the low-frequency interference magnetic field elimination system includes an acquisition module, a phase module, an adjustment module and an elimination module.

[0078] Among them, the acquisition module collects the low-frequency interference magnetic field signal in the target environment and pre-processes it to obtain an analog electrical signal; The phase module extracts the interference signal of the preset characteristic frequency band from the analog signal; and adjusts the phase of the interference signal of the preset characteristic frequency band respectively; The adjustment module superimposes the phase-adjusted multi-channel signals to obtain a comprehensive characteristic frequency band interference signal; and adjusts the amplitude of the comprehensive characteristic frequency band interference signal to obtain a characteristic frequency band signal; The elimination module amplifies the characteristic frequency band signal to obtain a power amplification voltage; the obtained power amplification voltage drives the coil load, and the driving voltage and the generated magnetic field are calibrated to generate a canceling magnetic field that is opposite to the interference magnetic field, thereby eliminating the original low-frequency interference magnetic field.

[0079] Example 3 The present invention provides a terminal device, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or may be other general-purpose processors, graphics processing units (GPUs), tensor processing units (TPUs), digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions to implement the corresponding method flow or corresponding function; the processor described in the embodiment of the present invention can be used for the operation of the low-frequency interference magnetic field elimination method, including: The low-frequency interference magnetic field signal in the target environment is collected and pre-processed to obtain an analog electrical signal; the interference signal of a preset characteristic frequency band is extracted from the analog signal; the phase of the interference signal of the preset characteristic frequency band is adjusted respectively; the multi-channel signals after phase adjustment are superimposed to obtain a comprehensive characteristic frequency band interference signal; the amplitude of the comprehensive characteristic frequency band interference signal is adjusted to obtain a characteristic frequency band signal; the characteristic frequency band signal is power-amplified to obtain a power-amplified voltage; the obtained power-amplified voltage is used to drive the coil load, and the driving voltage and the generated magnetic field are calibrated to generate a counteracting magnetic field that is opposite in phase to the interference magnetic field, thereby eliminating the original low-frequency interference magnetic field.

[0080] See also Figure 11 The terminal device is a computer device. The computer device 60 of this embodiment includes: a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable by the processor 61. When executed by the processor 61, the computer program 63 implements the low-frequency interference magnetic field elimination method of the embodiment. To avoid repetition, the details are not described here. Alternatively, when executed by the processor 61, the computer program 63 implements the functions of each model / unit in the low-frequency interference magnetic field elimination system of the embodiment. To avoid repetition, the details are not described here.

[0081] The computer device 60 may be a desktop computer, a notebook computer, a PDA, a cloud server, or other computing devices. The computer device 60 may include, but is not limited to, a processor 61 and a memory 62. It will be understood by those skilled in the art that Figure 11 This is merely an example of the computer device 60 and does not constitute a limitation of the computer device 60 . The computer device 60 may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the computer device may also include input and output devices, network access devices, buses, etc.

[0082] The processor 61 may be a central processing unit (CPU), or other general-purpose processors, a graphics processing unit (GPU), a tensor processing unit (TPU), a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor, etc.

[0083] The memory 62 may be an internal storage unit of the computer device 60, such as a hard disk or memory of the computer device 60. The memory 62 may also be an external storage device of the computer device 60, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the computer device 60.

[0084] Furthermore, the memory 62 may include both an internal storage unit of the computer device 60 and an external storage device. The memory 62 is used to store computer programs and other programs and data required by the computer device. The memory 62 may also be used to temporarily store data that has been output or is about to be output.

[0085] See also Figure 12 The terminal device is an electronic device 600, which is implemented as a general-purpose computing device. The components of the electronic device may include, but are not limited to, at least one processing unit 610, at least one storage unit 620, a bus 630 connecting different platform components (including the storage unit 620 and the processing unit 610), and a display unit 640.

[0086] The storage unit stores program codes, which can be executed by the processing unit 610, so that the processing unit 610 performs the steps according to various exemplary embodiments of the present invention described in the above method section of this specification. For example, the processing unit 610 can perform the following steps: Figure 1 Follow the steps shown in .

[0087] The storage unit 620 may include a readable medium in the form of a volatile storage unit, such as a random access memory unit (RAM) 6201 and / or a cache memory unit 6202 , and may further include a read-only memory unit (ROM) 6203 .

[0088] The storage unit 620 may also include a program / utility 6204 having a set (at least one) of program modules 6205, such program modules 6205 including but not limited to: an operating system, one or more application programs, other program modules, and program data, each of which or some combination may include an implementation of a network environment.

[0089] Bus 630 may represent one or more of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, a processing unit, or a local bus using any of a variety of bus architectures.

[0090] The electronic device 600 may also communicate with one or more external devices 700 (e.g., a keyboard, a pointing device, a Bluetooth device, etc.), one or more devices that enable a user to interact with the electronic device 600, and / or any device that enables the electronic device 600 to communicate with one or more other computing devices (e.g., a router, a modem). Such communication may occur via an input / output interface 650. Furthermore, the electronic device 600 may also communicate with one or more networks (e.g., a local area network, a wide area network, and / or a public network, such as the Internet) via a network adapter 660. The network adapter 660 may communicate with other modules of the electronic device 600 via a bus 630. It should be understood that, although not shown in the figures, other hardware and / or software modules may be used in conjunction with the electronic device 600, including but not limited to microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage platforms.

[0091] Example 4 The present invention also provides a storage medium, specifically a computer-readable storage medium. The computer-readable storage medium is a memory device in a terminal device, used to store programs and data. It is understood that the computer-readable storage medium herein may include both the built-in storage medium in the terminal device and, of course, the extended storage medium supported by the terminal device. It may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, the storage space also stores one or more instructions suitable for being loaded and executed by a processor. These instructions may be one or more computer programs (including program code). It should be noted that more specific examples of the computer-readable storage medium herein include: an electrical connection having one or more wires, a portable disk, a hard disk, a random access memory, a read-only memory, an erasable programmable read-only memory, an optical fiber, a portable compact disk read-only memory, an optical storage device, a magnetic storage device, or any suitable combination thereof.

[0092] Computer-readable storage media also include data signals propagated in baseband or as part of a carrier wave, which carry readable program code. Such propagated data signals can take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. The readable storage medium can also be any readable medium other than a readable storage medium, which can send, propagate, or transmit programs for use by or in conjunction with an instruction execution system, device, or device. The program code contained on the readable storage medium can be transmitted using any appropriate medium, including but not limited to wireless, wired, optical cable, radio frequency, etc., or any suitable combination of the above.

[0093] The program code for performing the operations of the present invention may be written in any combination of one or more programming languages, including object-oriented programming languages such as Java, C++, and the like, as well as conventional procedural programming languages such as "C" or similar programming languages. The program code may be executed entirely on the user computing device, partially on the user device, as a stand-alone software package, partially on the user computing device and partially on a remote computing device, or entirely on a remote computing device or server. In the case of a remote computing device, the remote computing device may be connected to the user computing device via any type of network, including a local area network or a wide area network, or may be connected to an external computing device (e.g., via the Internet using an Internet service provider).

[0094] The processor may load and execute one or more instructions stored in a computer-readable storage medium to implement the corresponding steps of the method for eliminating low-frequency interference magnetic fields in the above embodiment; the processor may load and execute the following steps: The low-frequency interference magnetic field signal in the target environment is collected and pre-processed to obtain an analog electrical signal; the interference signal of a preset characteristic frequency band is extracted from the analog signal; the phase of the interference signal of the preset characteristic frequency band is adjusted respectively; the multi-channel signals after phase adjustment are superimposed to obtain a comprehensive characteristic frequency band interference signal; the amplitude of the comprehensive characteristic frequency band interference signal is adjusted to obtain a characteristic frequency band signal; the characteristic frequency band signal is power-amplified to obtain a power-amplified voltage; the obtained power-amplified voltage is used to drive the coil load, and the driving voltage and the generated magnetic field are calibrated to generate a counteracting magnetic field that is opposite in phase to the interference magnetic field, thereby eliminating the original low-frequency interference magnetic field.

[0095] The databases involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processors involved in the various embodiments provided herein may include, but are not limited to, general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic units, data processing logic units based on quantum computing, and the like.

[0096] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0097] The low-frequency interference magnetic field elimination device provided by the present invention is combined with a signal processing circuit and a magnetic field output coil, which can effectively suppress the low-frequency interference magnetic field in the environment. Its advantage is that it can significantly improve the operating accuracy and stability of electronic equipment. It is suitable for fields that are sensitive to the magnetic field environment, such as medical equipment and precision instruments. Taking the image optimization of ultra-low field magnetic resonance imaging equipment as an example, the device provided by the present invention can effectively remove the low-frequency interference to such equipment, so as to reduce problems such as image artifacts and distortion caused by the low-frequency interference magnetic field. Specifically, the ultra-low field magnetic resonance imaging equipment relies on a main magnetic field with good uniformity during the imaging process. The interference of the external low-frequency alternating magnetic field can easily affect the uniformity of the main magnetic field of the equipment, further affecting the process of spatial positioning of protons in the tissue, resulting in problems such as inaccurate proton positioning, and finally causing the image after mathematical reconstruction to be distorted.

[0098] See also Figure 13 、 14 , 15, 16 and Figure 17 The system device provided by the present invention first uses a high-precision and high-sensitivity magnetic signal sensor to collect the interference magnetic field signal in the environment in real time, and after converting it into an analog voltage signal, it is passed into a signal processing circuit to extract the characteristic interference frequency signal. After the amplitude and phase adjustment processes in the signal processing circuit, the amplification drive coil of the power amplifier module generates a canceling magnetic field to suppress the external interference magnetic field. This process needs to be completed within an extremely short response time to ensure that the interference magnetic field can be effectively removed during the sensitive period of the imaging sequence. The overlapping artifacts and distortion of the image caused by low-frequency interference are significantly reduced, and the image clarity is significantly improved. In terms of signal-to-noise ratio changes, taking a certain application experiment test as an example, the image signal-to-noise ratio under interference-free conditions is 18.7; the image signal-to-noise ratio when affected by a low-frequency interference magnetic field is 7.0; after the system device eliminates the low-frequency interference magnetic field, the image signal-to-noise ratio is increased to 16.7, restoring to 90% of the original conditions.

[0099] The above is an example of the present invention in image optimization of ultra-low field magnetic resonance imaging equipment. In addition, the application scenarios of this system can be further expanded to fields with high requirements for magnetic environment, such as precision scientific research equipment and semiconductor manufacturing, to provide a stable electromagnetic environment guarantee for such scenarios. In summary, the present invention provides a method and system for eliminating low-frequency interference magnetic fields. By constructing a multi-band adaptive processing architecture, the dynamic range extension technology (DRE) is innovatively combined with digital pre-distortion compensation to reduce the nonlinear error of the conversion circuit to below 0.5%; a programmable analog filter array is used to achieve 17Hz / 50Hz / 60Hz three-band coordinated processing, and the roll-off characteristic is improved to -48dB / octave; a digital phase synthesizer (DPS) is designed to replace the traditional phase shift circuit, compressing the phase error to ±0.5° and shortening the response time to 10ms; an adaptive gain control system based on deep reinforcement learning is established to achieve 100ms-level real-time adjustment; a hybrid power amplifier topology is developed to reduce the THD in the 0-100Hz frequency band to below 1.2%; the magnetic field vector feedback technology is innovatively used to achieve joint optimization of amplitude, phase, and temperature parameters through a three-dimensional orthogonal sensor array, and finally at 0.5m 3 The residual magnetic field strength in the spatial domain is stably controlled at the order of 10nT, and the dynamic response time is increased by 5 times compared with existing technologies.

[0100] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In actual applications, the above-mentioned functions can be distributed and completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0101] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0102] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in the present invention can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present invention.

[0103] In the embodiments provided by the present invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are merely illustrative. For example, the division of the modules or units is merely a logical functional division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be through some interface, indirect coupling or communication connection of devices or units, and can be electrical, mechanical, or other forms.

[0104] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0105] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0106] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the process in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, it can implement the steps of the above-mentioned various method embodiments. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electric carrier signals and telecommunication signals.

[0107] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices, and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0108] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0109] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0110] The above content is only for explaining the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for eliminating low-frequency interference magnetic fields, characterized in that: The following steps are involved: Collect low-frequency interference magnetic field signals in the target environment and pre-process them to obtain analog electrical signals; Extracting interference signals of preset characteristic frequency bands from the analog signal; and performing phase adjustment on the interference signals of the preset characteristic frequency bands respectively; The phase-adjusted multi-path signals are superimposed to obtain a comprehensive characteristic frequency band interference signal; the amplitude of the comprehensive characteristic frequency band interference signal is adjusted to obtain a characteristic frequency band signal; The characteristic frequency band signal is power amplified to obtain a power amplified voltage; the obtained power amplified voltage is used to drive the coil load, and the driving voltage and the generated magnetic field are calibrated to generate a canceling magnetic field that is opposite to the interference magnetic field, thereby eliminating the original low-frequency interference magnetic field.

2. The method for eliminating low-frequency interference magnetic fields according to claim 1, characterized in that: Perform preprocessing to obtain analog electrical signals, specifically: In the first stage circuit, a preamplifier circuit is used, and a low-noise operational amplifier is used to build a common-mode amplifier circuit. The amplification factor is determined by the operational amplifier circuit parameters to enhance the weak signal output by the sensor. In the second stage circuit, an anti-aliasing filter circuit is used, and a second-order active low-pass filter is used to suppress high-frequency noise in the mixed signal, including radio frequency interference and switching noise, to obtain an analog electrical signal.

3. The method for eliminating low-frequency interference magnetic fields according to claim 1, characterized in that: The interference signals in the preset characteristic frequency bands include those in the frequency bands of 0~10Hz, 17Hz, and 50Hz / 60Hz. A second-order voltage-controlled low-pass filter is used for 0~10Hz, and a second-order active band-pass filter is used for 17Hz and 50Hz / 60Hz.

4. The method for eliminating low-frequency interference magnetic fields according to claim 1, wherein: Phase adjustment is as follows: The analog phase shift circuit is used for adjustment, and the topology is to generate 0~ The first-level integrator produces 0~ A first-stage inverting amplifier is used, and the phase shift amount is adjusted by a variable resistor. In the 50Hz / 60Hz channel, two different power frequency interference bands are switched by jumpers, so that the generated offset magnetic field is opposite to the phase of the original interference signal.

5. The method for eliminating low-frequency interference magnetic fields according to claim 1, characterized in that: The phase-adjusted multi-path signals are superimposed to obtain the comprehensive characteristic frequency band interference signal, specifically: A multi-input inverting addition circuit is built through high-precision operational amplifiers to support weighted superposition of three independent signals; input signal 1 comes from the phase-shifted signal of characteristic frequency band 1, input signal 2 comes from the phase-shifted signal of characteristic frequency band 2, and input signal 3 comes from the phase-shifted signal of characteristic frequency band 3. Each input is connected in series with a precision adjustable resistor to support dynamic adjustment of the superposition weight.

6. The method for eliminating low-frequency interference magnetic fields according to claim 5, characterized in that: At the input front end, each signal is isolated by a voltage follower, and the gain of each channel is set by a digital potentiometer. The relationship between the output signal and the input signal is expressed as: in, The output voltage of the operational amplifier circuit; It is the feedback resistor of the operational amplifier circuit, connecting the output terminal and the inverting input terminal of the operational amplifier; is the input resistance of the first channel, is the input resistance of the second channel, is the input resistance of the third channel, which controls the gain ratio of each channel respectively; is the input voltage signal of the first channel, is the input voltage signal of the second channel, is the input voltage signal of the third channel.

7. The method for eliminating low-frequency interference magnetic fields according to claim 1, characterized in that: The amplitude of the comprehensive characteristic frequency band interference signal is adjusted to obtain the characteristic frequency band signal, as follows: The external voltage signal is mapped to the gain range in an analog manner and is compatible with manual adjustment. This is achieved by adjusting the feedback resistor. The input signal comes from the integrated offset signal and is amplified by the operational integrated circuit before output. A voltage follower is set at the input front end for isolation. The gain range is 1 to 100 times and the bandwidth is 0 to 1kHz.

8. The method for eliminating low-frequency interference magnetic fields according to claim 1, characterized in that: The characteristic frequency band signal is power amplified to obtain a power amplified voltage, specifically: It adopts hierarchical voltage amplification. The front-stage voltage amplification is based on a high-speed operational amplifier with adjustable gain. The rear-stage current drive adopts a class AB power amplifier and directly drives the coil load. After voltage-current conversion, power output is performed, and overcurrent protection and temperature protection modules are set in the circuit.

9. The method for eliminating low-frequency interference magnetic fields according to claim 1, characterized in that: The obtained power amplified voltage drives the coil load. The driving voltage and the generated magnetic field are calibrated to generate a canceling magnetic field that is in opposite phase to the interfering magnetic field. Specifically: A Helmholtz coil pair is used to generate a canceling magnetic field according to Ampere's loop law. The residual interference signal after cancellation is monitored in real time. Dynamic optimization is achieved through feedback control to ensure that the interference elimination effect is continuously optimized.

10. A low-frequency interference magnetic field elimination system, characterized in that: include: The acquisition module collects low-frequency interference magnetic field signals in the target environment and pre-processes them to obtain analog electrical signals; The phase module extracts the interference signal of the preset characteristic frequency band from the analog signal; and adjusts the phase of the interference signal of the preset characteristic frequency band respectively; The adjustment module superimposes the phase-adjusted multi-channel signals to obtain a comprehensive characteristic frequency band interference signal; and adjusts the amplitude of the comprehensive characteristic frequency band interference signal to obtain a characteristic frequency band signal; The elimination module amplifies the characteristic frequency band signal to obtain a power amplified voltage; the obtained power amplified voltage drives the coil load, and the driving voltage and the generated magnetic field are calibrated to generate a canceling magnetic field that is opposite to the interference magnetic field, thereby eliminating the original low-frequency interference magnetic field.

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