Vector magnetic field intensity measurement method and digital vector magnetoresistive magnetometer

Abstract

The present application provides a method for measuring vector magnetic field intensity and a digital vector magnetoresistive magnetometer, which can solve the problems of complex circuit design, difficulty in miniaturization, and high material cost of existing magnetoresistive magnetometers. The method for measuring vector magnetic field intensity is applied to a digital vector magnetoresistive magnetometer and includes: obtaining a first analog signal, a second analog signal, and a third analog signal according to the magnetic field intensity of the environment; respectively performing signal processing on the first analog signal, the second analog signal, and the third analog signal to obtain a first digital signal, a second digital signal, and a third digital signal; respectively performing digital quadrature demodulation and digital compensation on the first digital signal, the second digital signal, and the third digital signal to obtain the magnetic field intensity values and phases of the magnetic field intensity in the first direction, the second direction, and the third direction.

Description

Technical Field

[0001] The present application relates to the technical field of vector magnetic field measurement, and particularly to a method for measuring vector magnetic field intensity and a digital vector magnetoresistive magnetometer. Background Art

[0002] A vector magnetoresistive magnetometer is a sensor that works based on the principle of magnetoresistive effect. It has advantages such as a high voltage magnetic field conversion coefficient, low power consumption, and strong anti-interference ability, which have enabled it to be widely used in fields such as navigation, non-destructive testing, automotive electronics, and intelligent devices. For example, it is applied to portable non-destructive testing equipment to detect defects, corrosion, or stress in materials, or to spacecraft, satellites, and space probes to detect the magnetic field characteristics of the cosmic space.

[0003] Existing magnetoresistive magnetometers generally use analog circuits for modulation, demodulation, and compensation. The main disadvantages of using analog circuits for modulation, demodulation, and compensation are as follows: The circuit design is complex, it is difficult to miniaturize, and the material cost is relatively high; Adjusting the working parameters of the magnetoresistive magnetometer requires replacing electronic components, the operation is complex, and the technical difficulty is relatively large. Summary of the Invention

[0004] In view of the above technical problems, the advantage of the present application lies in providing a method for measuring vector magnetic field intensity and a digital vector magnetoresistive magnetometer, which can solve the problems of complex circuit design, difficulty in miniaturization, and relatively high material cost of existing magnetoresistive magnetometers.

[0005] Another advantage of the present application is to provide a digital vector magnetoresistive magnetometer. To achieve the above advantage, expensive materials or complex structures do not need to be adopted in the present application. Therefore, the solution provided by the present application can successfully and effectively solve the above problems, not only providing a simple digital vector magnetoresistive magnetometer, but also increasing the practicality and reliability of the digital vector magnetoresistive magnetometer.

[0006] Based on this, in order to achieve at least one of the above advantages or other advantages and purposes of the present application, the present application provides a method for measuring vector magnetic field intensity, which is applied to a digital vector magnetoresistive magnetometer. The method includes:

[0007] According to the magnetic field intensity of the environment where the digital vector magnetoresistive magnetometer is located, a first analog signal, a second analog signal, and a third analog signal are obtained. The first analog signal represents the component of the magnetic field intensity in the first direction, the second analog signal represents the component of the magnetic field intensity in the second direction, and the third analog signal represents the component of the magnetic field intensity in the third direction. The first direction, the second direction, and the third direction are perpendicular to each other;

[0008] Perform signal processing on the first analog signal, the second analog signal, and the third analog signal respectively to obtain a first digital signal, a second digital signal, and a third digital signal;

[0009] Perform digital quadrature demodulation and digital compensation on the first digital signal, the second digital signal, and the third digital signal respectively to obtain the magnetic field strength values and phases of the magnetic field strength in the first direction, the second direction, and the third direction.

[0010] With such a setting, the vector magnetic field strength measurement method provided by this application converts the first analog signal, the second analog signal, and the third analog signal into a first digital signal, a second digital signal, and a third digital signal, and then performs digital quadrature demodulation and digital compensation on the first digital signal, the second digital signal, and the third digital signal through digital operations, so as to obtain the magnetic field strength values and phases of the magnetic field strength in the first direction, the second direction, and the third direction, thereby solving the problems of complex circuit design, difficulty in miniaturization, and high material cost in the prior art.

[0011] According to an embodiment of the present application, performing digital quadrature demodulation and digital compensation on the first digital signal, the second digital signal, and the third digital signal respectively to obtain the magnetic field strength values and phases of the components of the magnetic field strength in the first direction, the second direction, and the third direction includes:

[0012] Generate a first phase reference signal and a second phase reference signal based on the demodulation frequency input by an external device;

[0013] Perform digital quadrature demodulation based on the first digital signal, the second digital signal, the third digital signal, the first phase reference signal, and the second phase reference signal to obtain the amplitude and phase of the first digital signal, the amplitude and phase of the second digital signal, and the amplitude and phase of the third digital signal;

[0014] Based on the relationship between the preset zero drift and temperature, the relationship between the preset voltage-magnetic field conversion coefficient and temperature, and the real-time ambient temperature, convert the amplitudes of the first digital signal, the second digital signal, and the third digital signal into the magnetic field strength values of the first digital signal, the magnetic field strength value of the second digital signal, and the magnetic field strength value of the third digital signal respectively, and perform digital compensation.

[0015] With such a setting, by means of the generated first phase reference signal and second phase reference signal, digital quadrature demodulation can be performed on the first digital signal, second digital signal, and third digital signal, which can improve the anti-interference ability of the signal, improve the signal quality, simplify the hardware design, and reduce the dependence on analog circuit devices. In addition, using digital quadrature demodulation to demodulate the signal can be more conveniently integrated with other digital signal processing modules, reduce the overall hardware cost of the system, improve the overall reliability and stability of the system, and support the compatibility of multiple standards to meet the diverse requirements of modern communication systems.

[0016] According to an embodiment of the present application, performing digital quadrature demodulation based on the first digital signal, second digital signal, third digital signal, the first phase reference signal, and the second phase reference signal to obtain the amplitude and phase of the first digital signal, the amplitude and phase of the second digital signal, and the amplitude and phase of the third digital signal includes:

[0017] Mixing and multiplying the first digital signal, second digital signal, and third digital signal with the first phase reference signal and the second phase reference signal respectively to obtain a first mixed signal and a second mixed signal corresponding to the first digital signal, a third mixed signal and a fourth mixed signal corresponding to the second digital signal, and a fifth mixed signal and a sixth mixed signal corresponding to the third digital signal;

[0018] Performing digital filtering on the first mixed signal and the second mixed signal, the third mixed signal and the fourth mixed signal, and the fifth mixed signal and the sixth mixed signal respectively to obtain a first in-phase component and a first quadrature component, a second in-phase component and a second quadrature component, and a third in-phase component and a third quadrature component;

[0019] Performing polar coordinate conversion on the first in-phase component and the first quadrature component, the second in-phase component and the second quadrature component, and the third in-phase component and the third quadrature component to obtain the amplitude and phase of the first digital signal, the amplitude and phase of the second digital signal, and the amplitude and phase of the third digital signal.

[0020] According to an embodiment of the present application, based on the relationship between the preset zero drift and temperature, the relationship between the preset voltage-magnetic field conversion coefficient and temperature, and the real-time ambient temperature, the amplitudes of the first digital signal, second digital signal, and third digital signal are respectively converted into the magnetic field intensity values of the first digital signal, second digital signal, and third digital signal, and digital compensation is performed. Specifically:

[0021] Based on the relationship between the preset voltage - magnetic field conversion coefficient and temperature, convert the amplitudes of the first digital signal, the second digital signal, and the third digital signal into the magnetic field intensity values of the first digital signal, the second digital signal, and the third digital signal respectively;

[0022] Based on the relationship between the preset zero - point drift and temperature, the relationship between the preset voltage - magnetic field conversion coefficient and temperature, and the real - time ambient temperature, perform digital compensation on the magnetic field intensity values of the first digital signal, the second digital signal, and the third digital signal.

[0023] With such a setting, digital compensation can be performed based on the relationship between the preset zero - point drift and temperature, the relationship between the preset voltage - magnetic field conversion coefficient and temperature, and the real - time ambient temperature. That is, the errors of the measured magnetic field intensity values are corrected by means of digital software operations, avoiding the situation that the accuracy of the measured magnetic field intensity values is affected by errors. Moreover, the digital compensation method adopted in this solution can be correspondingly modified or adjusted for the algorithm or code according to different actual requirements. In the prior art, the solution of compensating through an analog circuit requires modifying the real analog circuit according to different actual requirements. Therefore, the solution provided in this application, without the need to modify the hardware, is more flexible and more adaptable to the environment than the prior - art solutions.

[0024] According to an embodiment of the present application, the generating the first phase reference signal and the second phase reference signal based on the demodulation frequency input by an external device includes:

[0025] Generate a first phase reference signal based on the demodulation frequency input by an external device;

[0026] Perform a phase shift on the first phase reference signal to obtain a second phase reference signal.

[0027] According to an embodiment of the present application, the vector magnetic field intensity measurement method further includes:

[0028] Heat the digital vector magnetoresistive magnetometer to a first temperature, and record the first relationship between the measured value of the digital vector magnetoresistive magnetometer and temperature during the process of cooling from the first magnetic field intensity to a second temperature;

[0029] Cool the digital vector magnetoresistive magnetometer to a third temperature, and record the second relationship between the measured value of the digital vector magnetoresistive magnetometer and temperature during the process of naturally warming from the first magnetic field intensity to the second temperature;

[0030] Based on the first relationship and the second relationship, obtain the relationship between the preset zero - point drift and temperature;

[0031] Heat the digital vector magnetoresistive magnetometer to a first temperature, and record the third relationship between the voltage-magnetic field conversion coefficient and temperature of the digital vector magnetoresistive magnetometer during the process of cooling it to a second temperature under a second magnetic field intensity;

[0032] Cool the digital vector magnetoresistive magnetometer to a third temperature, and record the fourth relationship between the voltage-magnetic field conversion coefficient and temperature of the digital vector magnetoresistive magnetometer during the process of naturally heating it to the second temperature under the second magnetic field intensity;

[0033] Based on the third relationship and the fourth relationship, obtain the relationship between the preset voltage-magnetic field conversion coefficient and temperature.

[0034] According to an embodiment of the present application, the step of respectively performing signal processing on the first analog signal, the second analog signal, and the third analog signal to obtain a first digital signal, a second digital signal, and a third digital signal includes the following steps:

[0035] Generate a square wave modulation signal with a specific frequency, and based on the square wave modulation signal, respectively perform square wave modulation on the first analog signal, the second analog signal, and the third analog signal;

[0036] Respectively perform differential amplification and filtering on the first analog signal, the second analog signal, and the third analog signal;

[0037] Based on a trigger signal, simultaneously perform analog-to-digital conversion on the first analog signal, the second analog signal, and the third analog signal respectively to obtain a first digital signal, a second digital signal, and a third digital signal.

[0038] With such a setting, before converting the analog signal into a digital signal, respectively performing differential amplification and filtering on the analog signal can significantly improve the signal quality and the accuracy of subsequent digital processing. Differential amplification enhances the useful signal by eliminating common-mode noise (such as power supply noise or environmental interference), and is particularly suitable for weak signals or high-noise environments, thereby improving the signal-to-noise ratio of the signal. Filtering can remove high-frequency noise or low-frequency interference in the signal, retain the signal components in the target frequency band, avoid aliasing effects, and ensure that the digitized signal is more pure and accurate. In addition, such differential amplification and filtering can reduce the influence of temperature drift and nonlinear distortion on the digital signal, so as to improve the overall stability of the system, and lay a good foundation for subsequent digital quadrature demodulation and digital compensation of the digital signal.

[0039] According to another aspect of the present application, the present application further provides a digital vector magnetoresistive magnetometer, which is used to measure the magnetic field intensity of a three-dimensional vector magnetic field. The digital vector magnetoresistive magnetometer includes:

[0040] A three-axis magnetoresistive module, a signal processing module, and a digital processing module;

[0041] The three-axis magnetoresistive module is configured to obtain a first analog signal, a second analog signal, and a third analog signal according to the magnetic field strength of the environment where it is located. The first analog signal represents the component of the magnetic field strength in the first direction, the second analog signal represents the component of the magnetic field strength in the second direction, and the third analog signal represents the component of the magnetic field strength in the third direction. The first direction, the second direction, and the third direction are perpendicular to each other;

[0042] The signal processing module is configured to perform signal processing on the first analog signal, the second analog signal, and the third analog signal respectively to obtain a first digital signal, a second digital signal, and a third digital signal;

[0043] The digital processing module is configured to perform digital quadrature demodulation and digital compensation on the first digital signal, the second digital signal, and the third digital signal respectively to obtain the magnetic field strength values and phases of the magnetic field strength in the first direction, the second direction, and the third direction.

[0044] According to an embodiment of the present application, the signal processing module includes a square wave modulation unit, a signal conditioning unit, and a synchronous acquisition unit;

[0045] The square wave modulation unit is configured to perform square wave modulation on the first analog signal, the second analog signal, and the third analog signal respectively based on a square wave modulation signal;

[0046] The signal conditioning unit is configured to perform differential amplification and filtering on the first analog signal, the second analog signal, and the third analog signal respectively;

[0047] The synchronous acquisition unit is configured to perform analog-to-digital conversion on the first analog signal, the second analog signal, and the third analog signal respectively based on a trigger signal to obtain a first digital signal, a second digital signal, and a third digital signal;

[0048] The digital processing module is further configured to generate a square wave modulation signal and a trigger signal with a specific frequency.

[0049] According to an embodiment of the present application, the signal conditioning unit includes a differential amplification circuit and an active low-pass filter circuit, and the operational amplifier in the differential amplification circuit is a zero-drift operational amplifier, and the resistors in the signal conditioning unit are low-temperature-drift resistors.

[0050] With such settings, using a zero-drift operational amplifier and low-temperature-drift resistors in a differential amplifier circuit can significantly improve the overall accuracy and stability of the system. The zero-drift operational amplifier can effectively eliminate the input offset voltage and temperature drift through its internal calibration technology, ensuring high precision within a wide temperature range; while the low-temperature-drift resistors can reduce the impact of temperature changes on the circuit gain and bias, thereby reducing system errors to ensure the accuracy of signals in complex environments.

[0051] Advantageous effects: Compared with the prior art solution of modulating, demodulating, and compensating the first analog signal, the second analog signal, and the third analog signal through an analog circuit to obtain the magnetic field strength values and phases in the first direction, the second direction, and the third direction of the magnetic field strength, the vector magnetic field strength measurement method provided in this application converts the first analog signal, the second analog signal, and the third analog signal into the first digital signal, the second digital signal, and the third digital signal, and then performs digital quadrature demodulation and digital compensation on the first digital signal, the second digital signal, and the third digital signal through digital operations, thereby obtaining the magnetic field strength values and phases in the first direction, the second direction, and the third direction of the magnetic field strength. This solves the problems in the prior art of complex circuit design, difficulty in miniaturization, and high material costs, not only improving the overall integration of the digital vector magnetoresistive magnetometer but also reducing the cost of the digital vector magnetoresistive magnetometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0053] Figure 1 It is a flowchart of the vector magnetic field strength measurement method provided by an embodiment of the present application;

[0054] Figure 2 It is a structural block diagram of a digital vector magnetoresistive magnetometer provided by another embodiment of the present application;

[0055] Figure 3 It is a structural block diagram of a digital vector magnetoresistive magnetometer provided by other embodiments of the present application;

[0056] Figure 4 It is a circuit connection schematic diagram of a differential amplifier circuit and an active filter circuit provided by another embodiment of the present application;

[0057] Figure 5A structural block diagram of a digital processing module provided for another embodiment of the present application;

[0058] Figure 6 An effect diagram of digital processing provided for another embodiment of the present application;

[0059] Figure 7 An effect diagram of digital compensation provided for another embodiment of the present application. Detailed implementation manners

[0060] To make the above objects, features, and advantages of the present application more obvious and understandable, the following will describe the detailed implementation manners of the present application with reference to the accompanying drawings. Many specific details are set forth in the following description to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0061] Considering that existing magnetoresistive magnetometers generally use analog circuits for modulation, demodulation, and compensation, and there are mainly the following disadvantages in using analog circuits for modulation, demodulation, and compensation: the circuit design is complex, it is difficult to miniaturize, and the material cost is relatively high; adjusting the working parameters of the magnetoresistive magnetometer requires replacing electronic components, the operation is complex, and the technical difficulty is relatively large. To solve this problem, the present application provides a method for measuring vector magnetic field intensity and a digital vector magnetoresistive magnetometer, which can solve the problems of complex circuit design, difficulty in miniaturization, and relatively high material cost of existing magnetoresistive magnetometers.

[0062] Specifically, please refer to the appendix Figure 1 , an embodiment of the present application provides a method for measuring vector magnetic field intensity, which is applied to a digital vector magnetoresistive magnetometer, and the method includes:

[0063] S1. According to the magnetic field intensity of the environment where the digital vector magnetoresistive magnetometer is located, obtain a first analog signal, a second analog signal, and a third analog signal, where the first analog signal represents the component of the magnetic field intensity in a first direction, the second analog signal represents the component of the magnetic field intensity in a second direction, the third analog signal represents the component of the magnetic field intensity in a third direction, and the first direction, the second direction, and the third direction are perpendicular to each other.

[0064] Exemplarily, the first analog signal is an analog signal representing the magnetic field strength component of the magnetic field strength in the first direction, the second analog signal is an analog signal representing the magnetic field strength component of the magnetic field strength in the second direction, and the third analog signal is an analog signal representing the magnetic field strength component of the magnetic field strength in the third direction. The first direction, the second direction, and the third direction are the positive or negative directions of the X-axis, the Y-axis, or the Z-axis.

[0065] S2. Perform signal processing on the first analog signal, the second analog signal, and the third analog signal respectively to obtain a first digital signal, a second digital signal, and a third digital signal.

[0066] Exemplarily, the process of the signal processing includes steps such as square wave modulation, differential amplification, filtering, and analog-to-digital conversion.

[0067] S3. Perform digital quadrature demodulation and digital compensation on the first digital signal, the second digital signal, and the third digital signal respectively to obtain the magnetic field strength values and phases of the magnetic field strength in the first direction, the second direction, and the third direction.

[0068] That is, perform digital quadrature demodulation and digital compensation on the first digital signal to obtain the magnetic field strength value and phase of the magnetic field strength in the first direction, perform digital quadrature demodulation and digital compensation on the second digital signal to obtain the magnetic field strength value and phase of the magnetic field strength in the second direction, and perform digital quadrature demodulation and digital compensation on the third digital signal to obtain the magnetic field strength value and phase of the magnetic field strength in the third direction.

[0069] Exemplarily, digital quadrature demodulation is a process of performing quadrature demodulation on a digital signal through software code to obtain the amplitude and phase of the digital signal, and digital compensation is a process of performing temperature compensation on a digital signal based on the real-time ambient temperature through software code to avoid the influence of the ambient temperature on the measured magnetic field strength.

[0070] It should be noted that, compared with the prior art where the first analog signal, the second analog signal, and the third analog signal are modulated, demodulated, and compensated through an analog circuit to obtain the magnetic field strength values and phases in the first direction, the second direction, and the third direction of the magnetic field strength, the vector magnetic field strength measurement method provided in this application converts the first analog signal, the second analog signal, and the third analog signal into a first digital signal, a second digital signal, and a third digital signal, and then performs digital quadrature demodulation and digital compensation on the first digital signal, the second digital signal, and the third digital signal through digital operations, so as to obtain the magnetic field strength values and phases in the first direction, the second direction, and the third direction of the magnetic field strength, thereby solving the problems in the prior art such as complex circuit design, difficulty in miniaturization, and high material cost. This not only improves the overall integration of the digital vector magnetoresistive magnetometer but also reduces the cost of the digital vector magnetoresistive magnetometer.

[0071] In other embodiments of this application, the step of respectively performing digital quadrature demodulation and digital compensation on the first digital signal, the second digital signal, and the third digital signal to obtain the magnetic field strength values and phases of the components of the magnetic field strength in the first direction, the second direction, and the third direction includes:

[0072] S31. Generate a first phase reference signal and a second phase reference signal based on the demodulation frequency input by an external device.

[0073] It should be noted that the demodulation frequency is the frequency of the first phase reference signal and the second phase reference signal.

[0074] S32. Perform digital quadrature demodulation based on the first digital signal, the second digital signal, the third digital signal, the first phase reference signal, and the second phase reference signal to obtain the amplitude and phase of the first digital signal, the amplitude and phase of the second digital signal, and the amplitude and phase of the third digital signal.

[0075] That is, perform digital quadrature demodulation and digital compensation on the first digital signal to obtain the magnetic field strength value and phase in the first direction of the magnetic field strength, perform digital quadrature demodulation and digital compensation on the second digital signal to obtain the magnetic field strength value and phase in the second direction of the magnetic field strength, and perform digital quadrature demodulation and digital compensation on the third digital signal to obtain the magnetic field strength value and phase in the third direction of the magnetic field strength.

[0076] S33. Based on the relationship between the preset zero drift and temperature, the relationship between the preset voltage - magnetic field conversion coefficient and temperature, and the real - time ambient temperature, convert the amplitudes of the first digital signal, the second digital signal, and the third digital signal into the magnetic field intensity values of the first digital signal, the second digital signal, and the third digital signal respectively, and perform digital compensation.

[0077] That is, based on the relationship between the preset zero drift and temperature, the relationship between the preset voltage - magnetic field conversion coefficient and temperature, and the real - time ambient temperature, convert the amplitude of the first digital signal into the magnetic field intensity value of the first digital signal and perform digital compensation, convert the amplitude of the second digital signal into the magnetic field intensity value of the second digital signal and perform digital compensation, and convert the amplitude of the third digital signal into the magnetic field intensity value of the third digital signal and perform digital compensation.

[0078] It should be noted that the relationship between the zero drift and temperature is the relationship between the measurement zero point of the word - vector magnetoresistive magnetometer and temperature change, and the relationship between the voltage - magnetic field conversion coefficient and temperature is the relationship between the conversion coefficient of converting the amplitude of the digital signal into the magnetic field intensity and temperature change.

[0079] It should be noted that by means of the generated first phase reference signal and second phase reference signal, digital quadrature demodulation of the first digital signal, the second digital signal, and the third digital signal can improve the anti - interference ability of the signal, improve the signal quality, simplify the hardware design, and reduce the dependence on analog circuit devices. In addition, using digital quadrature demodulation to demodulate the signal can be more conveniently integrated with other digital signal processing modules, reduce the overall hardware cost of the system, improve the overall reliability and stability of the system, and support the compatibility of multiple standards to meet the diverse needs of modern communication systems.

[0080] In other embodiments of the present application, the digital quadrature demodulation based on the first digital signal, the second digital signal, the third digital signal, the first phase reference signal, and the second phase reference signal to obtain the amplitudes and phases of the first digital signal, the second digital signal, and the third digital signal includes:

[0081] S321. Mix and multiply the first digital signal, the second digital signal, and the third digital signal with the first phase reference signal and the second phase reference signal respectively to obtain the first mixed - frequency signal and the second mixed - frequency signal corresponding to the first digital signal, the third mixed - frequency signal and the fourth mixed - frequency signal corresponding to the second digital signal, and the fifth mixed - frequency signal and the sixth mixed - frequency signal corresponding to the third digital signal.

[0082] Mix the first digital signal with the first phase reference signal and the second phase reference signal through frequency mixing multiplication to obtain a first frequency-mixed signal and a second frequency-mixed signal corresponding to the first digital signal, mix the second digital signal with the first phase reference signal and the second phase reference signal through frequency mixing multiplication to obtain a third frequency-mixed signal and a fourth frequency-mixed signal corresponding to the second digital signal, and mix the third digital signal with the first phase reference signal and the second phase reference signal through frequency mixing multiplication to obtain a fifth frequency-mixed signal and a sixth frequency-mixed signal corresponding to the third digital signal.

[0083] It should be noted that the frequency mixing multiplication refers to the operation of directly multiplying two signals in the time domain.

[0084] S322: Perform digital filtering on the first frequency-mixed signal and the second frequency-mixed signal, the third frequency-mixed signal and the fourth frequency-mixed signal, and the fifth frequency-mixed signal and the sixth frequency-mixed signal respectively to obtain a first in-phase component and a first quadrature component, a second in-phase component and a second quadrature component, and a third in-phase component and a third quadrature component.

[0085] That is, perform digital filtering on the first frequency-mixed signal and the second frequency-mixed signal to obtain a first in-phase component and a first quadrature component, perform digital filtering on the third frequency-mixed signal and the fourth frequency-mixed signal to obtain a second in-phase component and a second quadrature component, and perform digital filtering on the fifth frequency-mixed signal and the sixth frequency-mixed signal to obtain a third in-phase component and a third quadrature component.

[0086] It is worth noting that the digital filtering includes digital low-pass filtering and integrator comb filtering.

[0087] S323: Perform polar coordinate conversion on the first in-phase component and the first quadrature component, the second in-phase component and the second quadrature component, and the third in-phase component and the third quadrature component to obtain the amplitude and phase of the first digital signal, the amplitude and phase of the second digital signal, and the amplitude and phase of the third digital signal.

[0088] That is, perform polar coordinate conversion on the first in-phase component and the first quadrature component to obtain the amplitude and phase of the first digital signal, perform polar coordinate conversion on the second in-phase component and the second quadrature component to obtain the amplitude and phase of the second digital signal, and perform polar coordinate conversion on the third in-phase component and the third quadrature component to obtain the amplitude and phase of the third digital signal.

[0089] It should be noted that the polar coordinate conversion refers to the process of converting a signal or data in a rectangular coordinate system (Cartesian coordinate system) into a polar coordinate system representation, that is, converting from the form of (x, y) or (I, Q) to the form of amplitude (modulus) and phase (angle) (r, θ).

[0090] In other embodiments of the present application, based on the relationship between the preset zero drift and temperature, the relationship between the preset voltage-magnetic field conversion coefficient and temperature, and the real-time ambient temperature, the amplitudes of the first digital signal, the second digital signal, and the third digital signal are respectively converted into the magnetic field intensity values of the first digital signal, the second digital signal, and the third digital signal, and digital compensation is performed, including:

[0091] S331. Based on the relationship between the preset voltage-magnetic field conversion coefficient and temperature, the amplitudes of the first digital signal, the second digital signal, and the third digital signal are respectively converted into the magnetic field intensity values of the first digital signal, the second digital signal, and the third digital signal, that is, the amplitude of each digital signal is multiplied by the above voltage-magnetic field conversion coefficient to obtain the magnetic field intensity value of each digital signal.

[0092] That is, based on the relationship between the preset voltage-magnetic field conversion coefficient and temperature, the amplitude of the first digital signal is converted into the magnetic field intensity value of the first digital signal, the amplitude of the second digital signal is converted into the magnetic field intensity value of the second digital signal, and the amplitude of the third digital signal is converted into the magnetic field intensity value of the third digital signal.

[0093] S332. Based on the relationship between the preset zero drift and temperature, the relationship between the preset voltage-magnetic field conversion coefficient and temperature, and the real-time ambient temperature, digital compensation is performed on the magnetic field intensity values of the first digital signal, the second digital signal, and the third digital signal.

[0094] It should be noted that digital compensation can be performed based on the relationship between the preset zero drift and temperature, the relationship between the preset voltage-magnetic field conversion coefficient and temperature, and the real-time ambient temperature, that is, the errors of the measured magnetic field intensity values are corrected by means of digital software operations, avoiding the occurrence of the situation that the accuracy of the measured magnetic field intensity values is affected by errors. Moreover, the digital compensation method adopted in this solution can be correspondingly modified or adjusted for the algorithm or code according to different actual requirements. In the prior art, the solution of compensating through an analog circuit requires modifying the real analog circuit according to different actual requirements. Therefore, the solution provided in the present application is more flexible and more adaptable to the environment than the prior art solution because it does not require modifying the hardware.

[0095] In other embodiments of the present application, the generating the first phase reference signal and the second phase reference signal based on the demodulation frequency input by an external device includes:

[0096] S311. Generate the first phase reference signal based on the demodulation frequency input by an external device.

[0097] It should be noted that the external device is a terminal or the upper computer module described below.

[0098] S312. Phase-shift the first phase reference signal to obtain a second phase reference signal.

[0099] In another embodiment of the present application, the generation of the first phase reference signal and the second phase reference signal based on the demodulation frequency input by the external device is specifically as follows:

[0100] Generate a first phase reference signal based on the demodulation frequency input by the external device;

[0101] Perform a 90° phase shift on the first phase reference signal to obtain a second phase reference signal.

[0102] In other embodiments of the present application, the vector magnetic field strength measurement method further includes:

[0103] S4. Heat the digital vector magnetoresistive magnetometer to a first temperature, and record the first relationship between the measured value and the temperature of the digital vector magnetoresistive magnetometer during the process of cooling from the first magnetic field strength to a second temperature.

[0104] S5. Cool the digital vector magnetoresistive magnetometer to a third temperature, and record the second relationship between the measured value and the temperature of the digital vector magnetoresistive magnetometer during the process of naturally heating from the first magnetic field strength to a second temperature.

[0105] S6. Based on the first relationship and the second relationship, obtain the relationship between the preset zero drift and the temperature.

[0106] S7. Heat the digital vector magnetoresistive magnetometer to a first temperature, and record the third relationship between the voltage-magnetic field conversion coefficient and the temperature of the digital vector magnetoresistive magnetometer during the process of cooling from the second magnetic field strength to a second temperature.

[0107] S8. Cool the digital vector magnetoresistive magnetometer to a third temperature, and record the fourth relationship between the voltage-magnetic field conversion coefficient and the temperature of the digital vector magnetoresistive magnetometer during the process of naturally heating from the second magnetic field strength to a second temperature.

[0108] S9. Based on the third relationship and the fourth relationship, obtain the relationship between the preset voltage-magnetic field conversion coefficient and the temperature.

[0109] It should be noted that in another embodiment of the present application, the vector magnetic field strength measurement method further includes:

[0110] Step 1: Place the digital vector magnetoresistive magnetometer in a high and low temperature device, set the temperature to +50°C. After the temperature of the magnetometer is uniform, place it in a Permalloy shielding cylinder and let it cool naturally to room temperature. Synchronously record the changes of temperature and magnetic field output (in the form of analog signal and digital signal) over time.

[0111] It should be noted that the Permalloy shielding cylinder is a device for electromagnetic shielding, usually made of Permalloy with high magnetic permeability. Permalloy is a nickel-iron alloy (usually with nickel content of 70%-80% and iron content of 20%-30%), which has extremely high magnetic permeability and low coercivity, and can effectively shield low-frequency magnetic fields and electromagnetic interference (EMI).

[0112] Step 2: Place the digital vector magnetoresistive magnetometer in a high and low temperature device, set the temperature to -40°C. After the temperature of the magnetometer is uniform, place it in a Permalloy shielding cylinder and let it warm up naturally to room temperature. Synchronously record the changes of temperature and magnetic field output (in the form of analog signal and digital signal) over time.

[0113] It should be noted that the high and low temperature device is a device for simulating environmental temperature changes, which can quickly raise and lower the environmental temperature within a specific temperature range.

[0114] Step 3: Obtain the curve of the measurement value (zero point) of the digital vector magnetoresistive magnetometer at zero magnetic field versus temperature through Step 1 and Step 2, and perform least squares fitting to obtain the fitting parameters of the relationship between zero point drift and temperature.

[0115] It should be noted that the Least Squares Method is a mathematical optimization technique used to find the best function matching for data by minimizing the sum of the squares of errors. Its basic idea is to fit a curve or function so that the sum of the squares of the errors between the curve and the actual observed data is minimized, so it is also applied to curve fitting;

[0116] The fitting parameters of the relationship between zero point drift and temperature are the relationship between the measurement zero point of the digital vector magnetoresistive magnetometer and temperature change.

[0117] Step 4: Use a coil to generate a vector magnetic field with a specific intensity inside the Permalloy shielding cylinder, and then perform Step 1 and Step 2 to obtain the curve of the voltage-magnetic field conversion coefficient of the digital vector magnetoresistive magnetometer versus temperature, and perform least squares fitting to obtain the fitting parameters of the relationship between the voltage-magnetic field conversion coefficient and temperature.

[0118] It should be noted that the fitting parameters of the relationship between the voltage-magnetic field conversion coefficient and temperature are the relationship between the conversion coefficient of converting the amplitude of the digital signal into magnetic field intensity and temperature change.

[0119] Step Five: Perform digital compensation on the output value of the digital vector magnetoresistive magnetometer according to the fitting parameters of the relationship between zero drift and temperature, the fitting parameters of the relationship between the voltage-magnetic field conversion coefficient and temperature, and the real-time ambient temperature, that is, according to the obtained relationship between the measurement zero point of the digital vector magnetoresistive magnetometer and temperature change, the conversion coefficient of converting the amplitude of the digital signal into magnetic field strength and temperature change, and the real-time ambient temperature, remove the errors in the output value of the digital vector magnetoresistive magnetometer.

[0120] In other embodiments of the present application, the steps of respectively performing signal processing on the first analog signal, the second analog signal, and the third analog signal to obtain the first digital signal, the second digital signal, and the third digital signal include the following steps:

[0121] Generate a square wave modulation signal with a specific frequency, and based on the square wave modulation signal, perform square wave modulation on the first analog signal, the second analog signal, and the third analog signal respectively.

[0122] It should be noted that the square wave modulation refers to the process of using the square wave with the specific frequency as the carrier wave to perform signal modulation on each analog signal.

[0123] Perform differential amplification and filtering on the first analog signal, the second analog signal, and the third analog signal respectively;

[0124] It should be noted that differential amplification means that by amplifying the differential mode signal and suppressing the common mode signal, the fidelity and anti-interference ability of the signal are improved.

[0125] Based on the trigger signal, simultaneously perform analog-to-digital conversion on the first analog signal, the second analog signal, and the third analog signal respectively to obtain the first digital signal, the second digital signal, and the third digital signal.

[0126] It should be noted that before converting the analog signal into a digital signal, performing differential amplification and filtering on the analog signal respectively can significantly improve the signal quality and the accuracy of subsequent digital processing. Differential amplification enhances the useful signal by eliminating common mode noise (such as power supply noise or environmental interference), and is especially suitable for weak signals or high-noise environments, thereby improving the signal-to-noise ratio of the signal. Filtering can remove high-frequency noise or low-frequency interference in the signal, retain the signal components in the target frequency band, avoid aliasing effects, and ensure that the digitized signal is more pure and accurate. In addition, such differential amplification and filtering can reduce the influence of temperature drift and nonlinear distortion on the digital signal to improve the overall stability of the system, laying a good foundation for subsequent digital quadrature demodulation and digital compensation of the digital signal.

[0127] In other embodiments of the present application, such asFigure 2 As shown, a digital vector magnetoresistive magnetometer is provided. The digital vector magnetoresistive magnetometer is used to measure the magnetic field intensity of a three-dimensional vector magnetic field. The digital vector magnetoresistive magnetometer includes:

[0128] A three-axis magnetoresistive module, a signal processing module, and a digital processing module;

[0129] The three-axis magnetoresistive module is used to obtain a first analog signal, a second analog signal, and a third analog signal according to the magnetic field intensity of the environment where it is located. The first analog signal represents the component of the magnetic field intensity in the first direction, the second analog signal represents the component of the magnetic field intensity in the second direction, and the third analog signal represents the component of the magnetic field intensity in the third direction. The first direction, the second direction, and the third direction are perpendicular to each other.

[0130] It should be noted that, in an embodiment of the present application, the three-axis magnetoresistive module has the function of multi-axis measurement (magnetic field components in the X, Y, and Z axis directions) and can provide the ability of three-dimensional magnetic field measurement. The three output voltages of the three-axis magnetoresistive module are all in differential output mode, that is, two signals with equal amplitude and opposite phase are output, which are respectively called positive output (+) and negative output (-).

[0131] The signal processing module is used to perform signal processing on the first analog signal, the second analog signal, and the third analog signal respectively to obtain a first digital signal, a second digital signal, and a third digital signal.

[0132] In other embodiments of the present application, as Figure 3 shown, the signal processing module includes a square wave modulation unit, a signal conditioning unit, and a synchronous acquisition unit;

[0133] The square wave modulation unit is used to perform square wave modulation on the first analog signal, the second analog signal, and the third analog signal respectively based on a square wave modulation signal;

[0134] The signal conditioning unit is used to perform differential amplification and filtering on the first analog signal, the second analog signal, and the third analog signal respectively;

[0135] The synchronous acquisition unit is used to perform analog-to-digital conversion on the first analog signal, the second analog signal, and the third analog signal respectively based on a trigger signal to obtain a first digital signal, a second digital signal, and a third digital signal;

[0136] The digital processing module is further used to generate a square wave modulation signal and a trigger signal with a specific frequency.

[0137] Exemplarily, the circuit connection schematic diagram of the signal conditioning unit of the X axis is as Figure 4As shown, Ux+ and Ux- are the first analog signals in the form of differential voltage outputs of the X-axis of the three-axis magnetoresistive module. The signal conditioning unit includes operational amplifiers U1 and U2, resistors R1, R2, R3, R4, R5, R6, and capacitors C1 and C2. Their connection relationship is as follows: One end of resistor R1 is connected to the inverting output terminal of the X-axis of the three-axis magnetoresistive module, and the other end is connected to the inverting input terminal of operational amplifier U1. One end of resistor R2 is connected to the non-inverting output terminal of the X-axis of the three-axis magnetoresistive module, and the other end is connected to the non-inverting input terminal of operational amplifier U1. One end of resistor R3 is connected to the inverting input terminal of operational amplifier U1, and the other end is connected to the output terminal of operational amplifier U1. One end of resistor R4 is connected to the non-inverting input terminal of operational amplifier U1, and the other end is grounded. One end of resistor R5 is connected to the output terminal of operational amplifier U1, and the other end is connected to resistor R6 and capacitor C2. The other end of resistor R6 is connected to the non-inverting input terminal of operational amplifier U2, and the other end of capacitor C2 is connected to the output terminal of operational amplifier U2. One end of capacitor C1 is connected to the non-inverting input terminal of operational amplifier U2, and the other end is grounded. The output terminal of operational amplifier U2 is connected to its inverting input terminal. In order to reduce low-frequency drift and reduce system noise, U1 and U2 are selected as zero-drift operational amplifiers. In this embodiment, the resistors used are all precision resistors with low temperature drift coefficients.

[0138] The digital processing module is used to perform digital quadrature demodulation and digital compensation on the first digital signal, the second digital signal, and the third digital signal respectively to obtain the magnetic field intensity values and phases in the first direction, the second direction, and the third direction of the magnetic field intensity.

[0139] It should be noted that if the sampling times of the analog-to-digital conversions of different axes are different, it may cause time deviations or data inconsistencies between the measurement results, thereby affecting the accuracy of the final magnetic field vector. Therefore, in one embodiment, such as Figure 5 In order to avoid measurement errors caused by different sampling times of the three-axis analog-to-digital conversion, in this embodiment, a trigger signal is generated by the digital processing module. When the synchronous acquisition unit receives the trigger signal, the three axes start sampling simultaneously. And the synchronous acquisition unit adjusts the sampling rate to a set value according to the sampling clock signal sent by the digital processing module.

[0140] In other embodiments of the present application, the digital vector magnetoresistive magnetometer further includes a host computer module. The host computer module is used to send working parameters to the digital processing module to indirectly control the three-axis magnetoresistive module, the square wave modulation unit, the signal conditioning unit, and the synchronous acquisition unit through the digital processing module.

[0141] The digital processing module is further configured to control the three-axis magnetoresistive module, the square wave modulation unit, the signal conditioning unit, and the synchronous acquisition unit according to the working parameters, and send the magnetic field intensity values and phases of the components of the magnetic field intensity in the first direction, the second direction, and the third direction to the host computer module. The working parameters include the frequency of the generated square wave modulation signal, the digital filtering mode of the digital processing module, the sampling rate of the synchronous acquisition unit, the frequency of the generated reference signal, i.e., the demodulation frequency, the conversion coefficient for converting the amplitude into the magnetic field intensity value, and the data upload rate at which the digital processing module sends data to the host computer module.

[0142] It should be noted that, as Figure 5 shown, in other embodiments of the present application, after receiving the working parameters sent by the host computer module, the digital processing module sends the sampling rate in the working parameters to the synchronous acquisition unit, generates a square wave modulation signal according to the frequency of the generated square wave modulation signal and sends it to the square wave modulation unit, generates a first phase reference signal based on the frequency of the generated reference signal in the working parameters, and performs phase shift (digital synthesis) on the first phase reference signal to obtain a second phase reference signal. Through a mixer, the first digital signal, the second digital signal, and the third digital signal are respectively mixed and multiplied with the first phase reference signal and the second phase reference signal to obtain a first mixed signal and a second mixed signal corresponding to the first digital signal, a third mixed signal and a fourth mixed signal corresponding to the second digital signal, and a fifth mixed signal and a sixth mixed signal corresponding to the third digital signal;

[0143] The first mixed signal and the second mixed signal, the third mixed signal and the fourth mixed signal, and the fifth mixed signal and the sixth mixed signal are respectively digitally filtered to obtain a first in-phase component and a first quadrature component, a second in-phase component and a second quadrature component, and a third in-phase component and a third quadrature component;

[0144] The first in-phase component and the first quadrature component, the second in-phase component and the second quadrature component, and the third in-phase component and the third quadrature component are subjected to polar coordinate conversion to obtain the amplitude and phase of the first digital signal, the amplitude and phase of the second digital signal, and the amplitude and phase of the third digital signal;

[0145] Based on the relationship between the preset zero drift and temperature, the relationship between the preset voltage-magnetic field conversion coefficient and temperature, and the real-time ambient temperature, digital compensation is performed, and the scale factor of voltage-magnetic field conversion (i.e., the voltage-magnetic field conversion coefficient) is adjusted. The amplitudes of the first digital signal, the second digital signal, and the third digital signal are respectively converted into the magnetic field intensity values of the first digital signal, the second digital signal, and the third digital signal. Finally, according to the data upload rate in the working parameters, the magnetic field intensities of each digital signal are uploaded to the host computer module for output.

[0146] It should be noted that modulation and demodulation can eliminate the interference of external strong magnetic fields and avoid the low-frequency noise of backend devices such as operational amplifiers and acquisition cards, further improving the signal-to-noise ratio of the magnetoresistive magnetometer, which is crucial for improving the performance of the magnetoresistive magnetometer. In one embodiment, the digital processing module selects an FPGA as the core processing chip. The modulation frequency of the square wave modulation signal is set to 100 Hz, the demodulation frequency is set to 100 Hz, the sampling rate of the synchronous acquisition unit is set to 10 kHz, and the data upload rate is set to upload 20 groups of data per second through the host computer module. Exemplarily, as Figure 6 shown, the original magnetic measurement signal (i.e., the first analog signal) is a constant magnetic field superimposed with a sinusoidal fluctuation with a frequency of 2 Hz, and the direction of the magnetic field to be measured flips at the 0.5 s moment. The amplitude of the signal after square wave modulation changes with the original magnetic measurement signal. The synchronous acquisition unit converts the signal after square wave modulation into a digital signal.

[0147] According to the demodulation frequency, the first phase reference signal , the second phase reference signal , are respectively multiplied by the acquired digital signal to obtain two mixed-frequency signals. The two mixed-frequency signals are digitally filtered to filter out the sum-frequency signals and retain the difference-frequency signals, obtaining the first in-phase component a and the first quadrature component b. Convert a and b to polar coordinates and calculate the amplitude R and phase φ of the input signal. The calculation formulas are as follows:

[0148]

[0149] As Figure 6 shown, after digital demodulation and filtering, the digital demodulation amplitude signal R restores the amplitude information of the original magnetic measurement signal, and the digital demodulation phase signal Φ represents the direction of the original magnetic measurement signal. The phase flips by π radians at 0.5 s, indicating a direction reversal, and correctly demodulates the direction reversal information of the magnetic field to be measured.

[0150] Among them, the digital filtering process uses a digital low-pass filter and an integrator comb filter. Among them, in this embodiment, the digital low-pass filter is set as a 220-order finite impulse response filter by the host computer module, with a passband frequency of 10 Hz, a stopband frequency of 100 Hz, and a stopband attenuation of 60 dB. The comb stopband of the integrator comb filter is set to the demodulation frequency and the frequencies of its higher harmonics. When the filter bandwidth is equivalent to or greater than the demodulation frequency, the demodulated output contains the frequency components of the demodulation frequency and its higher harmonics, and the integrator comb filter can attenuate these unwanted harmonic components. Compared with analog filtering, digital filtering can easily implement high-order filters, which usually require a large number of components to achieve in analog circuits, and digital filtering can implement complex types of filtering, such as the integrator comb filter in this embodiment, which requires a more complex circuit to achieve its function in analog circuits.

[0151] In this embodiment, as Figure 7 shown, the curve of zero drift versus temperature is obtained through the above-mentioned Step 1 and Step 2, and the data is fitted by the least squares method using matlab software to obtain the fitting formula:

[0152]

[0153] In Equation (3), A 0 represents the voltage output value (µV) of the digital vector magnetoresistive magnetometer under zero magnetic field, and T represents the temperature (°C).

[0154] The curve of the relationship between the voltage-magnetic field conversion coefficient and temperature is obtained through the above-mentioned Step 1, Step 2, and Step 4, and the data is fitted by the least squares method using matlab software to obtain the fitting formula:

[0155]

[0156] In Equation (4), A 1 represents the relationship between the voltage-magnetic field conversion coefficient and temperature (µV / nT), and T represents the temperature (°C).

[0157] When the externally applied magnetic field strength is MnT and the ambient temperature is T °C, the voltage output value U of the digital vector magnetoresistive magnetometer is:

[0158]

[0159] It should be noted that the sensitivity is the voltage-magnetic field conversion coefficient.

[0160] This embodiment uses the zero point and the voltage-magnetic field conversion coefficient at 25 °C as the reference: A 0 (25) = -99.6 µV, A 1(25) = 4.975 μV / nT, that is, the conversion coefficient is set to 4.975 μV / nT. According to formula (5), when no digital compensation is performed, the magnetic field measurement value M of the digital vector magnetoresistive magnetometer 2 is as follows:

[0161]

[0162] In formula (6), M 2 is the uncompensated measurement value, M is the true value of the magnetic field strength, and the conversion relationship between M 2 and M is known. It can be deduced from formula (6) that when the ambient temperature is T 0 , the digital compensation formula is as follows:

[0163]

[0164] In formula (7), M 3 is the measured value of the magnetic field strength after compensation.

[0165] It should be noted that in this embodiment, the zero point and the sum voltage magnetic field conversion coefficient at 25 °C are used as the reference. In other embodiments, the zero point and the sum voltage magnetic field conversion coefficient at other temperatures can be used as the reference. Exemplarily, the zero point and the sum voltage magnetic field conversion coefficient at any temperature from -40 °C to 50 °C can be used as the reference, and the present application does not make any limitations in this regard.

[0166] Exemplarily, in another embodiment, the ambient temperature is 5 °C and the external magnetic field strength is 10000 nT. The resolution of the synchronous acquisition unit is 24 bits and the full-scale input is 5 V, that is, the acquisition accuracy of the synchronous acquisition unit is 0.3 μV, and the digital compensation accuracy is approximately 0.3 / 4.975 = 0.06 nT. Under this condition, the voltage output value of the digital vector magnetoresistive magnetometer is: U = 10000 × A 1 (5) + A 0 (5) = 49909.5 μV. According to formula (6), when no digital compensation is performed, the magnetic field measurement value M 2 = (U + 99.6) / 4.975 = 10052.1 nT. When digital compensation is performed, first calculate the fitting parameters of the zero drift and the relationship drift between the sum voltage magnetic field conversion coefficient and temperature at this ambient temperature. According to formulas (3), (4) and (7), at 5 °C, A 0 = -40.5 μV, A 1 = 4.995 μV / nT, and the magnetic field measurement value M 3 after compensation is 10000.02 nT, with a difference of 0.02 nT from the actual value.

[0167] In another embodiment, the ambient temperature is 5°C and the external magnetic field strength is 10,000 nT. The resolution of the synchronous acquisition unit is 12 bits, and the full-scale input is 5V, that is, the acquisition accuracy of the synchronous acquisition unit is 1221 μV, and the digital compensation accuracy is approximately 1221 / 4.975 = 245 nT. Under this condition, limited by the acquisition accuracy of the synchronous acquisition unit, the voltage output value of the digital vector magnetoresistive magnetometer is 50,049 μV. According to formula (6), when no digital compensation is performed, the magnetic field measurement value M 2 =(U + 99.6) / 4.975 = 10,080.1 nT. When digital compensation is performed, first calculate the fitting parameters of the zero drift and the relationship drift between the voltage-magnetic field conversion coefficient and temperature at this ambient temperature. From formulas (3), (4), and (7), it can be seen that at 5°C, A 0 =-40.5 μV, A 1 =4.995 μV / nT. The compensated magnetic field measurement value M 3 =10,027.9 nT, with a difference of 27.9 nT from the actual value.

[0168] As can be seen from the above embodiments, the accuracy of digital compensation is limited by the acquisition accuracy of the synchronous acquisition unit, and is also limited by the overall noise of the system. Therefore, by using a high-resolution synchronous acquisition unit and a low-noise design, the accuracy of digital compensation can be less than 1 nT, which is much higher than the compensation accuracy of analog devices. And for magnetoresistive sensor chips with different temperature drift characteristics, the fitting parameters can be obtained by least squares fitting, and the compensation method has better generality compared with analog devices.

[0169] In other embodiments of the present application, the signal conditioning unit includes a differential amplifier circuit and an active low-pass filter circuit, and the operational amplifier in the differential amplifier circuit is a zero-drift operational amplifier, and the resistors in the signal conditioning unit are low-temperature-drift resistors.

[0170] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, database, or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memories. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc. The databases involved in the embodiments provided in the present application can include at least one of relational databases and non-relational databases. Non-relational databases can include distributed databases based on blockchain, etc., and are not limited thereto. The processors involved in the embodiments provided in the present application can be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, data processing logics based on quantum computing, etc., and are not limited thereto.

[0171] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0172] The above-described embodiments merely represent several implementation manners of the present application. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A method for measuring vector magnetic field strength, characterized in that: Applied to a digital vector magnetoresistive magnetometer, the method comprises: According to the magnetic field strength of the environment in which the digital vector magnetoresistive magnetometer is located, a first analog signal, a second analog signal and a third analog signal are obtained, wherein the first analog signal represents a component of the magnetic field strength in a first direction, the second analog signal represents a component of the magnetic field strength in a second direction, and the third analog signal represents a component of the magnetic field strength in a third direction, and the first direction, the second direction and the third direction are perpendicular to each other; Performing signal processing on the first analog signal, the second analog signal and the third analog signal respectively to obtain a first digital signal, a second digital signal and a third digital signal; Performing digital orthogonal demodulation and digital compensation on the first digital signal, the second digital signal, and the third digital signal, respectively, to obtain magnetic field intensity values ​​and phases of the magnetic field intensity in the first direction, the second direction, and the third direction; The performing digital orthogonal demodulation and digital compensation on the first digital signal, the second digital signal and the third digital signal respectively to obtain the magnetic field intensity values ​​and phases of the components of the magnetic field intensity in the first direction, the second direction and the third direction includes: Generate a first phase reference signal and a second phase reference signal based on a demodulation frequency input by an external device; Mix and multiply the first digital signal, the second digital signal and the third digital signal with the first phase reference signal and the second phase reference signal, respectively, to obtain a first mixing signal and a second mixing signal corresponding to the first digital signal, a third mixing signal and a fourth mixing signal corresponding to the second digital signal, and a fifth mixing signal and a sixth mixing signal corresponding to the third digital signal, respectively; Digitally filter the first mixing signal and the second mixing signal, the third mixing signal and the fourth mixing signal, the fifth mixing signal and the sixth mixing signal to obtain a first in-phase component and a first quadrature component, a second in-phase component and a second quadrature component, and a third in-phase component and a third quadrature component respectively; Performing polar coordinate conversion on the first in-phase component and the first quadrature component, the second in-phase component and the second quadrature component, and the third in-phase component and the third quadrature component to obtain the amplitude and phase of the first digital signal, the amplitude and phase of the second digital signal, and the amplitude and phase of the third digital signal; Based on the relationship between the preset zero point drift and temperature, the relationship between the preset voltage-magnetic field conversion coefficient and temperature, and the real-time ambient temperature, the amplitude of the first digital signal, the amplitude of the second digital signal, and the amplitude of the third digital signal are respectively converted into the magnetic field strength value of the first digital signal, the magnetic field strength value of the second digital signal, and the magnetic field strength value of the third digital signal, and digital compensation is performed.

2. The method for measuring vector magnetic field strength according to claim 1, characterized in that: Based on the relationship between the preset zero drift and the temperature, the relationship between the preset voltage-magnetic field conversion coefficient and the temperature, and the real-time ambient temperature, the amplitude of the first digital signal, the amplitude of the second digital signal, and the amplitude of the third digital signal are respectively converted into the magnetic field intensity value of the first digital signal, the magnetic field intensity value of the second digital signal, and the magnetic field intensity value of the third digital signal, and digital compensation is performed, including: Based on the relationship between the preset voltage magnetic field conversion coefficient and the temperature, the amplitude of the first digital signal, the amplitude of the second digital signal and the amplitude of the third digital signal are converted into the magnetic field intensity value of the first digital signal, the magnetic field intensity value of the second digital signal and the magnetic field intensity value of the third digital signal respectively; Based on the relationship between the preset zero point drift and temperature, the relationship between the preset voltage magnetic field conversion coefficient and temperature, and the real-time ambient temperature, the magnetic field strength value of the first digital signal, the magnetic field strength value of the second digital signal, and the magnetic field strength value of the third digital signal are digitally compensated.

3. The method for measuring vector magnetic field strength according to claim 1, characterized in that: The method of generating a first phase reference signal and a second phase reference signal based on a demodulation frequency input by an external device comprises: Generate a first phase reference signal based on a demodulation frequency input by an external device; The first phase reference signal is phase-shifted to obtain a second phase reference signal.

4. The method for measuring vector magnetic field strength according to claim 1, characterized in that: The vector magnetic field strength measurement method further includes: heating the digital vector magnetoresistive magnetometer to a first temperature, and recording a first relationship between a measurement value of the digital vector magnetoresistive magnetometer and temperature during cooling to a second temperature under the first magnetic field strength; Cooling the digital vector magnetoresistive magnetometer to a third temperature, and recording a second relationship between a measurement value of the digital vector magnetoresistive magnetometer and temperature during a process of naturally heating up to a second temperature under the first magnetic field strength; Based on the first relationship and the second relationship, obtaining a relationship between a preset zero drift and a temperature; heating the digital vector magnetoresistive magnetometer to a first temperature, and recording a third relationship between a voltage-to-magnetic-field conversion coefficient and temperature of the digital vector magnetoresistive magnetometer during cooling to a second temperature at a second magnetic field strength; Cooling the digital vector magnetoresistive magnetometer to a third temperature, and recording a fourth relationship between a voltage-to-magnetic-field conversion coefficient and temperature of the digital vector magnetoresistive magnetometer during a process of naturally heating to the second temperature under a second magnetic field strength; Based on the third relationship and the fourth relationship, a relationship between a preset voltage-magnetic field conversion coefficient and temperature is obtained.

5. The method for measuring vector magnetic field strength according to claim 1, characterized in that: The processing of the first analog signal, the second analog signal and the third analog signal to obtain a first digital signal, a second digital signal and a third digital signal comprises: Generate a square wave modulation signal of a specific frequency, and based on the square wave modulation signal, perform square wave modulation on the first analog signal, the second analog signal, and the third analog signal respectively; performing differential amplification and filtering on the first analog signal, the second analog signal and the third analog signal respectively; Based on the trigger signal, the first analog signal, the second analog signal and the third analog signal are respectively converted into analog-to-digital signals to obtain a first digital signal, a second digital signal and a third digital signal.

6. A digital vector magnetoresistive magnetometer, characterized in that: The digital vector magnetoresistive magnetometer is used to measure the magnetic field strength of a three-dimensional vector magnetic field. The digital vector magnetoresistive magnetometer comprises: Three-axis magnetoresistive module, signal processing module and digital processing module; The three-axis magnetic resistance module is used to obtain a first analog signal, a second analog signal and a third analog signal according to the magnetic field strength of the environment, wherein the first analog signal represents the component of the magnetic field strength in a first direction, the second analog signal represents the component of the magnetic field strength in a second direction, and the third analog signal represents the component of the magnetic field strength in a third direction, and the first direction, the second direction and the third direction are perpendicular to each other; The signal processing module is used to perform signal processing on the first analog signal, the second analog signal and the third analog signal respectively to obtain a first digital signal, a second digital signal and a third digital signal; The digital processing module is used to perform digital orthogonal demodulation and digital compensation on the first digital signal, the second digital signal and the third digital signal respectively, to obtain the magnetic field intensity value and phase of the magnetic field intensity in the first direction, the second direction and the third direction; The performing digital orthogonal demodulation and digital compensation on the first digital signal, the second digital signal and the third digital signal respectively to obtain the magnetic field intensity values ​​and phases of the components of the magnetic field intensity in the first direction, the second direction and the third direction includes: Generate a first phase reference signal and a second phase reference signal based on a demodulation frequency input by an external device; Mix and multiply the first digital signal, the second digital signal and the third digital signal with the first phase reference signal and the second phase reference signal, respectively, to obtain a first mixing signal and a second mixing signal corresponding to the first digital signal, a third mixing signal and a fourth mixing signal corresponding to the second digital signal, and a fifth mixing signal and a sixth mixing signal corresponding to the third digital signal, respectively; Digitally filter the first mixing signal and the second mixing signal, the third mixing signal and the fourth mixing signal, the fifth mixing signal and the sixth mixing signal to obtain a first in-phase component and a first quadrature component, a second in-phase component and a second quadrature component, and a third in-phase component and a third quadrature component respectively; Performing polar coordinate conversion on the first in-phase component and the first quadrature component, the second in-phase component and the second quadrature component, and the third in-phase component and the third quadrature component to obtain the amplitude and phase of the first digital signal, the amplitude and phase of the second digital signal, and the amplitude and phase of the third digital signal; Based on the relationship between the preset zero point drift and temperature, the relationship between the preset voltage-magnetic field conversion coefficient and temperature, and the real-time ambient temperature, the amplitude of the first digital signal, the amplitude of the second digital signal, and the amplitude of the third digital signal are respectively converted into the magnetic field strength value of the first digital signal, the magnetic field strength value of the second digital signal, and the magnetic field strength value of the third digital signal, and digital compensation is performed.

7. The digital vector magnetoresistive magnetometer according to claim 6, characterized in that: The signal processing module includes a square wave modulation unit, a signal conditioning unit and a synchronous acquisition unit; The square wave modulation unit is used to perform square wave modulation on the first analog signal, the second analog signal and the third analog signal respectively based on the square wave modulation signal; The signal conditioning unit is used to perform differential amplification and filtering on the first analog signal, the second analog signal and the third analog signal respectively; The synchronous acquisition unit is used to perform analog-to-digital conversion on the first analog signal, the second analog signal and the third analog signal respectively based on the trigger signal to obtain a first digital signal, a second digital signal and a third digital signal; The digital processing module is also used to generate a square wave modulation signal and a trigger signal of a specific frequency.

8. The digital vector magnetoresistive magnetometer according to claim 7, characterized in that: The signal conditioning unit comprises a differential amplifier circuit and an active low-pass filter circuit, the operational amplifier in the differential amplifier circuit is a zero-drift operational amplifier, and the resistor in the signal conditioning unit is a low-temperature drift resistor.

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