Wideband noise optimization method for inductive magnetic field sensor and magnetic field sensor

Abstract

The present invention provides a method for optimizing the wideband noise of an inductive magnetic field sensor and a magnetic field sensor, which can be applied to the field of magnetic variable measurement and inductive magnetic field sensor technology. The optimization method includes: determining the functional relationship between the sensor coil induced voltage and the effective magnetic permeability of the magnetic core; determining the equivalent voltage noise expression of the temperature variation noise of the magnetic permeability of the sensor magnetic core according to the functional relationship; determining the key influencing factor of the magnetic core according to the equivalent voltage noise expression of the temperature variation noise of the magnetic permeability of the sensor magnetic core; improving the magnetic core according to the key influencing factor of the magnetic core to complete the optimization of the temperature variation noise of the magnetic permeability of the magnetic core; and constructing a dual-channel composite multi-order modulation signal-to-noise separation circuit to optimize the low-band and high-band noise of the sensor.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic variable measurement and inductive magnetic field sensors, and more specifically, to a method for optimizing wide-band noise of an inductive magnetic field sensor and a magnetic field sensor. Background Art

[0002] Inductive magnetic field sensor is a sensor that uses Faraday's law of electromagnetic induction to measure magnetic field changes. As one of the common magnetic field sensors, it is widely used in geophysics, medical treatment, national defense and other fields. In practical geophysical applications, the measurement frequency range of inductive magnetic field sensors covers the range of 0.0001Hz-100kHz, and can be used in electromagnetic exploration instruments such as magnetotelluric sounding (MT), controlled source audio frequency magnetotelluric sounding (CSAMT), and transient electromagnetic method (TEM).

[0003] In the process of realizing the concept of the present invention, it is found through research that the inductive magnetic field sensor in the related art is at least affected by noise in the high frequency band and the low frequency band, thereby limiting the working bandwidth of the magnetic field sensor. Summary of the invention

[0004] In view of this, the present invention provides a method for optimizing wide-band noise of an inductive magnetic field sensor and a magnetic field sensor.

[0005] One aspect of the present invention provides a method for optimizing broadband noise of an inductive magnetic field sensor, comprising:

[0006] Determine the functional relationship between the induced voltage of the sensor coil and the effective magnetic permeability of the magnetic core; determine the equivalent voltage noise expression of the temperature variation noise of the sensor magnetic core magnetic permeability based on the functional relationship; determine the key influencing factors of the magnetic core based on the equivalent voltage noise expression of the temperature variation noise of the sensor magnetic core magnetic permeability; improve the magnetic core according to the key influencing factors of the magnetic core to complete the optimization of the temperature variation noise of the magnetic core magnetic permeability; and construct a dual-channel composite multi-order modulation signal-to-noise separation circuit to optimize the low-frequency and high-frequency band noise of the sensor.

[0007] According to an embodiment of the present invention, determining the functional relationship between the sensor coil induced voltage and the effective magnetic permeability of the magnetic core includes: considering that the relative magnetic permeability of the magnetic core material changes slowly with temperature, causing the effective magnetic permeability of the magnetic core to also change with temperature, and considering that the effective magnetic permeability of the magnetic core has both a DC component and an AC component, obtaining the functional relationship between the coil induced voltage in the time domain and the effective magnetic permeability of the magnetic core in a non-constant temperature environment.

[0008] According to an embodiment of the present invention, an equivalent voltage noise expression of the temperature variation noise of the magnetic permeability of the sensor core is determined according to a functional relationship, including: determining the noise term introduced by the temperature variation factor of the magnetic permeability of the core in the functional relationship between the induced voltage of the sensor coil and the effective magnetic permeability of the magnetic core; excluding the negligible terms in the noise term introduced by the temperature variation factor of the magnetic permeability of the core; and obtaining the equivalent voltage noise expression of the temperature variation noise of the magnetic permeability of the core.

[0009] According to an embodiment of the present invention, the expression of the functional relationship between the sensor coil induced voltage and the effective magnetic permeability of the magnetic core is recorded as:

[0010] ;

[0011] Among them, the DC component and AC component of the effective magnetic permeability are μ appDC , μ appAC The DC component and AC component of the magnetic induction intensity B are B DC and B AC , N represents the number of coil turns, S represents the cross-sectional area of ​​the coil and the core, μ app Indicates the effective magnetic permeability of the core.

[0012] According to an embodiment of the present invention, the expression of the functional relationship between the induced voltage of the sensor coil and the effective magnetic permeability of the magnetic core includes three noise terms introduced by the temperature change factor of the magnetic permeability of the magnetic core, which are respectively , the third item Item 4 , considering the AC component B of the magnetic induction intensity AC Much smaller than the DC component B DC , and the DC component of the effective magnetic permeability μ appDC The change over time is zero, so the third and fourth terms in the noise term introduced by the temperature change factor of the magnetic core permeability are ignored. f represents the frequency, and the equivalent voltage noise of the temperature change noise of the magnetic core permeability in the frequency domain is expressed as:

[0013] .

[0014] According to an embodiment of the present invention, the key influencing factor of the magnetic core is determined to be the AC component of the effective magnetic permeability that reflects the rate of change of the magnetic core magnetic permeability with temperature based on the equivalent voltage noise expression of the temperature variation noise of the sensor magnetic core magnetic permeability.

[0015] According to an embodiment of the present invention, improving the magnetic core according to the key influencing factors of the magnetic core includes: selecting a magnetic core of suitable material according to the application environment of the sensor; annealing the magnetic core in a vacuum magnetic field at a set temperature on the premise of ensuring the effective magnetic permeability of the magnetic core, so as to adjust the anisotropy of the magnetic core material and reduce internal structural defects, and reduce the rate of change of the effective magnetic permeability of the magnetic core with temperature; and optimizing the magnetic circuit of the magnetic core, including: respectively arranging flat disk-shaped flux concentrators at both ends of the magnetic core, and the centers of the flux concentrators are respectively tightly fitted to the two ends of the magnetic core, and the overall shape is a barbell.

[0016] According to an embodiment of the present invention, constructing a dual-channel composite multi-order modulation signal-to-noise separation circuit to optimize the low-frequency band and high-frequency band noise of the sensor includes: constructing a low-frequency channel, modulating the low-frequency component of the magnetic field signal to a frequency band range far away from the 1 / f noise of the amplifier in the low-frequency channel, amplifying it and then demodulating it back to the low-frequency band, and filtering it to achieve signal-to-noise separation to obtain the low-frequency component of the magnetic field signal; constructing a high-frequency channel, amplifying the magnetic field signal, and filtering out the 1 / f noise of the amplifier in the high-frequency channel to obtain the high-frequency component of the magnetic field signal; constructing a high-and-low-frequency channel composite unit, fusing the low-frequency component and the high-frequency component of the magnetic field signal, and optimizing the low-frequency band and high-frequency band noise of the sensor.

[0017] Another aspect of the present invention provides a broadband noise-optimized inductive magnetic field sensor, comprising:

[0018] The magnetic core is annealed in a vacuum magnetic field at a set temperature to adjust the anisotropy of the magnetic core material and reduce internal structural defects, thereby reducing the rate of change of the effective magnetic permeability of the magnetic core with temperature; a coil is wound around the periphery of the magnetic core; a dual-channel composite multi-order modulation signal-to-noise separation circuit is connected to the coil, including: a low-frequency channel, configured to modulate the low-frequency component of the magnetic field signal to a frequency band range far away from the 1 / f noise of the amplifier in the low-frequency channel, and then demodulate it back to the low-frequency band after amplification, and achieve signal-to-noise separation after filtering to obtain the low-frequency component of the magnetic field signal; a high-frequency channel is set in parallel with the low-frequency channel, configured to amplify the magnetic field signal, and filter out the 1 / f noise of the amplifier in the high-frequency channel to obtain the high-frequency component of the magnetic field signal; a high-low frequency channel composite unit is connected to the low-frequency channel and the high-frequency channel, and configured to fuse the low-frequency component and the high-frequency component of the magnetic field signal to optimize the low-frequency band and high-frequency band noise of the sensor.

[0019] According to an embodiment of the present invention, the low-frequency channel includes a first modulation unit, a transformer, a first amplifier, a second modulation unit, and a low-pass filter circuit unit: the first modulation unit is configured to modulate the low-frequency component of the received magnetic field signal to a frequency band range far away from the 1 / f noise of the first amplifier; the transformer is configured to passively amplify the signal modulated by the first modulation unit; the first amplifier is configured to further amplify the signal amplified by the transformer; the second modulation unit is configured to demodulate the amplified magnetic field signal back to the low-frequency band, and modulate the bias and 1 / f noise of the first amplifier to the high-frequency band; the low-pass filter circuit unit is configured to filter out the high-frequency band. Noise interference; the high-frequency channel includes a high-pass filter composed of a third amplifier, a capacitor, and a resistor connected in sequence, which amplifies the magnetic field signal and filters out the 1 / f noise of the amplifier in the high-frequency channel to obtain the high-frequency component of the magnetic field signal; the high- and low-frequency channel composite unit includes a fourth amplifier, a capacitor and a plurality of resistors, the negative input end of the fourth amplifier is connected to a resistor, and a capacitor and a resistor are connected in parallel between the negative input end and the output end, and the positive input end of the amplifier is connected to the output end of the low-frequency channel and the output end of the high-frequency channel through resistors, respectively, so that the high- and low-frequency channel composite unit can fuse the low-frequency component and the high-frequency component of the magnetic field signal, thereby optimizing the low-frequency band and high-frequency band noise of the sensor.

[0020] According to an embodiment of the present invention, the functional relationship between the sensor coil induced voltage and the effective magnetic permeability of the magnetic core is determined, and then the equivalent voltage noise expression of the temperature variation noise of the magnetic permeability of the sensor core is determined according to the functional relationship, and the key influencing factors of the magnetic core are determined according to the equivalent voltage noise expression of the temperature variation noise of the magnetic permeability of the sensor core. The magnetic core is improved according to the key influencing factors of the magnetic core to complete the optimization of the temperature variation noise of the magnetic permeability of the magnetic core, and a dual-channel composite multi-order modulation signal-noise separation circuit is constructed to optimize the low-band and high-band noise of the sensor. Since the magnetic core is improved according to the key influencing factors of the magnetic core, the rate at which the effective magnetic permeability of the magnetic core changes with temperature is reduced, thereby reducing the temperature variation noise of the magnetic core. At the same time, by constructing a dual-channel composite multi-order modulation signal-noise separation circuit to separate the noise of the low-frequency band and the high-frequency band, the inductive magnetic field sensor has high sensitivity and low noise characteristics under a wide bandwidth, and can be applied to a wider range of application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0022] Figure 1 The flowchart of the method for optimizing wide-band noise of an inductive magnetic field sensor according to an embodiment of the present invention is schematically shown.

[0023] Figure 2A noise curve comparison diagram of an inductive magnetic field sensor according to an embodiment of the present invention is schematically shown.

[0024] Figure 3 The schematic diagram of a long straight cylindrical magnetic core and a coil according to an embodiment of the present invention is schematically shown.

[0025] Figure 4 The diagram schematically shows a variation curve of effective magnetic permeability corresponding to different magnetic core aspect ratios according to an embodiment of the present invention.

[0026] Figure 5 A schematic diagram of a magnetic flux concentrator according to an embodiment of the present invention is schematically shown.

[0027] Figure 6 The schematic diagram of the dimensions of a magnetic flux concentrator and a magnetic core according to an embodiment of the present invention is shown schematically.

[0028] Figure 7 The circuit principle diagram of a broadband noise-optimized inductive magnetic field sensor according to an embodiment of the present invention is schematically shown. DETAILED DESCRIPTION

[0029] Below, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0030] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0031] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0032] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0033] In the embodiments of the present invention, the collection, updating, analysis, processing, use, transmission, provision, disclosure, storage and other aspects of the data involved (for example, including but not limited to user personal information) are in compliance with the provisions of relevant laws and regulations, are used for legitimate purposes, and do not violate public order and good morals. In particular, necessary measures are taken for user personal information to prevent illegal access to user personal information data and maintain the security of user personal information and network security.

[0034] After years of development, inductive electromagnetic sensors have relatively mature products in related technologies.

[0035] Among them, an inductive magnetic field sensor X1 has a coverage bandwidth of 10 -4 Hz~10 4 Hz, the noise level is 1.1pT / √Hz at a frequency of 0.1Hz, 0.11pT / √Hz at a frequency of 1Hz, and 0.02pT / √Hz at a frequency of 10Hz. The length of this magnetic field sensor X1 is 1.2m, the diameter is 75mm, and the weight is about 9kg. The coverage bandwidth of another inductive magnetic field sensor X2 is 10 -4 Hz~10 3 Hz, the noise level is 1pT / √Hz at a frequency of 0.1Hz, the noise level is 0.1pT / √Hz at a frequency of 1Hz, and the noise level is 0.01pT / √Hz at a frequency of 100Hz. The length of this magnetic field sensor X2 is 1.24m, the diameter is 85mm, and the weight is about 6.7kg. There is also an inductive magnetic field sensor X3 with a coverage bandwidth of 10 -5 Hz~400Hz, the noise level is 1.5pT / √Hz at a frequency of 0.1Hz, the noise level is 0.15pT / √Hz at a frequency of 1Hz, and the noise level is 0.15pT / √Hz at a frequency of 10Hz. The length of this magnetic field sensor X3 is 0.95m and the diameter is 60mm.

[0036] It can be seen that the length of the inductive magnetic field sensor in the related art is about 1.2m-1.4m, and the bandwidth that can be covered is 10 -5 Hz~10 4Hz, and it is difficult to take both low-frequency and high-frequency into account. For example, the low frequency of the inductive magnetic field sensor X3 can reach 10 -5 Hz, but the high frequency can only reach 400Hz, and the high frequency of the inductive magnetic field sensor X1 can reach 10 4 Hz, but the low frequency is only up to 10 -4 Hz.

[0037] The magnetic core is the magnetic gathering part of the inductive magnetic field sensor and is a key factor affecting the sensor's noise level. On the one hand, the initial magnetic permeability of the core material is affected by temperature, which will introduce additional low-frequency noise, thereby limiting the sensor's low-frequency working bandwidth; on the other hand, the traditional inductive magnetic field sensor core is in the shape of a long rod. Under the effect of the demagnetization field, the effective magnetic permeability of the soft magnetic material with an initial magnetic permeability of tens of thousands is only a few hundred after it is made into a core. Therefore, when space is limited, it is difficult to increase the aspect ratio, which results in an upper limit on the effective magnetic permeability of the core and the probe induced voltage.

[0038] In addition, for the 1 / f inherent noise in the low frequency band, the related technologies often use auto-zero or chopper amplification technology. Among them, the auto-zero amplifier has more in-band noise voltage than the standard operational amplifier, and in order to reduce the low-frequency noise voltage, the sampling frequency needs to be increased, but this also leads to additional charge injection. Although the chopper amplifier has a lower low-frequency noise voltage within its frequency band, it will generate a large number of spike signals at the chopping frequency and its harmonics, resulting in a larger noise current in the high frequency band.

[0039] In view of this, an embodiment of the present invention provides a method for optimizing the wide-band noise of an inductive magnetic field sensor, including: determining the functional relationship between the induced voltage of the sensor coil and the effective magnetic permeability of the magnetic core; determining the equivalent voltage noise expression of the temperature variation noise of the magnetic permeability of the sensor magnetic core according to the functional relationship; determining the key influencing factors of the magnetic core according to the equivalent voltage noise expression of the temperature variation noise of the magnetic permeability of the sensor magnetic core; improving the magnetic core according to the key influencing factors of the magnetic core to complete the optimization of the temperature variation noise of the magnetic permeability of the magnetic core; and constructing a dual-channel composite multi-order modulation signal-to-noise separation circuit to optimize the low-frequency band and high-frequency band noise of the sensor.

[0040] Another embodiment of the present invention also discloses an inductive magnetic field sensor with wide-band noise optimization, comprising: a magnetic core, which is annealed in a vacuum magnetic field at a set temperature to adjust the anisotropy of the magnetic core material and reduce internal structural defects, thereby reducing the rate of change of the effective magnetic permeability of the magnetic core with temperature; a coil, which is wound around the periphery of the magnetic core; a dual-channel composite multi-order modulation signal-to-noise separation circuit, which is connected to the coil, comprising: a low-frequency channel, which is configured to modulate the low-frequency component of the magnetic field signal to a frequency band range far away from the 1 / f noise of the amplifier in the low-frequency channel, and then demodulate it back to the low-frequency band after amplification, and achieve signal-to-noise separation after filtering to obtain the low-frequency component of the magnetic field signal; a high-frequency channel, which is arranged in parallel with the low-frequency channel, and is configured to amplify the magnetic field signal and filter out the 1 / f noise of the amplifier in the high-frequency channel to obtain the high-frequency component of the magnetic field signal; a high-low frequency channel composite unit, which is connected to the low-frequency channel and the high-frequency channel, and is configured to fuse the low-frequency component and the high-frequency component of the magnetic field signal to achieve optimization of the low-frequency band and high-frequency band noise of the sensor.

[0041] Figure 1 The flowchart of the method for optimizing wide-band noise of an inductive magnetic field sensor according to an embodiment of the present invention is schematically shown.

[0042] like Figure 1 As shown, the method 100 includes operations S110 to S150.

[0043] In operation S110 , a functional relationship between the sensor coil induced voltage and the effective magnetic permeability of the magnetic core is determined.

[0044] In operation S120 , an equivalent voltage noise expression of the temperature variation noise of the magnetic permeability of the sensor core is determined according to the functional relationship.

[0045] In operation S130 , a key influencing factor of the magnetic core is determined according to an equivalent voltage noise expression of the temperature variation noise of the magnetic permeability of the sensor magnetic core.

[0046] In operation S140, the magnetic core is improved according to the key influencing factors of the magnetic core to complete the optimization of the temperature variation noise of the magnetic permeability of the magnetic core.

[0047] In operation S150 , a dual-channel composite multi-order modulation signal-to-noise separation circuit is constructed to optimize the low-band and high-band noise of the sensor.

[0048] In addition to the core permeability temperature variation noise (TC noise), the inductive magnetic field sensor also includes other noise sources, such as: core loss noise (RC noise), coil resistance thermal noise (TR noise), coil resistance 1 / f noise (FR noise), circuit equivalent input voltage noise (CV noise), circuit voltage bias temperature drift noise (CT noise), circuit equivalent input current noise (CI noise), feedback resistor noise (FB noise) and attenuation resistor noise (TT noise). The inventor team has carried out noise reduction optimization processing on other noise sources. For example, the contents recorded in patents such as CN202410607657.8 and CN202410776684.8 are mostly about research and improvement of other noise sources. The present invention focuses on optimizing TC noise, and realizes an inductive magnetic field sensor with improved low-frequency and high-frequency full-band noise through a specially arranged dual-channel composite multi-order modulation signal-noise separation circuit.

[0049] According to an embodiment of the present invention, based on Faraday's law of electromagnetic induction, the ideal induced voltage e(t) of the coil can be expressed as:

[0050] (1);

[0051] Where N is the number of turns of the coil, Φ is the magnetic flux through the coil, S is the area of ​​the coil and the core, and μ is app It represents the effective magnetic permeability of the magnetic core, which characterizes the degree to which the magnetic core gathers the magnetic field. B represents the magnetic induction intensity and t represents the time.

[0052] Under ideal conditions, the number of coil turns N, the area of ​​the coil and the core S, and the effective magnetic permeability μ of the core are app It does not change with time t. Therefore, the ideal induced voltage e(t) is only proportional to the rate of change of the magnetic induction intensity B, that is, the induced voltage of the coil can be expressed as:

[0053] (2);

[0054] According to an embodiment of the present invention, considering that the relative magnetic permeability of the magnetic core material changes slowly with temperature, resulting in the effective magnetic permeability of the magnetic core also changing with temperature, and considering that the effective magnetic permeability of the magnetic core has both a DC component and an AC component, the functional relationship between the coil induced voltage in the time domain and the effective magnetic permeability of the magnetic core in a non-constant temperature environment is obtained.

[0055] In most application environments, the relative permeability μ of the core material r The effective magnetic permeability μ of the magnetic core in the inductive magnetic field sensor changes slowly with temperature. app It will also change with temperature. Therefore, in a non-constant temperature environment (generally, the application environment is not constant temperature), the effective magnetic permeability μ appIt is no longer just a DC component, it also has an AC component, so the expression of the functional relationship between the sensor coil induced voltage and the effective magnetic permeability of the magnetic core is expressed as:

[0056] (3);

[0057] Indicates that considering temperature change and effective magnetic permeability μ app Coil induced voltage under DC component and AC component. μ appDC Represents the DC component of the effective permeability, μ appAC represents the AC component of the effective magnetic permeability, B DC Represents the DC component of magnetic induction intensity B, B AC Represents the AC component of magnetic induction intensity B, μ appDC and B DC Does not change over time.

[0058] According to an embodiment of the present invention, an equivalent voltage noise expression of the temperature variation noise of the magnetic permeability of the sensor core is determined according to a functional relationship, including: determining the noise term introduced by the temperature variation factor of the magnetic permeability of the core in the functional relationship between the induced voltage of the sensor coil and the effective magnetic permeability of the magnetic core; excluding the negligible terms in the noise term introduced by the temperature variation factor of the magnetic permeability of the core; and obtaining the equivalent voltage noise expression of the temperature variation noise of the magnetic permeability of the core.

[0059] It can be seen from formula (3) that the induced voltage is obtained by summing four parts, which are the four terms in the addition operation of formula (3). Except for the first term representing the original coil induced voltage, each of the following three terms can represent a noise term introduced by the temperature variation factor of the magnetic core permeability. The negligible term introduced by the temperature variation factor of the magnetic core permeability is excluded from the noise term, and the equivalent voltage noise expression of the temperature variation noise of the magnetic core permeability is obtained according to the target noise term.

[0060] Specifically, the functional relationship of the above formula (3) is a polynomial form. In addition to the first term representing the original coil induced voltage, the expression of the functional relationship between the sensor coil induced voltage and the effective magnetic permeability of the magnetic core includes three noise terms introduced by the temperature change factor of the magnetic permeability of the magnetic core, which are the second term , the third item Item 4 , considering the AC component B of the magnetic induction intensity AC Much smaller than the DC component B DC , and the DC component of the effective magnetic permeability μ appDC The change over time is zero, so the third and fourth terms in the noise term introduced by the temperature change factor of the magnetic core permeability are ignored. f represents the frequency, and the equivalent voltage noise expression of the temperature change noise of the magnetic core permeability in the frequency domain can be expressed as:

[0061] (4);

[0062] in, The equivalent voltage noise expression of TC noise is expressed in units of .

[0063] According to an embodiment of the present invention, the key influencing factors of the magnetic core are used to reduce the change of effective magnetic permeability caused by temperature change, and may include the material of the magnetic core, the geometric structure of the magnetic core, the heat treatment process of the magnetic core, etc.

[0064] According to an embodiment of the present invention, a dual-channel composite multi-order modulation signal-to-noise separation circuit includes a high-frequency channel and a low-frequency channel, which can separate noise from the high-frequency channel and the low-frequency channel, ensuring that the inductive magnetic field sensor has a lower noise voltage and noise current in the entire frequency band.

[0065] According to an embodiment of the present invention, the functional relationship between the sensor coil induced voltage and the effective magnetic permeability of the magnetic core is determined, and then the equivalent voltage noise expression of the temperature variation noise of the magnetic permeability of the sensor core is determined according to the functional relationship, and the key influencing factors of the magnetic core are determined according to the equivalent voltage noise expression of the temperature variation noise of the magnetic permeability of the sensor core. The magnetic core is improved according to the key influencing factors of the magnetic core to complete the optimization of the temperature variation noise of the magnetic permeability of the magnetic core, and a dual-channel composite multi-order modulation signal-noise separation circuit is constructed to optimize the low-band and high-band noise of the sensor. Since the magnetic core is improved according to the key influencing factors of the magnetic core, the rate at which the effective magnetic permeability of the magnetic core changes with temperature is reduced, thereby reducing the temperature variation noise of the magnetic core. At the same time, by constructing a dual-channel composite multi-order modulation signal-noise separation circuit to separate the noise of the low-frequency band and the high-frequency band, the inductive magnetic field sensor has high sensitivity and low noise characteristics under a wide bandwidth, and can be applied to a wider range of application scenarios.

[0066] According to an embodiment of the present invention, the influence of the effective magnetic permeability of the magnetic core on the coil induced voltage is analyzed through the functional relationship between the sensor coil induced voltage and the effective magnetic permeability of the magnetic core, which can be used for subsequent optimization of noise from sources such as core temperature variation noise.

[0067] Figure 2 A noise curve comparison diagram of an inductive magnetic field sensor according to an embodiment of the present invention is schematically shown.

[0068] like Figure 2 As shown in the figure, the experimental data is the equivalent voltage noise result actually measured in the shielded room. The sensor temperature change is recorded as 0.1℃ / 4000s, and the DC geomagnetic field magnetic induction intensity of the sensor in the axial direction is 198nT. By comparing the simulation data and the experimental data, it can be seen that the equivalent voltage noise of the temperature variation noise of the magnetic core permeability in the frequency domain of the sensor is more obvious in the low frequency band.

[0069] According to an embodiment of the present invention, the key influencing factor of the magnetic core is determined to be the AC component of the effective magnetic permeability that reflects the rate of change of the magnetic core magnetic permeability with temperature based on the equivalent voltage noise expression of the temperature variation noise of the sensor magnetic core magnetic permeability.

[0070] According to an embodiment of the present invention, improving the magnetic core according to the key influencing factors of the magnetic core includes: selecting a magnetic core of suitable material according to the application environment of the sensor; annealing the magnetic core in a vacuum magnetic field at a set temperature on the premise of ensuring the effective magnetic permeability of the magnetic core, so as to adjust the anisotropy of the magnetic core material and reduce internal structural defects, and reduce the rate of change of the effective magnetic permeability of the magnetic core with temperature; and optimizing the magnetic circuit of the magnetic core, including: respectively arranging flat disk-shaped flux concentrators at both ends of the magnetic core, and the centers of the flux concentrators are respectively tightly fitted to the two ends of the magnetic core, and the overall shape is a barbell.

[0071] According to an embodiment of the present invention, the effective magnetic permeability μ of the magnetic core is app With the initial magnetic permeability μ of the core material r increases with the increase of r When it increases to a certain extent, μ app It will only be related to the aspect ratio of the core and no longer depend on μ r Infinite increase.

[0072] According to an embodiment of the present invention, under the condition of ensuring that the effective magnetic permeability of the magnetic core remains unchanged, it is necessary to reduce the rate at which the magnetic core material changes with temperature through stress release, thereby reducing the temperature variation noise of the magnetic permeability of the magnetic core.

[0073] According to an embodiment of the present invention, magnetic field annealing can adjust the anisotropy of the magnetic core material and reduce internal structural defects, while the vacuum environment can protect the material from being oxidized during the annealing process. Selecting vacuum magnetic field annealing at an appropriate set temperature can adjust the easy magnetization direction of the soft magnetic material to reduce the rate of change of the magnetic core with temperature. The magnetic field intensity range in vacuum magnetic field annealing can be 0T~0.1T, and the annealing time can be 1 hour~24 hours, which can be adjusted according to actual application and is not limited here.

[0074] According to an embodiment of the present invention, taking a cylindrical magnetic core as an example, the aspect ratio m can be expressed as the following formula (5):

[0075] (5);

[0076] Among them, l core Indicates the length of the core, d core Indicates the diameter of the magnetic core.

[0077] Figure 3 The schematic diagram of a long straight cylindrical magnetic core and a coil according to an embodiment of the present invention is schematically shown.

[0078] like Figure 3 As shown, the magnetic lines of force will converge in the core, thus greatly enhancing the magnetic flux through the coil cross section. However, since the core is limited in length and not closed, the magnetic lines of force diverge at both ends of the core, thus affecting the magnetic gathering ability of the core, that is, the demagnetization effect occurs. The strength of the demagnetization effect is determined by the demagnetization factor N. B Indicates that N B It is determined by and only by the shape of the core and has nothing to do with the core material.

[0079] According to an embodiment of the present invention, for Figure 3 For a medium-length straight cylindrical core, the process of accurately estimating the demagnetization factor can be expressed as the following formula (6):

[0080] (6).

[0081] According to an embodiment of the present invention, for a cylindrical magnetic core with a more slender shape, that is, when the aspect ratio m>10, a simple estimation process of the demagnetization factor can be expressed as the following formula (7):

[0082] (7).

[0083] According to an embodiment of the present invention, under the effect of demagnetization, the relationship between the effective magnetic permeability and the initial magnetic permeability can be expressed as the following formula (8):

[0084] (8).

[0085] Figure 4 The diagram schematically shows a variation curve of effective magnetic permeability corresponding to different magnetic core aspect ratios according to an embodiment of the present invention.

[0086] like Figure 4 As shown, for the same initial magnetic permeability, the effective magnetic permeability of the magnetic cores with aspect ratios of 10, 30, 50, and 100 increases successively.

[0087] According to the embodiment of the present invention, it is difficult to increase the aspect ratio of the magnetic core indefinitely because the length of the magnetic core of the inductive magnetic field sensor is limited by the application occasion and cannot be increased indefinitely, and the cross section of the magnetic core is also limited by the process and cannot be reduced indefinitely. The reduction of the cross-sectional area will also lead to a decrease in the output voltage. At the same time, when the magnetic core is placed in the earth's magnetic field, μ app When it is too large, the magnetic core will be saturated by the earth's magnetic field, causing nonlinear saturation distortion in the sensor.

[0088] According to an embodiment of the present invention, the maximum value of the geomagnetic field is assumed to be H max , the saturation magnetic flux of the core material is B s, the tolerable error rate of the inductive magnetic field sensor is δ, then the maximum effective magnetic permeability of the magnetic core is μ appmax It can be expressed as the following formula (9):

[0089] (9);

[0090] According to an embodiment of the present invention, when the length of the magnetic core remains unchanged, a magnetic flux concentrator can be used to reduce the divergence of magnetic lines of force at the core port, thereby improving the magnetic concentration effect and enhancing the effective magnetic permeability.

[0091] For example, a pair of flat disk-shaped magnetic flux concentrators may be provided to fit closely at both ends of the magnetic core, so that more magnetic lines of force are gathered inside the magnetic core.

[0092] Figure 5 A schematic diagram of a magnetic flux concentrator according to an embodiment of the present invention is schematically shown.

[0093] like Figure 5 As shown, the centers of the magnetic flux concentrators are closely fitted to the two ends of the magnetic core, forming a barbell shape with the magnetic core.

[0094] Figure 6 The schematic diagram of the dimensions of a magnetic flux concentrator and a magnetic core according to an embodiment of the present invention is shown schematically.

[0095] like Figure 6 As shown, the diameter of the flux concentrator 610 is D core , length t core The physical representation of the magnetic flux concentrator is 611, and the physical representation of the magnetic core 620 is 621.

[0096] According to an embodiment of the present invention, for a magnetic core including a pair of magnetic flux concentrators at both ends, the aspect ratio m′ can be expressed as the following formula (10):

[0097] (10);

[0098] According to an embodiment of the present invention, the above formula (10) is substituted into the expression of the demagnetization factor to obtain the demagnetization factor N′ at this time, and the effective magnetic permeability μ at this time is app ′ can be expressed as the following formula (11).

[0099] (11).

[0100] According to the embodiment of the present invention, when the diameter of the magnetic core is much smaller than the diameter of the magnetic flux concentrator, the magnetic flux concentrator can play a more obvious effect, that is, significantly improve the effective magnetic permeability of the magnetic core. core =10mm, l core =200mm, Dcore =110mm, t core =10mm magnetic core as an example, when no magnetic flux concentrator is set, the magnetic core μ app =145, set the μ of the magnetic core after the flux concentrator app ′=634. It can be seen that the flux concentrator will greatly enhance the effective magnetic permeability of the magnetic core.

[0101] According to an embodiment of the present invention, a vacuum magnetic field annealing process is used to reduce the temperature variation noise source of the magnetic permeability of the magnetic core, and a magnetic flux concentrator is provided to change the shape of the magnetic core, thereby reducing the influence of the demagnetization effect on the effective magnetic permeability and improving the sensitivity of the inductive magnetic field sensor.

[0102] According to an embodiment of the present invention, constructing a dual-channel composite multi-order modulation signal-to-noise separation circuit to optimize the low-frequency band and high-frequency band noise of the sensor includes: constructing a low-frequency channel, modulating the low-frequency component of the magnetic field signal to a frequency band range far away from the 1 / f noise of the amplifier in the low-frequency channel, amplifying it and then demodulating it back to the low-frequency band, and filtering it to achieve signal-to-noise separation to obtain the low-frequency component of the magnetic field signal; constructing a high-frequency channel, amplifying the magnetic field signal, and filtering out the 1 / f noise of the amplifier in the high-frequency channel to obtain the high-frequency component of the magnetic field signal; constructing a high-and-low-frequency channel composite unit, fusing the low-frequency component and the high-frequency component of the magnetic field signal, and optimizing the low-frequency band and high-frequency band noise of the sensor.

[0103] According to an embodiment of the present invention, the low-frequency channel modulates and amplifies the low-frequency component of the magnetic field signal so that the low-frequency component is amplified without being affected by 1 / f noise, and then demodulates it back to the original low-frequency band. After demodulation, a filter is used to filter out high-frequency noise to achieve signal-to-noise separation and obtain a clear low-frequency component of the magnetic field signal.

[0104] According to an embodiment of the present invention, the high-frequency component is directly amplified through a high-frequency channel and the 1 / f noise of the amplifier is filtered out.

[0105] According to the embodiment of the present invention, the low-frequency component and the high-frequency component of the magnetic field signal are fused to obtain a complete magnetic field signal, thereby effectively reducing the low-frequency band and high-frequency band noise of the sensor.

[0106] Figure 7 The circuit principle diagram of a broadband noise-optimized inductive magnetic field sensor according to an embodiment of the present invention is schematically shown.

[0107] Another embodiment of the present invention, as Figure 7As shown, a wide-band noise optimized inductive magnetic field sensor is disclosed, comprising: a magnetic core, which is annealed in a vacuum magnetic field at a set temperature to adjust the anisotropy of the magnetic core material and reduce internal structural defects, thereby reducing the rate of change of the effective magnetic permeability of the magnetic core with temperature; a coil, which is wound around the periphery of the magnetic core; a dual-channel composite multi-order modulation signal-to-noise separation circuit, which is connected to the coil, comprising: a low-frequency channel, which is configured to modulate the low-frequency component of the magnetic field signal to a frequency band range far away from the 1 / f noise of the amplifier in the low-frequency channel, and then demodulate it back to the low-frequency band after amplification, and achieve signal-to-noise separation after filtering to obtain the low-frequency component of the magnetic field signal; a high-frequency channel, which is arranged in parallel with the low-frequency channel, and is configured to amplify the magnetic field signal and filter out the 1 / f noise of the amplifier in the high-frequency channel to obtain the high-frequency component of the magnetic field signal; a high-low frequency channel composite unit, which is connected to the low-frequency channel and the high-frequency channel, and is configured to fuse the low-frequency component and the high-frequency component of the magnetic field signal to achieve optimization of the low-frequency band and high-frequency band noise of the sensor.

[0108] It should be noted that the broadband noise optimized inductive magnetic field sensor part in the embodiment of the present invention corresponds to the broadband noise optimization method part of the inductive magnetic field sensor in the embodiment of the present invention. The description of the sensor part specifically refers to the noise optimization method part, which will not be repeated here.

[0109] According to an embodiment of the present invention, by annealing in a vacuum magnetic field at a set temperature, the anisotropy of the magnetic core material is adjusted and the internal structural defects are reduced, the rate of change of the effective magnetic permeability of the magnetic core with temperature is reduced, thereby reducing the temperature-dependent noise of the magnetic permeability of the sensor core. The low-frequency channel of the dual-channel composite multi-order modulation signal-to-noise separation circuit modulates the low-frequency component of the magnetic field signal to a frequency band range far away from the 1 / f noise of the amplifier in the low-frequency channel, amplifies it and then demodulates it back to the low-frequency band, and realizes signal-noise separation after filtering. The high-frequency channel amplifies the magnetic field signal and filters out the 1 / f noise of the amplifier in the high-frequency channel to obtain the high-frequency component of the magnetic field signal. The high- and low-frequency channel composite unit fuses the low-frequency component and the high-frequency component of the magnetic field signal to provide a complete magnetic field signal, reduce the noise in the high-frequency band and the low-frequency band, enhance the application range of the sensor, and make it suitable for a wider range of magnetic field measurement scenarios.

[0110] According to an embodiment of the present invention, the low-frequency channel includes a first modulation unit, a transformer, a first amplifier, a second modulation unit, and a low-pass filter circuit unit: the first modulation unit is configured to modulate the low-frequency component of the received magnetic field signal to a frequency band range far away from the 1 / f noise of the first amplifier; the transformer is configured to passively amplify the signal modulated by the first modulation unit; the first amplifier is configured to further amplify the signal amplified by the transformer; the second modulation unit is configured to demodulate the amplified magnetic field signal back to the low-frequency band, and modulate the bias and 1 / f noise of the first amplifier to the high-frequency band; the low-pass filter circuit unit is configured to filter out the high-frequency band noise Interference; the high-frequency channel includes a high-pass filter composed of a third amplifier, a capacitor, and a resistor connected in sequence, which amplifies the magnetic field signal and filters out the 1 / f noise of the amplifier in the high-frequency channel to obtain the high-frequency component of the magnetic field signal; the high-low frequency channel composite unit includes a fourth amplifier, a capacitor and a plurality of resistors, the negative input end of the amplifier is connected to a resistor, and a capacitor and a resistor are connected in parallel between the negative input end and the output end, the positive input end of the fourth amplifier is connected to the output end of the low-frequency channel and the output end of the high-frequency channel through resistors, so that the high-low frequency channel composite unit can fuse the low-frequency component and the high-frequency component of the magnetic field signal, thereby optimizing the low-frequency band and high-frequency band noise of the sensor.

[0111] According to an embodiment of the present invention, Figure 7 As shown, the coil is connected to a dual-channel composite multi-order modulation signal-to-noise separation circuit, L s Indicates the feedback coil, L pc Indicates the main coil. The first modulation unit includes a first modulator M1 and a second modulator M2. One end of the received magnetic field signal is input by IN+, and the other end is input by IN-. The IF pin of the first modulator M1 is connected to IN+, and the LO pin of the first modulator M1 is connected to the first modulation signal CW1. The IF pin of the second modulator M2 is connected to IN-, and the LO pin of the second modulator M2 is connected to the modulation signal , CW1 and The frequency and amplitude are the same, but the phases are opposite. The RF pins of the first modulator M1 and the second modulator M2 are connected to the input end of the transformer T1, and the output end of the transformer T1 is connected to the first amplifier A1. The transformer T1 can passively amplify the signal modulated by the first modulation unit, and the first amplifier A1 further amplifies the signal amplified by the transformer. The second modulation unit includes a first demodulator M3 and a second demodulator M4. The positive output end of the first amplifier A1 is connected to the RF pin of the first demodulator M3, and the negative output end of the first amplifier A1 is connected to the RF pin of the second demodulator M4. The LO pin of the first demodulator M3 is connected to the demodulation signal CW1, the IF pin of the first demodulator M3 is connected to the resistor R1, and the LO pin of the second demodulator M4 is connected to the demodulation signal , the IF pin of the second demodulator M4 is connected to the resistor R2. The low-pass filter circuit unit includes the second amplifier A2 and the resistor R1, the resistor R3, the capacitor C1, the capacitor C2, and the resistor R4, wherein the resistor R3 and the capacitor C1 are arranged in parallel between the negative input terminal and the output terminal of the second amplifier A2; the positive input terminal of the second amplifier A2 is connected to the resistor R2, and one side of the capacitor C2 and the resistor R4 is connected in parallel between the positive input terminal of the second amplifier A2 and the resistor R2, and the other side is grounded. The second modulation unit demodulates the amplified magnetic field signal back to the low frequency band, and modulates the bias and 1 / f noise of the first amplifier A1 to the high frequency band, thereby realizing the separation of signal and noise. The low-pass filter circuit unit is configured to filter out the high frequency band noise interference.

[0112] According to an embodiment of the present invention, Figure 7 As shown, the high-frequency channel includes a third amplifier A3, a capacitor C3, and a resistor R5. The third amplifier A3 amplifies the magnetic field signal. The capacitor C3 and the resistor R5 form a high-pass filter connected to the output end of the third amplifier A3 to filter out the low-frequency 1 / f noise of the third amplifier A3 and only retain the high-frequency component of the magnetic field signal. The negative (-) input end of the third amplifier A3 is connected to IN+, the positive (+) input end of the third amplifier A3 is connected to IN-, the output of the third amplifier A3 is connected to one end of the capacitor C3, the other end of the capacitor C3 is connected to the resistors R5 and R9, and the other end of the resistor R5 is grounded.

[0113] According to an embodiment of the present invention, Figure 7 As shown, the high-low frequency channel composite unit includes a fourth amplifier A4, a capacitor C4 and a plurality of resistors (resistors R6, R7, R8 and R9). Based on the principle of the addition circuit, the low frequency channel signal and the high frequency channel signal are merged to achieve broadband signal amplification. The positive input end of the fourth amplifier A4 is connected to the output end of the low frequency channel and the output end of the high frequency channel through the resistor R8, respectively. The other end of the resistor R8 is connected to the positive (+) input end of the fourth amplifier A4. One end of the resistor R9 is connected to the output end of the high frequency channel, and the other end is connected to the positive (+) input end of the fourth amplifier A4. The negative (-) input end of the amplifier is connected to the resistor R6, the resistor R7 and the capacitor C4. The output end of the amplifier A4 is connected to the circuit output signal Vout. The circuit output signal Vout is connected to the feedback coil L through the feedback resistor Rfb. s , a feedback current is introduced into the feedback coil of the magnetic field sensor to form a closed-loop feedback structure.

[0114] The broadband noise optimization method and magnetic field sensor of the inductive magnetic field sensor of the present invention are based on dual-channel composite multi-order modulation signal-noise separation technology, breaking through the 1 / f inherent noise restriction in the low-frequency band, and at the same time, by suppressing the demagnetization effect of the open-loop magnetic circuit and the magnetic circuit distribution control technology, breaking through the principle restriction of Faraday's electromagnetic induction law in a confined space, breaking through the restriction of the demagnetization coefficient and the effective magnetic permeability, and being able to take into account 10 -8 Hz~10 6 It can accurately detect the femtosecond magnetic field signals in the low-frequency band of Hz and the high-frequency band, and effectively suppress the noise in the whole frequency band.

[0115] It will be appreciated by those skilled in the art that the features described in the various embodiments of the present invention may be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, without departing from the spirit and teachings of the present invention, the features described in the various embodiments of the present invention may be combined and / or combined in various ways. All of these combinations and / or combinations fall within the scope of the present invention.

[0116] The embodiments of the present invention are described above. However, these embodiments are only for the purpose of illustration, and are not intended to limit the scope of the present invention. Although each embodiment is described above, it does not mean that the measures in each embodiment cannot be used in combination advantageously. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present invention.

Claims

1. A method for optimizing broadband noise of an inductive magnetic field sensor, characterized in that: include: Determine the functional relationship between the sensor coil induced voltage and the effective magnetic permeability of the magnetic core; Determine the equivalent voltage noise expression of the temperature variation noise of the sensor core magnetic permeability according to the functional relationship; Determine the key influencing factors of the magnetic core based on the equivalent voltage noise expression of the temperature variation noise of the magnetic permeability of the sensor core; The magnetic core is improved according to the key influencing factors of the magnetic core to optimize the temperature variation noise of the magnetic permeability of the magnetic core; as well as Construct a dual-channel composite multi-order modulation signal-to-noise separation circuit to optimize the sensor's low-frequency and high-frequency noise; Determining the equivalent voltage noise expression of the temperature variation noise of the magnetic permeability of the sensor core according to the functional relationship includes: determining the noise term introduced by the temperature variation factor of the magnetic permeability of the magnetic core in the functional relationship between the induced voltage of the sensor coil and the effective magnetic permeability of the magnetic core; excluding the negligible terms in the noise term introduced by the temperature variation factor of the magnetic permeability of the magnetic core; and obtaining the equivalent voltage noise expression of the temperature variation noise of the magnetic permeability of the magnetic core; The expression of the functional relationship between the induced voltage of the sensor coil and the effective magnetic permeability of the magnetic core is recorded as: ； Among them, the DC component and AC component of the effective magnetic permeability are μ appDC , μ appAC The DC component and AC component of the magnetic induction intensity B are B DC and B AC , N represents the number of coil turns, S represents the cross-sectional area of ​​the coil and the core, μ app Indicates the effective magnetic permeability of the core; The expression of the functional relationship between the induced voltage of the sensor coil and the effective magnetic permeability of the magnetic core includes three noise terms introduced by the temperature change factor of the magnetic permeability of the magnetic core, which are the second term , the third item Item 4 , considering the AC component B of the magnetic induction intensity AC Much smaller than the DC component B DC , and the DC component of the effective magnetic permeability μ appDC The change over time is zero, so the third and fourth terms in the noise term introduced by the temperature change factor of the magnetic core permeability are ignored. f represents the frequency, and the equivalent voltage noise of the temperature change noise of the magnetic core permeability in the frequency domain is expressed as: ； According to the equivalent voltage noise expression of the temperature variation noise of the magnetic permeability of the sensor core, the key influencing factor of the magnetic core is determined to be the AC component of the effective magnetic permeability that reflects the rate of change of the magnetic permeability of the magnetic core with temperature; Improvements to the magnetic core based on the key influencing factors of the magnetic core include: selecting a magnetic core of suitable material according to the sensor application environment; annealing the magnetic core in a vacuum magnetic field at a set temperature to adjust the anisotropy of the magnetic core material and reduce internal structural defects, thereby reducing the rate of change of the effective magnetic permeability of the magnetic core with temperature, while ensuring the effective magnetic permeability of the magnetic core; and optimizing the magnetic circuit of the magnetic core, including: providing flat disk-shaped flux concentrators at both ends of the magnetic core, with the centers of the flux concentrators tightly fitting at the two ends of the magnetic core, and forming a barbell shape as a whole.

2. The noise optimization method according to claim 1, characterized in that: Determining the functional relationship between the sensor coil induced voltage and the effective magnetic permeability of the magnetic core includes: Considering that the relative magnetic permeability of the core material changes slowly with temperature, the effective magnetic permeability of the core will also change with temperature. Considering that the effective magnetic permeability of the core has both DC and AC components, the functional relationship between the coil induced voltage in the time domain and the effective magnetic permeability of the core in a non-constant temperature environment is obtained.

3. The noise optimization method according to claim 1, characterized in that: The construction of a dual-channel composite multi-order modulation signal-to-noise separation circuit to optimize the low-frequency band and high-frequency band noise of the sensor includes: Construct a low-frequency channel, modulate the low-frequency component of the magnetic field signal to a frequency band far away from the 1 / f noise of the amplifier in the low-frequency channel, amplify it and then demodulate it back to the low-frequency band, achieve signal-noise separation after filtering, and obtain the low-frequency component of the magnetic field signal; A high-frequency channel is constructed to amplify the magnetic field signal and filter out the 1 / f noise of the amplifier in the high-frequency channel to obtain the high-frequency component of the magnetic field signal; A high- and low-frequency channel composite unit is constructed to fuse the low-frequency and high-frequency components of the magnetic field signal to optimize the low-frequency and high-frequency band noise of the sensor.

4. A broadband noise-optimized inductive magnetic field sensor, characterized in that: include: The magnetic core is annealed in a vacuum magnetic field at a set temperature to adjust the anisotropy of the magnetic core material and reduce internal structural defects, thereby reducing the rate of change of the effective magnetic permeability of the magnetic core with temperature; A coil, which is wound around the periphery of the magnetic core; A dual-channel composite multi-order modulation signal-to-noise separation circuit is connected to the coil, comprising: The low-frequency channel is configured to modulate the low-frequency component of the magnetic field signal to a frequency band far away from the 1 / f noise of the amplifier in the low-frequency channel, amplify it and then demodulate it back to the low-frequency band, and perform signal-noise separation after filtering to obtain the low-frequency component of the magnetic field signal; The high-frequency channel is arranged in parallel with the low-frequency channel and is configured to amplify the magnetic field signal and filter out the 1 / f noise of the amplifier in the high-frequency channel to obtain a high-frequency component of the magnetic field signal; The high-low frequency channel composite unit is connected to the low frequency channel and the high frequency channel, and is configured to fuse the low frequency component and the high frequency component of the magnetic field signal to optimize the low frequency band and high frequency band noise of the sensor.

5. The inductive magnetic field sensor according to claim 4, characterized in that: The low-frequency channel includes a first modulation unit, a transformer, a first amplifier, a second modulation unit, and a low-pass filter circuit unit: The first modulation unit is configured to modulate the low-frequency component of the received magnetic field signal to a frequency band range far away from the 1 / f noise of the first amplifier; The transformer is configured to passively amplify the signal modulated by the first modulation unit; The first amplifier is configured to further amplify the signal amplified by the transformer; The second modulation unit is configured to demodulate the amplified magnetic field signal back to the low frequency band, and modulate the bias and 1 / f noise of the first amplifier to the high frequency band; The low-pass filter circuit unit is configured to filter out high-frequency noise interference; The high-frequency channel includes a high-pass filter composed of a third amplifier, a capacitor, and a resistor connected in sequence, which amplifies the magnetic field signal and filters out the 1 / f noise of the amplifier in the high-frequency channel to obtain a high-frequency component of the magnetic field signal; The high-low frequency channel composite unit includes a fourth amplifier, a capacitor and a plurality of resistors. The negative input terminal of the amplifier is connected to a resistor, and a capacitor and a resistor are connected in parallel between the negative input terminal and the output terminal. The positive input terminal of the fourth amplifier is connected to the output terminal of the low frequency channel and the output terminal of the high frequency channel through resistors, respectively, so that the high-low frequency channel composite unit can fuse the low frequency component and the high frequency component of the magnetic field signal, thereby optimizing the low frequency band and high frequency band noise of the sensor.

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