A differential magnetic gradient emission system based on the principle of magnetic field superposition

Abstract

This invention discloses a differential magnetic gradient transmission system based on the principle of magnetic field superposition, relating to the field of magnetic communication. The differential magnetic gradient transmission system includes: a magnetic conductive sheet and at least two differential coils; the differential coils are connected in parallel; the magnetic conductive sheet is inserted into each differential coil, ensuring continuity between all differential coils; after current is passed through the differential coils, the transmitting magnetic fields excited by each differential coil are superimposed to obtain magnetic field information of the superimposed magnetic field; the magnetic field information includes: magnetic field strength information and magnetic field gradient information. This invention can slow down the spatial attenuation rate of the transmitting magnetic field in the medium, improve the magnetic field energy utilization rate, and enhance the anti-interference capability of the transmitting magnetic field.

Description

Technical Field

[0001] This invention relates to the field of magnetic communication, and in particular to a differential magnetic gradient transmission system based on the principle of magnetic field superposition. Background Technology

[0002] Due to the rapid decay of magnetic field energy in space, the design of magnetic field transmission is crucial in magnetic detection, magnetic energy transmission, and magnetic communication. Existing magnetic field transmission technologies suffer from several drawbacks: small amplitude at the endpoint of the transmitted magnetic field, rapid spatial decay of the magnetic field, and low magnetic energy propagation efficiency. Furthermore, traditional point magnetic field transmission structures based on single-field sources are highly susceptible to interference from background magnetic fields.

[0003] In the fields of magnetic detection, magnetic energy transmission, or magnetic communication, most conventional methods of magnetic field excitation and emission involve applying an alternating voltage of a certain amplitude and frequency to the ends of a single coil or passing an alternating current of a certain amplitude and frequency through a single coil. Essentially, these methods all involve passing an alternating current through the coil circuit. According to the basic conclusions of the classical Maxwell's equations, this method of magnetic field emission is characterized by its simplicity and convenience; the alternating current in the coil can directly excite an outwardly emitted alternating magnetic field or electromagnetic wave. However, this simplicity and directness also leads to some unavoidable drawbacks: First, because a simple single-point magnetic field decays inversely proportionally to the cube of the distance in space, the magnetic field emitted by this method decays rapidly, resulting in a short transmission distance. Second, since the magnetic field is a passive, rotating field, this method cannot effectively focus the magnetic field, causing it to disperse outwards in large quantities, resulting in low magnetic field energy utilization and a small magnetic field value at a certain point in space. Third, because this method only transmits magnetic field strength information, it is easily affected by background magnetic field interference. Fourth, because this method only transmits one magnetic field signal, the amount of information loaded in magnetic communication applications is small, the signal anti-interference ability is weak, and the information error rate is high. Summary of the Invention

[0004] Based on this, embodiments of the present invention provide a differential magnetic gradient transmission system based on the principle of magnetic field superposition, which transmits magnetic field strength information and magnetic field gradient information to slow down the spatial decay rate of the transmitted magnetic field in the medium, improve the magnetic field energy utilization rate, and improve the anti-interference capability of the transmitted magnetic field.

[0005] To achieve the above objectives, embodiments of the present invention provide the following solutions:

[0006] A differential magnetic gradient emission system based on the principle of magnetic field superposition includes: a magnetic conductive sheet and at least two differential coils; the differential coils are connected in parallel; the magnetic conductive sheet is inserted into each of the differential coils, so that all the differential coils are connected in series.

[0007] After current is passed through the differential coils, the transmitting magnetic fields generated by each differential coil are superimposed to obtain magnetic field information of the superimposed magnetic field; the magnetic field information includes: magnetic field strength information and magnetic field gradient information.

[0008] Optionally, the differential coil includes: a helical coil and a plurality of magnetic rods; the plurality of magnetic rods are distributed circumferentially along the inner ring side of the helical coil.

[0009] Optionally, all differential coils have the same design parameters; these design parameters include: geometric parameters, circuit parameters, wire material, and number of coil turns.

[0010] The design parameters of the differential coil were determined based on Maxwell's equations.

[0011] Optionally, the spacing between the differential coils is determined by a test to measure the intensity of the transmitting magnetic field based on the principle of magnetic field superposition.

[0012] Optionally, there are two differential coils; the corresponding terminals of the two differential coils are connected in parallel.

[0013] The method for determining the spacing between the two differential coils specifically includes:

[0014] An alternating current signal with a set amplitude and a set frequency is introduced into the two differential coils using a signal generator and a power amplifier;

[0015] A fluxgate is set at a predetermined distance on the coaxial line of the two differential coils;

[0016] The two differential coils on the magnetic conductive sheet are gradually moved in opposite directions at a constant speed, and the magnetic field strength information collected by the fluxgate during the movement of the differential coils is recorded.

[0017] During the movement of the differential coil, the position of the differential coil is determined as the relative position of the differential coil when the magnetic field strength information collected by the fluxgate remains unchanged.

[0018] The spacing between the two differential coils is determined based on their relative positions.

[0019] Optionally, there are three differential coils; the terminals of the three differential coils with the same name are connected in parallel.

[0020] The method for determining the spacing between the three differential coils specifically includes:

[0021] An alternating current signal with a set amplitude and a set frequency is introduced into the three differential coils using a signal generator and a power amplifier;

[0022] A fluxgate is set at a predetermined distance on the coaxial line of the three differential coils;

[0023] The differential coil at the middle position on the fixed magnetic sheet is gradually moved at a constant speed in opposite directions by the two differential coils at both ends of the magnetic sheet, and the magnetic field strength information collected by the fluxgate during the movement of the three differential coils is recorded.

[0024] During the movement of the differential coils at both ends, the relative positions of the differential coils at both ends are determined when the magnetic field strength information collected by the fluxgate remains unchanged.

[0025] The spacing between the three differential coils is determined based on the relative positions of the differential coils at both ends and the differential coil in the middle position.

[0026] Optionally, the differential coil further includes: a coil frame;

[0027] The coil frame is used to fix the helical coil and the plurality of magnetic rods.

[0028] Optionally, the geometric parameters include the radius and thickness of the differential coil; the circuit parameters include resistance, inductance, and capacitance.

[0029] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0030] The differential magnetic gradient transmission system based on the principle of magnetic field superposition proposed in this invention includes: a magnetic sheet and at least two differential coils connected in parallel. The magnetic sheet is inserted into each differential coil, making all differential coils interconnected. After current is passed through the differential coils, the transmission magnetic fields excited by each differential coil are superimposed to obtain the magnetic field strength information and magnetic field gradient information of the superimposed magnetic field. This invention achieves high-efficiency transmission of magnetic fields in the fields of magnetic energy transmission, magnetic detection, and magnetic communication. The transmitted magnetic field information includes magnetic field strength information and magnetic field spatial gradient information. The amplitude of the transmitted magnetic field is stable and large, the spatial attenuation rate of the transmitted magnetic field in the medium is slow, and the magnetic field energy utilization rate is high. This effectively increases the gradient information of the transmitted magnetic field and effectively suppresses the interference of the background magnetic field on the transmitted magnetic field, thus improving the anti-interference capability of the transmitted magnetic field. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1This is a schematic diagram of a differential magnetic field gradient emission dual-coil structure provided in an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of a differential magnetic field gradient emission three-coil structure provided in an embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of the differential coil structure provided in an embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram of the experiment and results of measuring the transmitting magnetic field strength of the differential magnetic field gradient transmitting three-coil structure provided in an embodiment of the present invention;

[0036] Figure 5 This is a schematic diagram of the experiment and results of measuring the transmission magnetic field gradient of the differential magnetic field gradient emission three-coil structure provided in an embodiment of the present invention. Detailed Implementation

[0037] The technical solutions of the present invention will now be described with reference to the accompanying drawings in the embodiments of the present invention.

[0038] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] The differential magnetic gradient emission system based on the principle of magnetic field superposition provided in this embodiment includes: a magnetic sheet and at least two differential coils; the differential coils are connected in parallel; the magnetic sheet is inserted into each of the differential coils, so that all the differential coils are connected.

[0040] After current is passed through the differential coils, the transmitting magnetic fields generated by each differential coil are superimposed to obtain magnetic field information of the superimposed magnetic field; the magnetic field information includes: magnetic field strength information and magnetic field gradient information. Figure 1 This illustrates a differential magnetic gradient emission system based on the principle of magnetic field superposition, consisting of two differential coils, also known as a differential magnetic field gradient emission dual-coil structure. Figure 2 This diagram illustrates a differential magnetic gradient emission system based on the principle of magnetic field superposition, consisting of three differential coils, also known as a differential magnetic field gradient emission three-coil structure. Here, 1 represents a differential coil, and 2 represents a magnetic sheet.

[0041] The magnetic sheet 2 can further concentrate the transmitting magnetic field near the central axis of the spatially differential coil, and increase the energy utilization rate of the transmitting magnetic field between the differential coils of the differential magnetic gradient transmitting system.

[0042] In one example, see Figure 3 The differential coil 1 includes: a spiral coil 3, a coil frame 5, and multiple magnetic rods 4.

[0043] The spiral coil 3 is a conductive spiral coil with a certain current-carrying capacity, which generates a transmitting magnetic field after current is applied. Multiple magnetic rods 4 are distributed circumferentially along the inner ring side of the spiral coil 3 to concentrate the transmitting magnetic field as close as possible to the edge of the spatially differential coil. In this embodiment, the magnetic rods 4 are cylindrical, and multiple cylindrical magnetic rods are evenly and symmetrically distributed around the inner ring side of the spiral coil perpendicular to the conductor direction. The coil frame 5 is used to support and fix the spiral coil 3 and the multiple magnetic rods 4. To avoid the coil frame 5 disturbing the strength and gradient distribution of the transmitting magnetic field, a material with good tensile strength and non-magnetic insulation is generally selected as the coil frame. This differential coil is a magnetically concentrated structure.

[0044] In one example, all differential coils 1 have the same design parameters; these parameters include geometric parameters, circuit parameters, wire material, wire diameter, and number of turns. The geometric parameters include the radius and thickness of the differential coil; the circuit parameters include resistance, inductance, and capacitance.

[0045] The design parameters of the differential coil are determined based on Maxwell's equations. Specifically:

[0046] The selection of differential coil wire and the winding of differential coils are mainly determined based on the required transmission distance and intensity of the emitted magnetic field. The current carrying capacity of the wire, the wire diameter, and the number of turns of the differential coil can all be derived from the classical Maxwell's equations.

[0047] In the fields of magnetic detection and magnetic communication, the medium for transmitting magnetic fields is generally a linear isotropic medium such as air or pure water, which has no free charges and conduction currents. The parameters ρ0 = 0, j0 = 0, and D = ε0ε in the classical Maxwell's equations can be assumed to be... r E, B = μ0μ r H, then the differential form of Maxwell's equations becomes:

[0048]

[0049]

[0050]

[0051]

[0052] Where ρ0 is the free charge, j0 is the free current density, D is the electric displacement vector, E is the electric field intensity vector, ε0 is the vacuum permittivity, and ε r It is the relative permittivity, B is the magnetic flux density vector, H is the magnetic field density vector, μ0 is the free permeability, and μ r t is the relative permeability, and t is time.

[0053] By substituting the boundary conditions—namely, the required transmission distance and intensity of the emitted magnetic field—the required current (represented as E in the equation) and the magnitude of the emitted magnetic field generated at the location of the differential coil (represented as B in the equation) can be solved. Based on this, wires with different current-carrying capacities can be selected, such as superconducting tape, silver wire, and the most commonly used copper wire. Then, the number of turns in the differential coil can be determined according to the current-carrying capacity of the wire.

[0054] like Figure 1 and Figure 2 The diagram shows two differential magnetic gradient emission structures: a dual-coil structure and a three-coil structure. Both structures have a certain spacing between the differential coils. Since the magnetic field is a curl field, without a magnetic guide plate, some magnetic field lines would leak outwards from the gaps between the differential coils, resulting in inefficient utilization of this magnetic energy. By connecting the differential coils of the differential magnetic gradient emission system with a magnetic guide plate (which can be cylindrical), the magnetic field lines between the differential coils will concentrate in the cylindrical area enclosed by the guide plate. This ensures that the magnetic field is emitted only from both ends of the differential magnetic gradient emission system, preventing any leakage or dissipation within the system and maximizing the utilization of magnetic energy.

[0055] In one example, there are two differential coils; the corresponding terminals of the two differential coils are connected in parallel. Specifically, the two differential coils are coaxially fixed using a non-magnetic insulating material, and the two differential coils are connected using a spatial differential method, that is, the two differential coils are connected in parallel according to their corresponding terminals of inductive coupling. The spacing between the differential coils is determined by an experimental measurement of the emitted magnetic field strength based on the principle of magnetic field superposition.

[0056] The method for determining the spacing between the two differential coils specifically includes:

[0057] An alternating current signal with a set amplitude and frequency is introduced into the two differential coils using a signal generator and a power amplifier; a fluxgate is placed at a set distance on the coaxial line of the two differential coils; the two differential coils on the magnetic sheet are gradually moved in opposite directions at a constant speed, and the magnetic field strength information collected by the fluxgate during the movement of the differential coils is recorded; the position of the differential coils when the magnetic field strength information collected by the fluxgate remains unchanged during the movement of the differential coils is determined as the relative position of the differential coils; the distance between the two differential coils is determined based on the relative position of the two differential coils.

[0058] In one example, there are three differential coils; the corresponding terminals of the three differential coils are connected in parallel. The three differential coils are coaxially fixed using a non-magnetic insulating material, and the three differential coils are connected in a spatial differential manner, that is, two differential coils are connected in parallel according to their corresponding terminals of inductive coupling. The spacing between the differential coils is determined by an experimental measurement of the emitted magnetic field strength based on the principle of magnetic field superposition.

[0059] The method for determining the spacing between the three differential coils specifically includes:

[0060] An alternating current signal with a set amplitude and frequency is fed into the three differential coils using a signal generator and a power amplifier. A fluxgate is placed at a set distance on the coaxial line of the three differential coils. The differential coil in the middle position on the magnetic sheet is fixed, and the two differential coils at both ends of the magnetic sheet are gradually moved in opposite directions at a constant speed. The magnetic field strength information collected by the fluxgate during the movement of the three differential coils is recorded. When the magnetic field strength information collected by the fluxgate remains unchanged during the movement of the differential coils at both ends, the position of the differential coils at both ends is determined as the relative position of the differential coils at both ends. The spacing between the three differential coils is determined based on the relative position of the differential coils at both ends and the differential coil in the middle position.

[0061] In summary, when there are an odd number of differential coils (more than 3), first fix the position of the middle differential coil. Then, move the two differential coils from their positions near the middle coil towards both ends to determine their positions. Repeat this process, moving the next pair of differential coils from their positions near the innermost coil towards both ends to determine their positions, until the relative positions of all differential coils are determined. When there are an even number of differential coils (more than 2), first slowly move the two differential coils from their closest positions towards both ends to determine their relative positions. Then, repeat this process, moving the next pair of differential coils from their positions near the innermost coil towards both ends to determine their positions, until the relative positions of all differential coils are determined.

[0062] The embodiments of the present invention have the following advantages:

[0063] (1) It not only transmits magnetic field strength information, but also magnetic field gradient information. The magnetic field strength information contains unstable background magnetic field noise, while the magnetic field gradient information can automatically subtract the background noise. Therefore, it can slow down the magnetic field attenuation speed and transmit over a long distance.

[0064] (2) Set up a magnetic sheet so that the magnetic field lines between the differential coils are concentrated in the area enclosed by the magnetic sheet, so that the magnetic field is emitted from both ends of the differential magnetic gradient emission system to the maximum extent, and no part of the magnetic field is lost in the system, thereby maximizing the utilization of magnetic field energy.

[0065] (3) Set at least two differential coils. The transmitting magnetic fields generated by multiple differential coils are superimposed to obtain the magnetic field strength information and magnetic field gradient information of the superimposed magnetic field. This can reduce the interference of the background magnetic field and transmit multiple magnetic field signals, which can enhance the anti-interference capability of the signal and reduce the information error rate.

[0066] The process of determining the relative position of the coils will be explained in further detail below.

[0067] Once the differential coils are fabricated, their relative positions can be determined through experiments measuring the intensity and gradient of the transmitting magnetic field, based on the principle of magnetic field superposition. For example... Figure 1 and Figure 2 The differential magnetic field gradient emission dual-coil structure and differential magnetic field gradient emission three-coil structure are shown.

[0068] The transmitting magnetic field is also a vector field, and the transmission medium of the transmitting magnetic field generally does not have directional free charges flowing, i.e., J = 0. Therefore, in classical Maxwell's electromagnetic theory, the two fundamental equations describing the transmitting magnetic field are:

[0069]

[0070]

[0071] According to the above two equations, the transmitting magnetic field is a source-free, rotational field, and the curl of the magnetic field B depends on the first derivative of the excitation source electric field E with respect to time. When there are multiple excitation source electric fields, the electric field intensity at the field point satisfies the principle of vector superposition. Therefore, the magnetic induction intensity of the magnetic field generated by the electric field at the field point in the magnetic field transmitting region also conforms to the principle of vector superposition. Thus, when using multiple differential coils to transmit the magnetic field, the vector sum of the transmitting magnetic fields should be maximized. Therefore, multiple differential coils should be placed coaxially, and then the relative positions of each coil on the coaxial line are determined according to the principle of magnetic field superposition.

[0072] like Figure 4 Part (a) shows a schematic diagram of the experiment for measuring the transmission magnetic field strength of the differential magnetic field gradient transmission three-coil structure. Based on the experimental results, the relative positions of the three differential coils can be analyzed to maximize the transmission magnetic field strength. The specific implementation steps are as follows.

[0073] First, the three spiral coils with the determined magnetic focusing structure are connected in a differential manner and placed adjacent to each other in the middle of the magnetic sheet. At the same time, the three coils can move horizontally in the axial direction relative to the magnetic sheet.

[0074] Second, a signal generator is used to pass an alternating current signal of a certain amplitude and frequency into the three differential spiral coils through a power amplifier.

[0075] Third, a magnetic sensor for measuring the magnetic field strength is placed at a certain distance along the coaxial line of the three differential coils.

[0076] Fourth, Figure 4 In part (a), the two differential coils at both ends of the magnetic sheet move slowly outward at a constant speed to ensure that the distance the coil moves relative to the magnetic sheet in a unit time (1 second) is not greater than the coil thickness in a quasi-stationary state (i.e., the relative displacement is close to zero in a unit time). The magnetic field strength signal collected by the fluxgate during the movement of the coil is continuously recorded.

[0077] like Figure 4 Part (b) shows the experimental results of measuring the transmitting magnetic field strength of the differential magnetic field gradient transmitting three-coil structure. According to the experimental results, the horizontal axis corresponds to the position of one differential coil on the magnetic sheet, and the other differential coil is symmetrical about the stationary differential coil in the middle. The vertical axis corresponds to the magnetic field strength at each position of the differential coil on the magnetic sheet. By correlating the magnitude of the magnetic field strength with the position of the differential coil on the magnetic sheet, the relative positions of the differential coils in the differential magnetic field gradient transmitting three-coil structure can be determined. Therefore, by fixing the three differential coils with their determined relative positions on the magnetic sheet, a novel differential magnetic gradient transmitting three-coil system based on the principle of magnetic field superposition can be obtained.

[0078] like Figure 5 Part (a) shows a schematic diagram of the experiment for measuring the transmission magnetic field gradient of the differential magnetic field gradient transmission three-coil structure. The experimental results can be used to verify the stability of the magnetic field gradient value of the differential magnetic field gradient transmission three-coil structure, thereby achieving the purpose of suppressing background magnetic field interference and increasing the amount of loaded information. The specific implementation steps are as follows.

[0079] First, fix the differential magnetic field gradient transmitting three-coil structure at the magnetic field transmitting end, and then use a signal generator to pass an alternating current signal of a certain amplitude and frequency into the differential magnetic field gradient transmitting three coils through a power amplifier.

[0080] Second, place a fluxgate to measure the magnetic field strength at a certain distance on the central axis of the three differential magnetic field gradient transmitting coils. After the fluxgate reading stabilizes, record the value of the magnetic field strength at this point and use it as the starting point for calibrating the magnetic field gradient.

[0081] Third, the fluxgate is continuously moved at at least eleven equal intervals along the central axis away from the direction of the differential magnetic field gradient emission three coils, while the magnetic field strength value measured by the fluxgate at each interval is recorded.

[0082] Fourth, subtracting the magnetic field strength value at the starting point from the magnetic field strength value at the second spacing point and then dividing by twice the spacing length yields a value that approximates the magnetic field gradient value at the first spacing point. Similarly, subtracting the magnetic field strength value at the first spacing point from the magnetic field strength value at the third spacing point and then dividing by twice the spacing length yields a value that approximates the magnetic field gradient value at the second spacing point. This process can be repeated to obtain at least ten magnetic field gradient values ​​along the central axis of the three differential magnetic field gradient transmitting coils.

[0083] like Figure 5 Part (b) shows the experimental results of measuring the transmission magnetic field gradient of the differential magnetic field gradient transmitting three-coil structure. According to the experimental results, the horizontal axis corresponds to the field point coordinates of the transmission magnetic field of the differential magnetic field gradient transmitting three-coil system, and the vertical axis represents the magnetic field gradient value at the corresponding field point. By observing the magnitude of the magnetic field gradient value corresponding to the field point, it can be seen that the transmission magnetic field gradient value of the differential magnetic field gradient transmitting three-coil structure system is stable, and its attenuation rate is significantly less than that of the magnetic field strength value. Furthermore, the magnetic field gradient value is not affected by the background magnetic field, which is beneficial for loading more information.

[0084] Thus, a novel differential magnetic gradient transmitting three-coil system based on the principle of magnetic field superposition can be obtained.

[0085] The construction of the differential magnetic gradient emission dual-coil system based on the principle of magnetic field superposition is similar to the construction method of the differential magnetic gradient emission three-coil system based on the principle of magnetic field superposition described above.

[0086] The specific implementation steps for measuring the transmitting magnetic field strength of the differential magnetic field gradient transmitting dual-coil structure are as follows.

[0087] First, two spiral coils with predetermined magnetic structures are connected differentially and placed adjacent to each other in the middle of the magnetic sheet. At the same time, the two coils can move horizontally in the axial direction relative to the magnetic sheet.

[0088] Second, a signal generator is used to pass an alternating current signal of a certain amplitude and frequency into the two differential spiral coils through a power amplifier.

[0089] Third, a fluxgate for measuring the magnetic field strength is placed at a certain distance on the coaxial line of the two differential coils.

[0090] Fourth, slowly move the two differential coils on the magnetic sheet in opposite directions at a constant speed, ensuring that the coils are nearly stationary relative to the magnetic sheet during the movement. Continuously record the magnetic field strength signal collected by the fluxgate during the coil movement.

[0091] Based on this, the relative positions of each differential coil in the differential magnetic field gradient emission dual-coil structure can be analyzed.

[0092] The specific implementation steps for measuring the emission magnetic field gradient of the differential magnetic field gradient emission dual-coil structure are as follows.

[0093] First, fix the differential magnetic field gradient transmitting dual coil structure at the magnetic field transmitting end, and then use a signal generator to pass an alternating current signal of a certain amplitude and frequency into the differential magnetic field gradient transmitting dual coil through a power amplifier.

[0094] Second, place a fluxgate to measure the magnetic field strength at a certain distance on the coaxial line of the differential magnetic field gradient transmitting double coil. After the fluxgate reading stabilizes, record the value of the magnetic field strength at this point and use it as the starting point for calibrating the magnetic field gradient.

[0095] Third, the fluxgate is continuously moved along the central axis away from the direction of the differential magnetic field gradient emission double coil at at least eleven equal intervals, and the magnetic field strength value measured by the fluxgate at each interval is recorded.

[0096] Fourth, subtracting the magnetic field strength value at the starting point from the magnetic field strength value at the second spacing point and then dividing by twice the spacing length yields a value that approximates the magnetic field gradient value at the first spacing point. Similarly, subtracting the magnetic field strength value at the first spacing point from the magnetic field strength value at the third spacing point and then dividing by twice the spacing length yields a value that approximates the magnetic field gradient value at the second spacing point. This process can be repeated to obtain at least ten magnetic field gradient values ​​along the central axis of the differential magnetic field gradient transmitting dual coils.

[0097] Based on this, the stability of the transmitting magnetic field gradient of the differential magnetic field gradient transmitting dual-coil structure can be analyzed.

[0098] By following the specific steps described above, a novel differential magnetic gradient transmitting dual-coil system based on the principle of magnetic field superposition can be obtained.

[0099] In summary, the magnetic focusing structure of the differential coils significantly increases the stability of the transmitted magnetic field strength and the utilization rate of the transmitted magnetic field energy. The transmitted magnetic field strength measurement experiment based on the principle of magnetic field superposition determined the relative positions of each differential coil in the novel differential magnetic gradient transmission system structure. Then, the stability of the transmitted magnetic field gradient and the ability to suppress background magnetic field interference were obtained based on the transmitted magnetic field gradient measurement experiment. Finally, a differential magnetic gradient transmission system structure based on the principle of magnetic field superposition was constructed.

[0100] Furthermore, experiments were conducted to measure the intensity of the transmitting magnetic field and the gradient of the transmitting magnetic field based on the principle of magnetic field superposition. By analyzing the experimental results, the relative positions of the differential coils in the structure of the novel differential magnetic gradient transmitting system based on the principle of magnetic field superposition were determined intuitively and effectively. Effective information on the gradient of the transmitting magnetic field and the system's ability to suppress background magnetic field interference were also obtained.

[0101] A differential magnetic field gradient transmitting dual-coil structure based on the principle of magnetic field superposition was constructed, as shown in the schematic diagram. Figure 1 As shown, a differential magnetic field gradient transmitting three-coil structure based on the principle of magnetic field superposition was constructed, as illustrated in the schematic diagram. Figure 2 As shown.

[0102] This embodiment presents experiments on measuring the intensity and gradient of the transmitted magnetic field based on the principle of magnetic field superposition. It also incorporates a magnetic focusing structure using a magnetic rod and a magnetic sheet to design a differential magnetic gradient transmission system based on the principle of magnetic field superposition. This differential magnetic gradient transmission system enables the transmission of magnetic fields in magnetic detection and communication. The transmitted magnetic field information includes both magnetic field intensity and gradient information. The amplitude of the transmitted magnetic field is stable and relatively large, with a slow attenuation rate and high energy utilization. This effectively increases the amount of information in the transmitted magnetic field gradient and effectively suppresses interference from the background magnetic field.

[0103] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0104] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the system and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A differential magnetic gradient transmission system based on the principle of magnetic field superposition, characterized in that include: A magnetic sheet and at least two differential coils; the differential coils are connected in parallel; the magnetic sheet is inserted into each of the differential coils, so that all the differential coils are connected in series. After current is passed through the differential coils, the transmitting magnetic fields generated by each differential coil are superimposed to obtain magnetic field information of the superimposed magnetic field; the magnetic field information includes: magnetic field strength information and magnetic field gradient information; The corresponding terminals of the two differential coils are connected in parallel; The method for determining the spacing between the two differential coils specifically includes: An alternating current signal with a set amplitude and a set frequency is introduced into the two differential coils using a signal generator and a power amplifier; A fluxgate is set at a predetermined distance on the coaxial line of the two differential coils; The two differential coils on the magnetic conductive sheet are gradually moved in opposite directions at a constant speed, and the magnetic field strength information collected by the fluxgate during the movement of the differential coils is recorded. During the movement of the differential coil, the position of the differential coil is determined as the relative position of the differential coil when the magnetic field strength information collected by the fluxgate remains unchanged. The spacing between the two differential coils is determined based on their relative positions.

2. The differential magnetic gradient transmission system based on the principle of magnetic field superposition according to claim 1, characterized in that, The differential coil includes a helical coil and a plurality of magnetic rods; the plurality of magnetic rods are distributed circumferentially along the inner ring side of the helical coil.

3. The differential magnetic gradient emission system based on the principle of magnetic field superposition according to claim 1, characterized in that, All differential coils have the same design parameters; these design parameters include: geometric parameters, circuit parameters, wire material, and number of coil turns. The design parameters of the differential coil were determined based on Maxwell's equations.

4. The differential magnetic gradient emission system based on the principle of magnetic field superposition according to claim 1, characterized in that, The spacing between the differential coils was determined by a test to measure the intensity of the transmitting magnetic field based on the principle of magnetic field superposition.

5. The differential magnetic gradient emission system based on the principle of magnetic field superposition according to claim 4, characterized in that, There are three differential coils; the corresponding terminals of the three differential coils are connected in parallel. The method for determining the spacing between the three differential coils specifically includes: An alternating current signal with a set amplitude and a set frequency is introduced into the three differential coils using a signal generator and a power amplifier; A fluxgate is set at a predetermined distance on the coaxial line of the three differential coils; The differential coil at the middle position on the fixed magnetic sheet is gradually moved at a constant speed in opposite directions by the two differential coils at both ends of the magnetic sheet, and the magnetic field strength information collected by the fluxgate during the movement of the three differential coils is recorded. During the movement of the differential coils at both ends, the relative positions of the differential coils at both ends are determined when the magnetic field strength information collected by the fluxgate remains unchanged. The spacing between the three differential coils is determined based on the relative positions of the differential coils at both ends and the differential coil in the middle position.

6. The differential magnetic gradient emission system based on the principle of magnetic field superposition according to claim 2, characterized in that, The differential coil further includes: a coil frame; The coil frame is used to fix the helical coil and the plurality of magnetic rods.

7. The differential magnetic gradient emission system based on the principle of magnetic field superposition according to claim 3, characterized in that, The geometric parameters include the radius and thickness of the differential coil; the circuit parameters include resistance, inductance, and capacitance.

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