Electromagnetic field propagation analysis method, device, electronic equipment and storage medium

Abstract

The present invention provides an electromagnetic field propagation analysis method, device, electronic device and storage medium, belonging to the field of electromagnetic field propagation technology, the method comprising: obtaining the refractive index and polarization parameter of the low-frequency ordinary wave of the ionospheric plasma for a preset extremely low frequency band; calculating the surface impedance of the multi-layer anisotropic medium of the ionosphere based on the refractive index and polarization parameter of the low-frequency ordinary wave of the ionosphere plasma, and obtaining the ionosphere surface impedance matrix; for each point on the propagation path, based on the ionosphere surface impedance matrix and the horizontal current source radiation characteristic data, by analyzing the horizontal electromagnetic field excited by the horizontal antenna, the field intensity data of each point on the propagation path is determined. By analyzing the inhomogeneous anisotropic characteristics of the ionosphere and combining the radiation capability that the transmitting antenna can actually achieve, the calculation accuracy of the electromagnetic field propagation project can be effectively improved.

Description

Technical Field

[0001] The present invention belongs to the field of electromagnetic field propagation, and more specifically, relates to an electromagnetic field propagation analysis method, device, electronic equipment and storage medium. Background Art

[0002] Extremely low frequency (ELF) electromagnetic waves (frequency below 30Hz) are located at the lowest frequency band of electromagnetic waves. The wavelength of radio waves in this frequency band (more than 10,000 kilometers) is comparable to the circumference of the earth. They propagate in the range of hundreds to thousands of kilometers in the form of standing waves. The amplitude changes with the distance, and there will be peaks and troughs, and the ratio of peaks to troughs will be different at different frequencies.

[0003] When ELF electromagnetic waves propagate in the Earth-ionosphere cavity, they are greatly affected by the environmental electrical parameters (especially the ionosphere electrical parameters) on the propagation path. How to accurately calculate the extremely low frequency electromagnetic field propagation process is a technical problem that needs to be solved in this field. Summary of the invention

[0004] In view of the problems existing in the prior art, the embodiments of the present invention provide an electromagnetic field propagation analysis method, device, electronic device and storage medium.

[0005] In a first aspect, the present invention provides an electromagnetic field propagation analysis method, comprising:

[0006] For the preset extremely low frequency ELF band, obtain the refractive index and polarization parameters of the ionospheric plasma low-frequency ordinary wave;

[0007] Based on the refractive index and polarization parameter of the ionospheric plasma low-frequency ordinary wave, the surface impedance of the multi-layer anisotropic medium of the ionosphere is calculated to obtain the ionospheric surface impedance matrix;

[0008] For each point on the propagation path, based on the ionospheric surface impedance matrix and the horizontal current source radiation characteristic data, the field strength data of each point on the propagation path is determined by analyzing the horizontal electromagnetic field excited by the horizontal antenna;

[0009] The horizontal current source radiation characteristic data is used to characterize the radiation capability of the horizontal antenna.

[0010] Optionally, according to an electromagnetic field propagation analysis method provided by the present invention, the surface impedance of the multi-layer anisotropic medium of the ionosphere is calculated based on the refractive index and polarization parameter of the low-frequency ordinary wave of the ionosphere plasma to obtain the ionosphere surface impedance matrix, including:

[0011] Based on the electron concentration data and collision frequency data of the ionosphere, the ionosphere is decomposed into a plurality of anisotropic layers along a vertical direction, and any anisotropic layer has uniform electron concentration and collision frequency;

[0012] Based on the refractive index and polarization parameters of the ionospheric plasma low-frequency ordinary wave, the electromagnetic field components corresponding to each anisotropic layer are determined in the form of wave field superposition propagating upward and downward;

[0013] Based on the electromagnetic field components and boundary conditions corresponding to each anisotropic layer, layer-by-layer recursion is performed to obtain the ionospheric surface impedance matrix.

[0014] Optionally, according to an electromagnetic field propagation analysis method provided by the present invention, the determining of the electromagnetic field components corresponding to each anisotropic layer based on the refractive index and polarization parameter of the ionospheric plasma low-frequency ordinary wave in the form of wave field superposition propagating upward and downward includes:

[0015] The electromagnetic field component corresponding to the anisotropic layer is determined by the following formula;

[0016]

[0017]

[0018] in,

[0019] represents the electric field component corresponding to the anisotropic layer, represents the magnetic field component corresponding to the anisotropic layer, z represents the height in the vertical direction, i represents the imaginary unit, E1 represents the electric field component of the wave propagating upward in the layer, and E2 represents the electric field component of the wave propagating downward in the layer;

[0020] k1=k0n1 represents the wave number of the wave propagating upward in each layer, k2=k0n2 represents the wave number of the wave propagating downward in each layer, n1 and n2 represent the refractive index of the wave propagating upward and downward in each layer, k0 represents the wave number of the wave propagating in vacuum, P1 and P2 represent the polarization parameters of the wave propagating upward and downward in each layer.

[0021] Optionally, a method for analyzing electromagnetic field propagation provided by the present invention further includes:

[0022] The boundary conditions corresponding to each anisotropic layer are determined by the following formula;

[0023]

[0024] in, represents the surface impedance matrix corresponding to the anisotropic layer, and N represents the number of the anisotropic layer.

[0025] Optionally, according to an electromagnetic field propagation analysis method provided by the present invention, the horizontal current source radiation characteristic data includes the current amplitude, the length of the current line and the conductivity of the crust below the source point, and the field intensity data includes the magnetic field component excited by the horizontal antenna and the electric field component excited by the horizontal antenna;

[0026] The method of determining the field strength data of each point on the propagation path by analyzing the horizontal electromagnetic field excited by the horizontal antenna based on the ionospheric surface impedance matrix and the horizontal current source radiation characteristic data for each point on the propagation path includes:

[0027] determining a horizontal current source moment based on the current amplitude, the length of the current line, and the conductivity of the earth's crust below the source point;

[0028] For a target point, based on the horizontal current source moment and the target distance, the magnetic field component excited by the horizontal antenna at the target point is calculated, the target point is any point on the propagation path, and the target distance is the distance between the target point and the horizontal antenna;

[0029] The electric field component excited by the horizontal antenna at the target point is calculated based on the ionospheric surface impedance matrix and the magnetic field component excited by the horizontal antenna at the target point.

[0030] Optionally, according to an electromagnetic field propagation analysis method provided by the present invention, determining the horizontal current source moment based on the current amplitude, the length of the current line and the conductivity of the crust below the source point includes:

[0031] The horizontal current source moment is determined by the following formula;

[0032]

[0033]

[0034] in,

[0035] M1 represents the horizontal current source moment in the east-west direction, M2 represents the horizontal current source moment in the north-south direction, I1 represents the current amplitude in the east-west direction, I2 represents the current amplitude in the north-south direction, L1 represents the length of the current line in the east-west direction, L2 represents the length of the current line in the north-south direction, σ represents the conductivity of the crust below the source point, and f0 represents the operating frequency.

[0036] Optionally, according to an electromagnetic field propagation analysis method provided by the present invention, the calculation of the electric field component excited by the horizontal antenna at the target point based on the ionospheric surface impedance matrix and the magnetic field component excited by the horizontal antenna at the target point includes:

[0037] The magnetic field component excited by the horizontal antenna at the target point is calculated by the following magnetic field component formula:

[0038] When the horizontal antenna points to the east-west direction, the magnetic field component formula is as follows:

[0039]

[0040]

[0041] Wherein, H1 represents the magnetic field component when the horizontal antenna points to the east-west direction, H1 φ Represents the horizontal magnetic field component in the φ direction in spherical coordinates, H1 θ represents the horizontal magnetic field component in the θ direction under spherical coordinates, r represents the propagation distance, k0 represents the propagation wave number of the wave in vacuum, D S represents the average matrix component, a represents the radius of the earth, A φθ A represents the component generated by the current source in the θ direction in the φ direction. φφ represents the component generated by the current source in the φ direction, and φ1 represents the angle between the direction to the receiver and the antenna;

[0042] When the horizontal antenna points to the north-south direction, the magnetic field component formula is as follows:

[0043]

[0044]

[0045] Wherein, H2 represents the magnetic field component when the horizontal antenna points to the north-south direction, H2 φ represents the horizontal magnetic field component in the φ direction in spherical coordinates, H2 θ represents the horizontal magnetic field component in the θ direction under spherical coordinates, and φ2 represents the angle between the receiver and the antenna direction.

[0046] In a second aspect, the present invention further provides an electromagnetic field propagation analysis device, comprising:

[0047] The ionospheric parameter acquisition module is used to obtain the refractive index and polarization parameters of the ionospheric plasma low-frequency ordinary wave for the preset extremely low frequency ELF band;

[0048] A surface impedance matrix acquisition module is used to calculate the surface impedance of the multi-layer anisotropic medium of the ionosphere based on the refractive index and polarization parameter of the low-frequency ordinary wave of the ionosphere plasma, and obtain the ionosphere surface impedance matrix;

[0049] An electromagnetic field propagation calculation module is used to determine the field strength data of each point on the propagation path by analyzing the horizontal electromagnetic field excited by the horizontal antenna based on the ionospheric surface impedance matrix and the horizontal current source radiation characteristic data for each point on the propagation path;

[0050] The horizontal current source radiation characteristic data is used to characterize the radiation capability of the horizontal antenna.

[0051] In a third aspect, the present invention provides an electronic device comprising: at least one memory for storing programs; and at least one processor for executing the programs stored in the memory, wherein when the programs stored in the memory are executed, the processor is used to execute the method described in the first aspect or any possible implementation of the first aspect.

[0052] In a fourth aspect, the present invention provides a computer-readable storage medium storing a computer program. When the computer program runs on a processor, the processor executes the method described in the first aspect or any possible implementation of the first aspect.

[0053] It can be understood that the beneficial effects of the second to fourth aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0054] In general, the above technical scheme conceived by the present invention has the following beneficial effects compared with the prior art: by decomposing the ionosphere into multiple layers of anisotropic media and obtaining the corresponding ionosphere surface impedance matrix, the ionosphere surface impedance matrix can reflect the polarization characteristics of electromagnetic waves propagating in space, and the matrix parameters can be used to realize the conversion between the components of the electric field and the magnetic field, and then combined with the horizontal current source radiation characteristic data, the horizontal electromagnetic field excited by the horizontal antenna can be calculated under the premise of considering the actual radiation capability of the transmitting antenna, and the field strength data of each point on the propagation path can be determined. By analyzing the inhomogeneous anisotropic characteristics of the ionosphere and combining the actual radiation capability of the transmitting antenna, the calculation accuracy of the electromagnetic field propagation engineering can be effectively improved, and accurate calculation of the extremely low frequency electromagnetic field propagation process can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0056] Figure 1 It is a schematic diagram of the flow of the electromagnetic field propagation analysis method provided by the present invention;

[0057] Figure 2 It is a schematic diagram of the calculation process of extremely low frequency electromagnetic field propagation characteristics provided by the present invention;

[0058] Figure 3 It is a structural schematic diagram of the electromagnetic field propagation analysis device provided by the present invention. DETAILED DESCRIPTION

[0059] In order to facilitate a clearer understanding of the embodiments of the present invention, some relevant background knowledge is first introduced as follows.

[0060] On the one hand, in the prior art, the existing studies on the propagation characteristics of ELF electromagnetic waves in the Earth-ionosphere cavity are all carried out under the condition that the ionosphere is regarded as a uniform isotropic medium. There are certain errors in the calculation according to the equivalent reflection height of the ionosphere and the conductivity under the uniform medium. Under actual propagation conditions, the ionosphere is a gradient medium, and its electron concentration and collision frequency change with altitude according to a certain law. Since the ELF frequency is very low, the radio waves can penetrate and penetrate into the ionosphere to reach the F2 layer, so the cross-sectional structure of the entire ionosphere has a certain influence on the characteristic parameters of ELF radio wave propagation (phase velocity and attenuation rate, etc.). Therefore, in actual engineering calculations, the ionosphere cannot be regarded as a uniform sharp-boundary medium, but should be regarded as a gradient layered inhomogeneous medium.

[0061] On the other hand, in the prior art, existing studies on the propagation characteristics of ELF electromagnetic waves in the Earth-ionosphere cavity are all conducted after idealizing the transmitting antenna as a superposition of the electromagnetic field vectors generated by a unit dipole source. The radiation capability that can be achieved by the actual transmitting antenna is not considered in combination with the ground conductivity and antenna impedance characteristics, which deviates from the actual engineering implementation capability.

[0062] In order to overcome the above-mentioned defects, the present invention provides an electromagnetic field propagation analysis method, device, electronic device and storage medium, which can effectively improve the calculation accuracy of electromagnetic field propagation engineering by analyzing the uneven anisotropic characteristics of the ionosphere and combining the actual radiation capacity that the transmitting antenna can achieve.

[0063] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0064] The term "and / or" in this article is a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The symbol " / " in this article indicates that the associated objects are in an or relationship, for example, A / B means A or B.

[0065] The terms "first" and "second" in the specification and claims herein are used to distinguish different objects rather than to describe a specific order of the objects. For example, a first response message and a second response message are used to distinguish different response messages rather than to describe a specific order of the response messages.

[0066] In the embodiments of the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0067] In the description of the embodiments of the present invention, unless otherwise specified, “multiple” means two or more than two. For example, multiple processing units means two or more processing units, etc.; multiple elements means two or more elements, etc.

[0068] Next, the technical solution provided in the embodiments of the present invention is introduced.

[0069] Figure 1 Schematic diagram of the electromagnetic field propagation analysis method provided by the present invention. Figure 1 As shown, the execution subject of the electromagnetic field propagation analysis method can be an electronic device, such as a server, etc. The method includes:

[0070] Step S101, for a preset extremely low frequency ELF band, obtaining the refractive index and polarization parameters of the ionospheric plasma low frequency ordinary wave.

[0071] Specifically, the ionosphere exhibits strong anisotropy in the ELF band, and the ELF electromagnetic waves propagating in the ionosphere can be decomposed into two characteristic waves: ordinary waves (i.e., ionospheric plasma low-frequency ordinary waves) and extraordinary waves. For a preset extremely low frequency ELF band (e.g., a band with a frequency below 30 Hz), the corresponding ionospheric plasma low-frequency ordinary waves can be determined, and then the refractive index and polarization parameters of the ionospheric plasma low-frequency ordinary waves can be obtained.

[0072] Step S102, based on the refractive index and polarization parameters of the ionospheric plasma low-frequency ordinary wave, the surface impedance of the multi-layer anisotropic medium of the ionosphere is calculated to obtain the ionospheric surface impedance matrix.

[0073] It can be understood that the core part of the ionospheric parameter calculation is the calculation of the non-uniform anisotropic ionospheric surface impedance matrix. The non-uniform anisotropic ionospheric surface impedance matrix is ​​the basic physical quantity for solving different types of ground excitation problems in the Earth-ionosphere waveguide, which acts on the upper wall of the Earth-ionosphere waveguide. The ionospheric surface impedance matrix reflects the polarization characteristics of electromagnetic waves propagating in space, and the matrix parameters can be used to realize the conversion between the components of the electric field and the magnetic field.

[0074] Step S103, for each point on the propagation path, based on the ionospheric surface impedance matrix and the horizontal current source radiation characteristic data, by analyzing the horizontal electromagnetic field excited by the horizontal antenna, the field strength data of each point on the propagation path is determined;

[0075] Among them, the horizontal current source radiation characteristic data is used to characterize the radiation capability of the horizontal antenna.

[0076] Specifically, by decomposing the ionosphere into multiple layers of anisotropic media and obtaining the corresponding ionospheric surface impedance matrix, the ionospheric surface impedance matrix can reflect the polarization characteristics of electromagnetic waves propagating in space. The matrix parameters can be used to realize the conversion between the components of the electric field and the magnetic field. Then, combined with the horizontal current source radiation characteristic data, the horizontal electromagnetic field excited by the horizontal antenna can be calculated under the premise of considering the actual radiation capability of the transmitting antenna, and the field strength data of each point on the propagation path can be determined.

[0077] It is understandable that the prior art regards the ionosphere as a uniform sharp-boundary medium and idealizes the transmitting antenna as a superposition of electromagnetic field vectors generated by a unit dipole source, resulting in low calculation accuracy of electromagnetic field propagation engineering. In contrast, the present invention can effectively improve the calculation accuracy of electromagnetic field propagation engineering by analyzing the inhomogeneous anisotropic characteristics of the ionosphere and combining the actual radiation capacity of the transmitting antenna, and realize accurate calculation of the extremely low frequency electromagnetic field propagation process.

[0078] Optionally, for a preset extremely low frequency ELF band, obtaining the refractive index and polarization parameters of the ionospheric plasma low frequency ordinary wave includes:

[0079] Based on the preset ELF band and environmental parameter model, the collision frequency data of the ionosphere and the plasma cyclotron frequency data are obtained;

[0080] Determine the ionospheric dielectric constant tensor based on the ionospheric collision frequency data and plasma cyclotron frequency data;

[0081] Based on the ionospheric dielectric constant tensor, the refractive index and polarization parameters of the low-frequency ordinary wave of the ionospheric plasma are obtained.

[0082] Optionally, according to an electromagnetic field propagation analysis method provided by the present invention, based on the refractive index and polarization parameters of the low-frequency ordinary wave of the ionospheric plasma, the surface impedance of the multi-layer anisotropic medium of the ionosphere is calculated to obtain the ionospheric surface impedance matrix, including:

[0083] Based on the electron concentration data and collision frequency data of the ionosphere, the ionosphere is decomposed into multiple anisotropic layers along the vertical direction, and any anisotropic layer has uniform electron concentration and collision frequency;

[0084] Based on the refractive index and polarization parameters of the low-frequency ordinary wave of the ionospheric plasma, the electromagnetic field components corresponding to each anisotropic layer are determined according to the superposition form of the wave fields propagating upward and downward;

[0085] Based on the electromagnetic field components and boundary conditions corresponding to each anisotropic layer, layer-by-layer recursion is performed to obtain the ionospheric surface impedance matrix.

[0086] Specifically, the present invention adopts a repeated calculation method of surface impedance: the matrix components of the lower boundary of the layer with a thickness of d can be expressed by the known matrix components of the upper boundary. Compared with the numerical integration method, the advantages of this method are: the obtained solution is more stable, the calculation time is less, and the required computer storage space is smaller. First, based on the electron concentration and the collision frequency, the ionosphere is decomposed into several layers of uniform anisotropic layers, and the electric field and magnetic field components in each layer are written in the form of a superposition of wave fields propagating upward and downward. Then, the boundary conditions of each layer are used to establish an identity, and the surface impedance of the multi-layer anisotropic medium is finally obtained by recursion layer by layer.

[0087] For example, assuming that the ionosphere is a planar layered model, in the Cartesian coordinate system, the magnetic field is located in the (Y, Z) plane, the Z axis is vertically upward, and the angle between the Z axis and the geomagnetic field is θ. The impedance boundary condition is given at the bottom of the ionosphere (z = h, h represents the height of the bottom of the ionosphere), and the electromagnetic field of the electromagnetic wave propagating vertically along the Z axis in the ionosphere at the boundary is expressed as follows:

[0088] E x =Z xx H x +Z xy H y , E y =Z yx H x +Z yy H y (1);

[0089] Here, Z xx , Z xy , Z yx and Z yy are the components of the anisotropic ionospheric surface impedance matrix in the Cartesian coordinate system, Z xx represents the component of the ionospheric surface impedance matrix in the x direction, Z xy represents the component of the ionospheric surface impedance matrix in the xy direction, Z yx represents the component of the ionospheric surface impedance matrix in the yx direction, Z yy represents the component of the ionospheric surface impedance matrix in the yy direction, E x and E y represents the electric field components in the x and y directions, H x and H y It represents the magnetic field components in the x and y directions. Considering the inhomogeneity of the ionosphere in the vertical direction, the ionosphere is divided into several uniform anisotropic layers. is a matrix of a planar multi-layered medium.

[0090] Using the repeated calculation method of surface impedance: the matrix components of the lower boundary of the layer with thickness d ("lower boundary" refers to the lower boundary of each layer of medium) can be expressed by the known matrix components of the upper boundary. Next, consider the surface impedance matrix of a series of uniform anisotropic layers and write the relationship between the electromagnetic field components in the matrix form of the (XY) plane:

[0091]

[0092]

[0093] in, represents the electric field component corresponding to the anisotropic layer, represents the magnetic field component corresponding to the anisotropic layer, z represents the height in the vertical direction, i represents the imaginary unit, E1 represents the electric field component of the wave propagating upward in the layer, and E2 represents the electric field component of the wave propagating downward in the layer;

[0094] k1=k0n1 represents the wave number of the wave propagating upward in each layer, k2=k0n2 represents the wave number of the wave propagating downward in each layer, n1 and n2 represent the refractive index of the wave propagating upward and downward in each layer, k0 represents the wave number of the wave propagating in vacuum, P1 and P2 represent the polarization parameters of the wave propagating upward and downward in each layer, P 1,2 Indicates P1 or P2.

[0095] Assume that the plane electromagnetic wave propagates along the positive and negative directions of the z-axis (for the top layer, only the positive direction of the z-axis), and assume that there are N+1 layers in total, the top layer is numbered "0", and the bottom layer (the layer farthest from the electromagnetic wave source) is numbered "-N". In the "-N"-"-(N-1)" layer (that is, between the "-N" layer and the "-(N-1)" layer), we can get:

[0096]

[0097] Among them, the surface impedance matrix of the two layers of anisotropic medium is The thickness of the layer is equal to d).

[0098]

[0099] here Repeating this process for the "-(N-2)" layer, using the upper boundary of this layer ("upper boundary" refers to the upper boundary of each layer of the medium), the relationship between the tangential components is as follows:

[0100]

[0101] The surface impedance matrix expression of three-layer anisotropic medium is:

[0102] By performing this process for all layers, the surface impedance of the multilayer anisotropic medium can be determined.

[0103] Optionally, according to an electromagnetic field propagation analysis method provided by the present invention, the horizontal current source radiation characteristic data includes the current amplitude, the length of the current line and the conductivity of the crust below the source point, and the field intensity data includes the magnetic field component excited by the horizontal antenna and the electric field component excited by the horizontal antenna;

[0104] For each point on the propagation path, based on the ionospheric surface impedance matrix and the horizontal current source radiation characteristic data, the field strength data of each point on the propagation path is determined by analyzing the horizontal electromagnetic field excited by the horizontal antenna, including:

[0105] Determine the source moment of horizontal current based on the current amplitude, the length of the current line, and the conductivity of the crust below the source point;

[0106] For the target point, based on the horizontal current source moment and the target distance, the magnetic field component excited by the horizontal antenna at the target point is calculated. The target point is any point on the propagation path, and the target distance is the distance between the target point and the horizontal antenna.

[0107] Based on the ionospheric surface impedance matrix and the magnetic field component excited by the horizontal antenna at the target point, the electric field component excited by the horizontal antenna at the target point is calculated.

[0108] For example, for a non-uniform horizontal spherical waveguide, the two-dimensional telegraph equation method can be used to obtain a calculation method for the horizontal component of the horizontal dipole magnetic field. Under the conditions of impedance approximation and k0r<<1 (the product of the electromagnetic wave number and the distance is much less than 1), when the horizontal antenna points in the east-west direction, the magnetic field component formula is as follows:

[0109]

[0110]

[0111] Where H1 represents the magnetic field component when the horizontal antenna points to the east-west direction, H1 φ Represents the horizontal magnetic field component in the φ direction in spherical coordinates, H1 θ represents the horizontal magnetic field component in the θ direction under spherical coordinates, r represents the propagation distance, k0 represents the propagation wave number of the wave in vacuum, D S represents the average matrix component, a represents the radius of the earth, A φθ A represents the component generated by the current source in the θ direction in the φ direction. φφ Represents the component generated by the current source in the φ direction, φ1=-φ(1)+π / 2, φ1 represents the angle between the receiver and the antenna direction, M1 represents the polar moment of the horizontal current source in the east-west direction, that is, the product of the effective height of the antenna and the current.

[0112] When the horizontal antenna points in the north-south direction, the magnetic field component formula is as follows:

[0113]

[0114]

[0115] Where H2 represents the magnetic field component when the horizontal antenna points to the north-south direction, H2 φ represents the horizontal magnetic field component in the φ direction in spherical coordinates, H2 θ represents the horizontal magnetic field component in the θ direction under spherical coordinates, φ2=-φ(1), φ2 represents the angle between the receiver and the antenna direction, and M2 represents the polar moment of the horizontal current source in the north-south direction.

[0116] The calculation formulas for M1 and M2 are:

[0117]

[0118]

[0119] in,

[0120] M1 represents the horizontal current source moment in the east-west direction, M2 represents the horizontal current source moment in the north-south direction, I1 represents the current amplitude in the east-west direction, I2 represents the current amplitude in the north-south direction, L1 represents the length of the current line in the east-west direction, L2 represents the length of the current line in the north-south direction, σ represents the conductivity of the crust below the source point (the source point is the location of the horizontal antenna), and f0 represents the operating frequency.

[0121]

[0122] The following symbols are used in formula (9):

[0123]

[0124] in, D S are the components of the mean matrix.

[0125] are all matrices of source and receiver points The subscript (1,2) indicates that the value is 1 or 2. When the value of (1,2) is 1, it means that the antenna points to the east-west direction. When the value of (1,2) is 2, it means that the antenna points to the north-south direction.

[0126] For example, assuming that the transmission power is 500 kW, the data listed in Table 1 for the electrical parameters of the transmitting antenna (i.e., the above-mentioned horizontal antenna) used for field strength calculation are actual measured data. In order to avoid the influence of the Schumann resonance frequency on communication, the electrical parameters of the transmitting antenna at the noise valley frequency for channel calculation under several typical frequency points can be obtained by interpolation method (see Table 2).

[0127] Table 1 Transmitting antenna electrical parameters (500kW)

[0128]

[0129]

[0130] Table 2 Calculation of the transmitting antenna current at the frequency point (500kW)

[0131] Frequency (Hz) East-West Antenna Current (A) North-South antenna current (A) 5 193 248.5 10 187.5 242.5 17 180.3 234.3 23 174.5 227.5 29.5 168 221

[0132] Figure 2is a schematic diagram of the calculation process of the extremely low frequency electromagnetic field propagation characteristics provided by the present invention, such as Figure 2 The specific calculation process is described as follows:

[0133] (1) Select the transmitting antenna type as "horizontal";

[0134] (2) Select the coordinate type as "spherical coordinates";

[0135] (3) Enter the date and time to be calculated;

[0136] (4) Load the solar activity index F10.7;

[0137] (5) Save the environmental parameter model in the form of a text file locally, including: ionosphere model (International Ionosphere Standard Model IRI-2007), atmosphere model (Atmosphere Standard Model MSIS-E-00) and geomagnetic field model (IGRF model), and save the F10.7 index to the working directory IRI-2007 and MSIS-E-00;

[0138] (6) Call the environmental parameter model according to the input date and time, and compile and generate an EXE file;

[0139] (7) Input the receiving point location information, combined with the transmitting antenna longitude and latitude and time information, to obtain the trajectory parameters, including: the great-circle distance between the transmitting and receiving points, the angle between the trajectory and the meridian plane, and the angle between the geomagnetic field and the vertical line;

[0140] (8) Input the operating frequency and combine it with the environmental parameter model to obtain the height of the lower edge of the ionosphere, collision frequency, and plasma cyclotron frequency;

[0141] (9) The ionospheric dielectric constant tensor can be obtained based on the collision frequency and plasma cyclotron frequency;

[0142] (10) The refractive index and polarization parameters of the low-frequency ordinary wave of the ionospheric plasma can be obtained based on the ionospheric dielectric constant tensor;

[0143] (11) The ionospheric surface impedance matrix can be obtained based on the refractive index and polarization parameters of the ionospheric plasma low-frequency ordinary wave;

[0144] (12) The horizontal electromagnetic field excited by the horizontal antenna can be obtained based on the ionospheric surface impedance matrix and the radiation characteristics of the horizontal current source;

[0145] (13) Calculate the magnetic field component and electric field component at each point on the path and establish the law of change of field strength and distance.

[0146] According to the above calculation steps, three sets of theoretical calculated values ​​of field strength under different transmission powers are given. See Table 3 to Table 5. The transmitting antenna is located in central China. The calculation of field strength components requires structural data of the ionosphere and neutral atmosphere and data on the direction of the earth's magnetic field strength. The International Reference Ionosphere (IRI) model provides data on the number of different types of ions at each altitude, the Mass Spectrometer and Incoherent Scatter (MSIS) model provides neutral atmosphere data, and the International Geomagnetic Reference Field (IGRF) model provides earth magnetic field data.

[0147] Table 3 Theoretical calculation values ​​of field strength at 500kW transmission power and 706.7km distance

[0148]

[0149] Table 4 Theoretical calculation values ​​of field strength at 200kW transmission power and 1467.6km distance

[0150]

[0151]

[0152] Table 5 Theoretical calculation values ​​of field strength at 2000kW transmission power and 2044.4km distance

[0153]

[0154]

[0155] In order to verify the calculation accuracy of this method, a set of comparison results between the measured values ​​and the theoretical calculated values ​​at the 6000km measurement point is given, as shown in Table 6. According to the statistical results, the average absolute error of the five frequency points is 1.1dB. It should be noted that this error is not only caused by the theoretical calculation method and model, but also includes the measurement error.

[0156] Table 6 Comparison of theoretical and measured field strength at 500kW and 6000km

[0157]

[0158] It can be understood that the present invention analyzes the ionospheric parameter model used for calculating the ordinary wave refractive index according to the propagation characteristics of extremely low frequency electromagnetic waves, and provides an ionospheric plasma surface impedance matrix; then derives the extremely low frequency field strength calculation formula of the horizontal electric dipole under different earth-ionosphere waveguide models; finally, combined with the analysis results of the radiation parameters of the horizontal current source, an engineering calculation model for the propagation characteristics of the extremely low frequency electromagnetic field is established.

[0159] The electromagnetic field propagation analysis device provided by the present invention is described below. The electromagnetic field propagation analysis device described below and the electromagnetic field propagation analysis method described above can be referenced to each other.

[0160] Figure 3 is a schematic diagram of the structure of the electromagnetic field propagation analysis device provided by the present invention, such as Figure 3 As shown, the device includes: an ionospheric parameter acquisition module 10, a surface impedance matrix acquisition module 20 and an electromagnetic field propagation calculation module 30, wherein:

[0161] The ionospheric parameter acquisition module 10 is used to obtain the refractive index and polarization parameters of the ionospheric plasma low-frequency ordinary wave for a preset extremely low frequency ELF band;

[0162] The surface impedance matrix acquisition module 20 is used to calculate the surface impedance of the multi-layer anisotropic medium of the ionosphere based on the refractive index and polarization parameters of the low-frequency ordinary wave of the ionosphere plasma, and obtain the ionosphere surface impedance matrix;

[0163] The electromagnetic field propagation calculation module 30 is used to determine the field strength data of each point on the propagation path by analyzing the horizontal electromagnetic field excited by the horizontal antenna based on the ionospheric surface impedance matrix and the horizontal current source radiation characteristic data for each point on the propagation path;

[0164] Among them, the horizontal current source radiation characteristic data is used to characterize the radiation capability of the horizontal antenna.

[0165] It should be understood that the above-mentioned device is used to execute the method in the above-mentioned embodiment. The implementation principle and technical effect of the corresponding program module in the device are similar to those described in the above-mentioned method. The working process of the device can refer to the corresponding process in the above-mentioned method, which will not be repeated here.

[0166] Based on the method in the above embodiment, an embodiment of the present invention provides an electronic device. The device may include: at least one memory for storing programs and at least one processor for executing the programs stored in the memory. When the program stored in the memory is executed, the processor is used to execute the method described in the above embodiment.

[0167] Based on the method in the above embodiment, an embodiment of the present invention provides a computer-readable storage medium, which stores a computer program. When the computer program runs on a processor, the processor executes the method in the above embodiment.

[0168] It is understandable that the processor in the embodiment of the present invention may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, transistor logic devices, hardware components or any combination thereof. The general-purpose processor may be a microprocessor or any conventional processor.

[0169] The method steps in the embodiments of the present invention can be implemented by hardware or by a processor executing software instructions. The software instructions can be composed of corresponding software modules, and the software modules can be stored in random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, mobile hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can be located in an ASIC.

[0170] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented by software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiment of the present invention is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted through the computer-readable storage medium. The computer instructions can be transmitted from a website site, computer, server or data center to another website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more available media integrated. The available medium can be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid state disk (SSD)), etc.

[0171] It should be understood that the various numerical numbers involved in the embodiments of the present invention are only used for the convenience of description and are not used to limit the scope of the embodiments of the present invention.

[0172] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for analyzing electromagnetic field propagation, characterized in that: include: For the preset extremely low frequency ELF band, obtain the refractive index and polarization parameters of the ionospheric plasma low-frequency ordinary wave; Based on the refractive index and polarization parameter of the ionospheric plasma low-frequency ordinary wave, the surface impedance of the multi-layer anisotropic medium of the ionosphere is calculated to obtain the ionospheric surface impedance matrix; For each point on the propagation path, based on the ionospheric surface impedance matrix and the horizontal current source radiation characteristic data, the field strength data of each point on the propagation path is determined by analyzing the horizontal electromagnetic field excited by the horizontal antenna; Wherein, the horizontal current source radiation characteristic data is used to characterize the radiation capability of the horizontal antenna; The radiation characteristic data of the horizontal current source include the current amplitude, the length of the current line and the conductivity of the crust below the source point, and the field intensity data include the magnetic field component excited by the horizontal antenna and the electric field component excited by the horizontal antenna; The method of determining the field strength data of each point on the propagation path by analyzing the horizontal electromagnetic field excited by the horizontal antenna based on the ionospheric surface impedance matrix and the horizontal current source radiation characteristic data for each point on the propagation path includes: determining a horizontal current source moment based on the current amplitude, the length of the current line, and the conductivity of the earth's crust below the source point; For a target point, based on the horizontal current source moment and the target distance, the magnetic field component excited by the horizontal antenna at the target point is calculated, the target point is any point on the propagation path, and the target distance is the distance between the target point and the horizontal antenna; The electric field component excited by the horizontal antenna at the target point is calculated based on the ionospheric surface impedance matrix and the magnetic field component excited by the horizontal antenna at the target point.

2. The electromagnetic field propagation analysis method according to claim 1, characterized in that: The method of calculating the surface impedance of the multi-layer anisotropic medium of the ionosphere based on the refractive index and polarization parameter of the ionosphere plasma low-frequency ordinary wave to obtain the ionosphere surface impedance matrix includes: Based on the electron concentration data and collision frequency data of the ionosphere, the ionosphere is decomposed into a plurality of anisotropic layers along a vertical direction, and any anisotropic layer has uniform electron concentration and collision frequency; Based on the refractive index and polarization parameters of the ionospheric plasma low-frequency ordinary wave, the electromagnetic field components corresponding to each anisotropic layer are determined in the form of wave field superposition propagating upward and downward; Based on the electromagnetic field components and boundary conditions corresponding to each anisotropic layer, layer-by-layer recursion is performed to obtain the ionospheric surface impedance matrix.

3. The electromagnetic field propagation analysis method according to claim 2, characterized in that: The determining of the electromagnetic field components corresponding to each anisotropic layer based on the refractive index and polarization parameters of the ionospheric plasma low-frequency ordinary wave in the form of wave field superposition propagating upward and downward includes: The electromagnetic field component corresponding to the anisotropic layer is determined by the following formula; ； ； in, , , ; represents the electric field component corresponding to the anisotropic layer, represents the magnetic field component corresponding to the anisotropic layer, Indicates the height in the vertical direction. represents the imaginary unit, represents the electric field component of the wave propagating upward in the layer, represents the electric field component of the wave propagating downward in the layer; represents the number of waves propagating upward in each layer, represents the number of waves propagating downward in each layer, and represents the refractive index of the wave propagating upward and downward in each layer, represents the wave number of the wave propagating in vacuum, and The polarization parameters representing the wave propagation upward and downward in each layer.

4. The electromagnetic field propagation analysis method according to claim 2, characterized in that: Also includes: The boundary conditions corresponding to each anisotropic layer are determined by the following formula; ； in, represents the surface impedance matrix corresponding to the anisotropic layer, represents the number of the anisotropic layer, represents the electric field component corresponding to the anisotropic layer, Represents the magnetic field component corresponding to the anisotropic layer.

5. The electromagnetic field propagation analysis method according to claim 1, characterized in that: The determining of the horizontal current source moment based on the current amplitude, the length of the current line and the conductivity of the crust below the source point comprises: The horizontal current source moment is determined by the following formula; ； ； in, ; represents the horizontal current source moment in the east-west direction, represents the horizontal current source moment in the north-south direction, represents the current magnitude in the east-west direction, represents the current amplitude in the north-south direction, represents the length of the current line in the east-west direction, represents the length of the current line in the north-south direction, represents the conductivity of the crust beneath the source point, Indicates the operating frequency.

6. The electromagnetic field propagation analysis method according to claim 5, characterized in that: The calculating the electric field component excited by the horizontal antenna at the target point based on the ionospheric surface impedance matrix and the magnetic field component excited by the horizontal antenna at the target point includes: The magnetic field component excited by the horizontal antenna at the target point is calculated by the following magnetic field component formula: When the horizontal antenna points to the east-west direction, the magnetic field component formula is as follows: ； ； in, represents the magnetic field component when the horizontal antenna points in the east-west direction, In spherical coordinates The horizontal magnetic field component in the direction of In spherical coordinates The horizontal magnetic field component in the direction of represents the propagation distance, represents the wave number of the wave propagating in vacuum, represents the average matrix component, represents the radius of the Earth, express The current source in the direction The component generated by the direction, express The current source in the direction The component generated by the direction, express The current source in the direction The component generated by the direction, express The current source in the direction The component generated by the direction, Represents the angle between the receiver and the antenna direction; When the horizontal antenna points to the north-south direction, the magnetic field component formula is as follows: ； ； in, represents the magnetic field component when the horizontal antenna points in the north-south direction, In spherical coordinates The horizontal magnetic field component in the direction of In spherical coordinates The horizontal magnetic field component in the direction of Represents the angle between the receiver and the antenna direction.

7. An electromagnetic field propagation analysis device, characterized in that: include: The ionospheric parameter acquisition module is used to obtain the refractive index and polarization parameters of the ionospheric plasma low-frequency ordinary wave for the preset extremely low frequency ELF band; A surface impedance matrix acquisition module is used to calculate the surface impedance of the multi-layer anisotropic medium of the ionosphere based on the refractive index and polarization parameter of the ionosphere plasma low-frequency ordinary wave, and obtain the ionosphere surface impedance matrix; An electromagnetic field propagation calculation module is used to determine the field strength data of each point on the propagation path by analyzing the horizontal electromagnetic field excited by the horizontal antenna based on the ionospheric surface impedance matrix and the horizontal current source radiation characteristic data for each point on the propagation path; Wherein, the horizontal current source radiation characteristic data is used to characterize the radiation capability of the horizontal antenna; The radiation characteristic data of the horizontal current source include the current amplitude, the length of the current line and the conductivity of the crust below the source point, and the field intensity data include the magnetic field component excited by the horizontal antenna and the electric field component excited by the horizontal antenna; The method of determining the field strength data of each point on the propagation path by analyzing the horizontal electromagnetic field excited by the horizontal antenna based on the ionospheric surface impedance matrix and the horizontal current source radiation characteristic data for each point on the propagation path includes: determining a horizontal current source moment based on the current amplitude, the length of the current line, and the conductivity of the earth's crust below the source point; For a target point, based on the horizontal current source moment and the target distance, the magnetic field component excited by the horizontal antenna at the target point is calculated, the target point is any point on the propagation path, and the target distance is the distance between the target point and the horizontal antenna; The electric field component excited by the horizontal antenna at the target point is calculated based on the ionospheric surface impedance matrix and the magnetic field component excited by the horizontal antenna at the target point.

8. An electronic device, characterized in that: include: at least one memory for storing a program; At least one processor is used to execute the program stored in the memory. When the program stored in the memory is executed, the processor is used to execute the method according to any one of claims 1 to 6.

9. A non-transitory computer-readable storage medium storing a computer program, characterized in that: When the computer program runs on a processor, the processor is caused to execute the method according to any one of claims 1 to 6.

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