Mine electromagnetic wave analysis method

Abstract

The application discloses a mine electromagnetic wave analysis method, which solves the problem that the ray tracing method cannot calculate the mine electromagnetic wave characteristics when the transmitting and receiving antennas are close to the roadway sides at the same time, and solves the problem that the finite difference time domain method cannot calculate the characteristics of the mine electromagnetic field above GHz in a large-section long roadway. Different calculation regions are divided in the simulation roadway, a data transmission interface between the ray tracing method and the finite difference time domain method is designed according to the law of conservation of energy, and the accuracy and efficiency of the mine electromagnetic wave propagation characteristics when the transmitting and receiving antennas are close to the roadway sides at the same time are improved. Guidance is provided for mine wireless communication base station planning and layout and installation position of the transmitting and receiving antennas, and the wireless transmission distance of the wireless communication system is improved under the premise that the transmitting power and the receiving sensitivity are unchanged.

Description

TECHNICAL FIELD

[0001] The present application relates to a mine electromagnetic wave analysis method, which relates to the fields of mine electromagnetic wave propagation characteristics, mine wireless communication, etc. BACKGROUND

[0002] Under certain conditions of wireless transmission power, receiving sensitivity, antenna gain, wireless working frequency band, etc., the communication base station antenna is located in the center of the roadway, and the wireless transmission loss is the smallest and the wireless transmission distance is the farthest; the communication base station antenna is close to the roadway side, although it does not affect pedestrians and vehicles, but the wireless transmission loss is large and the wireless transmission distance is short. In order to prevent affecting vehicle or personnel communication, the communication base station antenna in the mine needs to be arranged near the roadway side or the roof, and the mine electromagnetic wave propagation characteristics of the transceiver antenna near the roadway side or the roof need to be studied.

[0003] When the transceiver antenna is in the center and the vicinity of the roadway section, the ray tracing method has fast calculation speed and high accuracy, but it cannot calculate the electromagnetic wave propagation characteristics when the transceiver antenna is close to the roadway side at the same time. The finite difference time domain method can obtain the electromagnetic wave energy distribution in the entire roadway at one time, but for high-frequency electromagnetic wave signals, a finer grid space needs to be divided, and in a long roadway model, TByte level server memory needs to be occupied, even the high-end server cannot meet the simulation demand.

[0004] In order to take advantage of the high calculation accuracy and efficiency of the ray tracing method in the center of the roadway section and the vicinity, and the high accuracy of the finite difference time domain method in the entire calculation space, and to abandon the shortcomings of the ray tracing method that cannot calculate the mine electromagnetic wave characteristics when the transceiver antenna is close to the roadway side at the same time and the large memory required by the finite difference time domain method, a data transmission interface of the ray tracing method and the finite difference time domain method needs to be designed, different calculation regions are divided, so as to improve the accuracy and efficiency of the mine electromagnetic wave propagation characteristics when the transceiver antenna is close to the roadway side at the same time, provide guidance for the planning and arrangement of the mine wireless communication base station and the installation position of the transceiver antenna, and improve the wireless transmission distance of the wireless communication system under the premise of unchanged transmission power and receiving sensitivity. SUMMARY

[0005] The present application aims to provide a mine electromagnetic wave analysis method, which is used to solve the problem that the ray tracing method cannot calculate the electromagnetic wave propagation characteristics when the transceiver antenna is close to the roadway side at the same time, and is used to solve the problem that the finite difference time domain method cannot calculate the electromagnetic wave propagation characteristics above GHz frequency in a large-section long-distance roadway.

[0006] The application firstly calculates the electromagnetic wave propagation characteristics of the transmitting and receiving antennas in the area near the center of the roadway cross section by using the ray tracing method, designs the data transmission interface of the ray tracing method and the finite-difference time-domain method, takes the electric field intensity calculated by the ray tracing method as the excitation source of the finite-difference time-domain method, and then calculates the electromagnetic wave propagation characteristics of the area near the roadway sides by using the finite-difference time-domain method.

[0007] The technical scheme adopted by the application is as follows:

[0008] Suppose that the roadway width of the rectangular mine roadway is W, the roadway height is H, the roadway length is L, and the coordinate origin is at the center of the roadway cross section.

[0009] In the rectangular simulation roadway, a vertical plane is arranged in the area near the center of the roadway cross section along the axial direction of the roadway, the vertical plane and the roadway roof, one side of the roadway sides and the roadway floor form a cuboid region, the vertical plane can also form a cuboid region with a plane parallel to the roadway roof, one side of the roadway sides and a plane parallel to the roadway floor; the coordinate range of the vertical plane along the roadway width (x direction), height (y direction) and length (z direction) satisfies:

[0010]

[0011] In the rectangular simulation roadway, a plane parallel to the roadway roof is arranged, and the coordinate range of the plane along the roadway width (x direction), height (y direction) and length (z direction) satisfies:

[0012]

[0013] In the rectangular simulation roadway, a plane parallel to the roadway floor is arranged, and the coordinate range of the plane along the roadway width (x direction), height (y direction) and length (z direction) satisfies:

[0014]

[0015] In the rectangular simulation roadway, a plane parallel to the roadway cross section is arranged, and the coordinate range of the plane along the roadway width (x direction), height (y direction) and length (z direction) satisfies:

[0016]

[0017] The cuboid region is divided into a cuboid surface and a cuboid internal space, the electric field intensity of each discrete grid of the discrete cuboid surface is solved by using the ray tracing method, and the electric field intensity of the discrete grid in the cuboid internal space is solved by using the finite-difference time-domain method.

[0018] The coordinate of the transmitting point T is (x0, y0, 0), and the electric field intensity of the vertical plane, the plane parallel to the roof of the roadway and the plane parallel to the floor of the roadway is solved by using the ray tracing method, and the steps include:

[0019] Step 1: The coordinates (x, y, 0) of the transmitting point about the roof of the roadway, the floor of the roadway and the two sides of the roadway are calculated. pq p q

[0020] x p = Wp+ (-1) p x0, y q = Wq+ (-1) q y0

[0021] Wherein, p and q are integers, p is positive, indicating the reflection number of the transmitting point relative to the roof, p is negative, indicating the reflection number of the transmitting point relative to the floor, q is positive, indicating the reflection number of the transmitting point relative to the coordinate positive roadway, and q is negative, indicating the reflection number of the transmitting point relative to the coordinate negative roadway;

[0022] Step 2: The distance between the transmitting point T and the receiving point R after p, q times of reflection is equal to the distance between the image point I of the transmitting point and the receiving point R; the coordinate of the receiving point R is (x, y, z), and the distance r between R and the image point I is: pq pq p,q

[0023]

[0024] Step 3: Assuming that the angle between the incident ray and the normal vector of the two sides of the roadway, the roof and the floor is θ || and θ ⊥ , respectively, the calculation formula of θ || and θ ⊥ is as follows:

[0025]

[0026] Step 4: The electric field vector E t of the incident wave is decomposed into the vertical polarization and horizontal polarization electric field vectors E t⊥ and E t‖ , and the calculation formula of E t⊥ and E t‖ is as follows:

[0027]

[0028] Wherein, n is the normal vector of the reflection point; r is the direction vector of the incident wave;

[0029] ​​​​​​Step 5: The electromagnetic parameters of the roadway wall are the same as those of the same material or similar material, and the reflection coefficient Γ on the two sides of the roadway and the roof and floor is calculated by using the angle between the incident ray and the reflection surface and the electromagnetic parameters of the roadway wall || and Γ ⊥ , Γ || and Γ ⊥ The calculation formula is as follows:

[0030]

[0031] Wherein, the complex permittivity of the roadway wall j is the imaginary symbol; ε r is the relative permittivity of the roadway wall; ω is the angular frequency of the electromagnetic wave; σ is the conductivity of the electromagnetic wave propagation medium; ε0 is the vacuum permittivity;

[0032] Step 6: The electric field intensity E r of the receiving point R is solved by using the ray tracing method r The calculation formula is as follows:

[0033]

[0034] Wherein, j is the imaginary symbol; k is the electromagnetic wave number;

[0035] Step 7: The electric field intensity of one vertical plane discretized by a space grid is solved by using the ray tracing method, and the electric field intensity of the one vertical plane is taken as the excitation source of the vertical plane parallel to the roadway side of the cuboid region solved by the finite difference time domain method;

[0036] Step 8: The electric field intensity of one plane parallel to the roadway roof discretized by a space grid is solved by using the ray tracing method, and the electric field intensity of the one plane parallel to the roadway roof is taken as the excitation source of the plane close to the roof and parallel to the roof of the cuboid region solved by the finite difference time domain method;

[0037] Step 9: The electric field intensity of one plane parallel to the roadway floor discretized by a space grid is solved by using the ray tracing method, and the electric field intensity of the one plane parallel to the roadway floor is taken as the excitation source of the plane close to the floor and parallel to the floor of the cuboid region solved by the finite difference time domain method;

[0038] Step 10: The electric field intensity of one plane parallel to the roadway cross section discretized by a space grid is solved by using the ray tracing method, and the electric field intensity of the one plane parallel to the roadway cross section is taken as the excitation source of the plane close to the emission point and parallel to the roadway cross section of the cuboid region solved by the finite difference time domain method.

[0039] The electric field intensity of each spatial grid in the cuboid region along the x, y, z and the like three directions is calculated by using the finite-difference time-domain method, and the calculation formula is as follows:

[0040]

[0041]

[0042]

[0043] Wherein, the superscripts n, n+1 / 2, n+1 of the electric field intensity and the magnetic field intensity in the x, y, z and the like three directions represent the time discrete time step in the finite-difference time-domain method; i, j, k are all integers, representing the position of the spatial discrete grid in the x, y, z and the like three directions in the cuboid; CA and CB are two coefficients in the finite-difference time-domain electric field iteration equation, respectively And Δt is the time discrete step length; σ is the conductivity of the electromagnetic wave propagation medium; ε is the dielectric constant of the electromagnetic wave propagation medium; n is an integer representing the time step in the finite-difference time-domain iteration process; the electric field is sampled at an integer time, and the magnetic field is sampled at a half-integer time, and the electric field component at the n time step and the magnetic field component at the n+1 / 2 time step can be used to calculate the electric field component at the n+1 time step;

[0044] The magnetic field intensity of each spatial grid in the cuboid region along the x, y, z three directions is calculated by using the finite-difference time-domain method, and the calculation formula is as follows:

[0045]

[0046]

[0047]

[0048] Wherein, CC is the coefficient in the finite-difference time-domain magnetic field iteration equation, and the size is Δt is the unit grid time step length; μ is the magnetic permeability of the electromagnetic wave propagation medium; the magnetic field component at the n+1 / 2 time step can be calculated according to the magnetic field component at the n-1 / 2 time step and the electric field component at the n time step.

[0049] The calculation formula of the time step number nt of the finite-difference time-domain method is as follows:

[0050]

[0051] Wherein, L is the simulation tunnel length; c is the speed of light in vacuum; Δt is the unit grid time step length; M is the magnification, and the value is between 1.1 and 2.

[0052] The mine electromagnetic wave analysis method based on ray tracing and finite-difference time-domain of the present application has the beneficial effects that:

[0053] 1. The problem that the electromagnetic wave propagation characteristics cannot be calculated when the receiving and transmitting antennas are close to the sidewall of the roadway at the same time by using the ray tracing method alone is solved.

[0054] 2. The problem that the electromagnetic wave propagation characteristics above GHz cannot be calculated in a large-section long roadway by using the finite-difference time-domain method alone is solved.

[0055] 3. The mine electromagnetic wave analysis method based on ray tracing and finite-difference time-domain satisfies the law of conservation of energy and can accurately and efficiently calculate the electromagnetic wave propagation characteristics of the receiving and transmitting antennas at any position of the roadway section. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 It is a mine electromagnetic wave analysis method principle diagram based on ray tracing and finite-difference time-domain of the present application.

[0057] Figure 2 It is a principle diagram for calculating different image points of the emission point T in the present application. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical scheme and advantages of the present application clearer, the specific embodiments and technical scheme of the present application will be described in detail below in combination with the mine electromagnetic wave analysis method principle diagram and the corresponding drawings.

[0059] As shown in Figure 1 , the x direction is the width direction of the rectangular roadway, the y direction is the height direction of the roadway, and the z direction is the length direction of the roadway. Wall1, Wall2, Wall3 and Wall4 are the walls of the roadway, and the four surfaces form a complete roadway environment.

[0060] 101 is the cuboid region, which is divided into a cuboid surface and a cuboid internal space.

[0061] 102 is a vertical plane parallel to the sidewall of the roadway in the cuboid region.

[0062] 103 is a plane of the cuboid region close to the roof and parallel to the roof.

[0063] 104 is a plane of the cuboid region close to the floor and parallel to the floor.

[0064] 105 is a plane parallel to the roadway section.

[0065] The emission point T can be located at any position within the tunnel cross-section. Using the ray tracing method, the electric field intensity of each grid on the following planes is calculated: a vertical plane 102 parallel to the tunnel wall of the cuboid region 101; a plane 103 near the top plate and parallel to the top plate of the cuboid region 101; a plane 104 near the bottom plate and parallel to the bottom plate of the cuboid region 101; and a plane 105 parallel to the tunnel cross-section of the cuboid region 101. These are used as surface excitation sources for finite-difference time-domain excitation.

[0066] The coordinate range of a vertical plane 102 parallel to the roadway side of the cuboid region 101 along the roadway width (x direction), height (y direction), and length (z direction) satisfies:

[0067]

[0068] The coordinate range of plane 103 of cuboid region 101, which is close to and parallel to the roof, along the width (x direction), height (y direction), and length (z direction) of the roadway satisfies:

[0069]

[0070] The coordinate ranges of the cuboid region 101 and the plane 104, which is close to and parallel to the bottom plate, along the width (x direction), height (y direction), and length (z direction) of the roadway satisfy the following:

[0071]

[0072] The coordinate range of the cuboid region 101 and the plane 105 parallel to the tunnel cross-section along the tunnel width (x direction), height (y direction), and length (z direction) satisfies:

[0073]

[0074] The steps for solving for the excitation source of the finite-difference surface in the time domain include:

[0075] Step 1: As Figure 2 In the middle, the launch point is related to the tunnel roof, tunnel floor, and tunnel sidewalls as image point I. pq coordinates (x) p ,y q ,0) Calculation formula:

[0076] x p =Wp+(-1) p x0, y q =Wq+(-1) q y0

[0077] Wherein, p, q are integers, p is positive indicating the reflection times of the emitting point relative to the roof, p is negative indicating the reflection times of the emitting point relative to the floor, q is positive indicating the reflection times of the emitting point relative to the positive coordinate side wall, q is negative indicating the reflection times of the emitting point relative to the negative coordinate side wall;

[0078] Step 2: the distance between the ray emitted by the emitting point T and the receiving point R after p, q times of reflection and the image point I of the emitting point pq The distance between the receiving point R and the image point I is equal; the coordinate of the receiving point R is (x, y, z), then the distance r between R and the image point I pq is: p,q

[0079]

[0080] Step 3: assuming the angle between the incident ray and the normal vector of the two side walls, the roof and the floor is θ || and θ ⊥ , the calculation formula of θ || and θ ⊥ is as follows:

[0081]

[0082] Step 4: the electric field vector E t of the incident wave is decomposed into the electric field vectors E t⊥ and E t‖ of vertical polarization and horizontal polarization, the calculation formula of E t⊥ and E t‖ is as follows:

[0083]

[0084] Wherein, n is the normal vector of the reflection point; r is the direction vector of the incident wave;

[0085] Step 5: the electromagnetic parameters of the same material or similar material of the roadway wall are the same, the reflection coefficients Γ || and Γ ⊥ on the two side walls and the roof and floor are calculated by using the angle between the incident ray and the reflection surface and the electromagnetic parameters of the roadway wall, the calculation formula of Γ || and Γ ⊥ is as follows:

[0086]

[0087] Wherein, the complex dielectric constant of the roadway wall j is the imaginary unit symbol; ε r is the relative dielectric constant of the roadway wall; ω is the angular frequency of the electromagnetic wave; σ is the conductivity of the electromagnetic wave propagation medium; ε0 is the vacuum dielectric constant; ​

[0088] Step 6: Solve the electric field intensity E of the receiving point R by ray tracing method r , E r The calculation formula is as follows:

[0089]

[0090] Wherein, j is the imaginary number consistent; k is the electromagnetic wave number;

[0091] Step 7: Recycle the electric field intensity calculation formula in step 6, solve a vertical plane 102 discretized by spatial grid by ray tracing method, and take the electric field intensity of the vertical plane 102 as the excitation source of the vertical plane parallel to the roadway side of the cuboid region by time domain finite difference method;

[0092] Step 8: Recycle the electric field intensity calculation formula in step 6, solve a plane 103 parallel to the roadway roof by ray tracing method discretized by spatial grid, and take the electric field intensity of the plane 103 parallel to the roadway roof as the excitation source of the plane close to the roof and parallel to the roof of the cuboid region by time domain finite difference method;

[0093] Step 9: Recycle the electric field intensity calculation formula in step 6, solve a plane 104 parallel to the roadway floor by ray tracing method discretized by spatial grid, and take the electric field intensity of the plane 104 parallel to the roadway floor as the excitation source of the plane close to the floor and parallel to the floor of the cuboid region by time domain finite difference method;

[0094] Step 10: Recycle the electric field intensity calculation formula in step 6, solve a plane 105 parallel to the roadway section by ray tracing method discretized by spatial grid, and take the electric field intensity of the plane 105 parallel to the roadway section as the excitation source of the plane close to the emission point and parallel to the roadway section of the cuboid region by time domain finite difference method.

[0095] The electric field intensity of each spatial grid in the cuboid region 101 along x, y, z and other three directions is calculated by time domain finite difference method, and the calculation formula is as follows:

[0096]

[0097]

[0098]

[0099] Wherein, the superscripts n, n+1 / 2, n+1 of the electric field intensity and the magnetic field intensity in the three directions of x, y, z represent the time discrete time step in the finite difference time domain method; i, j, k are all integers, representing the position of the space discrete grid in the cuboid in the three directions of x, y, z; CA and CB are two coefficients in the finite difference time domain electric field iteration equation, respectively And Δt is the time discrete step; σ is the conductivity of the electromagnetic wave propagation medium; ε is the dielectric constant of the electromagnetic wave propagation medium; n is an integer representing the time step in the finite difference time domain iteration process; the electric field is sampled at an integer time, and the magnetic field is sampled at a half-integer time, and the electric field component at the n time step and the magnetic field component at the n+1 / 2 time step can be used to calculate the electric field component at the n+1 time step;

[0100] The magnetic field intensity of each space grid in the cuboid region 101 along the three directions of x, y and z is calculated by the finite difference time domain method, and the calculation formula is as follows:

[0101]

[0102]

[0103]

[0104] Wherein, CC is a coefficient in the finite difference time domain magnetic field iteration equation, and the size is Δt is the unit grid time step; μ is the magnetic permeability of the electromagnetic wave propagation medium; the magnetic field component at the n+1 / 2 time step can be calculated according to the magnetic field component at the n-1 / 2 time step and the electric field component at the n time step.

[0105] The calculation formula of the time step number nt of the finite difference time domain method is as follows:

[0106]

[0107] Wherein, L is the simulation tunnel length; c is the speed of light in vacuum; Δt is the unit grid time step; M is the magnification, and the value is between 1.1 and 2.

[0108] The application solves the problem that the ray tracing method alone cannot calculate the electromagnetic wave propagation characteristics when the receiving and transmitting antennas are close to the tunnel sides at the same time, and solves the problem that the finite difference time domain method alone cannot calculate the electromagnetic wave propagation characteristics above GHz in a large cross-section long tunnel; the mine electromagnetic wave analysis method based on ray tracing and finite difference time domain satisfies the law of conservation of energy, and can accurately and efficiently calculate the electromagnetic wave propagation characteristics of the receiving and transmitting antennas at any position of the tunnel cross-section.

Claims

1. A method of mine electromagnetic wave analysis, characterized by, Comprise: In the simulation mine roadway, a vertical plane is arranged near the center of the roadway section along the axial direction of the roadway, the vertical plane and the roadway roof, one side of the roadway, the roadway floor form a cuboid region, the vertical plane can also form a cuboid region with a plane parallel to the roadway roof, one side of the roadway, a plane parallel to the roadway floor, the cuboid region is divided into two parts of the cuboid surface and the cuboid internal space; the electromagnetic wave propagation characteristics in the cuboid region are calculated by using the ray tracing method and the finite difference time domain method, the ray tracing method is used to calculate the electromagnetic wave propagation characteristics on the cuboid surface, the finite difference time domain method is used to calculate the electromagnetic wave propagation characteristics in the cuboid internal space; an arbitrary transmitting point position is selected in the roadway section, the electric field intensity of each discrete grid on the cuboid surface is calculated by using the ray tracing method first; then the electric field intensity is taken as the excitation source of the finite difference time domain method for finite difference time domain iteration, and finally the electromagnetic field intensity of the cuboid internal space is obtained; the size of the cuboid internal space grid and the size of the discrete grid on the cuboid surface are determined by the finite difference time domain method; The electric field intensity of the cuboid internal region is calculated by using the finite difference time domain method, and the solving steps include: Step 1: a simulation roadway model composed of a rectangular roadway space, roadway walls and ideal absorption boundary conditions is established; Step 2: a cuboid region composed of one side of the roadway, a vertical plane parallel to the roadway, a horizontal plane close to the roof and parallel to the roof, and a horizontal plane close to the floor and parallel to the floor is established in the simulation roadway model; Step 3: the finite difference time domain method is used to discretize the space grid of the cuboid region, the ray tracing method is used to calculate the surface excitation source of the cuboid region, and is coupled to the finite difference time domain iteration equation corresponding to the surface grid of the cuboid region; Step 4: the electric field intensity of each space grid in the cuboid region along x, y, z three directions is calculated, and the calculation formula is as follows: Wherein, the superscripts n, n+1 / 2, n+1 of the electric field intensity and the magnetic field intensity in x, y, z three directions represent the time discrete time step in the finite difference time domain method; i, j, k are all integers, representing the position of the space discrete grid in the cuboid in x, y, z three directions; CA and CB are two coefficients in the finite difference time domain electric field iteration equation, respectively and Δt is the time discrete step; σ is the conductivity of the electromagnetic wave propagation medium; ε is the dielectric constant of the electromagnetic wave propagation medium; n is an integer representing the time step in the finite difference time domain iteration process; the electric field is sampled at integer time, and the magnetic field is sampled at half-integer time, and according to the electric field component at the n time step and the magnetic field component at the n+1 / 2 time step, the electric field component at the n+1 time step can be calculated; Step 5: the magnetic field intensity of each space grid in the cuboid region along x, y, z three directions is calculated, and the calculation formula is as follows: Wherein, CC is the coefficient in the time domain finite difference magnetic field iterative equation, and the size is Δt is the unit grid time step; μ is the magnetic permeability of the electromagnetic wave propagation medium; the magnetic field component at the n+1 / 2 time step can be calculated according to the magnetic field component at the n-1 / 2 time step and the electric field component at the n time step.

2. The mine electromagnetic wave analysis method according to claim 1, characterized by, The roadway width is W, the roadway height is H, the roadway length is L, and the coordinate origin is in the center of the roadway section; the coordinate range of a vertical plane along the roadway width (x direction), height (y direction) and length (z direction) satisfies:

3. The mine electromagnetic wave analysis method according to claim 1, characterized by, The coordinate range of a plane parallel to the roadway roof along the roadway width (x direction), height (y direction) and length (z direction) satisfies:

4. The mine electromagnetic wave analysis method according to claim 1, characterized by, The coordinate range of a plane parallel to the roadway floor along the roadway width (x direction), height (y direction) and length (z direction) satisfies:

5. The mine electromagnetic wave analysis method according to claim 1, characterized by, In the rectangular simulation roadway, the coordinate range of a plane parallel to the roadway section along the roadway width (x direction), height (y direction) and length (z direction) satisfies:

6. The mine electromagnetic wave analysis method of claim 1, wherein the step of providing a model of the mine is performed by a computer. The coordinate of the transmitting point T is (x0, y0, 0), and the method for calculating the electric field intensity of the vertical plane, the plane parallel to the roadway roof and the plane parallel to the roadway floor by using the ray tracing method includes: Step 1: The coordinates (x, y, 0) of the emitting point about the roof, floor, and sidewall of the roadway like point I pq are calculated by the formula: p q ​​ x p = Wp + (-1) p x0, y q = Wq + (-1) q y0 Wherein, p, q are integers, p is positive indicating the reflection times of the emitting point relative to the roof, p is negative indicating the reflection times of the emitting point relative to the floor, q is positive indicating the reflection times of the emitting point relative to the positive coordinate side of the roadway, q is negative indicating the reflection times of the emitting point relative to the negative coordinate side of the roadway; Step 2: The distance between the ray emitted by the transmitting point T and the receiving point R after p, q times of reflection and the image point I of the transmitting point pq The distance between the receiving point R and the image point I of the transmitting point is equal; the coordinates of the receiving point R are (x, y, z), and the distance r pq between R and the image point I of the transmitting point is: p,q ​ Step 3: Assume the angles between the incident ray and the normal vectors of the side walls, roof, and floor are θ. || and θ ⊥ θ || and θ ⊥ The calculation formula is as follows: Step 4: Electric field vector E of the incident wave t Decomposition of the electric field vector E into vertical and horizontal polarization t⊥ and E t‖ , E t⊥ and E t‖ The calculation formulas are as follows: Wherein, n is the normal vector of the plane where the reflection point is located; r is the incident wave direction vector; Step 5: the electromagnetic parameters of the same material or similar material of the roadway wall are the same, the reflection coefficient Γ on the two sides of the roadway and the roof and floor is calculated by using the angle between the incident ray and the reflection surface and the electromagnetic parameters of the roadway wall || and Γ ⊥ , Γ || and Γ ⊥ The calculation formula is as follows: wherein the complex permittivity of the roadway wall ε r is the relative permittivity of the roadway wall; ω is the angular frequency of the electromagnetic wave; σ is the conductivity of the medium in which the electromagnetic wave propagates; and ε0 is the vacuum permittivity. Step 6: Solve for the electric field strength E at the receiving point R using ray tracing r , E r The formula for the calculation of E is as follows: Wherein, j is the imaginary number; k is the electromagnetic wave number; Step 7: using the electric field intensity calculation formula in step 6, the electric field intensity on one vertical plane, one plane parallel to the roof, one plane parallel to the floor and one plane parallel to the cross section of the roadway after the space grid is discretized is solved by ray tracing method.

7. The mine electromagnetic wave analysis method according to claim 1, characterized by, The electric field intensity on the one vertical plane is taken as the excitation source of the time domain finite difference method for solving the cuboid region and the plane parallel to the side of the roadway; the electric field intensity on the one plane parallel to the roof is taken as the excitation source of the time domain finite difference method for solving the cuboid region and the plane parallel to the roof; the electric field intensity on the one plane parallel to the floor is taken as the excitation source of the time domain finite difference method for solving the cuboid region and the plane parallel to the floor; the electric field intensity on the one plane parallel to the cross section of the roadway is taken as the excitation source of the time domain finite difference method for solving the cuboid region and the plane parallel to the cross section of the roadway.

8. The mine electromagnetic wave analysis method according to claim 1, characterized by, The calculation formula of the time step number nt of the time domain finite difference method is Wherein, L is the length of the simulated roadway; c is the speed of light in vacuum; Δt is the unit grid time step; M is the magnification, and the value is between 1.1 and 2.

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