A method for detecting enemy tunnels through electromagnetic waves and reconstructing three-dimensional images of tunnels

Abstract

The present invention discloses a method for detecting enemy tunnels through electromagnetic waves and reconstructing a three-dimensional stereogram of the tunnels, which can enable operators to quickly and accurately collect spatial geometric data of enemy tunnels in a safe manner. A method for detecting enemy tunnels through electromagnetic waves and reconstructing a three-dimensional stereogram of the tunnels includes: a signal source, a transmitting antenna, a receiving antenna, an amplifying circuit, a communication module, a computer with dedicated analysis software installed, and an algorithm of the analysis software.

Description

Technical Field

[0001] The invention belongs to the field of military technology and relates to a method for detecting enemy tunnels through electromagnetic waves and reconstructing a three-dimensional stereogram of the tunnel. Background Art

[0002] Although tunnel warfare is an ancient way of fighting, it is still used by many countries and armed organizations today, and often poses a great threat to the enemy. In order to deal with this threat, the present invention provides a method for detecting enemy tunnels through electromagnetic waves and reconstructing a three-dimensional stereogram of the tunnel, so that the army can intuitively understand the enemy's tunnel depth, tunnel cross-sectional shape, tunnel extension direction and other geometric data, so as to take corresponding countermeasures and reduce casualties on the army's side. Summary of the invention

[0003] The present invention provides a method for detecting enemy tunnels through electromagnetic waves and reconstructing a three-dimensional stereogram of the tunnels, which can enable operators to quickly and accurately collect enemy tunnel geometry data in a safe manner. In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0004] A method for detecting enemy tunnels through electromagnetic waves and reconstructing a three-dimensional stereogram of the tunnels includes: a signal source, a transmitting antenna, a receiving antenna, an amplifying circuit, a communication module, a computer with dedicated analysis software installed, and an algorithm of the analysis software.

[0005] The specific requirements of the above-mentioned parts of the present invention are as follows:

[0006] Signal source: It is a frequency-adjustable voltage source; the signal source is connected to the transmitting antenna through a wire, and electromagnetic waves are emitted through the transmitting antenna; the signal source is connected to the communication module through a data line, and the two can communicate; the signal source receives the command of setting the frequency value from the computer installed with special analysis software through the data line, and the signal source can change the signal frequency according to the command; the signal source receives the command of starting to emit electromagnetic waves from the computer installed with special analysis software through the data line, and the signal source can act according to the command; after the signal source receives the command of starting to emit electromagnetic waves, it acts according to the command, and at the same time, it must store the time value of the start time of the action, and upload the time value to the computer installed with special analysis software; the signal source must be synchronized with the clock of the amplifier circuit;

[0007] Transmitting antenna: The transmitting antenna is an antenna that transmits linearly polarized electromagnetic waves. The transmitting antenna is connected to the signal source through a wire;

[0008] Receiving antenna: The receiving antenna is two antennas with the same structure and parameters for receiving electromagnetic waves. The receiving antenna is connected to the amplifying circuit through a wire;

[0009] Amplifier circuit: The amplifier circuit is connected to two receiving antennas through wires to collect, amplify, and perform analog-to-digital conversion on the data of the two receiving antennas; the amplifier circuit is connected to the communication module through a data line to send the data of the two receiving antennas to the communication module; each data sent by the amplifier circuit must be associated with a high-precision time value; the amplifier circuit must be synchronized with the signal source clock;

[0010] Communication module: The communication module is connected to the signal source through a data line, the communication module is connected to the amplification circuit through a data line, and the communication module is connected to the computer installed with special analysis software through a data line. The communication module is the bridge for communication between these devices;

[0011] Computer with dedicated analysis software installed: The computer with dedicated analysis software installed is connected to the communication module through a data cable. The computer can communicate with the signal source and the amplifying circuit; the computer can send the working frequency setting value to the signal source; the computer can receive the time value data of the start time of the electromagnetic wave emission uploaded by the signal source; the computer can receive the "No. 1 receiving antenna electric field strength-time" data and "No. 2 receiving antenna electric field strength-time" data uploaded by the amplifying circuit; the computer can judge whether there is a tunnel under the detection point according to the data uploaded by the signal source and the amplifying circuit according to the algorithm of the analysis software, and if so, how many meters deep and how many meters high inside the tunnel; the computer must install a database to store the logical judgment and calculation results of all detection points; the computer must have the function of drawing a three-dimensional stereogram, and draw a three-dimensional stereogram of the tunnel under a certain area according to the data in the database;

[0012] Analysis software algorithm:

[0013] The analysis software algorithm of the present invention is divided into two parts, namely, the working principle and the conclusion, which are as follows:

[0014] 1. Working principle:

[0015] The transmitting antenna of the present invention transmits a linearly polarized sinusoidal electromagnetic wave, which can be regarded as a TEM wave (transverse electromagnetic wave), and is vertically directed downward to the ground. Above the ground is a semi-infinite space, and the medium of the upper half space is air. The magnetic permeability and dielectric constant of the air are μ respectively. k and ε k , the space below the ground is also semi-infinite. The medium of the lower half space is soil. The magnetic permeability and dielectric constant of the soil are μ t and ε t The ground is the boundary between the upper half space and the lower half space. The TEM wave can be decomposed into incident wave and reflected wave in the upper half space (see equations ① and ② below), and only refracted wave in the lower half space (see equations ③ and ④ below).

[0016]

[0017] annotation:

[0018] The phase constants β1 and β2 in the equations ①, ②, ③, and ④ above represent the phase constant in the air and the phase constant of electromagnetic wave propagation in the soil, respectively. The wave impedance Z k , Z t Represent the wave impedance in the air and the wave impedance in the soil respectively, and the calculation formula is as follows:

[0019]

[0020] The electric field strength is continuous on both sides of the ground (see equation ⑤ below). At the same time, since there is no surface conduction current on the interface between the air and soil media, the magnetic field strength is continuous on both sides of the ground (see equation ⑥ below).

[0021]

[0022] Since the propagation directions of electromagnetic waves in the upper half space and the lower half space are both perpendicular to the ground, equation ⑤ can give equation ⑦, and equation ⑥ can give equation ⑧ on the ground interface.

[0023]

[0024] On the dividing interface of the ground, substitute x=0 into both sides of equation ① to obtain equation ⑨, and substitute x=0 into both sides of equation ② to obtain equation ⑩.

[0025]

[0026] On the ground interface, substitute x=0 into both sides of equation ③, and we get the equation Substitute x=0 into both sides of equation ④, and we get the equation

[0027]

[0028] Equation ⑨ and Substituting into equation ⑦, we get the equation Equation ⑩ and Substituting into equation ⑧, we get the equation

[0029]

[0030] Put the equation and equation Divide the left and right sides to get the equation

[0031]

[0032] Rearrange the equation The equation

[0033]

[0034] Г is the electric field intensity reflection coefficient on the upper side of the ground, that is:

[0035]

[0036] Put the equation Substituting into the equation The equation

[0037]

[0038] Solving equations The equation

[0039]

[0040] Put the equation Substituting into equation ①, after deformation, we get the complex solution of the electric field strength above the ground:

[0041]

[0042] Put the equation Converted into the form of instantaneous solution, we get the equation as follows:

[0043]

[0044] Observation equation The right side of the equation is the sum of two terms. Obviously, in the upper half space, the electric wave in the electromagnetic wave is a traveling standing wave, that is, the first term is a traveling wave that moves vertically downward, and the traveling wave propagates downward, and the second term is a standing wave, and the standing wave does not move downward or upward, but only oscillates in place and cycles back and forth. The traveling wave and the standing wave are superimposed to form a traveling standing wave; similarly, the magnetic wave in the electromagnetic wave is also a traveling standing wave. The main difference between the two is that the x-coordinate values ​​of the node points and antinode points of the electric wave and the magnetic wave are exactly opposite. Since it is a traveling standing wave, the electric field intensity must be maximum at some points and minimum at some points. Combining the two medium characteristic parameters of the present invention (the magnetic permeability of air μ k and dielectric constant ε k , the magnetic permeability of the soil μ t and dielectric constant ε t ), we know that the equation The numerator of the right-hand side term is greater than 0, so the reflection coefficient Г is greater than 0. The two receiving antennas of the present invention must be located at the maximum and minimum points of the radio wave, respectively. Since Г is greater than 0, the x-coordinate of the maximum point is The x-coordinate of the minimum point is the equation

[0045]

[0046] With the maximum value point x 最大 The coordinate value corresponds to the maximum electric field strength E at that location 1最大 For the equation With the above minimum point x 最小 The coordinate value corresponds to the minimum electric field strength E at that location 1最小 For the equation

[0047] According to the equation Equation Calculate the standing wave coefficient S and get the equation

[0048]

[0049] Summarizing the above principles, we can get the following judgment logic:

[0050] (1) Because the magnetic permeability of air is μ k and dielectric constant ε k , the magnetic permeability of the soil μ t and dielectric constant ε t is a constant, the frequency of the transmitting antenna is a constant value, that is, ω is a constant value, so the phase constants β1, β2, and the wave impedance Z k , Z t are all constants; due to the wave impedance Z k , Z t are all constants, so the reflection coefficient Г of the electric field strength on the ground is a constant; since the reflection coefficient Г of the electric field strength on the ground is a constant, the magnetic permeability μ of the air k and dielectric constant ε k is a constant, so the standing wave coefficient S above the ground is a constant;

[0051] (2) Method to determine whether there is a tunnel under the ground: Assume that there are two locations on the ground (for example, one is called point A and the other is called point B), and there is no tunnel under point A or point B, then the standing wave coefficient S of point A is A , the standing wave coefficient S at point B B are equal, that is, S A =S B , and, look up the table (check the magnetic permeability of air μ k and dielectric constant ε k , the magnetic permeability of the soil μ t and dielectric constant ε t Rated standing wave coefficient S calculated from the table) 额定 , obviously there is S A=S B =S 额定 It is established because there is no tunnel under point A. The ground under point A is a semi-infinite space filled with soil. The electromagnetic wave emitted by the transmitting antenna propagates vertically downward. There is only one interface on the propagation path of the electromagnetic wave, namely: interface 1-ground. The refracted wave propagating downward through the ground is under the semi-infinite soil medium. The refracted wave will not encounter other interfaces (interfaces are obstacles) and will not generate reflected waves. There is no refracted wave that passes through the ground from below to change the standing wave ratio S above the ground. A ; If there is a tunnel below point A, but not below point B, then there are three interfaces below point A, namely: interface 1-ground, interface 2-top surface of the tunnel, interface 3-bottom surface of the tunnel. Obviously, there are two more interfaces below point A than below point B. The newly added interfaces will cause additional electromagnetic waves propagating from bottom to top to refract through interface 1, refract from the soil medium into the air medium, and be received by the two receiving antennas, thereby changing S A , so that S A ≠S B =S 额定 , this equation shows that there is a tunnel under point A, but not under point B;

[0052] (3) Method for calculating the distance between the top of the tunnel and the ground: If a tunnel is found under the ground, the distance between the top of the tunnel and the ground is calculated based on the time t0 and x when the transmitting antenna starts transmitting electromagnetic waves. 最大 The time difference Δt between the earliest mutation time t1 of the electric field strength value at the receiving antenna and the phase velocity v of the electromagnetic wave propagation in the soil pt , the phase velocity v of electromagnetic wave propagation in air pk , the distance between the transmitting antenna and the ground l f 、x 最大 The distance between the receiving antenna and the ground is l s The "speed-time-distance" relationship between them is used to calculate the distance from interface 2-the top surface of the tunnel to interface 1-the ground;

[0053] (4) Method for calculating the height of the tunnel: Once it is determined that there is a tunnel below point A, the frequency of the signal source at point A is continuously adjusted to change the frequency ω of the electromagnetic wave emitted by the transmitting antenna. Since the frequency changes, the wavelength in the air will change, and the x-coordinates of the two receiving antennas will also change. At this time, it is necessary to follow the equation Equation Adjust the x coordinates of the two receiving antennas so that the two receiving antennas are exactly located at x 最大 、x 最小 The standing wave ratio S of point A (with a tunnel below) is calculated according to the sampling values ​​of the two receiving antennas. A; According to this method, constantly adjust the frequency → adjust the receiving antenna position → calculate the standing wave ratio of point A → compare S A , S B , S 额定 The size of the three, until point A (with a tunnel below) the standing wave ratio S A , the standing wave ratio S at point B (no tunnel below) B , Rated standing wave ratio S 额定 The three values ​​are equal, that is, S A =S B =S 额定 , so that the electromagnetic wave frequency ω′ at point A, where the equation holds true, corresponds to 1 / 2 of the electromagnetic wave wavelength in the air, which is equal to the height inside the tunnel (the distance between interface 3-the bottom surface of the tunnel and interface 2-the top surface of the tunnel). The principle is: the inside of the tunnel is air, and "the soil medium above the tunnel + the air medium in the tunnel + the semi-infinite thickness of the soil medium below the tunnel" constitutes a "half-wavelength window". The electromagnetic waves refracted vertically downward from the ground into the soil (corresponding to equations ③ and ④) propagating vertically downward along the positive x-axis will not be reflected back to the ground because of the tunnel, affecting S A ).

[0054] 2. Conclusion:

[0055] Advantages and disadvantages of the present invention and methods for solving the problems:

[0056] (1) Advantages:

[0057] The device corresponding to the present invention for detecting enemy tunnels through electromagnetic waves and reconstructing a three-dimensional stereogram of the tunnels can be installed on an unmanned aerial vehicle for use. It can automatically fly along a pre-set route in a complex and dangerous battlefield environment, scan suspicious areas, and quickly, accurately and timely understand the enemy situation, thereby minimizing the work intensity and casualties of one's own soldiers.

[0058] (2) Disadvantages:

[0059] The present invention is suitable for use in areas where the soil characteristic parameters (magnetic permeability, dielectric constant, electrical conductivity) are linear, uniform, isotropic, and the electrical conductivity is relatively small (not too humid, high in salt and alkali content, or with too many metal objects).

[0060] (3) Solutions to the problem:

[0061] In order to address the above shortcomings, a database should be built for some specific suspicious areas to compare the differences between data horizontally (adjacent points) and vertically (current and historical) to reduce the possibility of false alarms and missed alarms. BRIEF DESCRIPTION OF THE DRAWINGS The attached drawings of the specification include 2 drawings, which are the above Figure 1 , Figure 2,in, Figure 1 is a topological diagram of the present invention, Figure 2 It is a working principle diagram of the present invention.

Claims

1. A method for detecting an enemy tunnel by electromagnetic waves and reconstructing a three-dimensional stereogram of the tunnel comprises: Signal source, transmitting antenna, receiving antenna, amplifying circuit, communication module, computer with dedicated analysis software installed, and algorithm of analysis software.

2. The signal source in the method for detecting enemy tunnels by electromagnetic waves and reconstructing a three-dimensional stereogram of the tunnel according to claim 1 is a voltage source with adjustable frequency; the signal source is connected to a transmitting antenna by a wire, and electromagnetic waves are emitted by the transmitting antenna; The signal source and the communication module are connected via a data line, and the two can communicate; the signal source receives the command of setting the frequency value from the computer installed with the special analysis software via the data line, and the signal source can change the signal frequency according to the command; the signal source receives the command of starting to emit electromagnetic waves from the computer installed with the special analysis software via the data line, and the signal source can act according to the command; after the signal source receives the command of starting to emit electromagnetic waves, it acts according to the command, and at the same time, it needs to store the time value of the start time of the action, and upload the time value to the computer installed with the special analysis software; The signal source must be synchronized with the amplifier circuit clock.

3. According to the transmitting antenna in the method for detecting enemy tunnels by electromagnetic waves and reconstructing a three-dimensional stereogram of the tunnel as described in claim 1: the transmitting antenna is an antenna that emits linearly polarized electromagnetic waves, and the transmitting antenna is connected to the signal source by a wire.

4. The receiving antenna in the method for detecting enemy tunnels by electromagnetic waves and reconstructing a three-dimensional stereogram of the tunnel according to claim 1: the receiving antenna is two antennas for receiving electromagnetic waves with the same structure and parameters, and the receiving antenna is connected to the amplifying circuit by wires.

5. According to the amplifying circuit in the method for detecting enemy tunnels by electromagnetic waves and reconstructing a three-dimensional stereogram of the tunnels as described in claim 1: the amplifying circuit is connected to two receiving antennas by wires, and the data of the two receiving antennas are collected, amplified, and analog-to-digital converted respectively; the amplifying circuit is connected to the communication module by a data line, and the data of the two receiving antennas are sent to the communication module; each data sent by the amplifying circuit must be associated with a high-precision time value; the amplifying circuit must be synchronized with the signal source clock.

6. According to claim 1, a communication module in a method for detecting enemy tunnels by electromagnetic waves and reconstructing a three-dimensional stereogram of the tunnels: the communication module is connected to the signal source via a data line, the communication module is connected to the amplification circuit via a data line, and the communication module is connected to a computer installed with special analysis software via a data line, and the communication module is a bridge for communication between these devices.

7. According to claim 1, a computer equipped with special analysis software in a method for detecting enemy tunnels by electromagnetic waves and reconstructing a three-dimensional stereogram of the tunnel: the computer equipped with special analysis software is connected to the communication module by a data cable, and the computer can communicate with the signal source and the amplifying circuit; the computer can send a working frequency setting value to the signal source; the computer can receive the time value data of the start time of transmitting electromagnetic waves uploaded by the signal source; the computer can receive the "electric field strength of receiving antenna No. 1-time" data and "electric field strength of receiving antenna No. 2-time" data uploaded by the amplifying circuit; the computer can judge whether there is a tunnel under the detection point according to the data uploaded by the signal source and the amplifying circuit according to the algorithm of the analysis software, and if so, how many meters is the depth and how many meters is the height inside the tunnel; the computer must install a database to store the logical judgment and calculation results of all detection points; the computer must have the function of drawing a three-dimensional stereogram, and draw a three-dimensional stereogram of the tunnel under a certain area according to the data in the database.

8. The algorithm of the analysis software in the method of detecting enemy tunnels by electromagnetic waves and reconstructing a three-dimensional stereogram of the tunnels as described in claim 1.

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