A high anti-vibration geological radar probe and method suitable for coal mine underground drilling

Abstract

The application provides a high-vibration-resistant geological radar probe and method suitable for underground drilling of a coal mine, and relates to the technical field of coal mine safety exploration. The probe comprises a main pipe section, a connecting structure connected to the upper part of the main pipe section, and a probe pipe section connected to the lower part of the main pipe section. The probe pipe section comprises a sealed pressure-bearing outer pipe, an axial water passage formed in the inner part of the sealed pressure-bearing outer pipe, an omnidirectional transmitting antenna and a reconfigurable directional receiving antenna array arranged on the inner wall of the sealed pressure-bearing outer pipe, and a water-proof isolation cabin. A transceiver circuit module is arranged in the water-proof isolation cabin. The transceiver circuit module is electrically connected to the omnidirectional transmitting antenna and the reconfigurable directional receiving antenna array. The application adopts a mechanical motion-free directional receiving scheme of "cross-shaped dipole array + PIN diode electrically-controlled switching", and is free of rotating components and bearing structures, so that mechanical damage caused by drilling vibration in the underground is fundamentally avoided.

Description

Technical Field

[0001] This invention relates to the field of coal mine safety exploration technology, specifically to a high vibration-resistant ground radar probe and method suitable for underground coal mine boreholes. Background Technology

[0002] In underground geological exploration in coal mines, borehole radar probes are often used to obtain geological information around the borehole, enabling the detection and location of coal-rock interfaces, faults, and water-rich areas.

[0003] Traditional borehole radar probes have the following problems:

[0004] 1. The rotating directional structure using a motor has many mechanical parts, poor vibration resistance, and is prone to damage to the motor and bearings due to drilling vibrations, resulting in low reliability. This type of structure mounts the radar antenna on a rotating mechanism driven by a motor. By driving the antenna to physically rotate, the antenna's direction can be adjusted, thereby achieving directional detection in different directions.

[0005] 2. Traditional borehole radar probes are mainly used for stand-alone non-drilling operations. Their antennas and circuit modules are typically located in the central area of ​​the probe, occupying the central space inside. There is no axial water or slag removal path inside the probe. When these probes are coaxially connected to the drill pipe during drilling operations, they are incompatible with the drill pipe's central channel and cannot be directly applied for synchronous detection during the drilling process. Summary of the Invention

[0006] This invention provides a high vibration-resistant ground-penetrating radar probe and method suitable for underground coal mine boreholes, in order to solve at least one of the technical problems mentioned in the background art.

[0007] To solve the above-mentioned technical problems, this invention discloses a high vibration-resistant ground radar probe suitable for underground coal mine boreholes, comprising:

[0008] The main section has a connecting structure connected to its upper part;

[0009] A detection pipe section is connected to the lower part of the main pipe section. The detection pipe section includes: a sealed pressure-bearing outer pipe, the interior of which forms an axially penetrating water passage; an omnidirectional transmitting antenna, a reconfigurable directional receiving antenna array, and a water-proof isolation chamber are arranged on the inner wall of the sealed pressure-bearing outer pipe; a transceiver circuit module is arranged inside the water-proof isolation chamber; the transceiver circuit module is electrically connected to the omnidirectional transmitting antenna and the reconfigurable directional receiving antenna array, respectively.

[0010] Preferably, the detection tube segment is detachably connected to the main tube segment.

[0011] Preferably, the connection structure includes:

[0012] A connecting block is provided with a connecting groove. The lower end of the connecting block is connected to a cylindrical connecting section, which is detachably connected to the upper part of the main pipe section.

[0013] Preferably, the cylindrical connecting section is threadedly connected to the main pipe section, and an annular block is fixedly provided on the upper outer side of the main pipe section. The annular block is connected to a screw, which penetrates the annular block radially and abuts against the outer wall of the cylindrical connecting section.

[0014] Preferably, the reconfigurable directional receiving antenna array includes four dipole units arranged in a cross shape and a cross-connecting structure; the cross-connecting structure connects the four dipole units arranged in a cross shape, and PIN diodes are electrically connected to each dipole unit to control the working state of the dipole unit; at any given time, only one dipole unit is in the receiving working state, and the other three dipole units are switched to the reflection state under the conduction control of the corresponding PIN diodes and together form a reflector to achieve electrically controlled directional reception in four directions: 0 degrees, 90 degrees, 180 degrees, and 270 degrees.

[0015] Preferably, the sealed pressure-bearing outer pipe is made of FRP or titanium alloy round pipe. The pipe wall of the sealed pressure-bearing outer pipe is leak-proof and sealed. The sealed pressure-bearing outer pipe has two layers of pipe wall, an inner and outer layer, and an annular pipe wall sandwich layer is formed between the two layers of pipe wall. The two ends of the annular pipe wall sandwich layer are sealed to form a closed cavity. The closed cavity is filled with insulating oil, and the water passage is provided on the inner side of the inner pipe wall.

[0016] Preferably, the exterior of the omnidirectional transmitting antenna, the reconfigurable directional receiving antenna array, and the water-proof isolation chamber are respectively encapsulated with silicone to form a buffer and vibration-damping layer.

[0017] This invention also provides a method for operating a high-vibration-resistant ground-penetrating radar probe suitable for underground coal mine boreholes, comprising the following steps:

[0018] S1: After the probe is lowered into the borehole along with the drill pipe and reaches the predetermined depth, the pulse signal source generates a 6-7ns first-order Gaussian pulse signal, which is then radiated by the omnidirectional transmitting antenna into the surrounding strata of the borehole as a ground-penetrating radar pulse electromagnetic wave.

[0019] S2: The control circuit switches the working state of the reconfigurable directional receiving antenna array in sequence through PIN diodes, so that the reconfigurable directional receiving antenna array forms directional receiving beams in four directions in sequence.

[0020] S3: Electromagnetic waves are reflected by the strata around the borehole to form an echo signal. The echo signal is picked up by a reconfigurable directional receiving antenna array, amplified and filtered, and then collected by the acquisition module.

[0021] S4: The FPGA processes the acquired echo data, extracts the echo amplitude, propagation delay and corresponding azimuth information, and inverts the calculation to obtain the three-dimensional positioning results of the distance and azimuth of the target geological interface.

[0022] Preferably, S1 includes:

[0023] S11: The probe is lowered into the borehole along with the drill rod. After the probe reaches the predetermined depth, the real-time temperature data of the transceiver circuit module inside the probe is collected simultaneously.

[0024] S12: Based on the real-time temperature data, call the pre-stored circuit temperature-compensated pulse width control parameter calibration curve to pre-compensate the pulse signal source;

[0025] S13: After pre-compensation, the pulse signal source generates the first-level power test pulse. The waveform and rise time of the first-level power test pulse are self-checked by the signal detection circuit built into the probe. If the self-check fails, the corrected pulse width control parameters are determined by combining the real-time temperature data and the waveform and rise time of the first-level power test pulse.

[0026] S14: Based on the pulse width control parameters finally determined in S13, the pulse signal source generates a second-stage power test pulse, which is transmitted to the ground through an omnidirectional transmitting antenna; the echo signal is received, and the echo signal-to-noise ratio is calculated; the second-stage power is greater than the first-stage power;

[0027] S15: Determine the pulse transmission power during formal detection based on the echo signal-to-noise ratio measured in S14;

[0028] S16: Based on the transmission power of the pulse during formal detection, the pulse signal source generates a 6-7ns first-order Gaussian pulse signal, which is then radiated into the surrounding strata of the borehole by the omnidirectional transmitting antenna as ground-penetrating radar pulse electromagnetic waves.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. This invention abandons the traditional mechanical orientation method of physical rotation of the antenna driven by a motor, and adopts a mechanical motion-free orientation receiving scheme of "cross-shaped dipole array + PIN diode electronic control switching". It has no rotating parts and no bearing structure, which fundamentally avoids mechanical damage caused by downhole drilling vibration and greatly improves the vibration resistance and long-term working reliability of the probe.

[0031] By using electronic switches to control the receiving / reflection states of different dipole units in a time-division manner, directional beamforming in four directions is achieved. This results in fast response speed, no switching delay, and is unaffected by vibration, ensuring the stability of directional reception and the accuracy of azimuth resolution.

[0032] 2. The probe section of the present invention has a water passage running along the axis inside the sealed pressure-bearing outer pipe, which is fully compatible with the drill pipe center channel, realizing mud circulation and slag removal during drilling, and solving the defects of traditional probes that have no center channel and cannot be applied to drilling conditions.

[0033] Both the antenna and circuit module are arranged on the inner wall of the sealed pressure-bearing outer tube, without occupying the central space of the probe tube, ensuring the smooth flow of water and realizing simultaneous drilling and detection, which greatly improves the construction efficiency of downhole drilling.

[0034] 3. The probe adopts a modular and detachable structure. The main pipe section and the probe section can be separated, which facilitates maintenance and replacement and reduces the operating cost of the equipment.

[0035] The sealed pressure-bearing outer tube is made of FRP (fiber reinforced composite material) or titanium alloy thin-walled round tube, which is lightweight, high-strength, and has good corrosion resistance. The interior is filled with insulating oil and the antenna and water-proof isolation chamber are potted with silicone to form a buffer and vibration-resistant layer, which further improves the sealing, insulation and impact resistance of the probe tube and adapts to complex downhole working conditions.

[0036] Employing a 6-7ns first-order Gaussian pulse signal with narrow pulse width and clean spectrum, combined with high-speed data processing using FPGA, ensures high resolution and positioning accuracy of the detection, enabling clear identification of geological anomalies such as thin coal-rock interfaces, faults, and water-rich areas. Attached Figure Description

[0037] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0038] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0039] Figure 2 This is an internal cross-sectional view of the detection tube section of the present invention;

[0040] Figure 3 This is a top view of the reconfigurable directional receiving antenna array of the present invention.

[0041] In the diagram: 1. Main pipe section; 11. Ring block; 2. Connecting structure; 21. Connecting block; 211. Connecting groove; 22. Cylindrical connecting section; 3. Detection pipe section; 31. Sealed pressure-bearing outer pipe; 32. Water passage; 33. Omnidirectional transmitting antenna; 34. Reconfigurable directional receiving antenna array; 341. Dipole unit; 342. Cross connection structure; 3421. Cross plate; 3422. Threaded hole one; 35. Waterproof isolation chamber; 36. Transceiver circuit module. Detailed Implementation

[0042] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0043] Furthermore, in this invention, the use of terms such as "first" and "second" is for descriptive purposes only and does not specifically refer to any order or sequence, nor is it intended to limit the invention. They are merely used to distinguish components or operations described using the same technical terms and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions and features of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If a combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0044] The present invention provides the following embodiments:

[0045] Example 1: This embodiment of the invention provides a high vibration-resistant ground-penetrating radar probe suitable for underground coal mine boreholes, such as... Figures 1-3 As shown, it includes:

[0046] Main section 1, with connecting structure 2 connected to the upper part of main section 1;

[0047] The detection pipe section 3 is connected to the lower part of the main pipe section 1. The detection pipe section 3 includes: a sealed pressure-bearing outer pipe 31, a water passage 32 is provided on the inner side of the sealed pressure-bearing outer pipe 31, and an omnidirectional transmitting antenna 33, a reconfigurable directional receiving antenna array 34 and a water-proof isolation chamber 35 are provided on the inner wall of the sealed pressure-bearing outer pipe 31. A transceiver circuit module 36 is provided in the water-proof isolation chamber 35. The transceiver circuit module 36 is electrically connected to the omnidirectional transmitting antenna 33 and the reconfigurable directional receiving antenna array 34 respectively.

[0048] The detection tube section 3 is detachably connected to the main tube section 1.

[0049] The connection structure 2 includes:

[0050] Connecting block 21, with connecting groove 211 inside, and columnar connecting section 22 connected to the lower end of connecting block 21. Columnar connecting section 22 is detachably connected to the upper part of main pipe section 1.

[0051] The cylindrical connecting section 22 is threadedly connected to the main pipe section 1, and an annular block 11 is fixedly installed on the upper outer side of the main pipe section 1. The annular block 11 is connected to a screw, which penetrates the annular block 11 radially and presses against the outer wall of the cylindrical connecting section 22.

[0052] The reconfigurable directional receiving antenna array 34 includes four dipole sub-units 341 arranged in a cross shape and a cross-connecting structure 342. The cross-connecting structure 342 connects the four dipole sub-units 341 arranged in a cross shape. PIN diodes are electrically connected to each dipole sub-unit 341 to control the working state of the dipole sub-units 341. At any given time, only one dipole sub-unit 341 is in the receiving working state. The other three dipole sub-units 341 are switched to the reflection state under the conduction control of the corresponding PIN diodes and together form a reflector to achieve four-directional electrically controlled directional reception at 0 degrees, 90 degrees, 180 degrees and 270 degrees. The cross-shaped connection structure 342 includes a cross plate 3421. The front, rear, left and right sides of the cross plate 3421 are provided with threaded holes 3422. Four dipole units 341 arranged in a cross shape are provided with threaded holes 2 that correspond one-to-one with the threaded holes 3422. The four dipole units 341 arranged in a cross shape are connected to the corresponding threaded holes by screws, so as to achieve a fixed connection between the cross plate 3421 and the four dipole units 341 arranged in a cross shape.

[0053] The sealed pressure-bearing outer pipe 31 has a leak-proof seal on its pipe wall. The sealed pressure-bearing outer pipe 31 has two layers of pipe wall, an inner and an outer layer, and an annular pipe wall interlayer is formed between the two layers of pipe wall. The two ends of the annular pipe wall interlayer are sealed to form a closed cavity. The closed cavity is filled with insulating oil, and the water passage 32 is provided on the inner side of the inner pipe wall.

[0054] The exteriors of the omnidirectional transmitting antenna 33, the reconfigurable directional receiving antenna array 34, and the water-proof isolation chamber 35 are respectively encapsulated with silicone to form a buffer and vibration-resistant layer.

[0055] This invention also discloses a working method for a high vibration-resistant ground-penetrating radar probe suitable for underground coal mine boreholes, comprising the following steps:

[0056] S1: After the probe is lowered into the borehole along with the drill pipe and reaches the predetermined depth, the pulse signal source generates a 6-7ns first-order Gaussian pulse signal, which is then radiated as ground radar pulse electromagnetic waves to the strata around the borehole radially through the omnidirectional transmitting antenna 33.

[0057] S2: The control circuit switches the working state of the reconfigurable directional receiving antenna array 34 in sequence through the PIN diode, so that the reconfigurable directional receiving antenna array 34 forms directional receiving beams in four directions in sequence.

[0058] S3: Electromagnetic waves are reflected by the strata around the borehole to form an echo signal. The echo signal is picked up by the reconfigurable directional receiving antenna array 34, amplified and filtered, and then collected by the acquisition module.

[0059] S4: The FPGA (Field Programmable Gate Array) processes the acquired echo data, extracting the amplitude, propagation delay, and corresponding azimuth information of the echo (in step S2, the FPGA synchronously records the azimuth number of the dipole unit corresponding to each round of PIN diode conduction, and this number is bound to the current directional beam; each set of echo data is accompanied by a corresponding beam azimuth identifier, thereby obtaining the unique azimuth information of each echo), and inverts to calculate the distance and azimuth three-dimensional positioning results of the target geological interface.

[0060] The target geological interface refers to the stratigraphic interface around the borehole where there is a difference in dielectric constant, including the interface between coal seam and rock strata, the boundary of fault fracture zone, the interface between aquifer and surrounding rock, and other stratigraphic interfaces that can generate electromagnetic wave reflection.

[0061] Inversion calculation method: First, based on the propagation speed of electromagnetic waves in the strata and the propagation delay of the echo, calculate the radial straight-line distance from the reflecting target to the probe. Then, combine the four sets of orthogonal detection azimuths (arranged in four fixed directions of 0 degrees, 90 degrees, 180 degrees and 270 degrees in the horizontal plane with the probe axis as the center) and the depth coordinates of the probe in the borehole, and obtain the three-dimensional spatial coordinates of the target geological interface through spatial geometric transformation.

[0062] 3D positioning result data format: The output data is a set of 3D parameters, namely the depth value of the probe along the borehole, the orthogonal azimuth numbers of the target geological interface at 0 degrees, 90 degrees, 180 degrees, and 270 degrees, and the radial straight-line distance from the reflected target to the probe. Based on this set of parameters, a 2D profile or 3D spatial distribution map of the strata anomalies around the borehole can be drawn.

[0063] The reconfigurable directional receiving antenna array 34 is an antenna system that can dynamically change the direction of the electromagnetic wave receiving beam through electronic control. By switching the working mode of the antenna elements in the array with an electric switch, it can form multiple fixed-direction directional receiving beams in time division without mechanical rotation. It can synchronously record the directional information corresponding to the signal, and realize accurate directional detection and three-dimensional positioning of the target medium.

[0064] Among them, (1) 6-7ns first-order Gaussian pulse: This is the core transmission signal of the ground-penetrating radar, which directly determines the detection performance:

[0065] 6-7ns pulse width: Narrow pulses on the nanosecond scale are key to high-resolution detection by ground-penetrating radar. The narrower the pulse width, the wider the signal bandwidth, and the smaller the details of the stratigraphy that can be distinguished (such as distinguishing thin coal-rock interfaces).

[0066] 6-7ns is a typical compromise for downhole detection: it ensures sufficient resolution without resulting in low transmission power or insufficient detection range due to excessive narrowing.

[0067] First-order Gaussian waveform: A pulse waveform with concentrated energy and a clean spectrum. Its small sidelobes effectively reduce signal tailing and interference, preventing echoes from different interfaces from overlapping. Compared to square waves and triangular waves, Gaussian pulses are easier to extract time delay information from during receiver processing, resulting in more accurate positioning.

[0068] (2) Amplitude, propagation delay, and azimuth information of the echo:

[0069] Propagation delay (a key distance parameter): the time difference between the transmission and reception of an electromagnetic wave.

[0070] Formula: Distance = speed of electromagnetic wave propagation in medium × time delay / 2 (dividing by 2 is because the electromagnetic wave travels a two-way journey "out + back").

[0071] The electromagnetic wave velocity of the underground medium (coal / rock) is known, so the time delay is the direct basis for calculating the distance to the reflecting interface.

[0072] Echo amplitude (medium difference parameter): The intensity of the echo signal reflects the difference in electromagnetic properties between the media on both sides of the interface. The greater the difference (e.g., between a coal seam and a water-bearing strata), the stronger the reflection and the higher the echo amplitude. The smaller the difference, the weaker the reflection and the lower the echo amplitude. Amplitude is a key indicator for determining the properties of the interface (whether it is water-rich or mined out).

[0073] Orientation information (spatial position parameters): corresponds to the directions of the four directional receiving beams in S2 (e.g., front, back, left, right). With the orientation, we can know which direction the reflected signal comes from in the borehole, and by combining this with the distance, we can achieve three-dimensional positioning.

[0074] (3) Predetermined depth: The location of the target borehole section that needs to be detected by radar, which is determined in advance according to the design and geological tasks during downhole operations.

[0075] The working principle of the above technical solution is as follows:

[0076] This high-vibration-resistant ground-penetrating radar probe is connected between the upper and lower drill rod sections. The upper end of the probe is connected to the lower end of the upper drill rod via connecting structure 2, and the lower end of the probe directly connects to the upper end of the lower drill rod, allowing it to be lowered into the borehole along with the drill rod for drilling-while-drilling detection. Connecting structure 2 consists of connecting block 21 and cylindrical connecting section 22. The cylindrical connecting section 22 has internal threads, and the lower end of the upper drill rod has an external thread end, which is directly screwed into the internal thread hole of the cylindrical connecting section 22 for locking. Connecting block 21 is fitted on the outside of cylindrical connecting section 22 for positioning, limiting, and straightening. Auxiliary screws can be radially connected to connecting block 21, and these screws are used to tighten against the outer wall of the upper drill rod, achieving a reliable connection between the probe and the upper drill rod. By simply changing the connecting structure of different specifications, it can be adapted to drill rods of different sizes, offering good versatility. The probe's through-type water passage 32 is connected to the central water passage of the upper and lower drill rods, allowing for normal mud circulation and in-hole slag removal during drilling operations without affecting normal drilling work.

[0077] During actual exploration operations, the drill rod and probe are lowered as a whole to the predetermined exploration depth of the borehole. After the probe comes to rest and its attitude stabilizes, the exploration operation is started. The pulse signal source outputs a 6-7ns first-order Gaussian pulse signal, which is radiated radially to the formation around the borehole through the omnidirectional transmitting antenna 33. Using the control circuit in conjunction with the PIN diode electronic switch, the working state of the reconfigurable directional receiving antenna array 34 is switched in a time-division manner to form four directional receiving beams in sequence (the control circuit drives the four PIN diode electronic switches in a time-division manner to cyclically select a single dipole unit 341, and the other three dipole units 341 are synchronously switched to the reflection state to form a single directional receiving beam). The pure electronic control switching method is adopted, abandoning the mechanical structure of the traditional motor rotating antenna.

[0078] When electromagnetic waves encounter geological lithological interfaces, faults, water-rich areas, etc., they are reflected to form echo signals. The reconfigurable directional receiving antenna array 34 completes the signal pickup, and after amplification, filtering and noise reduction, it is sent to the acquisition module to complete analog-to-digital conversion. Finally, it is transmitted to the FPGA for high-speed computing and processing, accurately extracting the echo propagation delay, signal amplitude and corresponding azimuth information, and inverting the calculation to obtain the distance and spatial orientation of geological anomalies around the borehole, thus completing all-round geological exploration.

[0079] The beneficial effects of the above technical solution are as follows:

[0080] 1. This invention abandons the traditional mechanical orientation method of physical rotation of the antenna driven by a motor, and adopts a mechanical motion-free orientation receiving scheme of "cross-shaped dipole array + PIN diode electronic control switching". It has no rotating parts and no bearing structure, which fundamentally avoids mechanical damage caused by downhole drilling vibration and greatly improves the vibration resistance and long-term working reliability of the probe.

[0081] By using electronic switches to control the receiving / reflection states of different dipole units 341 in a time-division manner, directional beamforming in four directions is achieved. This results in fast response speed, no switching delay, and is unaffected by vibration, ensuring the stability of directional reception and the accuracy of azimuth resolution.

[0082] 2. The detection pipe section 3 of the present invention has a water passage 32 running through the axis inside the sealed pressure-bearing outer pipe 31, which is fully compatible with the drill pipe center channel, realizing mud circulation and slag removal during drilling, and solving the defects of traditional detection pipes that have no center channel and cannot be applied to drilling conditions.

[0083] The omnidirectional transmitting antenna 33, the reconfigurable directional receiving antenna array 34, and the circuit module are all arranged on the inner wall of the sealed pressure-bearing outer tube 31, without occupying the central space of the probe tube, ensuring the smooth flow of water through the channel 32, realizing simultaneous drilling and detection, and greatly improving the construction efficiency of downhole drilling.

[0084] 3. The probe adopts a modular and detachable structure. The main pipe section 1 and the probe section 3 can be separated, which facilitates maintenance and replacement and reduces the operating cost of the equipment.

[0085] The sealed pressure-bearing outer tube 31 is made of FRP (fiber reinforced composite material) or titanium alloy thin-walled round tube, which is lightweight, high-strength, and has good corrosion resistance. The interior is filled with insulating oil and the omnidirectional transmitting antenna 33, the reconfigurable directional receiving antenna array 34 and the water-proof isolation chamber 35 are encapsulated with silicone to form a buffer and vibration-damping layer, which further improves the sealing, insulation and impact resistance of the probe tube and adapts to complex downhole working conditions.

[0086] Employing a 6-7ns first-order Gaussian pulse signal with narrow pulse width and clean spectrum, combined with high-speed data processing using FPGA, ensures high resolution and positioning accuracy of the detection, enabling clear identification of geological anomalies such as thin coal-rock interfaces, faults, and water-rich areas.

[0087] Example 2: Based on Example 1, S1 includes:

[0088] S11: The probe is lowered into the borehole along with the drill rod. After the probe reaches the predetermined depth (after the probe reaches the predetermined depth and stands still for 30 seconds), the real-time temperature data of the transceiver circuit module 36 inside the probe is collected simultaneously.

[0089] S12: Based on the real-time temperature data, call the pre-stored circuit temperature-compensated pulse width control parameter calibration curve to pre-compensate the pulse signal source;

[0090] S13: After pre-compensation, the pulse signal source generates the first-level power test pulse. The waveform and rise time of the first-level power test pulse are self-checked by the signal detection circuit built into the probe. If the self-check fails, the pulse width control parameters are corrected by combining the real-time temperature data and the waveform and rise time of the first-level power test pulse. After correction, the self-check is performed again. If it still fails, the process is terminated and the fault is reported (the FPGA immediately issues an instruction to shut down the pulse signal source, terminate all geological exploration processes, and upload the waveform and rise time of the first-level power test pulse corresponding to the self-check failure to the ground host via the transceiver circuit module, reminding the staff that there is an irreversible fault in the probe pulse transmission unit).

[0091] S14: Based on the pulse width control parameters finally determined in S13 ("pulse width control parameters for the pulse signal source to generate the first-level power test pulse after pre-compensation" or modified pulse width control parameters), the pulse signal source generates the second-level power test pulse, which is transmitted to the ground through the omnidirectional transmitting antenna 33; the echo signal is received, and the echo signal-to-noise ratio is calculated; the second-level power is greater than the first-level power;

[0092] S15: Determine the pulse transmission power during formal detection based on the echo signal-to-noise ratio measured in S14;

[0093] S16: Based on the transmission power of the pulse during formal detection (by adjusting the power supply voltage of the pulse drive circuit to make the actual pulse transmission power the same as the transmission power of the pulse during formal detection), the pulse signal source generates a 6-7ns first-order Gaussian pulse signal, which is then radiated into the strata around the borehole radially by the omnidirectional transmitting antenna 33 to form ground-penetrating radar pulse electromagnetic waves.

[0094] Among them, 1. (1) Standard pulse width: refers to the ideal pulse output width for formal geological detection specified in the design of this device, which is set to 6-7ns. It is the benchmark qualification index for pulse signal transmission. All detection operations are carried out based on this standard pulse width for signal transmission and echo analysis.

[0095] Standard pulse width control parameters: Under ideal conditions of normal temperature (e.g., 25℃) and no temperature drift, the pulse signal source can stably and accurately output a pulse signal with a standard pulse width using standard pulse width control parameters.

[0096] Before the probe leaves the factory, the transceiver circuit module and pulse signal source are calibrated for the temperature range of commonly used circuits, specifically including:

[0097] The probe is placed in a high and low temperature test chamber to simulate the temperature changes of the transceiver circuit module during underground operations. Multiple calibration points (circuit temperature points) are set within a preset circuit temperature range (e.g., -20℃ to 100℃). This range covers the actual working temperature range that the circuit module in the underground coal mine borehole may reach, ensuring effective compensation under all working conditions.

[0098] After stabilizing the temperature at each circuit temperature point and ensuring that the internal temperature of the transceiver circuit module is completely balanced with the temperature of the test chamber, a pulse signal source is driven using fixed standard pulse width control parameters. The actual output pulse width at this time is tested and recorded, and the difference between this pulse width and the standard pulse width is calculated, i.e., the pulse width deviation (actual output pulse width - standard pulse width).

[0099] Based on the measured pulse width deviation, adjust the pulse width control parameters until the actual output pulse width of the pulse signal source is consistent with the standard pulse width. Record the control parameters at this point, which are the compensated pulse width control parameters.

[0100] The circuit temperature (horizontal axis) at different circuit temperature points is fitted with the corresponding compensation pulse width control parameters (vertical axis) data to generate a circuit temperature compensation pulse width control parameter calibration curve with circuit temperature as the horizontal axis and compensation pulse width control parameters as the vertical axis. This curve is then stored in the non-volatile memory of the FPGA for real-time retrieval during downhole operations.

[0101] (2) Based on the real-time temperature data, the pre-stored circuit temperature-compensated pulse width control parameter calibration curve is called to pre-compensate the pulse signal source, specifically as follows:

[0102] After the probe is lowered into the borehole with the drill rod and reaches the predetermined depth, the temperature sensor on the transceiver circuit module collects the circuit operating temperature in real time and sends the temperature data to the FPGA.

[0103] The FPGA reads the real-time circuit temperature and retrieves the compensated pulse width control parameters corresponding to the current temperature from the pre-stored calibration curve of the circuit temperature-compensated pulse width control parameters.

[0104] The FPGA writes the acquired compensated pulse width control parameters into the control register of the pulse signal source, replacing the original standard pulse width control parameters, and completes the temperature compensation adjustment of the pulse signal source.

[0105] This adjustment offsets the effect of circuit temperature drift on the pulse signal source, enabling the width of the subsequent first-order Gaussian pulse output from the pulse signal source to be stabilized within the standard pulse width range of 6-7ns, providing a reference signal that meets design requirements for subsequent self-tests, test transmissions, and formal detection.

[0106] (3) Standard power: refers to the rated output power level of the formal geological exploration pulse specified in the design of this device. It is the benchmark qualification index for the transmitted signal strength and is used to ensure that the signal-to-noise ratio of the echo signal and the penetration depth of the formation meet the design requirements. The standard power is determined by the hardware parameters such as the power supply voltage and load impedance of the pulse drive circuit. It is a fixed value at room temperature and does not change with the pulse width control parameters.

[0107] The first-level low-power test pulse operates with compensated pulse width control parameters. By reducing the power supply voltage of the pulse drive circuit, the power is adjusted to 30% to 40% of the standard power. It is only used for internal self-test and does not emit effective detection energy into the formation.

[0108] Waveform parameter acquisition: The high-speed sampling channel in the signal detection circuit (e.g., a high-speed ADC; configured with a high-speed sampling circuit of at least 10 GSa / s) performs high-speed sampling of the test pulse at equal intervals to obtain a discrete data point sequence of the pulse signal (pulse voltage). The sampled discrete data points are stitched together along the time axis to form an actual waveform curve; this curve is compared with a standard first-order Gaussian waveform template pre-stored in the FPGA; through correlation calculation, the degree of matching between the actual waveform and the standard waveform (i.e., the standard first-order Gaussian waveform template) is obtained, which serves as the waveform parameter. The system then determines whether the pulse has distortion, ringing, or overshoot, verifying whether the signal source is operating normally.

[0109] The waveform correlation is obtained by calculating the Pearson correlation coefficient between the test pulse sampling data and the pre-stored standard first-order Gaussian waveform template data: after aligning the test pulse and the standard template on the time axis, the correlation coefficient is calculated based on the sampling data sequence; when the correlation coefficient is ≥0.95, the waveform is deemed qualified.

[0110] The standard waveform of this device specifically refers to the standard first-order Gaussian pulse waveform that matches the standard pulse width (6-7ns). It is the ideal signal form for ground-penetrating radar detection and also the unified reference template for the factory calibration and downhole self-testing of pulse signal sources. Its full width at half maximum (FWHM) is 6-7ns, and it features single-peak symmetry, no ringing, and no overshoot.

[0111] 2. Rise Time: Sharing the same high-speed ADC sampling data set as the waveform parameters, the rise time is determined by identifying two points in the discrete data point sequence of the sampled pulse signal (pulse voltage): 10% and 90% of the peak value. The time difference between these two points is the rise time. Acceptance Criterion: Rise time ≤ 1ns. Purpose: This parameter is a core parameter for verifying the effectiveness of temperature compensation. Circuit temperature drift causes the pulse edge to slow down and the rise time to lengthen. This parameter directly determines whether the pulse width after pre-compensation has been corrected to the standard value.

[0112] 3. Self-test failure means that in step S13, the waveform correlation and rise time of the first-level low-power test pulse did not meet the corresponding pass criteria at the same time (the pass criteria for waveform correlation is waveform correlation <0.95 and the pass criteria for rise time is rise time >1ns).

[0113] 4. "Determine the corrected pulse width control parameters by combining temperature data and the waveform and rise time of the first-stage power test pulse," specifically:

[0114] Based on the current probe circuit temperature T, the corresponding compensated pulse width control parameters (referred to as the current reference pulse width control parameters) are read from the pre-stored calibration curve of the circuit temperature compensated pulse width control parameters.

[0115] Rise time deviation coefficient = ( ) ÷ Standard rise time;

[0116] Waveform deviation coefficient = ( ) ÷ Pass / Fail Relevance Threshold;

[0117] The standard rise time is 1 ns, and the pass / fail correlation threshold is 0.95.

[0118] Corrected pulse width control parameter = Current reference pulse width control parameter × Rise time correction ratio × Waveform correction ratio;

[0119] The rise time deviation coefficient is positive: In fact, the rise time is >1ns, the edge becomes gentler, and the pulse width is wider overall (reducing the control parameter → the pulse width becomes narrower and the edge becomes steeper).

[0120] The rise time deviation coefficient is negative: the actual rise time is <1ns, the edge is too steep, and the pulse width is too narrow overall (increase the control parameters, prolong the conduction time, and make the edge smoother).

[0121] Rising edge correction: Resolves the issue of overall edge flattening / steepening caused by temperature drift;

[0122] Waveform correction: Resolves waveform distortion and decreased matching caused by conduction time deviation;

[0123] Specifically, rising edge correction ratio (two-way, quantized):

[0124] Rising edge deviation coefficient ∈ [-0.2, -0.1]: The rising edge time correction ratio is 1.05;

[0125] Rising edge deviation coefficient ∈ (-0.1, 0): The rising edge time correction ratio is 1.02;

[0126] Rising edge deviation coefficient = 0: Rising edge time correction ratio is 1.00;

[0127] Rising edge deviation coefficient ∈ (0, 0.1): The rising edge time correction ratio is 0.98;

[0128] Rising edge deviation coefficient ∈ [0.1, 0.2]: The rising edge time correction ratio is 0.95.

[0129] Waveform correction ratio:

[0130] When there is a deviation at the rising edge (≠0) (the rising edge deviation itself is the "main cause" of waveform distortion, and correction in the same direction can solve the problem at its root):

[0131] The waveform correction direction is consistent with the rising edge correction direction; the greater the deviation, the greater the correction magnitude.

[0132] Waveform deviation coefficient ∈ [0, 0.05]: Waveform correction ratio is 1.01 (shorter rising edge) / 0.99 (longer rising edge).

[0133] Waveform deviation coefficient ∈ (0.05, 0.1]: Waveform correction ratio is 1.03 (shorter rising edge) / 0.97 (longer rising edge).

[0134] Waveform deviation coefficient ∈ (0.1, 0.2]: Waveform correction ratio is 1.05 (shorter rising edge) / 0.95 (longer rising edge).

[0135] When the rising edge deviation is 0, only a slight shortening of the conduction time is made to optimize details such as waveform width and tailing (the rising edge is already qualified, the root cause of the waveform deviation is the long conduction time, so the conduction time must be shortened to narrow the waveform and suppress tailing).

[0136] Waveform deviation coefficient ∈ [0, 0.05]: Waveform correction ratio is 0.99;

[0137] Waveform deviation coefficient ∈ (0.05, 0.1]: Waveform correction ratio is 0.97;

[0138] Waveform deviation coefficient ∈ (0.1, 0.2]: Waveform correction ratio is 0.95.

[0139] An abnormal operating condition is indicated by a rise edge deviation greater than 0.2 or less than -0.2, or a waveform deviation coefficient greater than 0.2. An alarm will be triggered to terminate the process in a timely manner, thereby avoiding invalid detection and equipment damage, and at the same time prompting ground personnel to troubleshoot the fault.

[0140] The pulse width control parameter is a count configuration value of the timing circuit inside the pulse signal source, which directly determines the conduction duration of the pulse signal. By adjusting this count configuration value, pulse width deviation caused by circuit temperature drift can be compensated, and closed-loop correction can be performed based on the self-test results of waveform correlation and rise time, so that the output pulse width is stabilized at the standard pulse width (6-7ns), ensuring the matching degree between the transmitted waveform and the standard first-order Gaussian template. The above-mentioned corrected pulse width control parameter is a correction of the conduction duration of the pulse signal. The rise time directly reflects the overall width deviation of the pulse width and is a direct manifestation of temperature drift. Waveform correlation reflects the degree of distortion of waveform details (such as ringing, overshoot, and tailing), and is a manifestation of circuit nonlinearity, noise, and other factors.

[0141] 5. The second-stage power is used for echo signal-to-noise ratio testing. It needs to provide sufficient energy to penetrate the formation to obtain an effective echo signal, thereby providing a reliable basis for setting the power of subsequent formal detection pulses.

[0142] The second-level power test pulse operates with the pulse width control parameters finally determined by S13 (when S13 does not need to be corrected, the final pulse width control parameters of S13 are the current reference pulse width control parameters; when S13 needs to be corrected, the final pulse width control parameters of S13 are the corrected pulse width control parameters). By adjusting the power supply voltage of the pulse drive circuit, the power is adjusted to 70% to 80% of the standard power.

[0143] 6. Echo signal-to-noise ratio (SNR) is a comparative indicator used to distinguish between effective reflected signals from the formation and interference signals from the surrounding environment. During geological exploration, the signals received by the equipment include both effective detection echoes reflected back from the underground medium and useless interference signals such as circuit noise, spatial electromagnetic interference, and downhole environmental clutter.

[0144] Determining the echo signal-to-noise ratio, for example:

[0145] After the device completes pulse transmission, it fully acquires all received waveform data.

[0146] Data from multiple idle periods before launch, without detection reflection, and without launch crosstalk are extracted, and the average energy of all sampling points in each period is calculated as the background noise energy (power).

[0147] Based on the time window corresponding to the preset detection depth (e.g.) The effective echo period data is extracted from the effective echo period data formed by the reflection of the formation medium. The average energy of all sampling points in this period is calculated (the waveform collected by the receiving circuit is the voltage sampling value, and the signal energy is reflected by the sampling voltage. The sum of the squares of all sampling voltages in a certain period of time represents the total energy of that period. The total energy divided by the number of sampling points is the average energy), which is used as the effective signal energy (power). Effective echo period data: within the time window corresponding to the preset detection depth, the entire ADC voltage sampling dataset is formed by electromagnetic waves reflected from the interface of the underground formation medium and interference is removed (sampling points with instantaneous changes in voltage sampling value and significant deviations from the normal reflected voltage sampling value of the formation are directly removed, and sampling data of flat sub-segments with voltage sampling value that are continuously equal to the background noise voltage sampling value are also removed).

[0148] By combining the average energy of the effective signal P1 and the average energy of the background noise P2, the actual echo signal-to-noise ratio R is finally obtained.

[0149] ;

[0150] The method for calculating the electromagnetic wave signal-to-noise ratio is a well-known existing technology in this field.

[0151] 7. Based on the echo signal-to-noise ratio measured in S14, determine the pulse transmission power during formal detection, specifically as follows:

[0152] If the echo signal-to-noise ratio is ≥30dB, the formal detection power is taken as [95%, 100%) of the standard power;

[0153] If 25dB ≤ echo signal-to-noise ratio < 30dB, the formal detection power shall be 100% of the standard power;

[0154] If 20dB ≤ echo signal-to-noise ratio < 25dB, the formal detection power is taken as (100%, 105%) of the standard power;

[0155] During formal detection, the pulse transmission power shall not exceed the rated power of the equipment (the rated power of the equipment is the maximum transmission power that the pulse signal source and the omnidirectional transmitting antenna 33 hardware circuit can stably output for a long period of time).

[0156] The normal effective signal-to-noise ratio range is 20dB to 40dB;

[0157] Low power is used in low-noise environments: This avoids excessively strong signals that could cause ground reflection signal saturation, and also extends the lifespan of the equipment.

[0158] High power for high-noise environments: By increasing signal strength, noise interference is canceled out, ensuring that the echo signal can be effectively identified.

[0159] The beneficial effects of the above technical solution are as follows:

[0160] 1.S11: Enables actual perception of the working status of the core circuit of the downhole probe, providing accurate input basis for subsequent temperature compensation and pulse width correction.

[0161] 2. S12: Using the curve calibrated across the entire temperature range before shipment, initial coarse compensation for temperature drift is completed, enabling the output pulse width of the pulse signal source to quickly approach the standard value of 6-7ns. This step significantly reduces the pulse width deviation range, lowers the difficulty and computational load of subsequent S13 closed-loop correction, and avoids oscillations or divergences caused by excessive initial deviations during direct closed-loop correction.

[0162] 3.S13: Employs low-power pulses (30%–40% of standard power) for internal self-testing only, without emitting effective energy into the formation. This avoids the impact of high-power pulses on the circuitry and environmental interference, ensuring the safety of downhole operations. Pulse width quality is verified from two dimensions—"waveform morphology" and "edge characteristics"—using waveform correlation and rise time as indicators, respectively, and quantitative correction is achieved through a deviation coefficient. This closed-loop correction mechanism thoroughly improves residual deviations caused by circuit aging and other factors, ultimately stabilizing the output pulse width within the standard range and providing a highly consistent reference signal for subsequent detection.

[0163] Early fault warning: Self-testing can promptly detect faults such as pulse signal source distortion and ringing, avoiding invalid detection and improving work efficiency.

[0164] 4.S14: The field transmission is carried out at 70% to 80% of the standard power, which ensures sufficient formation penetration capability and avoids the blindness of transmitting at full power from the beginning. The obtained echo signal-to-noise ratio truly reflects the comprehensive attenuation of the current downhole environment (including formation medium, wellbore coupling, circuit loss, environmental noise, etc.).

[0165] By calculating the signal-to-noise ratio, an objective quantification of signal quality was achieved, providing a scientific basis for fine-tuning the subsequent formal detection power and avoiding the subjectivity of empirical settings.

[0166] This step eliminates the need for additional attenuation rate calculations; operational condition assessment can be completed directly using echo data. This simplifies the control logic, reduces the computational burden on the FPGA, and achieves a balance between performance and cost.

[0167] 5.S15: Based on the signal-to-noise ratio, the standard power is finely adjusted to ensure that the actual detection power is accurately matched with the current formation attenuation. This not only ensures low power consumption and low interference in weak attenuation environments, but also compensates for the insufficient echo energy in strong attenuation environments, significantly improving the quality of the detection data.

[0168] 6.S16: Based on the pulse width and power calibrated in all previous steps, a standard 6-7ns first-order Gaussian pulse signal is output, achieving high-quality ground-penetrating radar electromagnetic wave radiation. Since all errors in the previous steps (temperature drift, pulse width deviation, formation attenuation) have been corrected or compensated, the output signal in this step is highly consistent with the design target, ultimately achieving high-precision and high-reliability downhole geological exploration.

[0169] 7. This solution achieves the following through a progressive process: "temperature pre-compensation → low-power closed-loop correction → high-power operating condition assessment → adaptive power fine-tuning → high-quality formal detection":

[0170] (1) Control accuracy level: This scheme combines "pre-compensation" with "low-power closed-loop correction":

[0171] Pre-compensation quickly eliminates most of the temperature drift; closed-loop correction uses both waveform and rising edge indicators to accurately correct residual deviations; ultimately, it achieves a significant improvement in pulse width control accuracy, ensures the consistency of all detection signals, and provides a reliable benchmark for subsequent data analysis.

[0172] (2) Traditional downhole detection often uses fixed power transmission, which cannot adapt to different formation attenuation conditions and is prone to problems such as "insufficient echo in strong attenuation formations and excessive power consumption in weak attenuation formations". This solution adopts a three-level power mechanism of "low power self-test → medium power condition evaluation → standard power fine-tuning": the low power stage realizes pulse width calibration, avoiding the drawbacks of high power self-test; the medium power stage obtains the signal-to-noise ratio data of the actual working condition; the formal stage performs fine-tuning based on the signal-to-noise ratio; and achieves accurate matching between power and formation attenuation.

[0173] Example 3, based on Example 1, S3 includes:

[0174] S31: The antenna signal output terminal of the reconfigurable directional receiving antenna array 34 is equipped with a signal sampling branch. The weak echo signal from the same source that has not been amplified by the pre-amplifier circuit is picked up through the signal sampling branch. The branch signal is converted into a corresponding voltage signal. M sets of echo peak data (peak voltage) are continuously collected (M is 3 to 8, preferably 5) and the echo peak fluctuation coefficient is calculated. The echo signal output from the antenna signal output terminal of the reconfigurable directional receiving antenna array 34 is amplified by the RF amplifier circuit.

[0175] The signal sampling branch is connected in parallel between the antenna output and the pre-amplifier circuit via a directional coupler to shunt a small amount of the original echo signal. It is paired with a DC blocking capacitor and an impedance matching resistor to eliminate signal reflection and DC interference. The impedance matching resistor is used to keep the impedance of the directional coupler and the main path of the antenna output consistent, eliminate signal reflection during RF signal transmission, avoid echo amplitude distortion, and ensure that the sampled voltage can accurately reproduce the original formation echo strength.

[0176] Weak echo signals from the same source: refer to the RF signals reflected from the ground that are picked up by the receiving antenna array but have not yet been sent to the pre-amplifier circuit for gain enhancement. "Same source" means that the signal picked up by the sampling branch and the main echo detected into the pre-amplifier circuit come from the same electromagnetic wave reflected from the ground and the same antenna output. The two have the same ground reflection characteristics and environmental interference conditions, and can equivalently reflect the original echo fluctuation characteristics.

[0177] Branch signals are converted into corresponding voltage signals: The branch signals split from the directional coupler are high-frequency radio frequency AC signals, and the amplitude cannot be directly identified by the device chip; the strength envelope of the radio frequency signal is extracted by the detection circuit, and the high-frequency alternating radio frequency signal is converted into a DC voltage that varies with the strength of the echo. Then, the voltage is adjusted by the buffer circuit to the adaptation range of the ADC analog-to-digital converter circuit (the standard input range of the ADC chip), and finally an analog voltage signal that can be collected and calculated for peak data is obtained. Finally, the high-speed ADC analog-to-digital converter circuit collects the voltage to obtain the digitized peak voltage data.

[0178] The formula for calculating the echo peak fluctuation coefficient h is as follows:

[0179]

[0180] in, This represents the i-th value of the M sets of continuously acquired echo peak data; This represents the average value of the M sets of echo peak data collected continuously.

[0181] S32: Based on the echo peak fluctuation coefficient, determine the adjusted amplification gain G of the preamplifier circuit, and control the actual amplification gain of the preamplifier circuit to be the adjusted amplification gain (the FPGA converts the calculated adjusted amplification gain G into a digital control code of the matching circuit and sends it down. The preamplifier circuit receives the control code by relying on the built-in digitally controlled adjustable attenuation unit, and increases or decreases the amplification factor in real time by changing the internal signal attenuation, and finally adjusts the actual amplification gain of the circuit to the adjusted amplification gain).

[0182] When 0≤h<0.1, it is determined to be a case of uniform formation and stable echo, and G=G1;

[0183] When 0.1≤h<0.2, it is determined to be a case of slight formation change and small echo fluctuation, G=0.95G1;

[0184] When 0.2≤h<0.3, it is determined to be a case of significant formation change and large echo fluctuation, G=0.9G1;

[0185] The echo peak fluctuation coefficient is used to quantify the degree of fluctuation of the received echo peak voltage. The larger the value, the more obvious the difference in amplitude of multiple continuously acquired echoes, which directly reflects whether the downhole formation medium is uniform, whether there is strong electromagnetic interference or equipment detection anomaly. A small coefficient value indicates that the formation is stable and the echo amplitude is stable. A coefficient exceeding the standard indicates that the formation is abrupt, external interference or equipment failure causes violent echo fluctuations.

[0186] The post-adjustment amplification gain G is always limited to the safe gain range of the pre-amplifier circuit. The initial gain of the preamplifier circuit before adjustment. Pick The above-mentioned gain adjustment is always not lower than the minimum effective gain limit of the circuit, ensuring that the weak echo signal at the maximum detection depth can still be effectively amplified and identified, and avoiding the loss of deep signals due to excessive gain reduction.

[0187] The safe gain range of the preamplifier circuit refers to the range of amplification gain that the preamplifier circuit hardware allows for long-term stable operation. The upper limit of the safe gain range is determined by the chip's maximum linear output, anti-saturation, and anti-distortion performance, while the lower limit is the lowest effective gain limit. When the gain is adjusted to this safe gain range, the amplifier circuit will not experience signal clipping, device overheating, or RF distortion. It can fully amplify the ground echo and ensure long-term reliable operation of the circuit.

[0188] Abnormal fluctuation range: h≥0.3 Judgment basis: Exceeding the normal echo fluctuation range of geological strata, indicating strong electromagnetic interference, detection failure, signal distortion, or severe external disturbance. Abnormal detection status handling method: Do not adjust the gain, immediately trigger the system abnormal alarm signal (a dedicated alarm digital signal output by the FPGA when it detects abnormal echo conditions), and simultaneously prompt the staff to check the detection environment and equipment status, and suspend the adaptive gain control process.

[0189] The basic amplification gain of the preamplifier RF amplifier circuit is determined by the pre-designed reference amplification gain under standard detection conditions in stable formations. This gain is based on the mainstream conventional detection environment of ground-penetrating radar, standard detection depth, and average signal level of normal echoes, combined with the impedance matching of the preamplifier RF amplifier circuit and the unified design of device operating points. Its performance has been verified as satisfactory through actual amplification testing.

[0190] Weak signal amplification capability is qualified: at the maximum detection depth, the deep echo, after being amplified by this gain, can meet the effective identification level requirements of the subsequent circuit; Linear distortion-free amplification is qualified: within the preset signal input range, the circuit output has no clipping or distortion, meeting the distortion-free amplification requirements; Normal signal adaptability is qualified: in stable formation measurements, the normal echo, after amplification, is stably within the optimal input range of the subsequent sampling circuit; Signal-to-noise ratio and noise control are qualified: the signal-to-noise ratio of the deep echo at this gain meets the specifications, and there is no excessive increase in the noise floor; Operating point stability is qualified: the circuit's static operating point is stable across the entire temperature range, and the amplification performance shows no significant drift; In practical applications... The value can be adjusted within the range of 35~45dB depending on the equipment model and detection requirements; The typical value is 40dB.

[0191] The beneficial effects of the above scheme are as follows:

[0192] This scheme acquires the peak fluctuation of the original echo in real time through a sampling branch before the echo signal enters the preamplifier circuit, thus predicting the degree of drastic changes in the formation. When the echo peak fluctuation coefficient increases, it indicates a sudden change in the formation interface and a more severe jump in the strength of the echo signal. At this time, by adjusting the amplification gain according to a preset level, the risk of strong echoes entering outside the linear region of the amplifier is effectively suppressed, avoiding signal saturation and clipping distortion, ensuring the integrity of the echo signal, and improving the ground-penetrating radar's ability to identify complex formation interfaces.

[0193] This scheme divides the detection conditions into multiple levels based on the echo peak fluctuation coefficient. Under conditions of stable strata with small echo fluctuations, a higher reference gain is adopted to effectively amplify the weak echo signal in deep layers, ensuring the signal identifiability at conventional detection depths. Under conditions of slight strata changes and significant fluctuations, the gain is gradually reduced by a fixed factor, which avoids signal distortion without excessively suppressing the signal level, achieving dynamic matching between the amplification gain and the strata conditions, thus balancing detection depth and signal fidelity.

[0194] This solution has a separate alarm handling procedure for abnormal signals that exceed the normal fluctuation range of geological strata. Without adjusting the gain, it directly triggers the system alarm and prompts an investigation into the detection environment and equipment status.

[0195] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A high vibration-resistant ground-penetrating radar probe suitable for underground coal mine boreholes, characterized in that: include: Main section (1), the upper part of which is connected to a connecting structure (2); The detection pipe section (3) is connected to the lower part of the main pipe section (1). The detection pipe section (3) includes: a sealed pressure-bearing outer pipe (31), which forms an axially penetrating water passage (32) inside. The inner wall of the sealed pressure-bearing outer pipe (31) is provided with an omnidirectional transmitting antenna (33), a reconfigurable directional receiving antenna array (34), and a water-proof isolation chamber (35). The water-proof isolation chamber (35) is provided with a transceiver circuit module (36). The transceiver circuit module (36) is electrically connected to the omnidirectional transmitting antenna (33) and the reconfigurable directional receiving antenna array (34) respectively.

2. The high vibration-resistant ground-penetrating radar probe suitable for underground coal mine boreholes according to claim 1, characterized in that: The detection tube section (3) is detachably connected to the main tube section (1).

3. The high vibration-resistant ground-penetrating radar probe suitable for underground coal mine boreholes according to claim 1, characterized in that: The connection structure (2) includes: A connecting block (21) is provided with a connecting groove (211) and a cylindrical connecting section (22) is connected to the lower end of the connecting block (21). The cylindrical connecting section (22) is detachably connected to the upper part of the main pipe section (1).

4. The high vibration-resistant ground-penetrating radar probe suitable for underground coal mine boreholes according to claim 3, characterized in that: The cylindrical connecting section (22) is threadedly connected to the main pipe section (1), and an annular block (11) is fixedly provided on the upper outer side of the main pipe section (1). The annular block (11) is connected to a screw, which penetrates the annular block (11) radially and abuts against the outer wall of the cylindrical connecting section (22).

5. A high vibration-resistant ground-penetrating radar probe suitable for underground coal mine boreholes according to claim 1, characterized in that: The reconfigurable directional receiving antenna array (34) includes four dipole sub-units (341) arranged in a cross shape and a cross-connecting structure (342). The cross-connecting structure (342) connects the four dipole sub-units (341) arranged in a cross shape. PIN diodes are electrically connected to each dipole sub-unit (341) to control the working state of the dipole sub-units (341). At any given time, only one dipole sub-unit (341) is in the receiving working state. The other three dipole sub-units (341) are switched to the reflection state under the conduction control of the corresponding PIN diodes and together form a reflector to realize four-directional electrically controlled directional reception at 0 degrees, 90 degrees, 180 degrees and 270 degrees.

6. The high vibration-resistant ground-penetrating radar probe for use in underground coal mine boreholes according to claim 1, characterized in that: The sealed pressure-bearing outer pipe (31) is made of FRP or titanium alloy round pipe. The pipe wall of the sealed pressure-bearing outer pipe (31) is leak-proof and sealed. The sealed pressure-bearing outer pipe (31) has two layers of pipe wall, an inner and outer layer, and an annular pipe wall interlayer is formed between the two layers of pipe wall. The two ends of the annular pipe wall interlayer are sealed to form a closed cavity. The closed cavity is filled with insulating oil, and the water passage (32) is provided on the inner side of the inner pipe wall.

7. A high vibration-resistant ground-penetrating radar probe suitable for underground coal mine boreholes according to claim 1, characterized in that: The exterior of the omnidirectional transmitting antenna (33), the reconfigurable directional receiving antenna array (34), and the water-proof isolation chamber (35) are respectively encapsulated with silicone to form a buffer and vibration-resistant layer.

8. The working method of a high vibration-resistant ground-penetrating radar probe suitable for underground coal mine boreholes according to any one of claims 1-7, characterized in that: Includes the following steps: S1: After the probe is lowered into the borehole with the drill rod and reaches the predetermined depth, the pulse signal source generates a 6-7ns first-order Gaussian pulse signal, which is then radiated by the omnidirectional transmitting antenna (33) to the strata around the borehole as a ground radar pulse electromagnetic wave. S2: The control circuit switches the working state of the reconfigurable directional receiving antenna array (34) in sequence through the PIN diode, so that the reconfigurable directional receiving antenna array (34) forms directional receiving beams in four directions in sequence; S3: Electromagnetic waves are reflected by the strata around the borehole to form an echo signal. The echo signal is picked up by the reconfigurable directional receiving antenna array (34), amplified and filtered, and then collected by the acquisition module. S4: The FPGA processes the acquired echo data, extracts the echo amplitude, propagation delay and corresponding azimuth information, and inverts the calculation to obtain the three-dimensional positioning results of the distance and azimuth of the target geological interface.

9. The working method of a high vibration-resistant ground-penetrating radar probe suitable for underground coal mine boreholes according to claim 8, characterized in that: S1 includes: S11: The probe is lowered into the borehole along with the drill rod. After the probe reaches the predetermined depth, the real-time temperature data of the transceiver circuit module (36) inside the probe is collected synchronously. S12: Based on the real-time temperature data, call the pre-stored circuit temperature-compensated pulse width control parameter calibration curve to pre-compensate the pulse signal source; S13: After pre-compensation, the pulse signal source generates the first-level power test pulse. The waveform and rise time of the first-level power test pulse are self-checked by the signal detection circuit built into the probe. If the self-check fails, the correction pulse width control parameters are determined by combining the real-time temperature data and the waveform and rise time of the first-level power test pulse. S14: Based on the pulse width control parameters finally determined in S13, the pulse signal source generates a second-level power test pulse and transmits it to the ground through the omnidirectional transmitting antenna (33); the echo signal is received and the echo signal-to-noise ratio is calculated; the second-level power is greater than the first-level power; S15: Determine the pulse transmission power during formal detection based on the echo signal-to-noise ratio measured in S14; S16: Based on the transmission power of the pulse during formal detection, the pulse signal source generates a 6-7ns first-order Gaussian pulse signal, which is then radiated into the strata around the borehole by the omnidirectional transmitting antenna (33) to form ground-penetrating radar pulse electromagnetic waves.

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