Underground radio wave signal enhancement system

Abstract

The invention discloses an underground radio wave signal enhancement system, which belongs to the technical field of radio wave signal enhancement, and comprises a periodic analog signal amplitude extraction module, a radio wave perspective reflection signal analysis module and a result analysis module, the output end of the periodic analog signal amplitude extraction module is connected with the input end of the analog signal digital conversion module; according to the invention, a reference signal having the same frequency and phase relation with a measured signal is used as a comparison reference, and the phase-locked loop amplification circuit is adopted to amplify the signal, so that a weak analog signal can be amplified and extracted, the amplified analog signal is converted into a digital signal, and the signal-to-noise ratio can be improved to the maximum extent; the capability of capturing weak signals is improved, and then the enhanced radio wave perspective reflection signals are analyzed and reconstructed; therefore, radio wave perspective detection signals with a penetration distance of more than 300m can be received and analyzed, and the system is very suitable for internal structure detection of a long-distance fully mechanized coal mining face in an underground environment of a mining area.

Description

Technical Field

[0001] The invention belongs to the technical field of radio wave signal enhancement, and in particular relates to an underground radio wave signal enhancement system. Background Art

[0002] Radio waves refer to electromagnetic waves with a frequency below 3000GHz that propagate in space without artificial waveguides. Radio waves occupy a wide frequency band from low frequency to high frequency in the electromagnetic spectrum, and are divided into different bands such as long wave, medium wave, short wave, ultra short wave and microwave according to the frequency and wavelength. Radio wave perspective method (also called pit perspective method) is a commonly used method for detecting geological structures inside the mining face in coal mines.

[0003] The existing radio wave fluoroscopy equipment has a penetration range that is mainly limited by the effective transmission power of the transmitter antenna, the background noise of the receiving equipment, and the signal frequency selection and processing capabilities. The penetration ability is mostly within 260m, which is not suitable for long-distance (greater than 300m) working face detection in mining areas. There are problems such as unstable received signals or even no signals, resulting in poor application effects.

[0004] The mine environment has strict intrinsic safety and explosion-proof requirements for instruments. When using radio wave equipment, in order to ensure that the radio wave data passing through the working surface can be obtained, the transmitter is required to have a large transmission power and a precise frequency of the transmitted radio wave signal. Therefore, under the condition that the output power of the equipment is certain, the higher the effective transmission power, the better, requiring the equipment to have a high conversion rate and high performance requirements for the equipment.

[0005] The patent document with the patent publication number CN114549684A and the patent name of the improved mine radio wave perspective imaging reconstruction method based on discrete cosine transform and algebraic reconstruction algorithm discloses a radio wave perspective imaging reconstruction method, which first pre-processes the coal rock electromagnetic wave detection injection and reception data; secondly, the algorithm influencing factors are processed, namely the selection of the iteration initial value and the transformation of the electromagnetic wave angle; again, the magnetic field strength is solved based on the Maxwell equations; then, based on the ART (algebraic reconstruction algorithm) reconstruction algorithm, the algebraic iterative image reconstruction algorithm D-ART based on DCT (discrete cosine transform) transformation is solved; finally, the D-ART algorithm is used to reconstruct the coal rock to obtain a reconstructed image, but it still cannot solve the problems of poor extraction effect of received weak signals, low signal detection sensitivity and signal-to-noise ratio. In order to solve the above problems, an underground radio wave signal enhancement system is urgently needed. Summary of the invention

[0006] The purpose of the present invention is to solve the problems of existing radio wave perspective equipment, the penetration range of which is mainly limited by the effective transmission power of the transmitter antenna, the background noise of the receiving equipment and the signal frequency selection processing capability, and the penetration capability is mostly within 260m, which is not suitable for long-distance working face detection in mining areas greater than 300m, and there is an unstable receiving signal or even no signal, resulting in poor application effect. An underground radio wave signal enhancement system is proposed.

[0007] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a downhole radio wave signal enhancement system, comprising a periodic analog signal amplitude extraction module, a radio wave perspective reflection signal analysis module and a result analysis module, wherein the output end of the periodic analog signal amplitude extraction module is connected to the input end of the analog signal digital conversion module, the output end of the analog signal digital conversion module is connected to the input end of the radio wave perspective reflection signal analysis module, and the output end of the radio wave perspective reflection signal analysis module is connected to the input end of the radio wave perspective reflection signal strength testing module.

[0008] As a further description of the above technical solution:

[0009] The output end of the radio wave perspective reflection signal strength test module is connected to the input end of the result analysis module, the output end of the result analysis module is connected to the input end of the data feedback module, and the output end of the data feedback module is connected to the input end of the data receiving module.

[0010] As a further description of the above technical solution:

[0011] The periodic analog signal amplitude extraction module includes a reference signal setting module and a phase-locked loop amplifier circuit signal amplification module, the output end of the reference signal setting module is connected to the input end of the phase-locked loop amplifier circuit signal amplification module, and the output end of the phase-locked loop amplifier circuit signal amplification module is connected to the input end of the ADC device import module.

[0012] As a further description of the above technical solution:

[0013] The output end of the ADC device import module is connected to the input end of the analog signal detection module, the output end of the analog signal detection module is connected to the input end of the analog signal conversion module, the output end of the analog signal conversion module is connected to the input end of the DSP circuit setting module, and the output end of the DSP circuit setting module is connected to the input end of the signal amplitude calculation module.

[0014] As a further description of the above technical solution:

[0015] The radio wave perspective reflection signal analysis module includes a conversion signal collection module and a conversion signal marking module, the output end of the conversion signal collection module is connected to the input end of the conversion signal marking module, the output end of the conversion signal marking module is connected to the input end of the signal filtering processing module, and the output end of the signal filtering processing module is connected to the input end of the signal denoising processing module.

[0016] As a further description of the above technical solution:

[0017] The output end of the signal denoising processing module is connected to the input end of the signal parameter extraction module, and the output end of the signal parameter extraction module is connected to the input end of the reconstructed image generation module.

[0018] As a further description of the above technical solution:

[0019] The result analysis module includes a signal strength evaluation module and an evaluation result recording module, the output end of the signal strength evaluation module is connected to the input end of the evaluation result recording module, the output end of the evaluation result recording module is connected to the input end of the improvement plan generation module, the output end of the improvement plan generation module is connected to the input end of the improvement plan concentration module, the output end of the improvement plan concentration module is connected to the input end of the improvement plan selection module, and the number of improvement plans generated by the improvement plan generation module is 4-6.

[0020] The present invention also discloses a method for enhancing underground radio wave signals, comprising the following steps:

[0021] S1. Periodic analog signal amplitude extraction: Using a reference signal with the same frequency and phase relationship as the measured signal as a comparison benchmark, a phase-locked loop amplifier circuit is used to amplify the signal. The phase-locked loop amplifier circuit is used to respond to the measured signal itself and the noise component with the same frequency or multiple frequency and the same phase as the reference signal, and does not respond to other frequencies;

[0022] S2, analog signal digital conversion: the extracted and amplified analog signal is converted into a digital signal through the ADC device, and then the signal amplitude is obtained using the DSP circuit. The amplitude extraction algorithm uses DFT discrete Fourier transform;

[0023] S3. Analysis of radio wave perspective reflection signals: The signal processed in step S2 is analyzed and reconstructed by using a comprehensive curve method, a tomographic imaging method or a combination of the two to obtain a reconstructed image.

[0024] As a further description of the above technical solution:

[0025] In S2, the DFT discrete Fourier transform adopts butterfly operation.

[0026] As a further description of the above technical solution:

[0027] In S3, the tomographic imaging method uses the SIRT algorithm to invert the absorption coefficient value of each pixel to realize the inversion imaging of the absorption system in the imaging area of ​​the working surface, wherein the SIRT algorithm is used to invert the calculation results to draw the absorption coefficient contour map and chromatogram of the imaging area, and then the abnormal area is identified according to the chromatogram corresponding to the contour line.

[0028] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0029] 1. The present invention uses a reference signal with the same frequency and phase relationship as the measured signal as a comparison benchmark, and adopts a phase-locked loop amplifier circuit to amplify the signal, which can amplify and extract weak analog signals, and then convert the amplified analog signals into digital signals, which can maximize the signal-to-noise ratio and improve the ability to capture weak signals. The enhanced radio wave perspective reflection signal is then analyzed and reconstructed; thereby, the radio wave perspective detection signal with a penetration distance of more than 300m can be received and analyzed, which is very suitable for the internal structure detection of long-distance comprehensive mining working faces in underground mining environments.

[0030] 2. When the present invention converts the analog signal into a digital signal, the signal amplitude is obtained by using the DSP circuit. The amplitude extraction algorithm adopts DFT discrete Fourier transform. The time domain signal is converted to the frequency domain through DFT discrete Fourier transform. The known transmitting frequency and the amplitude and phase of the corresponding frequency are selected in the frequency domain. A large amount of data is collected and the data of multiple cycles are superimposed and averaged according to a fixed number of cycles to reduce the interference of random noise, thereby realizing the extraction of useful signals.

[0031] 3. The present invention adopts comprehensive curve method, tomography method or a combination of the two to analyze the radio wave perspective reflection signal. The analytical calculation results can draw the absorption coefficient contour map and chromatogram of the imaging area to obtain the reconstructed image, which is very suitable for the detection of comprehensive mining working faces of different widths in different coal seams in the mining area.

[0032] 4. The present invention is also provided with a radio wave perspective reflection signal strength test module and a result analysis module, which can perform a strength test on the final enhanced signal and evaluate the signal strength at the same time, and automatically generate some improvement suggestions according to the evaluation results, so as to be more conducive to the subsequent signal enhancement processing effect and improve the actual application effect of the overall system. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The figure is a schematic diagram of the module structure of an underground radio wave signal enhancement system.

[0034] Figure 2The present invention is a schematic diagram of the submodule structure of a periodic analog signal amplitude extraction module in a downhole radio wave signal enhancement system.

[0035] Figure 3 The diagram is a submodule structure diagram of a radio wave perspective reflection signal analysis module in a downhole radio wave signal enhancement system.

[0036] Figure 4 The figure is a schematic diagram of the submodule structure of a result analysis module in a downhole radio wave signal enhancement system.

[0037] Legend:

[0038] 1. Periodic analog signal amplitude extraction module; 2. Radio wave perspective reflection signal analysis module; 3. Result analysis module. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] Example 1

[0041] See also Figure 1-Figure 4 The present invention provides a technical solution: a downhole radio wave signal enhancement system, comprising a periodic analog signal amplitude extraction module 1, a radio wave perspective reflection signal analysis module 2 and a result analysis module 3. The periodic analog signal amplitude extraction module 1 transmits the extracted periodic analog signal amplitude related data to the analog signal digital conversion module. After the analog signal digital conversion module processes the received data, the converted digital signal data is transmitted to the radio wave perspective reflection signal analysis module 2. After the radio wave perspective reflection signal analysis module 2 analyzes the received digital signal data, the analyzed radio wave perspective reflection signal related data is sent to the radio wave perspective reflection signal strength test module for testing the signal strength.

[0042] In the present invention, the radio wave perspective reflection signal strength test module transmits the relevant data about the radio wave perspective reflection signal strength obtained by the test to the result analysis module 3. After the result analysis module 3 analyzes and processes the received data, it sends the analysis result related data to the data feedback module. After the data feedback module performs feedback processing according to the received analysis result data, it transmits the feedback data to the data receiving module.

[0043] In the present invention, the periodic analog signal amplitude extraction module 1 includes a reference signal setting module and a phase-locked loop amplifier circuit signal amplification module. The reference signal setting module transmits the set reference signal data to the phase-locked loop amplifier circuit signal amplification module. The phase-locked loop amplifier circuit signal amplification module processes and amplifies the received reference signal data, and then transmits the amplified signal data to the ADC device import module.

[0044] In the present invention, the ADC device import module transmits the processed relevant data to the analog signal detection module. After the analog signal detection module detects the received data, the detection result data is sent to the analog signal conversion module. After the analog signal conversion module converts the received detection result data, the converted data is passed to the DSP circuit setting module. After the DSP circuit setting module performs circuit setting according to the received data, the relevant circuit setting information data is transmitted to the signal amplitude calculation module.

[0045] In the present invention, the radio wave perspective reflection signal analysis module 2 includes a conversion signal collection module and a conversion signal marking module. The conversion signal collection module transmits the collected conversion signal related data to the conversion signal marking module, the conversion signal marking module performs marking processing on the received conversion signal data, and then sends the marked signal data to the signal filtering processing module, the signal filtering processing module performs filtering processing on the received marked signal data, and then transmits the filtered signal data to the signal denoising processing module.

[0046] In the present invention, the signal denoising processing module transmits the denoised signal data to the signal parameter extraction module. After the signal parameter extraction module performs parameter extraction processing on the received denoised signal data, the extracted signal parameter data is sent to the reconstructed image generation module.

[0047] In the present invention, the result analysis module 3 includes a signal strength evaluation module and an evaluation result recording module. The signal strength evaluation module transmits the signal strength related data obtained by evaluation to the evaluation result recording module. After the evaluation result recording module records the received signal strength evaluation data, the recorded result data is sent to the improvement plan generation module. After the improvement plan generation module generates 4 to 6 improvement plans based on the received recorded result data, the improvement plan data is passed to the improvement plan concentration module. After the improvement plan concentration module performs centralized processing on the received improvement plan data, the processed improvement plan data is transmitted to the improvement plan selection module.

[0048] The present invention also discloses a method for enhancing a downhole radio wave signal system, comprising the following steps:

[0049] S1. Periodic analog signal amplitude extraction: Using a reference signal with the same frequency and phase relationship as the measured signal as a comparison benchmark, a phase-locked loop amplifier circuit is used to amplify the signal. The phase-locked loop amplifier circuit is used to respond to the measured signal itself and the noise component with the same frequency or multiple frequency and the same phase as the reference signal, and does not respond to other frequencies;

[0050] S2, analog signal digital conversion: the extracted and amplified analog signal is converted into a digital signal through the ADC device, and then the signal amplitude is obtained using the DSP circuit. The amplitude extraction algorithm uses DFT discrete Fourier transform;

[0051] S3. Analysis of radio wave perspective reflection signals: The signal processed in step S2 is analyzed and reconstructed by using a comprehensive curve method, a tomographic imaging method or a combination of the two to obtain a reconstructed image.

[0052] In S2 of the present invention, DFT discrete Fourier transform adopts butterfly operation.

[0053] In S3 of the present invention, the tomographic imaging method adopts the SIRT algorithm to invert the absorption coefficient value of each pixel, so as to realize the inversion imaging of the absorption system in the imaging area of ​​the working surface, wherein the SIRT algorithm is used to invert the calculation results to draw the absorption coefficient contour map and chromatogram of the imaging area, and then the abnormal area is identified according to the chromatogram corresponding to the contour line.

[0054] In this embodiment, a basic data collection module is provided in the system, and a large amount of comprehensive information can be collected in the module. This information can be helpful for analyzing the specific causes after livestock become sick and help find practical solutions.

[0055] Example 2

[0056] See also Figure 1-Figure 4 The present invention provides a technical solution: a downhole radio wave signal enhancement system, comprising a periodic analog signal amplitude extraction module 1, a radio wave perspective reflection signal analysis module 2 and a result analysis module 3, wherein the output end of the periodic analog signal amplitude extraction module 1 is connected to the input end of the analog signal digital conversion module, the output end of the analog signal digital conversion module is connected to the input end of the radio wave perspective reflection signal analysis module 2, the output end of the radio wave perspective reflection signal analysis module 2 is connected to the input end of the radio wave perspective reflection signal strength test module, the output end of the radio wave perspective reflection signal strength test module is connected to the input end of the result analysis module 3, the output end of the result analysis module 3 is connected to the input end of the data feedback module, and the output end of the data feedback module is connected to the input end of the data receiving module.

[0057] The periodic analog signal amplitude extraction module 1 includes a reference signal setting module and a phase-locked loop amplifier circuit signal amplification module, the output end of the reference signal setting module is connected to the input end of the phase-locked loop amplifier circuit signal amplification module, the output end of the phase-locked loop amplifier circuit signal amplification module is connected to the input end of the ADC device import module, the output end of the ADC device import module is connected to the input end of the analog signal detection module, the output end of the analog signal detection module is connected to the input end of the analog signal conversion module, the output end of the analog signal conversion module is connected to the input end of the DSP circuit setting module, and the output end of the DSP circuit setting module is connected to the input end of the signal amplitude calculation module.

[0058] The radio wave perspective reflection signal analysis module 2 includes a conversion signal collection module and a conversion signal marking module, the output end of the conversion signal collection module is connected to the input end of the conversion signal marking module, the output end of the conversion signal marking module is connected to the input end of the signal filtering processing module, the output end of the signal filtering processing module is connected to the input end of the signal denoising processing module, the output end of the signal denoising processing module is connected to the input end of the signal parameter extraction module, and the output end of the signal parameter extraction module is connected to the input end of the reconstructed image generation module.

[0059] The result analysis module 3 includes a signal strength evaluation module and an evaluation result recording module, the output end of the signal strength evaluation module is connected to the input end of the evaluation result recording module, the output end of the evaluation result recording module is connected to the input end of the improvement plan generation module, the output end of the improvement plan generation module is connected to the input end of the improvement plan concentration module, the output end of the improvement plan concentration module is connected to the input end of the improvement plan selection module, and the number of improvement plans generated by the improvement plan generation module is 6.

[0060] In this embodiment, the system is provided with not only a physiological parameter monitoring module but also a feeding environment monitoring module. The physiological parameter monitoring module can effectively and intuitively monitor the physiological condition of the livestock, thereby directly judging the specific health status of the livestock. The feeding environment monitoring module can monitor the feeding environment, thereby predicting potential disease risks, which is helpful to carry out early risk prevention and control, reduce the morbidity of livestock, and greatly improve the actual application effect of the system.

[0061] Example 3

[0062] The present invention also discloses a method for enhancing underground radio wave signals, comprising the following steps:

[0063] S1. Periodic analog signal amplitude extraction: Use a reference signal with the same frequency and phase relationship as the measured signal as a comparison benchmark, and use a phase-locked loop amplifier circuit to amplify the signal. The phase-locked loop amplifier circuit is used to respond to the measured signal itself and the noise components with the same frequency or multiple frequency and the same phase as the reference signal, and does not respond to other frequencies. It can greatly suppress useless noise and improve signal detection sensitivity and signal-to-noise ratio; signal amplification and signal digital conversion circuit refer to the attached Figure 1 As shown;

[0064] S2, analog signal digital conversion: the extracted and amplified analog signal is converted into a digital signal through the ADC device, and then the signal amplitude is obtained using the DSP circuit. The amplitude extraction algorithm uses DFT discrete Fourier transform;

[0065] Since the frequency spectrum of a periodic signal contains the three parameters of frequency, amplitude and initial phase of all cosine signals of different frequencies contained in the periodic signal, information such as the frequency, phase, amplitude, energy, etc. of each harmonic can be seen in the frequency domain after Fourier transform. The Fourier principle shows that any continuously measured time series or signal can be expressed as an infinite superposition of sinusoidal signals of different frequencies. The Fourier transform algorithm created based on this principle uses the original signal directly measured to calculate the frequency, amplitude and phase of different sinusoidal signals in the signal in an accumulative manner. At the same time, the Fourier transform transforms the function into sine or cosine. The advantage of the sine and cosine function is that its differential and integral are also sine and cosine, which is very convenient for calculation. At the same time, according to Euler's formula, the sine and cosine function is an exponential function with a complex exponent, and the differential and integral of the exponential function is also itself, which is very convenient for analysis and calculation;

[0066] Since the useful signal received by the receiver is weak and the surrounding background interference noise is strong, the signal-to-noise ratio of the signal is very low. It is basically impossible to extract the effective received signal in the time domain. Therefore, it is necessary to transfer it to the frequency domain for processing. The time domain signal is converted to the frequency domain through DFT discrete Fourier transform. The known transmission frequency and its corresponding frequency amplitude and phase are selected in the frequency domain. In addition, a large amount of data is collected and multiple cycles of data are superimposed and averaged according to a fixed number of cycles to reduce the interference of random noise, thereby realizing the extraction of useful signals.

[0067] The implementation process of the DFT discrete Fourier transform is as follows: if N signal samples {x(0),

[0068] x(1), ..., x(N-1)}, the DFT calculation formula is (1-1):

[0069]

[0070] in is called the rotation factor or butterfly factor, From the formula, we can see that when the signal sample is complex, calculating a single X(k) requires N complex multiplications and N-1 complex additions, which is equivalent to 4N real multiplications and 2*(2*N-1) real additions; completing all N-point DFT calculations requires N 2 Complex multiplications and N*(N-1) complex additions. As N continues to increase, the amount of DFT calculations is quite large. The periodicity and symmetry can greatly reduce the computational complexity.

[0071] When the signal sample N is an even number, the signal sequence x(n) is decomposed into two subsequences, odd and even. The corresponding DFT calculation formula is decomposed into two N / 2 point calculation formulas:

[0072]

[0073] In the above formulas (1-2) and (1-3), G(k) and H(k) represent the N / 2 even sequence points and odd sequence points obtained after decomposing x(n), respectively. According to formulas (1-2) and (1-3), we only need to find G(k) and H(k), and the DFT of the first N / 2 points and the last N / 2 points of x(n) can get the DFT of the entire sequence. In this way, it only takes about N times N to calculate the DFT of N points. 2 / 2 complex multiplications, the total amount of calculation is about half of the direct calculation of DFT; similarly, when N / 2 is an even number, each N / 2 point DFT can be decomposed into two N / 4 point DFTs, thereby further reducing the complexity of DFT calculations, and so on, until the decomposition cannot be continued. At the end of the decomposition, the minimum number of DFT points is called the cardinality. When N=2 L (L is a positive integer), after L-1 decompositions, the FFT operation with a base of 2 is obtained, which reduces the number of complex multiplications required for DFT to (N / 2)log2 N .

[0074] The core of the DFT discrete Fourier transform algorithm based on 2FFT is butterfly operation. Butterfly operation adopts the principle of in-situ operation and the law of reverse order. In-situ operation means that after N data of a column are sent to the memory, they are operated by butterfly, and the result is the next column of data. They are still stored in the same group of memories in units of butterfly until the final output, and no other memory is required in the middle. That is, the two output values ​​of the butterfly are still put back into the memory where the two inputs of the butterfly are located. After all N / 2 butterfly operations of each column are completed, the butterfly operation of the next column will start. The law of reverse order is obtained based on the natural order and reverse order of binary.

[0075] For example, when N=8, a 4096-point FFT can be divided into eight 512-point FFTs, a 512-point FFT can be divided into eight 64-point FFTs, and a 64-point FFT can be decomposed into eight 8-point FFTs according to the same method. Thus, after four levels, 4096-point Fourier coefficients can be obtained.

[0076] The above-mentioned tomography method uses the SIRT algorithm to invert the absorption coefficient value of each pixel to realize the inversion imaging of the absorption system in the imaging area of ​​the working surface. The absorption coefficient contour map and chromatogram of the imaging area are drawn using the inversion calculation results of the SIRT algorithm, and then the abnormal area is identified according to the chromatogram corresponding to the contour line.

[0077] S3. Analysis of radio wave perspective reflection signals: The signal processed in step S2 is analyzed and reconstructed by using a comprehensive curve method, a tomographic imaging method or a combination of the two to obtain a reconstructed image.

[0078] Since the receiving end of the radio wave perspective system measures a component of the electromagnetic wave emitted by the transmitter in the horizontal direction, when the electromagnetic wave sent by the transmitter passes through a medium with different electromagnetic properties, it will cause a change in the electromagnetic field strength. Therefore, analyzing the change in the electromagnetic field strength can predict the change in the physical properties of the medium in the working surface.

[0079] In an infinitely uniform, isotropic medium, the electromagnetic field intensity H at a distance r from the electromagnetic wave radiation source is:

[0080]

[0081] In the above formula, H0 is the initial field strength, which is determined by the transmitter power and the surrounding medium; β is the absorption coefficient of the coal seam to the electromagnetic wave energy; r is the distance from the measuring point to the origin of the radiation source; sinθ is the directional factor, and θ is the angle between the antenna axis and the observation direction. When receiving signals: β is the main parameter affecting the field strength radiation. The field strength decays with r in an exponential law of e-β-γ. The larger β is, the faster the field strength decays. The relationship is:

[0082]

[0083] In the above formula, ω is the angular frequency; μ is the magnetic permeability; ε is the dielectric constant; σ is the electrical conductivity;

[0084] When the frequency f=2πω remains unchanged, β=f(ε, μ, σ), that is, β is a function of ε, μ, σ; when electromagnetic waves pass through coal and rock layers with different electrical properties, the difference in μ is not too large; therefore, changes in ε and σ will obviously cause changes in β and H values.

[0085] The comprehensive curve method compares the measured field strength H value of each receiving point with the corresponding theoretical calculated field strength H0 value (the calculated field strength value is obtained through conditional test). The data obtained is called the attenuation coefficient η, that is, η=H / H0 or lgη=lgH-lgH0. The receiving point position is taken as the horizontal coordinate, and the logarithm or arithmetic value of H, H0 and η is taken as the vertical coordinate. The measured field strength H value, theoretical strong field H0 value and attenuation coefficient η value of the same transmitting point corresponding to the receiving point are plotted in proportion to obtain three curves about H, H0 and η values, which are called comprehensive curve diagrams.

[0086] In a uniform isotropic medium, the measured field strength is equal to the theoretical field strength, that is, H = H0, η = 1, lgη = 0. However, due to the heterogeneity of the coal seam, the η value is generally close to 1 or 0 but not equal to 1 or 0. When the η value is far from 1 or less than 0, a negative decibel value appears, indicating that a geological anomaly is encountered within the perspective distance. According to the change of the η value and with reference to the measured strong field H and the theoretical field strength H0 curve, the properties of the anomaly are analyzed and interpreted. According to the anomaly shown on the η value curve, the boundary point (or center point) of the anomaly can be determined, and the boundary point (or center point) is connected to the corresponding emission point. This line represents the geometric shadow range (or center point) of the anomaly. According to the intersection of multiple such lines, the general outline of the anomaly can be delineated.

[0087] The tomography method is to mark each emission point and the corresponding receiving point on the plane engineering map of the mining area. The boundary point is determined according to the comprehensive curve, and the point is connected with the corresponding emission point. Then the corresponding boundary ray is drawn from the receiving point corresponding to the different emission points. The range enclosed by each ray is the plane position of the abnormal body.

[0088] The pit working surface is divided into several small units (pixels) with different absorption coefficients. The medium in each small unit can be regarded as uniform. Assuming that the i-th propagation path of the electromagnetic wave is ri, it can be expressed as the sum of the distances of several small units:

[0089]

[0090] For small cells that no ray passes through, it is visible ij =0, so the formula becomes:

[0091]

[0092] Taking logarithms at both ends gives:

[0093]

[0094] If multiple observations of the field strength are made at multiple emission points, a matrix equation can be formed:

[0095] [X][D]=[Y], where [X] is the unknown number matrix, [D] is the coefficient matrix, and [Y] is the known number matrix and the measured value.

[0096] The above-mentioned tomography method adopts SIRT (Simultaneous Iterative Reconstruction Techniques) algorithm, which uses all rays passing through the pixel. The update amount of each pixel of the image in the iterative process is the weighted average of the corrections of all projection lines according to the contribution factors, and then back-projected. Unlike ART, which updates the image once for each projection line, the SIRT algorithm combines the contributions of all projection lines, which can avoid the error on one projection line from having too much impact on the reconstruction result, and thus can effectively suppress the noise in the reconstructed image.

[0097] The specific implementation steps of the algorithm are as follows:

[0098] ① For the °i°th ray, calculate the estimated projection value;

[0099]

[0100] ② Calculate the error between the actual projection and the estimated projection:

[0101]

[0102] ③Back projection value:

[0103]

[0104] Where I is the set of light rays at all projection angles;

[0105] ④Correct the value of the °j-th pixel:

[0106]

[0107] ⑤Use the result of the previous round as the initial value and repeat the process (1) to (4) until the convergence requirement or the specified number of iterations is reached; therefore, the iteration formula of the SIRT algorithm is:

[0108]

[0109] ⑥Wherein, °λ is the relaxation factor and °k is the number of iterations.

[0110] The SIRT algorithm is used to calculate the matrix equation to invert the absorption coefficient value of each pixel, thereby realizing the inversion imaging of the absorption system in the imaging area of ​​the working surface. The inversion calculation results can be used to draw the absorption coefficient contour map and chromatogram of the imaging area, and then the abnormal area can be identified according to the chromatogram corresponding to the contour line.

[0111] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A downhole radio wave signal enhancement system, comprising a periodic analog signal amplitude extraction module (1), a radio wave perspective reflection signal analysis module (2) and a result analysis module (3), characterized in that: The periodic analog signal amplitude extraction module (1) transmits the extracted periodic analog signal amplitude related data to the analog signal digital conversion module. After the analog signal digital conversion module processes the received data, the converted digital signal data is transmitted to the radio wave perspective reflection signal analysis module (2). After the radio wave perspective reflection signal analysis module (2) analyzes the received digital signal data, the analyzed radio wave perspective reflection signal related data is sent to the radio wave perspective reflection signal strength test module for the module to test the signal strength.

2. A downhole radio wave signal enhancement system according to claim 1, characterized in that: The radio wave perspective reflection signal strength test module transmits the relevant data on the radio wave perspective reflection signal strength obtained by the test to the result analysis module (3). After the result analysis module (3) analyzes and processes the received data, it sends the analysis result related data to the data feedback module. After the data feedback module performs feedback processing according to the received analysis result data, it transmits the feedback data to the data receiving module.

3. A downhole radio wave signal enhancement system according to claim 2, characterized in that: The periodic analog signal amplitude extraction module (1) comprises a reference signal setting module and a phase-locked loop amplifier circuit signal amplification module. The reference signal setting module transmits the set reference signal data to the phase-locked loop amplifier circuit signal amplification module. The phase-locked loop amplifier circuit signal amplification module processes and amplifies the received reference signal data, and then transmits the amplified signal data to the ADC device import module.

4. The downhole radio wave signal enhancement system according to claim 3, characterized in that: The ADC device import module transmits the processed relevant data to the analog signal detection module. After the analog signal detection module detects the received data, the detection result data is sent to the analog signal conversion module. After the analog signal conversion module converts the received detection result data, the converted data is passed to the DSP circuit setting module. After the DSP circuit setting module performs circuit setting according to the received data, the relevant circuit setting information data is transmitted to the signal amplitude calculation module.

5. The downhole radio wave signal enhancement system according to claim 4, characterized in that: The radio wave perspective reflection signal analysis module (2) comprises a conversion signal collection module and a conversion signal marking module. The conversion signal collection module transmits the collected conversion signal related data to the conversion signal marking module. The conversion signal marking module performs marking processing on the received conversion signal data and then sends the marked signal data to the signal filtering processing module. The signal filtering processing module performs filtering processing on the received marked signal data and then transmits the filtered signal data to the signal denoising processing module.

6. A downhole radio wave signal enhancement system according to claim 5, characterized in that: The signal denoising processing module transmits the denoised signal data to the signal parameter extraction module. After the signal parameter extraction module performs parameter extraction processing on the received denoised signal data, the extracted signal parameter data is sent to the reconstructed image generation module.

7. A downhole radio wave signal enhancement system according to claim 6, characterized in that: The result analysis module (3) comprises a signal strength evaluation module and an evaluation result recording module. The signal strength evaluation module transmits the signal strength related data obtained by evaluation to the evaluation result recording module. After the evaluation result recording module records the received signal strength evaluation data, it sends the recorded result data to the improvement plan generation module. After the improvement plan generation module generates 4 to 6 improvement plans based on the received recorded result data, it transmits the improvement plan data to the improvement plan concentration module. After the improvement plan concentration module performs centralized processing on the received improvement plan data, it transmits the processed improvement plan data to the improvement plan optimization module.

8. A method for implementing the downhole radio wave signal enhancement system according to any one of claims 1 to 7, characterized in that: The steps include: S1. Periodic analog signal amplitude extraction: Using a reference signal with the same frequency and phase relationship as the measured signal as a comparison benchmark, a phase-locked loop amplifier circuit is used to amplify the signal. The phase-locked loop amplifier circuit is used to respond to the measured signal itself and the noise component with the same frequency or multiple frequency and the same phase as the reference signal, and does not respond to other frequencies; S2, analog signal digital conversion: the extracted and amplified analog signal is converted into a digital signal through the ADC device, and then the signal amplitude is obtained using the DSP circuit. The amplitude extraction algorithm uses DFT discrete Fourier transform; S3. Analysis of radio wave perspective reflection signals: The signal processed in step S2 is analyzed and reconstructed by using a comprehensive curve method, a tomographic imaging method or a combination of the two to obtain a reconstructed image.

9. A method for enhancing underground radio wave signals according to claim 8, characterized in that: In S2, the DFT discrete Fourier transform adopts butterfly operation.

10. A method for enhancing underground radio wave signals according to claim 8, characterized in that: In S3, the tomographic imaging method uses the SIRT algorithm to invert the absorption coefficient value of each pixel to realize the inversion imaging of the absorption system in the imaging area of ​​the working surface, wherein the SIRT algorithm is used to invert the calculation results to draw the absorption coefficient contour map and chromatogram of the imaging area, and then the abnormal area is identified according to the chromatogram corresponding to the contour line.

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