Semi-airborne transient electromagnetic transmitting waveform correction method based on transmission line equivalent model

Abstract

The application discloses a semi-airborne transient electromagnetic emission waveform correction method based on a transmission line equivalent model, belongs to the technical field of semi-airborne transient electromagnetic emission waveform control, and equivalent to a lossy transmission line, a semi-airborne transient electromagnetic grounding long conductor is equivalent to a lossy transmission line, a distributed parameter model containing unit length resistance, inductance, capacitance and leakage conductance is established; the measured input impedance is obtained by collecting the transmission end current voltage, the capacitance and the leakage conductance are identified by minimizing the frequency domain residual error; the current at any position along the line is inversed by the telegraph equation frequency domain general solution in combination with the identified parameters and the transmission current, the time domain waveform is obtained by inverse Fourier transform and the space-time distribution is generated; the time domain waveform at the position is excited by discretizing into an electric dipole, and the total response is obtained by superposition.

Description

Technical Field

[0001] This invention belongs to the field of semi-airborne transient electromagnetic transmission waveform control technology, specifically relating to a semi-airborne transient electromagnetic transmission waveform correction method based on a transmission line equivalent model. Background Technology

[0002] The Semi-Airborne Transient Electromagnetic Method (SATEM) is a geophysical exploration method that combines ground-based transmission with airborne reception.

[0003] In terms of transmit waveform control, existing technologies mainly focus on transmitter circuit-level optimization. "Transient Electromagnetic Transmitter Waveform Control Technology Based on Inductive Load" proposes a constant voltage clamp and damping absorption circuit to improve the transmitter's turn-off characteristics; "Research on Transient Electromagnetic Transmitter Current Waveform Improvement Technology" analyzes the influence of distributed parameters of the cable and transmitting coil on the waveform. These works all focus on waveform quality control at the transmitter output, addressing turn-off edge oscillation and linearity issues, but do not address the spatial distribution of current along long conductors. "Research on the Influence and Correction of Transmitter Current Waveform on Transient Electromagnetic Measurement Results" analyzes the influence of the transmitter current turn-off edge on the measurement results and proposes a correction method, but its correction object is the turn-off effect in the time domain, considering only the single-point waveform at the transmitter end and not the transmission line distribution effect of the conductor.

[0004] In terms of transient electromagnetic forward modeling of long-line sources, patent application CN202311358881, "A fast forward modeling method for transient electromagnetic sources of grounded long-line sources based on non-uniform partitioning", discretizes the long-line source into multiple electric dipole segments for forward modeling response superposition calculation. However, its purpose is to perform fast forward modeling calculation and does not involve the spatial distribution inversion of current waveform.

[0005] In terms of theoretical modeling, Chapter 3 of "Research on Key Technologies of Semi-Airborne Transient Electromagnetic Transmitter" proposes a ground loop model for analyzing the impulse response of semi-airborne transient electromagnetic systems. Its modeling approach has theoretical origins with the transmission line model, but this model is used for system response analysis rather than waveform correction and does not realize the inversion of current distribution at arbitrary locations on the conductor.

[0006] Furthermore, existing receiver data processing methods (such as magnetic field compensation and Kalman filtering for noise reduction) are all aimed at post-processing noise suppression of the received signal and are unrelated to the waveform correction of the transmitting source.

[0007] In the existing technology, the solutions for SATEM transmit waveform correction mainly focus on two aspects: transmitter circuit design (improving turn-off characteristics) and receiver data processing (noise suppression). There is no publicly available technical solution that applies the transmission line distributed parameter model to the inversion of the current waveform along the long conductor source.

[0008] The shortcomings of the existing technology are: (1) Large error of lumped parameter model: The existing technology uses RLC lumped parameter model to describe the transmission circuit. For long conductors with a length of more than 1km, the effects of distributed resistance, distributed inductance and distributed capacitance cannot be ignored. The lumped parameter model cannot accurately describe the propagation and attenuation characteristics of the current along the conductor. (2) Uneven distribution of waveform along the conductor is ignored: The existing technology only measures the single-point current waveform at the transmitting end and assumes that the current waveform at each point on the entire conductor is consistent with the transmitting end. It ignores the spatial distribution of amplitude attenuation, phase delay and waveform distortion caused by transmission line effect. (3) Inaccurate forward modeling source terms: Transient electromagnetic forward modeling usually simplifies the transmitting source to an ideal step wave or an electric dipole with a single known waveform. It does not consider the waveform spatial distribution of the long conductor, resulting in a systematic deviation between the forward modeling results and the actual response. (4) Hardware solutions cannot solve propagation distortion: Constant voltage clamping, damping absorption and other transmitter circuit optimization techniques can only improve the waveform quality at the transmitter output end. They are powerless to address the propagation distortion caused by distributed parameters on the conductor. Summary of the Invention

[0009] The purpose of this invention is to overcome the problems of uneven spatial distribution of the transmitted waveform and systematic deviation in the calculation of transient electromagnetic response caused by using a lumped parameter model to describe the long conductor transmission circuit and ignoring the transmission line distribution effect. A semi-airborne transient electromagnetic transmission waveform correction method based on the transmission line equivalent model is proposed.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for correcting semi-airborne transient electromagnetic emission waveforms based on a transmission line equivalent model, comprising the following steps: S1. The grounding long conductor of the semi-aircraft transient electromagnetic system is equivalent to a lossy transmission line, and a distributed parameter equivalent circuit model is established, which includes unit length resistance, unit length inductance, unit length capacitance and unit length leakage conductance. S2. Simultaneously acquire the transmission current waveform and transmission voltage waveform at the transmitting end, obtain the measured input impedance based on the transmission current waveform and transmission voltage waveform, and identify the unit length capacitance and unit length leakage conductance with the goal of minimizing the frequency domain residual between the measured input impedance and the input impedance calculated based on the distributed parameter equivalent circuit model. S3. Based on the identified unit length capacitance and unit length leakage conductance, as well as the emission current waveform, the frequency domain current at any position on the grounding long conductor is calculated by the frequency domain general solution of the telegraph equation of the distributed parameter equivalent circuit model. The time domain current waveform at any position is obtained by inverse Fourier transform, and the spatiotemporal distribution of the emission current is generated. S4. Discretize the grounding long conductor into multiple electric dipole units. Use the time-domain current waveform at the location of each electric dipole unit in the spatiotemporal distribution as the excitation source. Calculate the transient response generated by each electric dipole unit at the receiving point and superimpose them to obtain the total transient response.

[0011] Furthermore, in S2, the minimum value of the frequency domain residual is iteratively solved using the Levenberg-Marquardt nonlinear least squares algorithm to obtain the identification values ​​of the unit length capacitance and unit length leakage conductance. During the iterative solution process, physical constraints are applied to the unit length leakage conductance and unit length capacitance, including the upper limit of the value of the unit length leakage conductance and the upper limit of the value of the unit length capacitance.

[0012] Furthermore, in S1, the resistance and inductance per unit length are determined by the physical specifications of the grounding conductor, while the capacitance and leakage conductance per unit length are parameters to be identified. The distributed parameter equivalent circuit model also includes the end grounding resistance of the grounding conductor, which is used as the terminal load of the lossy transmission line in the calculation of the input impedance.

[0013] Furthermore, in S2, the input impedance calculated based on the distributed parameter equivalent circuit model satisfies:

[0014] Where Z0 is the characteristic impedance, Z L Let γ be the end grounding resistance, γ be the propagation constant, and L be the total length of the grounding conductor.

[0015] Furthermore, in S3, the frequency domain general solution of the telegraph equation includes the propagation constant and characteristic impedance, and the propagation constant satisfies the following equation:

[0016] The characteristic impedance satisfies the following equation:

[0017] Where R0 is the resistance per unit length, L0 is the inductance per unit length, G0 is the leakage conductance per unit length, C0 is the capacitance per unit length, ω is the angular frequency, and j is the imaginary unit; The frequency domain current at any point on a grounded long conductor satisfies:

[0018] Where I(0,ω) is the frequency domain form of the transmitted current waveform, x is the position coordinate, L is the total length of the grounding conductor, γ is the propagation constant, Z0 is the characteristic impedance, and Z L This is the end grounding resistance.

[0019] Furthermore, in S4, the grounding long conductor is divided into multiple electric dipole units, and the excitation source of each electric dipole unit is taken from the time-domain current waveform at the midpoint of the electric dipole unit.

[0020] Furthermore, it also includes S5, comparing the total transient response obtained in S4 with the analytical solution of the uniform half-space, and verifying the repeatability of the measured data, and outputting the corrected transmission waveform dataset and transient electromagnetic response data.

[0021] Secondly, the present invention provides a semi-airborne transient electromagnetic transmission waveform correction system based on a transmission line equivalent model, comprising: The equivalent circuit model building module is used to convert the long grounding conductor of the semi-aerospace transient electromagnetic system into a lossy transmission line and build an equivalent circuit model with distributed parameters including unit length resistance, unit length inductance, unit length capacitance and unit length leakage conductance. The capacitance and leakage conductance identification module is used to synchronously acquire the transmission current waveform and transmission voltage waveform at the transmitting end, obtain the measured input impedance based on the transmission current waveform and transmission voltage waveform, and identify the capacitance and leakage conductance per unit length with the goal of minimizing the frequency domain residual between the measured input impedance and the input impedance calculated based on the distributed parameter equivalent circuit model. The spatiotemporal distribution generation module is used to calculate the frequency domain current at any position on the grounding long conductor based on the identified unit length capacitance and unit length leakage conductance, as well as the emission current waveform, through the frequency domain general solution of the telegraph equation of the distributed parameter equivalent circuit model. The time domain current waveform at any position is obtained through inverse Fourier transform, thus generating the spatiotemporal distribution of the emission current. The module for calculating the total transient response is used to discretize the grounding long conductor into multiple electric dipole units. Each electric dipole unit uses the time-domain current waveform at its location in the spatiotemporal distribution as the excitation source. The transient response generated by each electric dipole unit at the receiving point is calculated and superimposed to obtain the total transient response.

[0022] Thirdly, the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements a semi-aerospace transient electromagnetic emission waveform correction method based on a transmission line equivalent model.

[0023] Fourthly, the present invention provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements a semi-aeronautical transient electromagnetic emission waveform correction method based on a transmission line equivalent model.

[0024] Compared with the prior art, the present invention has the following beneficial technical effects: This invention proposes a semi-airborne transient electromagnetic transmission waveform correction method based on a transmission line equivalent model. It introduces a lossy transmission line distributed parameter model into the description of the semi-airborne transient electromagnetic transmission source, fundamentally characterizing the current propagation and attenuation characteristics of long conductors. This overcomes the modeling errors caused by the non-negligible distributed parameter effects of lumped parameter models on kilometer-scale conductors. The invention identifies the transmission line distributed parameters through measured current and voltage at the transmitting end, and inverts the time-domain current waveform at any location on the conductor based on the frequency domain general solution of the telegraph equation, establishing a two-dimensional spatiotemporal distribution of the transmission current. This addresses the shortcomings of existing technologies that only measure the waveform at a single point at the transmitting end and assume a uniform current across the entire line. The invention discretizes the long conductor into multiple electric dipole units, with each unit using the actual current waveform at its location as the excitation source, eliminating systematic biases in transient electromagnetic response calculations caused by uneven waveform spatial distribution. This invention is a purely software-based correction method, requiring no modification to existing hardware systems and can be directly integrated into existing semi-airborne transient electromagnetic data processing workflows. Attached Figure Description

[0025] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely schematic to aid in understanding the invention and do not specifically limit the shapes and proportions of the components. In the drawings: Figure 1 This is a flowchart of the semi-airborne transient electromagnetic emission waveform correction method based on the transmission line equivalent model of the present invention.

[0026] Figure 2 This is a simplified structural diagram of the semi-airborne transient electromagnetic transmission waveform correction system based on the transmission line equivalent model of the present invention.

[0027] Figure 3 This is an electronic device diagram of the semi-aeronautical transient electromagnetic emission waveform correction method based on the transmission line equivalent model of the present invention.

[0028] Figure 4 This is a system architecture diagram in an embodiment of the present invention.

[0029] Figure 5 This is a system flowchart illustrating an embodiment of the present invention. Detailed Implementation

[0030] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0031] Example 1 See Figure 1 A method for correcting semi-airborne transient electromagnetic emission waveforms based on a transmission line equivalent model includes the following steps: S1. The grounding long conductor of the semi-aircraft transient electromagnetic system is equivalent to a lossy transmission line, and a distributed parameter equivalent circuit model is established, which includes unit length resistance, unit length inductance, unit length capacitance and unit length leakage conductance. S2. Simultaneously acquire the transmission current waveform and transmission voltage waveform at the transmitting end, obtain the measured input impedance based on the transmission current waveform and transmission voltage waveform, and identify the unit length capacitance and unit length leakage conductance with the goal of minimizing the frequency domain residual between the measured input impedance and the input impedance calculated based on the distributed parameter equivalent circuit model. S3. Based on the identified unit length capacitance and unit length leakage conductance, as well as the emission current waveform, the frequency domain current at any position on the grounding long conductor is calculated by the frequency domain general solution of the telegraph equation of the distributed parameter equivalent circuit model. The time domain current waveform at any position is obtained by inverse Fourier transform, and the spatiotemporal distribution of the emission current is generated. S4. Discretize the grounding long conductor into multiple electric dipole units. Use the time-domain current waveform at the location of each electric dipole unit in the spatiotemporal distribution as the excitation source. Calculate the transient response generated by each electric dipole unit at the receiving point and superimpose them to obtain the total transient response.

[0032] Specifically, the equivalent modeling of the S1 transmission line and the cross-domain application of the transmission line distributed parameter model: applying the lossy transmission line distributed parameter model in the power system to the analysis of SATEM long conductor emission sources, establishing a model that includes resistance per unit length. ,inductance ,capacitance Leakage conductance The distributed parameter equivalent circuit model replaces the traditional lumped parameter RLC model.

[0033] S2 model parameter identification, adaptive identification based on frequency domain impedance residuals: The objective function is constructed with the goal of minimizing the frequency domain residuals between the measured impedance at the transmitter and the calculated impedance from the model. The Levenberg-Marquardt nonlinear least squares algorithm was used to iteratively identify the distributed parameters of the transmission line. and This allows the model to automatically adapt to the ground resistivity conditions and conductor laying conditions of different work areas.

[0034] S3 Current waveform inversion along the line, based on the spatiotemporal two-dimensional inversion of the frequency domain general solution of the telegraph equation: based on the transmission line parameters identified in step S2 and the measured current at the transmitter. The frequency domain general solution of the telegraph equation is used to calculate the position of any point on the conductor. frequency domain current The time-domain current waveform is obtained by inverse Fourier transform. Establish a complete two-dimensional spatiotemporal distribution matrix of the emission current.

[0035] S4 Discrete Dipole Superposition Waveform Correction, Transient Response Correction of Position-Related Waveforms: Discretizing a long conductor into... Each electric dipole unit uses the corrected current waveform obtained in step S3 for the corresponding position. As the excitation source, the sum of the transient responses generated by each dipole unit at the receiving point is calculated using the superposition principle to obtain the total field response considering the waveform spatial distribution.

[0036] S5 correction effect verification, method effectiveness verification: through methods such as comparison of uniform half-space analytical solutions and verification of the repeatability of measured data, the accuracy of the correction method is quantitatively evaluated, and the corrected emission waveform dataset and transient electromagnetic response data are output.

[0037] The above five steps S1–S5 constitute a complete transmission waveform correction method flow.

[0038] This invention is the first to introduce a distributed parameter model of power transmission lines into SATEM waveform correction, achieving spatiotemporal two-dimensional inversion of the current waveform at any location on the conductor, whereas existing technologies all assume that the current waveform along the entire conductor is consistent with that at the transmitting end. Without modifying existing SATEM hardware systems, this invention accurately obtains the actual transmitted current waveform at any location on a long conductor through five steps (S1–S5), eliminating calculation errors in transient electromagnetic response caused by uneven waveform spatial distribution. This invention is applied to a semi-airborne transient electromagnetic (SATEM) exploration system. This system consists of two parts: a ground-based transmitting subsystem and an airborne receiving subsystem. The ground-based transmitting subsystem comprises a transmitter, a long grounded conductor, and a grounding electrode. The transmitter outputs a bipolar square wave current, which is injected into the ground via the long conductor to form an excitation source. The airborne receiving subsystem uses a receiving coil mounted on a UAV or other flight platform to collect the secondary field transient response signal generated by the underground medium in the air.

[0039] Long conductors are typically 1–5 km in length. In traditional lumped-parameter models, the entire conductor is treated as a single RLC lumped element, assuming the current waveform at each point is consistent with the transmitting end. However, in reality, when conductor lengths reach the kilometer level, the transmission line effects of distributed resistance, distributed inductance, distributed capacitance, and ground leakage conductance cannot be ignored—amplitude attenuation and phase delay occur as the current propagates along the conductor, distortion occurs at the turn-off edge, and the actual transmitted waveform differs significantly at different locations on the conductor. The core of this invention lies in applying the lossy transmission line distributed parameter model from power transmission line theory to a SATEM long conductor source. Through frequency domain solutions to the telegraph equations and parameter identification from measured data, the spatiotemporal distribution of current at any location on the conductor is accurately inverted, thereby achieving waveform correction of the transient electromagnetic response.

[0040] See Figure 4 The system architecture specifically includes: Current and voltage sensors: The transmitted current waveform is synchronously acquired at the transmitter output (x=0) at a sampling rate of not less than 1MHz. and transmit voltage waveform , which serves as the input data for parameter identification.

[0041] Transmission line modeling module: Establishes a model containing unit length resistance. ,inductance ,capacitance Leakage conductance The lossy transmission line distributed parameter model. and Calculated in advance based on the physical specifications of the conductor. and These are the parameters to be identified.

[0042] Parameter identification module: Based on the measured frequency domain impedance information of the port, the Levenberg-Marquardt nonlinear least squares algorithm is used for identification. and The optimal value is found to minimize the residual between the calculated impedance and the measured impedance.

[0043] Waveform inversion module: Utilizing identified transmission line parameters and measured current at the transmitter. The general solution of the telegraph equation in the frequency domain is used to calculate the position of any point on the conductor. frequency domain current The time-domain waveform is obtained by inverse Fourier transform. The spatiotemporal two-dimensional distribution of the emission current is generated.

[0044] Response correction module: Discretizes the long conductor into Each electric dipole unit is positioned at a corresponding location. Corrected current waveform As the excitation source, the transient responses of each dipole are superimposed to obtain the total field.

[0045] Output module: Outputs corrected transmit waveform dataset and transient electromagnetic response data, supporting integration with existing SATEM data processing software.

[0046] See Figure 5 System process description: S1 Transmission Line Equivalent Modeling: The long grounding conductor is equivalent to a lossy uniform transmission line, establishing a model that includes distributed parameters. The equivalent circuit model.

[0047] S2 model parameter identification: Synchronous current acquisition at the transmitting end and voltage Frequency domain data is obtained by FFT. , ; Calculate the measured input impedance ; Construct the objective function ,in Calculated using the transmission line impedance formula; Iterative optimization using the LM algorithm and Physical constraints are applied to ensure the parameters are reasonable.

[0048] Distinguishing characteristics: Over a wide frequency range, the frequency domain response is primarily affected by... and Sensitive, to Its sensitivity is low (because) (This holds true in most frequency bands). To avoid ill-conditioned problems, it is recommended to adjust the frequency band during LM iteration. Apply strong prior constraints, or use fixed... (set as) (S / m scale) Only identifies The step-by-step strategy.

[0049] Applicability prerequisite: The quasi-TEM approximation of the transmission line model requires a conductor height of... Much smaller than the electromagnetic wavelength Within the typical operating frequency range of SATEM (DC~100kHz), (km), this condition holds. For scenarios with significant variations in traverse height under complex terrain, The variability should also be taken into account.

[0050] Current waveform inversion along line S3: Based on the identified and Substitute into the frequency domain general solution of the transmission line equation; Calculate any position on the conductor Frequency domain current at ; right Perform IFFT to obtain the time-domain current waveform. .

[0051] S4 Discrete Dipole Forward Modeling Correction: Divide the long conductor into equal parts The first electric dipole unit, the second The midpoint of each unit is located at... Its excitation waveform is ; Calculate the transient response of each dipole unit at the receiving point; The total response is obtained by superimposing the responses of all units.

[0052] S5 correction effect verification: The correction accuracy is quantitatively evaluated by comparing the analytical solution of the uniform half-space and verifying the repeatability of measured data.

[0053] The details of the symbols and formulas mentioned above are shown below, and Table 1 is the symbol table: Table 1 Symbol Table (Transmission Line Parameters and Variables)

[0054] Lossy transmission line telegraph equations (time domain): (1) (2) Frequency domain form of the calculation equation: After Fourier transform, equations (1) and (2) are transformed into a system of ordinary differential equations: (3) (4) Frequency domain general solution: (5) (6) Where the propagation constant Characteristic impedance .

[0055] Input impedance formula (for calculating the objective function used for parameter identification): (7) Formula for current distribution along the line (derived from measured current at the transmitter): (8) Performing an inverse Fourier transform on equation (8) yields the time-domain current waveform: (9) Frequency dependence explanation: in equations (1)-(9) and Theoretically, it exhibits frequency dependence—the skin effect at high frequencies makes... Enlarge Reduce. For typical SATEM operating conditions (16mm² copper wire, turn-off edge equivalent frequency 20–60kHz), the skin depth is on the same order of magnitude as the wire diameter; it is recommended to introduce a reduction in this area in future improvements. Frequency correction. This invention uses the DC value as an engineering approximation, suitable for exploration scenarios with medium accuracy requirements; for high-precision applications, Carson integrals or Sunde approximations can be used. , Frequency-dependent correction is performed.

[0056] Discrete dipole superposition: dividing a long wire into equal parts The first electric dipole unit, the second Midpoint of each unit ( Its excitation current is Receiving point The total transient response at is: (10) in For the first Each dipole unit in The magnetic field strength generated by the point for Point to number The horizontal distance between the dipoles It represents the electrical conductivity of the earth.

[0057] Key technical parameters are shown in Table 2 below: Table 2 Key Technical Parameters

[0058] Physical constraints: applied during parameter identification. S / m, F / m ensures the physical rationality of the parameters.

[0059] This invention offers high modeling accuracy, introducing a distributed parameter transmission line model for the first time into the correction of semi-airborne transient electromagnetic transmission waveforms, fundamentally describing the current propagation characteristics of long conductors. Compared to traditional lumped parameter models, the transmission waveform calculation error is reduced from 15%–30% to less than 5%. It also boasts high spatial resolution, capable of inverting current values ​​at any location and time on the conductor, establishing a two-dimensional spatiotemporal distribution of the transmission current, and providing accurate source term input for high-precision forward modeling. Furthermore, it exhibits strong adaptive identification capabilities; the parameter identification steps, based on measured data, automatically adapt to different ground resistivity conditions and conductor layouts in various work areas, eliminating the need for manual adjustment of model parameters. Finally, it enhances deep exploration capabilities; after correction using this method, the calculation accuracy of late-stage signals is significantly improved, deep inversion errors are reduced by over 40%, and the effective exploration depth is increased by approximately 20%. Finally, it demonstrates strong engineering practicality; the method is a pure software solution, requiring no modification to existing hardware, and can be directly integrated into existing SATEM data processing workflows. It can also be used for the reprocessing and reinterpretation of historical exploration data. This invention has good compatibility. The method of this invention can be used in conjunction with existing data processing methods such as noise suppression, motion correction, and terrain correction to form a complete SATEM data processing chain.

[0060] The following example, using SATEM transmit waveform correction with a 2km long conductor, will further explain and illustrate this invention: Test conditions: Wire length: m, using 16mm² copper core wire (radius) mm); Transmission current: peak 40A, fundamental frequency 25Hz, bipolar square wave; Earth resistivity: approximately 100 (Uniform half-space assumption); Reception altitude: Flight altitude 30m.

[0061] The transmission line parameters are shown in Table 3 below: Table 3 Transmission line parameters

[0062] Waveform distortion characteristics: conductor end ( m) The current amplitude is attenuated by approximately 0.5% compared to the fundamental frequency (25Hz) at the transmitter, and the high-frequency transient component (equivalent frequency of the turn-off edge is approximately 20–60kHz) is attenuated by approximately 12%; the rise time of the turn-off edge is reduced from 8 at the transmitter. s increased to 15 at the end The current waveform exhibits a transmission delay, with the end lagging behind the transmitter by approximately 6.7 seconds. The aforementioned 12% amplitude attenuation is mainly caused by the transmission loss of the high-frequency transient components, while the attenuation of the fundamental component at 25Hz is minimal.

[0063] The correction results are shown in Table 4 below: Table 4 Correction Results

[0064] This embodiment verifies the effectiveness of the SATEM transmit waveform correction method based on the transmission line equivalent model: after correction, the forward modeling error decreased from 18.3% to 4.2%, the late signal error decreased from 27.5% to 6.8%, and the effective detection depth was increased by approximately 23%. It is particularly suitable for SATEM exploration scenarios with long conductors (1–5 km) and great depths.

[0065] Example 2 See Figure 2 A semi-airborne transient electromagnetic transmission waveform correction system based on a transmission line equivalent model includes: The equivalent circuit model building module is used to convert the long grounding conductor of the semi-aerospace transient electromagnetic system into a lossy transmission line and build an equivalent circuit model with distributed parameters including unit length resistance, unit length inductance, unit length capacitance and unit length leakage conductance. The capacitance and leakage conductance identification module is used to synchronously acquire the transmission current waveform and transmission voltage waveform at the transmitting end, obtain the measured input impedance based on the transmission current waveform and transmission voltage waveform, and identify the capacitance and leakage conductance per unit length with the goal of minimizing the frequency domain residual between the measured input impedance and the input impedance calculated based on the distributed parameter equivalent circuit model. The spatiotemporal distribution generation module is used to calculate the frequency domain current at any position on the grounding long conductor based on the identified unit length capacitance and unit length leakage conductance, as well as the emission current waveform, through the frequency domain general solution of the telegraph equation of the distributed parameter equivalent circuit model. The time domain current waveform at any position is obtained through inverse Fourier transform, thus generating the spatiotemporal distribution of the emission current. The module for calculating the total transient response is used to discretize the grounding long conductor into multiple electric dipole units. Each electric dipole unit uses the time-domain current waveform at its location in the spatiotemporal distribution as the excitation source. The transient response generated by each electric dipole unit at the receiving point is calculated and superimposed to obtain the total transient response.

[0066] Example 3 See Figure 3 An electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements a semi-aerospace transient electromagnetic emission waveform correction method based on a transmission line equivalent model.

[0067] Example 4 A computer-readable storage medium storing a computer program that, when executed by a processor, implements a semi-aeronautical transient electromagnetic emission waveform correction method based on a transmission line equivalent model.

[0068] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, read-only optical discs, optical storage, etc.) containing computer-usable program code.

[0069] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0070] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0071] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for correcting semi-airborne transient electromagnetic emission waveforms based on a transmission line equivalent model, characterized in that, Includes the following steps: S1. The grounding long conductor of the semi-aircraft transient electromagnetic system is equivalent to a lossy transmission line, and a distributed parameter equivalent circuit model is established, which includes unit length resistance, unit length inductance, unit length capacitance and unit length leakage conductance. S2. Simultaneously acquire the transmission current waveform and transmission voltage waveform at the transmitting end, obtain the measured input impedance based on the transmission current waveform and the transmission voltage waveform, and identify the unit length capacitance and the unit length leakage conductance with the goal of minimizing the frequency domain residual between the measured input impedance and the input impedance calculated based on the equivalent circuit model of the distributed parameters. S3. Based on the identified unit length capacitance and unit length leakage conductance, as well as the emission current waveform, calculate the frequency domain current at any position on the grounding long conductor through the frequency domain general solution of the telegraph equation of the distributed parameter equivalent circuit model, and obtain the time domain current waveform at the arbitrary position through inverse Fourier transform to generate the spatiotemporal distribution of the emission current. S4. Discretize the grounding long conductor into multiple electric dipole units. Each electric dipole unit uses the time-domain current waveform at its location in the spatiotemporal distribution as the excitation source. Calculate the transient response generated by each electric dipole unit at the receiving point and superimpose them to obtain the total transient response.

2. The semi-airborne transient electromagnetic transmission waveform correction method based on the transmission line equivalent model according to claim 1, characterized in that, In S2, the minimum value of the frequency domain residual is iteratively solved using the Levenberg-Marquardt nonlinear least squares algorithm to obtain the identification values ​​of the unit length capacitance and the unit length leakage conductance. During the iterative solution process, physical constraints are applied to the unit length leakage conductance and the unit length capacitance. The physical constraints include the upper limit of the value of the unit length leakage conductance and the upper limit of the value of the unit length capacitance.

3. The semi-airborne transient electromagnetic transmission waveform correction method based on the transmission line equivalent model according to claim 1, characterized in that, In S1, the unit length resistance and the unit length inductance are determined by the physical specifications of the grounding long conductor, and the unit length capacitance and the unit length leakage conductance are parameters to be identified; the distributed parameter equivalent circuit model also includes the end grounding resistance of the grounding long conductor, and the end grounding resistance participates in the calculation of the input impedance as the terminal load of the lossy transmission line.

4. The semi-airborne transient electromagnetic transmission waveform correction method based on the transmission line equivalent model according to claim 3, characterized in that, In S2, the input impedance calculated based on the equivalent circuit model with distributed parameters satisfies: Where Z0 is the characteristic impedance, Z L Let γ be the end grounding resistance, γ be the propagation constant, and L be the total length of the grounding conductor.

5. The semi-airborne transient electromagnetic transmission waveform correction method based on the transmission line equivalent model according to claim 4, characterized in that, In S3, the frequency domain general solution of the telegraph equation includes the propagation constant and characteristic impedance, and the propagation constant satisfies the following equation: The characteristic impedance satisfies the following equation: Where R0 is the resistance per unit length, L0 is the inductance per unit length, G0 is the leakage conductance per unit length, C0 is the capacitance per unit length, ω is the angular frequency, and j is the imaginary unit; The frequency domain current at any position on the grounding long conductor satisfies: Where I(0,ω) is the frequency domain form of the transmitted current waveform, x is the position coordinate, L is the total length of the grounding conductor, γ is the propagation constant, Z0 is the characteristic impedance, and Z L This is the end grounding resistance.

6. The semi-airborne transient electromagnetic transmission waveform correction method based on the transmission line equivalent model according to claim 1, characterized in that, In S4, the grounding long conductor is divided into multiple electric dipole units, and the excitation source of each electric dipole unit is taken from the time-domain current waveform at the midpoint of the electric dipole unit.

7. The semi-airborne transient electromagnetic transmission waveform correction method based on the transmission line equivalent model according to claim 1, characterized in that, It also includes S5, comparing the total transient response obtained in S4 with the analytical solution of the uniform half-space, and verifying the repeatability of the measured data, and outputting the corrected transmission waveform dataset and transient electromagnetic response data.

8. A semi-airborne transient electromagnetic transmission waveform correction system based on a transmission line equivalent model, characterized in that, include: The equivalent circuit model building module is used to convert the long grounding conductor of the semi-aerospace transient electromagnetic system into a lossy transmission line and build an equivalent circuit model with distributed parameters including unit length resistance, unit length inductance, unit length capacitance and unit length leakage conductance. The capacitance and leakage conductance identification module is used to synchronously acquire the transmission current waveform and transmission voltage waveform at the transmitting end, obtain the measured input impedance based on the transmission current waveform and the transmission voltage waveform, and identify the unit length capacitance and the unit length leakage conductance with the goal of minimizing the frequency domain residual between the measured input impedance and the input impedance calculated based on the distributed parameter equivalent circuit model. A spatiotemporal distribution generation module is used to calculate the frequency domain current at any position on the grounding long conductor based on the identified unit length capacitance and unit length leakage conductance, as well as the emission current waveform, through the frequency domain general solution of the telegraph equation of the equivalent circuit model of the distributed parameters, and obtain the time domain current waveform at the arbitrary position through inverse Fourier transform, thereby generating the spatiotemporal distribution of the emission current. The total transient response calculation module is used to discretize the grounding long conductor into multiple electric dipole units. Each electric dipole unit uses the time-domain current waveform at its location in the spatiotemporal distribution as the excitation source. The transient response generated by each electric dipole unit at the receiving point is calculated and superimposed to obtain the total transient response.

9. An electronic device, characterized in that, The method includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the semi-aerospace transient electromagnetic emission waveform correction method based on the transmission line equivalent model as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the semi-aerospace transient electromagnetic emission waveform correction method based on a transmission line equivalent model as described in any one of claims 1-7.

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