Pseudo-random multi-frequency wide-area electromagnetic method signal reconstruction method and device

Abstract

This application proposes a pseudo-random multi-frequency wide-area electromagnetic method signal reconstruction method and device. Through pseudo-random signal encoding, constructing pseudo-random multi-frequency transmitted signals, constructing equivalent currents of pseudo-random signals, calculating the electromagnetic response of pseudo-random signals based on geoelectric models, reconstructing the spectrum of pseudo-random signals with geoelectric information, and generating waveforms of pseudo-random signals with geoelectric information, it is possible to obtain pseudo-random signals after coupling with the earth medium, realize the reconstruction of the true waveform of wide-area electromagnetic method signals after passing through the strata, and thus obtain high-precision noise-free signals, providing a foundation for subsequent noise suppression, waveform compensation, and apparent resistivity estimation.

Description

[0001] A Pseudo-random Multi-Frequency Electromagnetic Signal Reconstruction Method Including Ground Electricity Information Technical Field

[0002] This application relates to the field of data processing technology, and in particular to a pseudo-random multi-frequency wave wide-area electromagnetic signal reconstruction method and device. Background Technology

[0003] Currently, the Wide-field Electromagnetic Method (WFEM) uses pseudo-random multi-frequency signals as the field source, which is affected by natural source noise, industrial noise, line coupling noise, and instrument noise during field observations. To eliminate noise interference, existing methods generally adopt the following procedure:

[0004] (1) Construct pseudo-random multi-frequency wave signal waveforms in free space;

[0005] (2) Directly superimpose noise, such as random noise, triangular noise, rectangular noise, etc., onto the waveform to form a noisy signal;

[0006] (3) Based on (2), noise identification and analysis are carried out.

[0007] As can be seen from the above, these simulated pseudo-random multi-frequency wave signals do not contain information about the earth's medium and are unrelated to the earth's electrical structure. However, the actual electrical structure of the earth's medium will affect the propagation of pseudo-random multi-frequency wave signals through attenuation, dispersion, phase changes, and frequency selectivity. In particular, pseudo-random multi-frequency waves will exhibit significant waveform distortion under different geological conditions. Electromagnetic signals are not coupled through the earth's electrical medium; noise is artificially added to the signal only in free space. The resulting "noisy signal" differs significantly from the actual received signal, causing current noise processing methods to fail due to the mismatch between the noise model and the measured model. Summary of the Invention

[0008] This application proposes a pseudo-random multi-frequency wave wide-area electromagnetic signal reconstruction method and device, which can solve one of the problems existing in the background technology.

[0009] To achieve the above objectives, this application adopts the following technical solution:

[0010] Firstly, a pseudo-random multi-frequency wave wide-area electromagnetic signal reconstruction method is provided, including:

[0011] Based on pseudo-random coding rules, a pseudo-random multi-frequency transmission signal is constructed.

[0012] The amplitude information of each frequency component is extracted from the spectrum of the pseudo-random multi-frequency transmitted signal and used as the current excitation parameter in the electromagnetic detection method to construct the equivalent current.

[0013] The equivalent current is used as the source current parameter in the constructed geoelectric model to calculate the electromagnetic response of the pseudo-random multi-frequency transmitted signal along its propagation path.

[0014] The real and imaginary parts are separated from the electromagnetic response to form an equivalent spectrum;

[0015] Furthermore, an inverse Fourier transform is performed on the equivalent spectrum to obtain a pseudo-random signal waveform with ground electrical information.

[0016] In one possible design of the first aspect, the pseudo-random multi-frequency wide-area electromagnetic signal reconstruction method further includes:

[0017] According to the balancing strategy, the spectrum of the pseudo-random multi-frequency transmitted signal is truncated. The balancing strategy is used to balance computational efficiency and waveform accuracy.

[0018] In one possible design approach of the first aspect, the balancing strategy specifically involves introducing the maximum relative error and the first-order difference normalized cross-correlation coefficient as evaluation quantities for waveform changes before and after harmonic truncation, wherein the maximum relative error is:

[0019] in, It is the maximum relative error; It is the value of the original signal at the i-th sampling point; It is the value of the reconstructed signal at the i-th sampling point; This is the total number of signal sampling points; It is an absolute value operation; It takes the maximum value among all sampled points;

[0020] The first-order difference normalized cross-correlation coefficient is:

[0021] Where R is the first-order difference-normalized cross-correlation coefficient; It is the first-order difference of the original signal; It is the first-order difference of the reconstructed signal; It is the value of the original signal at the i-th sampling point; It is the value of the reconstructed signal at the i-th sampling point; This represents the total number of signal sampling points.

[0022] In one possible design approach for the first aspect, take ≤5%, R≥0.98 are used as harmonic cutoff criteria.

[0023] In one possible design of the first aspect, the electromagnetic response is the horizontal component E of the electric field under the excitation of the galvanic source. x :

[0024] Among them, E x It is the electric field component of the electromagnetic field; n is the number of strata; R and R * These are functions characterizing the electrical parameters of different formations; IdL is the dipole moment, I is the harmonic current, and represents the amplitude of each frequency component of the spectrum of the pseudo-random multi-frequency transmitted signal. The angle between the observation direction and the dipole moment axis represents the distance between the two poles; dL is the length of the conductor element; r is the transmit / receive distance; ω is the angular frequency; μ is the air permeability; m is the spatial frequency, with dimensions [L]. -1 ]; where m is defined i =(m²+k² i ) 1 / 2 ,and k i Let be the wavenumber of the i-th electrical layer. The corresponding layer resistivity; where and Let mr represent the zeroth and first-order Bessel functions, respectively.

[0025] In one possible design approach of the first aspect, the pseudo-random coding rule is: 2 n A sequence pseudo-random signal is a multi-frequency signal encoded in a binary distribution manner, containing k main frequency components. The signal 2... n The sequence of pseudo-random signals passes through the set Z of three elements {1, 0, -1}. |Z|<2 The additive synthesis rule combines multiple square wave signals of different frequencies to form a signal. The additive synthesis rule includes:

[0026] (1) Set Z |Z|<2 In Z, the sum of any two elements is still contained in the set Z. |Z|<2 In this context, the result of finitely many additions of any element is still the element itself.

[0027] (2) If the addition of the three elements {1, 0, -1} is a single operation, it satisfies the associative and commutative laws.

[0028] (3) In the same expression, if any of the three elements {1, 0, -1} is added twice or more, they must be added in order, and neither the associative law nor the commutative law applies.

[0029] (4) Element 0 cannot be split into the sum of operations of the other two elements {1, -1} and then the operation is performed.

[0030] In one possible design approach for the first aspect, the periodic function f i (t) is the constituent of 2 n The generating function of the sequence pseudo-random coding function:

[0031] Where i = 1, 2, ..., n; k = 0, ±1, ±2, ±3, ... i, are integers ranging from 1 to n, and k is an integer whose absolute value increases from 0, including positive and negative integers; t is the independent variable of the horizontal axis of the function.

[0032] in, 2 n Sequence pseudo-random signal encoding, Z is a set of three elements |Z|<2 The self-enclosed addition in the equation.

[0033] In one possible design approach of the first aspect, when n=7, the pseudo-random signal code A7 is:

[0034] In one possible design approach of the first aspect, 2 n Sequence pseudo-random signal encoding {A n The general formula for the Fourier coefficients of} for:

[0035] Where k is a natural number greater than 1; ω is the angular frequency; represent The first two of the encoding n-2 The cycle continues in this manner.

[0036] In a second aspect, an electronic device is provided, comprising: a processor and a memory coupled to the processor, the memory for storing a computer program; the processor for executing the computer program stored in the memory such that the electronic device performs the pseudo-random multi-frequency wide-area electromagnetic signal reconstruction method as described in any possible implementation of the first aspect.

[0037] Beneficial effects:

[0038] Based on the above technical solution, through pseudo-random signal encoding, construction of pseudo-random multi-frequency transmission signals, construction of equivalent current of pseudo-random signals, calculation of electromagnetic response of pseudo-random signals based on geoelectric models, reconstruction of the spectrum of pseudo-random signals with geoelectric information, and generation of waveforms of pseudo-random signals with geoelectric information, it is possible to obtain pseudo-random signals after coupling with the earth medium, realize the reconstruction of the true waveform of wide-area electromagnetic signals after passing through the strata, thereby obtaining high-precision noise-free signals, providing a foundation for subsequent noise suppression, waveform compensation and apparent resistivity estimation. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a flowchart of the pseudo-random 7-frequency wide-area electromagnetic method signal reconstruction method based on real stratum response provided in the embodiments of this application;

[0041] Figure 2 This is a pseudo-random signal waveform diagram provided in the embodiments of this application;

[0042] Figure 3 This is a spectrum diagram of the 7-frequency group signal provided in the embodiments of this application;

[0043] Figure 4 This is a diagram of the truncated real and imaginary parts provided in an embodiment of this application;

[0044] Figure 5 This is a truncated pseudo-random multi-frequency signal spectrum diagram provided in the embodiments of this application;

[0045] Figure 6 This is a pseudo-random signal spectrum diagram of a grounded electrical signal provided in an embodiment of this application;

[0046] Figure 7 This is a pseudo-random signal waveform diagram of a grounded electrical signal provided in an embodiment of this application. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0048] It should be noted that although functional modules are divided in the device schematic diagram and the logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than the module division in the device or the order in the flowchart. The terms "first," "second," etc., in the specification and the above-mentioned figures are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0050] This embodiment relates to a pseudo-random 7-frequency wide-area electromagnetic method signal reconstruction method based on real stratum response, which can be used as a reference input for wide-area electromagnetic method noise suppression, signal processing and inversion algorithms.

[0051] This embodiment provides an experimental method for minimizing the impact on the signal and shortening the computation time during forward modeling by removing a certain number of harmonics based on a pseudo-random 7-frequency wave, including the similarity error between the original signal and the reconstructed signal. For example... Figure 1 As shown. Specifically:

[0052] Step S1: Pseudo-random signal encoding;

[0053] 2 n A sequence pseudo-random signal is a multi-frequency signal encoded in a binary distribution, containing k dominant frequency components. This signal is constructed by combining multiple square wave signals of different frequencies using an additive synthesis rule based on a set of three elements. This principle was invented by Academician He Jishan, assuming the existence of a set Z. |Z|<2 The set consists of integers whose absolute value is less than 2, Z. |Z|<2 The array contains only elements {1, 0, -1}, and satisfies the following addition rules:

[0054] (1) Set Z |Z|<2 In this set, the sum of any two elements is still included in the set, and the sum of any element itself is still itself after a finite number of sums.

[0055] (2) If the addition of the three elements {-1, 0, 1} is a single operation (the three elements appear only once), it satisfies the associative and commutative laws.

[0056] (3) In the same expression, if any of the three elements -1, 0, and 1 are added more than twice (including twice), they must be added in order, and neither the associative law nor the commutative law applies.

[0057] (4) Element 0 cannot be split into the sum of operations on the other two elements and then operated on again;

[0058] Periodic function f i (t) is the constituent of 2 n The generating function of the sequence pseudo-random coding function:

[0059] In the formula, i = 1, 2, ..., n, k = 0, ±1, ±2, ±3, ..., i is an integer ranging from 1 to n, k is an integer whose absolute value increases from 0 (including positive and negative integers), and t is the independent variable of the horizontal axis of the function.

[0060] Z represents the set of three elements (additive group) as defined by Academician He Jishan. |Z|<2 The self-enclosed addition in the equation.

[0061] For example: ;

[0062] From the above, we can conclude that when n=7, the code for the pseudo-random signal is (A7):

[0063] Its pseudo-random signal waveform is as follows Figure 2 As shown.

[0064] Step S2: Construct a pseudo-random multi-frequency transmission signal;

[0065] A pseudo-random signal is a signal that appears random on the surface but actually exhibits deterministic patterns. In the field of electrical exploration, A sequence is a typical pseudo-random coded signal, where a and k are natural numbers greater than 1, with a typically being 2, and p represents the number of dominant frequencies. Pseudo-random signals have a defined coding structure, distributing p dominant frequency components in a base-a manner. n Taking a sequence as an example, its encoding {A n} is a period T=2 n The coefficients of an odd function in its Fourier series can be expressed as:

[0066] Since the encoding {An} has semi-periodic symmetry, the above formula can be simplified to:

[0067] According to the recursive formula:

[0068] in: ,represent The first 2n-2 cycles of the encoding, , ;

[0069] Therefore, 2 n Sequence pseudo-random encoding {A n The general formula for the Fourier coefficients of} is:

[0070] This embodiment uses a pseudo-random 7-frequency waveform as an example. Here, the 7-frequency waveform refers to the 7 main frequencies of the pseudo-random coded waveform. When p=7, the spectrum is as follows: Figure 3 As shown, its seven main frequencies are 1, 2, 4, 8, 16, 32, and 64 Hz.

[0071] Step S3: Pseudo-random signal spectrum truncation strategy;

[0072] Figure 3 The spectrum shown contains many harmonic components, and the harmonic amplitudes at most frequencies are very small, especially the high-frequency harmonics, whose intensity is close to zero. These harmonics are not considered in electromagnetic signal processing and can therefore be truncated. However, improper truncation can cause distortion of the pseudo-random waveform. The purpose of the pseudo-random signal harmonic truncation strategy is to reduce high-frequency harmonic components while maintaining waveform accuracy. The more frequency components retained, the greater the subsequent computational load. To balance computational efficiency and waveform accuracy, this patent introduces the maximum relative error (RErr) and the first-order differential normalized cross-correlation coefficient (RNCC) as evaluation metrics for waveform changes before and after harmonic truncation. A smaller maximum relative error and a larger first-order differential normalized cross-correlation coefficient indicate higher waveform similarity. This patent uses RErr ≤ 5% and RNCC ≥ 0.98 as harmonic truncation criteria. If RErr does not meet the requirement of less than 5%, some harmonics are truncated until the requirement is met. The same applies to RNCC. Assuming the current value of RNCC is 0.98, and the value of RErr is not exactly 5%, it can still be used. RErr is as follows: RNCC is also known as R below. Simultaneously, the spectrum of a pseudo-random signal after harmonic truncation can be separated into real and imaginary parts, as shown below. Figure 4 As shown.

[0073] The expression for the maximum relative error is as follows:

[0074] Maximum relative error;

[0075] : The value of the original signal at the i-th sampling point;

[0076] : Reconstruct the value of the signal at the i-th sampling point;

[0077] Total number of signal sampling points;

[0078] Absolute value operation;

[0079] Take the maximum value among all sampled points;

[0080] The expression for the normalized correlation coefficient is as follows:

[0081] R: Normalized cross-correlation coefficient;

[0082] x(i): The value of the original signal at the i-th sampling point;

[0083] y(i): The value of the reconstructed signal at the i-th sampling point;

[0084] N: Total number of signal sampling points;

[0085] : Summation symbol;

[0086] The range of this coefficient is -1≤R≤1, where R=1 means the two signals are completely identical; R=0 means the two signals are uncorrelated; and R=-1 means the two signals are completely out of phase. Generally, in signal reconstruction problems, the closer R is to 1, the higher the signal similarity.

[0087] First-order difference normalized cross-correlation coefficient:

[0088] R: First-order difference-normalized cross-correlation coefficient;

[0089] The first-order difference of the original signal;

[0090] The first-order difference of the reconstructed signal;

[0091] : The value of the original signal at the i-th sampling point;

[0092] : Reconstruct the value of the signal at the i-th sampling point;

[0093] Total number of signal sampling points;

[0094] Compared to the normalized cross-correlation coefficient, the first-difference normalized correlation coefficient is more sensitive to abrupt changes and is better able to determine the magnitude of the impact of abrupt changes caused by harmonic truncation.

[0095] Step S4: Construct the equivalent current of the truncated pseudo-random signal;

[0096] Pseudo-random spectrum after spectral truncation, such as Figure 5 As shown, the amplitude information of each frequency component is extracted from the truncated pseudo-random multi-frequency signal spectrum and used as the current excitation parameter in electromagnetic detection, called the equivalent current. For example, the equivalent current for 2Hz is 23.6903A. Through this method, the correspondence between the frequency components in the pseudo-random signal spectrum and the current intensity of the excitation source parameters in electromagnetic detection is realized, ensuring that the excitation intensity of each frequency component in the electromagnetic field calculation remains consistent with the spectral energy distribution of the pseudo-random signal.

[0097] Step S5: Establish an underground electrical model;

[0098] Step 5.1: Parameter example, taking a two-layer horizontal medium as an example, number of layers: 2 layers.

[0099] First layer: resistivity ρ1=100Ω·m, thickness of first layer: h1=500m;

[0100] The second layer has a resistivity of ρ2 = 1000 Ω·m and a thickness of h2 that is infinite.

[0101] Transmit / receive distance (horizontal distance from source to receiver): r = 8000m;

[0102] Vacuum permeability: μ0 = 4π × 10 −7 H / m;

[0103] Step 5.2: Modeling Assumptions;

[0104] Utilizing a layered medium model and a low-frequency electromagnetic diffusion approximation (quasi-static), neglecting displacement current, this method is applicable to wide-field electromagnetic methods and controlled-source audio-frequency magnetotelluric methods. The electric field intensity along the propagation path is calculated using the precise expression of the horizontal electric field of an electric dipole source, with the aim of obtaining the electric field signal acting through the strata.

[0105] Step S6: Calculation of electromagnetic response of pseudo-random signal based on geoelectric model;

[0106] After the geoelectric model and equivalent excitation current are constructed, the equivalent current parameters are used as the source current parameters of the wide-area electromagnetic method in the geoelectric model to calculate the electromagnetic response of the pseudo-random signal on its propagation path. The frequency parameters are all frequencies of the truncated pseudo-random signal.

[0107] The formula for calculating the horizontal component E(x) of the electric field under thermocouple source excitation is as follows:

[0108] Where E x The electric field component of the electromagnetic field, n is the number of strata, and R and R * It is a function characterizing the electrical parameters of different strata; the dipole moment is IdL, and I is the harmonic current; The angle between the observation direction and the dipole moment axis represents the distance between the two poles; dL is the length of the conductor element; r is the transmit / receive distance; ω is the angular frequency; μ is the permeability of free space; m is the spatial frequency, with dimensions [L]. -1 ]; where m is defined i =(m²+k² i ) 1 / 2 ,and k i Let be the wavenumber of the i-th electrical layer. The corresponding layer resistivity; where and Let mr represent the zeroth and first-order Bessel functions, respectively.

[0109] In this formula, the current I is the amplitude corresponding to each frequency of the truncated signal spectrum, μ = 4π × 10⁻⁶. −7 H / m, R and R * These are functions characterizing the electrical parameters of different strata. The values ​​R and R' for each stratum can be derived from the last stratum using their formulas. * dL=1000 , , For example, with r=8000m and a current of 2Hz, the current is 23.6903A. Substituting the geoelectric parameters and current into the above formula, the electric field strength is 6.715915833488501e. -9 +9.327734491715964e -9i It is a complex number. Therefore, the electric field strength at each frequency can be calculated.

[0110] Step S7: Reconstruct the spectrum of the pseudo-random signal with ground electricity information;

[0111] Electromagnetic response E x Since it is a complex number, its real and imaginary parts are separated and used to replace the real and imaginary parts of the pseudo-random signal spectrum after truncation in step "S3", respectively, to form the pseudo-random signal spectrum of the grounded electrical signal, which is called the equivalent spectrum.

[0112] Figure 6 This is the spectrum of a pseudo-random signal with grounded electrical signal.

[0113] Step S8: Generate a pseudo-random signal waveform with grounding information;

[0114] Performing an inverse Fourier transform on the equivalent spectrum yields a pseudo-random signal waveform with ground electrical information. (Comparison) Figure 2 The waveform, after passing through the strata, is no longer a strictly square wave; the edges become gentler, and the waveform undulations are continuous, but it still retains the characteristics of a pseudo-random signal. In terms of magnitude, it is reduced by 10 orders of magnitude. The number of steps in the waveform is reduced. Figure 7 This is a pseudo-random signal waveform with grounded electrical signal.

[0115] This embodiment has the following advantages and positive effects:

[0116] ① For the first time, a real pseudo-random multi-frequency reference signal after passing through the strata was obtained, avoiding the serious deviation of existing methods based on "theoretical waveforms";

[0117] ②The synthesized signal is highly consistent with the real WFEM received signal and can be used for training actual denoising models;

[0118] ③ It can adapt to different formation resistivity models and generate corresponding waveforms based on formation parameters, which has good engineering applicability.

[0119] This application also provides an electronic device, including: a processor, and a memory coupled to the processor, the memory being used to store a computer program; the processor being used to execute the computer program stored in the memory, so that the electronic device performs the method as described in any of the above embodiments.

[0120] Electronic devices can be computing devices such as desktop computers, laptops, handheld computers, and cloud servers. These electronic devices may include, but are not limited to, processors and memory.

[0121] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor. The processor is the control center of the electronic device, connecting various parts of the device via various interfaces and lines.

[0122] The memory can be used to store the computer program, and the processor implements various functions of the electronic device by running or executing the computer program stored in the memory and calling the data stored in the memory.

[0123] The memory may primarily include a program storage area and a data storage area. The program storage area may store the operating system, applications required for at least one function, etc.; the data storage area may store data created based on the use of the mobile phone, etc. In addition, the memory may include high-speed random access memory, and may also include non-volatile memory, such as hard disk, memory, plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, at least one disk storage device, flash memory device, or other volatile solid-state storage device.

[0124] This application also provides a storage medium, which is a computer-readable storage medium. The computer program is stored in the computer-readable storage medium, and when executed by a processor, the computer program can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable file, or some intermediate form. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0125] This application also provides a computer program product, including: a computer program or instructions that, when the computer program or instructions are run on a computer, cause the computer to perform any of the above possible implementation methods.

[0126] The above description is the preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications are also considered to be within the scope of protection of this application.

Claims

1. A pseudo-random multi-frequency wave wide-area electromagnetic signal reconstruction method, characterized in that, include: Based on pseudo-random coding rules, a pseudo-random multi-frequency transmission signal is constructed. The amplitude information of each frequency component is extracted from the spectrum of the pseudo-random multi-frequency transmitted signal and used as the current excitation parameter in the electromagnetic detection method to construct the equivalent current. The equivalent current is used as the source current parameter in the constructed geoelectric model to calculate the electromagnetic response of the pseudo-random multi-frequency transmitted signal along its propagation path. The real and imaginary parts are separated from the electromagnetic response to form an equivalent spectrum; Furthermore, an inverse Fourier transform is performed on the equivalent spectrum to obtain a pseudo-random signal waveform with ground electrical information.

2. The pseudo-random multi-frequency wave wide-area electromagnetic signal reconstruction method as described in claim 1, characterized in that, The pseudo-random multi-frequency wave wide-area electromagnetic signal reconstruction method further includes: According to the balancing strategy, the spectrum of the pseudo-random multi-frequency transmitted signal is truncated. The balancing strategy is used to balance computational efficiency and waveform accuracy.

3. The pseudo-random multi-frequency wave wide-area electromagnetic signal reconstruction method as described in claim 2, characterized in that, The balancing strategy specifically involves introducing the maximum relative error and the first-order difference normalized cross-correlation coefficient as evaluation quantities for waveform changes before and after harmonic truncation, where the maximum relative error is: in, It is the maximum relative error; It is the value of the original signal at the i-th sampling point; It is the value of the reconstructed signal at the i-th sampling point; This is the total number of signal sampling points; It is an absolute value operation; It takes the maximum value among all sampled points; The first-order difference normalized cross-correlation coefficient is: Where R is the first-order difference-normalized cross-correlation coefficient; It is the first-order difference of the original signal; It is the first-order difference of the reconstructed signal; It is the value of the original signal at the i-th sampling point; It is the value of the reconstructed signal at the i-th sampling point; This represents the total number of signal sampling points.

4. The pseudo-random multi-frequency wave wide-area electromagnetic signal reconstruction method as described in claim 3, characterized in that, Pick ≤5%, R≥0.98 are used as harmonic cutoff criteria.

5. The pseudo-random multi-frequency wave wide-area electromagnetic signal reconstruction method as described in claim 1, characterized in that, The electromagnetic response is the horizontal component E of the electric field under the excitation of the dipole source. x : Among them, E x It is the electric field component of the electromagnetic field; n is the number of strata; R and R * These are functions characterizing the electrical parameters of different formations; IdL is the dipole moment, I is the harmonic current, and represents the amplitude of each frequency component of the spectrum of the pseudo-random multi-frequency transmitted signal. The angle between the observation direction and the dipole moment axis represents the distance between the two poles; dL is the length of the conductor element; r is the transmit / receive distance; ω is the angular frequency; μ is the permeability of free space; m is the spatial frequency, with dimensions [L]. -1 ]; where m is defined i =(m²+k² i ) 1 / 2 ,and k i Let be the wavenumber of the i-th electrical layer. The corresponding layer resistivity; where and Let mr represent the zeroth and first-order Bessel functions, respectively.

6. The pseudo-random multi-frequency wave wide-area electromagnetic signal reconstruction method as described in claim 1, characterized in that, The pseudo-random coding rule is: 2 n A sequence pseudo-random signal is a multi-frequency signal encoded in a binary distribution manner, containing k main frequency components. The signal 2... n The sequence of pseudo-random signals passes through the set Z of three elements {1, 0, -1}. |Z|<2 The additive synthesis rule combines multiple square wave signals of different frequencies to form a signal. The additive synthesis rule includes: (1) Set Z |Z|<2 In Z, the sum of any two elements is still contained in the set Z. |Z|<2 In this context, the result of finitely many additions of any element is still the element itself. (2) If the addition of the three elements {1, 0, -1} is a single operation, it satisfies the associative and commutative laws. (3) In the same expression, if any of the three elements {1, 0, -1} is added twice or more, they must be added in order, and neither the associative law nor the commutative law applies. (4) Element 0 cannot be split into the sum of operations of the other two elements {1, -1} and then the operation is performed.

7. The pseudo-random multi-frequency wave wide-area electromagnetic signal reconstruction method as described in claim 1, characterized in that, Periodic function f i (t) is the constituent of 2 n The generating function of the sequence pseudo-random coding function: Where i = 1, 2, ..., n; k = 0, ±1, ±2, ±3, ... i, are integers ranging from 1 to n, and k is an integer whose absolute value increases from 0, including positive and negative integers; t is the independent variable of the horizontal axis of the function. in, 2 n Sequence pseudo-random signal encoding, Z is a set of three elements |Z|<2 The self-enclosed addition in the equation.

8. The pseudo-random multi-frequency wave wide-area electromagnetic signal reconstruction method as described in claim 7, characterized in that, When n=7, the pseudo-random signal code A7 is:

9. The pseudo-random multi-frequency wave wide-area electromagnetic signal reconstruction method as described in claim 8, characterized in that, 2 n Sequence pseudo-random signal encoding {A n The general formula for the Fourier coefficients of} for: Where k is a natural number greater than 1; ω is the angular frequency; represent The first two of the encoding n-2 The cycle continues in this manner.

10. An electronic device, characterized in that, The electronic device includes: a processor, and a memory coupled to the processor. The memory is used to store computer programs; The processor is configured to execute the computer program stored in the memory, so that the electronic device performs the pseudo-random multi-frequency wide-area electromagnetic signal reconstruction method as described in any one of claims 1-9.

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