Very low frequency signal field intensity calculation method and system

Abstract

The invention discloses a very low frequency signal field intensity calculation method and system, and the method comprises the steps: obtaining a source region electromagnetic pulse signal, and carrying out the Fourier transform of the source region electromagnetic pulse signal, and obtaining the amplitude and phase of the electric field intensity of different frequency components of the source region electromagnetic pulse signal; establishing an ionosphere model in the long wave propagation model, respectively setting initial calculation parameters of the ionosphere model, and according to the ionosphere model, obtaining field intensities and phases of grid points corresponding to all frequency point values and having a fixed step length from a source point on an electromagnetic pulse signal propagation path; determining a first three-dimensional matrix according to the calculation results of the field intensity and the phase of the grid points, the total number of the grid points and the number of the frequency point values; and determining a second three-dimensional matrix representing the field intensity attenuation amount and the phase change amount of the grid points, and obtaining a third three-dimensional matrix representing the electric field intensity amplitudes and the phase values of the electromagnetic pulse signals of different frequency points at the grid points according to the first three-dimensional matrix and the second three-dimensional matrix. According to the invention, the problem of low accuracy during field intensity attenuation calculation in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of data processing, and in particular to a very low frequency signal field strength calculation method and system. Background Art

[0002] Very low frequency / low frequency signals (3-300kHz) have long wavelengths and are capable of long-distance waveguide propagation in the Earth-ionosphere. They are widely used in submarine communications, lightning detection, nuclear explosion detection, etc. In the field of very low frequency / low frequency detection, field strength attenuation calculation is of great significance to the deployment of communication / detection station networks, lightning / nuclear explosion source location and identification, etc.

[0003] The widely used engineering VLF / LF signal field strength calculation model is the LWPC model (Long-Wavelength Propagation Capability), but the existing calculations are all for single-frequency signals. When the frequency components of the signal are complex, it will become inappropriate to use a single frequency point to calculate the field strength attenuation. For example, the signal generated by lightning or nuclear explosion is a pulse signal with very rich frequency components. If a single frequency point is used to calculate the field strength attenuation, a large error will occur. Summary of the invention

[0004] In view of this, an object of the present invention is to provide a very low frequency signal field strength calculation method and system, aiming to solve the problem of low accuracy in calculating field strength attenuation in the prior art.

[0005] The present invention is achieved in that:

[0006] A method for calculating the field strength of a very low frequency signal, the method comprising:

[0007] Acquire a source area electromagnetic pulse signal, and perform Fourier transform on the source area electromagnetic pulse signal to obtain the electric field intensity amplitude and phase of different frequency components of the source area electromagnetic pulse signal;

[0008] Establishing an ionosphere model in the long-wave propagation model, and setting initial calculation parameters of the ionosphere model respectively, and obtaining the field strength and phase of the grid points with a fixed step length from the source point on the electromagnetic pulse signal propagation path corresponding to all frequency point values ​​according to the ionosphere model;

[0009] Determine a first three-dimensional matrix according to the calculation results of the field strength and phase of the grid points, the total number of the grid points, and the number of the frequency point values;

[0010] A second three-dimensional matrix characterizing the field strength attenuation and phase change of the grid points is determined, and a third three-dimensional matrix characterizing the electric field strength amplitude and phase value of the electromagnetic pulse signal at different frequencies at the grid points can be obtained based on the first three-dimensional matrix and the second three-dimensional matrix.

[0011] Furthermore, in the above-mentioned very low frequency signal field strength calculation method, the step of obtaining the source area electromagnetic pulse signal and performing Fourier transform on the source area electromagnetic pulse signal to obtain the electric field strength amplitude and phase of different frequency components of the source area electromagnetic pulse signal includes:

[0012] The electric field strength of the electromagnetic pulse signal in the source area is:

[0013] E(t)=E0k(e -βt -e -αt );

[0014] Where E0 is the peak field intensity; k is the correction coefficient; α and β are parameters that characterize the front and rear edges of the pulse;

[0015] The time domain waveform of the electromagnetic pulse signal in the source area is subjected to fast Fourier transformation to obtain its amplitude spectrum and phase spectrum at the source point, and the electric field intensity amplitude and phase of different frequency components of the electromagnetic pulse signal in the source area are obtained.

[0016] Furthermore, in the above-mentioned very low frequency signal field strength calculation method, the first three-dimensional matrix is ​​expressed as:

[0017]

[0018] Among them, A mn and P mn They respectively represent the electric field intensity amplitude and phase at the nth frequency point to be calculated at the mth grid point when the source area power is set to the preset value;

[0019] The second three-dimensional matrix is ​​expressed as:

[0020]

[0021] Among them, A' mn =A mn -A m0 , P m ' n =P mn -P m0 , A m0 and P m0 are the electric field intensity amplitude and phase of the first grid point respectively;

[0022] The third three-dimensional matrix is ​​expressed as:

[0023]

[0024] Among them, A m ” n =A 0n -A' mn , P m ” n =P 0n -P m ' n .

[0025] Furthermore, the above-mentioned very low frequency signal field strength calculation method, wherein the method also includes:

[0026] Acquire a discrete frequency domain signal composed of an amplitude spectrum and a phase spectrum of a grid point on the propagation path, and represent the discrete frequency domain signal using a complex number;

[0027] The discrete frequency domain signal is subjected to an inverse Fourier transform, and then the discrete time domain waveform of each grid point on the propagation path is peaked to obtain a sequence value of the peak field intensity varying with distance, thereby obtaining a field intensity attenuation curve after the electromagnetic pulse signal propagates a certain distance.

[0028] Furthermore, in the above-mentioned very low frequency signal field strength calculation method, the discrete frequency domain signal is expressed as:

[0029]

[0030] The formula for performing inverse Fourier transform on the discrete frequency domain signal is:

[0031]

[0032] Among them, |X m (n)|=A' m ' n ,φ m (n) = P m ” n , x m (k) is the value of the time domain signal at the mth grid point of the propagation path at time point k, and K is the length of the signal.

[0033] Furthermore, in the above-mentioned very low frequency signal field strength calculation method, the initial calculation parameters include use case ID, calculation frequency, source point latitude, source point longitude, transmitter power of the source area, ionosphere model type, azimuth, maximum calculation distance, and calculation step size.

[0034] Furthermore, in the above-mentioned method for calculating the field strength of a very low frequency signal, the electric field strength of the source region is:

[0035]

[0036] Among them, P s is the transmitter power and P0 is the reference power.

[0037] Another object of the present invention is to provide a very low frequency signal field strength calculation system, the system comprising:

[0038] An acquisition module is used to acquire the electromagnetic pulse signal of the source area, and perform Fourier transform on the electromagnetic pulse signal of the source area to obtain the electric field intensity amplitude and phase of different frequency components of the electromagnetic pulse signal of the source area;

[0039] An establishment module is used to establish an ionosphere model in the long wave propagation model, and to set initial calculation parameters of the ionosphere model respectively, and to obtain the field strength and phase of the grid points with a fixed step length from the source point on the electromagnetic pulse signal propagation path corresponding to all frequency point values ​​according to the ionosphere model;

[0040] A determination module, configured to determine a first three-dimensional matrix according to the calculation results of the field strength and phase of the grid points, the total number of the grid points, and the number of the frequency point values;

[0041] A calculation module is used to determine a second three-dimensional matrix characterizing the field strength attenuation and phase change of the grid points, and based on the first three-dimensional matrix and the second three-dimensional matrix, a third three-dimensional matrix characterizing the electric field strength amplitude and phase value of the electromagnetic pulse signal at different frequencies at the grid points can be obtained.

[0042] Another object of the present invention is to provide an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of any of the above-described methods when executing the program.

[0043] The present invention obtains the electromagnetic pulse signal in the source area, and performs Fourier transform on the electromagnetic pulse signal in the source area to obtain the electric field intensity amplitude and phase of different frequency components of the electromagnetic pulse signal in the source area; establishes an ionosphere model in the long wave propagation model, and sets the initial calculation parameters of the ionosphere model respectively, and obtains the field intensity and phase of the grid points with a fixed step length from the source point on the electromagnetic pulse signal propagation path corresponding to all frequency point values ​​according to the ionosphere model; determines the first three-dimensional matrix according to the calculation results of the field intensity and phase of the grid points, the total number of grid points and the number of frequency point values; determines the second three-dimensional matrix representing the field intensity attenuation and phase change of the grid points, and obtains the third three-dimensional matrix representing the electric field intensity amplitude and phase value of the electromagnetic pulse signal at different frequency points at the grid points according to the first three-dimensional matrix and the second three-dimensional matrix, and performs multi-frequency field intensity decay simulation by using LWPC, thereby realizing the calculation of field intensity attenuation, and by performing attenuation modeling on the entire frequency band, the obtained field intensity calculation result will be more in line with the physical principle, and will also be more in line with the decay characteristics of the very low frequency signal characteristics of the source area. Thus, the problem of low accuracy in calculating field intensity attenuation in the prior art is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Flow chart of a method for calculating the field strength of a very low frequency signal in a first embodiment of the present invention;

[0045] Figure 2 A schematic diagram of a field intensity attenuation curve in a very low frequency signal field intensity calculation method in one embodiment of the present invention;

[0046] Figure 3 FIG. 4 is a structural block diagram of a very low frequency signal field strength calculation system in a third embodiment of the present invention.

[0047] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0048] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. Several embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0049] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed types.

[0051] The following will describe in detail how to improve the accuracy of VLF signal field strength attenuation calculation in conjunction with specific embodiments and drawings.

[0052] Embodiment 1

[0053] See also Figure 1 , which shows a very low frequency signal strength calculation method in the first embodiment of the present invention, and the method includes steps S10 to S13.

[0054] Step S10, acquiring a source electromagnetic pulse signal, and performing Fourier transform on the source electromagnetic pulse signal to obtain the electric field intensity amplitude and phase of different frequency components of the source electromagnetic pulse signal.

[0055] Among them, the source area electromagnetic pulse signal is Fourier transformed to obtain the electric field intensity amplitude and phase of different frequency components of the source area signal. The source area electromagnetic pulse signal is a double exponential function, and its electric field intensity can be expressed as:

[0056] E(t)=E0k(e -βt -e -αt );

[0057] Where E0 is the peak field intensity; k is the correction coefficient; α and β are parameters that characterize the front and rear edges of the pulse;

[0058] The time domain waveform is subjected to Fast Fourier Transform (FFT) to obtain its amplitude spectrum and phase spectrum at the source point, and further the electric field intensity amplitude and phase of different frequency components at the source point are obtained.

[0059] Generally, when electromagnetic pulses propagate in the atmosphere, their high-frequency components decay quickly. After propagating about 100 km, their main energy is concentrated in the very low frequency / low frequency band, about 3-60kHz, which is suitable for using LWPC to calculate the field strength attenuation curve. Assuming that the time domain waveform length is 1ms, the frequency domain resolution after Fourier transform is 1kHz, and the corresponding number of frequency points to be calculated is N = 58 (3, 4, ..., 60), and the nth frequency point is recorded as f i The field intensity and phase of the nth frequency point after Fourier transformation are recorded as A and 0n and P 0n .

[0060] Step S11, establish an ionosphere model in the long wave propagation model, and set the initial calculation parameters of the ionosphere model respectively, and obtain the field strength and phase of the grid points with a fixed step length from the source point on the electromagnetic pulse signal propagation path corresponding to all frequency point values ​​according to the ionosphere model.

[0061] Specifically, set the LWPC calculation parameters: through experimental verification, set the following fixed initial parameters, where the key parameters are the subsequent fields of tx-data, which are use case ID, calculation frequency, source point latitude, source point longitude, transmitter power (kW), ionospheric model type, azimuth, maximum calculation distance, and calculation step. Assuming that the maximum distance is 12000km, the source point represents the 0km point, and the step length is 100km, the starting calculation point is the second step point (ie 200km), and the number of points to be calculated on the propagation path is M = 119 (200,...,12000), and the mth point to be calculated is recorded as Dm. The setting of the transmitter power has no effect on the propagation field strength calculation carried out by the present invention. Generally, we set the transmitter power to 100kW.

[0062] More specifically, the following formula can be used to convert the numerical value of the electric field unit, where Es is the electric field intensity in the source region, the unit is V / m, Ps is the transmitter power, and P0 is the reference power, which is usually set to 1kW.

[0063]

[0064] Among them, LWPC is used to calculate the field strength and phase value of each frequency component on the propagation path: according to the frequency point value obtained by performing FFT on the source, the parameter setting file is written cyclically through the written automatic processing program, and other parameters are set by default. Then the LWPC model is run cyclically to obtain the field strength and phase of the grid points with a fixed step length from the source point on the set propagation path corresponding to all frequency point values.

[0065] Step S12, determining a first three-dimensional matrix according to the calculation results of the field strength and phase of the grid points, the total number of the grid points, and the number of the frequency point values.

[0066] To facilitate subsequent processing, the calculation results of different frequency points are placed in a three-dimensional matrix, which includes the calculation results of propagation parameters (electric field strength amplitude and phase), distance, and frequency. It is a 2×M×N matrix, where 2 represents two parameters (i.e., electric field strength amplitude and phase), M represents the total number of points (grid points) to be calculated on the propagation path, and N represents the total number of frequency points to be calculated. The three-dimensional matrix is ​​denoted as B, and the expression can be expressed as:

[0067]

[0068] Among them, A mn and P mn They respectively represent the electric field intensity amplitude and phase at the nth frequency point to be calculated at the mth grid point when the source area power is set to the preset value.

[0069] Step S13, determine a second three-dimensional matrix representing the field strength attenuation and phase change of the grid points, and obtain a third three-dimensional matrix representing the electric field strength amplitude and phase value of the electromagnetic pulse signal at different frequencies at the grid points based on the first three-dimensional matrix and the second three-dimensional matrix.

[0070] Among them, the field strength and phase of the signal at different frequencies in the source area are taken as the initial values, denoted as A 0n and P 0m Through the obtained propagation parameter result model of different frequency points changing with the path segment, the field intensity attenuation and phase change of the point to be calculated on the propagation path can be further obtained, which is represented by the second three-dimensional matrix:

[0071]

[0072] Among them, A' mn =A mn -A m0 , P m ' n =P mn -P m0 , A m0 and P m0 are the electric field intensity amplitude and phase of the first grid point respectively;

[0073] Among them, A' mn =A mn -A m0 , P m ' n =P mn -P m0 , A m0 and P m0 are the electric field intensity amplitude and phase of the first step point respectively. Then, the initial electric field intensity amplitude and phase values ​​of the source area signals at different frequencies are subtracted from the field intensity attenuation and phase change, respectively, to obtain the electric field intensity amplitude and phase values ​​of the signals at different frequencies at the points to be calculated, which are expressed by the third three-dimensional matrix B":

[0074]

[0075] In summary, the very low frequency signal field strength calculation method in the above embodiment of the present invention obtains the electromagnetic pulse signal in the source area, and performs Fourier transform on the electromagnetic pulse signal in the source area to obtain the electric field strength amplitude and phase of different frequency components of the electromagnetic pulse signal in the source area; establishes an ionosphere model in the long wave propagation model, and sets the initial calculation parameters of the ionosphere model respectively, and obtains the field strength and phase of the grid points with a fixed step length from the source point on the electromagnetic pulse signal propagation path corresponding to all frequency points according to the ionosphere model; determines the first three-dimensional matrix according to the calculation results of the field strength and phase of the grid points, the total number of grid points and the number of frequency points; determines the second three-dimensional matrix representing the field strength attenuation and phase change of the grid points, and obtains the third three-dimensional matrix representing the electric field strength amplitude and phase value of the electromagnetic pulse signal at different frequencies at the grid points according to the first three-dimensional matrix and the second three-dimensional matrix, and uses LWPC to perform multi-frequency field strength decay simulation, thereby realizing the calculation of field strength attenuation, and by performing attenuation modeling on the entire frequency band, the obtained field strength calculation result will be more in line with physical principles, and will also be more in line with the decay characteristics of the very low frequency signal characteristics of the source area. This solves the problem of low accuracy in calculating field intensity attenuation in the prior art.

[0076] Embodiment 2

[0077] This embodiment also proposes a method for calculating the field strength of a very low frequency signal. The difference between the method for calculating the field strength of a very low frequency signal proposed in this embodiment and the method for calculating the field strength of a very low frequency signal proposed in the first embodiment is that:

[0078] The method further comprises:

[0079] Acquire a discrete frequency domain signal composed of an amplitude spectrum and a phase spectrum of a grid point on the propagation path, and represent the discrete frequency domain signal using a complex number;

[0080] The discrete frequency domain signal is subjected to an inverse Fourier transform, and then the discrete time domain waveform of each grid point on the propagation path is peaked to obtain a sequence value of the peak field intensity varying with distance, thereby obtaining a field intensity attenuation curve after the electromagnetic pulse signal propagates a certain distance.

[0081] Among them, the inverse Fourier transform is used to obtain the signal waveform of the point to be calculated on the propagation path, and its time domain field intensity peak is extracted to obtain the field intensity attenuation curve. According to the obtained third three-dimensional matrix, that is, the amplitude spectrum and phase spectrum of the point to be calculated on the propagation path, the discrete frequency domain signal can be expressed by a complex number as follows:

[0082]

[0083] The formula for performing inverse Fourier transform on the discrete frequency domain signal is:

[0084]

[0085] Among them, |X m (n)|=A m ” n ,φ m (n) = P m ” n , x m (k) is the value of the time domain signal at the mth grid point of the propagation path at time point k, and K is the length of the signal.

[0086] In this way, the discrete time domain waveform synthesis of the points to be calculated on the propagation path is completed. Then, the peak value of the discrete time domain waveform of each calculation point on the propagation path is taken to obtain the sequence value of the peak field strength changing with distance, which is recorded as:

[0087] E m =max[x m (k)];

[0088] By E m The field strength attenuation curve of the electromagnetic pulse signal after it propagates a certain distance in the ground-ionosphere waveguide can be obtained.

[0089] In addition, in order to visualize the results, Figure 3 As shown, the obtained field strength attenuation curve can be plotted using programming languages ​​such as matlab, Python or VC++. For example, the source area coordinates are set to (30N, 30E), the receiving point coordinates are set to (30N, 120E), the maximum propagation distance is 13000km, the calculation step is 100km, and the source time is set to 08UT and 20UT on September 12, 2023. The source signal adopts the standard waveform of the electromagnetic pulse of the early high-altitude nuclear explosion specified in GB / T 18039.10-2018 / IEC 6100-2-9:1996, where E0 = 50000V / m, k = 1.3, β = 4×10 7 s -1 , α=6×10 8 s -1 . According to the steps, the field strength attenuation curve can be drawn.

[0090] In summary, the very low frequency signal field strength calculation method in the above embodiment of the present invention obtains the electromagnetic pulse signal in the source area, and performs Fourier transform on the electromagnetic pulse signal in the source area to obtain the electric field strength amplitude and phase of different frequency components of the electromagnetic pulse signal in the source area; establishes an ionosphere model in the long wave propagation model, and sets the initial calculation parameters of the ionosphere model respectively, and obtains the field strength and phase of the grid points with a fixed step length from the source point on the electromagnetic pulse signal propagation path corresponding to all frequency points according to the ionosphere model; determines the first three-dimensional matrix according to the calculation results of the field strength and phase of the grid points, the total number of grid points and the number of frequency points; determines the second three-dimensional matrix representing the field strength attenuation and phase change of the grid points, and obtains the third three-dimensional matrix representing the electric field strength amplitude and phase value of the electromagnetic pulse signal at different frequencies at the grid points according to the first three-dimensional matrix and the second three-dimensional matrix, and uses LWPC to perform multi-frequency field strength decay simulation, thereby realizing the calculation of field strength attenuation, and by performing attenuation modeling on the entire frequency band, the obtained field strength calculation result will be more in line with physical principles, and will also be more in line with the decay characteristics of the very low frequency signal characteristics of the source area. This solves the problem of low accuracy in calculating field intensity attenuation in the prior art.

[0091] Embodiment 3

[0092] See also Figure 3 , shown is a very low frequency signal field strength calculation system proposed in the third embodiment of the present invention, the system comprising:

[0093] The acquisition module 100 is used to acquire the electromagnetic pulse signal of the source area, and perform Fourier transform on the electromagnetic pulse signal of the source area to obtain the electric field intensity amplitude and phase of different frequency components of the electromagnetic pulse signal of the source area;

[0094] Establishing module 200, for establishing an ionosphere model in the long wave propagation model, and respectively setting initial calculation parameters of the ionosphere model, and obtaining the field strength and phase of the grid points with a fixed step length from the source point on the electromagnetic pulse signal propagation path corresponding to all frequency point values ​​according to the ionosphere model;

[0095] A determination module 300, configured to determine a first three-dimensional matrix according to the calculation results of the field strength and phase of the grid points, the total number of the grid points, and the number of the frequency point values;

[0096] The calculation module 400 is used to determine a second three-dimensional matrix representing the field strength attenuation and phase change of the grid points, and based on the first three-dimensional matrix and the second three-dimensional matrix, a third three-dimensional matrix representing the electric field strength amplitude and phase value of the electromagnetic pulse signal at different frequencies at the grid points can be obtained.

[0097] Furthermore, in the above-mentioned very low frequency signal field strength calculation system, the step of obtaining the source area electromagnetic pulse signal and performing Fourier transform on the source area electromagnetic pulse signal to obtain the electric field strength amplitude and phase of different frequency components of the source area electromagnetic pulse signal includes:

[0098] The electric field strength of the electromagnetic pulse signal in the source area is:

[0099] E(t)=E0k(e -βt -e -αt );

[0100] Where E0 is the peak field intensity; k is the correction coefficient; α and β are parameters that characterize the front and rear edges of the pulse;

[0101] The time domain waveform of the electromagnetic pulse signal in the source area is subjected to fast Fourier transformation to obtain its amplitude spectrum and phase spectrum at the source point, and the electric field intensity amplitude and phase of different frequency components of the electromagnetic pulse signal in the source area are obtained.

[0102] Further, in some optional embodiments of the present invention, the first three-dimensional matrix is ​​expressed as:

[0103]

[0104] Among them, A mn and P mn They respectively represent the electric field intensity amplitude and phase at the nth frequency point to be calculated at the mth grid point when the source area power is set to the preset value;

[0105] The second three-dimensional matrix is ​​expressed as:

[0106]

[0107] Among them, A' mn =A mn -A m0 , P m ' n =P mn -P m0 , A m0 and P m0 are the electric field intensity amplitude and phase of the first grid point respectively;

[0108] The third three-dimensional matrix is ​​expressed as:

[0109]

[0110] Among them, A m ” n =A 0n -A' mn , P m ”n =P 0n -P m ' n .

[0111] Furthermore, in some optional embodiments of the present invention, the method further includes:

[0112] Acquire a discrete frequency domain signal composed of an amplitude spectrum and a phase spectrum of a grid point on the propagation path, and represent the discrete frequency domain signal using a complex number;

[0113] The discrete frequency domain signal is subjected to an inverse Fourier transform, and then the discrete time domain waveform of each grid point on the propagation path is peaked to obtain a sequence value of the peak field intensity varying with distance, thereby obtaining a field intensity attenuation curve after the electromagnetic pulse signal propagates a certain distance.

[0114] Further, in some optional embodiments of the present invention, the discrete frequency domain signal is expressed as:

[0115]

[0116] The formula for performing inverse Fourier transform on the discrete frequency domain signal is:

[0117]

[0118] Among them, |X m (n)|=A m ” n ,φ m (n) = P m ” n , x m (k) is the value of the time domain signal at the mth grid point of the propagation path at time point k, and K is the length of the signal.

[0119] Furthermore, in some optional embodiments of the present invention, the initial calculation parameters include use case ID, calculation frequency, source point latitude, source point longitude, transmitter power of the source area, ionosphere model type, azimuth, maximum calculation distance, and calculation step size.

[0120] Further, in some optional embodiments of the present invention, the electric field strength of the source region is:

[0121]

[0122] Among them, P s is the transmitter power and P0 is the reference power.

[0123] The functions or operation steps implemented when the above modules are executed are substantially the same as those in the above method embodiments, and will not be repeated here.

[0124] Embodiment 4

[0125] Another aspect of the present invention further provides a readable storage medium having a computer program stored thereon, and when the program is executed by a processor, the steps of the method described in any one of the above embodiments 1 to 2 are implemented.

[0126] Embodiment 5

[0127] Another aspect of the present invention provides an electronic device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method described in any one of the above-mentioned embodiments one to two when executing the program.

[0128] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0129] Those skilled in the art will appreciate that the logic and / or steps represented in the flowchart or otherwise described herein, for example, may be considered as an ordered list of executable instructions for implementing logical functions, and may be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For purposes of this specification, a "computer-readable medium" may be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0130] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0131] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or a combination thereof: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0132] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0133] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for calculating the field strength of a very low frequency signal, characterized in that: The method comprises: Acquire a source area electromagnetic pulse signal, and perform Fourier transform on the source area electromagnetic pulse signal to obtain the electric field intensity amplitude and phase of different frequency components of the source area electromagnetic pulse signal; Establishing an ionosphere model in the long-wave propagation model, and setting initial calculation parameters of the ionosphere model respectively, and obtaining the field strength and phase of the grid points with a fixed step length from the source point on the electromagnetic pulse signal propagation path corresponding to all frequency point values ​​according to the ionosphere model; Determine a first three-dimensional matrix according to the calculation results of the field strength and phase of the grid points, the total number of the grid points, and the number of the frequency point values; A second three-dimensional matrix characterizing the field strength attenuation and phase change of the grid points is determined, and a third three-dimensional matrix characterizing the electric field strength amplitude and phase value of the electromagnetic pulse signal at different frequencies at the grid points can be obtained based on the first three-dimensional matrix and the second three-dimensional matrix.

2. The method for calculating the VLF signal strength according to claim 1, characterized in that: The step of acquiring the source electromagnetic pulse signal and performing Fourier transform on the source electromagnetic pulse signal to obtain the electric field intensity amplitude and phase of different frequency components of the source electromagnetic pulse signal comprises: The electric field strength of the electromagnetic pulse signal in the source area is: E(t)=E0k(e -βt -e -αt ); Where E0 is the peak field intensity; k is the correction coefficient; α and β are parameters that characterize the front and rear edges of the pulse; The time domain waveform of the electromagnetic pulse signal in the source area is subjected to fast Fourier transformation to obtain its amplitude spectrum and phase spectrum at the source point, and the electric field intensity amplitude and phase of different frequency components of the electromagnetic pulse signal in the source area are obtained.

3. The method for calculating the VLF signal strength according to claim 1, characterized in that: The first three-dimensional matrix is ​​expressed as: Among them, A mn and P mn They respectively represent the electric field intensity amplitude and phase at the nth frequency point to be calculated at the mth grid point when the source area power is set to the preset value; The second three-dimensional matrix is ​​expressed as: Among them, A' mn =A mn -A m0 , P′ mn =P mn -P m0 , A m0 and P m0 are the electric field intensity amplitude and phase of the first grid point respectively; The third three-dimensional matrix is ​​expressed as: Among them, A″ mn =A 0n -A' mn , P″ mn =P 0n -P′ mn .

4. The method for calculating the VLF signal strength according to claim 1, characterized in that: The method further comprises: Acquire a discrete frequency domain signal composed of an amplitude spectrum and a phase spectrum of a grid point on the propagation path, and represent the discrete frequency domain signal using a complex number; The discrete frequency domain signal is subjected to an inverse Fourier transform, and then the discrete time domain waveform of each grid point on the propagation path is peaked to obtain a sequence value of the peak field intensity varying with distance, thereby obtaining a field intensity attenuation curve after the electromagnetic pulse signal propagates a certain distance.

5. The method for calculating the very low frequency signal field strength according to claim 4, characterized in that: The discrete frequency domain signal is expressed as: The formula for performing inverse Fourier transform on the discrete frequency domain signal is: Among them, |X m (n)|=A″ mn ,φ m (n) = P″ mn , x m (k) is the value of the time domain signal at the mth grid point of the propagation path at time point k, and K is the length of the signal.

6. The method for calculating the VLF signal strength according to claim 1, characterized in that: The initial calculation parameters include use case ID, calculation frequency, source point latitude, source point longitude, transmitter power of the source area, ionosphere model type, azimuth, maximum calculation distance, and calculation step size.

7. The method for calculating the VLF signal strength according to claim 6, characterized in that: The electric field strength of the source region is: Among them, P s is the transmitter power and P0 is the reference power.

8. A very low frequency signal field strength calculation system, characterized in that: The system comprises: An acquisition module is used to acquire the electromagnetic pulse signal of the source area, and perform Fourier transform on the electromagnetic pulse signal of the source area to obtain the electric field intensity amplitude and phase of different frequency components of the electromagnetic pulse signal of the source area; An establishment module is used to establish an ionosphere model in the long wave propagation model, and to set initial calculation parameters of the ionosphere model respectively, and to obtain the field strength and phase of the grid points with a fixed step length from the source point on the electromagnetic pulse signal propagation path corresponding to all frequency point values ​​according to the ionosphere model; A determination module, configured to determine a first three-dimensional matrix according to the calculation results of the field strength and phase of the grid points, the total number of the grid points, and the number of the frequency point values; A calculation module is used to determine a second three-dimensional matrix characterizing the field strength attenuation and phase change of the grid points, and based on the first three-dimensional matrix and the second three-dimensional matrix, a third three-dimensional matrix characterizing the electric field strength amplitude and phase value of the electromagnetic pulse signal at different frequencies at the grid points can be obtained.

9. A readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

10. An electronic device, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of the method according to any one of claims 1 to 7 are implemented.

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