Prediction method of time-domain transient field of ultra-wide spectrum electromagnetic pulse on super-large electric platform

Abstract

The invention discloses a method for predicting the time-domain transient field of ultra-wide spectrum electromagnetic pulse of super-electric platform, which belongs to the technical field of electromagnetic pulse protection design, including: performing Fourier transform on the time-domain excitation signal of ultra-wide spectrum electromagnetic pulse to obtain the spectrum curve, and then determining the discrete frequency point set that needs to calculate the frequency domain field according to the size of the super-electric platform and the distribution of the calculation area; using the parallel multi-layer fast multipole full-wave solution method to solve the frequency-domain electromagnetic environment of the low-frequency discrete frequency points in the discrete frequency point concentration; using the high-low frequency collaborative solution method to solve the frequency-domain electromagnetic environment of the high-frequency discrete frequency points in the discrete frequency point concentration; aligning and multiplying the frequency-domain electromagnetic environment data of each discrete frequency point in the calculation area of ​​the super-electric platform with the corresponding frequency points of the spectrum curve of the time-domain excitation signal, and then performing inverse Fourier transform to obtain the time-domain transient field of ultra-wide spectrum electromagnetic pulse of super-electric platform. It solves the problem of solving the time-domain transient field of ultra-wide spectrum electromagnetic pulse of super-electric platform.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic pulse protection design, and more specifically, relates to a method for predicting a time-domain transient field of an ultra-wide spectrum electromagnetic pulse on an ultra-large electric platform. Background Art

[0002] Ultra-wide spectrum electromagnetic pulses have the characteristics of wide instantaneous coverage spectrum, high energy, and narrow pulse width. They can easily enter sensitive electronic devices through coupling channels such as antennas, holes, and cables of sensitive electronic devices, causing disturbances, damage, or even destruction to their key sensitive electronic devices. Therefore, it is necessary to carry out ultra-wide spectrum electromagnetic pulse time domain transient field simulation on platforms equipped with many sensitive electronic devices, reveal the electromagnetic pulse coupling mechanism, and quantitatively support electromagnetic pulse protection design.

[0003] At present, the main methods for transient simulation of electromagnetic pulses in the time domain are the Finite Difference Time Domain (FDTD) method and the Finite Integration Time Domain (FITD) method. FDTD is a widely used time domain simulation method. It uses Yee cells to discretize the electromagnetic space to be calculated. The electric field and the magnetic field are staggered on the Yee cells. At the same time, the so-called "leapfrog format" is used in time, that is, the electric field is calculated once and the magnetic field is calculated again at each time step. Therefore, FDTD does not need to solve equations when calculating the electric field and magnetic field in space. It is a completely explicit iterative format with extremely fast calculation speed. However, when the electrical size of the calculation object is too large, the number of grids that need to be divided will increase rapidly, and the unknown quantity to be solved is as high as hundreds of millions, resulting in extremely slow calculation speed or even incomprehensible calculation. FITD uses a unique Perfect Boundary Approximation (PBA) technique to conformally map the medium boundary onto the hexahedral mesh, thereby taking into account the precise matrix element values ​​under partial medium filling, greatly improving the accuracy of the Yee mesh. At the same time, it still maintains the advantages of low memory and efficient solution of the hexahedral mesh explicit time-domain integration algorithm. Therefore, FITD has the advantages of both the fast solution of FDTD and the accurate solution of complex structures and materials by the finite element method (FEM). However, FITD also has the problem of being unable to solve the time-domain transient field of ultra-large-sized objects. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention proposes a method for predicting the time-domain transient field of ultra-wide spectrum electromagnetic pulses of an ultra-large electric platform to solve the problem of solving the time-domain transient field of ultra-wide spectrum electromagnetic pulses of an ultra-large electric platform.

[0005] To achieve the above object, the present invention provides a method for predicting the time domain transient field of an ultra-wide spectrum electromagnetic pulse on an ultra-large electric platform, comprising:

[0006] (1) Perform Fourier transform on the time domain excitation signal of the ultra-wide spectrum electromagnetic pulse to obtain the spectrum curve corresponding to the time domain excitation signal, and then determine the discrete frequency point set that needs to calculate the frequency domain field according to the size of the ultra-large electric platform and the distribution of the calculation area;

[0007] (2) The frequency domain electromagnetic environment of low-frequency discrete frequency points in the discrete frequency point concentration is solved by using the parallel multi-layer fast multipole full-wave solution method;

[0008] (3) The frequency domain electromagnetic environment of the high-frequency discrete frequency points in the discrete frequency point concentration is solved by using the high-frequency and low-frequency collaborative solution method;

[0009] (4) After aligning and multiplying the frequency domain electromagnetic environment data of each discrete frequency point in the calculation area of ​​the super-electric platform with the corresponding frequency point of the spectrum curve of the time domain excitation signal, an inverse Fourier transform is performed to obtain the time domain transient field of the ultra-wide spectrum electromagnetic pulse of the super-electric platform.

[0010] In some optional embodiments, step (1) comprises:

[0011] The expression of the discrete spectrum of the time-domain excitation signal is derived from the Fourier series expansion expression of the time-domain excitation signal, and the spectrum curve corresponding to the time-domain excitation signal is obtained by using the expression of the discrete spectrum;

[0012] At the same time, the size of the super-electric platform and the distribution of the calculation area are taken into consideration, and the contribution of the signal reflected back to the calculation area after the transmitted time domain signal encounters an obstacle is fully considered to determine the discrete frequency point set that needs to be calculated for the frequency domain field.

[0013] In some optional embodiments, step (2) comprises:

[0014] The surface current basis functions of the platform to be calculated are grouped, and the interactions between any basis functions are calculated using different methods according to their relative position relationships. According to the grouping relationships in which they are located, if the strong coupling effect belongs to the near-field group, the moment method needs to be directly calculated. If the weak coupling effect belongs to the far-field group, MLFMA calculation is used. In the aggregation process of MLFMA calculation, the current effects of all basis functions in each group are aggregated to the center of the group. Secondly, the transfer process transfers the effect of the group center to the center of all far-field groups of the group. Finally, the configuration process configures the effect of the far-field group center to all basis functions of the group.

[0015] In some optional implementations, the surface current basis functions of the platform to be calculated are grouped, including:

[0016] The platform to be calculated is surrounded by a cubic bounding box, and then the bounding box is divided into a spatial octree. Each small bounding box after division continues to be recursively divided until the smallest cube side length ranges from 0.2λ to 0.5λ. The first bounding box is called the 0th layer, followed by the 1st, 2nd, ..., Lth layers, λ is the wavelength of the electromagnetic wave corresponding to the calculation frequency point, and L is the total number of layers of the platform to be calculated.

[0017] In some optional embodiments, step (3) comprises:

[0018] For ultra-wide spectrum electromagnetic pulse radiation antennas, a low-frequency full-wave electromagnetic algorithm solution method based on the multi-layer fast multipole method is used. For ultra-large electric platform structures, a high-frequency electromagnetic algorithm solution method based on the consistent geometric diffraction theory (UTD) is used.

[0019] In some optional implementation schemes, a high-frequency solution method of consistent geometric diffraction theory UTD is used for the ultra-large electric platform structure, including:

[0020] Determine the direct field based on the line-of-sight field strength when the ray path from the UWSP radiation antenna to the field point in the calculation area is not blocked by obstacles;

[0021] When the electromagnetic pulse irradiates the surface of the platform structure, a reflection effect will be generated on the surface of the platform structure to determine the reflection field;

[0022] When the electromagnetic pulse irradiates the surface of the platform structure, a diffraction effect will be generated on the platform structure, and the diffraction field will be determined;

[0023] The direct field, reflected field and diffraction field are synthesized to obtain the frequency domain electromagnetic environment distribution of the calculation area under the influence of the platform structure.

[0024] In some optional embodiments, step (4) comprises:

[0025] The spectrum data within the sampling frequency is completed, wherein the first area is the spectrum data after the spectrum data of the time domain excitation source signal is multiplied by the spectrum data obtained by electromagnetic calculation, and the second area is the supplementary data. The data in the first area and the second area are about f s / 2 conjugate symmetry, and finally the completed spectrum data is discretely inverse Fourier transformed to obtain the time-domain transient field of the ultra-wide spectrum electromagnetic pulse of the super-electric platform, f s is the sampling frequency.

[0026] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0027] (1) A method for solving the time-domain transient field of ultra-wide spectrum electromagnetic pulses of an ultra-large electric platform is provided. The present invention proposes a frequency domain + Fourier transform method with high and low frequency coordination. When solving the frequency domain field, a full-wave electromagnetic algorithm is used in the low-frequency band, and a high and low-frequency coordinated algorithm is used in the high-frequency band. This fully takes into account the solution accuracy and solution scale of the frequency domain field, thereby solving the problem of solving the time-domain transient field of ultra-wide spectrum electromagnetic pulses of an ultra-large electric platform.

[0028] (2) The transient fields of various time-domain excitation signals can be quickly solved. The high-low-frequency coordinated frequency domain + Fourier transform method proposed in the present invention decouples the time-domain excitation signal from the time-consuming frequency domain field simulation. When solving the transient fields of different time-domain excitation signals, the time-consuming frequency domain field simulation data can be shared, thereby quickly solving the transient fields of various time-domain excitation signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of three-dimensional target space division provided by an embodiment of the present invention;

[0030] Figure 2 It is a discrete Fourier transform of a non-periodic discrete signal provided by an embodiment of the present invention;

[0031] Figure 3 A data completion method within a sampling frequency range provided by an embodiment of the present invention;

[0032] Figure 4 is a time domain waveform of an excitation signal provided by an embodiment of the present invention;

[0033] Figure 5 is a spectrum distribution corresponding to an excitation time domain signal provided by an embodiment of the present invention;

[0034] Figure 6 It is a super-electric platform computing area model diagram provided by an embodiment of the present invention;

[0035] Figure 7 It is a frequency domain electric field distribution of a typical frequency point of a super electric platform computing area provided by an embodiment of the present invention, wherein (a) is the electric field distribution of a frequency point of 3.5 MHz, and (b) is the electric field distribution of a frequency point of 756 MHz;

[0036] Figure 8 It is a transient field distribution at typical moments of a super-electric platform computing area provided by an embodiment of the present invention, wherein (a) is the transient field distribution at 45ns, and (b) is the transient field distribution at 90ns. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] In the examples of the present invention, "first", "second", etc. are used to distinguish different objects rather than to describe a specific order or sequence.

[0039] The technical solution adopted by the present invention is as follows:

[0040] (1) Fourier transform and frequency discretization of time domain excitation signal;

[0041] When using the high- and low-frequency coordinated frequency domain field + Fourier transform to calculate the time domain transient field of the ultra-wide spectrum electromagnetic pulse of the super-electric platform, the time domain excitation signal of the ultra-wide spectrum electromagnetic pulse should be Fourier transformed first to obtain the spectrum curve corresponding to the time domain excitation signal, and then the discrete frequency point set that needs to be calculated for the frequency domain field is determined according to the size of the super-electric platform and the distribution of the calculation area.

[0042] The spectrum curve corresponding to the time domain excitation signal is calculated using the Fourier transform related formula. Formula (1) gives the periodic time domain excitation signal f T (t) can be expanded by Fourier series, thus the periodic time domain excitation signal f can be derived. T The discrete spectrum c of (t) n The expression of . Using formula (2), the spectrum curve corresponding to the periodic time domain excitation signal is obtained.

[0043]

[0044]

[0045]

[0046] Among them, f T (t) is the periodic time domain excitation signal, c n is the nth discrete spectral component, f T (τ ) is a periodic function f T (t) In the expression of one cycle, ω is the angular frequency, T is the period of the time domain excitation signal, and τ is the time variable of one period of the time domain excitation signal.

[0047] When selecting the discrete frequency point set of the frequency domain field, it is necessary to consider the size of the super-large electric platform and the distribution of the calculation area at the same time, and fully consider the contribution of the signal reflected back to the calculation area after the transmitted time domain signal encounters an obstacle.

[0048] (2) Solving the frequency domain electromagnetic environment of the platform’s low-frequency discrete frequency points;

[0049] The spectrum distribution of the time domain excitation signal of the ultra-wide spectrum electromagnetic pulse is very wide, covering several MHz to about 1GHz. For the solution of the frequency domain electromagnetic environment of a large platform, the low frequency band of discrete frequency points (generally below 600MHz) is an electrically large-scale calculation problem, and the high frequency band of discrete frequency points (generally above 600MHz) is an ultra-electrically large-scale calculation problem. Therefore, for the solution of the frequency domain electromagnetic environment of the platform's low-frequency discrete frequency points, it is suitable to use the parallel multi-layer fast multipole full-wave solution method (Multilevel Fast Multipole Algorithm, MLFMA); for the solution of the frequency domain electromagnetic environment of the platform's high-frequency discrete frequency points, it is suitable to use the high-low frequency collaborative solution method, which can not only ensure the solution accuracy of the frequency domain electromagnetic environment of each discrete frequency point, but also ensure the calculation speed.

[0050] The basic idea of ​​the parallel multi-layer fast multipole full-wave solution method for solving the frequency-domain electromagnetic environment of the platform to be calculated at discrete frequency points in the low-frequency band is to group the surface current basis functions of the platform to be calculated, and the interaction between any basis functions is calculated using different methods according to their relative position relationship. According to the grouping relationship, if the strong coupling effect belongs to the near-field group, the moment method needs to be directly calculated, and if it belongs to the weak coupling effect of the far-field group, MLFMA is used for calculation. The calculation process of MLFMA can be divided into three stages: aggregation, transfer, and configuration. The aggregation process is to aggregate the current effects of all basis functions in each group to the center position of the group. Secondly, the transfer process transfers the effect of the group center to the center position of all far-field groups of the group. Finally, the configuration process configures the effect of the far-field group center to all basis functions of the group, thereby realizing the fast calculation of far-field weak coupling effects and reducing the calculation complexity from the original O(N). 2 ) down to

[0051] Before using MLFMA, the computing platform needs to be spatially hierarchical and grouped. Considering a three-dimensional computing platform, the computing platform is first surrounded by a cubic bounding box, and then the bounding box is divided into a spatial octree. Each small bounding box after division continues to be recursively divided until the smallest cube side length ranges from 0.2λ to 0.5λ (λ is the wavelength of the electromagnetic wave corresponding to the calculation frequency point). The first bounding box is called the 0th layer, followed by the 1st, 2nd, ..., Lth layers (L is the total number of layers of the computing platform), as shown in Figure 1 shown.

[0052] From the calculation process of MLFMA, we can see that its computational complexity can be reduced to O(N log N), and the computational memory requirements are reduced to O(N log N) because the calculations between levels often use interpolation and anti-interpolation techniques. Compared with the computational and storage complexity of the traditional method of moments (MOM), the computational and storage complexity of MLMFA has been greatly improved, which is very suitable for solving the frequency domain electromagnetic environment of the platform's low-frequency discrete frequency points.

[0053] (3) Solving the frequency domain electromagnetic environment of the platform’s high-frequency discrete frequency points;

[0054] The frequency domain electromagnetic environment solution of the platform's high-frequency discrete frequency points belongs to the ultra-large size, which is suitable for the collaborative solution of high-low frequency electromagnetic algorithm (MLMFA-UTD), which can not only ensure the solution accuracy of the frequency domain electromagnetic environment of each discrete frequency point, but also ensure the simulation speed. For the ultra-wide spectrum electromagnetic pulse radiation antenna, the low-frequency full-wave electromagnetic algorithm is used for solution--Multilayer Fast Multipole Method (MLMFA); for the ultra-large platform structure, the high-frequency electromagnetic algorithm is used for solution--Uniform Theory of Diffraction (UTD). The UTD high-frequency method can fully consider the direct, reflection and diffraction effects of the platform structure and improve the accuracy of the calculation.

[0055] For the direct field, it is the line-of-sight field intensity when the ray path from the ultra-wide spectrum electromagnetic pulse radiation antenna to the field point in the calculation area is not blocked by obstacles. Assume that the two main curvature radii of the incident wavefront are ρ1 and ρ2, respectively, and they are not equal. The ultra-wide spectrum electromagnetic pulse radiation antenna is located at point S, the field point in the calculation area is located at point R, and the distance between the two points is d. Therefore, the direct field of geometric optics propagating in a uniform medium can be expressed as:

[0056]

[0057] Among them, E(R) is the electric field intensity at the field point R in the calculation area, E(S) is the electric field intensity at the ultra-wide spectrum electromagnetic pulse radiation antenna S, k is the propagation constant, ρ1 and ρ2 represent the two main curvature radii of the incident wavefront, and for spherical waves, these two main curvature radii are equal, that is, ρ1=ρ2. .

[0058] For the reflection field, it means that when the electromagnetic pulse irradiates the surface of the platform structure, a reflection effect will be generated on the surface of the platform structure. When the platform structure is pure metal, all the energy of the electromagnetic pulse will be reflected. Let W be the reflection point on the surface of the platform structure, the position of the ultra-wide spectrum electromagnetic pulse radiation antenna is at point S, the position of the calculation area field point is at point R, the two main curvature radii of the reflected wavefront are ρ1 and ρ2 respectively, and d is the path length between the reflection point W and the calculation area field point R. Therefore, the reflection field at the calculation area field point R can be expressed as follows:

[0059]

[0060] Among them, E r (R) is the reflected electric field intensity at the field point R, E i (S) is the incident electric field intensity at the source point S, k is the propagation constant, is the dyadic reflection coefficient, ρ1 and ρ2 are the two main curvature radii of the reflected wavefront, and d is the path length between the reflection point W and the field point R in the calculation area.

[0061] The diffraction field refers to the diffraction effect generated on the surface, edge, top and other structures of the platform structure when the electromagnetic pulse irradiates the surface of the platform structure. The calculation formula of the diffraction field can be expressed as:

[0062]

[0063] in, and D is the projection of the diffraction field vector at the diffraction point to the direction parallel to the diffraction plane and the direction perpendicular to the diffraction plane. / / and D ⊥ are the diffraction coefficients parallel to the diffraction plane and perpendicular to the diffraction plane, respectively. and are the projections of the incident field vector at the diffraction point in the direction parallel to the incident plane and in the direction perpendicular to the incident plane, respectively. A(s) is the spatial attenuation factor, e -jβs represents the phase factor, β is the propagation constant of the electromagnetic wave, and s is the distance between the diffraction point and the field point.

[0064] After obtaining the direct field, reflected field and diffraction field, the frequency domain electromagnetic environment distribution of the calculation area under the influence of the platform structure can be obtained through appropriate synthesis.

[0065] (4) Ultra-wideband transient field solution based on frequency domain discrete single-field inverse Fourier transform.

[0066] After obtaining the frequency domain electromagnetic environment data of each discrete frequency point in the calculation area of ​​the super-electric platform, it is necessary to align and multiply it with the corresponding frequency point of the spectrum data of the time domain excitation source signal obtained in Section (1), and then perform inverse Fourier transform. Figure 2 According to the knowledge of discrete Fourier transform, when a discrete Fourier transform is performed on a time-domain non-periodic discrete signal, its spectrum will undergo periodic extension.

[0067]

[0068] in, is the amplitude of the spectrum, x(nT) is the amplitude of the time domain signal, Ω is the angular frequency variable, and T is the sampling time interval. In fact, the frequency domain electric field data obtained by electromagnetic calculation is located in the range of 0<f<f s / 2(f s is the sampling frequency) range, while the discrete inverse Fourier transform requires 0<f<f s The spectrum data within the range requires the spectrum data within the sampling frequency to be completed. The specific completion method is as follows: Figure 3 As shown, region 1 is the spectrum data after the spectrum data of the time domain excitation source signal is multiplied by the spectrum data obtained by electromagnetic calculation, and region 2 is the supplementary data. The data of region 1 and region 2 are about f s / 2 conjugate symmetry, and finally the completed spectrum data is subjected to discrete inverse Fourier transform to obtain the time-domain transient field of the ultra-wide spectrum electromagnetic pulse of the super-electric platform.

[0069] The following is a case study of the time-domain transient field prediction of ultra-wide spectrum electromagnetic pulses on the super-electric platform.

[0070] According to the above steps, first Figure 4 The time domain excitation signal of the ultra-wide spectrum electromagnetic pulse is Fourier transformed to obtain the spectrum curve corresponding to the time domain excitation signal, such as Figure 5 As shown; according to the physical size of the platform and the location of the calculation area, as shown Figure 6 As shown in FIG. 1 , the frequency points for calculating the frequency domain electromagnetic environment are from 3.5 MHz to 756 MHz, with a frequency interval of 3.5 MHz, and the electric field distribution of a total of 216 frequency points; then, using the solution method in step (2) and step (3), the frequency domain electric field distribution of each frequency point in the calculation area of ​​the super-electric platform is simulated and calculated. Figure 7 The frequency domain electric field distribution of typical frequency points is given, among which (a) is the electric field distribution of 3.5MHz frequency point, and (b) is the electric field distribution of 756MHz frequency point. Finally, according to the calculated frequency domain field electromagnetic environment data of each frequency point and the spectrum data corresponding to the time domain excitation signal, the inverse Fourier transform is performed to obtain the time domain transient field distribution of the ultra-wide spectrum electromagnetic pulse of the super-electric platform. Figure 8The time domain transient field distribution at typical moments is given, where (a) is the transient field distribution at 45ns, and (b) is the transient field distribution at 90ns.

[0071] The present invention makes full use of the advantages of frequency domain field calculation methods in solving ultra-large-scale objects. The full-wave electromagnetic algorithm is used in the low-frequency band, and the high- and low-frequency collaborative algorithm is used in the high-frequency band, thereby fully taking into account the solution accuracy and solution scale of the frequency domain field, and sharing the frequency domain field data at the same time, so as to quickly solve the transient fields of various time domain excitation signals. The present invention is particularly suitable for solving the time domain transient field solution problem of ultra-wide spectrum electromagnetic pulses of ultra-large platforms, and carrying out protection optimization design of electromagnetic pulses with different time domain excitation waveforms.

[0072] It should be pointed out that, according to the needs of implementation, the various steps / components described in this application can be split into more steps / components, and two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

[0073] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for predicting the time domain transient field of ultra-wide spectrum electromagnetic pulses on an ultra-large electric platform, characterized in that: include: (1) Perform Fourier transform on the time domain excitation signal of the ultra-wide spectrum electromagnetic pulse to obtain the spectrum curve corresponding to the time domain excitation signal, and then determine the discrete frequency point set that needs to calculate the frequency domain field according to the size of the ultra-large electric platform and the distribution of the calculation area; (2) The frequency domain electromagnetic environment of low-frequency discrete frequency points in the discrete frequency point concentration is solved by using the parallel multi-layer fast multipole full-wave solution method; (3) The frequency domain electromagnetic environment of the high-frequency discrete frequency points in the discrete frequency point concentration is solved by using the high-frequency and low-frequency collaborative solution method; (4) After aligning and multiplying the frequency domain electromagnetic environment data of each discrete frequency point in the calculation area of ​​the super-electric platform with the corresponding frequency point of the spectrum curve of the time domain excitation signal, an inverse Fourier transform is performed to obtain the time domain transient field of the ultra-wide spectrum electromagnetic pulse of the super-electric platform.

2. The method according to claim 1, characterized in that Step (1) comprises: The expression of the discrete spectrum of the time-domain excitation signal is derived from the Fourier series expansion expression of the time-domain excitation signal, and the spectrum curve corresponding to the time-domain excitation signal is obtained by using the expression of the discrete spectrum; At the same time, the size of the super-electric platform and the distribution of the calculation area are taken into consideration, and the contribution of the signal reflected back to the calculation area after the transmitted time domain signal encounters an obstacle is fully considered to determine the discrete frequency point set that needs to be calculated for the frequency domain field.

3. The method according to claim 1 or 2, characterized in that: Step (2) comprises: The surface current basis functions of the platform to be calculated are grouped, and the interactions between any basis functions are calculated using different methods according to their relative position relationships. According to the grouping relationships in which they are located, if the strong coupling effect belongs to the near-field group, the moment method needs to be directly calculated. If the weak coupling effect belongs to the far-field group, MLFMA calculation is used. In the aggregation process of MLFMA calculation, the current effects of all basis functions in each group are aggregated to the center of the group. Secondly, the transfer process transfers the effect of the group center to the center of all far-field groups of the group. Finally, the configuration process configures the effect of the far-field group center to all basis functions of the group.

4. The method according to claim 3, characterized in that: The surface current basis functions of the platform to be calculated are grouped into groups, including: The platform to be calculated is surrounded by a cubic bounding box, and then the bounding box is divided into a spatial octree. Each small bounding box after division continues to be recursively divided until the smallest cube side length ranges from 0.2λ to 0.5λ. The first bounding box is called the 0th layer, followed by the 1st, 2nd, ..., Lth layers, λ is the wavelength of the electromagnetic wave corresponding to the calculation frequency point, and L is the total number of layers of the platform to be calculated.

5. The method according to claim 3, characterized in that: Step (3) includes: For ultra-wide spectrum electromagnetic pulse radiation antennas, a low-frequency full-wave electromagnetic algorithm solution method based on the multi-layer fast multipole method is used. For ultra-large electric platform structures, a high-frequency electromagnetic algorithm solution method based on the consistent geometric diffraction theory (UTD) is used.

6. The method according to claim 5, characterized in that For the ultra-large electric platform structure, the high-frequency solution method of the consistent geometric diffraction theory UTD is used, including: Determine the direct field based on the line-of-sight field strength when the ray path from the UWSP radiation antenna to the field point in the calculation area is not blocked by obstacles; When the electromagnetic pulse irradiates the surface of the platform structure, a reflection effect will be generated on the surface of the platform structure to determine the reflection field; When the electromagnetic pulse irradiates the surface of the platform structure, a diffraction effect will be generated on the platform structure, and the diffraction field will be determined; The direct field, reflected field and diffraction field are synthesized to obtain the frequency domain electromagnetic environment distribution of the calculation area under the influence of the platform structure.

7. The method according to claim 6, characterized in that Step (4) comprises: The spectrum data within the sampling frequency is completed, wherein the first area is the spectrum data after the spectrum data of the time domain excitation source signal is multiplied by the spectrum data obtained by electromagnetic calculation, and the second area is the supplementary data. The data in the first area and the second area are about f s / 2 conjugate symmetry, and finally the completed spectrum data is discretely inverse Fourier transformed to obtain the time-domain transient field of the ultra-wide spectrum electromagnetic pulse of the super-electric platform, f s is the sampling frequency.

Images