A high-fidelity volumetric target simulation method based on multiple scattering points

Abstract

The present invention discloses a highly realistic volumetric target simulation method based on multiple scattering points. The method uses a multi-layer fast multipole algorithm to calculate the electromagnetic scattering characteristics of typical targets corresponding to different microwave frequency bands, obtaining radar echo data. The spatial distribution of targets at strong scattering points is extracted to establish a target echo characteristic model library. The number, location, and intensity of the target's strong scattering points are obtained in real time from the database. The distance and radial velocity of each strong scattering point are calculated in real time, and the delay, micro-Doppler frequency, and transmit power of each strong scattering point are obtained. A fractional-order high-precision delay circuit, a digital orthogonal up-conversion circuit, and a digital orthogonal modulation circuit are used to simulate the echo characteristics of each scattering point. Digital convolution and digital AGC circuits are used to achieve vector synthesis and normalization of the scattering point data, ultimately generating surface or volume target signals with time-domain scalability and frequency-domain scalability. The present invention can realistically simulate the electromagnetic wave reflection characteristics of typical targets.

Description

Technical Field

[0001] The invention relates to electronic countermeasure technology, in particular to a high-fidelity body target simulation method based on multiple scattering points. Background Art

[0002] Radar, known as the "eyes of the armed forces," is a vital component of national defense and firepower strikes. On the one hand, troops need to conduct regular confrontation exercises to train radar operators' combat proficiency and battlefield adaptability. On the other hand, as radars age in service, their performance gradually declines, necessitating regular evaluations of their operational performance and technical specifications to inform subsequent maintenance and improvements. To save costs and reduce the launch time of various target aircraft, it is necessary to develop various radar target simulators to facilitate radar performance testing and combat training.

[0003] At present, radar target simulators in the industry mainly include point target simulation and SAR / ISAR target simulation. Point target simulation samples and stores the radar transmission signal, and forwards it after path delay, Doppler modulation and Swerlling modulation. The signal does not contain the subtle characteristics of the target reflection signal (such as multipath, micro-Doppler, scintillation, etc.). For large targets and targets with micro-motion characteristics (such as fighter jets, helicopters, missiles, etc.), it cannot accurately reflect the target's multi-scattering point distance ductility and Doppler spread characteristics; although SAR / ISAR target simulation can simulate the target's subtle characteristic information, the amount of calculation is large and it cannot be simulated in real time in engineering. Summary of the Invention

[0004] To address the challenges of the existing technology, the present invention provides a highly realistic volumetric target simulation method based on multiple scattering points. This method uses specialized target electromagnetic scattering characteristics analysis software to analyze electromagnetic wave reflection data from typical targets under different frequency bands and posture conditions. The method then extracts the number, location, and scattering magnitude of the target's strong scattering points under these conditions, obtaining precise distance, Doppler, and amplitude information for each scattering point. This information is then corrected using field-detected data from a darkroom. An FPGA circuit then accurately simulates the echo signal from each strong scattering point, including its time-domain scalability and frequency-domain expansion characteristics, as well as a vector composite signal of all strong scattering point signals. This method realistically simulates the electromagnetic wave reflection characteristics of each typical target.

[0005] The purpose of the present invention is achieved through the following technical solutions.

[0006] A high-fidelity object simulation method based on multiple scattering points, comprising the following steps:

[0007] 1) Using the multi-layer fast multipole algorithm to calculate the electromagnetic scattering characteristics of typical targets corresponding to different microwave frequency bands, the radar echo data at different azimuth, pitch, and roll angles are obtained;

[0008] 2) Extract the spatial distribution of strong scattering points of the target at different locations and frequency bands, as well as the distance, angle, and reflection intensity of each scattering point, and establish a target echo characteristic model library;

[0009] 3) During radar target simulation, the three-dimensional spatial situation between the radar and the target is planned. The number, location, and intensity of strong scattering points of the target at different times are obtained in real time through the database and downloaded to the DRFM module in real time via the VPX bus.

[0010] 4) The DRFM module calculates the distance and radial velocity of each strong scattering point in real time based on the downlink data, and obtains the delay, micro-Doppler frequency and transmission power of each strong scattering point;

[0011] 5) The echo characteristics of each scattering point are simulated by a fractional-order high-precision delay circuit, a digital orthogonal up-conversion circuit, and a digital orthogonal modulation circuit;

[0012] 6) Through digital convolution and digital AGC circuits, vector synthesis and normalization processing of the data of each scattering point are realized, and finally a surface target or volume target signal with time domain scalability and frequency domain scalability is formed.

[0013] The fractional-order delay circuit generates echo signals from each scattering point with an accuracy better than 1ns; the DDS circuit generates micro-Doppler signals with an accuracy better than 0.1Hz; the orthogonal modulation circuit independently controls the amplitude of each scattering point; and the complex convolution circuit achieves vector synthesis of the data from each scattering point. Ultimately, the system generates signals for both surface and volume targets with multi-scattering point modulation characteristics, and the intensity, distance, and velocity of each strong scattering point can be independently set.

[0014] The target electromagnetic scattering data is calculated using the GTD scattering center model, and the signal characteristics of the target's strong scattering points are extracted, including the number of scattering points, the position of each scattering point, and the scattering intensity, to form a target echo characteristic model library.

[0015] The target's motion trajectory relative to the radar is obtained according to the scenario planning software. The target scattering point data at different positions on the motion trajectory are obtained by looking up the table. The target scattering point data at different positions on the motion trajectory are converted into range delay, normalized power value, and micro-Doppler frequency information, and transmitted to the DRFM module.

[0016] Fractional-order programmable digital delay and high-precision digital delay technology based on digital filtering are used to achieve programmable delay of the data of each strong scattering point of the target. The delay step and delay accuracy are both less than 1ns, which is used to accurately simulate the spatial position of each strong scattering point.

[0017] According to the obtained signal strength of each strong scattering point of the target, the target echo data is subjected to Hilbert transform and digital orthogonal modulation to accurately simulate the intensity of the echo signal of each strong scattering point.

[0018] Based on the acquired spatial position of each strong scattering point of the target and the target's motion trajectory relative to the radar, the radial velocity and micro-Doppler frequency of each strong scattering point relative to the radar are calculated in real time. The DDS module generates two orthogonal micro-Doppler signal data, which are digitally converted with the corresponding scattering point echo data. The micro-Doppler frequency is superimposed on the echo signal to accurately simulate the velocity characteristics of the echo signal of each strong scattering point.

[0019] In the FPGA module, multi-phase parallel processing and orthogonal complex convolution technology are used to perform vector superposition on the echo data of each strong scattering point, and the digital AGC technology is used to normalize the echo data to realistically simulate surface targets and volume targets with multipath and micro-Doppler characteristics.

[0020] The multi-layer fast multipole algorithm is used to group the studied targets layer by layer, including signal aggregation, interpolation, transfer, deinterpolation and configuration processes.

[0021] Scattering centers include mirror scattering centers, edge scattering centers, multiple reflection scattering centers, spire scattering centers, and scattering centers generated by traveling waves and creeping waves.

[0022] The DRFM circuit performs analog-to-digital conversion, sampling, and waveform storage on the baseband signal. It first passes through a time delay control circuit to precisely control the delay time for the echo signal to reach the radar receiver. The digital-to-analog converter then outputs the delayed baseband signal. The delayed radar baseband signal undergoes digital orthogonal mixing via precise frequency data generated by a high-speed DDS, simulating the target to produce the overall Doppler frequency shift and micro-Doppler characteristics of each scattering point. The IQ modulator performs amplitude modulation on each echo signal, simulating the amplitude fluctuation characteristics of each strong scattering element of the target. Finally, the echo signals from each strong scattering point are vector-superimposed to form the final target echo signal.

[0023] Compared with the existing technology, the advantages of the present invention are: 1. The present invention can use the multi-layer fast multipole algorithm (MLFMA) to analyze the electromagnetic scattering characteristics of various electrically large targets, and use methods such as aggregation, interpolation, transfer, and inverse interpolation to effectively reduce the amount of calculation and storage;

[0024] 2. Based on the target's motion characteristics, the present invention proposes to use target position characteristic parameters, dispersion characteristic parameters, distribution characteristic parameters and motion characteristic parameters to characterize the target's subtle features, and establish a target model library based on this;

[0025] 3. The present invention uses the GTD (Geometrical Theory of Diffraction) scattering center model to analyze the target electromagnetic scattering data and extract the position, intensity and micro-Doppler characteristics of strong scattering points;

[0026] 4. The present invention can adopt fractional-order programmable digital delay and high-precision digital delay technology based on digital filtering to achieve programmable delay of data from each strong scattering point of the target, with delay step size and delay accuracy better than 1ns;

[0027] 5. The present invention can adopt technologies such as digital orthogonal modulation, digital complex convolution and digital AGC to realize amplitude modulation, micro-Doppler modulation, high-speed data vector superposition and normalization processing of the data of each strong scattering point. The micro-Doppler accuracy is better than 0.05Hz and the echo amplitude accuracy is better than 0.1dB. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Flowchart for analysis and calculation of electromagnetic scattering data of complex targets, extraction of characteristic parameters of strong scattering points, and establishment of target feature library.

[0029] Figure 2 Flowchart of the high-frequency estimation method for electrically large targets.

[0030] Figure 3 Block diagram of logic circuit for volume target simulation based on multiple scattering points.

[0031] Figure 4 DRFM module circuit composition block diagram.

[0032] Figure 5 The distance delay test results of a certain type of aircraft at a strong scattering point.

[0033] Figure 6 Micro-Doppler frequency test results of a certain type of aircraft at a strong scattering point.

[0034] Figure 7 Test results of amplitude fluctuations of strong scattering points of a certain type of aircraft. DETAILED DESCRIPTION

[0035] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] A high-fidelity object simulation method based on multiple scattering points, comprising the following steps:

[0037] 1) Using the multi-layer fast multipole algorithm to calculate the electromagnetic scattering characteristics of typical targets corresponding to different microwave frequency bands, the radar echo data at different azimuth, pitch, and roll angles are obtained;

[0038] 2) Extract the spatial distribution of strong scattering points of the target at different locations and frequency bands, as well as the distance, angle, and reflection intensity of each scattering point, and establish a target echo characteristic model library;

[0039] 3) During radar target simulation, the three-dimensional spatial situation between the radar and the target is planned. The number, location, and intensity of strong scattering points of the target at different times are obtained in real time through the database and downloaded to the DRFM module in real time via the VPX bus.

[0040] 4) The DRFM module calculates the distance and radial velocity of each strong scattering point in real time based on the downlink data, and obtains the delay, micro-Doppler frequency and transmission power of each strong scattering point;

[0041] 5) The echo characteristics of each scattering point are simulated by a fractional-order high-precision delay circuit, a digital orthogonal up-conversion circuit, and a digital orthogonal modulation circuit;

[0042] 6) Through digital convolution and digital AGC circuits, vector synthesis and normalization processing of the data of each scattering point are realized, and finally a surface target or volume target signal with time domain scalability and frequency domain scalability is formed.

[0043] The target electromagnetic scattering data is calculated using the GTD scattering center model, and the signal characteristics of the target's strong scattering points are extracted, including the number of scattering points, the position of each scattering point, and the scattering intensity, to form a target echo characteristic model library.

[0044] The target's motion trajectory relative to the radar is obtained according to the scenario planning software. The target scattering point data at different positions on the motion trajectory are obtained by looking up the table. The target scattering point data at different positions on the motion trajectory are converted into range delay, normalized power value, and micro-Doppler frequency information, and transmitted to the DRFM module.

[0045] Fractional-order programmable digital delay and high-precision digital delay technology based on digital filtering are used to achieve programmable delay of the data of each strong scattering point of the target. The delay step and delay accuracy are both less than 1ns, which is used to accurately simulate the spatial position of each strong scattering point.

[0046] According to the obtained signal strength of each strong scattering point of the target, the target echo data is subjected to Hilbert transform and digital orthogonal modulation to accurately simulate the intensity of the echo signal of each strong scattering point.

[0047] Based on the acquired spatial position of each strong scattering point of the target and the target's motion trajectory relative to the radar, the radial velocity and micro-Doppler frequency of each strong scattering point relative to the radar are calculated in real time. The DDS module generates two orthogonal micro-Doppler signal data, which are digitally converted with the corresponding scattering point echo data. The micro-Doppler frequency is superimposed on the echo signal to accurately simulate the velocity characteristics of the echo signal of each strong scattering point.

[0048] In the FPGA module, multi-phase parallel processing and orthogonal complex convolution technology are used to perform vector superposition on the echo data of each strong scattering point, and the digital AGC technology is used to normalize the echo data to realistically simulate surface targets and volume targets with multipath and micro-Doppler characteristics.

[0049] Target Radar Cross Section (RCS) Simulation Solution: This solution uses the Multilevel Fast Multipole Algorithm (MLFMA) to group the targets layer by layer, including signal aggregation, interpolation, transfer, deinterpolation, and configuration. This algorithm not only greatly accelerates the calculation speed of matrix-vector multiplication, but also greatly reduces the storage requirements. Compared with traditional multipole algorithms, this algorithm reduces both the computational complexity and storage requirements to O(NlogN), making it very suitable for solving electromagnetic scattering problems of electrically large targets such as aircraft and missiles.

[0050] Target database classification modeling characterization parameters: Position characteristic parameters describe the average position and distribution of each scattering point of the target, mainly including mean, quantile, minimum and maximum values; Scatter characteristic parameters represent the distribution pattern of the target RCS sequence on the entire real axis. Scatter characteristic parameters include range, variance and standard deviation, standard mean deviation and coefficient of variation; Distribution characteristic parameters describe the graphical characteristics of the overall density function of the target RCS statistical distribution, including distribution density function, cumulative distribution function, standard skewness coefficient and standard kurtosis coefficient; Motion characteristic parameters describe that the target scattered wave is a complex function of frequency, polarization, time and space. The rotation characteristics of the target have a modulation effect on the radar electromagnetic wave, which is reflected in the amplitude characteristics, frequency characteristics and polarization characteristics of the target scattered wave. Different modulation characteristics are reflected in different target models.

[0051] Target scattering center type: corresponding to different target types, the scattering centers mainly include specular scattering centers, edge (ridge) scattering centers, multiple reflection scattering centers, spire scattering centers, scattering centers generated by traveling waves and creeping waves

[0052] Scattering center mathematical model: The target's characteristics can be mathematically approximated using a scattering center model. The scattering center model used in this invention is the GTD (Geometrical Theory of Diffraction) model. This model takes into account the amplitude variation in frequency response of scattering centers formed by different structures.

[0053] Multi-scattering point target simulation solution: The DRFM circuit performs analog-to-digital conversion on the baseband signal, samples it, and stores the waveform. After passing through a time delay control circuit to precisely control the delay before the echo signal reaches the radar receiver, the D / A converter outputs the delayed baseband signal. The delayed radar baseband signal undergoes digital orthogonal mixing using precise frequency data generated by a high-speed DDS to simulate the target, generating the overall Doppler shift and micro-Doppler characteristics of each scattering point (e.g., JEM characteristics). An IQ modulator amplitude modulates each echo signal to simulate the amplitude fluctuation characteristics of each strong scattering point on the target. Finally, the echo signals from each strong scattering point are vector-added to form the final target echo signal.

[0054] The technical indicators achieved by this patent are as follows:

[0055] a) Frequency range: 0.35-18GHz

[0056] b) Instantaneous bandwidth: 1GHz

[0057] c) Maximum number of scattering points: ≤16

[0058] d) Distance extension characteristics

[0059] 1) Range: 0-1000ns

[0060] 2) Step size: 1ns

[0061] e) Micro-Doppler characteristics

[0062] 1) Range: 0-100Hz

[0063] 2) Step size: 0.05Hz

[0064] f) Amplitude fluctuation

[0065] 1) Range: 0-30dB

[0066] 2) Step size: 0.1dB.

[0067] The present invention has the following advantages:

[0068] 1) The simulated target is no longer simply viewed as a single scattering point model. Instead, it is equivalent to a model composed of multiple strong scattering centers based on different electromagnetic signal incident angles. The target echo signal is the coherent superposition of the echoes generated by each scattering center.

[0069] 2) The RCS of the simulated target no longer uses the Swerlling model in the existing technology, but instead adopts the electrically large-scale complex target estimation technology to simulate the RCS of complex targets more realistically;

[0070] 3) By analyzing the Doppler effects of different scattering centers, the echo of the simulated target includes the Doppler effects due to the target's translation and micro-motion.

[0071] Example 1

[0072] 1. Target radar cross section (RCS) simulation

[0073] The Multi-Level Fast Multipole Algorithm (MLFMA) and its extensions, as fast algorithms for the integral equation method of moments, not only significantly accelerate the computational speed of matrix-vector multiplication but also significantly reduce storage requirements. This paper uses the fast multipole algorithm to analyze the electromagnetic scattering characteristics of complex targets. Combined with target strong scattering point extraction software, this method obtains parameters such as the spatial distribution of strong scattering points corresponding to different frequencies and spatial locations, micro-Doppler frequency, and scattering intensity. These parameters, combined with target model characterization parameters, form a target model library.

[0074] The mathematical basis of the fast multipole method is the vector addition theorem, which uses the vector addition theorem to process the free-space Green's function in the integral equation. By expanding it in the angular spectrum space and using plane waves to diagonalize the operator, the product of a dense full matrix and a vector is converted into the product of several sparse matrices and vectors.

[0075] The 3D fast multipole method is based on two important mathematical identities. The first is the vector addition theorem, also known as Gegenbauer's addition theorem:

[0076]

[0077] Where: j l (kd) is the spherical Bessel function of the first kind, is a spherical Hankel function of the first kind, is a Legendre polynomial.

[0078] Formula (1) shows that the spherical wave is expanded into spherical harmonics. When l→∞, the first kind of spherical Bessel function j l (kd) approaches 0, the first kind of spherical Hankel function h l (1) (kr) approaches infinity. However, since the spherical Bessel function approaches zero faster than the spherical Hankel function, the infinite sum of the addition theorem can be truncated to a finite term, and the truncation is:

[0079]

[0080] Another important mathematical identity is the following:

[0081]

[0082] Including: points represents the integral over the unit sphere.

[0083] Substituting formula (2) into formula (3), we can get:

[0084]

[0085] Where L is the number of truncated terms in the infinite sum of the vector addition theorem.

[0086] make The Green function is expressed as follows:

[0087]

[0088] Equation (5) represents a spherical wave, that is, the multipole expansion of the free-space scalar Green's function. The scalar Green's function can be expanded using plane waves on the unit sphere.

[0089] The impedance matrix element Z discretized by the moment method ij , represents the single-step direct effect of current element j on current element i. In order to use the fast multipole method, the matrix element Z ij Decompose into

[0090]

[0091] Vector V l'j The term represents the information transfer between point j and Hub l', and the matrix The term represents the information transfer between two Hub l and Hub l'. Finally, the vector The term represents the information transfer from Hub l to point i, transforming one direct action into three indirect actions, each of which is called aggregation, transfer, and configuration. Therefore, the matrix-vector product can be expressed as

[0092]

[0093] The impedance matrix element Z in the above expression is ij , is represented as a vector multiplied by a matrix multiplied by a vector, and it seems that the solution becomes more complicated. However, if the matrix Can be diagonalized, then the information transfer between the two groups can become more efficient, which may save a lot of computation and storage, because the matrix It can be reused to improve computing efficiency.

[0094] The use of the multi-layer fast multipole method to analyze the electromagnetic scattering characteristics of various electrically large and complex targets such as aircraft and missiles can not only greatly accelerate the calculation speed of matrix-vector multiplication, but also greatly reduce the storage requirements. The matrix-vector product of the electric field integral equation can be expressed as follows:

[0095]

[0096] Among them: NG (Near Group) represents the neighboring group, and FG (Far Group) represents the far group. represents the aggregation factor, represents the configuration factor, Represents the transfer factor, and the expressions are as follows:

[0097]

[0098]

[0099]

[0100] The storage and computational complexity of the traditional iterative method for solving the moment method is O(N 2 ), while the storage and computational complexity of the fast multipole method are both O(N 1.5 By grouping the research targets layer by layer and using processes such as aggregation, interpolation, transfer, deinterpolation, and configuration, we can obtain the Multilevel Fast Multipole Algorithm (MLFMA). The computational complexity and storage requirements of this algorithm are reduced to O(NlogN), making it very suitable for solving electromagnetic scattering problems from electrically large targets. Figure 2 The flow chart of the high frequency estimation method for electrically large size targets is given.

[0101] 2. Multi-scattering point target simulation method

[0102] like Figure 3 As shown, the characterization data of each strong scattering point is read from the target model library and sorted according to the spatial position (arrival time). The delay τ and Doppler frequency shift f of each scattering point are d , amplitude A are independently controllable. Orthogonal baseband signal and The data is sent to the high-speed DDR memory via the VPX bus. The system requires high data delay accuracy, which cannot be achieved by the commonly used delay circuit. It is necessary to use the digital filter in the FPGA chip to achieve it. The micro-Doppler frequency of the scattering point is realized by the digital orthogonal frequency modulation circuit. The mathematical formula for the realization is: The amplitude modulation of the scattering point is realized by a real number amplitude modulation circuit, and the mathematical formula for the realization is:

[0103] Finally, the outputs of N scattering points are vector superimposed and AGC normalized, and the mathematical formula for this is: In this way, the Doppler frequency shift, micro-Doppler modulation, amplitude modulation and range delay of different scattering points are completed, and a realistic radar target signal with range extension and Doppler expansion characteristics is obtained.

[0104] When simulating radar target echo signals, the mathematical model involved in converting spatial position parameters into electrical signal parameters is as follows:

[0105] (1) Calculation of target radial velocity: Assume the target position is P(X T ,Y T ,Z T ), the speed is V(V X ,V Y ,V Z ), then the radial velocity is v r =|v|cosθ.

[0106] in,

[0107] (2) Doppler frequency: f d =(2v r / c)f, where v r The target radial motion speed, c is the speed of light, and f is the signal carrier frequency.

[0108] (3) Delay: τ = 2R0 / C, where

[0109] After completing the multi-scattering point echo signal simulation, the circuit can be integrated into the DRFM module to achieve high-fidelity target echo signal simulation. The circuit block diagram is as follows: Figure 4 shown.

[0110] 3. High-precision delay

[0111] Assume that the simulation object is a certain type of fighter, whose external parameters are 19.6 meters in length, 5 meters from the nose to the wings, and 7 meters in wingspan. If the radar is irradiated from its oblique direction, the strong scattering points are projected at 0 meters, 1.7 meters, 4.9 meters, and 14.4 meters in the distance direction. The corresponding delays are 0ns, 11ns, 33ns, and 96ns respectively. The coordinates of the four strong scattering points of the simulated aircraft target of the present invention are 977317ns, 977328ns, 977350ns, and 977413ns respectively. The test results are as follows: Figure 5 As shown in the figure, the relative delays of the four scattering points are 0ns, 11ns, 33ns, and 96ns, respectively, which are consistent with the theoretical values.

[0112] 4. Micro-Doppler simulation

[0113] Since the micro-Doppler frequency is very small, the amount of data required for frequency analysis is very large. To facilitate analysis, it is assumed that the radar transmit signal is a 50MHz continuous wave. Based on the relative motion relationship between the target and the radar, the Doppler frequency shifts of the four strong scattering points are set to 0Hz, 70Hz, 90Hz, and 100Hz. After actual testing, the echo frequencies of the four strong scattering points of the simulated aircraft target of the present invention are 49.99961MHz, 49.99968MHz, 49.99970MHz, and 49.99971MHz respectively. The test results are as follows: Figure 6 As shown in Figure 1, the frequency differences of the four scattering points are 0 Hz, 70 Hz, 90 Hz, and 100 Hz, respectively, which are consistent with the theoretical values.

[0114] 5. Amplitude fluctuation simulation

[0115] Assuming that the simulation object is a certain type of fighter, after fast multipole algorithm simulation analysis, it is determined that the aircraft has four strong scattering points, and the amplitude fluctuation values of each scattering point are: -10dB, -5dB, -1.5dB, and 0dB. After physical testing, the echo power fluctuation values of the four strong scattering points of the simulated aircraft target of the present invention are -9.7dB, -4.4dB, -1.5dB, and 0d respectively. Figure 7 As shown, it is consistent with the theoretical value.

Claims

1. A high-fidelity object simulation method based on multiple scattering points, characterized by the following steps: include: 1) Using the multi-layer fast multipole algorithm to calculate the electromagnetic scattering characteristics of typical targets corresponding to different microwave frequency bands, the radar echo data at different azimuth, pitch, and roll angles are obtained; 2) Extract the spatial distribution of strong scattering points of the target at different locations and frequency bands, as well as the distance, angle, and reflection intensity of each scattering point, and establish a target echo characteristic model library; 3) During radar target simulation, the three-dimensional spatial situation between the radar and the target is planned. The number, location, and intensity of strong scattering points of the target at different times are obtained in real time through the database and downloaded to the DRFM module in real time via the VPX bus. 4) The DRFM module calculates the distance and radial velocity of each strong scattering point in real time based on the downlink data, and obtains the delay, micro-Doppler frequency and transmission power of each strong scattering point; 5) The echo characteristics of each scattering point are simulated by a fractional-order high-precision delay circuit, a digital orthogonal up-conversion circuit, and a digital orthogonal modulation circuit; 6) Through digital convolution and digital AGC circuits, vector synthesis and normalization processing of the data of each scattering point are realized, and finally a surface target or volume target signal with time domain scalability and frequency domain scalability is formed.

2. The method for simulating a high-fidelity object based on multiple scattering points according to claim 1, wherein: The target electromagnetic scattering data is calculated using the GTD scattering center model, and the signal characteristics of the target's strong scattering points are extracted, including the number of scattering points, the position of each scattering point, and the scattering intensity, to form a target echo characteristic model library.

3. The method for simulating a high-fidelity object based on multiple scattering points according to claim 2, wherein: The target's motion trajectory relative to the radar is obtained according to the scenario planning software. The target scattering point data at different positions on the motion trajectory are obtained by looking up the table. The target scattering point data at different positions on the motion trajectory are converted into range delay, normalized power value, and micro-Doppler frequency information, and transmitted to the DRFM module.

4. The method for simulating a high-fidelity volumetric target based on multiple scattering points according to claim 1, wherein: Fractional-order programmable digital delay and high-precision digital delay technology based on digital filtering are used to achieve programmable delay of the data of each strong scattering point of the target. The delay step and delay accuracy are both less than 1ns, which is used to accurately simulate the spatial position of each strong scattering point.

5. The method for simulating a high-fidelity volumetric target based on multiple scattering points according to claim 1, wherein: According to the obtained signal strength of each strong scattering point of the target, the target echo data is subjected to Hilbert transform and digital orthogonal modulation to accurately simulate the intensity of the echo signal of each strong scattering point.

6. The method for simulating a high-fidelity volumetric target based on multiple scattering points according to claim 1, wherein: Based on the acquired spatial position of each strong scattering point of the target and the target's motion trajectory relative to the radar, the radial velocity and micro-Doppler frequency of each strong scattering point relative to the radar are calculated in real time. The DDS module generates two orthogonal micro-Doppler signal data, which are digitally converted with the corresponding scattering point echo data. The micro-Doppler frequency is superimposed on the echo signal to accurately simulate the velocity characteristics of the echo signal of each strong scattering point.

7. The method for simulating a high-fidelity object based on multiple scattering points according to claim 1, wherein: In the FPGA module, multi-phase parallel processing and orthogonal complex convolution technology are used to perform vector superposition on the echo data of each strong scattering point, and the digital AGC technology is used to normalize the echo data to realistically simulate surface targets and volume targets with multipath and micro-Doppler characteristics.

8. The method for simulating a high-fidelity volumetric target based on multiple scattering points according to claim 1, wherein: The multi-layer fast multipole algorithm is used to group the studied targets layer by layer, including signal aggregation, interpolation, transfer, deinterpolation and configuration processes.

9. The method for simulating a high-fidelity object based on multiple scattering points according to claim 2, wherein: Scattering centers include mirror scattering centers, edge scattering centers, multiple reflection scattering centers, spire scattering centers, and scattering centers generated by traveling waves and creeping waves.

10. The method for simulating a high-fidelity volumetric target based on multiple scattering points according to claim 1, wherein: The DRFM circuit performs analog-to-digital conversion, sampling, and waveform storage on the baseband signal. After passing through a time delay control circuit to precisely control the delay time for the echo signal to reach the radar receiver, the digital-to-analog converter outputs the delayed baseband signal. The delayed radar baseband signal undergoes digital orthogonal mixing using precise frequency data generated by a high-speed DDS, simulating the target to generate the overall Doppler frequency shift of the target and the micro-Doppler characteristics of each scattering point. The IQ modulator performs amplitude modulation on each echo signal to simulate the amplitude fluctuation characteristics of each strong scattering point of the target. Finally, the echo signals of each strong scattering point are vector-superimposed to form the final target echo signal.

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