Distributed MIMO clutter echo simulation method based on GIS information

Abstract

The invention provides a distributed MIMO clutter echo simulation method based on GIS information, and the method comprises the steps: obtaining the GIS information of a geographic information system, and dividing a surface scatterer irradiated by an MIMO radar into a plurality of basic scattering units based on the GIS information; calculating slope distances, Doppler frequencies, terrain elevation values and land cover types of the plurality of basic scattering units to form a scene model element set; mapping a plurality of basic scattering units to a radar resolution unit by combining a backscattering coefficient empirical model and a resolution adaptive grid mapping method according to the scene model element set; dividing the radar resolution unit into a permanent scattering area and a dynamic scattering area according to GIS information; performing clutter statistical characteristic simulation processing on the permanent scattering region and the dynamic scattering region to obtain a clutter amplitude sequence; and performing echo analysis processing on the clutter amplitude sequence in a time-frequency domain to obtain clutter echo simulation data. And the simulation precision of clutter echo simulation data is integrally improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radar clutter modeling, and particularly relates to a distributed MIMO clutter echo simulation method based on GIS information. BACKGROUND

[0002] With the rapid development of space exploration technology, space-based radar systems have become an indispensable tool in the field of modern national defense and earth observation. However, the performance of traditional single radar is close to the bottleneck due to the limitation of power and aperture size. To break through this limitation, distributed multiple-input multiple-output (MIMO) radar technology emerges as the times require, which significantly improves the signal-to-noise ratio and detection performance of the target through the cooperative detection of multiple nodes. However, space-based distributed MIMO radar systems still face severe challenges in practical application, especially the problem of complex ground clutter interference. Since the radar works in a downward-looking state, the ground echo and target signal are highly coupled, and the dynamic characteristics of the satellite orbit cause the geometry of the formation satellite to change constantly, making the space-time coupling relationship and distribution characteristics of the clutter extremely complex, which undoubtedly brings great challenges to the design of clutter modeling and suppression algorithm.

[0003] In the field of clutter characteristic analysis, existing technical solutions are mainly divided into two categories: one is based on real system measurement analysis, and the other is based on digital modeling simulation technology. The former can reflect the actual clutter characteristics by deploying real radar systems to collect environmental data, but it has high hardware cost, poor scene adaptability, and is difficult to cover complex and variable detection environments; the latter simulates the clutter generation process through theoretical models and algorithms, which has the advantages of flexibility and economy.

[0004] However, the prior art still has significant limitations: first, the simplification of the ground environment by the traditional model leads to distortion of the clutter characteristics. In the actual scene, the terrain undulation will cause the radar resolution unit size to change abruptly and the incident angle to be complex, and the backscattering coefficients of vegetation, water and other ground object types differ significantly, but the existing technology mostly uses the homogenization assumption, which is difficult to accurately depict the non-uniform scattering characteristics; second, the lack of dynamic scattering mechanism restricts the environmental adaptability of the traditional model. In the real detection environment, the view angle changes caused by wind-induced vegetation shaking, water surface fluctuation and platform movement will all cause the clutter to present non-stationary characteristics, and the existing technology mostly models based on static scenes, which cannot reflect the time-varying characteristics in the dynamic environment; third, the coupling effect of system configuration and detection geometry has not been fully decoupled. The influence of the time-varying characteristics of the distributed MIMO radar formation configuration and the complex detection geometry on the radar echo is still lacking in-depth analysis, which makes it difficult for the existing method to support the clutter characteristic analysis and suppression algorithm research in the complex satellite formation scene. These defects not only cause the simulation results of the clutter to be significantly mismatched with the real environment, but also directly restrict the performance optimization potential and engineering application process of the space-based distributed MIMO radar system. SUMMARY

[0005] In order to solve the above problems existing in the prior art, the present application provides a distributed MIMO clutter echo simulation method based on GIS information.

[0006] The technical problem to be solved by the present application is realized by the following technical scheme: In a first aspect, the present application provides a distributed MIMO clutter echo simulation method based on GIS information, comprising: obtaining geographic information system (GIS) information, and dividing the surface scatterers irradiated by the MIMO radar into a plurality of basic scattering units based on the GIS information; calculating the slant range, Doppler frequency, terrain elevation value and surface coverage type of the plurality of basic scattering units to obtain a set of scene model elements corresponding to the plurality of basic scattering units; mapping the plurality of basic scattering units to the radar resolution unit of the MIMO radar according to the set of scene model elements, in combination with the backscattering coefficient empirical model and the resolution adaptive grid mapping method; dividing the radar resolution unit into a permanent scattering area and a dynamic scattering area according to the GIS information; performing clutter statistical characteristic simulation processing on the permanent scattering area and the dynamic scattering area to obtain a clutter amplitude sequence; performing echo analysis processing on the clutter amplitude sequence in the time-frequency domain to obtain clutter echo simulation data.

[0007] Optionally, geographic information system (GIS) information is acquired, and based on the GIS information, a surface scatterer irradiated by the MIMO radar is divided into a plurality of basic scattering units, including: Interpolation processing is performed on digital elevation map (DEM) data and digital land cover (DLC) data in the GIS information to obtain a scene interpolation processing result. The scene interpolation processing result is used to divide the surface scatterer into a plurality of basic scattering units.

[0008] Optionally, slant ranges, Doppler frequencies, terrain elevation values, and land cover types of the plurality of basic scattering units are calculated to obtain a scene model element set corresponding to the plurality of basic scattering units, including: The slant ranges and Doppler frequencies of each basic scattering unit are calculated according to ephemeris data of a satellite corresponding to the basic scattering unit and geometric relationship information between the satellite and the earth, and the MIMO radar is deployed on the satellite. The terrain elevation value of each basic scattering unit is obtained according to DEM data in GIS information corresponding to the basic scattering unit. The land cover type of each basic scattering unit is obtained by matching processing using a nearest neighbor interpolation method based on DLC data in GIS information corresponding to the basic scattering unit. The slant ranges, Doppler frequencies, terrain elevation values, and land cover types constitute the scene model element set.

[0009] Optionally, the plurality of basic scattering units are mapped to radar resolution units of the MIMO radar according to the scene model element set, in combination with an empirical backscatter coefficient model and a resolution adaptive grid mapping method, including: The average backscatter coefficient of the plurality of basic scattering units is calculated using the empirical backscatter coefficient model according to the scene model element set. The plurality of basic scattering units are mapped to the MIMO radar resolution units using the resolution adaptive grid mapping method based on the average backscatter coefficient and the scene model element set to obtain the radar resolution units.

[0010] Optionally, the empirical backscatter coefficient model includes a Morchin model and an improved NRL model, and the average backscatter coefficient of the plurality of basic scattering units is calculated using the empirical backscatter coefficient model according to the scene model element set, including: When the land cover type in the scene model element set corresponding to a current basic scattering unit is a land background, the average backscatter coefficient of the current basic scattering unit is calculated using the Morchin model. When the land cover type in the scene model element set corresponding to a current basic scattering unit is a sea background, the average backscatter coefficient of the current basic scattering unit is calculated using the improved NRL model.

[0011] Optionally, based on GIS information, the radar resolution unit is divided into permanent scattering areas and dynamic scattering areas, including: Calculate the scattering fields of all basic scattering units in the radar resolution unit; All scattered fields in each radar resolution unit are summed to obtain the composite field of each radar resolution unit; The average scattering cross-sectional area of ​​the radar resolution unit is calculated according to the composite field, the clutter energy of the radar resolution unit is calculated using the average scattering cross-sectional area, and the clutter energy of the radar resolution unit is divided by the noise energy of the MIMO radar to obtain the normalized clutter energy; When the normalized clutter energy is less than the energy threshold, the radar resolution unit is divided into a dynamic scattering area; When the normalized clutter energy is greater than the energy threshold, the radar resolution unit is divided into a permanent scattering area.

[0012] Optionally, the clutter amplitude sequence includes: a K-distributed clutter amplitude sequence and a Gaussian-distributed clutter amplitude sequence, and clutter statistical characteristic simulation processing is performed on the permanent scattering region and the dynamic scattering region to obtain the clutter amplitude sequence, including: In the dynamic scattering region, the K distribution model is used to simulate the statistical characteristics of clutter and obtain the fluctuation of the first backscattering cross-sectional area; Summing the first backscattering cross-sectional area fluctuation and the average scattering cross-sectional area of ​​the dynamic scattering region to obtain the backscattering cross-sectional area of ​​the dynamic scattering region; The K-distributed clutter amplitude sequence is calculated using the backscattering cross-section of the dynamic scattering region. In the permanent scattering region, the Gaussian distribution model is used to simulate the statistical characteristics of clutter and obtain the fluctuation of the second backscattering cross-section. Summing the second backscattering cross-sectional area fluctuation and the average scattering cross-sectional area of ​​the permanent scattering region to obtain the backscattering cross-sectional area of ​​the permanent scattering region; The Gaussian distribution clutter amplitude sequence is calculated using the backscattering cross-section of the permanent scattering region.

[0013] Optionally, the clutter echo simulation data is expressed as: ; Indicates that the MIMO radar is slow in receiving time and frequency Next The receiving node The clutter echo simulation data received by each receiving channel, Indicates the Transmitting nodes, represents the total number of transmitting nodes, Indicates the Row and Column of radar resolution units, represents the total number of rows of radar resolution units, represents the total number of radar resolution units, Indicates that the MIMO radar is slow in receiving time and frequency Next Rank Column of clutter echo simulation data of radar resolution unit; ; Indicates slow time at the receiving moment Next Row and The clutter amplitude sequence of the radar resolution unit is No. The receiving node The Fourier transform of the channel response function corresponding to the receiving channel, Indicates the The Fourier transform of the channel response function corresponding to the transmitting node, Indicates the The baseband waveform transmitted by the transmitting node, represents the imaginary unit, Indicates slow time at the receiving moment Next Row and The transmit and receive delays corresponding to the radar resolution units in the column are: represents the carrier frequency of the MIMO radar, Indicates the launch time slow time Next The time error of the transmitting node, Indicates slow time at the receiving moment Next The time error of the receiving node, represents the pulse repetition interval, Indicates the launch time slow time Next The frequency error of the transmitting node, Indicates the slow time of receiving time Next The frequency error of each receiving node.

[0014] In a second aspect, the present invention provides a distributed MIMO clutter echo simulation device based on GIS information, the distributed MIMO clutter echo simulation device based on GIS information includes: an acquisition unit, a calculation unit, a mapping unit, a division unit, a statistical simulation unit, and a time-frequency processing unit; The acquisition unit is used to: acquire geographic information system (GIS) information, and divide the surface scatterer illuminated by the MIMO radar into a plurality of basic scattering units based on the GIS information; The calculation unit is used to calculate the slant range, Doppler frequency, terrain elevation value and surface coverage type of multiple basic scattering units, and obtain a scene model element set corresponding to the multiple basic scattering units; The mapping unit is used to map multiple basic scattering units to radar resolution units of the MIMO radar based on a scene model element set, combined with an empirical model of backscatter coefficients and a resolution adaptive grid mapping method; The division unit is used to: divide the radar resolution unit into permanent scattering area and dynamic scattering area according to GIS information; The statistical simulation unit is used to simulate the clutter statistical characteristics of the permanent scattering area and the dynamic scattering area to obtain the clutter amplitude sequence; The time-frequency processing unit is used to perform echo analysis on the clutter amplitude sequence in the time-frequency domain to obtain clutter echo simulation data.

[0015] In a third aspect, the present invention provides a distributed MIMO clutter echo simulation device based on GIS information, comprising: a processor, a storage medium and a bus, wherein the storage medium stores machine-readable instructions executable by the processor. When the distributed MIMO clutter echo simulation device based on GIS information is running, the processor and the storage medium communicate via the bus, and the processor executes the machine-readable instructions to perform the steps of the distributed MIMO clutter echo simulation method based on GIS information in the first aspect as described above.

[0016] The application provides a distributed MIMO clutter echo simulation method based on GIS information, which comprises the following steps: acquiring geographic information system (GIS) information, and dividing surface scatterers irradiated by a MIMO radar into a plurality of basic scattering units based on the GIS information; calculating slant ranges, Doppler frequencies, terrain elevation values and ground cover types of the plurality of basic scattering units to obtain a scene model element set corresponding to the plurality of basic scattering units; mapping the plurality of basic scattering units to radar resolution units of the MIMO radar according to the scene model element set, in combination with a backscattering coefficient empirical model and a resolution adaptive grid mapping method; dividing the radar resolution units into permanent scattering areas and dynamic scattering areas according to the GIS information; performing clutter statistical characteristic simulation processing on the permanent scattering areas and the dynamic scattering areas to obtain a clutter amplitude sequence; and performing echo analysis processing on the clutter amplitude sequence in a time-frequency domain to obtain clutter echo simulation data. In the application, the scene model element set corresponding to the basic scattering units is constructed by comprehensively considering multiple data dimensions, so that the considered data information is more comprehensive, and the accuracy of the clutter echo simulation data is improved. Furthermore, the influence of terrain elevation and ground cover type on scattering characteristics is reflected to a large extent by dividing the plurality of basic scattering units and mapping the basic scattering units to the radar resolution units by using the resolution adaptive grid mapping method, so that the scene accuracy of the clutter echo simulation data is improved, and the mismatch problem between the clutter echo simulation data and the real environment is alleviated. In addition, the characteristics of the unstable reflection characteristic area are considered by using the method of dividing the permanent scattering areas and the dynamic scattering areas, so that the dynamic characteristics of the clutter echo are better reflected. Finally, the echo analysis processing on the clutter amplitude sequence in the time-frequency domain not only improves the simulation accuracy of the clutter echo simulation data as a whole, but also improves the performance of the obtained clutter echo simulation data for the clutter suppression algorithm in a complex satellite formation scenario.

[0017] The application will be further described in detail below in combination with the drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 A flowchart of a distributed MIMO clutter echo simulation method based on GIS information provided by the embodiments of the application is shown; Figure 2 A DEM map of an observation scene is exemplarily shown; Figure 3 A result map of clutter echo simulation data is exemplarily shown; Figure 4 Interference phase maps of a first receiving channel and a second receiving channel of a MIMO radar are exemplarily shown; Figure 5 Distribution maps of eigenvalues of a clutter covariance matrix in different backgrounds are exemplarily shown; Figure 6A structure schematic diagram of a distributed MIMO clutter echo simulation device based on GIS information provided by an embodiment of the present application is shown in FIG. 1. Figure 7 A structure schematic diagram of a distributed MIMO clutter echo simulation device based on GIS information provided by an embodiment of the present application is shown in FIG. 1. DETAILED DESCRIPTION

[0019] The present application will be further described in detail below with reference to specific embodiments, but the embodiments of the present application are not limited thereto.

[0020] In order to alleviate the mismatch problem between clutter echo simulation data and real environment, and improve the simulation accuracy of the clutter echo simulation data, an embodiment of the present application provides a distributed MIMO clutter echo simulation method based on GIS information. Figure 1 A flowchart of a distributed MIMO clutter echo simulation method based on GIS information provided by an embodiment of the present application is shown in FIG. 2, which includes the following steps. Figure 1 S101, acquiring geographic information system (GIS) information, and dividing a surface scatterer irradiated by a MIMO radar into a plurality of basic scattering units based on the GIS information. S101, acquiring geographic information system (GIS) information, and dividing a surface scatterer irradiated by a MIMO radar into a plurality of basic scattering units based on the GIS information.

[0021] Optionally, S101 can specifically include the following steps. interpolating digital elevation map (DEM) data and digital land cover (DLC) data in the GIS information to obtain a scene interpolation result; dividing the surface scatterer into the plurality of basic scattering units by using the scene interpolation result.

[0022] It should be noted that the DEM data and the GLC data are usually obtained from different sensors or have different resolutions. The interpolation processing can unify the two to the same spatial resolution grid. In addition, in the present embodiment, the DEM data can be processed by bilinear interpolation or cubic convolution interpolation, and the GLC data can be processed by mode interpolation or nearest neighbor interpolation. The specific interpolation operation method can be flexibly adjusted according to actual application, and the present embodiment is not limited thereto.

[0023] Furthermore, a preliminary demarcation can be performed along the GLC land class boundaries. Based on this, the surface scatterers can be finely cut based on the interpolated DEM data to generate several irregular triangulated networks, with each triangulated network being considered a basic scattering unit. Geographic characteristic parameters such as terrain elevation, ground slope, curvature, and feature type are obtained for each basic scattering unit based on the DEM and GLC data and used to construct scene model elements. In this embodiment, resolving the consistency issue of GIS data through interpolation and then finely cutting the surface scatterers based on geographic characteristics are the core technical foundation for constructing a coupled clutter model for high vacuum conditions. This step directly determines the physical rationality and engineering practicality of the clutter simulation.

[0024] Figure 2 The DEM diagram of the observation scene is shown as an example. Figure 2 The horizontal axis represents the range resolution unit, and the vertical axis represents the Doppler resolution unit. This displays the digital elevation model data for the observed area. Each pixel represents the surface elevation of the corresponding basic scattering unit, visually reflecting the distribution of topographical fluctuations. The method of the present invention takes into account the influence of topographical fluctuations, resulting in more accurate clutter modeling and simulation.

[0025] S102: Calculate the slant range, Doppler frequency, terrain elevation value, and surface coverage type of multiple basic scattering units to obtain a scene model element set corresponding to the multiple basic scattering units.

[0026] Optionally, S102 may specifically include: The slant range and Doppler frequency of each basic scattering unit are calculated based on the satellite ephemeris data corresponding to the multiple basic scattering units and the geometric relationship information between the satellite and the earth; the MIMO radar is deployed on the satellite; According to the DEM data in the GIS information corresponding to the multiple basic scattering units, the terrain elevation value of each basic scattering unit is obtained; Based on the DLC data in the GIS information corresponding to multiple basic scattering units, the proximity interpolation method is used for matching processing to obtain the surface cover type of each basic scattering unit; The slant range, Doppler frequency, terrain elevation value and surface cover type constitute a scene model element set.

[0027] In this embodiment, the scene model element set is represented as: ; in, Represents a collection of scene model elements, Indicates the The slant range of a basic scattering unit, Indicates the The Doppler frequency of the basic scattering unit, Indicates the a terrain elevation value of the i-th basic scattering unit, a land cover type of the i-th basic scattering unit, a coordinate corresponding to the i-th basic scattering unit in the Earth-Cartesian coordinate system, a horizontal coordinate, a vertical coordinate and a vertical coordinate corresponding to the i-th basic scattering unit in the Earth-Cartesian coordinate system, respectively, a coordinate corresponding to the satellite phase center in the Earth-Cartesian coordinate system, a horizontal coordinate, a vertical coordinate and a vertical coordinate corresponding to the satellite phase center in the Earth-Cartesian coordinate system, denotes the transpose of a matrix.

[0028] wherein, a velocity of the satellite in the Earth-Cartesian coordinate system, a horizontal velocity, a vertical velocity and a vertical velocity of the satellite in the Earth-Cartesian coordinate system, respectively, an angular velocity of the Earth rotation, a wavelength. S103, according to the scene model element set, combining the backscattering coefficient empirical model and the resolution adaptive grid mapping method, mapping a plurality of basic scattering units to radar resolution units of the MIMO radar.

[0029] Optionally, S103 can specifically include: According to the scene model element set, the average backscattering coefficient of the plurality of basic scattering units is calculated by using the backscattering coefficient empirical model; Based on the average backscattering coefficient and the scene model element set, the plurality of basic scattering units are mapped to the MIMO radar resolution units by using the resolution adaptive grid mapping method, to obtain the radar resolution units.

[0030] In this embodiment, the mapping relationship between the basic scattering units and the radar resolution units is represented as: wherein, denotes the i-th subset in the basic scattering unit set denotes the i-th row and the j-th column radar resolution unit.

[0031] ;​​​​​​​​​​ express Middle The slope distance of the line, express Middle The slope distance of the line, express Middle The Doppler frequency of the column, express Middle The Doppler frequency of the column.

[0032] Optionally, according to the scene model element set, an empirical model of backscatter coefficient is used to calculate the average backscatter coefficient of multiple basic scattering units, including: When the surface coverage type in the scene model element set corresponding to the current basic scattering unit is land background, the Morchin model is used to calculate the average backscattering coefficient of the current basic scattering unit; When the surface coverage type in the scene model element set corresponding to the current basic scattering unit is ocean background, the improved NRL model is used to calculate the average backscattering coefficient of the current basic scattering unit.

[0033] In this embodiment, the Morchin model is also called the Morchin model, and the improved NRL model is also called the improved U.S. Naval Research Laboratory model.

[0034] S104. Divide the radar resolution unit into a permanent scattering area and a dynamic scattering area according to the GIS information.

[0035] Optionally, S104 may specifically include: Calculate the scattering fields of all basic scattering units in the radar resolution unit; All scattered fields in each radar resolution unit are summed to obtain the composite field of each radar resolution unit; The average scattering cross-sectional area of ​​the radar resolution unit is calculated according to the composite field, the clutter energy of the radar resolution unit is calculated using the average scattering cross-sectional area, and the clutter energy of the radar resolution unit is divided by the noise energy of the MIMO radar to obtain the normalized clutter energy; When the normalized clutter energy is less than the energy threshold, the radar resolution unit is divided into a dynamic scattering area; When the normalized clutter energy is greater than the energy threshold, the radar resolution unit is divided into a permanent scattering area. The scattering field of the basic scattering unit is expressed as: ; Indicates the radar resolution unit The scattered field of a basic scattering unit, denotes an energy normalization coefficient, denotes an average backscattering coefficient of the th elementary scattering element in the radar resolution cell, denotes the imaginary unit, denotes the reception slant range of the th elementary scattering element, denotes the reception slant range of the th elementary scattering element.

[0036] The average scattering cross section of the radar resolution cell is denoted by ; denotes the average scattering cross section, denotes the physical area of the elementary scattering element, denotes the total number of elementary scattering elements in the radar resolution cell. It should be noted that the energy threshold in the embodiment is generally denoted as follows: ; denotes the mean value of the normalized clutter energy, denotes the standard deviation of the normalized clutter energy, denotes an adjustment coefficient, which in the embodiment may take the value 2, corresponding to a confidence interval of 95%.

[0037] S105, the clutter statistical feature simulation processing is performed on the permanent scattering area and the dynamic scattering area, to obtain a clutter amplitude sequence.

[0038] Optionally, S105 can specifically include: In the dynamic scattering area, the K distribution model is used for clutter statistical feature simulation processing, to obtain a first backscattering cross section fluctuation; The first backscattering cross section fluctuation and the average scattering cross section of the dynamic scattering area are summed, to obtain a backscattering cross section of the dynamic scattering area; The K distribution clutter amplitude sequence is calculated by using the backscattering cross section of the dynamic scattering area; In the permanent scattering area, the Gaussian distribution model is used for clutter statistical feature simulation processing, to obtain a second backscattering cross section fluctuation; The second backscattering cross section fluctuation and the average scattering cross section of the permanent scattering area are summed, to obtain a backscattering cross section of the permanent scattering area; The Gaussian distribution clutter amplitude sequence is calculated by using the backscattering cross section of the permanent scattering area.

[0039] In this embodiment, the backscattering cross-sectional area of ​​the dynamic scattering region is It can be expressed as: ; in, represents the first backscattering cross-sectional area fluctuation, Represents the average scattering cross-sectional area in the dynamic scattering region. The K-distributed clutter amplitude sequence can be expressed as: ; in, represents the value of the K-distributed clutter amplitude sequence, is the radar transmission power, are the radar transmitting slant range and receiving slant range respectively, Indicates the transmit and receive antenna gain, is the Boltzmann constant, is the ambient temperature, is the receiver bandwidth, represents the total loss of the radar system, is the receiver noise figure. S106 , performing echo analysis processing on the clutter amplitude sequence in the time-frequency domain to obtain clutter echo simulation data.

[0040] Optionally, the clutter echo simulation data is expressed as: ; Indicates that the MIMO radar is slow in receiving time and frequency Next The receiving node The clutter echo simulation data received by each receiving channel, Indicates the Transmitting nodes, represents the total number of transmitting nodes, Indicates the Row and Column of radar resolution units, represents the total number of rows of radar resolution units, represents the total number of columns of radar resolution units, Indicates that the MIMO radar is slow in receiving time and frequency Next Rank Column of clutter echo simulation data of radar resolution unit; ; Indicates slow time at the receiving moment Next row and column of radar resolution cells, a clutter amplitude sequence of the row and column of radar resolution cells, a Fourier transform of a channel response function corresponding to the row and column of radar resolution cells, a Fourier transform of a channel response function corresponding to the row and column of radar resolution cells, a baseband waveform transmitted by the row and column of radar resolution cells, denotes the imaginary unit, denotes a slow time at a reception time instant, a transmit-receive time delay corresponding to the row and column of radar resolution cells, denotes a carrier frequency of the MIMO radar, denotes a time error of the row and column of radar resolution cells, denotes a time error of the row and column of radar resolution cells, denotes a frequency error of the row and column of radar resolution cells, denotes a pulse repetition interval, denotes a frequency error of the row and column of radar resolution cells, denotes a frequency error of the row and column of radar resolution cells. row and column of radar resolution cells.

[0041] ​The embodiment of the application provides a distributed MIMO clutter echo simulation method based on GIS information, comprising: acquiring geographic information system (GIS) information, and dividing surface scatterers irradiated by a MIMO radar into a plurality of basic scattering units based on the GIS information; calculating slant range, Doppler frequency, terrain elevation value and ground cover type of the plurality of basic scattering units to obtain a scene model element set corresponding to the plurality of basic scattering units; mapping the plurality of basic scattering units to radar resolution units of the MIMO radar according to the scene model element set, in combination with an empirical model of backscattering coefficient and a resolution adaptive grid mapping method; dividing the radar resolution units into permanent scattering areas and dynamic scattering areas according to the GIS information; performing clutter statistical characteristic simulation processing on the permanent scattering areas and the dynamic scattering areas to obtain a clutter amplitude sequence; and performing echo analysis processing on the clutter amplitude sequence in a time-frequency domain to obtain clutter echo simulation data. In the embodiment of the application, the scene model element set corresponding to the basic scattering units is constructed by comprehensively considering multiple data dimensions, so that the considered data information is more comprehensive, and the accuracy of the clutter echo simulation data is improved. Secondly, the plurality of basic scattering units are divided, and the basic scattering units are mapped to the radar resolution units by using the resolution adaptive grid mapping method, so that the influence of the terrain elevation and the ground cover type on the scattering characteristics can be reflected to a large extent, the scene accuracy of the clutter echo simulation data is improved, and the mismatch problem of the clutter echo simulation data and the real environment is alleviated. In addition, the method of dividing the permanent scattering areas and the dynamic scattering areas is adopted, the characteristics of the unstable reflection area are considered, and the dynamic characteristics of the clutter echo are better reflected. Finally, the echo analysis processing is performed on the clutter amplitude sequence in the time-frequency domain, so that the simulation accuracy of the clutter echo simulation data is improved as a whole, and the performance of the obtained clutter echo simulation data for the clutter suppression algorithm in a complex satellite formation scenario is improved.

[0042] In order to verify the effectiveness of the distributed MIMO clutter echo simulation method based on GIS information provided by the application, a simulation experiment is also performed.

[0043] 1. The simulation conditions are as follows: The simulation experiment of the embodiment takes a distributed aperture coherent MIMO radar system as an example, and simulation parameter configuration is as follows: orbital height 693 km, number of formation satellites 3, working waveband 0.23 m, and antenna aperture 40 m. In the simulation experiment, real satellite ephemeris data, DEM data and LCD data are used. The observation scene is divided into 4177 basic scattering units. The detailed parameters are shown in Table 1. Table 1. Radar system parameters

[0044] 2. Simulation content and result analysis: The simulation content is as follows: This embodiment is based on the distributed MIMO clutter echo simulation method based on GIS information provided in the above embodiment, and performs echo modeling simulation on clutter in complex terrain conditions.

[0045] Result analysis: See Figures 3-5 . Specifically, Figure 3 The result diagram of the clutter echo simulation data is shown as an example. Figure 3 Figure (a) reflects the echo scattering intensity of the observation scene clutter. Figure 3 Figure (b) is the clutter range-Doppler diagram. Figure 3 It can be seen that the clutter characteristics of the simulated data accurately reflect the characteristics of the scene, and the fluctuations in clutter intensity match the fluctuations in the scene's terrain elevation. Specifically, in flat land areas, the scattering intensity generally fluctuates less and is more consistent. However, in mountainous areas with large terrain fluctuations, there are both strong scattering areas (yellow in the figure) and obscured shadow areas (dark blue in the figure), and the clutter is highly non-uniform.

[0046] Figure 4 The interference phase diagram of the first receiving channel and the second receiving channel of the MIMO radar is shown as an example. Figure 4 It can be seen that the clutter energy in the main lobe area is strong and the interference fringes are obvious, while the interference performance in the side lobe area is reduced due to the low clutter noise ratio; due to the existence of mixed baselines and the influence of terrain undulations, the interference phase changes with the range unit, and the local variation characteristics of the interference phase are consistent with the gradient change direction of the terrain. Figure 4 The clutter interference phase characteristics of the simulation data can truly and accurately reflect the coupling relationship between system configuration, terrain undulation and other factors and clutter.

[0047] Figure 5 The distribution diagram of the eigenvalues ​​of the clutter covariance matrix under different backgrounds is shown as an example. Figure 5 Figure (a) shows the distribution of eigenvalues ​​of the clutter covariance matrix under a flat terrain background. Figure 5 Figure (b) shows the distribution of eigenvalues ​​of the clutter covariance matrix under the background of undulating terrain. Figure 5 It can be seen that Figure 5 The first eigenvalue ratio of (b) Figure 5 The first eigenvalue in (a) is about 2dB smaller, while Figure 5 The second to sixth eigenvalues ​​in Figure (b) are higher than Figure 5The first eigenvalue of the clutter energy ratio in the spatial feature spectrum of the flat terrain background is 94.4%, the first two eigenvalues of the clutter energy ratio is 98.59%, and the first three eigenvalues of the clutter energy ratio is 99.93%. In the spatial feature spectrum of the terrain fluctuation background, the first eigenvalue of the clutter energy ratio is reduced to 52.1%, the first two eigenvalues of the clutter energy ratio is 80.06%, and the first three eigenvalues of the clutter energy ratio is 99.63%. Therefore, due to the influence of the terrain interference phase, the first eigenvalue is no longer highly concentrated, the clutter covariance matrix no longer presents a low-rank structure, but is distributed in multiple feature directions, thereby causing the clutter spatial subspace to be severely diffused.

[0048] It can be seen from the simulation experiment result that the method considers the influence of various factors such as system configuration, detection geometry, ground object type, terrain elevation and dynamic change on the clutter, more accurately restores the clutter in a complex background environment, improves the clutter simulation precision, and can provide more accurate simulation data for clutter suppression of the distributed MIMO radar.

[0049] The application value of the present application is that the core value of the space-based distributed MIMO radar clutter simulation is to solve the unprecedented complexity problem caused by "dynamic configuration + complex ground + cooperative detection", and the core role is embodied as follows: 1. Breakthrough of theoretical bottleneck: provide a unique feasible test platform for developing new models and algorithms for solving high-dimensional space-time coupled clutter.

[0050] 2. Drive system design: guide the selection of optimal formation configuration and orthogonal waveform design before system transmission, and maximize the clutter suppression potential.

[0051] 3. Ensure the algorithm combat capability: through high-fidelity, long-time and full-dynamic simulation, ensure the robustness of the algorithm under complex terrain, dynamic scattering and orbital motion.

[0052] Without high-quality clutter echo simulation, it is almost impossible to successfully design and functionally and stably implement the processing algorithm of the space-based distributed MIMO radar, which is a cutting-edge system. It is directly related to whether the theoretical performance gain brought by the MIMO system can be fully utilized, and whether the effective detection capability of the slow-speed target on the ground under long-distance, high-precision and strong clutter background can be realized.

[0053] The method provided by the embodiment of the present application can be applied to an electronic device. Specifically, the electronic device can be a desktop computer, a portable computer, a smart mobile terminal, a server, etc., and the embodiment of the present application is not limited thereto.

[0054] Based on the same inventive concept, the embodiment of the present application also provides a distributed MIMO clutter echo simulation device based on GIS information. Figure 6A structural diagram of a distributed MIMO clutter echo simulation device based on GIS information provided by an embodiment of the present invention is shown in FIG. Figure 6 As shown, it includes: an acquisition unit 601, a calculation unit 602, a mapping unit 603, a division unit 604, a statistical simulation unit 605 and a time-frequency processing unit 606; The acquisition unit 601 is used to: acquire geographic information system (GIS) information, and divide the surface scatterer illuminated by the MIMO radar into a plurality of basic scattering units based on the GIS information; The calculation unit 602 is used to calculate the slant range, Doppler frequency, terrain elevation value and surface coverage type of multiple basic scattering units to obtain a scene model element set corresponding to the multiple basic scattering units; The mapping unit 603 is used to map multiple basic scattering units to radar resolution units of the MIMO radar based on the scene model element set, combined with the backscatter coefficient empirical model and the resolution adaptive grid mapping method; The division unit 604 is used to: divide the radar resolution unit into permanent scattering areas and dynamic scattering areas according to GIS information; The statistical simulation unit 605 is used to simulate the clutter statistical characteristics of the permanent scattering area and the dynamic scattering area to obtain a clutter amplitude sequence; The time-frequency processing unit 606 is used to perform echo analysis processing on the clutter amplitude sequence in the time-frequency domain to obtain clutter echo simulation data.

[0055] Figure 7 A schematic diagram of the structure of a GIS-based distributed MIMO clutter echo simulation device provided in an embodiment of the present invention includes: a processor 710, a storage medium 720, and a bus 730. The storage medium 720 stores machine-readable instructions executable by the processor 710. When the GIS-based distributed MIMO clutter echo simulation device is in operation, the processor 710 communicates with the storage medium 720 via the bus 730, and the processor 710 executes the machine-readable instructions to perform the steps of the above-mentioned method embodiment. The specific implementation methods and technical effects are similar and will not be repeated here.

[0056] The storage medium may include random access memory (RAM) or non-volatile memory (NVM), such as at least one disk storage. Alternatively, the storage medium may be at least one storage device located away from the processor.

[0057] The processor described above can be a general processor, including a central processing unit (CPU), a network processor (NP), etc.; can also be a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component.

[0058] It should be noted that the terms "first", "second", and so on are used to distinguish similar objects, and do not necessarily have to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the application described herein can be implemented in an order other than those illustrated or described herein. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Rather, they are merely examples of devices and methods consistent with some aspects of the present application.

[0059] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" means that the specific features or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in the present specification.

[0060] Although the present application is described herein in conjunction with various embodiments, other variations of the disclosed embodiments can be understood and implemented by those skilled in the art with reference to the drawings and the disclosure. In the description of the present specification, the word "comprising" does not exclude other components or steps, "one" or "an" does not exclude a plurality, and "plurality" means two or more, unless otherwise explicitly specified. In addition, some measures are described in different embodiments, but this does not mean that these measures cannot be combined to produce good results.

[0061] The above is further detailed description of the present application in combination with specific preferred embodiments, and cannot be deemed as limitation of the specific implementation of the present application to these descriptions. For those skilled in the art to which the present application belongs, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, and all of them shall be deemed as falling within the protection scope of the present application.

Claims

1. A distributed MIMO clutter echo simulation method based on GIS information, characterized in that: include: Obtaining geographic information system (GIS) information, and dividing the surface scatterer illuminated by the MIMO radar into a plurality of basic scattering units based on the GIS information; Calculating the slant range, Doppler frequency, terrain elevation value, and surface cover type of the multiple basic scattering units to obtain a scene model element set corresponding to the multiple basic scattering units; According to the scene model element set, the plurality of basic scattering units are mapped to radar resolution units of the MIMO radar in combination with an empirical model of backscatter coefficients and a resolution adaptive grid mapping method; Dividing the radar resolution unit into a permanent scattering area and a dynamic scattering area according to the GIS information; performing clutter statistical characteristic simulation processing on the permanent scattering region and the dynamic scattering region to obtain a clutter amplitude sequence; The clutter amplitude sequence is subjected to echo analysis processing in the time-frequency domain to obtain clutter echo simulation data.

2. The distributed MIMO clutter echo simulation method based on GIS information according to claim 1, characterized in that: The acquiring of geographic information system (GIS) information and dividing the surface scatterer illuminated by the MIMO radar into a plurality of basic scattering units based on the GIS information includes: Performing interpolation processing on the digital elevation map (DEM) data and the ground feature coverage data (DLC) data in the GIS information to obtain a scene interpolation processing result; The surface scatterer is divided into the plurality of basic scattering units using the scene interpolation processing result.

3. The distributed MIMO clutter echo simulation method based on GIS information according to claim 1, characterized in that: The calculating of the slant ranges, Doppler frequencies, terrain elevation values, and surface coverage types of the multiple basic scattering units to obtain scene model element sets corresponding to the multiple basic scattering units includes: Calculating the slant range and Doppler frequency of each basic scattering unit according to the ephemeris data of the satellites corresponding to the multiple basic scattering units and the geometric relationship information between the satellites and the earth; the MIMO radar is deployed on the satellite; Obtaining a terrain elevation value of each basic scattering unit according to DEM data in the GIS information corresponding to the multiple basic scattering units; Based on the DLC data in the GIS information corresponding to the multiple basic scattering units, a matching process is performed using a proximity interpolation method to obtain the surface cover type of each basic scattering unit; The slant range, the Doppler frequency, the terrain elevation value, and the surface coverage type constitute the scene model element set.

4. The distributed MIMO clutter echo simulation method based on GIS information according to claim 1, characterized in that: Mapping the plurality of basic scattering units to radar resolution units of the MIMO radar based on the scene model element set in combination with an empirical model of backscatter coefficients and a resolution adaptive grid mapping method includes: Calculating an average backscattering coefficient of the plurality of basic scattering units using a backscattering coefficient empirical model according to the scene model element set; Based on the average backscatter coefficient and the scene model element set, the multiple basic scattering units are mapped into MIMO radar resolution units using the resolution adaptive grid mapping method to obtain the radar resolution units.

5. The distributed MIMO clutter echo simulation method based on GIS information according to claim 4, characterized in that: The backscatter coefficient empirical model includes: a Morchin model and an improved NRL model. The backscatter coefficient empirical model is used to calculate the average backscatter coefficient of the plurality of basic scattering units according to the scene model element set, including: When the surface coverage type in the scene model element set corresponding to the current basic scattering unit is land background, the Morchin model is used to calculate the average backscattering coefficient of the current basic scattering unit; When the surface coverage type in the scene model element set corresponding to the current basic scattering unit is ocean background, the improved NRL model is used to calculate the average backscattering coefficient of the current basic scattering unit.

6. The distributed MIMO clutter echo simulation method based on GIS information according to claim 1, characterized in that: The dividing the radar resolution unit into a permanent scattering area and a dynamic scattering area according to the GIS information includes: Calculating the scattering fields of all basic scattering units in the radar resolution unit; summing all the scattered fields in each radar resolution unit to obtain a composite field for each radar resolution unit; calculating an average scattering cross-sectional area of ​​the radar resolution unit according to the composite field, calculating the clutter energy of the radar resolution unit using the average scattering cross-sectional area, and dividing the clutter energy of the radar resolution unit by the noise energy of the MIMO radar to obtain normalized clutter energy; When the normalized clutter energy is less than an energy threshold, dividing the radar resolution unit into the dynamic scattering zone; When the normalized clutter energy is greater than an energy threshold, the radar resolution unit is divided into the permanent scattering area.

7. The distributed MIMO clutter echo simulation method based on GIS information according to claim 6, characterized in that: The clutter amplitude sequence includes: a K-distributed clutter amplitude sequence and a Gaussian-distributed clutter amplitude sequence. The clutter statistical characteristic simulation processing is performed on the permanent scattering region and the dynamic scattering region to obtain the clutter amplitude sequence, including: In the dynamic scattering region, a K distribution model is used to simulate the statistical characteristics of clutter to obtain a first backscattering cross-sectional area fluctuation; summing the first backscattering cross-sectional area fluctuation and the average scattering cross-sectional area of ​​the dynamic scattering region to obtain a backscattering cross-sectional area of ​​the dynamic scattering region; A K-distributed clutter amplitude sequence is calculated using the backscattering cross-sectional area of ​​the dynamic scattering region; In the permanent scattering region, a Gaussian distribution model is used to simulate the statistical characteristics of clutter to obtain a second backscattering cross-sectional area fluctuation; summing the second backscattering cross-sectional area fluctuation and the average scattering cross-sectional area of ​​the permanent scattering region to obtain the backscattering cross-sectional area of ​​the permanent scattering region; The Gaussian distribution clutter amplitude sequence is calculated using the backscattering cross-sectional area of ​​the permanent scattering region.

8. The distributed MIMO clutter echo simulation method based on GIS information according to claim 1, characterized in that: The clutter echo simulation data is expressed as: ； Indicates that the MIMO radar is slow in receiving time and frequency Next The receiving node The clutter echo simulation data received by each receiving channel, Indicates the Transmitting nodes, represents the total number of transmitting nodes, Indicates the Row and Column of radar resolution units, represents the total number of rows of radar resolution units, represents the total number of columns of radar resolution units, Indicates that the MIMO radar is slow in receiving time and frequency Next Rank Column of clutter echo simulation data of radar resolution unit; ； Indicates slow time at the receiving moment Next Row and The clutter amplitude sequence of the radar resolution unit is No. The receiving node The Fourier transform of the channel response function corresponding to the receiving channel, Indicates the The Fourier transform of the channel response function corresponding to the transmitting node, Indicates the The baseband waveform transmitted by the transmitting node, represents the imaginary unit, Indicates slow time at the receiving moment Next Row and The transmit and receive delays corresponding to the radar resolution units in the column are: represents the carrier frequency of the MIMO radar, Indicates the launch time slow time Next The time error of the transmitting node, Indicates slow time at the receiving moment Next The time error of the receiving node, represents the pulse repetition interval, Indicates the launch time slow time Next The frequency error of the transmitting node, Indicates the slow time of receiving time Next The frequency error of each receiving node.

9. A distributed MIMO clutter echo simulation device based on GIS information, characterized in that: The distributed MIMO clutter echo simulation device based on GIS information includes: an acquisition unit, a calculation unit, a mapping unit, a division unit, a statistical simulation unit and a time-frequency processing unit; The acquisition unit is used to: acquire geographic information system (GIS) information, and divide the surface scatterer illuminated by the MIMO radar into a plurality of basic scattering units based on the GIS information; The calculation unit is used to calculate the slant range, Doppler frequency, terrain elevation value and surface coverage type of the multiple basic scattering units to obtain a scene model element set corresponding to the multiple basic scattering units; The mapping unit is configured to map the plurality of basic scattering units to radar resolution units of the MIMO radar according to the scene model element set, in combination with a backscatter coefficient empirical model and a resolution adaptive grid mapping method; The division unit is used to: divide the radar resolution unit into a permanent scattering area and a dynamic scattering area according to the GIS information; The statistical simulation unit is used to perform clutter statistical feature simulation processing on the permanent scattering area and the dynamic scattering area to obtain a clutter amplitude sequence; The time-frequency processing unit is used to perform echo analysis processing on the clutter amplitude sequence in the time-frequency domain to obtain clutter echo simulation data.

10. A distributed MIMO clutter echo simulation device based on GIS information, characterized in that: include: A processor, a storage medium, and a bus, wherein the storage medium stores machine-readable instructions executable by the processor. When the distributed MIMO clutter echo simulation device based on GIS information is running, the processor and the storage medium communicate via the bus, and the processor executes the machine-readable instructions to perform the steps of the distributed MIMO clutter echo simulation method based on GIS information according to any one of claims 1 to 8.

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