Gain control parameter management method and device for high-orbit SAR (Synthetic Aperture Radar)

Abstract

The invention discloses a gain control parameter management method and device for a high-orbit SAR, and relates to the technical field of synthetic aperture radars, and the method comprises the steps: dividing a preset geographic space region into a plurality of geographic grids; collecting scene data of a corresponding scene in each geographic grid, wherein the scene data comprises geometric model data and physical parameters of each ground feature; collecting a high-orbit SAR satellite track and a satellite-ground relative position; acquiring radar position parameters of each ground feature; calculating scattering characteristics of each ground feature according to the scene data; establishing a corresponding relation between a load manual gain control parameter of the radar and the scattering characteristic of each ground object to obtain manual gain control data; a relational database is used for storing ground feature geometric module data, ground feature physical parameters, ground feature scattering characteristics, high-orbit SAR satellite tracks, satellite-ground relative motion and manual gain control data. The effectiveness of gain control parameter management of the SAR is improved.

Description

Technical Field

[0001] The present application relates to the technical field of synthetic aperture radar, and in particular to a gain control parameter management method and device for a high-orbit SAR. Background Art

[0002] There are many complex factors in the imaging process of high-orbit synthetic aperture radar (SAR). It is necessary to deeply analyze the geometric model and physical parameters of the objects in different typical imaging scenes (such as mountains, farmland, cities, forests, sea-land boundary, islands and sea surface, etc.). This includes studying the scattering characteristics and echo calculation theory of typical scenes, and then establishing a typical ground object scattering data set. At the same time, it is also necessary to consider the impact of various factors such as platform trajectory, relative motion relationship between satellite and ground, imaging wave position change, ionosphere change, etc. on radar echoes. In addition, it is necessary to simulate the echo intensity change and gain control of typical scenes in the process of high-orbit SAR aperture synthesis, and establish the correspondence between typical ground object scattering characteristics and payload manual gain control (MGC) and MGC database. However, there is currently a lack of effective MGC data management methods for high-orbit SAR, which seriously restricts the ability of high-orbit SAR systems to operate efficiently and accurately image. Summary of the invention

[0003] The purpose of this application is to provide a gain control parameter management method and device for a high-orbit SAR, which can improve the effectiveness of manual gain control parameter management, thereby improving the imaging accuracy of SAR.

[0004] To achieve the above objectives, this application provides the following solutions:

[0005] In a first aspect, the present application provides a gain control parameter management method for a high-orbit SAR, comprising:

[0006] Divide the preset geospatial area into a plurality of geographic grids;

[0007] Collecting scene data corresponding to scenes in each of the geographic grids, the scene data including geometric model data and physical parameters of each object;

[0008] Collect high-orbit SAR satellite trajectories and the relative positions of satellites and the ground;

[0009] Collecting radar position parameters of each of the ground objects;

[0010] Calculating the scattering characteristics of each of the ground objects according to the scene data;

[0011] Establishing a corresponding relationship between the radar payload manual gain control parameter and the scattering characteristics of each of the ground objects to obtain manual gain control data;

[0012] A relational database is used to store ground object geometry module data, ground object physical parameters, ground object scattering characteristics, high-orbit SAR satellite trajectory, satellite-ground relative motion and manual gain control data; the relational database is used for high-orbit SAR to image various objects.

[0013] Optionally, collecting radar position parameters of each of the ground objects specifically includes:

[0014] Determining imaging wave position change data using radar system monitoring data of the radar;

[0015] Use ionospheric detection equipment to collect ionospheric parameter change data;

[0016] Radar echo data of various objects are collected, and radar position parameters are determined according to the radar echo data.

[0017] Optionally, the relational database is used to store imaging wave position change data, ionospheric parameter change data and radar echo data.

[0018] Optionally, establishing a corresponding relationship between a radar payload manual gain control parameter and the scattering characteristics of each of the ground objects to obtain manual gain control data specifically includes:

[0019] According to the formula Obtaining the corresponding relationship between the radar payload manual gain control parameter and the scattering characteristics of each of the ground objects;

[0020] Among them, MGC is the load manual gain control parameter, G cg represents the channel gain, λ represents the wavelength, σ 0 represents the backscattering coefficient, P n represents the sum of internal and external losses of the radar system, P t Indicates the transmitter power, G 2 represents the dual-path antenna gain, θ represents the incident angle in the direction of the antenna aperture, R represents the distance between the radar and the ground target, φ represents the azimuth of the antenna, C represents the empirical constant, and K L Indicates the temperature influence coefficient, P t represents the radar transmitter power, r a represents the azimuth resolution, r y Indicates the range resolution.

[0021] Optionally, the types of the scenes include mountain scenes, farmland scenes, urban scenes, forest scenes, sea-land boundary areas, island scenes and sea scenes;

[0022] The physical parameters of the mountain scene include soil type and soil roughness;

[0023] The physical parameters of the farmland scene include crop type, crop growth stage, vegetation coverage and soil moisture;

[0024] The physical parameters of the urban scene include building height, building density and building material properties;

[0025] The physical parameters of the forest scene include tree height, tree diameter, tree density and vegetation coverage;

[0026] The physical parameters of the land-sea interface area include sea depth, wave height and beach type;

[0027] The physical parameters of the island scene include island outline, altitude and rock type;

[0028] The physical parameters of the sea surface scene include sea water temperature, sea water salinity, sea wave height and sea wave period.

[0029] Optionally, the relational database includes a ground object geometry model table, a ground object physical parameter table, a scattering characteristic table, a platform trajectory table, a satellite-ground relative motion table, and a manual gain control data table;

[0030] The object geometry model table is used to store the object geometry module data, and the fields of the object geometry model table include object ID, scene, geometry model file path and creation time; the primary key of the object geometry model table is the object ID;

[0031] The ground object physical parameter table is used to store the ground object physical parameters, the fields of the ground object physical parameter table include ground object ID, physical parameter name, parameter value and measurement time, and the primary key of the ground object physical parameter table is a combination of ground object ID and physical parameter name;

[0032] The scattering characteristic table is used to store the scattering characteristics of the ground object; the fields of the scattering characteristic table include the ground object ID, electromagnetic wave frequency, scattering center position, scattering intensity, measurement conditions and measurement time, the measurement conditions include environmental conditions and radar parameters, and the primary key of the scattering characteristic table is a combination of the ground object ID, electromagnetic wave frequency and measurement time;

[0033] The platform trajectory table is used to store high-orbit SAR satellite trajectories; the fields of the platform trajectory table include platform trajectory ID, timestamp, position coordinates, speed, acceleration and orbit parameter ID, the primary key of the platform trajectory table is the platform trajectory ID, and the foreign key is the orbit parameter ID;

[0034] The satellite-to-ground relative motion table is used to store the satellite-to-ground relative position, velocity and acceleration; the fields of the satellite-to-ground relative motion table include relative motion ID, timestamp, satellite-to-ground relative distance, relative velocity, relative acceleration, object ID and platform trajectory ID; the primary key of the satellite-to-ground relative motion table is the relative motion ID, and the foreign keys are the object ID and platform trajectory ID; the satellite-to-ground relative distance is the distance between the high-orbit SAR satellite and the ground target on the earth;

[0035] The manual gain control data table is used to store data related to gain control. The fields of the manual gain control data table include manual gain control parameter ID, ground object ID, electromagnetic wave frequency, manual gain control parameter value, and calibration time. The primary key is the manual gain control parameter ID, and the foreign keys are the ground object ID and the electromagnetic wave frequency.

[0036] Optionally, the geometric model file corresponding to the geometric model file path is in a three-dimensional model file format or a geographic information system data format.

[0037] Optionally, the relational database further includes an echo data table, an imaging wave position change table and an ionosphere change table;

[0038] The echo data table is used to store the radar echo data. The fields of the echo data table include echo ID, object ID, timestamp, echo intensity, echo phase, radar parameter ID, the primary key is echo ID, and the foreign keys are object ID and radar parameter ID;

[0039] The imaging wave position change table is used to store imaging wave position change data. The fields of the imaging wave position change table include wave position change ID, timestamp, azimuth, pitch angle and radar parameter ID. The primary key is the wave position change ID and the foreign key is the radar parameter ID.

[0040] The ionospheric change table is used for ionospheric parameter change data. The fields of the ionospheric change table include ionospheric change ID, timestamp, ionospheric electron density, ionospheric height, and detection device ID. The primary key is the ionospheric change ID, and the foreign key is the detection device ID.

[0041] Optionally, the preset geographic space area is divided into a plurality of geographic grids, specifically including:

[0042] The preset geographic space area is divided into multiple geographic grids according to longitude and latitude.

[0043] In a second aspect, the present application provides a gain control parameter management device for a high-orbit SAR, comprising:

[0044] A geographic grid division module, used for dividing a preset geographic space area into a plurality of geographic grids;

[0045] A scene data acquisition module, used to acquire scene data corresponding to scenes in each of the geographic grids, wherein the scene data includes geometric model data and physical parameters of each feature;

[0046] High-orbit SAR satellite trajectory and satellite-to-ground relative position data acquisition module, used to collect high-orbit SAR satellite trajectory and satellite-to-ground relative position;

[0047] A radar position parameter acquisition module, used to acquire radar position parameters of each of the above-mentioned objects;

[0048] A scattering characteristic calculation module, used to calculate the scattering characteristic of each of the ground objects according to the scene data;

[0049] A manual gain control data determination module is used to establish a corresponding relationship between the radar load manual gain control parameters and the scattering characteristics of each of the ground objects to obtain manual gain control data;

[0050] The storage module uses a relational database to store ground object geometry module data, ground object physical parameters, ground object scattering characteristics, high-orbit SAR satellite trajectory, satellite-ground relative motion and manual gain control data; the relational database is used for high-orbit SAR to image various objects.

[0051] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0052] The present application provides a gain control parameter management method and device for a high-orbit SAR. By establishing a corresponding relationship between the manual gain control parameters of the radar payload and the scattering characteristics of various objects, manual gain control data is obtained. Object geometry module data, object physical parameters, object scattering characteristics, high-orbit SAR satellite trajectory, satellite-to-ground relative motion, and manual gain control data are stored in a relational database, thereby realizing the integration of various types of data, improving the effectiveness of data management such as manual gain control parameters, and thus improving the imaging accuracy of SAR. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0054] Figure 1 A schematic diagram of a flow chart of a gain control parameter management method for a high-orbit SAR provided in one embodiment of the present application;

[0055] Figure 2 A schematic diagram of a stationary target SAR imaging geometric model provided in an embodiment of the present application. DETAILED DESCRIPTION

[0056] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0057] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0058] Different imaging scenes have unique ground features, which directly affect the radar echo signal. For example, the complex terrain of mountains, the growth of vegetation in farmland, the distribution of buildings in cities, the tree density in forests, the special medium changes at the sea-land interface, the unique terrain of islands, and the dynamic changes of the sea surface all make their scattering characteristics and echo calculation theories different. Accurately grasping these characteristics is crucial to establishing an accurate database and achieving high-quality imaging.

[0059] Factors that affect radar echoes include: platform trajectory, relative motion between satellite and ground, imaging wave position changes and ionosphere changes.

[0060] Platform trajectory and relative motion between satellite and ground: The trajectory of the high-orbit SAR platform and its relative position, velocity and acceleration with ground targets are constantly changing, which causes the radar illumination angle, distance and other parameters to change continuously, thus affecting the intensity and phase of the echo signal. The high-orbit SAR platform is a high-orbit SAR satellite.

[0061] Imaging wave position change: The change of imaging wave position will cause the direction and coverage of the radar beam to change, which in turn changes the scattering characteristics. It will also cause problems such as echo delay, which will interfere with the imaging results.

[0062] Ionosphere changes: Changes in ionosphere parameters can cause refraction, scattering and delay effects on radar signals, reducing signal quality and affecting imaging accuracy and clarity.

[0063] At present, there is a lack of MGC data management methods specifically for high-orbit SAR, which makes it impossible to systematically integrate various types of data, and it is difficult to achieve efficient use and accurate matching of data, resulting in the inability to fully realize its potential during the operation and imaging process of the high-orbit SAR system, and the imaging quality and efficiency are limited. Therefore, this application provides a gain control parameter management method for high-orbit SAR, such as Figure 1 As shown, the gain control parameter management method of the high-orbit SAR includes:

[0064] Step 101: Divide a preset geographic space area into a plurality of geographic grids.

[0065] Step 102: collecting scene data corresponding to scenes in each of the geographic grids, wherein the scene data includes geometric model data and physical parameters of each feature.

[0066] Step 103: Collect the high-orbit SAR satellite trajectory and the relative position between the satellite and the ground.

[0067] Step 104: Collect radar position parameters of each of the ground objects.

[0068] Step 105: Calculate the scattering characteristics of each of the ground objects according to the scene data.

[0069] Step 106: Establish a corresponding relationship between the radar payload manual gain control parameter and the scattering characteristics of each of the ground objects to obtain manual gain control data.

[0070] Step 107: using a relational database to store ground feature geometry module data, ground feature physical parameters, ground feature scattering characteristics, high-orbit SAR satellite trajectory, satellite-ground relative motion, and manual gain control data; the relational database is used for high-orbit SAR to image various features.

[0071] The present application obtains manual gain control data by establishing a corresponding relationship between the manual gain control parameters of the radar payload and the scattering characteristics of various objects. The object geometry module data, object physical parameters, object scattering characteristics, high-orbit SAR satellite trajectory, satellite-to-ground relative motion and manual gain control data are stored in a relational database, thereby realizing the integration of various types of data and achieving efficient data management of high-orbit SAR gain parameters, thereby improving the imaging accuracy of SAR.

[0072] In an exemplary embodiment, step 101 specifically includes: dividing the preset geographic space area into multiple geographic grids according to longitude and latitude. The purpose of dividing the geographic grids is to facilitate data retrieval, and the corresponding geographic grid can be quickly located through the longitude and latitude information.

[0073] The preset geographic space area can be the entire earth.

[0074] The types of scenes include mountain scenes, farmland scenes, urban scenes, forest scenes, land-sea boundary areas, island scenes and sea scenes.

[0075] The physical parameters of the mountain scene include soil type and soil roughness. The geometric shape of the mountain scene is accurately obtained using high-resolution satellite images and digital elevation models, and the physical parameters such as soil type and roughness are determined through field measurements or reference to geological data.

[0076] For example, when measuring a mountainous area, satellite images can clearly show the outline of the mountain, digital elevation models can provide altitude information, and field measurements can obtain the actual texture and roughness data of the soil, laying the foundation for subsequent analysis of scattering characteristics.

[0077] The physical parameters of the farmland scene include crop type, crop growth stage, vegetation coverage and soil moisture. The parameters such as crop type, growth stage, vegetation coverage and soil moisture are determined by combining agricultural remote sensing data and field surveys. Agricultural remote sensing data can monitor the distribution and growth trend of farmland crops at a macro level, while field surveys can accurately obtain the specific variety of crops, the current growth stage (such as seedling stage, heading stage, etc.), the proportion of vegetation covering the ground and the humidity of the soil. These parameters are of great significance for studying the scattering characteristics and echo calculation of farmland scenes.

[0078] The physical parameters of the urban scene include building height, building density and building material properties. This application uses urban geographic information system data and building models to obtain information such as building height, density, material properties, etc. Urban geographic information system data covers urban building layout, road planning, etc. The building model can intuitively present the three-dimensional structure of the building, thereby determining its height, distribution density and the characteristics of the building materials (such as concrete, steel structure, etc.), which is helpful for analyzing radar echoes in urban environments.

[0079] The physical parameters of the forest scene include tree height, tree diameter, tree density and vegetation coverage. This application determines parameters such as tree height, diameter, density, vegetation coverage, etc. through forest resource survey data and LiDAR measurement. Forest resource survey data provides the overall resource status of the forest, and LiDAR measurement can accurately obtain information such as the height and diameter of a single tree, and then calculate tree density and vegetation coverage. These data are indispensable for understanding the scattering mechanism and echo characteristics of the forest scene.

[0080] The physical parameters of the land-sea boundary area include sea depth, wave height and beach type. This application uses ocean and land remote sensing images combined with coastline measurement data to determine parameters such as sea depth, wave height, and beach type. Ocean remote sensing images can observe sea surface conditions, land remote sensing images are used to monitor changes in the land edge, and coastline measurement data clarifies the exact location of the land-sea boundary. Combining these data can accurately grasp the complex environmental parameters of the land-sea boundary area.

[0081] The physical parameters of the island scene include the island outline, altitude and rock type. This application determines the island outline, altitude, rock type and other information based on satellite images and topographic survey data. Satellite images can fully display the shape of the island and the surrounding sea conditions, and topographic survey data can accurately measure the altitude changes of the island. At the same time, combined with geological analysis, the rock type is determined, providing a basis for studying the radar scattering characteristics of the island scene.

[0082] The physical parameters of the sea scene include seawater temperature, seawater salinity, wave height and wave period. This application uses ocean observation data to obtain parameters such as seawater temperature, salinity, wave height, and wave period. The seawater temperature and salinity data provided by the ocean observation station or satellite observation system reflect the physical properties of the sea surface, while the wave height and period data describe the dynamic changes of the sea surface. These parameters are crucial to the scattering characteristics and echo calculation of the sea scene.

[0083] In an exemplary embodiment, step 103 specifically includes:

[0084] 1) Collect platform trajectory and satellite-to-ground relative motion data: Use satellite orbit data and ground positioning systems to determine the high-orbit SAR platform trajectory and the satellite-to-ground relative position, and continuously monitor the platform motion status to record position, velocity, acceleration and other data.

[0085] Satellite orbit data provides the initial orbit information of the platform, and the ground positioning system (such as GPS) monitors the actual position changes of the platform in real time. The combination of the two can accurately determine the platform trajectory and the relative position relationship between the satellite and the ground, and accurately record the dynamic parameters of the platform during movement.

[0086] 2) Processing platform trajectory and satellite-ground relative motion data: interpolating and fitting the platform trajectory data to obtain more continuous and accurate trajectory information.

[0087] Parameters such as the relative position, velocity and acceleration between the satellite and the ground are calculated to analyze the impact of platform motion on imaging and to perform compensation and correction in the imaging algorithm.

[0088] Considering the earth and the satellite (high-orbit SAR satellite) as two mass points, and combining the law of universal gravitation and Kepler's law, the orbit equation of the artificial satellite can be obtained as follows:

[0089]

[0090] Among them, r(t a ) represents the radius of the satellite from the earth, a s represents the semi-major axis of the orbit, f(t a ) represents the true anomaly angle, t a Indicates time.

[0091] Based on the coordinate system established by the Geosynchronous Orbit Synthetic Aperture Radar (GEOSAR) and its spatial structure characteristics, the radar position coordinate P in the coordinate system is s_E (t a ) can be expressed as: P s_E (t a )=r(t a )W B (t a )W A (t a )W C (t a ).

[0092] Among them, W B (t a )、W A (t a ) and W C (t a ) respectively represent the relationship between the x, y, and z coordinate axes corresponding to the coordinate transformation. In an exemplary embodiment, step 104 specifically includes:

[0093] The radar system monitoring data of the radar is used to determine the imaging wave position change data.

[0094] Ionospheric detection equipment is used to collect ionospheric parameter change data.

[0095] Radar echo data of various objects are collected, and radar position parameters are determined according to the radar echo data.

[0096] The relational database is used to store imaging wave position change data, ionospheric parameter change data and radar echo data.

[0097] The monitoring device inside the radar system records the angle, direction and other changes of the imaging wave position in real time. The ionosphere detection equipment (such as ionosphere detectors, etc.) obtains the changes in parameters such as the electron density and height of the ionosphere by transmitting detection signals and receiving reflected signals.

[0098] For echo calculation, according to the Born approximation theory, the scene can be considered to be composed of a series of scattering points. The radar echo is the linear superposition of the echoes of many scattering points within the coverage range of the antenna beam. The task of the radar imaging module is to use the impulse response of SAR to point targets to process the input two-dimensional (range and azimuth) echo sequence, so as to obtain a planar image of the scene with many scattering points distributed according to their original distribution.

[0099] Taking the positive side-looking SAR model as an example, Figure 2 The figure shows the geometric model of SAR imaging of a stationary target: the radar platform flies along the Y axis, at an altitude of H and a flight speed of v aThe position of the stationary target P is (x, y, 0), the distance of the target perpendicular to the route is R0, and the radar position at time zero is (0, 0, H).

[0100] After the radar echo is demodulated to baseband, the radar signal model of a single point target is:

[0101]

[0102] Among them, s0(τ,η) is the radar signal of a single point target, A0 is a complex constant, τ is the range time, η is the azimuth time, and η c is the beam center deviation time, ω r is the distance envelope, ω a is the azimuth envelope, f0 is the radar center frequency, K r is the range modulation frequency, ω r represents the distance envelope, c represents the speed of light, R(η) represents the instantaneous slant distance, and j is the imaginary unit.

[0103] The expression for instantaneous slope distance is:

[0104] Where R0 is the closest slope distance, v a is the platform movement speed.

[0105] The change in the distance between the radar platform and the target will cause the Doppler effect, which will affect the frequency of the echo signal, thereby obtaining the Doppler center frequency f of the point target. dc and Doppler modulation frequency K a They are:

[0106]

[0107] Here, λ represents the wavelength.

[0108] In the subsequent imaging process, a range matched filter can be constructed to perform range compression, and the radar image can be obtained through range migration correction, azimuth compression and other processes. The expression of the point target signal (echo signal) can be written as: s0(τ,η)=A0sinc[B r (τ-2R0 / c)]sinc[B d (η-y / v a )].

[0109] Among them, B d is the Doppler bandwidth, B r Indicates the transmit signal bandwidth.

[0110] 3) Establish a mathematical model to correct the echo data: Considering the changes in scattering characteristics and echo delay caused by the change in the wave position angle, the echo data is corrected by establishing a mathematical model to eliminate the imaging error caused by the change in the wave position. According to the platform trajectory and the relative motion data of the satellite and the ground, the distance R0 between the radar and the ground target can be obtained. Substituting R0 into the formula s0(τ,η)=A0sinc[B r (τ-2R0 / c)]sinc[B d (η-y / v a )], and obtain the corrected echo signal. The principle of ionospheric loss modeling is as follows:

[0111] For the total electron volume TEC, in reality it is the ionosphere on the path from the satellite to the receiver, also known as the slant delay. The projection function can be used to convert the slant delay into the vertical ionospheric delay in the zenith direction:

[0112] TEC=VTEC·F(Z).

[0113] The projection function F(Z) is defined as:

[0114] Among them, Z represents the satellite zenith distance, R represents the radius of the earth, and H represents the height of the single-layer model.

[0115] The total amount of electrons at oblique incidence can be deduced from the total amount of electrons at vertical incidence VTEC: TEC = VTEC·F(e),

[0116] Among them, α represents the empirical coefficient.

[0117] The calculation formula of Faraday electromagnetic rotation is: H i is the ionosphere thickness, N Te is the total electron content, Ω represents the Faraday electromagnetic rotation, C0 represents the Faraday constant, f represents the incident wave frequency, and f H represents the magnetic rotation frequency, θ b represents the angle between the geomagnetic field and the incident wave direction, N e represents the total electron content, and h represents the thickness of the ionosphere.

[0118] Under normal propagation conditions, N Te =10 16 Electronic / m 2 , f = 500MHz, cos Z = 1, Ω = 6 × 10 -2 rad, so the inverse Faraday rotation can be written as:

[0119]

[0120] Take the operating frequency as 1.25GHz, NTe =10 17 Electronic / m 2 , the incident angle is 26.1° to 54.1°, and the Faraday rotation angle is derived to change with the incident angle e. Considering that the pitch angle of the aircraft is about 5°, the polarization loss can be calculated to change with the incident angle.

[0121] In an exemplary embodiment, step 105 specifically includes: modeling and predicting the scattering characteristics of the target (ground object) in different scenes, and calculating the scattering characteristics based on the physical optics method, as follows:

[0122]

[0123] Among them, Z0 represents the wave impedance, r represents the distance from the far field, represents the position vector of the incident wave, is the unit vector representing the scattering direction, represents the scattered electric field, S′ represents the surface area of ​​the illuminated area, represents the normal vector of the patch, represents the incident magnetic field, represents the incident electric field, i represents the imaginary unit, k represents the free space wave number of the electromagnetic wave, Represents the electromagnetic wave unit vector. According to the definition of scattering characteristics, the following formula can be obtained:

[0124]

[0125] Among them, σ (dBsm) represents the radar cross-section, dBsm represents the unit of the radar cross-section, and the scattering characteristics directly affect the size of the radar cross-section.

[0126] Let E0 represent the amplitude of the incident field, then define the incident field as:

[0127] Since electromagnetic and electric field polarizations have different characteristics, they need to be decomposed during the solution process, which requires the processing of approximate tangent planes. Since different polarizations have different characteristics, the reflection and transmission of electromagnetic waves have different transmission coefficients. Therefore, electromagnetic waves cannot be simply processed at the boundary, and the physical characteristics of the boundary itself need to be considered. This requires the electromagnetic field to be decomposed according to horizontal polarization and vertical polarization, and the polarization variables are defined:

[0128] In the formula is the unit vector of the incident direction, is the unit normal vector to the incident direction, so and The two are perpendicular to each other, and The same plane where the vectors are located is defined as the incident plane. The component of the electric field in the incident plane is called horizontal polarization. If it is perpendicular to the incident plane, it is called vertical polarization.

[0129] According to Maxwell's boundary conditions, the Fresnel reflection coefficient formula can be obtained. By setting the Fresnel coefficient, calculations for different types of objects can be achieved. The Fresnel coefficient calculation formula is as follows:

[0130]

[0131] in ε1 and ε2 refer to the dielectric constants of the upper and lower dielectric layers, respectively. i Represents the incident angle of electromagnetic wave, R TM represents the TM wave Fresnel coefficient, R TE TE wave Fresnel coefficient.

[0132] In an exemplary embodiment, step 106 specifically includes:

[0133] Based on the radar equation, the relationship between MGC and scattering characteristics can be obtained:

[0134]

[0135] After sorting out, the relationship between the expression of MGC and other parameters can be obtained as follows. The other parameters in the formula can be obtained from the above process:

[0136] Among them, σ 0 r a r y =σ(dBsm), MGC is the load manual gain control parameter, G cg represents the channel gain, λ represents the wavelength, σ 0 represents the backscattering coefficient, P n represents the sum of internal and external losses of the radar system, P t Indicates the transmitter power, G 2 represents the dual-path antenna gain, θ represents the incident angle in the direction of the antenna aperture, R represents the distance between the radar and the ground target, φ represents the azimuth of the antenna, C represents the empirical constant, and K L Indicates the temperature influence coefficient, P t represents the radar transmitter power, r a represents the azimuth resolution, r y Indicates the range resolution.

[0137] The Fresnel coefficients of different scenes are different, so σ 0 Different. R needs to be calculated using motion data and radar position parameters.

[0138] The relational database includes a ground object geometric model table, a ground object physical parameter table, a scattering characteristic table, a platform trajectory table, a satellite-ground relative motion table and a manual gain control data table.

[0139] The feature geometry model table is used to store the feature geometry module data. The fields of the feature geometry model table include feature ID (uniquely identifying each feature geometry model), scene (such as mountains, farmland, etc.), geometry model file path (the location where the feature geometry model file is stored, the file format can be STL format or Shapefile format, etc.) and creation time (recording the timestamp of model creation); the primary key of the feature geometry model table is the feature ID to ensure the uniqueness of each feature geometry model.

[0140] The geometric model data is stored in a three-dimensional model file format or a geographic information system data format to intuitively present the shape and spatial distribution of the features.

[0141] The terrain physical parameter table is used to store the terrain physical parameters. The fields of the terrain physical parameter table include the terrain ID (associated with the terrain ID in the terrain geometric model table to establish a relationship between the two), the physical parameter name (such as soil type, vegetation coverage, etc.), the parameter value (storing the specific physical parameter value) and the measurement time (recording the time of parameter measurement). The primary key of the terrain physical parameter table is a combination of the terrain ID and the physical parameter name to ensure the uniqueness of each physical parameter of each terrain.

[0142] Physical parameters and scattering characteristics data are stored in tabular form, such as CSV files or database table fields, to facilitate data query, analysis and processing.

[0143] The scattering characteristic table is used to store the scattering characteristics of the ground objects; the fields of the scattering characteristic table include the ground object ID (the ground object ID in the associated ground object geometric model table and the ground object physical parameter table), the electromagnetic wave frequency, the scattering center position (the position information of the scattering center is stored in the form of coordinates), the scattering intensity (the scattering intensity value is recorded), the measurement conditions (the environmental conditions and radar parameter settings when measuring the scattering characteristics are described) and the measurement time, the measurement conditions include the environmental conditions and the radar parameters, and the primary key of the scattering characteristic table is the combination of the ground object ID, the electromagnetic wave frequency and the measurement time, so as to accurately distinguish the scattering characteristic data under different conditions.

[0144] The platform trajectory table is used to store the high-orbit SAR satellite trajectory; the fields of the platform trajectory table include platform trajectory ID (uniquely identifying the platform trajectory record), timestamp (recording the position information of the platform at that moment), position coordinates (storing the position of the platform in the form of three-dimensional coordinates), speed (platform movement speed), acceleration (platform acceleration) and orbital parameter ID (associated with the orbital parameter information in the orbital parameter table). The primary key of the platform trajectory table is the platform trajectory ID, and the foreign key is the orbital parameter ID, which is associated with the orbital parameter table.

[0145] The satellite-to-ground relative motion table is used to store the satellite-to-ground relative position, speed and acceleration; the fields of the satellite-to-ground relative motion table include relative motion ID (uniquely identifying the satellite-to-ground relative motion record), timestamp, satellite-to-ground relative distance, relative speed (relative motion speed between satellite and ground), relative acceleration (relative acceleration between satellite and ground), object ID and platform trajectory ID (associated with the platform trajectory information in the platform trajectory table), the primary key of the satellite-to-ground relative motion table is the relative motion ID, and the foreign keys are the object ID and the platform trajectory ID; the satellite-to-ground relative distance is the distance between the high-orbit SAR satellite and the ground target on the earth.

[0146] The manual gain control data table is used to store data related to gain control. The fields of the manual gain control data table include manual gain control parameter ID, ground object ID, electromagnetic wave frequency, manual gain control parameter value (storing MGC value related to gain control), calibration time (recording the time of MGC value calibration), the primary key is manual gain control parameter ID, the foreign keys are ground object ID and electromagnetic wave frequency, and an association relationship is established with other tables so as to quickly obtain corresponding MGC data according to scattering characteristics.

[0147] The MGC data is stored in association with the scattering characteristic data. By establishing a data association relationship, the corresponding MGC data can be quickly obtained according to the scattering characteristics, thereby improving data management efficiency.

[0148] The geometric model file corresponding to the geometric model file path is in a three-dimensional model file format or a geographic information system data format.

[0149] The relational database also includes an echo data table, an imaging wave position change table and an ionosphere change table.

[0150] The echo data table is used to store the radar echo data. The fields of the echo data table include echo ID (uniquely identifying each echo data record), object ID, timestamp, echo intensity (storing the intensity value of the echo signal), echo phase (recording the phase information of the echo signal), radar parameter ID (associated with the radar parameter information in the radar parameter table), the primary key is the echo ID, the foreign keys are the object ID and the radar parameter ID, and an association relationship is established with other tables.

[0151] The echo data is stored in binary file format to efficiently save large amounts of echo signal data.

[0152] The imaging wave position change table is used to store imaging wave position change data. The fields of the imaging wave position change table include wave position change ID (uniquely identifies imaging wave position change record), timestamp, azimuth (records azimuth change of radar beam), pitch angle (records pitch angle change of radar beam), radar parameter ID (associated with radar parameter information in radar parameter table). The primary key is wave position change ID, and the foreign key is radar parameter ID, which is associated with radar parameter table.

[0153] The ionosphere change table is used for ionosphere parameter change data. The fields of the ionosphere change table include ionosphere change ID (uniquely identifies ionosphere change records), timestamp, electron density (records changes in electron density of the ionosphere), ionosphere altitude (records changes in altitude of the ionosphere), and detection device ID (associated detection device related information, if there are multiple detection devices). The primary key is the ionosphere change ID, and the foreign key is the detection device ID.

[0154] The platform trajectory, satellite-ground relative motion, imaging wave position change and ionosphere change data are stored in time series data format, such as HDF5 files, to facilitate the analysis of data change trends in chronological order.

[0155] The database management method of this application can quickly retrieve the required control parameters in complex radar load operation scenarios to achieve the function of timely radar regulation. For time-varying data types, such as changes in forest coverage and sea surface wind speed, the database management of this application can quickly update data to adapt to time-varying landforms.

[0156] Based on the same inventive concept, the embodiment of the present application also provides a gain control parameter management device for a high-orbit SAR for implementing the gain control parameter management method for a high-orbit SAR involved above. The implementation scheme for solving the problem provided by the device is similar to the implementation scheme recorded in the above method, so the specific limitations in the embodiments of the gain control parameter management device for one or more high-orbit SARs provided below can refer to the limitations of the gain control parameter management method for the high-orbit SAR above, and will not be repeated here.

[0157] In an exemplary embodiment, the present application provides a gain control parameter management device for a high-orbit SAR, including:

[0158] The geographic grid division module is used to divide a preset geographic space area into multiple geographic grids.

[0159] The scene data acquisition module is used to acquire scene data corresponding to the scenes in each of the geographic grids, wherein the scene data includes geometric model data and physical parameters of each feature.

[0160] The high-orbit SAR satellite trajectory and satellite-to-ground relative position data acquisition module is used to collect the high-orbit SAR satellite trajectory and satellite-to-ground relative position.

[0161] The radar position parameter acquisition module is used to acquire the radar position parameters of each of the above-mentioned objects.

[0162] The scattering characteristic calculation module is used to calculate the scattering characteristic of each of the ground objects according to the scene data.

[0163] The manual gain control data determination module is used to establish a corresponding relationship between the radar load manual gain control parameters and the scattering characteristics of each of the ground objects to obtain manual gain control data.

[0164] The storage module uses a relational database to store ground object geometry module data, ground object physical parameters, ground object scattering characteristics, high-orbit SAR satellite trajectory, satellite-ground relative motion and manual gain control data; the relational database is used for high-orbit SAR to image various objects.

[0165] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0166] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A method for managing gain control parameters of a high-orbit SAR, characterized in that: The gain control parameter management method of the high-orbit SAR includes: Divide the preset geospatial area into a plurality of geographic grids; Collecting scene data corresponding to scenes in each of the geographic grids, the scene data including geometric model data and physical parameters of each feature; Collect high-orbit SAR satellite trajectories and the relative positions of satellites and the ground; Collecting radar position parameters of each of the ground objects; Calculating the scattering characteristics of each of the ground objects according to the scene data; Establishing a corresponding relationship between the radar payload manual gain control parameter and the scattering characteristics of each of the ground objects to obtain manual gain control data; A relational database is used to store ground feature geometry module data, ground feature physical parameters, ground feature scattering characteristics, high-orbit SAR satellite trajectory, satellite-ground relative motion and manual gain control data; the relational database is used for high-orbit SAR to image various features.

2. The gain control parameter management method of high-orbit SAR according to claim 1, characterized in that: Collecting radar position parameters of each of the above-mentioned objects specifically includes: Determine imaging wave position change data using radar system monitoring data of the radar; Use ionospheric detection equipment to collect ionospheric parameter change data; Radar echo data of various objects are collected, and radar position parameters are determined according to the radar echo data.

3. The gain control parameter management method for high-orbit SAR according to claim 2, characterized in that: The relational database is used to store imaging wave position change data, ionospheric parameter change data and radar echo data.

4. The gain control parameter management method for high-orbit SAR according to claim 1, characterized in that: Establishing a corresponding relationship between the radar payload manual gain control parameter and the scattering characteristics of each of the ground objects to obtain manual gain control data, specifically including: According to the formula Obtaining the corresponding relationship between the radar payload manual gain control parameter and the scattering characteristics of each of the ground objects; Among them, MGC is the load manual gain control parameter, G cg represents the channel gain, λ represents the wavelength, σ 0 represents the backscattering coefficient, P n represents the sum of internal and external losses of the radar system, P t Indicates the transmitter power, G 2 represents the dual-path antenna gain, θ represents the incident angle in the direction of the antenna aperture, R represents the distance between the radar and the ground target, φ represents the azimuth of the antenna, C represents the empirical constant, and K L Indicates the temperature influence coefficient, P t represents the radar transmitter power, r a represents the azimuth resolution, r y Indicates the range resolution.

5. The gain control parameter management method for high-orbit SAR according to claim 1, characterized in that: The types of scenes include mountain scenes, farmland scenes, urban scenes, forest scenes, sea-land boundary areas, island scenes and sea scenes; The physical parameters of the mountain scene include soil type and soil roughness; The physical parameters of the farmland scene include crop type, crop growth stage, vegetation coverage and soil moisture; The physical parameters of the urban scene include building height, building density and building material properties; The physical parameters of the forest scene include tree height, tree diameter, tree density and vegetation coverage; The physical parameters of the land-sea interface area include sea depth, wave height and beach type; The physical parameters of the island scene include island outline, altitude and rock type; The physical parameters of the sea surface scene include sea water temperature, sea water salinity, sea wave height and sea wave period.

6. The gain control parameter management method for high-orbit SAR according to claim 3, characterized in that: The relational database includes a ground object geometric model table, a ground object physical parameter table, a scattering characteristic table, a platform trajectory table, a satellite-ground relative motion table and a manual gain control data table; The object geometry model table is used to store the object geometry module data, and the fields of the object geometry model table include object ID, scene, geometry model file path and creation time; The primary key of the feature geometry model table is the feature ID; The ground object physical parameter table is used to store the ground object physical parameters, the fields of the ground object physical parameter table include ground object ID, physical parameter name, parameter value and measurement time, and the primary key of the ground object physical parameter table is a combination of ground object ID and physical parameter name; The scattering characteristic table is used to store ground object scattering characteristics; The fields of the scattering characteristics table include object ID, electromagnetic wave frequency, scattering center position, scattering intensity, measurement conditions and measurement time, the measurement conditions include environmental conditions and radar parameters, and the primary key of the scattering characteristics table is a combination of object ID, electromagnetic wave frequency and measurement time; The platform trajectory table is used to store high-orbit SAR satellite trajectories; the fields of the platform trajectory table include platform trajectory ID, timestamp, position coordinates, speed, acceleration and orbit parameter ID, the primary key of the platform trajectory table is the platform trajectory ID, and the foreign key is the orbit parameter ID; The satellite-to-ground relative motion table is used to store the satellite-to-ground relative position, velocity and acceleration; the fields of the satellite-to-ground relative motion table include relative motion ID, timestamp, satellite-to-ground relative distance, relative velocity, relative acceleration, object ID and platform trajectory ID; the primary key of the satellite-to-ground relative motion table is the relative motion ID, and the foreign keys are the object ID and platform trajectory ID; the satellite-to-ground relative distance is the distance between the high-orbit SAR satellite and the ground target on the earth; The manual gain control data table is used to store data related to gain control. The fields of the manual gain control data table include manual gain control parameter ID, ground object ID, electromagnetic wave frequency, manual gain control parameter value, and calibration time. The primary key is the manual gain control parameter ID, and the foreign keys are the ground object ID and the electromagnetic wave frequency.

7. The gain control parameter management method for high-orbit SAR according to claim 6, characterized in that: The geometric model file corresponding to the geometric model file path is in a three-dimensional model file format or a geographic information system data format.

8. The gain control parameter management method for high-orbit SAR according to claim 6, characterized in that: The relational database also includes an echo data table, an imaging wave position change table and an ionosphere change table; The echo data table is used to store the radar echo data. The fields of the echo data table include echo ID, object ID, timestamp, echo intensity, echo phase, radar parameter ID, the primary key is echo ID, and the foreign keys are object ID and radar parameter ID; The imaging wave position change table is used to store imaging wave position change data. The fields of the imaging wave position change table include wave position change ID, timestamp, azimuth, pitch angle and radar parameter ID. The primary key is the wave position change ID and the foreign key is the radar parameter ID. The ionospheric change table is used for ionospheric parameter change data. The fields of the ionospheric change table include ionospheric change ID, timestamp, ionospheric electron density, ionospheric height, and detection device ID. The primary key is the ionospheric change ID, and the foreign key is the detection device ID.

9. The gain control parameter management method for high-orbit SAR according to claim 1, characterized in that: Divide the preset geographic space area into multiple geographic grids, including: The preset geographic space area is divided into multiple geographic grids according to longitude and latitude.

10. A gain control parameter management device for a high-orbit SAR, characterized in that: The gain control parameter management device of the high-orbit SAR comprises: A geographic grid division module, used for dividing a preset geographic space area into a plurality of geographic grids; A scene data acquisition module, used to acquire scene data corresponding to scenes in each of the geographic grids, wherein the scene data includes geometric model data and physical parameters of each feature; High-orbit SAR satellite trajectory and satellite-to-ground relative position data acquisition module, used to collect high-orbit SAR satellite trajectory and satellite-to-ground relative position; A radar position parameter acquisition module, used to acquire radar position parameters of each of the above-mentioned objects; A scattering characteristic calculation module, used to calculate the scattering characteristic of each of the ground objects according to the scene data; A manual gain control data determination module is used to establish a corresponding relationship between the radar load manual gain control parameters and the scattering characteristics of each of the ground objects to obtain manual gain control data; The storage module uses a relational database to store ground feature geometry module data, ground feature physical parameters, ground feature scattering characteristics, high-orbit SAR satellite trajectories, satellite-ground relative motion, and manual gain control data; The relational database is used for high-orbit SAR to image various objects.

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