A method for constructing interior scenes of ship targets

Abstract

The present invention discloses a method for constructing an interior scene of a ship target, which relates to the technical field of electromagnetic scene simulation and solves the technical problems in the prior art of distortion of echo characteristics and poor fidelity of target polarization characteristics simulation in interior electromagnetic scenes. The method comprises: selecting a target scattering characteristic model from an omnidirectional ship target characteristic library according to the scene setting requirements of the interior scene; generating a radar simulated target echo in the interior scene according to the scene setting requirements and the retrieved target scattering characteristic model of each simulated target; superimposing background noise data on the generated radar simulated target echo to obtain a radar simulated echo signal in the interior scene, thereby completing the construction of the interior scene. The method fully combines a pre-constructed omnidirectional ship target characteristic library with the scene and parameters of the interior electromagnetic scene to realize the simulation of coherent system radar echoes. The simulated scene echo characteristics after coherent accumulation have high fidelity.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic scene simulation, and in particular to a method for constructing an interior scene of a ship target. Background Art

[0002] Currently, the use of indoor simulated interference to counter electromagnetic scenarios is a future development direction. Indoor electromagnetic scenario simulation allows for interaction between radar and signal sources within an anechoic chamber, simulating the echoes of targets and false targets detected by the radar, enabling testing of radar hardware and software. Indoor electromagnetic scenarios require realistic simulation of the polarization and range profile characteristics of the indoor electromagnetic scene.

[0003] Existing methods for simulating internal electromagnetic scenes mainly simulate point targets detected by radar through signal sources, or simulate echoes of scene targets with one-dimensional range profile characteristics by modulating the target electromagnetic model. However, for the simulation of false target countermeasures, these methods have the following shortcomings:

[0004] 1) It can only simulate single-pulse non-coherent radar echoes, but lacks the ability to simulate coherent radar echoes. The echo characteristics of the simulated scene after coherent accumulation are distorted.

[0005] 2) When simulating the full-polarization signal echo in the indoor field, there is a problem of poor simulation fidelity of the target polarization characteristics, which cannot meet the requirements of verifying the target and false target identification algorithm based on polarization information. Summary of the Invention

[0006] In view of the above analysis, an embodiment of the present invention aims to provide a method for constructing an interior field scene of a ship target, which can solve the technical problems in the prior art of echo characteristic distortion in simulation of interior field electromagnetic scenes and poor fidelity in simulation of target polarization characteristics.

[0007] The present invention discloses a method for constructing an interior scene of a ship target, comprising:

[0008] According to the scene setting requirements of the indoor scene, the target scattering characteristic model is selected from the omnidirectional ship target characteristic library;

[0009] In the indoor scene, according to the scene setting requirements and the target scattering characteristic model of each simulated target, the radar simulated target echo is generated;

[0010] The background noise data is superimposed on the generated radar simulated target echo to obtain the radar simulated echo signal in the interior scene, thus completing the construction of the interior scene.

[0011] On the basis of the above solution, the present invention also makes the following improvements:

[0012] Furthermore, the ship target characteristic library includes the ship type, radar equipment parameters, target parameters and corresponding target scattering characteristic models of the ship target; wherein,

[0013] The target scattering characteristic model is composed of the range image positions, scattering point phases and scattering point amplitudes of several stable scattering points on four polarization channels: HH, HV, VH and VV.

[0014] Furthermore, the scene setting requirements include:

[0015] The target type of the simulation target, which can be one or more;

[0016] Radar equipment parameters, including radar band and polarization state;

[0017] Scenario environment parameters, including sea conditions, radar equipment altitude, and radar-target distance.

[0018] Furthermore, the radar simulated target echo is generated by performing the following operations:

[0019] Generate radar transmission signals according to radar equipment parameters in the scenario setting requirements;

[0020] Based on the target scattering characteristic model of each simulated target and the radar transmission signal, a radar simulated target echo of the corresponding simulated target is obtained;

[0021] If the scene setting requirements only include one simulated target, the radar simulated target echo of the simulated target is used as the radar simulated target echo in the indoor field scene; otherwise, the radar simulated target echoes of all simulated targets are superimposed with electromagnetic waves to obtain the radar simulated target echo in the indoor field scene.

[0022] Further, the radar simulated target echo of the simulated target is obtained by performing the following operations:

[0023] Obtaining one-dimensional range image data of the simulated target in each polarization channel according to the retrieved target scattering characteristic model of the simulated target;

[0024] According to the radar-target distance in the scenario setting requirements, the one-dimensional range image data of each polarization channel is superimposed to the corresponding position of the radar-target distance to form the range image target scattering point set of the simulated target;

[0025] The target characteristic of the range image target scattering point set of the simulated target is modulated by using the radar transmission signal to generate the radar simulated target echo of the simulated target.

[0026] Further, selecting a target scattering characteristic model from the target characteristic library includes:

[0027] Based on the scene environment parameters of the simulation target, obtaining the target parameters of the simulation target;

[0028] According to the target type, radar band and target parameters of each simulated target, the target scattering characteristic model matching each simulated target is retrieved from the target characteristic library.

[0029] Furthermore, the omnidirectional ship target characteristic library is constructed in the following manner:

[0030] Conduct omnidirectional data acquisition tests at different incident angles on ship targets in the field to obtain measured high-speed echo data;

[0031] Based on the normalized basis function, the target characteristics of the target area in the range-Doppler data corresponding to each frame of measured high-speed echo data are extracted to obtain the corresponding target characteristic range-Doppler data;

[0032] At each grazing angle, based on the target characteristic range-Doppler data component of each frame of target characteristic range-Doppler data in the main polarization channel, the omnidirectional stable scattering point sequence of the main polarization channel at the corresponding grazing angle is obtained;

[0033] Mapping the omnidirectional stable scattering point sequence of the main polarization channel at each grazing angle to other polarization channels, and obtaining the omnidirectional stable scattering point sequence of other polarization channels at the corresponding grazing angle;

[0034] The omnidirectional stable scattering point sequences of each polarization channel under different grazing angles are modeled respectively to construct an omnidirectional ship target characteristic library.

[0035] Furthermore, the omnidirectional stable scattering point sequence of the main polarization channel under the corresponding grazing angle is obtained, including:

[0036] Perform decoherence processing on the target characteristic range-Doppler data components of each frame of the main polarization channel, and take the prt with the largest amplitude as the one-dimensional range image of the frame under the main polarization channel;

[0037] Determine, based on the one-dimensional range image of each frame in the main polarization channel and its corresponding sideways angle, a one-dimensional range image sequence of a vertical sideways frame interval in the main polarization channel and a one-dimensional range image sequence of a non-vertical sideways frame interval;

[0038] Target characteristics are correlated for the one-dimensional range images of each frame in the non-perpendicular sideways frame interval to obtain a stable scattering point sequence in the non-perpendicular sideways frame interval under the main polarization channel;

[0039] Based on the stable scattering point sequence in the non-vertical sideways frame interval under the main polarization channel, a stable scattering point sequence in the vertical sideways frame interval under the main polarization channel is obtained;

[0040] The stable scattering point sequences in the non-vertical and vertical sideways frame intervals under the main polarization channel are sorted according to the frame sequence number to obtain the omnidirectional stable scattering point sequence of the main polarization channel under the corresponding grazing angle of incidence.

[0041] Furthermore, a stable scattering point sequence in the non-vertical sideways frame interval under the main polarization channel is obtained, including:

[0042] According to the preset number of associated segment frames, the temporally adjacent one-dimensional range images in the non-vertical side frame interval are segmented, and the one-dimensional range images of each frame in the segment are sequentially spliced ​​according to the frame sequence number to obtain a plurality of segment data;

[0043] Preprocess each fragment data to obtain corresponding stable scattering point fragment data;

[0044] Perform range image principal component analysis and cluster analysis on each stable scattering point segment data, and output the stable scattering point sequence and cluster center associated between frames in the corresponding segment;

[0045] According to the stable scattering point sequence and cluster center of the inter-frame correlation in each segment, the inter-segment correlation is performed to obtain the stable scattering point sequence in the non-vertical side frame interval under the main polarization channel.

[0046] Furthermore, the target parameters include incident grazing angle, broadside angle and radial velocity; an omnidirectional ship target characteristic library is constructed by the following method:

[0047] The omnidirectional scattering point modeling is performed on the omnidirectional stable scattering point sequence of each polarization channel under different grazing angles, and the omnidirectional scattering point model of the ship under multi-polarization channels is obtained.

[0048] According to the structure of the omnidirectional ship target characteristic library, the data in the ship omnidirectional scattering point model under multi-polarization channel are reorganized to construct the omnidirectional ship target characteristic library.

[0049] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0050] The method for constructing an interior scene of a ship target provided by the present invention has the following advantages:

[0051] 1. This method fully combines the pre-built omnidirectional ship target characteristic library with the scenes and parameters of the internal field electromagnetic scene to realize the simulation of the coherent system radar echo. The echo characteristics of the simulated scene after coherent accumulation are highly realistic.

[0052] 2. The target polarization characteristics of the signal echoes in various polarization states simulated in the indoor field are simulated with high fidelity, which can reliably meet the needs of verifying the target recognition algorithm based on polarization information.

[0053] 3. Compared with the existing technology, the indoor scene construction method provided by the present invention is more reliable. The echo characteristics when simulating the ship target scene in the indoor field are consistent with the characteristics of the outdoor field acquisition data. The range image and Doppler dimension characteristics are highly realistic, which can meet the requirements of the high-resolution radar recognition performance test environment.

[0054] 4. Through the omnidirectional ship target characteristic library construction method provided in the present invention, the omnidirectional scattering point data of the ship target can be obtained, which greatly facilitates the selection of the target scattering characteristic model during the interior field construction and effectively expands the application scenarios of the interior field scene construction.

[0055] In the present invention, the above-mentioned technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of the present invention will be described in the following description, and some advantages will become apparent from the description or be learned through practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The accompanying drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like parts throughout the drawings.

[0057] Figure 1 Flowchart of the method for constructing interior scene of ship target;

[0058] Figure 2 This is a flow chart of the method for constructing an omnidirectional ship target characteristic library;

[0059] Figure 3 Schematic diagram of the correspondence between the range image position of the kth stable scattering point and the range image position of the center of mass of the ship target in the current frame when the broadside angle is 0° in the example;

[0060] Figure 4 Schematic diagram of the correspondence between the range image position of the kth stable scattering point and the range image position of the center of mass of the ship target in the current frame when the broadside angle is 45° in the example;

[0061] Figure 5 Schematic diagram of the method for obtaining the radial velocity of the stable scattering point in the beam direction in the example.

[0062] Figure 6 Schematic diagram of the ship's omnidirectional scattering point model structure. DETAILED DESCRIPTION

[0063] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, and are not used to limit the scope of the present invention.

[0064] Example 1

[0065] A specific embodiment 1 of the present invention discloses a method for constructing an interior scene of a ship target, the flow chart of which is as follows: Figure 1 As shown, the method for constructing the interior scene includes:

[0066] Step S1: According to the scene setting requirements of the indoor scene, a target scattering characteristic model is selected from the omnidirectional ship target characteristic library;

[0067] In this embodiment, based on the customary representation method in the scene test, the scene setting requirements for the indoor scene are set; preferably, the scene setting requirements include:

[0068] (1) Target type of simulated target

[0069] The simulation target is one or more;

[0070] (2) Radar equipment parameters

[0071] Radar equipment parameters in the indoor field scenario include radar band and polarization state. It should be noted that, since the corresponding data in the horizontal and vertical polarization directions can be obtained based on the target scattering characteristic model under the full polarization state, and at the same time, the test conditions of the outdoor test scenario can be effectively utilized, when constructing the omnidirectional ship target characteristic library, the polarization state of the radar should be set to full polarization. In the indoor field scenario, the polarization state of the radar can be limited according to the scenario setting requirements, such as horizontal polarization, vertical polarization or full polarization.

[0072] (3) Scene environment parameters

[0073] The scene environment parameters of ship-type targets include sea conditions, altitude of radar equipment, radar-target distance, heading and speed.

[0074] Step S11: acquiring target parameters of the simulation target based on the scene environment parameters of the simulation target;

[0075] The target parameters are the same as those in the omnidirectional ship target characteristic library, including incident grazing angle, broadside angle and radial velocity;

[0076] (1) Grazing angle

[0077] Based on the radar altitude and radar-target distance in the scene environment parameters of the simulated target, the corresponding incidence angle is determined; specifically, the incidence angle refers to the angle between the beam direction and the horizontal plane of the target position. The incidence angle can be calculated using the formula Calculate and obtain, where A target 、A radar 、Dr,t Represents the target's altitude, radar's altitude, and radar-target distance, respectively. In actual application, the default altitude of the ship target is 0.

[0078] (2) Sideways angle

[0079] The side angle is calculated by taking the port side as negative and the starboard side as positive, based on the direction of the radar pointing directly at the target and the heading of the ship.

[0080] (3) Radial velocity

[0081] The radial velocity is obtained by calculating the ship's heading and speed.

[0082] Step S12: According to the target type, radar band and target parameters of each simulated target, a target scattering characteristic model matching each simulated target is retrieved from the target characteristic library.

[0083] In this embodiment, the ship target characteristic library includes the ship type, radar equipment parameters, target parameters of the ship target and the target scattering characteristic models corresponding to different combinations of ship types, radar equipment parameters and target parameters; wherein, the target scattering characteristic model is composed of the range image position, scattering point phase and scattering point amplitude of several stable scattering points on the four polarization channels of HH, HV, VH and VV.

[0084] It should be noted that the matching in step S12 refers to:

[0085] A target data is searched in the target characteristic library for a target type and radar band consistent with the simulated target, and target parameters that meet the preset threshold deviation requirements, and the target scattering characteristic model in the target data is used as the target scattering characteristic model of the simulated target.

[0086] Preferably, the target parameters satisfy the preset threshold deviation requirement, which means that each parameter in the target parameters of the simulated target is compared with the corresponding parameter in the target characteristic library, and each parameter should satisfy the threshold deviation of the parameter.

[0087] Step S2: In the indoor scene, according to the scene setting requirements and the target scattering characteristic model of each simulated target, generate a radar simulated target echo;

[0088] Step S21: Generate a radar transmission signal according to the radar device parameters in the scene setting requirements;

[0089] Specifically, the band to which the radar transmit signal belongs is determined according to the radar band in the radar equipment parameters; the polarization wave of the radar transmit signal is determined according to the polarization state in the radar equipment parameters; illustratively, if the polarization state is horizontal polarization, the radar transmit signal is a horizontally polarized wave; if the polarization state is vertically polarized, the radar transmit signal is a vertically polarized wave; if the polarization state is full polarization, the radar transmit signal includes horizontally polarized waves and vertically polarized waves transmitted simultaneously.

[0090] Step S22: obtaining a radar simulated target echo of the corresponding simulated target based on the target scattering characteristic model of each simulated target and the radar transmission signal;

[0091] For each simulated target, obtain the radar simulated target echo of the simulated target by performing the following operations:

[0092] Step S221: obtaining one-dimensional range image data of the simulated target in each polarization channel according to the retrieved target scattering characteristic model of the simulated target;

[0093] It should be noted that based on the information in the target scattering characteristic model, the information of each stable scattering point in the one-dimensional range image can be directly restored. The remaining positions without stable scattering points in the one-dimensional range image are set to 0, thereby obtaining the one-dimensional range image data of the simulated target in each polarization channel;

[0094] Step S222: According to the radar-target distance in the scenario setting requirements, the one-dimensional range image data of each polarization channel is superimposed to the corresponding position of the radar-target distance to form a range image target scattering point set of the simulated target.

[0095] Step S223: using the radar transmission signal to perform target characteristic modulation on the range profile target scattering point set of the simulated target to generate a radar simulated target echo of the simulated target;

[0096] The formula for target characteristic echo modulation is expressed as:

[0097]

[0098]

[0099] Among them, S HH 、S HV 、S VH and S VV The range image target scattering point sets of the four polarization channels HH, HV, VH, and VV are respectively, H is the horizontally polarized wave emitted by the radar, st V is the vertically polarized wave emitted by the radar, rt H is the horizontal polarization simulated target echo obtained by modulation, rt VThe vertical polarization simulated target echo is obtained by modulation.

[0100] Step S23: If the scene setting requirement includes only one simulated target, the radar simulated target echo of the simulated target is used as the radar simulated target echo in the indoor scene;

[0101] Otherwise, the radar simulated target echoes of all simulated targets are superimposed with electromagnetic waves to obtain the radar simulated target echoes in the indoor scene.

[0102] After completing the target characteristic echo modulation, the echo generation of the multi-target scenario can be completed based on the target characteristics after echo modulation by utilizing the superposition of electromagnetic waves. Specifically, in this embodiment, utilizing the superposition of electromagnetic waves, assuming that each target within the radar beam illumination range is at a certain distance and there is no electromagnetic mutual coupling, a multi-target scenario such as a ship formation is generated by superposition of single target echoes. By selecting multiple targets and setting their spatial positions, a single target is first simulated separately, and then time-series echo superposition is performed based on the target distance. The echoes of multiple targets in the beam at the same time in the multi-target scenario can be expressed as follows:

[0103]

[0104] Among them, Rt H , Rt V They represent the horizontal polarization simulated target echo and vertical polarization simulated target echo in the indoor scene, rt H_l ,rt V_l They respectively represent the horizontally polarized simulated target echo and the vertically polarized simulated target echo of the lth simulated target in the scene setting requirements.

[0105] Step S3: Background noise data is superimposed on the generated radar simulated target echo to obtain the radar simulated echo signal in the interior scene, thereby completing the construction of the interior scene.

[0106] Furthermore, in the present invention, in order to realistically simulate the echo background noise, after generating the radar simulated target echo in the indoor scene, the background noise is superimposed on it, and the radar simulated echo signal in the indoor scene is obtained after superposition. The expression is as follows:

[0107] r H =Rt H +rn H

[0108] r V =Rt V +rn V

[0109] Among them, r H 、r VRespectively represent the horizontal polarization radar simulation echo signal and vertical polarization radar simulation echo signal in the indoor scene; H 、rn V Here, the background noise data that matches the sea condition can be selected based on the sea condition information in the scene setting requirements.

[0110] The indoor scene can be either an indoor darkroom or a digital simulation. The difference is that in the indoor darkroom scenario, the actual radar equipment needs to receive the radar analog echo signal through the antenna; in the digital simulation mode, the radar equipment samples the digital circuit form of simulation implementation, without the need for an antenna, and directly transmits the radar analog echo signal to the radar's signal processing module, so that the radar signal processing module can perform subsequent processing operations based on the radar analog echo signal and the radar transmission signal.

[0111] In summary, this embodiment provides a method for constructing an interior scene for a ship target. This method fully combines a pre-constructed omnidirectional ship target characteristic library with the scene and parameters of the interior electromagnetic scene to simulate coherent radar echoes. The echo characteristics of the simulated scene after coherent accumulation are highly realistic. At the same time, the target polarization characteristics are simulated with high fidelity in the signal echoes of various polarization states simulated in the interior field, which can reliably meet the requirements for verifying target recognition algorithms based on polarization information. Therefore, compared with the existing technology, the interior scene construction method provided by the present invention is more reliable. The echo characteristics when simulating the ship target scene in the interior field are consistent with the characteristics of the external field acquisition data, and the range image and Doppler dimension characteristics are highly realistic.

[0112] Example 2

[0113] To facilitate those skilled in the art to better implement the technical solutions in this application, this embodiment also provides a process for constructing an omnidirectional ship target characteristic library, which is described as follows:

[0114] The flow chart of the construction method of the omnidirectional ship target characteristic library is as follows: Figure 2 As shown, the following steps are included:

[0115] Step S1: conducting an omnidirectional data acquisition test on a ship target at different incident grazing angles in the field to obtain measured high-speed echo data;

[0116] In the field test scenarios constructed in this embodiment, each field test scenario contains only one ship target; at the same time, after the field test scenarios are constructed, the echo data in the field test scenarios are collected by radar as the corresponding field measured high-speed echo data. The incident angle refers to the angle between the beam direction and the horizontal plane of the target position. Since the characteristics of the ship target at different incident angles are different, it is necessary to conduct omnidirectional data collection tests on the ship target at different incident angles to obtain omnidirectional measured high-speed echo data at different incident angles. At the same time, since the omnidirectional scattering point characteristics of the ship target on each polarization channel are obtained based on the high-speed echo data in the full polarization state, it is also a test condition for effectively utilizing the field test scenarios. Therefore, in the field test scenario, the polarization state of the radar should be set to full polarization.

[0117] During the omnidirectional data acquisition test, the ship target rotates in a circle, so the entire time sequence of the measured high-speed echo data obtained corresponds to a 0-360° broadside angle.

[0118] Step S2: Based on the normalized basis function, target characteristics are extracted for the target area in the range-Doppler data corresponding to each frame of measured high-speed echo data to obtain corresponding target characteristic range-Doppler data;

[0119] In this step, the corresponding range-Doppler data is obtained by performing pulse compression and coherent accumulation processing on each frame of measured high-speed echo data;

[0120] Specifically, step S2 includes:

[0121] Step S21: Select a target area for each frame of range-Doppler data, and annotate the selected target area with target information;

[0122] Based on the mapping relationship between the field test scene and each frame of range-Doppler data, the target area can be framed out from each frame of range-Doppler data. After the target area is framed out, the target area can be annotated with target information. In this embodiment, the annotated target information includes: target attribute information, target location information, and target scene information;

[0123] Target attribute information includes target type and hull number / model; for example, target type includes warship and civilian ship, and hull number / model includes 835, etc.

[0124] The target location information refers to the range Doppler area where the target area is located;

[0125] Ship target parameter information includes: side angle, heading, speed and hull geometry (such as length, width and height);

[0126] Target scene information refers to the meteorological information of the field test scene, such as weather, sea conditions, wind speed, wind direction, ocean currents, ocean direction, etc.

[0127] Since in this embodiment, omnidirectional data collection is required for a ship target in an outdoor test scenario, each omnidirectional data collection test involves only one ship target. Accordingly, only one target area can be selected from the range-Doppler data.

[0128] In particular, if the outdoor scene also contains non-cooperative targets, the non-cooperative targets in the range-Doppler data are removed and replaced with background clutter;

[0129] Since non-cooperative targets (i.e., non-predetermined ship-like targets) inevitably appear in field measurement data, such as unknown small fishing boats and drilling platforms, they are marked as non-cooperative targets during data annotation. When extracting ship target characteristics, these non-cooperative targets need to be removed. Here, background clutter replacement is used to remove non-cooperative targets. Specifically, after the target area is selected and the target information is annotated, the range-Doppler range of the ship target and other non-cooperative targets is determined based on the annotated information of all targets in the current frame's range-Doppler data. The non-cooperative targets in the range-Doppler data are then removed and replaced with background clutter.

[0130] Step S22: Acquire all target scattering points in the range-Doppler data of the target area; specifically, including:

[0131] Step S221: obtaining the scattering point with the largest amplitude in the range-Doppler data of the target area;

[0132] Specifically, in step S221, when the process is executed for the first time, the range-Doppler data of the target area is determined based on the target position information of the marked target area. When the process is not executed for the first time, the range-Doppler data of the target area refers to the range-Doppler data of the target area updated in step S222.

[0133] Step S222: Determine whether the amplitude of the scattering point is greater than or equal to the clutter amplitude threshold.

[0134] If yes, the scattering point is extracted as a target scattering point, and the product of the maximum amplitude of the scattering point and the normalized basis function is used as the characteristic data of the target scattering point;

[0135] Update the total number of target scattering points and determine whether the total number of target scattering points is greater than or equal to the preset number of target scattering points.

[0136] If so, then end;

[0137] Otherwise, the target scattering point is removed from the range-Doppler data of the target area, and the range-Doppler data of the target area is updated, and the process jumps to step S221, i.e., the scattering point with the largest amplitude is searched again in the updated range-Doppler data of the target area;

[0138] Otherwise, end;

[0139] After step S22 is performed (ie, after the process ends), characteristic data of all target scattering points can be obtained.

[0140] In step S222, a corresponding clutter amplitude threshold is determined based on the clutter data in the current frame range-Doppler data and a preset clutter probability threshold. Specifically, the clutter amplitude threshold is determined in the following manner: the clutter amplitude threshold β is calculated from the cumulative probability distribution P of the clutter data Z in the current frame range-Doppler data. The relationship between the clutter probability threshold α and the clutter amplitude threshold β is expressed as α=P(Z≤β), that is, the clutter probability threshold α is the probability that the clutter Z is less than or equal to the clutter amplitude threshold β. Therefore, when the clutter probability threshold is predetermined, the clutter amplitude threshold can be determined based on the clutter data in the current frame range-Doppler data. α∈(0,1], the higher the limit on the number of extracted target scattering points, the higher the value of the corresponding clutter probability threshold. At the same time, the amplitude of the extracted scattering points must be greater than the clutter amplitude threshold at the α quantile.

[0141] It should be noted that the normalized basis function in step S222 is determined in the following manner:

[0142] During the omnidirectional test of the ship target in the field test scenario, the radar equipment parameters remain unchanged. Therefore, in this embodiment, the baseband transmission signal is determined according to the radar equipment parameters, and the corresponding basis function is obtained by convolving the baseband transmission signal with itself; the basis function is coherently accumulated and normalized to obtain the normalized basis function. Exemplarily, in this embodiment, the radar equipment parameters include information such as the radar working state, polarization mode, working frequency band, signal bandwidth and code type. Specifically, the baseband transmission signal st is convolved with itself to obtain the basis function set of each PRT in the current frame, where the basis function Base of the i-th PRT is recorded as i for:

[0143]

[0144] Where Window is the matched filter window function, i = 1, 2, ..., m, m is the number of pulse accumulation, and the current frame basis function set Base is as follows:

[0145] Base=fft([Base1; Base2; ...; Base m ]) (2)

[0146] By coherently accumulating and normalizing the basis function set, the normalized basis function NBase can be obtained.

[0147] In step S222, the characteristic data of the target scattering point is obtained based on the normalized basis function, and the process of removing the target scattering point from the range-Doppler data of the target area is described as follows:

[0148] The scattering points are extracted in descending order according to the amplitude of the target scattering points in the range-Doppler data. Assume that the amplitude of the j-th target scattering point in the target area is I j , the coordinates are (a, b), the normalized basis function NBase is matrix translated (the redundant and missing parts are spliced ​​end to end after the translation), the basis of the translation is to move the maximum amplitude point of the normalized basis function NBase to (a, b), and the moved basis function is recorded as NBase j , will I j *NBase j As the characteristic data of the jth target scattering point in the current target area, I is then filtered out from the target area. j *NBase j , in order to eliminate the target scattering point from the range-Doppler data of the target area.

[0149] Step S23: The characteristic data of all target scattering points are superimposed and normalized by radar-target centroid distance to obtain target characteristic distance-Doppler data of the current frame.

[0150] For example, the target characteristic range-Doppler data C of the rth frame r Expressed as:

[0151]

[0152] d r =rangegate+D r .fbl (4)

[0153] Among them, d s is the target feature normalized distance, d r represents the actual distance between the radar and the center of mass of the ship target corresponding to the range-Doppler data of the rth frame, rangegate represents the gate position, and D r Indicates the range image position of the center of mass of the ship target in the range-Doppler data of the rth frame, fbl represents the range resolution of the radar, and n is the total number of frames. rIt includes the data information of all target scattering points that constitute the target characteristics of the frame data. It is a two-dimensional RD complex matrix, which contains the distance, Doppler position and phase information of all target scattering points that constitute the target characteristics.

[0154] Step S3: At each grazing angle, based on the target characteristic range-Doppler data component of each frame of target characteristic range-Doppler data in the main polarization channel, obtaining an omnidirectional stable scattering point sequence of the main polarization channel at the corresponding grazing angle;

[0155] This embodiment involves four polarization channels: HH, HV, VH, and VV. In actual implementation, the polarization channel with the highest signal-to-noise ratio (SNR) of the target characteristic range-Doppler data is selected as the primary polarization channel. Because data from the same polarization channel has identical characteristics, to simplify implementation, the polarization channel with the highest SNR of the target characteristic range-Doppler data in the first frame can be directly selected as the primary polarization channel.

[0156] In this step, perform the following operations:

[0157] Step S31: performing decoherence processing on the target characteristic range-Doppler data components of each frame of the main polarization channel, and taking the prt with the largest amplitude (corresponding to a row in the decoherence data) as the one-dimensional range image of the frame in the main polarization channel;

[0158] Step S32: Determine, based on the one-dimensional range image of each frame in the main polarization channel and its corresponding sideways angle, a one-dimensional range image sequence of a vertical sideways frame interval and a one-dimensional range image sequence of a non-vertical sideways frame interval in the main polarization channel; wherein the non-vertical sideways frame interval refers to a frame interval in other sideways except the vertical sideways frame interval.

[0159] Since the radial size of the ship is the smallest in the vertical broadside frame interval (around plus or minus 90 degrees), the range images of the various target scattering points will overlap. Therefore, in the main polarization channel, the one-dimensional range images of the vertical broadside frame interval and the non-vertical broadside frame interval can be divided by judging whether the one-dimensional range images corresponding to each broadside angle overlap. At the same time, to solve this problem, this embodiment implements two different correlation technology solutions for the target characteristic range-Doppler data components in the non-vertical broadside frame interval and the vertical broadside frame interval respectively. Specifically,

[0160] Step S33: performing target characteristic correlation on the one-dimensional range images of each frame in the non-perpendicular sideways frame interval to obtain a stable scattering point sequence in the non-perpendicular sideways frame interval under the main polarization channel;

[0161] Step S331: dividing the temporally adjacent one-dimensional range images in the non-vertical side frame interval into segments according to a preset number of associated segment frames, and sequentially splicing the one-dimensional range images of each frame in the segment according to the frame sequence number to obtain a plurality of segment data;

[0162] Step S332: pre-process each segment data to obtain corresponding stable scattering point segment data;

[0163] Since the scattering point characteristics do not necessarily exist at all broadside angles, the extracted target characteristic range-Doppler data component contains several target scattering points with discontinuous and unstable time series. Therefore, it is necessary to preprocess each data segment, including outlier removal and missing value interpolation, to solve the problem of discontinuous and unstable time series of target scattering point data.

[0164] Outlier removal: Using the existing MAD algorithm, the target scattering point is judged as an outlier by determining whether the deviation between the range image of each target scattering point and the median value of the range images of all target scattering points is within a reasonable range. By executing this process, unstable target scattering points can be removed and the remaining target scattering points can be regarded as stable scattering points.

[0165] Missing value interpolation: Using the filling method of regression analysis, missing values ​​are calculated by fitting the regression mathematical model, that is, missing stable scattering points are filled.

[0166] After the preprocessing is completed, the stable scattering point segment data can be obtained. At this time, the intra-segment inter-frame correlation is performed first, and then the inter-segment correlation is performed to solve the problem that the omnidirectional data scattering points with large spans are difficult to distinguish, effectively reducing the correlation difficulty and improving the accuracy of the correlation results. Specifically,

[0167] Step S333: performing range image principal component analysis and cluster analysis on each stable scattering point segment data, and outputting the stable scattering point sequence and cluster centers associated between frames within the corresponding segment;

[0168] For each stable scattering point segment, first, principal component analysis (PCA) is performed on the range images of all stable scattering points within the segment to maximize their discrimination within the range image. Then, K-means clustering is performed on the range image using the PCA results, with the number of clustering categories equal to the number of stable scattering points. This results in a stable scattering point subsequence and its cluster center associated with each stable scattering point within the current segment. The stable scattering point subsequence records the stable scattering point information for each stable scattering point in each frame. This information includes: frame number, broadside angle, incident grazing angle, radial velocity, range image position, scattering point phase, and scattering point amplitude. The range image position, scattering point phase, and scattering point amplitude are obtained from the corresponding one-dimensional range image. The frame number refers to the frame data corresponding to the measured high-speed echo data collected in the field test scenario. The stable scattering point subsequences associated with each stable scattering point within the current segment are summarized to form a stable scattering point sequence associated with each stable scattering point within the corresponding segment.

[0169] Step S334: performing inter-segment correlation based on the inter-frame correlated stable scattering point sequences and cluster centers within each segment to obtain a stable scattering point sequence in the non-vertical sideways frame interval under the main polarization channel.

[0170] After all inter-frame correlations within each segment are completed, for adjacent stable scattering point segment data, the cluster centers of each stable scattering point segment data are predicted based on the ship's geometry and the stable scattering point positional relationships. Based on the distance relationship between the predicted cluster centers of each segment data and the cluster centers obtained by cluster analysis (step S333), the corresponding relationships between the same stable scattering point in each stable scattering point segment data are determined. Based on this corresponding relationship, inter-segment correlation is performed to obtain a stable scattering point sequence in the non-vertical sideways frame interval for the main polarization channel. Specifically, the inter-segment correlation method is as follows:

[0171] For the same target scattering point, the stable scattering point subsequences in different stable scattering point segments are spliced ​​according to the frame sequence number to form the stable scattering point sequence of the stable scattering point in the non-vertical sideways frame interval; the stable scattering point sequences of all stable scattering points in the non-vertical sideways frame interval are summarized to form the final stable scattering point sequence in the non-vertical sideways frame interval.

[0172] For the correlation of target characteristic data components in the vertical broadside frame interval, since the radial size of the ship is the smallest in the vertical broadside frame interval, the range images of each target scattering point overlap. Therefore, it is necessary to combine the frequency domain information to correlate the stable scattering points. The specific steps are as follows:

[0173] Step S34: Based on the stable scattering point sequence in the non-vertical sideways frame interval under the main polarization channel, obtain the stable scattering point sequence in the vertical sideways frame interval under the main polarization channel; specifically,

[0174] Step S341: Establish a geometric model of the hull scattering position based on the stable scattering point sequence in the non-vertical sideways frame interval and the hull geometry; specifically,

[0175] Step S3411: establishing a hull geometric model based on the hull geometric structure;

[0176] Step S3412: For each stable scattering point, select several frames of stable scattering point information from the stable scattering point sequence in the non-vertical sideways frame interval to determine the physical position of the stable scattering point in establishing the hull geometric model;

[0177] In step S3412, for each stable scattering point, each frame of stable scattering point information is selected, and the linear position of the stable scattering point at the current broadside angle is determined based on the corresponding relationship between the broadside angle and the range image position corresponding to the frame and the range image position of the center of mass of the ship target in the current frame. Based on the linear positions of the stable scattering point at multiple broadside angles, the physical position of the stable scattering point in the ship hull geometric model can be determined.

[0178] For example, for the kth stable scattering point, it is assumed that the stable scattering point sequence in the non-vertical sideways frame interval contains stable scattering point information with sideways angles of 0° and 45°; when the sideways angle is 0°, as shown in FIG. Figure 3 As shown in , according to the correspondence between the range image position of the kth stable scattering point and the range image position of the center of mass of the ship target in the current frame, the radial position of the stable scattering point can be obtained. It can be seen that the kth scattering point is on a straight line in the hull that is perpendicular to the beam direction at this time. When the broadside angle is 45°, as Figure 4 As shown, it can be seen that the kth stable scattering point is located on another straight line in the hull that is perpendicular to the beam direction at this time. The intersection of these two lines is the physical location of the stable scattering point in the hull geometric model. More precisely, stable scattering point information corresponding to more broadside angles can be selected to more accurately determine the physical location of the stable scattering point in the hull geometric model. Similarly, the physical locations of all stable scattering points in the hull geometric model can be determined using this method.

[0179] Step S3413: Establishing a hull scattering position geometric model according to the physical position of each stable scattering point in the hull geometric model.

[0180] Step S342: determining the stable scattering point information of each stable scattering point at each broadside angle within the vertical broadside frame interval according to the ship scattering position geometry model, the speed and heading of the ship target;

[0181] Specifically, for each stable scattering point at each broadside angle within the vertical broadside frame interval, the following operations are performed:

[0182] Step S3421: Calculate the radial velocity of the stable scattering point in the beam direction based on the geometric model of the ship scattering position, the speed and heading of the ship target, and convert the radial velocity into the corresponding Doppler channel number;

[0183] Example: Calculate the stable scattering points (such as Figure 5 The Doppler channel number corresponding to the kth stable scattering point is shown in the figure (using the kth stable scattering point as an example): After obtaining the ship's motion state (speed and heading) for that frame, the velocity vector is projected onto the beam direction based on the ship's scattering position geometry model to obtain the radial velocity of the stable scattering point in the beam direction. The radial velocity is then converted to the corresponding Doppler channel number l according to the following formula:

[0184]

[0185] Where v is the radial velocity, PRT is the pulse repetition period, N is the Doppler dimension, and λ is the carrier wavelength.

[0186] Step S3422: The Doppler channel number is mapped to the target characteristic range-Doppler data component of the corresponding frame in the main polarization channel to determine the range position of the stable scattering point; the target scattering point corresponding to the range position is located in the one-dimensional range image of the corresponding frame in the main polarization channel as the stable scattering point, and stable scattering point information of the located stable scattering point is obtained.

[0187] This process can solve the overlapping problem of the range images of the stable scattering point positions in the vertical side frame interval.

[0188] Step S343: Obtain a stable scattering point sequence in the vertical sideways frame interval under the main polarization channel according to the obtained stable scattering point information of each stable scattering point in the vertical sideways frame interval.

[0189] In the vertical sideways frame interval, for the same stable scattering point, the stable scattering point information is spliced ​​according to the frame sequence number to form a stable scattering point sequence of the stable scattering point in the vertical sideways frame interval under the main polarization channel; the stable scattering point sequences of all stable scattering points in the vertical sideways frame interval are summarized to form a final stable scattering point sequence in the vertical sideways frame interval under the main polarization channel.

[0190] Step S35: sorting the stable scattering point sequences in the non-vertical and vertical sideways frame intervals of the main polarization channel according to the frame sequence numbers to obtain the omnidirectional stable scattering point sequence of the main polarization channel under the corresponding grazing angle.

[0191] In the obtained omnidirectional stable scattering point sequence, assuming that the main polarization channel is the HH channel, the main polarization channel omnidirectional stable scattering point sequence of the kth stable scattering point is S HH_k , S HH_kIt can be expressed as follows: HH_k1 ,S HH_k2 ,...,S HH_kr ,...,S HH_kn}; k = 1, 2, ..., K, K is the total number of stable scattering points; where S HH_kr Indicates the stable scattering point information of the kth stable scattering point in the rth frame of range-Doppler data under the HH channel.

[0192] Step S4: mapping the omnidirectional stable scattering point sequence of the main polarization channel at each grazing angle to other polarization channels, and obtaining the omnidirectional stable scattering point sequence of other polarization channels at the corresponding grazing angle;

[0193] Specifically, the range image position of each stable scattering point in the omnidirectional stable scattering point sequence of the main polarization channel is mapped onto the one-dimensional range images of other polarization channels. The omnidirectional stable scattering point sequences of other polarization channels at corresponding grazing angles are then obtained using the corresponding one-dimensional range images of the other polarization channels. It should be noted that the positions of the stable scattering points on the one-dimensional range images of different polarization channels are the same, but the scattering point phases and scattering point amplitudes are different. Therefore, the scattering point phases and scattering point amplitudes of each scattering point in other polarization channels can be obtained using the corresponding one-dimensional range images of other polarization channels, ultimately forming an omnidirectional stable scattering point sequence in the other polarization channels.

[0194] Step S5: performing omnidirectional scattering point modeling on the omnidirectional stable scattering point sequences of each polarization channel under different grazing angles of incidence, and constructing an omnidirectional ship target characteristic library;

[0195] Specifically, for different incident angles, in the omnidirectional stable scattering point sequence of each polarization channel, the deviation of the sideways angle corresponding to two adjacent frames may be relatively large. In this case, it is necessary to interpolate the omnidirectional stable scattering point sequence based on the sideways angle, fit the sideways angle, range image position, scattering point phase and scattering point amplitude, and adjust the frame number to achieve omnidirectional scattering point modeling of each polarization channel, summarize the omnidirectional scattering point modeling results of each polarization channel, and form an omnidirectional scattering point model of the ship target under multi-polarization channels. For example, the corresponding fitting function is selected by the grid search method to obtain the mathematical model of each scattering point of the ship target under each polarization channel, and the omnidirectional scattering point modeling of the corresponding polarization channel is performed to obtain the full-angle characterization model of the ship azimuth, that is, the omnidirectional scattering point model of the ship target under multi-polarization channels. The schematic diagram of the model structure is shown in FIG. Figure 6 Based on this model, target characteristics can be reconstructed according to the broadside angle, achieving incremental expansion of typical ship target sample data and scene reconstruction.

[0196] After the omnidirectional scattering point model of the ship target under the multi-polarization channel is formed, the data in the omnidirectional scattering point model of the ship under the multi-polarization channel can be re-aggregated according to the structure of the omnidirectional ship target characteristic library to construct the omnidirectional ship target characteristic library.

[0197] Those skilled in the art will appreciate that all or part of the process steps of the above-described embodiments can be implemented by instructing related hardware through a computer program, and the program can be stored in a computer-readable storage medium, such as a magnetic disk, an optical disk, a read-only memory, or a random access memory.

[0198] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for constructing an interior scene of a ship target, characterized in that: include: According to the scene setting requirements of the indoor scene, the target scattering characteristic model is selected from the omnidirectional ship target characteristic library; In the indoor scene, according to the scene setting requirements and the target scattering characteristic model of each simulated target, the radar simulated target echo is generated; The background noise data is superimposed on the generated radar simulated target echo to obtain the radar simulated echo signal in the indoor scene, thus completing the construction of the indoor scene. The omnidirectional ship target characteristic library is constructed in the following way: Conduct omnidirectional data acquisition tests at different incident angles on ship targets in the field to obtain measured high-speed echo data; Based on the normalized basis function, the target characteristics of the target area in the range-Doppler data corresponding to each frame of measured high-speed echo data are extracted to obtain the corresponding target characteristic range-Doppler data; At each grazing angle, based on the target characteristic range-Doppler data component of each frame of target characteristic range-Doppler data in the main polarization channel, the omnidirectional stable scattering point sequence of the main polarization channel at the corresponding grazing angle is obtained; Mapping the omnidirectional stable scattering point sequence of the main polarization channel at each grazing angle to other polarization channels, and obtaining the omnidirectional stable scattering point sequence of other polarization channels at the corresponding grazing angle; The omnidirectional stable scattering point sequences of each polarization channel under different grazing angles are modeled respectively to construct an omnidirectional ship target characteristic library.

2. The method for constructing an interior scene of a ship target according to claim 1, characterized in that: The omnidirectional ship target characteristic library includes the ship type, radar equipment parameters, target parameters and corresponding target scattering characteristic models of the ship target; wherein, The target scattering characteristic model is composed of the range image positions, scattering point phases and scattering point amplitudes of several stable scattering points on four polarization channels: HH, HV, VH and VV.

3. The method for constructing an interior scene of a ship target according to claim 2, characterized in that: The scenario setting requirements include: The target type of the simulation target, which can be one or more; Radar equipment parameters, including radar band and polarization state; Scenario environment parameters, including sea conditions, radar equipment altitude, and radar-target distance.

4. The method for constructing an interior scene of a ship target according to claim 3, characterized in that: Generate radar simulated target returns by doing the following: Generate radar transmission signals according to radar equipment parameters in the scenario setting requirements; Based on the target scattering characteristic model of each simulated target and the radar transmission signal, a radar simulated target echo of the corresponding simulated target is obtained; If the scene setting requirements only include one simulated target, the radar simulated target echo of the simulated target is used as the radar simulated target echo in the indoor field scene; otherwise, the radar simulated target echoes of all simulated targets are superimposed with electromagnetic waves to obtain the radar simulated target echo in the indoor field scene.

5. The method for constructing an interior scene of a ship target according to claim 4, characterized in that: Get the radar simulated target echo of the simulated target by doing the following: Obtaining one-dimensional range image data of the simulated target in each polarization channel according to the retrieved target scattering characteristic model of the simulated target; According to the radar-target distance in the scenario setting requirements, the one-dimensional range image data of each polarization channel is superimposed to the corresponding position of the radar-target distance to form the range image target scattering point set of the simulated target; The target characteristic of the range image target scattering point set of the simulated target is modulated by using the radar transmission signal to generate the radar simulated target echo of the simulated target.

6. The method for constructing an interior scene of a ship target according to claim 3, characterized in that: Selecting a target scattering characteristic model from the target characteristic library includes: Based on the scene environment parameters of the simulation target, obtaining the target parameters of the simulation target; According to the target type, radar band and target parameters of each simulated target, the target scattering characteristic model matching each simulated target is retrieved from the target characteristic library.

7. The method for constructing an interior scene of a ship target according to any one of claims 2 to 6, characterized in that: Obtain the omnidirectional stable scattering point sequence of the main polarization channel under the corresponding grazing angle, including: Perform decoherence processing on the target characteristic range-Doppler data components of each frame of the main polarization channel, and take the prt with the largest amplitude as the one-dimensional range image of the frame under the main polarization channel; Determine, based on the one-dimensional range image of each frame in the main polarization channel and its corresponding sideways angle, a one-dimensional range image sequence of a vertical sideways frame interval in the main polarization channel and a one-dimensional range image sequence of a non-vertical sideways frame interval; Target characteristics are correlated for the one-dimensional range images of each frame in the non-perpendicular sideways frame interval to obtain a stable scattering point sequence in the non-perpendicular sideways frame interval under the main polarization channel; Based on the stable scattering point sequence in the non-vertical sideways frame interval under the main polarization channel, a stable scattering point sequence in the vertical sideways frame interval under the main polarization channel is obtained; The stable scattering point sequences in the non-vertical and vertical sideways frame intervals under the main polarization channel are sorted according to the frame sequence number to obtain the omnidirectional stable scattering point sequence of the main polarization channel under the corresponding grazing angle of incidence.

8. The method for constructing an interior scene of a ship target according to claim 7, characterized in that: Obtain a stable scattering point sequence in the non-vertical sideways frame interval under the main polarization channel, including: According to the preset number of associated segment frames, the temporally adjacent one-dimensional range images in the non-vertical side frame interval are segmented, and the one-dimensional range images of each frame in the segment are sequentially spliced ​​according to the frame sequence number to obtain a plurality of segment data; Preprocess each fragment data to obtain corresponding stable scattering point fragment data; Perform range image principal component analysis and cluster analysis on each stable scattering point segment data, and output the stable scattering point sequence and cluster center associated between frames in the corresponding segment; According to the stable scattering point sequence and cluster center of the inter-frame correlation in each segment, the inter-segment correlation is performed to obtain the stable scattering point sequence in the non-vertical side frame interval under the main polarization channel.

9. The method for constructing an interior scene of a ship target according to claim 8, characterized in that: The target parameters include incident grazing angle, broadside angle and radial velocity; The omnidirectional ship target characteristic library is constructed by the following methods: The omnidirectional scattering point modeling is performed on the omnidirectional stable scattering point sequence of each polarization channel under different grazing angles, and the omnidirectional scattering point model of the ship under multi-polarization channels is obtained. According to the structure of the omnidirectional ship target characteristic library, the data in the ship omnidirectional scattering point model under multi-polarization channel are reorganized to construct the omnidirectional ship target characteristic library.

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