Method and system for imaging complex moving ship target by distributed platform inverse synthetic aperture radar, storage device and electronic equipment

Abstract

The invention discloses a method and a system for imaging a complex moving ship target by a distributed platform inverse synthetic aperture radar, a storage device and an electronic medium. The method comprises the following steps: establishing a geometric model of the distributed platform inverse synthetic aperture radar in a working state; compensating different initial phases of the collected echoes caused by different distances between each platform and the target, and enabling the initial phases of the echoes of each platform to be consistent; data segments, most suitable for imaging processing, of all platform echoes are obtained and then spliced in a time domain; and reconstructing the data of the missing aperture echo to obtain complete echo data, then carrying out motion compensation, and carrying out imaging processing to obtain a high-resolution image of the target ship. According to the method, when the distributed inverse synthetic aperture radar images the ship target, under the condition that the echo data is incomplete due to the fact that the imaging accumulation angle of the data acquired by each platform is discontinuous, the echo is reconstructed and imaged, and the applicability of the distributed inverse synthetic aperture radar to ship target imaging is enhanced.

Description

Technical Field

[0001] The present invention relates to the field of signal processing technology, and in particular to a distributed platform inverse synthetic aperture radar imaging method, system, storage device and electronic medium for complex moving ship targets. Background Art

[0002] At present, Inverse Synthetic Aperture Radar (ISAR) is an active microwave remote sensing device that can be used for imaging dynamic targets, especially for monitoring and tracking mobile targets at sea, such as ships and aircraft. ISAR uses the movement of the target itself (such as rotation or other complex movements) to achieve synthetic aperture, thereby obtaining a high-resolution radar image of the target. ISAR does not rely on the movement of the platform, so it is suitable for imaging from a fixed platform or a relatively slow-moving platform, and is particularly suitable for countering fast-moving or changing targets. At the same time, ships are important marine monitoring targets, and monitoring marine ship targets is of great significance for maintaining maritime safety and preventing maritime collisions.

[0003] In order to perform ISAR imaging of ship targets at sea, researchers have proposed a large number of motion compensation and imaging algorithms to obtain ISAR images of ship targets. The range resolution of ISAR imaging mainly depends on the bandwidth of the radar pulse, while the azimuth resolution mainly depends on the imaging accumulation angle of the ISAR system detecting the target. Under low sea conditions, constrained by the actual imaging scene, that is, in long-distance observations such as ISAR imaging, the large change in the spatial position of the ISAR platform itself can bring about a small change in the observation angle, resulting in a small imaging accumulation angle; under high sea conditions, although the ship target rotates greatly relative to the ISAR radar, its relative rotation is complex. After the optimal imaging data segment is selected, its effective imaging accumulation angle is still small. In recent years, the development of multi-platform joint combat mode has brought new possibilities for improving the resolution of ISAR images of ship targets.

[0004] Researchers have proposed a large number of methods for imaging ship targets using distributed ISAR. These methods often require the pre-arrangement of the positions of each platform based on the motion parameters of the ship target, and have very strict constraints on the relative motion of the radar and the target, so that the data collected by each platform is continuous in the imaging accumulation angle. However, in actual application scenarios, it is more common that the data collected by each platform does not meet the continuity in the imaging accumulation angle. Therefore, the existing methods cannot meet actual needs. Summary of the invention

[0005] The purpose of the present invention is to provide a distributed platform inverse synthetic aperture radar imaging method, system, storage device and electronic medium for complex moving ship targets, which can overcome the very limited applicability constraints caused by the overly strict constraints on the relative motion between the radar and the target in previous method models, and is conducive to enhancing the applicability of distributed inverse synthetic aperture radar for ship target imaging and enhancing the monitoring capability of maritime ship targets.

[0006] The technical solution adopted by the present invention is:

[0007] A distributed platform inverse synthetic aperture radar imaging method for complex moving ship targets.

[0008] The steps include:

[0009] Step S101, establishing a geometric model and a radar echo model of a distributed inverse synthetic aperture radar in a working state;

[0010] Step S102, compensating for different initial phases of collected echoes caused by different distances between each platform and the target, so that the initial phases of echoes from each platform are consistent;

[0011] Step S103, selecting the optimal imaging time to obtain the data segment of each platform echo that is most suitable for imaging processing;

[0012] Step S104, splicing the data segments used for imaging by each platform in the time domain to obtain echo data of the missing aperture;

[0013] Step S105, reconstructing the echo data of the missing aperture to obtain complete echo data;

[0014] Step S106: Perform motion compensation on the complete echo data and perform imaging processing to obtain a high-resolution image of the target ship.

[0015] In step S101, a geometric model and a radar echo model of a distributed inverse synthetic aperture radar in a working state are established, specifically:

[0016] In distributed ISAR observation, each ISAR carrier aircraft is traveling at the same speed v a Flying in the same direction, in the flight direction, a virtual ISAR system is equivalent between every two adjacent ISAR systems, and its position is located at the middle point of the line connecting the two adjacent ISAR systems;

[0017] According to the geographic location information provided by the motion sensor in the inertial measurement unit, the spatial position of each ISAR carrier is known, and the distance between each ISAR carrier and the imaging target is set to R Γ , then the echo received by each ISAR at a scattering point on the imaging target can be expressed as:

[0018]

[0019] Where Γ represents different ISAR carriers, t∈[-T / 2,T / 2] represents the time range of the ISAR platform to collect echoes, φ represents the initial observation angle of each ISAR platform, λ is the radar wavelength, r represents the distance between the scattering point and the target center, ω Γ represents the effective angular velocity of the target relative to the carrier Γ. When the ISAR platform is a real platform, k Γ = 0, when the ISAR platform is an equivalent virtual platform, k Γ =1,α AB represents the bistatic angle, that is, the angle between the two adjacent ISAR platforms that produce an equivalent platform and the target center, and j is a unit complex number.

[0020] The step S102 specifically includes the following steps:

[0021] The phase compensation is performed on the echoes received by each ISAR platform, and the compensation factor is:

[0022]

[0023] The compensated echo can be expressed as:

[0024]

[0025] It should be noted that for equivalent virtual platforms, the R Γ It is equivalent to the distance between the midpoint of the line connecting two adjacent ISAR systems of the platform and the center of the imaging target.

[0026] The step S103 specifically includes the following steps:

[0027] Take the echo of any platform after initial phase compensation, use the optimal imaging time selection algorithm to calculate the data segment most suitable for imaging, and apply the start and end time of this data segment to the data collected by all platforms; within the optimal imaging time data segment, the effective imaging rotation of the ship target relative to the ISAR platform is uniform.

[0028] The step S104 specifically includes the following steps:

[0029] For two adjacent ISAR platforms A and B, and the equivalent virtual platform C obtained from these two platforms, the data after the optimal imaging time period is selected are intercepted according to the following formula:

[0030]

[0031] in, is the initial observation angle of platform A, is the initial observation angle of platform B, ω is the effective imaging rotation angular velocity of the ship target relative to the platform; the intercepted data segments are time-shifted, and the time-shift amounts are:

[0032]

[0033] Then the time-shifted data segments are directly spliced ​​in the time domain;

[0034] For more than two ISAR platforms, the above operations can be performed on two adjacent platforms respectively, and it can be considered that ω = ω Γ , that is, the effective imaging rotation angular velocity of the ship target relative to any platform can represent the effective imaging rotation angular velocity relative to all platforms.

[0035] The step S105 specifically includes the following steps:

[0036] The obtained echo data with missing aperture are divided according to the azimuth as follows:

[0037] g={g1,g2,…,g i ,…,g Nr}

[0038] Where Nr is the number of sampling points in azimuth, g is the echo data with missing aperture, and g i is the data of the i-th azimuth direction, which can be expressed as follows:

[0039] g i =[x1,x2,…,x Na ] T

[0040] Where Na is the number of sampling points in the distance direction of the data, [·] T Represents a vector transposition operation; the data g in the i-th direction is i Converted to Hankel matrix, it is expressed as follows:

[0041]

[0042] Where L is a random constant that satisfies the power of 2, M = Na + 1 - L

[0043] To recover the matrix T(g i ), first define the weight matrix as follows:

[0044]

[0045] in, is T(g i) is row-augmented to make it half-circular to obtain the matrix, the initial value of ε is 0, I is the unit matrix, 0≤p≤1; the annihilation filter is defined as:

[0046] Among them, h i yes The i-th column of Construct the Gram matrix G and use the eigendecomposition of the matrix G to update the annihilation filter h in each iteration;

[0047]

[0048] VΛV * =G

[0049] in, is the set of orthogonal bases of eigenvectors, is the diagonal matrix of relevant eigenvalues; the weight matrix H is updated as:

[0050]

[0051]

[0052] Among them, q = 1-p / 2; then we have

[0053] Then, solve for missing values ​​in the matrix:

[0054]

[0055]

[0056] q (n) =q (n-1) +Fy (n) -MX (n)

[0057] available: Where D is obtained by converting h into weights, γ>0 is an adjustable fixed parameter, P is the column restriction operator, F is the discrete Fourier transform, M is an arbitrary linear transformation, and C p is a multi-level circulant matrix; finally, the phase space matrix is ​​reconstructed by the binary averaging method to obtain the missing i-th azimuth echo data; the above operation is performed on all azimuth echo data to reconstruct complete echo data.

[0058] The step S106 specifically includes the following steps:

[0059] The ISAR motion compensation algorithm is used to process the reconstructed complete echo data to complete motion compensation. Then, the motion compensated echo data is fast Fourier transformed along the azimuth direction to obtain the image of the target ship and complete the imaging processing.

[0060] A distributed platform inverse synthetic aperture radar imaging system for complex moving ship targets, comprising:

[0061] A model building unit, configured to build a geometric model and an echo model of the inverse synthetic aperture radar in a working state;

[0062] A phase compensation unit is configured to compensate for different initial phases of collected echoes caused by different distances between each platform and the target, so that the initial phases of echoes from each platform are consistent;

[0063] An imaging time determination unit configured to obtain a data segment of each platform echo that is most suitable for imaging processing;

[0064] A data stitching unit is configured to stitch the data segments used for imaging by each platform in the time domain to obtain echo data of the missing aperture;

[0065] a data reconstruction unit configured to reconstruct data of missing aperture echoes to obtain complete echo data;

[0066] The motion compensation and imaging unit is configured to use the reconstructed complete echo data to perform motion compensation and imaging processing to obtain a high-resolution image of the target ship.

[0067] A storage device stores a plurality of programs, wherein the programs are loaded and executed by a processor to implement the above-mentioned method for imaging a complex moving ship target using an inverse synthetic aperture radar containing a distributed platform.

[0068] An electronic device comprises a storage device and a processor; the processor is suitable for executing various programs; the memory is used to store multiple programs; when the memory executes the programs on the processor, the imaging method of complex moving ship targets by using an inverse synthetic aperture radar containing a distributed platform as described above is implemented.

[0069] The present invention establishes a geometric model and an echo model of an inverse synthetic aperture radar in a working state; compensates for the different initial phases of the collected echoes caused by the different distances between each platform and the target, so that the initial phases of the echoes of each platform are consistent; obtains the data segment of each platform echo that is most suitable for imaging processing; splices the data segments used for imaging of each platform in the time domain to obtain the echo data of the missing aperture; a data reconstruction unit is configured to reconstruct the data of the missing aperture echo to obtain complete echo data; finally, the reconstructed complete echo data is used for motion compensation and imaging processing to obtain a high-resolution image of the target ship. Through the present invention, when the distributed inverse synthetic aperture radar images the ship target, the imaging accumulation angle of the collected data of each platform is discontinuous, resulting in incomplete echo data, and the echo is reconstructed and imaged, which is conducive to enhancing the applicability of the distributed inverse synthetic aperture radar to ship target imaging and enhancing the monitoring capability of marine ship targets. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0071] Figure 1 is a flow chart of the present invention;

[0072] Figure 2 A diagram of a geometric model of a distributed inverse synthetic aperture radar in a working state of the present invention;

[0073] Figure 3 This is a unit configuration diagram of the present invention. DETAILED DESCRIPTION

[0074] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0075] like Figure 1 , 2 As shown in 3, the present invention comprises the following steps:

[0076] Step S101, establishing a geometric model of a distributed inverse synthetic aperture radar in a working state;

[0077] Specifically, in distributed ISAR observation, each ISAR carrier aircraft flies at the same speed va Flying in the same direction (with different flight altitudes and azimuths), in the flight direction, a virtual ISAR system can be equivalent between every two adjacent ISAR systems, and its position is located at the middle point of the line connecting the two adjacent ISAR systems.

[0078] According to the geographic location information provided by the motion sensor in the inertial measurement unit, the spatial position of each ISAR carrier can be known. Suppose the distance between each ISAR carrier and the imaging target is R Γ , then the echo received by each ISAR at a scattering point on the imaging target can be expressed as:

[0079]

[0080] Where Γ represents different ISAR carriers, t∈[-T / 2,T / 2] represents the time range of the ISAR platform to collect echoes, φ represents the initial observation angle of each ISAR platform, λ is the radar wavelength, r represents the distance between the scattering point and the target center, ω Γ represents the effective angular velocity of the target relative to the carrier Γ. When the ISAR platform is a real platform, k Γ = 0, when the ISAR platform is an equivalent virtual platform, k Γ =1,α AB represents the bistatic angle, i.e., the angle between the two adjacent ISAR platforms that produce an equivalent platform and the target center. In addition, j is a unit complex number and π is pi.

[0081] Step S102, compensating for different initial phases of collected echoes caused by different distances between each platform and the target, so that the initial phases of echoes from each platform are consistent;

[0082] Specifically, phase compensation is performed on the echoes received by each ISAR platform, and the compensation factor is:

[0083]

[0084] The compensated echo can be expressed as:

[0085]

[0086] It should be noted that for equivalent virtual platforms, the R Γ It is equivalent to the distance between the midpoint of the line connecting two adjacent ISAR systems of the platform and the center of the imaging target.

[0087] Step S103, selecting the optimal imaging time to obtain the data segment of each platform echo that is most suitable for imaging processing;

[0088] Specifically, take the echo of any platform after initial phase compensation, use the optimal imaging time selection algorithm to calculate the most suitable data segment for imaging, and apply the start and end time of this data segment to the data collected by all platforms. In the optimal imaging time data segment, the effective imaging rotation of the ship target relative to the ISAR platform is uniform.

[0089] Step S104, splicing the data segments used for imaging by each platform in the time domain to obtain echo data of the missing aperture;

[0090] Specifically, for two adjacent ISAR platforms A and B, and the equivalent virtual platform C obtained from these two platforms, the data after the optimal imaging time period is selected are intercepted according to the following formula:

[0091]

[0092] in, is the initial observation angle of platform A, is the initial observation angle of platform B, and ω is the effective imaging rotation angular velocity of the ship target relative to the platform. The intercepted data segments are time-shifted, and the time-shift amounts are:

[0093]

[0094] Then the time-shifted data segments are directly spliced ​​in the time domain.

[0095] For more than two ISAR platforms, the above operations can be performed on two adjacent platforms respectively, and it can be considered that ω = ω Γ , that is, the effective imaging rotation angular velocity of the ship target relative to any platform can represent the effective imaging rotation angular velocity relative to all platforms.

[0096] Step S105, reconstructing the data of the missing aperture echo to obtain complete echo data;

[0097] Specifically, the obtained echo data with missing aperture is divided according to the azimuth direction as follows:

[0098] g={g1,g2,…,g i ,…,g Nr} (6)

[0099] Where Nr is the number of sampling points in azimuth, g is the echo data with missing aperture, and g i is the data of the i-th azimuth direction, which can be expressed as follows:

[0100] g i =[x1,x2,…,x Na ] T (7)

[0101] Where Na is the number of sampling points in the distance direction of the data, [·] T Represents a vector transposition operation. Transpose the data g in the i-th direction i Converted to Hankel matrix, it is expressed as follows:

[0102]

[0103] Where L is a random constant that satisfies the power of 2, M = Na + 1 - L.

[0104] To recover the matrix T(g i ), first define the weight matrix as follows:

[0105]

[0106] in, is T(g i ) is row-augmented to make it half-circular, the initial value of ε is 0, I is the unit matrix, 0≤p≤1. The annihilation filter is defined as:

[0107]

[0108] Among them, h i yes ith column of . At each iteration, according to The Gram matrix G is constructed and the eigendecomposition of the matrix G is used to update the annihilation filter h in each iteration.

[0109]

[0110] VΛV * =G (12)

[0111] in, is the set of orthogonal bases of eigenvectors, is the diagonal matrix of relevant eigenvalues. The weight matrix H is updated as:

[0112]

[0113]

[0114] Among them, q = 1-p / 2. Then we have

[0115]

[0116] Then, solve for missing values ​​in the matrix:

[0117]

[0118]

[0119] q (n) =q (n-1) +Fy (n) -MX (n) (18)

[0120] available:

[0121]

[0122] Where D is obtained by converting h into weights, γ>0 is an adjustable fixed parameter, P is the column restriction operator, F is the discrete Fourier transform, M is an arbitrary linear transformation, and C p is a multi-level circulant matrix. Finally, the phase space matrix is ​​reconstructed by the binary average method to obtain the missing i-th azimuth echo data.

[0123] By performing the above operations on all azimuth echo data, complete echo data can be reconstructed.

[0124] Step S106: Perform motion compensation on the complete echo data and perform imaging processing to obtain a high-resolution image of the target ship;

[0125] Specifically, the ISAR motion compensation algorithm is used to process the reconstructed complete echo data to complete motion compensation, and then the motion compensated echo data is fast Fourier transformed along the azimuth direction to obtain the image of the target ship and complete the imaging processing.

[0126] The present invention establishes a geometric model and an echo model of an inverse synthetic aperture radar in a working state; compensates for the different initial phases of the collected echoes caused by the different distances between each platform and the target, so that the initial phases of the echoes of each platform are consistent, and the consistency of the initial phases is the basis for the joint processing of the echo data of each platform; obtains the data segment of each platform echo that is most suitable for imaging processing; splices the data segments used for imaging of each platform in the time domain to obtain the echo data of the missing aperture, so that the data collected by each platform are aligned in time, which is the basis for data reconstruction; the data reconstruction unit is configured to reconstruct the data of the missing aperture echo to obtain complete echo data; finally, the reconstructed complete echo data is used for motion compensation and imaging processing to obtain a high-resolution image of the target ship. Through the present invention, when the distributed inverse synthetic aperture radar images the ship target, the imaging accumulation angle of the collected data of each platform is discontinuous, resulting in incomplete echo data, and the echo is reconstructed and imaged, which is conducive to enhancing the applicability of the distributed inverse synthetic aperture radar to ship target imaging and enhancing the monitoring capability of marine ship targets.

[0127] Exemplary Systems

[0128] The embodiment of the present application also provides a distributed platform inverse synthetic aperture radar imaging system for complex motion ship targets, including: a model building unit, configured to establish a geometric model and an echo model of the inverse synthetic aperture radar in a working state; a phase compensation unit, configured to compensate for the different initial phases of the collected echoes caused by the different distances between each platform and the target, so that the initial phases of the echoes of each platform are consistent; an imaging time determination unit, configured to obtain the data segment of each platform echo that is most suitable for imaging processing; a data splicing unit, configured to splice the data segments used for imaging of each platform in the time domain to obtain echo data of the missing aperture; a data reconstruction unit, configured to reconstruct the data of the missing aperture echo to obtain complete echo data; a motion compensation and imaging unit, configured to use the reconstructed complete echo data to perform motion compensation and imaging processing to obtain a high-resolution image of the target ship.

[0129] The distributed platform inverse synthetic aperture radar imaging system for complex motion ship targets provided in the embodiments of the present application can implement any of the above-mentioned distributed platform inverse synthetic aperture radar imaging steps and processes for complex motion ship targets and achieve the same technical effects, which will not be repeated here one by one.

[0130] Exemplary Devices

[0131] The present application provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the device where the computer-readable storage medium is located executes the above-mentioned distributed platform inverse synthetic aperture radar imaging method for complex moving ship targets. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device that can carry the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory and other memory.

[0132] An electronic device comprises a storage device and a processor, wherein the processor is adapted to execute various programs; and the memory is used to store a plurality of programs. When the memory executes the programs on the processor, the imaging method of a complex moving ship target by a distributed platform inverse synthetic aperture radar as described above is implemented.

[0133] Since the steps of imaging complex moving ship targets by distributed platform inverse synthetic aperture radar have been introduced in detail in the specific implementation method example, they will not be repeated here.

[0134] The processor includes a central processing unit (CPU), a network processor (NP), etc. It can also be a digital signal processor, an application-specific integrated circuit, a readily available programmable gate array or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component. The disclosed methods, steps and logic block diagrams in the embodiments of the present application can be implemented or executed. The general processor can be a microprocessor or the processor can also be any conventional processor, etc.

[0135] The processor can be specifically configured as follows: establishing a geometric model and an echo model of the inverse synthetic aperture radar in a working state; compensating for different initial phases of collected echoes caused by different distances between each platform and the target, so that the initial phases of the echoes of each platform are consistent; obtaining the data segment of each platform echo that is most suitable for imaging processing; splicing the data segments used for imaging of each platform in the time domain to obtain echo data of the missing aperture; a data reconstruction unit is configured to reconstruct the data of the missing aperture echo to obtain complete echo data; using the reconstructed complete echo data to perform motion compensation and imaging processing to obtain a high-resolution image of the target ship.

[0136] It should be pointed out that, according to the needs of implementation, the various components / steps described in the embodiments of the present application can be split into more components / steps, or two or more components / steps or partial operations of components / steps can be combined into new components / steps to achieve the purpose of the embodiments of the present application.

[0137] The above-mentioned method according to the embodiment of the present application can be implemented in hardware, firmware, or implemented as software or computer code that can be stored in a recording medium (such as a CD ROM, RAM, floppy disk, hard disk or magneto-optical disk), or implemented as a computer code originally stored in a remote recording medium or a non-temporary machine storage medium downloaded through a network and to be stored in a local recording medium, so that the method described herein can be stored in such software processing on a recording medium using a general-purpose computer, a dedicated processor or programmable or dedicated hardware (such as an ASIC or FPGA). It can be understood that a computer, a processor, a microprocessor controller or programmable hardware includes a storage component (e.g., RAM, ROM, flash memory, etc.) that can store or receive software or computer code. When the software or computer code is accessed and executed by a computer, a processor or hardware, the single-track synthetic aperture radar interference source positioning method described herein is implemented. In addition, when a general-purpose computer accesses the code for implementing the method shown herein, the execution of the code converts the general-purpose computer into a dedicated computer for executing the method shown herein.

[0138] Those of ordinary skill in the art will appreciate that the units and method steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and constraints involved in the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the embodiments of the present application.

[0139] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device and system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiments.

[0140] The device and system embodiments described above are merely illustrative, wherein the units not shown as separate may or may not be physically separated, and the units not shown as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Those of ordinary skill in the art may understand and implement it without creative work.

[0141] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for imaging complex moving ship targets using a distributed platform inverse synthetic aperture radar, characterized in that: The steps include: Step S101, establishing a geometric model and a radar echo model of a distributed inverse synthetic aperture radar in a working state; Step S102, compensating for different initial phases of collected echoes caused by different distances between each platform and the target, so that the initial phases of echoes from each platform are consistent; Step S103, selecting the optimal imaging time to obtain the data segment of each platform echo that is most suitable for imaging processing; Step S104, splicing the data segments used for imaging by each platform in the time domain to obtain echo data of the missing aperture; Step S105, reconstructing the echo data of the missing aperture to obtain complete echo data; Step S106: Perform motion compensation on the complete echo data and perform imaging processing to obtain a high-resolution image of the target ship.

2. The method for imaging complex moving ship targets using a distributed platform inverse synthetic aperture radar according to claim 1 is characterized in that: In step S101, a geometric model and a radar echo model of a distributed inverse synthetic aperture radar in a working state are established, specifically: In distributed ISAR observation, each ISAR carrier aircraft is traveling at the same speed v a Flying in the same direction, in the flight direction, a virtual ISAR system is equivalent between every two adjacent ISAR systems, and its position is located at the middle point of the line connecting the two adjacent ISAR systems; According to the geographic location information provided by the motion sensor in the inertial measurement unit, the spatial position of each ISAR carrier is known, and the distance between each ISAR carrier and the imaging target is set to R Γ , then the echo received by each ISAR at a scattering point on the imaging target can be expressed as: Where Γ represents different ISAR carriers, t∈[-T / 2,T / 2] represents the time range of the ISAR platform to collect echoes, φ represents the initial observation angle of each ISAR platform, λ is the radar wavelength, r represents the distance between the scattering point and the target center, ω Γ represents the effective angular velocity of the target relative to the carrier Γ. When the ISAR platform is a real platform, k Γ = 0, when the ISAR platform is an equivalent virtual platform, k Γ =1,α AB represents the bistatic angle, that is, the angle between the two adjacent ISAR platforms that produce an equivalent platform and the target center, and j is a unit complex number.

3. The method for imaging complex moving ship targets using a distributed platform inverse synthetic aperture radar according to claim 1 is characterized in that: The step S102 specifically includes the following steps: The phase compensation is performed on the echoes received by each ISAR platform, and the compensation factor is: The compensated echo can be expressed as: It should be noted that for equivalent virtual platforms, the R Γ It is equivalent to the distance between the midpoint of the line connecting two adjacent ISAR systems of the platform and the center of the imaging target.

4. The method for imaging complex moving ship targets using a distributed platform inverse synthetic aperture radar according to claim 1 is characterized in that: The step S103 specifically includes the following steps: Take the echo of any platform after initial phase compensation, use the optimal imaging time selection algorithm to calculate the data segment most suitable for imaging, and apply the start and end time of this data segment to the data collected by all platforms; within the optimal imaging time data segment, the effective imaging rotation of the ship target relative to the ISAR platform is uniform.

5. The distributed platform inverse synthetic aperture radar imaging method for complex moving ship targets according to claim 1 is characterized in that: The step S104 specifically includes the following steps: For two adjacent ISAR platforms A and B, and the equivalent virtual platform C obtained from these two platforms, the data after the optimal imaging time period is selected are intercepted according to the following formula: in, is the initial observation angle of platform A, is the initial observation angle of platform B, ω is the effective imaging rotation angular velocity of the ship target relative to the platform; the intercepted data segments are time-shifted, and the time-shift amounts are: Then the time-shifted data segments are directly spliced ​​in the time domain; For more than two ISAR platforms, the above operations can be performed on two adjacent platforms respectively, and it can be considered that ω = ω Γ , that is, the effective imaging rotation angular velocity of the ship target relative to any platform can represent the effective imaging rotation angular velocity relative to all platforms.

6. The distributed platform inverse synthetic aperture radar imaging method for complex moving ship targets according to claim 1 is characterized in that: The step S105 specifically includes the following steps: The obtained echo data with missing aperture are divided according to the azimuth as follows: g={g1,g2,…,g i ,…,g Nr } Where Nr is the number of sampling points in azimuth, g is the echo data with missing aperture, and g i is the data of the i-th azimuth direction, which can be expressed as follows: g i =[x1,x2,…,x Na ] T Where Na is the number of sampling points in the distance direction of the data, [·] T Represents a vector transposition operation; the data g in the i-th direction is i Converted to Hankel matrix, it is expressed as follows: Where L is a random constant that satisfies the power of 2, M = Na + 1 - L To recover the matrix T(g i ), first define the weight matrix as follows: in, is T(g i ) is row-augmented to make it half-circular to obtain the matrix, the initial value of ε is 0, I is the unit matrix, 0≤p≤1; the annihilation filter is defined as: Among them, h i yes The i-th column of Construct the Gram matrix G and use the eigendecomposition of the matrix G to update the annihilation filter h in each iteration; VΛV * =G in, is the set of orthogonal bases of eigenvectors, is the diagonal matrix of relevant eigenvalues; the weight matrix H is updated as: Among them, q = 1-p / 2; then we have Then, solve for missing values ​​in the matrix: q (n) =q (n-1) +Fy (n) -MX (n) available: Where D is obtained by converting h into weights, γ>0 is an adjustable fixed parameter, P is the column restriction operator, F is the discrete Fourier transform, M is an arbitrary linear transformation, and C p is a multi-level circulant matrix; finally, the phase space matrix is ​​reconstructed by the binary averaging method to obtain the missing i-th azimuth echo data; the above operation is performed on all azimuth echo data to reconstruct complete echo data.

7. The distributed platform inverse synthetic aperture radar imaging method for complex moving ship targets according to claim 1 is characterized in that: The step S106 specifically includes the following steps: The ISAR motion compensation algorithm is used to process the reconstructed complete echo data to complete motion compensation. Then, the motion compensated echo data is fast Fourier transformed along the azimuth direction to obtain the image of the target ship and complete the imaging processing.

8. A distributed platform inverse synthetic aperture radar imaging system for complex moving ship targets, characterized by: include: A model building unit, configured to build a geometric model and an echo model of the inverse synthetic aperture radar in a working state; A phase compensation unit is configured to compensate for different initial phases of collected echoes caused by different distances between each platform and the target, so that the initial phases of echoes from each platform are consistent; An imaging time determination unit configured to obtain a data segment of each platform echo that is most suitable for imaging processing; A data stitching unit is configured to stitch the data segments used for imaging by each platform in the time domain to obtain echo data of the missing aperture; a data reconstruction unit configured to reconstruct data of missing aperture echoes to obtain complete echo data; The motion compensation and imaging unit is configured to use the reconstructed complete echo data to perform motion compensation and imaging processing to obtain a high-resolution image of the target ship.

9. A storage device storing a plurality of programs, characterized in that: The program application is loaded and executed by a processor to implement the method for imaging complex moving ship targets using a distributed platform inverse synthetic aperture radar as described in any one of claims 1-7.

10. An electronic device, comprising a storage device and a processor; the processor is adapted to execute various programs; and the memory is adapted to store a plurality of programs; characterized in that: When the memory executes the program on the processor, the method for imaging complex moving ship targets using a distributed platform inverse synthetic aperture radar as described in any one of claims 1-7 is implemented.

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