Spaceborne SAR large-width sea surface target imaging intelligent reconstruction method

Abstract

The invention relates to a spaceborne SAR large-width sea surface target imaging intelligent reconstruction method. The method comprises the following steps that a spaceborne GNSS-S radar is used for obtaining target information of a plurality of key targets in a detection area of a large-width sea surface; the target information is transmitted to a rear satellite-borne SAR through an inter-satellite link to serve as priori target information of intelligent reconstruction; the spaceborne SAR constructs a multi-target optimization mathematical model through imaging performance and system resource analysis based on prior target information; solving the multi-objective optimization model by using a genetic algorithm to obtain an optimal system resource allocation result; and according to the optimal system resource allocation result, obtaining a high-resolution and high-signal-to-noise-ratio image through SAR imaging. According to the method, intelligent resource coordination of sea surface large-width multi-target observation can be realized, so that high-resolution and high-signal-to-noise-ratio images of a plurality of key targets can be acquired at the same time, and the imaging efficiency and the recognition accuracy are improved.

Description

Technical Field

[0001] The invention relates to the technical field of spaceborne SAR imaging intelligent reconstruction, and in particular to a spaceborne SAR large-width sea surface target imaging intelligent reconstruction method. Background Art

[0002] GNSS-S radar has multi-angle and multi-frequency imaging capabilities. It can obtain high signal-to-noise ratio images of sea surface targets through multi-dimensional information fusion methods, which is convenient for target detection and signal-to-noise ratio analysis, thereby extracting the target's precise location information and RCS value. However, due to the small bandwidth of GNSS-S radar signals, the imaging resolution is poor (about 100m) when imaging sea surface targets, making it difficult to identify targets.

[0003] Phased array spaceborne SAR uses an array antenna structure to increase the sea surface scanning range, making it possible to image targets on a wide sea surface with high resolution. At present, in the detection of targets on a wide sea surface, phased array spaceborne SAR has the problem of limited multi-target detection and recognition capabilities, that is, it is difficult to simultaneously achieve high-performance imaging and high-precision recognition of multiple targets that are discretely distributed on a wide sea surface.

[0004] Therefore, how to use phased array spaceborne SAR and GNSS-S radar for intelligent imaging and detection of wide sea surface targets is an urgent problem to be solved in this field. Summary of the invention

[0005] In order to solve the technical problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a spaceborne SAR large-width sea surface target imaging intelligent reconstruction method, which can realize the intelligent coordination of resources for large-width multi-target observation of the sea surface, so as to ensure the simultaneous acquisition of high-resolution, high signal-to-noise ratio images of multiple key targets, thereby improving imaging efficiency and recognition accuracy.

[0006] To achieve the above-mentioned invention object, the present invention provides a spaceborne SAR large-width sea surface target imaging intelligent reconstruction method, comprising a spaceborne GNSS-S radar and a spaceborne SAR respectively arranged on two satellites, a first satellite carrying the spaceborne GNSS-S radar flies in front of a second satellite carrying the spaceborne SAR, forming a dual-satellite sea surface target detection system, comprising the following steps:

[0007] Step S1, using the satellite-borne GNSS-S radar to obtain target information of multiple key targets in a detection area of ​​a large sea surface;

[0008] Step S2: transmitting the target information to the satellite-borne SAR at the rear via the inter-satellite link as a priori target information for intelligent reconstruction;

[0009] Step S3, the spaceborne SAR constructs a multi-objective optimization mathematical model based on prior target information through imaging performance and system resource analysis;

[0010] Step S4, using genetic algorithm to solve the multi-objective optimization model to obtain the optimal system resource allocation result;

[0011] Step S5: Acquire high-resolution and high-signal-to-noise ratio images through SAR imaging according to the optimal system resource allocation result.

[0012] According to a technical solution of the present invention, in step S1, the spaceborne GNSS-S radar uses the global navigation satellite system as a signal source and utilizes a low-orbit GNSS-S radar for reception, thereby forming a passive radar detection system;

[0013] The satellite-borne GNSS-S radar obtains target information of multiple targets in the detection area, the target position information, and RCS information by performing low-resolution dual-station SAR imaging and target detection on a wide sea surface.

[0014] According to a technical solution of the present invention, in step S2, the detection area is regarded as a rectangular area, the vertices are recorded as A, B, C, and D, and the AB side and the CD side are perpendicular to the second satellite sub-satellite point trajectory EF, wherein the AB side is the side closer to the SAR satellite, the AD side and the BC side are parallel to EF, which are defined as azimuth directions, and EF is located at the center line of the rectangular area;

[0015] Set the origin of the plane coordinate system to the midpoint of AB, the x-axis along EF, and the y-axis along AB, then the position coordinates of the key target are expressed as: (x i ,y i ), and satisfy: x1≤x2≤...≤x N , i=1,2,...,N is the target number, and N is the number of key targets in the detection area;

[0016] Among them, the target that meets RCS ≥ 40dBsm in the detection area is taken as the key target.

[0017] According to a technical solution of the present invention, in step S3, the spaceborne SAR uses a phased array antenna to generate a high-gain narrow beam, the beam angle along the azimuth direction is less than 5°, the beam angle along the range direction is less than 2°, a normal downward observation method is adopted, the beam azimuth scanning range is greater than ±10°, and the beam range scanning range is greater than ±15° to ±55°;

[0018] The system resources of the spaceborne SAR include at least beam resources, transmission signal time width T bi 、Transmitted signal bandwidth B i , observation time T sum , wherein the beam resources include the number of beams and the beam scanning capability, and the observation time T sumIt indicates the observation time of the detection area by the spaceborne SAR, that is, the time of flying over the detection area;

[0019] The imaging performance of the spaceborne SAR at least includes range resolution, azimuth resolution and NESZ.

[0020] According to a technical solution of the present invention, in step S4, constructing a multi-objective optimization mathematical model specifically includes:

[0021] Step S401: observe the first target in the detection area using the spaceborne SAR, and calculate the time when the spaceborne SAR observes each target at the previous viewing angle α: V represents the flight speed of the second satellite, and the front viewing angle α represents the maximum value of the beam azimuth scanning range;

[0022] Step S402: The satellite-borne SAR uses a single beam to scan in ascending order of target numbers. p If there is a target j q , q=1,2,...,Q and target i p When the difference between the distance and observation time is small, the target j is scanned at the same time using one beam scan. q With target i p observation, p = 1, 2, ..., P is the beam scan number, P represents the number of beam scans, T p represents the beam scanning time;

[0023] Step S403: Calculate the azimuth imaging resolution Δr of each target ai , range imaging resolution Δr i and the equivalent backscatter coefficient NESZ i ;

[0024] Step S404, construct a multi-objective optimization mathematical model to optimize the allocation of resources such as beam pointing and scanning order, transmission signal time width and bandwidth, and observation time of each target, so that the imaging performance of targets with different RCS is different: when σ i ∈[40dBsm,48dBsm], the imaging resolution is better than: 3m×3m, when σ i ∈[49dBsm,57dBsm], the imaging resolution is better than: 5m×5m, when σ i ≥58dBsm, imaging resolution better than: 7m×7m, and all targets meet: NESZ i ≤NESZ0, the value range of NESZ0 is -20dB to -15dB:

[0025]

[0026] Among them, st represents the constraint condition, T ci ′ represents the observation time of SAR on each target, which is the synthetic aperture time of the target;

[0027] H is the flying height of the satellite, Δr a 1=Δr1=3m,Δr a 2=Δr2=5m,Δr a 3=Δr3=7m,T bmin 、T bmax are the minimum and maximum transmission signal time widths provided by the SAR system, B min , B max They are respectively the minimum and maximum transmitted signal bandwidths provided by the SAR system.

[0028] According to a technical solution of the present invention, in step S402, when the observed target i p If there is a target j q With target i p When the difference between the distance and observation time is small, the target j is scanned at the same time using one beam scan. q With target i p Observations include:

[0029] Step S4021, calculate the radial distance of each target when SAR observes it, target i p The radial distance is: i p ≥2, the radial distance of the first target is: Then the observed target i p The size of the beam footprint along the x-axis is: The magnitude along the y-axis is: D a , D r are the dimensions of the antenna along the x and y axes, respectively;

[0030] Step S4022, calculate target i p The distances to other targets along the x and y axes are: Find conditions that simultaneously meet: The goal of m , m=1,2,...,M;

[0031] Step S4023, calculate the center O of the p-th beam scan p The coordinates are: Among them, η m For the target m The weight of whether it is observed in this scan, its value is: It changes during the scan;

[0032] Step S4024, during the pth beam scan, the observed target j q The coordinates of satisfy the conditions: For the target q With point O p distance;

[0033] Step S4025, when When the target i is updated p The observation time is: And define:

[0034] Step S4026, when the observed target i p When there is no target j q ,definition:

[0035] According to a technical solution of the present invention, in step S403, the azimuth imaging resolution Δr of each target is calculated. ai , range imaging resolution Δr i , and the equivalent backscatter coefficient NESZ i , the specific calculation formula is as follows:

[0036]

[0037] Among them, R i is the radial distance observed by SAR to target i, sinθ i is the downward viewing angle of SAR observing target i, λ and c are the wavelength of electromagnetic signal and the propagation speed in vacuum, k is the Boltzmann constant, T is the receiver temperature, and F n is the receiver noise factor, L s is the loss factor, D a is the length of the antenna in azimuth, P t is the transmission power, G t is the transmission gain, G r for receiving gain;

[0038] When the observed target i p When there is a target j q Sometimes, there are

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The present invention proposes a method for intelligent reconstruction of large-width sea surface target imaging by spaceborne SAR. In the application of spaceborne SAR sea surface target imaging and recognition, it innovatively proposes to use intelligent reconstruction of SAR multi-dimensional resources to enable a single high-gain narrow beam generated by a phased array antenna to achieve high-resolution, high signal-to-noise ratio imaging of multiple targets on a large-width sea surface, thereby improving imaging efficiency and recognition accuracy.

[0041] The present invention proposes a SAR multi-dimensional resource intelligent reconstruction method, which fully utilizes the observation time of SAR and optimizes the allocation of resources such as beam scanning sequence and direction, the time width and bandwidth of the transmitted signal, and the observation time of each target, so that multiple targets on a wide sea surface can be imaged with high performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0043] Figure 1 A diagram schematically showing a detection scene of a method for intelligent reconstruction of large-width sea surface target imaging by spaceborne SAR according to an embodiment of the present invention;

[0044] Figure 2 A schematic diagram schematically shows detection of a wide sea surface target by a spaceborne SAR and a spaceborne GNSS-S radar according to an embodiment of the present invention;

[0045] Figure 3 A schematic diagram schematically shows the detection area, coordinate system establishment and beam scanning of a wide-width sea surface target by a space-borne SAR according to an embodiment of the present invention;

[0046] Figure 4 The specific implementation flow chart of constructing a multi-objective optimization mathematical model according to an embodiment of the present invention is schematically shown. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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.

[0048] like Figures 1 to 4As shown, a spaceborne SAR wide-width sea surface target imaging intelligent reconstruction method of the present invention comprises a spaceborne GNSS-S radar and a spaceborne SAR respectively arranged on two satellites, a first satellite carrying the spaceborne GNSS-S radar flies in front of a second satellite carrying the spaceborne SAR, forming a dual-satellite sea surface target detection system, comprising the following steps:

[0049] Step S1: using the satellite-borne GNSS-S radar to obtain target information of multiple key targets in a detection area of ​​a large sea surface.

[0050] Spaceborne GNSS-S radar uses the global navigation satellite system (GNSS) as a signal source and a low-orbit GNSS-S radar as a receiver to form a passive radar detection system;

[0051] The satellite-borne GNSS-S radar obtains target information of multiple targets in the detection area, the target position information, and RCS information by performing low-resolution dual-station SAR imaging and target detection on a wide sea surface.

[0052] Step S2: The target information is transmitted to the satellite-borne SAR at the rear via the inter-satellite link as the prior target information for intelligent reconstruction.

[0053] like Figure 3 As shown, the detection area is regarded as a rectangular area, with vertices marked as A, B, C, and D, and the AB side and the CD side are perpendicular to the second satellite sub-satellite point track EF, where the AB side is the side closer to the SAR satellite, the AD side and the BC side are parallel to EF, defined as the azimuth, and EF is located at the center line of the rectangular area;

[0054] Set the origin of the plane coordinate system to the midpoint of AB, the x-axis along EF, and the y-axis along AB, then the position coordinates of the key target are expressed as: (x i ,y i ), and satisfy: x1≤x2≤...≤x N , i=1,2,...,N is the target number, and N is the number of key targets in the detection area;

[0055] Among them, the target that meets RCS ≥ 40dBsm in the detection area is taken as the key target.

[0056] Step S3: Based on the prior target information, the spaceborne SAR constructs a multi-objective optimization mathematical model through imaging performance and system resource analysis.

[0057] The spaceborne SAR uses a phased array antenna to generate a high-gain narrow beam. The beam angle along the azimuth is less than 5°, and the angle along the range is less than 2°. It adopts a downward-looking observation method. The beam azimuth scanning range is greater than ±10°, which meets the needs of simultaneous observation of multiple targets. The beam range scanning range is greater than ±15° to ±55°, which meets the conditions for wide-bandwidth detection.

[0058] The system resources of the spaceborne SAR at least include beam resources, transmission signal time width T bi 、Transmitted signal bandwidth B i , observation time T sum , wherein the beam resources include the number of beams and the beam scanning capability, and the observation time T sum It indicates the observation time of the detection area by the spaceborne SAR, that is, the time of flying over the detection area;

[0059] The imaging performance of spaceborne SAR includes at least range resolution, azimuth resolution and NESZ.

[0060] Step S4: using a genetic algorithm to solve the multi-objective optimization model to obtain the optimal system resource allocation result.

[0061] In step S4, a multi-objective optimization mathematical model is constructed, such as Figure 4 As shown, specifically including:

[0062] Step S401: observe the first target in the detection area using the spaceborne SAR, and calculate the time when the spaceborne SAR observes each target at the previous viewing angle α: V represents the flight speed of the second satellite, and the front viewing angle α represents the maximum value of the beam azimuth scanning range;

[0063] Step S402: The satellite-borne SAR uses a single beam to scan in ascending order of target numbers. p If there is a target j q , q=1,2,...,Q and target i p When the difference between the distance and observation time is small (the preset value of distance difference and the preset value of time difference can be introduced to judge whether the difference is small based on the preset value), one beam scan is used to complete the simultaneous observation of target j q With target i p observation, p = 1, 2, ..., P is the beam scan number, P represents the number of beam scans, T p represents the beam scanning time;

[0064] Step S403: Calculate the azimuth imaging resolution Δr of each target ai , range imaging resolution Δr i and the equivalent backscatter coefficient NESZi , the specific calculation formula is as follows:

[0065]

[0066] Among them, R i is the radial distance observed by SAR to target i, sinθ i is the downward viewing angle of SAR observing target i, λ and c are the wavelength of electromagnetic signal and the propagation speed in vacuum, k is the Boltzmann constant, T is the receiver temperature, and F n is the receiver noise factor, L s is the loss factor, D a is the length of the antenna in azimuth, P t is the transmission power, G t is the transmission gain, G r for receiving gain;

[0067] When the observed target i p When there is a target j q Sometimes, there is

[0068] Step S404, construct a multi-objective optimization mathematical model to optimize the allocation of resources such as beam pointing and scanning order, transmission signal time width and bandwidth, and observation time of each target, so that the imaging performance of targets with different RCS is different to meet the needs of target recognition: when σ i ∈[40dBsm,48dBsm], the imaging resolution is better than: 3m×3m, when σ i ∈[49dBsm,57dBsm], the imaging resolution is better than: 5m×5m, when σ i ≥58dBsm, imaging resolution better than: 7m×7m, and all targets meet: NESZ i ≤NESZ0, the value range of NESZ0 is -20dB to -15dB:

[0069]

[0070] Among them, st represents the constraint condition, T ci ′ represents the observation time of SAR on each target, which is the synthetic aperture time of the target;

[0071] H is the flying height of the satellite, Δr a 1=Δr1=3m,Δr a 2=Δr2=5m,Δr a 3=Δr3=7m,T bmin 、T bmax are the minimum and maximum transmission signal time widths provided by the SAR system, B min , Bmax They are respectively the minimum and maximum transmitted signal bandwidths provided by the SAR system.

[0072] The above constraints enable the spaceborne SAR to fully utilize the observable time of the detection area without affecting the imaging and recognition performance of the next detection area.

[0073] In step S402, when the observed target i p If there is a target j q With target i p When the difference between the distance and observation time is small, the target j is scanned at the same time using one beam scan. q With target i p Observations include:

[0074] Step S4021, calculate the radial distance of each target when SAR observes it, target i p The radial distance is: i p ≥2, the radial distance of the first target is: Then the observed target i p The size of the beam footprint along the x-axis is: The magnitude along the y-axis is: D a , D r are the dimensions of the antenna along the x and y axes, respectively;

[0075] Step S4022, calculate target i p The distance to other targets along the x and y axes is: Find conditions that simultaneously meet: The goal of m , m=1,2,...,M;

[0076] Step S4023, calculate the center O of the p-th beam scan p The coordinates are: Among them, η m For the target m The weight of whether it is observed in this scan, its value is: It changes during the scan;

[0077] Step S4024, during the pth beam scan, the observed target j q The coordinates of satisfy the conditions: For the target q With point O p distance;

[0078] Step S4025, when When the target i is updated p The observation time is: And define:

[0079] Step S4026, when the observed target i p When there is no target j q ,definition:

[0080] Step S5: Acquire high-resolution and high-signal-to-noise ratio images through SAR imaging according to the optimal system resource allocation result.

[0081] The invention discloses a satellite-borne SAR wide-width sea surface target imaging intelligent reconstruction method. The satellite-borne GNSS-S radar flies in front of the satellite-borne SAR to form a dual-satellite sea surface target detection system with the satellite-borne SAR. The satellite-borne GNSS-S radar is used to obtain distribution information of multiple key targets in a sea surface detection area, including the position and radar cross-section (RCS) information of the targets, and transmits the information to the satellite-borne SAR at the rear through an inter-satellite link. The satellite-borne SAR builds a multi-objective optimization model according to the prior information of the targets in the detection area, analyzes the imaging performance and system resources, and ensures that all the key targets in the detection area are imaged with high resolution and high signal-to-noise ratio, thereby improving the imaging efficiency and recognition accuracy of the sea surface key targets. The imaging performance mainly includes azimuth resolution, range resolution and equivalent backscatter coefficient (NESZ), and the system resources mainly include the beam, time width, bandwidth and observation time of the SAR. The genetic algorithm is used to solve the multi-objective optimization model to obtain the beam scanning timing and observation angle in the detection area, as well as the observation time, imaging resolution and NESZ of each key target. The present invention can realize intelligent coordination of resources for large-scale, wide-area, multi-target observation of the sea surface, so as to ensure simultaneous acquisition of high-resolution, high-signal-to-noise ratio images of multiple key targets, thereby improving imaging efficiency and recognition accuracy.

[0082] Parts of the present invention that are not described in detail belong to the well-known technology in the art.

[0083] It should be noted that, although the embodiments of the present invention described above are illustrative, they are not intended to limit the present invention, and therefore the present invention is not limited to the above specific embodiments. Without departing from the principles of the present invention, any other embodiments obtained by those skilled in the art under the guidance of the present invention are deemed to be within the protection of the present invention.

Claims

1. A spaceborne SAR wide-width sea surface target imaging intelligent reconstruction method, characterized in that: The invention comprises a satellite-borne GNSS-S radar and a satellite-borne SAR respectively arranged on two satellites, wherein a first satellite carrying the satellite-borne GNSS-S radar flies in front of a second satellite carrying the satellite-borne SAR, forming a dual-satellite sea surface target detection system, and comprises the following steps: Step S1, using the satellite-borne GNSS-S radar to obtain target information of multiple key targets in a detection area of ​​a large sea surface; Step S2: transmitting the target information to the satellite-borne SAR at the rear via the inter-satellite link as a priori target information for intelligent reconstruction; Step S3, the spaceborne SAR constructs a multi-objective optimization mathematical model based on prior target information through imaging performance and system resource analysis; Step S4, using genetic algorithm to solve the multi-objective optimization model to obtain the optimal system resource allocation result; Step S5: Acquire high-resolution and high-signal-to-noise ratio images through SAR imaging according to the optimal system resource allocation result.

2. The method for intelligent reconstruction of large-width sea surface target imaging by spaceborne SAR according to claim 1, characterized in that: In step S1, the spaceborne GNSS-S radar uses the global navigation satellite system as a signal source and utilizes the low-orbit GNSS-S radar for reception, thereby forming a passive radar detection system; The satellite-borne GNSS-S radar obtains target information of multiple targets in the detection area, the target position information, and RCS information by performing low-resolution dual-station SAR imaging and target detection on a wide sea surface.

3. The method for intelligent reconstruction of large-width sea surface target imaging by spaceborne SAR according to claim 2, characterized in that: In step S2, the detection area is regarded as a rectangular area, the vertices are recorded as A, B, C, and D, and the AB side and the CD side are perpendicular to the second satellite sub-satellite point trajectory EF, wherein the AB side is the side closer to the SAR satellite, the AD side and the BC side are parallel to EF, defined as the azimuth direction, and EF is located at the center line of the rectangular area; Set the origin of the plane coordinate system to the midpoint of AB, the x-axis along EF, and the y-axis along AB, then the position coordinates of the key target are expressed as: (x i ,y i ), and satisfy: x1≤x2≤...≤x N , i=1,2,...,N is the target number, and N is the number of key targets in the detection area; Among them, the target that meets RCS ≥ 40dBsm in the detection area is taken as the key target.

4. The method for intelligent reconstruction of large-width sea surface target imaging by spaceborne SAR according to claim 3 is characterized in that: In step S3, the spaceborne SAR uses a phased array antenna to generate a high-gain narrow beam, the beam angle along the azimuth is less than 5°, the beam angle along the range is less than 2°, a normal downward observation method is used, the beam azimuth scanning range is greater than ±10°, and the beam range scanning range is greater than ±15° to ±55°; The system resources of the spaceborne SAR include at least beam resources, transmission signal time width T bi 、Transmitted signal bandwidth B i , observation time T sum , wherein the beam resources include the number of beams and the beam scanning capability, and the observation time T sum It indicates the observation time of the detection area by the spaceborne SAR, that is, the time of flying over the detection area; The imaging performance of the spaceborne SAR at least includes range resolution, azimuth resolution and NESZ.

5. The method for intelligent reconstruction of large-width sea surface target imaging by spaceborne SAR according to claim 4, characterized in that: In step S4, a multi-objective optimization mathematical model is constructed, which specifically includes: Step S401: observe the first target in the detection area using the spaceborne SAR, and calculate the time when the spaceborne SAR observes each target at the previous viewing angle α: V represents the flight speed of the second satellite, and the front viewing angle α represents the maximum value of the beam azimuth scanning range; Step S402: The satellite-borne SAR uses a single beam to scan in ascending order of target numbers. p If there is a target j q , q=1,2,...,Q and target i p When the difference between the distance and observation time is small, the target j is scanned at the same time using one beam scan. q With target i p observation, p = 1, 2, ..., P is the beam scan number, P represents the number of beam scans, T p represents the beam scanning time; Step S403: Calculate the azimuth imaging resolution Δr of each target ai , range imaging resolution Δr i and the equivalent backscatter coefficient NESZ i ; Step S404, construct a multi-objective optimization mathematical model to optimize the allocation of resources such as beam pointing and scanning order, transmission signal time width and bandwidth, and observation time of each target, so that the imaging performance of targets with different RCS is different: when σ i ∈[40dBsm,48dBsm], the imaging resolution is better than: 3m×3m, when σ i ∈[49dBsm,57dBsm], the imaging resolution is better than: 5m×5m, when σ i ≥58dBsm, imaging resolution better than: 7m×7m, and all targets meet: NESZ i ≤NESZ0, the value range of NESZ0 is -20dB to -15dB: Among them, st represents the constraint condition, T ci ′ represents the observation time of SAR on each target, which is the synthetic aperture time of the target; H is the flying height of the satellite, Δr a 1=Δr1=3m,Δr a 2=Δr2=5m,Δr a 3=Δr3=7m,T bmin , T bmax are the minimum and maximum transmission signal time widths provided by the SAR system, B min , B max They are respectively the minimum and maximum transmitted signal bandwidths provided by the SAR system.

6. The method for intelligent reconstruction of large-width sea surface target imaging by spaceborne SAR according to claim 5, characterized in that: In step S402, when the observed target i p If there is a target j q With target i p When the difference between the distance and observation time is small, the target j is scanned at the same time using one beam scan. q With target i p Observations include: Step S4021, calculate the radial distance of each target when SAR observes it, target i p The radial distance is: The radial distance to the first target is: Then the observed target i p The size of the beam footprint along the x-axis is: The magnitude along the y-axis is: D a , D r are the dimensions of the antenna along the x and y axes, respectively; Step S4022, calculate target i p The distance to other targets along the x and y axes is: Find conditions that simultaneously meet: The goal of m , m=1,2,...,M; Step S4023, calculate the center O of the p-th beam scan p The coordinates are: Among them, η m For the target m The weight of whether it is observed in this scan, its value is: It changes during the scan; Step S4024, during the pth beam scan, the observed target j q The coordinates of satisfy the conditions: For the target q With point O p distance; Step S4025, when When the target i is updated p The observation time is: And define: Step S4026, when the observed target i p When there is no target j q ,definition:

7. The method for intelligent reconstruction of large-width sea surface target imaging by spaceborne SAR according to claim 6, characterized in that: In step S403, the azimuth imaging resolution Δr of each target is calculated. ai , range imaging resolution Δr i , and the equivalent backscatter coefficient NESZ i , the specific calculation formula is as follows: Among them, R i is the radial distance observed by SAR to target i, sinθ i is the downward viewing angle of SAR observing target i, λ and c are the wavelength of electromagnetic signal and the propagation speed in vacuum, k is the Boltzmann constant, T is the receiver temperature, and F n is the receiver noise factor, L s is the loss factor, D a is the length of the antenna in azimuth, P t is the transmission power, G t is the transmission gain, G r for receiving gain; When the observed target i p When there is a target j q Sometimes, there are

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