Large-width sea surface detection and non-uniform resolution intelligent imaging system based on double-star SAR (Synthetic Aperture Radar)

Abstract

The invention provides a large-breadth sea surface detection and non-uniform resolution intelligent imaging system based on a double-star SAR, and the system comprises a large-breadth sea surface detection system which is used for carrying out the large-breadth sea surface detection based on a collected SAR echo signal; the intelligent imaging system performs non-uniform resolution intelligent imaging based on the detection result of the large-width sea surface detection; the SAR emission subsystem adopts a phased-array antenna to carry out high-gain narrow-beam scanning emission in a range-direction large-width area, and covers a large-range sea surface area; the SAR receiving subsystem adopts a multi-channel antenna to carry out wide-range parallel receiving on echo signals; the SAR receiving subsystem is configured with a DBF processing module and a resource management and control processing module; and the SAR emission subsystem carries out signal emission based on the antenna beam parameters and the emission signal parameters fed back by the resource management and control processing module. The invention has the advantage of high echo power density, and can effectively reduce the requirement on the sensitivity of a receiving system.

Description

Technical Field

[0001] The present invention relates to the field of radar technology in the electronic information industry, and in particular to a wide-band sea surface detection and non-uniform resolution intelligent imaging system based on dual-satellite SAR. Background Art

[0002] For a long time, high-resolution wide-swath SAR imaging technology has attracted much attention in the field of radar technology. Limited by the inherent contradiction between the mapping width and azimuth sampling rate of a single-station SAR, it is difficult for traditional SAR to achieve high-resolution wide-swath imaging. To this end, relevant research institutions have proposed new working modes such as Scan SAR, TOPS SAR, Staggered SAR, and Mosaic SAR to increase the imaging width of SAR. Among them, Scan SAR and TOPS SAR use the range scanning of the beam to increase the imaging width in the range direction, and distribute the beam azimuth dwell time in the strip mode to each wave position in the range direction, but this method will sacrifice a large amount of beam azimuth dwell time, thereby limiting the azimuth resolution of the image; Staggered SAR reduces the receiving blind area and increases the imaging width in the range direction by continuously changing the PRI emitted by the system, but this method will also sacrifice part of the beam azimuth dwell time; Mosaic SAR combines spotlight SAR with Scan SAR, and the beam scans in the azimuth and range directions at the same time, increasing the imaging width of SAR while improving the beam azimuth dwell time, but sacrificing the azimuth observation range.

[0003] In recent years, the time-frequency-space synchronization capability of distributed satellite platforms has been greatly improved, laying a technical foundation for intelligent detection of distributed SAR systems. Distributed SAR places radar transmitters and receivers on different platforms, which can eliminate the detection blind spots caused by the transmission of high-power signals by single-station SAR, thus becoming an important technical approach for high-resolution wide-band SAR imaging.

[0004] However, the wide echo signal of distributed SAR will fill the entire pulse repetition period, and the echo signals of each wave position and the echo signals of adjacent periods of the same wave position will interfere with each other. It is necessary to design the signal orthogonality to address this problem. At the same time, the power resources of the space-based platform and the legal radar detection bandwidth resources are relatively limited. Using the traditional uniform imaging mode to detect a large area of ​​the ocean with sparse target distribution characteristics will greatly waste limited system resources.

[0005] Therefore, it is urgent to explore new intelligent imaging modes to achieve more efficient marine imaging detection. Summary of the invention

[0006] In order to solve the technical problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a large-width sea surface detection and non-uniform resolution intelligent imaging system based on dual-star SAR, which has the advantages of large width and high resource utilization, and is particularly suitable for large-scale sea surface ship target search and imaging.

[0007] To achieve the above-mentioned purpose, the present invention provides a wide-band sea surface detection and non-uniform resolution intelligent imaging system based on dual-satellite SAR, comprising:

[0008] A transmitting satellite equipped with a SAR transmitting subsystem, a receiving satellite equipped with a SAR receiving subsystem, and an intersatellite link between the transmitting satellite and the receiving satellite, wherein the transmitting satellite and the receiving satellite are two satellites flying in the same low orbit and following each other;

[0009] A large-scale wide sea surface detection system is used to perform large-scale wide sea surface detection based on the collected SAR echo signals;

[0010] Intelligent imaging system, which performs non-uniform resolution intelligent imaging based on the detection results of wide-width sea surface detection;

[0011] The SAR transmitting subsystem uses a phased array antenna to perform high-gain narrow beam scanning transmission over a wide area at a distance, covering a large range of sea surface areas;

[0012] The SAR receiving subsystem uses a multi-channel antenna to perform wide-band parallel reception of echo signals;

[0013] The SAR receiving subsystem is configured with a DBF processing module and a resource management and control processing module;

[0014] The SAR transmitting subsystem transmits signals based on the antenna beam parameters and transmission signal parameters fed back by the resource control processing module.

[0015] According to a technical solution of the present invention, the SAR transmitting subsystem performs high-gain narrow beam scanning transmission from far to near in a wide range in the range direction, and the number of wave positions scanned in the range direction is N. r The signal orthogonal processing is performed on each transmitting wave position and the adjacent pulse repetition period of the same wave position. Different wave positions transmit orthogonal signals with orthogonal frequencies or different frequency modulation polarities.

[0016] The adjacent 2 to 3 pulse repetition periods of any wave position at the far end transmit orthogonal signals with the same carrier frequency but different frequency modulation polarities and frequency modulation rates.

[0017] According to a technical solution of the present invention, the range receiving range of any receiving channel of the SAR receiving subsystem is greater than the total range width corresponding to all transmitting wave positions;

[0018] The receiving antenna of the SAR receiving subsystem adopts a unit-level array in the pitch direction, and the phase center spacing of the receiving channels is smaller than the wavelength.

[0019] According to a technical solution of the present invention, when the DBF processing module processes the SAR echo signal of each receiving channel, the weight is optimized for the grating lobe direction and the sub-satellite point direction within the width, and the null of the directional pattern is achieved at the corresponding angle;

[0020] The beam parameters of each receiving wave position processed by the DBF processing module are the same as the beam parameters of each transmitting wave position.

[0021] The beam parameters include at least the number, direction and width of the beam.

[0022] According to a technical solution of the present invention, the resource management and control processing module uses target information and satellite orbit information as input conditions and system resource constraints as boundary conditions to solve antenna beam parameters and transmission signal parameters;

[0023] The constructed evaluation function is used to evaluate the system performance, and the optimal antenna beam parameters and transmission signal parameters are iteratively obtained based on the parallel genetic optimization intelligent search method;

[0024] The optimized antenna beam parameters and transmission signal parameters are configured to the SAR transmitting subsystem and the SAR receiving subsystem.

[0025] According to a technical solution of the present invention, the parallel genetic optimization intelligent search method comprises:

[0026] Establish a multi-objective optimization problem model with image resolution, equivalent noise factor, peak / integrated sidelobe ratio and ambiguity as optimization objectives and evaluation functions, and power, beam position, time width and bandwidth as supporting domains;

[0027] Intelligent optimization algorithms such as parallel genetic algorithms are used to find the best antenna beam parameters and transmission signal parameters.

[0028] According to a technical solution of the present invention, the SAR transmitting subsystem transmits N r The transmission wave positions are scanned quickly from far to near, and the bandwidth and pulse width of each transmission wave position are B N and T N , N=1,2,…,N r ;

[0029] The transmitting wave position is divided into a secondary fuzzy wave position, a primary fuzzy wave position and an unfuzzy wave position;

[0030] For the secondary ambiguous wave position, the orthogonal signals within the three adjacent pulse repetition periods are designed to be positive frequency modulation, negative frequency modulation and variable frequency modulation signals in the same frequency band, and their expressions are as follows:

[0031] Positive frequency modulation: S1=A.exp{j[2πf1t+πK r t 2 +φ0]}, t∈(0,t p )

[0032] Negative frequency modulation: S2 = A.exp{j[2πf2t-πK r t 2 +φ0]}, t∈(0,t p )

[0033] Variable frequency modulation:

[0034] In the formula, A is the amplitude, f1 is the starting frequency, f2 is the ending frequency, K r is the modulation frequency, t p is the pulse width;

[0035] For an ambiguous wave position, the orthogonal signals within two adjacent pulse repetition periods are designed to be positive frequency modulation and negative frequency modulation signals in the same frequency band.

[0036] For unambiguous wave positions, the orthogonal signals within each pulse repetition period all use the same positive frequency modulation or negative frequency modulation signal or variable frequency modulation signal, and several different unambiguous wave positions can reuse the same frequency band.

[0037] According to a technical solution of the present invention, it also includes:

[0038] The orthogonal demodulation submodule and the bandpass filtering submodule in the SAR receiving subsystem, the N el The intermediate frequency SAR echo signal is intercepted into N according to the echo timing of each wave position. r The signal to be processed by the DBF processing module and the orthogonal demodulation submodule is mixed with the orthogonal demodulation. The data is band-pass filtered and down-sampled by the band-pass filter submodule to form N r Roadbed with echo signal.

[0039] According to a technical solution of the present invention, the wide sea surface detection system comprises a SAR signal imaging processing module and an RD imaging submodule. r The roadbed echo signal is cached and stacked, and the signal is imaged into N r images, each image is processed by N a Pulses are formed, and N rThe images are stitched together to obtain a wide detection image with full width.

[0040] According to a technical solution of the present invention, the intelligent imaging system controls the SAR transmitting subsystem to increase the allocation of bandwidth resources for key areas with more high-value ship targets to perform high-resolution imaging; and controls the SAR transmitting subsystem to reduce the allocation of bandwidth resources for medium-resolution imaging for non-key areas with fewer high-value ship targets.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The present invention proposes a large-width sea surface detection and non-uniform resolution intelligent imaging system based on dual-satellite SAR, which has the advantages of large width and high resource utilization, and is particularly suitable for large-scale sea surface ship target search and imaging.

[0043] The present invention utilizes two low-orbit satellites flying one after the other on the same orbit to form a dual-satellite SAR large-width sea surface detection system, and adopts a phased array antenna to perform high-gain narrow-beam scanning transmission in a large-width area to cover a large range of sea surface areas. Compared with the transmission method of covering a large range of sea surface with a wide beam, it has the advantage of high echo power density and can effectively reduce the requirements on the sensitivity of the receiving system.

[0044] The present invention adopts a multi-channel antenna to perform wide-band parallel reception and DBF processing on the echo signal, and adopts a combination of frequency domain orthogonality, frequency modulation polarity and variable modulation frequency coding to perform signal orthogonality design for each transmitting wave position and adjacent pulse repetition period of the same wave position, so as to avoid mutual interference between echo signals of different wave positions and adjacent periods, and realize large-scale sea surface ship target imaging.

[0045] In view of the sparse distribution characteristics of sea surface ship targets, the present invention adopts a parallel genetic optimization intelligent search method to allocate system resources such as beam width, transmission time width, and transmission bandwidth, thereby improving the utilization efficiency of system resources, realizing non-uniform resolution imaging of large-scale sea surface targets, and improving the imaging performance of key areas and key targets. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] 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 are briefly introduced below. 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.

[0047] Figure 1 A schematic diagram of a scenario of a large-width sea surface detection and non-uniform resolution intelligent imaging system based on dual-satellite SAR in one embodiment of the present invention;

[0048] Figure 2 A schematic diagram of the timing of transmitting and receiving signals at each wave position in an embodiment of the present invention;

[0049] Figure 3 A schematic diagram of the design of orthogonal signals of various types of wave positions in one embodiment of the present invention;

[0050] Figure 4 The data processing flow of a wide-width sea surface detection system in one embodiment of the present invention;

[0051] Figure 5 It is a resource intelligent management and control processing flow in one embodiment of the present invention;

[0052] Figure 6 The present invention is a flowchart of an imaging method implemented based on a dual-satellite SAR wide-width sea surface detection and non-uniform resolution intelligent imaging system in one embodiment of the present invention. DETAILED DESCRIPTION

[0053] The description of the embodiments of this specification should be combined with the corresponding drawings, which should be considered as part of the complete specification. In the drawings, the shape or thickness of the embodiments may be enlarged and indicated for simplification or convenience. Furthermore, the parts of each structure in the drawings will be described separately. It is worth noting that the elements not shown in the drawings or not described in words are in a form known to ordinary technicians in the relevant technical field.

[0054] The description of the embodiments herein and any reference to directions and orientations are only for the convenience of description and are not to be construed as any limitation on the scope of protection of the present invention. The following description of the preferred embodiments may involve combinations of features, which may exist independently or in combination, and the present invention is not particularly limited to the preferred embodiments. The scope of the present invention is defined by the claims.

[0055] like Figures 1 to 5 As shown, the present invention provides a dual-satellite SAR-based wide-width sea surface detection and non-uniform resolution intelligent imaging system, comprising:

[0056] A transmitting satellite equipped with a SAR transmitting subsystem, a receiving satellite equipped with a SAR receiving subsystem, and an intersatellite link between the transmitting satellite and the receiving satellite, wherein the transmitting satellite and the receiving satellite are two satellites flying in the same low orbit and following each other;

[0057] A large-scale wide sea surface detection system is used to perform large-scale wide sea surface detection based on the collected SAR echo signals;

[0058] Intelligent imaging system, which performs non-uniform resolution intelligent imaging based on the detection results of wide-width sea surface detection;

[0059] The SAR transmitting subsystem uses a phased array antenna to perform high-gain narrow beam scanning transmission over a wide area at a distance, covering a large range of sea surface areas;

[0060] The SAR receiving subsystem uses a multi-channel antenna to perform wide-band parallel reception of echo signals;

[0061] The SAR receiving subsystem is configured with a DBF processing module and a resource management and control processing module;

[0062] The SAR transmitting subsystem transmits signals based on the antenna beam parameters and transmission signal parameters fed back by the resource control processing module.

[0063] In some embodiments of the present invention, the SAR transmitting subsystem performs high-gain narrow beam scanning transmission from far to near in a wide range of distances. The scanning sequence from far to near can reduce the receiving time window of each wave position echo. Compared with the single wide beam transmission scheme commonly used in the existing system, the high-gain narrow beam scanning transmission can effectively improve the echo signal-to-noise ratio and reduce the performance requirements of the receiver;

[0064] The number of wave positions scanned in the range direction is N r The signal orthogonal processing is performed on each transmitting wave position and the adjacent pulse repetition period of the same wave position. Different wave positions transmit orthogonal frequencies or orthogonal signals with different frequency modulation polarities to avoid mutual interference between different wave positions.

[0065] In the adjacent 2 to 3 pulse repetition periods of any wave position at the far end, orthogonal signals with the same carrier frequency but different frequency modulation polarity and frequency modulation are transmitted to avoid mutual interference between echo signals of adjacent periods.

[0066] In some embodiments of the present invention, the range receiving range of any receiving channel of the SAR receiving subsystem is greater than the total range width corresponding to all transmission wave positions;

[0067] The receiving antenna of the SAR receiving subsystem adopts a unit-level array in the elevation direction, and the phase center spacing of the receiving channels is smaller than the wavelength, so that the grating lobes generated by the DBF are less.

[0068] In some embodiments of the present invention, when the DBF processing module processes the SAR echo signal of each receiving channel, the weight is optimized for the grating lobe direction and the sub-satellite point direction within the width, and the null of the directional pattern is achieved at the corresponding angle;

[0069] The beam parameters of each receiving wave position processed by the DBF processing module are the same as the beam parameters of each transmitting wave position.

[0070] The beam parameters include at least the number, direction and width of the beam.

[0071] In some embodiments of the present invention, the resource management and control processing module uses target information and satellite orbit information as input conditions and system resource constraints as boundary conditions to solve antenna beam parameters and transmission signal parameters;

[0072] The constructed evaluation function is used to evaluate the system performance, and the optimal antenna beam parameters and transmission signal parameters are iteratively obtained based on the parallel genetic optimization intelligent search method;

[0073] The optimized antenna beam parameters and transmission signal parameters are configured to the SAR transmitting subsystem and the SAR receiving subsystem.

[0074] In some embodiments of the present invention, the parallel genetic optimization intelligent search method includes:

[0075] Establish a multi-objective optimization problem model with image resolution, equivalent noise factor, peak / integrated sidelobe ratio and ambiguity as optimization objectives and evaluation functions, and power, beam position, time width and bandwidth as supporting domains;

[0076] Intelligent optimization algorithms such as parallel genetic algorithms are used to find the best antenna beam parameters and transmission signal parameters.

[0077] The parallel genetic optimization intelligent search method is used to allocate system resources such as beam width, transmission time width, and transmission bandwidth, and high-resolution imaging is performed on key areas, and medium-resolution imaging is performed on non-key areas, thereby improving the utilization efficiency of system resources and achieving non-uniform resolution imaging of wide-band sea targets. Compared with traditional satellite-borne SAR systems, this dual-satellite SAR wide-band imaging system has the advantages of large bandwidth and high resource utilization, and is very suitable for large-scale sea surface ship target search and imaging.

[0078] In some embodiments of the present invention, Figure 2 As shown in the figure, the transmitting star has a pulse repetition period (PRP) of N r The bandwidth and pulse width of each wave position are B N and T N , N=1,2,…,N r The echo signals of each transmitting wave position and the echo signals of adjacent periods of the same wave position received by the receiving satellite will fill the entire pulse repetition period. It is difficult to separate the echo signals of each wave position by relying solely on DBF processing. It is also necessary to perform signal orthogonal design for each transmitting wave position and the adjacent pulse repetition period of the same wave position.

[0079] like Figure 3 As shown, N rThe transmitting wave positions are divided into three categories: secondary ambiguous wave positions, which are at the farthest end of the entire width range. In the same receiving window, in addition to the expected echo period, two adjacent cycle signals are also received; primary ambiguous wave positions, which are at the farthest end of the entire width range. In the same receiving window, in addition to the expected echo period, one adjacent cycle signal is also received; unambiguous wave positions, which are at the near end of the entire width range. In the same receiving window, only the expected echo period is received.

[0080] For the secondary ambiguous wave position, the orthogonal signals within the three adjacent pulse repetition periods are designed to be positive frequency modulation, negative frequency modulation and variable frequency modulation signals in the same frequency band, and their expressions are as follows:

[0081] Positive frequency modulation: S1=A.exp{j[2πf1t+πK r t 2 +φ0]}, t∈(0,t p ) (1)

[0082] Negative frequency modulation: S2 = A.exp{j[2πf2t-πK r t 2 +φ0]}, t∈(0,t p ) (2)

[0083] Variable frequency modulation:

[0084] Among them, A is the amplitude, f1 is the starting frequency, f2 is the ending frequency, K r is the modulation frequency, t p is the pulse width;

[0085] For an ambiguous wave position, the orthogonal signals within two adjacent pulse repetition periods are designed to be positive frequency modulation and negative frequency modulation signals in the same frequency band, as shown in equations (1) and (2);

[0086] For unambiguous wave positions, the orthogonal signals within each pulse repetition period all use the same positive frequency modulation or negative frequency modulation signal or variable frequency modulation signal, and several different unambiguous wave positions can reuse the same frequency band.

[0087] In this embodiment, a combination of frequency domain orthogonality, frequency modulation polarity and variable frequency coding is adopted to perform signal orthogonality design for each transmitting wave position and adjacent pulse repetition periods of the same wave position, so as to avoid mutual interference between echo signals of different wave positions and adjacent periods.

[0088] In some embodiments of the present invention, Figure 4As shown in Figure 1, the data processing flow of the wide-band sea surface detection system includes the SAR signal preprocessing process and the SAR signal imaging detection process. The SAR signal preprocessing module includes the intermediate frequency DBF and orthogonal demodulation submodule and the bandpass filter submodule. This module first converts the N collected by the system into el The intermediate frequency echo signal of the channel is intercepted into N according to the echo timing of each wave position. r The signal to be processed is then processed by the intermediate frequency DBF and orthogonal demodulation submodule, and the data is mixed by DBF processing and orthogonal demodulation. Next, the data is bandpass filtered and downsampled by the bandpass filter submodule to form N r Roadbed with echo signal;

[0089] SAR signal imaging processing module, including N r A range Doppler (RD) imaging submodule, which first converts the preprocessed N r The roadbed echo signal is cached and stacked, and then the signal is imaged into N r images, each image is processed by N a Pulses are formed, and then N r The images are stitched together to obtain a wide detection image with full width.

[0090] In some embodiments of the present invention, Figure 5 As shown, the intelligent imaging system includes an input condition submodule, a system resource intelligent optimization processing submodule, a SAR system resource configuration submodule and a detection mode forming submodule.

[0091] The input condition submodule is used to input the orbit information of the transmitting and receiving satellites, as well as the target distribution information obtained by other detection means;

[0092] System resource intelligent optimization processing submodule, used to intelligently optimize antenna beam parameters and transmission signal parameters;

[0093] A SAR system resource configuration submodule, used to configure the optimized antenna beam parameters and transmission signal parameters to the SAR transmission electronic system and the SAR receiving electronic system;

[0094] The detection mode forming submodule is used to form the final non-uniform resolution imaging detection mode to achieve ultra-wide width non-uniform resolution imaging detection.

[0095] For key areas with more high-value ship targets, the SAR transmitting subsystem is controlled to increase the allocation of bandwidth resources, perform high-resolution imaging, and improve the target recognition capability; for non-key areas with fewer high-value ship targets, the SAR transmitting subsystem is controlled to reduce the allocation of bandwidth resources, perform medium-resolution imaging, and improve the utilization efficiency of bandwidth resources.

[0096] In the above-mentioned resource intelligent management and control process, a multi-objective optimization problem model is established with image resolution, equivalent noise factor (NESZ), peak / integrated sidelobe ratio and ambiguity as the main optimization objectives and evaluation functions, and resources such as power, wave position, time width and bandwidth as the supporting domains to make a trade-off between image resolution, equivalent noise factor (NESZ), peak / integrated sidelobe ratio and ambiguity.

[0097] like Figure 6 As shown, the imaging method implemented by the dual-satellite SAR wide-width sea surface detection and non-uniform resolution intelligent imaging system of the present invention comprises the following steps:

[0098] Step S1, determine whether there is prior information on the distribution of targets over a large sea surface, if yes, execute step S2, if no, execute step S3;

[0099] Step S2: intelligently optimizing the SAR transmitting subsystem and the SAR receiving subsystem based on the prior information;

[0100] Step S3, the receiving subsystem uses a multi-channel antenna to perform wide-band parallel reception and DBF processing on the echo signal to perform large-band wide sea surface detection;

[0101] Step S4: Based on the detection result of step S3, perform non-uniform resolution intelligent imaging.

[0102] In this embodiment, when there is prior information on the target distribution over a large wide sea surface (target distribution information obtained by other detection means), based on the orbital information of the transmitting satellite and the receiving satellite, the system resource intelligent optimization processing submodule is used to intelligently optimize the antenna beam parameters and the transmission signal parameters to obtain the optimal antenna beam parameters and the transmission signal parameters, and then the optimal antenna beam parameters and the transmission signal parameters are used to control the transmitting satellite to transmit the signal. Finally, the receiving satellite is used to receive the echo signal to perform large wide sea surface detection, and based on the echo signal, key areas with more high-value ship targets and non-key areas with fewer high-value ship targets are determined, and the intelligent imaging system is controlled to perform intelligent imaging according to the division of key areas and non-key areas.

[0103] In the absence of prior information, the SAR echo signals received by the receiving satellite can be directly used to conduct wide-area sea surface detection, determine key areas and non-key areas, and then perform intelligent imaging.

[0104] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. It can also be a reasonable combination of the features recorded in the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A wide-band sea surface detection and non-uniform resolution intelligent imaging system based on dual-satellite SAR, characterized in that: include: A transmitting satellite equipped with a SAR transmitting subsystem, a receiving satellite equipped with a SAR receiving subsystem, and an intersatellite link between the transmitting satellite and the receiving satellite, wherein the transmitting satellite and the receiving satellite are two satellites flying in the same low orbit and following each other; A large-scale wide sea surface detection system is used to perform large-scale wide sea surface detection based on the collected SAR echo signals; Intelligent imaging system, which performs non-uniform resolution intelligent imaging based on the detection results of wide-width sea surface detection; The SAR transmitting subsystem uses a phased array antenna to perform high-gain narrow beam scanning transmission over a wide area at a distance, covering a large range of sea surface areas; The SAR receiving subsystem uses a multi-channel antenna to perform wide-band parallel reception of echo signals; The SAR receiving subsystem is configured with a DBF processing module and a resource management and control processing module; The SAR transmitting subsystem transmits signals based on the antenna beam parameters and transmission signal parameters fed back by the resource control processing module.

2. The dual-satellite SAR large-width sea surface detection and non-uniform resolution intelligent imaging system according to claim 1 is characterized in that: The SAR transmitting subsystem performs high-gain narrow beam scanning transmission from far to near in a wide range in the range direction, and the number of wave positions scanned in the range direction is N r The signal orthogonal processing is performed on each transmitting wave position and the adjacent pulse repetition period of the same wave position. Different wave positions transmit orthogonal signals with orthogonal frequencies or different frequency modulation polarities. The adjacent 2 to 3 pulse repetition periods of any wave position at the far end transmit orthogonal signals with the same carrier frequency but different frequency modulation polarities and frequency modulation rates.

3. The dual-satellite SAR large-width sea surface detection and non-uniform resolution intelligent imaging system according to claim 2 is characterized in that: The range receiving range of any receiving channel of the SAR receiving subsystem is greater than the total range width corresponding to all transmitting wave positions; The receiving antenna of the SAR receiving subsystem adopts a unit-level array in the pitch direction, and the phase center spacing of the receiving channels is smaller than the wavelength.

4. The dual-satellite SAR large-width sea surface detection and non-uniform resolution intelligent imaging system according to claim 1 is characterized in that: When the DBF processing module processes the SAR echo signals of each receiving channel, the weights are optimized for the grating lobe direction and the sub-satellite point direction within the width, and the null of the directional pattern is achieved at the corresponding angle; The beam parameters of each receiving wave position processed by the DBF processing module are the same as the beam parameters of each transmitting wave position. The beam parameters include at least the number, direction and width of the beam.

5. The dual-satellite SAR large-width sea surface detection and non-uniform resolution intelligent imaging system according to claim 1 is characterized in that: The resource control processing module uses target information and satellite orbit information as input conditions and system resource constraints as boundary conditions to solve antenna beam parameters and transmission signal parameters; The constructed evaluation function is used to evaluate the system performance, and the optimal antenna beam parameters and transmission signal parameters are iteratively obtained based on the parallel genetic optimization intelligent search method; The optimized antenna beam parameters and transmission signal parameters are configured to the SAR transmitting subsystem and the SAR receiving subsystem.

6. The dual-satellite SAR large-width sea surface detection and non-uniform resolution intelligent imaging system according to claim 5 is characterized in that: The parallel genetic optimization intelligent search method comprises: Establish a multi-objective optimization problem model with image resolution, equivalent noise factor, peak / integrated sidelobe ratio and ambiguity as optimization objectives and evaluation functions, and power, beam position, time width and bandwidth as supporting domains; Intelligent optimization algorithms such as parallel genetic algorithms are used to find the best antenna beam parameters and transmission signal parameters.

7. The dual-satellite SAR large-width sea surface detection and non-uniform resolution intelligent imaging system according to claim 1 is characterized in that: The SAR transmitting subsystem transmits N r The transmission wave positions are scanned quickly from far to near, and the bandwidth and pulse width of each transmission wave position are B N and T N , N=1,2,…,N r ; The transmitting wave position is divided into a secondary fuzzy wave position, a primary fuzzy wave position and an unfuzzy wave position; For the secondary ambiguous wave position, the orthogonal signals within the three adjacent pulse repetition periods are designed to be positive frequency modulation, negative frequency modulation and variable frequency modulation signals in the same frequency band, and their expressions are as follows: Positive frequency modulation: S1=A.exp{j[2πf1t+πK r t 2 +φ0]}, t∈(0,t p ) Negative frequency modulation: S2 = A.exp{j[2πf2t-πK r t 2 +φ0]}, t∈(0,t p ) Variable frequency modulation: In the formula, A is the amplitude, f1 is the starting frequency, f2 is the ending frequency, K r is the modulation frequency, t p is the pulse width; For an ambiguous wave position, the orthogonal signals within two adjacent pulse repetition periods are designed to be positive frequency modulation and negative frequency modulation signals in the same frequency band. For unambiguous wave positions, the orthogonal signals within each pulse repetition period all use the same positive frequency modulation or negative frequency modulation signal or variable frequency modulation signal, and several different unambiguous wave positions can reuse the same frequency band.

8. The dual-satellite SAR large-width sea surface detection and non-uniform resolution intelligent imaging system according to claim 1 is characterized in that: Also includes: The orthogonal demodulation submodule and the bandpass filtering submodule in the SAR receiving subsystem, the N el The intermediate frequency SAR echo signal is intercepted into N according to the echo timing of each wave position. r The signal to be processed by the DBF processing module and the orthogonal demodulation submodule is mixed with the orthogonal demodulation. The data is band-pass filtered and down-sampled by the band-pass filter submodule to form N r Roadbed with echo signal.

9. The dual-satellite SAR large-width sea surface detection and non-uniform resolution intelligent imaging system according to claim 8, characterized in that: The large-width sea surface detection system includes a SAR signal imaging processing module and an RD imaging submodule. r The roadbed echo signal is cached and stacked, and the signal is imaged into N r images, each image is processed by N a Pulses are formed, and N r The images are stitched together to obtain a wide detection image with full width.

10. The dual-satellite SAR large-width sea surface detection and non-uniform resolution intelligent imaging system according to claim 9, characterized in that: The intelligent imaging system controls the SAR transmitting subsystem to increase the allocation of bandwidth resources for key areas with more high-value ship targets to perform high-resolution imaging; and controls the SAR transmitting subsystem to reduce the allocation of bandwidth resources for medium-resolution imaging for non-key areas with fewer high-value ship targets.

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