A novel bi-static SAR target localization system and method

Abstract

This invention proposes a target localization method and system based on bistatic SAR, comprising: a radar transmitter, a radar receiver, and an image processing center mounted on two moving platforms; the image processing center includes: a position and attitude information recording module, a bistatic SAR imaging processing and back-projection geometric correction module, an image center slant range calculation module, a receiver-image center distance calculation module, a target detection module, and a target position calculation module; the position and attitude information recording module is used to acquire and record the attitude information of the moving platforms and two frames of bistatic SAR images at two consecutive synthetic apertures; the bistatic SAR imaging processing and back-projection geometric correction module performs geometric correction on the images; the image center slant range calculation module is used to calculate the slant range between the target and the moving platforms, and the receiver-image center distance calculation module calculates the target slant range; the target position calculation module outputs the target's range, azimuth, elevation, and position information.

Description

Technical Field

[0001] This invention belongs to the field of target positioning technology of imaging radar, and particularly relates to a novel bistatic SAR target positioning system and positioning method. Background Technology

[0002] Bi-static synthetic aperture radar (SAR) such as Figure 1 As shown, by placing the radar transmitting and receiving antennas on two cooperative moving platforms, the application range of monostatic SAR is expanded. It can perform high-resolution imaging of targets directly in front, fill the inherent defects of monostatic SAR radar, and enable bistatic SAR to play an important role in fields such as battlefield reconnaissance, disaster detection, material delivery, and airport blind landing.

[0003] Some applications of bistatic SAR require target localization within images. Currently, a common localization method is based on image matching point information. This method first finds pre-selected image matching points in the bistatic SAR image to determine the location information of these points, then calculates the relative positional relationship between the target and the image matching points, thereby calculating the target's location information.

[0004] However, in many situations, such as ships in vast ocean areas, the lack of definite image matching points renders image-matching point-based positioning methods ineffective. Some published bistatic forward-looking SAR target positioning methods are only applicable when the target is located directly below and in front of the receiving radar, lacking universal applicability. Therefore, designing a novel bistatic SAR target positioning method is of great significance. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention proposes a bistatic SAR target positioning system, which includes: a radar transmitter set on a first motion platform, a radar receiver set on a second motion platform, and an image processing center, wherein the image processing center processes the signal received by the radar receiver.

[0006] The image processing center includes: a position and attitude information recording module 1, a dual-base SAR imaging processing and back-projection geometric correction module 2, an image center slant range and calculation module 3, a receiver-to-image center distance calculation module 4, a target detection module 5, and a target position calculation module 6.

[0007] The position and attitude information recording module is used to acquire and record the attitude information of the first motion platform and the second motion platform during two consecutive synthetic aperture times. The position and attitude information recording module is also used to acquire and record two frames of bistatic SAR images during the two consecutive synthetic aperture times.

[0008] The bistatic SAR imaging processing and back-projection geometric correction module is used to perform geometric correction on the two frames of bistatic SAR images;

[0009] The image center slant range and calculation module is used to calculate the sum of the slant ranges between the target and the first motion platform and the second motion platform in the two frames of bistatic SAR images, and output the calculation results;

[0010] The receiver and image center distance calculation module calculate the slant distance information between the second motion platform and the target according to the spatial geometric configuration based on the position of the second motion platform, the slant distance of the image center, and the calculation results output by the calculation module.

[0011] The target detection module outputs the position information of the target relative to the second motion platform;

[0012] The target position calculation module calculates the target's azimuth and pitch information based on the target's position information relative to the second motion platform, and outputs the target's azimuth, pitch, and position information relative to the second motion platform.

[0013] Furthermore, the position and attitude information calculation module records the position, velocity, and angle information of the first and second motion platforms of the bistatic SAR at different times.

[0014] Furthermore, the bistatic SAR imaging processing and back-projection geometric correction module performs imaging processing and geometric correction on two frames of radar echoes acquired at different times according to a predetermined algorithm, thereby obtaining the ground distance of the two frames of bistatic SAR images of the detection area.

[0015] Furthermore, the first motion platform includes a radar transmitting antenna disposed on the first motion platform, and the second motion platform includes a radar receiving antenna disposed on the second motion platform.

[0016] Furthermore, both the first motion platform and the second motion platform are in motion during the time period of positioning the target.

[0017] This invention also proposes a bistatic SAR target localization method, which is implemented based on the aforementioned target localization system, and the method includes the following steps:

[0018] Step 1: Deploy the bistatic SAR target positioning system by placing the radar transmitter and radar transmitting antenna on the first moving platform; and placing the image processing center, radar receiver, and radar receiving antenna on the second moving platform.

[0019] Establish communication connections between the radar transmitter, the radar receiver, and the image processing center, and perform radar system initialization and time synchronization;

[0020] Step 2: The first motion platform and the second motion platform move along a predetermined direction, and the radar receiver on the second motion platform receives: the attitude information of the first motion platform and the second motion platform for two consecutive synthetic aperture times, and two frames of bistatic SAR image signals for the two consecutive synthetic aperture times; and sends the attitude information and the bistatic SAR image signals to the position and attitude information recording module.

[0021] Step 3: The bistatic SAR imaging processing and back-projection geometric correction module performs geometric correction on the two bistatic SAR images based on the recorded two frames of bistatic SAR images;

[0022] Step 4: The image center slant range calculation module calculates the sum of the slant ranges between the target and the first and second motion platforms in the two frames of bistatic SAR images based on the attitude information signals acquired and recorded in Step 3 and the two frames of bistatic SAR images, and outputs the calculation results.

[0023] Step 5: The receiver and image center distance calculation module calculate the slant distance information between the second motion platform and the target according to the spatial geometric configuration based on the calculation results output in step 4.

[0024] Step 6: The target detection module outputs the position information of the target relative to the second motion platform;

[0025] Step 7: The target position calculation module calculates the target's range, azimuth, and pitch information, and outputs the target's range, azimuth, pitch, and position information relative to the second motion platform.

[0026] Furthermore, the position and attitude information recording module records the position, velocity, and angle information of the first motion platform and the second motion platform of the bistatic SAR target positioning system at different times.

[0027] Furthermore, the target position calculation module calculates the distance, azimuth, and pitch angle of the target relative to the second motion platform based on the preset positioning geometry, thus completing the positioning calculation.

[0028] Furthermore, the receiver and image center distance calculation module calculate the distance between the second motion platform and the target based on the preset positioning geometry.

[0029] Furthermore, both the first motion platform and the second motion platform are in motion during the time period of positioning the target.

[0030] The method of this invention comprehensively utilizes the results of two target imaging detections and combines them with the geometric configuration parameters of the dual-base detection imaging to calculate the target position information, making the method adaptable to the target positioning requirements in most cases. Attached Figure Description

[0031] Figure 1 This is an imaging detection configuration diagram;

[0032] Figure 2 This is a flowchart of the target localization solution process;

[0033] Figure 3 It is a target location solution combined with a configuration diagram. Detailed Implementation

[0034] In order to overcome the steps of the prior art, the purpose of this invention is to design a novel bistatic SAR target localization method to solve the target localization problem in bistatic SAR images.

[0035] The method of this invention establishes a coordinate system with the nadir point of the bistatic SAR receiver as the origin, such as... Figure 1 As shown. Receiver along The transmitter moves along the axis. Axis motion. During imaging, the receiver's positions at the center of the two synthetic apertures, T1 and T2, are A and B, respectively. The angles between the receiver's beamline and the radar platform's velocity direction at T1 and T2 are a and b, respectively. The transmitter's positions at T1 and T2 are C and D, respectively. The angles between the transmitter's beamline and the radar platform's velocity direction are c and d, respectively. The center of the image scene in both imaging processes is the focal point S between the transmitter and receiver's beam centers and the ground. The receiver's beam grazing angle at T2 is γ.

[0036] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0037] This invention proposes a bistatic SAR target positioning system, which includes: a radar transmitter mounted on a first motion platform, a radar receiver mounted on a second motion platform, and an image processing center, wherein the image processing center processes the signals received by the radar receiver.

[0038] The image processing center includes: a position and attitude information recording module 1, a dual-base SAR imaging processing and back-projection geometric correction module 2, an image center slant range and calculation module 3, a receiver-to-image center distance calculation module 4, a target detection module 5, and a target position calculation module 6.

[0039] The position and attitude information recording module is used to acquire and record the attitude information of the first motion platform and the second motion platform during two consecutive synthetic aperture times. The position and attitude information recording module is also used to acquire and record two frames of bistatic SAR images during the two consecutive synthetic aperture times.

[0040] The bistatic SAR imaging processing and back-projection geometric correction module is used to perform geometric correction on the two frames of bistatic SAR images;

[0041] The image center slant range and calculation module is used to calculate the sum of the slant ranges between the target and the first motion platform and the second motion platform in the two frames of bistatic SAR images, and output the calculation results;

[0042] The receiver and image center distance calculation module calculate the slant distance information between the second motion platform and the target according to the spatial geometric configuration based on the position of the second motion platform, the slant distance of the image center, and the calculation results output by the calculation module.

[0043] The target detection module outputs the position information of the target relative to the second motion platform;

[0044] The target position calculation module calculates the target's azimuth and pitch information based on the target's position information relative to the second motion platform, and outputs the target's azimuth, pitch, and position information relative to the second motion platform.

[0045] Furthermore, the position and attitude information calculation module records the position, velocity, and angle information of the first and second motion platforms of the bistatic SAR at different times.

[0046] Furthermore, the bistatic SAR imaging processing and back-projection geometric correction module performs imaging processing and geometric correction on two frames of radar echoes acquired at different times according to a predetermined algorithm, thereby obtaining the ground distance of the two frames of bistatic SAR images of the detection area.

[0047] Furthermore, the first motion platform includes a radar transmitting antenna disposed on the first motion platform, and the second motion platform includes a radar receiving antenna disposed on the second motion platform.

[0048] Furthermore, both the first motion platform and the second motion platform are in motion during the time period of positioning the target.

[0049] This invention also proposes a bistatic SAR target localization method, which is implemented based on the aforementioned target localization system, and the method includes the following steps:

[0050] Step 1: Deploy the bistatic SAR target positioning system by placing the radar transmitter and radar transmitting antenna on the first moving platform; and placing the image processing center, radar receiver, and radar receiving antenna on the second moving platform.

[0051] Establish communication connections between the radar transmitter, the radar receiver, and the image processing center, and perform radar system initialization and time synchronization;

[0052] Step 2: The first motion platform and the second motion platform move along a predetermined direction, and the radar receiver on the second motion platform receives: the attitude information of the first motion platform and the second motion platform for two consecutive synthetic aperture times, and two frames of bistatic SAR image signals for the two consecutive synthetic aperture times; and sends the attitude information and the bistatic SAR image signals to the position and attitude information recording module.

[0053] Specifically, the position and attitude information recording module 1 records the position, velocity, and angle of the bistatic SAR radar transmitter and receiver at times T1 and T2, respectively: the transmitter's position at time T1 is (tx1, ty1, tz1), and the transmitter's position at time T2 is (tx2, ty2, tz2); the receiver's position at time T1 is (rx1, ry1, rz1), and the receiver's position at time T2 is (rx2, ry2, rz2); the transmitter's velocity at time T1 is (Vtx1, Vty1, Vt). The transmitter's velocity at time T1 is (Vtx2, Vty2, Vtz2), the receiver's velocity at time T2 is (Vrx1, Vry1, Vrz1), the transmitter's velocity at time T2 is (Vrx2, Vry2, Vrz2), the angle between the transmitter's motion direction and the beam direction at time T1 is a, the angle between the transmitter's motion direction and the beam direction at time T2 is b, the angle between the receiver's motion direction and the beam direction at time T1 is c, and the angle between the receiver's motion direction and the beam direction at time T2 is d.

[0054] Step 3: The bistatic SAR imaging processing and back-projection geometric correction module performs geometric correction on the two bistatic SAR images based on the recorded two-frame bistatic SAR image signals;

[0055] The dual-base SAR imaging processing and back-projection geometric correction module 2 uses industry-standard algorithms to process and geometrically correct the two acquired radar echo frames, obtaining two ground distance images of the detection area. The image target detection module 5 performs target detection based on the ground distance image at time T2, outputting the target's position (Δx, Δy) relative to the image center. The image center slant distance calculation module 3 calculates the image center slant distance sum at times T1 and T2 based on the two ground distance images.

[0056] R1 = R t1 +Rr1 (1)

[0057] R2 = R t2 +R r2 (2)

[0058] Where R t1 Let R be the distance between the transmitter and the center of the image scene at time T1. r1 Let R1 be the distance between the receiver and the center of the imaged scene at time T1, and R1 be the sum of the distances at time T1. t2 Let R be the distance between the transmitter and the center of the image scene at time T2. r2 R2 is the distance between the receiver and the center of the imaging scene at time T2, and R2 is the sum of the distances at time T2.

[0059] Step 4: The image center slant range calculation module calculates the sum of the slant ranges between the target and the first and second motion platforms in the two frames of bistatic SAR images based on the attitude information signals and the two frames of bistatic SAR image signals acquired and recorded in Step 3, and outputs the calculation results.

[0060] The specific calculation method is as follows: the distance calculation module 4 between the receiver and the image center is as follows: Figure 1 Based on the detection geometry shown, the distance between the decoupled receiver and the image center is calculated using the following formula:

[0061]

[0062] Here, α and β are temporary variables;

[0063]

[0064] γ is the angle between the receiver beam and the ground, also known as the ground grazing angle; κ is a temporary variable; Δx is the distance of the target point relative to the center of the scene in the x-direction; Rrp is the target distance, Rrb is the distance to the center of the scene; Δy is the distance of the target point relative to the center of the scene in the y-direction.

[0065] Step 5: The receiver and image center distance calculation module calculate the slant distance information between the second motion platform and the target according to the spatial geometric configuration based on the calculation results output in step 5.

[0066] Step 6: The target detection module outputs the position information of the target relative to the second motion platform;

[0067] Step 7: The target position calculation module calculates the target's range, azimuth, and pitch information, and outputs the target's range, azimuth, pitch, and position information relative to the second motion platform.

[0068] Furthermore, the position and attitude information recording module records the position, velocity, and angle information of the first motion platform and the second motion platform of the bistatic SAR target positioning system at different times.

[0069] Furthermore, the target position calculation module calculates the distance, azimuth, and pitch angle of the target relative to the second motion platform based on the preset positioning geometry, thus completing the positioning calculation.

[0070] Furthermore, the receiver and image center distance calculation module calculate the distance between the second motion platform and the target based on the preset positioning geometry.

[0071] Furthermore, both the first and second motion platforms are in motion during the target positioning time. The method of this invention establishes a coordinate system with the nadir point of the bistatic SAR receiver as the origin, such as... Figure 1 As shown. Receiver along The transmitter moves along the axis. Axis motion. During imaging, the receiver's positions at the center of the two synthetic apertures (T1 and T2) are A and B, respectively, and the angles between the receiver's beamline and the radar platform's velocity direction at T1 and T2 are a and b, respectively. The transmitter's positions at T1 and T2 are C and D, respectively, and the angles between the beamline and the radar platform's velocity direction are c and d, respectively. The center of the image scene for both imaging sessions is the focal point S between the transmitter and receiver's beam centers and the ground, and the receiver's beam grazing angle at T2 is γ.

[0072] The present invention will now be described in further detail with reference to the accompanying drawings:

[0073] A bistatic SAR target localization method is designed, such as Figure 2 As shown in the flowchart, it consists of a position and attitude information recording module 1, a dual-base SAR imaging processing and back-projection geometric correction module 2, an image center slant range and calculation module 3, a receiver-to-image center distance calculation module 4, an image target detection module 5, and a target position information calculation module 6.

[0074] Position and attitude information recording module 1 records the position, velocity, and angle of the bistatic SAR radar transmitter and receiver at times T1 and T2, respectively: the transmitter's position at time T1 is (tx1, ty1, tz1), and the transmitter's position at time T2 is (tx2, ty2, tz2); the receiver's position at time T1 is (rx1, ry1, rz1), and the receiver's position at time T2 is (rx2, ry2, rz2); the transmitter's velocity at time T1 is (Vtx1, Vty1, Vtz1). At time T2, the transmitter's velocity is (Vtx2, Vty2, Vtz2), and at time T1, the receiver's velocity is (Vrx1, Vry1, Vrz1). At time T2, the transmitter's velocity is (Vrx2, Vry2, Vrz2). At time T1, the angle between the transmitter's motion direction and the beam direction is a, at time T2, the angle between the transmitter's motion direction and the beam direction is b, at time T1, the angle between the receiver's motion direction and the beam direction is c, and at time T2, the angle between the receiver's motion direction and the beam direction is d.

[0075] The dual-base SAR imaging processing and back-projection geometric correction module 2 uses industry-standard algorithms to process and geometrically correct the two acquired radar echo frames, obtaining two ground distance images of the detection area. The image target detection module 5 performs target detection based on the ground distance image at time T2, outputting the target's position (Δx, Δy) relative to the image center. The image center slant distance calculation module 3 calculates the image center slant distance sum at times T1 and T2 based on the two ground distance images.

[0076] R1 = R t1 +R r1 (6)

[0077] R2 = R t2 +R r2 (7)

[0078] Where R t1 Let R be the distance between the transmitter and the center of the image scene at time T1. r1 Let R1 be the distance between the receiver and the center of the imaged scene at time T1, and R1 be the sum of the distances at time T1. t2 Let R be the distance between the transmitter and the center of the image scene at time T2. r2 R2 is the distance between the receiver and the center of the imaging scene at time T2, and R2 is the sum of the distances at time T2.

[0079] Receiver and image center distance calculation module 4 as follows Figure 1 and Figure 3 Based on the detection geometry shown, the distance between the decoupled receiver and the image center is calculated using the following formula:

[0080]

[0081] Here, α and β are temporary variables;

[0082]

[0083] γ is the angle between the receiver beam and the ground, also known as the ground grazing angle; κ is a temporary variable; Δx is the distance of the target point relative to the center of the scene in the x-direction; Rrp is the target distance, Rrb is the distance to the center of the scene; Δy is the distance of the target point relative to the center of the scene in the y-direction.

[0084] Based on two consecutively detected bistatic SAR images, this invention fully utilizes the geometric configuration information established in space by the radar transmitter and receiver to calculate the distance between the receiver and the center of the detected image scene with high precision, thereby performing target localization calculation.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the present invention and are not intended to limit them. Although the embodiments of the present invention have been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the embodiments of the present invention should not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A bistatic SAR target positioning system, characterized in that, The bi-base SAR target positioning system includes: a radar transmitter mounted on a first motion platform, a radar receiver mounted on a second motion platform, and an image processing center, wherein the image processing center processes the signals received by the radar receiver; The image processing center includes: a position and attitude information recording module (1), a dual-base SAR imaging processing and back projection geometric correction module (2), an image center slant range and calculation module (3), a receiver and image center distance calculation module (4), a target detection module (5), and a target position calculation module (6); The position and attitude information recording module is used to acquire and record the attitude information of the first motion platform and the second motion platform during two consecutive synthetic aperture times. The position and attitude information recording module is also used to acquire and record two frames of bistatic SAR images during the two consecutive synthetic aperture times. The position and attitude information calculation module records the position, velocity and angle information of the first motion platform and the second motion platform of the bistatic SAR at different times. The bistatic SAR imaging processing and back-projection geometric correction module is used to perform geometric correction on the two frames of bistatic SAR images; The image center slant range and calculation module is used to calculate the sum of the slant ranges between the target and the first motion platform and the second motion platform in the two frames of bistatic SAR images, and output the calculation results; The receiver and image center distance calculation module calculate the slant distance information between the second motion platform and the target according to the spatial geometric configuration based on the position of the second motion platform, the slant distance of the image center, and the calculation results output by the calculation module. The target detection module outputs the position information of the target relative to the second motion platform; The target position calculation module calculates the target's range, azimuth, and pitch information based on the target's position information relative to the second motion platform. The target's range, azimuth, and pitch information are determined by the following formulas: Where γ is the angle between the receiver beam and the ground, also known as the ground grazing angle; κ is a temporary variable; Δx is the distance of the target point relative to the center of the scene in the x-direction; R rp R is the target distance. rb It is the distance from the center of the scene; R r2 At time T2, Δy is the distance between the receiver and the center S of the imaging scene; Δy is the distance of the target point relative to the center of the scene in the y-direction. It also outputs the target's distance, azimuth, pitch, and position information relative to the second motion platform.

2. The system as described in claim 1, characterized in that, The bistatic SAR imaging processing and back-projection geometric correction module performs imaging processing and geometric correction on two frames of radar echoes acquired at different times according to a predetermined algorithm, thereby obtaining the ground distance of the two frames of bistatic SAR images of the detection area.

3. The system as described in claim 1, characterized in that, The first motion platform includes a radar transmitting antenna disposed on the first motion platform, and the second motion platform includes a radar receiving antenna disposed on the second motion platform.

4. The system as described in claim 1, characterized in that, Both the first motion platform and the second motion platform are in motion during the time period of positioning the target.

5. A target localization method for bistatic SAR, characterized in that, The target localization method is implemented based on the bistatic SAR target localization system according to any one of claims 1-4, and the method includes the following steps: Step 1: Deploy the bistatic SAR target positioning system by placing the radar transmitter and radar transmitting antenna on the first moving platform; and placing the image processing center, radar receiver, and radar receiving antenna on the second moving platform. Establish communication connections between the radar transmitter, the radar receiver, and the image processing center, and perform radar system initialization and time synchronization; Step 2: The first motion platform and the second motion platform move along predetermined directions respectively. The radar receiver on the second motion platform receives: the attitude information of the first motion platform and the second motion platform for two consecutive synthetic aperture times, and two frames of bistatic SAR image signals for the two consecutive synthetic aperture times; and sends the attitude information and the bistatic SAR image signals to the position and attitude information recording module; the position and attitude information recording module records the position, velocity and angle information of the first motion platform and the second motion platform of the bistatic SAR target positioning system at different times. Step 3: The bistatic SAR imaging processing and back-projection geometric correction module performs geometric correction on the two bistatic SAR images based on the recorded two frames of bistatic SAR images; Step 4: The image center slant range calculation module calculates the sum of the slant ranges between the target and the first and second motion platforms in the two frames of bistatic SAR images based on the attitude information signals acquired and recorded in Step 3 and the two frames of bistatic SAR images, and outputs the calculation results. Step 5: The receiver and image center distance calculation module calculate the slant distance information between the second motion platform and the target according to the spatial geometric configuration based on the calculation results output in step 4. Step 6: The target detection module outputs the position information of the target relative to the second motion platform; Step 7: The target position calculation module calculates the target's range, azimuth, and pitch information, and outputs the target's range, azimuth, pitch, and position information relative to the second motion platform.

6. The method as described in claim 5, characterized in that, The target position calculation module calculates the distance, azimuth, and pitch angle of the target relative to the second motion platform based on the preset positioning geometry, thus completing the positioning calculation.

7. The method as described in claim 5, characterized in that, The receiver and image center distance calculation module calculate the distance between the second motion platform and the target based on the preset positioning geometry.

8. The method as described in claim 5, characterized in that, Both the first motion platform and the second motion platform are in motion during the time period of positioning the target.

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