A GEO-based optimal resolution-based GEO satellite-ground bistatic SAR aperture optimization method and device

Abstract

The present application belongs to synthetic aperture radar technical field, especially to a kind of GEO star ground bistatic SAR aperture optimization method and device based on resolution optimum, the specific process of this method is as follows: based on the resolution ellipse obtained by multiplying two main lobes when GEO star ground bistatic SAR two-dimensional imaging, construct resolution ellipse long axis model;Select core imaging area, according to ground plane range resolution and azimuth resolution, construct ground plane range and azimuth resolution mean model of core imaging area;Set the traversal step of trajectory, traverse to obtain the long axis of ellipse and resolution mean of full track section, select trajectory section that meets the requirement of set long axis of ellipse and resolution mean;Set two constraint conditions of core imaging area without blur and GEO star ground bistatic SAR visibility, complete imaging arc segment final selection using constraint condition, thus complete imaging aperture optimization based on double constraint joint screening.

Description

Technical Field

[0001] This invention belongs to the field of synthetic aperture radar technology, and particularly relates to a method and apparatus for optimal selection of GEO bistatic SAR aperture based on resolution optimization. Background Technology

[0002] Bistatic Synthetic Aperture Radar (SS-BiSAR), as a novel Earth observation technology, employs a heterogeneous architecture of space-based transmission and ground-based reception to achieve separate signal transmission and reception. Currently, the verification of this technology is mainly based on two types of space platforms: navigation and communication satellites (such as GNSS systems like BeiDou and Galileo) and low-Earth orbit SAR satellites (such as the LT-1 series). However, both types of platforms have significant limitations: low-Earth orbit SAR satellites are constrained by orbital mechanics, resulting in low observation frequency and narrow coverage for their bistatic systems; while navigation satellites, limited by narrowband signal characteristics and low-power radiation, suffer from technical bottlenecks such as insufficient signal-to-noise ratio and limited spatial resolution in radar images.

[0003] It is noteworthy that high-orbit SAR platforms deployed in geosynchronous orbit (GEO, at an altitude of approximately 36,000 kilometers) exhibit unique advantages—their orbital characteristics can significantly improve observation timeliness and expand imaging coverage. Based on this, constructing a dual-base, space-to-ground collaborative observation system dominated by high-orbit SAR provides a solution for overcoming existing technological bottlenecks.

[0004] However, the orbital characteristics of GEO bistatic SAR significantly impact the observational performance of the system. On one hand, the unique spatial geometry caused by orbital altitude makes the Earth's rotation effect unmanageable, resulting in time-varying slant angles in the bistatic slant range geometry. This causes non-orthogonal distortions in the azimuth and range resolution axes, rendering traditional two-dimensional resolution analysis methods based on short-term observation assumptions theoretically inapplicable. On the other hand, the slant range variation gradients corresponding to different GEO bistatic SAR trajectory segments differ, and the selection of these trajectory segments significantly affects the imaging resolution and ambiguity of the system. Therefore, establishing a strongly coupled model between the GEO bistatic SAR orbit and system parameters under long-term observation, solving the problem of dynamic selection of the optimal imaging aperture and joint optimization of system parameters under long-term observation, and achieving intelligent optimization of the imaging aperture segment are the main technical challenges faced by GEO bistatic SAR systems in practical experimental design. Summary of the Invention

[0005] In view of this, the present invention provides a method and apparatus for optimal aperture selection of GEO bistatic SAR based on resolution. The method constructs a resolution ellipse major axis model and a core region resolution mean model of the GEO bistatic SAR system, and performs systematic analysis of the full-orbit data based on the joint optimization criteria of the resolution ellipse major axis index and the core region resolution mean index.

[0006] The technical solution for implementing the present invention is as follows:

[0007] In a first aspect, the present invention provides a method for optimizing the aperture of a GEO bistatic SAR system based on optimal resolution, the specific process of which is as follows:

[0008] Constructing a resolution ellipse major axis model: Based on the resolution ellipse obtained by multiplying the two main lobes during GEO bistatic SAR two-dimensional imaging, a resolution ellipse major axis model is constructed.

[0009] Constructing a resolution mean model: Select the core imaging region, and construct a resolution mean model of the core imaging region in the ground plane range direction and azimuth direction based on the ground plane range resolution and azimuth resolution;

[0010] Initial selection of imaging arc segments: Set the traversal step size of the trajectory, and according to the resolution ellipse major axis model and resolution mean model, traverse to obtain the ellipse major axis and resolution mean corresponding to all trajectory segments, and select the trajectory segments that meet the set requirements of ellipse major axis and resolution mean.

[0011] Imaging aperture optimization: Two constraints are set: no ambiguity in the core imaging area and GEO bistatic SAR visibility. From the initially selected trajectory segments, trajectory segments that meet the two constraints are selected, thereby completing the imaging aperture optimization based on dual constraint joint screening.

[0012] Optionally, the resolution ellipse model obtained by multiplying the two main lobes during GEO bistatic SAR two-dimensional imaging, as described in this invention, is constructed using the following process:

[0013] To obtain the resolution ellipse after multiplying the two main lobes in a two-dimensional image, the -3dB contour lines of the two main lobes are denoted as... , and , The width of the two main lobes is denoted as and ;

[0014] Let the center of the parallelogram formed by the -3dB isopleths of the two main lobes be denoted as . ,from Draw a point perpendicular to The straight line intersects the contour lines. At The intersection resolution ellipse is at ,get and The ratio is: , This represents the angle between the unit distance vector and the unit azimuth vector;

[0015] According to the ratio Construct a resolution ellipse major axis model.

[0016] Optionally, the resolution ellipse major axis model described in this invention is represented as:

[0017]

[0018] in, The major axis of the resolution ellipse is represented.

[0019] Optionally, the resolution mean model described in this invention is:

[0020]

[0021] in, and This represents the mean resolution in the range direction and the mean resolution in the azimuth direction on the ground plane. and This indicates the range resolution and azimuth resolution on the ground plane. This indicates the coordinate range of the core imaging region.

[0022] Optionally, the ground plane range resolution of the present invention and azimuth resolution for:

[0023]

[0024]

[0025] in, To normalize the 3dB width of the sinc function, At the speed of light, For signal bandwidth, For the target (located in) The bibasal angle at ) For the signal wavelength, For the time to synthesize the pore size, Let be the effective angular velocity of the irradiation source relative to the target; let be... Direction unit vector is , Direction unit vector is ,but The unit vector in the direction of the bibase bisector at the target location. and The included angle, The effective equivalent angular velocity vector at the target location and The included angle.

[0026] Optionally, the specific process for the initial selection of the imaging arc segment in this invention is as follows:

[0027] Set the traversal step size for the trajectory;

[0028] Get the width of the two main lobes under the current trajectory segment. and Obtain the angle between the distance unit vector and the azimuth unit vector. Based on the aforementioned resolution ellipse major axis model, calculate the ellipse major axis. ;

[0029] Calculate the ground-plane range resolution of the core imaging region under the current trajectory segment. and azimuth resolution Based on the aforementioned resolution mean model, the mean resolution in the ground plane range direction is calculated. and azimuth resolution mean ;

[0030] The major axis and average resolution of the ellipse corresponding to all trajectory segments are obtained through traversal. The trajectory segments that meet the requirements of the set major axis and average resolution of the ellipse are selected to achieve the initial selection of the imaging arc segment.

[0031] Optionally, the present invention sets the traversal step size of the trajectory to be... , This represents rounding down. Represents 1 day. The time for synthesizing the aperture is denoted as .

[0032] Optionally, the constraint model for GEO bistatic SAR visualization in this invention is as follows:

[0033]

[0034] In the formula: For the GEO satellite-to-ground bistatic SAR beam coverage area, This indicates the coordinate range of the core imaging region.

[0035] Optionally, the present invention takes the satellite coordinates of the midpoint of the imaging arc segment. Position the echo antenna Projected onto the imaging plane At the connection point With point The point where it intersects with the imaging plane is called point. The unfuzzy constraint model is represented as:

[0036]

[0037] in, This indicates the coordinate range of the core imaging region.

[0038] Secondly, the present invention provides a GEO bistatic SAR aperture selection device based on optimal resolution, comprising:

[0039] The resolution ellipse major axis module is based on the resolution ellipse obtained by multiplying the two main lobes during GEO bistatic SAR two-dimensional imaging, and a resolution ellipse major axis model is constructed.

[0040] The resolution mean module is used to select the core imaging region and construct the mean resolution models of the core imaging region in the ground plane range direction and azimuth direction based on the ground plane range resolution and azimuth resolution.

[0041] The imaging arc segment initial selection module is used to set the traversal step size of the trajectory. Based on the resolution ellipse major axis model and the resolution mean model, it traverses to obtain the ellipse major axis and resolution mean value corresponding to all trajectory segments, and selects the trajectory segments that meet the requirements of the set ellipse major axis and resolution mean value.

[0042] The imaging aperture optimization module is used to set two constraints: no ambiguity in the core imaging area and visibility of GEO bistatic SAR. It selects trajectory segments that meet the two constraints from the initially selected trajectory segments, thus completing the imaging aperture optimization based on the dual-constraint joint screening.

[0043] Beneficial effects:

[0044] First, this invention constructs a resolution ellipse major axis model and a core imaging region mean resolution model for a GEO bistatic SAR system. Under visual constraints and unambiguous constraints, it systematically analyzes the full-track data. Based on the joint optimization criteria of the resolution ellipse major axis index and the core region mean resolution index, it achieves intelligent optimization of the imaging aperture segment, providing theoretical support and engineering implementation path for the optimization of GEO bistatic SAR imaging parameters.

[0045] Second, under visibility constraints and unambiguous constraints, a systematic analysis of the full-orbit data is conducted, further providing theoretical support and engineering implementation path for the optimization of GEO bistatic SAR imaging parameters. Attached Figure Description

[0046] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 The resolution ellipse is the result of multiplying the two main lobes, and the two main lobes are transformed; (a) is the resolution ellipse, and (b) is the result of the projection transformation.

[0048] Figure 2 It is a GEO bistatic SAR system configuration.

[0049] Figure 3 Schematic diagram of equidistant rings and equidoppler lines of a GEO bistatic SAR system; (a) shows the unambiguous case, and (b) shows the ambiguous case.

[0050] Figure 4 This is a schematic diagram of the ambiguity determination method for a GEO bistatic SAR system. Observation scenario 1 is unambiguous, while observation scenario 2 is ambiguous.

[0051] Figure 5 Full trajectory information (ECEF coordinates) for four types of GEO bistatic SAR orbits.

[0052] Figure 6 The results for (a) the ground plane distance resolution, (b) the ground plane azimuth resolution, and (c) the angle between the resolutions for each segment of the GEO1 trajectory are shown.

[0053] Figure 7 The results for the major axis of the ellipse for each segment of the GEO1 trajectory are shown in (a) and (b) (magnification of the major axis of the ellipse in the 0–37 range of the Y-axis).

[0054] Figure 8 For each trajectory of GEO1, there are (a) the mean resolution in the distance direction of the core scene and (b) the mean resolution in the azimuth direction of the core scene.

[0055] Figure 9 The result of the GEO1 fuzzy constraint determination;

[0056] Figure 10 For each segment of GEO2 trajectory, (a) the size of the major axis of the ellipse, (b) the size of the major axis of the ellipse (with local magnification of the Y-axis interval of 0–62), (c) the mean range resolution of the core scene, (d) the mean azimuth resolution of the core scene, and (e) the distribution of the antenna beam coverage area and the fuzzy intersection point.

[0057] Figure 11For each segment of GEO3 trajectory, (a) the size of the major axis of the ellipse, (b) the size of the major axis of the ellipse (with local magnification of the Y-axis range of 0–68), (c) the mean range resolution of the core scene, (d) the mean azimuth resolution of the core scene, and (e) the distribution of the antenna beam coverage area and the fuzzy intersection point.

[0058] Figure 12 For each segment of GEO4 trajectory, the following are the following values: (a) the size of the major axis of the ellipse, (b) the size of the major axis of the ellipse (with local magnification of the Y-axis range of 0–40), (c) the mean range resolution of the core scene, (d) the mean azimuth resolution of the core scene, and (e) the distribution of the antenna beam coverage area and the fuzzy intersection point. Detailed Implementation

[0059] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0060] It should be noted that, in the absence of conflict, the following embodiments and features can be combined with each other; and, based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0061] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0062] Figure 2 The configuration of a GEO bistatic SAR system is shown, in which the ground receiving system includes a direct wave antenna and an echo antenna. The GEO bistatic SAR illuminates the observation scene, and the scattered signal from the scene is received by the echo channel.

[0063] This application provides an embodiment of a method for optimizing the aperture of a GEO bistatic SAR based on optimal resolution. The specific process is as follows:

[0064] Constructing a resolution ellipse major axis model: Based on the resolution ellipse obtained by multiplying the two main lobes during GEO bistatic SAR two-dimensional imaging, a resolution ellipse major axis model is constructed.

[0065] Constructing a resolution mean model: Select the core imaging region, and construct a resolution mean model of the core imaging region in the ground plane range direction and azimuth direction based on the ground plane range resolution and azimuth resolution;

[0066] Initial selection of imaging arc segments: Set the traversal step size of the trajectory, and according to the resolution ellipse major axis model and resolution mean model, traverse to obtain the ellipse major axis and resolution mean corresponding to all trajectory segments, and select the trajectory segments that meet the set requirements of ellipse major axis and resolution mean.

[0067] Imaging aperture optimization: Two constraints are set: no ambiguity in the core imaging area and GEO bistatic SAR visibility. From the initially selected trajectory segments, trajectory segments that meet the two constraints are selected, thereby completing the imaging aperture optimization based on dual constraint joint screening.

[0068] The above process will be explained in detail below with specific examples.

[0069] Step 1: Obtain relevant parameters of the GEO bistatic SAR system.

[0070] Step 1.1: Obtain the parameters of the ground receiving system of the GEO bistatic SAR system, including the latitude, longitude, and altitude coordinates of the receiver. Core imaging region coordinate range and the receiving antenna beam range ;

[0071] Step 1.2: Obtain the payload parameters of the GEO bistatic SAR, including the center frequency. Time width ,bandwidth and synthesis pore size time ;

[0072] Step 1.3: Obtain full orbit information of GEO bistatic SAR. (Trajectory information within one heavy orbit cycle, GEO satellite-to-ground bistatic SAR for one day's trajectory), assuming the full orbit information is from 00:00:00 to 23:59:59 Beijing time on a certain day, with an interval of 1 second.

[0073] At this point, the parameter acquisition is complete.

[0074] Step 2: Through analysis of bistatic slant range geometry and Doppler history, and using the analytical expressions for the ground-plane azimuth and range resolutions of the bistatic SAR system, a dynamic resolution ellipse major axis model that updates in real time with the satellite position is constructed. The specific process is as follows:

[0075] Ground-plane range resolution of bistatic SAR system and azimuth resolution It can be represented as:

[0076] (1)

[0077] (2)

[0078] in, , is the 3dB width of the normalized sinc function. At the speed of light, For signal bandwidth, For the target (located in) The bibasal angle at ) For the signal wavelength, For the time to synthesize the pore size, Let be the effective angular velocity of the irradiation source relative to the target; let be... Direction unit vector is , Direction unit vector is .but for and The included angle, for and The included angle. It is easy to see that, The unit vector whose direction is the bibase bisector direction Projection on the ground plane The direction is the effective equivalent angular velocity vector. Projection onto the ground plane.

[0079] Assuming the resolution ellipse after multiplying the two main lobes in two-dimensional imaging is as follows: Figure 1 As shown in (a), , The -3dB contour line is for main lobe 1, and the main lobe width is... ; , The -3dB contour line is for main lobe 2, and the main lobe width is... . It could be equidistant lines (the direction of the azimuth sidelobes), in which case... The direction corresponds to the distance. The center of the parallelogram formed by the -3dB contour lines of the two main lobes is... It is easy to see that the midpoint of the four line segments is the -3dB point, so we can determine that the ellipse is tangent to each of the four line segments at their respective midpoints. At M, intersecting the ellipse at A parallelogram can be transformed into a square through two projection transformations (e.g., Figure 1 (b) shows that after the transformation, the inscribed ellipse becomes the inscribed circle. According to the properties of linear transformations, and proportion and and The proportion remains constant. In an ellipse, Thus, we can obtain and The ratio is:

[0080] (3)

[0081] Based on the representation of the major and minor axes of the ellipse, the worst and best resolutions are determined, according to the properties of the ellipse and... and proportion The expressions for the major and minor axes of the resolution ellipse model are obtained as follows:

[0082] (4)

[0083] In the formula, The distance-oriented unit vector With azimuth unit vector The included angle, Indicates the major axis of the resolution ellipse. The minor axis of the resolution ellipse is represented.

[0084] This completes the construction of the model for resolving the major axis of the ellipse.

[0085] Step 3: Select the core imaging region and construct a resolution mean model that is updated in real time with the satellite position.

[0086] Based on the coordinate range of the core imaging region in step 1 and the distance from the ground plane in step 2 and orientation The resolution model can obtain the mean resolution models of the ground plane range and azimuth directions of the core imaging scene area under any time period trajectory. and They are respectively:

[0087] (5)

[0088] in, and This represents the mean resolution in the range direction and the mean resolution in the azimuth direction on the ground plane. and This indicates the range resolution and azimuth resolution on the ground plane. This indicates the coordinate range of the core imaging region.

[0089] This completes the construction of the core region resolution mean model.

[0090] Step 4: Perform full-track traversal and imaging arc selection on the resolution ellipse major axis model and the resolution mean model.

[0091] Step 4.1: First, based on the full track information and the system parameters from Step 1, determine the traversal step size. ( This represents rounding down. (This represents 1 day, or 86,400 seconds).

[0092] Step 4.2, Obtain the current trajectory segment Width of the two lower main lobes and and the angle between the unit vector of distance and the unit vector of azimuth. ;

[0093] Step 4.3, calculate the trajectory according to formulas (1)-(2). Under the condition of ground plane range resolution and azimuth resolution of core imaging area, the results of ground plane range resolution and azimuth resolution of core imaging area are obtained, and the average resolution information is calculated by using the average resolution model (Equation (5)).

[0094] Step 4.4 repeats steps 4.2 and 4.3 to obtain the ellipse major axis and average resolution results for the entire orbit information (i.e., all trajectory segments). For example, using an ellipse major axis less than 20m and an average resolution less than 15m as the standard, the optimal resolution aperture segment is initially obtained for GEO bistatic SAR.

[0095] This completes the full orbital traversal and the optimal selection of imaging arc segments.

[0096] Step 5: Under the constraints of no blurring in the core imaging area and visibility of GEO bistatic SAR, complete the final imaging arc selection.

[0097] Specifically: First, considering the left and right look-ahead observation capabilities of GEO bistatic SAR, the transmit antenna beam range and direction are set using the Satellite Tool Kit (STK). Visual constraints are then applied to the optimal resolution aperture segment obtained in step 4 to obtain the imaging arc segment under visual constraints. The visual constraint model is expressed as follows:

[0098] (7)

[0099] In the formula: This refers to the coverage area of ​​the GEO satellite-to-ground bistatic SAR beam.

[0100] Secondly, in a bistatic SAR system, when two points of intersection of identical equidistant rings and identical Doppler lines occur, ambiguity will occur, such as... Figure 3As shown, the dark red and blue lines represent equidistant lines and equal Doppler lines, respectively. Targets with the same bistatic distance and Doppler frequency will be located on the same pixel. The area circled in green indicates the blurred area (the area where the interference phase changes rapidly), which is caused by the image blurring in the area circled in blue. Let the yellow area represent the receiving beam range of the receiving antenna, assuming that the antenna does not receive echo signals within other beam angle ranges. Figure 3 (a) shows the unambiguous case, where the receiving beam only receives the echo from green area 2 and not the echo from blue area 1. That is, there is no signal blurring from blue area 1 to green area 2, and it does not affect the imaging of the imaging area; however, Figure 3 (b) shows the case where there is blur, that is, the receiving beam receives echoes from both the blue area 1 and the green area 2 at the same time, resulting in blurring of the imaging area.

[0101] Therefore, adopting such Figure 4 The determination method shown selects the imaging arc segment obtained in step 4. The equidistant ring is... In the scenario shown in the figure, observation area 1 exhibits no blurring, while observation area 2 shows blurring. The satellite coordinates of the midpoint of the imaging arc are taken. Position the echo antenna Projected onto the imaging plane At the connection point With point The point where it intersects with the imaging plane is called point. (referred to as the fuzzy intersection point), where the projection of the echo antenna onto the imaging plane is a point. It can be observed that when point When the image area is within the receiving antenna beam, blurring occurs. Therefore, this projection method can be used to impose fuzziness constraints on the imaging arc segment. This results in the selection of the final imaging arc segment under the constraint of no fuzziness in the core imaging region. The fuzz-free constraint model is expressed as:

[0102] (8)

[0103] This completes all the steps.

[0104] This embodiment discloses a GEO bistatic SAR aperture selection device based on optimal resolution, comprising:

[0105] The resolution ellipse major axis module is based on the resolution ellipse obtained by multiplying the two main lobes during GEO bistatic SAR two-dimensional imaging, and constructs the resolution ellipse major axis model.

[0106] The resolution mean module is used to select the core imaging region and construct the mean resolution models of the core imaging region in the ground plane range direction and azimuth direction based on the ground plane range resolution and azimuth resolution.

[0107] The imaging arc segment initial selection module is used to set the traversal step size of the trajectory. Based on the resolution ellipse major axis model and the resolution mean model, it traverses to obtain the ellipse major axis and resolution mean value corresponding to all trajectory segments, and selects the trajectory segments that meet the requirements of the set ellipse major axis and resolution mean value.

[0108] The imaging aperture optimization module is used to set two constraints: no ambiguity in the core imaging area and visibility of GEO bistatic SAR. It selects trajectory segments that meet the two constraints from the initially selected trajectory segments, thus completing the imaging aperture optimization based on the dual-constraint joint screening.

[0109] The following provides an implementation example with specific parameters.

[0110] In this example, six different types of GEO bistatic SAR orbits were set up, including multi-angle GEO bistatic SAR with the same inclination and GEO bistatic SAR with different inclinations. The simulated orbital element information is shown in Table 1. Based on the orbital element information, the relationship between the satellite nadir point trajectory position and the receiver position was obtained.

[0111] Table 1 Simulation Track Element Information

[0112]

[0113] Other simulation system parameters are shown in Table 2.

[0114] Table 2 Simulation System Parameter Information

[0115]

[0116] After performing step 1.3, the full trajectory information of the four orbits in the ECEF coordinate system is as follows: Figure 5 As shown.

[0117] Taking GEO1 as an example, after executing steps 2, 3, and 4, the following parameters are obtained under the simulation system: ground plane range resolution, ground plane azimuth resolution, and resolution angle at the center of the core imaging region of each trajectory segment: Figure 6 As shown, the major axis of the ellipse for each trajectory segment is as follows: Figure 7 As shown, the average resolution results for the core scene are as follows: Figure 8 As shown. According to the criteria in step 4.4, the optimization can be performed, and it can be found that the conditions are met when the center time of the GEO1 trajectory segment is located at 04:54:23~11:21:57 and 15:28:01~23:46:19.

[0118] Execute step 5. First, use STK to set the beam information of the left and right looking transmitting antennas. The beamwidth is 120° and the downward viewing angle range is 1°-8°. The analysis shows that the visible aperture segment of GEO1 in Table 3 is visible for 24 hours.

[0119] Traversing the GEO1 trajectory segments that meet the conditions, we obtain the coordinate information of the projection points. Assuming the antenna coverage area has a radius of 200m, we obtain the following: Figure 9 As shown in the results, all ambiguity intersections are located outside the receiving antenna beam range, satisfying the condition of no ambiguity constraint. Therefore, the final optimal imaging aperture results are 04:54:23~11:21:57 and 15:28:01~23:46:19.

[0120] The results for GEO2, GEO3, and GEO4 are as follows: Figure 10 , Figure 11 , Figure 12 As shown in Table 3, the optimal imaging aperture results for the four orbit types are presented.

[0121] Table 3. Optimal Imaging Aperture Results for Four Track Types

[0122]

[0123] from Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 , Figure 11 , Figure 12 As shown in Table 3, the proposed method constructs a resolution ellipse major axis model and a core region resolution mean model for a GEO bistatic SAR system, and performs systematic analysis of full-orbit data under both visual and unambiguous constraints. Based on the joint optimization criterion of the resolution ellipse major axis index and the core region resolution mean index, intelligent optimization of the imaging aperture segment is achieved. These results demonstrate the effectiveness of this patent in aperture optimization for GEO bistatic SAR systems based on optimal resolution.

[0124] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A method for optimizing the aperture of a GEO satellite-to-ground bistatic SAR based on optimal resolution, characterized in that, The specific process is as follows: Constructing the major axis model of the resolution ellipse: Based on the resolution ellipse obtained by multiplying the two main lobes during GEO bistatic SAR two-dimensional imaging, construct the major axis model of the resolution ellipse. Constructing a resolution mean model: Select the core imaging region, and construct a resolution mean model of the core imaging region in the ground plane range direction and azimuth direction based on the ground plane range resolution and azimuth resolution; Initial selection of imaging arc segments: Set the traversal step size of the trajectory, and according to the resolution ellipse major axis model and resolution mean model, traverse to obtain the ellipse major axis and resolution mean corresponding to all trajectory segments, and select the trajectory segments that meet the set requirements of ellipse major axis and resolution mean. Imaging aperture optimization: Two constraints are set: no ambiguity in the core imaging area and GEO bistatic SAR visibility. From the initially selected trajectory segments, trajectory segments that meet the two constraints are selected, thereby completing the imaging aperture optimization based on dual constraint joint screening.

2. The method for optimizing the aperture of a GEO satellite-to-ground bistatic SAR based on optimal resolution as described in claim 1, characterized in that, The resolution ellipse obtained by multiplying the two main lobes during GEO bistatic SAR two-dimensional imaging is used to construct the major axis model of the resolution ellipse. The specific process is as follows: To obtain the resolution ellipse after multiplying the two main lobes in a two-dimensional image, the -3dB contour lines of the two main lobes are denoted as... , and , The width of the two main lobes is denoted as and ; Let the center of the parallelogram formed by the -3dB isopleths of the two main lobes be denoted as . ,from Draw a point perpendicular to The straight line intersects the contour lines. At The intersection resolution ellipse is at ,get and The ratio is: , This represents the angle between the unit distance vector and the unit azimuth vector; According to the ratio Construct a resolution ellipse major axis model.

3. The method for optimizing the aperture of a GEO satellite-to-ground bistatic SAR based on optimal resolution as described in claim 2, characterized in that, The resolution ellipse major axis model is represented as follows: in, The major axis of the resolution ellipse is represented.

4. The method for optimizing the aperture of a GEO satellite-to-ground bistatic SAR based on optimal resolution as described in claim 3, characterized in that, The resolution mean model is as follows: in, and This represents the mean resolution in the range direction and the mean resolution in the azimuth direction on the ground plane. and This indicates the range resolution and azimuth resolution on the ground plane. This indicates the coordinate range of the core imaging region.

5. The method for optimizing the aperture of a GEO satellite-to-ground bistatic SAR based on optimal resolution as described in claim 4, characterized in that, Ground plane range resolution and azimuth resolution for: in, To normalize the 3dB width of the sinc function, At the speed of light, For signal bandwidth, The bistatic angle at the target location, For the signal wavelength, For the time to synthesize the pore size, Let be the effective angular velocity of the irradiation source relative to the target; let be... Direction unit vector is , Direction unit vector is ,but The unit vector in the direction of the bibase bisector at the target location. and The included angle, The effective equivalent angular velocity vector at the target location and The included angle.

6. The method for optimizing the aperture of a GEO satellite-to-ground bistatic SAR based on optimal resolution as described in claim 5, characterized in that, The specific process for the initial selection of the imaging arc segment is as follows: Set the traversal step size for the trajectory; Get the width of the two main lobes under the current trajectory segment. and Obtain the angle between the distance unit vector and the azimuth unit vector. Calculate the major axis of the ellipse based on the aforementioned resolution ellipse major axis model. ; Calculate the ground-plane range resolution of the core imaging region under the current trajectory segment. and azimuth resolution Based on the aforementioned resolution mean model, the mean resolution in the ground plane range direction is calculated. and azimuth resolution mean ; The major axis and average resolution of the ellipse corresponding to all trajectory segments are obtained through traversal. The trajectory segments that meet the requirements of the set major axis and average resolution of the ellipse are selected to achieve the initial selection of the imaging arc segment.

7. The method for optimizing the aperture of a GEO satellite-to-ground bistatic SAR based on optimal resolution as described in claim 6, characterized in that, Set the traversal step size of the trajectory to be , This represents rounding down. Represents 1 day. The time for synthesizing the aperture is denoted as .

8. The method for optimizing the aperture of a GEO satellite-to-ground bistatic SAR based on optimal resolution as described in claim 1, characterized in that, The constraint model for GEO bistatic SAR visualization is as follows: in, For GEO SAR beam coverage, This indicates the coordinate range of the core imaging region.

9. The method for optimizing the aperture of a GEO satellite-to-ground bistatic SAR based on optimal resolution as described in claim 1, characterized in that, Take the satellite coordinates of the midpoint of the imaging arc. Position the echo antenna Projected onto the imaging plane At the connection point With point The point where it intersects with the imaging plane is called point. The unfuzzy constraint model is represented as: in, This indicates the coordinate range of the core imaging region.

10. A GEO-based bistatic SAR aperture optimization device based on optimal resolution, characterized in that, include: The resolution ellipse major axis module is based on the resolution ellipse obtained by multiplying the two main lobes during GEO bistatic SAR two-dimensional imaging, and constructs the resolution ellipse major axis model. The resolution mean module is used to select the core imaging region and construct the mean resolution models of the core imaging region in the ground plane range direction and azimuth direction based on the ground plane range resolution and azimuth resolution. The imaging arc segment initial selection module is used to set the traversal step size of the trajectory. Based on the resolution ellipse major axis model and the resolution mean model, it traverses to obtain the ellipse major axis and resolution mean value corresponding to all trajectory segments, and selects the trajectory segments that meet the requirements of the set ellipse major axis and resolution mean value. The imaging aperture optimization module is used to set two constraints: no ambiguity in the core imaging area and visibility of GEO bistatic SAR. It selects trajectory segments that meet the two constraints from the initially selected trajectory segments, thus completing the imaging aperture optimization based on the dual-constraint joint screening.

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