Sar imaging method and apparatus for spatially time-varying acceleration

Abstract

The present application relates to the technical field of SAR imaging, and provides a curve trajectory SAR imaging method and device of spatial time-varying acceleration, which is aimed at a high-speed maneuverable radar platform carrying a synthetic aperture radar, constructs a SAR imaging echo model based on spatial time-varying acceleration, and acquires a real slant range history between the high-speed maneuverable radar platform and a target object, acquires a to-be-processed echo signal in a spatial wave number domain according to the real slant range history, and performs non-space-variant motion and distance cell migration compensation on the to-be-processed echo signal according to a preset Deramp compensation function constructed by a motion error. The echo signal is subjected to interpolation processing according to a rotation interpolation kernel function determined by a real motion trajectory, to obtain an interpolated echo signal, and a coarse-focusing SAR image is acquired according to the interpolated echo signal. A target SAR image is obtained by performing wavefront curvature phase compensation on the coarse-focusing SAR image according to a wavefront curvature phase compensation factor determined by the real motion trajectory.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of SAR imaging technology, in particular to a curve trajectory SAR imaging method and device of spatial time-varying acceleration. BACKGROUND

[0002] At present, synthetic aperture radar (SAR) is a kind of high-resolution imaging radar. Synthetic aperture radar can obtain high-resolution radar images similar to optical photographs under extremely low visibility weather conditions. In recent years, synthetic aperture radar imaging technology has developed rapidly, especially for high-speed maneuvering platform motion.

[0003] In the prior art, the traditional synthetic aperture radar imaging technology includes a back-projection algorithm and a range migration algorithm. The back-projection algorithm realizes the reconstruction of the ground scene by projecting the echo signal pulse by pulse through the slant range history of the ground grid, so as to obtain SAR imaging. The range migration algorithm realizes the purpose of two-dimensional phase linearization by resampling the distance frequency axis using interpolation, and further establishes a high-order Taylor expansion slant range model, so as to obtain SAR imaging.

[0004] However, for the synthetic aperture radar imaging of high-speed maneuvering platform motion, the back-projection algorithm has high complexity and cannot compensate for the motion error of the high-speed maneuvering platform during motion, so the existing method is not suitable for real-time imaging of synthetic aperture radar of high-speed maneuvering platform motion. For the range migration algorithm, due to the excessive dependence on the limited order radar slant range model, the non-space-variant compensation characteristics of the two-dimensional frequency domain will have serious defocusing under wide scene, so that the existing method cannot obtain high-quality synthetic aperture radar imaging for high-speed maneuvering platform motion. SUMMARY

[0005] Therefore, it is necessary to provide a curve trajectory SAR imaging method and device of spatial time-varying acceleration to solve the above technical problems.

[0006] In a first aspect, an embodiment of the present application provides a curve trajectory SAR imaging method of spatial time-varying acceleration, the method comprising:

[0007] For a high-speed maneuvering radar platform carrying a synthetic aperture radar, a SAR imaging echo model of the high-speed maneuvering radar platform is constructed based on spatial time-varying acceleration, and a real slant range history between the high-speed maneuvering radar platform and a target object is obtained.

[0008] According to the real slant range history, a to-be-processed echo signal in a spatial wave number domain is obtained.

[0009] According to a preset Deramp compensation function, non-convolutional motion and range cell migration compensation is performed on the to-be-processed echo signal to obtain a motion-compensated echo signal, wherein the preset Deramp compensation function is constructed according to motion errors of the high-speed maneuverable radar platform;

[0010] According to a rotation interpolation kernel function, interpolation processing is performed on the motion-compensated echo signal to obtain an interpolated echo signal;

[0011] According to the interpolated echo signal, a coarsely focused SAR image is obtained;

[0012] According to a wavefront curvature phase compensation factor, wavefront curvature phase compensation is performed on the coarsely focused SAR image to obtain a target SAR image, wherein the rotation interpolation kernel function and the wavefront curvature phase compensation factor are determined according to a real motion trajectory of the high-speed maneuverable radar platform.

[0013] In a second aspect, an embodiment of the present application provides a SAR imaging device for a curve trajectory of a spatial time-varying acceleration, and the device comprises:

[0014] A model construction module is configured to, for a high-speed maneuverable radar platform carrying a synthetic aperture radar, construct a SAR imaging echo model of the high-speed maneuverable radar platform based on a spatial time-varying acceleration, and obtain a real slant range history between the high-speed maneuverable radar platform and a target object;

[0015] A to-be-processed echo signal acquisition module is configured to obtain a to-be-processed echo signal in a spatial wave number domain according to the real slant range history;

[0016] A motion compensation module is configured to, according to a preset Deramp compensation function, perform non-convolutional motion and range cell migration compensation on the to-be-processed echo signal to obtain a motion-compensated echo signal, wherein the preset Deramp compensation function is constructed according to motion errors of the high-speed maneuverable radar platform;

[0017] An interpolation processing module is configured to, according to a rotation interpolation kernel function, perform interpolation processing on the motion-compensated echo signal to obtain an interpolated echo signal;

[0018] A coarsely focused SAR image acquisition module is configured to obtain a coarsely focused SAR image according to the interpolated echo signal;

[0019] A phase compensation module is configured to, according to a wavefront curvature phase compensation factor, perform wavefront curvature phase compensation on the coarsely focused SAR image to obtain a target SAR image, wherein the rotation interpolation kernel function and the wavefront curvature phase compensation factor are determined according to a real motion trajectory of the high-speed maneuverable radar platform.

[0020] The technical scheme provided by the embodiment of the present application has the following advantages compared with the prior art.

[0021] The curve trajectory SAR imaging method of the spatial time-varying acceleration provided by the embodiment of the present application firstly constructs a high-speed maneuvering radar platform SAR imaging echo model based on the spatial time-varying acceleration for a high-speed maneuvering radar platform carrying a synthetic aperture radar, and obtains a real slant range history between the high-speed maneuvering radar platform and a target object, then obtains the echo signal to be processed in the spatial wave number domain according to the real slant range history, and further compensates the echo signal to be processed for non-space-variant motion and range cell migration according to a preset Deramp compensation function constructed by the motion error of the high-speed maneuvering radar platform, to obtain the echo signal after motion compensation, in this way, the non-space-variant error introduced by the high-speed maneuvering radar platform in the motion process under the spatial time-varying acceleration is compensated, the spectrum of the echo signal to be processed is recovered and compressed, and a high-quality SAR image is obtained. Further, the echo signal after motion compensation is interpolated according to a rotation interpolation kernel function determined by the real motion trajectory of the high-speed maneuvering radar platform, to obtain the echo signal after interpolation, and a coarsely focused SAR image is obtained according to the echo signal after interpolation, in this way, the spectrum loss of the echo signal is reduced, and since the rotation interpolation kernel function is derived by using the real motion trajectory, the change of the frequency support domain caused by the spatial time-varying acceleration signal can be more accurately reflected, accurate two-dimensional interpolation processing of the echo signal is realized, and the quality of the SAR image is improved. Finally, the wavefront curvature phase compensation factor determined by the real motion trajectory of the high-speed maneuvering radar platform is used to compensate the wavefront curvature phase of the coarsely focused SAR image, to obtain a target SAR image, in this way, the defocusing of the SAR image in the azimuth direction caused by the wavefront curvature is reduced, and the quality of the SAR image is improved. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A flowchart of a curve trajectory SAR imaging method of spatial time-varying acceleration provided by the embodiment of the present application is shown in the figure.

[0023] Figure 2 A schematic diagram of a spatial coordinate system provided by the embodiment of the present application is shown in the figure.

[0024] Figure 3 A structure diagram of a curve trajectory SAR imaging device of spatial time-varying acceleration provided by the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0025] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the scheme of the present application will be further described below. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0026] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one skilled in the art that the present application can be practiced without the specific details set forth in this description. In other instances, well-known methods have not been described in detail in order to avoid obscuring the present application.

[0027] At present, synthetic aperture radar is a kind of high-resolution imaging radar, and high-resolution radar images similar to optical photographs can be obtained under extremely low visibility weather conditions by using synthetic aperture radar. In recent years, synthetic aperture radar imaging technology has developed rapidly, especially for high-mobility platform motion synthetic aperture radar imaging.

[0028] In the prior art, the traditional synthetic aperture radar imaging technology includes a back-projection algorithm and a range migration algorithm. The back-projection algorithm realizes reconstruction of a ground scene by projecting echo signals pulse by pulse through a slant range history of a ground grid to obtain SAR imaging. The range migration algorithm realizes two-dimensional phase linearization by resampling a distance frequency axis by using interpolation, and further establishes a high-order Taylor expansion slant range model to obtain SAR imaging.

[0029] However, for high-mobility platform motion synthetic aperture radar imaging, the back-projection algorithm has high complexity and cannot compensate for motion errors existing in the motion process of the high-mobility platform, so the existing method is not suitable for real-time imaging of the synthetic aperture radar of the high-mobility platform. For the range migration algorithm, due to excessive dependence on a limited-order radar slant range model, the non-space-variant compensation characteristics of the two-dimensional frequency domain will have serious defocusing under a wide scene, so that the existing method cannot obtain high-quality synthetic aperture radar imaging for high-mobility platform motion.

[0030] Therefore, the application provides a spatial time-varying acceleration curved trajectory SAR imaging method, which comprises the following steps:

[0031] In one embodiment, as shown in Figure 1 , Figure 1 a flowchart of a spatial time-varying acceleration curved trajectory SAR imaging method provided by the application, specifically comprising the following steps:

[0032] S10: for a high-speed maneuverable radar platform carrying a synthetic aperture radar, constructing a SAR imaging echo model of the high-speed maneuverable radar platform based on spatial time-varying acceleration, and obtaining a real slant range history between the high-speed maneuverable radar platform and a target object.

[0033] The spatial time-varying acceleration refers to acceleration that is changed in real time in a spatial domain during the movement of the high-speed maneuverable radar platform carrying the synthetic aperture radar.

[0034] The SAR imaging echo model refers to a model used to obtain instantaneous position information of the high-speed maneuverable radar platform during movement.

[0035] The true slant range history refers to the actual trajectory of the slant range (i.e., straight-line distance) between the target object and the sensor (such as the radar antenna) changing over time during the synthetic aperture radar imaging process.

[0036] Specifically, according to the spatial time-varying acceleration of the high-speed mobile radar platform during its motion, a SAR imaging echo model of the high-speed mobile radar platform is constructed, and the real slant range history between the high-speed mobile radar platform and the target object is obtained.

[0037] Optionally, based on the above embodiment, in some embodiments of the present invention, an implementation method for constructing a SAR imaging echo model of a high-speed mobile radar platform based on spatial time-varying acceleration may be:

[0038] S101: Establish a spatial coordinate system with the center of the scene as the coordinate origin.

[0039] The X-axis and Y-axis of the spatial coordinate system are parallel to the ground, and the Z-axis is perpendicular to the ground. For example, Figure 2 As shown. Among them, Point is the coordinate origin, The dots represent high-speed mobile radar platforms. The dot represents the target object. and They represent any two points in the space that the high-speed mobile radar platform passes through during its movement. Indicates the height of the high-speed mobile radar platform itself.

[0040] S102: Determine the speed and spatial time-varying acceleration of the high-speed maneuvering radar platform in a spatial coordinate system.

[0041] S103: Constructing a SAR imaging echo model according to the velocity and spatial time-varying acceleration.

[0042] Specifically, a spatial coordinate system is established with the center of the scene as the coordinate origin. The X-axis and Y-axis of the spatial coordinate system are parallel to the ground, and the Z-axis is perpendicular to the ground. Furthermore, the speed and spatial time-varying acceleration of the high-speed mobile radar platform are obtained in the spatial coordinate system. Finally, based on the speed and spatial time-varying acceleration of the high-speed mobile radar platform, a method for obtaining the instantaneous position information of the high-speed mobile radar platform during movement is constructed ( , , ) SAR imaging echo model, where Indicates the instantaneous position of the azimuth slow-time high-speed mobile radar platform on the X axis, Indicates the instantaneous position of the azimuth slow-time high-speed mobile radar platform on the Y axis, Indicates the instantaneous position of the Z-axis of the azimuth slow-time high-speed mobile radar platform.

[0043] Optionally, based on the above-mentioned embodiments, in some embodiments of the present application, the SAR imaging echo model can be defined by the following expression:

[0044] ;

[0045] wherein, denotes the azimuth slow time, denotes the velocity of the high-speed maneuverable radar platform in the X-axis, Y-axis and Z-axis directions, denotes the corresponding synthetic aperture center position coordinates on the high-speed maneuverable radar platform, denotes the acceleration of the high-speed maneuverable radar platform in the X-axis direction, denotes the first-order time derivative of , denotes the second-order time derivative of , denotes the acceleration of the high-speed maneuverable radar platform in the Y-axis direction, denotes the first-order time derivative of , denotes the second-order time derivative of , denotes the acceleration of the high-speed maneuverable radar platform in the Z-axis direction, denotes the first-order time derivative of , denotes the second-order time derivative of .

[0046] Optionally, based on the above-mentioned embodiments, in some embodiments of the present application, the true slant range history is defined by the following expression:

[0047] ;

[0048] wherein, denotes the position coordinates of the target object, denotes the true slant range history between the target object and the high-speed maneuverable radar platform in the azimuth slow time.

[0049] For example, as shown in Figure 2 , point is the target object. point is the corresponding synthetic aperture center position coordinates of the high-speed maneuverable radar platform, and the coordinates are . The line connecting the target object and the high-speed maneuverable radar platform is the true slant range history.

[0050] S11: According to the true slant range history, the echo signal to be processed in the spatial wave number domain is obtained.

[0051] Specifically, after the real slant range history is determined, the echo signal to be processed in the spatial wave number domain is obtained according to the real slant range history.

[0052] Optionally, in the foregoing embodiment, in some embodiments of the present application, an implementation of S11 can be:

[0053] S111: receiving the baseband signal scattered back by the target object based on the real slant range history.

[0054] Specifically, the baseband signal scattered back by the target object is received through the radar antenna carried on the high-speed maneuvering radar platform according to the real slant range history obtained between the high-speed maneuvering radar platform and the target object.

[0055] Optionally, in the foregoing embodiment, in some embodiments of the present application, the baseband signal can be defined by the following expression:

[0056] ;

[0057] wherein, denotes a time-domain expression of a range window function, denotes fast time, denotes a time-domain expression of an azimuth window function, denotes a frequency modulation rate of a transmitted signal, denotes the speed of light, is a virtual part symbol.

[0058] S112: performing range direction Fourier transform and range direction pulse compression processing on the baseband signal to obtain the echo signal to be processed in the spatial wave number domain.

[0059] Specifically, the received baseband signal is subjected to range direction Fourier transform and range direction pulse compression processing to obtain the echo signal to be processed in the spatial wave number domain.

[0060] Optionally, in the foregoing embodiment, in some embodiments of the present application, the echo signal to be processed can be defined by the following expression:

[0061] ;

[0062] wherein, denotes a range wave number, denotes a spatial wave number domain form of a range window function, denotes a carrier frequency, denotes a range frequency.

[0063] S12: performing non-empty variable motion and range cell migration compensation on the echo signal to be processed according to a preset Deramp compensation function to obtain a motion-compensated echo signal.

[0064] wherein the preset Deramp compensation function is a function constructed according to the motion error of the high-speed maneuvering radar platform.

[0065] Optionally, based on the above-mentioned embodiments, in some embodiments of the present application, one implementation manner of constructing the preset Deramp compensation function according to the motion error of the high-speed maneuvering radar platform can be:

[0066] S20: obtaining the motion error of the high-speed maneuvering radar platform according to the real motion trajectory and the ideal motion trajectory of the high-speed maneuvering radar platform.

[0067] wherein the motion error can be determined according to the difference between the slant ranges of the real motion trajectory and the ideal motion trajectory to the target object respectively.

[0068] S21: constructing the preset Deramp compensation function according to the motion error.

[0069] Specifically, for the high-speed maneuvering radar platform, the real motion trajectory and the ideal motion trajectory of the high-speed maneuvering radar platform are obtained, and the slant ranges of the real motion trajectory and the ideal motion trajectory of the high-speed maneuvering radar platform to the target object are further calculated, the difference between the two slant ranges is calculated, thereby obtaining the motion error of the high-speed maneuvering radar platform, and the preset Deramp compensation function is constructed according to the motion error.

[0070] Optionally, based on the above-mentioned embodiments, in some embodiments of the present application, the preset Deramp compensation function is defined by the following expression:

[0071]

[0072] wherein, denotes the distance wave number, denotes the real slant range history of the center point corresponding to the center of the scene, denotes the Deramp compensation factor for compensating the non-space-varying phase error.

[0073] Specifically, according to the preset Deramp compensation function constructed according to the motion error of the high-speed maneuvering radar platform, non-space-varying motion and distance cell migration compensation is performed on the to-be-processed echo signal, thereby obtaining the motion-compensated echo signal.

[0074] Optionally, based on the above-mentioned embodiments, the non-space-varying motion and distance cell migration compensation on the to-be-processed echo signal to obtain the motion-compensated echo signal can be defined by the following expression:

[0075]

[0076] ​​In this way, the preset Deramp compensation function is constructed, non-variant motion and range cell migration compensation is performed on the echo signal to be processed, non-variant errors introduced by the high-speed maneuvering radar platform in the motion process under the space time-varying acceleration are compensated, the recovery and compression of the spectrum of the echo signal to be processed are realized, and thus the high-quality SAR image can be obtained.

[0077] S13: performing interpolation processing on the motion-compensated echo signal according to the rotation interpolation kernel function, to obtain an interpolated echo signal.

[0078] The rotation interpolation kernel function is determined according to the real motion trajectory of the high-speed maneuvering radar platform, can be used to reduce the spectrum loss, and can more accurately reflect the change of the frequency support domain caused by the space time-varying acceleration signal because the rotation interpolation kernel function is derived by using the real motion trajectory of the radar platform, thereby realizing accurate two-dimensional interpolation processing on the echo signal and improving the quality of the SAR image.

[0079] Specifically, the rotation interpolation kernel function is constructed by using the real motion trajectory of the high-speed maneuvering radar platform, and the motion-compensated echo signal is interpolated according to the rotation interpolation kernel function, to obtain an interpolated echo signal.

[0080] Optionally, in some embodiments of the present application, one implementation of S13 can be:

[0081] S131: obtaining a second echo signal in the spatial wave number domain corresponding to the first-order Taylor expansion formula of the motion-compensated echo signal.

[0082] S132: multiplying the rotation interpolation kernel function and the second echo signal, to obtain an interpolated echo signal.

[0083] The rotation interpolation kernel function is defined by the following expression:

[0084] ;

[0085] wherein, denotes the azimuth wave number, denotes the range wave number, denotes the included angle between the line-of-sight direction of the synthetic aperture radar and the motion direction relative to the ground projection, denotes the azimuth wave number after the rotation processing, denotes the range wave number after the rotation processing.

[0086] Specifically, the first-order Taylor expansion is performed on the motion-compensated echo signal to obtain a first-order Taylor expansion formula of the motion-compensated echo signal, and a second echo signal in a spatial wave number domain of the first-order Taylor expansion formula is further obtained, the rotated interpolation kernel function is multiplied by the second echo signal to obtain the interpolated echo signal.

[0087] Optionally, for the motion-compensated echo signal, the first-order Taylor expansion is performed, and the first-order Taylor expansion formula can be defined by the following expression:

[0088] ;

[0089] wherein, , are Taylor expansion coefficients, which can be simply written as , .

[0090] , can be defined by the following expression:

[0091] ;

[0092] Further, the second echo signal in the spatial wave number domain of the first-order Taylor expansion formula is obtained, and the second echo signal can be defined by the following expression:

[0093] ;

[0094] Finally, the rotated interpolation kernel function is multiplied by the second echo signal to obtain the interpolated echo signal, and the interpolated echo signal can be defined by the following expression:

[0095] ;

[0096] In this way, the motion-compensated echo signal is interpolated by the rotated interpolation kernel function, the spectrum loss of the echo signal can be reduced, and since the rotated interpolation kernel function is derived by using the real motion trajectory of the radar platform, the change of the signal spectrum support domain caused by the spatial time-varying acceleration can be more accurately reflected, so that accurate two-dimensional interpolation processing of the echo signal is realized, and the quality of the SAR image is improved.

[0097] S14: A coarsely focused SAR image is obtained according to the interpolated echo signal.

[0098] Optionally, on the basis of the above embodiment, in some embodiments of the present application, one implementation manner of S14 can be: the interpolated echo signal is subjected to inverse Fourier transform processing in the range direction and Fourier transform processing in the azimuth direction to obtain the coarsely focused SAR image.

[0099] S15: performing wavefront curvature phase compensation on the coarse focus SAR image according to a wavefront curvature phase compensation factor to obtain a target SAR image.

[0100] The wavefront curvature phase compensation factor is determined according to the actual motion track of the high-speed maneuvering radar platform, and is used to further compensate geometric distortion and defocusing in the azimuth direction caused by motion errors of the high-speed maneuvering radar platform and positions of the target object.

[0101] Optionally, in some embodiments of the present application, one implementation of S15 can be based on the above embodiments, and is as follows:

[0102] S151: obtaining motion-compensated echo signals corresponding to a plurality of sub-SAR images of the coarse focus SAR image.

[0103] S152: obtaining a second-order Taylor expansion formula of the echo signals for the motion-compensated echo signals corresponding to each sub-SAR image.

[0104] For example, the second-order Taylor expansion formula of the motion-compensated echo signals corresponding to each initial sub-SAR image in the azimuth direction can be defined by the following expression:

[0105] ;

[0106] wherein, The coefficient expression of the Taylor expansion can be defined by the following expression:

[0107] ;

[0108] wherein, denotes an included angle between a line-of-sight direction of the synthetic aperture radar and a projection of the motion direction on the ground 、 and can be defined by the following expression:

[0109] ;

[0110] wherein, 、 、 、 、 are first-order derivatives of corresponding parameters.

[0111] S153: determining the wavefront curvature phase compensation factor according to the second-order Taylor expansion formula.

[0112] Specifically, the wavefront curvature phase compensation factor is determined according to the obtained second-order Taylor expansion formula.

[0113] Optionally, based on the above embodiments, in some embodiments of the present application, an implementation of S153 can be: and The position of the target object in the azimuth direction and the range direction of the SAR image is determined, and when the quadratic coefficient is only non-0, the wavefront curvature causes defocusing in the azimuth direction of the SAR image. Based on this, in order to reduce the defocusing in the azimuth direction of the SAR image caused by the wavefront curvature, the wavefront curvature phase compensation factor is defined by the following expression:

[0114] ;

[0115] wherein, represents the quadratic coefficient in the second-order Taylor expansion formula, represents the azimuth wave number after rotation processing, represents the wavefront curvature phase compensation factor.

[0116] S154: Inverse Fourier transform is performed on the plurality of sub-SAR images in the azimuth direction to obtain a plurality of third echo signals.

[0117] S155: The wavefront curvature phase compensation factor is multiplied by the plurality of third echo signals, and Fourier transform is performed to obtain a plurality of target sub-SAR images.

[0118] S156: The target SAR image is obtained according to the plurality of target sub-SAR images.

[0119] Specifically, the coarse focusing SAR image is subjected to block processing to obtain a plurality of sub-SAR images corresponding to the coarse focusing SAR image, and the echo signals after motion compensation corresponding to each sub-SAR image are obtained. The second-order Taylor expansion formula of the echo signals in the azimuth direction is obtained, the wavefront curvature phase compensation factor is determined according to the second-order Taylor expansion formula, inverse Fourier transform is performed on the plurality of sub-SAR images in the azimuth direction to obtain a plurality of third echo signals, the wavefront curvature phase compensation factor is multiplied by the plurality of third echo signals, and Fourier transform is performed to obtain a plurality of target sub-SAR images. The plurality of target sub-SAR images are spliced to obtain the target SAR image.

[0120] In this way, the wavefront curvature phase compensation factor is used to perform wavefront curvature phase compensation on the coarse focusing SAR image, which can reduce the defocusing in the azimuth direction of the SAR image caused by the wavefront curvature and improve the quality of the SAR image.

[0121] Thus, the curved trajectory SAR imaging method with spatial time-varying acceleration provided in this embodiment first constructs a SAR imaging echo model of a high-speed mobile radar platform equipped with a synthetic aperture radar based on spatial time-varying acceleration, and obtains the true slant range history between the high-speed mobile radar platform and the target object. Then, based on the true slant range history, a to-be-processed echo signal in the spatial wavenumber domain is obtained. Furthermore, based on a preset Deramp compensation function constructed from the motion error of the high-speed mobile radar platform, the to-be-processed echo signal is compensated for non-space-varying motion and range unit migration to obtain a motion-compensated echo signal. In this way, the non-space-varying error introduced by the high-speed mobile radar platform during its motion under spatial time-varying acceleration is compensated, thereby achieving recovery and compression of the spectrum of the to-be-processed echo signal and obtaining a high-quality SAR image. Furthermore, the motion-compensated echo signal is interpolated using a rotational interpolation kernel function determined by the actual motion trajectory of the high-speed mobile radar platform to obtain an interpolated echo signal. A coarsely focused SAR image is then acquired based on the interpolated echo signal, thereby reducing spectral loss in the echo signal. Furthermore, because the rotational interpolation kernel function is derived using the actual motion trajectory, it can more accurately reflect the changes in the frequency support domain caused by the spatial time-varying acceleration signal, achieving precise two-dimensional interpolation of the echo signal and improving the quality of the SAR image. Finally, the coarsely focused SAR image is subjected to wavefront phase compensation based on a wavefront curvature phase compensation factor determined by the actual motion trajectory of the high-speed mobile radar platform to obtain a target SAR image. This reduces azimuth defocusing of the SAR image caused by wavefront curvature and improves the quality of the SAR image.

[0122] It should be understood that although Figure 1 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. In addition, Figure 1 At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.

[0123] In one embodiment, Figure 3 As shown, a curved trajectory SAR imaging device with spatial time-varying acceleration is provided, which includes: a model building module 11, a module for obtaining echo signals to be processed 12, a motion compensation module 13, an interpolation processing module 14, a coarse focusing SAR image acquisition module 15, and a phase compensation module 16.

[0124] The model construction module 11 is configured to construct a SAR imaging echo model of the high-speed maneuverable radar platform based on the spatial time-varying acceleration, and obtain a real slant range history between the high-speed maneuverable radar platform and the target object.

[0125] The echo signal to be processed acquisition module 12 is configured to acquire the echo signal to be processed in the spatial wave number domain according to the real slant range history.

[0126] The motion compensation module 13 is configured to perform non-ambispatial motion and range cell migration compensation on the echo signal to be processed according to a preset Deramp compensation function, to obtain a motion-compensated echo signal, wherein the preset Deramp compensation function is constructed according to the motion error of the high-speed maneuverable radar platform.

[0127] The interpolation processing module 14 is configured to perform interpolation processing on the motion-compensated echo signal according to a rotation interpolation kernel function, to obtain an interpolated echo signal.

[0128] The coarse-focusing SAR image acquisition module 15 is configured to acquire a coarse-focusing SAR image according to the interpolated echo signal.

[0129] The phase compensation module 16 is configured to perform wavefront curvature phase compensation on the coarse-focusing SAR image according to a wavefront curvature phase compensation factor, to obtain a target SAR image, wherein the rotation interpolation kernel function and the wavefront curvature phase compensation factor are determined according to the real motion trajectory of the high-speed maneuverable radar platform.

[0130] In the above embodiment, firstly, a SAR imaging echo model of a high-speed maneuverable radar platform carrying a synthetic aperture radar is constructed based on a spatial time-varying acceleration by a model construction module, a true slant range history between the high-speed maneuverable radar platform and a target object is obtained, then a to-be-processed echo signal acquisition module acquires the to-be-processed echo signal in a spatial wave number domain according to the true slant range history, further, a motion compensation module compensates the to-be-processed echo signal for non-space-variant motion and range cell migration according to a preset Deramp compensation function constructed by motion error of the high-speed maneuverable radar platform, to obtain the echo signal after motion compensation, in this way, the non-space-variant error introduced by the high-speed maneuverable radar platform in the motion process under the spatial time-varying acceleration is compensated, the spectrum of the to-be-processed echo signal is recovered and compressed, and a high-quality SAR image is acquired. Further, an interpolation processing module performs interpolation processing on the echo signal after motion compensation according to a rotation interpolation kernel function determined by the true motion trajectory of the high-speed maneuverable radar platform, to obtain the echo signal after interpolation, and a coarse focus SAR image acquisition module acquires a coarse focus SAR image according to the echo signal after interpolation, in this way, the spectrum loss of the echo signal is reduced, and since the rotation interpolation kernel function is derived using the true motion trajectory, the change of the frequency support domain caused by the spatial time-varying acceleration signal can be more accurately reflected, accurate two-dimensional interpolation processing of the echo signal is realized, and the quality of the SAR image is improved. Finally, a phase compensation module performs wavefront curvature phase compensation on the coarse focus SAR image according to a wavefront curvature phase compensation factor determined by the true motion trajectory of the high-speed maneuverable radar platform, to obtain a target SAR image, in this way, the defocusing of the SAR image in the azimuth direction caused by the wavefront curvature is reduced, and the quality of the SAR image is improved.

[0131] The specific limitations of the SAR imaging device for the curve trajectory of the spatial time-varying acceleration can be referred to the limitations of the SAR imaging method for the curve trajectory of the spatial time-varying acceleration in the above, which will not be repeated here. Each module in the above device can be realized by software, hardware and combinations thereof, in whole or in part. The above modules can be embedded in or independent of the processor in the computer device in hardware form, or can be stored in the memory in the computer device in software form, so as to be called and executed by the processor to perform the operations corresponding to the above modules.

[0132] Those skilled in the art can understand that all or part of the processes in the above embodiment methods can be completed by instructing related hardware through a computer program, which can be stored in a non-volatile computer readable storage medium, and when executed, can include the processes of the above embodiments of each method.

[0133] Any combination of the technical features in the above embodiments can be made, and for the sake of brevity, not all possible combinations are described above, however, as long as the combination of the technical features does not exist in contradiction, it shall be considered within the scope of the present disclosure.

[0134] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it shall not be understood as a limitation on the scope of the patent. It should be pointed out that, for those skilled in the art, some modifications and improvements can be made without departing from the concept of the present application, and these shall be within the protection scope of the present application.

Claims

1. A curved trajectory SAR imaging method with spatial time-varying acceleration, characterized in that: The method comprises: For a high-speed mobile radar platform equipped with a synthetic aperture radar, a SAR imaging echo model of the high-speed mobile radar platform is constructed based on spatial time-varying acceleration, and the true slant range history between the high-speed mobile radar platform and the target object is obtained; According to the true slant range history, obtaining an echo signal to be processed in a spatial wavenumber domain; performing non-space-varying motion and range unit migration compensation on the to-be-processed echo signal according to a preset Deramp compensation function, to obtain a motion-compensated echo signal, wherein the preset Deramp compensation function is constructed based on the motion error of the high-speed mobile radar platform; According to the rotation interpolation kernel function, the motion-compensated echo signal is interpolated to obtain an interpolated echo signal; Obtain a coarse-focused SAR image based on the interpolated echo signal; performing wavefront curvature phase compensation on the coarsely focused SAR image according to the wavefront curvature phase compensation factor to obtain a target SAR image, wherein the rotation interpolation kernel function and the wavefront curvature phase compensation factor are determined according to an actual motion trajectory of the high-speed maneuverable radar platform; The preset Deramp compensation function is defined by the following expression: in, Indicates the direction of slow time, represents the distance wave number, Indicates the true slant distance history of the center point corresponding to the scene center, is the symbol of the imaginary part, represents the Deramp compensation factor used to compensate for the non-space-varying phase error; The step of performing wavefront bending phase compensation on the coarsely focused SAR image according to the wavefront bending phase compensation factor to obtain a target SAR image includes: Acquiring motion-compensated echo signals corresponding to a plurality of sub-SAR images of the coarsely focused SAR image; For each motion-compensated echo signal corresponding to the sub-SAR image, obtaining a second-order Taylor expansion formula of the echo signal; Determining the wavefront curvature phase compensation factor according to the second-order Taylor expansion formula; Perform inverse Fourier transform on multiple sub-SAR images in azimuth direction to obtain multiple third echo signals; Multiplying the wavefront bending phase compensation factor with the plurality of third echo signals and performing Fourier transform to obtain a plurality of target sub-SAR images; Obtaining the target SAR image according to the multiple target sub-SAR images; The wavefront curvature phase compensation factor is defined by the following expression: ； in, represents the coefficient of the quadratic term in the second-order Taylor expansion formula, represents the azimuthal wave number after rotation processing, represents the wavefront bending phase compensation factor.

2. The method according to claim 1, characterized in that The method of constructing a SAR imaging echo model of a high-speed mobile radar platform based on spatial time-varying acceleration includes: Establishing a spatial coordinate system with the center of the scene as the coordinate origin, wherein the X-axis and Y-axis of the spatial coordinate system are parallel to the ground, and the Z-axis is perpendicular to the ground; determining a speed of the high-speed maneuverable radar platform in the spatial coordinate system; A SAR imaging echo model is constructed according to the velocity and the spatial time-varying acceleration.

3. The method according to claim 2, characterized in that The SAR imaging echo model is defined by the following expression: ； in, Indicates the direction of slow time, represents the speed of the high-speed mobile radar platform in the X-axis, Y-axis and Z-axis directions, represents the corresponding synthetic aperture center position coordinates on the high-speed mobile radar platform, represents the acceleration in the X-axis direction on the high-speed mobile radar platform, express The first time derivative of express The second-order time derivative of represents the acceleration in the Y-axis direction on the high-speed mobile radar platform, express The first time derivative of express The second-order time derivative of represents the acceleration in the Z-axis direction on the high-speed mobile radar platform, express The first time derivative of express The second-order time derivative of ; represents the instantaneous position of the high-speed mobile radar platform on the X axis in azimuth slow time, represents the instantaneous position of the high-speed mobile radar platform on the Y axis in the azimuth slow time, represents the instantaneous position of the high-speed mobile radar platform on the Z axis during azimuth slow time; The true slope range history is defined by the following expression: ； in, Indicates the location coordinates of the target object, It represents the actual slant range history between the slow-time target object and the high-speed mobile radar platform in azimuth.

4. The method according to claim 1, wherein The step of obtaining the echo signal to be processed in the spatial wavenumber domain according to the true slant range history includes: Based on the true slant range history, receiving a fundamental frequency signal scattered back by the target object; The baseband signal is subjected to range-direction Fourier transform and range-direction pulse compression processing to obtain an echo signal to be processed in a spatial wavenumber domain.

5. The method according to claim 1, wherein The method of constructing the preset Deramp compensation function includes: Obtaining a motion error of the high-speed mobile radar platform according to the actual motion trajectory and the ideal motion trajectory of the high-speed mobile radar platform; A preset Deramp compensation function is constructed according to the motion error.

6. The method according to claim 1, characterized in that The interpolation processing is performed on the motion-compensated echo signal according to the rotation interpolation kernel function to obtain the interpolated echo signal, including: Acquire a second echo signal in the spatial wavenumber domain corresponding to a first-order Taylor expansion formula of the motion-compensated echo signal; multiplying the rotation interpolation kernel function by the second echo signal to obtain an interpolated echo signal; The rotation interpolation kernel function is defined by the following expression: ； in, represents the azimuthal wave number, represents the range wave number, It represents the angle between the line of sight of the synthetic aperture radar and the projection of the motion direction relative to the ground. represents the azimuthal wave number after rotation processing, Represents the range wavenumber after rotation processing.

7. The method according to claim 1, characterized in that The method of acquiring a coarse-focused SAR image according to the interpolated echo signal includes: The interpolated echo signal is subjected to inverse Fourier transform processing in the range direction and Fourier transform processing in the azimuth direction to obtain a coarse-focused SAR image.

8. A curved trajectory SAR imaging device with spatial time-varying acceleration, characterized in that: The device comprises: A model building module is used to build a SAR imaging echo model of a high-speed mobile radar platform equipped with a synthetic aperture radar based on spatial time-varying acceleration, and obtain a true slant range history between the high-speed mobile radar platform and a target object; a module for acquiring an echo signal to be processed, configured to acquire an echo signal to be processed in a spatial wavenumber domain according to the true slant range history; a motion compensation module, configured to perform non-space-variant motion and range unit migration compensation on the to-be-processed echo signal according to a preset Deramp compensation function, to obtain a motion-compensated echo signal, wherein the preset Deramp compensation function is constructed based on the motion error of the high-speed mobile radar platform; The preset Deramp compensation function is defined by the following expression: ； in, Indicates the direction of slow time, represents the distance wave number, Indicates the true slant distance history of the center point corresponding to the scene center, is the symbol of the imaginary part, represents the Deramp compensation factor used to compensate for the non-space-varying phase error; An interpolation processing module is used to perform interpolation processing on the motion-compensated echo signal according to a rotation interpolation kernel function to obtain an interpolated echo signal; A coarse-focused SAR image acquisition module, configured to acquire a coarse-focused SAR image based on the interpolated echo signal; a phase compensation module, configured to perform wavefront curvature phase compensation on the coarsely focused SAR image according to a wavefront curvature phase compensation factor to obtain a target SAR image, wherein the rotation interpolation kernel function and the wavefront curvature phase compensation factor are determined according to an actual motion trajectory of the high-speed maneuverable radar platform; The step of performing wavefront bending phase compensation on the coarsely focused SAR image according to the wavefront bending phase compensation factor to obtain a target SAR image includes: Acquiring motion-compensated echo signals corresponding to a plurality of sub-SAR images of the coarsely focused SAR image; For each motion-compensated echo signal corresponding to the sub-SAR image, obtaining a second-order Taylor expansion formula of the echo signal; Determining the wavefront curvature phase compensation factor according to the second-order Taylor expansion formula; Perform inverse Fourier transform on multiple sub-SAR images in azimuth direction to obtain multiple third echo signals; Multiplying the wavefront bending phase compensation factor with the plurality of third echo signals and performing Fourier transform to obtain a plurality of target sub-SAR images; Obtaining the target SAR image according to the multiple target sub-SAR images; The wavefront curvature phase compensation factor is defined by the following expression: ； in, represents the coefficient of the quadratic term in the second-order Taylor expansion formula, represents the azimuthal wave number after rotation processing, represents the wavefront bending phase compensation factor.

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