Curve track SAR (Synthetic Aperture Radar) imaging method and device based on space time-varying acceleration

Abstract

The invention relates to the technical field of SAR imaging, provides a curve track SAR imaging method and device based on space time-varying acceleration, and aims at a high-speed maneuvering radar platform carrying a synthetic aperture radar, an SAR imaging echo model is constructed based on the space time-varying acceleration, and a real slope distance process between the high-speed maneuvering radar platform and a target object is obtained. And obtaining a to-be-processed echo signal in the spatial wave number domain according to the real slant range history, and performing non-space-variant motion and range unit migration compensation on the to-be-processed echo signal according to a preset Deramp compensation function constructed by the motion error. And performing interpolation processing on the echo signal according to a rotation interpolation kernel function determined by the real motion trail to obtain an interpolated echo signal, and obtaining a coarse focusing SAR image according to the interpolated echo signal. And carrying out wavefront bending phase compensation on the coarse focusing SAR image according to a wavefront bending phase compensation factor determined by the real motion trail to obtain a target SAR image.

Description

Technical Field

[0001] The present invention relates to the technical field of SAR imaging, and in particular to a curved trajectory SAR imaging method and device based on spatial time-varying acceleration. Background Art

[0002] At present, Synthetic Aperture Radar (SAR) is a high-resolution imaging radar that can obtain high-resolution radar images similar to optical photography under extremely low visibility weather conditions. In recent years, SAR imaging technology has made great progress, especially SAR imaging for highly maneuverable platform motion.

[0003] Conventional synthetic aperture radar imaging technologies include backprojection and range migration. The backprojection algorithm reconstructs the ground scene by projecting the echo signal pulse by pulse through the slant range history of a ground grid, thereby acquiring SAR images. The range migration algorithm resamples the range-frequency axis through interpolation to achieve two-dimensional phase linearization, and then constructs a slant range model based on a high-order Taylor expansion to acquire SAR images.

[0004] However, existing methods are unsuitable for real-time SAR imaging of highly maneuverable platforms due to the high complexity of the backprojection algorithm and its inability to compensate for the motion errors inherent in the platform's motion. For range migration algorithms, their overreliance on a finite-order radar slant range model results in severe defocusing of the two-dimensional frequency domain's non-space-variant compensation characteristics over a wide range of scenes, hindering existing methods from acquiring high-quality SAR imaging of highly maneuverable platforms. Summary of the Invention

[0005] Based on this, it is necessary to provide a curved trajectory SAR imaging method and device based on spatial time-varying acceleration to address the above technical problems.

[0006] In a first aspect, an embodiment of the present invention provides a curved trajectory SAR imaging method based on spatial time-varying acceleration, the method comprising: 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; Acquiring a coarse-focused SAR image according to the interpolated echo signal; According to the 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 the actual motion trajectory of the high-speed maneuverable radar platform.

[0007] In a second aspect, an embodiment of the present invention provides a curved trajectory SAR imaging device based on spatial time-varying acceleration, the device comprising: 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; 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 is used 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 the actual motion trajectory of the high-speed maneuvering radar platform.

[0008] The technical solution provided by the embodiment of the present invention has the following advantages compared with the existing technology: The curved trajectory SAR imaging method based on spatial time-varying acceleration provided by an embodiment of the present invention 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, the spectrum of the to-be-processed echo signal is restored and compressed, and a high-quality SAR image is obtained. 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 A schematic flow chart of a curved trajectory SAR imaging method based on spatial time-varying acceleration provided by an embodiment of the present invention; Figure 2 A schematic diagram of a spatial coordinate system provided by an embodiment of the present invention; Figure 3 A schematic structural diagram of a curved trajectory SAR imaging device based on spatial time-varying acceleration provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0010] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein can be combined with each other.

[0011] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all the embodiments.

[0012] At present, synthetic aperture radar is a high-resolution imaging radar. It can obtain high-resolution radar images similar to optical photography under extremely low visibility weather conditions. In recent years, synthetic aperture radar imaging technology has made great progress, especially synthetic aperture radar imaging for high-maneuverability platform movement.

[0013] Conventional synthetic aperture radar imaging technologies include backprojection and range migration. The backprojection algorithm reconstructs the ground scene by projecting the echo signal pulse by pulse through the slant range history of a ground grid, thereby acquiring SAR images. The range migration algorithm resamples the range-frequency axis through interpolation to achieve two-dimensional phase linearization, and then constructs a slant range model based on a high-order Taylor expansion to acquire SAR images.

[0014] However, existing methods are unsuitable for real-time SAR imaging of highly maneuverable platforms due to the high complexity of the backprojection algorithm and its inability to compensate for the motion errors inherent in the platform's motion. For range migration algorithms, their overreliance on a finite-order radar slant range model results in severe defocusing of the two-dimensional frequency domain's non-space-variant compensation characteristics over a wide range of scenes, hindering existing methods from acquiring high-quality SAR imaging of highly maneuverable platforms.

[0015] Therefore, the present invention provides a curved trajectory SAR imaging method based on spatial time-varying acceleration. First, 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. Then, based on the true slant range history, a to-be-processed echo signal in the spatial wavenumber domain is obtained. Furthermore, according to a preset Deramp compensation function constructed from the motion error of the high-speed mobile radar platform, non-space-varying motion and range unit migration compensation is performed on the to-be-processed echo signal 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 movement under spatial time-varying acceleration is compensated, the frequency spectrum of the to-be-processed echo signal is restored and compressed, and a high-quality SAR image is obtained. 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.

[0016] In one embodiment, Figure 1 As shown, Figure 1 A flow chart of a curved trajectory SAR imaging method based on spatial time-varying acceleration provided by an embodiment of the present invention specifically includes the following steps: S10: 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 actual slant range history between the high-speed mobile radar platform and the target object is obtained.

[0017] Among them, spatial time-varying acceleration refers to the acceleration that changes in real time during the movement of a high-speed mobile radar platform equipped with a synthetic aperture radar in the spatial domain.

[0018] The above-mentioned SAR imaging echo model refers to a model used to obtain the instantaneous position information of a high-speed mobile radar platform during movement.

[0019] 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.

[0020] 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.

[0021] 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: S101: Establish a spatial coordinate system with the center of the scene as the coordinate origin.

[0022] 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.

[0023] S102: Determine the speed and spatial time-varying acceleration of the high-speed maneuvering radar platform in a spatial coordinate system.

[0024] S103: Constructing a SAR imaging echo model according to the velocity and spatial time-varying acceleration.

[0025] 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.

[0026] Optionally, based on the above embodiment, in some embodiments of the present invention, the SAR imaging echo model may be defined by the following expression: ; in, Indicates the direction of slow time, Indicates the speed of the high-speed mobile radar platform in the X-axis, Y-axis and Z-axis directions, Indicates the coordinates of the synthetic aperture center position corresponding to 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 .

[0027] Optionally, based on the above embodiment, in some embodiments of the present invention, the true slant range history is defined by the following expression: ; in, Indicates the location coordinates of the target object, Indicates the true slant range history between the slow-time target object and the high-speed maneuvering radar platform in azimuth.

[0028] Exemplary, reference Figure 2 As shown, The point is the target object. Point is the coordinate of the synthetic aperture center corresponding to the high-speed mobile radar platform, and its coordinates are The line between the target object and the high-speed mobile radar platform is the true slant range course.

[0029] S11: According to the true slant range history, the echo signal to be processed in the spatial wavenumber domain is obtained.

[0030] Specifically, after the true slant range history is determined, an echo signal to be processed for imaging in the spatial wavenumber domain is obtained according to the true slant range history.

[0031] Optionally, based on the above embodiment, in some embodiments of the present invention, an implementation of S11 may be: S111: Based on the actual slant range history, receiving the baseband signal scattered back by the target object.

[0032] Specifically, based on the acquired true slant range history between the high-speed mobile radar platform and the target object, a baseband signal scattered back by the target object is received by a radar antenna mounted on the high-speed mobile radar platform.

[0033] Optionally, based on the above embodiment, in some embodiments of the present invention, the baseband signal may be defined by the following expression: ; in, represents the time domain expression of the range window function, Indicates fast time, represents the time domain expression of the azimuth window function, Indicates the frequency modulation of the transmitting signal. represents the speed of light, is the symbol of the imaginary part.

[0034] S112: Perform range-direction Fourier transform and range-direction pulse compression processing on the baseband signal to obtain an echo signal to be processed in the spatial wavenumber domain.

[0035] Specifically, the received baseband signal is subjected to range Fourier transform and range pulse compression processing to obtain an echo signal to be processed in the spatial wavenumber domain.

[0036] Optionally, following the above embodiment, in some embodiments of the present invention, the echo signal to be processed may be defined by the following expression: ; in, represents the distance wave number, Represents the spatial wavenumber domain form of the range window function, Indicates the carrier frequency, Indicates distance frequency.

[0037] S12: performing non-space-variant motion and range unit migration compensation on the echo signal to be processed according to a preset Deramp compensation function to obtain a motion-compensated echo signal.

[0038] Among them, the preset Deramp compensation function is a function constructed based on the motion error of the high-speed maneuvering radar platform.

[0039] Optionally, based on the above embodiment, in some embodiments of the present invention, one implementation method for constructing a preset Deramp compensation function based on the motion error of the high-speed mobile radar platform may be: S20: Obtain the 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.

[0040] The motion error can be specifically determined according to the difference between the slant distances from the actual motion trajectory and the ideal motion trajectory to the target object.

[0041] S21: Constructing a preset Deramp compensation function based on the motion error.

[0042] Specifically, for a high-speed mobile radar platform, the actual motion trajectory and ideal motion trajectory of the high-speed mobile radar platform are obtained, the slant distances from the actual motion trajectory and the ideal motion trajectory of the high-speed mobile radar platform to the target object are further calculated, and the difference between the two slant distances is calculated to obtain the motion error of the high-speed mobile radar platform. According to the motion error, a preset Deramp compensation function is constructed.

[0043] Optionally, based on the above embodiment, in some embodiments of the present invention, the preset Deramp compensation function is defined by the following expression: ; in, represents the distance wave number, Indicates the true slant distance history of the center point corresponding to the scene center, represents the Deramp compensation factor used to compensate for the non-space-varying phase error.

[0044] Specifically, according to a preset Deramp compensation function constructed from the motion error of a high-speed mobile radar platform, non-space-variant motion and range unit migration compensation is performed on the echo signal to be processed, thereby obtaining a motion-compensated echo signal.

[0045] Optionally, continuing with the above embodiment, non-space-variant motion and range unit migration compensation is performed on the echo signal to be processed, and the obtained motion-compensated echo signal can be defined by the following expression: .

[0046] In this way, this embodiment constructs a preset Deramp compensation function to achieve non-space-varying motion and range unit migration compensation for the echo signal to be processed, which can compensate for the non-space-varying errors introduced by the high-speed mobile radar platform during the movement under spatial time-varying acceleration, and achieve recovery and compression of the spectrum of the echo signal to be processed, thereby obtaining high-quality SAR images.

[0047] S13: performing interpolation processing on the motion-compensated echo signal according to the rotation interpolation kernel function to obtain an interpolated echo signal.

[0048] Among them, the rotation interpolation kernel function is determined according to the actual motion trajectory of the high-speed maneuvering radar platform, which can be used to reduce spectrum loss. Moreover, since the rotation interpolation kernel function is derived using the actual motion trajectory of the radar platform, it can more accurately reflect the changes in the frequency support domain caused by the spatial time-varying acceleration signal, thereby realizing accurate two-dimensional interpolation processing of the echo signal and improving the quality of the SAR image.

[0049] Specifically, a rotation interpolation kernel function is constructed using the real motion trajectory of the high-speed mobile radar platform, and the motion-compensated echo signal is interpolated according to the rotation interpolation kernel function to obtain the interpolated echo signal.

[0050] Optionally, based on the above embodiment, in some embodiments of the present invention, an implementation of S13 may be: S131: Acquire a second echo signal in the spatial wavenumber domain corresponding to a first-order Taylor expansion formula of the motion-compensated echo signal.

[0051] S132: Multiply the rotation interpolation kernel function and the second echo signal to obtain an interpolated echo signal.

[0052] 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.

[0053] Specifically, a first-order Taylor expansion is performed on the motion-compensated echo signal to obtain the first-order Taylor expansion formula of the motion-compensated echo signal, and the second echo signal of the first-order Taylor expansion formula in the spatial wavenumber domain is further obtained. The rotation interpolation kernel function is multiplied with the second echo signal to obtain the interpolated echo signal.

[0054] Optionally, continuing with the above embodiment, a first-order Taylor expansion is performed on the motion-compensated echo signal. The first-order Taylor expansion formula can be defined by the following expression: ; in, , are Taylor expansion coefficients, which can be abbreviated as , .

[0055] , They can be defined by the following expressions: ; Furthermore, the second echo signal of the first-order Taylor expansion formula in the spatial wavenumber domain is obtained. The second echo signal can be defined by the following expression: ; Finally, the rotation interpolation kernel function is multiplied by the second echo signal to obtain the interpolated echo signal. The interpolated echo signal can be defined by the following expression: ; In this way, this embodiment interpolates the motion-compensated echo signal through the rotation interpolation kernel function, which can reduce the spectrum loss of the echo signal. Moreover, since the rotation interpolation kernel function is derived using the actual motion trajectory of the radar platform, it can more accurately reflect the changes in the signal spectrum support domain caused by spatial time-varying acceleration, thereby achieving accurate two-dimensional interpolation processing of the echo signal and improving the quality of the SAR image.

[0056] S14: Acquire a coarse-focused SAR image according to the interpolated echo signal.

[0057] Optionally, based on the above embodiments, in some embodiments of the present invention, an implementation method of S14 may be: performing inverse Fourier transform processing on the interpolated echo signal in the range direction and performing Fourier transform processing in the azimuth direction to obtain a coarsely focused SAR image.

[0058] S15: Perform wavefront curvature phase compensation on the coarse-focused SAR image according to the wavefront curvature phase compensation factor to obtain a target SAR image.

[0059] Among them, the wavefront bending phase compensation factor is determined according to the actual motion trajectory of the high-speed mobile radar platform, and is used to further compensate for the geometric distortion and azimuth defocusing problems caused by the motion error of the high-speed mobile radar platform and the position of the target object.

[0060] Optionally, based on the above embodiment, in some embodiments of the present invention, an implementation of S15 may be: S151: Acquire motion-compensated echo signals corresponding to multiple sub-SAR images of the coarsely focused SAR image.

[0061] S152: For the motion-compensated echo signal corresponding to each sub-SAR image, obtain a second-order Taylor expansion formula of the echo signal.

[0062] For example, the second-order Taylor expansion formula of the motion-compensated echo signal corresponding to each initial sub-SAR image in the azimuth direction can be defined by the following expression: ; in, , the coefficient expression of Taylor expansion can be defined by the following expression: ; in, The angle between the line of sight of the synthetic aperture radar and the projection of the motion direction relative to the ground 、 as well as It can be qualified by the following expression: ; in, 、 、 、 、 are the first-order derivatives of the corresponding parameters.

[0063] S153: Determine the wavefront curvature phase compensation factor according to a second-order Taylor expansion formula.

[0064] Specifically, the wavefront curvature phase compensation factor is determined according to the obtained second-order Taylor expansion formula.

[0065] Optionally, based on the above embodiment, in some embodiments of the present invention, an implementation of S153 may be: and Determine the position of the target object in the SAR image in the azimuth and range directions. When it is not 0, the wavefront curvature will cause defocusing of the SAR image in the azimuth direction. Based on this, in order to reduce the defocusing of the SAR image in the azimuth direction caused by the wavefront curvature, 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.

[0066] S154: Perform inverse Fourier transform on the multiple sub-SAR images in azimuth direction to obtain multiple third echo signals.

[0067] S155: Multiply the wavefront bending phase compensation factor with the multiple third echo signals, and perform Fourier transform to obtain multiple target sub-SAR images.

[0068] S156: Obtain a target SAR image based on the multiple target sub-SAR images.

[0069] Specifically, a coarsely focused SAR image is processed in blocks to obtain motion-compensated echo signals corresponding to multiple sub-SAR images corresponding to the coarsely focused SAR image. For each motion-compensated echo signal corresponding to each sub-SAR image, a second-order Taylor expansion formula in azimuth is obtained. A wavefront curvature phase compensation factor is determined based on the second-order Taylor expansion formula. Inverse Fourier transforms are performed on the multiple sub-SAR images in azimuth to obtain multiple third echo signals. The wavefront curvature phase compensation factor is multiplied by the multiple third echo signals and Fourier transforms are performed to obtain multiple target sub-SAR images. The multiple target sub-SAR images are then spliced ​​together to obtain a target SAR image.

[0070] In this way, this embodiment performs wavefront curvature phase compensation on the coarsely focused SAR image through the wavefront curvature phase compensation factor, thereby reducing the defocusing of the SAR image in the azimuth direction caused by the wavefront curvature and improving the quality of the SAR image.

[0071] Thus, the curved trajectory SAR imaging method based on 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.

[0072] 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.

[0073] In one embodiment, Figure 3As shown, a curved trajectory SAR imaging device based on 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.

[0074] Among them, the model construction module 11 is used to construct 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 the actual slant range history between the high-speed mobile radar platform and the target object.

[0075] The to-be-processed echo signal acquisition module 12 is used to acquire the to-be-processed echo signal in the spatial wavenumber domain according to the true slant range history.

[0076] The motion compensation module 13 is used to perform non-space-varying motion and range unit 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 based on the motion error of the high-speed mobile radar platform.

[0077] 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.

[0078] The coarse-focused SAR image acquisition module 15 is configured to acquire a coarse-focused SAR image according to the interpolated echo signal.

[0079] The phase compensation module 16 is used to perform wavefront curvature phase compensation on the coarse-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 the actual motion trajectory of the high-speed maneuvering radar platform.

[0080] In the above embodiment, first, a SAR imaging echo model of a high-speed mobile radar platform equipped with a synthetic aperture radar is constructed by a model construction module based on spatial time-varying acceleration for the high-speed mobile radar platform, and the actual slant range history between the high-speed mobile radar platform and the target object is obtained. Then, the to-be-processed echo signal acquisition module obtains the to-be-processed echo signal in the spatial wavenumber domain based on the actual slant range history. Furthermore, the motion compensation module performs non-space-varying motion and range unit migration compensation on the to-be-processed echo signal based on a preset Deramp compensation function constructed from the motion error of the high-speed mobile radar platform 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 movement under spatial time-varying acceleration is compensated, thereby realizing the recovery and compression of the to-be-processed echo signal spectrum and obtaining a high-quality SAR image. Furthermore, the interpolation processing module interpolates the motion-compensated echo signal based on a rotational interpolation kernel function determined by the actual motion trajectory of the high-speed mobile radar platform to obtain an interpolated echo signal. The coarse-focused SAR image acquisition module obtains a coarse-focused SAR image based on the interpolated echo signal, thereby reducing the spectral loss of the echo signal. Since 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 processing of the echo signal and improving the quality of the SAR image. Finally, the phase compensation module performs wavefront curvature phase compensation on the coarse-focused SAR image based on the 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 the defocus of the SAR image in the azimuth direction caused by the wavefront curvature and improves the quality of the SAR image.

[0081] The specific limitations of the curved trajectory SAR imaging device based on spatial time-varying acceleration can be found in the limitations of the curved trajectory SAR imaging method based on spatial time-varying acceleration above and will not be repeated here. Each module in the aforementioned device may be implemented in whole or in part via software, hardware, or a combination thereof. Each module may be embedded in or independent of a processor in a computer device in hardware form, or may be stored in a computer device memory in software form, so that the processor can call and execute the corresponding operations of each module.

[0082] Those skilled in the art will understand that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing related hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods.

[0083] The technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0084] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A curved trajectory SAR imaging method based on 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; According to the 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 the actual motion trajectory of the high-speed maneuverable radar platform.

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; Constructing a preset Deramp compensation function according to the motion error; 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.

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 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; The target SAR image is obtained according to the multiple target sub-SAR images.

8. The method according to claim 7, characterized in that 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, is the symbol of the imaginary part, represents the azimuthal wave number after rotation processing, Represents the wavefront bending phase compensation factor.

9. The method according to claim 1, characterized in that The step of acquiring a coarse-focused SAR image according to the interpolated echo signal comprises: 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.

10. A curved trajectory SAR imaging device based on 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; 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 is used 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 the actual motion trajectory of the high-speed maneuvering radar platform.

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