Airborne front-side view overlapped sub-aperture imaging method and device

Abstract

The invention provides an airborne front-side-looking overlapped sub-aperture imaging method and device, and particularly relates to the technical field of radar imaging processing, and the method comprises the steps: carrying out the preprocessing of original echo data, and obtaining first echo data and second echo data; performing azimuth segmentation on the first echo data to obtain a plurality of pieces of first sub-aperture data; utilizing a phase gradient self-focusing method to extract a phase error from the plurality of pieces of first sub-aperture data; compensating the second echo data based on the phase error to obtain third echo data; calculating a linear phase error according to the third echo data; combining the linear phase error with the phase error to obtain a total phase error; compensating the plurality of first sub-aperture data based on the total phase error to obtain a plurality of second sub-aperture data; obtaining a plurality of sub-aperture images according to the plurality of pieces of second sub-aperture data; and splicing the plurality of sub-aperture images, and outputting a full-aperture image.

Description

Technical Field

[0001] The present disclosure relates to the field of radar imaging processing technology, and more specifically, to an airborne front-view and side-view overlapping sub-aperture imaging method and device. Background Art

[0002] SAR (Synthetic Aperture Radar) imaging is an important method for terrain mapping, target observation and other applications because of its all-day and all-weather real-time detection of the ground. The key research directions of airborne SAR imaging are high-resolution, wide-bandwidth, high-efficiency imaging technology, and highly robust airborne SAR motion compensation methods. Airborne SAR imaging includes positive side-view imaging and oblique side-view imaging. Positive side-view imaging means that the aircraft motion direction is perpendicular to the antenna beam during imaging.

[0003] In airborne SAR real-time imaging systems, due to the requirement of high-resolution imaging, the accuracy of motion measurement errors needs to reach the wavelength level. However, the accuracy of inertial navigation is usually not achieved. Therefore, inertial navigation motion compensation combined with self-focusing motion compensation algorithm is often used to compensate for motion errors. In the case of limited inertial navigation accuracy, residual phase error compensation through self-focusing can improve imaging quality and achieve high-resolution imaging that is not affected by the motion of the carrier platform.

[0004] OSA (Overlapped Subaperture Algorithm) can compensate for wavefront curvature, correct space-variant phase errors, increase imaging range, and generate high-resolution images. It is an imaging method suitable for real-time processing. The PGA (Phase Gradient Autofocus) method is based on data estimation and corrects phase errors of any order except the first order. It has advantages in estimating high-order phase errors and is highly applicable.

[0005] At present, for airborne SAR imaging methods, after using the PGA method to compensate for the residual carrier motion error, the PGA method cannot estimate the impact of the linear phase error on the imaging quality.

[0006] Although the residual linear phase error will not affect the focusing effect of the sub-image in the OSA algorithm, it will cause the phase compensation mismatch in the processing process, resulting in a decrease in the ratio of the target energy in the main area and the energy in the blurred area, affecting the effect of image stitching in OSA and ultimately reducing the image quality. Summary of the invention

[0007] In view of this, the present disclosure provides an airborne front-side-view overlapping sub-aperture imaging method and device.

[0008] One aspect of the present disclosure provides an airborne positive side-view overlapping sub-aperture imaging method, comprising: preprocessing the original echo data to obtain first echo data and second echo data; wherein the preprocessing only considers the line of sight motion error; segmenting the first echo data in azimuth to obtain multiple first sub-aperture data; extracting the phase error from the multiple first sub-aperture data using a phase gradient self-focusing method; compensating the second echo data based on the phase error to obtain third echo data; calculating the linear phase error based on the third echo data; combining the linear phase error with the phase error to obtain a total phase error; compensating the multiple first sub-aperture data based on the total phase error to obtain multiple second sub-aperture data; obtaining multiple sub-aperture images based on the multiple second sub-aperture data; and splicing the multiple sub-aperture images to output a full-aperture image.

[0009] According to an embodiment of the present disclosure, the method further includes: performing azimuth segmentation on the second echo data to obtain a plurality of third sub-aperture data; and estimating the linear phase error based on the plurality of third sub-aperture data.

[0010] According to an embodiment of the present disclosure, calculating the linear phase error according to the third echo data includes: estimating the Doppler center according to the third echo data; and calculating the linear phase error according to the Doppler center.

[0011] According to an embodiment of the present disclosure, a phase gradient self-focusing method is used to extract a phase error from the above-mentioned multiple first sub-aperture data, including: performing a range-direction inverse Fourier transform on the above-mentioned multiple first sub-aperture data to obtain multiple two-dimensional image information; and extracting a phase error from the above-mentioned multiple two-dimensional image information using a phase gradient self-focusing method.

[0012] According to an embodiment of the present disclosure, the above-mentioned method also includes: before compensating the above-mentioned second echo data, removing the outstanding points of the above-mentioned second echo data, including: in the process of extracting the above-mentioned phase error using the above-mentioned phase gradient self-focusing method, extracting the distance index of the outstanding points of the above-mentioned first echo data, and removing the outstanding points in the above-mentioned second echo data according to the above-mentioned distance index, wherein the outstanding points in the above-mentioned second echo data represent the strong scattering points in the above-mentioned second echo data.

[0013] According to an embodiment of the present disclosure, the first echo data is segmented in azimuth to obtain a plurality of first sub-aperture data, including: discretizing the first echo data to obtain discretized first echo data, wherein the discretization includes time domain discretization in azimuth and frequency domain discretization in range; segmenting the discretized first echo data in azimuth to obtain a plurality of sub-aperture data; performing linear frequency modulation Z transform on the plurality of sub-aperture data to obtain the plurality of first sub-aperture data.

[0014] According to an embodiment of the present disclosure, a plurality of sub-aperture images are obtained based on the above-mentioned plurality of second sub-aperture data, including: estimating the target azimuth position based on the above-mentioned plurality of second sub-aperture data; estimating a first error parameter based on the above-mentioned target azimuth position; estimating a first precise phase error based on the above-mentioned first error parameter; compensating the above-mentioned plurality of second sub-aperture data based on the above-mentioned first precise phase error to obtain a plurality of fourth sub-aperture data; performing inverse Fourier transform in the range direction on the above-mentioned plurality of fourth sub-aperture data to obtain a plurality of fifth sub-aperture data; and obtaining the above-mentioned plurality of sub-aperture images based on the above-mentioned plurality of fifth sub-aperture data.

[0015] According to an embodiment of the present disclosure, the multiple sub-aperture images are obtained based on the multiple fifth sub-aperture data, including: estimating the target range position based on the multiple fifth sub-aperture data; estimating the second error parameter based on the target range position and the target azimuth position; estimating the second precise phase error based on the second error parameter; compensating the multiple fifth sub-aperture data based on the second precise phase error to obtain multiple sixth sub-aperture data; performing inter-subaperture Fourier transform on the multiple sixth sub-aperture data to obtain multiple seventh sub-aperture data; generating the multiple sub-aperture images based on the multiple seventh sub-aperture data.

[0016] According to an embodiment of the present disclosure, the original echo data is preprocessed to obtain first echo data and second echo data, including: performing a range-direction Fourier transform on the original echo data after inertial navigation compensation to obtain echo data after Fourier transform; filtering the above-mentioned echo data after Fourier transform through a filter to obtain preprocessed echo data; performing range-direction interpolation on the above-mentioned preprocessed echo data to obtain the above-mentioned first echo data; performing range-direction sampling on the above-mentioned preprocessed echo data to obtain the above-mentioned second echo data.

[0017] Another aspect of the present disclosure provides an airborne positive side-view overlapping sub-aperture imaging device, comprising: a first obtaining module, used to pre-process the original echo data to obtain first echo data and second echo data; a second obtaining module, used to perform azimuth segmentation on the above-mentioned first echo data to obtain multiple first sub-aperture data; an extraction module, used to extract phase errors from the above-mentioned multiple first sub-aperture data using a phase gradient self-focusing method; a first compensation module, used to compensate the above-mentioned second echo data based on the above-mentioned phase error to obtain third echo data; a calculation module, used to calculate the linear phase error according to the above-mentioned third echo data; a third obtaining module, used to combine the above-mentioned linear phase error with the above-mentioned phase error to obtain a total phase error; a second compensation module, used to compensate the above-mentioned multiple first sub-aperture data based on the above-mentioned total phase error to obtain multiple second sub-aperture data; a fourth obtaining module, used to obtain multiple sub-aperture images according to the above-mentioned multiple second sub-aperture data; and an output module, used to splice the above-mentioned multiple sub-aperture images to output a full-aperture image.

[0018] Another aspect of the present disclosure provides an electronic device, comprising:

[0019] one or more processors;

[0020] a memory for storing one or more programs,

[0021] When the one or more programs are executed by the one or more processors, the one or more processors implement the method as described above.

[0022] According to an embodiment of the present disclosure, a plurality of sub-aperture images are obtained by performing azimuth segmentation on the first echo data, and the full-aperture phase error is extracted from the sub-aperture image using a phase gradient self-focusing method and compensated to the second echo data. The Doppler center and its corresponding linear phase error are estimated based on the third echo data compensated by the phase gradient self-focusing method, and the phase error extracted by the phase gradient self-focusing method is combined with the linear phase error to obtain a total phase error, which is then compensated to the sub-aperture data of the first echo data. The residual linear phase error can be compensated, thereby improving the imaging performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0024] Figure 1 An exemplary system architecture 100 to which an airborne positive side-view overlapping sub-aperture imaging method can be applied according to an embodiment of the present disclosure is schematically shown;

[0025] Figure 2The flowchart of the airborne positive side-view overlapping sub-aperture imaging method according to an embodiment of the present disclosure is schematically shown;

[0026] FIG3( a ) schematically shows an imaging result diagram with linear phase error compensation according to an embodiment of the present disclosure;

[0027] FIG3( b ) schematically shows an imaging result diagram of a non-linear phase error compensation according to an embodiment of the present disclosure;

[0028] Figure 4 A schematic diagram schematically shows an airborne positive side-view overlapping sub-aperture imaging device according to an embodiment of the present disclosure; and

[0029] Figure 5 A block diagram of an electronic device suitable for implementing an airborne positive side-view overlapping sub-aperture imaging method according to an embodiment of the present disclosure is schematically shown. DETAILED DESCRIPTION

[0030] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0031] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0032] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0033] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0034] Airborne synthetic aperture radar (SAR) operates by transmitting microwave radar signals to the earth and receiving the reflected signals. The radar antenna moves with the airborne platform and can obtain target echo data at different azimuths. These target echo data are processed and stitched together to form a complete navigation radar image. The resolution of SAR images is divided into range resolution and azimuth resolution. Range resolution is the resolution in the direction of the antenna beam line of sight, which is related to the radar's ability to distinguish between two targets at different distances but close to each other. It depends on the pulse bandwidth of the radar signal. Azimuth resolution is the resolution along the flight direction, which involves the radar's ability to distinguish between two targets that are closely located together in the vertical direction of the radar line of sight.

[0035] Airborne synthetic aperture radar SAR obtains synthetic aperture images through radar echo data. The overlapping sub-aperture algorithm OSA divides the large synthetic aperture image data into multiple overlapping sub-aperture data, performs imaging processing on each sub-aperture data, and then aligns and fuses multiple sub-aperture images to obtain a full-aperture image with higher imaging quality and resolution. After motion compensation based on inertial navigation data, residual motion errors will have a greater impact on imaging when data is resampled.

[0036] The self-focusing technology based on echo data plays an important role in high-resolution imaging. The self-focusing technology effectively compensates for the residual motion error after motion compensation and the phase error caused by various other factors. The self-focusing technology includes the phase gradient self-focusing method, namely the PGA algorithm, which uses the estimation of the SAR echo data itself to remove the residual phase error. The PGA algorithm directly estimates the phase error. It can compensate for low-order and high-order phase errors and is a highly robust self-focusing technology. The PGA algorithm has a good suppression of image defocusing, but cannot compensate for the image translation caused by linear phase error.

[0037] In the related art, an airborne real-time imaging system that forms high-quality images using the OSA method and the phase gradient autofocus PGA method is used. In the OSA method, the complete synthetic aperture in azimuth is divided into multiple overlapping sub-apertures for processing. The system performs real-time motion compensation by adjusting the parameters of the transmitter and the receiver, and performs de-skewing at the receiving end. The received signal is a signal after de-skewing and range interpolation. The received signal is processed by azimuth coarse resolution and range fine resolution to obtain an azimuth coarse resolution image of the sub-aperture, and then the phase gradient autofocus PGA method is used to remove residual motion errors, and after azimuth fine resolution processing, finally, a full-aperture fine resolution image is obtained by screening and splicing.

[0038] In the related art, a non-de-slanted reception method is also used to perform pulse compression and interpolation on the received signal in the range direction, and an OSA method is used in the azimuth direction.

[0039] In the overlapping sub-aperture algorithm OSA, the phase gradient self-focusing method has great advantages in estimating high-order phase errors. However, the linear phase error is ignored in the phase error estimated by the phase gradient self-focusing method, and the residual linear error will affect the alignment of the images between sub-apertures in the OSA method, resulting in a decrease in the ratio of the target energy in the main area and the energy in the blurred area, affecting the stitching effect and reducing the image quality.

[0040] The embodiment of the present disclosure provides an airborne positive side-view overlapping sub-aperture imaging method, comprising: preprocessing the original echo data to obtain first echo data and second echo data; wherein the preprocessing only considers the line of sight motion error; segmenting the first echo data in azimuth to obtain multiple first sub-aperture data; extracting the phase error from the multiple first sub-aperture data using a phase gradient self-focusing method; compensating the second echo data based on the phase error to obtain third echo data; calculating the linear phase error based on the third echo data; combining the linear phase error with the phase error to obtain a total phase error; compensating the multiple first sub-aperture data based on the total phase error to obtain multiple second sub-aperture data; obtaining multiple sub-aperture images based on the multiple second sub-aperture data; and splicing the multiple sub-aperture images to output a full-aperture image.

[0041] The present invention obtains the first echo data and the second echo data by preprocessing the original echo data, extracts the phase error by using the phase gradient self-focusing method, and compensates it to the second echo data to obtain the third echo data, calculates the linear phase error according to the third echo data, combines the linear phase error with the phase error to obtain the total phase error, compensates the total phase error to the first sub-aperture data, and finally outputs the full-aperture image. In the imaging process of the sub-aperture image corresponding to the first echo data, the residual linear phase error is estimated, and the residual linear phase error is combined with the phase error extracted by the phase gradient self-focusing method. By using the phase gradient self-focusing method, a sub-aperture image with a good focusing effect can be obtained. At the same time, the residual linear phase error is combined and compensated, which can improve the stitching effect of the sub-aperture images and obtain a full-aperture image with better image quality.

[0042] Figure 1 The exemplary system architecture 100 to which the airborne positive side-view overlapping sub-aperture imaging method can be applied according to an embodiment of the present disclosure is schematically shown. It should be noted that: Figure 1 What is shown is merely an example of a system architecture to which the embodiments of the present disclosure can be applied, in order to help those skilled in the art understand the technical content of the present disclosure, but it does not mean that the embodiments of the present disclosure cannot be used in other devices, systems, environments or scenarios.

[0043] like Figure 1 As shown, the system architecture 100 according to this embodiment may include a first terminal device 101, a second terminal device 102, a third terminal device 103, a network 104, and a server 105. The network 104 is used to provide a medium for a communication link between the first terminal device 101, the second terminal device 102, the third terminal device 103, and the server 105. The network 104 may include various connection types, such as wired and / or wireless communication links, etc.

[0044] The user may use the first terminal device 101, the second terminal device 102, and the third terminal device 103 to interact with the server 105 through the network 104 to receive or send messages, etc. Various communication client applications may be installed on the first terminal device 101, the second terminal device 102, and the third terminal device 103, such as shopping applications, web browser applications, search applications, instant messaging tools, email clients, and / or social platform software, etc. (only for example).

[0045] The first terminal device 101, the second terminal device 102, and the third terminal device 103 may be various electronic devices having display screens and supporting web browsing, including but not limited to smart phones, tablet computers, laptop computers, desktop computers, and the like.

[0046] The server 105 may be a server that provides various services, such as a background management server (only as an example) that provides support for websites browsed by users using the first terminal device 101, the second terminal device 102, and the third terminal device 103. The background management server may analyze and process the received data such as user requests, and feed back the processing results (such as web pages, information, or data obtained or generated according to user requests) to the terminal device.

[0047] It should be noted that the airborne positive side view overlapping sub-aperture imaging method provided in the embodiment of the present disclosure can generally be executed by the server 105. Accordingly, the airborne positive side view overlapping sub-aperture imaging device provided in the embodiment of the present disclosure can generally be set in the server 105. The airborne positive side view overlapping sub-aperture imaging method provided in the embodiment of the present disclosure can also be executed by a server or server cluster that is different from the server 105 and can communicate with the first terminal device 101, the second terminal device 102, the third terminal device 103 and / or the server 105. Accordingly, the airborne positive side view overlapping sub-aperture imaging device provided in the embodiment of the present disclosure can also be set in a server or server cluster that is different from the server 105 and can communicate with the first terminal device 101, the second terminal device 102, the third terminal device 103 and / or the server 105. Alternatively, the airborne positive and side-view overlapping sub-aperture imaging method provided in the embodiment of the present disclosure may also be performed by the first terminal device 101, the second terminal device 102, or the third terminal device 103, or may also be performed by other terminal devices different from the first terminal device 101, the second terminal device 102, or the third terminal device 103. Accordingly, the airborne positive and side-view overlapping sub-aperture imaging apparatus provided in the embodiment of the present disclosure may also be provided in the first terminal device 101, the second terminal device 102, or the third terminal device 103, or may be provided in other terminal devices different from the first terminal device 101, the second terminal device 102, or the third terminal device 103.

[0048] It should be understood that Figure 1 The number of terminal devices, networks and servers in the embodiment is only for illustration. Any number of terminal devices, networks and servers may be provided according to implementation requirements.

[0049] Figure 2 The flowchart of the airborne positive side-view overlapping sub-aperture imaging method according to an embodiment of the present disclosure is schematically shown.

[0050] like Figure 2 As shown, the airborne positive side-view overlapping sub-aperture imaging method includes operations S210 to S290.

[0051] In operation S210, the original echo data is preprocessed to obtain first echo data and second echo data.

[0052] In operation S220, the first echo data is segmented in azimuth to obtain a plurality of first sub-aperture data.

[0053] In operation S230, a phase error is extracted from the plurality of first sub-aperture data using a phase gradient self-focusing method.

[0054] In operation S240, the second echo data is compensated based on the phase error to obtain third echo data.

[0055] In operation S250, a linear phase error is calculated according to the third echo data.

[0056] In operation S260, the linear phase error is combined with the phase error to obtain a total phase error.

[0057] In operation S270, the plurality of first sub-aperture data are compensated based on the total phase error to obtain a plurality of second sub-aperture data.

[0058] In operation S280, a plurality of sub-aperture images are obtained according to the plurality of second sub-aperture data.

[0059] In operation S290, the plurality of sub-aperture images are stitched together to output a full-aperture image.

[0060] According to an embodiment of the present disclosure, the original echo data is an echo signal in a strip imaging mode obtained based on the front and side views of an airborne SAR.

[0061] According to an embodiment of the present disclosure, the original echo data is digital echo data containing motion errors after demodulation, wherein the pre-processing only considers the motion error in the line of sight direction.

[0062] According to an embodiment of the present disclosure, the original echo data can be expressed as:

[0063] (1)

[0064] in, Indicates the direction and time, represents distance to time, , They are synthetic aperture time and range pulse width, , are the distance from the antenna phase center to the target position and the line of sight distance error, is the range modulation frequency, is the radar frequency. j represents the imaginary unit and c represents the speed of light.

[0065] According to an embodiment of the present disclosure, inertial navigation information is used to perform phase compensation on the original echo data in the time domain. The original echo data after inertial navigation compensation can be expressed as:

[0066] (2)

[0067] According to an embodiment of the present disclosure, the original echo data after inertial navigation compensation is subjected to a range Fourier transform to obtain echo data after Fourier transform, which can be expressed as:

[0068] (3)

[0069] According to an embodiment of the present disclosure, the echo data after Fourier transformation contains frequency domain information in the range direction and time domain information in the azimuth direction.

[0070] According to an embodiment of the present disclosure, the echo data after Fourier transformation is filtered by a filter to obtain preprocessed echo data.

[0071] According to an embodiment of the present disclosure, the filter function can be expressed as:

[0072] (4)

[0073] The first term is the matching function of the range-directed linear frequency modulation signal, and the second term is the matching function centered on the imaging scene. is the distance from the antenna phase center to the center of the imaging scene.

[0074] According to an embodiment of the present disclosure, range interpolation is performed on the preprocessed echo data to obtain first echo data.

[0075] According to an embodiment of the present disclosure, range sampling is performed on the pre-processed echo data to obtain second echo data.

[0076] According to the embodiment of the present disclosure, the pre-processed echo data is interpolated in the range direction, which can eliminate the time variation of the range information part in the azimuth information. The pre-processed echo data is sampled in the range direction, and the second echo data is stored for subsequent use.

[0077] According to an embodiment of the present disclosure, the first echo data is discretized to obtain discretized first echo data, wherein the discretization includes time domain discretization in azimuth and frequency domain discretization in range.

[0078] According to an embodiment of the present disclosure, the azimuth time domain discretization representation is to represent the first echo data in a discrete form in azimuth time. The azimuth time discretization can be expressed as:

[0079] (5)

[0080] Where T is the pulse sampling time interval, represents the discretized variable of azimuth time, , N represents the number of complete aperture sampling points in azimuth.

[0081] According to an embodiment of the present disclosure, the range-to-frequency-domain discretization representation is to represent the first echo data in a discrete form in the range-to-frequency-domain. The range-to-frequency-domain discretization can be represented as:

[0082] (6)

[0083] in, and Respectively represent the distance sampling frequency and the number of distance sampling points, represents the discretized variable of distance in frequency domain, , I represents the number of sampling points in the distance direction.

[0084] According to an embodiment of the present disclosure, the discretized first echo data is segmented in azimuth to obtain a plurality of sub-aperture data.

[0085] According to an embodiment of the present disclosure, the sub-apertures are divided according to a phase error limitation principle.

[0086] According to an embodiment of the present disclosure, the discretized first echo data is divided into azimuth sub-apertures, which can be expressed as:

[0087] (7)

[0088] in, , , .

[0089] According to an embodiment of the present disclosure, formula (7) represents the division of the azimuth sub-aperture of the discretized first echo data. After the division, the complete azimuth variable Become a variable within the subaperture and inter-subaperture variation , the azimuths overlap in a certain ratio, and the certain ratio range includes 75%±5%: for example, the ratio is 75%.

[0090] According to the embodiment of the present disclosure, N represents the number of sampling points of the complete aperture in azimuth, N1 represents the number of sampling points of each sub-aperture in azimuth, N2 represents the number of sub-apertures, Indicates the number of sampling points between the starting positions of two adjacent sub-apertures in azimuth.

[0091] According to an embodiment of the present disclosure, a plurality of sub-aperture data are subjected to linear frequency modulation Z-transformation to obtain a plurality of first sub-aperture data.

[0092] According to an embodiment of the present disclosure, The chirp-z transform (CZT) is used in the dimensional space to eliminate the change of the azimuth information with the sampling variable in the range direction and realize the orthogonal uniform sampling in the range and azimuth directions.

[0093] According to the embodiment of the present disclosure, the full aperture corresponding to the first echo data is divided into sub-apertures to obtain multiple sub-aperture data, and the data between two adjacent sub-aperture data has a certain proportion of overlap to ensure smooth splicing of the sub-apertures. The multiple sub-aperture data are subjected to linear frequency modulation Z transformation, and the target azimuth position no longer migrates with the range frequency, thereby achieving coarse resolution processing in azimuth.

[0094] According to an embodiment of the present disclosure, multiple first sub-aperture data are subjected to range-direction inverse Fourier transform to obtain multiple two-dimensional image information, and phase errors are extracted from the multiple two-dimensional image information using a phase gradient self-focusing method.

[0095] According to an embodiment of the present disclosure, a phase gradient self-focusing method is used to extract multiple sub-aperture phase errors from multiple two-dimensional image information. The second-order derivatives of the sub-aperture phase errors are spliced, and after the splicing is completed, a second-order integration is performed to obtain the full-aperture phase error.

[0096] According to the embodiment of the present disclosure, during the phase gradient autofocusing PGA method processing of multiple first sub-aperture data, the estimated phase error gradient is accumulated or integrated to obtain a phase error function, the phase error function is multiplied by the original phase history data, and then the distance inverse Fourier transform is performed to obtain multiple two-dimensional image information. The processing is repeated until the convergence of the strong scattering points in the multiple two-dimensional image information is achieved, the image is focused, and finally multiple sub-aperture phase errors are obtained.

[0097] According to an embodiment of the present disclosure, a phase gradient self-focusing method is used to extract multiple sub-aperture phase errors, which are processed and then spliced ​​to obtain a full-aperture phase error, thereby removing the influence of the phase gradient error between sub-apertures.

[0098] According to an embodiment of the present disclosure, before compensating the second echo data, the outstanding points of the second echo data are removed, including: in the process of extracting the phase error using the phase gradient self-focusing method, extracting the distance index of the outstanding points of the first echo data, and removing the outstanding points in the second echo data according to the distance index, wherein the outstanding points in the second echo data represent strong scattering points in the second echo data.

[0099] According to an embodiment of the present disclosure, in the process of extracting phase errors from a plurality of first sub-aperture data using a phase gradient self-focusing method, the strong scattering points are repeatedly acted on until the corresponding image is focused, and the phase error is finally extracted. The strong scattering points in the second echo data are removed according to the distance index of the strong scattering points obtained in the extraction process, so that the linear phase error is subsequently extracted from the third echo data without interference from the strong scattering points.

[0100] According to an embodiment of the present disclosure, the obtained full-aperture phase error is used to compensate the second echo data, that is, the phase of the second echo data is corrected to obtain the third echo data.

[0101] According to an embodiment of the present disclosure, calculating the linear phase error according to the third echo data includes: estimating the Doppler center according to the third echo data ; Calculate the linear phase error based on the Doppler center .

[0102] According to an embodiment of the present disclosure, based on the characteristic that the Doppler center is zero in the positive side view imaging, the linear phase error is estimated by the amplitude-based Doppler center method. The linear phase error can be expressed as:

[0103] (8)

[0104] in, is the azimuth sampling frequency, is a discrete variable of azimuth time, , N represents the number of complete aperture sampling points in azimuth.

[0105] According to an embodiment of the present disclosure, the linear phase error is combined with the phase error to obtain a total phase error.

[0106] According to an embodiment of the present disclosure, the full-aperture phase error extracted by the phase gradient self-focusing method is , plus the full aperture linear phase error obtained according to formula (8) , and obtain the total phase error in the azimuth direction including the linear phase error.

[0107] According to an embodiment of the present disclosure, based on the total phase error, compensation is performed on a plurality of first sub-aperture data, that is, phase correction is performed to obtain a plurality of second sub-aperture data.

[0108] According to an embodiment of the present disclosure, a total phase error is compensated for a plurality of first sub-aperture data using a phase gradient self-focusing method and an amplitude-based Doppler center method.

[0109] According to an embodiment of the present disclosure, the target azimuth position is estimated based on a plurality of second sub-aperture data, and the estimated value of the target azimuth position can be expressed as:

[0110] (9)

[0111] in, , is the radar antenna phase center elevation angle at the center of the aperture.

[0112] According to an embodiment of the present disclosure, It is the ratio of the heading velocity to the distance from the antenna phase center to the center of the imaging scene. Considering the wavefront curvature error, , , They are respectively expressed as the constant term, the first-order term and the second-order term of the wavefront bending error, and are the target azimuth position Distance to target position function. Peacekeeping Dimensional representation Peacekeeping The corresponding frequency domain of the 2D Fourier transform.

[0113] According to an embodiment of the present disclosure, the target distance to the position is estimated .

[0114] According to an embodiment of the present disclosure, a first error parameter is estimated according to the target azimuth position. , , .

[0115] According to an embodiment of the present disclosure, the first error parameter , , , respectively, by the wavefront bending error , , The calculation formula is estimated. The expansion of the wavefront bending error is derived. The wavefront bending error can be Taylor expanded when the azimuth time is zero and retained to the second-order term. At this time, the constant term, first-order term, and second-order term of the wavefront bending error are expressed as follows:

[0116] (10)

[0117] (11)

[0118] (12)

[0119] According to an embodiment of the present disclosure, a first precise phase error is estimated based on a first error parameter.

[0120] According to an embodiment of the present disclosure, based on the first precise phase error, a plurality of second sub-aperture data are compensated to obtain a plurality of fourth sub-aperture data, and the fourth sub-aperture data can be expressed as:

[0121] (13)

[0122] in, , , is the distance sampling frequency.

[0123] According to an embodiment of the present disclosure, multiple fourth sub-aperture data are subjected to distance inverse Fourier transform to obtain multiple fifth sub-aperture data, and the fifth sub-aperture data can be expressed as:

[0124] (14)

[0125] According to the embodiments of the present disclosure, at this time, there is no range migration caused by linear phase error between the multiple sub-apertures.

[0126] According to an embodiment of the present disclosure, a first precise phase error is estimated based on a plurality of second sub-aperture data, and the first precise phase error is compensated for the plurality of second sub-aperture data to achieve range-direction precise resolution processing.

[0127] According to an embodiment of the present disclosure, the target range position is estimated based on a plurality of fifth sub-aperture data, and the estimation of the target range position can be expressed as:

[0128] (15)

[0129] According to an embodiment of the present disclosure, a second error parameter is estimated based on the target range position and the target azimuth position. , , .

[0130] According to an embodiment of the present disclosure, a second precise phase error is estimated based on a second error parameter.

[0131] According to an embodiment of the present disclosure, based on the second precise phase error, a plurality of fifth sub-aperture data are compensated to obtain a plurality of sixth sub-aperture data, and the sixth sub-aperture data can be expressed as:

[0132] (16)

[0133] According to an embodiment of the present disclosure, a plurality of sixth sub-aperture data are subjected to inter-sub-aperture Fourier transform to obtain a plurality of seventh sub-aperture data, and the seventh sub-aperture data can be expressed as:

[0134] (17)

[0135] According to an embodiment of the present disclosure, a plurality of sub-aperture images are generated according to a plurality of seventh sub-aperture data.

[0136] According to an embodiment of the present disclosure, a second precise phase error is estimated based on multiple fifth sub-aperture data, the second precise phase error is compensated for the multiple fifth sub-aperture data, and then Fourier transform is performed between sub-apertures to achieve azimuth precise resolution processing.

[0137] According to an embodiment of the present disclosure, multiple sub-aperture images are subjected to azimuth data screening and splicing to output a full-aperture image.

[0138] The present invention obtains the first echo data and the second echo data by performing range interpolation and range sampling on the pre-processed original echo data; based on the phase error extracted from the first echo data, the second echo data is subjected to phase error compensation and linear phase error estimation; based on the estimated linear phase error estimation and phase error, the total phase error for compensation is obtained; the first echo data is subjected to the following operations in sequence: azimuth coarse resolution processing, phase error extraction, total phase error compensation, range fine resolution processing, azimuth fine resolution processing and sub-aperture image stitching. The influence of the linear phase error is considered, and on the basis of extracting the phase error using the phase gradient self-focusing method, the linear phase error compensation is added to achieve the output of a high-quality full-aperture image. Inertial navigation motion error compensation, matched filtering and compensation of errors in each step are achieved by multiplication, which reduces the amount of calculation.

[0139] According to an embodiment of the present disclosure, the second echo data is segmented in azimuth to obtain a plurality of third sub-aperture data; and the linear phase error is estimated based on the plurality of third sub-aperture data.

[0140] According to an embodiment of the present disclosure, the second echo data is firstly removed of the prominent points, and then the second echo data is segmented in azimuth, which is the same as the segmentation method for the first echo data in azimuth, to obtain a plurality of third sub-aperture data. Among the plurality of sub-aperture phase errors, a sub-aperture phase error located in the middle is compensated to the third sub-aperture data at the corresponding position, and the Doppler center is estimated based on the compensated third sub-aperture data, and the linear phase error is calculated. The linear phase error is combined with the plurality of sub-aperture phase errors to obtain a plurality of sub-aperture total phase errors. The plurality of sub-aperture total phase errors are compensated to the plurality of first sub-aperture data, and then subsequent range-direction fine resolution processing and azimuth-direction fine resolution processing are performed to output a full-aperture image.

[0141] According to an embodiment of the present disclosure, without estimating and adding a linear phase error, the phase error extracted by the PGA is directly compensated for a plurality of first sub-aperture data to obtain a plurality of second sub-aperture data without compensating for the linear phase error. The three-dimensional time-domain discrete data of the second sub-aperture data without compensating for the linear phase error can be expressed as:

[0142] (18)

[0143] in: ,

[0144] According to an embodiment of the present disclosure, as shown in formula (18), the second exponential term of formula (18) is and the fifth exponent It can represent the linear phase error. According to the displacement property of Fourier transform, the residual linear phase error after PGA estimation will cause multiple second sub-aperture data to be Peacekeeping Dimensional translation occurs.

[0145] According to an embodiment of the present disclosure, according to formula (18), the target azimuth position of the uncompensated linear phase error is estimated, and then the next step of range precision resolution processing is performed. Based on the target azimuth position of the uncompensated linear phase error, the first precise phase error of the uncompensated linear phase error is estimated, and after phase compensation, a plurality of fourth sub-aperture data of the uncompensated linear phase error are obtained. The fourth sub-aperture data of the uncompensated linear phase error can be expressed as:

[0146] (19)

[0147] According to an embodiment of the present disclosure, when performing phase compensation, the estimation of the target azimuth position of the uncompensated linear phase error is:

[0148] (20)

[0149] According to an embodiment of the present disclosure, due to the influence of the linear phase error, the estimation of the actual target azimuth position can be expressed as:

[0150] (twenty one)

[0151] in, yes The signal is shifted by an unknown amount.

[0152] According to an embodiment of the present disclosure, the actual azimuth position of the target point The unknown unit is offset to , , , It is also affected by the change of the target position and becomes , , At this time, using the target azimuth position estimation in formula (20) to calculate the first precise phase error will reduce the accuracy of the phase compensation in formula (19) and introduce unknown errors.

[0153] According to an embodiment of the present disclosure, a plurality of fourth sub-aperture data of uncompensated linear phase errors are subjected to range inverse Fourier transform to generate a plurality of coarse resolution images of sub-apertures of uncompensated linear phase errors, which can be expressed as:

[0154] (twenty two)

[0155] According to an embodiment of the present disclosure, an estimate of the target range position of the uncompensated linear phase error is obtained based on the fourth sub-aperture data of the plurality of uncompensated linear phase errors, which can be expressed as:

[0156] (twenty three)

[0157] As shown in formula (23), the last two terms are The steep motion is generated. In the absence of linear phase error causing the target azimuth position to shift, the steep motion is generally less than one range resolution unit and can be ignored. However, in the case of phase compensation mismatch, the last two terms follow The resulting abrupt motion cannot be ignored. Therefore, if the linear phase error is not compensated, there will be a mismatch in the phase compensation during the range-direction fine-resolution processing, resulting in the inability to align the target ranges of each sub-aperture after the range-direction fine-resolution processing, affecting subsequent imaging.

[0158] According to the embodiments of the present disclosure, although the existence of linear phase error will not affect the focusing effect of a single sub-aperture image in the OSA algorithm, it can be seen based on formulas (21) and (23) that the existence of linear phase error will affect the alignment of images between sub-apertures in the OSA, affect the azimuth focusing effect during full-aperture imaging, and ultimately reduce the imaging quality of the full-aperture image.

[0159] According to an embodiment of the present disclosure, under simulation experimental conditions, a front-side imaging scene of a point target with a phase error added is simulated.

[0160] FIG. 3( a ) schematically shows an imaging result diagram with linear phase error compensation according to an embodiment of the present disclosure.

[0161] FIG3( b ) schematically shows an imaging result diagram of a non-linear phase error compensation according to an embodiment of the present disclosure.

[0162] As shown in Figure 3 (b), it shows the imaging result of the scene without linear phase error compensation. Affected by the linear phase error, after the phase error compensation of PGA extraction, multiple first sub-aperture data are directly processed for range precision resolution and subsequent steps. The defocus phenomenon of the positive side view imaging result is relatively serious, and the target side lobe is distorted in azimuth.

[0163] As shown in Figure 3 (a), it shows the imaging result of the simulated scene after linear phase error compensation. The imaging result of the point target after linear phase error compensation is very good in focusing effect, and the target side lobe is in a "cross" shape without distortion.

[0164] As shown in Figure 3 (a) and Figure 3 (b), point A is the center point of the image, point B is the upper left edge point of the image, and point C is the lower right edge point. The point target is analyzed, and the PSLR (Peak Side Lobe Ratio) and ISLR (Integral Side Lobe Ratio) of point A, point B, and point C in azimuth are given respectively. Point A, point B, and point C are analyzed when linear phase error compensation is performed and when linear phase error compensation is not performed, and the analysis results are shown in Table 1.

[0165] surface

[0166]

[0167] According to the embodiments of the present disclosure, the lower the PSLR and ISLR, the better the focusing effect. Based on the data shown in Table 1, the analysis results can indicate that when linear phase error compensation is performed, the focusing effect of the imaging result is better and the overall imaging quality is improved.

[0168] Figure 4 A schematic diagram of an airborne positive side-view overlapping sub-aperture imaging device according to an embodiment of the present disclosure is schematically shown.

[0169] like Figure 4 As shown, the airborne positive side-view overlapping sub-aperture imaging device 400 includes a first obtaining module 410, a second obtaining module 420, an extraction module 430, a first compensation module 440, a calculation module 450, a third obtaining module 460, a second compensation module 470, a fourth obtaining module 480 and an output module 490.

[0170] The first obtaining module 410 is used to pre-process the original echo data to obtain the first echo data and the second echo data. In one embodiment, the first obtaining module 410 can be used to perform the operation S210 described above, which will not be described in detail here.

[0171] The second obtaining module 420 is used to perform azimuth segmentation on the first echo data to obtain a plurality of first sub-aperture data. In one embodiment, the second obtaining module 420 can be used to perform the operation S220 described above, which will not be described in detail herein.

[0172] The extraction module 430 is used to extract the phase error from the plurality of first sub-aperture data using a phase gradient self-focusing method. In one embodiment, the extraction module 430 can be used to perform the operation S230 described above, which will not be described in detail herein.

[0173] The first compensation module 440 is used to compensate the second echo data based on the phase error to obtain the third echo data. In one embodiment, the first compensation module 440 can be used to perform the operation S240 described above, which will not be described in detail here.

[0174] The calculation module 450 is used to calculate the linear phase error according to the third echo data. In one embodiment, the calculation module 450 can be used to perform the operation S250 described above, which will not be described in detail here.

[0175] The third obtaining module 460 is used to combine the linear phase error with the phase error to obtain a total phase error. In one embodiment, the third obtaining module 460 can be used to perform the operation S260 described above, which will not be described in detail here.

[0176] The second compensation module 470 compensates the plurality of first sub-aperture data based on the total phase error to obtain a plurality of second sub-aperture data. In one embodiment, the second compensation module 470 may be used to perform the operation S270 described above, which will not be described in detail herein.

[0177] The fourth obtaining module 480 is used to obtain a plurality of sub-aperture images according to the plurality of second sub-aperture data. In one embodiment, the fourth obtaining module 480 may be used to perform the operation S280 described above, which will not be described in detail herein.

[0178] The output module 490 is used to stitch the multiple sub-aperture images together to output a full-aperture image. In one embodiment, the output module 490 can be used to perform the operation S290 described above, which will not be described in detail here.

[0179] It should be noted that the part of the airborne positive side view overlapping sub-aperture imaging device in the embodiment of the present disclosure corresponds to the part of the airborne positive side view overlapping sub-aperture imaging method in the embodiment of the present disclosure. The description of the part of the airborne positive side view overlapping sub-aperture imaging device specifically refers to the part of the airborne positive side view overlapping sub-aperture imaging method, which will not be repeated here.

[0180] Figure 5 A block diagram of an electronic device suitable for implementing an airborne positive side-view overlapping sub-aperture imaging method according to an embodiment of the present disclosure is schematically shown. Figure 5 The electronic device shown is only an example and should not bring any limitation to the functions and scope of use of the embodiments of the present disclosure.

[0181] like Figure 5As shown, the electronic device 500 according to an embodiment of the present disclosure includes a processor 501, which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 502 or a program loaded from a storage part 508 to a random access memory (RAM) 503. The processor 501 may include, for example, a general-purpose microprocessor (such as a CPU), an instruction set processor and / or a related chipset and / or a special-purpose microprocessor (for example, an application-specific integrated circuit (ASIC)), etc. The processor 501 may also include an onboard memory for caching purposes. The processor 501 may include a single processing unit or multiple processing units for performing different actions of the method flow according to an embodiment of the present disclosure.

[0182] In RAM 503, various programs and data required for the operation of electronic device 500 are stored. Processor 501, ROM 502 and RAM 503 are connected to each other via bus 504. Processor 501 performs various operations of the method flow according to the embodiment of the present disclosure by executing the program in ROM 502 and / or RAM 503. It should be noted that the program can also be stored in one or more memories other than ROM 502 and RAM 503. Processor 501 can also perform various operations of the method flow according to the embodiment of the present disclosure by executing the program stored in the one or more memories.

[0183] According to an embodiment of the present disclosure, the electronic device 500 may further include an input / output (I / O) interface 505, which is also connected to the bus 504. The electronic device 500 may further include one or more of the following components connected to the input / output (I / O) interface 505: an input portion 506 including a keyboard, a mouse, etc.; an output portion 507 including a cathode ray tube (CRT), a liquid crystal display (LCD), etc., and a speaker, etc.; a storage portion 508 including a hard disk, etc.; and a communication portion 509 including a network interface card such as a LAN card, a modem, etc. The communication portion 509 performs communication processing via a network such as the Internet. A drive 510 is also connected to the input / output (I / O) interface 505 as needed. A removable medium 511, such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, etc., is installed on the drive 510 as needed, so that a computer program read therefrom is installed into the storage portion 508 as needed.

[0184] According to an embodiment of the present disclosure, the method flow according to an embodiment of the present disclosure can be implemented as a computer software program. For example, an embodiment of the present disclosure includes a computer program product, which includes a computer program carried on a computer-readable storage medium, and the computer program contains a program code for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from the network through the communication part 509, and / or installed from the removable medium 511. When the computer program is executed by the processor 501, the above-mentioned functions defined in the system of the embodiment of the present disclosure are executed. According to an embodiment of the present disclosure, the system, equipment, device, module, unit, etc. described above can be implemented by a computer program module.

[0185] The present disclosure also provides a computer-readable storage medium, which may be included in the device / apparatus / system described in the above embodiments; or may exist independently without being assembled into the device / apparatus / system. The above computer-readable storage medium carries one or more programs, and when the above one or more programs are executed, the method according to the embodiment of the present disclosure is implemented.

[0186] According to an embodiment of the present disclosure, the computer-readable storage medium may be a non-volatile computer-readable storage medium. For example, it may include, but is not limited to: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In the present disclosure, a computer-readable storage medium may be any tangible medium containing or storing a program that may be used by or in combination with an instruction execution system, apparatus, or device.

[0187] For example, according to an embodiment of the present disclosure, the computer-readable storage medium may include the ROM 502 and / or the RAM 503 described above and / or one or more memories other than the ROM 502 and the RAM 503 .

[0188] An embodiment of the present disclosure also includes a computer program product, which includes a computer program, and the computer program contains program code for executing the method provided by the embodiment of the present disclosure. When the computer program product runs on an electronic device, the program code is used to enable the electronic device to implement the airborne positive and side-view overlapping sub-aperture imaging method provided by the embodiment of the present disclosure.

[0189] When the computer program is executed by the processor 501, the above functions defined in the system / device of the embodiment of the present disclosure are executed. According to the embodiment of the present disclosure, the system, device, module, unit, etc. described above can be implemented by a computer program module.

[0190] In one embodiment, the computer program may rely on tangible storage media such as optical storage devices, magnetic storage devices, etc. In another embodiment, the computer program may also be transmitted and distributed in the form of signals on a network medium, and downloaded and installed through the communication part 509, and / or installed from the removable medium 511. The program code contained in the computer program may be transmitted using any appropriate network medium, including but not limited to: wireless, wired, etc., or any suitable combination of the above.

[0191] According to an embodiment of the present disclosure, the program code for executing the computer program provided by the embodiment of the present disclosure can be written in any combination of one or more programming languages. Specifically, these computing programs can be implemented using high-level process and / or object-oriented programming languages, and / or assembly / machine languages. Programming languages ​​include, but are not limited to, Java, C++, python, "C" language or similar programming languages. The program code can be executed entirely on the user computing device, partially on the user device, partially on the remote computing device, or entirely on the remote computing device or server. In the case of a remote computing device, the remote computing device can be connected to the user computing device through any type of network, including a local area network (LAN) or a wide area network (WAN), or can be connected to an external computing device (for example, using an Internet service provider to connect through the Internet).

[0192] The flowcharts and block diagrams in the accompanying drawings illustrate the possible implementation architecture, functions and operations of the systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, each box in the flowchart or block diagram may represent a module, a program segment, or a part of a code, and the above-mentioned module, program segment, or a part of the code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box may also occur in an order different from that marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram or flowchart, and the combination of boxes in the block diagram or flowchart, can be implemented with a dedicated hardware-based system that performs a specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions. It can be understood by those skilled in the art that the features recorded in the various embodiments of the present disclosure can be combined and / or combined in a variety of ways, even if such a combination or combination is not explicitly recorded in the present disclosure. In particular, without departing from the spirit and teaching of the present disclosure, the features described in the various embodiments of the present disclosure may be combined and / or combined in a variety of ways. All of these combinations and / or combinations fall within the scope of the present disclosure.

[0193] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present disclosure. Although the embodiments are described above, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. Without departing from the scope of the present disclosure, those skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. An airborne front-side-view overlapping sub-aperture imaging method, characterized in that: include: Preprocessing the original echo data to obtain first echo data and second echo data; wherein the preprocessing only considers the motion error in the line of sight direction; Performing azimuth segmentation on the first echo data to obtain a plurality of first sub-aperture data; Extracting phase errors from the plurality of first sub-aperture data using a phase gradient self-focusing method; Based on the phase error, compensating the second echo data to obtain third echo data; Calculating a linear phase error according to the third echo data; combining the linear phase error with the phase error to obtain a total phase error; Based on the total phase error, compensating the plurality of first sub-aperture data to obtain a plurality of second sub-aperture data; Obtaining a plurality of sub-aperture images according to the plurality of second sub-aperture data; and The multiple sub-aperture images are stitched together to output a full-aperture image.

2. The method according to claim 1, characterized in that: Also includes: performing azimuth segmentation on the second echo data to obtain a plurality of third sub-aperture data; The linear phase error is estimated based on the plurality of third sub-aperture data.

3. The method according to claim 1, characterized in that Calculating a linear phase error according to the third echo data includes: estimating a Doppler center according to the third echo data; The linear phase error is calculated based on the Doppler center.

4. The method according to claim 1, characterized in that: Extracting phase errors from the plurality of first sub-aperture data using a phase gradient self-focusing method, comprising: Performing inverse Fourier transform on the plurality of first sub-aperture data in the range direction to obtain a plurality of two-dimensional image information; A phase gradient self-focusing method is used to extract phase errors from the plurality of two-dimensional image information.

5. The method according to claim 1, further comprising: Before compensating the second echo data, removing the prominent points from the second echo data includes: In the process of extracting the phase error using the phase gradient self-focusing method, the distance index of the prominent point of the first echo data is extracted, and the prominent point in the second echo data is removed according to the distance index, wherein the prominent point in the second echo data represents the strong scattering point in the second echo data.

6. The method according to claim 1 or 2, characterized in that: The first echo data is segmented in azimuth to obtain a plurality of first sub-aperture data, including: Discretizing the first echo data to obtain discretized first echo data, wherein the discretization includes time domain discretization in azimuth and frequency domain discretization in distance; Performing azimuth segmentation on the discretized first echo data to obtain a plurality of sub-aperture data; The plurality of sub-aperture data are subjected to linear frequency modulation Z transformation to obtain the plurality of first sub-aperture data.

7. The method according to claim 1 or 2, characterized in that: According to the plurality of second sub-aperture data, a plurality of sub-aperture images are obtained, including: estimating the target azimuth position according to the plurality of second sub-aperture data; estimating a first error parameter according to the target azimuth position; estimating a first precise phase error according to the first error parameter; Based on the first precise phase error, compensating the plurality of second sub-aperture data to obtain a plurality of fourth sub-aperture data; Performing a distance-direction inverse Fourier transform on the plurality of fourth sub-aperture data to obtain a plurality of fifth sub-aperture data; The multiple sub-aperture images are obtained according to the multiple fifth sub-aperture data.

8. The method according to claim 7, characterized in that Obtaining the plurality of sub-aperture images according to the plurality of fifth sub-aperture data includes: estimating a target range position according to the plurality of fifth sub-aperture data; estimating a second error parameter according to the target range position and the target azimuth position; estimating a second precise phase error according to the second error parameter; Based on the second precise phase error, compensating the plurality of fifth sub-aperture data to obtain a plurality of sixth sub-aperture data; Performing inter-subaperture Fourier transform on the plurality of sixth sub-aperture data to obtain a plurality of seventh sub-aperture data; The plurality of sub-aperture images are generated according to the plurality of seventh sub-aperture data.

9. The method according to any one of claims 1 to 5, characterized in that: Preprocessing the original echo data to obtain first echo data and second echo data includes: Performing a range-direction Fourier transform on the original echo data after inertial navigation compensation to obtain Fourier-transformed echo data; Filtering the Fourier transformed echo data through a filter to obtain preprocessed echo data; Performing range interpolation on the preprocessed echo data to obtain the first echo data; The preprocessed echo data is sampled in the range direction to obtain the second echo data.

10. An airborne front-side-view overlapping sub-aperture imaging device, comprising: A first obtaining module is used to pre-process the original echo data to obtain first echo data and second echo data; A second obtaining module is used to perform azimuth segmentation on the first echo data to obtain a plurality of first sub-aperture data; An extraction module, configured to extract a phase error from the plurality of first sub-aperture data using a phase gradient self-focusing method; a first compensation module, configured to compensate the second echo data based on the phase error to obtain third echo data; A calculation module, used for calculating a linear phase error according to the third echo data; A third obtaining module is used to combine the linear phase error with the phase error to obtain a total phase error; A second compensation module, based on the total phase error, compensates the plurality of first sub-aperture data to obtain a plurality of second sub-aperture data; A fourth obtaining module, used for obtaining a plurality of sub-aperture images according to the plurality of second sub-aperture data; as well as The output module is used to stitch the multiple sub-aperture images together to output a full-aperture image.

Images