Imaging method and device for suppressing moving targets by geosynchronous orbit synthetic aperture radar

Abstract

The present invention provides an imaging method, device and electronic equipment for suppressing moving targets by a geosynchronous orbit synthetic aperture radar, which are applied to the fields of synthetic aperture radar signal processing and artificial intelligence technology. The method comprises: receiving echo data sent by a synthetic aperture radar; performing aperture segmentation on the echo data to obtain a plurality of sub-aperture data; performing the following operations on each sub-aperture data: performing range compression and back-projection on the sub-aperture data to obtain an imaging result of the sub-aperture data; determining phase information and amplitude information of the sub-aperture data based on the imaging result; determining a background image of the sub-aperture data based on the amplitude information; combining the phase information and the background image to obtain complex-valued data of the sub-aperture data; and coherently fusing the complex-valued data of a plurality of sub-aperture data to obtain a target image.

Description

Technical Field

[0001] The present invention relates to the field of synthetic aperture radar signal processing and artificial intelligence technology, and more specifically, to an imaging method and device for suppressing moving targets by a geosynchronous orbit synthetic aperture radar. Background Art

[0002] With the development of spaceborne synthetic aperture radar (SAR) technology, a remote sensor that places SAR payloads on geosynchronous orbit satellites has become an emerging research hotspot in the SAR field. Compared with low-orbit SAR, geosynchronous orbit SAR has the advantages of large coverage, short revisit period, strong anti-strike and anti-destruction capabilities, and has a very broad application prospect.

[0003] SAR is mainly used to image static scenes. When moving targets are present, the motion of these targets makes them susceptible to Doppler shift, resulting in a defocusing effect along the azimuth direction. The resulting SAR images often have obvious problems including defocusing, blurring, and objects deviating from their actual positions. The position of a moving target changes at each azimuth reception moment. This position difference is not only the result of the target's own motion, but is further exacerbated by the continuous motion of the synthetic aperture radar platform. Therefore, the longer the synthetic aperture time, the more severe the defocusing. Especially for SAR with long-term observations, moving targets may produce long and complex motion trajectories.

[0004] In order to solve the problem of SAR moving target defocus affecting image quality, the existing technology mainly adopts two technical approaches: moving target focusing and moving target removal. For geosynchronous orbit SAR, due to the long synthetic aperture time, the moving target will produce a long and complex motion trajectory. The existing technology mainly has the following two problems: The current moving target imaging algorithm is aimed at slow-moving targets. And due to the interference of clutter / noise on the moving target signal and the inherent resolution of these methods themselves, the imaging quality is limited. Or based on a multi-channel system for moving target removal, this method requires multiple channels, which will greatly increase the complexity of the system. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] The present invention provides a method and device for suppressing imaging of moving targets by using a geosynchronous orbit synthetic aperture radar, which are used to at least partially solve one of the above technical problems.

[0007] (II) Technical solution

[0008] One aspect of the present invention provides an imaging method for suppressing moving targets by a geosynchronous orbit synthetic aperture radar, comprising: receiving echo data sent by a radar; performing aperture segmentation on the echo data to obtain a plurality of sub-aperture data; performing the following operations on each sub-aperture data: performing range compression and back-projection on the sub-aperture data to obtain an imaging result of the sub-aperture data; determining phase information and amplitude information of the sub-aperture data based on the imaging result; determining a background image of the sub-aperture data based on the amplitude information; combining the phase information and the background image to obtain complex-valued data of the sub-aperture data; and coherently fusing the complex-valued data of a plurality of sub-aperture data to obtain a target image.

[0009] According to an embodiment of the present invention, sub-aperture data is distance compressed and back-projected to obtain an imaging result of the sub-aperture data, including: signal demodulation and distance compression are performed on the sub-aperture data to obtain an echo signal of the sub-aperture data; and back-projecting the echo signal based on an imaging geometry model to obtain an imaging result of the sub-aperture data.

[0010] According to an embodiment of the present invention, the echo signal is back-projected based on an imaging geometry model to obtain an imaging result of sub-aperture data, including: determining the position offset and quadratic phase error caused by target motion according to the imaging geometry model; performing phase compensation on the echo signal based on the slant range and time delay between the radar and the imaging grid point, and determining the imaging result of the sub-aperture data based on the echo signal after phase compensation.

[0011] According to an embodiment of the present invention, phase compensation is performed on the echo signal based on the slant range and time delay between the radar and the imaging grid point, including: at each azimuth time, based on the radar coordinates and the imaging grid point coordinates, calculating the slant range between the radar and each grid point; determining the time delay value of each imaging grid point based on the calculated slant range; determining the compensation function of each imaging grid point according to the slant range and the time delay value; and compensating the echo signal of each imaging grid point based on the compensation function to obtain a compensated echo signal.

[0012] According to an embodiment of the present invention, determining the imaging result of the sub-aperture data based on the phase-compensated echo signal includes: accumulating the compensated echo signal in each imaging grid point to obtain the imaging result of the sub-aperture data.

[0013] According to an embodiment of the present invention, a background image of sub-aperture data is determined based on amplitude information, including: encoding the amplitude image of the imaging result to obtain a feature map of the amplitude image; decoding the feature map to obtain a sub-aperture noise segmentation image; and removing noise in the amplitude image based on the sub-aperture noise segmentation image to obtain a background image of the sub-aperture data.

[0014] According to an embodiment of the present invention, removing noise in an amplitude image based on a sub-aperture noise segmentation image to obtain a background image of sub-aperture data includes: subtracting the sub-aperture segmentation image from the amplitude image to obtain a background image of sub-aperture data.

[0015] According to an embodiment of the present invention, the phase information and the background image are combined to obtain complex valued data of the sub-aperture data, including: taking the background image as the real part and the phase information as the imaginary part to obtain the complex valued data of the sub-aperture data.

[0016] Another aspect of the present invention provides an imaging device for suppressing moving targets using a geosynchronous orbit synthetic aperture radar, comprising: a receiving module for receiving echo data sent by a radar; an aperture segmentation module for performing aperture segmentation on the echo data to obtain multiple sub-aperture data; a sub-aperture data processing module for performing the following operations on each sub-aperture data: performing distance compression and back-projection on the sub-aperture data to obtain an imaging result of the sub-aperture data; determining phase information and amplitude information of the sub-aperture data based on the imaging result; determining a background image of the sub-aperture data based on the amplitude information; combining the phase information and the background image to obtain complex-valued data of the sub-aperture data; and a fusion module for coherently fusing the complex-valued data of multiple sub-aperture data to obtain a target image.

[0017] Another aspect of the present invention provides an electronic device, comprising: one or more processors; and a memory for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors implement the above-mentioned method.

[0018] (III) Beneficial effects

[0019] The method and device for suppressing the imaging of moving targets by geosynchronous orbit synthetic aperture radar provided by the present invention at least have the following beneficial effects:

[0020] The echo data is processed by aperture division, which effectively improves the processing efficiency of the echo data. In addition, during the processing, the imaging method provided by the present invention also specially separates the phase information of the sub-aperture diagram, processes the amplitude information separately, and uses the phase information again during coherent fusion, retaining the original phase characteristics of the signal and ensuring the image detail restoration. By combining the traditional BP imaging algorithm with the deep learning method, the moving target defocus segmentation diagram is obtained using the Unet segmentation model, and the moving target defocus can be removed during the imaging process, effectively solving the defocus problem caused by the moving target without using a multi-channel system, reducing the system complexity. In addition, the present invention utilizes the characteristics of the long synthetic aperture time of the geosynchronous orbit SAR, and divides the echo data into sub-apertures when the echo data is received. Different sub-aperture data are echo signals of the same imaging area and are processed under the same imaging grid. Therefore, there is no need to perform image registration between the complex valued data of the sub-aperture data. Through coherent fusion, a target image with high resolution and clarity can be obtained, providing strong support for subsequent related tasks. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0022] Figure 1 A schematic diagram showing a principle diagram of an imaging method for suppressing moving targets using a geosynchronous orbit synthetic aperture radar according to an embodiment of the present invention;

[0023] Figure 2 A flow chart schematically shows a method for suppressing moving target imaging by a geosynchronous orbit synthetic aperture radar according to an embodiment of the present invention;

[0024] Figure 3 A flowchart schematically shows an imaging result of obtaining sub-aperture data by back-projecting an echo signal based on an imaging geometry model according to an embodiment of the present invention;

[0025] Figure 4 A flowchart schematically shows a method of performing phase compensation on an echo signal based on the slant range and time delay between a radar and an imaging grid point to obtain an imaging result of sub-aperture data according to an embodiment of the present invention;

[0026] Figure 5 Schematically shows a flow chart of determining a background image of sub-aperture data based on amplitude information according to an embodiment of the present invention;

[0027] Figure 6 A structural block diagram of a data processing device according to an embodiment of the present invention is schematically shown;

[0028] Figure 7A block diagram of an electronic device suitable for implementing a data processing method according to an embodiment of the present invention is schematically shown. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the existence of features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0031] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or can communicate with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] In the description of the present invention, it should be understood that the terms "longitudinal", "length", "circumferential", "front", "rear", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the subsystem or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0033] Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or configurations will be omitted when they may cause confusion in the understanding of the present invention. The shapes, sizes, and positional relationships of the components in the drawings do not reflect the actual size, proportion, and actual positional relationship.

[0034] Similarly, in order to simplify the present invention and help understand one or more of the various disclosed aspects, in the above description of exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. The description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0035] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0036] Before introducing the specific embodiments of the present invention, the relevant technical background and related terms in the present invention are first introduced.

[0037] Synthetic Aperture Radar (SAR): An imaging sensor installed on a satellite. SAR is an active earth observation system that uses the principle of synthetic aperture to achieve high-resolution microwave imaging.

[0038] Echo data: The electromagnetic wave signal reflected by the target and received by the synthetic aperture radar.

[0039] Imaging geometry model: A mathematical model used to describe the relative position relationship between the radar and the target. In geosynchronous orbit SAR imaging, this model usually takes into account factors such as the orbital parameters of the radar satellite, the geographic location of the target, and the direction of the radar beam.

[0040] Imaging grid: A network used for imaging established on the earth's surface based on the latitude and longitude parameters obtained by satellites.

[0041] Figure 1 The principle diagram of the imaging method of suppressing moving targets by using a geosynchronous orbit synthetic aperture radar according to an embodiment of the present invention is schematically shown.

[0042] Figure 2 A flow chart of a method for suppressing moving target imaging by a geosynchronous orbit synthetic aperture radar according to an embodiment of the present invention is schematically shown.

[0043] like Figure 2 As shown, the imaging method of the geosynchronous orbit synthetic aperture radar for suppressing moving targets includes operations S110 to S170.

[0044] In operation S110 , echo data transmitted by a synthetic aperture radar is received.

[0045] In operation S120, aperture segmentation is performed on the echo data to obtain a plurality of sub-aperture data.

[0046] In some embodiments, the received echo data is divided into a plurality of sub-aperture data to reduce the complexity of subsequent data processing and improve the flexibility and resolution of imaging. The rules and number of aperture divisions can be determined according to factors such as the motion trajectory of the radar platform, the size and shape of the antenna, etc.

[0047] In the specific implementation process, the high-orbit SAR echo data is aperture segmented, and the full aperture is divided into n sub-aperture data, where each sub-aperture data contains N a Azimuth pulse sampling.

[0048] In some embodiments, the following operations S130 to S160 are performed on each sub-aperture data obtained in operation S120:

[0049] In operation S130 , range compression and back-projection are performed on the sub-aperture data to obtain an imaging result of the sub-aperture data (ie, a sub-aperture image).

[0050] In some embodiments, the sub-aperture data is first demodulated and range compressed to obtain an echo signal of the sub-aperture data, wherein the echo signal The representation is as follows:

[0051]

[0052] in, is the azimuth time within an azimuth subaperture, λ is the radar wavelength, c is the speed of light, is the azimuth window function, B represents the signal bandwidth, R p is the distance history between the moving target P and the satellite, R p The expression is as follows:

[0053]

[0054] Among them, r so is the satellite position vector, V s is the satellite velocity vector, V t is the target motion velocity vector, and η is the azimuth time.

[0055] After the echo signal of the sub-aperture data is obtained, the echo signal is back-projected based on the imaging geometry model to obtain the imaging result of the sub-aperture data.

[0056] Range compression can improve the resolution of the image. Through matched filtering or correlation processing, the echo data is matched with the known transmission information to obtain the range-compressed signal. The range-compressed signal has a higher resolution in the distance direction and can more clearly reflect the position and shape of the target. Back projection can reconstruct high-resolution imaging results by delaying and superimposing the echo signal.

[0057] In operation S140, phase information and amplitude information of the sub-aperture data are determined based on the imaging result.

[0058] In some embodiments, amplitude information and phase information are extracted from the imaging result. sub It can be expressed as:

[0059]

[0060] Among them, I sub represents the imaging result, and (i, j) represents the corresponding pixel point.

[0061] Phase information It can be expressed as:

[0062]

[0063] In operation S150, a background image of the sub-aperture data is determined based on the amplitude information.

[0064] In some embodiments, the amplitude information is input into the Unet network, and the Unet network accurately performs the segmentation task pixel by pixel to determine the background image of the sub-aperture data. The background image represents the static or low-frequency part of the imaged image, and the amplitude information is a real number part, which is relatively simple to process, and can effectively simplify the processing flow and improve the processing efficiency. In addition, the amplitude information is more stable than the phase information and is less affected by noise. Determining the background image based only on the amplitude information can reduce the impact of noise on the imaging results and improve the imaging quality.

[0065] The Unet network can accurately perform segmentation tasks pixel by pixel, identify and learn unique features that represent image defocus, segment the defocused area, and obtain a segmentation map of moving target defocus. It can reduce the noise of moving targets, remove the defocus of moving targets, and solve the defocus problem caused by moving targets.

[0066] In operation S160, the phase information is combined with the background image to obtain complex-valued data of the sub-aperture data.

[0067] In some embodiments, the obtained background image is combined with the phase information obtained in operation S140 to obtain complex valued data. Specifically, the background image is used as the real part and the phase information is used as the imaginary part to obtain complex valued data of the sub-aperture data. The phase information retains the original phase characteristics of the echo signal, effectively improving the accuracy of image detail restoration. By adding the phase information to the background image, the complete complex valued data can be restored, thereby more comprehensively reflecting the information of the imaging scene.

[0068] In operation S170, coherent fusion is performed on the complex-valued data of the plurality of sub-aperture data to obtain a target image.

[0069] In some embodiments, complex-valued data of multiple sub-aperture data are merged and processed to obtain a final target image.

[0070] The expression of this process is:

[0071]

[0072] in, represents the nth sub-aperture background image after removing the influence of the moving target, is the phase information corresponding to the nth sub-aperture background image.

[0073] The imaging method of the geosynchronous orbit synthetic aperture radar for suppressing moving targets provided by the embodiment of the present invention can effectively reduce the noise of moving targets and improve the imaging quality of the geosynchronous orbit SAR. The present invention combines the traditional BP imaging algorithm with the deep learning method, and uses the Unet segmentation model to obtain the moving target defocus segmentation map, so that the moving target defocus can be removed during the imaging process, effectively solving the defocus problem caused by the moving target without using a multi-channel system, thereby reducing the system complexity.

[0074] In addition, the present invention utilizes the characteristics of the long synthetic aperture time of the geosynchronous orbit SAR. When the echo data is received, the echo data is divided into sub-apertures. Different sub-aperture data are echo signals of the same imaging area and are processed under the same imaging grid. Therefore, image registration is not required between the complex valued data of the sub-aperture data. Through coherent fusion, a target image with high resolution and clarity can be obtained, ensuring the accuracy of image restoration. The obtained imaging result can achieve a high spatial resolution and will not be affected by the previous moving target defocus noise, providing strong support for subsequent related tasks.

[0075] Figure 3 The flowchart schematically shows an imaging result of obtaining sub-aperture data by back-projecting the echo signal based on the imaging geometry model according to an embodiment of the present invention.

[0076] like Figure 3As shown, in this embodiment, back-projecting the echo signal based on the imaging geometry model to obtain the imaging result of the sub-aperture data includes operations S310 to S320.

[0077] In operation S310, a position offset and a quadratic phase error caused by target motion are determined according to an imaging geometric model.

[0078] In some embodiments, the imaging geometric model is a geometric model used to describe the relationship between the image and the object projection. The target movement will cause its position on the imaging plane to change, that is, position shift. The position shift ΔR caused by the target movement can be expressed as:

[0079]

[0080] Among them, r so,xy is the satellite position vector r so The vector projected onto the xy plane, V s,xy V is the speed of food intake s Vector projected onto the xy plane.

[0081] Due to the movement of the target, the relative position between the radar beam and the target will change, which will cause the phase of the echo signal to change, causing a secondary phase error. It can be expressed as:

[0082]

[0083] Among them, T s is the synthetic aperture time.

[0084] In operation S320, phase compensation is performed on the echo signal based on the slant range and time delay between the synthetic aperture radar and the imaging grid point to obtain an imaging result of the sub-aperture data.

[0085] In some embodiments, the slant range between the SAR and the target will change as the target moves. This change will cause the time delay of the echo signal to change. According to the changes in the slant range and time delay, the echo signal is phase compensated to eliminate the phase error caused by the target movement and improve the clarity and quality of the imaging.

[0086] Figure 4 The flowchart schematically shows a flow chart of performing phase compensation on an echo signal based on the slant range and time delay between a radar and an imaging grid point to obtain an imaging result of sub-aperture data according to an embodiment of the present invention.

[0087] like Figure 4As shown, this embodiment performs phase compensation on the echo signal based on the slant range and delay between the radar and the imaging grid point to obtain the imaging result of the sub-aperture data, including operations S3201 to S3204.

[0088] In operation S3201, at each azimuth time, the slant range between the radar and each grid point is calculated based on the synthetic aperture radar coordinates and the imaging grid point coordinates.

[0089] In some embodiments, at the azimuth time n, the instantaneous distance R between the satellite and the imaging grid is t (η) can be expressed as:

[0090]

[0091] Among them, (X η ,Y η ,Z η ) is the satellite S η The coordinates of (X G ,Y G ,Z G ) are the coordinates of the imaging grid points.

[0092] Then the slant distance between the synthetic aperture radar and each imaging grid point can be expressed as R G (η sub ), where the synthetic aperture radar is installed on a satellite. Therefore, the slant distance between the synthetic aperture radar and the imaging grid point can be expressed as the instantaneous distance R between the satellite and the imaging grid. t (η) represents.

[0093] In operation S3202, a time delay value of each imaging grid point is determined based on the calculated slant distance.

[0094] In operation S3203, a compensation function of each imaging grid point is determined according to the slant range and the time delay value.

[0095] In some embodiments, at each azimuth moment within the sub-aperture, the time delay of the imaging grid points is calculated in sequence, wherein the time delay value can be expressed as 2R G (η sub ) / c. A compensation function H for performing phase compensation on the signal is determined based on the slant distance and the delay value, wherein the phase compensation function H can be expressed as:

[0096]

[0097] In operation S3204, the echo signal of each imaging grid point is compensated based on the compensation function to obtain an imaging result of the sub-aperture data.

[0098] In some embodiments, based on the phase compensation function H, phase compensation is performed on the signal in each azimuth moment in the sub-aperture in turn to obtain a compensated echo signal in each imaging grid point, and the compensated echo signals are accumulated to obtain an imaging result I of the sub-aperture data. sub (i,j), where the imaging result I sub (i,j) can be expressed as:

[0099]

[0100] Figure 5 A flowchart for determining a background image of sub-aperture data based on amplitude information according to an embodiment of the present invention is schematically shown.

[0101] like Figure 5 As shown, the process of determining the background image of the sub-aperture data based on the amplitude information in this embodiment includes operations S510 to S530.

[0102] In operation S510, the amplitude image of the imaging result is encoded to obtain a feature map of the amplitude image.

[0103] In operation S520, the feature map is decoded to obtain a sub-aperture noise segmented image.

[0104] In operation S530, noise in the amplitude image is removed based on the sub-aperture noise segmentation image to obtain a background image of the sub-aperture data.

[0105] In some embodiments, part of the imaging results is input into a pre-trained Unet segmentation model, and the ability of Unet to accurately perform segmentation tasks pixel by pixel is used to identify and learn unique features representing image defocus, thereby segmenting the defocused area.

[0106] In the specific implementation process, the amplitude image (amplitude information) in the imaging result is taken as input and input into the encoding path of the Unet network for encoding to obtain the amplitude image. Among them, the Unet network encoding path is composed of an encoder, which is used to perform a series of convolution and maximum pooling operations. The process is as follows: First, the amplitude image passes through two 3×3 convolution layers, each followed by a ReLU activation function. Then a 2×2 maximum pooling operation is performed to reduce the size of the image while doubling the number of feature channels. This process is repeated until the bottom layer of the network is reached. The i-th layer encoder in the Unet encoding path is:

[0107]

[0108] Where Encoder represents the downsampling result in the encoding path, Conv represents the convolution operation, ReLu represents the linear rectification function, and Maxpool represents the maximum pooling operation.

[0109] After encoding, the feature map is input into the decoding path to decode the feature map, where the decoding path consists of a series of decoders. Specifically, it includes: upsampling the feature map, concatenating the upsampled feature map with the corresponding feature map in the encoding path, and the concatenated combined feature map undergoes two 3×3 convolutions and ReLU activations. The i-th layer decoder in the Unet decoding path is:

[0110]

[0111] Among them, Decoder represents the upsampling result in the decoding path, Upconv represents the upsampling operation, and Concat is the concatenation of the feature maps between the channels of the i-th layer of the decoder part.

[0112] After being processed by the Unet encoder and decoder, a sub-aperture noise segmentation image is obtained. In order to perform segmentation, UNet uses the cross entropy loss function to calculate the logarithmic loss score, which is mainly used to update the network weights during training. The loss function can be expressed as:

[0113]

[0114] Among them, y i Indicates the value of the i-th category in the true label, which is 0 or 1, p i represents the probability of the model predicting the i-th category, Indicates the sum of all categories.

[0115] The output sub-aperture segmentation result can be expressed as

[0116]

[0117] Among them, W ε and b ε are the convolution kernel weights and biases of the output layer, and Softmax is the activation function used to calculate the probability.

[0118] According to the sub-aperture segmentation result, the amplitude image is subtracted from the sub-aperture noise segmentation image corresponding to the amplitude image to remove the noise (i.e., the moving target) in the sub-aperture image and obtain a clear sub-aperture background image. The process of removing the moving target can be expressed as follows:

[0119]

[0120] in, represents the sub-image without moving target noise (i.e., background image), A sub (i, j) represents the original sub-image (i.e., amplitude image) containing the moving target, ε sub (i, j) represents the sub-aperture noise segmentation image, and (i, j) represents the corresponding pixel point.

[0121] After removing the sub-aperture image After there are pixels of moving objects in the sub-aperture image The amplitude of the sub-aperture image is used to complement the In, with There is no moving target in the pixels corresponding to the moving target segmentation map. In this way, the supplemented sub-aperture image is restored and maintains the original energy level, which improves the integrity and accuracy of the image. The supplemented sub-aperture image is expressed as:

[0122]

[0123] in, Represents a sub-aperture image Moving target segmentation map.

[0124] It should be noted that the Unet segmentation model used in the present invention is only exemplary and can be replaced by other deep learning models for performing segmentation tasks, and the present invention is not limited thereto.

[0125] The imaging method for suppressing moving targets by using a geosynchronous orbit synthetic aperture radar provided in an embodiment of the present invention performs sub-aperture processing on echo data, effectively improving the processing efficiency of the echo data. Moreover, during the processing, the imaging method provided by the present invention also specifically separates the phase information of the sub-aperture diagram, processes the amplitude information separately, and uses the phase information again during coherent fusion, thereby retaining the original phase characteristics of the signal and ensuring the restoration of image details.

[0126] Figure 6 The structure block diagram of the imaging device for suppressing moving targets using a geosynchronous orbit synthetic aperture radar according to an embodiment of the present invention is schematically shown.

[0127] like Figure 6 As shown, the imaging device 600 for suppressing moving targets using a geosynchronous orbit synthetic aperture radar of this embodiment includes a receiving module 610 , an aperture segmentation module 620 , a sub-aperture data processing module 630 and a fusion module 640 .

[0128] The receiving module 610 is used to receive the echo data sent by the radar. In one embodiment, the receiving module 610 can be used to perform the operation S110 described above, which will not be described in detail here.

[0129] The aperture segmentation module 620 is used to perform aperture segmentation on the echo data to obtain a plurality of sub-aperture data. In one embodiment, the aperture segmentation module 620 can be used to perform the operation S120 described above, which will not be described in detail here.

[0130] The sub-aperture data processing module 630 is used to perform the following operations on each sub-aperture data: perform distance compression and back-projection on the sub-aperture data to obtain an imaging result of the sub-aperture data; determine the phase information and amplitude information of the sub-aperture data based on the imaging result; determine the background image of the sub-aperture data based on the amplitude information; combine the phase information and the background image to obtain complex value data of the sub-aperture data. In one embodiment, the second acquisition module 630 can be used to perform the operation S130 described above, which will not be repeated here.

[0131] The fusion module 640 is used to coherently fuse the complex-valued data of the plurality of sub-aperture data to obtain a target image. In one embodiment, the fusion module 640 can be used to perform the operation S140 described above, which will not be described in detail herein.

[0132] According to an embodiment of the present invention, any multiple modules among the receiving module 610, the aperture segmentation module 620, the sub-aperture data processing module 630 and the fusion module 640 can be combined into one module for implementation, or any one of the modules can be split into multiple modules. Alternatively, at least part of the functions of one or more of these modules can be combined with at least part of the functions of other modules and implemented in one module. According to an embodiment of the present invention, at least one of the receiving module 610, the aperture segmentation module 620, the sub-aperture data processing module 630 and the fusion module 640 can be at least partially implemented as a hardware circuit, such as a field programmable gate array (FPGA), a programmable logic array (PLA), a system on a chip, a system on a substrate, a system on a package, an application specific integrated circuit (ASIC), or can be implemented by hardware or firmware such as any other reasonable way of integrating or packaging the circuit, or implemented in any one of the three implementation methods of software, hardware and firmware or in a proper combination of any of them. Alternatively, at least one of the receiving module 610, the aperture segmentation module 620, the sub-aperture data processing module 630 and the fusion module 640 may be at least partially implemented as a computer program module, and when the computer program module is executed, the corresponding function may be performed.

[0133] Figure 7 A block diagram of an electronic device suitable for implementing an imaging method for suppressing moving targets by a geosynchronous orbit synthetic aperture radar according to an embodiment of the present invention is schematically shown.

[0134] like Figure 7As shown, the electronic device 700 according to an embodiment of the present invention includes a processor 701, which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 702 or a program loaded from a storage part 708 to a random access memory (RAM) 703. The processor 701 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 701 may also include an onboard memory for caching purposes. The processor 701 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 invention.

[0135] In RAM 703, various programs and data required for the operation of electronic device 700 are stored. Processor 701, ROM 702 and RAM 703 are connected to each other via bus 704. Processor 701 performs various operations of the method flow according to the embodiment of the present invention by executing the programs in ROM 702 and / or RAM 703. It should be noted that the program can also be stored in one or more memories other than ROM 702 and RAM 703. Processor 701 can also perform various operations of the method flow according to the embodiment of the present invention by executing the programs stored in one or more memories.

[0136] According to an embodiment of the present invention, the electronic device 700 may further include an input / output (I / O) interface 705, which is also connected to the bus 704. The electronic device 700 may further include one or more of the following components connected to the input / output (I / O) interface 705: an input portion 706 including a keyboard, a mouse, etc.; an output portion 707 including a cathode ray tube (CRT), a liquid crystal display (LCD), etc., and a speaker, etc.; a storage portion 708 including a hard disk, etc.; and a communication portion 709 including a network interface card such as a LAN card, a modem, etc. The communication portion 709 performs communication processing via a network such as the Internet. A drive 710 is also connected to the input / output (I / O) interface 705 as needed. A removable medium 711, such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, etc., is installed on the drive 710 as needed, so that a computer program read therefrom is installed into the storage portion 708 as needed.

[0137] The present invention also provides a computer-readable storage medium, which may be included in the device / apparatus / system described in the above embodiment; 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 invention is implemented.

[0138] According to an embodiment of the present invention, 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 invention, the computer-readable storage medium may be any tangible medium containing or storing a program, which may be used by or in combination with an instruction execution system, an apparatus or a device. For example, according to an embodiment of the present invention, the computer-readable storage medium may include the ROM 702 and / or RAM 703 described above and / or one or more memories other than ROM 702 and RAM 703.

[0139] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architecture, functions and operations of the systems, methods and computer program products according to various embodiments of the present invention. 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 the order 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 the 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 invention can be combined and / or combined in various ways, even if such a combination or combination is not explicitly recorded in the present invention. In particular, without departing from the spirit and teachings of the present invention, the features recorded in the various embodiments of the present invention can be combined and / or combined in various ways. All these combinations and / or combinations fall within the scope of the present invention.

[0140] The embodiments of the present invention are described above. However, these embodiments are only for the purpose of illustration, and are not intended to limit the scope of the present invention. Although each embodiment is described above, it does not mean that the measures in each embodiment cannot be used in combination advantageously. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present invention.

Claims

1. A method for suppressing moving target imaging by using a geosynchronous orbit synthetic aperture radar, comprising: receiving echo data sent by synthetic aperture radar; Performing aperture segmentation on the echo data to obtain a plurality of sub-aperture data; Perform the following operations on each sub-aperture data: Performing range compression and back-projection on the sub-aperture data to obtain an imaging result of the sub-aperture data; Determine the phase information and amplitude information of the sub-aperture data based on the imaging result; determining a background image of the sub-aperture data based on the amplitude information; Combining the phase information with the background image to obtain complex-valued data of the sub-aperture data; The complex-valued data of the plurality of sub-aperture data are coherently fused to obtain a target image.

2. The imaging method according to claim 1, characterized in that: The performing range compression and back-projection on the sub-aperture data to obtain an imaging result of the sub-aperture data includes: Performing signal demodulation and range compression on the sub-aperture data to obtain an echo signal of the sub-aperture data; The echo signal is back-projected based on an imaging geometry model to obtain an imaging result of the sub-aperture data.

3. The imaging method according to claim 2, characterized in that: The back-projecting of the echo signal based on the imaging geometry model to obtain the imaging result of the sub-aperture data includes: Determine the position offset and the quadratic phase error caused by the target motion according to the imaging geometric model; Based on the slant range and time delay between the synthetic aperture radar and the imaging grid point, the echo signal is phase compensated to obtain the imaging result of the sub-aperture data.

4. The imaging method according to claim 3, characterized in that: The phase compensation of the echo signal based on the slant range and the time delay between the radar and the imaging grid point includes: At each azimuth time, the slant distance between the radar and each grid point is calculated based on the synthetic aperture radar coordinates and the imaging grid point coordinates; Determine the time delay value of each imaging grid point based on the calculated slant range; Determine a compensation function for each imaging grid point according to the slant range and the time delay value; The echo signal of each imaging grid point is compensated based on the compensation function to obtain a compensated echo signal.

5. The imaging method according to claim 4, characterized in that: The performing phase compensation on the echo signal to obtain the imaging result of the sub-aperture data includes: The compensated echo signals in each imaging grid point are accumulated to obtain the imaging result of the sub-aperture data.

6. The imaging method according to claim 1, characterized in that: The determining the background image of the sub-aperture data based on the amplitude information comprises: Encoding the amplitude image of the imaging result to obtain a feature map of the amplitude image; Decoding the feature map to obtain a sub-aperture noise segmentation image; The noise in the amplitude image is removed based on the sub-aperture noise segmentation image to obtain a background image of the sub-aperture data.

7. The imaging method according to claim 6, characterized in that: The removing noise in the amplitude image based on the sub-aperture noise segmentation image to obtain the background image of the sub-aperture data includes: The sub-aperture noise segmentation image is subtracted from the amplitude image to obtain a background image of the sub-aperture data.

8. The imaging method according to claim 1, characterized in that: The step of combining the phase information with the background image to obtain complex-valued data of the sub-aperture data includes: The background image is taken as the real part and the phase information is taken as the imaginary part to obtain complex-valued data of the sub-aperture data.

9. An imaging device for suppressing moving targets using a geosynchronous orbit synthetic aperture radar, characterized in that: The device comprises: A receiving module, used for receiving echo data sent by the radar; An aperture segmentation module, used for performing aperture segmentation on the echo data to obtain a plurality of sub-aperture data; The sub-aperture data processing module is used to perform the following operations on each sub-aperture data: performing distance compression and back-projection on the sub-aperture data to obtain an imaging result of the sub-aperture data; determining phase information and amplitude information of the sub-aperture data based on the imaging result; determining a background image of the sub-aperture data based on the amplitude information; and combining the phase information and the background image to obtain complex-valued data of the sub-aperture data; The fusion module is used to perform coherent fusion on the complex-valued data of the plurality of sub-aperture data to obtain a target image.

10. An electronic device, comprising: one or more processors; a memory for storing one or more computer programs, It is characterized in that the one or more processors execute the one or more computer programs to implement the steps of the method according to any one of claims 1 to 8.

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