A residual phase error correction coefficient estimation method based on subaperture cancellation combined with quadratic fitting

Abstract

The present invention discloses a residual phase error correction coefficient estimation method based on a sub-aperture cancellation combined quadratic fitting method, comprising the following steps: (1) using the satellite orbit velocity and the beam movement velocity to preliminarily estimate the approximate value of the radar velocity, using the wKA algorithm to roughly image the SAR echo data, and generating a complex image; (2) windowing and intercepting the complex image, setting the initial correction parameters, dividing the sub-aperture and pre-processing, constructing the objective function E1(X), and calculating the image difference after sub-aperture imaging; (3) gradually approaching the optimal solution of the phase error through reflection, expansion, and contraction optimization strategies; (4) after reaching the termination condition, constructing the objective function #imgabs0#, and performing fine optimization based on quadratic fitting to obtain the optimal phase correction value x; (5) using the wKA algorithm to azimuthally compress the obtained optimal phase correction value x to achieve azimuth imaging; the present invention can work stably under different scenarios and radar configurations.

Description

Technical Field

[0001] The invention relates to the technical field of synthetic aperture radar (SAR) imaging, and in particular to a residual phase error correction coefficient estimation method based on a sub-aperture cancellation combined quadratic fitting method. Background Art

[0002] As a high-resolution remote sensing tool, spaceborne synthetic aperture radar (SAR) has been widely used in surface mapping, ocean monitoring, disaster warning and other fields. SAR forms a long-aperture synthetic aperture through the relative motion between the radar and the ground, and uses the transmitted and received microwave signals to obtain high-resolution images of the surface. Its working principle relies on the Doppler frequency shift generated by the relative motion between the platform and the target to achieve high resolution in azimuth. However, in practical applications, the instability of platform motion, orbital errors and system errors will cause phase errors in the imaging process, which in turn affects the clarity and contrast of the image. If the residual phase error is not corrected, it will seriously affect the quality of SAR imaging.

[0003] Residual phase error is mainly caused by the nonlinear motion of the platform during the synthetic aperture process, especially in spaceborne or airborne SAR systems under long exposure. It manifests as a phase shift in the echo signal, causing the SAR image to defocus, which in turn reduces the image contrast and resolution. Existing SAR imaging technology often introduces phase errors due to factors such as platform motion and sensor deviation in high-speed and complex environments, resulting in image distortion and affecting imaging quality. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a residual phase error correction coefficient estimation method based on sub-aperture cancellation combined with quadratic fitting method, which estimates the phase error of SAR images by using the sub-aperture cancellation method and further refines the error compensation in combination with the quadratic fitting method to solve the problems of poor focusing and image blur caused by phase error.

[0005] Technical solution: The present invention discloses a residual phase error correction coefficient estimation method based on sub-aperture destructive combined quadratic fitting method, comprising the following steps:

[0006] (1) Using the satellite orbit velocity and beam movement speed, the radar velocity is preliminarily estimated. The algorithm roughly images the SAR echo data and generates a complex image ;

[0007] (2) Window and intercept the complex image to obtain the intercepted complex image Set initial correction parameters, segment subapertures and preprocess, and construct objective function , calculate the image difference after sub-aperture imaging;

[0008] (3) Based on the objective function , gradually approaching the optimal solution of phase error through reflection, expansion, and contraction optimization strategies ;

[0009] (4) After reaching the termination condition, construct the objective function , and perform fine optimization based on quadratic fitting to obtain the precise optimal solution x, i.e. the optimal phase correction value;

[0010] (5) The optimal phase correction value x is obtained using Algorithm azimuth compression to achieve azimuth imaging.

[0011] Furthermore, step (1) is as follows: Using the satellite orbit velocity and the beam movement velocity, the formula for preliminarily calculating the radar velocity is as follows:

[0012] ;

[0013] in, is a rough calculation value of the radar speed, represents the satellite orbital velocity, Indicates the beam movement speed.

[0014] Furthermore, step (2) includes the following steps:

[0015] (21) The complex image after interception The expression is as follows:

[0016] ;

[0017] in, and are the original SAR complex images The lengths in the distance and azimuth directions, , and are two constants less than 1; and are the lengths of the rectangular window in range and azimuth respectively, and Denote fast time and slow time respectively;

[0018] Then perform a two-dimensional Fourier transform to obtain frequency domain data ;

[0019] (22) Calculate the azimuth frequency modulation coefficient :

[0020] ;

[0021] in, is the wavelength, To indicate the Block frequency domain data The corresponding slant distance from the scene center to the radar is a rough value of the radar speed; is the rough value of radar speed;

[0022] (23) Set the initial calibration parameters as follows:

[0023] ;

[0024] in, and are the two initial points used to calculate the objective function value; is the initial estimated step length; is the tolerance threshold, used to terminate the iteration;

[0025] (24) The captured complex image Perform phase error correction according to the correction coefficient to obtain the corrected data , the formula is as follows:

[0026] ;

[0027] in, Express The corrected data, and represent fast time frequency and Doppler frequency respectively, It represents the phase compensation matrix generated according to the correction coefficient, and the expression is as follows:

[0028] ;

[0029] in, represents the Doppler frequency, for the Doppler center;

[0030] (25) SAR data Divided into two sub-apertures according to azimuth and , the expression is as follows:

[0031] ;

[0032] in, Indicates The first subaperture of the block echo data, Indicates The second subaperture of the block echo data;

[0033] (26) Perform two-dimensional inverse Fourier transform on the two sub-aperture data to obtain the time domain image result and , respectively intercept and Central area and , the expression is as follows:

[0034] ;

[0035] in, represents the image after the first sub-aperture time domain image is intercepted, represents the image after the second sub-aperture time domain image is intercepted; Describes the clipping range in the azimuth direction. is a scaling constant less than 1;

[0036] (27) Calculate the subaperture image difference and take its logarithmic scale to construct the objective function :

[0037] ;

[0038] in, reflects the image difference between sub-apertures, and represents the time domain images of two sub-apertures, Represents the mathematical expectation operator for calculating two-dimensional images.

[0039] Furthermore, in step (3), the objective function The optimization problem is expressed as follows:

[0040] ;

[0041] in, Indicates the initial search range, Indicates that The value of the independent variable that is minimized, Based on the objective function The value of .

[0042] Furthermore, step (3) includes the following steps:

[0043] (31) Based on the two initial points and Calculate the objective function value and And sort, if , then and Swap so that after the swap:

[0044] ;

[0045] (32) Based on the current point, calculate about Reflection point , and calculate the objective function value at the reflection point :

[0046] ;

[0047] (33) According to , and The size relationship between the three is as follows:

[0048] like, but Replace the original , get a new , then jump to (35);

[0049] like, The expansion point is calculated according to the following formula And the objective function value :

[0050] ;

[0051] Then, use Replace the original , get a new ; Then according to and To determine the size relationship between the two, perform the following operations:

[0052] like , then jump to (35), if , then execute (34);

[0053] (34) Repeat steps (31) to (33);

[0054] (35) If , then swap and , so that ,like , then calculate the line segment External contraction point :

[0055] ;

[0056] Then use replace , get a new , and recalculate ;like , then calculate the line segment Internal contraction point :

[0057] ;

[0058] Then Replace with , get a new , and recalculate ;

[0059] (36) Repeat the iteration step (35) until the following iteration termination condition is met:

[0060] ;

[0061] in, is the set objective function tolerance threshold;

[0062] (37) Calculation and The average :

[0063] ;

[0064] Then Optimal correction factor.

[0065] Furthermore, step (4) includes the following steps:

[0066] (41) Repeat steps (21) to (25) to obtain the time domain image results of the two sub-apertures. and Separately intercepted, the expression is as follows:

[0067] ;

[0068] in, is a scaling constant less than 1, Indicates that the interception range is narrower and precise optimization is performed;

[0069] (42) The optimal correction result is Generate multiple test points in the center and left and right , and calculate the objective function value of each point, calculate the sub-aperture image difference and take its logarithmic scale to construct the objective function :

[0070] ;

[0071] in, Reflects the objective function value of the test point;

[0072] (43) Fitting a quadratic polynomial, we obtain the fitting function:

[0073] ;

[0074] Among them, a determines the opening direction of the fitting function, b determines the inclination of the fitting function; c is The value at

[0075] (44) Calculate the minimum point of the fitting function :

[0076] ;

[0077] but Represents the refined result of the optimization process.

[0078] Furthermore, in step (5), the optimal phase correction value is obtained ,use The algorithm uses azimuth imaging, where the two-dimensional frequency domain reference function expression is as follows:

[0079] .

[0080] The present invention provides a residual phase error correction coefficient estimation system based on sub-aperture destructive combined quadratic fitting method, comprising:

[0081] Preliminary estimation module: It is used to use the satellite orbit speed and beam movement speed to preliminarily estimate the radar speed approximation. The algorithm roughly images the SAR echo data and generates a complex image ;

[0082] Image difference module: used to perform windowing and interception on the complex image to obtain the intercepted complex image Set initial correction parameters, segment subapertures and preprocess, and construct objective function , calculate the image difference after sub-aperture imaging;

[0083] Optimization strategy module: used to optimize the , gradually approaching the optimal solution of phase error through reflection, expansion, and contraction optimization strategies ;

[0084] Correction module: used to build the objective function after reaching the termination condition , and perform fine optimization based on quadratic fitting to obtain the precise optimal solution x, i.e. the optimal phase correction value;

[0085] Imaging module: used to obtain the optimal phase correction value x, using Algorithm azimuth compression to achieve azimuth imaging.

[0086] An electronic device described in the present invention includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is loaded into the processor, any one of the residual phase error correction coefficient estimation methods based on sub-aperture destructive combined quadratic fitting method is implemented.

[0087] A storage medium described in the present invention stores a computer program, and when the computer program is executed by a processor, it implements any one of the residual phase error correction coefficient estimation methods based on sub-aperture destructive combined quadratic fitting method.

[0088] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) Combining the sub-aperture cancellation method with the quadratic fitting technology, it is possible to more accurately estimate and correct the residual phase error in the SAR image. Through iterative optimization and fine adjustment of the quadratic fitting method, compared with the traditional algorithm based on simple phase correction, the present invention can achieve higher-precision error compensation in a larger range, avoiding image distortion caused by rough estimation; (2) Through the combined use of the sub-aperture cancellation method and the quadratic fitting method, the present invention can effectively eliminate the phase error caused by factors such as platform motion and sensor deviation, and significantly improve the focusing quality and resolution of the SAR image. Compared with the prior art, the correction method of the present invention is more stable in complex scenes and can effectively reduce image blur; the present invention has stronger robustness and can work stably in different scenes and radar configurations. BRIEF DESCRIPTION OF THE DRAWINGS

[0089] Figure 1 It is the overall flow chart of the present invention;

[0090] Figure 2 The SAR image obtained according to the rough velocity of the present invention;

[0091] Figure 3 It is the quadratic fitting fine optimization curve of the present invention;

[0092] Figure 4 The SAR image obtained by the estimated residual error correction coefficient of the present invention. DETAILED DESCRIPTION

[0093] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0094] like Figure 1As shown, an embodiment of the present invention provides a residual phase error correction coefficient estimation method based on sub-aperture cancellation combined with quadratic fitting method, comprising the following steps:

[0095] S1, using the satellite orbit speed and beam movement speed, preliminarily estimates the radar speed approximation:

[0096] ;

[0097] in, is a rough calculation value of the radar speed, represents the satellite orbital velocity, Indicates the beam movement speed.

[0098] Calculating Contrast The expression is as follows:

[0099] ;

[0100] in, is to use The algorithm roughly images the complex image of the SAR echo data, the operator Indicates the mathematical expectation of calculating a two-dimensional image. Indicates that the corresponding The original data of the block; the SAR image obtained according to the rough velocity is as follows Figure 2 As shown, the image contrast is 1.7277.

[0101] S2 Image Perform windowing and capture to obtain the captured complex image , set initial correction parameters, segment subapertures and preprocess, and construct objective function , calculate the image difference after sub-aperture imaging;

[0102] Objective Function The calculation steps are as follows:

[0103] (21) The complex image after interception The expression is as follows:

[0104] ;

[0105] in, and are the original SAR complex images The lengths in the distance and azimuth directions, , and are two constants less than 1; and are the lengths of the rectangular window in range and azimuth respectively, and Denote fast time and slow time respectively;

[0106] Then perform a two-dimensional Fourier transform to obtain frequency domain data ;

[0107] (22) Calculate the azimuth frequency modulation coefficient :

[0108] ;

[0109] in, is the wavelength, To indicate the Block frequency domain data The corresponding slant distance from the scene center to the radar is a rough value of the radar speed; is the rough value of radar speed;

[0110] (23) Set the initial calibration parameters as follows:

[0111] ;

[0112] in, and are the two initial points used to calculate the objective function value; is the initial estimated step length; is the tolerance threshold, used to terminate the iteration;

[0113] (24) The captured complex image Perform phase error correction according to the correction coefficient to obtain the corrected data , the formula is as follows:

[0114] ;

[0115] in, Express The corrected data, and represent fast time frequency and Doppler frequency respectively, It represents the phase compensation matrix generated according to the correction coefficient, and the expression is as follows:

[0116] ;

[0117] in, represents the Doppler frequency, for the Doppler center;

[0118] (25) SAR data Divided into two sub-apertures according to azimuth and , the expression is as follows:

[0119] ;

[0120] in, Indicates The first subaperture of the block echo data, Indicates The second subaperture of the block echo data;

[0121] (26) Perform two-dimensional inverse Fourier transform on the two sub-aperture data to obtain the time domain image result and , respectively intercept and Central area and , the expression is as follows:

[0122] ;

[0123] in, represents the image after the first sub-aperture time domain image is intercepted, represents the image after the second sub-aperture time domain image is intercepted; Describes the clipping range in the azimuth direction. is a scaling constant less than 1;

[0124] (27) Calculate the subaperture image difference and take its logarithmic scale to construct the objective function :

[0125] ;

[0126] in, reflects the image difference between sub-apertures, and represents the time domain images of two sub-apertures, Represents the mathematical expectation operator for calculating two-dimensional images.

[0127] Based on the objective function, S3 gradually approaches the optimal solution of phase error through reflection, expansion, and contraction optimization strategies; among them, the objective function The optimization problem is expressed as follows:

[0128] ;

[0129] in, Indicates the initial search range, Indicates that The value of the independent variable that is minimized, Based on the objective function The value of .

[0130] The specific implementation steps are as follows:

[0131] (31) Based on the two initial points and Calculate the objective function value and And sort, if , then and Swap so that after the swap:

[0132] ;

[0133] (32) Based on the current point, calculate about Reflection point , and calculate the objective function value at the reflection point :

[0134] ;

[0135] (33) According to , and The size relationship between the three is as follows:

[0136] like, but Replace the original , get a new , then jump to (35);

[0137] like, The expansion point is calculated according to the following formula And the objective function value :

[0138] ;

[0139] Then, use Replace the original , get a new ; Then according to and To determine the size relationship between the two, perform the following operations:

[0140] like , then jump to (35), if , then execute (34);

[0141] (34) Repeat steps (31) to (33);

[0142] (35) If , then swap and , so that ,like , then calculate the line segment External contraction point :

[0143] ;

[0144] Then use replace , get a new , and recalculate ;like , then calculate the line segment Internal contraction point :

[0145] ;

[0146] Then Replace with , get a new , and recalculate ;

[0147] (36) Repeat the iteration step (35) until the following iteration termination condition is met:

[0148] ;

[0149] in, is the set objective function tolerance threshold;

[0150] (37) Calculation and The average :

[0151] ;

[0152] Then Optimal correction factor.

[0153] After S4 reaches the termination condition, construct the objective function , and perform fine optimization based on quadratic fitting to obtain the precise optimal solution x, that is, the optimal phase correction value; the specific steps are as follows:

[0154] (41) Repeat steps (21) to (25) to obtain the time domain image results of the two sub-apertures. and Separately intercepted, the expression is as follows:

[0155] ;

[0156] in, is a scaling constant less than 1, Indicates that the interception range is narrower and precise optimization is performed;

[0157] (42) The optimal correction result is Generate multiple test points in the center and left and right , and calculate the objective function value of each point, calculate the sub-aperture image difference and take its logarithmic scale to construct the objective function :

[0158] ;

[0159] in, Reflects the objective function value of the test point;

[0160] (43) Fitting a quadratic polynomial, we obtain the fitting function:

[0161] ;

[0162] Among them, a determines the opening direction of the fitting function, b determines the inclination of the fitting function; c is The value at

[0163] (44) Calculate the minimum point of the fitting function :

[0164] ;

[0165] but Represents the refined result of the optimization process. The fitting curve obtained by the quadratic fitting refinement optimization is as follows Figure 3 As shown, the blue curve is the objective function value as the variable The line connecting the changing discrete data points reflects the objective function value at different phase error coefficients. The red curve is the smooth fitting curve obtained by fitting the discrete data points with a quadratic polynomial. The fitting curve is used to approximate the changing trend of the objective function value.

[0166] S5 obtains the optimal phase correction value x, using The algorithm compresses the azimuth and realizes azimuth imaging. The expression of the two-dimensional frequency domain reference function is as follows:

[0167] .

[0168] The SAR image obtained by using the residual error correction coefficient estimated by the method of the present invention is as follows: Figure 4 As shown, the final image contrast is 1.7594.

[0169] After the combined use of subaperture cancellation and quadratic fitting, the image contrast is improved from 1.7277 to 1.7594. This shows that the combined method is effective in improving image quality. Specifically, the improvement of image contrast means that the grayscale difference between the target and the background is enhanced, which generally reflects the further correction of the residual phase error during the imaging process, making the image clearer and sharper.

[0170] The embodiment of the present invention further provides a residual phase error correction coefficient estimation system based on sub-aperture cancellation combined with quadratic fitting method, comprising:

[0171] Preliminary estimation module: It is used to use the satellite orbit speed and beam movement speed to preliminarily estimate the radar speed approximation. The algorithm roughly images the SAR echo data and generates a complex image ;

[0172] Image difference module: used to perform windowing and interception on the complex image to obtain the intercepted complex image Set initial correction parameters, segment subapertures and preprocess, and construct objective function , calculate the image difference after sub-aperture imaging;

[0173] Optimization strategy module: used to optimize the , gradually approaching the optimal solution of phase error through reflection, expansion, and contraction optimization strategies ;

[0174] Correction module: used to build the objective function after reaching the termination condition , and perform fine optimization based on quadratic fitting to obtain the precise optimal solution x, i.e. the optimal phase correction value;

[0175] Imaging module: used to obtain the optimal phase correction value x, using Algorithm azimuth compression to achieve azimuth imaging.

[0176] An embodiment of the present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is loaded into the processor, it implements any one of the methods for estimating residual phase error correction coefficients based on sub-aperture elimination and combined quadratic fitting.

[0177] An embodiment of the present invention further provides a storage medium storing a computer program, wherein when the computer program is executed by a processor, the residual phase error correction coefficient estimation method based on sub-aperture cancellation and combined quadratic fitting method described in any one of the above is implemented.

Claims

1. A residual phase error correction coefficient estimation method based on sub-aperture cancellation combined with quadratic fitting method, characterized in that: The steps include: (1) Using the satellite orbit velocity and beam movement speed, the radar velocity is preliminarily estimated. The algorithm roughly images the SAR echo data and generates a complex image ; (2) Window and intercept the complex image to obtain the intercepted complex image Set initial correction parameters, segment subapertures and preprocess, and construct objective function , calculating the image difference after sub-aperture imaging; comprising the following steps: (21) The complex image after interception The expression is as follows: ； in, and are the original SAR complex images The lengths in the distance and azimuth directions, , and are two constants less than 1; and are the lengths of the rectangular window in range and azimuth respectively, and represent fast time and slow time respectively; Then perform a two-dimensional Fourier transform to obtain frequency domain data ; (22) Calculate the azimuth frequency modulation coefficient : ； in, is the wavelength, To indicate the Block frequency domain data The corresponding slant distance from the scene center to the radar is a rough value of the radar speed; is the rough value of radar speed; (23) Set the initial calibration parameters as follows: ； in, and are the two initial points used to calculate the objective function value; is the initial estimated step length; is the tolerance threshold, used to terminate the iteration; (24) The captured complex image Perform phase error correction according to the correction coefficient to obtain the corrected data , the formula is as follows: ； in, Express The corrected data, and represent fast time frequency and Doppler frequency respectively, It represents the phase compensation matrix generated according to the correction coefficient, and the expression is as follows: ； in, represents the Doppler frequency, for the Doppler center; (25) SAR data Divided into two sub-apertures according to azimuth and , the expression is as follows: ； in, Indicates The first subaperture of the block echo data, Indicates The second subaperture of the block echo data; (26) Perform two-dimensional inverse Fourier transform on the two sub-aperture data to obtain the time domain image result and , respectively intercept and Central area and , the expression is as follows: ； in, represents the image after the first sub-aperture time domain image is intercepted, represents the image after the second sub-aperture time domain image is intercepted; Describes the clipping range in the azimuth direction. is a scaling constant less than 1; (27) Calculate the subaperture image difference and take its logarithmic scale to construct the objective function : ； in, reflects the image difference between sub-apertures, and represents the time domain images of two sub-apertures, Represents the mathematical expectation operator for calculating two-dimensional images; (3) Based on the objective function , gradually approaching the optimal solution of phase error through reflection, expansion, and contraction optimization strategies ; (4) After reaching the termination condition, construct the objective function , and perform fine optimization based on quadratic fitting to obtain the precise optimal solution x, i.e. the optimal phase correction value; (5) The optimal phase correction value x is obtained using Algorithm azimuth compression to achieve azimuth imaging.

2. The residual phase error correction coefficient estimation method based on subaperture elimination combined with quadratic fitting method according to claim 1 is characterized in that: Step (1) is as follows: Using the satellite orbit velocity and beam movement velocity, the formula for preliminarily calculating the radar velocity is as follows: ； in, is a rough calculation value of the radar speed, represents the satellite orbital velocity, Indicates the beam movement speed.

3. The residual phase error correction coefficient estimation method based on subaperture elimination combined with quadratic fitting method according to claim 1 is characterized in that: In step (3), the objective function The optimization problem is expressed as follows: ； in, Indicates the initial search range, Indicates that The value of the independent variable that is minimized, Based on the objective function The value of .

4. The residual phase error correction coefficient estimation method based on subaperture elimination combined with quadratic fitting method according to claim 3 is characterized in that: Step (3) includes the following steps: (31) Based on the two initial points and Calculate the objective function value and And sort, if , then and Swap so that after the swap: ； (32) Based on the current point, calculate about Reflection point , and calculate the objective function value at the reflection point : ； (33) According to , and The size relationship between the three is as follows: like, but Replace the original , get a new , then jump to (35); like, The expansion point is calculated according to the following formula And the objective function value : ； Then, use Replace the original , get a new ; Then according to and To determine the size relationship between the two, perform the following operations: like , then jump to (35), if , then execute (34); (34) Repeat steps (31) to (33); (35) If , then swap and , so that ,like , then calculate the line segment External contraction point : ； Then use replace , get a new , and recalculate ;like , then calculate the line segment Internal contraction point : ； Then Replace with , get a new , and recalculate ; (36) Repeat the iteration step (35) until the following iteration termination condition is met: ； in, is the set objective function tolerance threshold; (37) Calculation and The average : ； Then Optimal correction factor.

5. The residual phase error correction coefficient estimation method based on sub-aperture destructive combined quadratic fitting method according to claim 4 is characterized in that: Step (4) includes the following steps: (41) Repeat steps (21) to (25) to obtain the time domain image results of the two sub-apertures. and Separately intercepted, the expression is as follows: ； in, is a scaling constant less than 1, Indicates that the interception range is narrower and precise optimization is performed; (42) The optimal correction result is Generate multiple test points in the center and left and right , and calculate the objective function value of each point, calculate the sub-aperture image difference and take its logarithmic scale to construct the objective function : ； in, Reflects the objective function value of the test point; (43) Fitting a quadratic polynomial, we obtain the fitting function: ； Among them, a determines the opening direction of the fitting function, b determines the inclination of the fitting function; c is The value at (44) Calculate the minimum point of the fitting function : ； but Represents the refined result of the optimization process.

6. The residual phase error correction coefficient estimation method based on sub-aperture destructive combined quadratic fitting method according to claim 5, characterized in that: In step (5), the optimal phase correction value is obtained ,use The algorithm uses azimuth imaging, where the two-dimensional frequency domain reference function expression is as follows: 。 7. A residual phase error correction coefficient estimation system based on sub-aperture cancellation combined with quadratic fitting method, characterized in that: include: Preliminary Estimation module: It is used to use the satellite orbit speed and beam movement speed to preliminarily estimate the radar speed approximation. The algorithm roughly images the SAR echo data and generates a complex image ; Image difference module: used to perform windowing and interception on the complex image to obtain the intercepted complex image Set initial correction parameters, segment subapertures and preprocess, and construct objective function , calculating the image difference after sub-aperture imaging; comprising the following steps: (21) The complex image after interception The expression is as follows: ； in, and are the original SAR complex images The lengths in the distance and azimuth directions, , and are two constants less than 1; and are the lengths of the rectangular window in range and azimuth respectively, and represent fast time and slow time respectively; Then perform a two-dimensional Fourier transform to obtain frequency domain data ; (22) Calculate the azimuth frequency modulation coefficient : ； in, is the wavelength, To indicate the Block frequency domain data The corresponding slant distance from the scene center to the radar is a rough value of the radar speed; is the rough value of radar speed; (23) Set the initial calibration parameters as follows: ； in, and are the two initial points used to calculate the objective function value; is the initial estimated step length; is the tolerance threshold, used to terminate the iteration; (24) The captured complex image Perform phase error correction according to the correction coefficient to obtain the corrected data , the formula is as follows: ； in, Express The corrected data, and represent fast time frequency and Doppler frequency respectively, It represents the phase compensation matrix generated according to the correction coefficient, and the expression is as follows: ； in, represents the Doppler frequency, for the Doppler center; (25) SAR data Divided into two sub-apertures according to azimuth and , the expression is as follows: ； in, Indicates The first subaperture of the block echo data, Indicates The second subaperture of the block echo data; (26) Perform two-dimensional inverse Fourier transform on the two sub-aperture data to obtain the time domain image result and , respectively intercept and Central area and , the expression is as follows: ； in, represents the image after the first sub-aperture time domain image is intercepted, represents the image after the second sub-aperture time domain image is intercepted; Describes the clipping range in the azimuth direction. is a scaling constant less than 1; (27) Calculate the subaperture image difference and take its logarithmic scale to construct the objective function : ； in, reflects the image difference between sub-apertures, and represents the time domain images of two sub-apertures, Represents the mathematical expectation operator for calculating two-dimensional images; Optimization strategy module: used to optimize the , gradually approaching the optimal solution of phase error through reflection, expansion, and contraction optimization strategies ; Correction module: used to build the objective function after reaching the termination condition , and perform fine optimization based on quadratic fitting to obtain the precise optimal solution x, i.e. the optimal phase correction value; Imaging module: used to obtain the optimal phase correction value x, using Algorithm azimuth compression to achieve azimuth imaging.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the computer program is loaded into a processor, the residual phase error correction coefficient estimation method based on sub-aperture destructive combined quadratic fitting method according to any one of claims 1 to 6 is implemented.

9. A storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, a residual phase error correction coefficient estimation method based on sub-aperture destructive combined quadratic fitting method according to any one of claims 1 to 6 is implemented.

Images