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SAR Image Sidelobe Suppression Method Based on Nonlinear Polynomial Filtering

A side lobe suppression, polynomial technology, applied in image enhancement, image analysis, image data processing and other directions, can solve the problem that the noise or non-systematic error of SAR image cannot be reduced, the luminous cross of SAR image cannot be effectively reduced, and the image quality is not effective. It can improve the quality of SAR images, improve the side lobe effect, and reduce noise and non-systematic errors.

Active Publication Date: 2019-11-26
XIDIAN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] In the existing technology, the width of the main lobe of the SAR image processed by the SVA algorithm will widen, resulting in a decrease in resolution, and the SVA algorithm cannot weaken the original noise or non-systematic errors of the SAR image, and it cannot be very good in the case of multiple sinc functions. Good suppression of side lobes, so that the luminous cross in the SAR image cannot be effectively reduced, resulting in the area blocked by the luminous cross in the SAR image is still invisible, and the image quality is not effectively guaranteed

Method used

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  • SAR Image Sidelobe Suppression Method Based on Nonlinear Polynomial Filtering

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Embodiment 1

[0031] In the existing nonlinear sidelobe suppression technology, the SVA algorithm is not good enough for sidelobe suppression in the case of multiple sinc functions, the resolution of the SAR image processed by the SVA algorithm is reduced, and the existing noise and non-systematic errors of the SAR image cannot be weakened. . Aiming at this current situation, the present invention proposes a kind of high-resolution SAR image side lobe suppression method based on nonlinear polynomial filtering through research and experiment, see figure 1 . The side lobe suppression method that the present invention is used for SAR image also can be referred to as the concrete process step of second-order NPF algorithm as follows:

[0032] (1) Input the SAR image to be processed: input a high-resolution SAR image with side lobe effect, and obtain a two-dimensional matrix with N rows and M columns. It can be seen that the number of points in the azimuth direction of the SAR image is M, and t...

Embodiment 2

[0051] The method for sidelobe suppression of high-resolution SAR images based on nonlinear polynomial filtering is the same as in embodiment 1. In order to obtain the best effect, according to the simulation experiment results, the upper and lower limits of the SVA algorithm in the prior art have been modified. The steps of the present invention The upper bound χ of the weight function described in (4) max =0.96, the lower limit of the weight function χ min =-1.23.

[0052] The present invention reduces the lower limit of the weight function on the basis of the SVA algorithm, thereby reducing the width of the main lobe, and solves the problem that the image resolution of the SAR image is reduced after being processed by the SVA algorithm; increases the upper limit of the weight function, effectively weakening the The noise and non-systematic errors of SAR images are eliminated.

Embodiment 3

[0054] The method of high-resolution SAR image side lobe suppression based on nonlinear polynomial filtering is the same as embodiment 1-2, and the mth sample point described in step (5) and step (7) is implemented after the nonlinear polynomial filter The output value of the part I NPF (m) and the output value Q of the imaginary part NPF In the calculation formula of (m), in order to best suppress the side lobe effect of the SAR image, it has been verified by simulation experiments that

[0055] The present invention involves more adjacent sample points and widens the range of influence of adjacent sample points. The output value of the second-order NPF algorithm adopted is the sum of the product of the sample point and four adjacent sample points and their weight coefficients. Compared with the SVA algorithm, it suppresses the side lobe effect better.

[0056] A comprehensive example is given below to further describe the present invention in detail.

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Abstract

The invention discloses a SAR image side lobe suppression method based on nonlinear polynomial filtering, which solves the problem that the SVA algorithm cannot suppress the side lobe effect well. The implementation steps include: input the SAR image to be processed; obtain the complex value of the sample point; calculate the weight function of the real part and the imaginary part respectively; establish the nonlinear polynomial filter output mathematical model of the sample point by comparing the weight function with its upper and lower limits; sample points one by one Move the rows backward to calculate the output values ​​of all points; return to the initial sample points and move back column by column to calculate the output values ​​of all points; image the processed data to obtain the SAR image after side lobe suppression. The present invention broadens the influence range of sample points, sets appropriate weight coefficients, better suppresses the side lobe effect of SAR images, increases the upper limit of the weight function, weakens the noise and non-systematic errors of the SAR image, and reduces the lower limit of the weight function, so that The main lobe width is reduced and the image resolution is improved.

Description

technical field [0001] The invention belongs to the technical field of SAR image processing, in particular to SAR image sidelobe suppression, specifically a method for high-resolution SAR image sidelobe suppression based on nonlinear polynomial filtering, which can be applied to nonlinear sidelobe suppression in SAR image processing field. [0002] technical background [0003] Sidelobes are small beamlets next to the main lobe of maximum radiation waves, and appear as bright crosses in SAR images. Weakly scattered points in a SAR image may be obscured by surrounding bright crosses. If many strong scattering points are located in a small scene, they may also affect each other and blur the whole image. Therefore, sidelobe suppression is a key step to improve the quality of SAR images. [0004] Existing sidelobe suppression methods are mainly divided into the following two categories: linear techniques and nonlinear techniques. Linear technology refers to the use of linear ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G06T5/00
CPCG06T2207/10032G06T5/70
Inventor 熊涛孙璐焦李成王蓉芳黄宇王爽
Owner XIDIAN UNIV
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