Focus Improvement of High-Squint SAR Based on Azimuth Dependence of Quadratic Range Cell Migration Correction

Lin

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

et al. 2017

The results of the linear range cell migration (RCM) correction and inherent range-dependent squint angle in the case of high-resolution highly squinted synthetic aperture radar (SAR) imaging produce two-dimensional (2-D) spatial-variant RCMs and azimuth-dependent Doppler parameters (i.e., highly varying Doppler centroid and frequency modulation rates), which make highly squinted SAR imaging difficult. However, the most existing algorithms failed to consider these problems. To obtain highquality SAR image, in this study, both the 2-D spatial-variant RCMs and the azimuth-dependent Doppler parameters are stud- ied. First, a reference range linear RCM correction (RCMC) is used to remove the most of the linear RCM components and to mitigate the range-azimuth coupling of the 2-D spectrum. And then, in the azimuth time dimension, a new perturbation function is designed in the extended nonlinear chirp scaling (CS) (ENLCS) algorithm to overcome the azimuth-dependent RCM and to equalize Doppler parameters. To remove both the inherent range-dependent RCM and the linear RCM caused by the range-dependent squint angle, a modified CS (MCS) algorithm with a new scaling function isproposed, and for the residual RCMs, a bulk RCMC and second range compression (SRC) are utilized to compensate them. With the proposed ENLCS and MCS operation, the 2-D spatial-variant RCMC and the azimuth-dependent Doppler equalization are, thus, achieved. The experimental results with simulated data in the case of the high-resolution highly squinted SAR demonstrate the superior performance of the proposed algorithm.Index Terms-Azimuth-dependent Doppler Equalization, extended nonlinear chirp scaling (ENLCS) algorithm, modified CS (MCS) algorithm, synthetic aperture radar (SAR),

Section: Introductionmentioning

confidence: 99%

Focus Improvement for High-Resolution Highly Squinted SAR Imaging Based on 2-D Spatial-Variant Linear and Quadratic RCMs Correction and Azimuth-Dependent Doppler Equalization

Lin

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

et al. 2017

Journal of Electrical and Computer Engineering

“…According to the Taylor expansion theorem, the ranges between the radar and targets can be expressed as polynomials for both monostatic radar and bistatic radar [22][23][24][25]. A polynomial fitting method based on the least squares principle [26] is presented to compensate the range migration.…”

Section: Introductionmentioning

confidence: 99%

Signal Processing Based Remote Sensing Data Simulation in Radar System

Hao

Guo

2017

Range cell migration has a serious impact on the precision of image formation, especially for high-resolution and large-scale imaging. To get the full resolution and high quality of the image, the range cell migration correction in the azimuth time domain must be considered. For tackling this problem, this paper presents a novel and efficient range cell migration correction method based on curve fitting and signal processing. By emulating a curve to approximate the range-compressed echo of a strong point, the range location indexes of the strong point along the azimuth direction can be obtained under the least squares criterion. The merits of the proposed method are twofold: (1) the proposed method is robust to the uncertainty of system parameters (strong tolerance) under real flights and (2) the generalization of the proposed method is better and can be easily adapted to different synthetic aperture radar (SAR) modes (e.g., monostatic and bistatic). The experimental results on real remote sensing data from both the monostatic and the bistatic SAR demonstrate the effectiveness. The regressed distance curve is completely coincident with the trajectory of strong points of the echo. Finally, the imaging focus results also validate the efficiency of the proposed method.

Cybernetics and Information Technologies

“…Peng Sui-Yang and others [3][4][5], firstly removed the time offset in the time domain, and then corrected the RCM consistence at different range by the chirp scaling, without considering the high order curves effects on the azimuth processing. The azimuth nonlinear CS Algorithm proposed by Zhang Shuang-Xi and others [6][7][8] pushed the limits for the horizontal focus depth, and formed high-resolution images at larger azimuth scenes. However, due to the computation complexity, the two mentioned methods do not meet the realtime SAS requirements.…”

Section: Introductionmentioning

confidence: 99%

Improved Chirp Scaling Algorithm for Processing Squinted Mode Synthetic Aperture Sonar Data

Fan¹,

Wang²,

lv³

2016