scholarly journals A Novel Motion Compensation Scheme for Airborne Very High Resolution SAR

2021 ◽  
Vol 13 (14) ◽  
pp. 2729
Author(s):  
Zhen Chen ◽  
Zhimin Zhang ◽  
Yashi Zhou ◽  
Pei Wang ◽  
Jinsong Qiu
Keyword(s):  
High Resolution ◽  
Motion Compensation ◽  
Phase Error ◽  
Measurement Unit ◽  
Motion Error ◽  
Invariant Approximation ◽  
Range Cell ◽  
Range Cell Migration ◽  
Synthetic Aperture Radars ◽  
Very High

Due to the atmospheric turbulence, the motion trajectory of airborne very high resolution (VHR) synthetic aperture radars (SARs) is inevitably affected, which introduces range-variant range cell migration (RCM) and aperture-dependent azimuth phase error (APE). Both types of errors consequently result in defocused images, as residual range- and aperture-dependent motion errors are significant in VHR-SAR images. Nevertheless, little work has been devoted to the range-variant RCM auto-correction and aperture-dependent APE auto-correction. In this paper, a precise motion compensation (MoCo) scheme for airborne VHR-SAR is studied. In the proposed scheme, the motion error is obtained from inertial measurement unit and SAR data, and compensated for with respect to both range and aperture. The proposed MoCo scheme compensates for the motion error without space-invariant approximation. Simulations and experimental data from an airborne 3.6 GHz bandwidth SAR are employed to demonstrate the validity and effectiveness of the proposed MoCo scheme.

scholarly journals Modified Chirp Scaling Algorithm for Ultra-High Resolution Spaceborne-SAR

2021 ◽  
Vol 2083 (3) ◽  
pp. 032048
Author(s):  
Tao He ◽  
Pengbo Wang ◽  
Jixiang Ma ◽  
Xinkai Zhou ◽  
Lingling Xue
Keyword(s):  
High Resolution ◽  
Phase Error ◽  
Equation Model ◽  
Synthetic Aperture ◽  
Signal Spectrum ◽  
Integration Time ◽  
Range Cell ◽  
Range Cell Migration ◽  
Range Equation ◽  
Chirp Scaling Algorithm

Abstract The hyperbolic range equation model (HREM) and equivalent squint range model (ESRM) are applied in traditional chirp scaling algorithm (CSA). However, these range models cannot describe the satellite range history in the high-resolution case accurately because of the long azimuth integration time. The non-negligible phase error caused by this will lead the targets distort. In this paper, a modified chirp scaling algorithm (MCSA) is proposed by introducing a novel high-precision range model. A more accurate signal spectrum is calculated through it. Then, the modified chirp scaling factor, range compression filter, range cell migration correction (RCMC) filter and azimuth compression filter can be derived based on this signal spectrum, and the focused target obtained at last. Finally, the experimental results, to validate the proposed algorithm, adopted by the sliding spotlight synthetic aperture radar (SAR) simulation are provided.

scholarly journals A Fast High-Resolution Imaging Algorithm for Helicopter-Borne Rotating Array SAR Based on 2-D Chirp-Z Transform

2019 ◽  
Vol 11 (14) ◽  
pp. 1669 ◽  
Author(s):  
Qin ◽  
Li ◽  
Tang ◽  
Zeng ◽  
Li ◽  
...  
Keyword(s):  
High Resolution ◽  
Taylor Series Expansion ◽  
High Resolution Imaging ◽  
Imaging Algorithm ◽  
Range Cell ◽  
Distortion Effect ◽  
Resolution Imaging ◽  
Range Cell Migration ◽  
Azimuth Resolution ◽  
Space Variant

In view of the azimuth resolution of the helicopter-borne rotating array synthetic aperture radar (RoASAR) depending on the azimuth reconstruction angle and the sector distortion caused by the azimuth Deramp processing, this paper proposes an efficient helicopter-borne RoASAR high-resolution imaging algorithm based on two-dimensional (2-D) chirp-z transform (CZT). First, the high-order Taylor series expansion is performed on the slant range, and the accurate 2-D spectral expression of the point target is obtained by using the method of series reversion (MSR). Based on that, the space-variant characteristics of the range cell migration (RCM) terms are analyzed. After that, the space-variant RCM and the sector distortion effect caused by the azimuth Deramp processing are removed by using efficient 2-D CZT, thereby increasing the azimuth reconstruction angle and improving the azimuth resolution. The proposed algorithm is efficient without the interpolation operation, and it is easy to implement in real-time. Finally, the simulations are provided to verify the effectiveness of the proposed algorithm.

scholarly journals A New Rang-Instantaneous Doppler ISAR Imaging Algorithm

2012 ◽  
Vol 6-7 ◽  
pp. 682-687
Author(s):  
Bao Ping Wang ◽  
Chao Sun ◽  
Jun Jie Guo
Keyword(s):  
High Resolution ◽  
Sparse Representation ◽  
Motion Compensation ◽  
Noise Suppression ◽  
Phase Error ◽  
Doppler Imaging ◽  
Imaging Algorithm ◽  
Time Frequency ◽  
Maneuvering Target ◽  
Isar Imaging

ISAR imaging algorithm based on sparse representation has the advantages of high resolution, noise suppression and dealing with gapped data effectively. The method is based on the hypothesis that the imaging targets move smoothly. But the movement of ISAR imaging targets is usually of high maneuverability, which results in big phase error after motion compensation. Using the traditional RD imaging algorithm and the imaging algorithm based on sparse representation will make the resultant image fuzzy, and can't even be identified. This paper introduces a new range- instantaneous Doppler imaging algorithm based on sparse representation and time-frequency transform, which can effectively image the maneuvering target. The experimental results validate the feasibility of this approach.

scholarly journals Processing Missile-Borne SAR Data by Using Cartesian Factorized Back Projection Algorithm Integrated with Data-Driven Motion Compensation

2021 ◽  
Vol 13 (8) ◽  
pp. 1462
Author(s):  
Min Bao ◽  
Song Zhou ◽  
Mengdao Xing
Keyword(s):  
Time Domain ◽  
Motion Compensation ◽  
Phase Error ◽  
Data Driven ◽  
Projection Algorithm ◽  
Compressed Domain ◽  
Fast Time ◽  
Back Projection ◽  
Motion Error ◽  
Efficient Data

Due to the independence of azimuth-invariant assumption of an echo signal, time-domain algorithms have significant performance advantages for missile-borne synthetic aperture radar (SAR) focusing with curve moving trajectory. The Cartesian factorized back projection (CFBP) algorithm is a newly proposed fast time-domain implementation which can avoid massive interpolations to improve the computational efficiency. However, it is difficult to combine effective and efficient data-driven motion compensation (MOCO) for achieving high focusing performance. In this paper, a new data-driven MOCO algorithm is developed under the CFBP framework to deal with the motion error problem for missile-borne SAR application. In the algorithm, spectrum compression is implemented after a CFBP process, and the SAR images are transformed into the spectrum-compressed domain. Then, the analytical image spectrum is obtained by utilizing wavenumber decomposition based on which the property of motion induced error is carefully investigated. With the analytical image spectrum, it is revealed that the echoes from different scattering points are aligned in the same spectrum range and the phase error becomes a spatial invariant component after spectrum compression. Based on the spectrum-compressed domain, an effective and efficient data-driven MOCO algorithm is accordingly developed for accurate error estimation and compensation. Both simulations of missile-borne SAR and raw data experiment from maneuvering highly-squint airborne SAR are provided and analyzed, which show high focusing performance of the proposed algorithm.

scholarly journals A Novel Imaging Algorithm for High-Resolution Wide-Swath Space-Borne SAR Based on a Spatial-Variant Equivalent Squint Range Model

2022 ◽  
Vol 14 (2) ◽  
pp. 368
Author(s):  
Yanan Guo ◽  
Pengbo Wang ◽  
Jie Chen ◽  
Zhirong Men ◽  
Lei Cui ◽  
...  
Keyword(s):  
High Resolution ◽  
Spatial Variation ◽  
Doppler Spectrum ◽  
Two Dimensional ◽  
Imaging Processing ◽  
Range Cell ◽  
Phase Perturbation ◽  
Distributed Target ◽  
Range Cell Migration ◽  
Wide Swath

High-Resolution Wide-Swath (HRWS) is an important development direction of space-borne Synthetic Aperture Radar (SAR). The two-dimensional spatial variation of the Doppler parameters is the most significant characteristic of the sliding spotlight space-borne SAR system under the requirements of HRWS. Therefore, the compensation of the two-dimensional spatial variation is the most challenging problem faced in the imaging of HRWS situations. The compensatory approach is then proposed to address this problem in this paper. The spatial distribution of the Doppler parameters for the HRWS space-borne SAR data in the sliding spotlight working mode is firstly analyzed, based on which a Spatial-Variant Equivalent Slant Range Model (SV-ESRM) is put forward to accurately formulate the range history for the distributed target. By introducing an azimuth-varying term, the SV-ESRM can precisely describe the range history for not only central targets but also marginal targets, which is more adaptive to the HRWS space-borne SAR requirements. Based on the SV-ESRM, a Modified Hybrid Correlation Algorithm (MHCA) for HRWS space-borne SAR imaging is derived to focus the full-scene data on one single imaging processing. A Doppler phase perturbation incorporated with the sub-aperture method is firstly performed to eliminate the azimuth variation of the Doppler parameters and remove the Doppler spectrum aliasing. Then, an advanced hybrid correlation is employed to achieve the precise differential Range Cell Migration (RCM) correction and Doppler phase compensation. A range phase perturbation method is also utilized to eliminate the range profile defocusing caused by range-azimuth coupling for marginal targets. Finally, a de-rotation processing is performed to remove the azimuth aliasing and the residual azimuth-variance and obtain the precisely focused SAR image. Simulation shows that the SAR echoes for a 20 km × 20 km scene with a 0.25 m resolution in both the range and azimuth directions could be focused precisely via one single imaging processing, which validates the feasibility of the proposed algorithm.

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