Blind NCS-Based Autofocus for Airborne Wide-Beam SAR Imaging

Chen, Jianlai; Zhang, Junchao; Yu, Hanwen; Xu, Gang; Liang, Buge; Yang, Dongkai; Wang, Hui

doi:10.1109/tci.2022.3194745

Cited by 14 publications

(6 citation statements)

References 37 publications

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“…For 2-D space-variant and frequency-dependent motion error estimation of UWB and ultrawidebeam SAR, a method based on multi-subband local autofocus and fast factorized back projection (FFBP) framework was proposed [126]. Moreover, a wide-beam autofocus algorithm was proposed based on blind nonlinear chirp scaling to improve optimization, achieving well-focused images [127].…”

Section: B Airborne Vhr Sar Imagingmentioning

confidence: 99%

Very High Resolution Synthetic Aperture Radar Systems and Imaging: A Review

Chen,

Dong,

Zhang

et al. 2024

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

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Given its capacity to generate 2-D fine images of observation areas, very high-resolution (VHR) synthetic aperture radar (SAR) has become increasingly popular in myriad fields, including remote sensing, geoscience, and surveillance. In this article, we present a comprehensive overview of VHR SAR systems and imaging to highlight the related research and promote further development. First, we provide a summary of VHR SAR applications and summarize the typical airborne and spaceborne systems. Subsequently, a detailed overview is provided to demonstrate the range VHR technologies by introducing dechirp processing, stepped-frequency, and microwave photonic. Additionally, VHR imaging methods on different platforms, i.e., ideal trajectory, airborne, and spaceborne, are reviewed. Finally, the challenges and prospects of VHR SAR are presented to inform future research directions. This work provides a valuable resource to improve the system design and signal processing of VHR SAR.

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Section: B Airborne Vhr Sar Imagingmentioning

confidence: 99%

Very High Resolution Synthetic Aperture Radar Systems and Imaging: A Review

Chen,

Dong,

Zhang

et al. 2024

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

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“…Then, they can hardly be applied to the case of high-squint angle due to extremely severe RAC [36,37]. Therefore, multiple nonlinear CS (NCS) algorithms [38][39][40][41][42][43][44][45][46] are presented to decoupled the RAC. To remove more severe RAC of the signal, the third-order CS function was used at first [38][39][40][41].…”

Section: Introductionmentioning

confidence: 99%

“…To further increase the image precision, the CS function was then upgraded to the fourth order [42]. Afterwards, NCS processing has been used for numerous processing methods or working modes, such as fractional chirp scaling algorithm (FrCSA) [43], 2D NCS [44], Blind NCS [45], and Mosaic SAR [46]. Specifically, An et al [47] proposed a modified azimuth NCS algorithm by using a fourth-order CS function to realize highly squint airborne SAR imaging.…”

Section: Introductionmentioning

confidence: 99%

A Modified Frequency Nonlinear Chirp Scaling Algorithm for High-Speed High-Squint Synthetic Aperture Radar with Curved Trajectory

Deng,

Huang,

Chen

et al. 2024

Remote Sensing

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The imaging of high-speed high-squint synthetic aperture radar (HSHS-SAR), which is mounted on maneuvering platforms with curved trajectory, is a challenging task due to the existence of 3-D acceleration and the azimuth spatial variability of range migration and Doppler parameters. Although existing imaging algorithms based on linear range walk correction (LRWC) and nonlinear chirp scaling (NCS) can reduce the range–azimuth coupling of the frequency spectrum (FS) and the spatial variability of the Doppler parameter to some extent, they become invalid as the squint angle, speed, and resolution increase. Additionally, most of them ignore the effect of acceleration phase calibration (APC) on NCS, which should not be neglected as resolution increases. For these issues, a modified frequency nonlinear chirp scaling (MFNCS) algorithm is proposed in this paper. The proposed MFNCS algorithm mainly includes the following aspects. First, a more accurate approximation of range model (MAARM) is established to improve the accuracy of the instantaneous slant range history. Second, a preprocessing of the proposed algorithm based on the first range compression, LRWC, and a spatial-invariant APC (SIVAPC) is implemented to eliminate most of the effects of high-squint angle and 3-D acceleration on the FS. Third, a spatial-variant APC (SVAPC) is performed to remove azimuth spatial variability introduced by 3-D acceleration, and the range focusing is accomplished by the bulk range cell migration correction (BRCMC) and extended secondary range compression (ESRC). Fourth, the azimuth-dependent characteristics evaluation based on LRWC, SIVAPC, and SVAPC is completed to derive the MFNCS algorithm with fifth-order chirp scaling function for azimuth compression. Consequently, the final image is focused on the range time and azimuth frequency domain. The experimental simulation results verify the effectiveness of the proposed algorithm. With a curved trajectory, HSHS-SAR imaging is carried out at a 50° geometric squint angle and 500 m × 500 m imaging width. The integrated sidelobe ratio and peak sidelobe ratio of the point targets at the scenario edges approach the theoretical values, and the range-azimuth resolution is 1.5 m × 3.0 m.

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“…S YNTHETIC aperture radar (SAR), as a unique sensor technology, which provides high-resolution all-weather imaging on a global scale, has been widely used in many civilian and security-related applications [1], [2], [3]. SAR data may be acquired with a squinted geometry, either by design or through platform motion, with squint angles up to several tens of degrees [4].…”

Section: Introductionmentioning

confidence: 99%

Performance Analysis of Wavenumber Domain Algorithms for Highly Squinted SAR

Chen

Hou

Dong

et al. 2023

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

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Wavenumber domain algorithms have unique advantages in processing highly squinted synthetic aperture radar data. This article studies the performance of three commonly used wavenumber domain algorithms including the classical wavenumber domain (CWD) algorithm, extended wavenumber domain (EWD) algorithm, and squint wavenumber domain (SWD) algorithm. First, the wavenumber domain signal expression under the zero-Doppler and acquisition-Doppler reference geometries are both derived. Second, the internal relationship between three wavenumber domain algorithms is analyzed. A new interpretation of the relationship between the three algorithms and an interpolation strategy are given. The analysis not only provides a deeper understanding of the three algorithms, but also provides a basis for comparing them. Then, the performance of the three wavenumber domain algorithms is evaluated from the perspectives of computational complexity, image quality, and geometric position through theoretical analysis and simulation experiments. Aiming at the problem that the range and azimuth profiles are not orthogonal, a method to calculate resolution and extract profile is proposed. The results show that all three algorithms can obtain a well-focused images if full-resolution interpolation is performed, and the computational complexities of CWD and SWD are less than that of EWD.

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Blind NCS-Based Autofocus for Airborne Wide-Beam SAR Imaging

Cited by 14 publications

References 37 publications

Very High Resolution Synthetic Aperture Radar Systems and Imaging: A Review

Very High Resolution Synthetic Aperture Radar Systems and Imaging: A Review

A Modified Frequency Nonlinear Chirp Scaling Algorithm for High-Speed High-Squint Synthetic Aperture Radar with Curved Trajectory

Performance Analysis of Wavenumber Domain Algorithms for Highly Squinted SAR

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