Spaceborne Synthetic Aperture Radar Imaging Algorithms: An overview

Sun, Guang-Cai; Liu, Yanbin; Xiang, Jixiang; Liu, Wenkang; Xing, Mengdao; Chen, Jianlai

doi:10.1109/mgrs.2021.3097894

Cited by 45 publications

(28 citation statements)

References 115 publications

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“…Then, for static and moving targets with the same initial position, their range histories can be modeled uniformly in Equation (1). For CF-SAR with different modes, including stripmap, spotlight, sliding spotlight, and TOPS modes, etc., the main differences corresponding to the signal pattern between them depend on the beam steering and the position of the rotation center [10]. According to Equation (1), the echo signal of CF-SAR in Figure 3 after down-conversion can be expressed as follows: Remark 1.…”

Section: Unified Modelmentioning

confidence: 99%

“…Then, the 'ideal-propagation' assumption is no longer valid, since the plasma sheath is a kind of dielectric medium that influences the propagation of electromagnetic waves, such as the nonuniform and time-varying distribution of the reflection coefficient in magnitude attenuation and in dispersion along the frequency axis [12]. The common propagation For CF-SAR with different modes, including stripmap, spotlight, sliding spotlight, and TOPS modes, etc., the main differences corresponding to the signal pattern between them depend on the beam steering and the position of the rotation center [10]. According to Equation (1), the echo signal of CF-SAR in Figure 3 after down-conversion can be expressed as follows:…”

Section: Unified Modelmentioning

confidence: 99%

“…Therefore, the reference rotation position vector R rot can be defined to describe different working modes. The so-called reference rotation position vector is the vector from the position of the radar platform at the reference moment to the rotation center [10]. The specific values of |R rot | for different modes are summarized in Table 3.…”

Section: Beam Steeringmentioning

confidence: 99%

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Curvilinear Flight Synthetic Aperture Radar (CF-SAR): Principles, Methods, Applications, Challenges and Trends

et al. 2022

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The research into curvilinear flight synthetic aperture radar (CF-SAR) is the inevitable result of the comprehensive practicality of SAR. The flight path of the SAR platform in real applications, which is highly nonlinear or curvy due to three-dimensional velocity and acceleration, cannot be described by the traditional uniform linear motion model. New mathematical models, signal characteristics, imaging algorithms, and system design criteria must be proposed and investigated for CF-SAR. This paper provides a comprehensive overview of CF-SAR. Firstly, the basic concept, unified model, and general signal characteristics of CF-SAR are defined, derived, and analyzed, respectively. Additionally, the advantages and drawbacks of current methodologies are reviewed. Discussions on the CF-SAR’s applications are presented from the perspective of typical platforms, new configurations, and advanced technologies, which are suitable means to fulfill the increasing user requirements. Finally, the challenges faced by CF-SAR are summarized, and some future trends for the study of CF-SAR are explored. Hopefully, this paper will serve as a reference for SAR researchers/engineers and stimulate the future development and actual application of CF-SAR.

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Section: Unified Modelmentioning

confidence: 99%

Section: Unified Modelmentioning

confidence: 99%

Section: Beam Steeringmentioning

confidence: 99%

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Curvilinear Flight Synthetic Aperture Radar (CF-SAR): Principles, Methods, Applications, Challenges and Trends

et al. 2022

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“…Most of the classic SAR imaging algorithms [13], such as the range Doppler algorithm (RDA) [14][15][16], the chirp scaling algorithm (CSA) [17][18][19], and back projection algorithms (BPA) [20][21][22] are generally based on Equivalent Squint Range Model (ESRM) [23][24][25], which does not introduce significant phase errors for airborne and LEO SAR imaging. However, as the curvature and orbit height increase, a higher-order range model needs to be established to accurately compensate the phase errors.…”

Section: Introductionmentioning

confidence: 99%

An Improved Equivalent Squint Range Model and Imaging Approach for Sliding Spotlight SAR Based on Highly Elliptical Orbit

Wang

Zeng

et al. 2021

Remote Sensing

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As an emerging orbital system with flexibility and brand application prospects, the highly elliptical orbit synthetic aperture radar (HEO SAR) can achieve both a low orbit detailed survey and continuous earth surface observation in high orbit, which could be applied to marine reconnaissance and surveillance. However, due to its large eccentricity, two challenges have been faced in the signal processing of HEO SAR at present. The first challenge is that the traditional equivalent squint range model (ESRM) fails to accurately describe the entire range for the whole orbit period including the perigee, the apogee, and the squint subduction section. The second one is to exploit an efficient HEO SAR imaging algorithm in the squinted case which solves the problem that traditional imaging algorithm fails to achieve the focused imaging processing of HEO SAR during the entire orbit period. In this paper, a novel imaging algorithm for HEO SAR is presented. Firstly, the signal model based on the geometric configuration of the large elliptical orbit is established and the Doppler parameter characteristics of SAR are analyzed. Secondly, due to the particularity of Doppler parameters variation in the whole period of HEO, the equivalent velocity and equivalent squint angle used in MESRM can no longer be applied, a refined fourth-order equivalent squint range model(R4-ESRM) that is suitable for HEO SAR is developed by introducing fourth-order Doppler parameter into Modified ESRM (MESRM), which accurately reconstructs the range history of HEO SAR. Finally, a novel imaging algorithm combining azimuth resampling and time-frequency domain hybrid correlation based on R4-ESRM is derived. Simulation is performed to demonstrate the feasibility and validity of the presented algorithm and range model, showing that it achieves the precise phase compensation and well focusing.

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“…weather day/night capability, which makes it well suited for polar sea ice monitoring. Synthetic aperture radar (SAR) has multimode image capability [3][4] and can provide highresolution images of sea ice that can be used to produce reasonable sea ice classification results [5][6][7]. However, the spatial coverage of SAR imagery remains limited [8], so it is important to establish a new approach to monitor sea ice type on the large scale (or even globally).…”

mentioning

confidence: 99%

Assessment of Arctic Sea Ice Classification Ability of Chinese HY-2B Dual-Band Radar Altimeter During Winter to Early Spring Conditions

Zhang¹,

Zhu²,

Zhang³

et al. 2021

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

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Accurate identification of sea ice type from altimeter data is important for inversion of sea ice freeboard by radar altimeter, as well as for maritime navigation in polar regions. Previous sea ice classification studies have rarely involved multifrequency altimeter data. In this study, benefiting from the dual-frequency observation capability of the Chinese HY-2B altimeter, differences between waveform features of C-and Kuband radar altimeter over different types of sea ice were investigated and analyzed for the first time. To validate and evaluate the sea ice classification capability of different feature combinations of the different bands, we extracted 14 features from the waveforms of C-and Ku-band HY-2B altimeter data acquired between December 2019 and April 2020. Our experiments demonstrated that the C-and Ku-band radar waveforms are sensitive to sea ice type, and that sea ice type classification could be improved by combining Ku-and C-band data. This work also proposed a sea ice classification methodology using C-and Kuband altimeter waveforms. Comparison with results from previous studies indicated that the overall accuracy of the proposed method (up to 93.45%) is much higher than that of existing state-of-the-art methods.Index Terms-dual-band radar altimeter, HY-2B, sea ice classification, waveform features. I. INTRODUCTIONITH climate change, drastic changes in Arctic sea ice have had global impact that cannot be ignored. Sea ice type and thickness is an important parameter used to describe the state of sea ice, and it is of considerable importance in relation to global climate change research, Arctic ecology, and monitoring of navigational safety in polar regions [1][2]. In comparison with in situ surveys, microwave remote sensing has received increasing attention recently owing to its near all-Manuscript received XXX.

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Spaceborne Synthetic Aperture Radar Imaging Algorithms: An overview

Cited by 45 publications

References 115 publications

Curvilinear Flight Synthetic Aperture Radar (CF-SAR): Principles, Methods, Applications, Challenges and Trends

Curvilinear Flight Synthetic Aperture Radar (CF-SAR): Principles, Methods, Applications, Challenges and Trends

An Improved Equivalent Squint Range Model and Imaging Approach for Sliding Spotlight SAR Based on Highly Elliptical Orbit

Assessment of Arctic Sea Ice Classification Ability of Chinese HY-2B Dual-Band Radar Altimeter During Winter to Early Spring Conditions

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