scholarly journals Squint Mode GEO SAR Imaging Using Bulk Range Walk Correction on Received Signals

2018 ◽  
Vol 11 (1) ◽  
pp. 17
Author(s):  
Jiwen Geng ◽  
Ze Yu ◽  
Chunsheng Li ◽  
Wei Liu
Keyword(s):  
Imaging Method ◽  
Sensing Applications ◽  
Imaging Result ◽  
Range Cell ◽  
Sar Imaging ◽  
Disaster Monitoring ◽  
Imaging Mode ◽  
Range Cell Migration ◽  
Long Term Observation

Geosynchronous synthetic aperture radar (GEO SAR) has the potential for conducting long-term observation of target zones, which is essential for remote sensing applications such as disaster monitoring and vegetation measurements. The squint imaging mode is crucial for long-term observation using GEO SAR. However, this type of SAR imaging is problematic because the squint mode introduces a nonzero range cell walk, which increases the prevalence of invalid data in echoes and intensifies the coupling between the azimuth and range. Therefore, this paper proposes a novel squint mode GEO SAR imaging method based on the correction of the bulk range walk of received signals. Adjusting the starting time of the receiving window significantly reduces the redundancy in echoes. Then, first-order filtering, range cell migration correction, range compression, partial dechirp, and azimuth compression are used to obtain the imaging result. Simulation results for the GEO SAR imaging of Wenchuan County in China demonstrate that the proposed algorithm can achieve a resolution of 5 m within a 30 × 30 km swath over 48% of the orbital period.

scholarly journals High-Resolution Squinted SAR Imaging Algorithm Applied in the Near-Field Environment

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Shijia Wang ◽  
Shibo Wang ◽  
Wanli Liu
Keyword(s):  
Cell Migration ◽  
Near Field ◽  
Synthetic Aperture ◽  
Distortion Compensation ◽  
Imaging Algorithm ◽  
Field Environment ◽  
Imaging Result ◽  
Range Cell ◽  
Sar Imaging ◽  
Range Cell Migration

In the squinted synthetic aperture radar (SAR) imaging of the near-field environment, range-dependent characteristic of squint angle cannot be ignored, which causes azimuth-dependent range cell migration (RCM) after linear range walk correction (LRWC). In this study, an efficient SAR imaging algorithm applied in the near-field environment is proposed. In the processing of the range focusing, LRWC is firstly used to remove the linear RCM. Then, the residual LRCM is expanded into azimuth-invariant and azimuth-variant terms in consideration of the residual LRCM of azimuth-dependent. Range cell migration azimuth scaling (RCMAS) is designed to remove the azimuth-variant term before secondary range compression (SRC) and range compression (RC). In the azimuth focusing, azimuth distortion compensation (ADC) is performed to compensate the azimuth distortion, following which azimuth nonlinear chirp scaling (ANCS) is applied to equalize the frequency modulation (FM) rate for azimuth compression (AC). The simulated results show that more accurate and improved imaging result can be obtained with the proposed algorithm.

scholarly journals Extended Subaperture Imaging Method for Airborne Low Frequency Ultrawideband SAR Data

Sensors ◽  
2019 ◽  
Vol 19 (20) ◽  
pp. 4516
Author(s):  
Daoxiang An ◽  
Wu Wang ◽  
Leping Chen
Keyword(s):  
Low Frequency ◽  
Synthetic Aperture ◽  
Imaging Method ◽  
Theory Analysis ◽  
Range Cell ◽  
Imaging Results ◽  
Sar Imaging ◽  
Sar Data ◽  
Range Cell Migration

The subaperture processing is one of the essential strategies for low frequency ultrawideband synthetic aperture radar (LF UWB SAR) imaging, especially for the real-time LF UWB SAR imaging because it can improve the parallelization of the imaging algorithm. However, due to the longer synthetic aperture of LF UWB SAR, the traditional subaperture imaging encounters an azimuth ambiguities problem, which severely degrades the focused quality of the imaging results. In this paper, the reason for the presence of azimuth ambiguities in the LF UWB SAR subaperture imaging and its influence on image quality is first analyzed in theory. Then, an extended subaperture imaging method based on the extension of subaperture length before Range Cell Migration Correction (RCMC) was proposed. By lengthening the subaperture length, the azimuth ambiguities are effectively eliminated. Finally, the extended part of subaperture is wiped off before the azimuth compression (AC), and the LF UWB SAR image of high focused quality is obtained. The correctness of the theory analysis and the effectiveness of the proposed method have been validated through simulated and real LF UWB SAR data.

scholarly journals Elevation Spatial Variation Analysis and Compensation in GEO SAR Imaging

2021 ◽  
Vol 13 (10) ◽  
pp. 1888
Author(s):  
Faguang Chang ◽  
Dexin Li ◽  
Zhen Dong ◽  
Yang Huang ◽  
Zhihua He ◽  
...  
Keyword(s):  
Spatial Variation ◽  
Three Dimensional ◽  
Integration Time ◽  
Imaging Method ◽  
Imaging Geometry ◽  
Sensing Applications ◽  
Sar Imaging ◽  
High Orbit ◽  
Long Term Observation ◽  
Space Variant

Due to geosynchronous synthetic aperture radar’s (GEO SAR) high orbit and low relative speed, the integration time reaches up to hundreds of seconds for a fine resolution. The short revisit cycle is essential for remote sensing applications such as disaster monitoring and vegetation measurements. Three-dimensional (3D) scene imaging mode is crucial for long-term observation using GEO SAR. However, this mode will bring a new kind of space-variant error in elevation. In this paper, we focus on the analysis of the elevation space-variant error. First, the decorrelation problems caused by the spatial variation are presented. Second, by combining with the SAR imaging geometry, the elevation spatial variation is decomposed into two-dimensional (2D) space variation of range and azimuth. Third, an imaging algorithm is proposed to solve the 3D space variation and improve the focusing depth. Finally, simulations with dot-matrix targets and distributed targets are performed to validate the imaging method.

scholarly journals Modulus Stretch-Based Circular SAR Imaging with Contour Thinning

2019 ◽  
Vol 9 (13) ◽  
pp. 2728 ◽  
Author(s):  
Rongchun Hu ◽  
Zhenming Peng ◽  
Kelong Zheng
Keyword(s):  
Synthetic Aperture Radar ◽  
Target Recognition ◽  
Transformation Function ◽  
Synthetic Aperture ◽  
Imaging Method ◽  
Imaging Result ◽  
Target Imaging ◽  
Sar Imaging ◽  
Line Target ◽  
Subsequent Target

This paper presents a modulus stretch-based circular Synthetic Aperture Radar (SAR) imaging method. This method improves the traditional backprojection algorithm for circular SAR imaging, and introduces the modulus stretch transformation function in the imaging process. By performing a modulus stretch transformation on the intermediate results, the target contour in the final imaging result is thinner and clearer. A thinner and clearer contour can help to increase the recognizability of the target and provide a basis for subsequent target recognition. The proposed method is demonstrated on the line target imaging simulations and Gothca dataset.

scholarly journals Robust Clutter Suppression and Ground Moving Target Imaging Method for a Multichannel SAR with High-Squint Angle Mounted on Hypersonic Vehicle

2021 ◽  
Vol 13 (11) ◽  
pp. 2051
Author(s):  
Jiusheng Han ◽  
Yunhe Cao ◽  
Tat-Soon Yeo ◽  
Fengfei Wang
Keyword(s):  
Hypersonic Vehicle ◽  
Imaging Method ◽  
Moving Target ◽  
Clutter Suppression ◽  
Range Cell ◽  
Target Imaging ◽  
Moving Target Imaging ◽  
Suppression Method ◽  
Range Cell Migration ◽  
First Order Phase

This paper investigates a robust clutter suppression and detection of ground moving target (GMT) imaging method for a multichannel synthetic aperture radar (MC-SAR) with high-squint angle mounted on hypersonic vehicle (HSV). A modified coarse-focused method with cubic chirp Fourier transform (CFT) is explored first that permits the coarsely focused imageries to be recovered, thus alleviated the impacts of GMT Doppler ambiguity and range cell migration (RCM). After that, in combination with joint-pixel model, a robust clutter suppression method which enhances the GMT integration, and improving the accuracy of radial speed (RS) recovery by modifying the matching between the beamformer center and GMT, is proposed. Due to that the first-order phase compensation and RS retrieval are predigested, the proposed algorithm has lower the algorithmic complexity. Finally, the feasibility of our proposed method are verified via experimental results based on simulated and real measured data.

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