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 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 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.

Presenting a New Technique for Multi-Target Tracking in Inverse Synthetic Aperture Radar based on PHD Filter in the Presence of Clutters

Frequenz ◽  
2018 ◽  
Vol 72 (7-8) ◽  
pp. 391-399 ◽  
Author(s):  
Hamid Dehghani ◽  
Navid Daryasafar
Keyword(s):  
Cell Migration ◽  
Synthetic Aperture Radar ◽  
Synthetic Aperture ◽  
Moving Targets ◽  
Inverse Synthetic Aperture Radar ◽  
Probability Hypothesis Density ◽  
Implementation Phase ◽  
Range Cell ◽  
Range Cell Migration ◽  
Aperture Radar

Abstract Using Probability Hypothesis Density (PHD) filtering, a novel approach is proposed in this paper for simultaneous tracking of multiple moving targets in received data by Inverse Synthetic Aperture Radar (ISAR) system. Since PHD filtering approach is implemented successively in prediction and update steps, its performance quality will obviously be higher in “Spotlight” imaging mode than in “Stripmap”. Thus, its application to Spotlight mode is generally more logical. The idea to integrate tracking capability into ISAR system processor is to sort radar received data to correct Range Cell Migration (RCM) prior to tracking operations. Clearly, Range Cell Migration Compensation (RCMC) approach is different from this approach in image formation process, in terms of their implementation phase. However, they are implemented in a similar way. As simulation results reveal, applying Range Cell Migration Compensation to the raw data received by ISAR before tracking operation, results in high quality tracking of moving targets.

scholarly journals Focusing of Spotlight Tandem-Configuration Bistatic Data with Frequency Scaling Algorithm

2016 ◽  
Vol 2016 ◽  
pp. 1-15
Author(s):  
Shichao Chen ◽  
Ming Liu ◽  
Jun Wang ◽  
Fugang Lu ◽  
Mengdao Xing
Keyword(s):  
Cell Migration ◽  
Data Processing ◽  
High Precision ◽  
Frequency Scaling ◽  
Tandem Configuration ◽  
Imaging Algorithm ◽  
Bistatic Sar ◽  
Range Cell ◽  
Sar Data ◽  
Range Cell Migration

A frequency scaling (FS) imaging algorithm is proposed for spotlight bistatic SAR data processing. Range cell migration correction (RCMC) is realized through phase multiplication. The proposed algorithm is insensitive to the length of the baseline due to the high precision of the point target (PT) spectrum that we are based on. It is capable of handling bistatic SAR data with a large baseline to range ratio. The algorithms suitable for small and high squint angles are both discussed according to whether the range dependence of the second range compression (SRC) can be neglected or not. Simulated experiments validate the effectiveness of the proposed algorithm.

Estimation and correction of vibration-induced range cell migration for FMCW synthetic aperture ladar

2020 ◽  
Vol 59 (9) ◽  
pp. 2874
Author(s):  
Guangzuo Li ◽  
Zenghui Zhang ◽  
Yifei Zhang ◽  
Sujuan Fang ◽  
Wen Hong ◽  
...  
Keyword(s):  
Cell Migration ◽  
Synthetic Aperture ◽  
Range Cell ◽  
Range Cell Migration ◽  
Estimation And Correction
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