scholarly journals Focus Improvement of Airborne High-Squint Bistatic SAR Data Using Modified Azimuth NLCS Algorithm Based on Lagrange Inversion Theorem

2021 ◽  
Vol 13 (10) ◽  
pp. 1916
Author(s):  
Chuang Li ◽  
Heng Zhang ◽  
Yunkai Deng
Keyword(s):  
Large Range ◽  
Cross Coupling ◽  
Synthetic Aperture ◽  
Phase Point ◽  
Lagrange Inversion ◽  
Inversion Theorem ◽  
Range Cell ◽  
Higher Order Terms ◽  
Bistatic Synthetic Aperture Radar ◽  
Range Cell Migration

In this paper, a modified azimuth nonlinear chirp scaling (NLCS) algorithm is derived for high-squint bistatic synthetic aperture radar (BiSAR) imaging to solve its inherent difficult issues, including the large range cell migration (RCM), azimuth-dependent Doppler parameters, and the sensibility of the higher order terms. First, using the Lagrange inversion theorem, an accurate spectrum suitable for processing airborne high-squint BiSAR data is introduced. Different from the spectrum that is based on the method of series reversion (MSR), it is allowed to derive the bistatic stationary phase point while retaining the double square root (DSR) of the slant range history. Based the spectrum, a linear RCM correction is used to remove the most of the linear RCM components and mitigate the range-azimuth coupling, and, then, bulk secondary range compression is implemented to compensate the residual RCM and cross-coupling terms. Following this, a modified azimuth NLCS operation is applied to eliminate the azimuth-dependence of Doppler parameters and equalize the azimuth frequency modulation for azimuth compression. The experimental results, with better focusing performance, prove the high accuracy and effectiveness of the proposed algorithm.

scholarly journals Moving Target Imaging Using GNSS-Based Passive Bistatic Synthetic Aperture Radar

2020 ◽  
Vol 12 (20) ◽  
pp. 3356
Author(s):  
Zhen-Yu He ◽  
Yang Yang ◽  
Wu Chen ◽  
Duo-Jie Weng
Keyword(s):  
Parameter Estimation ◽  
Cell Migration ◽  
Synthetic Aperture ◽  
Moving Target ◽  
Chirp Rate ◽  
Range Cell ◽  
Target Imaging ◽  
Moving Target Imaging ◽  
Bistatic Synthetic Aperture Radar ◽  
Range Cell Migration

Current studies of global navigation satellite systems (GNSS)-based bistatic synthetic aperture radar (GNSS-SAR) is focused on static objects on land. However, moving target imaging is also very significant for modern SAR systems. Imaging a moving target has two main problems. One is the unknown range cell migration; the other is the motion parameter estimation, such as the target’s velocity. This paper proposes a moving target imaging formation algorithm for GNSS-SAR. First, an approximate bistatic range history is derived to describe the phase variation of the target signal along the azimuth time. Then, a keystone transform is employed to correct the range cell migration. To address the motion parameter estimation, a chirp rate estimation method based on short-time Fourier transform and random sample consensus is proposed with high processing efficiency and robust estimation errors in low signal-to-noise ratio scenes. The estimated chirp rate can calculate the target’s velocity. Finally, azimuth compression derivation is performed to accomplish GNSS-SAR imaging. A maritime experimental campaign is conducted to validate the effectiveness of the proposed algorithm. The two cargo ships in the SAR images have good accordance with the ground truth in terms of the target-to-receiver vertical distances along the range and the ships’ length along the cross-range.

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 An Improved Generalized Chirp Scaling Algorithm Based on Lagrange Inversion Theorem for High-Resolution Low Frequency Synthetic Aperture Radar Imaging

2019 ◽  
Vol 11 (16) ◽  
pp. 1874 ◽  
Author(s):  
Xing Chen ◽  
Tianzhu Yi ◽  
Feng He ◽  
Zhihua He ◽  
Zhen Dong
Keyword(s):  
High Resolution ◽  
Stationary Phase ◽  
Low Frequency ◽  
Synthetic Aperture ◽  
Phase Coupling ◽  
Lagrange Inversion ◽  
Inversion Theorem ◽  
Coupling Phase ◽  
Large Bandwidth ◽  
Chirp Scaling Algorithm

The high-resolution low frequency synthetic aperture radar (SAR) has serious range-azimuth phase coupling due to the large bandwidth and long integration time. High-resolution SAR processing methods are necessary for focusing the raw data of such radar. The generalized chirp scaling algorithm (GCSA) is generally accepted as an attractive solution to focus SAR systems with low frequency, large bandwidth and wide beam bandwidth. However, as the bandwidth and/or beamwidth increase, the serious phase coupling limits the performance of the current GCSA and degrades the imaging quality. The degradation is mainly caused by two reasons: the residual high-order coupling phase and the non-negligible error introduced by the linear approximation of stationary phase point using the principle of stationary phase (POSP). According to the characteristics of a high-resolution low frequency SAR signal, this paper firstly presents a principle to determine the required order of range frequency. After compensating for the range-independent coupling phase above 3rd order, an improved GCSA based on Lagrange inversion theorem is analytically derived. The Lagrange inversion enables the high-order range-dependent coupling phase to be accurately compensated. Imaging results of P- and L-band SAR data demonstrate the excellent performance of the proposed algorithm compared to the existing GCSA. The image quality and focusing depth in range dimension are greatly improved. The improved method provides the possibility to efficiently process high-resolution low frequency SAR data with wide swath.

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

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.

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