scholarly journals A Modified Cartesian Factorized Backprojection Algorithm Integrating with Non-Start-Stop Model for High Resolution SAR Imaging

2020 ◽  
Vol 12 (22) ◽  
pp. 3807
Author(s):  
Da Liang ◽  
Heng Zhang ◽  
Tingzhu Fang ◽  
Haoyu Lin ◽  
Dacheng Liu ◽  
...  
Keyword(s):  
High Resolution ◽  
Frequency Modulation ◽  
Simulation Experiment ◽  
Synthetic Aperture ◽  
Time Varying ◽  
Sar Image ◽  
Imaging Processing ◽  
Sar Imaging ◽  
Disaster Monitoring ◽  
Modulation Rate

High resolution synthetic aperture radar (SAR) imaging has extensive application value especially in military reconnaissance and disaster monitoring. The motion of the satellite during the transmission and reception of the signal introduces notable errors in the high resolution SAR spotlight mode, which will lead to a defocused SAR image if not handled. To address this problem, an accurate correct echo model based on non-start-stop model is derived to describe the property of the SAR signal in the paper. Then, in the imaging processing, an azimuth-time-varying range frequency modulation rate is used for range compression. The range history and compensation phase are also derived based on the correct echo model. Then, combining the correct echo model and Cartesian factorized backprojection (CFBP) algorithm, a modified CFBP algorithm is proposed for SAR imaging to improve the accuracy and efficiency of processing. Besides, the influence of residual error due to mismatch is analyzed in detail. In the end, the simulation experiment and Gaofen-3 (GF-3) data experiment are carried out to demonstrate the feasibility of the proposed algorithm.

Bistatic Noise SAR Experiment with a Non-Cooperative Illuminator

2011 ◽  
Vol 57 (1) ◽  
pp. 85-89
Author(s):  
Łukasz Maślikowski ◽  
Krzysztof Kulpa
Keyword(s):  
Signal Processing ◽  
Synthetic Aperture Radar ◽  
Noise Signal ◽  
Synthetic Aperture ◽  
Sar Image ◽  
Measurement Campaign ◽  
Bistatic Sar ◽  
Sar Imaging ◽  
Commercial Off The Shelf ◽  
Build System

Bistatic Noise SAR Experiment with a Non-Cooperative IlluminatorThe paper describes the results of a conception-stage experiment with a ground-based bistatic noise SAR (Synthetic Aperture Radar) demonstrator. Its aim was to research the ability of a simple Commercial-Off-The-Shelf (COTS) build system to provide a bistatic SAR image using non-cooperative illuminator. The noise signal used in the experiment is similar to a signal used in many transmission systems such as DVB-T that can be employed in passive bistatic radars. The paper presents the system setup, details of the measurement campaign, signal processing and the results of SAR imaging.

scholarly journals A New Synthetic Aperture Radar (SAR) Imaging Method Combining Match Filter Imaging and Image Edge Enhancement

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4133 ◽  
Author(s):  
Bing Sun ◽  
Chuying Fang ◽  
Hailun Xu ◽  
Anqi Gao
Keyword(s):  
Image Processing ◽  
Image Segmentation ◽  
Synthetic Aperture Radar ◽  
Synthetic Aperture ◽  
Imaging Method ◽  
Sar Image ◽  
Sar Images ◽  
Gradient Operator ◽  
Sar Imaging ◽  
Aperture Radar

In general, synthetic aperture radar (SAR) imaging and image processing are two sequential steps in SAR image processing. Due to the large size of SAR images, most image processing algorithms require image segmentation before processing. However, the existence of speckle noise in SAR images, as well as poor contrast and the uneven distribution of gray values in the same target, make SAR images difficult to segment. In order to facilitate the subsequent processing of SAR images, this paper proposes a new method that combines the back-projection algorithm (BPA) and a first-order gradient operator to enhance the edges of SAR images to overcome image segmentation problems. For complex-valued signals, the gradient operator was applied directly to the imaging process. The experimental results of simulated images and real images validate our proposed method. For the simulated scene, the supervised image segmentation evaluation indexes of our method have more than 1.18%, 11.2% and 11.72% improvement on probabilistic Rand index (PRI), variability index (VI), and global consistency error (GCE). The proposed imaging method will make SAR image segmentation and related applications easier.

A New Evaluation Method of Jamming Effect on ISAR

2013 ◽  
Vol 380-384 ◽  
pp. 4132-4135
Author(s):  
Cui Rui ◽  
Ji Fei Pan ◽  
Li Min Gi Chen ◽  
Jing Zhu
Keyword(s):  
High Resolution ◽  
Synthetic Aperture Radar ◽  
Amplitude Modulation ◽  
Frequency Modulation ◽  
Evaluation Method ◽  
Synthetic Aperture ◽  
High Resolution Imaging ◽  
Imaging Radar ◽  
Resolution Imaging ◽  
Jamming Effect

The Inverse Synthetic Aperture Radar (ISAR) is a high resolution imaging radar. Some methods used to evaluate the jamming effect of general radar are unsuitable to ISAR. A new evaluation method of jamming effect on ISAR is presented in the paper through comparing the change of moment character and area character, The amplitude modulation (AM) noise jamming and frequency modulation (FM) noise jamming are carried out in the paper, the results of simulation prove the method is corrective and effective.

scholarly journals High-Squint FMCW SAR Imaging via Wavenumber Domain Algorithm

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Hui Bi ◽  
Hao Li ◽  
Wei Liang
Keyword(s):  
High Resolution ◽  
Continuous Wave ◽  
Synthetic Aperture ◽  
Transmission Power ◽  
Wavenumber Domain ◽  
Radar Systems ◽  
Pulsed Mode ◽  
Sar Imaging ◽  
Good Potential ◽  
Common Technique

Nowadays, because the frequency modulation continuous-wave (FMCW) synthetic aperture radar (SAR) shows good potential in minimal transmission power and weight reduction of radar systems, it has been widely used and has become a common technique in modern short-range high-resolution earth observation. Different from the conventional pulsed mode, the stop-to-go approximation is not valid in FMCW SAR. Thus, the typical SAR imaging methods need to be modified to adapt the continuous-wave scheme in practical data processing. In this letter, a wavenumber domain algorithm (WDA) is derived and used for the FMCW SAR imaging under squint and high-squint cases. With the help of the exact scene recovery ability of the proposed WDA, we can achieve the accurate recovery of the considered scene even when using the collected high-squint data and hence obtain the well-focused high-resolution image of the considered scene. Experimental results with simulated and airborne data verify the effectiveness of the proposed method.

scholarly journals High-Resolution SAR Image Despeckling Based on Nonlocal Means Filter and Modified AA Model

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Qiao Ke ◽  
Sun Zeng-guo ◽  
Yang Liu ◽  
Wei Wei ◽  
Marcin Woźniak ◽  
...  
Keyword(s):  
High Resolution ◽  
Synthetic Aperture Radar ◽  
Iterative Algorithm ◽  
Synthetic Aperture ◽  
Sar Image ◽  
Sar Images ◽  
Edge Information ◽  
Nonlocal Means ◽  
Proposed Model ◽  
Effective Performance

A new speckle suppression algorithm is proposed for high-resolution synthetic aperture radar (SAR) images. It is based on the nonlocal means (NLM) filter and the modified Aubert and Aujol (AA) model. This method takes the nonlocal Dirichlet function as a linear regularization item, which constructs the weight by measuring the similarity of images. Then, a new despeckling model is introduced by combining the regularization item and the data item of the AA model, and an iterative algorithm is proposed to solve the new model. The experiments show that, compared with the AA model, the proposed model has more effective performance in suppressing speckle; namely, ENL and DCV measures are 21.75% and 4.5% higher, respectively, than for NLM. Moreover, it also has better performance in keeping the edge information.

Oil Spills Identification in SAR Image Using Mahalanobis Distance

2012 ◽  
Vol 466-467 ◽  
pp. 246-250
Author(s):  
Peng Chen ◽  
Hui Zhou ◽  
Xiao Tian Wang
Keyword(s):  
High Resolution ◽  
Mahalanobis Distance ◽  
Oil Spills ◽  
Feature Vector ◽  
Weather Conditions ◽  
Target Object ◽  
The Other ◽  
Synthetic Aperture ◽  
Sar Image ◽  
Accuracy Rate

This paper presents a method of oil spills identification in Synthetic Aperture Radar (SAR) image based on feature vector, it makes use of the advantages of SAR which can work on day and night and all weather conditions with high resolution monitoring for oil spills. Use the algorithm of Mahalanobis distance to identify the target object and gain the feature vector through evaluating SAR image of the dark area boundary. It is proved by experiment that the number of selected feature value is reasonable and more effective for estimating whether has oil spills than the traditional one. The accuracy rate can reach 96% or even more for using the algorithm of Mahalanobis distance and compare to the other methods of oil spills identification it is easy for programming implementation with less conditions .

scholarly journals High-Precision Spotlight SAR Imaging with Joint Modified Fast Factorized Backprojection and Autofocus

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Man Zhang ◽  
Haolin Li ◽  
Guanyong Wang
Keyword(s):  
Fourier Transform ◽  
High Resolution ◽  
Time Domain ◽  
High Efficiency ◽  
High Accuracy ◽  
Synthetic Aperture ◽  
Image Domain ◽  
Phase Gradient ◽  
Phase Errors ◽  
Sar Imaging

Fast factorized backprojection (FFBP) takes advantage of high accuracy of time-domain algorithms while also possessing high efficiency comparable with conventional frequency domain algorithms. When phase errors need to be compensated for high-resolution synthetic aperture radar (SAR) imaging, however, neither polar formatted subimages within FFBP flow nor the final Cartesian image formed by FFBP is suitable for phase gradient autofocus (PGA). This is because these kinds of images are not capable of providing PGA with a clear Fourier transform relationship (FTR) between image domain and range-compressed phase history domain. In this paper, we make some essential modifications to the original FFBP and present a scheme to incorporate overlapped-subaperture frame for an accurate PGA processing. The raw data collected by an airborne high-resolution spotlight SAR are used to demonstrate the performance of this algorithm.

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