Subjects: Electronics and Communication Technology >> Radar Engineering submitted time 2024-01-31
Abstract： Among various methods to detect the ship targets in Synthetic Aperture Radar（SAR） image, the Constant False Alarm Rate (CFAR) detection algorithm with an adaptive detection threshold is the most important and extensively used one. In order to improve the detection performance of the ships in SAR image, various statistical distributions are used, with an attempt to accurately model the SAR clutter backgrounds, such as Gamma, K, log-normal, G0, the alpha-stable distribution, etc. In modern radar systems, the use of the CFAR technique is necessary to keep the false alarms at a suitably low rate in an a priori unknown time varying and spatially nonhomogeneous backgrounds, and to improve the detection probability as much as possible. The clutter background in SAR images is complicated and variable, when the actual clutter background deviates from the assumed statistical distribution, the performance of the parametric CFAR detectors will deteriorate, whereas the nonparametric CFAR method will exhibit its advantage. In this work, the Wilcoxon nonparametric CFAR scheme for ship detection in SAR image is proposed and analyzed. By comparison with several typical parametric CFAR schemes on 3 real SAR images of Radarsat-2, ICEYE-X6 and Gaofen-3, the robustness of the Wilcoxon nonparametric detector to maintain a good false alarm performance in these different detection backgrounds is revealed, and its detection performance for the weak ship is improved evidently. Moreover, the detection speed of the Wilcoxon nonparametric detector is fast and it has the simplicity of hardware implementation.
Peer Review Status:
Awaiting Review
Subjects: Electronics and Communication Technology >> Radar Engineering submitted time 2020-09-08
Abstract： Monopulse lobing has been applied in scanning radars to improve image quality in the forward-looking area. However, monopulse measurements fail to resolve multiple targets in the same resolution bin because of angle glint, which may lead to imaging blurring. To tackle the problem, we propose a monopulse forward-looking imaging method via Doppler estimates of sum-difference measurements. Firstly, target multiplicity is resolved by exploiting the different Doppler slopes caused by relative motion between the platform and targets at different directions. Secondly, the azimuthal angles of the Doppler estimates are accurately measured by using sum-difference amplitude comparison (SDAC). Subsequently, the intensity of the sum channel estimates is projected onto the image plane according to the range and angle measurements. To further improve the precision of angle measurements, a chirp-z transform (CZT) based algorithm is proposed to reconstruct the Doppler estimates of sum-difference channels. Simulation results demonstrate the capability of our proposed methods to resolve multiple targets at the large-squint scanning angles. Real data experiments validate that the CZT based algorithm significantly improves the profile of the scene compared to that of the traditional monopulse imaging method. "
Peer Review Status:Awaiting Review
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