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128 results on '"Vu, Viet T."'

12. Phase Control in Interpolation for Backprojection of THz FMCW SAR Signals

Author

Ivanenko, Yevhen, Vu, Viet T., Barowski, Jan, Hellsten, Hans, Pettersson, Mats I., Ivanenko, Yevhen, Vu, Viet T., Barowski, Jan, Hellsten, Hans, and Pettersson, Mats I.

Abstract

The THz frequency spectrum opens a lot of applications in the imaging at sub-mm level. The increase of the operating frequency band for SAR imaging systems to the THz range has proportionally affected the amount of raw data to be stored and used for accurate image reconstruction. As a consequence, improvements in the existing SAR imaging algorithms to reduce the amount of data needed to achieve the appropriate quality of imaging is desired. This paper introduces the phase control procedure as an extension to the existing sinc interpolator for backprojecting complex-valued FMCW SAR data into a defined image plane. The proposed extension controls the phase of interpolated complex-valued SAR data parameters so that it includes appropriate information about the range distance between the SAR system and the given point of space. The extended algorithm is incorporated into the global backprojection algorithm and examined on the measurement data acquired via the 2pSENSE FMCW SAR system. The efficiency of the extended algorithm is evaluated through the comparison with the conventional nearest neighbor and sinc interpolation algorithms. © 2022 Warsaw University of Technology.

Published
2022
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19. A wavelength-resolution sar change detection method based on image stack through robust principal component analysis

Author

Ramos, Lucas P., Campos, Alexandre B., Schwartz, Christofer, Duarte, Leonardo T., Alves, Dimas I., Pettersson, Mats I., Vu, Viet T., and Machado, Renato

Subjects
Wavelength resolution, Synthetic aperture radar (SAR) images, Errors, Configurable parameter, Alarm systems, Synthetic aperture radar, Signalbehandling, Image analysis, Multi-temporal SAR images, blind source separation, robust principal component analysis, Source separation, False alarm reductions, change detection, lcsh:Science, Robust principal component analysis, CARABAS-II, Probability of detection, Radar imaging, Ultra-wideband (UWB), Principal Components, Signal Processing, Blind source separation, Change detection, lcsh:Q, synthetic aperture radar
Abstract

Recently, it was demonstrated that low-frequency wavelength-resolution synthetic aperture radar (SAR) images could be considered to follow an additive mixing model due to their backscatter characteristics. This simplification allows for the use of source separation methods, such as robust principal component analysis (RPCA) via principal component pursuit (PCP), for detecting changes in those images. In this manuscript, a change detection method for wavelength-resolution SAR images based on image stack through RPCA is proposed. The method aims to explore both the temporal and flight heading diversity of a set of wavelength-resolution multitemporal SAR images in order to detect concealed targets in forestry areas. A heuristic based on three rules for better exploring the RPCA results is introduced, and a new configurable parameter for false alarm reduction based on the analysis of image windows is proposed. The method is evaluated using real data obtained from measurements of the ultrawideband (UWB) very high-frequency (VHF) SAR system CARABAS-II. Experiments for stacks of four and seven reference images are conducted, and the use of reference images acquired with different flight headings is explored. The results indicate that a gain in performance can be achieved by using large image stacks containing, at least, one image of each possible flight heading of the data set, which can result in a probability of detection (PD) above 99% for a false alarm rate (FAR) as low as one false alarm per three square kilometers. Furthermore, it is demonstrated that high PD and low FAR can be achieved, also considering images from similar flight headings as reference images. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. open access

Published
2021

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