48 research outputs found
Beyond the spatio-temporal limits of atmospheric radars: inverse problem techniques and MIMO systems
The Earth’s upper atmosphere (UA) is a highly dynamic region dominated by atmospheric waves and stratified turbulence covering a wide range of spatio-temporal scales. A comprehensive study of the UA requires measurements over a broad range of frequencies and spatial wavelengths, which are prohibitively costly. To improve the understanding of the UA, an investment in efficient and large observational infrastructures is required. This work investigates remote sensing techniques based on MIMO and inverse problems techniques to improve the capabilities of current atmospheric radars
Multibeam radar system based on waveform diversity for RF seeker applications
Existing radiofrequency (RF) seekers use mechanically steerable antennas. In order to
improve the robustness and performance of the missile seeker, current research is investigating the replacement of mechanical 2D antennas with active electronically controlled
3D antenna arrays capable of steering much faster and more accurately than existing solutions. 3D antenna arrays provide increased radar coverage, as a result of the conformal
shape and flexible beam steering in all directions. Therefore, additional degrees of freedom
can be exploited to develop a multifunctional seeker, a very sophisticated sensor that can
perform multiple simultaneous tasks and meet spectral allocation requirements.
This thesis presents a novel radar configuration, named multibeam radar (MBR), to
generate multiple beams in transmission by means of waveform diversity. MBR systems
based on waveform diversity require a set of orthogonal waveforms in order to generate
multiple channels in transmission and extract them efficiently at the receiver with digital
signal processing. The advantage is that MBR transmit differently designed waveforms in
arbitrary directions so that waveforms can be selected to provide multiple radar functions
and better manage the available resources.
An analytical model of an MBR is derived to analyse the relationship between individual channels and their performance in terms of isolation and phase steering effects.
Combinations of linear frequency modulated (LFM) waveforms are investigated and the
analytical expressions of the isolation between adjacent channels are presented for rectangular and Gaussian amplitude modulated LFM signals with different bandwidths, slopes and frequency offsets. The theoretical results have been tested experimentally to corroborate the isolation properties of the proposed waveforms. In addition, the practical
feasibility of the MBR concept has been proved with a radar test bed with two orthogonal
channels simultaneously detecting a moving target
Very High Resolution Tomographic SAR Inversion for Urban Infrastructure Monitoring — A Sparse and Nonlinear Tour
The topic of this thesis is very high resolution (VHR) tomographic SAR inversion for urban infrastructure monitoring. To this end, SAR tomography and differential SAR tomography are demonstrated using TerraSAR-X spotlight data for providing 3-D and 4-D (spatial-temporal) maps of an entire high rise city area including layover separation and estimation of deformation of the buildings. A compressive sensing based estimator (SL1MMER) tailored to VHR SAR data is developed for tomographic SAR inversion by exploiting the sparsity of the signal. A systematic performance assessment of the algorithm is performed regarding elevation estimation accuracy, super-resolution and robustness. A generalized time warp method is proposed which enables differential SAR tomography to estimate multi-component nonlinear motion. All developed methods are validated with both simulated and extensive processing of large volumes of real data from TerraSAR-X
Characterising and modeling the co-evolution of transportation networks and territories
The identification of structuring effects of transportation infrastructure on
territorial dynamics remains an open research problem. This issue is one of the
aspects of approaches on complexity of territorial dynamics, within which
territories and networks would be co-evolving. The aim of this thesis is to
challenge this view on interactions between networks and territories, both at
the conceptual and empirical level, by integrating them in simulation models of
territorial systems.Comment: Doctoral dissertation (2017), Universit\'e Paris 7 Denis Diderot.
Translated from French. Several papers compose this PhD thesis; overlap with:
arXiv:{1605.08888, 1608.00840, 1608.05266, 1612.08504, 1706.07467,
1706.09244, 1708.06743, 1709.08684, 1712.00805, 1803.11457, 1804.09416,
1804.09430, 1805.05195, 1808.07282, 1809.00861, 1811.04270, 1812.01473,
1812.06008, 1908.02034, 2012.13367, 2102.13501, 2106.11996
Abstracts on Radio Direction Finding (1899 - 1995)
The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography).
Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM.
The contents of these files are:
1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format];
2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format];
3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion
Modeling and Simulation in Engineering
This book provides an open platform to establish and share knowledge developed by scholars, scientists, and engineers from all over the world, about various applications of the modeling and simulation in the design process of products, in various engineering fields. The book consists of 12 chapters arranged in two sections (3D Modeling and Virtual Prototyping), reflecting the multidimensionality of applications related to modeling and simulation. Some of the most recent modeling and simulation techniques, as well as some of the most accurate and sophisticated software in treating complex systems, are applied. All the original contributions in this book are jointed by the basic principle of a successful modeling and simulation process: as complex as necessary, and as simple as possible. The idea is to manipulate the simplifying assumptions in a way that reduces the complexity of the model (in order to make a real-time simulation), but without altering the precision of the results
Epilepsy
With the vision of including authors from different parts of the world, different educational backgrounds, and offering open-access to their published work, InTech proudly presents the latest edited book in epilepsy research, Epilepsy: Histological, electroencephalographic, and psychological aspects. Here are twelve interesting and inspiring chapters dealing with basic molecular and cellular mechanisms underlying epileptic seizures, electroencephalographic findings, and neuropsychological, psychological, and psychiatric aspects of epileptic seizures, but non-epileptic as well