224 research outputs found
Radar Technology
In this book “Radar Technology”, the chapters are divided into four main topic areas: Topic area 1: “Radar Systems” consists of chapters which treat whole radar systems, environment and target functional chain. Topic area 2: “Radar Applications” shows various applications of radar systems, including meteorological radars, ground penetrating radars and glaciology. Topic area 3: “Radar Functional Chain and Signal Processing” describes several aspects of the radar signal processing. From parameter extraction, target detection over tracking and classification technologies. Topic area 4: “Radar Subsystems and Components” consists of design technology of radar subsystem components like antenna design or waveform design
Target Tracking in UWB Multistatic Radars
Detection, localization and tracking of non-collaborative objects moving inside an area is of great interest to many surveillance applications. An ultra-
wideband (UWB) multistatic radar is considered as a good infrastructure
for such anti-intruder systems, due to the high range resolution provided by
the UWB impulse-radio and the spatial diversity achieved with a multistatic
configuration.
Detection of targets, which are typically human beings, is a challenging
task due to reflections from unwanted objects in the area, shadowing, antenna
cross-talks, low transmit power, and the blind zones arised from intrinsic peculiarities of UWB multistatic radars.
Hence, we propose more effective detection, localization, as well as clutter
removal techniques for these systems. However, the majority of the thesis
effort is devoted to the tracking phase, which is an essential part for improving
the localization accuracy, predicting the target position and filling out the
missed detections.
Since UWB radars are not linear Gaussian systems, the widely used tracking filters, such as the Kalman filter, are not expected to provide a satisfactory performance. Thus, we propose the Bayesian filter as an appropriate
candidate for UWB radars. In particular, we develop tracking algorithms
based on particle filtering, which is the most common approximation of
Bayesian filtering, for both single and multiple target scenarios. Also, we
propose some effective detection and tracking algorithms based on image
processing tools.
We evaluate the performance of our proposed approaches by numerical
simulations. Moreover, we provide experimental results by channel measurements for tracking a person walking in an indoor area, with the presence of a
significant clutter. We discuss the existing practical issues and address them by proposing more robust algorithms
Clutter rejection for MTI radar using a single antenna and a long integration time
Moving Target Indicators (MTI) are airborne radar systems
designed to detect and track moving vehicles or aircrafts. In this paper, we address the problem of detecting hazardous collision targets to avoid them. One of the best known solutions to solve this problem is given by the so-called Space-Time Adaptive Processing (STAP) algorithms which optimally filter the target signal from interference and noise exploiting the specific relationship between Direction Of Arrival (DOA) and Doppler for the ground clutter. However, these algorithms require an antenna array and multiple reception channels that increase cost and complexity.
The authors propose an alternative solution using a single antenna only.
In addition to the standard Doppler shift related to the radial speed, the orthoradial speed of any target can be estimated if using a long integration time. Dangerous targets and ground clutter have different signatures in the radial-orthoradial velocity plane. An optimal detector is then proposed based on the oblique projection onto the signal subspace orthogonal to the clutter subspace. The theoretical performances of this detector are derived and a realistic radar scene simulation shows the benefits of this new MTI detector
Enhancing automatic maritime surveillance systems with visual information
Automatic surveillance systems for the maritime
domain are becoming more and more important due to a constant
increase of naval traffic and to the simultaneous reduction of
crews on decks. However, available technology still provides only
a limited support to this kind of applications. In this paper,
a modular system for intelligent maritime surveillance, capable
of fusing information from heterogeneous sources, is described.
The system is designed to enhance the functions of the existing
Vessel Traffic Services systems and to be deployable in populated
areas, where radar-based systems cannot be used due to the high
electromagnetic radiation emissions. A quantitative evaluation
of the proposed approach has been carried out on a large
and publicly available data set of images and videos, collected
from multiple real sites, with different light, weather, and traffic
conditions
GNSS-based passive radar techniques for maritime surveillance
The improvement of maritime traffic safety and security is a subject of growing interest, since the traffic is constantly increasing. In fact, a large number of human activities take place in maritime domain, varying from cruise and trading ships up to vessels involved in nefarious activities such as piracy, human smuggling or terrorist actions. The systems based on Automatic Identification System (AIS) transponder cannot cope with non-cooperative or non-equipped vessels that instead can be detected, tracked and identified by means of radar system. In particular, passive bistatic radar (PBR) systems can perform these tasks without a dedicated transmitter, since they exploit illuminators of opportunity as transmitters. The lack of a dedicated transmitter makes such systems low cost and suitable to be employed in areas where active sensors cannot be placed such as, for example, marine protected areas. Innovative solutions based on terrestrial transmitters have been considered in order to increase maritime safety and security, but these kinds of sources cannot guarantee a global coverage, such as in open sea. To overcome this problem, the exploitation of global navigation satellites system (GNSS) as transmitters of opportunity is a prospective solution. The global, reliable and persistent nature of these sources makes them potentially able to guarantee the permanent monitoring of both coastal and open sea areas.
To this aim, this thesis addresses the exploitation of Global Navigation Satellite Systems (GNSS) as transmitters of opportunity in passive bistatic radar (PBR) systems for maritime surveillance. The main limitation of this technology is the restricted power budget provided by navigation satellites, which makes it necessary to define innovative moving target detection techniques specifically tailored for the system under consideration. For this reason, this thesis puts forward long integration time techniques able to collect the signal energy over long time intervals (tens of seconds), allowing the retrieval of suitable levels of signal-to-disturbance ratios for detection purposes.
The feasibility of this novel application is firstly investigated in a bistatic system configuration. A long integration time moving target detection technique working in bistatic range&Doppler plane is proposed and its effectiveness is proved against synthetic and experimental datasets. Subsequently the exploitation of multiple transmitters for the joint detection and localization of vessels at sea is also investigated. A single-stage approach to jointly detect and localize the ship targets by making use of long integration times (tens of seconds) and properly exploiting the spatial diversity offered by such a configuration is proposed. Furthermore, the potential of the system to extract information concerning the detected target characteristics for further target classification is assessed
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