29 research outputs found
Personal History and List of Main Publications of Professor
Other信州大学経済学論集 67: 59-64(2016)othe
Position Tracking for Passive UHF RFID Tags with the Aid of a Scanned Array
Thanks to the proliferation of radio frequency identification systems (RFID), applications have emerged concerning positioning techniques for inexpensive passive RFID tags. The most accurate approaches for tracking the tag's position, deliver precision in the order of 20 cm over a range of a few meters and require moving parts in a predefined pattern (mechanical antenna steering), which limits their application. Herein, we introduce an RFID tag positioning system that utilizes an active electronically-steered array, based on the principles of modern radar systems. We thoroughly examine and present the main attributes of the system with the aid of an finite element method simulation model and investigate the system performance with far-field tests. The demonstrated positioning precision of 1.5, which translates to under 1 cm laterally for a range of a few meters can be helpful in applications like mobile robot localization and the automated handling of packaged goods.DF
Cognitive radar network design and applications
PhD ThesisIn recent years, several emerging technologies in modern radar system
design are attracting the attention of radar researchers and practitioners
alike, noteworthy among which are multiple-input multiple-output
(MIMO), ultra wideband (UWB) and joint communication-radar technologies.
This thesis, in particular focuses upon a cognitive approach
to design these modern radars. In the existing literature, these technologies
have been implemented on a traditional platform in which the
transmitter and receiver subsystems are discrete and do not exchange
vital radar scene information. Although such radar architectures benefit
from these mentioned technological advances, their performance remains
sub-optimal due to the lack of exchange of dynamic radar scene
information between the subsystems. Consequently, such systems are
not capable to adapt their operational parameters “on the fly”, which
is in accordance with the dynamic radar environment. This thesis explores
the research gap of evaluating cognitive mechanisms, which could
enable modern radars to adapt their operational parameters like waveform,
power and spectrum by continually learning about the radar scene
through constant interactions with the environment and exchanging this
information between the radar transmitter and receiver. The cognitive
feedback between the receiver and transmitter subsystems is the facilitator
of intelligence for this type of architecture.
In this thesis, the cognitive architecture is fused together with modern
radar systems like MIMO, UWB and joint communication-radar designs
to achieve significant performance improvement in terms of target parameter
extraction. Specifically, in the context of MIMO radar, a novel
cognitive waveform optimization approach has been developed which facilitates
enhanced target signature extraction. In terms of UWB radar
system design, a novel cognitive illumination and target tracking algorithm
for target parameter extraction in indoor scenarios has been developed.
A cognitive system architecture and waveform design algorithm
has been proposed for joint communication-radar systems. This thesis
also explores the development of cognitive dynamic systems that allows
the fusion of cognitive radar and cognitive radio paradigms for optimal
resources allocation in wireless networks. In summary, the thesis provides
a theoretical framework for implementing cognitive mechanisms in
modern radar system design. Through such a novel approach, intelligent
illumination strategies could be devised, which enable the adaptation of
radar operational modes in accordance with the target scene variations
in real time. This leads to the development of radar systems which are
better aware of their surroundings and are able to quickly adapt to the
target scene variations in real time.Newcastle University, Newcastle upon Tyne:
University of Greenwich
Digital Beamforming Techniques for Passive UHF RFID Tag Localization
Radio-frequency identification (RFID) technology is on the way to substitute traditional
bar codes in many fields of application. Especially the availability of passive ultra-high
frequency (UHF) RFID transponders (or tags) in the frequency band between 860 MHz
and 960 MHz has fostered the global application in supply chain management. However,
the full potential of these systems will only be exploited if the identification of objects
is complemented by accurate and robust localization.
Passive UHF RFID tags are cost-effective, very small, extremely lightweight, maintenancefree,
rugged and can be produced as adhesive labels that can be attached to almost any
object. Worldwide standards and frequency regulations have been established and a
wide infrastructure of identification systems is operated today. However, the passive
nature of the technology requires a simple communication protocol which results in
two major limitations with respect to its use for localization purposes: the small signal
bandwidth and the small allocated frequency bandwidth. In the presence of multipath
reflections, these limitations reduce the achievable localization accuracy and reliability.
Thus, new methods have to be found to realize passive UHF RFID localization systems
which provide sufficient performance in typical multipath situations.
In this thesis, an enhanced transmission channel model for passive UHF RFID localization
systems has been proposed which allows an accurate estimation of the channel
behaviour to multipath. It has been used to design a novel simulation environment and
to identify three solutions to minimize multipath interference: a) by varying the channel
interface parameters, b) by applying diversity techniques, c) by installation of UHF
absorbers. Based on the enhanced channel model, a new method for tag readability
prediction with high reliability has been introduced. Furthermore, a novel way to rate
the magnitude of multipath interference has been proposed. A digital receiver beamforming
localization method has been presented which uses the Root MUSIC algorithm
for angulation of a target tag and multipath reducing techniques for an optimum localization
performance. A new multiangulation algorithm has been proposed to enable
the application of diversity techniques. A novel transmitter beamforming localization
approach has been presented which exploits the precisely defined response threshold
of passive tags in order to achieve high robustness against multipath. The basic technique
has been improved significantly with respect to angular accuracy and processing
times. Novel experimental testbeds for receiver and transmitter beamforming have been
designed, built and used for verification of the localization performance in real-world
measurements. All the improvements achieved contribute to an enhancement of the accuracy and especially
the robustness of passive UHF RFID localization systems in multipath environments
which is the main focus of this researc
Development of a chipless RFID based aerospace structural health monitoring sensor system
Chipless Radio Frequency Identification (RFID) is modern wireless technology that has been earmarked as being suitable for low-cost item tagging/tracking. These devices do not require integrated circuitry or a battery and thus, are not only are cheap, but also easy to manufacture and potentially very robust. A great deal of attention is also being put on the possibility of giving these tags the ability to sense various environmental stimuli such as temperature and humidity.
This work focusses on the potential use of chipless RFID as a sensor technology for aerospace Structural Health Monitoring. The project is focussed on the sensing of mechanical strain and temperature, with an emphasis placed on fabrication simplicity,
so that the final sensor designs could be potentially fabricated in-situ using existing printing technologies.
Within this project, a variety of novel chipless RFID strain and temperature sensors have been designed, fabricated and tested. A thorough discussion is also presented on the topic of strain sensor cross sensitivity, which places emphasis on issues like, transverse strain, dielectric constant variations and thermal swelling. Additionally, an exploration into other key technological challenges was also performed, with a focus on challenges such as: accurate and reliable stimulus detection, sensor polarization and multi-sensor support.
Several key areas of future research have also been identified and outlined, with aims related to: Enhancing strain sensor fabrication simplicity, enhancing temperature sensor sensitivity and simplicity and developing a fully functional interrogation system
Advances in UWB-based Indoor Position Estimation and its Application in Fall Detection
In an indoor propagation environment, the position of an Object of
Interest (OOI) is typically estimated by cleverly manipulating range
or proximity measurements that are obtained from a series of reference
node combinations. In a noise-free propagation scenario, these
measured parameters are fed into conventional position estimation
techniques and an accurate estimate of the OOI’s position is obtained.
In practice, the propagation scenario is never quite noise-free; hence
the OOI’s position estimate is obtained in error. Ultra-Wideband
(UWB) is a wireless communication technology that is able to resolve
individual multipath components and this ensures that it is capable
of estimating the arrival time of the first signal path. The implication
of this lies in the fact that the accuracy of the range or proximity
measurements obtained from the reference node combinations is guaranteed;
hence leading to a reliable estimate of the OOI’s position.
In the research work presented in this thesis, the body of knowledge
that relates to indoor position estimation is advanced upon. With a
primary focus of enhancing the estimation accuracy of indoor position
estimation systems, UWB is utilised as the underlying wireless
communications technology. The challenges faced by current UWBbased
position estimation systems are identified and tackled directly.
Specifically, the position estimation error that is due to multipath
propagation is addressed and a pre-localisation algorithm that serves
the purpose of resolving individual multipath UWB signals in the
immediate environment is proposed.
Additionally, a novel position estimation technique coined as Time
Reflection of Arrival (TROA) is presented in this thesis. Through a
series of Mean Squared Error (MSE) and Cram´er-Rao Lower Bound
(CRLB) analyses, TROA is shown to be very effective when compared
to TOA and the typically unvoiced TSOA technique. In the last section
of this thesis, an application of UWB in the area of Biomedical
Engineering is demonstrated. Specifically, UWB-based position estimation
is used to define a novel fall detection algorithm tailored for
Dementia patients
1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface
A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance
Beam scanning by liquid-crystal biasing in a modified SIW structure
A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium