66 research outputs found
Next-generation IoT devices: sustainable eco-friendly manufacturing, energy harvesting, and wireless connectivity
This invited paper presents potential solutions for tackling some of the main underlying challenges toward developing sustainable Internet-of-things (IoT) devices with a focus on eco-friendly manufacturing, sustainable powering, and wireless connectivity for next-generation IoT devices. The diverse applications of IoT systems, such as smart cities, wearable devices, self-driving cars, and industrial automation, are driving up the number of IoT systems at an unprecedented rate. In recent years, the rapidly-increasing number of IoT devices and the diverse application-specific system requirements have resulted in a paradigm shift in manufacturing processes, powering methods, and wireless connectivity solutions. The traditional cloud-centering IoT systems are moving toward distributed intelligence schemes that impose strict requirements on IoT devices, e.g., operating range, latency, and reliability. In this article, we provide an overview of hardware-related research trends and application use cases of emerging IoT systems and highlight the enabling technologies of next-generation IoT. We review eco-friendly manufacturing for next-generation IoT devices, present alternative biodegradable and eco-friendly options to replace existing materials, and discuss sustainable powering IoT devices by exploiting energy harvesting and wireless power transfer. Finally, we present (ultra-)low-power wireless connectivity solutions that meet the stringent energy efficiency and data rate requirements of future IoT systems that are compatible with a batteryless operation
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
Compact Reconfigurable Antennas for Wireless Systems and Wearable Applications
The fast growth of wireless communications has driven the necessity of exploiting technological solutions for the needs of faster connectivity. While bandwidth allocation and effective radiated power (ERP) are subjected to regulatory constrain, alternative solutions have been developed to overcome the challenges that arise in terms of wireless coverage and number of users. Reconfigurable antennas (RAs) technology is one of the hardware solutions developed to enhance the connectivity between wireless devices. These new class of radiating elements are able to adapt their physical characteristics in response to the environmental changes or users density and location. Reconfigurable antennas can be divided into two main categories: frequency reconfigurable antennas and pattern reconfigurable antennas. The former class of RAs are able to switch the operational frequency in order to move the communication within unoccupied channels. The latter category defines those antennas that are able to change their radiation characteristics (radiation pattern or polarization) in response to the dynamics of the surrounding environment. Unlike conventional static antennas where the energy is wasted around the surrounding space, the use of RAs allows for a smarter management of the radiated energy as the beam can be focused toward specific directions. As a result, not only data throughput between two devices can be improved but also the interference between adjacent networks can be reduced significantly. n this PhD thesis we focus on the design, prototyping and system application of compact RAs for wireless base stations and mobile devices. Specifically, the first task focuses on the design of a compact reconfigurable antenna capable of generating omnidirectional and directional beams in a single planar design. Next, we propose to apply a miniaturization technique in order to drastically reduce the size of Composite Right-Left Handed Reconfigurable Leaky Wave Antennas (CRLH RLWAs). The large beam steering capabilities along with the miniaturized dimension open new venues for the integration of this antenna technology into mobile devices such as laptop or tablets. Similarly for electrically reconfigurable antennas, characteristics such as input impedance and radiation properties of a radiating element can vary by mechanically change its physical dimension. In other words, instead of changing the metallic geometry through electrical components, the characteristics of an antenna can be changed through physical deformation of its geometry. This principle addresses the second main application of reconfigurable antennas this PhD thesis. Wearable technologies are gaining a lot of attentions due to their strong potential for sensing, communication and tactile interaction applications. Thanks to the progress in knitting facilities and techniques, smart fabrics are generally implemented through sewn-in sensors especially in the fields of medical and athletic applications. Such wearable sensors provide a means to monitor the wearers health through physiological measurements in a natural setting or can be used to detect or alert care providers to potential hazards around the wearer. The feasibility of building electrical devices using conductive fabrics has been analyzed through electrical characterization of textile transmission lines and antennas where conductive fabrics have been applied onto woven fabrics have been demonstrated in recent literature. Previous works show conductive copper foils or fabrics bonded to a flexible substrate. However, these techniques show limitations in terms of electrical losses caused by adhesives or glue chemicals. It is desirable to address these drawbacks by knitting conductive and non-conductive yarns in a single process resulting in smart textiles that are unobtrusively integrated into the host garment so as to eliminate the need for chemical adhesives that degrade electrical performance. The characteristics variations of a fabric-based antenna under physical deformations can be exploited to provide a fully wireless sensing of certain body movements. The second task of this PhD thesis, focuses on the design and testing of these purely textile wireless sensors for biomedical applications. The Radio-Frequency Identification (RFID) technology will be applied fordesigning fabric-based strain sensors through the use of novel inductively-coupled RFID microchips (MAGICSTRAP). As opposed to conventional surface-mount microchips, the MAGICSTRAP does not require any physical soldering connection as the RF energy is inductively coupled from the microchip pads to the antenna arms. A separate interrogator unit can communicate with this knit passive RFID architecture by sending a probing signal; the backscattered component received from the knit tag will indicate the level of stretch, and this information will be translated in the physical phenomenon being monitored. The change in the electrical characteristics of the textile antenna, along with the decoupling of the MAGICTRAP chip allow for more reliable detection of contraction/elongation movements. This study will include comprehensive design and characterization of the textile tag sensor along with performance analysis using a mechanical human mannequin.Ph.D., Electrical Engineering -- Drexel University, 201
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Design and Implementation of System Components for Radio Frequency Based Asset Tracking Devices to Enhance Location Based Services. Study of angle of arrival techniques, effects of mutual coupling, design of an angle of arrival algorithm, design of a novel miniature reconfigurable antenna optimised for wireless communication systems
The angle of arrival estimation of multiple sources plays a vital role in the field of array signal
processing as MIMO systems can be employed at both the transmitter and the receiver end
and the system capacity, reliability and throughput can be significantly increased by using array
signal processing. Almost all applications require accurate direction of arrival (DOA) estimation
to localize the sources of the signals. Another important parameter of localization systems is
the array geometry and sensor design which can be application specific and is used to
estimate the DOA.
In this work, various array geometries and arrival estimation algorithms are studied and then a
new scheme for multiple source estimation is proposed and evaluated based on the
performance of subspace and non-subspace decomposition methods. The proposed scheme
has shown to outperform the conventional Multiple Signal Classification (MUSIC) estimation
and Bartlett estimation techniques. The new scheme has a better performance advantage at
low and high signal to noise ratio values (SNRs).
The research work also studies different array geometries for both single and multiple incident
sources and proposes a geometry which is cost effective and efficient for 3, 4, and 5 antenna
array elements. This research also considers the shape of the ground plane and its effects on
the angle of arrival estimation and in addition it shows how the mutual couplings between the
elements effect the overall estimation and how this error can be minimised by using a decoupling
matrix.
At the end, a novel miniaturised multi element reconfigurable antenna to represent the receiver
base station is designed and tested. The antenna radiation patterns in the azimuth angle are
almost omni-directional with linear polarisation. The antenna geometry is uniplanar printed logspiral
with striplines feeding network and biased components to improve the impedance
bandwidth. The antenna provides the benefit of small size, and re-configurability and is very
well suited for the asset tracking applications
Desenho de antenas para sensores passivos em materiais não convencionais
Doutoramento em Engenharia EletrotécnicaMotivado pela larga expansão dos sistemas RFID e com o desenvolvimento
do conceito de Internet das Coisas, a evolução no desenho e métodos de
produção de antenas em suportes de materiais alternativos tem tido uma
exploração intensiva nos últimos anos. Isto permitiu, não só o desenvolvimento
de produtos no campo da interação homem-máquina, mas também
tornar estes produtos mais pequenos e leves. A procura de novas técnicas
e métodos para produzir eletrónica impressa e antenas em materiais alternativos
e, portanto, uma porta aberta para o aparecimento de novas
tecnologias. Isto aplica-se especialmente no mercado dos sensores, onde
o peso, o tamanho, o consumo energético, e a adaptabilidade a diversos
ambientes, têm grande relevância. Esta tese foca-se no desenvolvimento de
antenas com suporte em materiais não convenvionais, como os já testados
papel e têxteis, mas também na exploração de outros, desconhecidos do
ponto de vista eléctrico, como a cortiça e polímeros biodegradáveis usados
em impressão 3D. Estes materiais são portanto usados como substrato, ou
material de suporte, para diversas antenas e, como tal, as propriedades electromagnéticas destes materiais têm de ser determinadas. Assim, e apresentado
neste documento uma revisão de métodos de caracterização de materiais,
bem como a proposta de um método baseado em linhas de trasmissão
impressas, e a respectiva caracterização electromagnética de diversos materiais.
Além disso, são propostos desenhos de antenas para diversos cenários
e aplicações utilizando os materiais anteriormente mencionados. Com esta
tese concluiu-se que a utilização de materiais alternativos e hoje uma realidade
e os resultados obtidos são muito encorajodares para o desenvolvimento
de um conjunto de sensores para aplicações RFID com uma grande
capacidade de integração.The advancement of the design and fabrication of antennas using textiles
or paper as substrates has rapidly grown motivated by the boom of RFID
systems and the developing concept of the Internet of Things. These advancements
have allowed, not only the development of products for manmachine
interaction, but also to make these products smaller and lighter.
The search for new techniques and methods to produce printed electronics
and antennas in alternative materials is therefore an open door for new
technologies to emerge. Especially in the sensors market, where weight,
size, power consumption and the adaptability to the target application, are
of great importance. This thesis focuses on the development of antenna
design approaches with alternative materials, such as the already tested
paper and textiles, but also others relatively unknown, such as cork and
biodegradable polymers used in 3D printing. These materials are applied to
act as substrates, or support structures for the antennas. Therefore, their
electromagnetic properties need to be determined. Due to that, a review
of electromagnetic characterization methods, as well as the proposal of a
custom method based on printed transmission lines, is presented in this document.
Besides, several antenna designs, for di erent application scenarios,
using the previously mentioned materials, are proposed. With this thesis it
was proved that it is possible to develop passive sensors in di erent alternative
materials for RFID applications and others, which shows great promise
in the use of these materials to achieve higher integration in sensing and
identi cation applications
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