Near Field Coupling in Wireless Systems for Identification, Sensing and Communication

Antennas for radio communication systems (e.g. radio links, cellular networks, WLAN, remote sensing) are designed giving a lot of attention to antenna gain, polarization, radiation pattern characteristics (e.g. half power beam width, front to back ratio, etc.). All above parameters are defined in the antenna far-field (FF) region, so they are suitable to characterize a communication system in which the transmitter and the receiver antennas are far enough. On the other hand, some applications exist that exploit antenna features in its near-field (NF) region. In this context, NF coupling between antennas has been studied since a long time and most researches have been focused on coupling effects in antenna arrays, field sensing for near-field antenna scanning systems, magnetic coupling between loops operating at LF-HF frequency bands. During his PhD course, the author designed and tested several antennas for Near-Field applications such as UHF RFID Desktop Reader. Moreover, he developed numerical codes to analyze a novel method to estimate the deep human tissues status with a near-field sensor, determining its prediction capability and determining critical parameters that affect its accuracy. Finally, he studied the mutual coupling effect between antennas integrated in commercial PV panels for wireless communication systems

Wireless colorimetric readout to enable resource-limited point-of-care

Patientennahe Diagnostik in Entwicklungsländer birgt spezielle Herausforderungen, die ihren Erfolg bisher begrenzen. Diese Arbeit widmet sich daher der Entwicklung eines in seiner Herstellung skalierbaren und vielseitig einsetzbaren funkbasierten Auslesegerätes für Laborteststreifen. Durch die Kombination einer wachsenden Auswahl an papierbasierten Teststreifendiagnostiken mit gedruckter Elektronik und unter Berücksichtigung des diagnostischen Alltags im südlichen Afrika wurde ein Gerät entwickelt, das Teststreifen zuverlässig ausliest und die Daten per Funk an eine Datenbank übertragen kann. Die Technik basiert auf RFID-Tags (radio frequency identification devices), welche auf verschiedene flexible Substrate gedruckt wurden, um die technische Umsetzbarkeit und Funktionalität zu evaluieren. Um den Preis für die geplante Anwendung niedrig zu halten, wurden unter anderem Papier und Karton als Substrate genutzt. Das Ergebnis dieser Studie sind passive RFID-Tags auf unterschiedlichen, meist günstigen Substraten, die über eine Distanz von über 75 mm betrieben und ausgelesen werden können. Basierend auf der über RFID bereitgestellten Energie und Datenübertragung wurde eine Ausleseeinheit für Standardpapierstreifentests entwickelt und integriert. Durch das Auslesen verschiedener Teststreifen wurde das Gerät evaluiert und in seiner Aussagekraft mit einer scanner-basierten Aufnahme und anschließender Bildanalyse (ImageJ), einem kommerziellen Auslesegerät sowie einer manuellen Auslesung mit Hilfe von Farbtabellen verglichen. Das Gerät kann die Streifen zuverlässig auslesen und die Daten über die RFID-Schnittstelle übertragen. Die funkbasierte Ausleseeinheit ist mit verschiedenen kommerziellen Teststreifen sowohl im biodiagnostischen (lateral flow tests) wie auch im chemischen Bereich (pH-Wert) kompatibel. Die modulare Lösung erlaubt ein breites Einsatzgebiet und führt dadurch zu reduzierten Trainingszeiten der Anwender und einer zuverlässigen Handhabung. Die vorgestellte Lösung ist äußerst kostengünstig und bedarf keiner Wartung, wodurch sie sich sehr gut für den Einsatz in abgelegenen Feldkrankenhäusern eignet. Es wurde ein skalierbarer Prototyp entwickelt, der auf konventionellen Herstellungsverfahren der Verpackungsindustrie aufbaut. Aktuell handelt es sich noch um einen bogenbasierten Prozess, der sich aber prinzipiell auch auf Rolle-zu-Rolle Maschinen übertragen lässt. Bei der Entwicklung des Geräts spielte die Möglichkeit der lokalen Herstellung in den Einsatzländern eine große Rolle. Diese hätte neben der Generierung von Arbeitsplätzen auch den Vorteil einer einfacheren Verteilung der Geräte in ländliche Regionen, in denen sie den größten Nutzen für die Diagnostik erzielen würden

Dense and long-term monitoring of Earth surface processes with passive RFID -- a review

Billions of Radio-Frequency Identification (RFID) passive tags are produced yearly to identify goods remotely. New research and business applications are continuously arising, including recently localization and sensing to monitor earth surface processes. Indeed, passive tags can cost 10 to 100 times less than wireless sensors networks and require little maintenance, facilitating years-long monitoring with ten's to thousands of tags. This study reviews the existing and potential applications of RFID in geosciences. The most mature application today is the study of coarse sediment transport in rivers or coastal environments, using tags placed into pebbles. More recently, tag localization was used to monitor landslide displacement, with a centimetric accuracy. Sensing tags were used to detect a displacement threshold on unstable rocks, to monitor the soil moisture or temperature, and to monitor the snowpack temperature and snow water equivalent. RFID sensors, available today, could monitor other parameters, such as the vibration of structures, the tilt of unstable boulders, the strain of a material, or the salinity of water. Key challenges for using RFID monitoring more broadly in geosciences include the use of ground and aerial vehicles to collect data or localize tags, the increase in reading range and duration, the ability to use tags placed under ground, snow, water or vegetation, and the optimization of economical and environmental cost. As a pattern, passive RFID could fill a gap between wireless sensor networks and manual measurements, to collect data efficiently over large areas, during several years, at high spatial density and moderate cost.Comment: Invited paper for Earth Science Reviews. 50 pages without references. 31 figures. 8 table

A historical review of the development of electronic textiles

Textiles have been at the heart of human technological progress for thousands of years, with textile developments closely tied to key inventions that have shaped societies. The relatively recent invention of electronic textiles is set to push boundaries again and has already opened up the potential for garments relevant to defense, sports, medicine, and health monitoring. The aim of this review is to provide an overview of the key innovative pathways in the development of electronic textiles to date using sources available in the public domain regarding electronic textiles (E-textiles); this includes academic literature, commercialized products, and published patents. The literature shows that electronics can be integrated into textiles, where integration is achieved by either attaching the electronics onto the surface of a textile, electronics are added at the textile manufacturing stage, or electronics are incorporated at the yarn stage. Methods of integration can have an influence on the textiles properties such as the drapability of the textile

Power Management Techniques for Supercapacitor Based IoT Applications

University of Minnesota Ph.D. dissertation. January 2018. Major: Electrical Engineering. Advisor: Ramesh Harjani. 1 computer file (PDF); xi, 89 pages.The emerging internet of things (IoT) technology will connect many untethered devices, e.g. sensors, RFIDs and wearable devices, to improve health lifestyle, automotive, smart buildings, etc. This thesis proposes one typical application of IoT: RFID for blood temperature monitoring. Once the blood is donated and sealed in a blood bag, it is required to be stored in a certain temperature range (+2~+6°C for red cell component) before distribution. The proposed RFID tag is intended to be attached to the blood bag and continuously monitor the environmental temperature during transportation and storage. When a reader approaches, the temperature data is read out and the tag is fully recharged wirelessly within 2 minutes. Once the blood is distributed, the tag can be reset and reused again. Such a biomedical application has a strong aversion to toxic chemicals, so a batteryless design is required for the RFID tag. A passive RFID tag, however, cannot meet the longevity requirement for the monitoring system (at least 1 week). The solution of this thesis is using a supercapacitor (supercap) instead of a battery as the power supply, which not only lacks toxic heavy metals, but also has quicker charge time (~1000x over batteries), larger operating temperature range (-40~+65°C), and nearly infinite shelf life. Although nearly perfect for this RFID application, a supercap has its own disadvantages: lower energy density (~30x smaller than batteries) and unstable output voltage. To solve the quick charging and long lasting requirements of the RFID system, and to overcome the intrinsic disadvantages of supercaps, an overall power management solution is proposed in this thesis. A reconfigurable switched-capacitor DC-DC converter is proposed to convert the unstable supercap's voltage (3.5V~0.5V) to a stable 1V output voltage efficiently to power the subsequent circuits. With the help of the 6 conversion ratios (3 step-ups, 3 step-downs), voltage protection techniques, and low power designs, the converter can extract 98% of the stored energy from the supercap, and increase initial energy by 96%. Another switched-inductor buck-boost converter is designed to harvest the ambient RF energy to charge the supercap quickly. Because of the variation of the reader distance and incident wave angle, the input power level also has large fluctuation (5uW~5mW). The harvester handles this large power range by a power estimator enhanced MPPT controller with an adaptive integration capacitor array. Also, the contradiction between low power and high tracking speed is improved by adaptive MPPT frequency

Sensores passivos alimentados por transmissão de energia sem fios para aplicações de Internet das coisas

Nowadays, the Wireless Sensor Networks (WSNs) depend on the battery duration of the sensors and there is a renewed interest in creating a passive sensor network scheme in the area of Internet of Things (IoT) and space oriented WSN systems. The challenges for the future of radio communications have a twofold evolution, one being the low power consumption and, another, the adaptability and intelligent use of the available resources. Specially designed radios should be used to reduce power consumption, and adapt to the environment in a smart and e cient way. This thesis will focus on the development of passive sensors based on low power communication (backscatter) with Wireless Power Transfer (WPT) capabilities used in IoT applications. In that sense, several high order modulations for the communication will be explored and proposed in order to increase the data rate. Moreover, the sensors need to be small and cost e ective in order to be embedded in other technologies or devices. Consequently, the RF front-end of the sensors will be designed and implemented in Monolithic Microwave Integrated Circuit (MMIC).Atualmente, as redes de sensores sem fios dependem da duração da bateria e,deste modo, existe um interesse renovado em criar um esquema de rede de sensores passivos na área de internet das coisas e sistemas de redes de sensores sem fios relacionados com o espaço. Os desafios do futuro das comunicações de rádio têm uma dupla evolução, sendo um o baixo consumo de energia e, outro, a adaptação e o uso inteligente dos recursos disponíveis. Rádios diferentes dos convencionais devem ser usados para reduzir o consumo de energia e devem adaptar-se ao ambiente de forma inteligente e eficiente, de modo a que este use a menor quantidade de energia possível para estabelecer a comunicação. Esta tese incide sobre o desenvolvimento de sensores passivos baseados em comunicação de baixo consumo energético (backscatter) com recurso a transmissão de energia sem fios de modo a que possam ser usados em diferentes aplicações inseridas na internet das coisas. Nesse sentido, várias modulações de alta ordem para a comunicação backscatter serão exploradas e propostas com o objectivo de aumentar a taxa de transmissão de dados. Além disso, os sensores precisam de ser reduzidos em tamanho e económicos de modo a serem incorporados em outras tecnologias ou dispositivos. Consequentemente, o front-end de rádio frequência dos sensores será projetado e implementado em circuito integrado de microondas monolítico.Programa Doutoral em Engenharia Eletrotécnic

Energy Harvesting on New Jersey Roadways

NJDOT TO 361The project is to identify energy harvesting applications on roadways and bridges and conduct feasibility analysis and performance evaluation for large-scale and micro-scale energy generation. Solar energy harvesting can be achieved using different assets of roadway. The technical and economic feasibility of solar array in the right-of-way (ROW) was presented. Photovoltaic Noise Barriers (PVNBs) integrate solar panels with noise barriers to harvest solar energy while abating noise from the highway. The energy estimation models were first developed at project level and then used for state-level analysis, respectively, for top-mounted tilted, top-mounted bifacial, and shingles built-on designs of PVNB. On the other hand, piezoelectric energy harvesting can be achieved by compression or vibration modes. The new designs of vibration-based energy harvesters are proposed under multi-frequency bridge vibrations. A multiple degree-of-freedom (DOF) cantilever design concept was developed and tested in the laboratory. The optimized design was demonstrated and validated in full-scale tests for vibration-based energy harvesting. The research outcome provides recommendations for future implementation of energy harvesting in the roadway and bridge network of New Jersey for development of sustainable and smart transportation infrastructure

Electromagnetic Absorbers Based on Frequency Selective Surfaces

Frequency Selective Surfaces (FSSs) are bidimensional arrays of particles arranged in a periodic manner. These surfaces can be lossless or lossy, depending on the manufacturing process. They can be fabricated by using metallic or controlled-resistance surface deposition. Lossy surfaces can be also obtained through the integration of lumped components on a metallic surface. The use of FSSs has fostered new research lines in the design of electromagnetic absorbing surfaces, bringing improvements both in terms of bandwidth/thickness ratio maximization and in terms of customizability of the absorbing bandwidth (narrowband, multi-band, wideband, ultra-wideband) for specific applications. Artificial impedance surfaces (or HighImpedance Surfaces, - HIS) are thin resonant cavities synthesized by printing a periodic frequency selective surface on the top of a grounded dielectric slab. By proper tailoring of the geometrical and electrical properties of the FSS as well as the substrate, several electrically-thin absorbing designs can be obtained. Ultranarrowband absorbers with extremely stable angular behavior, often addressed as metamaterial absorbers, can be realized by exploiting only dielectric losses of commercial substrates. Narrowband, wideband and ultra-wideband configurations are instead implemented by also resorting to ohmic losses in a non-conductive FSS. A thorough review of the available absorbers will be presented together with multi-band and tunable design techniques. Manufacturing processes and practical examples will be also addressed, and the most interesting fields of application of the presented structures will be described

Applications of Additive Manufacturing Technologies to Ambient Energy Harvesters for Microwave and Millimeter-Wave Autonomous Wireless Sensing Networks and 3D Packaging Integration

The objectives of my researches are developing new RF and mm-wave energy harvester topologies and realizing them with new additive manufacturing fabrication processes. The proposed energy harvester topologies are utilized to achieve energy-autonomous wireless sensing networks for 5G communication and IoT solutions. The developed additive manufacturing fabrication process is adopted to realize not only energy harvesters but also mm-wave IC packaging process. Ambient energy harvesting techniques collect ambient energy such as solar, RF, heat, and vibration and convert them into DC power sources to support the energy requirement of electronics. Since the energy is provided autonomously and constantly, maintenance or replacement for the batteries inside wireless electronics is not necessary resulting in enormous cost reduction. The researches of energy harvester focus on three categories, new topologies to enhance the performances, increased harvested power levels, and applied energy harvester to find new killer applications. This work proposes new designs and improvements in all three categories. Various proof-of-concept backscattered sensing systems with integrated RF energy harvesters for 5G and IoT applications are demonstrated. In this research, high-efficiency and broadband rectifiers are proposed to support high-performance rectifications as well as increase harvested energy. New topologies to utilize both DC and harmonics are demonstrated to increase the reading range of on-body wireless sensing networks. Furthermore, energy-autonomous microfluidic sensing systems are demonstrated to unleash the potential of microfluidic applications. 5G energy harvester is proposed and integrated inside the multi-layered additive manufacturing IC packages to achieve fully-functional SiP modules. While determining the fabrication methods, low-cost, fast-prototyping, and scalable methods with great material and structural flexibilities are preferable, and thus, additive manufacturing technologies including inkjet printing, 3D printing, and glass semi-additive patterning process are adopted. This research utilizes inkjet-printed masks, substrates, and metal traces to simplify the conventional fabrication process. The new low-loss inkjet-printable ink is developed to push the additive manufacturing technologies to mm-wave ranges. The flexible 3D-printed materials are characterized and used for wearable sensor designs, microfluidic channels, and flexible packaging topologies. The 3D features are included inside the IC packages to achieve high-performance multi-layer packaging structures with shorter lengths, lower loss, and smaller parasitics. The high-precision glass semi-additive patterning process is used to realized AiP and SiP designs with great performances. Furthermore, through combining inkjet and 3D printing, this work proposes a fast, cost-effective, scalable, and environmentally-friendly fabrication process for various high-performance and compact antenna designs, microwave/mm-wave components, microfluidic channels, RF energy harvesters, and SiP designs. In summary, this work utilizes additive manufacturing processes to realize various innovative topologies of energy harvesters to harvest more power and achieve higher rectification efficiency with smaller sizes. Additive manufacturing processes and energy harvesting techniques are also used to demonstrate new applications including the first on-body long-range sensing network, the first energy-autonomous long-range microfluidic sensing system, and the first fully-functional energy-autonomous 5G SiP module design. The proposed topologies are suitable for smart cities, smart skin, and IoT applications.Ph.D