24 research outputs found
Wireless power transmission: R&D activities within Europe
Wireless power transmission (WPT) is an emerging technology that is gaining increased visibility in recent years. Efficient WPT circuits, systems and strategies can address a large group of applications spanning from batteryless systems, battery-free sensors, passive RF identification, near-field communications, and many others. WPT is a fundamental enabling technology of the Internet of Things concept, as well as machine-to-machine communications, since it minimizes the use of batteries and eliminates wired power connections. WPT technology brings together RF and dc circuit and system designers with different backgrounds on circuit design, novel materials and applications, and regulatory issues, forming a cross disciplinary team in order to achieve an efficient transmission of power over the air interface. This paper aims to present WPT technology in an integrated way, addressing state-of-the-art and challenges, and to discuss future R&D perspectives summarizing recent activities in Europe.The work of N. Borges Carvalho and A. J. S. Soares Boaventura was supported by the Portuguese Foundation for Science and Technology (FCT) under Project CREATION EXCL/EEI-TEL/0067/2012 and Doctoral Scholarship SFRH/BD/80615/2011. The work of H. Rogier was supported by BELSPO through the IAP Phase VII BESTCOM project and the Fund for Scientific Research-Flanders (FWO-V). The work of A. Georgiadis and A. Collado was supported by the European Union (EU) under Marie Curie FP7-PEOPLE-2009-IAPP 251557 and the Spanish Ministry of Economy and Competitiveness Project TEC 2012-39143. The work of J. A. GarcĂa and M. N. RuĂz was supported by the Spanish Ministries MICINN and MINECO under FEDER co-funded Project TEC2011-29126-C03-01 and Project CSD2008-00068. The work of J. Kracek and M. Mazanek was supported in part by the Czech Ministry of Education Youth and Sports under Project OC09075âNovel Emerging Wireless Systems
3D-printing technology applied to the development of bio-inspired functional acoustic systems
Examples of bio-inspired technology can be found almost everywhere in society: robots with specific capabilities, materials with unique physical and chemical properties, aerodynamic systems, and architectonic structures are a few examples of taking profit of evolution-driven processes to solve common engineering problems. One field of research taking advantage of bio-inspiration is that of acoustical engineering, aiming to find solutions to problems arising from the miniaturisation of microphones and loudspeakers. Studying the auditory organs of insects to seek inspiration for new design structures is one of the best ways to solve such an important problem. Another discipline of science that has experienced a research boom is that of materials science, as development of new materials has attracted the attention of researchers. In addition, three-dimensional (3D) printers have contributed to further development in materials science making the production process more efficient. The aim of this research is to bring these fields of science together to develop novel bioinspired, polymer-based sensors presenting functional specific acoustic properties after 3D-printing. While the study of complex biological hearing systems provides inspiration to develop sensors featuring specific properties, the use of polymer-based materials allows the customization of the manufacturing process, as the produced parts adapt to the desired needs. In this thesis one such insect auditory system that has been thoroughly studied is that of the desert locust Schistocerca gregaria as it presents a simple structure that allows for acoustic frequency selectivity and displays nonlinear acoustic phenomena. Prior to the development of a bio-inspired system, a mathematical description of the mechanical response of such a structure is presented. Furthermore, the physical behaviours measured on the locust tympanal membrane have been studied using finite element analysis. The 3D-printed functional sensors have been used to determine the degree of accuracy between experimental and theoretical results.Examples of bio-inspired technology can be found almost everywhere in society: robots with specific capabilities, materials with unique physical and chemical properties, aerodynamic systems, and architectonic structures are a few examples of taking profit of evolution-driven processes to solve common engineering problems. One field of research taking advantage of bio-inspiration is that of acoustical engineering, aiming to find solutions to problems arising from the miniaturisation of microphones and loudspeakers. Studying the auditory organs of insects to seek inspiration for new design structures is one of the best ways to solve such an important problem. Another discipline of science that has experienced a research boom is that of materials science, as development of new materials has attracted the attention of researchers. In addition, three-dimensional (3D) printers have contributed to further development in materials science making the production process more efficient. The aim of this research is to bring these fields of science together to develop novel bioinspired, polymer-based sensors presenting functional specific acoustic properties after 3D-printing. While the study of complex biological hearing systems provides inspiration to develop sensors featuring specific properties, the use of polymer-based materials allows the customization of the manufacturing process, as the produced parts adapt to the desired needs. In this thesis one such insect auditory system that has been thoroughly studied is that of the desert locust Schistocerca gregaria as it presents a simple structure that allows for acoustic frequency selectivity and displays nonlinear acoustic phenomena. Prior to the development of a bio-inspired system, a mathematical description of the mechanical response of such a structure is presented. Furthermore, the physical behaviours measured on the locust tympanal membrane have been studied using finite element analysis. The 3D-printed functional sensors have been used to determine the degree of accuracy between experimental and theoretical results
Characterisation and Modelling of Graphene FETs for Terahertz Mixers and Detectors
Graphene is a two-dimensional sheet of carbon atoms with numerous envisaged applications owing to its exciting properties. In particular, ultrahigh-speed graphene field effect transistors (GFETs) are possible due to the unprecedented carrier velocities in ideal graphene. Thus, GFETs may potentially advance the current upper operation frequency limit of RF electronics. In this thesis, the practical viability of high-frequency GFETs based on large-area graphene from chemical vapour deposition (CVD) is investigated. Device-level GFET model parameters are extracted to identify performance bottlenecks. Passive mixer and power detector terahertz circuits operating above the present active GFET transit time limit are demonstrated. The first device-level microwave noise characterisation of a CVD GFET is presented. This allows for the de-embedding of the noise parameters and construction of noise models for the intrinsic device. The correlation of the gate and drain noise in the PRC model is comparable to that of Si MOSFETs. This indicates higher long-term GFET noise relative to HEMTs. An analytical power detector model derived using Volterra analysis on the FET large-signal model is verified at frequencies up to 67 GHz. The drain current derivatives, intrinsic capacitors and parasitic resistors of the closed-form expressions for the noise equivalent power (NEP) are extracted from DC and S-parameter measurements. The model shows that a short gate length and a bandgap in the channel are required for optimal FET sensitivity. A power detector integrated with a split bow-tie antenna on a Si substrate demonstrates an optical NEP of 500 pW/Hz^1/2 at 600 GHz. This represents a state-of-the-art result for quasi-optically coupled, rectifying direct detectors based on GFETs operating at room temperature. The subharmonic GFET mixer utilising the electron-hole symmetry in graphene is scaled to operate with a centre frequency of 200 GHz, the highest frequency reported so far for graphene integrated circuits. The down-converter circuit is implemented in a coplanar waveguide (CPW) on Si and exhibits a conversion loss (CL) of 29 ± 2 dB in the 185-210 GHz band. In conclusion, the CVD GFETs in this thesis are unlikely to reach the performance required for high-end RF applications. Instead, they currently appear more likely to compete in niche applications such as flexible electronics
Simultaneous Data Communication and Power Transfer Technique with Multiport Interferometric Receiver
RĂSUMĂ Le problĂšme de la communication est gĂ©nĂ©ralement prĂ©sentĂ© comme un problĂšme de trans-mission dâun message gĂ©nĂ©rĂ© dâun point a un autre. Certains systĂšmes de communication modernes souËrent de contraintes Ă©nergĂ©tiques sĂ©vĂšres. Avec le dĂ©veloppement rapide des systĂšmes Ă©lectroniques sans fil de faible puissance, dâinnombrables activitĂ©s de recherche ont Ă©tĂ© menĂ©es en vue dâexplorer la faisabilitĂ© dâune alimentation Ă distance ou sans fil de ces systĂšmes. Par consĂ©quent, la transmission dâĂ©nergie sans fil (WPT) est en cours de dĂ©veloppe-ment en tant que technique prometteuse pour alimenter des appareils Ă©lectroniques Ă distance et pour prolonger la durĂ©e de vie des rĂ©seaux sans fil Ă contrainte dâĂ©nergie. Parmi les Ă©ner-gies renouvelables rĂ©coltĂ©es dans lâenvironnement, les signaux RF rayonnĂ©s par les Ă©metteurs peuvent ĂȘtre une ressource viable pour le transfert dâĂ©nergie sans fil, tandis que les signaux RF ont Ă©tĂ© largement utilisĂ©s comme vĂ©hicule pour la transmission dâinformations sans fil (WIT). Par consĂ©quent, le transfert simultanĂ© dâinformations et la plateforme de transfert de puissance sans fil (SWIPT) deviennent bĂ©nĂ©fiques, car il rĂ©alise les deux utilisations utiles des signaux RF en mĂȘme temps et il oËre ainsi potentiellement une grande commoditĂ© aux utilisateurs mobiles. Lâantenne redresseuse, qui combine des fonctionnalitĂ©s du redresseur et de lâantenne, est un Ă©lĂ©ment clĂ© pour la transmission et la rĂ©colte dâĂ©nergie sans fil. LâeĂżcacitĂ© de conversion du circuit de redressement dĂ©termine les performances globales de lâantenne redresseuse. Par consĂ©quent, pour concevoir une antenne redresseuse Ă haute eĂżcacitĂ© qui peut garantir la qualitĂ© dâun systĂšme WPT, il convient de se concentrer davantage sur lâinvestigation, lâanalyse et le dĂ©veloppement de redresseurs axĂ©s sur les performances en rĂ©fĂ©rence Ă une eĂżcacitĂ© de conversion radio frĂ©quence Ă courant continu. Dâun autre cĂŽtĂ©, les circuits redresseurs peuvent simplement rĂ©cupĂ©rer lâĂ©nergie et ils ne peuvent pas dĂ©coder le signal transmis pour fins de communication. Cependant, la transmission de donnĂ©es est une exigence essentielle des systĂšmes de communication sans fil. Par consĂ©quent, si la capacitĂ© de dĂ©tection et de traitement du signal peut ĂȘtre ajoutĂ©e Ă une architecture antenne redresseuse, un rĂ©cepteur avec transmission de puissance sans fil et communication de donnĂ©es simultanĂ©es peut ĂȘtre rĂ©alisĂ©. Ce mĂ©moire vise Ă Ă©tudier et Ă dĂ©montrer un rĂ©cepteur de multifonction et de multiport qui a la capacitĂ© de collecter simultanĂ©ment lâĂ©nergie sans fil et les donnĂ©es de communication fonctionnant Ă la frĂ©quence des microondes.----------ABSTRACT
The problem of communication is usually cast as one of transmitting a message generated at one point to another point. Some modern communication systems are known to suffer from severe energy constraints and power consumptions. With the rapid development of low power wireless electronic systems, countless research activities have been carried out to explore the feasibility of a remote or wireless powering of those systems. Therefore, wireless power transmission (WPT) is being developed as a promising technique, for powering electronic devices over distance and for prolonging the lifetime of energy constrained wireless networks. Among the renewable energy harvested from the environment, the RF signals radiated by transmitters can be a viable resource for wireless power transfer, while RF signals have been widely used as a vehicle for wireless information transmission (WIT). Therefore, simultaneous wireless information and power transfer (SWIPT) platform becomes appealing since it realizes both useful utilizations of RF signals at the same time, and thus potentially offers great convenience to mobile users. The rectenna, combining the functionalities of rectifier and antenna, is a key element for wireless power transmission and harvesting. The conversion efficiency of the rectifying circuit determines the overall performance of the rectenna. Therefore, to design a high-efficiency rectenna that can guarantee the quality of a WPT system, more focus should be concentrated on the investigation, analysis and development performance-driven rectifiers with reference to high RF-to-DC conversion efficiency. On the other hand, rectenna circuits can just scavenge energy and they cannot decode the transmitted signal for communication purpose. How-ever, the data transmission is an essential requirement of wireless communication systems. Therefore, if the ability of signal detection and processing can be added to a rectenna architecture then a multi-function receiver with simultaneous wireless power transmission and data communication can be realized.This dissertation aims to investigate and demonstrate a multi-function and multi-port receiver with the capability of simultaneous wireless energy harvesting and data communication operating at microwave frequency. To achieve these goals, it becomes interesting when a single receiver chain is able to convert the RF power to DC power, while at the same time converting the RF modulated signal to BaseBand (BB) signal. Therefore, the fundamental methodology to receive and convert the RF signal to BB while simultaneously harvesting power is derived and analyzed in this work
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Silicon - polymer hybrid integrated microwave photonic devices for optical interconnects and electromagnetic wave detection
textThe accelerating increase in information traffic demands the expansion of optical access network systems that require high-performance optical and photonic components. In short-range communication links, optical interconnects have been widely accepted as a viable approach to solve the problems that copper based electrical interconnects have encountered in keeping up with the surge in the data rate demand over the last decades. Low cost, ease of fabrication, and integration capabilities of low optical-loss polymers make them attractive for integrated photonic applications to support futuristic data communication networks. In addition to passive wave-guiding components, electro-optic (EO) polymers consisting of a polymeric matrix doped with organic nonlinear chromophores have enabled wide-RF-bandwidth and low-power active photonic devices. Beside board level passive and active optical components, on-chip micro- or nano-photonic devices have been made possible by the hybrid integration of EO polymers onto the silicon platform. In recent years, silicon photonics have attracted a significant amount of attentions, because it offers compact device size and the potential of complementary metalâoxideâsemiconductor (CMOS) compatible photonic integrated circuits. The combination of silicon photonics and EO polymers can enable miniaturized and high-performance hybrid integrated photonic devices, such as electro-optic modulators, optical interconnects, and microwave photonic sensors. Silicon photonic crystal waveguides (PCWs) exhibit slow-light effects which are beneficial for device miniaturization. Especially, EO polymer filled silicon slotted PCWs further reduce the device size and enhance the device performance by combining the best of these two systems. The potential applications of these silicon-polymer hybrid integrated devices include not only optical interconnects, but also optical sensing and microwave photonics. In this dissertation, the design, fabrication, and characterization of several types of silicon-polymer hybrid photonic devices will be presented, including EO polymer filled silicon PCW modulators for on-chip optical interconnects, antenna-coupled optical modulators for electromagnetic wave detections, and low-loss strip-to-slot PCW mode converters. In addition, some polymer-based devices and silicon-based photonic devices will also be presented, such as traveling wave electro-optic polymer modulators based on domain-inversion directional couplers, and silicon thermo-optic switches based on coupled photonic crystal microcavities. Furthermore, some microwave (or RF) components such as integrated broadband bowtie antennas for microwave photonic applications will be covered. Some on-going work or suggested future work will also be introduced, including in-device pyroelectric poling for EO polymer filled silicon slot PCWs, millimeter- or Terahertz-wave sensors based on EO polymer filled plasmonic slot waveguide, low-loss silicon-polymer hybrid slot photonic crystal waveguides fabricated by CMOS foundry, logic devices based on EO polymer microring resonators, and so on.Electrical and Computer Engineerin
Air Force Institute of Technology Research Report 2017
This Research Report presents the FY18 research statistics and contributions of the Graduate School of Engineering and Management (EN) at AFIT. AFIT research interests and faculty expertise cover a broad spectrum of technical areas related to USAF needs, as reflected by the range of topics addressed in the faculty and student publications listed in this report. In most cases, the research work reported herein is directly sponsored by one or more USAF or DOD agencies. AFIT welcomes the opportunity to conduct research on additional topics of interest to the USAF, DOD, and other federal organizations when adequate manpower and financial resources are available and/or provided by a sponsor. In addition, AFIT provides research collaboration and technology transfer benefits to the public through Cooperative Research and Development Agreements (CRADAs)
Realistic chipless RFID: protocol, encoding and system latency
Chiplose Identifikation ĂŒber Funkfrequenzen, RFID (engl., Radio Frequency IDentification) ist eine vielversprechende Technology, der man die FĂ€higkeit zuschreibt, in naher Zukunft den
optischen Barcode zu ersetzen. Letztgenannter hat EinschrĂ€nkungen durch i) RFID Tags sind bei nicht vorhandener Sichtverbindung (engl. Non-Line-Of-Sight, NLOS) auch nicht lesbar; ii) das Scannen der Barcodes benötigt in den meisten FĂ€llen manuelles Eingreifen; iii) es ist unmöglich mehrere Barcodes gleichzeitig auszulesen; iv) und als Folge davon entsprechende Verzögerungen beim Auslesen gröĂerer Mengen von Barcodes, da alle einzeln gescannt werden mĂŒssen.
Die BeitrĂ€ge der vorliegenden Dissertation konzentrieren sich auf drei Schwerpunkte von frequenzcodierten (engl. frequency coded, FC) chiplosen RFID Systemen. Der erste Schwerpunkt ist die gleichzeitige Identifikation von mehreren RFID Tags und kĂŒmmert sich um den Fall, dass sich mehrere RFID Tags in der Lesezone des RFID LesegerĂ€tes befinden. Der zweite Aspekt betrifft die Verzögerung des Systems, die Zeit, das LesegerĂ€t zum Identifizieren der RFID Tags benötigt. Und drittens die Coding KapazitĂ€t des Systems, sie ist verantwortlich fĂŒr die zu erreichende Bittiefe des RFID Systems. Ein real umsetzbares RFID System erfordert Lösungen in allen drei Aspekten.
Da chiplose RFID Tags keine integrierten Schaltungen (ICs) und somit auch keine Speicherbausteine besitzen, ist die Anzahl der auf dem RFID Tag speicherbaren Bits begrenzt.
Und als Folge davon sind die Standards und Protokolle, die fĂŒr die herkömmlichen chipbehafteten RFID Systeme entwickelt worden, nicht auf chiplose RFID Systeme ĂŒbertragbar. Das wesentliche Ziel des ersten Beitrages ist die EinfĂŒhrung eines neuen Multi-Tag Antikollisionsprotokolls, das auf der Modulation der Notchposition (engl. Notch Position Modulation, NPM) und Tabellen (engl. Look-Up-Table, LUT) zur Bestimmung der Netzwerk- und MAC- Layer des chiplosen RFID Systems basiert. Die erste Generation der vorgeschlagenen Protokolls (Gen-1) baut auf einer Zweiteilung des zur VerfĂŒgung stehenden Spektrums auf. Im unteren Frequenzbereich, als PrĂ€ambel Bandbreite bezeichnet, wird jedem RFID Tag seine individuelle Frequenzverschiebung ĂŒbermittelt und im zweiten Bereich, der sogenannten Frame Bandbreite, ist die Identifikationsnummer (ID) des RFID Tags hinterlegt. Mit dieser Anordnung lĂ€sst sich jegliche Interferenz zwischen den verschiedenen RFID Tags unterbinden, da sich die Antworten der RFID Tags nicht gegenseitig ĂŒberlagern. Die zweite Generation dieses Protokolls bringt eine Verbesserung sowohl bei der Coding KapazitĂ€t als auch bei der Nutzung des zur VerfĂŒgung stehenden Frequenzspektrums. Dies wird dadurch erreicht, dass die ID des RFID in einer Tabelle im LesegerĂ€t gespeichert wird. Die individuelle Frequenzverschiebung dient dabei als Adresse fĂŒr die gespeicherten IDs. Dieser Schritt vereinfacht die KomplexitĂ€t der Struktur des RFID Tags signifikant, wĂ€hrend gleichzeitig die Erkennungswahrscheinlichkeit erhöht wird. Des Weiteren werden die Key Performance Indikatoren untersucht um die LeistungsfĂ€higkeit der Protokolle zu beweisen. Beide Protokollversionen werden modelliert und in einer Umgebung mit 10 chiplosen RFID Tags simuliert, um die Randbedingungen fĂŒr die Entwicklung der RFID Tags und des RFID LesegerĂ€tes zu ermitteln. AuĂerdem wird eine neuartige Testumgebung fĂŒr ein MultiTag Ultra Breitband (engl. ultra wideband UWB) RFID System unter realen Testbedingungen basierend auf einem Software Defined Radio (SDR) Ansatz entwickelt. In dieser Testumgebung werden sowohl die gesendeten Signal als auch Detektierungstechniken, Leerraum Kalibrierung zur Reduzierung der Streustrahlung und die Identifikationsprotokolle untersucht.
Als zweiter Schwerpunkt dieser Arbeit werden neue Techniken zur Reduzierung der Systemlaufzeit (engl. System Latency) eingefĂŒhrt. Das Ziel dabei ist, die Zeit, die das RFID LesegerĂ€t zum Erkennen aller in Lesereichweite befindlichen chiplosen FC RFID Tags braucht, zu verkĂŒrzen. Der GroĂteil der Systemlaufzeit wird durch das gewĂ€hlte Frequenzscanverfahren, durch die Anzahl der Mittelungen zur Eliminierung der umgebenden Streustrahlung und durch die Dauer eines Frequenzsprungs bestimmt. In dieser werden dazu ein adaptives Frequenzsprungverfahren (engl. adaptive frequency hopping, AFH) sowie ein Verfahren Mittels adaptiver gleitender Fensterung (engl. adaptive sliding window, ASW) eingefĂŒhrt. Das ASW Verfahren ist dabei im Hinblick auf die Identifizierung der RFID Tags nach dem Gen-1 Protokoll entwickelt, da es ein gleitendes Fenster zur Detektierung der Notches mit einer variablen Breite zum Auslesen der ID erfordert. Im Gegensatz dazu wird das Auffinden der im Gen-2 Protokoll verwendeten Notchpattern durch das AFH Verfahren verbessert. Dies wird ĂŒber variable FrequenzsprĂŒnge, die auf die jeweiligen Notchpattern optimiert werden, erreicht. Beide Verfahren haben sich als effektiv sowohl im Hinblick auf die Systemlaufzeit als auch auf die Genauigkeit erwiesen. Das ASW und das AFH Verfahren wurden dazu in der oben erwĂ€hnten Testumgebung implementiert und mit dem klassischen Frequenzsprungverfahren, feste feingraduierte Frequenzschritte, verglichen. Die Experimente haben gezeigt, dass das vorgeschlagene AFH Verfahren in Kombination mit
ASW zu einer beachtlichen Reduzierung der Systemlaufzeit von 58% fĂŒhren.
Das Ziel des dritten Schwerpunkts dieser Arbeit ist die EinfĂŒhrung einer neuartigen Technik zur Erhöhung der Informationsdichte (engl. Coding capacity) in einem chiplosen FC RFID Systems. Die hierfĂŒr vorgeschlagene Modulation der Notchbreite (engl. notch width modulation, NWM) ermöglicht die Kodierung von 4 Bits (16 ZustĂ€nden) pro Resonator in dem die Notchbreite und die dazugehörige Frequenzlage ausgenutzt werden. FĂŒr jeden Notch werden 150MHz Bandbreite reserviert, innerhalb derer das Codebit durch eine bestimmte Bandbreiten an unterschiedlichen Frequenzen bestimmt wird Cj ( fk,Bl). Das bedeutet, bei einer Arbeitsfrequenz im Bereich von 2â5 GHz können so 80 Bits realisiert werden. Des Weiteren wurde eine smarte SingulĂ€rwertzerlegung (engl. smart singular value decomposition, SSVD) Technik entwickelt, um die Notchbreite zu ermitteln und eine geringe Fehlerwahrscheinlichkeit zu garantieren. Die Nutzung von Blockcodes zur Behebung von Fehlern wurde untersucht, um den gröĂtmöglichen Nutzen aus der so gewonnene Bittiefe zu erzielen. Als Folge konnte eine groĂe Bittiefe mit einer hohen Lesegenauigkeit bei vereinfachtem Aufbau des LesegerĂ€ts erzielt werden. AuĂerdem wurde eine neuartige RFID Tag Struktur entworfen, die bei einer GröĂe von 4Ă 5 cm2 eine Codedichte von 4 Bits/cm2 erreicht. Verschiedene RFID Tag Konfigurationen wurden erstellt und das neu eingefĂŒhrte Codierungsverfahren mit Hilfe von elektromagnetischen (EM) Simulation und der bereits erwĂ€hnten Testplattform ĂŒberprĂŒft.
Die erzielten Ergebnisse ermöglichen ein widerstandsfĂ€higes RFID System in einer realen Umgebung. Alle vorgeschlagenen BeitrĂ€ge sind durch analytische Modelle, Simulationen und Messungen auf mögliche Probleme und die Grenzen einer Realisierung unter realistischen Bedingungen geprĂŒft worden.Chipless Radio Frequency IDentification (RFID) is a promising technology predicted to replace the optical barcode in the near future. This is due to several problematic issues i) the barcode cannot read Non-Line-Of-Sight (NLOS) tags; ii) each barcode needs human assistance to be read; iii) it is impossible to identify multiple tags at the same time; and iv) the considerable time delay in case of massive queues because different types of objects need to be serially scanned.
The contributions included in this dissertation concentrate on three main aspects of the Frequency Coded (FC) chipless RFID system. The first one is the multi-tag identification, which deals with the existence of multiple tags in the readerâs interrogation region. The second aspect is the system latency that describes the time the reader needs to identify the tags. Finally, there is the coding capacity that is responsible for designing a chipless tag with larger information bits. The aim of these aspects is to realize a chipless RFID system.
Since the chipless tags are memoryless as they do not include Integrated Circuits (ICs), the number of bits to be stored in the chipless tag is limited. Consequently, the current RFID standards and protocols designed for the chipped RFID systems are not applicable to the chipless systems. The main objective of the first contribution is to introduce novel multi-tag anti-collision protocols based on Notch Position Modulation (NPM) and Look-Up-Table (LUT) schemes determining the network and MAC layers of the chipless RFID systems. The first generation of the proposed protocol (Gen-1) relies on dividing the spectrum into two parts; the first one is the preamble bandwidth that includes a unique frequency shift for each tag. The second part is the frame bandwidth which represents the tag ID. The tag ID is obtained based on the predefined frequency positions, making use of the unique frequency shift. Consequently, the interference is
avoided as there will not be any overlap between the tagsâ responses. The second generation of the protocol (Gen-2) introduces an improvement in the spectrum utilization and coding capacity. This is realized by transferring the tag-ID to be stored in a table in the main memory of the reader (look-up-table). The unique shift of each tag represents the address of the tagâs ID. Therefore, the complexity of the tag structure will be significantly reduced with an enhanced probability of detection. Furthermore, the key performance indicators for the chipless RFID system are explored to validate the protocolâs performance. Both protocols are modeled and simulated to identify 10-chipless tags in order to set the regulations of the tag and reader design. Moreover, a novel real-world testbed for a multi-tag Ultra Wideband (UWB) chipless RFID system based on Software Defined Radio (SDR) is introduced. In this testbed, all the signaling schemes related to the transmitted signal, the detection techniques, the empty room calibration for the clutter removal process, and the identification protocols are applied.
The aim of the second aspect is to introduce novel techniques that reduce the time required by the reader to identify the FC chipless RFID tags existent in the readerâs interrogation region.
This time delay is called system latency. The main parameters that significantly affect the overall system latency are the frequency scanning methodology, the number of spectrum scanning iterations for the clutter removal process, and the hop duration. Therefore, the Adaptive Frequency Hopping (AFH) and the Adaptive Sliding Window (ASW) methodologies are proposed to meet the requirements of the FC chipless RFID tags. Regarding the ASW technique, it is suitable to identify the tags using the Gen-1 protocol which utilizes a sliding window (for detecting the notch) with an adaptive size to extract the tagâs-ID. The second adaptive methodology, AFH, can identify the tags with the Gen-2 protocol by using a variable frequency step that fits the
corresponding notch patterns. These techniques are proven to be efficient for the chipless RFID systems with regard to latency and accuracy. Likewise, the designed AFH and ASW techniqueâs
performance is compared to the classical Fixed Frequency Hopping (FFH) methodology with a fine frequency step to validate the accuracy of the proposed techniques. A real-world SDR based testbed is designed and the proposed adaptive algorithms as well as the classical FFH methodology are implemented. The experiments show that the proposed AFH combined with the ASW algorithms significantly reduce the system latency by 58%.
The goal of the third aspect is to introduce a novel technique that increases the coding capacity of the FC chipless RFID system. The proposed Notch Width Modulation (NWM) scheme encodes 4 bits (16-combinations) per single resonator exploiting the notch bandwidth and its corresponding frequency position. Furthermore, each notch can reserve a window with a bandwidth of 150 MHz and inside this window the notch can obtain a certain bandwidth with a specific resonant frequency constructing the coding pairs Cj ( fk,Bl). Hence, 80-bits could be achieved at the operating frequency 2â5 GHz, preserving the operating frequency bandwidth. Also, a Smart Singular Value Decomposition (SSVD) technique is designed to estimate the notch bandwidth and to ensure a low probability of error. In addition, the utilization of a linear block code as an error correcting code is explored to make the best use of the obtained coding gain. Consequently, a high encoding efficiency and an accurate detection can be achieved in addition to a simplified reader design. Moreover, a novel 4Ă 5 cm2 tag structure is designed to meet the requirements of the NWM coding technique achieving a coding density of 4 bits/cm2. Different tag configurations are manufactured and validated by measurements using the SDR platform. The introduced coding methodology is conclusively validated using Electromagnetic (EM) simulations and real-world testbed measurements.
The considered achievements for the proposed aspects offer a robust chipless RFID system that can be considered in real scenarios. Furthermore, all the proposed contributions are validated using analytical modeling, simulation and measurements in order to list their difficulties and limitations
Structural, Magnetic, Dielectric, Electrical, Optical and Thermal Properties of Nanocrystalline Materials: Synthesis, Characterization and Application
This book is a collection of the research articles and review article, published in special issue "Structural, Magnetic, Dielectric, Electrical, Optical and Thermal Properties of Nanocrystalline Materials: Synthesis, Characterization and Application"
Gallium Nitride Resonators for Infrared Detector Arrays and Resonant Acoustoelectric Amplifiers.
This work presents the first comprehensive utilization of Gallium Nitride (GaN) in high-performance, high-frequency micromechanical resonators. It presents characterization of critical electromechanical properties of GaN and validation of high-performance designs.
The primary motivation behind this project is the use of GaN resonators as sensitive, low-noise, uncooled infrared (IR) detectors. IR response of micromechanical resonators is based on radiative absorption and a consequent shift in its resonant frequency. Mechanical resonators are expected to perform better than contemporary uncooled IR detectors as the noise equivalent temperature difference (NETD) is primarily limited by each resonatorâs thermomechanical noise, which is smaller than resistive bolometers. GaN is an ideal material for resonant IR detection as it combines piezoelectric, pyroelectric, and electrostrictive properties that lead to a high IR sensitivity up to -2000 ppm/K (~ 100Ă higher than other materials). To further improve IR absorption efficiency, we developed two thin-film absorbers: a carbon nanotube (CNT)-polymer nanocomposite material with broad-spectrum absorption efficiency (> 95%) and a plasmonic absorber with narrow-spectrum absorption (> 45% for a select wavelength) integrated on the resonator. Designs have also been successfully implemented using GaN-on-Si, aluminum nitride (AlN), AlN-on-Si, and lead-zirconate-titanate (PZT), and fabricated both in-house and using commercial foundry processes. Resonant IR detectors, sense-reference pairs, and small-format arrays (16 elements) are successfully implemented with NETD values of 10 mK, and ~1 ms-10 ms response times.
This work also presents the first measurements and analysis of an exciting, fairly unexplored phenomenon: the amplification of acoustic standing waves in GaN resonators using electrical energy, boosting the quality factor (Q) and reducing energy losses in the resonator. This phenomenon is based on phonon-electron interactions in piezoelectric semiconductors. Under normal conditions this interaction is a loss mechanism for acoustic energy, but as we discovered and consistently demonstrated, it can be reversed to provide acoustoelectric amplification (resulting in Q-amplification of up to 35%). We present corroborated analytical and experimental results that describe the phonon-electron loss/gain in context with other loss mechanisms in piezoelectric semiconductor resonators. Research into this effect can potentially yield insights into fundamental solid-state physics and lead to a new class of acoustoelectric resonant amplifiers.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/108759/1/vikrantg_1.pd
Biomedical Engineering
Biomedical engineering is currently relatively wide scientific area which has been constantly bringing innovations with an objective to support and improve all areas of medicine such as therapy, diagnostics and rehabilitation. It holds a strong position also in natural and biological sciences. In the terms of application, biomedical engineering is present at almost all technical universities where some of them are targeted for the research and development in this area. The presented book brings chosen outputs and results of research and development tasks, often supported by important world or European framework programs or grant agencies. The knowledge and findings from the area of biomaterials, bioelectronics, bioinformatics, biomedical devices and tools or computer support in the processes of diagnostics and therapy are defined in a way that they bring both basic information to a reader and also specific outputs with a possible further use in research and development