45 research outputs found
An energy-efficient routing protocol for Hybrid-RFID Sensor Network
Radio Frequency Identification (RFID) systems facilitate detection and identification of objects that are not easily detectable or distinguishable. However, they do not provide information about the condition of the objects they detect. Wireless sensor networks (WSNs), on the other hand provide information about the condition of the objects as well as the environment. The integration of these two technologies results in a new type of smart network where RFID-based components are combined with sensors. This research proposes an integration technique that combines conventional wireless sensor nodes, sensor-tags, hybrid RFID-sensor nodes and a base station into a smart network named Hybrid RFID-Sensor Network (HRSN)
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Transiently Powered Computers
Demand for compact, easily deployable, energy-efficient computers has driven the development of general-purpose transiently powered computers (TPCs) that lack both batteries and wired power, operating exclusively on energy harvested from their surroundings.
TPCs\u27 dependence solely on transient, harvested power offers several important design-time benefits. For example, omitting batteries saves board space and weight while obviating the need to make devices physically accessible for maintenance. However, transient power may provide an unpredictable supply of energy that makes operation difficult. A predictable energy supply is a key abstraction underlying most electronic designs. TPCs discard this abstraction in favor of opportunistic computation that takes advantage of available resources. A crucial question is how should a software-controlled computing device operate if it depends completely on external entities for power and other resources? The question poses challenges for computation, communication, storage, and other aspects of TPC design.
The main idea of this work is that software techniques can make energy harvesting a practicable form of power supply for electronic devices. Its overarching goal is to facilitate the design and operation of usable TPCs.
This thesis poses a set of challenges that are fundamental to TPCs, then pairs these challenges with approaches that use software techniques to address them. To address the challenge of computing steadily on harvested power, it describes Mementos, an energy-aware state-checkpointing system for TPCs. To address the dependence of opportunistic RF-harvesting TPCs on potentially untrustworthy RFID readers, it describes CCCP, a protocol and system for safely outsourcing data storage to RFID readers that may attempt to tamper with data. Additionally, it describes a simulator that facilitates experimentation with the TPC model, and a prototype computational RFID that implements the TPC model.
To show that TPCs can improve existing electronic devices, this thesis describes applications of TPCs to implantable medical devices (IMDs), a challenging design space in which some battery-constrained devices completely lack protection against radio-based attacks. TPCs can provide security and privacy benefits to IMDs by, for instance, cryptographically authenticating other devices that want to communicate with the IMD before allowing the IMD to use any of its battery power. This thesis describes a simplified IMD that lacks its own radio, saving precious battery energy and therefore size. The simplified IMD instead depends on an RFID-scale TPC for all of its communication functions.
TPCs are a natural area of exploration for future electronic design, given the parallel trends of energy harvesting and miniaturization. This work aims to establish and evaluate basic principles by which TPCs can operate
Front End of a 900MHz RFID for Biological Sensing
This thesis presents the front end of a 900MHz passive RFID for biological sensing. The components blocks of the front end consist of power harvester, switch capacitor voltage regulator, phase lock loop and a modulator and demodulator. As the RFID is passive so the power resource is limited hence the main focus while implementing all the block was low power and high efficiency power conversion. All the individual block were optimized to provide maximum efficiency. For the harvester to achieve high efficiency and high output voltage a design approach is discussed by which the device sizes are optimized and the values of the matching network components are solved. The efficiency achieved with this approach is 34% while supplying 74ïżœ[email protected]. The switch capacitor voltage regulator would supply power to the digital core of the RFID, which will operate at subtheshold or moderate inversion. The switch capacitor implemented in this work is a adaptive voltage regulator, as I intend to use the dynamic supply voltage scaling technique to compensate for the reduction in reliability of performance of the circuit due to variation of VTH across process due to random doping effects and temperature in subthreshold.The phase lock loop (PLL) block in this front end provide the system clock synchronized with the base station to all the backend blocks like the digital controller, memory, and the analog to digital converter ADC and the switch capacitor voltage regulator. The PLL is a low power with jitter of 24nsec and is capable of clock data recovery from EPC gen 2 protocol format data and consumes 3ïżœW of power Finally a ultra low power AM (amplitude modulation) demodulator is presented which is consumes only 100nW and is capable of demodulating a double-sideband amplitude modulated (DSB-AM) signal centered at 900MHz and the modulating frequency is 160KHz. The demodulator can demodulate signal having as low as -5dBm power and 50% modulation index. The modulation for transmitting signal is achieved by BPSK(back scatter phase shift keying).Electrical Engineerin
Radio frequency energy harvesting for autonomous systems
A thesis submitted to the University of Bedfordshire in partial fulfilment of the requirements for the degree of Doctor of PhilosophyRadio Frequency Energy Harvesting (RFEH) is a technology which enables wireless power delivery to multiple devices from a single energy source. The main components of this technology are the antenna and the rectifying circuitry that converts the RF signal into DC power. The devices which are using Radio Frequency (RF) power may be integrated into Wireless Sensor Networks (WSN), Radio Frequency Identification (RFID), biomedical implants, Internet of Things (IoT), Unmanned Aerial Vehicles (UAVs), smart meters, telemetry systems and may even be used to charge mobile phones. Aside from autonomous systems such as WSNs and RFID, the multi-billion portable electronics market â from GSM phones to MP3 players â would be an attractive application for RF energy harvesting if the power requirements are met. To investigate the potential for ambient RFEH, several RF site surveys were conducted around London. Using the results from these surveys, various harvesters were designed and tested for different frequency bands from the RF sources with the highest power density within the Medium Wave (MW), ultra- and super-high (UHF and SHF) frequency spectrum. Prototypes were fabricated and tested for each of the bands and proved that a large urban area around Brookmans park radio centre is suitable location for harvesting ambient RF energy.
Although the RFEH offers very good efficiency performance, if a single antenna is considered, the maximum power delivered is generally not enough to power all the elements of an autonomous system. In this thesis we present techniques for optimising the power efficiency of the RFEH device under demanding conditions such as ultra-low power densities, arbitrary polarisation and diverse load impedances. Subsequently, an energy harvesting ferrite rod rectenna is designed to power up a wireless sensor and its transmitter, generating dedicated Medium Wave (MW) signals in an indoor environment. Harvested power management, application scenarios and practical results are also presented
Sistemas eficientes de transmissĂŁo de energia sem-fios e identificação por radiofrequĂȘncia
Doutoramento em Engenharia EletrotécnicaIn the IoT context, where billions of connected objects are expected to be ubiquitously deployed worldwide, the frequent battery maintenance of ubiquitous wireless nodes is undesirable or even impossible. In these scenarios, passive-backscatter radios will certainly play a crucial role due to their low cost, low complexity and battery-free operation. However, as passive-backscatter devices are chiefly limited by the WPT link, its efficiency optimization has been a major research concern over the years, gaining even more emphasis in the IoT context.
Wireless power transfer has traditionally been carried out using CW signals, and the efficiency improvement has commonly been achieved through circuit design optimization. This thesis explores a fundamentally different approach, in which the optimization is focused on the powering waveforms, rather than the circuits. It is demonstrated through theoretical analysis, simulations and measurements that, given their greater ability to overcome the built-in voltage of rectifying devices, high PAPR multi-sine (MS) signals are capable of more efficiently exciting energy harvesting circuits when compared to CWs. By using optimal MS signals to excite rectifying devices, remarkable RF-DC conversion efficiency gains of up to 15 dB with respect to CW signals were obtained.
In order to show the effectiveness of this approach to improve the communication range of passive-backscatter systems, a MS front-end was integrated in a commercial RFID reader and a significant range extension of 25% was observed. Furthermore, a software-defined radio RFID reader, compliant with ISO18000-6C standard and with MS capability, was constructed from scratch. By interrogating passive RFID transponders with MS waveforms, a transponder sensitivity improvement higher than 3 dB was obtained for optimal MS signals. Since the amplification and transmission of high PAPR signals is critical, this work also proposes efficient MS transmitting architectures based on space power combining techniques.
This thesis also addresses other not less important issues, namely self-jamming in passive RFID readers, which is the second limiting factor of passive-backscatter systems. A suitable self-jamming suppression scheme was first used for CW signals and then extended to MS signals, yielding a CW isolation up to 50 dB and a MS isolation up 60 dB.
Finally, a battery-less remote control system was developed and integrated in a commercial TV device with the purpose of demonstrating a practical application of wireless power transfer and passive-backscatter concepts. This allowed battery-free control of four basic functionalities of the TV (CH+,CH-,VOL+,VOL-).No contexto da internet das coisas (IoT), onde sĂŁo esperados bilhĂ”es de objetos conectados espalhados pelo planeta de forma ubĂqua, torna-se impraticĂĄvel uma frequente manutenção e troca de baterias dos dispositivos sem fios ubĂquos. Nestes cenĂĄrios, os sistemas radio backscatter passivos terĂŁo um papel preponderante dado o seu baixo custo, baixa complexidade e nĂŁo necessidade de baterias nos nĂłs mĂłveis. Uma vez que a transmissĂŁo de energia sem fios Ă© o principal aspeto limitativo nestes sistemas, a sua otimização tem sido um tema central de investigação, ganhando ainda mais ĂȘnfase no contexto IoT.
Tradicionalmente, a transferĂȘncia de energia sem-fios Ă© feita atravĂ©s de sinais CW e a maximização da eficiĂȘncia Ă© conseguida atravĂ©s da otimização dos circuitos recetores. Neste trabalho explora-se uma abordagem fundamentalmente diferente, em que a otimização foca-se nas formas de onda em vez dos circuitos. Demonstra-se, teoricamente e atravĂ©s de simulaçÔes e medidas que, devido Ă sua maior capacidade em superar a barreira de potencial intrĂnseca dos dispositivos retificadores, os sinais multi-seno (MS) de elevado PAPR sĂŁo capazes de excitar os circuitos de colheita de energia de forma mais eficiente quando comparados com o sinal CW tradicional. Usando sinais MS Ăłtimos em circuitos retificadores, foram verificadas experimentalmente melhorias de eficiĂȘncia de conversĂŁo RF-DC notĂĄveis de atĂ© 15 dB relativamente ao sinal CW.
A fim de mostrar a eficĂĄcia desta abordagem na melhoria da distĂąncia de comunicação de sistemas backscatter passivos, integrou-se um front-end MS num leitor RFID comercial e observou-se um aumento significativo de 25% na distĂąncia de leitura. AlĂ©m disso, desenvolveu-se de raiz um leitor RFID baseado em software rĂĄdio, compatĂvel com o protocolo ISO18000-6C e capaz de gerar sinais MS, com os quais interrogou-se transponders passivos, obtendo-se ganhos de sensibilidade dos transponders maiores que 3 dB. Uma vez que a amplificação de sinais de elevado PAPR Ă© uma operação crĂtica, propĂŽs-se tambĂ©m novas arquiteturas eficientes de transmissĂŁo baseadas na combinação de sinais em espaço livre.
Esta tese aborda também outros aspetos não menos importantes, como o self-jamming em leitores RFID passivos, tido como o segundo fator limitativo neste tipo de sistemas. Estudou-se técnicas de cancelamento de self-jamming CW e estendeu-se o conceito a sinais MS, tendo-se obtido isolamentos entre o transmissor e o recetor de até 50 dB no primeiro caso e de até 60 dB no segundo.
Finalmente, com o objetivo de demonstrar uma aplicação pråtica dos conceitos de transmissão de energia sem fios e comunicação backscatter, desenvolveu-se um sistema de controlo remoto sem pilhas, cujo protótipo foi integrado num televisor comercial a fim de controlar quatro funcionalidades båsicas (CH+,CH-,VOL+,VOL-)
Integration of RFID and Industrial WSNs to Create A Smart Industrial Environment
A smart environment is a physical space that is seamlessly embedded with sensors, actuators, displays, and computing devices, connected through communication networks for data collection, to enable various pervasive applications. Radio frequency identification (RFID) and Wireless Sensor Networks (WSNs) can be used to create such smart environments, performing sensing, data acquisition, and communication functions, and thus connecting physical devices together to form a smart environment.
This thesis first examines the features and requirements a smart industrial environment. It then focuses on the realization of such an environment by integrating RFID and industrial WSNs. ISA100.11a protocol is considered in particular for WSNs, while High Frequency RFID is considered for this thesis. This thesis describes designs and implementation of the hardware and software architecture necessary for proper integration of RFID and WSN systems. The hardware architecture focuses on communication interface and AI/AO interface circuit design; while the driver of the interface is implemented through embedded software. Through Web-based Human Machine Interface (HMI), the industrial users can monitor the process parameters, as well as send any necessary alarm information. In addition, a standard Mongo database is designed, allowing access to historical and current data to gain a more in-depth understanding of the environment being created. The information can therefore be uploaded to an IoT Cloud platform for easy access and storage.
Four scenarios for smart industrial environments are mimicked and tested in a laboratory to demonstrate the proposed integrated system. The experimental results have showed that the communication from RFID reader to WSN node and the real-time wireless transmission of the integrated system meet design requirements. In addition, compared to a traditional wired PLC system where measurement error of the integrated system is less than 1%. The experimental results are thus satisfactory, and the design specifications have been achieved
Contactless Energy Transfer Techniques for Industrial Applications. Power and Data Transfer to Moving Parts
Contactless energy transfer (CET) systems are gaining increasing interest in the automatic machinery industries. For this reason, circuit equivalent networks of CET systems considered in the literature are introduced with emphasis on their industrial applicability. The main operating principles and the required compensating networks, along with different topologies of power supplies optimised for wireless powering, are discussed. The analysis of the wireless transfer, at the maximum efficiency, of high power levels shows that, in the kHz range, highly coupled inductive links are needed and soft-switching power sources required. The employment of CET units in controlled systems requires combining a link for data communication with the wireless power channel. At low frequencies, capacitive and inductive couplings are integrated in a unique platform to implement the wireless data and power links, respectively. Differently, at UHF, an increased data channel transfer efficiency is made possible by exploiting auto-resonant structures, such as split-ring resonators instead of capacitances, one at each far-end side of the link. The design procedure of a power CET system, including the dc/ac converter, a rotary transformer and its windings, is discussed and the results presented. A different version of a WPT system, which involves multiple transmitting coils and a sliding receiver, is also presented. A low frequency RFID capacitive data link is then combined with the rotary CET unit to provide the temperature feedback of a controlled system, wherein the rectifying part of a passive tag is exploited to simultaneously power and read a temperature probe. Subsequently, a split-ring based near-field UHF data link is designed to ensure an improved temperature detection in terms of accuracy and resolution. The sensor readout is performed at the transmitter side by measuring the reflected power by the load rectifier
Sensores passivos alimentados por transmissão de energia sem fios para aplicaçÔes 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 ĂĄrea de internet das coisas e sistemas de redes
de sensores sem fios relacionados com o espaço. Os desafios do futuro
das comunicaçÔes de rĂĄdio tĂȘm uma dupla evolução, sendo um o baixo
consumo de energia e, outro, a adaptação e o uso inteligente dos recursos
disponĂveis. RĂĄdios 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 possĂvel 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 aplicaçÔes inseridas na
internet das coisas. Nesse sentido, vårias modulaçÔes 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 econĂłmicos de modo a serem incorporados
em outras tecnologias ou dispositivos. Consequentemente, o front-end de
rĂĄdio frequĂȘncia dos sensores serĂĄ projetado e implementado em circuito
integrado de microondas monolĂtico.Programa Doutoral em Engenharia EletrotĂ©cnic
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