12 research outputs found

    Sistemas eficientes de transmissĂŁo de energia sem-fios e identificação por radiofrequĂȘncia

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    Doutoramento em Engenharia EletrotĂ©cnicaIn 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 tambĂ©m outros aspetos nĂŁo menos importantes, como o self-jamming em leitores RFID passivos, tido como o segundo fator limitativo neste tipo de sistemas. Estudou-se tĂ©cnicas 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 atĂ© 50 dB no primeiro caso e de atĂ© 60 dB no segundo. Finalmente, com o objetivo de demonstrar uma aplicação prĂĄtica dos conceitos de transmissĂŁo de energia sem fios e comunicação backscatter, desenvolveu-se um sistema de controlo remoto sem pilhas, cujo protĂłtipo foi integrado num televisor comercial a fim de controlar quatro funcionalidades bĂĄsicas (CH+,CH-,VOL+,VOL-)

    Introduction to Radio-frequency Identification (RFID)

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    This project presents the fundamental aspects of the RFID (Radio-frequency identifica-tion) technology used to establish wireless communications. The project focuses on thepassive mode of RFID, where the receiver does not have any power supply, which allowsits miniaturization and low cost.On the other hand, two articles from different authors are analyzed. The first consists onthe design of a very low power passive receiver through various techniques of optimizationin the hardware’s manufacture.In the second, a drone is used as an intermediate element between the transmitter and thereceiver to extend up to 10 times the typical range of passive RFID. The study focuses onthe treatment of the RF signal to considerably eliminate the interferences and to preciselylocalize the receiver.Outgoin

    Advanced Radio Frequency Identification Design and Applications

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    Radio Frequency Identification (RFID) is a modern wireless data transmission and reception technique for applications including automatic identification, asset tracking and security surveillance. This book focuses on the advances in RFID tag antenna and ASIC design, novel chipless RFID tag design, security protocol enhancements along with some novel applications of RFID

    IhmiskÀsivarren mallintaminen puettaville passiivisille UHF RFID tunniste -sovelluksille

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    Radio frequency identification (RFID) technology is rapidly emerging within bio-medical engineering applications. Particularly in harsh and challenging environments, RFID provide fast and reliable item identification and tracking solution. In a typical RFID system objects to be identified are marked with tags, consisting of an antenna and an integrated circuit. The tags are wirelessly read by a stationary reader unit. In the future, wearable RFID tags integrated into daily clothing could provide multi-functional garments for real-time remote bio-monitoring of humans without any human involvement. At ultra-high frequencies (UHF) the human body is electrically a challenging application environment for the tag due to its high permittivity and high losses. Modelling of the human body for UHF is not a straightforward task. The body in close proximity tends to interact with the tag in a disadvantageous manner, resulting in severe overall tag performance degradation. However, an accurate human model is of paramount importance for future design and optimisation of wearable antennas. In this project, a novel wireless approach is used to develop a UHF human arm model for wearable antenna applications. A reference tag is designed and its response is practically measured when the tag is directly attached to the human arm. The response serves as a reference response. A simple homogenous cylinder is used in electromagnetic simulations to represent the human arm. The cylinder material is defined with the electrical parameter variables effective relative permittivity, ɛr,eff, and loss tangent, tan ÎŽ. The reference tag is simulated on the cylinder. By adjusting the variables Δr,eff and tan ÎŽ properly, agreement is found between the reference response and the simulated tag response on the cylinder. The approach eliminates the need for any information about the electrical parameters of a particular tissue type. Further, the wireless approach removes the need for baluns or fixture required in wired tag antenna input impedance measurements. It is verified that the developed UHF human arm model is able to predict the wearable tag performance on the human arm with ±3 dB accuracy over the frequency band 800–1000 MHz. The simple human arm simulation model can hereby be used as a powerful tool for future wearable antenna design and optimisation.Radiotaajuinen tunnistustekniikka (engl. Radio Frequency Identification, RFID) löytÀÀ yhĂ€ enemmĂ€n ja enemmĂ€n sovelluskohteita lÀÀketieteellisessĂ€ tekniikassa. Erityisesti vaikeissa sekĂ€ haastavissa ympĂ€ristöissĂ€ RFID mahdollistaa kohteen nopean ja luotettavan tunnistus- sekĂ€ seuranata-ratkaisun. TyypillisessĂ€ RFID jĂ€rjestelmĂ€ssĂ€ tunnistettavat kohteet merkitÀÀn tunnisteilla, jotka koostuvat tunnisteantennista sekĂ€ mikropiiristĂ€. Tunnisteita luetaan langattomasti stationaarisella lukijalaitteella. Tulevaisuudessa, vaatteisiin integroidut puettavat RFID tunnisteet mahdollistavat monitoimi-vaatekappaleita ihmisten langatonta ja reaaliaikaista biomonitorointia varten. UHF taajuuksilla (0.3–3 GHz) ihmiskehon korkea permittiivisyys sekĂ€ korkeat hĂ€viöt muodostavat sĂ€hköisesti haastavan sovelluskohteen tunnisteelle. Ihmiskehon mallintaminen UHF taajuuksille ei ole suoraviivainen tehtĂ€vĂ€. Ihmiskeho vaikuttaa tĂ€mĂ€n lĂ€histössĂ€ olevaan tunnisteeseen epĂ€edullisesti, johtaen tunnisteen suorituskyvyn vakavaan heikkenemiseen. Tulevaisuudessa, ihmiskehon mallintaminen on kuitenkin erittĂ€in tĂ€rkeĂ€ osa puettavien antennien suunnittelussa ja optimoinnissa. TĂ€ssĂ€ työssĂ€ esitetÀÀn uudenlainen langaton lĂ€hestymistapa ihmiskĂ€sivarren mallintamiseen puettaville UHF sovelluksille. Tarkoituksena on mitata referenssitunnisteen vaste tunnisteen ollessa kiinni kĂ€sivarressa ja hyödyntÀÀ mitattua referenssivastetta mallin rakentamiseen. KĂ€sivarsi mallinnetaan kenttĂ€simulaattorissa yksinkertaisella homogeenisella lieriöllĂ€. Lieriölle annetaan sĂ€hköiset parametrimuuttujat suhteellinen permittiivisyys, Δr,eff, sekĂ€ hĂ€viökerroin, tan ÎŽ, kuvamaan lieriön materiaalisisĂ€ltöÀ. Asettamalla sĂ€hköisten parametrimuuttujien arvot oikein, referenssitunnisteen simuloitu vaste saadaan yhteensopivaksi mitatun referenssivasteen kanssa. KĂ€ytetty lĂ€hestymistapa ei vaadi tietĂ€mystĂ€ yksittĂ€isten kudoksien sĂ€hköisistĂ€ ominaisuuksista tai kudoksien suuruuksista. LisĂ€ksi esitetyssĂ€ langattomassa menetelmĂ€ssĂ€ ei tarvita baluunia tai erillistĂ€ kiinnityskappaletta, toisin kuin tunnisteantennin sisÀÀnmenoimpedanssin mittauksissa. TyössĂ€ vahvistetaan, ettĂ€ suunniteltu ihmiskĂ€sivarren malli UHF taajuuksille kykenee ennustamaan puettavan tunnisteen suorituskyvyn ihmiskĂ€sivarressa ±3 dB:n tarkkuudella taajuuskaistalla 800–1000 MHz. Suunniteltua yksinkertaista ihmiskĂ€sivarren simulointimallia voidaan nĂ€in ollen jatkossa hyödyntÀÀ tehokkaana työkaluna puettavien antennien suunnittelussa sekĂ€ optimoinnissa

    Optimization of the close coupling effect for passive UHF RFID tags in stacked applications

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    The use of the radio frequency identification has become more popular in recent years, since it has many advantages (such as operation without human involvement or detection non-line-of sight at several meters) than the other identification system. The RFID tags are utilized in many different applications. In a wide range of applications (e.g. in the retail business), the RFID tags are often stacked together. The stacked UHF RFID tags are known to have less read range compare to the stand-alone tags. In the other words, placing the tag in the close proximity of other tags, affects the performance of the tag, due to electromagnetic interference between the antennas of the tags. The most of the analysis about effect of the close coupling have been done for the UHF RFID tags in near-field application. Since many different factors are involved in the performance of the tag in far-field applications, it is more complicated to analyze the interaction between the tags when they are placed in the close proximity of each other inside the far-field region of the reader antenna. In this project, the effect of some design parameters on the close coupling has been studied and one practical approach for improvement of the performance of the tags in the stacked application has been introduced. The performance of a reference tag in stack is measured. Then the new versions of the reference tag are designed by adjusting some of the reference tag antenna’s parameters. The measurement of the new version designs in stack shows the performance enhancement for one of the new design. The comparison between the results of the different designs verifies that the design parameters can have influence to the minimizing of the close coupling effect

    CriptografĂ­a ligera en dispositivos de identificaciĂłn por radiofrecuencia- RFID

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    Esta tesis se centra en el estudio de la tecnologĂ­a de identificaciĂłn por radiofrecuencia (RFID), la cual puede ser considerada como una de las tecnologĂ­as mĂĄs prometedoras dentro del ĂĄrea de la computaciĂłn ubicua. La tecnologĂ­a RFID podrĂ­a ser el sustituto de los cĂłdigos de barras. Aunque la tecnologĂ­a RFID ofrece numerosas ventajas frente a otros sistemas de identificaciĂłn, su uso lleva asociados riesgos de seguridad, los cuales no son fĂĄciles de resolver. Los sistemas RFID pueden ser clasificados, atendiendo al coste de las etiquetas, distinguiendo principalmente entre etiquetas de alto coste y de bajo coste. Nuestra investigaciĂłn se centra fundamentalmente en estas Ășltimas. El estudio y anĂĄlisis del estado del arte nos ha permitido identificar la necesidad de desarrollar soluciones criptogrĂĄficas ligeras adecuadas para estos dispositivos limitados. El uso de soluciones criptogrĂĄficas estĂĄndar supone una aproximaciĂłn correcta desde un punto de vista puramente teĂłrico. Sin embargo, primitivas criptogrĂĄficas estĂĄndar (funciones resumen, cĂłdigo de autenticaciĂłn de mensajes, cifradores de bloque/flujo, etc.) exceden las capacidades de las etiquetas de bajo coste. Por tanto, es necesario el uso de criptografĂ­a ligera._______________________________________This thesis examines the security issues of Radio Frequency Identification (RFID) technology, one of the most promising technologies in the field of ubiquitous computing. Indeed, RFID technology may well replace barcode technology. Although it offers many advantages over other identification systems, there are also associated security risks that are not easy to address. RFID systems can be classified according to tag price, with distinction between high-cost and low-cost tags. Our research work focuses mainly on low-cost RFID tags. An initial study and analysis of the state of the art identifies the need for lightweight cryptographic solutions suitable for these very constrained devices. From a purely theoretical point of view, standard cryptographic solutions may be a correct approach. However, standard cryptographic primitives (hash functions, message authentication codes, block/stream ciphers, etc.) are quite demanding in terms of circuit size, power consumption and memory size, so they make costly solutions for low-cost RFID tags. Lightweight cryptography is therefore a pressing need. First, we analyze the security of the EPC Class-1 Generation-2 standard, which is considered the universal standard for low-cost RFID tags. Secondly, we cryptanalyze two new proposals, showing their unsuccessful attempt to increase the security level of the specification without much further hardware demands. Thirdly, we propose a new protocol resistant to passive attacks and conforming to low-cost RFID tag requirements. In this protocol, costly computations are only performed by the reader, and security related computations in the tag are restricted to very simple operations. The protocol is inspired in the family of Ultralightweight Mutual Authentication Protocols (UMAP: M2AP, EMAP, LMAP) and the recently proposed SASI protocol. The thesis also includes the first published cryptanalysis of xi SASI under the weakest attacker model, that is, a passive attacker. Fourthly, we propose a new protocol resistant to both passive and active attacks and suitable for moderate-cost RFID tags. We adapt Shieh et.’s protocol for smart cards, taking into account the unique features of RFID systems. Finally, because this protocol is based on the use of cryptographic primitives and standard cryptographic primitives are not supported, we address the design of lightweight cryptographic primitives. Specifically, we propose a lightweight hash function (Tav-128) and a lightweight Pseudo-Random Number Generator (LAMED and LAMED-EPC).We analyze their security level and performance, as well as their hardware requirements and show that both could be realistically implemented, even in low-cost RFID tags
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