Battery-less near field communications (nfc) sensors for internet of things (iot) applications

L’ implementació de la tecnologia de comunicació de camp proper (NFC) en els telèfons intel·ligents no para de créixer degut a l’ús d’aquesta per fer pagaments, això, junt amb el fet de poder aprofitar l’energia generada pel mòbil no només per la comunicació, sinó també per transmetre energia, el baix cost dels xips NFC, i el fet de que els telèfons tinguin connectivitat amb internet, possibilita i fa molt interesant el disseny d’etiquetes sense bateria incorporant-hi sensors i poder enviar la informació al núvol, dins del creixent escenari de l’internet de les coses (IoT). La present Tesi estudia la viabilitat d’aquests sensors, analitzant la màxima distància entre lector i sensor per proveir la potència necessària, presenta tècniques per augmentar el rang d’operació, i analitza els efectes de certs materials quan aquests estan propers a les antenes. Diversos sensors han estat dissenyats i analitzats i son presentats en aquest treball. Aquests son: Una etiqueta que mesura la humitat de la terra, la temperatura i la humitat relativa de l’aire per controlar les condicions de plantes. Un sensor per detectar la humitat en bolquers, imprès en material flexible que s’adapta a la forma del bolquer. Dues aplicacions, una per estimació de pH i una altre per avaluar el grau de maduració de fruites, basats en un sensor de color. I, per últim, s’estudia la viabilitat de sensors en implants per aplicacions mèdiques, analitzant l’efecte del cos i proposant un sistema per augmentar la profunditat a la que aquests es poden llegir utilitzant un telèfon mòbil. Tots aquests sensors poden ser alimentats i llegits per qualsevol dispositiu que disposin de connexió NFC.La implementación de la tecnología de comunicaciones de campo cercano (NFC) en los teléfonos inteligentes no para de crecer debido al uso de esta para llevar a cabo pagos, esto, junto con el hecho de poder aprovechar la energía generada por el móvil no sólo para la comunicación, sino también para transmitir energía, el bajo coste de los chips NFC, i el hecho que los teléfonos tengan conectividad a internet, posibilita y hace muy interesante el diseño de etiquetas sin batería que incorporen sensores i poder enviar la información a la nube, enmarcado en el creciente escenario del internet de las cosas (IoT). La presente Tesis estudia la viabilidad de estos sensores, analizando la máxima distancia entre lector i sensor para proveer la potencia necesaria, presenta técnicas para aumentar el rango de operación, y analiza los efectos de ciertos materiales cuando estos están cerca de las antenas. Varios sensores han sido diseñados y analizados y son presentados en este trabajo. Estos son: Una etiqueta que mide la humedad de la tierra, la temperatura y la humedad relativa del aire para controlar las condiciones de plantas. Un sensor para detectar la humedad en pañales, impreso en material flexible que se adapta a la forma del pañal. Dos aplicaciones, una para estimación de pH y otra para evaluar el grado de maduración de frutas, basados en un sensor de color. Y, por último, se estudia la viabilidad de sensores en implantes para aplicaciones médicas, analizando el efecto del cuerpo y proponiendo un sistema para aumentar la profundidad a la que estos se pueden leer usando un teléfono móvil. Todos estos sensores pueden ser alimentados y leídos por cualquier dispositivo que disponga de conexión NFC.The implementation of near field communication (NFC) technology into smartphones grows rapidly due the use of this technology as a payment system. This, altogether with the fact that the energy generated by the phone can be used not only to communicate but for power transfer as well, the low-cost of the NFC chips, and the fact that the smartphones have connectivity to internet, makes possible and very interesting the design of battery-less sensing tags which information can be sent to the cloud, within the growing internet of things (IoT) scenario. This Thesis studies the feasibility of these sensors, analysing the maximum distance between reader and sensor to provide the necessary power, presents techniques to increase the range of operation, and analyses the effects of certain materials when they are near to the antennas. Several sensors have been designed and analysed and are presented in this work. These are: a tag that measures the soil moisture, the temperature and the relative humidity of the air to control the conditions of plants. A moisture sensor for diapers, printed on flexible material that adapts to the diaper shape. Two applications, one for pH estimation and another for assessing the degree of fruit ripening, based on a colour sensor. And finally, the feasibility of sensors in implants for medical applications is studied, analysing the effect of the body and proposing a system to increase the depth at which they can be read using a mobile phone. All of these sensors can be powered and read by any NFC enabled device

RFID system evaluation against radiated transient noise

In this paper a radiofrequency identification system according to standard ISO/IEC 14443 type-B is evaluated in presence of transient noise. This real time communication system working at 13.56 MHz is interfered in a controlled environment by different transient bursts varying their level, frequency and duration. The transient burst interference is applied in an AC main wire close to the system and the effect over the digital communication system is evaluated using two different methods. The first one is observing directly an RFID equipment in presence of transient signals, and the second one is capturing the interference in time domain an evaluating its effect by means of simulation. The RFID system is affected by these transient noises causing different types of errors. It is shown that it is essential to measure and evaluate in time domain the transient phenomena to ensure that the RFID system do not have susceptibility problems.Peer ReviewedPostprint (published version

Communication system for a tooth-mounted RF sensor used for continuous monitoring of nutrient intake

In this Thesis, the communication system of a wearable device that monitors the user’s diet is studied. Based in a novel RF metamaterial-based mouth sensor, different decisions have to be made concerning the system’s technologies, such as the power source options for the device, the wireless technology used for communications and the method to obtain data from the sensor. These issues, along with other safety rules and regulations, are reviewed, as the first stage of development of the Food-Intake Monitoring projectOutgoin

Passive RFID-Based Inventory of Traffic Signs on Roads and Urban Environments

This paper presents a system with location functionalities for the inventory of traffic signs based on passive RFID technology. The proposed system simplifies the current video-based techniques, whose requirements regarding visibility are difficult to meet in some scenarios, such as dense urban areas. In addition, the system can be easily extended to consider any other street facilities, such as dumpsters or traffic lights. Furthermore, the system can perform the inventory process at night and at a vehicle’s usual speed, thus avoiding interfering with the normal traffic flow of the road. Moreover, the proposed system exploits the benefits of the passive RFID technologies over active RFID, which are typically employed on inventory and vehicular routing applications. Since the performance of passive RFID is not obvious for the required distance ranges on these in-motion scenarios, this paper, as its main contribution, addresses the problem in two different ways, on the one hand theoretically, presenting a radio wave propagation model at theoretical and simulation level for these scenarios; and on the other hand experimentally, comparing passive and active RFID alternatives regarding costs, power consumption, distance ranges, collision problems, and ease of reconfiguration. Finally, the performance of the proposed on-board system is experimentally validated, testing its capabilities for inventory purposesMinisterio de Economía y Competitividad TEC2016-80396-C2-2-

Magnetic Flux Leakage techniques for detecting corrosion of pipes

Oil and gas pipelines are subjected to corrosion due to harsh environmental conditions as in refinery and thermal power plants. Interesting problems such as internal and external corrosion, emerging from the increasing demand for pipeline protection have prompted this study. Thus, early detection of faults in pipes is essential to avoid disastrous outcomes. The research work presented in this thesis comprises investigations into the use of magnetic flux leakage (MFL) testing for pipe in extreme (underwater and high temperature) conditions. The design of a coil sensor (ferrite core with coil) with a magnetic circuit is carried out for high temperature conditions. The sensor thus developed lays the ground for non-destructive evaluation (NDE) of flaws in pipes through the MFL technique. The research focusses on the detection and characterization of MFL distribution caused by the loss of metal in ferromagnetic steel pipes. Experimental verifications are initially conducted with deeply rusted pipe samples of varying thicknesses in air. AlNiCo magnets are used along with Giant Magneto Resistance (GMR) sensor (AA002-02). The experiment is further repeated for saltwater conditions in relation to varying electrical conductivity with radio frequency identification (RFID) technique. A further study carried out in the research is the correlation between magnetic and underwater data communication. The study has resulted in the development and experimental evaluation of a coil sensor with its magnetic response at room and high temperatures. This makes the system effective under high temperature conditions where corrosion metal loss needs to be determined

Magnetic Flux Leakage techniques for detecting corrosion of pipes

Oil and gas pipelines are subjected to corrosion due to harsh environmental conditions as in refinery and thermal power plants. Interesting problems such as internal and external corrosion, emerging from the increasing demand for pipeline protection have prompted this study. Thus, early detection of faults in pipes is essential to avoid disastrous outcomes. The research work presented in this thesis comprises investigations into the use of magnetic flux leakage (MFL) testing for pipe in extreme (underwater and high temperature) conditions. The design of a coil sensor (ferrite core with coil) with a magnetic circuit is carried out for high temperature conditions. The sensor thus developed lays the ground for non-destructive evaluation (NDE) of flaws in pipes through the MFL technique. The research focusses on the detection and characterization of MFL distribution caused by the loss of metal in ferromagnetic steel pipes. Experimental verifications are initially conducted with deeply rusted pipe samples of varying thicknesses in air. AlNiCo magnets are used along with Giant Magneto Resistance (GMR) sensor (AA002-02). The experiment is further repeated for saltwater conditions in relation to varying electrical conductivity with radio frequency identification (RFID) technique. A further study carried out in the research is the correlation between magnetic and underwater data communication. The study has resulted in the development and experimental evaluation of a coil sensor with its magnetic response at room and high temperatures. This makes the system effective under high temperature conditions where corrosion metal loss needs to be determined

A compact dosimetric system for MOSFETs based on passive NFC tag and smartphone

The authors acknowledge the Servicio de Radiofísica (Radio-physics Service) of the Hospital Universitario San Cecilio (Granada, Spain) for permitting us to use their installations. This work was funded by the Spanish Government under project FPA2015-67694-P (Spanish Ministry of Economy, Industry and Competitiveness) and a R&D predoctoral grant (FPU13/05032, Spanish Ministry of Education, Culture and Sport). This project is partially supported by European Regional Development Funds (ERDF).In this work we describe and evaluate a dosimetric system based on an NFC (Near Field Communication) tag and a smartphone that uses commercial MOSFETs as radiation sensors. The tag is designed with commercial integrated circuits and the smartphone is the power source of the tag configured as a readout unit, user interface and storage unit. The NFC tag is supplied wirelessly by the smartphone via NFC, using a home-made structure to align the tag coil and smartphone coil in order to achieve a good inductive coupling. In this case, the commercial DMOS transistor ZVP3306 is used as dosimeter in unbiased mode, connected to the tag before and after each irradiation session to perform the sensor reading. An evaluation of the dosimetric system has been carried out irradiating three transistors with photon beam of 6 MV up to 20 Gy. The average sensitivity found is (4.75 ± 0.15) mV/Gy, which is in good agreement with the results found with our previously developed dosimetric system. Therefore, this miniaturised dosimetric system can be considered as a promising and low cost electronic architecture to be used for dosimetry control in radio-therapy treatments.Servicio de Radiofísica (Radio-physics Service) of the Hospital Universitario San Cecilio (Granada, Spain)Spanish Government under project FPA2015-67694-P (Spanish Ministry of Economy, Industry and Competitiveness) and a R&D predoctoral grant (FPU13/05032, Spanish Ministry of Education, Culture and Sport)European Regional Development Funds (ERDF

PRLS-INVES: A General Experimental Investigation Strategy for High Accuracy and Precision in Passive RFID Location Systems

Due to cost-effectiveness and easy-deployment, radio-frequency identification (RFID) location systems are widely utilized into many industrial fields, particularly in the emerging environment of the Internet of Things (IoT). High accuracy and precision are key demands for these location systems. Numerous studies have attempted to improve localization accuracy and precision using either dedicated RFID infrastructures or advanced localization algorithms. But these effects mostly consider utilization of novel RFID localization solutions rather than optimization of this utilization. Practical use of these solutions in industrial applications leads to increased cost and deployment difficulty of RFID system. This paper attempts to investigate how accuracy and precision in passive RFID location systems (PRLS) are impacted by infrastructures and localization algorithms. A general experimental-based investigation strategy, PRLS-INVES, is designed for analyzing and evaluating the factors that impact the performance of a passive RFID location system. Through a case study on passive high frequency (HF) RFID location systems with this strategy, it is discovered that: 1) the RFID infrastructure is the primary factor determining the localization capability of an RFID location system and 2) localization algorithm can improve accuracy and precision, but is limited by the primary factor. A discussion on how to efficiently improve localization accuracy and precision in passive HF RFID location systems is given

Circuits and systems for inductive power transfer

Recently, the development of Wireless Power Transfer (WPT) systems has shown to be a key factor for improving the robustness, usability and autonomy of many mobile devices. The WPT link relaxes the trade-off between the battery size and the power availability, enabling highly innovative applications. This thesis aims to develop novel techniques to increase efficiency and operating distance of inductive power transfer systems. We addressed the design of the inductive link and various circuits used in the receiver. Moreover, we performed a careful system-level analysis, taking into account the design of different blocks and their interaction. The analysis is oriented towards the development of low power applications, such as Active Implantable Medical Device (AIMD) or Radio-Frequency Identification (RFID) systems. Three main approaches were considered to increase efficiency and operating distance: 1) The use of additional resonant coils, placed between the transmitter and the receiver. 2) The receiver coil impedance matching. 3) The design of high-efficiency rectifiers and dc-dc converters. The effect of the additional coils in the inductive link is usually studied without considering its influence on other parts of the WPT system. In this work, we theoretically analyzed and compared 2 and 3-coil links, showing the advantages of using the additional coil together with a matching network in the receiver. The effect of the additional coils in a closed-loop regulated system is also addressed, demonstrating that the feedback-loop design should consider the number of coils used in the link. Furthermore, the inclusion of one additional resonant coil in an actual half-duplex RFID system at 134:2 kHz is presented. The maximum efficiency point can be achieved by adjusting the receiver coil load impedance in order to reach its optimum value. In inductive powering, this optimum impedance is often achieved by adapting the input impedance of a dc-dc converter in the receiver. A matching network can also be used for the same purpose, as have been analyzed in previous works. In this thesis, we propose a joint design using both, matching network and dc-dc converters, highlighting the benefits of using the combined approach. A rectifier must be included in any WPT receiver. Usually, a dc-dc converter is included after the rectifier to adjust the output voltage or control the rectifier load impedance. The efficiency of both, rectifier and dc-dc converter, impacts not only the load power but also the receiver dissipation. In applications such as AIMDs, to get the most amount of power with low dissipation is crucial to full safety requirements. We present the design of an active rectifier and a switched capacitor dc-dc converter. In low-power applications, the power consumption of any auxiliary block used in the circuit may decrease the efficiency due to its quiescent consumption. Therefore, we have carefully designed these auxiliary blocks, such as operational transconductance amplifiers and voltage comparators. The main contributions of this thesis are: . Deduction of simplified equations to compare 2 and 3-coil links with an optimized Matching Network (MN). . Development of a 3-coil link half-duplex RFID 134.2 kHz system. . Analysis of the influence of the titanium case in the inductive link of implantable medical devices. . Development of a joint design ow which exploits the advantages of using both MNs and dc-dc converters in the receiver to achieve load impedance matching. . Analysis of closed-loop postregulated systems, highlighting the effects that the additional coils, receiver resonance (series or parallel), and type of driver (voltage or current) used in the transmitter, have in the feedback control loop. . Proposal of systematic analysis and design of charge recycling switches in step-up dc-dc converters. . New architecture for low-power high slew-rate operational transconductance amplifier. Novel architecture for high-efficiency active rectifier. The thesis is essentially based on the publications [1{9]. During the PhD program, other publications were generated [10{15] that are partially or non-included in the thesis. Additionally, some contributions presented in the text, are in process of publication.Hace ya un buen tiempo que las redes inalámbricas constituyen uno de los temas de investigación más estudiados en el área de las telecomunicaciones. Actualmente un gran porcentaje de los esfuerzos de la comunidad científifica y del sector industrial están concentrados en la definición de los requerimientos y estándares de la quinta generación de redes móviles. 5G implicará la integración y adaptación de varias tecnologías, no solo del campo de las telecomunicaciones sino también de la informática y del análisis de datos, con el objetivo de lograr una red lo suficientemente flexible y escalable como para satisfacer los requerimientos para la enorme variedad de casos de uso implicados en el desarrollo de la “sociedad conectada”. Un problema que se presenta en las redes inalámbricas actuales, que por lo tanto genera un desafío más que interesante para lo que se viene, es la escasez de espectro radioeléctrico para poder asignar bandas a nuevas tecnologías y nuevos servicios. El espectro está sobreasignado a los diferentes servicios de telecomunicaciones existentes y las bandas de uso libre o no licenciadas están cada vez más saturadas de equipos que trabajan en ellas (basta pensar lo que sucede en la banda no licenciada de 2.4 GHz). Sin embargo, existen análisis y mediciones que muestran que en diversas zonas y en diversas escalas de tiempo, el espectro radioeléctrico, si bien está formalmente asignado a algún servicio, no se utiliza plenamente existiendo tiempos durante los cuales ciertas bandas están libres y potencialmente podrían ser usadas. Esto ha llevado a que las Redes Radios Cognitivas, concepto que existe desde hace un tiempo, sean consideradas uno de los pilares para el desarrollo de las redes inalámbricas del futuro. En los ultimos años la transferencia inalámbrica de energía (WPT) ha cobrado especial atención, ya que logra aumentar la robustez, usabilidad y autonomía de los dispositivos móviles. Transferir energía inalámbricamente relaja el compromiso entre el tamaño de la batería y la disponibilidad de energía, permitiendo aplicaciones que de otro modo no serían posibles. Esta tesis tiene como objetivo desarrollar técnicas novedosas para aumentar la eficiencia y la distancia de transmisión de sistemas de transferencia inalámbrica por acople inductivo (IPT). Se abordó el diseño del enlace inductivo y varios circuitos utilizados en el receptor de energía. Además, realizamos un cuidadoso análisis a nivel sistema, teniendo en cuenta el diseño conjunto de diferentes bloques. Todo el trabajo está orientado hacia el desarrollo de aplicaciones de bajo consumo, como dispositivos médicos implantables activos (AIMD) o sistemas de identificación por radio frecuencia (RFID). Se consideraron principalmente tres enfoques para lograr mayor eficienciay distancia: 1) El uso de bobinas resonantes adicionales, colocadas entre el transmisor y el receptor. 2) El uso de redes de adaptación de impedancia en el receptor. 3) El diseño de circuitos rectificdores y conversores dc-dc con alta eficiencia.El efecto ocasionado por las bobinas resonantes adicionales en el enlace inductivo es usualmente abordado sin tener en cuenta su influenciaen todas las partes del sistema. En este trabajo, analizamos teóricamente y comparamos sistemas de 2 y 3 bobinas, mostrando las ventajas que tiene la bobina adicional en conjunto con el uso de redes de adaptación. El efecto de dicha bobina, en sistemas de lazo cerrado fue también estudiado, demostrando que el diseño del lazo debe considerar el número de bobinas que utiliza el link. Se trabajó con un sistema real de RFID, analizando el uso de una bobina resonante en una aplicación práctica existente y de amplio uso en el Uruguay