Non-linear shunt regulator based on a PWM RF power detector for RFID applications

Radio Frequency Identification (RFID) is utilized in a variety of applications, includ ing tagging animals and objects to make their identification (ID) easier to read and man age, similar to a bar code or QR code. In this regard, the goal of this research is to improve RFID transponder power regulation in order to increase reader distance. This thesis de scribes a non-linear shunt regulator that employs a Radio Frequency (RF) power detector based on the Pulse Width Modulation (PWM) technique to aim magnetically coupled RFID transponders. A quick voltage-clamp loop and a slow-accurate power detector loop are used in the proposed regulator architecture. The first loop ensures over-voltage pro tection, while the second loop gradually corrects the first loop’s imprecision based on the measured input power. To contextualize the issues and improvements of the new design, the state-of-the-art in RFID power management and RF power detector are covered first. The new architecture is specified after theoretical development, electrical simulations, and the design of the new architecture is implemented. The entire regulator design was prototyped as part of a commercial low-frequency (134 kHz) RFID transponder in a 180 nm CMOS process. The regulator deal with a sinusoidal voltage at its input generated by the LC tank that extracts energy from the reader to supply its circuitry. The use of a 3.3V standard process for the analog circuitry in order to decrease the fabrication cost by not using the high voltage module (5 V for example) complicates the system design. Even though the proposed solution aims to regulate the input voltage precisely at 3.6 V maximum, the maximum voltage supported by 3.3 V standard module using two feedback is achieved. The total RFID transponder area of 870x870 µm² was obtained, with 130x230 µm² related to the regulator circuit area only. Both resonant and supply capacitors are imple mented on the chip. The complete system consumes a maximum current of 4.5 µA, over a wide RF input power range that is modulated by the distance between the reader and the transponder. As the power detector corrects the imprecision of the shunt regulator com posed by simple diodes due to its process, voltage and temperature (PVT), the transponder performance was measured with and without the shunt regulator enabled. Results show an improvement of 16.7 % in the communication distance between the transponder and the reader.Identificação por Rádio Frequência (RFID) é usada em muitas aplicações, colocando etiquetas eletrônicas em animais e objetos para facilitar a leitura a fim de melhorar o gerenciamento destes. Nesse contexto, essa dissertação tem como objetivo melhorar a regulação de potência em chips de RFID a fim de aumentar a distância de leitura. Essa dissertação apresenta um nova arquitetura de regulador paralelo, não linear, que usa um detector de potência de Rádio Frequência (RF) baseado em uma técnica de modulação de pulso (PWM) para aplicação de RFID que usam o princípio de comunicação por acopla mento magnético. A arquitetura de regulador proposto é composta de duas realimen tações: uma realimentação usa um limitador de tensão rápido e a outra usa um detector de potência lento porém preciso. O primeiro garante a proteção contra sobre tensão e o segundo corrige a imprecisão do primeiro de acordo com a potência do sinal de entrada. Primeiramente, o estado da arte em regulação de sitemas de RFID bem como em detectores de potência RF são feitos para contextualizar os problemas e melhorias da nova arquitetura. Um desenvolvimento teórico seguido por simulações elétricas e o projeto do circuito da nova arquitetura de regulador paralelo são abordadas em detalhes. A circuito foi implementado em um processo CMOS de 180 nm como parte de um Chip de RFID de baixa frequência (134 kHz). O regulador lida com uma tensão senoidal (134 kHz) na sua entrada, gerada por um tanque LC que extrai energia provinda do leitor e que é usada alimentar todo o chip. Devido ao uso de um processo padrão 3.3 V CMOS para implementação do circuitos analógicos a fim de diminuir o custo de fabricação com o não uso do modulo de alta tensão (Ex. 5 V), impondo dificuldades no projeto do sistema, mesmo assim a solução proposta regula a tensão de entrada do chip em 3.6 V, máxima suportada pela tecnologia, com o uso das duas malhas de realimentação. A área total do Chip de RFID é de 870x870 µm², com 130x230 µm² para apenas o circuito de regulação. Os capacitores de ressonância e de alimentação foram integrados no Chip. O sistema completo consome 4.5 µA, sobre uma ampla gama de potência de entrada que é modulada pela distância entre o leitor e a tag. Como o detector de potência corrige a imprecisão do limitador de tensão composto de diodos devido a variação em processo, tensão e temperatura (PVT), a distância de leitura foi medida com e sem o detector de potência habilitado. Os resultados mostraram uma melhoria de 16.7 % na distância de comunicação

Energy-Detecting Receivers for Wake-Up Radio Applications

In the energy-limited wireless sensor node applications, wake-up radios are required to reduce the average power consumption of the node. Energy-detecting receivers are the best fit for such low power operations. This thesis presents the energy-detecting receiver design; challenges; techniques to enhance sensitivity, selectivity; and multi-access operation. Self-mixers instead of the conventional envelope detectors are proposed and proved to be optimal for signal detection. A fully integrated wake-up receiver uses the self-mixer and time-encoded baseband signal processing to provide a sensitivity of -79.1dBm at 434MHz with 420pW of power, providing an 8dB better sensitivity at 10dB lower power consumption compared to the SoA. A novel approach using narrowband interferers as local oscillators will be presented to further enhance sensitivity and selectivity, effectively operating the energy-detector receiver as a direct down-conversion receiver. Additionally, a clockless continuous-time analog correlator will be introduced to enhance the selectivity to wide-band AM interferers. The architecture uses pulse-position-encoded analog signal processing with VCOs as integrators and pulse-controlled relaxation delays; it operates as a code-domain matched filter to de-spread asynchronous wake-up codes. This code-domain matched filtering also provides code-division multiple access (CDMA) for simultaneous wakeups. Additional enhancement in the link can be achieved using directional antennas, providing spatial gain and selectivity. Certain applications can leverage a nearby reflector similar to a Yagi antenna to enhance the directivity. A low power directional backscatter tag is proposed, it uses multiple antennas acting as a reflectarray by configuring constant phase gradients depending on the direction of arrival (DoA) of the signal. Thus, instead of harvesting energy, the same energy and the surrounding environment can be leveraged to enhance functionality (e.g. interferer as LO, using a backscatter tag on a wall) for low power operation. Innovations spanning both system and circuit architectures that leverage the ambient energy and environment to enable power-efficient solutions for next-generation wake-up radios are presented in this work

Design And Implementation Of An X-Band Passive Rfid Tag

This research presents a novel fully integrated energy harvester, matching network, matching network,matching network, matching network,matching network, matching network, matching network, multi-stage RF-DC rectifier, mode selector, RC oscillator, LC oscillator, and X-band power amplifier implemented in IBM 0.18-µm RF CMOS technology. We investigated different matching schemes, antennas, and rectifiers with focus on the interaction between building blocks. Currently the power amplifier gives the maximum output power of 5.23 dBm at 9.1GHz. The entire RFID tag circuit was designed to operate in low power consumption. Voltage sensor circuit which generates the enable signal was designed to operate in very low current. All the test blocks of the RFID tag were tested. The smaller size and the cost of the RFID tag are critical for widespread adoption of the technology. The cost of the RFID tag can be lowered by implementing an on-chip antenna. We were able to develop, fabricate, and implement a fully integrated RFID tag in a smaller size (3 mm X 1.5 mm) than the existing tags. With further modifications, this could be used as a commercial low cost RFID tag

MR4RF: MEM-device with impedance and their usage with impedance matching networks for passive RFID tags in the UHF

The passive RFID tag in the UHF has been employed in several different applications including, tracking, logistics, and as a sensing platform for the Internet of things (IoT). The tag is ideal for this industry due to its unique design. It harvests all of its energy from the environment, and is small, cheap, and requires little to no maintenance. However, there are two major issues limiting the potential of the passive RFID systems: the limited power harvested by the tag, and the high susceptibility to interference and coupling. In particular, dynamic environments render the traditionally fixed, RF impedance matching network ineffective. A novel design for a flexible Impedance-Switching Network (ISN) for passive RFID tags in the UHF is presented in this thesis. This novel approach can maximize power harvested by the tag. We propose two approaches to implementing the ISN. First, a more traditional design with a series of varactors is developed and studied. Each varactor is placed in parallel impedance lanes that are controlled via a feedback loop to maximize harvested power. A four-lane ISN is designed, tested, and tuned. The simulations and experiments demonstrate that ISN is capable of compensating for negative effect of mutual coupling in a ferromagnetic-reach environment. The second design employs a new material called a memristive switch that can replace the varactors in the ISN. State of a memristive switch is non-volatile and requires little energy to operate, thus making it ideal for passive RFID tags. We are the first to characterize the Co3O4 based memristive switch in UHF range. The results show that it can be employed as a varying capacitor in the RF front-end design. We propose three general configurations for the ISNs --Abstract, page iii

An Ultra-Low-Power RFID/NFC Frontend IC Using 0.18 μm CMOS Technology for Passive Tag Applications

Battery-less passive sensor tags based on RFID or NFC technology have achieved much popularity in recent times. Passive tags are widely used for various applications like inventory control or in biotelemetry. In this paper, we present a new RFID/NFC frontend IC (integrated circuit) for 13.56 MHz passive tag applications. The design of the frontend IC is compatible with the standard ISO 15693/NFC 5. The paper discusses the analog design part in details with a brief overview of the digital interface and some of the critical measured parameters. A novel approach is adopted for the demodulator design, to demodulate the 10% ASK (amplitude shift keying) signal. The demodulator circuit consists of a comparator designed with a preset offset voltage. The comparator circuit design is discussed in detail. The power consumption of the bandgap reference circuit is used as the load for the envelope detection of the ASK modulated signal. The sub-threshold operation and low-supply-voltage are used extensively in the analog design—to keep the power consumption low. The IC was fabricated using 0.18 μ m CMOS technology in a die area of 1.5 mm × 1.5 mm and an effective area of 0.7 m m 2 . The minimum supply voltage desired is 1.2 V, for which the total power consumption is 107 μ W. The analog part of the design consumes only 36 μ W, which is low in comparison to other contemporary passive tags ICs. Eventually, a passive tag is developed using the frontend IC, a microcontroller, a temperature and a pressure sensor. A smart NFC device is used to readout the sensor data from the tag employing an Android-based application software. The measurement results demonstrate the full passive operational capability. The IC is suitable for low-power and low-cost industrial or biomedical battery-less sensor applications. A figure-of-merit (FOM) is proposed in this paper which is taken as a reference for comparison with other related state-of-the-art researches

セキュアRFIDタグチップの設計論

In this thesis, we focus on radio frequency identification (RFID) tag. We design, implement, and evaluate hardware performance of a secure tag that runs the authentication protocol based on cryptographic algorithms. The cryptographic algorithm and the pseudorandom number generator are required to be implemented in the tag. To realize the secure tag, we tackle the following four steps: (A) decision of hardware architecture for the authentication protocol, (B) selection of the cryptographic algorithm, (C) establishment of a pseudorandom number generating method, and (D) implementation and performance evaluation of a silicon chip on an RFID system.(A) The cryptographic algorithm and the pseudorandom number generator are repeatedly called for each authentication. Therefore, the impact of the time needed for the cryptographic processes on the hardware performance of the tag can be large. While low-area requirements have been mainly discussed in the previous studies, it is needed to discuss the hardware architecture for the authentication protocol from the viewpoint of the operating time. In this thesis, in order to decide the hardware architecture, we evaluate hardware performance in the sense of the operating time. As a result, the parallel architecture is suitable for hash functions that are widely used for tag authentication protocols.(B) A lot of cryptographic algorithms have been developed and hardware performance of the algorithms have been evaluated on different conditions. However, as the evaluation results depend on the conditions, it is hard to compare the previous results. In addition, the interface of the cryptographic circuits has not been paid attention. In this thesis, in order to select a cryptographic algorithm, we design the interface of the cryptographic circuits to meet with the tag, and evaluate hardware performance of the circuits on the same condition. As a result, the lightweight hash function SPONGENT-160 achieves well-balanced hardware performance.(C) Implementation of a pseudorandom number generator based on the performance evaluation results on (B) can be a method to generate pseudorandom number on the tag. On the other hand, as the cryptographic algorithm and the pseudorandom number generator are not used simultaneously on the authentication protocol. Therefore, if the cryptographic circuit could be used for pseudorandom number generation, the hardware resource on the tag can be exploited efficiently. In this thesis, we propose a pseudorandom number generating method using a hash function that is a cryptographic component of the authentication protocol. Through the evaluation of our proposed method, we establish a lightweight pseudorandom number generating method for the tag.(D) Tag authentication protocols using a cryptographic algorithm have been developed in the previous studies. However, hardware implementation and performance evaluation of a tag, which runs authentication processes, have not been studied. In this thesis, we design and do a single chip implementation of an analog front-end block and a digital processing block including the results on (A), (B), and (C). Then, we evaluate hardware performance of the tag. As a result, we show that a tag, which runs the authentication protocol based on cryptographic algorithms, is feasible.電気通信大学201

Energy Management in RFID-Sensor Networks: Taxonomy and Challenges

Ubiquitous Computing is foreseen to play an important role for data production and network connectivity in the coming decades. The Internet of Things (IoT) research which has the capability to encapsulate identification potential and sensing capabilities, strives towards the objective of developing seamless, interoperable and securely integrated systems which can be achieved by connecting the Internet with computing devices. This gives way for the evolution of wireless energy harvesting and power transmission using computing devices. Radio Frequency (RF) based Energy Management (EM) has become the backbone for providing energy to wireless integrated systems. The two main techniques for EM in RFID Sensor Networks (RSN) are Energy Harvesting (EH) and Energy Transfer (ET). These techniques enable the dynamic energy level maintenance and optimisation as well as ensuring reliable communication which adheres to the goal of increased network performance and lifetime. In this paper, we present an overview of RSN, its types of integration and relative applications. We then provide the state-of-the-art EM techniques and strategies for RSN from August 2009 till date, thereby reviewing the existing EH and ET mechanisms designed for RSN. The taxonomy on various challenges for EM in RSN has also been articulated for open research directives

Design And Implementation Of Motion Sensitive UHF RFID System

Radio Frequency Identification (RFID) is a method of remotely storing and retrieving data using devices called RFID tags. RFID system components comprise of RFID tag and RFID reader. The RFID tag stores a unique identification of the object that is attached to it. However, it does not provide information about the conditions of the object that it detects. Sensor node in Wireless Sensor Network (WSN), on the other hand, provides information about the condition of the object and its environment. Therefore, with the integration of RFID and WSN technology, their disadvantages can be overcome and their advantages can be put into some important applications

Wireless sensor system for infrastructure health monitoring

In this thesis, radio frequency identification (RFID)-based wireless sensor system for infrastructure health monitoring (IHM) is designed and developed. It includes mountable semi-passive tag antenna integrated sensors capable of measuring critical responses of infrastructure such as dynamic acceleration and strain. Furthermore, the system is capable of measuring structural displacement. One of the most important parts of this system is the relatively small, tunable, construction material mountable RFID tag antenna. The tag antenna is electronically integrated with the sensors. Leading to the process of developing tag antenna integrated sensors having satisfactory wireless performance (sensitivity and read range) when mounted on concrete and metal structural members, the electromagnetic performance of the tag antenna is analyzed and optimized using both numerical and experimental procedures. Subsequently, it is shown that both the simulation and the experimental measurement results are in good agreement. The semi-passive RFID-based system is implemented in a wireless IHM system with multiple sensor points to measure dynamic acceleration and strain. The developed system can determine the natural frequencies of infrastructure and identify any state changes of infrastructure by measuring natural frequency shifts. Enhancement of the spectral bandwidth of the system has been performed under the constraints of the RFID hardware. The influence of the orientation and shape of the structural members on wireless power flow in the vicinity of those members is also investigated with the RFID reader-tag antenna system in both simulation and experiments. The antenna system simulations with a full-scale structural member have shown that both the orientation and the shape of the structural member influence the wireless power flow towards and in the vicinity of the member, respectively. The measurement results of the conducted laboratory experiments using the RFID antenna system in passive mode have shown good agreement with simulation results. Furthermore, the system’s ability to measure structural displacement is also investigated by conducting phase angle of arrival measurements. It is shown that the system in its passive mode is capable of measuring small structural displacements within a short wireless distance. The benchmarking of the developed system with independent, commercial, wired and wireless measurement systems has confirmed the ability of the RFID-based system to measure dynamic acceleration and strain. Furthermore, it has confirmed the system’s ability to determine the natural frequency of an infrastructure accurately. Therefore, the developed system with wireless sensors that do not consume battery power in data transmission and with the capability of dynamic response measurement is highly applicable in IHM

Radio frequency system for remote fish monitoring in aquaculture

Dissertação de mestrado, Engenharia Electrónica e Telecomunicações, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2017Stress is a factor that influences fish welfare. Some physiological and behavioral stress responses, such as the increase of cortisol release and heart rate, are triggered in fish and can show the severity of stress in fish. The objective of our work is to develop a system to monitor a device placed in free-swimming fish. The device has one or multiple sensors that measures parameters related with the stress or health state of the fish. The data recorded by the sensor is transmitted to a base station. Data transmission uses radio-frequency identification (RFID) technology. The tag is battery-less and receives the energy from the magnetic field provided by the base station. The system is low-cost, reliable and provides long-term monitoring. The project has been defined to use a commercial system operating at 134.2 kHz from Texas InstrumentsTM. The work carried out involved the optimization of the maximum distance between the tag and reader antenna to maintain a reliable communication. The maximum distance is defined as read range. The optimization of the read range is a crucial point on this thesis because radio waves are strongly attenuated underwater. The read range is influenced by the reader power, antennas size, antennas orientation as well as the presence of the metal in the antennas proximity. These aspects were studied in detail in this thesis. Measurements of the read range of the system were performed for a system with one reader antenna (single-antenna system) and a system with two reader antennas (multi-antenna system). For a multi-antenna system, we successfully covered the volume of a water tank with 70 cm length, 30 cm height and 40 cm width.A produção de peixes em aquacultura tem vindo a crescer exponencialmente. Atualmente, aproximadamente 50% do peixe consumido é produzido mundialmente em aquacultura. Com o objetivo de maximizar o rendimento de produção de peixe, são usadas densidades populacionais relativamente elevadas em espaços confinados. As condições de produção de peixe obrigam a ter um conjunto de preocupações com a saúde e bem-estar dos peixes por razões económicas e éticas. Em ambientes de aquacultura, é importante medir parâmetros que possam indiciar o desenvolvimento de alterações no estado de saúde dos peixes, sendo crucial para tomar medidas preventivas e impedir a propagação de doenças. Um dos indicadores mais relevantes que afeta a saúde do peixe é o stress. Quando submetidos a um stress prolongado, os peixes acabam por ficar suscetíveis a doenças, que se podem propagar rapidamente por toda a população com consequências catastróficas. É possível avaliar se um peixe está em estado de stress através de um conjunto de alterações fisiológicas e comportamentais, como por exemplo o aumento da hormona cortisol no sangue ou o aumento do batimento cardíaco. O objetivo do nosso projeto é desenvolver um sistema de monitorização capaz de detetar, em tempo real, as alterações fisiológicas ou comportamentais indicadoras de stress. O sistema implementado é constituído por um sensor ou vários sensores colocados no peixe a nadar livremente no tanque. Os dados recolhidos são então enviados por um sistema de transmissão de dados sem fios, através de ondas rádio, para uma estação base onde ocorre a monitorização dos dados. O consórcio onde foi realizado o nosso projeto (AquaExcell 2020) definiu que o sistema teria de ser um sistema comercial de identificação por rádio frequência (RFID) a funcionar a 134.2 kHz. Os sistemas RFID são usados vulgarmente na identificação e leitura de etiquetas de identificação eletrónica em animais ou objetos. O sistema RFID utilizado é um sistema passivo, em que a etiqueta eletrónica colocada no peixe não tem uma bateria. A energia que a etiqueta precisa é obtida através do sinal que é enviado pela antena do leitor. É um sistema de baixo custo, confiável e com um tempo de vida relativamente longo (duração de meses). Foi construído um sistema RFID a funcionar à frequência de 134.2 kHz usando equipamento comercial da Texas InstrumentsTM. O trabalho envolveu a otimização da distância máxima entre a etiqueta e a antena do leitor que permite obter leituras de forma confiável. Define-se a distância máxima como alcance de leitura. O alcance de leitura do sistema é um aspeto crucial porque as ondas eletromagnéticas são fortemente atenuadas pela água, que depende da frequência do sistema e da condutividade do meio. Tipicamente, um sistema a funcionar a 134.2 kHz tem um alcance inferior a um metro. O alcance de leitura do sistema depende do tipo de antenas usadas quer para a etiqueta quer para o leitor, da disposição espacial das antenas, do número de antenas e da forma como estas antenas são ligadas (em paralelo, em série, etc.). A presença de interferências externas (metais na proximidade das antenas) também condicionam o alcance. Foram realizadas experiências quer usando uma antena, quer usando duas antenas de leitura. Usando duas antenas, foi possível fazer uma monitorização em todo o volume de um tanque de água salgada de 70 cm de comprimento, 30 cm de altura e 40 cm de largura