Next generation RFID telemetry design for biomedical implants.

The design and development of a Radio Frequency Identification (RFID) based pressure-sensing system to increase the range of current Intra-Ocular Pressure (IOP) sensing systems is described in this dissertation. A large number of current systems use near-field inductive coupling for the transfer of energy and data, which limits the operational range to only a few centimeters and does not allow for continuous monitoring of pressure. Increasing the powering range of the telemetry system will offer the possibility of continuous monitoring since the reader can be attached to a waist belt or put on a night stand when sleeping. The system developed as part of this research operates at Ultra-High Frequencies (UHF) and makes use of the electromagnetic far field to transfer energy and data, which increases the potential range of operation and allows for the use of smaller antennas. The system uses a novel electrically small antenna (ESA) to receive the incident RF signal. A four stage Schottky circuit rectifies and multiplies the received RF signal and provides DC power to a Colpitts oscillator. The oscillator is connected to a pressure sensor and provides an output signal frequency that is proportional to the change in pressure. The system was fabricated using a mature, inexpensive process. The performance of the system compares well with current state of the art, but uses a smaller antenna and a less expensive fabrication process. The system was able to operate over the desired range of 1 m using a half-wave dipole antenna. It was possible to power the system over a range of at least 6.4 cm when the electrically small antenna was used as the receiving antenna

Design and analysis of field-powered transponders integrated in metallic objects

[no abstract

Design of Processing Circuitry for an RF Energy Harvester

Significant advancements in technology and the use of low power sensors in both commercial and industrial applications have made it essential to develop wireless solutions for low power devices. Once such solution, which has generated attention in university and R&D environments, is radio frequency (RF) energy harvesting. RF energy harvesting seeks to capture ambient RF energy by means of an antenna and convert this energy to useable DC power. The presence of ambient RF energy in the environment is a result of numerous high-frequency technologies including Wi-Fi, cell phones, microwave ovens, and radio broadcasting, as well as many others. The intention of this thesis is to design the processing circuitry necessary to convert a received RF signal into useable DC power, with the ability to charge a Lithium-Ion battery. The design presented here was performed to process an RF energy signal received from an antenna that targets both the 2.4GHz and 5GHz Wi-Fi bands. The final design consists of two bandpass filters (one for each Wi-FI band) two two-stage voltage doubler circuits (one for each Wi-Fi band), and a boost converter that is designed to achieve an output voltage of 3.2V in order to charge a Lithium-Ion battery. Testing of the RF energy harvester in an environment with ambient 2.4GHz Wi-Fi signals and a 470μF capacitor connected at the output demonstrates the circuit’s ability to harvest a measureable amount of energy. While the maximum measured voltage of 50mV does not meet the design specification of 3.2V, the circuit demonstrates proof-of-concept. Additional design improvements are necessary to make it a viable solution for charging a battery

High-throughput large-area plastic nanoelectronics

Large-area electronics (LAE) manufacturing has been a key focus of both academic and industrial research, especially within the last decade. The growing interest is born out of the possibility of adding attractive properties (flexibility, light weight or minimal thickness) at low cost to well-established technologies, such as photovoltaics, displays, sensors or enabling the realisation of emerging technologies such as wearable devices and the Internet of Things. As such there has been great progress in the development of materials specifically designed to be employed in solution processed (plastic) electronics, including organic, transparent metal oxide and nanoscale semiconductors, as well as progress in the deposition methods of these materials using low-cost high-throughput printing techniques, such as gravure printing, inkjet printing, and roll-to-roll vacuum deposition. Meanwhile, industry innovation driven by Moore’s law has pushed conventional silicon-based electronic components to the nanoscale. The processes developed for LAE must strive to reach these dimensions. Given that the complex and expensive patterning techniques employed by the semiconductor industry so far are not compatible with LAE, there is clearly a need to develop large-area high throughput nanofabrication techniques. This thesis presents progress in adhesion lithography (a-Lith), a nanogap electrode fabrication process that can be applied over large areas on arbitrary substrates. A-Lith is a self-alignment process based on the alteration of surface energies of a starting metal electrode which allows the removal of any overlap of a secondary metal electrode. Importantly, it is an inexpensive, scalable and high throughput technique, and, especially if combined with low temperature deposition of the active material, it is fundamentally compatible with large-area fabrication of nanoscale electronic devices on flexible (plastic) substrates. Herein, I present routes towards process optimisation with a focus on gap size reduction and yield maximisation. Asymmetric gaps with sizes below 10 nm and yields of > 90 % for hundreds of electrode pairs generated on a single substrate are demonstrated. These large width electrode nanogaps represent the highest aspect ratio nanogaps (up to 108) fabricated to date. As a next step, arrays of Schottky nanodiodes are fabricated by deposition of a suitable semiconductor from solution into the nanogap structures. Of principal interest is the wide bandgap transparent semiconductor, zinc oxide (ZnO). Lateral ZnO Schottky diodes show outstanding characteristics, with on-off ratios of up to 106 and forward current values up to 10 mA for obtained upon combining a-Lith with low-temperature solution processing. These unique devices are further investigated for application in rectifier circuits, and in particular for potential use in radio frequency identification (RFID) tag technology. The ZnO diodes are found to surpass the 13.56 MHz frequency bernchmark used in commercial applications and approach the ultra-high frequency (UHF) band (hundreds of megahertz), outperforming current state of the art printed diodes. Solution processed fullerene (C60) is also shown to approach the UHF band in this co-planar device configuration, highlighting the viability of a-Lith for enabling large-area flexible radio frequency nanoelectronics. Finally, resistive switching memory device arrays based on a-Lith patterned nanogap aluminium symmetric electrodes are demonstrated for the first time. These devices are based either on empty aluminium nanogap electrodes, or with the gap filled with a solution-processed semiconductor, the latter being ZnO, the semiconducting polymer poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) or carbon nanotube/polyfluorene blends. The switching mechanism, retention time and switching speed are investigated and compared with published data. The fabrication of arrays of these devices illustrates the potential of a-Lith as a simple technique for the realisation of large-area high-density memory applications.Open Acces

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

Tri-band CMOS Circuit Dedicated for Ambient RF Energy Harvesting

RÉSUMÉ L'utilisation de systèmes sans fil connait une croissance rapide dans divers domaines tels que les réseaux de téléphonie cellulaire, Wi-Fi, Wi-Max, la radiodiffusion et les communications par satellite. Cette croissance mènera à une quantité considérable d'énergie électromagnétique générée dans l'air ambiant, mais toujours en dessous des limites de sécurité internationales. Ainsi, la recherche au niveau des systèmes de récupération d'énergie RF pour alimenter des appareils électroniques miniaturisés à faible consommation de puissance devient attrayante et prometteuse. Le bloc principal dans un système de récupération d'énergie RF est le redresseur qui détermine l'efficacité et la sensibilité de l'ensemble du système. Étant donné que la puissance RF ambiante est très faible, la quantité d'énergie captée par l'antenne l’est également. En outre, il y a des pertes au niveau du réseau d'adaptation d’impédance qui réduisent encore plus la puissance transmise au bloc redresseur. Par conséquent, la puissance disponible est trop faible pour faire fonctionner des redresseurs classiques. Dans ce mémoire, nous proposons trois redresseurs à trois-étages et à grilles totalement croisées-couplées en utilisant des transistors à faible tension de seuil afin d’opérer à de faibles puissances d'entrée. Les trois redresseurs ont été conçus et intégrés au sein d’une même puce fabriquée en utilisant une technologie CMOS 130nm d’IBM. Ils ont été optimisés à des fréquences de 880MHz, 1960MHz et 2.45GHz respectivement. Les résultats expérimentaux démontrent qu’ils atteignent une efficacité de conversion de puissance maximale de 62%, 62% et 56.2% respectivement. Les mesures montrent également une grande amélioration de l'efficacité à de faibles niveaux de puissance d'entrée. Afin de récupérer l'énergie ambiante de trois principales sources RF au Canada – GSM-850, GSM-1900 et Wi-Fi, un système de redresseur utilisé pour la combinaison de la puissance de ces trois canaux est simulé et analysé. Le système utilise une topologie consistant simplement à connecter les sorties des redresseurs ensemble pour charger le condensateur de charge. En dépit de la grande amélioration de l'efficacité et de la sensibilité dans la plage de 0-5μW, une baisse d'efficacité indésirable se produit aux puissances plus élevées. Ainsi, un nouveau bloc de gestion de l'alimentation est proposé. De plus, une antenne tri-bande est conçue et simulée pour diminuer le volume de l'ensemble du système de récupération d'énergie RF. En particulier, les pertes par réflexion obtenues sont de -25.43dB, -13.92dB et -12.73dB aux fréquences citées plus haut respectivement.---------- ABSTRACT Nowadays, the use of wireless systems has grown rapidly in various domains such as cellular phone networks, Wi-Fi, Wi-Max, radio broadcasting and satellite communications. The growing use of these wireless systems leads to considerable amount of electromagnetic energy generated in ambient air (of course, still below international safety limits). Thus the research in ambient RF energy harvesting system dedicated for powering up low-power-consumption miniaturized electronic devices becomes attractive and promising. The main block in a RF harvesting system is the rectifier which determines the efficiency and sensitivity of the whole system. Since ambient RF power is very low, the amount of power captured by the antenna is extremely low. Besides, there is loss on matching networks, thus the available power given to the rectifier block is too low for traditional rectifiers to operate. Therefore, in this master thesis, three three-stage fully gate cross-coupled rectifiers using low-thresholdvoltage transistors are proposed to overcome the dead zone in low input power range. The three rectifiers optimized at 880MHz, 1960MHz and 2.45GHz frequencies respectively are designed on one chip layout. Their experimental results are retrieved from this custom fabricated integrated circuit using IBM 130nm CMOS technology. They achieve peak efficiencies of 62%, 62% and 56.2% respectively and show great improvements on power conversion efficiency at low input power level. In order to harvest ambient RF energy from the three main RF contributors in Canada – GSM-850, GSM-1900 and Wi-Fi 2.4GHz, a rectifier system used for power combination from these three channels is simulated and analyzed. The system employs a simple topology by connecting the outputs together to charge the load capacitor. In spite of its high improvements on efficiency and sensitivity in 0-5μW range, an undesirable efficiency drop happens at higher input power levels. Thus an idea of power management block is proposed. In addition, a tri-band antenna is designed and simulated so as to decrease the volume of the overall RF energy harvesting system. It achieves return loss of -25.43dB, -13.92dB and - 12.73dB at each desired band respectively

Energy Harvesting for Self-Powered Wireless Sensors

A wireless sensor system is proposed for a targeted deployment in civil infrastructures (namely bridges) to help mitigate the growing problem of deterioration of civil infrastructures. The sensor motes are self-powered via a novel magnetic shape memory alloy (MSMA) energy harvesting material and a low-frequency, low-power rectifier multiplier (RM). Experimental characterizations of the MSMA device and the RM are presented. A study on practical implementation of a strain gauge sensor and its application in the proposed sensor system are undertaken and a low-power successive approximation register analog-to-digital converter (SAR ADC) is presented. The SAR ADC was fabricated and laboratory characterizations show the proposed low-voltage topology is a viable candidate for deployment in the proposed sensor system. Additionally, a wireless transmitter is proposed to transmit the SAR ADC output using on-off keying (OOK) modulation with an impulse radio ultra-wideband (IR-UWB) transmitter (TX). The RM and SAR ADC were fabricated in ON 0.5 micrometer CMOS process. An alternative transmitter architecture is also presented for use in the 3-10GHz UWB band. Unlike the IR-UWB TX described for the proposed wireless sensor system, the presented transmitter is designed to transfer large amounts of information with little concern for power consumption. This second method of data transmission divides the 3-10GHz spectrum into 528MHz sub-bands and "hops" between these sub-bands during data transmission. The data is sent over these multiple channels for short distances (?3-10m) at data rates over a few hundred million bits per second (Mbps). An UWB TX is presented for implementation in mode-I (3.1-4.6GHz) UWB which utilizes multi-band orthogonal frequency division multiplexing (MB-OFDM) to encode the information. The TX was designed and fabricated using UMC 0.13 micrometer CMOS technology. Measurement results and theoretical system level budgeting are presented for the proposed UWB TX

UHF Energy Harvesting and Power Management

As we are entering the era of Internet of Things (i.e. IoT), the physical devices become increasingly connected with each other than ever before. The connection between devices is achieved through wireless communication schemes, which unfortunately consume a significant amount of energy. This is undesirable for devices which are not directly connected to power. This is because these devices will essentially carry batteries to supply the needed energy for these operations and the batteries will eventually be depleted. This motivates the need to operate these devices off harvested energy. UHF energy harvesting, as an enabling technology for the UHF RFID, stands out amongst other energy harvesting approaches as it does not heavily rely on the natural surrounding environment and also offers a very good wireless operating range from its radiating energy source. Unlike the RFID, the power consumption and the operational range requirement of these IoT devices can vary significantly. Thus, the design of the RF energy harvesting front-end and the power management need to be re-thought for specific applications. To that end, in this thesis, discussions mainly evolve around the design of UHF energy harvesters and their associated power management units using lower power analog approaches. First, we present the background of the low power UHF energy harvesting, specially threshold-compensated rectifiers will be presented as a key technology in this area and this will be used as a build practical harvester for the UHF RFID application. Secondly, key issues with the threshold compensation will be identified and this is exploited either (i) to improve the dynamic power conversion efficiency of the harvester, (ii) to improve dynamic settling behaviour of the harvester. To exploit the ”left-over” harvested energy, an intelligent integrated power management solution has been proposed. Finally, the charge-burst approach is exploited to implement an energy harvester with -40 dBm input power sensitivity.Thesis (Ph.D.) -- University of Adelaide, School of Electrical & Electronic Engineering, 201

A self-powered single-chip wireless sensor platform

Internet of things” require a large array of low-cost sensor nodes, wireless connectivity, low power operation and system intelligence. On the other hand, wireless biomedical implants demand additional specifications including small form factor, a choice of wireless operating frequencies within the window for minimum tissue loss and bio-compatibility This thesis describes a low power and low-cost internet of things system suitable for implant applications that is implemented in its entirety on a single standard CMOS chip with an area smaller than 0.5 mm2. The chip includes integrated sensors, ultra-low-power transceivers, and additional interface and digital control electronics while it does not require a battery or complex packaging schemes. It is powered through electromagnetic (EM) radiation using its on-chip miniature antenna that also assists with transmit and receive functions. The chip can operate at a short distance (a few centimeters) from an EM source that also serves as its wireless link. Design methodology, system simulation and optimization and early measurement results are presented