Inductively Coupled CMOS Power Receiver For Embedded Microsensors

Inductively coupled power transfer can extend the lifetime of embedded microsensors that save costs, energy, and lives. To expand the microsensors' functionality, the transferred power needs to be maximized. Plus, the power receiver needs to handle wide coupling variations in real applications. Therefore, the objective of this research is to design a power receiver that outputs the highest power for the widest coupling range. This research proposes a switched resonant half-bridge power stage that adjusts both energy transfer frequency and duration so the output power is maximally high. A maximum power point (MPP) theory is also developed to predict the optimal settings of the power stage with 98.6% accuracy. Finally, this research addresses the system integration challenges such as synchronization and over-voltage protection. The fabricated self-synchronized prototype outputs up to 89% of the available power across 0.067%~7.9% coupling range. The output power (in percentage of available power) and coupling range are 1.3× and 13× higher than the comparable state of the arts.Ph.D

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

A Three – tier bio-implantable sensor monitoring and communications platform

One major hindrance to the advent of novel bio-implantable sensor technologies is the need for a reliable power source and data communications platform capable of continuously, remotely, and wirelessly monitoring deeply implantable biomedical devices. This research proposes the feasibility and potential of combining well established, ‘human-friendly' inductive and ultrasonic technologies to produce a proof-of-concept, generic, multi-tier power transfer and data communication platform suitable for low-power, periodically-activated implantable analogue bio-sensors. In the inductive sub-system presented, 5 W of power is transferred across a 10 mm gap between a single pair of 39 mm (primary) and 33 mm (secondary) circular printed spiral coils (PSCs). These are printed using an 8000 dpi resolution photoplotter and fabricated on PCB by wet-etching, to the maximum permissible density. Our ultrasonic sub-system, consisting of a single pair of Pz21 (transmitter) and Pz26 (receiver) piezoelectric PZT ceramic discs driven by low-frequency, radial/planar excitation (-31 mode), without acoustic matching layers, is also reported here for the first time. The discs are characterised by propagation tank test and directly driven by the inductively coupled power to deliver 29 μW to a receiver (implant) employing a low voltage start-up IC positioned 70 mm deep within a homogeneous liquid phantom. No batteries are used. The deep implant is thus intermittently powered every 800 ms to charge a capacitor which enables its microcontroller, operating with a 500 kHz clock, to transmit a single nibble (4 bits) of digitized sensed data over a period of ~18 ms from deep within the phantom, to the outside world. A power transfer efficiency of 83% using our prototype CMOS logic-gate IC driver is reported for the inductively coupled part of the system. Overall prototype system power consumption is 2.3 W with a total power transfer efficiency of 1% achieved across the tiers

Interface Circuits for Microsensor Integrated Systems

ca. 200 words; this text will present the book in all promotional forms (e.g. flyers). Please describe the book in straightforward and consumer-friendly terms. [Recent advances in sensing technologies, especially those for Microsensor Integrated Systems, have led to several new commercial applications. Among these, low voltage and low power circuit architectures have gained growing attention, being suitable for portable long battery life devices. The aim is to improve the performances of actual interface circuits and systems, both in terms of voltage mode and current mode, in order to overcome the potential problems due to technology scaling and different technology integrations. Related problems, especially those concerning parasitics, lead to a severe interface design attention, especially concerning the analog front-end and novel and smart architecture must be explored and tested, both at simulation and prototype level. Moreover, the growing demand for autonomous systems gets even harder the interface design due to the need of energy-aware cost-effective circuit interfaces integrating, where possible, energy harvesting solutions. The objective of this Special Issue is to explore the potential solutions to overcome actual limitations in sensor interface circuits and systems, especially those for low voltage and low power Microsensor Integrated Systems. The present Special Issue aims to present and highlight the advances and the latest novel and emergent results on this topic, showing best practices, implementations and applications. The Guest Editors invite to submit original research contributions dealing with sensor interfacing related to this specific topic. Additionally, application oriented and review papers are encouraged.

Doctor of Philosophy

dissertationSince the late 1950s, scientists have been working toward realizing implantable devices that would directly monitor or even control the human body's internal activities. Sophisticated microsystems are used to improve our understanding of internal biological processes in animals and humans. The diversity of biomedical research dictates that microsystems must be developed and customized specifically for each new application. For advanced long-term experiments, a custom designed system-on-chip (SoC) is usually necessary to meet desired specifications. Custom SoCs, however, are often prohibitively expensive, preventing many new ideas from being explored. In this work, we have identified a set of sensors that are frequently used in biomedical research and developed a single-chip integrated microsystem that offers the most commonly used sensor interfaces, high computational power, and which requires minimum external components to operate. Included peripherals can also drive chemical reactions by setting the appropriate voltages or currents across electrodes. The SoC is highly modular and well suited for prototyping in and ex vivo experimental devices. The system runs from a primary or secondary battery that can be recharged via two inductively coupled coils. The SoC includes a 16-bit microprocessor with 32 kB of on chip SRAM. The digital core consumes 350 μW at 10 MHz and is capable of running at frequencies up to 200 MHz. The integrated microsystem has been fabricated in a 65 nm CMOS technology and the silicon has been fully tested. Integrated peripherals include two sigma-delta analog-to-digital converters, two 10-bit digital-to-analog converters, and a sleep mode timer. The system also includes a wireless ultra-wideband (UWB) transmitter. The fullydigital transmitter implementation occupies 68 x 68 μm2 of silicon area, consumes 0.72 μW static power, and achieves an energy efficiency of 19 pJ/pulse at 200 MHz pulse repetition frequency. An investigation of the suitability of the UWB technology for neural recording systems is also presented. Experimental data capturing the UWB signal transmission through an animal head are presented and a statistical model for large-scale signal fading is developed

Remote Powering and Communication of Implantable Biosensors Through Inductive Link

Nowadays there is an increasing interest in the field of implantable biosensors. The possibility of real-time monitoring of the human body from inside paves the way to a large number of applications and offers wide opportunities for the future. Within this scenario, the i-IronIC project aims to develop an implantable, low cost, health-care device for real-time monitoring of human metabolites. The contribution of this research work to the i-IronIC project consists of the design and realization of a complete platform to provide power, data communication and remote control to the implantable biosensor. High wearability of the transmitting unit, low invasivity of the implanted electronics, integration of the power management module within the sensor, and a reliable communication protocol with portable devices are the key points of this platform. The power is transmitted to the implanted sensor by exploiting an inductive link. Simulations have been performed to check the effects of several variables on the link performance. These simulations have finally confirmed the possibility to operate in the low megahertz range, where tissue absorption is minimum, even if a miniaturized receiving inductor is used. A wearable patch has been designed to transmit power through the body tissues by driving an external inductor. The same inductive link is used to achieve bidirectional data communication with the implanted device. The patch, named IronIC, is powered by lithium-ion polymer batteries and can be remotely controlled by means of a dedicated Android application running on smartphones and tablets. Long-range communication between the patch and portable devices is performed by means of Bluetooth protocol. Different typologies of receiving inductors have been designed to minimize the size of the implantable device and reduce the discomfort of the patience. Multi-layer, printed spiral inductors and microfabricated spiral inductors have been designed, fabricated and tested. Both the approaches involve a sensibly smaller size, as compared to classic “pancake” inductors used for remote powering. Furthermore, the second solution enables the realization of the receiving inductor directly on the silicon substrate hosting the sensor, thus involving a further miniaturization of the implanted device. An integrated power module has been designed and fabricated in 0.18 μm CMOS technology to perform power management and data communication with the external patch. The circuit, to be merged with the sensor readout circuit, consists of an half-wave voltage rectifier, a low-dropout regulator, an amplitude demodulator and a load modulator. The module receives the power from the implanted inductor and provides a stable voltage to the sensor readout circuit. Finally, the amplitude demodulator and the load modulator enable short-range communication with the patch

Enabling Deep Intelligence on Embedded Systems

As deep learning for resource-constrained systems become more popular, we see an increased number of intelligent embedded systems such as IoT devices, robots, autonomous vehicles, and the plethora of portable, wearable, and mobile devices that are feature-packed with a wide variety of machine learning tasks. However, the performance of DNNs (deep neural networks) running on an embedded system is significantly limited by the platform's CPU, memory, and battery-size; and their scope is limited to simplistic inference tasks only. This dissertation proposes on-device deep learning algorithms and supporting hardware designs, enabling embedded systems to efficiently perform deep intelligent tasks (i.e., deep neural networks) that are high-memory-footprint, compute-intensive, and energy-hungry beyond their limited computing resources. We name such on-device deep intelligence on embedded systems as Embedded Deep Intelligence. Specifically, we introduce resource-aware learning strategies devised to overcome the four fundamental constraints of embedded systems imposed on the way towards Embedded Deep Intelligence, i.e., in-memory multitask learning via introducing the concept of Neural Weight Virtualization, adaptive real-time learning via introducing the concept of SubFlow, opportunistic accelerated learning via introducing the concept of Neuro.ZERO, and energy-aware intermittent learning, which tackles the problems of the small size of memory, dynamic timing constraint, low-computing capability, and limited energy, respectively. Once deployed in the field with the proposed resource-aware learning strategies, embedded systems are not only able to perform deep inference tasks on sensor data but also update and re-train their learning models at run-time without requiring any help from any external system. Such an on-device learning capability of Embedded Deep Intelligence makes an embedded intelligent system real-time, privacy-aware, secure, autonomous, untethered, responsive, and adaptive without concern for its limited resources.Doctor of Philosoph

Diseño de circuitos para lectura de sensores MEMS en tecnología CMOS

En los últimos años el desarrollo de tecnologías Wireless ha permitido el desarrollo de redes de sensores. Dichas redes de sensores gozan cada vez más de mayor importancia, y permiten realizar sistemas cada vez más inteligentes al comunicar en tiempo real a distintos dispositivos entre sí y al permitirles a su vez obtener información vital para su funcionamiento. Todo esto ha permitido desarrollar un nuevo concepto conocido como internet de las cosas o Internet of Things. En el internet de las cosas distintos dispositivos se relacionan entre sí y con el medio. En muchos casos ello permite controlar distintos dispositivos así como recibir información de los mismos desde algo tan cotidiano como un teléfono móvil. Para poder realizar estos sistemas se necesitan sensores de bajo coste y bajo consumo que puedan interactuar con los dispositivos digitales. En el presente trabajo se presenta un diseño a alto nivel de un circuito para mediad de presión mediante un sensor microelectromecánico, MEM. Dicho circuito se caracteriza por su bajo consumo y su alta resolución que alcanza unos 18 bits. Para la realización de este circuito se emplea una topología de tipo doble rampa debido a su bajo coste y simplicidad. Para obtener una elevada resolución se diseña un modo de operación de dicho circuito que hace que este se comporte como un convertidor de tipo Sigma-Delta de primer orden. Así mismo dicho circuito se conecta directamente al sensor de forma que no son necesarios circuitos de adaptación adicionales. Por último se trata la implementación física de dicho circuito haciendo hincapié en el problema del ruido flicker. Para solucionarlo se estudia la forma más adecuada de implementación de la técnica para reducir los efectos del ruido flicker conocida como chopping.Ingeniería Electrónica Industrial y Automátic

Energy Reduction Techniques to Increase Battery Life for Electronic Sensor Nodes

Preserving battery life in duty-cycled sensor nodes requires minimizing energy use in the active region. Lowering the power supply of CMOS gates down into sub-threshold mode is a good way to decrease energy. In this work, a unique technique to control the current in CMOS gates to reliably operate them in sub-threshold mode is described. Compared to the current state-of-theart for running digital gates in the sub-threshold regime, this work is often superior in its lack of complexity and in reduced variance in delay caused by process variations. In addition to presenting the design considerations, a demonstration of a complete digital design flow is given using the custom gates. An AES128 encryption/decryption engine is designed using the aforementioned digital flow in a commercial 180nm process. The resulting design has a ratio of maximum to minimum frequency variation over corners of only 50% with a 0.3V power supply where the same ratio with standard CMOS gates biased under the same supply voltage is 5600%. In addition, the custom gates are used to design a Wallace tree multiplier in an SOI 45nm process that is fully functional with an optimum energy power supply level of 0.34V with a typical operating frequency of 8 MHz having a variation over corners of 80%. For a proof of concept memory chip designed in this work, the architecture uses a logiccompatible CMOS process particularly suitable for embedded applications. The differential pair construct causes the read and refresh power to be independent of any process parameter including the within-die threshold voltage. The current stop feature keeps the read voltage transition low to further minimize read power. The bit cell operates in both single bit BASE2 and multi-bit BASE4 modes. An expression for the read signal was verified with bit cell simulations. These simulations also compare the performance impact of threshold voltage variance in the architecture with a standard gain cell. A DRAM bit cell array was fabricated in the XFab 180nm CMOS process. Measured waveforms closely match theoretical results obtained from a system simulation. The silicon retention time was measured at room temperature and is greater than 150 ms in BASE2 mode and greater than 75 ms in BASE4 mode. 180nm, 25C analysis predicts 0.8uW/Mbit refresh power at 630 MHz, the lowest in the literature. Further: the memory bit cell architecture presented here has a refresh power delay product several times lower than any other published architecture. The current controlled memory architecture in this work improves or overcomes the drawbacks of the 1T1C and gain cell memory architectures. A current controlled memory design was fabricated as a 131K bit array in an 180nm process to provide silicon proof. The bit cell configuration with shared read and write bit cells gives effectively two memory banks. The grouping of rows together into common source domains allows only two opamps to control the current in all the bit cells across the whole chip. The sense amplifiers have a globally controlled switching threshold point and keep their static power in the nano-amp range. The bit cells can operate either in BASE2 or BASE4 mode and the read bit line transitions are reduced with a current stop construct. Parts were received from the foundry in an 84-pin PLCC and were tested at a number of locations on the die. They proved to be fully functional in BASE4. The silicon retention time was measured at room temperature and was greater than four seconds