542 research outputs found

    Analysis of RF-energy transducer for microwave harvesting system suitable for IoT applications

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    This project examines numerically the improved efficiency of energy transducer elements as RF antennas confined in metal cavities. To do so, parametric studies are performed using the 3D electromagnetic simulator CST transducers proposed using two RF antennas dual 2.4/5GHz antenna and a patch-designed 2.4 GHz. The results are contrasted with experimental measurements, demonstrating that the proposed transducers generate enough power to power a Texas Instruments BQ25570 chip or power IoT systems with μW power consumption.Aquest projecte analitza numèricament la millora en eficiència dels elements del transductor d'energia de RF d'antenes confinades en cavitats metàl·liques. Per fer-ho, es realitzen estudis paramètrics mitjançant el simulador electromagnètic 3D CST dels transductors de RF proposats utilitzant dues antenes duals a 2.4/5GHz i una patch-antenna dissenyada a 2.4GHz. Els resultats obtinguts es contrasten amb mesures experimentals, arribant a demostrar que els transductors proposats generen prou potència per a alimentar un sistema de gestió d'energia basat en el xip comercial BQ25570 de Texas Instruments o alimentar sistemes IoT amb consums en el rang del μW.El presente proyecto analiza numéricamente el aumento en eficiencia de los elementos del transductor de energía de RF de antenas confinadas en cavidades metálicas. Para ello, se realiza un estudio paramétrico mediante el simulador electromagnético 3D CST de los transductores de RF propuestos para dos antenas dipolos comerciales duales a 2.4/5GHz y una patch antena diseñada a 2.4GHz. Los resultados de las simulaciones se contrastan con medidas experimentales, llegando a demostrar que el transductor propuesto genera suficiente energía como para alimentar un sistema de gestión de energía estándar basado en el chip comercial BQ25570 de Texas Instrumentos alimentar sistemas IoT con consumos en el rango de los μW

    Theory of directed transportation of electronic excitation between single molecules through photonic coupling

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    The primary result of UV-Visible photon absorption by complex organic molecules is the population of short-lived electronic excited states. Transportation of their excitation energy between single molecules, formally mediated by near-field interactions, may occur between the initial absorption and eventual fluorescence emission events, commonly on an ultrafast timescale. The routing of energy flow is typically effected by a sequence of pairwise transfer steps over numerous molecules, rather than a single step over the same overall distance. Directionality emerges when there is structure in the molecular organisation. For a chemically heterogeneous system with local order, and with suitable molecular dispositions, automatically unidirectional transfer can be exhibited as the result of a 'spectroscopic gradient'. However it is also possible to exert control over the directionality of excitation flow by the operation of external influences. Examples are the application of an electrical or optical stimulus to the system - achieved by the incorporation of an ancillary polar species, the application of a static electric field or electromagnetic radiation. Most significantly, based on the latter option, an all-optical method has recently been determined that enables excitation transportation to be completely switched on or off, such that the energy flow is subject to controllable photoactivated gating. It is already apparent that this photonic process, termed Optically Controlled Resonance Energy Transfer, has potentially numerous applications. For example, it represents a new basis for optical transistor action

    Integration of Bulk Piezoelectric Materials into Microsystems.

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    Bulk piezoelectric ceramics, compared to deposited piezoelectric thin-films, provide greater electromechanical coupling and charge capacity, which are highly desirable in many MEMS applications. In this thesis, a technology platform is developed for wafer-level integration of bulk piezoelectric substrates on silicon, with a final film thickness of 5-100μm. The characterized processes include reliable low-temperature (200˚C) AuIn diffusion bonding and parylene bonding of bulk-PZT on silicon, wafer-level lapping of bulk-PZT with high-uniformity (±0.5μm), and low-damage micro-machining of PZT films via dicing-saw patterning, laser ablation, and wet-etching. Preservation of ferroelectric and piezoelectric properties is confirmed with hysteresis and piezo-response measurements. The introduced technology offers higher material quality and unique advantages in fabrication flexibility over existing piezoelectric film deposition methods. In order to confirm the preserved bulk properties in the final film, diaphragm and cantilever beam actuators operating in the transverse-mode are designed, fabricated and tested. The diaphragm structure and electrode shapes/sizes are optimized for maximum deflection through finite-element simulations. During tests of fabricated devices, greater than 12μmPP displacement is obtained by actuation of a 1mm2 diaphragm at 111kHz with <7mW power consumption. The close match between test data and simulation results suggests that the piezoelectric properties of bulk-PZT5A are mostly preserved without any necessity of repolarization. Three generations of resonant vibration energy harvesters are designed, simulated and fabricated to demonstrate the competitive performance of the new fabrication process over traditional piezoelectric deposition systems. An unpackaged PZT/Si unimorph harvester with 27mm3 active device volume produces up to 205μW at 1.5g/154Hz. The prototypes have achieved the highest figure-of-merits (normalized-power-density × bandwidth) amongst previously reported inertial energy harvesters. The fabricated energy harvester is utilized to create an autonomous energy generation platform in 0.3cm3 by system-level integration of a 50-80% efficient power management IC, which incorporates a supply-independent bias circuitry, an active diode for low-dropout rectification, a bias-flip system for higher efficiency, and a trickle battery charger. The overall system does not require a pre-charged battery, and has power consumption of <1μW in active-mode (measured) and <5pA in sleep-mode (simulated). Under 1g vibration at 155Hz, a 70mF ultra-capacitor is charged from 0V to 1.85V in 50 minutes.Ph.D.Electrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91479/1/aktakka_3.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/91479/2/aktakka_2.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/91479/3/aktakka_1.pd

    Microwave Devices for Wearable Sensors and IoT

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    The Internet of Things (IoT) paradigm is currently highly demanded in multiple scenarios and in particular plays an important role in solving medical-related challenges. RF and microwave technologies, coupled with wireless energy transfer, are interesting candidates because of their inherent contactless spectrometric capabilities and for the wireless transmission of sensing data. This article reviews some recent achievements in the field of wearable sensors, highlighting the benefits that these solutions introduce in operative contexts, such as indoor localization and microwave sensing. Wireless power transfer is an essential requirement to be fulfilled to allow these sensors to be not only wearable but also compact and lightweight while avoiding bulky batteries. Flexible materials and 3D printing polymers, as well as daily garments, are widely exploited within the presented solutions, allowing comfort and wearability without renouncing the robustness and reliability of the built-in wearable sensor

    Comparation of common ultra-low power harvesting RF rectifier circuits

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    This project has analysed and compared different types of common RF Harvesting rectifier circuits for ultra-low power. An antenna has been used as an energy harvesting element and the power available in the environment has been analysed, specifically in the GAEMI laboratories of the UAB. The simulations were carried out using the Keysisght ADS software. It has been demonstrated, by means of simulation, that the simple rectifier shows a higher efficiency than the other rectifiers and that the value of the load resistance is the predominant element in the calculation of this efficiency. It has been experimentally confirmed that the measurements do not deviate from the simulated measurements. The results obtained can be applied to the generation of prototypes of RF Harvesting systems

    A COMPREHENSIVE OVERVIEW OF RECENT DEVELOPMENTS IN RF-MEMS TECHNOLOGY-BASED HIGH-PERFORMANCE PASSIVE COMPONENTS FOR APPLICATIONS IN THE 5G AND FUTURE TELECOMMUNICATIONS SCENARIOS

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    The goal of this work is to provide an overview about the current development of radio-frequency microelectromechanical systems technology, with special attention towards those passive components bearing significant application potential in the currently developing 5G paradigm. Due to the required capabilities of such communication standard in terms of high data rates, extended allocated spectrum, use of massive MIMO (Multiple-Input-Multiple-Output) systems, beam steering and beam forming, the focus will be on devices like switches, phase shifters, attenuators, filters, and their packaging/integration. For each of the previous topics, several valuable contributions appeared in the last decade, underlining the improvements produced in the state of the art and the chance for RF-MEMS technology to play a prominent role in the actual implementation of the 5G infrastructure

    On-chip electrochemical capacitors and piezoelectric energy harvesters for self-powering sensor nodes

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    On-chip sensing and communications in the Internet of things platform have benefited from the miniaturization of faster and low power complementary-metal-oxide semiconductor (CMOS) microelectronics. Micro-electromechanical systems technology (MEMS) and development of novel nanomaterials have further improved the performance of sensors and transducers while also demonstrating reduction in size and power consumption. Integration of such technologies can enable miniaturized nodes to be deployed to construct wireless sensor networks for autonomous data acquisition. Their longevity, however, is determined by the lifetime of the power supply. Traditional batteries cannot fully fulfill the demands of sensor nodes that require long operational duration. Thus, we require solutions that produce their own electricity from the surroundings and store them for future utility. Furthermore, manufacturing of such a power supply must be compatible with CMOS and MEMS technology. In this thesis, we will describe on-chip electrochemical capacitors and piezoelectric energy harvesters as components of such a self-powered sensor node. Our piezoelectric microcantilevers confirm the feasibility of fabricating micro electro-mechanical-systems (MEMS) size two-degree-of-freedom systems which can address the major issue of small bandwidth of piezoelectric micro-energy harvesters. These devices use a cut-out trapezoidal cantilever beam, limited by its footprint area i.e. a 1 cm2^2 silicon die, to enhance the stress on the cantilever\u27s free end while reducing the gap remarkably between its first two eigenfrequencies in the 400 - 500 Hz and in the 1 - 2 kHz range. The energy from the M-shaped harvesters could be stored in rGO based on-chip electrochemical capacitors. The electrochemical capacitors are manufactured through CMOS compatible, reproducible, and reliable micromachining processes such as chemical vapor deposition of carbon nanofibers (CNF) and spin coating of graphene oxide based (GO) solutions. The impact of electrode geometry and electrode thickness is studied for CNF based electrodes. Furthermore, we have also demonstrated an improvement in their electrochemical performance and yield of spin coated electrochemical capacitors through surface roughening from iron and chromium nanoparticles. The CVD grown CNF and spin coated rGO based devices are evaluated for their respective trade-offs. Finally, to improve the energy density and demonstrate the versatility of the spin coating process, we manufactured electrochemical capacitors from various GO based composites with functional groups heptadecan-9-amine and octadecanamine. The materials were used as a stack to demonstrate high energy density for spin coated electrochemical capacitors. We have also examined the possibility of integrating these devices into a power management unit to fully realize a self-powering on-chip power supply through survey of package fabrication, choice of electrolyte, and device assembly

    Coupled resonator based wireless power transfer for bioelectronics

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    Implantable and wearable bioelectronics provide the ability to monitor and modulate physiological processes. They represent a promising set of technologies that can provide new treatment for patients or new tools for scientific discovery, such as in long-term studies involving small animals. As these technologies advance, two trends are clear, miniaturization and increased sophistication i.e. multiple channels, wireless bi-directional communication, and responsiveness (closed-loop devices). One primary challenge in realizing miniaturized and sophisticated bioelectronics is powering. Integration and development of wireless power transfer (WPT) technology, however, can overcome this challenge. In this dissertation, I propose the use of coupled resonator WPT for bioelectronics and present a new generalized analysis and optimization methodology, derived from complex microwave bandpass filter synthesis, for maximizing and controlling coupled resonator based WPT performance. This newly developed set of analysis and optimization methods enables system miniaturization while simultaneously achieving the necessary performance to safely power sophisticated bioelectronics. As an application example, a novel coil to coil based coupled resonator arrangement to wirelessly operate eight surface electromyography sensing devices wrapped circumferentially around an able-bodied arm is developed and demonstrated. In addition to standard coil to coil based systems, this dissertation also presents a new form of coupled resonator WPT system built of a large hollow metallic cavity resonator. By leveraging the analysis and optimization methods developed here, I present a new cavity resonator WPT system for long-term experiments involving small rodents for the first time. The cavity resonator based WPT arena exhibits a volume of 60.96 x 60.96 x 30.0 cm3. In comparison to prior state of the art, this cavity resonator system enables nearly continuous wireless operation of a miniature sophisticated device implanted in a freely behaving rodent within the largest space. Finally, I present preliminary work, providing the foundation for future studies, to demonstrate the feasibility of treating segments of the human body as a dielectric waveguide resonator. This creates another form of a coupled resonator system. Preliminary experiments demonstrated optimized coupled resonator wireless energy transfer into human tissue. The WPT performance achieved to an ultra-miniature sized receive coil (2 mm diameter) is presented. Indeed, optimized coupled resonator systems, broadened to include cavity resonator structures and human formed dielectric resonators, can enable the effective use of coupled resonator based WPT technology to power miniaturized and sophisticated bioelectronics
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