Broadband PIFA Rectenna Design for a Multi-Source Energy Harvesting Device

Combining different energy harvesting devices to optimize output power is crucial to the achievement of sustainable energy. This thesis focuses on the design, simulation and fabrication of a broadband Planar Inverted-F Antenna (PIFA) constructed for energy harvesting and its integration with a solar cell. An assessment of available ambient RF energy was performed by surveying power density levels from 700MHz to 18GHz. The measured spectrum was then used to determine the bandwidth for our rectifying antenna. The PIFA design was chosen for its small size and low profile, in order to limit the area covering the solar panel. The purpose of this antenna is to harvest power during the times that solar energy is unavailable. The thorough analysis, design and fabrication specifics of the antenna and its integration with the solar panel are discussed in detail. Future work involving the implementation of a PIFA array to optimize the amount of energy harvested is also presented

Rectifier design for radio frequency energy harvesting system

This thesis presents the development of rectifying circuits suitable for Radio Frequency (RF) energy harvesting application with dual-band capabilities. The main contribution of this thesis is the development of compact dual-band two-stage rectifier with high efficiency. Firstly, a voltage doubler rectifying circuit is designed to get a compact size. A source-pull simulation of matching circuit is used to find the optimal load impedance and enhance the conversion efficiency over the frequency range. The accuracy of the design has been justified by the simulation and measurement results. Secondly, a dual-band impedance matching network based on transmission line is developed. A short stub and general impedance transformer are designed to match different complex impedance at the two operating frequencies. Measurement results have fully demonstrated. Thirdly, a new rectifier circuit is proposed. It employs a dual-band multi resonant matching network and a high efficiency modified quadruplor rectifier for harvesting the ambient RF power at both 2.45 GHz Global System for Mobile Communications (GSM) and 5.8 GHz Wireless Local Area Network (WLAN). An attempt was made for matching network with a series of combination of a capacitor and inductor with a parallel LC tank. For rectifier circuit part, low power harvested from the RF is boosted up using two-stage of voltage multiplier and the input capacitor is rearranged to be in parallel connection to get smaller size and uniform pressure on diode. The prototypes are developed, and simulation results are obtained. The proposed rectifier is proven to exhibit greatly higher output voltage and efficiency compared to the conventional circuit. The rectifier is designed on the FR-4 board. Its capability of working within two frequency bands at 2.45 GHz and 5.8 GHz is verified by measurement. The proposed rectifier has met the requirement of high conversion efficiency (79.1% and 78.4% at the respective 2.45 GHz and 5.8 GHz), and able to boost up to the maximum voltage level of 14V at 20 dBm input power. Hence, the aims of this research have been achieved and are practically suitable for the use in wireless sensor networks and low power devices

Sistemas de WPT em campo próximo

A transferência de energia sem fios, ideia contemporânea para uns e futurista para outros, tem ganho um grande destaque ao longo dos anos. Estima-se que num futuro próximo os sistemas WPT dominem o mercado, e sejam uma opção promissora na técnica de alimentação dos dispositivos eletrónicos, reduzindo a quantidade exurbitante de baterias desperdiçadas e simplificando a implementação dos sistemas. O problema dos sistemas WPT desenvolvidos até ao presente é a reduzida eficiência energética. Nesta dissertação, é apresentado inicialmente um estudo sobre o estado da arte da transmissão de energia sem fios, contextualizando o leitor àcerca desta forma de transmissão de energia. Para tal, são apresentadas as leis que regem o funcionamento da transferência de energia sem fios, é exposta a constituição de um sistema WPT e são discutidas as técnicas de transmissão de energia sem fios existentes e a sua aplicabilidade nas diversas áreas. Após efetuar uma contextualização, o estudo apresentado nesta dissertação foca-se em colmatar uma das principais desvantagens dos sistemas WPT, a baixa eficiência energética. Para maximizar a eficiência destes sistemas, propõe-se a utilização de agregados de antenas com a capacidade de focar o campo elétrico num ponto especı́fico, localizado em campo próximo. Após o estudo dos agregados de antenas com capacidade de foco em campo próximo, projetaram-se e implementaram-se dois sistemas WPT a operar a duas frequências distintas (2.4 GHz, 5.8 GHz). Analisou-se, para cada um deles, a variação da eficiência energética com a distância entre as antenas constituintes do sistema para dois casos distintos: quando o sistema é formado por uma antena de transmissão com capacidade de foco em campo próximo e no caso em que a antena de transmissão é idêntica às normalmente utilizadas nos sistemas de comunicação e radar, frequentemente designadas como focais em campo distante. Após a devida análise dos resultados obtidos, concluiu-se que os sistemas WPT, constituı́dos por agregados de antenas com capacidade de foco em campo próximo, apresentam uma eficiência energética mais elevada.The wireless power transfer, a contemporary idea for some and futuristic for others, has gained a great prominence over the years. It is estimated that WPT systems will dominate the market soon and will be a promising option in powering electronic devices, reducing the exorbitant amount of wasted batteries and simplifying system implementation. The problem of WPT systems developed so far is the low energetic efficiency. In this dissertation, a study is proposed initially on the state of art of the wireless transmission of energy, contextualizing the reader about this form of energy transmission. For such purpose, the laws that govern the operation of the wireless power transfer are presented, the constitution of a WPT system is exposed and the existing wireless transmission techniques and their applicability in the various areas are discussed. After a brief contextualization, this study focuses on rectifying one of the main disadvantages of WPT systems, the low energetic efficiency. To maximize the efficiency of these systems it is proposed to use antenna arrays with the ability to focus the electric field at a specific point, located in near field. After the study of antenna arrays with near-field focus capability, two WPT systems were designed and implemented to operate at two distinct frequencies (2.4 GHz and 5.8 GHz). For each of them, the energetic efficiency variation with the distance between the constituent antennas of the system was analyzed for two distinct cases: when the system is formed by a transmission antenna with near-field focus capability and in the case in which the transmission antenna is identical to those normally used in communication and radar systems, often referred to as far-field focused antennas. After analyzing the obtained results, it was concluded that the WPT systems composed of antenna arrays with near-field focus capability have a higher energetic efficiency.Mestrado em Engenharia Eletrónica e Telecomunicaçõe

Towards Battery-Free Internet of Things (IoT) Sensors: Far-Field Wireless Power Transfer and Harmonic Backscattering

RÉSUMÉ Notre vie tend à être plus agréable, plus facile et plus efficace grâce à l'évolution rapide de la technologie de l'Internet des objets (IoT). La clef de voute de cette technologie repose essentiellement sur la quantité de capteurs IoT interconnectés, que l’on est en mesure de déployer dans notre environnement. Malheureusement, l’électronique conventionnelle fonctionnant sur piles ou relié au réseau électrique ne peut pas constituer une solution durable en raison des aspects de coût, de faisabilité et d'impact environnemental. Pendant ce temps, le changement climatique dû à la consommation excessive de combustibles fossiles continue de s'aggraver. Il devient donc urgent de trouver une solution pour l’alimentation électrique des capteurs IoT géographiquement répartis à grande échelle, afin de simultanément soutenir la mise en oeuvre de nombreux capteurs IoT tout en limitant leur poids environnemental. L'énergie radiofréquence (RF) ambiante, qui sert de support à l'information sans fil, est non seulement capitale pour notre société, mais aussi omniprésente dans les zones urbaines et suburbaines. Elle permet de réaliser des communications et des détections sans fil. Cependant, l'énergie RF ambiante est majoritairement « gaspillée » car seule une toute petite partie de la puissance transmise est effectivement reçu ou « consommée » par le destinataire. C'est pourquoi le recyclage de l'énergie RF ambiante est une solution prometteuse pour alimenter les capteurs IoT. Pour certains capteurs IoT consommant une puissance plus élevée, l’apport d'énergie sans fil pourra similairement se faire par des centrales électriques spécialisées, suivant le même schéma d’alimentation sans fil. Pour utiliser et récupérer cette énergie RF, cette thèse présente deux techniques principales : la récupération/réception de puissance sans fil en champ lointain (wireless power transfer: WPT) et la rétrodiffusion d'harmoniques. Le chapitre 2 aborde les différents mécanismes de conversion de fréquence entre le WPT en champ lointain et la rétrodiffusion d'harmoniques. La récupération de WPT en champ lointain consiste à convertir l'énergie RF en puissance continue. En revanche, la rétrodiffusion d'harmoniques a pour but de convertir l'énergie RF dans une autre fréquence, dans la plupart des cas, la composante harmonique de rang 2. A titre d'étape préliminaire de recherche et d'étude de faisabilité, une cartographie de la densité de l'énergie RF ambiante dans les zones centrales de l'île de Montréal est résumée au chapitre 3. Contrairement aux mesures traditionnelles précédentes effectuées à des endroits fixes, cette mesure dynamique a été réalisée le long des rues, des routes, des avenues et des autoroutes pour couvrir une large zone.----------ABSTRACT Our life is becoming more convenient, efficient, and intelligent with the aid of fast-evolving Internet of Things (IoT) technology. One essential foundation of IoT technology is the development of numerous interrelated IoT sensors that are distributed extensively in our environment. However, conventional batteries/cords-based powering solutions are certainly not an acceptable long-term solution, considering the incurred cost, feasibility, most of all, environmental impact. Meanwhile, climate change due to excessive consumption of fossil fuels is worsening day by day. Therefore, a transformative powering solution for such large-scale and geographically scattered IoT sensors is of extreme importance in support of such extensive IoT sensors implementation while simultaneously mitigating its environmental burden. Serving as a critical information carrier, ambient radiofrequency (RF) energy is pervasive in urban and suburban areas to realize wireless communication and sensing. However, part of ambient RF energy is dissipated due to path loss if not fully consumed by end-users. Hence, recycling the wasted ambient RF energy to power IoT sensors is a promising solution. The concept of harnessing wireless energy for powering IoT sensors requiring a higher power supply is also feasible through the dedicated wireless power delivery from specialized power stations, which can be an effective supplement. To realize the RF power scavenging, this thesis research introduces two mainstream techniques: far-field wireless power transfer (WPT) and harmonic backscattering. Chapter 2 discusses the different frequency conversion mechanisms applied for far-field or ambient WPT harvesting and harmonic backscattering. Far-field WPT harvesting converts RF energy into dc power (zeroth harmonic). In contrast, harmonic backscattering upconverts RF energy into its harmonics, in most cases, the second harmonic component. As a preliminary research step and a feasibility study, a survey of ambient RF energy density in the core areas on Montreal Island is summarized in Chapter 3. Different from the previously published traditional measurements at fixed locations, this dynamic measurement is carried out along streets, roads, avenues, and highways to cover a large area. Also, a stationary measurement in Downtown Montreal is to reveal whether human activities are able to bring visible change to ambient RF energy levels. This work demonstrates how much ambient RF energy is available in free space and acts as a significant reference for researchers and engineers designing ambient RF energy harvesting circuits/systems for practical applications