There are various situations in which electrical energy is desired but cannot by conveniently supplied. Since the days of Hienrich Hertz and Nikola Tesla, scientists have tried to solve this problem using different methods of wireless power transfer. Today, wireless power transfer has only been commercially demonstrated at small distances through use of induction. This thesis demonstrated the transfer of wireless power at relatively large distances through radio frequencies in the development of a prototype for a commercial product - a wireless household lamp.

Wireless power transfer (WPT) technologies have become important for our everyday life. The most commonly used near-field WPT method is inductive coupling, which suffers from low efficiency and small range. The Strongly Coupled Magnetic Resonance (SCMR) method was developed recently, and it can be used to wirelessly transfer power with higher efficiency over a longer distance than the inductive coupling method. This dissertation develops new SCMR systems that have better performance compared to standard SCMR systems. Specifically, two new 3-D SCMR systems are designed to improve the angular misalignment sensitivity of WPT systems. Their power transfer efficiency for different angular misalignment positions are studied and analyzed. Prototypes are built for both systems and their performance is validated through measurement. Furthermore, new planar broadband conformal SCMR (CSCMR) systems are developed that maintain high efficiency while providing significantly larger bandwidth than standard CSCMR systems. Such broadband CSCMR systems are used here for the first time to simultaneously accomplish highly efficient wireless power transfer and high data rate communication through the same wireless link. These systems that combine wireless power and communication are expected to enable next-generation applications with battery-less and “power-hungry” sensors. Example applications include implantable and wearable sensors as well as embedded sensors for structural health monitoring.

The objective of the proposed research is to advance the power efficiency of wireless neural stimulating systems in inductively powered implantable medical devices (IMD). Several innovative system- and circuit-level techniques are proposed towards the development of power-management circuits and wireless neural stimulating systems with inductive power transmission to improve the overall stimulation power efficiency. Neural stimulating IMDs have been proven as effective therapies to alleviate neurological diseases, while requiring high power and performance for more efficacious treatments. Therefore, power-management circuits and neural stimulators in IMDs should have high power efficiencies to operate with smaller received power from a larger distance. Neural stimulating systems are also required to have high stimulation efficacy for activating the target tissue with a minimum amount of energy, while ensuring charge-balanced stimulation. These features provide several advantages such as a long battery life in an external power transmitter, extended-range inductive power transfer, efficacious and safe stimulation, and less tissue damage from overheating. The proposed research presents several approaches to design and implement the power-efficient wireless neural stimulating IMDs: 1) optimized power-management circuits for inductively powered biomedical microsystems, 2) a power-efficient neural stimulating system with adaptive supply control, and 3) a wireless switched-capacitor stimulation (SCS) system, which is a combination structure of the power-management circuits and neural stimulator, to maximize both stimulator efficiency (before electrodes) and stimulus efficacy (after electrodes).

The wireless transfer of power is the enabling technology for realizing a true internet-of-things. Broad sensor networks capable of monitoring environmental pollutants, health-related biological data, and building utility usage are just a small fraction of the myriad of applications which are part of an ever evolving ubiquitous lifestyle. Realizing these systems requires a means of powering their electronics sans batteries. Removing the batteries from the billions or trillions of these envisioned devices not only reduces their size and lowers their cost, but also avoids an ecological catastrophe. Increasing the efficiency of microwave-to-DC power conversion in energy-harvesting circuits extends the range and reliability of passive sensor networks. Multi-frequency waveforms are one technique that assists in overcoming the energy-harvesting circuit diode voltage threshold which limit the energy-conversion efficiency at low RF input powers typically encountered by sensors at the fringe of their coverage area. This thesis discusses a systematic optimization approach to the design of energy-conversion circuits along with multi-frequency waveform excitation. Using this methodology, a low-power 5.8 GHz rectenna showed an output power improvement of over 20 dB at -20 dBm input power using a 3-POW (power-optimized waveform) compared to continuous waveforms (CW). The resultant efficiency is the highest reported efficiency for low-power 5.8 GHz energy harvesters. Additionally, new theoretical models help to predict the maximum possible range of the next generation of passive electronics based upon trends in the semiconductor industry. These models predict improvements in diode turn-on power of over 20 dB using modern Schottky diodes. This improvement in turn-on power includes an improvement in output power of hundreds of dB when compared to CW.

A transferência de energia sem fio (WPT) rege um importante papel no carregamento de aparelhos remotos. Em um acoplamento indutivo ressonante há várias topologias de sistemas WPT que podem ser implementados para realizar a transferência de energia. Neste trabalho é utilizado uma topologia que utiliza quatro capacitores de compensação para realizar o ajuste da potência entregue a carga, onde estes capacitores são calculados através das fixações dos demais parâmetros do circuito elétrico. Quando o sistema WPT é projetado, uma distância fixa entre as bobinas é almejada, todavia há incertezas e movimentos que podem provocar a alteração desta distância. Há várias técnicas na literatura que buscam realizar a sintonia do acoplamento indutivo para compensar estes desalinhamentos gerado entre as bobinas. Este trabalho apresenta um método multivariável para maximização da potência entregue a carga em um sistema de transferência sem fio. O método proposto utiliza os conceitos de um capacitor variável e a variação de frequência a fim de variar a potência entregue a carga. Os resultados experimentais obtidos para os fatores de acoplamento magnético k > 0;3 mostraram que controlando a frequência e uma capacitância da rede de compensação o desempenho do sistema é melhor que os casos onde apenas uma dessas variáveis é controlada. / Wireless power transfer (WPT) plays an important rule in charging remote devices. In a resonant inductive coupling there are several topologies of WPT systems that can be implemented to perform the energy transfer. In this work, a topology is used that uses four capacitors of compensation to realize the adjustment of the power delivered to load, where these capacitors are calculated through the xations of the other parameters of the electric circuit. When the WPT system is designed, a xed distance between coils is desired, however there are uncertainties and movements that may cause this distance to change. There are several techniques in the literature that seek to realize the tuning of the inductive coupling to compensate for these misalignments generated between the coils. This work presents a multivariable method to maximize the power delivered to the load in a wireless transfer system. The proposed method uses the concepts of a variable capacitor and the frequency variation in order to vary the power delivered to the load. The experimental results obtained for the magnetic coupling factors k > 0:3 showed that controlling the frequency and capacitance of the compensation network system performance is better than the cases where only one of these variables is controlled.

The wireless sensor network (WSN) is increasingly used in many areas nowadays. It can be applied to provide the solutions to environmental problems, help increasing security and safety systems, and make the detection of the problems more efficient, e.g. the earthquake or tidal wave, which will harmful to humans. The WNS is durable and resistant to all types of terrain and climate, but while the WSN system is more and more widespread, one of the obstacles hindering the growth of this technology and the demand for WSN applications is the limited battery lifespan. Consequently, there is a significant requirement for techniques for prolonging the battery’s lifespan. Therefore, one potential solution is to use alternative energy sources combined with the sensor nodes in WSN, specifically energy harvesting from existing environmental sources. This research project reviews the characteristics of each kind of energy harvesting, understanding the various energy sources (solar energy, vibration energy and wind power), including wireless power transfer (WPT) by using electromagnetic (EM) radiation energy transfer or RF radio-frequency emission and magnetic coupled energy transfer. They are adopted for extending node’s life in the WSN, based on published information. Then it compares these diverse alternative energy methods and identifies for the most suitable energy harvesting method for application to wireless sensor nodes in order to prolong the lifespan of the battery. The major findings from the researcher include that wireless power transfer energy harvesting (WPT) using the magnetic field is the most appropriate tool for extending the lifespan of the WSN system. In addition, the author also designed an experiment to test this alternative energy, achieving by modelling the wireless power transfer with four coils. From the experimental results, it can be seen that the WPT technique using energy harvesting with magnetic inductive source can be applied to prolong the lifespan of the WSN system.

A transferência de energia sem fio (WPT) rege um importante papel no carregamento de aparelhos remotos. Em um acoplamento indutivo ressonante há várias topologias de sistemas WPT que podem ser implementados para realizar a transferência de energia. Neste trabalho é utilizado uma topologia que utiliza quatro capacitores de compensação para realizar o ajuste da potência entregue a carga, onde estes capacitores são calculados através das fixações dos demais parâmetros do circuito elétrico. Quando o sistema WPT é projetado, uma distância fixa entre as bobinas é almejada, todavia há incertezas e movimentos que podem provocar a alteração desta distância. Há várias técnicas na literatura que buscam realizar a sintonia do acoplamento indutivo para compensar estes desalinhamentos gerado entre as bobinas. Este trabalho apresenta um método multivariável para maximização da potência entregue a carga em um sistema de transferência sem fio. O método proposto utiliza os conceitos de um capacitor variável e a variação de frequência a fim de variar a potência entregue a carga. Os resultados experimentais obtidos para os fatores de acoplamento magnético k > 0;3 mostraram que controlando a frequência e uma capacitância da rede de compensação o desempenho do sistema é melhor que os casos onde apenas uma dessas variáveis é controlada. / Wireless power transfer (WPT) plays an important rule in charging remote devices. In a resonant inductive coupling there are several topologies of WPT systems that can be implemented to perform the energy transfer. In this work, a topology is used that uses four capacitors of compensation to realize the adjustment of the power delivered to load, where these capacitors are calculated through the xations of the other parameters of the electric circuit. When the WPT system is designed, a xed distance between coils is desired, however there are uncertainties and movements that may cause this distance to change. There are several techniques in the literature that seek to realize the tuning of the inductive coupling to compensate for these misalignments generated between the coils. This work presents a multivariable method to maximize the power delivered to the load in a wireless transfer system. The proposed method uses the concepts of a variable capacitor and the frequency variation in order to vary the power delivered to the load. The experimental results obtained for the magnetic coupling factors k > 0:3 showed that controlling the frequency and capacitance of the compensation network system performance is better than the cases where only one of these variables is controlled.

Wireless power transfer (WPT) technologies for communication and recharging devices have recently attracted significant research attention. Conventional WPT systems based either on far-field or near-field coupling cannot provide simultaneously high efficiency and long transfer range. The Strongly Coupled Magnetic Resonance (SCMR) method was introduced recently, and it offers the possibility of transferring power with high efficiency over longer distances. Previous SCMR research has only focused on how to improve its efficiency and range through different methods. However, the study of optimal and miniaturized designs has been limited. In addition, no multiband and broadband SCMR WPT systems have been developed and traditional SCMR systems exhibit narrowband efficiency thereby imposing strict limitations on simultaneous wireless transmission of information and power, which is important for battery-less sensors. Therefore, new SCMR systems that are optimally designed and miniaturized in size will significantly enhance various technologies in many applications. The optimal and miniaturized SCMR systems are studied here. First, analytical models of the Conformal SCMR (CSCMR) system and thorough analysis and design methodology have been presented. This analysis specifically leads to the identification of the optimal design parameters, and predicts the performance of the designed CSCMR system. Second, optimal multiband and broadband CSCMR systems are designed. Two-band, three-band, and four-band CSCMR systems are designed and validated using simulations and measurements. Novel broadband CSCMR systems are also analyzed, designed, simulated and measured. The proposed broadband CSCMR system achieved more than 7 times larger bandwidth compared to the traditional SCMR system at the same frequency. Miniaturization methods of SCMR systems are also explored. Specifically, methods that use printable CSCMR with large capacitors, novel topologies including meandered, SRRs, and spiral topologies or 3-D structures, lower the operating frequency of SCMR systems, thereby reducing their size. Finally, SCMR systems are discussed and designed for various applications, such as biomedical devices and simultaneous powering of multiple devices.

In the past decades, there has been a noticeable growth in the deployment of wireless sensor networks. These sensors/stimulators are typically powered by a battery which has limited life span. Power harvesting is one of the solutions to this problem. According to a medical-care experiment, the recovery process of an injured nerve has been boosted with the help of electrical stimulator. The latter is not only preferable to be portable but to be implantable as well in order to make medical treatment easier on the patient. This work has implemented two prototype versions of rectification circuitry used to harvest RF signal to power an electrical stimulator for peripheral nerve regeneration. The system consists an efficient rectifier, DC-limiter, biasing circuitry and modest regulator. In order to gain higher rectification efficiency, ON-OFF offset methodology is reviewed. Moreover, a mixed-signal design is proposed to construct a delay compensation mechanism. It is designed with 0.35 um AMS technology and it is assumed to read 13.56 MHz NFC signal from loop antennas. Schematic and layout levels are introduced with corresponding simulation findings. Moreover, tape-out is made for both architectures along with comparative results/discussions.

<div>Electric vehicles (EVs) face a major issue before becoming the norm of society, that is, their lack of range when it comes to long trips. Fast charging stations are a good step forward to help make it simpler for EVs, but it is still not as convenient when compared to vehicles with an internal combustion engine (ICE). Plenty of infrastructure changes have been proposed in the literature attempting to tackle this issue, but they typically tend to be either an expensive solution or a difficult practical implementation.</div><div> </div><div> This dissertation presents two solutions to help increase the range of EVs: a novel wireless charging method and a multi-motor architecture for EVs. The first proposed solution involves the ability for EVs to charge while en route from another vehicle, which will be referred to from here on as vehicle-to-vehicle recharging (VVR). The aim of this system is to bring an innovative way for EVs to charge their battery without getting off route on a highway. The electric vehicle can request such a service from a designated charger vehicle on demand and receive electric power wirelessly while en route. The vehicles that provide energy (charger vehicles) through wireless power transfer (WPT) only need to be semi-autonomous in order to ``engage'' or ``disengage'' during a trip. Also, a novel method for wireless power transfer will be presented, where the emitter (TX) or receiver (RX) pads can change angles to improve the efficiency of power transmission. This type of WPT system would be suitable for the VVR system presented in this dissertation, along with other applications.</div><div> </div><div> The second solution presented here will be an architecture for EVs with three or more different electric motors to help prolong the state of charge (SOC) of the battery. The key here is to use motors with different high efficiency regions. The proposed control algorithm optimizes the use of the motors on-board to keep them running in their most efficient regions. With this architecture, the powertrain would see a combined efficiency map that incorporates the best operating points of the motors. Therefore, the proposed architecture will allow the EV to operate with a higher range for a given battery capacity.</div><div> </div><div> The state-of-the-art is divided into four subsections relevant to the proposed solutions and where most of the innovations to reduce the burden of charging EVs can be found: (1) infrastructure changes, (2) device level innovations, (3) autonomous vehicles, and (4) electric vehicle architectures. The infrastructure changes highlight some of the proposed systems that aim to help EVs become a convenient solution to the public. Device level innovations covers some of the literature on technology that addresses EVs in terms of WPT. The autonomous vehicle subsection covers the importance of such technology in terms of safety and reliability, that could be implemented on the VVR system. Finally, the EV architectures covers the current typologies used in EVs. Furthermore, modeling, analysis, and simulation is presented to validate the feasibility of the proposed VVR system, the WPT system, and the multi-motor architecture for EVs.</div>