Master of Science, Miami University, 2016, Computational Science and Engineering

Wireless power transfer (WPT) has become a common way to charge or power many types of devices, ranging from cell phones to electric toothbrushes. WPT became popular through the introduction of a transmission mode known as strongly coupled magnetic resonance (SCMR). This means of transmission is non-radiative and enables mid-range WPT. Shortly after the development of WPT via SCMR, a group of researchers introduced the concept of resonant repeaters, which allows power to hop from the source to the device. These repeaters are in resonance with the WPT system, which enables them to propagate the power wirelessly with minimal losses to the environment. Resonant repeaters have rekindled the dream of ubiquitous wireless power. Inherent risks come with the realization of such a dream. One of the most prominent risks, which we set out in this thesis to address, is that of accessibility to the WPT system. We propose the incorporation of a controlled access schema within a WPT system to prevent unwarranted use of wireless power. Our thesis discusses the history of electromagnetism, examines the inception of WPT via SCMR, evaluates recent developments in WPT, and further elaborates on the controlled access schema we wish to contribute to the field.

Committee: Dmitriy Garmatyuk PhD (Advisor); Mark Scott PhD (Committee Member); Herbert Jaeger PhD (Committee Member) Subjects: Computer Engineering; Electrical Engineering; Electromagnetics; Electromagnetism; Engineering

Doctor of Philosophy, Case Western Reserve University, 2020, EECS - Electrical Engineering

Methodologies for wireless power transfer (WPT) to implantable medical devices (IMDs) as an attractive solution toward obviating the need for primary battery have continuously evolved over the past decades. Capacitive WPT (C–WPT) is an emerging methodology that offers a higher dynamic range in power delivery when coping with biosafety limits as compared to its ultrasonic and inductive counterparts and introduces a unique advantage of flexible implementation with minimal costs on important link parameters. The C–WPT has been under investigation for delivering moderate-to-high levels of wireless power to centimeter-sized IMDs with an implantation depth of a few millimeters and thus suitable for IMDs in peripheral/autonomic applications. This work, for the first time, presents design and implementation of a complete C–WPT system for subcutaneously-implanted IMDs. That is a multidisciplinary research work involving co-design and co-development of capacitive link across a tissue layer and circuits/systems interfacing with the link on both external and implant sides including CMOS power management integrated circuits (PMICs) that interfaces with capacitive link on the implant side and performs efficient AC-to-DC conversion. One part of this work is focused on modeling, characterization, and development of a bio-safe capacitive link across tissue for C–WPT where an accurate circuit model for capacitive elements is proposed followed by a comprehensive circuit model for a series-resonant capacitive link setup. Electromagnetic simulations via ANSYS HFSS provide further insights into the capacitive link behavior and investigates the biosafety levels of the link. Flexible and conformal implementation of capacitive link on copper substrates is shown for ease of implantation. Following the link characterization, different PMIC designs are shown for capacitively-powered IMDs. First, a frequency-aware CMOS active rectifier IC with dual-loop adaptive delay compensation and (open full item for complete abstract)

Committee: Pedram Mohseni (Advisor); Hossein Miri Lavasani (Committee Member); Farncis Merat (Committee Member); Kevin Kilgore (Committee Member) Subjects: Biomedical Engineering; Biomedical Research; Design; Electrical Engineering; Electromagnetics; Energy; Engineering; Health Care

Master of Science (M.S.), University of Dayton, 2011, Electrical Engineering

In this thesis, the theory of coupled resonators for non-adiative wireless power transfer are explored from a lumped element circuit perspective. A basic circuit model is developed and standard circuit parameters are defined. A directly fed resonant shielded loop for wireless power transfer is presented. Basic lumped component values and circuit parameters are experimentally extracted for two resonant shielded loops. Optimal efficiency conditions are derived and used to design optimal matching networks. Matching networks are constructed and the system is tested for power transfer efficiency. Two means of producing a tunable system are explored: frequency tuned sources and dynamic matching networks. It is shown that frequency tuned systems cannot achieve maximum efficiencies. A tunable system is constructed and tested. Experimental results show excellent agreement with theory, and the ability to achieve maximum achievable efficiencies.

Committee: Robert Penno PhD (Committee Chair); Anthony Grbic PhD (Advisor); Monish Chatterjee PhD (Committee Member); Augustine Urbas PhD (Committee Member); John Weber PhD (Other); Tony Saliba PhD (Other) Subjects: Electrical Engineering; Electromagnetics; Electromagnetism; Energy; Engineering; Solid State Physics

Doctor of Philosophy, The Ohio State University, 2020, Electrical and Computer Engineering

With the continuous drop in the HV battery cost, Electric Vehicles are forecasted to become increasingly affordable. However, with more services being added to electric vehicles, the onboard system complexity and cost continues to increase. Currently, plug-in electric vehicles require an onboard conductive charger to regulate the power delivered to the HV battery and isolate the HV bus from the AC grid. In some cases, electric vehicles may offer the option for supplying AC power to connected loads thus providing the flexibility of using the onboard HV battery as a mobile source. Moreover, with increased consumer demand for hands-free charging, wireless power transfer can potentially be considered as an addon option to serve as an HV battery charger. Unfortunately, due to the limited onboard space and the high cost of the power conversion system, adoption of the wireless power transfer technology has not gained traction. This dissertation provides a comprehensive study outlining the challenges with adding a wireless HV battery charger to battery-electric and plug-in hybrid vehicles. Through system architecture analysis, a case is made for why there is a need to consolidate the redundant onboard circuit blocks through system-level integration. Opportunities for reducing the onboard bill-of-material cost and reducing the size of the onboard electronics are provided. Moreover, the technological challenges with the overall power conversion efficiency as it pertains to a highly integrated system are discussed. Also, the challenge of realizing system interoperability with the public charging infrastructure for the wireless power transfer system is addressed. Battery electric and plug-in hybrid vehicles capable of wirelessly charging the HV battery have the advantage of charging while in motion, during frequent stops, and automatically in public designated parking areas. With such flexibility in receiving power, the battery size can be reduced, allowing for a reduction (open full item for complete abstract)

Committee: Jin Wang (Advisor); Lee Robert (Committee Member); Zhang Julia (Committee Member); Illindala Mahesh (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, University of Akron, 2019, Electrical Engineering

In this dissertation, a core design is proposed to minimize the core loss of a high-power wireless charging system (WCS). The core-loss characteristics are investigated through finite element analysis (FEA). Compared to the traditional uniform thickness core, in the proposed core geometry, the core thickness in the pad is considered as a design variable. An FEA-based optimization algorithm is developed for the proposed core to decrease the variation of flux density in the core by optimizing the core thickness and thus minimize the core loss. The effectiveness of the proposed design and optimization is verified for a double-D (DD) coil-based 5 kW WCS prototype. Simulation and experimental results show that the core loss in the proposed core can be reduced by up to 25% compared to the traditional core made with ferrite blocks with uniform thickness. An advanced shield design method is proposed to suppress the electromagnetic field emissions in high-power WCS. To design a low-loss highly-effective shield for the high-power circular pads, a copper shield-ring is added with the traditional aluminum shield to provide an additional degree-of-freedom to the design. The shielding-effectiveness and loss of the proposed shield-ring are investigated through FEA and tested using a 7.0 kW WCS. The simulation and experimental results show that the shield loss was reduced by 20% using a copper shield ring compared to the traditional aluminum shield and the magnetic field emission was suppressed below the limits of the International Commission on Non-Ionized Radiation Protection (ICNIRP). For the DD charging pads, a hybrid-shield is proposed combining the magnetic and conductive shielding techniques. The effectiveness of the proposed hybrid-shield was investigated through FEA and tested for a DD coil-based 11 kW WCS. The simulation and experimental results show that using the proposed hybrid-shield, the leakage magnetic field can be suppressed by up to 37% compared to a tradition (open full item for complete abstract)

Committee: Malik Elbuluk (Advisor); Seungdeog Choi (Committee Co-Chair); Joan Carletta (Committee Member); Yi Ping (Committee Member); Espanol Malena (Committee Member) Subjects: Electrical Engineering; Electromagnetics

Doctor of Philosophy, The Ohio State University, 2018, Electrical and Computer Engineering

This dissertation gives guidelines for state-of-the-art power harvesters and for optimizing its components, e.g., rectifier, matching network, and antenna, in various applications. A single diode rectifier using a quarter-wave matching circuit with a measured efficiency of 73.7% is also presented. Several experimental demonstrations are included for powering a number of sensors and devices, such as a clock, computer mouse, calculator, thermometer, medical insulin pump, and super capacitor with power management circuitry. To increase the amount of RF harvested power, an array of rectifying antennas (rectennas) is presented and used in experiments up to 60 meters. Wireless power transfer demonstrations at near field distances are also presented. For the latter, we show a strong tolerance to misalignment while delivering high levels of power (1.2 mW over 42 cm). As an application, a medical pump is successfully powered over this distance. Further, bandwidth widening techniques are presented along with rectifier optimizations. To reduce the overall dimensions of the rectenna, miniaturization techniques are discussed. This leads to a rectenna size of 1.5 x 2.5 cm^2, making it ideal for medical or on-body applications. This rectenna was used to successfully activate a body-worn thermometer across 65 cm. In the case of implantable devices, a dielectric matching layer was found useful and validated using pig skin. A related SAR analysis ensured the safety of the proposed RF powering harvesting techniques.

Committee: John Volakis (Advisor); Asimina Kiourti (Advisor); Liang Guo (Committee Member) Subjects: Electrical Engineering; Electromagnetics

Master of Science in Electrical Engineering (MSEE), Wright State University, 2017, Electrical Engineering

Wireless power transfer (WPT) technology is becoming attractive in a wide variety of applications such as electric-vehicle charging, induction heating, charging portable applications, industrial robots, and biomedical implants. Recent studies have shown various techniques to implement wireless power transfer and these techniques differ based on the type of applications. For example, for electric vehicle charging, the power levels are in the range 5 kW to 25 kW and the operating frequency is in the range 70 kHz to 110 kHz. On the other hand, for consumer applications, the power levels vary from a few watts to hundreds of watts and operates at frequencies of the order of 5 MHz to 10 MHz. This thesis addresses the analysis, design, implementation, and simulation of a wireless charging system targeted towards a high-frequency, low-power portable application with wide separation between transmitter and receiver. The WPT system is composed of three important blocks: inverter (or transmitter), transformer (or coil), and rectifier (or receiver). Hard-switching inverters and rectifiers have major drawbacks at high frequencies due to large switching power loss. Therefore, soft-switching Class-E topology is chosen. The Class-E dc-ac inverter with CLL resonant tank, also referred to as pi2a impedance matching network is analyzed, designed, and simulated to observe its superior performance over other topologies at varying coupling coefficients and loads. Four soft-switching rectifier topologies are analyzed, designed, and simulated to evaluate their behavior at high frequencies. Their compatibility with Class-E inverters in the presence of loosely-coupled transformers is discussed. The physical and commercial limitations of using transformers with magnetic core is presented. Therefore, the preferred solution, an air-core transformer is designed and integrated with the rectifier to evaluate their characteristics at selected coupling coefficient. The overall system including t (open full item for complete abstract)

Committee: Marian Kazimierczuk Ph.D. (Advisor); Saiyu Ren Ph.D. (Committee Member); Yan Zhuang Ph.D. (Committee Member) Subjects: Electrical Engineering; Electromagnetics; Electromagnetism; Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2012, Electrical Engineering

This research presents several different platforms for detecting chemical or biological agents without the use of probes or wires and without the use of a battery. These platforms all use an interrogator to transmit power through either radio or low frequency electromagnetic waves to a sensor device. The sensor device has a functionalized surface which aids in selectivity to the analyte of interest. The sensor device sends back a portion of the power through radio frequency waves with altered frequency, amplitude and phase. The characteristics of the received signal contain the information about the analyte of interest. The platforms were tested with several volatile organic compounds, gasoline, sulfuric acid, hydraulic fluid, and chlorine. The results were statistically significant.

Committee: Guru Subramanyam Ph.D (Committee Chair); Partha Banerjee Ph.D (Committee Member); Malcolm Daniels Ph.D (Committee Member); James Grote Ph.D (Committee Member) Subjects: Biomedical Engineering; Electrical Engineering; Electromagnetics