On-Site Wireless Power Generation

Conventional wireless power transfer systems consist of a microwave power generator and a microwave power receiver separated by some distance. To realize efficient power transfer, the system is typically brought to resonance, and the coupled-antenna mode is optimized to reduce radiation into the surrounding space. In this scheme, any modification of the receiver position or of its electromagnetic properties results in the necessity of dynamically tuning the whole system to restore the resonant matching condition. It implies poor robustness to the receiver location and load impedance, as well as additional energy consumption in the control network. In this study, we introduce a new paradigm for wireless power delivery based on which the whole system, including transmitter and receiver and the space in between, forms a unified microwave power generator. In our proposed scenario the load itself becomes part of the generator. Microwave oscillations are created directly at the receiver location, eliminating the need for dynamical tuning of the system within the range of the self-oscillation regime. The proposed concept has relevant connections with the recent interest in parity-time symmetric systems, in which balanced loss and gain distributions enable unusual electromagnetic responses.Comment: 10 pages, 13 figure

Enhancing wireless power transfer efficiency for potential use in cardiovascular applications

Left Ventricular Assist Devices (LVAD) are being used to assist blood circulation in heart failure patients. The requirement to have a continuous energy supply is deteriorating the patients’ life quality since they need either to carry along two heavy battery packs or to attach a power cable. For this reason, a wireless power transmission (WPT) system is developed to power the LVAD. Within its effective charging region, the WPT system will offer an autonomous charging process which may lead to a smaller battery pack and cableless experience to the user. Previous WPT systems for cardiovascular applications are either compromised by poor transfer efficiency, short transmission distance or safety issues. To address these problems, an impedance matching WPT system is being designed. For increasing the overall transfer efficiency, both sides impedance matching technique and low loss matching networks are being worked on. In addition, efficiency specific design approach is being developed to reduce design complexity. As a result, the transfer efficiency and transmission distance of the impedance matched WPT have been increased by a factor of 7 and 6 times respectively. The conceptual idea for implementing such a system is also discussed in this thesis. Furthermore, safety measurements have been performed to ensure the system is safe to be used

Transmissão de energia sem fios baseada em acoplamento elétrico ressonante

Doutoramento em Engenharia EletrotécnicaContained in this document are theoretical and experimental results related to the feasibility of resonant electrical coupling as a method of wirelessly transferring power across non-negligible distances. As shown, resonant electrical coupling is remarkably similar to resonant magnetic coupling in several aspects. However, while resonant magnetic coupling is currently a method of wirelessly transferring power with a very strong presence in the literature, resonant electrical coupling is not. The lack of material related to resonant electrical coupling, together with the potential of achieving a balanced trade-off between critical features such as efficiency, distance, simplicity, size and power transfer capability, were the main motivations for considering this specific topic. The possibility of constructively combining resonant electrical coupling and resonant magnetic coupling is also addressed. A review of the state of the art of wireless power, not only in terms of scientific publications but also in terms of market adoption and international standards, is included in this document.Contidos neste documento estão resultados teóricos e experimentais relacionados com a viabilidade do uso de acoplamento elétrico ressonante como um método de transferência de energia sem fios através de distâncias não negligenciáveis. Conforme mostrado, o acoplamento elétrico ressonante é notavelmente semelhante ao acoplamento magnético ressonante em vários aspetos. No entanto, enquanto que o acoplamento magnético ressonante é atualmente um método de transferência de energia sem fios com uma presença muito forte na literatura, o acoplamento elétrico ressonante não é. A ausência de material relacionado com acoplamento elétrico ressonante, em conjunto com o potencial de atingir um compromisso equilibrado entre características críticas, tais como eficiência, distância, simplicidade, tamanho e capacidade de transferência de potência, foram as principais motivações para considerar este tóptico específico. A possibilidade de combinar de forma construtiva acoplamento elétrico ressonante e acoplamento magnético ressonante é também abordada. Uma revisão do estado da arte da transferência de energia sem fios, não só em termos de publicações científicas, mas também em termos de adoção do mercado e normas internacionais, é incluída neste documento

A Novel Power-Efficient Wireless Multi-channel Recording System for the Telemonitoring of Electroencephalography (EEG)

This research introduces the development of a novel EEG recording system that is modular, batteryless, and wireless (untethered) with the supporting theoretical foundation in wireless communications and related design elements and circuitry. Its modular construct overcomes the EEG scaling problem and makes it easier for reconfiguring the hardware design in terms of the number and placement of electrodes and type of standard EEG system contemplated for use. In this development, portability, lightweight, and applicability to other clinical applications that rely on EEG data are sought. Due to printer tolerance, the 3D printed cap consists of 61 electrode placements. This recording capacity can however extend from 21 (as in the international 10-20 systems) up to 61 EEG channels at sample rates ranging from 250 to 1000 Hz and the transfer of the raw EEG signal using a standard allocated frequency as a data carrier. The main objectives of this dissertation are to (1) eliminate the need for heavy mounted batteries, (2) overcome the requirement for bulky power systems, and (3) avoid the use of data cables to untether the EEG system from the subject for a more practical and less restrictive setting. Unpredictability and temporal variations of the EEG input make developing a battery-free and cable-free EEG reading device challenging. Professional high-quality and high-resolution analog front ends are required to capture non-stationary EEG signals at microvolt levels. The primary components of the proposed setup are the wireless power transmission unit, which consists of a power amplifier, highly efficient resonant-inductive link, rectification, regulation, and power management units, as well as the analog front end, which consists of an analog to digital converter, pre-amplification unit, filtering unit, host microprocessor, and the wireless communication unit. These must all be compatible with the rest of the system and must use the least amount of power possible while minimizing the presence of noise and the attenuation of the recorded signal A highly efficient resonant-inductive coupling link is developed to decrease power transmission dissipation. Magnetized materials were utilized to steer electromagnetic flux and decrease route and medium loss while transmitting the required energy with low dissipation. Signal pre-amplification is handled by the front-end active electrodes. Standard bio-amplifier design approaches are combined to accomplish this purpose, and a thorough investigation of the optimum ADC, microcontroller, and transceiver units has been carried out. We can minimize overall system weight and power consumption by employing battery-less and cable-free EEG readout system designs, consequently giving patients more comfort and freedom of movement. Similarly, the solutions are designed to match the performance of medical-grade equipment. The captured electrical impulses using the proposed setup can be stored for various uses, including classification, prediction, 3D source localization, and for monitoring and diagnosing different brain disorders. All the proposed designs and supporting mathematical derivations were validated through empirical and software-simulated experiments. Many of the proposed designs, including the 3D head cap, the wireless power transmission unit, and the pre-amplification unit, are already fabricated, and the schematic circuits and simulation results were based on Spice, Altium, and high-frequency structure simulator (HFSS) software. The fully integrated head cap to be fabricated would require embedding the active electrodes into the 3D headset and applying current technological advances to miniaturize some of the design elements developed in this dissertation

Antennas and Propagation

This Special Issue gathers topics of utmost interest in the field of antennas and propagation, such as: new directions and challenges in antenna design and propagation; innovative antenna technologies for space applications; metamaterial, metasurface and other periodic structures; antennas for 5G; electromagnetic field measurements and remote sensing applications

Inductive power transfer technology for mobile battery charger

Inductive power transfer (IPT) is an application of electromagnetic induction principle. Since electromagnetic induction phenomena is directly proportional to the operating frequency, so as we increase the operating frequency, amount of energy transfer from one coil to another coil will also increase. As our power supply frequency is 50Hz so at this frequency, amount of energy transfer from one coil to another coil will be very less. In this thesis it is shown that, to transfer maximum amount of energy from one coil to another coil, it is necessary to use IPT at high frequency. At high frequency skin effect is more pronounced but there is a resonant frequency where overall efficiency is more in spite skin effect. To increase the power factor of IPT circuit compensated capacitor has used. There are four types of compensated topology but to use the IPT circuit in mobile battery charger primary-series-secondary-parallel (P-S-S-P) is more useful

A Practical Guide to Estimating Coil Inductance for Magnetic Resonance Applications

Radiofrequency (RF) coils are employed to transmit and/or receive signals in Magnetic Resonance (MR) systems. The design of home-made, organ-specific RF coils with optimized homogeneity and/or Signal-to-Noise Ratio (SNR) can be a plus in many research projects. The first step requires accurate inductance calculation, this depending on the conductor's geometry, to later define the tuning capacitor necessary to obtain the desired resonance frequency. To fulfil such a need it is very useful to perform a priori inductance estimation rather than relying on the time-consuming trial-and-error approach. This paper describes and compares two different procedures for coil inductance estimation to allow for a fast coil-prototyping process. The first method, based on calculations in the quasi-static approximation, permits an investigation on how the cross-sectional geometry of the RF coil conductors affects the total inductance and can be easily computed for a wide variety of coil geometries. The second approach uses a numerical full-wave method based on the Finite-Difference Time-Domain (FDTD) algorithm, and permits the simulation of RF coils with any complex geometry, including the case of multi-element phased array. Comparison with workbench measurements validates both the analytical and numerical results for RF coils operating within a wide field range (0.18–7 T)