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This thesis proposes a theoretical and experimental framework for the modeling, analysis and design of a complete energy and data transfer system, which provides constant performances independently of the receiver position. The energy transfer is considered for industrial scenarios, which require high powers and efficiencies, as well as for biomedical implants, which have high distances but do not require necessarily high efficiency. In the former, the method provides a constant received voltage, independent of the load and position in one direction of the receiver and without any feedback loop. It is based on a geometrical optimization of an inductive link composed of three coils and on resonant inverters and rectifier, respectively in class EF and E, operating at 6.78MHz. Furthermore, it enables to passively localize the receiver, without requiring its involvement. In the latter, the proposed solution enables to power small implants without knowing their orientation. The high throughput data transfer is intended for the industrial scenario, where it integrates in a single system with the power link and enables every part to connect and cooperate with each other. It employs consumer hardware and provides bandwidths of over 100Mb/s, independently of the position and with high resistance to interference., Questa tesi propone un quadro teorico e pratico per la modellazione, l'analisi e il progetto di un sistema completo per il trasferimento di energia e dati indipendente dalla posizione del ricevitore. Il trasferimento di energia è trattato sia per scenari industriali, che richiedono alte potenze ed efficienze, sia per quelli di impianti biomedicali, che presentano distanze significative ma non necessitano di particolari efficienze. Nel primo caso, il metodo proposto consente una tensione al ricevitore costante, indipendente dalla posizione, in una direzione, e dal carico del ricevitore, senza nessuna necessità di controllo in retroazione. Si basa sulla ottimizzazione geometrica di un link induttivo composto da tre spire e su inverter e rettificatore risonanti, in classe EF ed E, rispettivamente, funzionanti a 6.78MHz. Consente inoltre di localizzare il ricevitore in maniera passiva e indipendente dal ricevitore. Nel secondo caso, la soluzione proposta consente di alimentare dispositivi impiantabili indipendentemente dalla loro rotazione. Il trasferimento dei dati a banda larga si inserisce nello scenario industriale, integrandosi in un unico sistema di potenza e dati, con la possibilità anche di interagire tra loro. Attraverso l'uso di hardware di consumo, consente bande superiori a 100Mb/s, indipendentemente dalla posizione, con ottima resistenza alle interferenze.

We present a new Resonant Wireless Power Transfer system based on a geometrically optimized coil and a double immittance inverter design. The receiver Tee immittance inverter is obtained by a coil identical to the receiver one, but orthogonally placed, whereas a discrete inductor is deployed on the transmitter side. The reference link consists of the receiving coil (implanted in bio-tissue/blood) and the external conformal transmitting coil at a distance of 50mm (20mm in blood, 30mm in free-space): the overall link design focuses on transmitting coil optimization for maximum coupling factor. The simulated link efficiency at 6.78 MHz reaches the promising value of 14.4%, with a load of 55 Ohm. The influence of coils copper thickness is also investigated: the replacement of the standard 35 μm-thick copper with a 0.5 mm-thick one allows to achieve a more than twice efficiency of 34%.

This paper discusses some significant design issues that are faced in resonant inductive system for wireless power transfer ‘on the move’. The targeted system adopts a single AC source to power a sequence of transmitting (Tx) coils, placed along theRxpath, whose geometry is optimized to minimize the variations of coupling for every possibleRxposition. To retain a constant coupling coefficient, two nearbyTxcoils are series-connected and simultaneously activated, establishing a path without any theoretical bound on its length, by a suitable switching network. This work analyzes the effects of asynchronous switching times, which are rigorously accounted for and minimized by a proper design of the compensating circuit elements, minimizing both the voltage spikes and the over currents on the coils, while keeping the system at resonance. A prototype operating at 6.78 MHz is built and experimental validations are carried out to verify the feasibility of a constant coupling link without experiencing the mentioned effects, but the adopted procedure is general and independent on its size or frequency.

In this paper we describe a geometry design solution to minimize performance variations of a wireless power transfer system “on the move” (WPT-Mob). A sequence of switchable couples of coils, connected in series or in parallel, is adopted at the fixed transmitting link side; the geometry of the moving receiver is optimized to keep the coupling factor, and thus the power transfer, constant during the movement. First the analytical formulation of the link coupling factor is derived as a function of its circuit-equivalent parameters computed by full-wave simulation. Then selected geometry parameters of the receiver side are optimized to keep the coupling factor constant while the link is moving. A set of TX-RX arrangements are simultaneously analysed to emulate the sliding movement of the WPT-Mob. The final optimized geometry demonstrates that a constant power transfer on-the-move is enabled, even for variable TX-to-RX link distances. Design and experimental verification are carried out for a geometry suitable for medium power transfer (tens of Watts) at 6.78 MHz, but the method is formulated in such a way that the system can be scaled up and down to accomplish different application needs.

The idea of this paper is to develop a moving resonant wireless power transfer (WPT) system capable of keeping the coupling factor, and thus the power transfer, invariable with respect to the reciprocal system sides positions. A typical scenario is the WPT to moving objects on a platform equipped with a sequence of coils underneath. If a single TX coil is active at a time, the receiver movement would cause the coupling coefficient, and consequently the transmitted power, to oscillate. To cope with this problem, in this work we propose to make use of two active Tx coils. Different coil geometries and coil connections have been investigated, trying to get an insight into the coupling mechanism. This have been done by full-wave simulations and measurements of the selected structures and by varying some key parameters of the geometry itself. The connections between coils have been done in post-processing and the results have been plotted for comparison. Future work has been proposed.

An increasing interest is arising in developing miniaturized antennas in the microwave range. However, even when the adopted antennas dimensions are small compared with the wavelength, radiation performances have to be preserved to keep the system-operating conditions. For this purpose, magneto-dielectric materials are currently exploited as promising substrates, which allows us to reduce antenna dimensions by exploiting both relative permittivity and permeability. In this paper, we address generic antennas in resonant conditions and we develop a general theoretical approach, not based on simplified equivalent models, to establish topologies most suitable for exploiting high permeability and/or high-permittivity substrates, for miniaturization purposes. A novel definition of the region pertaining to the antenna near-field and of the associated field strength is proposed. It is then showed that radiation efficiency and bandwidth can be preserved only by a selected combinations of antenna topologies and substrate characteristics. Indeed, by the proposed independent approach, we confirm that non-dispersive magneto-dielectric materials with relative permeability greater than unit, can be efficiently adopted only by antennas that are mainly represented by equivalent magnetic sources. Conversely, if equivalent electric sources are involved, the antenna performances are significantly degraded. The theoretical results are validated by full-wave numerical simulations of reference topologies. Published version available at: https://doi.org/10.1017/S1759078715000859