Abstract
Wireless power transfer (WPT) technologies can wirelessly power or charge electrical and electronic devices, which is useful in situations where continuous power is required but wired connections are hard or impossible. WPT is needed in various humaninvolved environments, such as human body for charging implants and electronics in a living room. The application of WPT systems are constrained by their rapid decrease in power transmission efficiency (PTE) when the transfer distance increases. Moreover, in a human-involved environment, PTE could dramatically drop due to a shift of resonating frequency caused by a human body. The Strongly Coupled Magnetic Resonance (SCMR) was introduced recently, which extends the transmission range from a few centimetres to a few meters and utilizes the non-radiative near field to transfer energy. These features make it a promising WPT technique. However, most SCMR systems are narrow-band, and their limited bandwidth resulted from the high quality factor of resonators may lead to dramatic efficiency drops when they are exposed to the interference caused by surrounding high-dielectric objects in human- involved environments. Although wide-band SCMR WPT is needed in such an environment, the existing studies of SCMR mainly focus on improving the transmission efficiency of these systems, and there is very few studies targeting on the efficiency drop problem due to the narrow bandwidth of a SCMR system. One solution of this problem is to turn a SCMR system wide-band. The circuit model of a wide-band SCMR system and accurate electromagnetic modelling of the resonators (especially solenoids of irregular shapes) for the system are essential but missing in the literature. Moreover, compact wide-band SCMR resonators are needed for various applications. These challenges are tackled in this dissertation. iii In this dissertation, firstly, a circuit model was successfully proposed for a wideband SCMR system to facilitate the understanding of how the system parameters, e.g., the configuration of the resonator and that of the system, affect the bandwidth of the system. For the EM modeling of SCMR resonators, fast and accurate models were proposed to calculate the intrinsic inductance and capacitance of irregular solenoid resonators that are commonly used in a SCMR WPT system and other resonating RF systems. Based on the theoretical models of both the resonators and the system, wide-band high-performance SCMR systems were proposed for different targeted human-involved environments. The bandwidths for the proposed SCMR systems are improved significantly, leading to a robust and stable power transfer when they are used in a dielectric-noisy human-involved environment where, traditionally, the PTE is always dramatically dropped mainly caused by a resonance frequency shift by human subjects. Moreover, electromagnetic bandgap (EBG) structures are applied to a SCMR system for a safe and efficient WPT for ingestible devices. For the various novel designs, experiments and simulations were conducted, successfully demonstrating the stability and high efficiency of the power transfer. With the proved competitive performance, i.e. wireless robust and stable power transfer, the proposed new SCMR systems are good candidates in various human-involved applications, e.g., consumer electronics, electric vehicles and biomedical implants. This dissertation offers three main contributions: a circuit model for wide-band SCMR systems, fast and accurate models for calculating the intrinsic inductance and capacitance of irregular solenoid resonator, and designing wide-band SCMR systems for various human-involved applications. They pave the way towards a high feasibility of WPT for our daily lives.