A. Alphones

Optimization of double spiral metamaterial for wireless power transfer

Metamaterials (MMs) have been proposed to improve the performance of wireless power transfer (WPT) systems. However, optimization of WPT systems with MM using complex electromagnetic analytical methods and slow finite element simulation methods have become increasingly tedious. A simple analytical approach using equivalent circuit method to optimize WPT systems with MMs is proposed in this paper. A Double spiral metamaterial (DSM) is introduced and analyzed using the proposed approach. Furthermore, a detailed optimization process is presented considering system level performance indices (efficiency and transferred power) and application level requirements (transfer distance, maximum misalignment and probability of alignment). A novel figure-of-merit is introduced to achieve better compromise between system level performance indices and application level requirements. The proposed optimization strategy is validated with the experimental results.

Coil enhancements for high efficiency wireless power transfer applications

Achieving high efficiency with improved power transfer range and misalignment tolerance is the major design challenge in realizing Wireless Power Transfer (WPT) systems for industrial applications. Resonant coils must be carefully designed to achieve highest possible system performance by fully utilizing the available space. High quality factor and enhanced electromagnetic coupling are key indices which determine the system performance. In this paper, design parameter extraction and quality factor optimization of multi layered helical coils are presented using finite element analysis (FEA) simulations. In addition, a novel Toroidal Shaped Spiral (TSS) coil is proposed to increase power transfer range and misalignment tolerance. The proposed shapes and recommendations can be used to design high efficiency WPT resonator in a limited space.

Repeater tuning against load variation for wireless power transfer

The incorporation of a repeater with a wireless power transfer (WPT) system for the performance improvement is investigated in this paper. Tuning of the self-resonance frequencies of transmitter, receiver and repeater coils is investigated as a promising approach to improve the performance against load variation. Theoretical analysis is presented using equivalent circuit method, and the 2-coil equivalent of WPT system with a repeaters is explored. Numerical results are presented along with experimental results to validate the proposed method.

Tunable metamaterials for optimization of wireless power transfer systems

Metamaterials (MMs) have been proposed to improve the performance of wireless power transfer (WPT) systems. The performance of identical unit cells having the same transmitter and receiver self-resonance is presented in the literature. This paper presents the optimization of tunable MM for performance improvement in WPT systems. Furthermore, a figure of merit (FOM) is proposed for the optimization of WPT systems with MMs. It is found that both transferred power and power transfer efficiency can be improved significantly by using the proposed FOM and tunable MM, particularly under misaligned conditions.

Wideband circularly polarized modified trapezoidal-shaped monopole antenna

A novel-shaped monopole antenna is proposed for wideband circularly polarized radiation and wireless systems. The antenna consists of a trapezoidal-shaped radiator and a microstrip feed line. A wideband circularly polarized radiation is achieved with modified trapezoidal-shaped radiator and ground plane. Impedance matching of the antenna is achieved by using quarter-wave transformer in tandem with microstrip feed line. The antenna prototype shows a 47% (2.84-4.58 GHz) for VSWR of 2 with a 3-dB axial ratio bandwidth of 36% (3.2 to 4.6 GHz). Overall antenna size is 38.0 mm× 40.0 mm× 0.8 mm with a maximum gain of 2 dBic.