Spherical Helices for Resonant Wireless Power Transfer

Maja Škiljo,Zoran Blažević

doi:10.1155/2013/426574

Maja Škiljo, Zoran Blažević

Open Access

https://doi.org/10.1155/2013/426574

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Abstract

The capabilities of electrically small spherical helical antennas for wireless power transmission at small and moderate distances are analyzed. Influence of design on antenna radiation resistance, efficiency, and mode ratio is examined. These are the factors that, according to the theoretical considerations depicted herein, govern the maximum transfer performances. Various designs and configurations are considered for the purpose, with accent on small-size receivers suitable for implementation in powering common-sized gadgets. It is shown that spherical helix design is easily manipulated to achieve a reduced antenna size. Good radiation characteristics and impedance match are maintained by multiple-arm folded antenna design and by adjusting the separation between the arms.

Highlights

Tesla’s great experimental work at the turnover of XIX and XX centuries [1,2,3,4,5,6] was the first consideration in history of applying radio-waves and principle of resonant coupling on transmission of energy without wires
The analysis clearly shows that, besides the radiation efficiency, the mode ratio match between the antennas is another crucial factor for maximizing power transfer efficiency (PTE) defined as the ratio of the power delivered to the load and the total power that enters the transmitting antenna port [11]
The theoretical bound for wireless power transfer (WPT) between two different electrically small antennas (ESAs) is examined by using the antennas of reduced size, that is, limited radiation efficiency

Summary

Introduction

Tesla’s great experimental work at the turnover of XIX and XX centuries [1,2,3,4,5,6] was the first consideration in history of applying radio-waves and principle of resonant coupling on transmission of energy without wires. According to Wheeler [14] and [17], for the wire geometries that occupy equal electrical volumes in self-resonance, the larger the physical volume of the antenna, the shorter the wire needed to achieve the self-resonance This is important for the WPT system design due to the ohmic loss problem that limits the radiation efficiency. The analysis clearly shows that, besides the radiation efficiency, the mode ratio match between the antennas is another crucial factor for maximizing power transfer efficiency (PTE) defined as the ratio of the power delivered to the load and the total power that enters the transmitting antenna port [11] This is important for all WPT systems that apply different antennas such as RFID, where there is still considerable space for improvement in performance related to the distance and reliability of reading tags.

The Optimization Parameters of Resonant WPT

Spherical Helical Antenna for WPT

WPT Example with SHAs

Findings

Conclusion