History and Innovation of Wireless Power Transfer via Microwaves

Naoki Shinohara

doi:10.1109/jmw.2020.3030896

Abstract

Wireless power transfer (WPT) has a long history of over 100 years since the first experiment conducted by Nicola Tesla. However, the most interesting innovation of WPT was born in the 21 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">st</sup> century. In this decade, near-field WPT commercialization was advanced, and we now use many near-field WPT products, such as wireless chargers for mobile phones and electric vehicles. In the next decade, we can expect the development of far-field WPT via microwaves, through which we can drive Internet of Things (IoT) sensors without batteries based on transmitted or ambient microwave power. We can charge mobile phones with microwave power. When we focus microwave power on a target by beam forming technology, we can transmit higher wireless power to fly drones or from space to the earth. In conjunction with the research & development of microwave-based WPT, radio regulations suitable for each country need to be discussed. In this paper, I review the history, innovation, and status of the radio regulations of WPT via microwaves with the classification of wide-beam WPT, including harvesting, and narrow-beam WPT.

Highlights

A wireless power transfer (WPT) is considered as one of the game-changing technologies
WPT innovation was initiated in the 21st century with the discovery of a resonance coupling WPT by a research group at Massachusetts Institute of Technology [1] in 2006
Before the innovation of resonance coupling WPT, inductive coupling applications of a transformer, an inductive heater, a near-field communication, and a contactless charger were in use for a wireless phone

Summary

INTRODUCTION

A wireless power transfer (WPT) is considered as one of the game-changing technologies. It is easy to find commercial products of near-field WPT based on inductive coupling technology via a high-frequency magnetic field with coils, such as wireless chargers for mobile phones and electric vehicles. The experiment failed because the transmitted power diffused in all directions using 150-kHz radio waves with a wavelength of 21 km It was a wide-beam WPT similar to a broadcasting system. The wide-beam WPT system is defined as a far-field (Fraunhofer region) WPT system to provide the wireless power to multi users without district target detection. Kyoto University, developed the wireless charger for a mobile phone at 2.45 GHz around 2000 It is based on a narrow beam WPT technology developed in Kyoto University from 1980s. The sensors had batteries; they could be driven without batteries (Fig. 1)

KEY TECHNOLOGY OF WIDE-BEAM WPT

KEY TECHNOLOGY OF NARROW-BEAM WPT

INNOVATION OF NARROW-BEAM WPT

DISCUSSION STATUS OF REGULATION OF NARROW-BEAM WPT

CONCLUSION