Fano Resonance Among Magnetic Coils for Midrange Position Sensing Capability

Taehwa Lee,Daniel Hashemi,Hideo Iizuka,Michio Yasunishi,Hiroshi Yoshimoto,Kenichi Yatsugi

doi:10.1109/access.2021.3052689

Abstract

A magnetically coupled three-coil system to have one transmitting and two receiving coils is considered. We show that the position of the transmitting coil can be estimated from the ratio of received wave amplitudes and its angular derivative when the two receiving coils are strongly coupled to each other and each of the receiving coils is weakly coupled to the transmitting coil, i.e., a Fano resonance phenomenon. A coupled mode theory is developed to elucidate the midrange position sensing mechanism, where the ratio of received wave amplitudes is inversely proportional to the ratio of the coupling strengths of each receiving coil to the transmitting coil at the intrinsic resonance frequency of the receiving coils.

Highlights

Midrange coupling via magnetic fields in the kilohertzmegahertz range has been extensively explored in wireless power transfer [1]–[16], and found various application scenarios in consumer electronics [17], [18], electric vehicles [19]–[22], and medical implants [23]–[25]
We show that in a magnetically-coupled system consisting of one transmitting and two receiving coils, both the angle and the distance of the transmitting coil can be estimated from the ratio of received wave amplitudes and its angular derivative when the two receiving coils are strongly coupled to each other and each of the receiving coils is weakly coupled to the transmitting coil
This is a Fano resonance phenomenon that can provide a unique ratio of received wave amplitudes in the receiving coils, enabling position sensing of coil 1

Summary

INTRODUCTION

Midrange coupling via magnetic fields in the kilohertzmegahertz range has been extensively explored in wireless power transfer [1]–[16], and found various application scenarios in consumer electronics [17], [18], electric vehicles [19]–[22], and medical implants [23]–[25]. Coil 1 is placed at position (R, θ) far away from the pair of coils 2 and 3, and is weakly coupled to each of coils 2 and 3 by magnetic fields, where R is the distance from the coil pair and θ is the angle from the z axis in the zx plane [θ and x have the same sign]. The axis of coil 1 directs to the origin of the coordinate system This is a Fano resonance phenomenon that can provide a unique ratio of received wave amplitudes in the receiving coils, enabling position sensing of coil 1. We will refer to scattering parameters Sji (coils i to j) or voltages Vj (coil j) for evaluating characteristics of the system of Fig. 1

THEORY

SYSTEM PERFORMANCE

CONCLUSION