Mu-Negative Metamaterials Seen as Band-Limited Non-Foster Impedances in Inductive Power Transmission Systems

Jorge V De Almeida,Carlos A F Sartori,Gláucio L Siqueira,Marbey M Mosso

doi:10.1590/2179-10742019v18i41625

Abstract

In the last decade, various works have demonstrated that a class of artificial material called metamaterials (MTM) can synthesize mu-negative (MNG) media capable of evanescent-wave focusing which largely enhances the magnetic coupling between coils, which is the basic mechanism of Inductive Power Transmission (IPT) systems. In the present work, MTM-enhanced coupling in IPT systems is examined through analytical and numerical results, which are validated by experimental data. Adopting a transmission-line (TL) based approach to describe the general MTM-enhanced IPT system, it is evidenced that MNG MTMs can be interpreted as a negative impedance from a circuital point of view.

Highlights

The exploitation of evanescent waves in the near field for power transfer purpose has gained a lot of interest recently [1]
It had been demonstrated that free-space magnetic coupling can be described as virtual TL and that a MTM can be interpreted as a virtual impedance added to this circuit
It has been shown that the amplification effect is not contradictory with the law of conservation of energy since it results from the exchange of energy between the reactive modes in the near field of the loops

Summary

INTRODUCTION

The exploitation of evanescent waves in the near field for power transfer purpose has gained a lot of interest recently [1]. To the radiation resistance of an antenna [12], it has no relationship with the thermal equilibrium of the circuit generating the flux From this fact comes the result shown in Eq (7) where the real part of Rm′ can be positive, negative or null depending on the balance of the energies stored in each field. As a pure positive reactance, it acts as conventional inductance and stores the surrounding magnetic field From this comes the conclusion that the observed gain at the resonance is taken its surplus of energy from the attenuation of the higher frequencies modes that are being “trapped” by the MTM. Both Z0 and γ will not be altered below the resonance, it will tend to diminish around the resonance and it will tend to increase above the resonance

APPLICATION

RESULTS AND DISCUSSION

CONCLUSION