# US 8,786,135 B2 · Wireless energy transfer with anisotropic metamaterials

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- Number: US 8,786,135 B2
- Document ID: US8786135B2
- Status: Granted
- Kind: B2
- Application number: 13/027,383
- Filed: 2011-02-15
- Published: 2012-02-16
- Granted: 2014-07-22
- Earliest claimed: 2010-03-25
- Assignees: Mitsubishi Electric Research Laboratories, Inc.
- Applicants: Bingnan Wang; Koon Hoo Teo; William Yerazunis
- Inventors: Bingnan Wang; Koon Hoo Teo; William Yerazunis
- Web page: https://patentgrep.com/patent/US8786135B2

## CPC

- B66B 7/00: Other common features of elevators
- H04B 5/26: using coils
- H04B 5/266: {One coil at each side, e.g. with primary and secondary coils}
- H04B 5/79: for data transfer in combination with power transfer
- B66B: ELEVATORS; ESCALATORS OR MOVING WALKWAYS ({apparatus for raising or lowering persons on theatrical stages or the like A63J5/12} ; funicular railbound systems with rigid ground-supported tracks and cable traction, e.g. cliff railways, B61B9/00; arrangements of ammunition handlers in vessels B63G3/00; hoists, lifts, or conveyors for loading or unloading in general B65G; braking or detent devices controlling normal movements of winding drums or barrels B66D; ship-lifting devices E02C; garages for many vehicles with mechanical means for lifting vehicles E04H6/12; hoists for feeding ammunition or projectiles to launching apparatus or to loading mechanisms F41A9/00)
- H04B: TRANSMISSION

## Abstract

A system includes a structure configured to exchange the energy wirelessly via a coupling of evanescent waves and an anisotropic metamaterial arranged within an electromagnetic near-field such that an amplitude of the evanescent waves is increased. The structure is electromagnetic and non-radiative, wherein the structure generates the electromagnetic near-field in response to receiving the energy.

## Claims

### Claim 1

A system configured to exchange energy wirelessly, comprising:
a source and a load exchanging the energy wirelessly via a coupling of evanescent waves along a particular direction, wherein the source and the load are electromagnetic (EM), non-radiative and resonant structures, wherein the coupling between the structures is strong and a strength of the coupling is represented by a coupling coefficient, and wherein dimensions of the structures are smaller than a wavelength of the evanescent waves;
a driver for supplying the energy to the source, wherein the source generates an EM near-field along the particular direction in response to receiving the energy, such that the EM near-field is an electric-dominant and the coupling is an electric-dominant coupling or the EM near-field is a magnetic-dominant and the coupling is a magnetic-dominant coupling; and
an anisotropic metamaterial arranged on the particular direction within the EM near-field of the source, wherein the anisotropic metamaterial is a single-negative (SNG) metamaterial having a type selected from a group consisting of an ∈-negative (ENG) metamaterial and a μ-negative (MNG) metamaterial, wherein the type is selected to correspond a dominant type of the coupling, such that the SNG metamaterial is the ENG metamaterial if the coupling is the electric-dominant coupling, or the SNG metamaterial is the MNG metamaterial if the coupling is the magnetic-dominant coupling, and wherein a metamaterial property of the SNG metamaterial is aligned with the particular direction such that the coupling coefficient is increased.

### Claim 2 (depends on 1)

The system of claim 1, wherein a plurality of anisotropic metamaterials is arranged on a path of an evanescent wave, such that the evanescent wave travels through each anisotropic metamaterial in the plurality of anisotropic metamaterials during the coupling.

### Claim 3 (depends on 1)

The system of claim 1, wherein the anisotropic metamaterial has a negative permittivity property and a positive permeability property along the particular direction.

### Claim 4 (depends on 1)

The system of claim 1, wherein the anisotropic metamaterial has a positive permittivity property and a negative permeability property along the particular direction.

### Claim 5

A method of transferring electromagnetic energy wirelessly via a coupling of evanescent waves, comprising steps of:
transferring the energy wirelessly via a strong coupling of evanescent waves along a particular direction, wherein a strength of the coupling is represented by a coupling coefficient, and wherein the coupling is an electric-dominant coupling or a magnetic-dominant coupling; and
increasing the strength of the coupling using an anisotropic metamaterial, wherein the anisotropic metamaterial is an ∈-negative (ENG) metamaterial if the coupling is the electric-dominant coupling or a μ-negative (MNG) metamaterial if the coupling is the magnetic-dominant coupling.

### Claim 6 (depends on 5)

The method of claim 5, further comprising:
providing a first resonator structure having a first mode with a resonant frequency ω1, an intrinsic loss rate Γ1 and a first Q-factor Q1=ω1/(2Γ1), wherein the first resonator structure is electromagnetic and designed so that Q1>100;
providing a second structure positioned distal from the first electromagnetic resonator structure and not electrically wired to the first resonator structure, the second resonator structure has a second mode with a resonant frequency ω2, an intrinsic loss rate Γ2, a second Q-factor Q2=ω2/(2Γ2), wherein the second resonator structure is electromagnetic and designed so that Q2>100;
arranging the anisotropic metamaterial between the first resonator structure and the second resonator structure, wherein the anisotropic metamaterial has a property of a metamaterial along the particular direction aligned with the particular direction of the energy transfer; and
transferring the electromagnetic energy from the first resonator structure through the anisotropic metamaterial to the second resonator structure over a distance D, wherein the distance D is smaller than each of the resonant wavelength λ1 and λ2 corresponding to the resonant frequencies ω1 and ω2 respectively.

### Claim 7 (depends on 5)

The method of claim 5, wherein the anisotropic metamaterial has a positive permittivity property and a negative permeability property only along the particular direction.

### Claim 8 (depends on 5)

The method of claim 5, wherein the anisotropic metamaterial has a negative permittivity property and a positive permeability property only along the particular direction.

### Claim 9 (depends on 5)

The method of claim 5, wherein the anisotropic metamaterial has a negative permittivity property and a negative permeability property only along the particular direction.

### Claim 10 (depends on 5)

The method of claim 5, wherein the anisotropic metamaterial is formed by inhomogeneities having dimensions smaller than a wavelength of the evanescent waves.

### Claim 11

A system configured to exchange electromagnetic energy wirelessly, comprising:
a first resonator structure having a first mode with a resonant frequency ω1, an intrinsic loss rate Γ1 and a first Q-factor Q1=ω1/(2Γ1), wherein the first resonator structure is electromagnetic and designed so that Q1>100;
a second resonator structure positioned distal from the first resonator structure and not electrically wired to the first resonator structure, the second resonator structure has a second mode with a resonant frequency ω2, an intrinsic loss rate Γ2, a second Q-factor Q2=ω2/(2Γ2), wherein the second resonator structure is electromagnetic and designed to have Q2>100; and
an anisotropic metamaterial arranged between the first resonator structure and the second resonator structure, wherein the first resonator structure transfers the electromagnetic energy through the anisotropic metamaterial to the second resonator structure via a strong coupling of evanescent waves over a distance D, wherein the distance D is smaller than each of the resonant wavelength λ1 and λ2 corresponding to the resonant frequencies ω1 and ω2 respectively, wherein a dominant type of the coupling is an electric-dominant coupling or a magnetic-dominant coupling, wherein the anisotropic metamaterial is a single-negative (SNG) metamaterial having a type selected from a group consisting of an ∈-negative (ENG) metamaterial and a μ-negative (MNG) metamaterial, wherein the type corresponds to the dominant type of the coupling, such that the SNG metamaterial is the ENG metamaterial if the coupling is the electric-dominant coupling or the SNG metamaterial if the coupling is the magnetic-dominant coupling.

### Claim 12 (depends on 11)

The system of claim 11, wherein dimensions of the structure are smaller than each of the resonant wavelength λ1 and λ2, and wherein the anisotropic metamaterial is the SNG metamaterial only along a direction of energy transfer.

### Claim 13 (depends on 12)

The system of claim 12, wherein the anisotropic metamaterial is formed by planar sheets of two-dimensional array of inhomogeneities, wherein the planar sheets are arranged in parallel.

### Claim 14 (depends on 13)

The system of claim 13, wherein the planar sheets are arranged such that the direction of the energy transfer is perpendicular to the planar sheets.