JP2011205881A - System configured to exchange energy wirelessly, method of transmitting electromagnetic energy wirelessly via coupling of evanescent wave, and system configured to exchange electromagnetic energy wirelessly - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system configured to exchange energy wirelessly.SOLUTION: The system includes a structure configured to exchange energy wirelessly via coupling of evanescent waves, wherein the structure is electromagnetic (EM) and non-radiative and includes a structure that generates an EM near-field in response to reception of energy and a metamaterial arranged within the EM near-field in such a manner that the coupling is enhanced.

Description

  The present invention relates to transferring energy, and more particularly to transferring energy wirelessly.

  This application was filed on December 3, 2009 by Koon Hoo Teo et al., Application number 12 / 630,498 “Wireless Energy Transfer Using Negative Refractive Index Material. with Negative Index Material) and claims priority from this patent application, which is hereby incorporated by reference.

Wireless energy transfer Inductive coupling is used in many wireless energy transfer applications, such as charging cordless electronic toothbrushes or hybrid vehicle batteries. In a coupled inductor, such as a transformer, the source, e.g. the primary coil, generates energy as an electromagnetic field, and the sink, e.g. The field is subtended to be as similar as possible. In order to optimize energy, the distance between the source and the sink should be as small as possible. This is because the guidance method becomes very ineffective as the distance increases.

Resonant coupling system In resonant coupling, two resonant electromagnetic objects, a source and a sink, interact with each other under resonant conditions. Resonant coupling transfers energy from the source to the sink over a medium distance, eg, a fraction of the resonant frequency wavelength.

  FIG. 12 shows a conventional resonant coupling system 100 for transferring energy from a resonant source 110 to a resonant sink 120. The general principle of operation of system 100 is similar to inductive coupling. A driver 140 inputs energy into the resonant source to form an oscillating electromagnetic field 115. The excited electromagnetic field decays at a rate relative to the excitation signal frequency at the driver, or the source and sink self-resonant frequencies for the resonant system. However, if the resonant sink absorbs more energy than it lost during each cycle, most of the energy is transferred to the sink. Operating the resonant source and resonant sink at the same resonant frequency ensures that the resonant sink has a low impedance at that frequency and that energy is optimally absorbed. Examples of resonant coupling systems are disclosed in US Patent Application Publication Nos. 2008/0278264 and 2007/0222542, which are incorporated herein by reference.

  Energy is transferred over a distance D between a plurality of resonant objects, eg, a resonant source having size L1 and a resonant sink having size L2. The driver connects the power supply to the source, and the resonant sink is connected to a power consuming device, such as a resistive load 150. Energy is supplied to the resonant source by the driver, transmitted wirelessly and non-radiatively from the resonant source to the resonant sink, and consumed by the load. Wireless non-radiative energy transfer is performed using a field 115, such as an electromagnetic or sound field of a resonant system. For simplicity of this specification, the field 115 is an electromagnetic field. During coupling of the resonant object, the evanescent wave 130 is propagated between the resonant source and the resonant sink.

Bond Strength According to the bond mode theory, the bond strength is represented by the coupling coefficient k. Coupling enhancement is represented by an increase in the absolute value of the coupling coefficient k. Based on coupled mode theory, the resonant frequency of the resonant coupled system is divided into multiple frequencies. For example, in a resonant coupling system of two objects, two resonant frequencies, called even mode frequency and odd mode frequency, can be observed due to coupling effects. The coupling coefficient of the resonant system of two objects formed by two identical resonant structures is calculated by dividing the even and odd modes according to the following equation (1).

κ = π | f _even −f _odd | (1)

US Patent Application Publication No. 2008/0278264 US Patent Application Publication No. 2007/0222542

  The challenge is to strengthen the bond. For example, a resonant object with a high quality factor is selected to optimize the coupling.

  Therefore, it is desirable to optimize wireless energy transfer between the source and sink.

  Embodiments of the present invention are based on the realization that evanescent wave coupling is enhanced by placing one or more metamaterials along the path of the evanescent wave coupling between the source and the sink.

  Embodiments of the present invention disclose a system configured to exchange energy wirelessly. The system is a structure that is configured to exchange energy wirelessly via coupling of evanescent waves, the structure being electromagnetic (EM) and non-radiating. The body comprises a structure that generates an EM near field in response to receiving energy, and a metamaterial disposed within the EM near field such that coupling is enhanced.

  Another embodiment is a method of wirelessly transmitting electromagnetic energy via evanescent wave coupling, using a metamaterial to increase the amplitude of the evanescent wave so that coupling is enhanced; Providing a first resonator structure having a first mode having a resonant frequency ω1, an intrinsic loss factor Γ1, and a first Q value Q1 = ω1 / (2Γ1), the first resonance The resonator structure is electromagnetic and is designed to have Q1> 100, providing a first resonator structure, positioned distally from the first resonator structure; Providing a second resonator structure that is not electrically wired to the one resonator structure, the second resonator structure comprising a resonant frequency ω2, an intrinsic loss factor Γ2, and a second Q value of 2 Q2 = ω2 / (2Γ Providing a second resonator structure having a second mode having 2), the second resonator structure being electromagnetic and designed to have Q2> 100; , Disposing the metamaterial between the first resonator structure and the second resonator structure, and a distance D from the first resonator structure to the second resonator structure through the metamaterial. And transmitting the electromagnetic energy over a distance D smaller than each of the resonant wavelengths λ1 and λ2 corresponding to the resonant frequencies ω1 and ω2, respectively.

  Yet another embodiment is a system configured to exchange electromagnetic energy wirelessly and has a resonance frequency ω1, an intrinsic loss factor Γ1, and a first Q value Q1 = ω1 / (2Γ1). A first resonator structure having one mode, the first resonator structure being electromagnetic and designed to have Q1> 100; and A second resonator structure positioned distally from the first resonator structure and not electrically wired to the first resonator structure, the second resonator structure Has a second mode having a resonant frequency ω2, an intrinsic loss factor Γ2, and a second Q value Q2 = ω2 / (2Γ2), the second resonator structure being electromagnetic, Q2 A second resonator structure, a first resonator structure, designed to have> 100 A metamaterial disposed between the second resonator structure and the first resonator structure transmits electromagnetic energy over a distance D to the second resonator structure through the metamaterial. Disclose a system comprising a metamaterial, wherein the distance D is smaller than each of the resonant wavelengths λ1 and λ2 corresponding to the resonant frequencies ω1 and ω2, respectively.

  This can optimize wireless energy transfer between the source and sink.

FIG. 1 illustrates an example of a system suitable for transmitting or receiving energy wirelessly. It is a block diagram which shows different embodiment of this invention. It is a figure which shows the evanescent wave coupling | bonding when not using NIM. It is a figure which shows the evanescent wave coupling | bonding in the case of using NIM. It is a block diagram which shows different embodiment of this invention. It is a block diagram which shows different embodiment of this invention. It is a block diagram which shows different embodiment of this invention. FIG. 1 illustrates an example of a system for wirelessly supplying energy to a moving device. It is a figure which shows the example of application of NIM in the capacity loading type | mold loop resonance system 800 resonating at about 8 MHz. FIG. 6 is a graph comparing energy transfer efficiency as a function of frequency with and without NIM. FIG. 6 is a table comparing energy transfer efficiency as a function of frequency with and without NIM. FIG. 1 illustrates an example of a system suitable for transmitting or receiving energy wirelessly. FIG. 5 is a graph comparing energy transfer efficiency as a function of frequency with metamaterial and without NIM. FIG. It is a block diagram of the conventional resonant coupling system.

  Embodiments of the present invention provide metamaterials, such as negative index material (NIM), placed in an electromagnetic (EM) near field on the path of an evanescent wave while energy is transmitted wirelessly. And / or is based on the recognition that a single-negative (SNG) metamaterial increases the amplitude of the evanescent wave and thus optimizes the efficiency of energy transfer.

  FIG. 1 shows a system 200 according to an embodiment of the present invention. The system is configured to exchange energy wirelessly, eg, transmit or receive, and includes an electromagnetic (EM) non-radiating structure 210. The structure 210 has a dimension 211, eg, a diameter, configured to generate an electromagnetic near field 220 when energy is received by the structure and to exchange energy wirelessly via coupling of evanescent waves. .

  Most of the energy is reactive, confined within the transmitter or resonator, and only a small portion of this energy can radiate into the far field (usually less than 10 percent).

  In this embodiment, energy 260 is supplied by a driver (not shown) known in the prior art. In this embodiment, structure 210 serves as the source of the wireless energy transfer system. In an alternative embodiment, energy 260 is supplied wirelessly from a source (not shown). In that embodiment, the structure 210 serves as a sink for the wireless energy transfer system.

  The system 200 further comprises a metamaterial 230 disposed in the near field 220. A metamaterial is a material having negative dielectric constant and / or negative permeability characteristics. Several unusual phenomena are known for this material, such as evanescent wave amplification, surface plasmon-like behavior, and negative refraction. The embodiment of the present invention is an amplification of an evanescent wave by understanding and utilizing the unique ability of a metamaterial. This optimizes wireless energy transfer.

  When energy 260 is received by structure 210, an RM near field is generated in substantially all directions around the EM structure. The near field is symmetric with the far field. Because the structure is non-radiating, most of the energy is confined in the near field and only a small portion of less than 10% of the energy is emitted in the far field.

  Within the near field, the shape and dimensions of this near field depend on the frequency of the external energy 260 and the resonant frequency of the EM structure 210. The resonant frequency of the EM structure 210 depends, in part, on the parameters of the EM structure, such as circular shape, spiral shape, cylindrical shape, and material of the EM structure such as conductivity, relative permittivity, and relative permeability. It depends on. In this embodiment, to minimize energy loss due to radiation, the size of the structure is much smaller than the length of the dominant wavelength of the system, for example 100 times smaller than this length.

  Usually, the near-field range 270 is a fraction of the length of the dominant wavelength of the system, for example 1/4 or 1/10 of this length. In a non-resonant system, the dominant wavelength is determined by the frequency of the external energy 260, ie the wavelength λ265. In a resonant system, the dominant wavelength is determined by the resonant frequency of the EM structure. Usually, the dominant wavelength is determined by the frequency of energy exchanged wirelessly.

  Resonance is characterized by a quality factor (Q value), a dimensionless ratio between stored energy and dissipated energy. Since the purpose of the system 200 is to transmit or receive energy wirelessly, the frequency of the driver or resonant frequency is selected, for example, to increase the size of the near field region. In some embodiments, the frequency of energy 260 and / or the resonant frequency is in the MHz to GHz range. In other embodiments, the above-described frequencies are in the optical domain.

Evanescent wave An evanescent wave is a near-field standing wave whose intensity decreases exponentially with the distance from the boundary where the wave is formed. The evanescent wave 250 is formed at the boundary between the structure 210 and another “medium” having different characteristics with respect to wave motion, such as air. The evanescent wave is formed when external energy is received by the EM structure and is most powerful within one third of the near-field wavelength from the surface of the EM structure 210.

  It should be understood that many different configurations of the system 200 are possible in addition to the embodiments described below. For example, in this embodiment, system 200 is a sink configured to receive energy wirelessly from a source. In another embodiment, system 200 is a source configured to transmit energy wirelessly to a sink. In yet another embodiment, the system 200 is a source configured to transfer energy to multiple sinks simultaneously.

  In some embodiments, during operation of the system 200, the structure 210 receives the evanescent wave 251 at the same time it emits the evanescent wave, whether it is a source or a sink. The metamaterial 230 is disposed on the path of at least one evanescent wave 250 or 251. If the desired direction of transmitted or received energy is known, the metamaterial, eg, metamaterial 230 or NIM 231 is optimally positioned based on the desired direction of energy exchange.

  In other embodiments, multiple metamaterials are optimally placed on the path of the evanescent wave to maximize the amplitude of this wave.

  FIG. 2A illustrates a system 300 according to another embodiment of the present invention. System 300 is a resonant coupling system and includes at least one metamaterial 230 disposed on the path of evanescent wave 330 within the near field of source 310. The energy 260 is provided to the system 300 by the driver 140, transmitted wirelessly by the source 310 via the evanescent wave 330 to the sink 320 and consumed by the load 150. In this embodiment, the load includes a processor.

  In a variation of system 300, metamaterial 230 is placed closer to the source than sink 320. In another variation, the metamaterial 231 is placed closer to the sink than to the source. In yet another variation, multiple metamaterials 230 and 231 are placed on the path of the evanescent wave 330 so that the evanescent wave travels through each metamaterial in the multiple metamaterials during combining. Typically, metamaterials are arranged to optimize the evanescent wave coupling between the source and sink during wireless energy transfer. In this embodiment, the metamaterial is positioned such that the distance between the metamaterial and the structure is proportional to the size of the metamaterial. Typically, the smaller the size of the metamaterial, the closer it is placed to the EM structure.

  A variation of system 300 improves upon the system described in US Patent Application No. 2007/0222542, filed July 5, 2006 and granted on February 3, 2010 by Joannopoulos et al. It is a thing. The electromagnetic energy transfer system of this embodiment includes a first resonator structure 310 having a first mode having a resonance frequency ω1, a loss rate Γ1, and a first Q value Q1 = ω1 / (2Γ1); A second resonator structure 320 positioned distally from the first resonator structure and not electrically wired to the first resonator structure. The second resonator structure has a second mode having a resonance frequency ω2, an intrinsic loss factor Γ2, and a second Q value Q2 = ω2 / (2Γ2).

  The first resonator structure transmits electromagnetic energy to the second resonator structure over a distance D that is smaller than each of the resonance wavelengths λ1 and λ2 corresponding to the resonance frequencies ω1 and ω2, respectively. Furthermore, the resonator structure is designed to have a first Q value and a second Q value greater than 100, ie Q1> 100 and Q2> 100.

  One of the main improvements of this embodiment over the system described by Joanopros is that the first resonator structure is electromagnetically moved over a distance D from the metamaterial to the second resonator structure. An arrangement of the metamaterial 230 between the first resonator structure and the second resonator structure to transfer energy. Here, the distance D is smaller than the resonance wavelengths λ1 and λ2 corresponding to the resonance frequencies ω1 and ω2, respectively.

  In different variants of this embodiment, the value of the Q value is greater than 200, greater than 500 or greater than 1000. Additionally or alternatively, the two frequencies ω1 and ω2 are close together in the smaller range of Γ1 and Γ2. Additionally or alternatively, different numbers, types, and / or arrangements of metamaterials are used.

Evanescent wave coupling Evanescent wave coupling is the process by which electromagnetic waves are transmitted from one medium to another by an evanescent, exponentially decaying electromagnetic field.

  Coupling is usually achieved by placing two or more electromagnetic elements, i.e. source and sink, at a distance D from each other so that the evanescent wave generated by this source does not attenuate much before reaching the sink. The If the sink supports a mode of the appropriate frequency, the evanescent field causes wave mode propagation, which leads (ie, couples) the wave from one waveguide to the next.

  Evanescent wave coupling is basically the same as near field coupling in electromagnetic field theory. Depending on the impedance of the source elements, evanescent waves are either mainly electrical (capacitive) or predominantly magnetic (inductive), and the components of these waves eventually It is different from the far field where the ratio of impedance in free space is reached and the waves propagate radiatively. Since evanescent wave coupling occurs in a non-radiating field near each medium, it is always associated with a partially reflecting surface matter, ie induced current and charge.

  FIG. 2B shows evanescent wave coupling when NIM is not used, and FIG. 2C shows evanescent wave coupling when NIM is used. When energy is supplied to the source, a near field is generated. Radiation loss and dielectric loss consume a fraction of the energy, but if the radiation is not strong, most of the energy is reflected back to the source. However, if the sink is located close enough to the source, i.e., at a distance D from the source, the evanescent waves 331 and / or 330 are coupled between the source and the sink, thereby transferring energy to the source. To the sink. As shown in FIG. 2B, when NIM is not used, energy is transferred through a combination of source and sink evanescent waves.

  However, if the metamaterial is placed in the near field generated by the source and / or sink during source and sink combination, the amplitude of the evanescent wave is as the wave travels through the metamaterial, as shown in FIG. 2C. Is increased (370). This enhances the evanescent wave coupling and more efficiently transfers energy and / or increases the distance D between the source and sink.

  FIG. 3 illustrates a system 400 according to another embodiment of the present invention. System 400 is a non-resonant system. Non-resonant systems are designed such that the source 410 and sink 420 have different resonant frequencies, as opposed to resonant systems. For example, in a variation of system 400, both the source and sink are resonant structures having different resonant frequencies. In another variation, the sink 420 is a non-resonant structure, such as a load 450. In another variation, source 410 is a non-resonant structure, such as driver 440.

  FIG. 4 shows a system 500 according to yet another embodiment of the present invention. In this embodiment, the material of the EM structure itself includes a metamaterial. For example, in a variation of this embodiment, the source 510 is made from a metamaterial. In other variations, sink 520 and / or both sink and source are made from metamaterial. In different variations, the source and sink are made from the same or different metamaterials. In yet another variation of this embodiment, a second metamaterial 231 is positioned on the path of the evanescent wave 530 in addition to the metamaterial included in the EM structure.

  FIG. 5 shows a system 600 according to yet another embodiment of the present invention. In this embodiment, metamaterial 640 substantially surrounds EM structure 610. For example, in a variation of this embodiment, the source 610 has a cylindrical shape and the metamaterial has a similar cylindrical shape with a slightly larger diameter. In other variations, sink 620 and / or both sink and source are surrounded by metamaterial. In another variation of this embodiment, a second metamaterial 231 is positioned on the path of the evanescent wave 630 in addition to the metamaterial 640. This embodiment is particularly advantageous in applications where multi-directional energy is exchanged or where the direction is not known a priori.

  The table of FIG. 9 shows the coupling coefficients calculated for different wireless energy transfer systems. The coupling coefficient is a measure of the strength of coupling between two EM structures and quantifies the rate at which energy transfer occurs between these EM structures. Based on FIG. 5, it is clear that the embodiment of the present invention increases the coupling coefficient, which increases the efficiency of the system. For example, a single block of metamaterial increases the coupling coefficient in one system from 3.88e4 to 7.60e4. Two blocks of metamaterial further increase the coupling coefficient to 14.8e4.

  Embodiments of the invention can be used in a variety of applications, systems and devices that require wireless energy transfer, such as automobiles, mobile communicators, laptops, audio / video devices.

  FIG. 6 illustrates a system 700 for wirelessly supplying energy to mobile devices such as elevator cars and electric vehicles. In this embodiment, an elevator car 750 without a cable, i.e. a load, is connected to an antenna 720, i.e. a sink, configured to receive energy wirelessly from the waveguide 760. The waveguide is installed in the hoistway and receives energy from the driver 710. The driver is connected to the power grid and can supply energy to the waveguide, eg, inductively. The waveguide is configured to generate an electromagnetic evanescent wave. For example, in this embodiment, the waveguide is mounted via a conducting wire. In another embodiment, one side of the waveguide has perforations or slots 780 that allow evanescent waves to exit the surface of the waveguide.

  The metamaterial 730 is disposed between the sink and the waveguide, and is fixed to the antenna 720, for example. When the antenna is moved, the metamaterial is moved accordingly. The metamaterial is positioned such that evanescent waves emitted from the energy transfer area 765 of the waveguide reach the antenna through the metamaterial. As the car is moved by the traction mechanism 760, the energy transfer area is adjusted accordingly.

  Antenna 720 and metamaterial 730 form system 200. When connected to devices with at least one degree of freedom, such as elevator cars, electric vehicles, and mobile phones, the system 200 allows those devices to be wireless but efficiently receive energy. To do.

Negative refractive index material (NIM)
Some embodiments of the present invention use NIM as a metamaterial. NIM is an artificial material having a negative dielectric constant characteristic ε and a negative magnetic permeability characteristic μ. Evanescent waves between the source and sink are amplified while propagating through the NIM with optimized energy transfer.

  In some embodiments, the NIM used in the system has electromagnetic characteristics of ε = −1, μ = −1. When the evanescent wave propagates through the NIM, the impedance of the NIM is matched with the free space impedance, no reflection occurs at the interface between the NIM and the free space (this is essential for power transmission), and the evanescent wave is Amplified through NIM.

  In other embodiments, the NIM has a negative dielectric constant characteristic ε and a negative magnetic permeability characteristic μ, but not exactly −1. In these embodiments, surface plasmons are excited at the interface between the NIM and other media such as air, gas, or vacuum while storing energy and EM field strength. NIM typically involves material loss due in part to dielectric loss and in part to dispersion loss. Material loss reduces evanescent wave amplification during propagation through the NIM. However, surface waves are excited and energy is stored at the interface between NIM and other media. This property extends evanescent wave propagation and optimizes energy coupling between the source and sink.

  There are many different ways to design a NIM. For example, a split ring resonator (SPR) with a metal wire structure is an example of a NIM artificial material design. SPR and inductive-capacitive (LC) resonators are other examples of NIM designs. Embodiments of the present invention use any type of NIM that meets the objective of evanescent wave enhancement. In this embodiment, the system is a resonant system and the NIM has a refractive index equal to −1 at the resonant frequency of the system.

  FIG. 7 shows an application example of NIM in a capacitively loaded loop resonant system 800 that resonates at about 8 MHz. The capacity loaded loop 810 serves as a source for the system 800. The capacitively loaded loop has a radius 815 of 30 cm, a copper wire cross-sectional radius 817 of 2 cm, and a capacitive dielectric disk area 819 of 138 cm 2 with a dielectric constant characteristic ε = 10. Energy is confined to the short distance of the LC loop in the form of evanescent waves.

  A metal loop structure 820 with a 50 ohm load is the driver for the system. Similarly, a metal loop 830 with a 240 ohm load is the system load. The NIM 840 is placed between the source and the load in the near field of the source. The driver and load radius 822 is 20 cm. The driver is placed at a distance of 20 cm from the source 824 and is inductively coupled with the source.

  The placement of the NIM in the near field relies on the driver and load design, especially when the impedance in the driver and load needs to be changed to achieve maximum power transfer efficiency.

  To obtain maximum coupling enhancement, the physical cross-sectional size, thickness, and position of the NIM relative to the energy transfer field is determined according to the configuration of the system elements, such as sources, sinks, drivers and loads, and the environment in which the system is located Need to optimize. In this embodiment, optimization is accomplished through computer modeling or experimentally, allowing for the best impedance matching that allows maximum power transfer.

  FIG. 8 is a graph comparing energy transfer efficiency as a function of frequency with and without NIM. As shown, the efficiency 920 of a system that includes NIM is three times greater than the efficiency 910 of a corresponding system that does not use NIM.

  NIM materials with strict electromagnetic properties occur only at a single frequency. This means that the strict material properties ε = −1, μ = −1 only occur at one frequency, such as f = 8 MHz. However, NIM exhibits negative electromagnetic characteristics in a bandwidth of about 5-10% of the resonance frequency. In systems where the NIM is designed to operate at 10 MHz, a bandwidth of about 0.5 MHz to 1 MHz is achieved around 10 MHz where the dielectric constant and permeability are negative. In this bandwidth, if the negative EM characteristic frequency range of the NIM covers the resonant frequency point of the resonant component, the NIM is utilized in the wireless power transfer system to enhance the coupling and power transfer efficiency.

Single Negative (SNG) Metamaterial Some embodiments of the present invention use a single negative (SNG) metamaterial as the metamaterial. An SNG metamaterial is a metamaterial that has only a negative dielectric constant, ie, ε <0, μ> 0, or has only a negative permeability, ie, ε> 0, μ <0. More specifically, a metamaterial having ε <0, μ> 0 is an ε negative (ENG) metamaterial, and a metamaterial having ε> 0, μ <0 is a μ negative (MNG) metamaterial. It is.

  In a variation of this embodiment, the dimension 211 of the system 200 is smaller than the wavelength 265, whereby the structure's EM far-field radiation is ignored and the electric and magnetic fields are independent of each other. The independence of the electric and magnetic fields allows the near field electric or magnetic dominant to be used separately. For near-fields with electrical dominance, metamaterials with only negative dielectric constant ε are used to enhance evanescent waves. In the case of a near field with a magnetic dominant, a metamaterial with only negative permeability μ is used to enhance the evanescent wave.

  Thus, in some embodiments, the type of SNG material that is configured to enhance the evanescent coupling is selected based on the type of coupling. For example, in this embodiment, the bond is an electrical dominant bond and the SNG metamaterial is an ENG metamaterial. In another embodiment, the bond is a magnetic dominant bond and the SNG metamaterial is an MNG metamaterial.

  Metamaterials are dispersible and have material loss. This affects the enhancement of evanescent waves during wireless energy transfer. A NIM typically includes two sets of resonant structures. One is for giving a negative dielectric constant (ε <0), and the other is for giving a negative permeability (μ <0). Two sets of structures contribute to metamaterial loss and dispersion. Also, the NIM design is relatively complex because these structures need to be designed such that the ε <0 and μ <0 regions occur simultaneously and give a negative refractive index.

  For SNG metamaterials, only one set of artificial structures is required to achieve ε <0 or μ <0 properties. SNG metamaterials have important advantages over NIM. First, the SNG metamaterial design is simpler. Second, the SNG metamaterial manufacturing process is simpler. Third, the loss associated with SNG metamaterial is typically less than the loss associated with NIM. Typically, the performance of a wireless energy transfer system using SNG metamaterial is better than the performance of a system using NIM.

  FIG. 10 shows an example of a wireless energy transfer system 1100 according to an embodiment of the present invention. Source 1110 and sink 1120 are the same self-resonant coil made from copper wire. The radius of this coil is 30 cm, and the radius of the copper wire is 5 mm. Each coil is composed of 5.25 turns of such copper wire and extends over 20 cm. The resonance frequency of the coil is about 10 MHz. The distance between the two coils is 2 m.

  Two metal loops with a radius equal to 20 cm are a driver 1150 and a load 1160. The positions of the two small metal loops are adjusted to optimize impedance matching and wireless energy transfer efficiency. In the system, two metamaterial slabs 1130 and 1140 are used to improve performance. The metamaterial has a cylindrical shape with a radius of 40 cm and a height of 4 cm. The optimized transmission efficiency of various systems is calculated and compared by the software.

  FIG. 11 is a graph comparing the efficiency of energy transfer systems, ie, the efficiency 1210 for a system without metamaterial and the meta of the parameters ε = −1 + 0.001i, μ = −1 + 0.001i (NIM). The efficiency 1220 in the case of the system using the material is compared with the efficiency 1230 in the case of the system using the metamaterial of the parameters ε = 1 and μ = −1 + 0.001i (MNG metamaterial).

  As shown by the graph, the system without metamaterial has a peak efficiency of about 33%. A system using NIM has a higher peak efficiency of about 40%. The peak efficiency of the system using MNG metamaterial is further increased to about 50%. In comparison, both NIM and MNG metamaterials improve the transmission efficiency of the system. NIM has losses in both permittivity and permeability, whereas SNG metamaterials have losses only in permittivity or permeability. Because of this advantage, higher efficiencies are achieved when using SNG metamaterials.

  Although the invention has been described by way of examples of preferred embodiments, it is to be understood that various other adaptations and modifications can be made within the spirit and scope of the invention. Accordingly, it is the object of the appended claims to cover all modifications and variations that fall within the true spirit and scope of the invention.

Claims (20)

A system configured to exchange energy wirelessly,
A structure configured to wirelessly exchange the energy via coupling of evanescent waves, the structure being electromagnetic (EM) and non-radiating, wherein the structure is the energy A structure that generates an EM near field in response to receiving
A metamaterial disposed in the EM near field such that the amplitude of the evanescent wave is increased;
A system configured to wirelessly exchange energy comprising. The structure is a source configured to transmit the energy to a sink;
The system
A driver configured to supply the energy to the structure;
A system configured to wirelessly exchange energy according to claim 1. The structure is a sink configured to receive the energy wirelessly from a source;
The system
Further comprising a load configured to receive the energy from the structure.
A system configured to wirelessly exchange energy according to claim 1.   The system configured to wirelessly exchange energy according to claim 1, wherein a dimension of the structure is smaller than a wavelength of the evanescent wave.   The system configured to wirelessly exchange energy according to claim 1, wherein the structure is a resonant structure.   The system configured to wirelessly exchange energy according to claim 1, wherein the metamaterial is optimally positioned based on a desired direction of the energy transfer.   The system configured to wirelessly exchange energy according to claim 1, wherein the metamaterial is disposed, for example, to surround the structure.   The energy of claim 1, wherein the plurality of metamaterials are disposed on the path of the evanescent wave such that the evanescent wave travels through each metamaterial in the plurality of metamaterials during the combining. System configured to do.   The system configured to wirelessly exchange energy according to claim 1, wherein the metamaterial has negative dielectric constant characteristics and positive permeability characteristics.   The system configured to wirelessly exchange energy according to claim 1, wherein the metamaterial has a positive permittivity characteristic and a negative permeability characteristic. A method of wirelessly transmitting electromagnetic energy through coupling of evanescent waves,
Increasing the amplitude of the evanescent wave using a metamaterial so that the coupling is enhanced. A method of wirelessly transmitting electromagnetic energy via evanescent wave coupling. Providing a first resonator structure having a first mode having a resonance frequency ω1, an intrinsic loss factor Γ1, and a first Q value Q1 = ω1 / (2Γ1), Providing a first resonator structure that is electromagnetic and is designed to have Q1>100;
Providing a second resonator structure positioned distally from the first resonator structure and not electrically wired to the first resonator structure, the second resonator structure comprising: The resonator structure has a second mode having a resonance frequency ω2, an intrinsic loss factor Γ2, and a second Q value Q2 = ω2 / (2Γ2), and the second resonator structure is electromagnetic Providing a second resonator structure designed to have Q2>100;
Disposing the metamaterial between the first resonator structure and the second resonator structure;
Transmitting the electromagnetic energy over a distance D from the first resonator structure through the metamaterial to the second resonator structure, the distance D corresponding to resonance frequencies ω1 and ω2, respectively. Transmitting, smaller than each of the resonant wavelengths λ1 and λ2,
The method of wirelessly transmitting electromagnetic energy via coupling of evanescent waves according to claim 11 further comprising:   The method for wirelessly transmitting electromagnetic energy through coupling of evanescent waves according to claim 11, wherein the metamaterial has positive dielectric constant characteristics and negative magnetic permeability characteristics.   The method of wirelessly transmitting electromagnetic energy through coupling of evanescent waves according to claim 11, wherein the metamaterial has a negative dielectric constant characteristic and a positive magnetic permeability characteristic.   The method of wirelessly transmitting electromagnetic energy through coupling of evanescent waves according to claim 11, wherein the metamaterial has a negative dielectric constant characteristic and a negative magnetic permeability characteristic.   12. The method of wirelessly transmitting electromagnetic energy through coupling of evanescent waves according to claim 11, wherein the size of the structure is smaller than the wavelength of the evanescent waves. A system configured to exchange electromagnetic energy wirelessly,
A first resonator structure having a first mode having a resonance frequency ω1, an intrinsic loss factor Γ1, and a first Q value Q1 = ω1 / (2Γ1), wherein the first resonator structure is A first resonator structure that is electromagnetic and designed to have Q1>100;
A second resonator structure positioned distally from the first resonator structure and not electrically wired to the first resonator structure, wherein the second resonator structure Has a second mode having a resonant frequency ω2, an intrinsic loss factor Γ2, and a second Q value Q2 = ω2 / (2Γ2), wherein the second resonator structure is electromagnetic, Q2 A second resonator structure designed to have>100;
A metamaterial disposed between the first resonator structure and the second resonator structure, wherein the first resonator structure passes through the metamaterial and the second resonator. Transmitting the electromagnetic energy to the structure over a distance D, wherein the distance D is smaller than each of the resonance wavelengths λ1 and λ2 corresponding to the resonance frequencies ω1 and ω2, respectively;
A system configured to exchange electromagnetic energy wirelessly.   The first resonator structure transmits the electromagnetic energy through evanescent wave coupling, the structure has a size smaller than each of the resonance wavelengths λ1 and λ2, and the metamaterial is a single The system configured to wirelessly exchange electromagnetic energy according to claim 17, which is a negative (SNG) metamaterial.   19. The electromagnetic energy of claim 18, wherein the coupling is an electrical dominant coupling, the SNG metamaterial is an ε negative (ENG) metamaterial, and ε is a dielectric constant property of the metamaterial. A system configured to be exchanged with.   19. The electromagnetic energy of claim 18, wherein the coupling is a magnetic dominant coupling, the SNG metamaterial is a μ negative (MNG) metamaterial, and μ is a permeability characteristic of the metamaterial. A system configured to be exchanged with.

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