Wireless power transmission system and method thereof

Abstract

A wireless power transfer system includes a resonator, the resonator including a capacitor. The capacitor includes at least two active electrodes, and a passive electrode adjacent to the active electrode. The passive electrode is configured to surround the active electrode to at least partially eliminate environmental effects affecting the active electrode and increase the overall capacitance of the system. The resonator also includes at least one induction coil electrically connected to the active electrode, wherein the resonator is configured to extract power from the generated electric field through resonant electric field coupling.

Description

Technical Field

[0001] The subject disclosure generally relates to wireless power transfer systems and methods thereof. Background Art

[0002] A variety of wireless power transfer systems are known. A typical wireless power transfer system includes a power source electrically connected to a wireless power transmitter and a wireless power receiver electrically connected to a load. Examples of wireless power transfer systems include magnetic wireless power transfer systems and electrical wireless power transfer systems.

[0003] In a magnetic wireless power transfer system, the transmitter has an induction coil that transfers electrical energy from a power source to an induction coil of a receiver. Power transfer occurs due to magnetic field coupling between the induction coils of the transmitter and receiver. When an electric field is present, the amplitude of the electric field is low compared to the amplitude of the magnetic field. Therefore, little, if any, power is transferred through electric field coupling. These magnetic wireless power transfer systems have a limited range, and to achieve efficient power transfer, the induction coils of the transmitter and receiver must be in optimal alignment. There are also resonant magnetic wireless power transfer systems in which power is transferred due to magnetic field coupling between the induction coils of the transmitter and receiver. In a resonant magnetic wireless power transfer system, the induction coil uses at least one capacitor to resonate. In a resonant magnetic wireless power transfer system, little, if any, power is transferred through resonant or non-resonant electric field coupling. The power transfer range in a resonant magnetic wireless power transfer system is increased compared to that in a non-resonant magnetic wireless power transfer system, and alignment problems are usually corrected.

[0004] In an electric wireless power transfer system, the transmitter and the receiver have capacitive electrodes. Power transfer occurs due to electric field coupling between the capacitive electrodes of the transmitter and the receiver. When a magnetic field is present, the amplitude of the magnetic field is low compared to the amplitude of the electric field. Therefore, little, if any, power is transferred through magnetic field coupling. Similar to resonant magnetic wireless power transfer systems, there are also resonant electric wireless power transfer systems in which at least one inductor is used to resonate the capacitive electrodes of the transmitter and the receiver. In a resonant electric wireless power transfer system, little, if any, power is transferred through resonant or non-resonant magnetic field coupling. The resonant electric wireless power transfer system has a larger power transfer range than the power transfer range of the non-resonant electric wireless power transfer system, and alignment problems are usually corrected.

[0005] Resonant electric wireless power transfer systems and resonant magnetic wireless power transfer systems require that both the transmitter and the receiver resonate at the same frequency. This frequency is the resonant frequency of the system. In a resonant electric wireless power transfer system, the reactance of the inductor is balanced by the capacitance of the capacitor electrode at the resonant frequency. In addition, in a resonant electric wireless power transfer system, the transmitter and receiver can be tuned to a desired resonant frequency (e.g., 13.56 MHz) by changing the inductance of the inductor and / or the capacitance of the capacitor electrode.

[0006] External conductors and dielectric materials (dielectrics) in the environment affect the electric field generated by the resonant electric wireless power transfer system, thereby affecting the range and efficiency of the system. Even considering the effects of static external conductors and dielectrics, any movement of external conductors and / or dielectrics may affect effective power transfer.

[0007] Specifically, the charges accumulated on the electrodes of the resonant electric wireless power transmission system interact with the charged particles (free charges) that are freely moving within the external conductor in the system environment. This effectively transforms the conductor into a floating electrode and increases the capacitance of the system. The movement of the external conductor relative to the capacitive electrode of the system will variably change the capacitance of the system, depending on the relative position of the external conductor and the capacitive electrode. The change in capacitance changes the resonant frequency of the system, detuning the system. In addition, the resonant frequency of the resonant electric wireless power transmission system is extremely susceptible to its environment because the capacitance of the capacitor depends on the dielectric constant (real part of the relative permittivity) of the medium surrounding the electrode. If the capacitance of the capacitive electrode of the system changes, for example due to the movement of the dielectric in the surrounding medium, the resonant frequency of the system will change.

[0008] The dielectric consists of polar molecules that orient themselves along an electric field. When an electric field is applied to the dielectric, the energy generated by the field causes the molecules to rotate. The polarity of the molecules is opposite to that of the electric field, reducing the strength of the electric field and thus the transmission range of the wireless power system. The free charges in the external conductor align themselves, creating an electric field that is opposite to the electric field generated by the system's capacitive electrodes. This opposition to the generated electric field reduces the range of the system. In addition, the moving charges in the external conductor dissipate energy in the form of heat due to the resistance of the conductor. When the electric field is removed or reversed, some of the rotational energy of the molecules is recovered, while the rest of the energy is lost in the form of heat. The energy lost as heat reduces the overall efficiency of the system. The ability of the dielectric to store and lose energy when an electric field is applied (compared to a vacuum) is expressed as the real and imaginary parts of the relative permittivity of the dielectric, respectively.

[0009] One of the most common and problematic dielectrics is water. Due to the high dielectric constant of water, a small amount of water can have a large effect on the capacitance of the system. A high dielectric constant also means low electric field amplitude and fast decay of the near field. Water easily dissolves charged particles, making it conductive. In addition, water usually contains at least a small amount of free charges. The free charges in the water are accelerated by the potential difference of the generated electric field. The acceleration given by the electric field extracts energy from the electric field, thereby reducing the amplitude of the electric field. At the same time, the electric field generated by the redirection of free charges in the water will also be opposite to the electric field generated by the system. In outdoor environments, resonant electric wireless power transfer systems will encounter varying amounts of water. Water vapor in the air and moisture in the soil may also be present in uncontrolled outdoor environments. Therefore, operating a resonant electric wireless power transfer system in an outdoor environment can pose challenges.

[0010] Resonant electric field coupling requires an inductor to achieve resonance. Inductors are unpopular because they are inefficient, intolerant to temperature changes, heavy, and bulky. The disadvantages of inductors need to be minimized by increasing the capacitance of the system, reducing the inductance required to achieve resonance.

[0011] U.S. Patent Application Publication No. 2015 / 0333538 to Kusunoki et al. discloses a rectangular hexahedral metal housing that surrounds a transmitting resonator or a receiving resonator to remove environmental influences. The rectangular cube structure has one open face to allow field coupling. The depth of the housing must be at least half the transmission distance. Such a housing can be bulky and does not significantly reduce the inductance required to achieve resonance. In addition, the cost of manufacturing such a housing in large quantities is high.

[0012] It is therefore an object of the present invention to at least partially alleviate the mentioned disadvantages. Summary of the invention

[0013] Therefore, in one aspect, a wireless power transfer system is provided, comprising: a resonator, the resonator comprising: a capacitor, the capacitor comprising: at least two active electrodes; and a passive electrode adjacent to the active electrode, the passive electrode being configured to surround the active electrode to at least partially eliminate environmental influences affecting the active electrode; and at least one induction coil electrically connected to the active electrode, wherein the resonator is configured to generate an electric field to transfer power or extract power from the generated electric field.

[0014] In one embodiment, the passive electrodes provide additional capacitance to the capacitor of the resonator and reduce the inductance of the induction coil required to make the system resonate.

[0015] In another embodiment, the resonator forms part of a transmitter configured to wirelessly transmit power, wherein the resonator is configured to generate an electric field. In another embodiment, the resonator is configured to generate a resonant electric field. In another embodiment, the area of ​​the passive electrode is larger than the area of ​​the active electrode of the transmitting resonator by at least the area between the active electrodes of the transmitting resonator.

[0016] In another embodiment, the resonator is a transmitting resonator and the system further includes a receiving resonator, the receiving resonator including at least two active electrodes.

[0017] In another embodiment, the resonator forms part of a receiver configured to extract power wirelessly, wherein the resonator is configured to extract power from the generated electric field by resonant electric field coupling. In another embodiment, the resonator is configured to extract power from the generated resonant electric field.

[0018] In another embodiment, the active electrodes are elongated plates. In another embodiment, the width of the passive electrodes is greater than or equal to twice the width of one of the active electrodes plus a lateral gap between the active electrodes, and the length of the passive electrodes is greater than or equal to the length of one of the active electrodes.

[0019] In another embodiment, the active electrodes are concentric.

[0020] In another embodiment, at least one of the active electrodes is a disk or a ring.

[0021] In another embodiment, the passive electrode is an elongated plate or disk.

[0022] In another embodiment, the passive electrode is a ring having an inner diameter less than or equal to the inner diameter of the inner active electrode.

[0023] In another embodiment, the passive electrode includes a dissipative material attached to an edge of the passive electrode and / or along a perimeter of the passive electrode.

[0024] In another embodiment, the induction coil is located on an opposite side of the passive electrode relative to the active electrode, and the induction coil is electrically connected to the active electrode through a hole in the passive electrode.

[0025] In another embodiment, the capacitor further comprises: a substrate to which the active electrode is attached; and an actuator extending between the substrate and the passive electrode, the actuator being controllable to change the spacing distance between the active electrode and the passive electrode. In another embodiment, the capacitor further comprises: at least two telescopic supports extending between the substrate and the passive electrode, the supports being configured to extend or compress as the spacing distance between the active electrode and the passive electrode changes. In another embodiment, actuation of the actuator is controlled by a microcontroller.

[0026] In another embodiment, the passive electrode is grounded.

[0027] In another embodiment, the passive electrode is not grounded.

[0028] According to another aspect, an unmanned aerial vehicle (UAV) is provided, comprising: a frame; a propulsion system mounted on the frame and configured to provide lift and thrust for the UAV; a power system mounted on the frame and configured to supply power to the propulsion system, the power system comprising: a resonator comprising: a capacitor comprising: at least two active electrodes; and a passive electrode adjacent to the active electrode, the passive electrode being configured to surround the active electrode to at least partially eliminate environmental influences affecting the active electrode, wherein the passive electrode is opposite to an electric field source relative to the active electrode; and at least one induction coil electrically connected to the active electrode, wherein the resonator is configured to extract power from the generated electric field through resonant electric field coupling; and a control system mounted on the frame and configured to control the propulsion system and the power system.

[0029] According to another aspect, a wireless power transfer system is provided, comprising a UAV as described above, and a transmitting resonator, the transmitting resonator comprising: at least two active electrodes; and at least one induction coil electrically connected to the active electrodes, wherein the transmitting resonator is configured to generate an electric field to transfer power to the UAV through resonant electric field coupling. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Embodiments will now be described more fully with reference to the accompanying drawings, in which:

[0031] Figure 1 is a schematic layout of a wireless power transfer system according to an aspect of the present disclosure;

[0032] Figure 2 yes Figure 1 A plan view of an active electrode of a transmitting resonator of a wireless power transfer system;

[0033] Figure 3 yes Figure 1 A graph of the self-impedance of an active electrode of a transmitting resonator of a wireless power transfer system compared to the dimensionless width of a passive electrode of the wireless power transfer system for different passive electrode lengths;

[0034] Figure 4 yes Figure 1 A graph of radio frequency (RF) efficiency of a wireless power system versus dimensionless width of a passive electrode of the wireless power transfer system for different passive electrode lengths;

[0035] Figure 5 yes Figure 1 An end view of components of a wireless power transfer system;

[0036] Figure 6 yes Figure 1 An end view of a passive electrode of a wireless power transfer system;

[0037] Figure 7 yes Figure 1 Electric field diagram of components of a wireless power transfer system;

[0038] Figure 8 yes Figure 1 Electric field diagram of components of a wireless power transfer system;

[0039] Fig. 9 yes Figure 1 A circuit diagram of self-capacitance and mutual capacitance of a wireless power transfer system;

[0040] Fig.10 yes Figure 1 A graph of self-capacitance of a wireless power transfer system versus separation distance;

[0041] Fig.11 yes Figure 1 A graph of mutual capacitance versus separation distance for a wireless power transfer system;

[0042] Fig.12 yes Figure 1 A graph of coupling coefficient of a wireless power transfer system versus separation distance;

[0043] Fig.13 yes Figure 1 A graph of the self-capacitance of a wireless power transfer system compared to the width of a passive electrode;

[0044] Fig.14 yes Figure 1 A graph of mutual capacitance of a wireless power transfer system compared to the width of a passive electrode;

[0045] Fig.15 yes Figure 1 A graph of the coupling coefficient of a wireless power transfer system compared to the width of a passive electrode;

[0046] Fig.16 yes Figure 1 A graph of the self-capacitance of a wireless power transfer system versus the rotation angle of a passive electrode;

[0047] Fig.17 yes Figure 1 A graph of mutual capacitance of a wireless power transfer system versus rotation angle of a passive electrode;

[0048] Fig.18 yes Figure 1A graph of the coupling coefficient of the wireless power transfer system versus the rotation angle of the passive electrode;

[0049] Fig.19 is a perspective view of elements of another embodiment of a wireless power transfer system;

[0050] Fig. 20 yes Fig.19 A plot of the impedance magnitude of the element versus displacement;

[0051] Fig.21 yes Fig.19 A plot of the impedance phase of the element versus displacement;

[0052] Fig. 22 yes Fig.19 A graph of RF efficiency of a wireless power transfer system for different test materials of components in FIG.

[0053] Fig.23 yes Fig.19 A graph showing the variation of the resonant frequency of different materials of the components;

[0054] Fig.24 yes Figure 1 A perspective view of another embodiment of an active electrode of a transmit resonator, an active electrode of a receive resonator, and a receive passive electrode of a wireless power transfer system;

[0055] Fig.25 yes Fig.24 A plan view of an active electrode of a transmitting resonator;

[0056] Fig.26 yes Fig.24 A plot of the self-impedance of the active electrode of the transmitting resonator compared to the normalized radius of the passive electrode;

[0057] Fig. 27 Yes Fig.24 The RF efficiency of the wireless power transfer system with active electrodes and passive electrodes is compared with Fig.24 A graph of the normalized radius of the passive electrode;

[0058] Fig.28 yes Fig.25 A plan view of the active electrode fabricated in FIG.

[0059] Fig.29 is with Fig.28 The active electrode is used together with Figure 1 A perspective view of another embodiment of a passive electrode of a wireless power transfer system;

[0060] Fig.30 Is it present and absent on different test materials Fig.29Capacitance diagram of the active electrode of the transmitting resonator in the case of the passive electrode;

[0061] Fig.31 is a schematic layout of another embodiment of a wireless power transfer system according to an aspect of the present disclosure;

[0062] Fig.32 is a schematic layout of another embodiment of a wireless power transfer system according to an aspect of the present disclosure;

[0063] Fig.33 yes Fig.32 A perspective view of another embodiment of a transmit resonator and a receive resonator and a passive electrode of a wireless power transfer system;

[0064] Fig.34 is from Fig.33 Contour plot of the electric field emitted by the system;

[0065] Fig.35 is from Fig.33 Another contour plot of the electric field emitted by the system;

[0066] Fig.36 is from Fig.33 Another contour plot of the electric field emitted by the system;

[0067] Fig.37 yes Figure 1 A side view of another embodiment of a capacitor of a wireless power transfer system;

[0068] Fig.38 is a front view of an autonomous vehicle equipped with a receiver and a passive electrode located above a transmitter;

[0069] Fig.39 It is shown Fig.38 Table of transmitter and receiver RF efficiency versus dielectric properties;

[0070] Fig.40 It is shown Fig.38 Table of transmitter and receiver RF efficiency versus dielectric constant;

[0071] Fig.41 is shown when the power is supplied Fig.38 Table of transmitter and receiver impedance phase compared to dielectric properties;

[0072] Fig.42 is shown when the power is supplied Fig.38 Table of the impedance phase of the transmitter and receiver compared to the dielectric constant;

[0073] Fig.43is a perspective view of a UAV according to an aspect of the present disclosure;

[0074] Fig.44 yes Fig.43 Bottom view of the UAV;

[0075] Fig.45 yes Fig.43 A side view of the UAV;

[0076] Fig.46 yes Fig.43 A perspective view of a capacitor of a UAV;

[0077] Fig.47 yes Fig.43 A bottom view of a capacitor of the UAV; and

[0078] Fig.48 Yes Fig.43 A perspective view of a wireless power transfer system with a portion of a capacitor of a UAV. DETAILED DESCRIPTION

[0079] When reading in conjunction with the accompanying drawings, the above overview and the following detailed description of some examples will be better understood.As used herein, the elements or features introduced in the singular and beginning with the word "one" or "an" should be understood as not necessarily excluding multiple elements or features.In addition, reference to "an example" or "an embodiment" is not intended to be interpreted as excluding the existence of additional examples or embodiments that also include the elements or features described.In addition, unless explicitly stated to the contrary, "including (comprising)" or "having (having)" or "including (including)" elements or features with specific attributes or examples or embodiments of multiple elements or multiple features may include additional elements or features that do not have this attribute.Similarly, it should be understood that the terms "including", "having", "including" mean "including but not limited to", and the terms "including", "having" and "including" have equivalent meanings.It should also be understood that throughout the specification and the accompanying drawings, the same figure symbols are used to refer to the same elements.

[0080] As used herein, the terms "suitable for" and "configured to" mean that an element, component, or other subject matter is designed and / or intended to perform a given function. Therefore, the use of the terms "suitable for" and "configured to" should not be interpreted as meaning that a given element, component, or other subject matter is simply "capable of" performing a given function, but rather that the element, component, and / or other subject matter is specifically selected, created, implemented, utilized, and / or designed for the purpose of performing the function. An element, component, and / or other subject matter described as being suitable for performing a particular function may additionally or alternatively be described as being configured to perform that function, and vice versa, which is also within the scope of the present application. Similarly, a subject matter described as being configured to perform a particular function may additionally or alternatively be described as being operable to perform that function.

[0081] It should be understood that when an element is referred to as being "on," "attached to," "connected to," "coupled to," "contacting," etc. another element, the element may be directly on, directly attached to, directly connected to, directly coupled to, or directly contacting the other element, or intervening elements may also be present.

[0082] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this subject disclosure belongs.

[0083] Now go to Figure 1 , a wireless power transfer system is shown and is generally identified by reference numeral 20. The wireless power transfer system 20 includes a resonator. The resonator includes a capacitor 52 and two induction coils 30. The capacitor 52 includes two active electrodes 28 and a passive electrode 60 adjacent to the active electrodes 28. The passive electrode 60 is configured to surround the active electrode 28 to at least partially eliminate environmental effects that affect the active electrode 28. The passive electrode 60 is configured to provide additional capacitance to the system. The passive electrode 60 is configured to reduce the inductance required to achieve resonance. Each induction coil 30 is electrically connected to the active electrode 28.

[0084] For purposes of the subject application, a passive electrode 60 is considered to surround an active electrode 28 when at least one of the following conditions occurs: (i) if the area defined by the perimeter of the active electrode 28 is projected onto the area of ​​the passive electrode 60, the projection is entirely within the area of ​​the passive electrode 60; (ii) the projected area of ​​the active electrode 28 is circumscribed by the area of ​​the passive electrode 60; or (iii) the area of ​​the passive electrode 60 is larger than the total area defined by the perimeter of the active electrode 28 by at least the area between the active electrodes 28.

[0085] The passive electrode 60 is placed between the active electrode 28 and the environment. Although the actual environment is located on the opposite side of the passive electrode 60 from the active electrode 28, the passive electrode at least partially eliminates environmental influences affecting the active electrode 28 by providing a substantially constant environment to the active electrode.

[0086] The passive electrode 60 increases the capacitance of the capacitor 52. The increase in capacitance reduces the inductance required for the induction coil to resonate at a particular frequency.

[0087] In this embodiment, the resonator is a transmit resonator 24. The transmit resonator 24 forms a part of the transmitter 22. As described below, the transmit resonator 24 is configured to generate an electric field to transmit power. The transmitter 22 includes a power supply 26 electrically connected to the transmit resonator 24. Specifically, the power supply 26 is electrically connected to the induction coil 30 of the transmit resonator 24.

[0088] In this embodiment, the components of the transmit resonator 24 are configured to operate in the near field, as described below. Accordingly, the passive electrode 60 is configured to operate in the near field.

[0089] In this embodiment, the power supply 26 is an RF power supply that outputs a source signal. The source signal is usually a sinusoidal signal. For example, in this embodiment, the frequency of the source signal is 13.56 MHz.

[0090] Although two induction coils 30 are shown connected in series to the power supply 26, those skilled in the art will appreciate that a single induction coil 30 may be used to transmit both active electrodes 28 of the resonator 24. In this embodiment, the single induction coil 30 is electrically connected to the power supply 26 and the active electrodes 28 in parallel.

[0091] Each active electrode 28 is electrically connected to an induction coil 30, which is electrically connected to a power source 26. Capacitor 52 is configured to resonate with the induction coil 30 to generate an electric field to transfer power, as will be described.

[0092] In this embodiment, the active electrodes 28 of the transmitting resonator 24 are spaced apart laterally. The active electrodes 28 are coplanar. The active electrodes 28 are conductors. In this embodiment, the conductors are elongated and generally rectangular flat plates. The conductors are formed of copper foil strips. Although two active electrodes 28 are depicted, those skilled in the art will appreciate that more active electrodes 28 may be used. The use of copper foil strips in this embodiment is not meant to limit the scope or spirit of the present disclosure, as those skilled in the art will appreciate that other conductive materials may be used, such as, but not limited to, aluminum foil or a printed circuit board (PCB).

[0093] In this embodiment, the passive electrode 60 comprises an elongate element. The elongate element is formed of an electrically conductive material. The elongate element is in the form of a generally rectangular plate having opposing major surfaces.

[0094] The passive electrode 60 is adjacent to the active electrode 28. The passive electrode 60 surrounds the active electrode 28. The passive electrode 60 and the active electrode 28 form a capacitor 52. In this embodiment, the passive electrode 60 is substantially parallel to the active electrode 28. The active electrode 28 and the passive electrode 60 are on substantially parallel planes.

[0095] In this embodiment, the passive electrode 60 is not grounded. The passive electrode 60 is separate.

[0096] In this embodiment, the passive electrode 60 is non-radiative.

[0097] In another embodiment, the passive electrode 60 is grounded.

[0098] In another embodiment, the passive electrode 60 is not separate.

[0099] In this embodiment, the passive electrode 60 is electrically small. When the physical length of the passive electrode 60 is less than λ / 10, the passive electrode 60 is electrically small. λ is the wavelength of the source signal from the power supply. For a source signal with a frequency of 13.56 MHz output by the power supply 26, λ is about 22 m. Therefore, when the physical length of the passive electrode 60 is less than about 2.2 m, the passive electrode 60 is electrically small.

[0100] The thickness of the passive electrode 60 is limited by the skin depth (d) of the current. The skin depth (d) is the depth below the surface of the conductor at which the current is reduced by e compared to the surface current. -1 times. The skin depth (d) depends on the conductivity (σ) and magnetic permeability (μ) of the passive electrode 60 and the current frequency (ω). It is defined by the following equation:

[0101]

[0102] The passive electrode 60 should be at least five times thicker than the skin depth to allow current to flow unimpeded on both major faces of the passive electrode 60 .

[0103] In this embodiment, the wireless power transfer system 20 also includes a receiver 42. The receiver 42 includes a receiving resonator 44 electrically connected to a load 46. The receiving resonator 44 is tuned to the resonant frequency of the transmitting resonator 24. The receiving resonator 44 includes two active electrodes 48 and two induction coils 50. The induction coils 50 are electrically connected to the active electrodes 48 and are electrically connected in series to the load 46. The load 46 includes a device that requires power. For example, the load 46 includes a battery.

[0104] Although two induction coils 50 are shown connected in series to the load 46 , those skilled in the art will appreciate that a single induction coil 50 may be used to receive both active electrodes 48 of the resonator 44 .

[0105] In this embodiment, two induction coils 50 are electrically connected in parallel to the load 46 and the active electrode 48 of the receiving resonator 44. Those skilled in the art will also appreciate that more than two induction coils 50 may be connected to the load 46 in series.

[0106] Each active electrode 48 is electrically connected to an inductive coil 44, which is electrically connected to a load 46. The active electrodes 48 are configured to resonate with the inductive coil 44 to extract power from the transmitter 22 through resonant electric field coupling, as will be described.

[0107] In this embodiment, the active electrodes 48 of the receiving resonator 44 are spaced apart laterally. The active electrodes 48 are coplanar. The active electrodes 48 are parallel to the active electrodes 28 of the transmitting resonator 24. The active electrodes 48 are conductors. In this embodiment, the conductors are elongated and generally rectangular flat plates. The conductors have opposing major surfaces. The conductors are formed of copper foil strips.

[0108] Although two active electrodes 48 are depicted, those skilled in the art will appreciate that more active electrodes 48 may be used. Although copper foil tape is mentioned, those skilled in the art will appreciate that other conductive materials may be used including, but not limited to, aluminum or PCB.

[0109] Although active electrodes 28 and 48 are described as laterally spaced, elongated and generally planar rectangular plates, those skilled in the art will appreciate that other configurations are possible, including but not limited to electrodes that are concentric, coplanar, circular, elliptical, disc-shaped, etc. Other suitable electrode configurations are described in U.S. Patent Application No. 14 / 846,152, the relevant portions of which are incorporated herein.

[0110] Other components may be connected to the load 46, but Figure 1 These include, but are not limited to, rectifiers and regulators.

[0111] Some components of the wireless power transfer system 20 are described in U.S. patent application Ser. No. 13 / 607,474 to Polu et al., filed Sep. 7, 2012, which was published as U.S. Pat. No. 9,653,948 on May 16, 2017, relevant portions of which are incorporated herein.

[0112] Although the active electrodes 28 and the passive electrodes 60 have been generally described, the specific dimensions and configurations are further described for use in testing and simulations. Figure 2, a plan view of the active electrode 28 of the transmitting resonator 24 is shown. As previously described, in this embodiment, the active electrodes 28 are coplanar. The active electrodes 28 are elongated and generally rectangular flat plates. Each plate has a length h=100 mm and a width w=50 mm. The lateral gap g between the plates is 50 mm. As previously described, the passive electrode 60 is parallel to the active electrode 28. The spacing between the passive electrode 60 and the active electrode 28 is 6 mm. Although the active electrode 28 of the transmitting resonator 24 is shown, the active electrode 48 of the receiving resonator 44 has the same dimensions.

[0113] As previously described, in this embodiment, the active electrode 28 of the transmit resonator 24 is parallel to the active electrode 48 of the receive resonator 44. The spacing between the active electrode 28 of the transmit resonator 24 and the active electrode 48 of the receive resonator 44 is 75 mm. Those skilled in the art will appreciate that while the active electrode 28 of the transmit resonator 24 is parallel to the active electrode 48 of the receive resonator 44 in this embodiment, other configurations in which the active electrode 28 of the transmit resonator 24 is not parallel to the active electrode 48 of the receive resonator 44 are possible.

[0114] In this embodiment, the passive electrode 60 has a width (x) and a length (y). Simulations were performed using the passive electrode 60 and active electrode 28 having the above dimensions. The results of these simulations are shown in FIG. Figure 3 and Figure 4 shown. Figure 3 is a graph depicting the relationship between the ratio (x / (2*w+g)) and the self-impedance of the transmit resonator 24 for different length ratios (y / h). The different curves shown in the figure have different lengths (y), which are shown in the legend as the ratio of the length (y) of the passive electrode 60 to the length (h) of the active electrode 28. As the ratio (y / h) increases from 0.25 to 1.00, the self-impedance of the transmit resonator 24 increases; however, increasing the ratio beyond (y / h)=1 does not further increase the effect of the passive electrode 60 on the self-impedance of the transmit resonator 24. When the ratio (x / (2*w+g)) is greater than or equal to 1, the self-impedance of the transmit resonator 24 remains constant. When the length (y) of the passive electrode 60 is less than the length (h) of the active electrode 28 and the width (x) of the passive electrode 60 is less than the value (2*w+g), the passive electrode 60 no longer surrounds the active electrode 28 of the transmit resonator 24; therefore, the self-impedance of the transmit resonator 24 is susceptible to environmental influences. Thus, the minimum length (y) of the passive electrode 60 is equal to the length (h) of the active electrode 28. The minimum width (x) of the passive electrode 60 is equal to the value (2*w+g). Thus, for an active electrode 28 having a width (w) of 50 mm, a lateral gap (g) of 50 mm, and a length (y) of 100 mm, the length (h) of the passive electrode 60 is 100 mm, and the width (x) of the passive electrode 60 is 150 mm.

[0115] Figure 4 is a graph depicting the relationship between the width ratio (x / (2*w+g)) of the passive electrode 60 and the RF efficiency of the system 20 for different length ratios (y / h). The RF efficiency of the system 20 is defined as the efficiency of wireless power transfer between the transmit resonator 24 and the receive resonator 44. The RF efficiency does not take into account the inefficiencies of other components present in the system 20, such as the power supply 26 and the load 46. The different curves shown in the figure have different lengths (y), which are shown in the legend as the ratio of the length (y) of the passive electrode 60 to the length (h) of the active electrode 28. As the ratio (y / h) increases from 0.25 to 1.25, the RF efficiency of the system 20 increases. As Figure 4 As shown, increasing the ratio (y / h) above 1.25 greatly improves the RF efficiency of the system 20. Figure 4 As shown, the RF efficiency of the system 20 remains relatively constant when the width (x) of the passive electrode 60 is greater than twice the width (w) of the active electrode 28 plus the lateral gap (2*w+g) and the length (y) of the passive electrode 60 is greater than the length (h) of the active electrode 28. For the passive electrode 60 having a length (y) greater than the length (h) of the active electrode 28 and a width (x) greater than the value (2*w+g), the RF efficiency is stable.

[0116] based on Figure 3 and Figure 4 In the relationship depicted in the figure, in order for the RF efficiency of the system 20 in this embodiment to exceed about 80%, and in order for the self-impedance of the transmit resonator 24 to be less than or equal to about 2700Ω, the passive electrode 60 must have a length (y) that exceeds the length (h) of the active electrode 28 and a width (x) that exceeds the value (2*w+g). In general, when the active electrodes 28 of the transmit resonator 24 are coplanar elongated parallel plates, they can be as shown. Figure 2 As depicted, the effective passive electrode 60 has a width (x) greater than or equal to the value (2*w+g), and has a length (y) greater than or equal to the length (h) of the active electrode 28 .

[0117] Although the system 20 has been generally described and specific dimensions have been provided for the active electrode 28 and the passive electrode 60, those skilled in the art will appreciate that variations are possible. In addition, specific values ​​for the components of the system 20 are provided for testing and simulation. Figure 2In another embodiment of the active electrode 28 of the transmitting resonator 24 shown, each plate of the active electrode 28 has a length of h=100 and a width of w=37.5 mm. The lateral gap g between the plates is 25 mm. In addition, in this embodiment, the passive electrode 60 has a width of x=120 mm and a length of y=120 mm. The active electrode 48 of the receiving resonator 44 has the same dimensions as the active electrode 28 of the transmitting resonator 24. The separation distance between the active electrode 28 of the transmitting resonator 24 and the active electrode 48 of the receiving resonator 44 is D=20 mm. The separation distance between the active electrode 28 of the transmitting resonator 24 and the passive electrode 60 is D1=2 mm.

[0118] In addition, in this embodiment, the inductance of the inductor 30 of the transmitting resonator 24 is 12.7 μH. In this embodiment, the quality factor of the transmitting resonator 24 is 250 (Q=250). The efficiency of the system 20 is 93%. The input impedance of the system 20 is Zin=70Ω. The input impedance is the impedance that the system 20 sees into the transmitter 22.

[0119] As previously described, the passive electrode 60 reduces the required inductance of the system 20. Removing the passive electrode 60 from the system 20 results in an increase in the required inductance. Specifically, in this embodiment, removing the passive electrode 60 from the system 20 results in the inductance of the inductor 30 of the transmit resonator 24 increasing from 12.7 μH to 63 μH. In order to maintain an acceptable quality factor of at least 30 (Q>30), the required size of the inductor 30 having an inductance of 63 μH is prohibitive for the system 20. This is particularly true if the power delivered by the system 20 is greater than 1 W.

[0120] The efficiency of the system 20 with the passive electrode 60 removed is 88%. The system 20 with the passive electrode 60 removed has an input impedance Zin=12.5kΩ. The input impedance Zin with the passive electrode 60 removed is too large for meaningful power transfer (>1W) because the output of the power supply 26 will be limited by its maximum output voltage. Therefore, a power supply 26 rated at 1.25 is required to power the system 20. Most high-efficiency RF power supplies (efficiency>80%, such as class D inverters) are designed to operate in the range of 10-100Ω. Therefore, these RF power supplies are not suitable for systems 20 with such a large input impedance. Therefore, the passive electrode 60 reduces the input impedance Zin. Specifically, in this embodiment, the passive electrode 60 reduces the input impedance Zin of the system 20 from 12.5kΩ to 80Ω.

[0121] Although specific dimensions have been provided for active electrodes 28 and 48 and passive electrode 60, those skilled in the art will appreciate that variations are possible. Figure 5, an end view of the active electrode 28 of the transmit resonator 24, the active electrode 48 of the receive resonator 44, and the passive electrode 60 is shown. W1 and W2 represent the width of the active electrode 28 of the transmit resonator 24. G1 represents the lateral gap between the two active electrodes 28 of the transmit resonator 24. W3 and W4 represent the width of the active electrode 48 of the receive resonator 44. G2 represents the lateral gap between the two active electrodes 48 of the receive resonator 44. D represents the spacing distance between the active electrode 28 of the transmit resonator 24 and the active electrode 48 of the receive resonator 44. Ws represents the width of the passive electrode 60. D1 represents the spacing distance between the active electrode 28 of the transmit resonator 24 and the passive electrode 60. In this embodiment, the active electrode 28 of the transmit resonator 24, the active electrode 48 of the receive resonator 44, and the passive electrode 60 are all in parallel planes. Furthermore, in this embodiment, W1 = W2 = W3 = W4 = 2 inches, G1 = G2 = 1 inch, D = D1 = 1 inch, and the length L of the electrodes (28, 48, and 60) in the page is 33 inches.

[0122] Now go to Figure 6 , shows an end view of the passive electrode 60. The rotation angle of the passive electrode 60 relative to a plane parallel to the plane of the active electrode 28 of the transmitting resonator 24 is given by Indicates the rotation angle. represents the longitudinal or lateral rotation of the passive electrode 60. In this embodiment, the rotation angle represents the longitudinal rotation of the passive electrode 60. Changing the rotation angle Affects system parameters as described below.

[0123] During operation, power is transferred from the power source 26 to the active electrode 28 through the induction coil 30 of the transmit resonator 24. The source signal from the power source 26, sent to the active electrode 28 via the induction coil 30, excites the transmit resonator 24, causing the transmit resonator 24 to generate an electric field. In this embodiment, the generated electric field is a near field. A differential voltage is applied to the active electrode 28 of the transmit resonator 24, which establishes an electric field in the surrounding environment. When the receive resonator 44 is placed within the generated electric field and coincides with the resonant frequency of the transmit resonator 24, the receive resonator 44 extracts electrical energy from the transmit resonator 24 through resonant electric field coupling. The extracted electrical energy is then transferred from the receive resonator 44 to the load 46 through the induction coil 50. Although the transmit resonator 24 generates a magnetic field, little, if any, power is transferred through magnetic field coupling.

[0124] Because the power transfer is highly resonant, the active electrodes 28 and 48 of the transmit resonator 24 and receive resonator 44, respectively, do not need to be as close or aligned as is the case with non-resonant electrical wireless power transfer systems.

[0125] As previously described, the passive electrode 60 is used to reduce the environmental impact on the active electrode 28 of the transmitting resonator 24, so that the active electrode 28 has a substantially constant environment regardless of the actual environment on the other side of the passive electrode 60 relative to the active electrode 28. In response to the electric field generated by the transmitting resonator 24, a surface charge is instantaneously induced on the passive electrode 60. For metals (such as copper and aluminum), alloys (such as steel and brass), and other conductors, such as graphene or conductive fabrics, the charge dissipation time is approximately 10 -19 When the resonant frequency of the system 20 is 13.56 MHz, the oscillation period of the electric field is approximately 10 -9 seconds. Therefore, the charge dissipation time is many orders of magnitude smaller than the oscillation period of the electric field. Therefore, the charge redistribution can be considered instantaneous.

[0126] The induced surface charge creates its own electric field that opposes the electric field generated by the transmitting resonator 24 because negatively charged particles will be attracted to areas on the high potential surface where their presence will cancel the electric field parallel to the surface. Therefore, the net electric field acting on the major surface of the passive electrode 60 adjacent to the active electrode 28 is perpendicular to the surface of the passive electrode 60. Therefore, the electric field generated by the transmitting resonator 24 terminates at the passive electrode 60 and does not bypass the passive electrode 60. The conductive surface of the passive electrode 60 opposite the active electrode 28 of the transmitting resonator 24 acts as a boundary for the electric field generated by the passive electrode 60. Therefore, changes in the environment on the opposite side of the passive electrode 60 do not affect the electric field on the other side.

[0127] As previously described, the electric field generated by the transmit resonator 24 induces a surface charge on the passive electrode 60. Therefore, the passive electrode 60 provides additional capacitance to the capacitor 52 of the transmit resonator 24 compared to a capacitor that includes the active electrode 28 but does not have the passive electrode 60. The net electric field on the surface of the passive electrode 60 acts as an energy storage medium for the capacitor 52 of the transmit resonator 24. In this way, the active electrode 28 and the passive electrode 60 of the transmit resonator 24 form a capacitor 52, and the capacitance of the capacitor 52 is greater than the capacitance of a capacitor that includes only the active electrode 28.

[0128] The additional capacitance provided by the capacitor 52 formed by the active electrode 28 and the passive electrode 60 reduces the amount of inductance required to resonate at the resonant frequency. As previously described, in this embodiment, the induction coils 30 and 50 of the transmit resonator 24 and the receive resonator 44, respectively, are ferrite core inductors. Conventional ferrite inductors are heavy, lossy, and power limited due to core saturation and heating. Therefore, it is desirable to reduce the inductance required for the induction coils 30 and 50. The additional capacitance of the capacitor 52 provided by the passive electrode 60 reduces the inductance required for each of the induction coils 30 and 50. The closer the passive electrode 60 is to the active electrode 28 of the transmit resonator 24, the greater the capacitance added to the capacitor 52 of the transmit resonator 24, and therefore the greater the reduction in the inductance required for the induction coils 30 and 50.

[0129] However, as previously described, the surface charge induced on the passive electrode 60 creates an electric field that opposes the electric field generated by the transmit resonator 24. The closer the passive electrode 60 is to the active electrode 28 of the transmit resonator 24, the greater the opposing electric field, which reduces the strength of the electric field generated by the active electrode 28 of the transmit resonator 24. This reduces the potential range of the electric field generated by the transmit resonator 24, thus requiring the receive resonator 44 to be closer to the transmit resonator 24 when the coupling field is weak.

[0130] Thus, the designer of the system 20 can balance the desired inductance of the inductive coils 30 and 50, the desired distance between the transmit resonator 24 and the receive resonator 44, and the desired additional capacitance added to the capacitor 52 of the transmit resonator 24. Depending on the application in which the system 20 will be used, the distance between the active electrode 28 and the passive electrode 60 of the transmit resonator 24 can be varied to obtain the desired inductance, distance between the resonators, and additional capacitance.

[0131] Furthermore, it will be appreciated that the distance between passive electrode 60 and active electrode 28 is selected to achieve a desired balance between the capacitance and coupling field strength of capacitor 52. The balance between the capacitance and coupling field strength of capacitor 52 may vary depending on the particular application of system 20.

[0132] Without the passive electrode 60, the active electrode 28 of the transmit resonator 24 may not provide sufficient capacitance to resonate at the resonant frequency unless a bulky inductor 30 is added, which would double the weight of the system 20, making the system 20 impractical. As described above, placing the passive electrode 60 near the active electrode 28 of the transmit resonator 24 increases the capacitance and reduces the required inductance. The smaller inductor 30 can provide reduced inductance and reduce the weight of the overall system 20 compared to a system 20 that does not include the passive electrode 60.

[0133] Now go to Figure 7 and Figure 8, shows an electric field diagram of the active electrode 28 and the passive electrode 60 of the system 20 during operation. Figure 7 and Figure 8 It is shown that when the passive electrode 60 is present, the electric field strength generated by the transmitting resonator 24 is reduced. Figure 7 is an electric field diagram that models the net electric field of the capacitor 52 formed by the active electrode 28 and the passive electrode 60 as the sum of two opposite dipole electric fields: the electric field generated by the transmitting resonator 24 and the opposing electric field created by the surface charge induced on the passive electrode 60.

[0134] Figure 7 and Figure 8 The electric field plot shown indicates that the presence of passive electrode 60 in system 20 produces a less strong dipole electric field than a dipole surrounded by a vacuum. Therefore, the model also indicates that the presence of passive electrode 60 in system 20 produces a less strong dipole electric field than a system that does not include passive electrode 60.

[0135] Now go to Fig. 9 , shows a circuit diagram of the capacitance of the system 20. The equivalent capacitance (C Tx ) is the capacitance generated in the transmitting capacitor 52, which does not contribute to the resonant electric field coupled with the active electrode 48 of the receiving resonator 44. The equivalent capacitance (C Rx ) is the capacitance generated between the active electrodes 48 of the receiving resonator 44, which does not contribute to the resonant electric field coupled with the active electrode 28 of the transmitting resonator 24. The capacitances of the transmitting capacitor 52 and the receiving capacitor 54 (C Tx and C Rx ) reduces the resonant frequency of the system 20. The mutual capacitance (C M ) is the capacitance generated between the active electrode 28 of the transmitting resonator 24 and the active electrode 48 of the receiving resonator 44. Mutual capacitance is responsible for the coupling between the transmitter 22 and the receiver 42, and therefore determines the coupling strength. The coupling coefficient between the transmitter 22 and the receiver 42 is (CC) and is given by the following formula:

[0136]

[0137] Electromagnetic simulations using the method of moments examined the equivalent capacitance (C Tx )’s impact.

[0138] Electromagnetic simulations using the method of moments examined the equivalent capacitance (C Tx ), the equivalent capacitance (C Rx ), mutual capacitance (C M) and the coupling coefficient (CC). In electromagnetic simulation, D1, Ws and The simulation results are as follows: Figures 10 to 18 As shown, the description is as follows.

[0139] Now go to Fig.10 , showing the equivalent capacitance (C Tx ) and the equivalent capacitance (C Rx ) compared to the spacing distance (D1) between the active electrode 28 and the passive electrode 60 of the transmit resonator 24. As the spacing distance (D1) between the active electrode 28 and the passive electrode 60 of the transmit resonator 24 increases from 0.5 inches to 2.5 inches, the equivalent capacitance (C Tx ) decreases from about 29 pF to about 18.5 pF. Conversely, as the spacing distance (D1) between the active electrode 28 and the passive electrode 60 of the transmitting resonator 24 increases from 0.5 inches to 2.5 inches, the equivalent capacitance (C Rx ) remain relatively constant.

[0140] Now go to Fig.11 , for D = 1, a graph depicting the mutual capacitance (C M ) compared to the separation distance (D1) between the active electrode 28 and the passive electrode 60 of the transmit resonator 24. As the separation distance (D1) increases from 0.5 inches to 2.5 inches, the mutual capacitance (C M ) increased from approximately 7.71pF to approximately 7.97pF.

[0141] Now go to Fig.12 , shows a graph depicting the coupling coefficient (CC) versus the separation distance (D1) between the active electrode 28 and the passive electrode 60 of the transmit resonator 24. As the separation distance (D1) increases from 0.5 inches to 2.5 inches, the coupling coefficient (CC) increases from approximately 0.115 to 0.195. Figures 10 to 12 The data shown, the width (Ws) of the passive electrode 60 is equal to 5 inches, and the rotation angle is 0°.

[0142] Now go to Fig.13 , showing the equivalent capacitance (C Tx ) and the equivalent capacitance (C Rx ) compared to the width (Ws) of the passive electrode 60. As the width (Ws) of the passive electrode 60 increases from 2.5 inches to 5.5 inches, the equivalent capacitance (C Tx) increases from about 23 pF to about 29.5 pF. Conversely, when the width (Ws) of the passive electrode 60 increases from 2.5 inches to 5.5 inches, the equivalent capacitance (C Rx ) remains relatively constant at approximately 18pF.

[0143] Now go to Fig.14 , showing a graph depicting the mutual capacitance (C M ) compared to the width (Ws) of the passive electrode 60. As the width (Ws) increases from 2.5 inches to 5.5 inches, the mutual capacitance (C M ) is reduced from approximately 8.02pF to approximately 7.60pF.

[0144] Now go to Fig.15 , shows a graph depicting the coupling coefficient (CC) versus the width (Ws) of the passive electrode 60. As the width (Ws) increases from 2.5 inches to 5.5 inches, the coupling coefficient (CC) decreases from about 0.16 to about 0.11. Figures 13 to 15 The data described in the figure are that the separation distance (D1) is equal to 1 inch and the rotation angle is is 0°.

[0145] Now go to Fig.16 , showing the equivalent capacitance (C Tx ) and the equivalent capacitance (C Rx ) compared to the rotation angle of the passive electrode 60 When the passive electrode 60 rotates and the rotation angle As the equivalent capacitance (C Tx ) increases from about 21.5 pF to about 23.5 pF. In addition, when the passive electrode 60 is rotated and the rotation angle When moving away from zero in either direction, the equivalent capacitance (C Rx ) is reduced from about 18.9 pF to about 18.8 pF. The equivalent capacitance (C Tx ) is affected by an increase in capacitance between one of the active electrodes 28 of the transmit resonator 24 and the passive electrode 60, and by a decrease in capacitance between another of the active electrodes 28 of the transmit resonator 24 and the passive electrode 60.

[0146] Now go to Fig.17 , showing a graph depicting the mutual capacitance (C M ) compared to the rotation angle of the passive electrode 60 As the passive electrode 60 rotates and the rotation angle Moving away from zero in either direction, the mutual capacitance (C M ) increases from about 7.80 pF to about 7.89 pF. This change of about 0.09 pF is less than the change of about 0.42 pF observed when the width (Ws) of the passive electrode 60 is varied, and is less than the change of about 0.26 pF observed when the separation distance (D1) between the active electrode 28 and the passive electrode 60 of the transmitting resonator 24 is varied.

[0147] Now go to Fig.18 , showing a graph depicting the coupling coefficient (CC) versus the rotation angle of the passive electrode 60 When the passive electrode 60 rotates and the rotation angle When moving away from zero in either direction, the coupling coefficient (CC) decreases from about 0.158 to about 0.149. Tx ) changes in mutual capacitance (C M ) and the receiver equivalent capacitance (C Rx ) dominates the change, so the coupling coefficient decreases. Since the active electrode 28 of the transmitting resonator 24 is rotated by the passive electrode 60 by the rotation angle As the passive electrode 60 is moved closer, the equivalent capacitance (C Tx ) increases. As the passive electrode 60 moves away from the gap (G1) between the active electrodes 28, the mutual capacitance (C M ) increases. Figures 16 to 18 According to the data depicted in , the width (Ws) of the passive electrode 60 is equal to 5 inches and the separation distance (D1) is equal to 1 inch.

[0148] Although a specific embodiment of the system 20 has been described, those skilled in the art will appreciate that variations are possible. In another embodiment, the system 20 also includes a dielectric located between the active electrode 28 and the passive electrode 60 of the transmitting resonator 24. The dielectric has the same length and width as the passive electrode 60. The dielectric constant of the dielectric is 3.48 and the loss tangent is 0.0037 at 10 GHz. The dielectric has a high breakdown voltage. A dielectric with a high breakdown voltage reduces the possibility of arcing. This allows the system 20 to operate at high power levels. Examples of dielectrics include: fiberglass and thermoplastics. Examples of thermoplastics include polyethylene and polypropylene.

[0149] Unless the passive electrode 60 is already grounded, the potential of the passive electrode 60 will float between the voltages of the active electrodes. The active electrode 28 of the transmitting resonator typically has a potential of several hundred volts, depending on the exact specifications of the system 20. In this embodiment, the potential of the active electrode 28 of the transmitting resonator is approximately 600V. An electric field is created between the active electrode 28 and the passive electrode 60, and the magnitude of the electric field will increase as the active electrode 28 and the passive electrode 60 move closer. When designing the system 20, care must be taken to avoid arcing between the passive electrode 60 and the active electrode 28. Arcing can damage components of the system 20 and start a fire.

[0150] By reducing the potential difference between the active electrode 28 and the passive electrode 60, the possibility of arcing can be reduced. In this embodiment, less than 3×10 6 The electric field of 3×10 V / m ensures that arc discharge will not occur. 6 V / m is the approximate dielectric breakdown voltage of air. To maintain the same power delivery, the current of the system 20 must be increased. The increase in current increases the resistive losses of the system 20. The likelihood of arcing can also be reduced by delivering less power. The dielectric located between the active electrode 28 and the passive electrode 60 of the transmitting resonator reduces the potential difference between the active electrode 28 and the passive electrode 60. Therefore, the dielectric reduces the likelihood of arcing.

[0151] Now go to Fig.19 , a perspective view of elements of another embodiment of a wireless power transfer system is shown. The wireless power system is generally identified by reference numeral 120. Fig.19 The wireless power transfer system 120 shown in FIG. 1 is similar to the wireless power transfer system 20 described previously, and like elements are referred to with like reference numerals increased by 100 . Fig.19 Active electrodes 128 and 148 of the transmit and receive resonators, respectively, are shown, as well as a passive electrode 160 of the system 120. Although the system 120 includes additional components, these are not shown in FIG. Fig.191. As previously described, the active electrode 128 of the transmit resonator and the passive electrode 160 form a capacitor 152. In this embodiment, for simulation purposes, the active electrodes 128 of the transmit resonator are electrically connected to each other, and the active electrodes 148 of the receive resonator are electrically connected to each other. In this embodiment, each active electrode 128 and 148 is formed of copper, however, those skilled in the art will understand that other metals are possible. In this embodiment, the resonant frequency of the transmit resonator is 13.56 MHz of the system 120. In this embodiment, each active electrode 128 and 148 is 50 mm by 200 mm. The active electrode 128 of the transmit resonator is 100 mm away from the active electrode 148 of the receive resonator. The passive electrode 160 is 400 mm by 600 mm.

[0152] In this embodiment, a block of test material 170 is located on the side of the passive electrode 160 opposite the active electrode 128. The block of test material 170 represents different media that may be present in the operating environment of the system 120. The block of test material 170 appears as a block of aluminum, concrete, dry land, wet land, water, seawater, or wood.

[0153] As previously described, the additional capacitance of the passive electrode 160 also reduces the inductance required for the inductive coil (not shown) in the wireless power transfer system 120 to operate at a resonant frequency of 13.56 MHz, compared to a wireless power transfer system that does not include the passive electrode 160. In this embodiment, the inductance required to make the inductive coil of the system 120 resonate is reduced from 43.2 μH to 39.5 μH.

[0154] Electromagnetic field simulations were performed using CST Microwave Studio software to demonstrate the stability of the system 120 for different materials of the test material block 170 over a range of longitudinal displacements between the transmitter and receiver. Fig. 20 and Fig.21 , shows a graph depicting the impedance magnitude and phase looking into the transmitting resonator, respectively, versus the longitudinal displacement of the receiver from the transmitter. Fig. 20 and Fig.21 In the first three cases, there is no passive electrode 160, and the mass of material 170 is concrete, salt water, and vacuum. Fig. 20 and Fig.21 In the last three cases, there is a passive electrode 160 and the mass of material 170 is concrete, salt water, and vacuum.

[0155] A constant impedance looking into the transmit resonator is desirable because power supplies are typically optimized to efficiently deliver power to a given load impedance. The input impedance of the transmit resonator varies significantly during operation depending on the tuning of the transmit and receive resonators, the system 120 load impedance, and the degree of coupling between the transmit and receive resonators. The passive electrode 160 minimizes environmental effects that affect the active electrode 128. The passive electrode 160 also provides additional capacitance to the system 120, reducing the required inductance.

[0156] like Fig. 20 As shown, the case with the passive electrode 160 is generally consistent in magnitude regardless of the test material of the test material block 170. Without the passive electrode 160, the magnitude of the impedance looking into the transmitting resonator varies significantly.

[0157] Now go to Fig.21 , when the passive electrode 160 is present, the phase variation between the transmitting electrode 128 and the receiving electrode 148 is less than 20 degrees within the displacement range of 90 mm to 180 mm. However, when the passive electrode 160 is not present, the variation is as high as 80 degrees. Generally, low phase angles are preferred because it is difficult to design the wireless power transfer system 120 so that all phases can be accommodated.

[0158] Now go to Fig. 22 , shows the RF efficiency of the system 120 in the case where the test material block 170 has a wider variety of materials. When the test material block 170 is not present, the RF efficiency is marked as vacuum. In other configurations, the test material block 170 is presented as a block of aluminum, concrete, dry land, wet land, water, seawater, or wood. The system 120 is tuned under vacuum of the test material and a displacement of 150 mm between the transmit electrode 128 and the receive electrode 148.

[0159] For each test material block 170, the system 120 with the passive electrode 160 had an almost constant RF efficiency of 87%, while the system 120 without the passive electrode 160 had an RF efficiency that varied from 56% when the test material block 170 was aluminum to 89% when the test material block 170 was not present (in Fig. 22 (marked as vacuum in the figure).

[0160] Now go to Fig.23 , shows the change in the resonant frequency of the system 120 with various materials of the test material block 170. When the test material block 170 is not present, the resonant frequency is marked as vacuum. The test material blocks are presented as blocks made of aluminum, concrete, dry land, wet land, water, seawater, or wood. As previously mentioned, the resonant frequency of the system 120 is 13.56 MHz. Fig.23As shown, when the passive electrode 160 is not present in the system 120, the resonant frequency of the system 120 varies according to the test material block 170. However, when the passive electrode 160 is present in the system 120, the resonant frequency of the system 120 is constant and does not vary. When the passive electrode 160 is present, the change in frequency (Δf) is zero regardless of the material of the test material block 170. The resonant frequency of the system 120 without the passive electrode 160 varies from 13.56 MHz to 13.30 MHz according to the test material block 170. When the passive electrode 160 is not present, the change in frequency (Δf) varies from 0 MHz to more than 0.25 MHz according to the material of the test material block 170.

[0161] While specific sizes and shapes of active electrodes 28 and 48 and passive electrode 60 have been described, those skilled in the art will appreciate that variations are possible. Fig.24 Another embodiment of active electrodes 228 and 248 and passive electrode 260 is shown.

[0162] In this embodiment, the active electrode 228 of the transmitting resonator is two concentric electrodes in the shape of a ring and a disk. The active electrode 248 of the receiving resonator is two concentric electrodes in the shape of a ring and a disk. The passive electrode 260 is a disk electrode. The active electrodes 228 and 248 and the passive electrode 260 are coplanar. As previously described, the active electrode 228 and the passive electrode 260 of the transmitting resonator form a capacitor 252.

[0163] Although the passive electrode 260 has been described as a disk electrode, those skilled in the art will appreciate that other configurations are possible. In another embodiment, the passive electrode 260 is a ring having an inner diameter less than or equal to the inner diameter of the inner active electrode.

[0164] For purposes of the present subject application, concentric is defined as including at least one of the following: (i) the two electrodes have a common central axis, (ii) the two electrodes have a common center of rotation, (iii) the two electrodes have a common center of mass, (iv) the two electrodes have a common center of volume, (v) the two electrodes have a common center of curvature, (vi) the outer electrode of the two electrodes surrounds the inner electrode of the two electrodes, (vii) a shape formed by extending the periphery of the outer electrode on the z-axis surrounds the inner electrode.

[0165] Now go to Fig.25 , shows a plan view of the active electrode 228 of the transmitting resonator. As previously described, the active electrode 228 is two concentric electrodes in the form of a ring 270 and a disk 272. The outer diameter R of the ring 270 is 50 mm, and the inner diameter R inThe outer diameter r of the disk 272 is 35 mm. The outer diameter r of the disk 272 is 25 mm. Therefore, the distance between the ring 270 and the disk 272 is 10 mm. In this embodiment, the gap between the active electrode 228 of the transmitting resonator and the active electrode 248 of the receiving resonator is 24 mm. The spacing distance between the active electrode 228 of the transmitting resonator and the passive electrode 260 is 3 mm. Although the active electrode 228 of the transmitting resonator is shown, the active electrode 248 of the receiving resonator has the same size.

[0166] Since the passive electrode 260 surrounds the active electrode 228 of the transmitting resonator, the radius of the passive electrode 260 must be larger than the outer diameter R of the disk 272 of the active electrode 228 of the transmitting resonator.

[0167] Now go to Fig.26 , shows a graph depicting the self-impedance of the active electrode 228 of the transmitting resonator compared to Fig.24 FIG. 2 is a graph of the normalized radius of the passive electrode 260 of FIG. The normalized radius is the radius of the passive electrode 260 divided by the outer diameter R of the ring 270. When the radius of the passive electrode 260 is smaller than the outer diameter R, the impedance of the active electrode 228 is affected by the material of the passive electrode 260. To avoid this effect, the radius of the passive electrode 260 should be larger than the outer diameter R of the ring 270.

[0168] Now go to Fig. 27 , depicts a graph depicting the RF efficiency of system 20 including active electrodes 228 and 248 and passive electrode 260 compared to Fig.24 When the radius of the passive electrode 260 is smaller than the outer diameter R of the ring 270, the RF efficiency drops significantly to below 90%.

[0169] Now go to Fig.28 , shows a plan view of a manufacturing embodiment of the active electrode 228 for the system 20. As previously described, the active electrode 228 includes two concentric electrodes in the form of a ring 270 and a disk 272, respectively. In this manufacturing embodiment, the ring 270 and the disk 272 are printed on a PCB. The outer diameter R of the ring 270 is 65 mm, and the inner diameter R in The outer diameter r of the disk 272 is 35 mm. The dimensions of the PCB are 180 mm by 180 mm by 1.6 mm. The PCB has essentially no other features except for the mounting holes.

[0170] Now go to Fig.29 , shows a perspective view of another embodiment of a passive electrode 274 for use with the active electrode 228. The passive electrode 274 is configured to be mounted on Fig.28270. In this embodiment, the passive electrode 274 is shaped like an open box so that the sides of the box support the active electrode 228 of the transmitting resonator. In this embodiment, the sides of the box also support the perimeter of the PCB so that the disk 272 and ring 270 are raised above the largest face of the passive electrode 274. The largest face of the passive electrode 274 is the bottom of the box. The depth of the box is 5.5 mm. The bottom of the box is 160 mm by 160 mm.

[0171] Now go to Fig.30 , showing the different test materials with and without Fig.29 Graph of the capacitance of capacitor 52 of the transmitting resonator of system 20 without passive electrode 274. The test materials were a grounded table, a wooden table, an electrostatic discharge (ESD) floor, a regular office floor, a tinned metal sheet, and Styrofoam. The capacitance of capacitor 52 was measured using a Rohde & Schwarz ZNB 4 vector network analyzer. As previously described, the passive electrode 274 provides additional capacitance to capacitor 52. When the test material is highly conductive (e.g., grounded table, metal sheet), the capacitance of capacitor 52 with and without passive electrode 274 is similar. The passive electrode 274 prevents the capacitance of capacitor 52 from varying between test materials. The standard deviation of the capacitance is 1.44 pF without passive electrode 274 and 0.46 pF with passive electrode 274. The Styrofoam material is representative of free space capacitance because Styrofoam is a breathable foam.

[0172] Although a system 20 has been described that includes a passive electrode 60 adjacent to two active electrodes 28 of a transmit resonator 24, those skilled in the art will appreciate that other configurations are possible. Fig.31 , another embodiment of a wireless power transfer system is shown and is generally identified by reference numeral 320. Unless otherwise noted, the elements of the wireless power transfer system 320 are similar to the elements of the previously described wireless power transfer system 20 and are referred to by the same reference numerals increased by 300. However, with Figure 1 Compared to the illustrated wireless power transfer system 20 , the wireless power transfer system 320 does not include the passive electrode 60 adjacent to the active electrode 328 of the transmit resonator 324 .

[0173] In this embodiment, the active electrode 348 of the receiving resonator 342 forms a receiving capacitor 382 with the passive electrode 380. In particular, the receiver 342 includes a receiving resonator 342 electrically connected to a load 346. The receiving resonator 342 includes a receiving capacitor 382 and two induction coils 350. The receiving capacitor 382 includes two active electrodes 348 and a passive electrode 380. Similar to the passive electrode 60 of the wireless power transfer system 20, the passive electrode 380 is configured to surround the active electrode 348 to at least partially eliminate environmental effects that affect the active electrode 348. The passive electrode 380 provides additional capacitance to the system, reducing the required inductance. Each induction coil 350 is electrically connected to the active electrode 348 and the load 346.

[0174] The passive electrode 380 is configured to surround the active electrode 348 to at least partially eliminate environmental influences affecting the active electrode 348, so that the active electrode 348 has a substantially constant environment regardless of the actual environment located on the opposite side of the passive electrode 380 relative to the active electrode 348, as previously described. The passive electrode 380 also provides additional capacitance to the system 320, reducing the required inductance.

[0175] In this embodiment, the passive electrode 380 comprises an elongated element. The elongated element is formed of a conductive material. The elongated element is in the form of a generally rectangular flat plate having opposing major surfaces. The passive electrode 380 is adjacent to the active electrode 348. The passive electrode 380 surrounds the active electrode 348. The passive electrode 380 and the active electrode 348 form a capacitor 382. In this embodiment, the passive electrode 380 is generally parallel to the active electrode 348. The active electrode 348 and the passive electrode 380 are on generally parallel planes.

[0176] In this embodiment, the passive electrode 380 is not grounded. The passive electrode 380 is separate.

[0177] In this embodiment, the passive electrode 380 is non-radiative.

[0178] In this embodiment, the components of the receive resonator 344 are configured to operate in the near field. Thus, the passive electrode 380 is configured to operate in the near field.

[0179] In this embodiment, the passive electrode 380 is electrically small. When the physical length of the passive electrode 380 is less than λ / 10, the passive electrode 380 is electrically small. λ is the wavelength of the source signal from the power supply. For a source signal with a frequency of 13.56 MHz output by the power supply 26, λ is about 22 m. Therefore, when the physical length of the passive electrode 380 is less than about 2.2 m, the passive electrode 380 is electrically small.

[0180] The receive resonator 344 is configured to extract power from the generated electric field through resonant electric field coupling, as previously described.

[0181] Although a system 20 has been described that includes a passive electrode 60 adjacent to two active electrodes 28 of a transmit resonator 24, those skilled in the art will appreciate that other configurations are possible. Fig.32 , another embodiment of a wireless power transfer system is shown and generally identified by reference numeral 420. Unless otherwise noted, elements of wireless power transfer system 420 are similar to elements of previously described wireless power transfer system 20 and are referred to with like reference numerals increased by 400.

[0182] In this embodiment, the active electrode 428 of the transmit resonator 424 forms a capacitor 452 with the first passive electrode 460, and the active electrode 448 of the receive resonator 444 forms a capacitor 482 with the second passive electrode 480. In particular, the transmitter 422 includes a transmit resonator 424 electrically connected to a power source 426. The transmit resonator 424 includes two active electrodes 428 and a first passive electrode 460. Each induction coil 430 is electrically connected to the active electrode 428 and the power source 426.

[0183] The receiver 442 includes a receiving resonator 444 electrically connected to a load 446. The receiving resonator 444 includes a capacitor 482 and two induction coils 450. The capacitor 482 includes two active electrodes 448 and a second passive electrode 480. Each induction coil 450 is electrically connected to an active electrode 448 and a load 446.

[0184] Similar to the passive electrode 60 of the wireless power transfer system 20, the first passive electrode 460 is configured to surround the active electrode 428 of the transmitting resonator 424 to at least partially eliminate the environmental impact affecting the active electrode 428, and the second passive electrode 480 is configured to surround the active electrode 448 of the receiving resonator 444 to at least partially eliminate the environmental impact affecting the active electrode 448. The first passive electrode 460 and the second passive electrode 480 also provide additional capacitance to the system 420, respectively, reducing the required inductance.

[0185] The first passive electrode 460 is configured to surround the active electrode 428 to at least partially eliminate environmental effects affecting the active electrode 428, so that the active electrode 428 has a substantially constant environment, regardless of the actual environment located on the opposite side of the first passive electrode 460 relative to the active electrode 428, as described above. The first passive electrode provides additional capacitance to the system, reducing the required inductance. Similarly, the second passive electrode 480 is configured to surround the active electrode 448 to at least partially eliminate environmental effects affecting the active electrode 448 of the receiving resonator 444, so that the active electrode 448 has a substantially constant environment, regardless of the actual environment located on the opposite side of the passive electrode 480 relative to the active electrode 448, as described above. The second passive electrode provides additional capacitance to the system, reducing the required inductance.

[0186] In this embodiment, each of the first passive electrode 460 and the second passive electrode 480 comprises an elongated element. The elongated element is formed of a conductive material. The elongated element is in the form of a generally rectangular plate having opposing major surfaces. The first passive electrode 460 is adjacent to the active electrode 428 of the transmitting resonator 424. The second passive electrode 480 is adjacent to the active electrode 448 of the receiving resonator 444. The first passive electrode 460 surrounds the active electrode 428 of the transmitting resonator 424. The second passive electrode 480 surrounds the active electrode 448 of the receiving resonator 444. The first passive electrode 460 and the active electrode 428 of the transmitting resonator 424 form a capacitor 452. The second passive electrode 480 and the active electrode 448 of the receiving resonator 444 form a capacitor 482. In this embodiment, the first passive electrode 460 and the second passive electrode 480 are generally parallel to the active electrodes 428 and 448. The active electrodes 428 and 448 and the first and second passive electrodes 460 and 480 are in substantially parallel planes.

[0187] In this embodiment, the first passive electrode 460 and the second passive electrode 480 are not grounded. The first passive electrode 460 and the second passive electrode 480 are separate.

[0188] In this embodiment, the first passive electrode 460 and the second passive electrode 480 are non-radiative.

[0189] In this embodiment, the components of the transmit resonator 424 and the receive resonator 444 are configured to operate in a near field.

[0190] In this embodiment, the first passive electrode 460 and the second passive electrode 480 are electrically small. When the physical length of each passive electrode 460 and 480 is less than λ / 10, the first passive electrode 460 and the second passive electrode 480 are electrically small. λ is the wavelength of the source signal from the power supply. For a source signal with a frequency of 13.56 MHz, λ is about 22 m. Therefore, when the physical length of the first passive electrode 460 and the second passive electrode 480 is less than about 2.2 m, the first passive electrode 460 and the second passive electrode 480 are electrically small.

[0191] In this embodiment, the resonant frequency of the transmitting resonator 424 is 13.56 MHz. In this embodiment, each active electrode 428 and 448 is 50 mm by 200 mm. The distance between the active electrode 428 of the transmitting resonator 424 and the active electrode 448 of the receiving resonator 444 is 100 mm. Each of the first passive electrode 460 and the second passive electrode 480 is 400 mm by 600 mm.

[0192] As previously described, the additional capacitance from the first passive electrode 460 and the second passive electrode 480 reduces the inductance required for the inductive coils 430 and 450 in the transmitter 422 and the receiver 442 to operate at a resonant frequency of 13.56 MHz, compared to a wireless power transfer system that does not include the first passive electrode 460 and the second passive electrode 480. In this embodiment, the inductance of the inductive coils 430 and 450 of the wireless power transfer system 420 is reduced from 43.2 μH to 39.5 μH.

[0193] Although embodiments of the first passive electrode 460 and the second passive electrode 480 have been described, those skilled in the art will appreciate that variations are possible. Fig.33 , respectively, show perspective views of elements of the first passive electrode 460 and the second passive electrode 480 and the active electrode 448 of the receiving resonator 444. The active electrode 428 of the transmitting resonator 424 is present but not shown.

[0194] In this embodiment, active electrodes 428 and 428 each have a length (h) equal to 100 mm and a width (w) equal to 37.5 mm. Passive electrodes 460 and 480 each have a length (y) equal to 110 mm and a width (x) equal to 110 mm. The lateral gap (g) between the active electrodes 428 of the transmit resonator 424 is equal to the lateral gap between the active electrodes 448 of the receive resonator 444 and is equal to 25 mm. The separation distance (D1) between the active electrode 428 of the transmit resonator 424 and the first passive electrode 460 is equal to 2 mm. The separation distance (D) between the active electrode 428 of the transmit resonator 424 and the active electrode 448 of the receive resonator 444 is equal to 20 mm. When the passive electrodes 460 and 480 are present, the inductance on each resonator is 12.6 μH. The efficiency of the system 420 is 88%. When the passive electrodes 460 and 480 are not present, the inductance of each resonator is 12.7 μH.

[0195] In this embodiment, the first passive electrode 460 and the second passive electrode 480 further include dissipative materials attached to the edge of each passive electrode 460 and 480 and / or along the perimeter of each passive electrode 460 and 480, respectively. The dissipative material is attached to the corresponding passive electrode on the face of the passive electrode opposite to the corresponding active electrode. The edges and corners of the passive electrodes 460 and 480 can be sources of high electric field strength through stray electric fields. These stray electric fields may cause electromagnetic interference. The dissipative materials on the edges of the passive electrodes 460 and 480 and / or along the perimeters of the passive electrodes 460 and 480 suppress the stray electric fields emitted from the passive electrodes 460 and 480.

[0196] The dissipative material attached to each of the passive electrodes 460 and 480 has a 10 -6 and 10 -12 S / m. This conductivity range provides ideal absorption of electric field energy. Below this range, the induced current encounters little resistance; therefore, little energy is lost. Above this range, the charge induced current is suppressed by the resistance of the dissipative material; therefore, only a small amount of energy is dissipated. For safety and electromagnetic interference (EMI) purposes, it is desirable to suppress stray electric fields. Examples of dissipative materials include plastics with carbon additives and carbon fibers. The dissipative material does not affect the efficiency of the system 420 because the dissipative material is located on the side of the corresponding passive electrodes 460 and 480 opposite to the active electrodes 428 and 448 of the transmitting resonator 424 and the receiving resonator 444, respectively.

[0197] In this embodiment, a first dissipative material 490 is attached to the first passive electrode 460, and a second dissipative material 492 is attached to the second passive electrode 480. The first dissipative material 490 is a plastic sheet placed adjacent to the first passive electrode 460, opposite to the active electrode 428 of the transmit resonator 424. The second dissipative material 492 is a plastic sheet placed adjacent to the second passive electrode 480, opposite to the active electrode 448 of the transmit resonator 444. The plastic sheets have the same dimensions. The dimensions of each plastic sheet are 121 mm (length) x 121 mm (width) x 1 mm (thickness).

[0198] Now go to Figure 34 to Figure 36 , shows a contour map of the electric field emitted from the wireless power system 420. The contour map is a cross-sectional view taken along the diagonal of the capacitors 452 and 482, and the cross section is perpendicular to the passive electrodes 460 and 480. The scale unit on the contour map is dBV / m, and the increment of each contour line is 2.5dBV / m.

[0199] Fig.34 is a contour plot of the electric field emanating from the wireless power system 420 when the first dissipative material 490 and the second dissipative material 492 are not present.

[0200] Fig.35 4 is a contour plot of the electric field emanating from the wireless power system 420 when the first dissipative material 490 and the second dissipative material 492 are present and the dissipative materials 490 and 492 are plastic sheets.

[0201] Fig.36 4 is a contour plot of the electric field emitted from the wireless power system 420 when the first dissipative material 490 and the second dissipative material 492 are present and the dissipative materials 490 and 492 are plastic sheets. The conductivity of the plastic sheet increases from 0 (ideal insulator) to 10 -8 S / m. At this conductivity, the plastic sheet becomes dissipative and easily absorbs RF energy. Fig.34 and Fig.35 Compared with the stray electric field existing in the contour map of , adding dissipative plastic sheets more effectively suppresses the stray electric field.

[0202] Although specific embodiments of the resonator have been described, those skilled in the art will appreciate that variations are possible. In another embodiment, the resonator includes a capacitor and a single induction coil. The capacitor includes two active electrodes and a passive electrode adjacent to the active electrode. The passive electrode is configured to surround the active electrode to at least partially eliminate environmental influences affecting the active electrode. The passive electrode is configured to provide additional capacitance to the system. The passive electrode is configured to reduce the inductance required to achieve resonance. The induction coil is electrically connected to the active electrode. In this embodiment, the induction coil is located on the opposite side of the passive electrode relative to the active electrode. The induction coil is electrically connected to the active electrode via one or more wires passing through a hole in the passive electrode. The hole in the passive electrode is larger than the radius of the wire. The hole is no larger than 10 times the radius of the wire connecting the induction coil and the active electrode.

[0203] In another embodiment, the holes are filled with an insulating material.

[0204] In another embodiment, the wire connecting the active electrode and the induction coil is insulated. The size of the hole is set to accommodate the insulation layer around the wire connecting the active electrode and the induction coil.

[0205] In another embodiment, the wire connecting the coil and the active electrode extends around the passive electrode.

[0206] Although a specific embodiment of the capacitor 52 of the wireless power transfer system 20 has been described, those skilled in the art will appreciate that variations are possible. Fig.37 , shows another embodiment of a capacitor 494. In general, the capacitor 494 is configured to control the separation distance between the passive electrode 60 and the active electrode 28 of the transmitting resonator 24.

[0207] In this embodiment, as previously described, the capacitor 494 includes the active electrode 28 and the passive electrode 60 of the transmitting resonator 24; and the capacitor 494 also includes a substrate 496 to which the active electrode 28 is attached, an actuator 498 and two (2) telescopic supports 499 extending between the substrate 496 and the passive electrode 60, and a microcontroller.

[0208] The substrate 496 is configured to not interfere with wireless power transfer between the transmit resonator 24 and the receive resonator 44 of the system 20. The active electrodes 28 are attached to the substrate 496, and the substrate 496 extends between the active electrodes 28. The major surface of each active electrode 28 is attached to the substrate 496. In this embodiment, the substrate 496 is plastic. In other embodiments, the substrate 496 is one of fiberglass, ceramic, and polystyrene foam. In another embodiment, the substrate 496 is a printed circuit board. The substrate 496 is an elongated rigid member that spans at least the perimeter of the active electrode 28. The substrate 496 has similar dimensions to the passive electrode 60. The substrate 496 is parallel to the passive electrode 60 on the xy axis. The x-axis and the y-axis are perpendicular to each other and perpendicular to the normal vectors of the passive electrode 60 and the major surface of the substrate 496.

[0209] The passive electrode 60 is spaced apart from the substrate 496. In the space extending between the passive electrode 60 and the substrate, the actuator 498 is located approximately at the center point of the passive electrode 60 and the substrate 496 on the xy axis defined by the passive electrode 60 and the substrate 496. The actuator 498 is attached to the major surface of the substrate 496 and the major surface of the passive electrode 60. In this embodiment, the actuator 498 is a motor. In another embodiment, the actuator 498 is a piezoelectric device.

[0210] Two (2) telescoping supports 499 are located in the space between the passive electrode 60 and the substrate 496. Each telescoping support 499 is attached to a major surface of the substrate 496 and a major surface of the passive electrode 60. The telescoping supports 499 are generally located at opposite ends of the substrate 496 and the passive electrode 60. The telescoping supports 499 are equidistant from the actuator 498. The telescoping supports 499 are configured to extend, thereby increasing the separation distance between the passive electrode 60 and the active electrode 28 of the transmit resonator 24, and are configured to compress, thereby decreasing the separation distance between the passive electrode 60 and the active electrode 28 of the transmit resonator 24. Although two (2) telescoping supports 499 are described, those skilled in the art will appreciate that more may be included.

[0211] In this embodiment, the actuation of the actuator 498 is controlled by a microcontroller (not shown). The microcontroller can be programmed by software to control the actuator 498. The microcontroller is located remotely from the actuator 498 and communicates with the actuator 498 via conventional communication methods, such as Bluetooth. TM or WiFi TM Communicates with actuator 498 .

[0212] In use, the actuator 498 is actuated to increase the separation distance between the passive electrode 60 and the active electrode 28, or to decrease the separation distance between the passive electrode 60 and the active electrode 28. As the actuator 498 increases or decreases the separation distance, the telescoping support 499 extends or compresses, respectively, so that the separation distance increases or decreases uniformly along the entire span of the active electrode 28 and the passive electrode 60.

[0213] As previously described, the actuation of the actuator 498 is controlled by a microcontroller. In another embodiment, the actuation of the actuator 498 is manually controlled. In another embodiment, the microcontroller receives input from a sensor that detects at least one of the separation distance and the electric field strength between the passive electrode 60 and the active electrode 28.

[0214] As previously described, capacitor 494 is configured to control the separation distance between passive electrode 60 and active electrode 28 of transmit resonator 24. As previously described, reducing the separation distance between passive electrode 60 and active electrode 28 reduces the potential range of the electric field generated by transmit resonator 24, which reduces the power transfer efficiency if the distance between transmit resonator 24 and receive resonator 44 is maintained. In addition, reducing the separation distance between passive electrode 60 and active electrode 28 increases the capacitance added to capacitor 494 and reduces the inductance required for system 20. By changing the capacitance added to capacitor 494 to change the capacitance of system 20, the resonant frequency of transmit resonator 24 is tuned.

[0215] The microcontroller is programmed to control the power transfer efficiency, the additional capacitance provided to the system 20 by the passive electrode 60, and the reduction in the required inductance of the system 20 by changing the separation distance between the passive electrode 60 and the active electrode 28 so that a desired balance between these parameters can be achieved. In addition, the microcontroller can control the capacitance of the system 20 by changing the separation distance, thereby tuning the resonant frequency of the transmitting resonator 24.

[0216] As will be appreciated by those skilled in the art, the various wireless power transfer systems 20, 120, 320, and 420 discussed can be used in a variety of different applications. For example, in one application, the wireless power transfer system 20 is used in conjunction with charging the battery of an autonomous vehicle. Autonomous vehicles are used for agriculture, golf course maintenance, and home monitoring, as well as robotic labor, such as robotic lawn mowers. In this application, the transmitter 22 is located on the soil or ground and is used to recharge the battery of the autonomous vehicle. The transmitter 22 is located on the soil or ground so that the soil material or ground material is not located between the passive electrode 60 and the active electrode 28. In addition, the transmitter 22 is located on the soil or ground so that the soil material or ground material is not in close proximity to the active electrode 28. The autonomous vehicle includes a receiver 42.

[0217] Wireless power transfer between the transmitter 22 on the soil and the receiver 42 in the autonomous vehicle allows the autonomous vehicle to be charged without user input. As previously described, when the transmitter 22 is located in or on the soil, the dielectric properties of the soil may affect the power transfer between the transmitter 22 and the receiver 42. Similarly, when the transmitter 22 is located underground, the power transfer between the transmitter 22 and the receiver 42 may be affected by environmental influences. Positioning the passive electrode 60 adjacent to the active electrode 28 of the transmit resonator 24, opposite the receiver 42, at least partially eliminates environmental influences that affect the active electrode 28 and provides additional capacitance, reducing the required inductance of the system, as previously described.

[0218] Thus, an example application of passive electrodes is provided. A front view of an autonomous vehicle is shown in FIG. Fig.38 As shown. The automatic vehicle is generally identified by reference numeral 500. The automatic vehicle 500 includes a propulsion system configured to propel the vehicle 500, a power system configured to power the propulsion system, a series of sensors (touch sensors, optical sensors, etc.) configured to detect environmental information (e.g., obstacles, barcodes, QR codes, colors), and a control system configured to process information from the sensors in order to control the propulsion system and the power system to achieve (multiple) predetermined goals. The propulsion system includes a motor connected to two or more wheels. The power system includes a receiving resonator electrically connected to a load in the form of a battery.

[0219] Those skilled in the art will appreciate that the propulsion system may include other components such as, but not limited to, tracks and / or actuators.

[0220] The receiving resonator includes a capacitor and two induction coils. The capacitor includes two active electrodes 502 electrically connected in series to the induction coils. The induction coils are electrically connected to a load. As previously described, the receiver is configured to extract power from the transmitter through wireless resonant electric field coupling. The transmitter includes a transmitting resonator electrically connected to a power source. The transmitting resonator includes a capacitor and two induction coils. The induction coils are electrically connected to a power source. The capacitor includes two active electrodes 504 and a passive electrode 506, the passive electrode 506 being adjacent to the active electrode 504 of the transmitting resonator and opposite to the automatic vehicle 500. The induction coils are electrically connected in series to the active electrode 504. The transmitting resonator is configured to generate an electric field to transmit power to the receiver through resonant electric field coupling, as previously described. The passive electrode 506 is configured to surround the active electrode 504 to at least partially eliminate environmental effects affecting the active electrode 504, so that the active electrode 28 has a substantially constant environment that is independent of soil conditions (or other substrates), as previously described. As previously described, the passive electrode 506 provides additional capacitance to the capacitor of the transmitting resonator. As previously described, the passive electrode 506 reduces the amount of inductance required to resonate at the resonant frequency. In this embodiment, the automated vehicle 500 does not include an auto-tuning circuit, which reduces cost and allows more power to be delivered to the load.

[0221] In this embodiment, the passive electrode 506 is not grounded. The passive electrode 506 is separate.

[0222] In this embodiment, the passive electrode 506 is non-radiative.

[0223] In this embodiment, the passive electrode 506 is electrically small. When the physical length of the passive electrode 506 is less than λ / 10, the passive electrode 506 is electrically small. λ is the wavelength of the source signal from the power source. For a source signal with a frequency of 13.56 MHz, λ is approximately 22 m. Therefore, when the physical length of the passive electrode 506 is less than about 2.2 m, the passive electrode 506 is electrically small.

[0224] During operation, power is transferred from a power source to an active electrode 504 of a transmit resonator via an induction coil. The power signal sent from the power source to the active electrode 504 via the induction coil excites the transmit resonator, causing the transmit resonator to generate an electric field. In this embodiment, the generated electric field is a near field. A differential voltage is applied to the active electrode 504 of the transmit resonator, which creates an electric field in the surrounding environment. When a receive resonator is placed within the generated electric field and tuned to the resonant frequency of the transmit resonator, the receive resonator extracts power from the transmit resonator through resonant electric field coupling. The extracted power is then transferred from the receive resonator to a load electrically connected to the receive resonator. Although the transmit resonator can generate a magnetic field, little, if any, power is transferred through magnetic field coupling.

[0225] Now go to Fig.39 The table shows that when the passive electrode 506 is present, the RF efficiency is compared to Fig.38 The dielectric constant and loss tangent (ratio of the imaginary to real part of the permittivity) range of dielectric properties for power transfer between the transmitter and receiver. Fig.39 As clearly shown, when the passive electrode 506 is present, the RF efficiency is generally uniform. In addition, the variation in RF efficiency is less than 5% over the entire range of dielectric properties. The variation in RF efficiency is so small that the gradient in RF efficiency is generally not discernible. The range of dielectric constants represents a variety of soil conditions and other surfaces such as wood, asphalt, and plastic.

[0226] Now go to Fig.40 , showing that when the passive electrode 506 does not exist, the RF efficiency is compared to Fig.38 A table of dielectric constants for power transfer between a transmitter and a receiver over a range of dielectric constants. Fig.39 Compared with the table, Fig.40 There are large areas where RF efficiency is less than 90%. The range of dielectric constants represents a variety of soil conditions and other surfaces such as wood and plastic.

[0227] Now go to Fig.41 The table shows the phase of the impedance seen when the power source is powered when the passive electrode 506 is present compared to the impedance seen when the power source is powered. Fig.38 The dielectric constant and loss tangent (the ratio of the imaginary to real part of the permittivity) are the dielectric properties within a range that allow power to be transferred between the transmitter and receiver. Fig.41 As clearly shown, the phase of the impedance is generally low (<70°) when the passive electrode 506 is present. The power supply preferentially sees an impedance with a low phase, especially for high power, and the power supply may automatically shut down for a phase above a predetermined value (e.g., 10). The range of dielectric constants represents a variety of soil conditions and other surfaces such as wood, asphalt, and plastic.

[0228] Now go to Fig.42 , the table shows the phase of the impedance seen when the power source is powered compared to when the passive electrode 506 is not present. Fig.38 The power transfer between the transmitter and receiver is within the dielectric constant range. Fig.41 Compared with the table, Fig.42 Most of the dielectric properties in have impedances with phase angles greater than 25°, making the power supply have unfavorable impedance. The range of dielectric constants represents a variety of soil conditions and other surfaces such as wood and plastic.

[0229] As will be appreciated, the passive electrodes 506 ensure that the transmitter is robust enough to operate consistently on a variety of substrates, such as different types of floors, pavement, and concrete, without requiring the receive resonator to be retuned to the resonant frequency of the transmit resonator.

[0230] Although one application has been described, those skilled in the art will appreciate that other applications are possible. Wireless power transfer systems 20, 120, 320, and 420 may be used in applications other than autonomous vehicles. For example, wireless power transfer system 320 may be used in a UAV. Figure 43 to Figure 45 , showing a UAV according to one aspect of the present disclosure. The UAV is generally identified by reference symbol 1000. The UAV 1000 employs the aforementioned wireless power transfer system 320. The UAV 1000 includes a support structure, a propulsion system mounted to the support structure and configured to provide lift and thrust for the UAV 1000, a power system mounted to the support structure and configured to power the propulsion system, and a control system mounted to the support structure and configured to control the propulsion system and the power system.

[0231] In this embodiment, the support structure includes a frame 1002 and four arms 1004. The frame 1002 is rigid. Each arm 1004 is coupled to the frame 1002. Each arm 1004 extends from the frame 1002. The arms 1004 are generally equidistant from each other. Those skilled in the art will appreciate that more or fewer arms 1004 may be used.

[0232] In this embodiment, the propulsion system includes four motors 1006 and four propellers 1008. Each motor 1006 is attached to the end of the arm 1004 opposite the frame 1002. Each motor 1006 is a brushless DC (BLDC) motor with an electronic speed controller (ESC) for variable thrust control. Each propeller 1008 is connected to the drive end of the corresponding motor 1006. In this embodiment, each propeller 1008 is a 28 cm long two-blade propeller mounted in a circular housing.

[0233] The power system includes a receiving resonator 1010 electrically connected to a battery 1012, a housing 1014, and a receiver board 1016. The receiving resonator 1010 and the battery 1012 are contained within the housing 1014. The battery 1012 is rechargeable. The housing 1014 is a dielectric material. The housing 1014 is thin enough so that it does not significantly affect the power transmission to the UAV 1000.

[0234] Now go to Fig.45, shows a view of the UAV 1000 with the housing 1014 partially removed. The receiving resonator 1010 includes a capacitor 1020 and two induction coils 1022. The capacitor 1020 includes two active electrodes 1024 and a passive electrode 1026 adjacent to the active electrodes 1024. The passive electrode 1026 is configured to surround the active electrode 1024. The passive electrode 1026 at least partially eliminates environmental effects affecting the active electrode 1024 and provides additional capacitance to the system, reducing the inductance required to resonate the receiving resonator at a desired resonant frequency. The passive electrode 1026 is opposite to the electric field source relative to the active electrode 1024, as described below. The passive electrode is 7.4 mm (D1) away from the active electrode. The induction coil 1022 is electrically connected in series to the active electrode 1024. The receiving resonator 1010 is configured to extract power from the generated electric field through resonant electric field coupling. In this embodiment, the induction coil 1022 is a ferrite core inductor. Those skilled in the art will appreciate that other types of induction coils are possible. Although two induction coils 1022 have been shown, those skilled in the art will appreciate that one or more induction coils may be used.

[0235] The receiver board 1016 includes a rectifier that converts the power extracted by the receiving resonator 1010 through resonant electric field coupling into regulated DC power. The regulated DC power charges the battery 1012. The receiver board 1016 also includes a wireless data transmitter. The wireless data transmitter wirelessly transmits telemetry data to the transmitter. The telemetry data includes the voltage and current at the receiving resonator 1010. The transmission of telemetry data allows tracking of the power extracted by the receiving resonator 1010. Tracking the power extracted by the receiving resonator 1010 is used to maintain and maintain a consistent charging rate of the battery 1012.

[0236] Now go to Fig.46 and Fig.47 , the capacitor 1020 of the UAV 1000 is shown separately. As previously described, the capacitor 1020 includes two active electrodes 1024 and a passive electrode 1026. In this embodiment, the active electrodes 1024 of the receiving resonator 1010 are laterally spaced apart. The active electrodes 1024 are formed of a conductive material. Although two active electrodes 1024 are depicted, it will be understood by those skilled in the art that more electrodes may be used.

[0237] Each active electrode 1024 includes an electrode plate 1050 and an arm 1052 extending diagonally from the electrode plate 1050. The arm 1052 has a center plate 1054 and two side walls 1056. Each side wall 1056 extends from a longitudinal side of the center plate 1054. Each side wall 1056 extends from the center plate 1054 at an angle of approximately 135° to the center plate 1054.

[0238] The passive electrode 1026 surrounds the active electrode 1024. In this embodiment, the passive electrode 1026 is approximately located between the active electrode 1024 and the receiver plate 1016. The passive electrode 1026 includes a passive electrode plate 1060 and a housing 1062. The passive electrode plate 1060 is attached to the housing 1062. In this embodiment, the passive electrode plate 1060 is a flat plate. The passive electrode plate 1060 is a metal plate. The housing 1062 is sized to contain the battery 1012. The housing 1062 is a metal housing. The battery 1012 is mounted within the housing 1062 of the passive electrode 1026.

[0239] Those skilled in the art will appreciate that while the passive electrode 1026 is shown as comprising a planar passive electrode plate 1060, other configurations are possible. For example, the passive electrode plate 1060 may be non-planar and still surround the active electrode 1028 of the UAV 1022.

[0240] In this embodiment, the passive electrode 1026 is not grounded. The passive electrode 1026 is separate.

[0241] In this embodiment, the passive electrode 1026 is non-radiative.

[0242] In this embodiment, the passive electrodes 1026 are configured to operate in the near field.

[0243] In this embodiment, the passive electrode 1026 is electrically small. When the physical length of the passive electrode 1026 is less than λ / 10, the passive electrode 1026 is electrically small. λ is the wavelength of the source signal from the power source. For a source signal with a frequency of 13.56 MHz, λ is approximately 22 m. Therefore, when the physical length of the passive electrode 1026 is less than approximately 2.2 m, the passive electrode 1026 is electrically small.

[0244] The passive electrode 1026 is configured to surround the active electrode 1024 to at least partially eliminate environmental effects affecting the active electrode 1024, so that the active electrode 1024 has a substantially constant environment regardless of the actual environment on the opposite side of the passive electrode 1026 relative to the active electrode 1024, and provide additional capacitance to the system, thereby reducing the inductance required to make the system resonate at a desired frequency.

[0245] In this embodiment, the minimum separation distance (Ds) between the passive electrode 1026 and the active electrode 1024 is equal to 7.4 mm.

[0246] As previously described, a surface charge is induced on the passive electrode 1026 in response to the electric field encountered by the receiving resonator 1010. For metals (e.g., copper and aluminum), alloys (e.g., steel and brass), and other conductors such as graphene or conductive fabrics, the charge dissipation time is approximately 10 -19s. When the resonant frequency is 13.56MHz, the oscillation period of the electric field is about 10 -9 seconds. Therefore, the charge dissipation time is many orders of magnitude smaller than the oscillation period of the electric field. Therefore, the charge redistribution can be considered instantaneous.

[0247] The induced surface charge creates its own electric field that opposes the electric field encountered by the receiving resonator 1010 because negatively charged particles will be attracted to areas on the high potential surface where their presence will cancel the electric field parallel to the surface. Therefore, the net electric field acting on the surface of the passive electrode 1026 is perpendicular to the surface of the passive electrode 1026. Therefore, the electric field extracted by the receiving resonator 1010 terminates at the passive electrode 1026 and does not bypass the passive electrode 1026. The conductive surface of the passive electrode 1026 opposite the active electrode 1024 acts as a boundary for the electric field generated by the passive electrode 1026. Therefore, changes in the environment on the opposite side of the passive electrode 1026 do not affect the electric field on the other side.

[0248] As previously described, the surface charge induced on the passive electrode 1026 provides additional capacitance to the UAV 1000. The net electric field on the surface of the passive electrode 1026 acts as an energy storage medium for the UAV 1000. Thus, the active electrode 1024 and the passive electrode 1026 form a capacitor 1020, the capacitance of which is greater than the capacitance of a capacitor including only the active electrode 1024. The passive electrode 1026 and the active electrode 1024 acting as a capacitor 1020 reduce the amount of inductance required to resonate at the resonant frequency.

[0249] As previously described, in this embodiment, the inductive coils 1022 of the receive resonator 1010 are ferrite core inductors. Commonly used ferrite inductors are heavy, lossy, and power limited due to core saturation and heating. Therefore, it is desirable to reduce the inductance required by the UAV 1000. The additional capacitance from the passive electrodes 1026 reduces the inductance required for each inductive coil 1022. Simulations of the UAV 1000 show that the passive electrodes 1026 of the UAV 1000 increase the capacitance of the UAV 1000 from 4.5 pF to 8.0 pF, an increase of approximately 79%.

[0250] Now go to Fig.48 , showing a partial wireless power transfer system. The wireless power transfer system includes a UAV 1010 and an electric field source. The capacitor 1020 of the UAV 1010 is connected to the electric field source at Fig.48. In this embodiment, the electric field source takes the form of a transmitter 1070. The transmitter 1070 includes a transmitting resonator. The transmitting resonator includes two active electrodes 1072 and two induction coils (not shown) electrically connected to the active electrodes 1072. The active electrodes 1072 are electrically connected in series to the induction coils. The active electrodes are spaced laterally. The active electrodes 1072 are coplanar. The active electrodes 1072 are conductors. In this embodiment, the conductors are elongated and generally rectangular flat plates. The conductors are made of copper foil tape. Although two active electrodes 1072 are depicted, it will be understood by those skilled in the art that more active electrodes 1072 may be used. It will also be understood by those skilled in the art that more than two induction coils may be used. It will also be understood by those skilled in the art that one induction coil may be used.

[0251] The active electrode 1072 and the induction coil of the transmitting resonator are configured to resonate and generate an electric field. The receiving resonator 1010 is consistent with the resonant frequency of the transmitting resonator. The receiving resonator 1010 is configured to extract power from the transmitter 1070 through resonant electric field coupling. Although the transmitting resonator can also generate a magnetic field, little or no power is transmitted through the generated magnetic field.

[0252] In this embodiment, the minimum separation distance (D) between the active electrode 1072 of the transmitting resonator and the active electrode 1024 of the receiving resonator 1010 is equal to 50 mm.

[0253] During operation, power is transmitted from the power supply to the active electrode 1072 of the transmitting resonator. The power signal sent from the power supply to the active electrode 1072 of the transmitting resonator via the induction coil excites the transmitting resonator, causing the transmitting resonator to generate an electric field. In this embodiment, the generated electric field is a near field. A differential voltage is applied to the active electrode 1072 of the transmitting resonator, which creates an electric field in the surrounding environment. When the receiving resonator 1010 is placed within the generated electric field and coincides with the resonant frequency of the transmitting resonator, the receiving resonator 1010 extracts power from the transmitter through resonant electric field coupling. The extracted power is then transmitted from the receiving resonator 1010 to the DC converter / regulator. The extracted power is then regulated / converted by the DC converter / regulator. The regulated / converted power is then used to charge the battery 1012.

[0254] In this embodiment, the active electrode 1072 is located on a landing platform (not shown) of the UAV 1000. When landed, there is a 50 mm gap (D) between the active electrode of the transmitter and the active electrode of the receiver.

[0255] In this embodiment, the control system includes a flight controller that communicates with the motor and power system. The flight controller is housed in the center of the frame 1002.

[0256] UAV 1000 also includes a sensor system including at least one sensor configured to detect at least one parameter and generate a signal to a control system. The sensor is encapsulated in frame 1002. In this embodiment, the sensor system includes at least one global positioning system (GPS) receiver unit; and an inertial measurement unit (IMU) composed of an accelerometer, a gyroscope, and a magnetometer.

[0257] In this embodiment, the control system includes a flight controller that communicates with the motor and power system. The flight controller is housed in the center of the frame 1002.

[0258] Although a propulsion system including four motors 1006, four propellers 1008, and four arms 1004 has been shown, those skilled in the art will appreciate that one or more motors, propellers, and arms may be used.

[0259] Those skilled in the art will appreciate that the passive electrode need not be planar, and may be cylindrical, for example, to conform to a cylindrical active electrode or to eliminate environmental effects of the conduit contents.

[0260] Those skilled in the art will recognize that the passive electrode may be annular when paired with an active electrode that is annular.

[0261] Those skilled in the art will recognize that spacers and / or standoffs may be used to maintain the spacing between the passive and active electrodes.

[0262] Those skilled in the art will recognize that passive electrodes may be perforated, but the effectiveness and increased capacitance of the passive electrodes will decrease as the number of perforations is increased.

[0263] Those skilled in the art will appreciate that although specific dimensions have been described, these are examples and the dimensions described may vary depending on the particular circumstances.

[0264] Those skilled in the art will appreciate that although specific embodiments of unmanned vehicles are provided, a variety of other applications and environments are possible.

[0265] Although the embodiments have been described above with reference to the accompanying drawings, those skilled in the art will appreciate that changes and modifications may be made without departing from the scope defined by the appended claims.

Claims

1. A wireless power transmission system, comprising: Resonator, including: Capacitors, including: at least two active electrodes; and a passive electrode adjacent to the active electrode, the passive electrode being configured to surround the active electrode to at least partially eliminate environmental influences affecting the active electrode; and at least one inductor electrically connected to the active electrode, wherein the at least one inductor is configured to excite the capacitor to generate an electric field to transfer power or extract power from the generated electric field, wherein the generated electric field induces surface charge on the passive electrode so that the passive electrode provides additional capacitance to the capacitor of the resonator and reduces the inductance of the inductor required to resonate the system.

2. The wireless power transmission system according to claim 1, wherein: The resonator forms part of a transmitter configured to wirelessly transfer power, wherein the resonator is configured to generate the electric field.

3. The wireless power transmission system according to claim 2, wherein: The resonator is configured to generate a resonant electric field.

4. The wireless power transmission system according to claim 1, wherein: The resonator is a transmitting resonator, wherein the system further comprises a receiving resonator, the receiving resonator comprising at least two active electrodes.

5. The wireless power transmission system according to claim 4, wherein: The area of ​​the passive electrode is larger than the area of ​​the active electrode of the transmitting resonator by at least the area between the active electrodes of the transmitting resonator.

6. The wireless power transmission system according to claim 1, wherein: The resonator forms part of a receiver configured to extract power wirelessly, wherein the resonator is configured to extract power from the generated electric field by resonant electric field coupling.

7. The wireless power transmission system according to claim 6, wherein: The resonator is configured to extract power from the generated resonant electric field.

8. The wireless power transmission system according to any one of claims 1 to 7, wherein: The active electrode is an elongated plate.

9. The wireless power transmission system according to claim 8, wherein: The passive electrode has a width greater than or equal to the sum of twice the width of one of the active electrodes and a lateral gap between the active electrodes, and a length greater than or equal to the length of one of the active electrodes.

10. The wireless power transmission system according to any one of claims 1 to 7, wherein: The active electrodes are concentric.

11. The wireless power transmission system according to any one of claims 1 to 7, wherein: At least one of the active electrodes is a disk or a ring.

12. The wireless power transmission system according to any one of claims 1 to 7, wherein: The passive electrode is an elongated plate or disk.

13. The wireless power transmission system according to any one of claims 1 to 7, wherein: The passive electrode is a ring having an inner diameter less than or equal to the inner diameter of the inner active electrode.

14. The wireless power transmission system according to any one of claims 1 to 7, wherein: The passive electrode includes a dissipative material attached to an edge of the passive electrode and / or along a perimeter of the passive electrode.

15. The wireless power transmission system according to any one of claims 1 to 7, wherein: The inductor is located on an opposite side of the passive electrode relative to the active electrode, wherein the inductor is electrically connected to the active electrode through a hole in the passive electrode.

16. The wireless power transmission system according to any one of claims 1 to 7, wherein: The capacitor further comprises: a substrate, wherein the active electrode is attached to the substrate; and An actuator extends between the substrate and the passive electrode, the actuator being controllable to change a spacing distance between the active electrode and the passive electrode.

17. The wireless power transmission system according to claim 16, wherein: The capacitor further comprises: At least two telescopic supports extend between the substrate and the passive electrode, the supports being configured to extend or compress as a separation distance between the active electrode and the passive electrode changes.

18. The wireless power transmission system according to claim 16, wherein: The actuation of the actuator is controlled by a microcontroller.

19. The wireless power transmission system according to any one of claims 1 to 7, wherein: The passive electrode is grounded.

20. The wireless power transmission system according to any one of claims 1 to 7, wherein: The passive electrode is not grounded.

21. An unmanned aerial vehicle comprising: frame; a propulsion system mounted on the frame and configured to provide lift and thrust to the UAV; a power system mounted on the frame and configured to supply power to the propulsion system, the power system comprising: Resonator, including: Capacitors, including: at least two active electrodes; and a passive electrode adjacent to the active electrode, the passive electrode being configured to surround the active electrode to at least partially eliminate environmental influences affecting the active electrode, wherein the passive electrode is opposite to an electric field source relative to the active electrode; and at least one inductor electrically connected to the active electrode, wherein the at least one inductor is configured to excite the capacitor to extract power from a generated electric field through resonant electric field coupling, wherein the generated electric field induces surface charge on the passive electrode such that the passive electrode provides additional capacitance to the capacitor of the resonator and reduces the inductance of the inductor required to resonate the power system; and A control system is mounted on the frame and configured to control the propulsion system and the power system.

22. A wireless power transmission system, comprising: The unmanned aerial vehicle according to claim 21; as well as A transmitting resonator comprising: at least two active electrodes; and At least one inductor is electrically connected to the active electrode, wherein the transmit resonator is configured to generate an electric field to transfer power to the UAV via resonant electric field coupling.

23. An unmanned aerial vehicle comprising: frame; a propulsion system located on the frame and configured to propel the UAV; A wireless power transfer system according to any one of claims 1 to 20 located on the frame; as well as A control system located on the frame is configured to control the propulsion system and the wireless power transfer system.

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