Patent Description:
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. In magnetic induction systems, the transmitter has an induction coil that transfers electrical energy from the power source to an induction coil of the receiver. Power transfer occurs due to coupling of magnetic fields between the induction coils of the transmitter and receiver. The range of these magnetic induction systems is limited and the induction coils of the transmitter and receiver must be in optimal alignment for power transfer. There also exist resonant magnetic systems in which power is transferred due to coupling of magnetic fields between the induction coils of the transmitter and receiver. However, in resonant magnetic systems the induction coils are resonated using at least one capacitor. The range of power transfer in resonant magnetic systems is increased over that of magnetic induction systems and alignment issues are rectified. While electromagnetic energy may be produced in magnetic induction and resonant magnetic systems, the majority of power transfer occurs via the magnetic field. Little, if any, power is transferred via electric induction or resonant electric induction.

In electrical induction systems, the transmitter and receiver have capacitive electrodes. Power transfer occurs due to coupling of electric fields between the capacitive electrodes of the transmitter and receiver. Similar, to resonant magnetic systems, there exist resonant electric systems in which the capacitive electrodes of the transmitter and receiver are made resonant using at least one inductor. Resonant electric systems have an increased range of power transfer compared to that of electric induction systems and alignment issues are rectified. While electromagnetic energy may be produced in electric induction and resonant electric systems, the majority of power transfer occurs via the electric field. Little, if any, power is transferred via magnetic induction or resonant magnetic induction.

<CIT> describes a electronic apparatus which includes a portable electronic device and a charger for capacitively charging the portable electronic device when the portable electronic device is temporarily placed adjacent the charger.

<CIT> describes an electric power transmitting apparatus and a method for controlling electric power transmission.

<CIT> describes an electrostatic coupling type contactless electric power supply device.

<CIT> describes an antenna coupled to a radiofrequency (RF) amplifier.

Although wireless power transfer techniques are known, improvements are desired. It is therefore an object to provide a novel wireless electric field power transfer system, a transmitter and receiver therefor and a method of wirelessly transmitting power.

It should be appreciated that this Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description of Embodiments. This Summary is not intended to be used to limit the scope of the claimed subject matter.

Accordingly, in an aspect, there is provided a transmit resonator comprising: at least two inductors; a switching network electrically connected to the inductors; a plurality of capacitive electrodes electrically connected to the switching network; a detector communicatively connected to the controller, the detector configured to detect impedance; and a controller communicatively connected to the switching network and the detector, the controller configured to control the switching network to control which electrodes are connected to the inductors based on the detected impedance, wherein the inductors and electrodes are configured to resonate to generate an electric field.

In one or more embodiments, the detector comprises a first detector and a second detector.

In one or more embodiments, the first detector is configured to detect impedance presented to the electrodes.

In one or more embodiments, the detector comprises at least one circuit and a phase detector. In one or more embodiments, the circuit is configured to measure impedance by applying a voltage and detecting a current.

In one or more embodiments, the second detector is configured to detect impedance during wireless power transfer.

In one or more embodiments, the switching network is configured to electrically connect each electrode to both inductors.

In one or more embodiments, the transmit resonator has an equal number of inductors as capacitive electrodes.

In one or more embodiments, the capacitive electrodes are electrically connected to the switching network In one or more embodiments, the detector is electrically connected to the controller and/or the controller is electrically connected to the switching network.

In one or more embodiments, the inductors are variable inductors. In one or more embodiments, the controller is electrically connected to the variable inductors, and wherein the controller is configured to control the inductance of the variable inductors. In one or more embodiments, the capacitive electrodes are electrically connected to the switching network via the variable inductors.

In one or more embodiments, the inductors and electrodes are configured to resonate to generate the electric field to transfer power via electric field coupling.

According to another aspect there is provided a wireless power transfer system comprising any of the described transmit resonators.

According to another aspect there is provided a wireless power transfer system comprising: a transmitter comprising: a power source configured to generate a power signal; and a transmit resonator electrically connected to the power source, the transmit resonator comprising: at least two transmit inductors; a switching network electrically connected to the transmit inductors; a plurality of transmit capacitive electrodes electrically connected to the switching network; a detector communicatively connected to the controller, the detector configured to detect impedance; and a controller communicatively connected to the switching network and the detector, the controller configured to control the switching network to control which transmit capacitive electrodes are connected to the transmit inductors based on the detected impedance, wherein the transmit inductors and transmit capacitive electrodes are configured to resonate to generate an electric field; and a receiver comprising: a load; and a receiver resonator electrically connected to the load, the receive resonator comprising: at least two receive inductors; and at least two receive capacitive electrodes electrically connected to the receive inductors, wherein the receive inductors and receive capacitive electrodes are configured to resonate in the generated electric field and extract power via resonant electric field coupling.

In one or more embodiments, the transmitter further comprises an inverter electrically connected between the power supply and the transmit resonator.

In one or more embodiments, the receiver further comprises a rectifier electrically between the load and the receive resonator.

According to another aspect there is provided a method of wireless power transfer, the method comprising: detecting impedances at at least two capacitive electrodes electrically connected to a switching network; communicating the impedances at the capacitive electrodes to a controller communicatively connected to the switching network; determining, at the controller, a subset of capacitive electrodes to connect to at least two inductors based on the impedances at the capacitive electrodes, the inductors electrically connected to the switching network; connecting the subset of capacitive electrodes to the inductors; and resonating the inductors and the subset of capacitive electrodes to generate an electric field.

In one or more embodiments, connecting the subset of capacitive electrodes comprises sending a signal from the controller to the switching network to connect the subset of capacitive electrodes to the inductors.

In one or more embodiments, the method further comprises: detecting impedances at the inductors; sending the impedances at the inductors to the controller; determining, at the controller, if the impedances at the inductors are within a range of impedances; and sending a signal from the controller to the switching network to disconnect all capacitive electrodes from the inductors if the impedances at the inductors are not within the range of impedances.

In one or more embodiments, the range of impedances are impedances at which power can be transferred from the capacitive electrodes and inductors via resonant electric coupling.

In one or more embodiments, the method further comprises: resonating inductors and capacitive electrodes of a receiver at the resonant frequency; and extracting power from the generated electric field via resonant electric field coupling.

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

The foregoing summary, as well as the following detailed description of certain embodiments will be better understood when read in conjunction with the accompanying drawings. As will be appreciated, like reference characters are used to refer to like elements throughout the description and drawings. As used herein, an element or feature recited in the singular and preceded by the word "a" or "an" should be understood as not necessarily excluding a plural of the elements or features. Further, references to "one example" or "one embodiment" are not intended to be interpreted as excluding the existence of additional examples or embodiments that also incorporate the recited elements or features of that one example or one embodiment. Moreover, unless explicitly stated to the contrary, examples or embodiments "comprising", "having" or "including" an element or feature or a plurality of elements or features having a particular property may further include additional elements or features not having that particular property. Also, it will be appreciated that the terms "comprises", "has" and "includes" mean "including but not limited to" and the terms "comprising", "having" and "including" have equivalent meanings.

As used herein, the term "and/or" can include any and all combinations of one or more of the associated listed elements or features.

It will be understood that when an element or feature is referred to as being "on", "attached" to, "connected" to, "coupled" with, "contacting", etc. another element or feature, that element or feature can be directly on, attached to, connected to, coupled with or contacting the other element or feature or intervening elements may also be present. In contrast, when an element or feature is referred to as being, for example, "directly on", "directly attached" to, "directly connected" to, "directly coupled" with or "directly contacting" another element of feature, there are no intervening elements or features present.

It will be understood that spatially relative terms, such as "under", "below", "lower", "over", "above", "upper", "front", "back" and the like, may be used herein for ease of describing the relationship of an element or feature to another element or feature as depicted in the figures. The spatially relative terms can however, encompass different orientations in use or operation in addition to the orientation depicted in the figures.

Reference herein to "example" means that one or more feature, structure, element, component, characteristic and/or operational step described in connection with the example is included in at least one embodiment and or implementation of the subject matter according to the present disclosure. Thus, the phrases "an example," "another example," and similar language throughout the present disclosure may, but do not necessarily, refer to the same example. Further, the subject matter characterizing any one example may, but does not necessarily, include the subject matter characterizing any other example.

Reference herein to "configured" denotes an actual state of configuration that fundamentally ties the element or feature to the physical characteristics of the element or feature preceding the phrase "configured to".

Moreover, reference to a "second" item does not require or preclude the existence of lower-numbered item (e.g., a "first" item) and/or a higher-numbered item (e.g., a "third" item).

As used herein, the terms "approximately" and "about" represent an amount close to the stated amount that still performs the desired function or achieves the desired result. For example, the terms "approximately" and "about" may refer to an amount that is within less than <NUM>% of, within less than <NUM>% of, within less than <NUM>% of, within less than <NUM>% of, or within less than <NUM>% of the stated amount.

<FIG> shows a wireless power transfer system generally identified by reference numeral <NUM>. The wireless power transfer system <NUM> comprises a transmitter <NUM> comprising a power source <NUM> electrically connected to a transmit element <NUM>, and a receiver <NUM> comprising a receive element <NUM> electrically connected to a load <NUM>. Power is transferred from the power source <NUM> to the transmit element <NUM>. The power is then transferred from the transmit element <NUM> to the receive element <NUM> via resonant or non-resonant electric or magnetic field coupling. The power is then transferred from the receive element <NUM> to the load <NUM>.

In one example embodiment, the wireless power transfer system may take the form of a resonant electric field wireless power transfer system. <FIG> shows a resonant electric field wireless power transfer system generally identified by reference numeral <NUM> such as that described in <CIT>.

The resonant electric field wireless power transfer system <NUM> comprises a transmitter <NUM> comprising a power source <NUM> electrically connected to a transmit resonator <NUM>. The transmit resonator <NUM> comprises a pair of laterally spaced, elongate transmit capacitive electrodes <NUM>, each of which is electrically connected to the power source <NUM> via a high quality factor (Q) transmit inductor <NUM>. The system <NUM> further comprises a receiver <NUM> comprising a receiver resonator <NUM> electrically connected to a load <NUM>. The receive resonator <NUM> is tuned to the resonant frequency of the transmit resonator <NUM>. The receive resonator <NUM> comprises a pair of laterally spaced, elongate receive capacitive electrodes <NUM>, each of which is electrically connected to the load <NUM> via a high Q receive inductor <NUM>.

In this embodiment, the inductors <NUM> and <NUM> are ferrite core inductors. One of skill in the art however will appreciate that other cores are possible.

In this embodiment, each transmit and receive capacitive electrode <NUM> and <NUM> comprises an elongate element formed of electrically conductive material. The transmit capacitive electrodes <NUM> are coplanar. The receive capacitive electrodes <NUM> are coplanar. In this embodiment, the transmit capacitive electrodes <NUM> and the receive capacitive electrodes <NUM> are in parallel planes. In this embodiment, the transmit capacitive electrodes <NUM> and the receive capacitive electrodes <NUM> are in the form of generally rectangular, planar plates.

While the transmit capacitive electrodes <NUM> and receive capacitive electrodes <NUM> have been described as laterally spaced, elongate electrodes, one of skill in the art will appreciate that other configurations are possible including, but not limited to, concentric, coplanar, circular, elliptical, disc, etc., electrodes. Other suitable electrode configurations are described in <CIT>.

While the inductors <NUM> and <NUM> are shown as being connected in series to the power source <NUM> and the load <NUM>, respectively, in <FIG>, one of skill in the art will appreciate that the inductors <NUM> and <NUM> may be connected to the power source <NUM> and the load <NUM>, respectively, in parallel.

During operation, power is transferred from the power source <NUM> to the transmit capacitive electrodes <NUM> via the high Q transmit inductors <NUM>. In particular, the power signal from the power source <NUM> that is transmitted to the transmit capacitive electrodes <NUM> via the high Q transmit inductors <NUM> excites the transmit resonator <NUM> causing the transmit resonator <NUM> to generate an electric field. When the receiver <NUM>, which is tuned to the same resonant frequency as the transmitter <NUM>, is placed within the resonant electric field, the receive resonator <NUM> extracts power from the transmit resonator <NUM> via resonant electric field coupling. The extracted power is then transferred from the receive resonator <NUM> to the load <NUM>. As the power transfer is highly resonant, the transmit and receive capacitive electrodes <NUM> and <NUM>, respectively, need not be as close together or as well aligned as is the case with the non-resonant electric field power transfer system. While the transmit resonator <NUM> may generate a magnetic field, little, if any, power is transmitted via magnetic field coupling.

When the transmit and receive capacitive electrodes <NUM> and <NUM>, respectively, are generally aligned power is transferred as previously described. When the capacitive electrodes <NUM> and <NUM> are not generally aligned, power transfer may decrease or may not be possible at all.

To provide greater positional freedom of the resonators, a transmit resonator in accordance with an aspect of the disclosure is provided. <FIG> shows a transmit resonator generally identified by reference numeral <NUM>. The transmit resonator <NUM> is configured to generate an electric field to transfer power to one or more receive resonators as will be described. The transmit resonator <NUM> comprises two inductors <NUM>, a switching network <NUM>, capacitive electrodes <NUM>, a detector <NUM> and a controller <NUM>.

The inductors <NUM> are configured to resonate with the capacitive electrodes <NUM> at a resonant frequency to generate an electric field as will be described. The inductors <NUM> are electrically connected to the switching network <NUM>. In this embodiment, the inductors <NUM> are ferrite core inductors. The inductors <NUM> are static inductors. One of skill in the art however will appreciate that other cores are possible. Furthermore, one of skill in the art will appreciate that more than two inductors <NUM> or fewer than two inductors <NUM> may be used.

The capacitive electrodes <NUM> are comprised of N × M capacitive electrodes. The capacitive electrodes <NUM> are arranged in a grid pattern, where Nis the number of columns in the grid and M is the number of rows in the grid. Each capacitive electrode <NUM> is electrically connected to the switching network <NUM>. The capacitive electrodes <NUM> are coplanar. The capacitive electrodes <NUM> are coplanar in the x-y plane. In this embodiment, each capacitive electrode <NUM> is a planar square plate electrode with identical dimensions.

The switching network <NUM> is configured to control which electrodes <NUM> resonate with the inductors <NUM> to generate an electric field. The switching network <NUM> is electrically connected to the inductors <NUM> and the controller <NUM>. The switching network <NUM> electrically connects both of the inductors <NUM> to each of the capacitive electrodes <NUM>. In this embodiment, the switching network <NUM> comprises multiple interconnected switches. In this embodiment, the switching network <NUM> comprises two inputs, one input for each inductor <NUM> and N × M × <NUM> outputs. Each output is electrically connected to a single capacitive electrode <NUM>. Each capacitive electrode <NUM> is electrically connected to two outputs of the switching network <NUM>. The switching network <NUM> is configured to control the connection of the capacitive electrodes <NUM> to the inductors <NUM>. At any given time, a capacitive electrode <NUM> may be connected, via the switching network <NUM>, to both inductors <NUM>, a single inductor <NUM> or no inductors <NUM>. When a capacitive electrode <NUM> is not connected to any of the inductors <NUM>, the capacitive electrode <NUM> may become electrically floating, or grounded, depending on the requirements of the transmit resonator <NUM>.

The detector is configured to detect impedance. The detector is electrically connected to the capacitive electrodes <NUM>. The detector is communicatively connected to the controller <NUM>. In this embodiment, the detector comprises a first detector <NUM> configured to detect impedance presented to the electrodes <NUM>. The first detector <NUM> comprises at least one circuit. In this embodiment, the first detector <NUM> further comprises a phase detector. The circuit comprises electrical components configured to detect impedance by applying a voltage and detecting a current. The phase detector is configured to detect a phase. The first detector <NUM> utilizes the detected current and the detected phase to determine the impedance presented to the electrodes <NUM>. The first detector <NUM> determines the impedance presented at each electrode <NUM>.

As previously stated, the detector is communicatively connected to the controller <NUM>. The detected impedances are communicated to the controller <NUM>. In this embodiment, the detector is electrically connected to the controller <NUM>. Specifically, in this embodiment, the first detector <NUM> communicates all of the detected impedances to the controller <NUM>. In this embodiment, the first detector <NUM> is electrically connected to the controller <NUM>. In this embodiment, the detected impedances are communicated to the controller <NUM> through the wired connection between the controller <NUM> and first detector <NUM>.

The controller <NUM> is configured to control the switching network <NUM> to determine which electrodes <NUM> are connected to which inductors <NUM>. The controller <NUM> is communicatively connected to the switching network <NUM> and the first detector <NUM>. In this embodiment, the controller <NUM> is electrically connected to the switching network <NUM> via a wired connection. The controller <NUM> is configured to send a control signal to the switching network <NUM> to control which electrodes <NUM> are connected to which inductors <NUM> based on the impedances from the first detector <NUM>. While the controller <NUM> and switching network <NUM> have been described as separate and unique elements, one of skill in the art will appreciate that the controller <NUM> and switching network <NUM> may be incorporated into a single element.

In this embodiment, the controller <NUM> is a microcontroller. While the controller <NUM> has been described as a microcontroller, one of skill in the art will appreciate that other configurations are possible. In another embodiment, the controller <NUM> comprises one or more of software, hardware, a digital logic controller (DLC) and microprocessor.

One of skill in the art will appreciate that other configurations are possible. In another embodiment, the detected impedances are sent to the controller <NUM> via wireless communication. The controller <NUM> and first detector <NUM> are not electrically connected via wired connection. Furthermore, in another embodiment, the controller <NUM> is configured to send a control signal to the switching network <NUM> via wireless communication. The controller <NUM> is not electrically connected to the switching network <NUM> via a wired connection. Exemplary wireless communication schemes include WiFi™ and Bluetooth™.

In this embodiment, the transmit resonator <NUM> further comprises a passive electrode <NUM> as described in <CIT>. The passive electrode <NUM> encompasses the electrodes <NUM> to at least partially eliminate environmental influences affecting the electrodes <NUM>. The passive electrode <NUM> is adjacent the electrodes <NUM>. In this embodiment, the passive electrode <NUM> and the electrodes <NUM> have parallel planes. The passive electrode <NUM> comprises an elongate element. The elongate element is formed of electrically conductive material. The elongate element is in the form of a generally rectangular, planar plate.

In operation, the first detector <NUM> detects impedances presented at the capacitive electrodes <NUM>. Specifically, the first detector <NUM> detects the impedance presented at each capacitive electrode <NUM> consecutively (electrode <NUM> by electrode <NUM>) or at all the electrodes <NUM> at once. The first detector <NUM> sends the detected impedances to the controller <NUM>. When at least one receive resonator is presented to two or more electrodes <NUM> (a subset of the capacitive electrodes <NUM> or all the capacitive electrodes <NUM>) and the detected impedances are greater than a threshold impedance. The threshold impedance is the lowest value of a range of impedances that allows the transmit resonator <NUM> to resonate at a resonant frequency. In this embodiment, the resonant frequency is <NUM>. The controller <NUM> applies logic to determine which of the electrodes <NUM> have been presented with the impedances.

One of ordinary skill in the art will recognize that logic may include the use of an algorithm, such as but not limited to, a binary search, to be used to find which transmit capacitive electrodes <NUM> should be connected to the transmit inductors <NUM> upon placing a receiver into the system. In another embodiment, depending on the known constraints of a given wireless power transfer system, more information regarding the possible sizes and shapes of the receive resonators may result in logic involving increasingly complex and time-efficient algorithms to be possible and available for use within the system. In another embodiment, logic may include the implementation of a genetic algorithm in combination with a neural network to assist the system in quickly finding receivers. One of ordinary skill in the art will recognize that other algorithms are possible.

The controller <NUM> then sends a signal to the switching network <NUM> to connect the two or more electrodes <NUM> presented with the receive resonator to the inductors <NUM> and disconnect all other electrodes <NUM> from the inductors <NUM>. The two or more electrodes <NUM> and the inductors <NUM> resonate at a resonant frequency to generate an electric field. The receive resonator, which is tuned to the same resonant frequency, extracts power from the electric field via resonant electric field coupling. While the transmit resonator <NUM> may generate electromagnetic energy, the majority of power transfer occurs via the electric field. Little, if any, power is transferred via magnetic induction or resonant magnetic induction.

As the capacitive electrodes <NUM> have identical dimensions the capacitance between capacitive electrodes <NUM> has certain repeated values. <FIG> show schematic representation of the capacitive electrodes <NUM> in a grid pattern, where N (the number of columns in the grid) is <NUM> and M (the number of rows in the grid) is <NUM>. The capacitances between distinct pairs of capacitance electrodes <NUM> are shown in <FIG> shows four distinct capacitance values, A, B, C and D, between adjacent capacitance electrodes <NUM>. <FIG> shows four distinct capacitance values, E, F, G and H, between diagonal capacitance electrodes <NUM>. Capacitance values between the capacitive electrodes <NUM> and the passive electrode <NUM> is not shown.

While a particular transmit resonator <NUM> has been described, one of skill in the art will appreciate that other configurations are possible. <FIG> shows another embodiment of a transmit resonator generally identified by reference numeral <NUM>. The transmit resonator <NUM> is configured to generate an electric field to transfer power to one or more receive resonators as will be described. The transmit resonator <NUM> comprises two inductors <NUM>, a switching network <NUM>, capacitive electrodes <NUM>, a detector and a controller <NUM>. In this embodiment, the transmit resonator <NUM> further comprises a passive electrode <NUM> as described in <CIT>, the relevant portions of which are incorporated herein by reference. The inductors <NUM>, switching network <NUM>, capacitive electrodes <NUM>, controller <NUM> and passive electrode <NUM> are identical to the inductors <NUM>, switching network <NUM>, capacitive electrodes <NUM>, controller <NUM> and passive electrode <NUM>, respectively, previously described unless otherwise stated.

The detector is configured to detect impedance. In this embodiment, the detector comprises a first detector <NUM> and a second detector <NUM>. The first detector <NUM> is configured to detect impedances presented to the electrodes <NUM>. The first detector <NUM> is electrically connected to the capacitive electrodes <NUM>. The first detector <NUM> is communicatively connected to the controller <NUM>.

The first detector <NUM> comprises at least one circuit. In this embodiment, the first detector <NUM> further comprises a phase detector. The circuit comprises electrical components configured to detect impedance by applying a voltage and detecting a current. The phase detector is configured to detect a phase. The first detector <NUM> utilizes the detected current and the detected phase to determine the impedance presented to the electrodes <NUM>. The first detector <NUM> determines the impedance presented at each electrode <NUM>.

As previously stated, the first detector <NUM> is communicatively connected to the controller <NUM>. The detected impedances are communicated to the controller <NUM>. In this embodiment, the first detector <NUM> is electrically connected to the controller <NUM>. The detected impedances are communicated to the controller <NUM> through the wired connection between the controller <NUM> and first detector <NUM>.

The second detector <NUM> is configured to detect impedances at the inductors <NUM>. The second detector <NUM> is electrically connected to the inductors <NUM>. The second detector <NUM> is communicatively connected to the controller <NUM>. The second detector <NUM> comprises at least one circuit. In this embodiment, the second detector <NUM> further comprises a phase detector. The circuit comprises electrical components configured to detect impedance by applying a voltage and detecting a current. The phase detector is configured to detect a phase. The second detector <NUM> utilizes the detected current and the detected phase to determine the impedances at the inductors <NUM>.

As previously stated, the second detector <NUM> is communicatively connected to the controller <NUM>. The detected impedances at the inductors <NUM> are communicated to the controller <NUM>. In this embodiment, the second detector <NUM> is electrically connected to the controller <NUM>. The detected impedances at the inductors <NUM> are communicated to the controller <NUM> through the wired connection between the controller <NUM> and second detector <NUM>.

One of skill in the art will appreciate that other configurations are possible. In another embodiment, the detected impedances are sent to the controller <NUM> via wireless communication. The controller <NUM> and the first detector <NUM> are not electrically connected via wired connection. The controller <NUM> and the second detector <NUM> are not electrically connected via wired connection. Furthermore, in another embodiment, the controller <NUM> is configured to communicate a control signal to the switching network <NUM> via wireless communication. The controller <NUM> is not electrically connected to the switching network <NUM> via a wired connection. Exemplary wireless communication schemes include WiFi™ and Bluetooth™.

In operation, the first detector <NUM> detects impedances presented at the capacitive electrodes <NUM>. When at least one receive resonator is presented to two or more capacitive electrodes <NUM> (a subset of the capacitive electrodes <NUM> or all the capacitive electrodes <NUM>) and the detected impedances are greater than a threshold impedance, the first detector <NUM> sends the detected impedances to the controller <NUM>. The threshold impedance is the lowest value of a range of impedances that allows the transmit resonator <NUM> to resonate at a resonant frequency. In this embodiment, the resonant frequency is <NUM>. The second detector <NUM> detects impedances at the inductors <NUM>. The second detector <NUM> sends the detected impedances at the inductors <NUM> to the controller <NUM>. The controller <NUM> applies logic to determine which of the electrodes <NUM> have been presented with the impedances.

The controller <NUM> then sends a signal to the switching network <NUM> to connect the two or more electrodes <NUM> presented with the receive resonator to the inductors <NUM> and disconnect all other electrodes <NUM> from the inductors <NUM>. The controller <NUM> compares the detected impedances presented at the capacitive electrodes <NUM> from the first detector <NUM> with the detected impedances at the inductors <NUM> from the second detector <NUM> to ensure the inductors <NUM> have impedances within the range of impedances that allows the transmit resonator <NUM> to resonate at a resonant frequency. If the inductors <NUM> have impedances within the range of impedances, the controller <NUM> takes no further action. If the inductors <NUM> have impedances that are not within the range of impedances, the controller <NUM> disconnects all capacitive electrodes <NUM> from the inductors <NUM> via a command to the switching network <NUM>. This ensures the components of the transmit resonator <NUM> are not damaged.

When the two or more electrodes <NUM> are connected to the inductors <NUM> via the switching network <NUM>, the two or more electrodes <NUM> resonate with the inductors <NUM> at a resonant frequency to generate an electric field. The receive resonator, which is tuned to the same resonant frequency, extracts power from the electric field via resonant electric field coupling. While the transmit resonator <NUM> may generate electromagnetic energy, the majority of power transfer occurs via the electric field. Little, if any, power is transferred via magnetic induction or resonant magnetic induction.

The transmit resonator <NUM> and <NUM> may be incorporated into a wireless power transfer system. <FIG> shows such a wireless power transfer system in accordance with an aspect of the disclosure generally identified by reference numeral <NUM>. The system <NUM> comprises a transmitter <NUM> and a receiver <NUM>.

The transmitter <NUM> comprises a power source <NUM>, an inverter <NUM> and the transmit resonator <NUM>. The power source <NUM> is configured to supply power to the inverter <NUM>. The power source <NUM> is electrically connected to the inverter <NUM>. The power source <NUM> supplies direct current (DC) power to the inverter <NUM>. The inverter <NUM> is configured to change the DC power from the power source <NUM> to alternating current (AC) power. The inverter <NUM> is electrically connected to the power source <NUM> and the second detector <NUM> of the transmit resonator <NUM>. In this embodiment, the inverter <NUM> comprises an impedance matching circuit. The impedance matching circuit is configured to match the input impedance of the transmitter <NUM> to the output impedance of the transmitter <NUM>.

The receiver <NUM> comprises a load <NUM>, a rectifier <NUM> and a receive resonator <NUM>. The load <NUM> comprises a device that requires power. For example, the load <NUM> comprises a battery. The load <NUM> is electrically connected to the rectifier <NUM>. The rectifier <NUM> is configured to convert the AC power from the receive resonator <NUM> to DC power. The rectifier <NUM> is electrically connected to the load <NUM> and the receive resonator <NUM>.

The receive resonator <NUM> is configured to extract power from the electric field generated by the transmit resonator <NUM> via resonant electric field coupling. The receive resonator <NUM> comprises two receive inductors <NUM> and two receive capacitive electrodes <NUM>. In this embodiment, the receive resonator further comprises a receive passive electrode <NUM>.

The receive inductors <NUM> are configured to resonate with the receive capacitive electrodes <NUM> to generate an electric field that has the same resonant frequency as the transmit resonator <NUM>. Each receive inductor <NUM> is connected to a single receive capacitive electrode <NUM>. In this embodiment, the receive inductors <NUM> are ferrite core inductors. The receive inductors <NUM> are static inductors. One of skill in the art however will appreciate that other cores are possible.

The receive capacitive electrodes <NUM> are coplanar. In this embodiment, each receive capacitive electrode <NUM> is a planar square plate electrode with identical dimensions. The receive capacitive electrodes <NUM> are aligned such that the receive capacitive electrodes <NUM> may overlap and be aligned with two capacitive electrodes <NUM> of the transmit resonator <NUM>.

The receive passive electrode <NUM> is as described in <CIT>, the relevant portions of which are incorporated herein by reference. The receive passive electrode <NUM> encompasses the receive capacitive electrodes <NUM> to at least partially eliminate environmental influences affecting the receive capacitive electrodes <NUM>. The receive passive electrode <NUM> is adjacent the receive capacitive electrodes <NUM>. The receive passive electrode <NUM> and the receive capacitive electrodes <NUM> have parallel planes. The receive passive electrode <NUM> comprises an elongate element. The elongate element is formed of electrically conductive material. The elongate element is in the form of a generally rectangular, planar plate with opposed major surfaces.

In operation, DC power is transferred from the power source <NUM> to the inverter <NUM>. The inverter <NUM> converts the DC power to AC power that is transferred to the transmit resonator <NUM>. The first detector <NUM> detects impedances presented at the capacitive electrodes <NUM>. When the receive capacitive electrodes <NUM> of the receive resonator <NUM> are at least partially aligned with two of the capacitive electrodes <NUM> (a subset of the capacitive electrodes <NUM>) of the transmit resonator <NUM> and the detected impedances are greater than a threshold impedance, the first detector <NUM> sends the detected impedances to the controller <NUM>. The threshold impedance is the lowest value of a range of impedances that allows the transmit resonator <NUM> to resonate at a resonant frequency. In this embodiment, the resonant frequency is <NUM>. The second detector <NUM> detects impedances at the inductors <NUM>. The second detector <NUM> sends the detected impedances at the inductors <NUM> to the controller <NUM>. The controller <NUM> applies logic to determine which of the electrodes <NUM> have been presented with the impedances.

The controller <NUM> then sends a signal to the switching network <NUM> to connect the two or more electrodes <NUM> presented with the receive capacitive electrodes <NUM> to the inductors <NUM> and disconnect all other electrodes <NUM> from the inductors <NUM>. The controller <NUM> compares the detected impedances presented at the capacitive electrodes <NUM> from the first detector <NUM> with the detected impedances at the inductors <NUM> from the second detector <NUM> to ensure the inductors <NUM> have impedances within the range of impedances that allows the transmit resonator <NUM> to resonate at a resonant frequency. If the inductors <NUM> have impedances within the range of impedances, the controller <NUM> takes no further action.

The AC power from the inverter <NUM> excites the two electrodes <NUM> and the inductors <NUM> causing the two electrodes <NUM> and the inductors <NUM> to resonate at a resonant frequency, and generate an electric field. The receive resonator <NUM>, which is tuned to the same resonant frequency, extracts power from the electric field via resonant electric field coupling. While the transmit resonator <NUM> may generate electromagnetic energy, the majority of power transfer occurs via the electric field. Little, if any, power is transferred via magnetic induction or resonant magnetic induction. The power received at the receive resonator <NUM> is converted from AC power to DC power by the rectifier <NUM> applied to the load <NUM>.

If the impedances detected at the inductors <NUM> are not within the range of impedances, the controller <NUM> disconnects all capacitive electrodes <NUM> from the inductors <NUM> via a signal sent to the switching network <NUM>. This ensures the components of the transmit resonator <NUM> are not damaged.

When the receive capacitive electrodes <NUM> of the receive resonator <NUM> are no longer sufficiently aligned with at least two of the capacitive electrodes <NUM> of the transmit resonator <NUM>, the first detector <NUM> detects that impedances presented at the respective electrodes <NUM> of the transmit resonator <NUM> are outside the range of impedances that allows the transmit resonator <NUM> to resonate at a resonant frequency. The first detector <NUM> sends the detected impedances to the controller <NUM>. The controller <NUM> applies logic and determines that the receive capacitive electrodes <NUM> are no longer sufficiently aligned.

The controller <NUM> determines that none of the capacitive electrodes <NUM> of the transmit resonator <NUM> should be connected to the inductors <NUM>. The controller <NUM> then sends a signal to the switching network <NUM> to disconnect all capacitive electrodes <NUM> from the inductors <NUM> such that no power is transferred from the transmit resonator <NUM>.

When the receive capacitive electrodes <NUM> move such that they are aligned with two different capacitive electrodes <NUM> of the transmit resonator <NUM>, the first detector <NUM> detects that impedances presented at the previously aligned two capacitive electrodes <NUM> have fallen below the threshold impedance and that the impedance presented at the different two capacitive electrodes <NUM> are greater than the threshold impedance. The first detector <NUM> sends all detected impedances to the controller <NUM>. The controller <NUM> then sends a signal to disconnect the previously aligned two capacitive electrodes <NUM> from the inductors <NUM> and connect the different two capacitive electrodes <NUM> to the inductors <NUM>. The AC power from the inverter <NUM> excites the different two electrodes <NUM> and the inductors <NUM> causing the different two electrodes <NUM> and the inductors <NUM> to resonate at a resonant frequency, and generate an electric field. The receive resonator <NUM>, which is tuned to the same resonant frequency, extracts power from the electric field via resonant electric field coupling. While the transmit resonator <NUM> may generate electromagnetic energy, the majority of power transfer occurs via the electric field. Little, if any, power is transferred via magnetic induction or resonant magnetic induction. The power received at the receive resonator <NUM> is converted from AC power to DC power by the rectifier <NUM> applied to the load <NUM>.

As will be appreciated, the wireless power transfer system <NUM> described allows for the receiver resonator <NUM> to move about the grid of capacitive electrodes <NUM> of the transmit resonator <NUM> and still maintain the resonant electric field coupling required for power transfer from the transmitter <NUM> to the receiver <NUM>.

While operation of the wireless power transfer system <NUM> has been described when the receive capacitive electrodes <NUM> overlap and are aligned with the capacitive electrodes <NUM> of the transmit resonator <NUM>, wireless power transfer may still occur when the receive capacitive electrodes <NUM> are not fully overlapping and/or aligned with the capacitive electrodes <NUM> of the transmit resonator <NUM>.

<FIG> shows a partial wireless power transfer system generally identified by reference numeral <NUM>. The wireless power transfer system <NUM> is identical to the previously-described wireless power transfer system <NUM> unless otherwise stated. The wireless power transfer system <NUM> comprises the transmitter <NUM> comprising the transmit resonator <NUM>. In this embodiment, the capacitive electrodes <NUM> of the transmit resonator <NUM> are arranged in the grid pattern, where N (the number of columns in the grid) is <NUM> and M (the number of rows in the grid) is <NUM>.

The wireless power transfer system <NUM> further comprises the receiver <NUM>. In this embodiment, the receive capacitive electrodes <NUM> only partially overlap the capacitive electrodes <NUM> of the transmit resonator <NUM>. In this embodiment, the receive capacitive electrodes <NUM> are not aligned with the capacitive electrodes <NUM> of the transmit resonator <NUM>.

During operation, the first detector <NUM> may still detect sufficient impedances from the receive resonator <NUM> to resonate two capacitive electrodes <NUM> of the transmit resonator <NUM> and the inductors <NUM> to generate an electric field that are partially overlapped by the receive capacitive electrodes <NUM>, and to resonate two other capacitive electrodes <NUM> of the transmit resonator <NUM> and the inductors <NUM> that are also partially overlapped by the receive capacitive electrodes <NUM>. The receive resonator <NUM> resonates at the resonant frequency of the transmit resonator <NUM> and extracts power via resonant electric field coupling from both of the generated electric fields. While efficiency of the power transfer from each individual electric field may be less than the efficiency of the power transfer from a single electric field generated when the receive capacitive electrodes <NUM> and the capacitive electrodes <NUM> of the transmit resonator <NUM> are aligned, some amount of wireless power transfer may still occur.

While a particular wireless power transfer system <NUM> with a single receiver <NUM> has been described, one of skill in the art will appreciate that the wireless power transfer system may comprise multiple receivers. <FIG> shows a partial wireless power transfer system generally identified by reference numeral <NUM>. The wireless power transfer system <NUM> is identical to the previously-described wireless power transfer system <NUM> unless otherwise stated. The wireless power transfer system <NUM> comprises the transmitter <NUM> comprising the transmit resonator <NUM>. In this embodiment, the capacitive electrodes <NUM> of the transmit resonator <NUM> are arranged in the grid pattern, where N (the number of columns in the grid) is <NUM> and M (the number of rows in the grid) is <NUM>.

The wireless power transfer system <NUM> further comprises the receiver <NUM> comprising the receive resonator <NUM>. The two receive capacitive electrodes <NUM> of the receive resonator <NUM> overlap and are aligned with two of the capacitive electrodes <NUM> of the transmit resonator <NUM> such that power is transferred from the transmit resonator <NUM> to the receive resonator <NUM> via resonant electric field coupling.

The wireless power transfer system <NUM> further comprises a second receiver. The second receiver is identical to the receiver <NUM> unless otherwise stated. The second receiver comprises a second receive resonator comprising four capacitive receive electrodes. The second receive resonator further comprises a second receive passive electrode <NUM>.

The second receive passive electrode <NUM> is as described in <CIT>, the relevant portions of which are incorporated herein by reference. The second receive passive electrode <NUM> encompasses the receive capacitive electrodes of the second receive resonator to at least partially eliminate environmental influences affecting the receive capacitive electrodes. The second receive passive electrode <NUM> is adjacent the receive capacitive electrodes of the second receive resonator. The second receive passive electrode <NUM> and the receive capacitive electrodes of the second receive resonator have parallel planes. The second receive passive electrode <NUM> comprises an elongate element. The elongate element is formed of electrically conductive material. The elongate element is in the form of a generally rectangular, planar plate with opposed major surfaces.

In this embodiment, the capacitive receive electrodes of the second receiver are arranged in a 2x2 grid pattern with identical spacing between adjacent electrodes to the capacitive electrodes <NUM> of the transmit resonator <NUM>. The capacitive receive electrodes of the second receive resonator are dimensioned identically to the capacitive electrodes <NUM> of the transmit resonator <NUM>. The receive capacitive electrodes of the second receive resonator overlap and are aligned with four of the capacitive electrodes <NUM> of the transmit resonator <NUM> such that power is transferred from the transmit resonator <NUM> to the second receive resonator via resonant electric field coupling.

As illustrated in <FIG>, the transmit resonator <NUM> may provide power to multiple receiver resonators at the same time. As the first detector <NUM> detects impedances at each of the capacitive electrodes <NUM> of the transmit resonator <NUM>, the first detector <NUM> detects multiple impedances at multiple capacitive electrodes <NUM> when multiple receiver resonators are presented to the transmit resonator <NUM>.

While a particular wireless power transfer system <NUM> has been described, one of skill in the art will appreciate that other configurations are possible. <FIG> shows a partial wireless power transfer system generally identified by reference numeral <NUM>. The wireless power transfer system <NUM> is identical to the previously-described wireless power transfer system <NUM> unless otherwise stated. In this embodiment, the capacitive electrodes <NUM> of the transmit resonator <NUM> are arranged in the grid pattern, where N (the number of columns in the grid) is <NUM> and M (the number of rows in the grid) is <NUM>. Each transmit capacitive electrodes <NUM> has a width (W) of <NUM> and a length (L) of <NUM>. The gap (G) between adjacent capacitive electrodes <NUM> is <NUM>. The receive capacitive electrodes <NUM> are shown only to illustrate their locations. One of skill in the art will appreciate that the receive passive electrode <NUM> would block the view of the receive capacitive electrodes <NUM> during operation. Similar to the capacitive electrodes <NUM> of the transmit resonator <NUM>, each receive capacitive electrode <NUM> has a width (W) of <NUM> and a length (L) of <NUM>. Furthermore, each receive capacitive electrode <NUM> is separated by a gap (G) of <NUM>. The wireless power transfer system <NUM> is operated at a resonant frequency of <NUM>. The inductance of the inductors <NUM> (not shown) is <NUM>µH.

While particular capacitive electrodes <NUM> and <NUM> have been described, one of skill in the art will appreciate that other configurations are possible. <FIG> shows another embodiment of capacitive electrodes generally identified by reference numeral <NUM> and a passive electrode <NUM> of a transmit resonator.

The capacitive electrodes <NUM> and the passive electrode <NUM> are identical to the capacitive electrodes <NUM> and passive electrode <NUM>, respectively, unless otherwise stated. In this embodiment, the capacitive electrodes <NUM> comprise twelve (<NUM>) capacitive electrodes. The capacitive electrodes <NUM> are arranged in a circular pattern. The capacitive electrodes <NUM> are generally arranged in two rings, an inner ring and an outer ring. The inner ring is surrounded by the outer ring. Each capacitive electrode <NUM> is a segment of one of the inner and outer ring. The capacitive electrodes <NUM> are coplanar in the x-y plane. In this embodiment, each capacitive electrode <NUM> is a planar electrode. Each capacitive electrode <NUM> is a segment of a generally circular ring.

The passive electrode <NUM> comprises an element. The element is formed of electrically conductive material. The element is in the form of a generally circular, planar plate with opposed major surfaces. The element encompasses the outer and inner ring. The plane defined by the passive electrode <NUM> is parallel with the plane defined by the capacitive electrodes <NUM>.

The wireless power transfer system <NUM> comprises the transmitter <NUM> comprising the transmit resonator <NUM> having inductors <NUM> that have static inductance. The static inductance of the inductors <NUM> may limit the ability to utilize multiple capacitive electrodes <NUM> of the transmit resonator <NUM> to transfer power. Transferring power through multiple capacitive electrodes <NUM> of the transmit resonator <NUM> may change the transmit-side capacitance, causing the wireless power transfer system <NUM> to detune, significantly reducing wireless power transfer efficiency and increasing losses.

While a particular wireless power transfer system <NUM> has been described, one of skill in the art will appreciate that other configurations are possible. <FIG> shows another embodiment of a wireless power transfer system generally identified by reference numeral <NUM>. The wireless power transfer system <NUM> is identical to the previously-described wireless power transfer system <NUM> unless otherwise stated. The wireless power transfer system <NUM> comprises a transmitter <NUM> and the receiver <NUM>.

The transmitter <NUM> comprises the power source <NUM>, the inverter <NUM> and a transmit resonator <NUM>. The power source <NUM> is electrically connected to the inverter <NUM> which is electrically connected to the transmit resonator <NUM>. The transmit resonator <NUM> comprises two variable inductors <NUM>, a switching network <NUM>, capacitive electrodes <NUM>, a detector and a controller <NUM>. In this embodiment, the transmit resonator <NUM> further comprises a passive electrode <NUM>. The detector further comprises a first detector <NUM> and a second detector <NUM>. The inverter <NUM> is electrically connected to the second detector <NUM>. The second detector <NUM> is electrically connected to the variable inductors <NUM>. The second detector <NUM> is communicatively connected to the controller <NUM>. The variable inductors <NUM> are electrically connected to the switching network <NUM>. The controller <NUM> is electrically connected to each variable inductor <NUM>. The switching network <NUM> is electrically connected to the capacitive electrodes <NUM>. The controller <NUM> is communicatively connected to the switching network <NUM>. The first detector <NUM> is communicatively connected to the controller <NUM>.

In this embodiment, the first detector <NUM> and second detector <NUM> are communicatively connected to the controller <NUM> via wired connections. Furthermore, in this embodiment, the controller <NUM> is communicatively connected to the switching network <NUM> via wired connection. One of skill in the art will appreciate that other configurations are possible. In another embodiment, the first detector <NUM>, second detector <NUM> and/or switching network <NUM> are not electrically connected to the controller <NUM> via wired connections. The detectors <NUM> and <NUM> are configured to communicate detected impedances to the controller <NUM> via wireless communication. The controller <NUM> is configured to send a control signal to the switching network <NUM> via wireless communication. Exemplary wireless communication schemes include WiFi™ and Bluetooth™.

The switching network <NUM>, capacitive electrodes <NUM>, controller <NUM> and passive electrode <NUM> are identical to the switching network <NUM>, capacitive electrodes <NUM>, controller <NUM> and passive electrode <NUM>, respectively, previously described unless otherwise stated. The first detector <NUM> and second detector <NUM> are identical to the first detector <NUM> and the second detector <NUM>, respectively, previously described unless otherwise stated.

In this embodiment, the variable inductors <NUM> are configured to resonate with the capacitive electrodes <NUM> at a resonant frequency to generate an electric field as will be described. In this embodiment, the inductors <NUM> are ferrite core inductors. One of skill in the art however will appreciate that other cores are possible. Furthermore, one of skill in the art will appreciate that more than two inductors <NUM> or fewer than two inductors <NUM> may be used.

During operation the wireless power system <NUM> operates identically to the wireless power system <NUM>, unless otherwise stated. The controller <NUM> receives impedances from the first detector <NUM> and the second detector <NUM>, and adjusts the inductances of the variable inductors <NUM> to maximize electric field coupling.

The transmitter <NUM> comprises the power source <NUM>, the inverter <NUM> and a transmit resonator <NUM>. The power source <NUM> is electrically connected to the inverter <NUM> which is electrically connected to the transmit resonator <NUM>. The transmit resonator <NUM> comprises variable inductors <NUM>, a switching network <NUM>, capacitive electrodes <NUM>, a detector and a controller <NUM>. In this embodiment, the transmit resonator <NUM> further comprises a passive electrode <NUM>. The detector further comprises a first detector <NUM> and a second detector <NUM>. The inverter <NUM> is electrically connected to the second detector <NUM>. The second detector <NUM> is electrically connected to switching network <NUM>. The second detector <NUM> is communicatively connected to the controller <NUM>. The switching network <NUM> is electrically connected to the variable inductors <NUM>. The variable inductors <NUM> are electrically connected to the capacitive electrodes <NUM>. The first detector <NUM> is communicatively connected to the controller <NUM>. The controller <NUM> is electrically connected to each variable inductor <NUM> and to the switching network <NUM>. The controller <NUM> is communicatively connected to the switching network <NUM>. The first detector <NUM> is communicatively connected to the controller <NUM>.

In this embodiment, there is one variable inductor <NUM> for each capacitive electrode <NUM>. Each capacitive electrode <NUM> is connected to the switching network <NUM> via a single variable inductor <NUM>. The variable inductors <NUM> are configured to resonate with the capacitive electrodes <NUM> at a resonant frequency to generate an electric field as will be described. In this embodiment, the inductors <NUM> are ferrite core inductors. One of skill in the art however will appreciate that other cores are possible.

During operation the wireless power system <NUM> operates identically to the wireless power system <NUM>, unless otherwise stated. The controller <NUM> receives impedances from the first detector <NUM> and the second detector <NUM>, and adjusts the inductances of the variable inductors <NUM> to maximize electric field coupling. The switching network <NUM> opens or closes connections between the variable inductors <NUM> and second detector <NUM> such that only capacitive electrodes <NUM> that are presented with a receive resonator are resonated with their associated variable inductors <NUM> to generate an electric field.

The transmitter <NUM> comprises the power source <NUM>, the inverter <NUM> and a transmit resonator <NUM>. The power source <NUM> is electrically connected to the inverter <NUM> which is electrically connected to the transmit resonator <NUM>. The transmit resonator <NUM> comprises inductors <NUM>, a switching network <NUM>, capacitive electrodes <NUM>, a detector and a controller <NUM>. In this embodiment, the transmit resonator <NUM> further comprises a passive electrode <NUM>. The detector further comprises a first detector <NUM> and a second detector <NUM>. The inverter <NUM> is electrically connected to the second detector <NUM>. The second detector <NUM> is electrically connected to switching network <NUM>. The second detector <NUM> is communicatively connected to the controller <NUM>. The switching network <NUM> is electrically connected to the inductors <NUM>. The inductors <NUM> are electrically connected to the capacitive electrodes <NUM>. The first detector <NUM> is communicatively connected to the controller <NUM>. The switching network 1514is electrically connected to each inductor <NUM>. The controller <NUM> is communicatively connected to the switching network <NUM>.

In this embodiment, there is one inductor <NUM> for each capacitive electrode <NUM>. Each capacitive electrode <NUM> is connected to the switching network <NUM> via a single inductor <NUM>. The inductors <NUM> are configured to resonate with the capacitive electrodes <NUM> at a resonant frequency to generate an electric field as will be described. The inductors <NUM> are static inductors. In this embodiment, the inductors <NUM> are ferrite core inductors. One of skill in the art however will appreciate that other cores are possible.

During operation the wireless power system <NUM> operates identically to the wireless power system <NUM>, except that the inductors <NUM> are static inductors.

While a particular wireless power transfer system <NUM> has been described, one of skill in the art will appreciate that other configurations are possible. <FIG> shows another embodiment of a partial wireless power transfer system generally identified by reference numeral <NUM>. The wireless power transfer system <NUM> is identical to the wireless power transfer system <NUM> unless otherwise stated. The wireless power transfer system <NUM> comprises a transmitter and a receiver. The transmitter comprises a power source (not shown), an inverter (not shown) and a transmit resonator. The power source is electrically connected to the inverter. The inverter is electrically connected to the transmit resonator.

The transmit resonator is configured to generate an electric field to transfer power to one or more receive resonators as previously described. The transmit resonator comprises two inductors (not shown) and two transmit capacitive electrodes <NUM>. The inductors are electrically connected to the transmit capacitive electrodes <NUM>. The transmit capacitive electrodes <NUM> are segments of rings. The transmit capacitive electrodes <NUM> comprise a first segment that is a segment of an outer ring and a second segment that is a segment of an inner ring. In this embodiment, each transmit capacitive electrode <NUM> is a planar electrode. The transmit capacitive electrodes <NUM> are coplanar.

The receiver comprises a receive resonator, a load (not shown) and a rectifier (not shown). The load is electrically connected to the rectifier. The rectifier is electrically connected to the receive resonator. The load and rectifier are identical to the load <NUM> and rectifier <NUM>, respectively, and will not be described further. The receive resonator is configured to extract power from the electric field generated by the transmit resonator <NUM> via resonant electric field coupling. The receive resonator comprises two inductors (not shown), receive capacitive electrodes <NUM>, a switching network (not shown), a detector and a controller (not shown). The switching network, detector and controller are identical to the previously described switching network <NUM>, detector and controller <NUM>, respectively, of the transmit resonator <NUM> unless otherwise stated. The inductors are electrically connected to the receive capacitive electrodes <NUM>.

The receive capacitive electrodes <NUM> are identical to the capacitive electrodes <NUM> unless otherwise stated. In this embodiment, the receive capacitive electrodes <NUM> comprise twelve (<NUM>) capacitive electrodes. The receive capacitive electrodes <NUM> are arranged in a circular pattern. The receive capacitive electrodes <NUM> are generally arranged in two rings, an inner ring and an outer ring. The inner ring is surrounded by the outer ring. Each receive capacitive electrode <NUM> is a segment of one of the inner or outer rings. The receive capacitive electrodes <NUM> are coplanar. In this embodiment, each receive capacitive electrode <NUM> is a planar electrode.

<FIG> shows another embodiment of a partial wireless power transfer system generally identified by reference numeral <NUM>. The wireless power transfer system <NUM> is identical to the wireless power transfer system <NUM> unless otherwise stated. The wireless power transfer system <NUM> comprises a transmitter and a receiver. The transmitter comprises a power source (not shown), an inverter (not shown) and a transmit resonator. The power source is electrically connected to the inverter. The inverter is electrically connected to the transmit resonator.

The receiver comprises a receive resonator, a load (not shown) and a rectifier (not shown). The load is electrically connected to the rectifier. The rectifier is electrically connected to the receive resonator. The load and rectifier are identical to the load <NUM> and rectifier <NUM>, respectively, and will not be described further. The receive resonator is configured to extract power from the electric field generated by the transmit resonator <NUM> via resonant electric field coupling. The receive resonator comprises two receive inductors (not shown), and two receive capacitive electrodes <NUM>. The inductors are electrically connected to the receive capacitive electrodes <NUM>.

The receive capacitive electrodes <NUM> are identical to the capacitive electrodes <NUM> unless otherwise stated. In this embodiment, the receive capacitive electrodes <NUM> comprise two ring electrodes, an outer ring electrode and an inner ring electrode. The inner ring electrode is surrounded by the outer ring electrode. The receive capacitive electrodes <NUM> are coplanar. In this embodiment, each receive capacitive electrode <NUM> is a planar electrode.

Simulations were performed on the wireless power transfer systems <NUM> and <NUM>. As shown in <FIG>, the two transmit capacitive electrodes <NUM> overlap and are aligned with two of the receive capacitive electrodes <NUM>.

In this embodiment, the outer receive capacitive electrodes <NUM> and the outer transmit capacitive electrodes <NUM> have an outer radius of <NUM> and an inner radius of <NUM>. The inner receive capacitive electrodes <NUM> and the inner transmit capacitive electrodes <NUM> have an outer radius of <NUM> and an inner radius of <NUM>. Each receive capacitive electrode <NUM> is separated from the adjacent receive capacitive electrode <NUM> in the same ring by <NUM>. The gap between the outer radius of the inner receive capacitive electrodes <NUM> and the inner radius of the outer receive capacitive electrodes <NUM> is <NUM>. Similarly, the gap between the outer radius of the inner transmit capacitive electrodes <NUM> and the inner radius of the outer transmit capacitive electrodes <NUM> is <NUM>. The wireless power transfer system <NUM> delivers <NUM> watts of power from the transmit resonator to the receive resonator. The separation distance between the transmit resonator and the receive resonator is <NUM>. The radiofrequency (RF) efficiency of the power transfer between the resonators is <NUM>%. The resonant frequency of the wireless power transfer system <NUM> is <NUM>. The inductance of the inductors of the transmit resonator is <NUM>µH. The inductance of the inductors of the receive resonator is <NUM>µH.

As shown in <FIG>, the transmit capacitive electrodes <NUM> overlap the receive capacitive electrodes <NUM>. In this embodiment, the outer receive capacitive electrodes <NUM> and the outer transmit capacitive electrodes <NUM> have an outer radius of <NUM> and an inner radius of <NUM>. The inner receive capacitive electrodes <NUM> and the inner transmit capacitive electrodes <NUM> have an outer radius of <NUM> and an inner radius of <NUM>. The gap between the outer radius of the inner receive capacitive electrodes <NUM> and the inner radius of the outer receive capacitive electrodes <NUM> is <NUM>. Similarly, the gap between the outer radius of the inner transmit capacitive electrodes <NUM> and the inner radius of the outer transmit capacitive electrodes <NUM> is <NUM>. The wireless power transfer system <NUM> delivers <NUM> watts of power from the transmit resonator to the receive resonator. The separation distance between the transmit resonator and the receive resonator is <NUM>. The RF efficiency of the power transfer between the resonators is <NUM>%. The resonant frequency of the wireless power transfer system <NUM> is <NUM>. The inductance of the inductors of the transmit resonator is <NUM>µH. The inductance of the inductors of the receive resonator is <NUM>µH.

The results of the simulation are shown in <FIG> is a graph of the electric field of the wireless power transfer system <NUM>. Specifically, <FIG> shows the electric field drawn on the center plane between the transmit resonator and receive resonator of the wireless power transfer system <NUM>.

<FIG> is a graph of the electric field of the wireless power transfer system <NUM>. Specifically, <FIG> shows the electric field drawn on the center plane between the transmit resonator and receive resonator of the wireless power transfer system <NUM>.

In both <FIG>, the electric field is greater in the region where the transmit capacitive electrodes <NUM> and <NUM> overlap with the receive capacitive electrodes <NUM> and <NUM>, respectively. The electric field of the wireless power transfer system <NUM> in the area where the transmit capacitive electrodes <NUM> do not overlap with the receive capacitive electrodes <NUM> is lower than the electric field of the wireless power transfer system <NUM> in the area where the transmit capacitive electrodes <NUM> do not overlap with the receive capacitive electrodes <NUM>. Thus, the wireless power transfer system <NUM> contains the electric field better than the wireless power transfer system <NUM>. Improved containment reduces human exposure to RF fields. Furthermore, improved containment prevents electromagnetic interference (EMI). In addition, improved containment reduces the specific absorption rate (SAR) value.

While a particular wireless power transfer system <NUM> has been described, one of skill in the art will appreciate that other configurations are possible. <FIG> shows another embodiment of a wireless power transfer system generally identified by reference numeral <NUM>. The wireless power transfer system <NUM> is identical to the wireless power transfer system <NUM> unless otherwise stated. In this embodiment, the transmit resonator comprises capacitive electrodes <NUM> that are in a grid pattern, where N (the number of columns in the grid) is <NUM> and M (the number of rows in the grid) is <NUM>. In this embodiment, the capacitive electrodes <NUM> are rectangular plate electrodes.

Simulations were performed on the wireless power transfer system <NUM>. In this embodiment, each capacitive electrode <NUM> has a length of <NUM> and a width of <NUM>. The gap between the long sides of the capacitive electrodes <NUM> is <NUM>. The gap between the short sides of the capacitive electrodes <NUM> is <NUM>. The receive capacitive electrodes <NUM> have a length of <NUM> and a width of <NUM>. The gap between the receive capacitive electrodes is <NUM>. The gap between the capacitive electrodes <NUM> of the transmit resonator and the receive capacitive electrodes <NUM> is <NUM>.

During the simulation, the receive capacitive electrodes <NUM> move from initially being overlapping and aligned with the two of capacitive electrodes <NUM> (Tx1) of the transmit resonator <NUM>. The receive capacitive electrodes <NUM> then moved toward the other two capacitive electrodes <NUM> (Tx2) of the transmit resonator <NUM> until they were overlapping and aligned with these other two capacitive electrodes <NUM> of the transmit resonator <NUM>.

<FIG> is a graph of the RF efficiency of the wireless power transfer system <NUM>. The RF efficiency of the wireless power transfer system <NUM> is defined as the efficiency of the wireless power transfer between the transmit resonator <NUM> and the receive resonator <NUM> of the wireless power transfer system <NUM>. The solid curved line in <FIG> represents when two capacitive electrodes <NUM> (Tx1) of the transmit resonator <NUM> are active. The dashed curved line in <FIG> represents when the other two of the capacitive electrodes <NUM> (Tx2) of the transmit resonator <NUM> are active. A distance of <NUM> indicates that the receive capacitive electrodes <NUM> are overlapping and aligned with Tx1. A distance of <NUM> indicates that the receive capacitive electrodes <NUM> are overlapping and aligned with Tx2.

The solid vertical line indicates the distance at which the receive capacitive electrodes <NUM> begin to overlap with Tx2. The dashed vertical line indicates the distance at which the receive capacitive electrodes <NUM> do not overlap with Tx1. By switching the capacitive electrode <NUM> pair that is generating an electric field to transfer power to the receive resonator <NUM>, the RF efficiency can remain greater than <NUM>% during movement of the receive capacitive electrodes <NUM>. For the distances between <NUM> to <NUM>, efficient wireless power transfer is achieved from either Tx1 or Tx2.

<FIG> is a graph of the input impedance of the transmit resonator <NUM> of the wireless power transfer system <NUM>. The solid curved line represents when Tx1 is generating an electric field to transfer power to the receive resonator <NUM>, and Tx2 is not generating an electric field. The dashed curved line represents when Tx2 is generating an electric field to transfer power to the receive resonator <NUM>, and Tx1 is not generating an electric field. When the receive capacitive electrodes <NUM> are overlapping and fully aligned with Tx1 or Tx2, the input impedance is approximately <NUM>Ω. As the receive capacitive electrodes <NUM> moves away from either Tx1 or Tx2, the input impedance decreases. At a distance of <NUM>, the receive capacitive electrodes <NUM> are centered between Tx1 and Tx2 and the input impedance is <NUM>Ω. In this embodiment, this value may be the threshold impedance. Thus, when any capacitive electrode <NUM> pair is presented with an impedance of <NUM>Ω or greater, the particular capacitive electrode <NUM> resonates with inductors as previously described.

While a particular wireless power transfer system <NUM> has been described, one of skill in the art will appreciate that other configurations are possible. <FIG> show another embodiment of a partial wireless power transfer system generally identified by reference numeral <NUM>. The wireless power transfer system <NUM> is identical to the wireless power transfer system <NUM> unless otherwise stated.

In this embodiment, the transmit resonator comprises capacitive electrodes <NUM> that are in a grid pattern, where N (the number of columns in the grid) is <NUM> and M (the number of rows in the grid) is <NUM>. In this embodiment, the capacitive electrodes <NUM> are rectangular plate electrodes. In this embodiment, the transmit resonator further comprises a transmit passive electrode <NUM>. The transmit passive electrode <NUM> is identical to passive electrode <NUM> unless otherwise stated. The receive resonator comprises two capacitive electrodes <NUM>. The receiver further comprises a receive passive electrode <NUM>. The receive passive electrode <NUM> is identical to receive passive electrode <NUM> unless otherwise stated.

<FIG> shows another embodiment of a partial wireless power transfer system generally identified by reference numeral <NUM>. The wireless power transfer system <NUM> is identical to the wireless power transfer system <NUM> unless otherwise stated.

Simulations were performed on the wireless power transfer systems <NUM> and <NUM>. In this embodiment, each capacitive electrode <NUM> of the transmit resonator has a length of <NUM> and a width of <NUM>. The gap between the long sides of the capacitive electrodes <NUM> of the transmit resonator is <NUM>. The gap between the short sides of the capacitive electrodes <NUM> is <NUM>. Each receive capacitive electrodes <NUM> has a length of <NUM> and a width of <NUM>. The gap between receive capacitive electrodes <NUM> is <NUM>. The gap between the capacitive electrodes <NUM> of the transmit resonator and the receive capacitive electrodes <NUM> is <NUM>. The gap between the capacitive electrodes <NUM> of the transmit resonator and the transmit passive electrode <NUM> is <NUM>. The gap between the receive capacitive electrodes <NUM> and the receive passive electrode <NUM> is <NUM>. The wireless power transfer system <NUM> delivers <NUM> watts of power.

In this embodiment, each capacitive electrode <NUM> is <NUM> in length and <NUM> in width. The gap between the capacitive electrodes <NUM> is <NUM>. Each receive capacitive electrodes <NUM> has a length of <NUM> and a width of <NUM>. The gap between the receive capacitive electrodes <NUM> is <NUM>. The gap between the capacitive electrodes <NUM> of the transmit resonator and the receive capacitive electrodes <NUM> is <NUM>. The gap between the capacitive electrodes <NUM> of the transmit resonator and the transmit passive electrode <NUM> is <NUM>. The gap between the receive capacitive electrodes <NUM> and the receive passive electrode <NUM> is <NUM>. The wireless power transfer system <NUM> delivers <NUM> watts of power.

The results of the simulations are shown in <FIG> is a graph of the SAR in W/kg for a <NUM> gram average mass of human feet located <NUM> away and overhead from the transmit resonator. During the simulation, the receive capacitive electrodes <NUM> were initially aligned with the two of capacitive electrodes <NUM> of the transmit resonator as shown in <FIG>. This configuration is labelled as "Segmented Tx - Aligned" in <FIG>. The receive capacitive electrodes <NUM> then moved toward the other two capacitive electrodes <NUM> of the transmit resonator until the receive capacitive electrodes <NUM> are between two sets of adjacent capacitive electrodes <NUM> of the transmit resonator as shown in <FIG>. This configuration is labelled as "Segmented Tx - Misaligned" in <FIG>. The wireless power transfer system <NUM> is labelled as "Long Tx" in <FIG>. The International Commission on Non-Ionizing Radiation Protection (ICNIRP) RF exposure limit is labelled as "ICNIRP RF exposure limit" in <FIG>.

As shown in <FIG>, when the receive capacitive electrodes <NUM> are aligned with the capacitive electrodes <NUM> of the transmit resonator, the SAR for the wireless power transfer system <NUM> is well below the ICNIRP RF exposure limit at distances between <NUM> and <NUM>. Similarly, when the receive capacitive electrodes <NUM> are not overlapping and aligned with the capacitive electrodes <NUM> of the transmit resonator, the SAR for the wireless power transfer system <NUM> is still below the ICNIRP RF exposure limit at distances between <NUM> and <NUM>. The SAR for the wireless power transfer system <NUM> is not below the ICNIRP RF exposure limit when the distance is less than approximately <NUM>. Clearly, the wireless power transfer system <NUM> produces reduced SAR providing a generally safer wireless power transfer system.

While a particular operation of the first detector <NUM> and controller <NUM> has been described, one of skill in the art will appreciate that variations are possible. In one embodiment, the controller <NUM> requests the impedances presented to the capacitive electrodes <NUM> from the first detector <NUM>. In response to the request from the controller <NUM>, the first detector <NUM> sends the impedances presented to the capacitive electrodes <NUM> to the controller <NUM>. The other embodiments of the first detector and controller discussed herein may function similarly. The embodiments of the second detector discussed herein may function similarly.

While a particular operation of the first detector <NUM> and controller <NUM> has been described, one of skill in the art will appreciate that variations are possible. In one embodiment, the controller <NUM> requests the impedance presented to a particular capacitive electrode <NUM> from the first detector <NUM>. In response to the request from the controller <NUM>, the first detector <NUM> sends the impedance presented to the particular capacitive electrode <NUM> to the controller <NUM>. The controller <NUM> may make multiple impedance requests over a period of time. The controller <NUM> may request impedances presented to more than one capacitive electrode <NUM>. The other embodiments of the first detector and controller discussed herein may function similarly. The embodiments of the second detector discussed herein may function similarly.

While particular first detectors <NUM> and <NUM> have been described, one of skill in the art will appreciate that other configurations are possible. In another embodiment, the single circuit is configured to apply a current and measure a voltage. In another embodiment, the first detector <NUM> and <NUM> comprises a plurality of circuits. In another embodiment, the first detector <NUM> and <NUM> is configured to detect the impedance differential between electrodes <NUM> and <NUM>, respectively. In another embodiment, the first detector <NUM> and <NUM> is configured to determine both the impedance presented at each electrode <NUM> and <NUM>, respectively, and the impedance differential between electrodes <NUM> and <NUM>, respectively.

While a particular second detector <NUM> has been described, one of skill in the art will appreciate that other configurations are possible. In another embodiment, the single circuit is configured to apply a current and measure a voltage. In another embodiment, the second detector <NUM> comprises a plurality of circuits.

While particular electrodes have been described, one of skill in the art will appreciate that other configurations are possible including, but not limited to, concentric, coplanar, circular, elliptical, disc, etc., electrodes. Other suitable electrode configurations are described in <CIT>.

Claim 1:
A transmit resonator (<NUM>, <NUM>) comprising:
at least two inductors (<NUM>, <NUM>);
a switching network (<NUM>, <NUM>) electrically connected to the inductors (<NUM>, <NUM>);
a plurality of capacitive electrodes (<NUM>, <NUM>) electrically connected to the switching network (<NUM>, <NUM>);
a detector communicatively connected to a controller (<NUM>, <NUM>), the detector configured to detect impedance, the detector comprising a first detector (<NUM>, <NUM>) configured to detect impedance presented to the electrodes (<NUM>, <NUM>); and
the controller (<NUM>, <NUM>) communicatively connected to the switching network (<NUM>, <NUM>) and the detector, the controller (<NUM>, <NUM>) configured to control the switching network (<NUM>, <NUM>) to connect two or more electrodes (<NUM>, <NUM>) to the inductors (<NUM>, <NUM>) based on the detected impedance being greater than a threshold impedance which is the lowest value of a range of impedances that allows the transmit resonator (<NUM>, <NUM>) to resonate at a resonant frequency, wherein the inductors (<NUM>, <NUM>) and electrodes (<NUM>, <NUM>) are configured to resonate at the resonant frequency to generate an electric field.