Patent Publication Number: US-2017366045-A1

Title: Wireless Power Utilization in a Local Computing Environment

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/476,840, filed on Mar. 31, 2017, which is a continuation of U.S. patent application Ser. No. 14/070,188, filed Nov. 1, 2013, which is a continuation of U.S. patent application Ser. No. 13/989,047, filed May 22, 2013, which is a national phase filing under 37 USC 371 of PCT/US2011/061384, filed Nov. 18, 2011, which claims benefit of provisional patent application No. 61/416,701, filed Nov. 23, 2010, which are incorporated herein by reference in their entireties for all purposes. 
    
    
     TECHNICAL FIELD 
     The described embodiments relate generally to wireless charging, and more specifically to devices, systems, and methods related to allocating power to receiver devices that may be located in wireless power systems. 
     BACKGROUND 
     It has been discovered (see “Efficient wireless non-radiative mid-range energy transfer” by Karalis et al., Annals of Physics 323 (2008) pgs. 34-38) that useable power can be transferred wirelessly from a power source to located within a distance referred to as a near field. What is desired are methods, systems, and apparatus for efficient and user friendly interaction between peripheral devices in a wirelessly powered local computing environment. 
     SUMMARY 
     This paper describes various embodiments that relate to a system, method, and apparatus for wirelessly providing power from a wireless power supply to any of a plurality peripheral devices. 
     A near field magnetic resonance (NFMR) power supply arranged to use a resonance channel to transfer energy to resonance circuits within a near field distance D, the distance D defining an outermost range of the NFMR power supply is described. The NFMR power supply includes at least a high frequency (HF) power source for providing a high frequency, orthogonal in-band power, a base plate that provides high frequency (HF) power coupled to the HF power source, and at least two “D” shaped resonators arranged to receive HF power from the base plate. The at least two “D” shaped resonators are driven 180° out of phase with each other such that the magnetic fields produced by the at least two “D” shaped resonators provide a symmetric magnetic field at a resonant frequency. 
     In one aspect of the described embodiments, the symmetric magnetic field is circularly polarized. The circularly polarized magnetic field being spatially symmetric about at least two axes provides a symmetric power reception at a peripheral device independent of the spatial relationship between the peripheral device and the NFMR power supply. 
     In yet another aspect, the resonant frequency of the NFMR power supply is dynamically tunable to any frequency by at least changing a shape of at least one resonator of the NFRM using, for example, a piezoelectric shaping technique. 
     In another embodiment, a method of determining a resonant frequency of a wirelessly powered local computing environment is disclosed. In the described embodiment, the wirelessly powered local computing environment includes at least a dynamically tunable near field magnetic resonance (NFMR) power supply arranged to wirelessly provide power to at least one receiving unit located within an effective range D of the NFMR power supply by way of a resonance channel, and a communication mechanism for providing a communication channel separate from the resonance channel between the NFMR power supply and the at least one receiving unit. 
     The method can be carried out by performing at least the following operations: providing a magnetic field at a first frequency by the NFMR power supply, receiving over the communication channel an indication of an amount of wireless power received at the receiving unit over the resonance channel from the NFMR power supply, updating the first frequency of the NFMR power supply to a second frequency by dynamically tuning the NFMR power supply if the received indication is less than a maximum power, otherwise setting the resonant frequency as the first frequency. 
     In yet another embodiment, a wirelessly powered local computing environment is disclosed. The wirelessly powered local computing environment includes at least a near field magnetic resonance (NFMR) power supply comprising a first symmetric magnetic resonator structure and at least one peripheral device. The peripheral device, in turn, includes a second symmetric magnetic resonance structure having a shape in accordance with the first symmetric resonator structure. The NFMR power supply uses the first symmetric magnetic resonance structure to create a symmetric magnetic field and a resonance channel coupling the NFMR power supply and the at least one peripheral device used to transfer useable energy from the first symmetric magnetic resonator structure and the second magnetic resonator structure. The wirelessly powered local computing environment also includes at least a central processing unit in communication with the NFMR power supply, the central processing unit providing processing resources to the NFMR power supply. 
     Other aspects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the described embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating a wireless power delivery system that includes a power transmitting unit and a target electronic device where power is delivered wirelessly employing magnetic waves. 
         FIG. 2  shows a simplified schematic diagram of a wireless power transfer system. 
         FIG. 3  is a simplified block diagram of a transmitter in accordance with an embodiment. 
         FIG. 4  shows an antenna used in exemplary embodiments may be configured as a “loop” antenna. 
         FIG. 5  shows wireless power source arranged to transfer power utilizing a circularly polarized magnetic field in accordance with the described embodiments. 
         FIGS. 6A-6E  illustrate a basic configuration of a wireless system in accordance with the described embodiments. 
         FIG. 7  illustrates an embodiment whereby peripheral device takes on the form of keyboard within effective range D of a wireless power supply. 
         FIGS. 8A and 8B  show a magnetic ground comb in accordance with the described embodiments. 
         FIG. 9  shows a flowchart detailing process in accordance with the described embodiments. 
         FIG. 10  shows a representative wireless local computing environment in accordance with the described embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary applications of apparatuses and methods according to the present invention are described in this section. These examples are being provided solely to add context and aid in the understanding of the invention. It will thus be apparent to one skilled in the art that the present invention may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order to avoid unnecessarily obscuring the present invention. Other applications are possible, such that the following examples should not be taken as limiting. 
     The following relates to techniques and apparatus for providing useful amounts of power wirelessly to devices within a wireless charging environment. In one embodiment, the wireless charging environment can include various computing devices along the lines of a desktop computer, a laptop computer, net book computer, tablet computer, etc. In some cases, a wireless power supply can be used to provide power wirelessly to various electronic devices such as a smart phone (such as an iPhone™ manufactured by Apple Inc. of Cupertino, Calif.) that include a portable power supply for mobile operation. The power provided by the wireless power supply can be used for operation of the electronic device, charging of a portable power supply within the electronic device, or any combination thereof. 
     In accordance with one embodiment, the magnetic coupling between a magnetic field generated by a power transmitting unit and a target device enables the power transfer. For example, the system of the present embodiment may use one or more coils disposed in a computing device. The computing device can take the form of a desktop computer along the lines of an iMac™ desktop computer or a portable computer such as a MacBook Pro™ each manufactured by Apple Inc. of Cupertino, Calif. It should be noted that in addition to a discreet coil arrangement, metallic components, such as a housing used to support internal components can also be configured to act as a resonator(s). 
     For example, at least a portion of the aluminum housing of the iMac™ desktop computer can be used as a resonator. In some cases, a small form factor electronic device, such as an iPhone™ can include a housing at least a portion of which is formed of metal. For example, a metallic band used to provide structural support for the iPhone4™ can be used as a single loop resonator. In this way the metal band can receive power wirelessly for both operating the electronic device and charging the battery, whichever is necessary. In another example, a metallic housing of a peripheral device, such as a mouse, can be used as resonator to provide power for operation of the mouse and/or charging the batteries used to store power for the operation of the mouse. Magnetic signals/fields created by the power source can be received by an antenna/coil of the target device. The received signals/fields charge capacitors through diodes at the target device. An array of such capacitors may be connected in series using a plurality of diodes. This array of capacitors and plurality of diodes helps in rectification of AC (alternating current) to DC (direct current) and may amplify the DC voltage to a value that is sufficient to charge a battery in the target device. 
     According to an aspect of the present embodiment, the resonant power wireless transmission supports communications at least from the power transmitting unit and the target device. These communications may include information relating to the power charging or other information. Because of the strong wireless coupling between the power transmitting unit and the target device, high data rate communications may be supported by using this technique. For communications from the target device to the power transmitting unit, the same principle may be employed. However, in some embodiments, communications from the target device to the power transmitting unit may be supported by other wireless techniques such as Wireless Local Area Network (WLAN) operations, e.g., IEEE 802,11x, Wireless Personal Area Network operations (WPAN) operations, e.g., Bluetooth, infrared communications, cellular communications and/or other techniques. 
     In one embodiment, wireless power can be provided by at least one wireless power source having a circularly polarized source resonator. The at least one wireless power source can include a high frequency, orthogonal in-band power transmitter. The at least one wireless power source can include a base plate that provides high frequency (HF) power and at least two “D” shaped resonators. The at least two “D” shaped resonators can be driven about 180° out of phase with each other. Hence, the magnetic fields produced by the at least two “D” shaped resonators can provide a circularly polarized magnetic field. The circularly polarized magnetic field can interact with a peripheral device, such as a mouse, having a corresponding shaped base and resonator antenna. In one embodiment, the peripheral base includes electronic components that can receive power delivered wirelessly from the wireless power source. The electronic components can include a battery that can receive a charging current from the wireless power supply. Due to the circular nature of the polarization of the magnetic field, the resonant coupling between the mouse and the wireless power supply can be substantially unaffected when the mouse is moved upon a surface on which the base plate is supported. It should be noted that the circularly polarized magnetic field can be “steered” by modifying the orientation of the at least two “D” shaped magnetic fields or by modifying the orientation of the axis of the elliptical shaped magnetic field. In one implementation, a target device can take the form of a single orientation receiver. 
     In one embodiment, a peripheral device can be shaped in such a way to form a resonator having a shape appropriate for interacting with the circularly polarized magnetic field emanating from the wireless power source. For example, a keyboard can have a metal stand used to support the keyboard at an ergonomically friendly angle with respect to a supporting surface. The metal stand can have a shape in accordance with the circularly polarized magnetic field formed by the at least two “D” shaped resonators. In this way, the metal stand can interact with the circularly polarized magnetic field to support wirelessly receiving power from the wireless power source. 
     In another embodiment, the resonant frequency of the wireless power supply can be tuned and de-tuned to any frequency. The tuning of the resonant frequency can be done dynamically by changing a shape of at least one resonator. In one embodiment, the changing of the shape of the at least one resonator can be carried out using, for example, a piezoelectric shaping techniques. In some embodiments, parasitic capacitance can be used to tune/detune a resonator. In some cases, the wireless power transmitter can vary a center resonance frequency in order to compensate for parasitic capacitance. The dynamic tuning can be used to provide identification of the resonator. For example, when a resonator is detuned (or tuned), resonant impedance associated with the resonator will be removed (or added) to a magnetic circuit between a primary resonator in a power supply and the resonator. The change in resonant impedance can be detected by the power supply and thus that resonator associated with the change in impedance can be deduced and stored for later use. 
     The dynamic tuning can also be used to arbitrate power amongst a plurality of receiving devices. For example, one or more modes can be tuned in succession followed by a query requesting a confirmation of how much power was received by those devices receiving power at a particular frequency. In this way, resonant modes not equal to the original center frequency can be determined. Hence, maximum power can be transferred at one of the determined resonant frequency. in this way, the most efficient power transfer can occur at the original center frequency but, however, the most amount of power can be transferred at one of the resonant mode frequencies. Resonant modes can be determined by nulling out a particular receiving device, using for example, a backchannel. In this way, the wireless power transmitter can look for a change in impedance when the wireless power transmitter is broadcasting on a resonant mode. In this way, by sweeping through a particular frequency band, a number of resonant modes can be determined. In some cases, resonators can be coupled together to form chained re-resonators. 
     In another embodiment, conductive material can be used as a waveguide and/or magnetic flux concentrator. In particular, metallic surfaces and structures can be used to guide/concentrate high frequency resonances by, for example, boosting coupling coefficient κ. Conductive surfaces (such as table tops, computer housing, etc.) can be used a flux concentrators as well as metal housings. 
     In yet another embodiment, a ground comb can be used to preferentially block magnetic flux and preferentially allow other magnetic flux to pass. The ground comb can be formed of magnetically active material in the form of fingers spaced apart to allow at least some magnetic flux to pass through the interstitial spacing. However, at least a second set of fingers can be applied across the first set of fingers for form apertures. The apertures allowing only selected portions and amounts of an incident magnetic field from passing, the remaining portions of the magnetic fields being blocked. 
     These and other embodiments are discussed below with reference to  FIGS. 1-10 . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes only and should not he construed as limiting. 
       FIG. 1  is a block diagram illustrating a wireless power delivery system  100  that includes a power transmitting unit  103  and a target electronic device  115 , wherein power is delivered wirelessly by way of a magnetic resonance channel. The power delivery system  100  is used to deliver electric power to one or more target devices, and the target devices use the delivered power for operation or for recharging a battery or both. The power delivery system  100  includes the power transmitting unit  103 , the target electronic device  115 , and other target devices capable of receiving power being transmitted. The power transmitting unit  103  includes a power source  105  capable of generating power for power transmission and sending transmitter  131  capable of power transmission using magnetic resonance channel  111 , such as non-radiated. magnetic field of a specified target resonant frequency. It also includes a source power manager  107  that manages power transmission. The power transmitting unit  103  is capable of dynamically tuning the power transmission to the target resonant frequency associated with the target electronic device  115 , wherein the target resonant frequency is specified dynamically. The power transmitting unit  103  also includes a communication module  110  operable to send a communication signal  113  to the target electronic device  115  in the form of, for example, Radio Frequency (RF) communications and as such, communication signal  113  can include Wireless Local Area Network (WLAN) communications such as IEEE 802.11x communications, Bluetooth communications, cellular communications, or other RF communication techniques. The communication module  110  can also include a wired communication link, e.g. Local Area Network (LAN) such as Ethernet, Cable Modem, Wide Area Network (WAN) and/or other wired communication means. For example, the wired communication link could provide a high speed uplink to the Internet. 
     The target electronic device  115  includes a resonant power charging module  117 , a source resonant frequency selector  123 , a communication module  125 , and a target device power manager  127 . The resonant power charging module  117  includes a power receiving component  141 , a power charging controller  119 , and a rechargeable battery  129 . The power receiving component  141 , is used to receive the power transmissions provided by the power transmitting unit  103  using the target resonant frequency. The target electronic device  115  uses the received power for operation of the target electronic device  115  as well as for charging the rechargeable battery  129  in the target electronic device  115 . The power delivery system  100  uses the power transmitting unit  103  to generate magnetic fields that are used to transmit power to the target devices, such as the target electronic device  115 . The power transmitting unit  103  includes a resonant circuit that generates a non-radiated magnetic field at the target resonant frequency that is received by the target electronic device  115  using the power receiving component  141 . The target electronic device  115  also includes a communication module  125  operable to communicate with the communication module  110  of the power transmitting unit  103  using communication signal  113 . 
     The power transmitting unit  103  that includes the power source  105  and the target electronic device  115  are communicatively coupled with each other during the resonant power delivery from the power source  105  to the target electronic device  115 . The resonant coupling is achieved wirelessly using magnetic resonance channel  111  The magnetic resonance channel  111  is the power delivery channel and communication signal  113  is the control and communication signal channel. The power transmitting unit  103  can be implemented in, for example, the base station of a mobile phone, where communication with the mobile phone (from the base station), resonant power transmission, and the control signal transmission are all conducted between the mobile phone (as a target electronic device) and the base station using different channels. 
       FIG. 2  shows a simplified schematic diagram of another embodiment  200  of wireless power transfer system  100  described with respect to  FIG. 1 . Wireless power system  200  can include at least transmitter  204  that, in turn, includes, an oscillator  222 , a power amplifier  224 . and a filter and matching circuit  226 . The oscillator  224  is configured to generate a desired frequency, which may be adjusted in response to adjustment signal  223 . The oscillator signal may be amplified by the power amplifier  224  with an amplification in accordance with control signal  225 . The filter and matching circuit  226  can be included to filter out harmonics or other unwanted frequencies and match the impedance of the transmitter  204  to the transmit antenna  214 . The receiver  208  can include a matching circuit  232  and a rectifier and switching circuit  234  to generate a DC power output to charge a battery  236  or power a device coupled to the receiver (not shown). The matching circuit  232  can be included to match the impedance of the receiver  208  to the receive antenna  218 . The receiver  208  and transmitter  204  can communicate using communication signal  113  (e.g. Bluetooth, cellular, WiFi etc). 
     As illustrated in  FIG. 3 , an antenna used in the described embodiments can be configured as antenna  350  shaped as a loop or other appropriate closed configuration. Efficient transfer of energy between the transmitter  204  and receiver  208  occurs during matched or nearly matched resonance between the transmitter  204  and the receiver  208  or lower efficiency when not matched. Transfer of energy occurs by coupling energy from the near-field of the transmitting antenna to the receiving antenna residing in the neighborhood where this near-field. is established rather than propagating the energy from the transmitting antenna into free space. 
     The resonant frequency of the loop or magnetic antennas is based on the inductance and capacitance, Inductance in a loop antenna is generally simply the inductance created by the loop, whereas, capacitance is generally added to the loop antenna&#39;s inductance to create a resonant structure at a desired resonant frequency. As an example, capacitor  352  and capacitor  354  can be added to the antenna  350  to create a resonant circuit that generates resonant signal  356 . Accordingly, for larger diameter loop antennas, the size of capacitance needed to induce resonance decreases as the diameter or inductance of the loop increases. Furthermore, as the diameter of the loop or magnetic antenna increases, the efficient energy transfers increases. In addition, resonant signal  356  can be an input to the loop antenna  350 . 
       FIG. 4  is a simplified block diagram of transmit circuitry  402 . and associated transmit antenna  404 . Generally, transmit circuitry  402  provides RF power to the transmit antenna  404  by providing an oscillating signal resulting in generation of near-field energy about the transmit antenna  404 . Transmit circuitry  402  includes a fixed impedance matching circuit  406  for matching the impedance of the transmit circuitry  402  (e.g. 50 ohms) to the transmit antenna  404  and a low pass filter (LPF)  408  reduces harmonic emissions. Other embodiments can include different filter topologies, for example, notch filters that attenuate specific frequencies while passing others. Transmit circuitry  402  further includes a power amplifier  410  configured to drive an RF signal as determined by an oscillator  412 . The transmit circuitry can include discrete devices or circuits, or alternately, an integrated circuit. 
     Transmit circuitry  402  further includes a controller  414  for enabling the oscillator  412  during transmit phases (or duty cycles) for specific receivers, for adjusting the frequency of the oscillator, and for adjusting the output power level for implementing a communication protocol for interacting with neighboring devices through their attached receivers. The transmit circuitry  402  may further include a load sensing circuit  416  for detecting the presence or absence of active receivers in the vicinity of the near-field generated by transmit antenna  404 . 
     An implementation of a transmit antenna  404  can be a fraction of the wavelength and tuned to resonate at lower usable frequencies by using capacitors to define the resonant frequency. Transmit circuitry  402  may gather and track information about the whereabouts and status of receiver devices that may be associated with the transmit circuitry  402 . 
     In one embodiment, wireless power can be provided by at least one wireless power source having a circularly polarized source resonator. More specifically,  FIG. 5  shows wireless power source  500  arranged to transfer power utilizing a circularly polarized magnetic field in accordance with the described embodiments. Wireless power source  500  can include power supply  502 . In the described embodiment, power supply  502  can take the form of high frequency, orthogonal in-band power transmitter that can supply high frequency (HF) power to base plate  504 . Base plate  504 , in turn, provides HF power to resonators  506  that can take the form of “D” shaped resonators. In this way, each of “D” shaped resonators  506  can act as a circular polarized magnetic field source resonator that can convert at least some of the HF power provided to base plate  504  to separate component magnetic fields B 1  and B 2  that can combine with each other to form resulting magnetic field  508 . In a particularly useful configuration, the at least two “D” shaped resonators  506  can be driven by base plate  504  about 180° out of phase with each other such that the resulting component magnetic fields B 1  and B 2  are also 180° out of phase with each other. The combining of the two out of phase component magnetic fields B 1  and B 2  can result in a resulting magnetic field that is circularly polarized. It should be noted that with a circularly polarized magnetic field, the plane of polarization rotates in a corkscrew pattern, making one complete revolution during each wavelength. In this way, a circularly polarized wave radiates energy in both the horizontal and vertical planes and all planes in between. If the rotation is clockwise looking in the direction of propagation, the sense is called right-hand-circular (RHC). if the rotation is counterclockwise, the sense is called left-hand circular (LHC). In this way, resulting circularly polarized magnetic field  508  can be transmitted in all planes, making it more likely for a mobile device (such as a computer mouse) to be able to establish a reliable resonance link regardless of the relative antenna orientation of the mobile device and wireless power supply  500 . 
       FIGS. 6A-6E  illustrates a basic configuration of wireless system  600  that includes wireless power supply  500  arranged to radiate circularly polarized magnetic field  508  in accordance with the described embodiments. In particular,  FIG. 6A  shows that a resonant channel can be formed between wireless power supply  500  and peripheral device  602 . Peripheral device  602  can be configured as a mobile device that can be moved to any position within effective distance d of wireless power supply  500 . Effective distance d can represent a distance from wireless power supply  500  over which a useful amount of power can be received by peripheral device  602  from wireless power supply  500 . Effective distance d can range from a few centimeters to a few meters. It should be noted that effective distance d can be affected by many factors in addition to the size and shape of resonators  504  and the size and shape of resonators  604  included in peripheral device  602 . In any case, the presumption for the remainder of this discussion is that peripheral device  602  remains within maximum distance of wireless power supply  500  by maintaining a current distance from wireless power supply  500  that is less than distance d max  at all times. It should be noted that maximum distance represents that area around power supply  500  where a minimum pre-determined amount of power P min  can be wirelessly received at peripheral device  602  from power supply  500 , For example power P min  can be set at 20 mW representing the least amount of power that can be transferred to peripheral device  602  in order for peripheral device  602  to operate in a fully operable manner. Of course, depending upon a current status of on-board power supplies (if any) power P min  can vary thereby altering effective range D of power supply  500 . 
     Resulting magnetic field  508  can be formed by combining component magnetic fields B 1  and B 2  generated by resonators  504  in wireless power supply  500 . In this embodiment, peripheral device  602  can take the form of computer mouse  602 . Computer mouse  602  can include resonators  604  each having a shape factor associated with resonators  506  included in wireless power supply  500 . In other words, resonators  604  can also be “D” shaped. In this way, the interaction of “D” shaped resonators  604  can be optimized for the most efficient wireless power transmission. In addition to providing an efficient wireless power transfer, the circular polarized nature of resulting magnetic field  508  allows computer mouse  602  to maintain any spatial orientation on a supporting surface or in free space and still maintain an essentially constant power transfer between wireless power supply  500  and computer mouse  602  (as shown below). 
     Accordingly,  FIG. 6B  shows cross section of peripheral device  602  along line AA illustrating housing  606  coupled to base portion  608 . In particular, housing  606  can enclose resonators  604  electrically coupled to battery  610  and operational components  612  in base portion  608 . In this way, battery  610  and operational components  612  can receive a relatively constant supply of power from wireless power supply  500  by way of resonators  604 . It should be noted that in some embodiments, battery  610  is not necessary as power can be received wirelessly from wireless power supply  500  thereby obviating the need for any on-board power supply. 
     As seen in  FIGS. 6C-6E , the symmetry of magnetic field  508  provides that power can be wirelessly received at peripheral device  602  at acceptable levels regardless of the orientation of peripheral device  602 . For example, as shown in  FIG. 6C , peripheral device  602  in the form of mouse  602  can include resonators  604  that are substantially equal in size and at about right angles to each other. In this way, the geometry of resonators  604  can be tuned to the properties of circularly polarized magnetic field  508 . Due to the matching symmetry between circularly polarized magnetic field  508  and resonators  604 , power from power supply  500  can be received at or above an acceptable level regardless of the spatial orientation of computer mouse  602 . with respect to power supply  500  (and more particularly resonators  504 ). As further illustrated in  FIG. 6D , peripheral device  602  can be rotated about ninety degrees from the orientation shown in  FIG. 6C  and still maintain an advantageous orientation with respect to resonators  506  in power supply  500  and resonators  604  in computer mouse  602 . 
     It should be noted that the magnetic field provided by power supply  500  can in fact take on an elliptical shape (a circle being a special case of an ellipse) as illustrated in  FIG. 6E . Accordingly, resonators  604  in peripheral device  602  can also take on a corresponding elliptical shape thereby optimizing an amount of power transferred from power supply  500  to peripheral device  602  as well as optimizing the power transfer efficiency, It should be noted that circularly polarized magnetic field  508  can be “steered” by modifying the orientation of the at least two “D” shaped magnetic fields generated by “D” shaped resonators  506  for example, by modifying the orientation of the axes of the elliptical shaped magnetic field. It should be noted that in one implementation, the target device (which in this representation takes the form of a computer mouse) can include only a single orientation receiver that although reduces the rate of power transfer that can be achieved from using more than one resonator, but nonetheless may be a suitable solution when available space or size is a significant consideration. 
       FIG. 7  illustrates an embodiment whereby peripheral device  602  takes on the form of keyboard  700  within maximum range D of wireless power supply  500 . In particular,  FIG. 7  shows a top view of keyboard  700  having wireless power receiver unit  702  incorporated as part of the structure of keyboard  700 . For example, keyboard  700  can be formed of metal such as aluminum. Wireless power receiver unit  702  can include at least one resonator  704 . In a particular embodiment, resonator  704  can take the form of a “D” shaped resonator matching resonator  504  in wireless power supply  500 . in this way, keyboard  700  can wirelessly receive power by way of circularly polarized magnetic field  508  regardless of the orientation of keyboard  700  with respect to wireless power supply  500 . It should be noted, however, that in some situations, wireless power supply  500  can be incorporated in another device, such as computing system  706 . In this situation, the actual spatial orientation of keyboard  700  with respect to computing system  706  is quite limited (unlike that of a computer mouse). Therefore, resonator  704  can be limited to a single “D” shaped resonator that can be fabricated as part of keyboard  700  without significant adverse effect on the ability of keyboard  700  from receiving at least an amount of power sufficient for full operation of keyboard  700 . 
     In yet another embodiment, ground comb  800  as shown in  FIG. 8A  can be used to selectively block some magnetic flux and preferentially allow other magnetic flux to pass. Ground comb  800  can be formed of magnetically active material in the form of first set of fingers  802  spaced apart to allow at least some magnetic flux B to pass through interstitial spacing. However, at least second set of fingers  804  can be applied across first set of fingers  802  for form apertures  806 . Apertures  806  are configured to allow only selected portions and amounts of incident magnetic field B inc  to pass through as magnetic field B out , the remaining portions of incident magnetic field B inc  being blocked as shown in  FIG. 8B . 
     It should be noted that by varying the geometry of the resonators, the resonant frequency of the wireless power supply can be tuned and de-tuned to any frequency. In one embodiment, the tuning of the resonant frequency can be done dynamically by changing a shape of at least one resonator. In one embodiment, the changing of the shape of the at least one resonator can be carried out using, for example, a piezoelectric shaping techniques. In some embodiment, parasitic capacitance can be used to tune/detune a resonator. In some cases, the wireless power transmitter can vary a center resonance frequency in order to compensate for parasitic capacitance. 
     In particular,  FIG. 9  shows a flowchart detailing process  900  for determining a resonant frequency of a magnetic power transfer system in accordance with the described embodiments. Process  900  can begin at  902  by providing a magnetic field at a frequency. In the described embodiment, the frequency of the magnetic field can be based at least in part upon the characteristic sizes of the constituents of the magnetic power transfer system. For example, the characteristic size of the power resonator as well as any of the receiving resonators can be used to determine the magnetic field frequency. In addition to the characteristic size, the amount of power to be transferred can also affect the frequency as more power may require a higher frequency. One the magnetic field has been provided at the frequency, an indication of an amount of power wirelessly received at a receiver is obtained at  904 . The indication can be obtained using a communication channel (sometimes referred to as a back channel) using any suitable manner of communication such as WiFi™ Bluetooth, and so on. Once the indication of the amount of power received has been obtained, a determination is made at  906  if the amount of power received is indicative of a maximum power. The determination can be based upon a predetermined power amount that has been designated as a maximum power for the particular system or the determination can be based upon a comparison of previous indications of received power. 
     In any case, if it is determined that the received amount of power is not maximum, then the frequency is updated at  908  and control is passed back to  902 . The updating of the frequency can be accomplished in many ways. For example, the frequency can be updated by varying the geometry of the resonators. In this way, the resonant frequency of the wireless power supply can be tuned and de-tuned to any frequency. In one embodiment, the tuning of the resonant frequency can be done dynamically by changing a shape of at least one resonator. In one embodiment, the changing of the shape of the at least one resonator can be carried out using, for example, a piezoelectric shaping techniques. In some embodiment, parasitic capacitance can be used to tune/detune a resonator. In some cases, the wireless power transmitter can vary a center resonance frequency in order to compensate for parasitic capacitance. On the other hand, if the power received is determined to be maximum, that at  910  the frequency is the resonant frequency and process  900  ends. 
     The dynamic tuning can also be used to arbitrate power amongst a plurality of receiving devices. For example, one or more nodes can be tuned in succession followed by a query requesting a confirmation of how much power was received by those devices receiving power at a particular frequency. In this way, resonant modes not equal to the original center frequency can be determined. Hence, maximum power can be transferred at one of the determined resonant frequency. In this way, the most efficient power transfer can occur at the original center frequency but, however, the most amount of power can be transferred at one of the other resonant mode frequencies. Resonant modes can be determined by nulling out a particular receiving device, using for example, a backchannel. In this way, the wireless power transmitter can look for a change in impedance when the wireless power transmitter is broadcasting on a resonant mode. In this way, by sweeping through a particular frequency band, a number of resonant modes can be determined. In some cases, resonators can be coupled together to form chained re-resonators. 
       FIG. 10  shows representative virtual charging area  1000  in accordance with the described embodiments. Virtual charging area  1000  provides region R of charging for suitably configured devices placed within the region R. NFMR power supply can be placed in central unit such as desktop computer. In this way, the desktop computer can provide the NFMR power supply with computing resources. It should be noted that the near field magnetic resonance (NFMR) power supply can include high Q circuit that relies upon near field magnetic coupling by way of a resonance channel formed between resonances of the power source and sink to transfer power. The NFMR power supply can be a standalone unit such as, for example, included in a desk top computer, laptop computer, tablet computer, and so on. In other embodiments, the NFMR power supply can take the form of a portable type unit such as a dongle that can be connected to a legacy device such as a desktop computer thereby providing the ability to retrofit devices. In still other embodiments, housing or a portion of a housing used to enclose the NFMR power source can act to extend a useful range of the NFMR power supply. 
     In this way, suitably configured peripheral devices can be powered directly from the NFMR power supply. In so doing, the peripheral devices when tuned to the appropriate frequency can receive power wirelessly from the NFMR power supply. In so doing, the appropriately tuned peripheral device can be considered to be part of a resonance circuit that can include the NFMR power supply and any other peripheral devices so tuned. As part of such a circuit, each device has associated with it a corresponding load that can be sensed by the NFMR power supply. As such, the resonance circuit can have a characteristic load that can change by the addition or deletion of devices from the resonance circuit. For example, if a suitably configured device such as a portable media player is brought within range of the NFMR power supply, then the load associated with the portable media player can be sensed by the NFMR power supply when (and if) the portable media player is appropriately tuned. It should be noted that in some cases, the device being brought into the range of the NFMR power supply can communicate its initial presence using a standard communication protocol such as WiFi or Bluetooth. However, once incorporated into the resonance circuit, the device can use a communication back channel described in detail below. Accordingly, any change in the characteristic load factor of the resonance circuit can convey information that can be used by the NFMR power supply to control the various devices in the resonance circuit by, for example, distributing power, and so on. 
     In some embodiments, certain of the peripheral devices can be configured to include a re-resonator circuit that can receive power directly from the NFMR power supply. Such devices can also transfer a portion of the power received to other of the peripheral devices. Virtual charging area  1000  includes central unit  1002  (desktop computer) that can include the NFMR power supply, keyboard  1004 , mouse  1006 , and portable media player  1008 . In one embodiment, keyboard  1004  can be configured to receive power directly from the NFMR power supply included in desktop computer  1002  as can mouse  1006  and portable media player  1008 . 
     In some cases, the ability of desktop computer  1002  to provide power directly to mouse  1006 , for example, can be reduced due to any number of factors. Such factors can include, for example, the addition of other devices into region R that require power from the NFMR power supply, obstacles interfering with the direct power channel formed between the NFMR and mouse  1006 , and so on. In this case, keyboard  1004  can act as a re-resonator such that a portion of the power delivered to keyboard  1004  from the NFMR power supply can be passed on by way of a re-resonator transmission unit (not shown) in keyboard  1004 . In this way, any power loss experienced by mouse  1006  can be ameliorated by the power received from keyboard  1004 . This arrangement can be transitory or can last for as long as mouse  1006  is not able to receive adequate power directly from the NFMR power supply. In other cases, the locating of portable media player  1008  within region R can reduce the amount of power available to keyboard  1004  and mouse  1006 . In this case, if a battery in keyboard  1006  is fully charged (or additional charge is not necessary) then keyboard  1006  can decouple a charging circuit while still maintaining a re-resonator circuit providing power to mouse  1006 . 
     It should be noted that conductive material  1012  can be used as a waveguide and/or magnetic flux concentrator. in particular, metallic surfaces and structures can be used to guide/concentrate high frequency resonances by, for example, boosting coupling coefficient κ. Conductive surfaces (such as table tops, computer housing, etc.) can be used a flux concentrators as well as metal housings. 
     The various aspects, embodiments, implementations or features of the described embodiments can be used separately or in any combination. Various aspects of the described embodiments can be implemented by software, hardware or a combination of hardware and software. The described embodiments can also be embodied as computer readable code on a non-transitory computer readable medium. The computer readable medium is defined as any data storage device that can store data which can thereafter be read by a computer system. Examples of the computer readable medium include read-only memory, random-access memory, CD-ROMs, DVDs, magnetic tape, and optical data storage devices. The computer readable medium can also be distributed over network-coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not target to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings. 
     The advantages of the embodiments described are numerous. Different aspects, embodiments or implementations can yield one or more of the following advantages. Many features and advantages of the present embodiments are apparent from the written description and, thus, it is intended by the appended claims to cover all such features and advantages of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, the embodiments should not be limited to the exact construction and operation as illustrated and described. Hence, all suitable modifications and equivalents can be resorted to as falling within the scope of the invention.