PATENT ABSTRACT
Techniques are described herein that are capable of increasing efficiency of wireless power transfer. A wireless power transfer system includes features that allow the system to be deployed in public spaces such as airports or in commercial establishments such as restaurants or hotels to allow a user to recharge one or more portable electronic devices while away from home. To accommodate wireless recharging of a variety of device types and states, the system may receive parameters and/or state information associated with a portable electronic device to be recharged and may control the wireless power transfer in accordance with such parameters and/or state information. For instance, the system may increase efficiency of the wireless power transfer based on such parameters and/or state information. The system may also provide a secure and efficient means for obtaining required payment information from the user prior to the wireless power transfer, thereby facilitating fee-based recharging.

PATENT DESCRIPTION
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a division of U.S. patent application Ser. No. 12/580,689, filed Oct. 16, 2009, which is a continuation-in-part of U.S. patent application Ser. No. 12/421,762, filed Apr. 10, 2009, which claims the benefit of U.S. Provisional Application No. 61/150,554, filed Feb. 6, 2009, the entireties of which are incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention generally relates to systems capable of transmitting electrical power without wires. 
         [0004]    2. Background 
         [0005]    As used herein, the term wireless power transfer refers to a process by which electrical energy is transmitted from a power source to an electrical load without interconnecting wires. Wireless power transfer is useful for applications in which instantaneous or continuous energy transfer is needed, but for which providing a wired connection is inconvenient, hazardous, or impossible. 
         [0006]    It has been observed that while electromagnetic radiation (such as radio waves) is excellent for transmitting information wirelessly, it is generally not suitable for transferring power wirelessly. For example, if power were transferred using omnidirectional electromagnetic waves, a vast majority of the power would end up being wasted in free space. Directed electromagnetic radiation such as lasers might be used to transfer power between a power source and a device, but this is not very practical and could even be dangerous. Such an approach would also require an uninterrupted line of sight between the power source and the device, as well as a sophisticated tracking mechanism when the device is mobile. 
         [0007]    For the foregoing reasons, conventional systems that transfer power wirelessly are typically based on the concept of electromagnetic induction rather than electromagnetic radiation. These systems include systems based on inductive coupling and systems based on so-called “resonant inductive coupling.” 
         [0008]    Inductive coupling refers to the transfer of energy from one circuit component to another through a shared electromagnetic field. In inductive coupling, a current running in an emitting coil induces another current in a receiving coil. The two coils are in close proximity, but do not touch. 
         [0009]    Inductive coupling has been used in a variety of systems, including but not limited to systems that wirelessly charge a battery in a portable electronic device. In such systems, the portable electronic device is placed in close proximity to a charging station. A first induction coil in the charging station is used to create an alternating electromagnetic field, and a second induction coil in the portable electronic device derives power from the electromagnetic field and converts it back into electrical current to charge the battery. Thus, in such systems, there is no need for direct electrical contact between the battery and the charging station. 
         [0010]    Some examples of various different types of charging systems based on the principle of inductive coupling are described in U.S. Pat. No. 3,938,018 to Dahl, entitled “Induction Charging System,” U.S. Pat. No. 4,873,677 to Sakamoto et al., entitled “Charging Apparatus for an Electronic Device,” U.S. Pat. No. 5,952,814 to Van Lerberghe, entitled “Induction Charging Apparatus and an Electronic Device,” U.S. Pat. No. 5,959,433 to Rohde, entitled “Universal Inductive Battery Charger System,” and U.S. Pat. No. 7,042,196 to Ka-Lai et al., entitled “Contact-less Power Transfer,” each of which is incorporated by reference as if fully set forth herein. Examples of some conventional devices that include batteries that may be recharged via inductive coupling include the Braun Oral B Plak Control Power Toothbrush, the Panasonic Digital Cordless Phone Solution KX-PH15AL and the Panasonic multi-head men&#39;s shavers ES70/40 series. 
         [0011]    Another example of a technology that supports the use of inductive coupling to wirelessly transfer power is called Near Field Communication (NFC). NFC is a short-range high frequency wireless communication technology that enables the exchange of data between devices over approximately a decimeter distance. NFC is an extension of the ISO/IEC 14443 proximity-card standard that combines the interface of a smartcard and a reader into a single device. An NFC device can communicate with both existing ISO/IEC 14443 smartcards and readers, as well as with other NFC devices, and is thereby compatible with existing contactless infrastructure already in use for public transportation and payment. The air interface for NFC is described in ISO/IEC 18092/ECMA-340: Near Field Communication Interface and Protocol-1 (NFCIP-1) and ISO/IEC 21481/ECMA-352: Near Field Communication Interface and Protocol-2 (NFCIP-2), which are incorporated by reference herein. 
         [0012]    NFC devices communicate via magnetic field induction, wherein two loop antennas are located within each other&#39;s near field, effectively forming an air-core transformer. In a passive communication mode, an initiator device provides a carrier field and a target device answers by modulating the existing field. In this mode, the target device may draw its operating power from the initiator-provided electromagnetic field. 
         [0013]    “Resonant inductive coupling” refers to a more recently-publicized type of inductive coupling that utilizes magnetically-coupled resonators for wirelessly transferring power. In a system that uses resonant inductive coupling, a first coil attached to a sending unit generates a non-radiative magnetic field oscillating at megahertz (MHz) frequencies. The non-radiative field mediates a power exchange with a second coil attached to a receiving unit, which is specially designed to resonate with the field. The resonant nature of the process facilitates a strong interaction between the sending unit and the receiving unit, while the interaction with the rest of the environment is weak. Power that is not picked up by the receiving unit remains bound to the vicinity of the sending unit, instead of being radiated into the environment and lost. 
         [0014]    Resonant inductive coupling is said to enable relatively efficient wireless power transfer over distances that are a few times the size of the device to be powered, therefore exceeding the performance of systems based on non-resonant inductive coupling. An example of a wireless power transfer system based on resonant inductive coupling is described in U.S. Patent Application Publication No. 2007/0222542 to Joannopoulos et al., entitled “Wireless Non-radiative Energy Transfer,” which is incorporated by reference herein. 
         [0015]    Given the explosive growth in the use of portable electronic devices such as laptop computers, cellular telephones, and portable media devices, it is anticipated that there will be a strong demand for systems that facilitate the wireless recharging of power sources based on various types of near field inductive coupling such as those described above. Indeed, it may be deemed desirable to make such systems available in public spaces such as airports or in commercial establishments such as restaurants or hotels to allow users to recharge their portable electronic devices while away from home. 
         [0016]    Such wireless transfer of power in public or commercial environments may be made available to users for a fee. However, in order to achieve this, the wireless power transfer system must provide a secure and efficient way of obtaining requisite payment information from a user prior to performing the wireless power transfer. Still further, to accommodate wireless recharging of a variety of device types and states, the desired system should be able to receive parameters and/or state information associated with a portable electronic device to be recharged and to control the wireless power transfer in accordance with such parameters and/or state information. 
         [0017]    Unfortunately, none of the foregoing systems based on inductive coupling or resonant inductive coupling provide such features. For example, although NFC devices may use magnetic field induction to wirelessly transfer power as well as payment information and other types of data, it does not appear that such NFC devices are designed to use the wirelessly transferred power to recharge a power source associated with a portable electronic device. Furthermore, it does not appear that such devices control the wireless power transfer based on parameters and/or state information received from the portable electronic device having a power source to be recharged. Moreover, conventional techniques for transferring power wirelessly do not allow for feedback to increase efficiency of the wireless power transfer. 
       BRIEF SUMMARY OF THE INVENTION 
       [0018]    A system and/or method for increasing efficiency of wireless power transfer, substantially as shown in and/or described in connection with at least one of the figures, as set forth more completely in the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES 
         [0019]    The accompanying drawings, which are incorporated herein and form part of the specification, illustrate embodiments of the present invention and, together with the description, further serve to explain the principles involved and to enable a person skilled in the relevant art(s) to make and use the disclosed technologies. 
           [0020]      FIG. 1  is a block diagram of an example wireless power transfer system in accordance with an embodiment described herein. 
           [0021]      FIG. 2  depicts a flowchart of a method for wirelessly transferring power from a charging station to a portable electronic device in accordance with an embodiment described herein. 
           [0022]      FIG. 3  depicts a flowchart of a method for wirelessly receiving power from a charging station by a portable electronic device in accordance with an embodiment described herein. 
           [0023]      FIG. 4  depicts a flowchart of an additional method for wirelessly transferring power from a charging station to a portable electronic device in accordance with an embodiment described herein. 
           [0024]      FIG. 5  depicts a flowchart of an additional method for wirelessly receiving power from a charging station by a portable electronic device in accordance with an embodiment described herein. 
           [0025]      FIG. 6  is a block diagram of a wireless power transfer system in accordance with an embodiment described herein in which a wireless power link is established using a receiver and transmitter and a wireless communication link is established using a separate pair of transceivers. 
           [0026]      FIG. 7  is a block diagram of a wireless power transfer system in accordance with an alternate embodiment described herein in which a wireless communication link between a portable electronic device and a charging station is unidirectional. 
           [0027]      FIG. 8  is a block diagram of a wireless power transfer system in accordance with an alternate embodiment described herein in which a charging station includes a plurality of different communication link transceivers to facilitate the establishment of wireless communication links with a plurality of different types of portable electronic devices. 
           [0028]      FIG. 9  depicts a flowchart of a method for increasing efficiency of wireless power transfer in accordance with an embodiment described herein. 
           [0029]      FIGS. 10 ,  12 ,  14 , and  16  are block diagrams of example implementations of a charging station in accordance with embodiments described herein. 
           [0030]      FIGS. 11A-11D  depict respective portions of a flowchart of a method for increasing efficiency of wireless power transfer in accordance with an embodiment described herein. 
           [0031]      FIGS. 13 ,  15 , and  17 - 21  depict flowcharts of methods for increasing efficiency of wireless power transfer in accordance with embodiments described herein. 
           [0032]      FIG. 22  is a block diagram of an example implementation of a portable electronic device in accordance with an embodiment described herein. 
       
    
    
       [0033]    The features and advantages of the disclosed technologies will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number. 
       DETAILED DESCRIPTION OF THE INVENTION 
     I. Introduction 
       [0034]    The following detailed description refers to the accompanying drawings that illustrate example embodiments of the present invention. However, the scope of the present invention is not limited to these embodiments, but is instead defined by the appended claims. Thus, embodiments beyond those shown in the accompanying drawings, such as modified versions of the illustrated embodiments, may nevertheless be encompassed by the present invention. 
         [0035]    References in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” or the like, indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to implement such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. 
         [0036]    Various approaches are described herein for, among other things, increasing efficiency of wireless power transfer. The efficiency of a wireless power transfer is defined as the magnitude of power that is consumed by a portable electronic device with respect to the wireless power transfer divided by the magnitude of power that is provided to the portable electronic device with respect to the wireless power transfer. The efficiency of the wireless power transfer therefore indicates the proportion of the power that is wirelessly transferred to the portable electronic device that is consumed by the portable electronic device. 
         [0037]    For example, a charging station may begin to wirelessly transfer power to a portable electronic device via a wireless power link. The portable electronic device may be configured to send an indicator to the charging station via a wireless communication link once the charging station begins to wirelessly transfer the power to the portable electronic device. The indicator specifies information regarding the portable electronic device, which may include but is not limited to a resonant frequency of the portable electronic device, a magnitude of power requested by the portable electronic device, a magnitude of power consumed by the portable electronic power with respect to the wireless power transfer, a maximum safe power that the portable electronic device is capable of consuming without substantial risk of damaging the portable electronic device, a position of the portable electronic device, etc. The charging station may be configured to increase the efficiency of the wireless transfer of the power based on the indicator. 
         [0038]    A method is described for increasing efficiency of wireless power transfer. In accordance with this method, a wireless power transfer is initiated from a charging station to a portable electronic device via a wireless power link. Parameter(s) regarding the portable electronic device are received at the charging station via a wireless communication link in response to initiation of the wireless power transfer. Efficiency of the wireless power transfer is increased based on the parameter(s). 
         [0039]    Another method is described for increasing efficiency of wireless power transfer. In accordance with this method, power is wirelessly transferred to a portable electronic device via a wireless power link. Parameter(s) received via a wireless communication link regarding the portable electronic device with respect to the wireless transfer of the power are analyzed. Efficiency with respect to the wireless transfer of the power is increased based on analysis of the parameter(s). 
         [0040]    Yet another method is described for increasing efficiency of wireless power transfer. In accordance with this method, power is wirelessly received for a first period of time at a portable electronic device from a charging station via a wireless power link having a first transmission efficiency. Parameter(s) regarding the portable electronic device with respect to receipt of the power during the first period of time are provided to the charging station via a wireless communication link. Power is wirelessly received for a second period of time at the portable electronic device from the charging station via the wireless power link having a second transmission efficiency in response to providing the parameter(s) to the charging station. The second transmission efficiency is greater than the first transmission efficiency. 
         [0041]    A system is described that includes a wireless power transfer module, a parameter receipt module, and an efficiency improvement module. The wireless power transfer module is configured to initiate a wireless power transfer to a portable electronic device via a wireless power link. A parameter receipt module is configured to receive parameter(s) regarding the portable electronic device via a wireless communication link in response to initiation of the wireless power transfer. An efficiency improvement module is configured to increase efficiency of the wireless power transfer based on the parameter(s). 
         [0042]    Another system is described that includes a wireless power transfer module, a parameter analysis module, and an efficiency improvement module. The wireless power transfer module is configured to wirelessly transfer power to a portable electronic device via a wireless power link. The parameter analysis module is configured to analyze parameter(s) received via a wireless communication link regarding the portable electronic device with respect to the wireless transfer of the power. The efficiency improvement module is configured to increase efficiency with respect to the wireless transfer of the power based on analysis of the parameter(s). 
         [0043]    Yet another system is described that includes a wireless power receipt module and a parameter module. The wireless power receipt module is configured to wirelessly receive power for a first period of time from a charging station via a wireless power link having a first transmission efficiency. The parameter module is configured to provide parameter(s) regarding the system with respect to receipt of the power during the first period of time to the charging station via a wireless communication link. The wireless power receipt module is further configured to wirelessly receive power for a second period of time from the charging station via the wireless power link having a second transmission efficiency in response to providing the parameter(s) to the charging station. The second transmission efficiency is greater than the first transmission efficiency. 
       II. Example Wireless Power Transfer System in Accordance with an Embodiment 
       [0044]      FIG. 1  is a block diagram of an example wireless power transfer system  100  in accordance with an embodiment described herein. System  100  includes a charging station  102  and a portable electronic device  104 . As will be described in more detail herein, charging station  102  is configured to wirelessly transfer power to portable electronic device  104  responsive to receipt of payment information therefrom. Charging station  102  is also configured to manage the wireless transfer of power to portable electronic device  104  based on certain parameters and/or state information received from portable electronic device  104 . 
         [0045]    As shown in  FIG. 1 , charging station  102  includes a power source  122  connected to a wireless power/communication link transceiver  124 . Wireless power/communication link transceiver  124  is configured to wirelessly transfer power supplied by power source  122  to a wireless power/communication link transceiver  146  associated with portable electronic device  104  via an inductive link  106 . As will be appreciated by persons skilled in the relevant art(s), such wireless power transfer may be carried out over inductive link  106  in accordance with the well-known principles of inductive coupling or resonant inductive coupling as discussed in the Background Section above. As will be further appreciated by persons skilled in the relevant art(s), the manner in which wireless power/communication link transceiver  124  and wireless power/communication link transceiver  146  are implemented will depend on the type of inductive coupling used. A variety of transceiver designs based on inductive coupling and resonant inductive coupling are available in the art and thus need not be described herein. 
         [0046]    Charging station  102  also includes a power link manager  126  connected between power source  122  and wireless power/communication link transceiver  124 . Power link manager  126  is configured to sense when wireless power/communication link transceiver  146  associated with portable electronic device  104  is inductively coupled to wireless power/communication link transceiver  124  and is thus capable of receiving power wirelessly therefrom. Power link manager  126  is further configured to transfer power wirelessly over inductive link  106  responsive to control signals from a communication link manager  128 . Power link manager  126  may be further configured to monitor the amount of power that is wirelessly transferred via inductive link  106  to portable electronic device  104 . 
         [0047]    Communication link manager  128  is connected both to power link manager  126  and to wireless power/communication link transceiver  124 . Communication link manager  128  is configured to establish and maintain a wireless communication link with portable electronic device  104  via wireless power/communication link transceiver  124  for the purpose of obtaining payment information and other information therefrom. Such other information may include, for example, device-specific parameters associated with portable electronic device  104  such as a maximum safe power that may be transferred to portable electronic device  104 . Such other information may also include, for example, state information associated with portable electronic device  104  such an amount of power currently consumed or needed by portable electronic device  104 . 
         [0048]    Communication link manager  128  is thus configured to use inductive link  106  for the wireless communication of data. Depending upon the implementation, communication link manager  128  may be configured to carry out the wireless communication of data in accordance with any standard or proprietary induction-based data communication protocol. For example, communication link manager  128  may be configured to carry out the wireless communication of data in accordance with an NFC protocol as described in the Background Section above, although this example is not intended to be limiting and other standard or proprietary induction-based data communication protocols may be used. 
         [0049]    Communication link manager  128  is further configured to transmit control signals to power link manager  126  to control whether and when power link manager  126  may transfer power wirelessly to portable electronic device  104 . Communication link manager  128  can thus ensure that power is transferred to portable electronic device  104  only after requisite payment information has been received from portable electronic device  104 . Communication link manager  128  can also control power link manager  126  to ensure that power is delivered to portable electronic device  104  in a manner that takes into account certain device-specific parameters such as a maximum safe power that may be transferred to portable electronic device  104  or state information such as an amount of power currently consumed or needed by portable electronic device  104 . 
         [0050]    Portable electronic device  104  within power transfer system  100  will now be described. As shown in  FIG. 1 , portable electronic device  104  includes a battery recharging unit  144  connected to wireless power/communication link transceiver  146 . Wireless power/communication link transceiver  146  is configured to transfer wireless power received over inductive link  106  to battery recharging unit  144 , which is configured to use such power to recharge a battery  142  connected thereto. Battery recharging unit  144  is also connected to a load  154  associated within portable electronic device  104 , which can be powered by battery  142  in a well-known manner. 
         [0051]    Portable electronic device  104  further includes a power link monitor  148  connected between wireless power/communication link transceiver  146  and battery recharging unit  144 . Power link monitor  148  may be configured to monitor an amount of power that is wirelessly received via inductive link  106  and to provide this information to a communication link manager  150 . Power link monitor  148  may provide other state information to communication link manager  150  including, for example, a current state of battery  142 . 
         [0052]    Communication link manager  150  is connected both to power link monitor  148  and to wireless power/communication link transceiver  146 . Communication link manager  150  is configured to establish and maintain a wireless communication link with charging station  102  via wireless power/communication link transceiver  146  for the purpose of providing payment information and other information thereto. As noted above, such other information may include, for example, device-specific parameters associated with portable electronic device  104 , such as a maximum safe power that may be transferred to portable electronic device  104 , or state information associated with portable electronic device  104  such an amount of power currently consumed or needed by portable electronic device  104 . This state information may be based on or derived from state information provided by power link monitor  148 . 
         [0053]    Communication link manager  150  is thus configured to use inductive link  106  for the wireless communication of data. Depending upon the implementation, communication link manager  150  may be configured to carry out the wireless communication of data in accordance with any standard or proprietary induction-based data communication protocol. For example, communication link manager  150  may be configured to carry out the wireless communication of data in accordance with an NFC protocol as described in the Background Section above, although this example is not intended to be limiting and other standard or proprietary induction-based data communication protocols may be used. 
         [0054]      FIG. 2  depicts a flowchart  200  of a method for wirelessly transferring power from a charging station to a portable electronic device in accordance with an embodiment described herein. The method of flowchart  200  will now be described in reference to certain elements of example wireless transfer system  100  as described above in reference to  FIG. 1 . However, the method is not limited to that implementation. 
         [0055]    As shown in  FIG. 2 , the method of flowchart  200  begins at step  202  in which power link manager  126  of charging station  102  establishes a wireless power link with portable electronic device  104 . Power link manager  126  performs this function by allowing power to flow from power source  122  to wireless power/communication link transceiver  124 , which has the effect of creating inductive link  106  between wireless power/communication link transceiver  124  of charging station  102  and wireless power/communication link transceiver  146  of portable electronic device  104 . As discussed above, depending upon the implementation of wireless power/communication link transceiver  124  and wireless power/communication link transceiver  146 , inductive link  106  may be created for example based on the principles of inductive coupling or resonant inductive coupling. 
         [0056]    At step  204 , communication link manager  128  of charging station  102  establishes a wireless communication link with portable electronic device  104 . Communication link manager  128  performs this function by transmitting and/or receiving signals via wireless power/communication link transceiver  124  to/from wireless power/communication link transceiver  146  associated with portable electronic device  104 . The wireless communication link is thus established via inductive link  106 . As discussed above, the wireless communication link may be established in accordance with any standard or proprietary inductance-based data communication protocol. 
         [0057]    At step  206 , communication link manager  128  of charging station  102  receives payment information from portable electronic device  104  via the wireless communication link. As will be appreciated by persons skilled in the relevant art(s), the type of payment information that is received during step  206  may vary depending on the manner in which the wireless power transfer service is to be paid for by the user of portable electronic device  104 . 
         [0058]    For example, if the user will pay for the wireless power transfer through the subsequent billing of a credit card account, checking account, or some other account from which funds may be transferred, then the payment information may include a unique account identifier, such as an account number. Alternatively, if the charge to the user will be added to a list of additional charges due from the user (e.g., the charge is to be added to a hotel bill for the user), then the payment information may include a unique identifier of the user. 
         [0059]    Furthermore, if the user has already paid for the wireless power transfer, then the payment information may include an electronic token indicating that such payment has occurred. Alternatively, if the user has purchased prepaid credits towards the wireless power transfer, then the payment information may include an electronic funds amount that is currently available to the user/owner for obtaining the service. The electronic funds amount may be stored on portable electronic device  104 , or a card inserted or attached to portable electronic device  104 . 
         [0060]    The foregoing description of the types of payment information that may be received during step  206  are provided by way of example only and are not intended to limit the present invention. Persons skilled in the relevant art(s) will readily appreciate that other types of payment information may be received during step  206  other than or in addition to those types described above. 
         [0061]    After the payment information has been received by communication link manager  128  during step  206 , communication link manager  128  sends one or more control signals to power link manager  126  and, responsive to receiving the control signal(s), power link manager  126  allows power to be transferred to portable electronic device  104  over the wireless power link. This is generally shown at step  208 . 
         [0062]    In an embodiment, communication link manager  128  validates and/or processes the payment information prior to sending the control signal(s) to power link manager  126 . In another embodiment, communication link manager  128  transmits the payment information to an external entity for validation and/or processing prior to sending the control signal(s) to power link manager  126 . For example, communication link manager  128  may provide the payment information to a network interface within charging station  102  (not shown in  FIG. 1 ) for wired or wireless communication to a network entity, such as a server, for processing and/or validation. 
         [0063]    In a further implementation of the foregoing method, power link manager  126  monitors or meters the amount of power wirelessly transferred to portable electronic device  104  via the wireless power link. The monitored amount can then be used to charge the user of portable electronic device  104  based on the amount of power transferred. In one embodiment, the monitored amount is transmitted to an external entity so that the user of portable electronic device  104  may be charged based on the monitored amount. The external entity may be, for example, a remote network entity, such as a server, or may be portable electronic device  104 . 
         [0064]    In the foregoing method of flowchart  200 , the establishment of the wireless power link in step  202  may occur before, contemporaneously with, or after the establishment of the wireless communication link in step  204  depending upon the implementation. Furthermore, the establishment of the wireless power link may occur responsive to the establishment of the wireless communication link or vice versa. With respect to the establishment of the wireless communication link, either charging station  102  or portable electronic device  104  may act as the initiator depending upon the implementation. 
         [0065]      FIG. 3  depicts a flowchart  300  of a method for wirelessly receiving power from a charging station by a portable electronic device in accordance with an embodiment described herein. In contrast to the steps of flowchart  200 , which are performed by a charging station, the steps of flowchart  300  are performed by a portable electronic device that is configured to interact with a charging station. Thus, the method of flowchart  300  may be thought of as a counterpart method to the method of flowchart  200 . 
         [0066]    The method of flowchart  300  will now be described in reference to certain elements of example wireless transfer system  100  as described above in reference to  FIG. 1 . However, the method is not limited to that implementation. 
         [0067]    As shown in  FIG. 3 , the method of flowchart  300  begins at step  302  in which a wireless power link is established between wireless power/communication link transceiver  146  of portable electronic device  104  and wireless power/communication link transceiver  124  of charging station  102 . The manner in which such a wireless power link is established was discussed above in reference to step  202  of flowchart  200 . 
         [0068]    At step  304 , communication link manager  150  of portable electronic device  104  establishes a wireless communication link with charging station  102 . Communication link manager  150  performs this function by transmitting and/or receiving signals via wireless power/communication link transceiver  146  to/from wireless power/communication link transceiver  124  associated with charging station  102 . The wireless communication link is thus established via inductive link  106 . As discussed above, the wireless communication link may be established in accordance with any standard or proprietary inductance-based data communication protocol. 
         [0069]    At step  306 , communication link manager  150  of portable electronic device  104  transmits payment information to charging station  102  via the wireless communication link. As will be appreciated by persons skilled in the relevant art(s), the type of payment information that is transmitted during step  306  may vary depending on the manner in which the wireless power transfer service is to be paid for by the user of portable electronic device  104 . Examples of various types of payment information were described above in reference to step  206  of flowchart  200 . 
         [0070]    Responsive to the receipt of the payment information by charging station  102 , charging station  102  transfers power to portable electronic device  104  over the wireless power link. The transferred power is received by wireless power/communication link transceiver  146  and applied to battery recharging unit  144 . This is generally shown at step  308 . 
         [0071]    In the foregoing method of flowchart  300 , the establishment of the wireless power link in step  302  may occur before, contemporaneously with, or after the establishment of the wireless communication link in step  304  depending upon the implementation. Furthermore, the establishment of the wireless power link may occur responsive to the establishment of the wireless communication link or vice versa. With respect to the establishment of the wireless communication link, either charging station  102  or portable electronic device  104  may act as the initiator depending upon the implementation. 
         [0072]      FIG. 4  depicts a flowchart  400  of an additional method for wirelessly transferring power from a charging station to a portable electronic device in accordance with an embodiment described herein. The method of flowchart  400  will now be described in reference to certain elements of example wireless transfer system  100  as described above in reference to  FIG. 1 . However, the method is not limited to that implementation. 
         [0073]    As shown in  FIG. 4 , the method of flowchart  400  begins at step  402  in which power link manager  126  of charging station  102  establishes a wireless power link with portable electronic device  104 . Power link manager  126  performs this function by allowing power to flow from power source  122  to wireless power/communication link transceiver  124 , which has the effect of creating inductive link  106  between wireless power/communication link transceiver  124  of charging station  102  and wireless power/communication link transceiver  146  of portable electronic device  104 . As discussed above, depending upon the implementation of wireless power/communication link transceiver  124  and wireless power/communication link transceiver  146 , inductive link  106  may be created based on the principles of inductive coupling or resonant inductive coupling for example. 
         [0074]    At step  404 , communication link manager  128  of charging station  102  establishes a wireless communication link with portable electronic device  104 . Communication link manager  128  performs this function by transmitting and/or receiving signals via wireless power/communication link transceiver  124  to/from wireless power/communication link transceiver  146  associated with portable electronic device  104 . The wireless communication link is thus established via inductive link  106 . As discussed above, the wireless communication link may be established in accordance with any standard or proprietary inductance-based data communication protocol. 
         [0075]    At step  406 , communication link manager  128  of charging station  102  receives parameters and/or state information from portable electronic device  104  via the wireless communication link. The parameters may include, for example, a maximum safe power that may be transmitted to portable electronic device  104 . The state information may include, for example, an amount of power currently consumed or needed by portable electronic device  104 . 
         [0076]    After receiving the parameters and/or state information, communication link manager  128  sends one or more control signals to power link manager  126  and, responsive to receiving the control signal(s), power link manager  128  transfers power to portable electronic device  104  over the wireless power link in a manner that takes into account the received parameters and/or state information. This is generally shown at step  408 . 
         [0077]    In one embodiment, controlling the power transfer in accordance with received parameters includes controlling the wireless power link to ensure that the amount of power transferred over the link does not exceed a maximum safe power that may be transmitted to portable electronic device  104 . In another embodiment, controlling the power transfer in accordance with received state information includes controlling the wireless power link to ensure that the amount of power that is transferred over the link is sufficient to recharge portable electronic device  104  or does not exceed an amount of power that is sufficient to recharge portable electronic device  104 . 
         [0078]    In the foregoing method of flowchart  400 , the establishment of the wireless power link in step  402  may occur before, contemporaneously with, or after the establishment of the wireless communication link in step  404  depending upon the implementation. Furthermore, the establishment of the wireless power link may occur responsive to the establishment of the wireless communication link or vice versa. With respect to the establishment of the wireless communication link, either charging station  102  or portable electronic device  104  may act as the initiator depending upon the implementation. 
         [0079]      FIG. 5  depicts a flowchart  500  of a method for wirelessly receiving power from a charging station by a portable electronic device in accordance with an embodiment described herein. In contrast to the steps of flowchart  400 , which are performed by a charging station, the steps of flowchart  500  are performed by a portable electronic device that is configured to interact with a charging station. Thus, the method of flowchart  500  may be thought of as a counterpart method to the method of flowchart  400 . 
         [0080]    The method of flowchart  500  will now be described in reference to certain elements of example wireless transfer system  100  as described above in reference to  FIG. 1 . However, the method is not limited to that implementation. 
         [0081]    As shown in  FIG. 5 , the method of flowchart  500  begins at step  502  in which a wireless power link is established between wireless power/communication link transceiver  146  of portable electronic device  104  and wireless power/communication link transceiver  124  of charging station  102 . The manner in which such a wireless power link is established was discussed above in reference to step  402  of flowchart  400 . 
         [0082]    At step  504 , communication link manager  150  of portable electronic device  104  establishes a wireless communication link with charging station  102 . Communication link manager  150  performs this function by transmitting and/or receiving signals via wireless power/communication link transceiver  146  to/from wireless power/communication link transceiver  124  associated with charging station  102 . The wireless communication link is thus established via inductive link  106 . As discussed above, the wireless communication link may be established in accordance with any standard or proprietary inductance-based data communication protocol. 
         [0083]    At step  506 , communication link manager  150  of portable electronic device  104  transmits parameters and/or state information to charging station  102  via the wireless communication link. As noted above, the parameters may include, for example, a maximum safe power that may be transmitted to portable electronic device  104  and the state information may include, for example, an amount of power currently consumed or needed by portable electronic device  104 . 
         [0084]    In an embodiment, communication link manager  150  generates or derives the state information from information collected by power link monitor  148 . For example, power link monitor  148  may monitor the wireless power link to determine an amount of power transferred over the link. This amount of power may then be reported as state information to charging station  102  over the wireless communication link. Additionally, power link monitor  148  may provide other state information to communication link manager  150  including, for example, a current state of battery  142 . 
         [0085]    Responsive to the receipt of the parameters and/or state information by charging station  102 , charging station  102  transfers power to portable electronic device  104  over the wireless power link, wherein the manner in which power is transferred is controlled in accordance with the parameters and/or state information. The transferred power is received by wireless power/communication link transceiver  146  and applied to battery recharging unit  144 . This is generally shown at step  508 . 
         [0086]    In the foregoing method of flowchart  500 , the establishment of the wireless power link in step  502  may occur before, contemporaneously with, or after the establishment of the wireless communication link in step  504  depending upon the implementation. Furthermore, the establishment of the wireless power link may occur responsive to the establishment of the wireless communication link or vice versa. With respect to the establishment of the wireless communication link, either charging station  102  or portable electronic device  104  may act as the initiator depending upon the implementation. 
       III. Alternative Wireless Power Transfer System Implementations 
       [0087]    Alternative implementations of wireless power transfer system  100  will now be described. Each of the alternative implementations is also capable of wirelessly transferring/receiving power in accordance with the methods of flowcharts  200 ,  300 ,  400  and  500  as described above in reference to  FIG. 2 ,  FIG. 3 ,  FIG. 4  and  FIG. 5 , respectively. 
         [0088]    For example,  FIG. 6  is a block diagram of a wireless power transfer system  600  that includes similar elements to those described in reference to  FIG. 1  except that the wireless power link between the charging station and the portable electronic device is implemented using a wireless power transmitter and receiver while the wireless communication link between the charging station and the portable electronic device is implemented using a separate pair of communication link transceivers. 
         [0089]    As shown in  FIG. 6 , wireless power transfer system  600  includes a charging station  602  and a portable electronic device  604 . Charging station  602  includes a power source  622 , a wireless power transmitter  624 , a power link manager  626 , a communication link manager  628 , and a communication link transceiver  630 . Portable electronic device  604  includes a battery  642 , a battery recharging unit  644 , a wireless power receiver  646 , a power link monitor  648 , a communication link manager  650 , a communication link transceiver  652 , and a load  654 . With the exception of certain elements discussed below, the elements of charging station  602  are configured to function in a similar manner to like-named elements of charging station  102  of  FIG. 1 . Likewise, with the exception of certain elements discussed below, the elements of portable electronic device  604  are configured to function in a similar manner to like-named elements of portable electronic device  104  of  FIG. 1 . 
         [0090]    Wireless power transmitter  624  is configured to operate under the control of power link manager  626  to wirelessly transfer power supplied by power source  622  to wireless power receiver  646  associated with portable electronic device  604  via an inductive link  606 . The wireless power transfer may be carried out over inductive link  606  in accordance with the well-known principles of inductive coupling or resonant inductive coupling as discussed in the Background Section above. The manner in which wireless power transmitter  624  and wireless power receiver  646  are implemented will depend on the type of inductive coupling used. A variety of transmitter and receiver designs based on inductive coupling and resonant inductive coupling are available in the art and thus need not be described herein. 
         [0091]    In the embodiment shown in  FIG. 6 , communication link transceivers  630  and  652  are used to establish and maintain a wireless communication link  608  between charging station  602  and portable electronic device  604  that is separate from inductive link  606 . Wireless communication link  608  is established for the purpose of transferring payment information and/or device-specific parameters or state information from portable electronic device  604  to charging station  602 . Charging station  602  may then use such information in a like manner to that described above with respect to charging station  102  of  FIG. 1 . 
         [0092]    As will be appreciated by persons skilled in the relevant art(s), the manner in which communication link transceivers  630  and  652  are implemented will depend on the type of wireless communication link to be established therebetween. In accordance with one embodiment, wireless communication link  608  may be established using NFC technology as described above in the Background Section. Alternatively, wireless communication link  608  may be established in accordance with certain RF-based short-range communication technologies such as Bluetooth™, as described in the various standards developed and licensed by the Bluetooth™ Special Interest Group, or technologies such as ZigBee® that are based on the IEEE 802.15.4 standard for wireless personal area networks (specifications describing ZigBee are publically available from the ZigBee® Alliance). Still further, wireless communication link  608  may be established in accordance with other RF-based communication technologies such as any of the well-known IEEE 802.11 protocols. However, these examples are not intended to be limiting, and wireless communication link  608  between charging station  602  and portable electronic device  604  may be established using a variety of other standard or propriety communication protocols. 
         [0093]      FIG. 7  is a block diagram of a wireless power transfer system  700  that includes similar elements to those described in reference to  FIG. 6  except that the wireless communication link between the portable electronic device and the charging station is unidirectional rather than bidirectional. 
         [0094]    As shown in  FIG. 7 , wireless power transfer system  700  includes a charging station  702  and a portable electronic device  704 . Charging station  702  includes a power source  722 , a wireless power transmitter  724 , a power link manager  726 , a communication link manager  728 , and a communication link receiver  730 . Portable electronic device  704  includes a battery  742 , a battery recharging unit  744 , a wireless power receiver  746 , a power link monitor  748 , a communication link manager  750 , a communication link transmitter  752 , and a load  754 . With the exception of certain elements discussed below, the elements of charging station  702  are configured to function in a similar manner to like-named elements of charging station  602  of  FIG. 6 . Likewise, with the exception of certain elements discussed below, the elements of portable electronic device  704  are configured to function in a similar manner to like-named elements of portable electronic device  604  of  FIG. 6 . 
         [0095]    Communication link manager  750  within portable electronic device  704  is configured to establish a unidirectional wireless communication link  708  with charging station  702  by transmitting signals via communication link transmitter  752  to communication link receiver  730 . This unidirectional wireless communication link may then be used to transmit payment information and/or device-specific parameters or state information from portable electronic device  704  to charging station  702 . Charging station  702  may then use such information in a like manner to that described above with respect to charging station  102  of  FIG. 1 . 
         [0096]      FIG. 8  is a block diagram of a wireless power transfer system  800  that includes similar elements to those described in reference to  FIG. 6  except that the charging station includes a plurality of different communication link transceivers to facilitate the establishment of wireless communication links with a plurality of different types of portable electronic devices. 
         [0097]    As shown in  FIG. 8 , wireless power transfer system  800  includes a charging station  802  and a portable electronic device  804 . Charging station  802  includes a power source  822 , a wireless power transmitter  824 , a power link manager  826 , a communication link manager  828 , and a plurality of communication link transceivers  830 A- 830 N. Portable electronic device  804  includes a battery  842 , a battery recharging unit  844 , a wireless power receiver  846 , a power link monitor  848 , a communication link manager  850 , a communication link transceiver  852 , and a load  854 . With the exception of certain elements discussed below, the elements of charging station  802  are configured to function in a similar manner to like-named elements of charging station  602  of  FIG. 6 . Likewise, with the exception of certain elements discussed below, the elements of portable electronic device  804  are configured to function in a similar manner to like-named elements of portable electronic device  604  of  FIG. 6 . 
         [0098]    Each of the communication link transceivers  830 A- 830 N is configured for wireless communication in accordance with a different wireless protocol. For example, first communication link transceiver  830 A may be configured for communication in accordance with NFC, second communication link transceiver  830 B may be configured for communication in accordance with Bluetooth™, and Nth communication link transceiver  830 N may be configured for communication in accordance with one of the IEEE 802.11 standards. This advantageously enables charging station  802  to receive payment information and device-specific parameters and/or state information from a plurality of different device types to facilitate the wireless transfer of power to such devices. 
       IV. Example Embodiments for Increasing Efficiency of Wireless Power Transfer 
       [0099]    Some example embodiments are capable of increasing efficiency of wireless power transfer. The efficiency of a wireless power transfer is defined as the magnitude of power that is consumed by a portable electronic device with respect to the wireless power transfer divided by the magnitude of power that is provided to the portable electronic device with respect to the wireless power transfer. The efficiency of the wireless power transfer therefore indicates the proportion of the power that is wirelessly transferred to the portable electronic device that is consumed by the portable electronic device. 
         [0100]    In accordance with some example embodiments, a charging station (e.g., charging station  102 ,  602 ,  702 , or  802 ) begins to wirelessly transfer power to a portable electronic device (e.g., portable electronic device  104 ,  604 ,  704 , or  804 ) via a wireless power link (e.g., link  106 ,  606 ,  706 , or  806 ). The portable electronic device sends an indicator to the charging station via a wireless communication link (e.g., link  106 ,  608 ,  708 , or  808 ) once the charging station begins to wirelessly transfer the power to the portable electronic device. The indicator specifies information regarding the portable electronic device, which may include but is not limited to a resonant frequency of the portable electronic device, a magnitude of power requested by the portable electronic device, a magnitude of power consumed by the portable electronic power with respect to the wireless power transfer, a maximum safe power that the portable electronic device is capable of consuming without substantial risk of damaging the portable electronic device, a position of the portable electronic device, etc. The charging station increases the efficiency of the wireless transfer of the power based on the indicator. 
         [0101]      FIG. 9  depicts a flowchart  900  of a method for increasing efficiency of wireless power transfer in accordance with an embodiment described herein. Flowchart  900  may be performed by charging station  102 ,  602 ,  702 , or  802  of respective wireless power transfer system  100 ,  600 ,  700 , or  800  shown in respective  FIG. 1 ,  6 ,  7 , or  8 , for example. For illustrative purposes, flowchart  900  is described with respect to a charging system  1000  shown in  FIG. 10 , which is an example of a charging station  102 ,  602 ,  702 , or  802 , according to an embodiment. 
         [0102]    As shown in  FIG. 10 , charging station  1000  includes a wireless power transfer module  1002 , a parameter receipt module  1004 , and an efficiency improvement module  1006 . Further structural and operational embodiments will be apparent to persons skilled in the relevant art(s) based on the discussion regarding flowchart  900 . Flowchart  900  is described as follows. 
         [0103]    As shown in  FIG. 9 , the method of flowchart  900  begins at step  902 . In step  902 , a wireless power transfer is initiated from a charging station to a portable electronic device via a wireless power link. The wireless power transfer may be performed in accordance with an inductive coupling technique, a resonant inductive coupling technique, or any other suitable technique. In an example implementation, wireless power transfer module  1002  initiates the wireless power transfer via the wireless power link. 
         [0104]    At step  904 , at least one parameter regarding the portable electronic device is received at the charging station via a wireless communication link. For instance, the at least one parameter may be received via the wireless communication link in accordance with a Near Field Communication (NFC) protocol, a Bluetooth™ protocol, a ZigBee® protocol, an IEEE 802.11 protocol, or any other suitable protocol. The wireless power link and the wireless communication link may be implemented as separate links or as a common link. The wireless power link and the wireless communication link may be inductive links, though the scope of the example embodiments is not limited in this respect. In an example implementation, parameter receipt module  1004  receives the at least one parameter. 
         [0105]    At step  906 , efficiency of the wireless power transfer is increased based on the at least one first parameter. In an example implementation, efficiency improvement module  1006  increases the efficiency of the wireless power transfer. Some example techniques for increasing the efficiency of wireless power transfer are described below with reference to  FIGS. 11A-11D ,  12 ,  15 , and  16 , for example. 
         [0106]      FIGS. 11A-11D  depict respective portions of a flowchart  1100  of a method for increasing efficiency of wireless power transfer in accordance with an embodiment described herein. Flowchart  1100  may be performed by charging station  102 ,  602 ,  702 , or  802  of respective wireless power transfer system  100 ,  600 ,  700 , or  800  shown in respective  FIG. 1 ,  6 ,  7 , or  8 , for example. For illustrative purposes, flowchart  1100  is described with respect to a charging system  1200  shown in  FIG. 12 , which is an example of a charging station  102 ,  602 ,  702 , or  802 , according to an embodiment. 
         [0107]    As shown in  FIG. 12 , charging station  1200  includes a wireless power transfer module  1202 , a parameter receipt module  1204 , a parameter determination module  1206 , a frequency comparison module  1208 , an efficiency improvement module  1210 , a power comparison module  1212 , and an orientation determination module  1214 . Further structural and operational embodiments will be apparent to persons skilled in the relevant art(s) based on the discussion regarding flowchart  1100 . Flowchart  1100  is described as follows. 
         [0108]    As shown in  FIG. 11 , the method of flowchart  1100  begins at step  1102 . In step  1102 , a wireless power transfer is initiated from a charging station to a portable electronic device via a wireless power link. In an example implementation, wireless power transfer module  1202  initiates the wireless power transfer via the wireless power link. 
         [0109]    At step  1104 , a determination is made whether a frequency parameter that specifies a resonant frequency of the portable electronic device is received via a wireless communication link. In an example implementation, parameter determination module  1206  determines whether a frequency parameter that specifies the resonant frequency of the portable electronic device is received. For instance, parameter receipt module  1204  may receive the frequency parameter. If the frequency parameter that specifies the resonant frequency of the portable electronic device is received via the wireless communication link, flow continues to step  1108 . Otherwise, flow continues to step  1110 . 
         [0110]    According to one example embodiment, the wireless power link and the wireless communication link are established via a common inductive link. According to another example embodiment, the wireless power link and the wireless communication link are established via respective inductive links. These example embodiments are provided for illustrative purposes and are not intended to be limiting. For instance, the wireless power link and the wireless communication link need not necessarily be inductive links. 
         [0111]    It should be noted that the frequency parameter may specify the resonant frequency of the portable electronic device in relative terms with respect to a reference frequency or in absolute terms. For example, the frequency parameter may specify a resonant frequency that is 5 megahertz (MHz) in relative terms by specifying the resonant frequency to be 3 MHz with respect to a reference frequency of 2 MHz. In another example, the frequency parameter may specify the same resonant frequency of 5 MHz in absolute terms to be 5 MHz, such that the resonant frequency is not specified with respect to a reference frequency. 
         [0112]    A reference frequency may be any suitable frequency. For example, a non-radiative magnetic field, which oscillates at an oscillating frequency, may mediate the wireless power transfer. For instance, the charging station may generate the non-radiative magnetic field, and power may be wirelessly transferred from the charging station to the portable electronic device through inductive coupling and/or resonant inductive coupling. In accordance with this example, the oscillating frequency at which the non-radiative magnetic field oscillates may serve as the reference frequency. 
         [0113]    At step  1106 , a determination is made whether a frequency at which a non-radiative magnetic field that mediates the wireless power transfer oscillates is substantially equal to the resonant frequency of the portable electronic device. In an example implementation, frequency comparison module  1208  determines whether the frequency at which the non-radiative magnetic field oscillates is substantially equal to the resonant frequency of the portable electronic device. If the frequency at which the non-radiative magnetic field oscillates is substantially equal to the resonant frequency of the portable electronic device, flow continues to step  1110 . Otherwise, flow continues to step  1108 . 
         [0114]    At step  1108 , the frequency at which the non-radiative magnetic field oscillates is changed to be substantially equal to the resonant frequency of the portable electronic device. In an example implementation, efficiency improvement module  1210  changes the frequency at which the non-radiative magnetic field oscillates. It will be recognized that steps  1106  and  1108  may be omitted if a non-radiative field does not mediate the wireless power transfer. 
         [0115]    At step  1110 , a determination is made whether a power parameter that specifies a magnitude of power requested by the portable electronic device is received via the wireless communication link. The power parameter may specify the magnitude of power requested by the portable electronic device in relative terms with respect to a reference magnitude of power or in absolute terms. For example, the magnitude of power provided to the portable electronic device with respect to the wireless power transfer from the charging station may serve as the reference magnitude of power. In an example implementation, parameter determination module  1206  determines whether a power parameter that specifies a magnitude requested by the portable electronic device is received via the wireless communication link. For instance, parameter receipt module  1204  may receive the power parameter. If a power parameter that specifies a magnitude of power requested by the portable electronic device is received, flow continues to step  1112  shown in  FIG. 11B . Otherwise, flow continues to step  1120  shown in  FIG. 11C . 
         [0116]    At step  1112 , a determination is made whether a magnitude of power that is provided by the charging station with respect to the wireless power transfer is greater than the magnitude of power requested by the portable electronic device. In an example implementation, power comparison module  1212  determines whether the magnitude of power that is provided by the charging station with respect to the wireless power transfer is greater than the magnitude of power requested by the portable electronic device. If the magnitude of power that is provided by the charging station with respect to the wireless power transfer is greater than the magnitude of power requested by the portable electronic device, flow continues to step  1114 . Otherwise, flow continues to step  1116 . 
         [0117]    At step  1114 , the magnitude of power that is provided by the charging station with respect to the wireless power transfer is reduced to be substantially equal to the magnitude of power requested by the portable electronic device. In an example implementation, efficiency improvement module  1210  reduces the magnitude of power that is provided by the charging station with respect to the wireless power transfer to be substantially equal to the magnitude of power requested by the portable electronic device. Upon completion of step  1114 , flow continues to step  1120 , which is shown in  FIG. 11C . 
         [0118]    At step  1116 , a determination is made whether the magnitude of power that is provided by the charging station with respect to the wireless power transfer is less than the magnitude of power requested by the portable electronic device. In an example implementation, power comparison module  1212  determines whether the magnitude of power that is provided by the charging station with respect to the wireless power transfer is less than the magnitude of power requested by the portable electronic device. If the magnitude of power that is provided by the charging station with respect to the wireless power transfer is less than the magnitude of power requested by the portable electronic device, flow continues to step  1118 . Otherwise, flow continues to step  1120 , which is shown in  FIG. 11C . 
         [0119]    At step  1118 , the magnitude of power that is provided by the charging station with respect to the wireless power transfer is increased to be substantially equal to the magnitude of power requested by the portable electronic device. In an example implementation, efficiency improvement module  1210  increases the magnitude of power that is provided by the charging station with respect to the wireless power transfer to be substantially equal to the magnitude of power requested by the portable electronic device. 
         [0120]    Persons skilled in the relevant art(s) will recognize that it may not be desirable to increase the magnitude of power that is provided by the charging station with respect to the wireless power transfer even if a determination is made that such magnitude of power is less than the magnitude of power requested by the portable electronic device. For example, efficiency of the wireless power transfer may be better served by not increasing the magnitude of power that is provided by the charging station with respect to the wireless power transfer. Accordingly, step  1118  need not necessarily be performed in response to an affirmative determination at step  1116 . 
         [0121]    Upon completion of step  1118 , flow continues to step  1120 , which is shown in  FIG. 11C . At step  1120 , a determination is made whether a power parameter that specifies a magnitude of power consumed by the portable electronic device with respect to the wireless power transfer is received via the wireless communication link. The power parameter may specify the magnitude of power consumed by the portable electronic device in relative terms with respect to a reference magnitude of power or in absolute terms. For example, the magnitude of power provided to the portable electronic device with respect to the wireless power transfer from the charging station may serve as the reference magnitude of power. In an example implementation, parameter determination module  1206  determines whether a power parameter that specifies the magnitude of power consumed by the portable electronic device with respect to the wireless power transfer is received via the wireless communication link. For instance, parameter receipt module  1204  may receive the power parameter. If a power parameter that specifies the magnitude of power consumed by the portable electronic device with respect to the wireless power transfer is received, flow continues to step  1122 . Otherwise, flow continues to step  1126 . 
         [0122]    At step  1122 , a determination is made whether the magnitude of power that is provided by the charging station with respect to the wireless power transfer is greater than the magnitude of power consumed by the portable electronic device with respect to the wireless power transfer. In an example implementation, power comparison module  1212  determines whether the magnitude of power that is provided by the charging station with respect to the wireless power transfer is greater than the magnitude of power consumed by the portable electronic device with respect to the wireless power transfer. If the magnitude of power that is provided by the charging station with respect to the wireless power transfer is greater than the magnitude of power consumed by the portable electronic device with respect to the wireless power transfer, flow continues to step  1124 . Otherwise, flow continues to step  1126 . 
         [0123]    At step  1124 , the magnitude of power that is provided by the charging station with respect to the wireless power transfer is reduced to be substantially equal to the magnitude of power consumed by the portable electronic device with respect to the wireless power transfer. In an example implementation, efficiency improvement module  1210  reduces the magnitude of power that is provided by the charging station with respect to the wireless power transfer. 
         [0124]    At step  1126 , a determination is made whether a power parameter that specifies a maximum safe power that the portable electronic device is capable of consuming without substantial risk of damaging the portable electronic device is received via the wireless communication link. In an example implementation, parameter determination module  1206  determines whether a power parameter that specifies the maximum safe power is received via the wireless communication link. For instance, parameter receipt module  1204  may receive the power parameter. If a power parameter that specifies the maximum safe power is received, flow continues to step  1128 , which is shown in  FIG. 11D . Otherwise, flow continues to step  1130 , which is also shown in  FIG. 11D . 
         [0125]    The substantial risk of damage may be defined as a relatively high likelihood that performance of the portable electronic device will become substantially hindered, that the portable electronic device will become inoperable, or any other suitable definition. The power parameter may specify the maximum safe power in relative terms with respect to a reference magnitude of power or in absolute terms. For example, the magnitude of power provided to the portable electronic device with respect to the wireless power transfer from the charging station may serve as the reference magnitude of power. 
         [0126]    At step  1128 , the magnitude of power that is provided by the charging station with respect to the wireless power transfer is controlled to be no greater than the maximum safe power. For instance, if the magnitude of power that is provided by the charging station with respect to the wireless power transfer is greater than the maximum safe power before performance of step  1128 , the magnitude of power that is provided by the charging station with respect to the wireless power transfer may be reduced at step  1128  to be no greater than the maximum safe power. If the magnitude of power that is provided by the charging station with respect to the wireless power transfer is less than or equal to the maximum safe power before performance of step  1128 , the magnitude of power that is provided by the charging station with respect to the wireless power transfer may be maintained at step  1128  to be no greater than the maximum safe power. In an example implementation, efficiency improvement module  1210  controls the magnitude of power that is provided by the charging station with respect to the wireless power to be no greater than the maximum safe power. 
         [0127]    At step  1130 , a determination is made whether a position parameter that specifies a position of the portable electronic device is received via the wireless communication link. The position parameter may specify the position of the portable electronic device in relative terms with respect to a reference position or in absolute terms. For example, the position of the charging station may serve as the reference position. In an example implementation, parameter determination module  1206  determines whether a position parameter that specifies a position of the portable electronic device is received via the wireless communication link. If a position parameter that specifies a position of the portable electronic device is received, flow continues to step  1136 . Otherwise, flowchart  1100  ends. 
         [0128]    At step  1132  a determination is made whether an orientation of a transfer element of the charging station that generates the magnetic field for performing the wireless power transfer is optimized with respect to the position of the portable electronic device. For instance, the transfer element may be a coil through which a current is provided to generate the magnetic field for performing the wireless power transfer. In an example implementation, orientation determination module  1214  determines whether the orientation of the transfer element is optimized with respect to the position of the portable electronic device. If the orientation of the transfer element is optimized with respect to the position of the portable electronic device, flowchart  1100  ends. Otherwise, flow continues to step  1134 . 
         [0129]    At step  1134 , the orientation of the transfer element is changed based on the position parameter to increase inductive coupling between the transfer element of the charging station and a receiving element of the portable electronic device. For instance, changing the orientation of the transfer element may include but is not limited to moving the transfer element vertically, horizontally, or in another direction; rotating the transfer element; etc. In an example implementation, efficiency improvement module  1210  changes the orientation of the transfer element. It will be recognized that steps  1130 ,  1132 , and  1134  may be omitted if the charging station does not generate a magnetic field for performing the wireless power transfer. 
         [0130]    In some example embodiments, one or more steps  1102 ,  1104 ,  1106 ,  1108 ,  1110 ,  1112 ,  1114 ,  1116 ,  1118 ,  1120 ,  1122 ,  1124 ,  1126 ,  1128 ,  1130 ,  1132 , and/or  1134  of flowchart  1100  may not be performed. Moreover, steps in addition to or in lieu of steps  1102 ,  1104 ,  1106 ,  1108 ,  1110 ,  1112 ,  1114 ,  1116 ,  1118 ,  1120 ,  1122 ,  1124 ,  1126 ,  1128 ,  1130 ,  1132 , and/or  1134  may be performed. 
         [0131]    It will be recognized that charging station  1200  may not include one or more of wireless power transfer module  1202 , parameter receipt module  1204 , parameter determination module  1206 , frequency comparison module  1208 , efficiency improvement module  1210 , power comparison module  1212 , and/or orientation determination module  1214 . Furthermore, charging station  1200  may include modules in addition to or in lieu of wireless power transfer module  1202 , parameter receipt module  1204 , parameter determination module  1206 , frequency comparison module  1208 , efficiency improvement module  1210 , power comparison module  1212 , and/or orientation determination module  1214 . 
         [0132]      FIG. 13  depicts a flowchart  1300  of a method for increasing efficiency of wireless power transfer in accordance with an embodiment described herein. Flowchart  1300  may be performed by charging station  102 ,  602 ,  702 , or  802  of respective wireless power transfer system  100 ,  600 ,  700 , or  800  shown in respective  FIG. 1 ,  6 ,  7 , or  8 , for example. For illustrative purposes, flowchart  1300  is described with respect to a charging system  1400  shown in  FIG. 14 , which is an example of a charging station  102 ,  602 ,  702 , or  802 , according to an embodiment. 
         [0133]    As shown in  FIG. 14 , charging station  1400  includes a wireless power transfer module  1402 , a parameter analysis module  1404 , and an efficiency improvement module  1406 . Further structural and operational embodiments will be apparent to persons skilled in the relevant art(s) based on the discussion regarding flowchart  1300 . Flowchart  1300  is described as follows. 
         [0134]    As shown in  FIG. 13 , the method of flowchart  1300  begins at step  1302 . In step  1302 , power is wirelessly transferred to a portable electronic device via a wireless power link. In an example implementation, wireless power transfer module  1402  wirelessly transfers the power to the portable electronic device via the wireless power link. 
         [0135]    At step  1304 , a parameter received via a wireless communication link regarding the portable electronic device with respect to the wireless transfer of the power is analyzed. For instance, the analysis may include but is not limited to comparing the parameter to a reference parameter to determine whether the parameter and the reference parameter are substantially same; comparing the parameter to a range of parameters to determine whether the parameter is within the range; comparing the parameter to a threshold to determine whether the parameter reaches the threshold; perform a mathematical operation with respect to the parameter to estimate the efficiency with respect to the wireless transfer of power; etc. In an example implementation, parameter analysis module  1404  analyzes the parameter received via the wireless communication link. 
         [0136]    At step  1306 , efficiency with respect to the wireless power transfer of the power is increased based on analysis of the parameter. In an example implementation, efficiency improvement module  1406  increases the efficiency with respect to the wireless transfer of the power. 
         [0137]      FIG. 15  depicts a flowchart  1500  of a method for increasing efficiency of wireless power transfer in accordance with an embodiment described herein. Flowchart  1500  may be performed by charging station  102 ,  602 ,  702 , or  802  of respective wireless power transfer system  100 ,  600 ,  700 , or  800  shown in respective  FIG. 1 ,  6 ,  7 , or  8 , for example. For illustrative purposes, flowchart  1500  is described with respect to a charging system  1600  shown in  FIG. 16 , which is an example of a charging station  102 ,  602 ,  702 , or  802 , according to an embodiment. 
         [0138]    As shown in  FIG. 16 , charging station  1600  includes a wireless power transfer module  1602 , a parameter analysis module  1604 , and an efficiency improvement module  1606 . Wireless power transfer module  1602  includes a field generation module  1608  and a coupling module  1610 . Efficiency improvement module  1606  includes a field manipulation module  1612 . Further structural and operational embodiments will be apparent to persons skilled in the relevant art(s) based on the discussion regarding flowchart  1500 . Flowchart  1500  is described as follows. 
         [0139]    As shown in  FIG. 15 , the method of flowchart  1500  begins at step  1502 . In step  1502 , a magnetic field is generated. In an example implementation, field generation module  1608  generates the magnetic field. For instance, field generation module  1608  may include coil through which a current is provided to generate the magnetic field. The field may be a non-radiative magnetic field, though the scope of the example embodiments is not limited in this respect. 
         [0140]    At step  1504 , power is wirelessly transferred to a portable electronic device via a wireless power link using the magnetic field. For example, the magnetic field may couple with a coil in the portable electronic device that is configured to be responsive to the magnetic field. In accordance with this example, the power may be wirelessly transferred in accordance with an inductive coupling technique, a resonant inductive coupling technique, or any other suitable technique. In an example implementation, coupling module  1610  wirelessly transfers the power to the portable electronic device. 
         [0141]    At step  1506 , a parameter received via a wireless communication link regarding the portable electronic device with respect to the wireless transfer of the power is analyzed. In an example implementation, parameter analysis module  1604  analyzes the parameter received via the wireless communication link. 
         [0142]    At step  1508 , a characteristic of the magnetic field is changed to increase efficiency with respect to the wireless transfer of the power based on analysis of the parameter. The characteristic may include but is not limited to a magnitude of the magnetic field, a directionality associated with the magnetic field, a frequency at which the magnetic field oscillates, etc. In an example implementation, field manipulation module  1612  changes the characteristic of the magnetic field to increase the efficiency with respect to the wireless transfer of the power. 
         [0143]      FIGS. 17-21  depict flowcharts  1700 ,  1800 ,  1900 ,  2000 , and  2100  of methods for increasing efficiency of wireless power transfer in accordance with embodiments described herein. Each of flowcharts  1700 ,  1800 ,  1900 ,  2000 , and  2100  may be performed by portable electronic device  104 ,  604 ,  704 , or  804  of respective wireless power transfer system  100 ,  600 ,  700 , or  800  shown in respective  FIG. 1 ,  6 ,  7 , or  8 , for example. For illustrative purposes, flowcharts  1700 ,  1800 ,  1900 ,  2000 , and  2100  are described with respect to portable electronic device  2200  shown in  FIG. 22 , which is an example of a portable electronic device  104 ,  604 ,  704 , or  804 , according to an embodiment. 
         [0144]    As shown in  FIG. 22 , portable electronic device  2200  includes a wireless power receipt module  2202  and a parameter module  2204 . Further structural and operational embodiments will be apparent to persons skilled in the relevant art(s) based on the discussion regarding flowcharts  1700 ,  1800 ,  1900 ,  2000 , and  2100 . Flowcharts  1700 ,  1800 ,  1900 ,  2000 , and  2100  are described in the following discussion. 
         [0145]    As shown in  FIG. 17 , the method of flowchart  1700  begins at step  1702 . In step  1702 , power is wirelessly received for a first period of time at a portable electronic device from a charging station via a wireless power link having a first transmission efficiency. Wirelessly receiving power for the first period of time may be performed in accordance with an inductive coupling technique, a resonant inductive coupling technique, or any other suitable technique. In an example implementation, wireless power receipt module  2202  wirelessly receives power for the first period of time. 
         [0146]    At step  1704 , at least one parameter regarding the portable electronic device with respect to receipt of power during the first period of time is provided to the charging station via a wireless communication link. For instance, the at least one parameter may be provided to the charging station via the wireless communication link in accordance with a Near Field Communication (NFC) protocol, a Bluetooth™ protocol, a ZigBee® protocol, an IEEE 802.11 protocol, or any other suitable protocol. The wireless power link and the wireless communication link may be implemented as separate links or as a common link. The wireless power link and the wireless communication link may be inductive links, though the scope of the example embodiments is not limited in this respect. In an example implementation, parameter module  2204  provides the at least one parameter to the charging station. 
         [0147]    At step  1706 , power is wirelessly received for a second period of time at the portable electronic device from the charging station via the wireless power link having a second transmission efficiency that is greater than the first transmission efficiency in response to providing the at least one parameter to the charging station. Wirelessly receiving power for the second period of time may be performed in accordance with an inductive coupling technique, a resonant inductive coupling technique, or any other suitable technique. In an example implementation, wireless power receipt module  2202  wirelessly receives power for the second period of time. 
         [0148]    As shown in  FIG. 18 , the method of flowchart  1800  begins at step  1802 . In step  1802 , power is wirelessly received for a first period of time at a portable electronic device from a charging station via a wireless power link having a first transmission efficiency. In an example implementation, wireless power receipt module  2202  wirelessly receives power for the first period of time. 
         [0149]    At step  1804 , a frequency parameter that specifies a resonant frequency of the portable electronic device is provided to charging station via a wireless communication link. The frequency parameter may specify the resonant frequency in relative terms with respect to a reference frequency or in absolute terms. In an example implementation, parameter module  2204  provides the frequency parameter to the charging station. 
         [0150]    At step  1806 , power is wirelessly received for a second period of time at the portable electronic device from the charging station via the wireless power link having a second transmission efficiency that is greater than the first transmission efficiency in response to providing the frequency parameter to the charging station. The first efficiency is based on resonant inductive coupling of a first coil in the portable electronic device with a second coil in the charging station that generates a non-radiative magnetic field oscillating at a first frequency that is not substantially same as the resonant frequency of the portable electronic device. The second efficiency is based on resonant inductive coupling of the first coil in the portable electronic device with the second coil in the charging station that generates a non-radiative magnetic field oscillating at a second frequency that is substantially same as the resonant frequency of the portable electronic device. In an example implementation, wireless power receipt module  2202  wirelessly receives power for the second period of time. 
         [0151]    As shown in  FIG. 19 , the method of flowchart  1900  begins at step  1902 . In step  1902 , a magnitude of power that is greater than a reference magnitude of power is wirelessly received for a first period of time at a portable electronic device from a charging station via a wireless power link having a first transmission efficiency. In an example implementation, wireless power receipt module  2202  wirelessly receives the magnitude of power that is greater than the reference magnitude of power for the first period of time. 
         [0152]    At step  1904 , a power parameter is provided to the charging station via a wireless communication link. The power parameter specifies the reference magnitude of power as being requested by the portable electronic device. The power parameter may specify the reference magnitude of power in relative terms with respect to a second reference magnitude of power or in absolute terms. For example, the magnitude of power wirelessly received for the first period of time at the portable electronic device may serve as the second reference magnitude of power. In an example implementation, parameter module  2204  provides the power parameter to the charging station. 
         [0153]    At step  1906 , a magnitude of power that is substantially same as the reference magnitude of power is wirelessly received for a second period of time at the portable electronic device from the charging station via the wireless power link having a second transmission efficiency that is greater than the first transmission efficiency in response to providing the power parameter to the charging station. In an example implementation, wireless power receipt module  2202  wirelessly receives the magnitude of power that is substantially same as the reference magnitude of power for the second period of time. 
         [0154]    As shown in  FIG. 20 , the method of flowchart  2000  begins at step  2002 . In step  2002 , a magnitude of power is wirelessly received at a portable electronic device for a first period of time from a charging station via a wireless power link having a first transmission efficiency. The magnitude of power wirelessly received for the first period of time is greater than a magnitude of power consumed by the portable electronic device for the first period of time. In an example implementation, wireless power receipt module  2202  wirelessly receives the magnitude of power for the first period of time. 
         [0155]    At step  2004 , a power parameter that specifies the magnitude of power consumed by the portable electronic device during the first period of time is provided to the charging station via a wireless communication link. The power parameter may specify the magnitude of power consumed by the portable electronic device during the first period of time in relative terms with respect to a reference magnitude of power or in absolute terms. For example, the magnitude of power wirelessly received at the portable electronic device for the first period of time may serve as the reference magnitude of power. In an example implementation, parameter module  2204  provides the power parameter to the charging station. 
         [0156]    At step  2006 , a magnitude of power is wirelessly received at the portable electronic device for a second period of time from the charging station via the wireless power link having a second transmission efficiency that is greater than the first transmission efficiency in response to providing the power parameter to the charging station. The magnitude of power wirelessly received for the second period of time is substantially same as the magnitude of power consumed by the portable electronic device for the second period of time. In an example implementation, wireless power receipt module  2202  wirelessly receives the magnitude of power for the second period of time. 
         [0157]    As shown in  FIG. 21 , the method of flowchart  2100  begins at step  2102 . In step  2102 , a magnitude of power that is greater than a maximum safe power, which a portable electronic device is capable of consuming without substantial risk of damaging the portable electronic device, is wirelessly received for a first period of time at the portable electronic device from a charging station via a wireless power link having a first transmission efficiency. In an example implementation, wireless power receipt module  2202  wirelessly receives the magnitude of power for the first period of time. 
         [0158]    At step  2104 , a power parameter that specifies the maximum safe power is provided to the charging station via a wireless communication link. The power parameter may specify the maximum safe power in relative terms with respect to a reference magnitude of power or in absolute terms. For example, the magnitude of power wirelessly received for the first period of time at the portable electronic device may serve as the reference magnitude of power. In an example implementation, parameter module  2204  provides the power parameter that specifies the maximum safe power to the charging station. 
         [0159]    At step  2106 , a magnitude of power that is no greater than the maximum safe power is wirelessly received for a second period of time at the portable electronic device from the charging station via the wireless power link having a second transmission efficiency that is greater than the first transmission efficiency in response to providing the power parameter to the charging station. In an example implementation, wireless power receipt module  2202  wirelessly receives the magnitude of power for the second period of time. 
       V. Conclusion 
       [0160]    While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be understood by those skilled in the relevant art(s) that various changes in form and details may be made to the embodiments described herein without departing from the spirit and scope of the invention as defined in the appended claims. Accordingly, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.