Patent Publication Number: US-9889754-B2

Title: System and method for reducing leakage flux in wireless electric vehicle charging systems

Description:
TECHNOLOGICAL FIELD 
     The present disclosure relates generally to wireless power transfer, and more specifically to devices, systems, and methods related to wireless power transfer to remote systems such as vehicles including batteries, and in particular to magnetic field distribution optimization for integration of electronic components in inductive power transfer systems. 
     BACKGROUND 
     Remote systems, such as vehicles, have been introduced that include locomotion power derived from electricity received from an energy storage device such as a battery. For example, hybrid electric vehicles include on-board chargers that use power from vehicle braking and traditional motors to charge the vehicles. Vehicles that are solely electric generally receive the electricity for charging the batteries from other sources. Battery electric vehicles (electric vehicles) are often proposed to be charged through some type of wired alternating current (AC) such as household or commercial AC supply sources. The wired charging connections require cables or other similar connectors that are physically connected to a power supply. Cables and similar connectors may sometimes be inconvenient or cumbersome and have other drawbacks. Wireless Electric Vehicle Charging (WEVC) systems that are capable of transferring power in free space (e.g., via a wireless field) to be used to charge electric vehicles may overcome some of the deficiencies of wired charging solutions. As such, wireless charging systems and methods that efficiently and safely transfer power for charging electric vehicles are desirable. 
     SUMMARY 
     The disclosure provides an apparatus for collecting leakage magnetic flux of a wireless field in a wireless power transfer system. The apparatus comprises a wireless power receiver configured to couple to the wireless field generated by a wireless power transmitter. A portion of the wireless field comprises the leakage magnetic flux. The apparatus further comprises a leakage collector comprising a ferromagnetic material and configured to absorb or redirect at least a portion of the leakage magnetic flux away from an outer edge of an electric vehicle. The leakage collector is positioned at a first distance from the wireless power receiver within the wireless field. 
     The disclosure provides method for collecting leakage magnetic flux of a wireless field in a wireless power transfer system. The method comprises providing a leakage collector positioned at a first distance from a wireless power receiver within the wireless field. The leakage collector comprises a ferromagnetic material. The method further comprises coupling the leakage collector to the wireless field generated by the wireless power transmitter. A portion of the wireless field comprises the leakage magnetic flux. The method further comprises absorbing or redirecting at least a portion of the leakage magnetic flux away from an outer edge of an electric vehicle. 
     The disclosure further provides an apparatus for collecting leakage magnetic flux of a wireless field in a wireless power transfer system. The apparatus comprises means for coupling to a wireless field generated by a wireless power transmitter. A portion of the wireless field comprises the leakage magnetic flux. The apparatus further comprises means for absorbing or redirecting at least a portion of the leakage magnetic flux away from an outer edge of an electric vehicle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of an exemplary wireless power transfer system for charging an electric vehicle, in accordance with an exemplary implementation. 
         FIG. 2  is a functional block diagram of a wireless power transfer system, in accordance with an exemplary implementation. 
         FIG. 3  is a functional block diagram of a wireless power transfer system having leakage field collectors, in accordance with an exemplary implementation. 
         FIG. 4  illustrates an electric vehicle charging induction coil housing and leakage field collectors along a lower surface of an electric vehicle, in accordance with an exemplary implementation. 
         FIG. 5A - FIG. 5I  are illustrations of the bottom of an electric vehicle fitted with a leakage field collector in accordance with an implementation. 
         FIG. 6A  is an internal view along a bottom portion of an electric vehicle according to an implementation. 
         FIG. 6B  is an internal view of a right hand side of the bottom portion of the electric vehicle of  FIG. 6A , according to an implementation. 
         FIG. 6C  is an internal view of a right hand side of the bottom portion of the electric vehicle of  FIG. 6A , according to an implementation. 
         FIG. 6D  is an internal view of a right hand side of the bottom portion of the electric vehicle of  FIG. 6A , according to an implementation. 
         FIG. 7A  depicts a magnetic field intensity diagram, according to an implementation. 
         FIG. 7B  depicts a magnetic field intensity diagram, according to another implementation. 
         FIG. 7C  shows a plot diagram illustrating a comparison of the attenuation of the magnitude of the leakage fields of  FIG. 7A  and  FIG. 7B  as a function of distance. 
         FIG. 8  is a flowchart depicting a method according to an implementation 
     
    
    
     The various features illustrated in the drawings may not be drawn to scale. Accordingly, the dimensions of the various features may be arbitrarily expanded or reduced for clarity. In addition, some of the drawings may not depict all of the components of a given system, method or device. Finally, like reference numerals may be used to denote like features throughout the specification and figures. 
     DETAILED DESCRIPTION 
     The detailed description set forth below in connection with the appended drawings is intended as a description of exemplary implementations and is not intended to represent the only implementations which may be practiced. The term “exemplary” used throughout this description means “serving as an example, instance, or illustration,” and should not necessarily be construed as preferred or advantageous over other exemplary implementations. The detailed description includes specific details for the purpose of providing a thorough understanding of the exemplary implementations. In some instances, some devices are shown in block diagram form. 
     Wirelessly transferring power may refer to transferring any form of energy associated with electric fields, magnetic fields, electromagnetic fields, or otherwise from a transmitter to a receiver without the use of physical electrical conductors (e.g., power may be transferred through free space). The power output into a wireless field (e.g., a magnetic field) may be received, captured by, or coupled by a “receiving coil” to achieve power transfer. 
     By way of example and not limitation, a wireless power receiver is described herein in the form of an electric vehicle (EV). Furthermore, other remote systems that may be at least partially powered using a chargeable energy storage device are also contemplated (e.g., electronic devices such as mobile or personal computing devices and the like). 
       FIG. 1  is a diagram of an exemplary wireless power transfer system for charging an electric vehicle, in accordance with an exemplary implementation. A wireless power transfer system  100  enables charging of an electric vehicle  105  while the electric vehicle  105  is parked near a base wireless charging system  102   a.    
     The electric vehicle  105  is used herein to describe a wireless power receiver. The vehicle  105  utilizes, as part of its locomotion capabilities, electrical power derived from a chargeable energy storage device (e.g., one or more rechargeable electrochemical cells or other type of battery). As non-limiting examples, some electric vehicles like the vehicle  105  may be hybrid electric vehicles that include besides electric motors, a traditional combustion engine for direct locomotion or to charge the vehicle&#39;s battery. In an implementation, the electric vehicle  105  may draw all locomotion ability from electrical power. Accordingly, the electric vehicle  105  is not limited to an automobile, as shown, and may include motorcycles, carts, scooters, and the like. 
     As shown, spaces for two electric vehicles are illustrated in a parking area to be parked over corresponding base wireless charging system  102   a  and  102   b . In some implementations, a local distribution center  130  may be connected to a power backbone  132  and configured to provide an alternating current (AC) or a direct current (DC) supply through a power link  110  to the base wireless charging system  102   a . The base wireless charging system  102   a  also includes a base system induction coil  104   a  for wirelessly transferring or receiving power. The electric vehicle  105  may include a battery unit  114 , an electric vehicle charging induction coil  116 , and an electric vehicle wireless charging system  118 . The electric vehicle charging induction coil  116  may interact with the base system induction coil  104   a  for example, via a region of the electromagnetic field generated by the base system induction coil  104   a . In certain implementations, the electric vehicle charging induction coil can be disposed within a volume of an electric vehicle charging induction coil housing (not illustrated in  FIG. 1 ). 
     In some exemplary implementations, the electric vehicle charging induction coil  116  may receive power when the electric vehicle charging induction coil  116  is located in an energy field produced by the base system induction coil  104   a . The field corresponds to a region where energy output by the base system induction coil  104   a  may be captured by an electric vehicle charging induction coil  116 . For example, the energy output by the base system induction coil  104   a  may be at a level sufficient to charge or power the electric vehicle  105 . In some cases, the field may correspond to the “near field” of the base system induction coil  104   a . The near-field may correspond to a region in which there are strong reactive fields resulting from the currents and charges in the base system induction coil  104   a  that do not radiate power away from the base system induction coil  104   a . In some cases the near-field may correspond to a region that is within about ½π of wavelength of the base system induction coil  104   a  (and vice versa for the electric vehicle charging induction coil  116 ). 
     Local distribution center  130  may be configured to communicate with external sources (e.g., a power grid) via a communication backhaul  134 , and with the base wireless charging system  102   a  via a communication link  168 . 
     In some implementations the electric vehicle charging induction coil  116  may be aligned with the base system induction coil  104   a  and, therefore, disposed within a near-field region simply by the driver positioning the electric vehicle  105  correctly relative to the base system induction coil  104   a . In other implementations, a sensor circuit or a controller (described with respect to  FIG. 2 ) may provide a driver with visual feedback, auditory feedback, or combinations thereof to indicate when the electric vehicle  105  is properly placed for wireless power transfer. In some implementations, an autopilot system (not shown in this figure) may move the electric vehicle  105  back and forth as required (e.g., in zig-zag movements) until an alignment error has reached a tolerable value. This function may be performed automatically and autonomously by the electric vehicle  105  without or with only minimal driver intervention provided that the electric vehicle  105  is equipped with a servo steering wheel, ultrasonic sensors, and intelligence to adjust the vehicle. In some implementations, the electric vehicle charging induction coil  116 , the base system induction coil  104   a , or a combination thereof may have functionality for displacing and moving the induction coils  116  and  104   a  relative to each other to more accurately orient them and develop more efficient magnetic coupling there between. 
     The base wireless charging system  102   a  may be located in a variety of locations. As non-limiting examples, some suitable locations include a parking area at a home of the electric vehicle  112  owner, parking areas reserved for electric vehicle wireless charging modeled after conventional petroleum-based filling stations, and parking lots at other locations such as shopping centers and places of employment. 
     Charging electric vehicles wirelessly may provide numerous benefits. For example, charging may be performed automatically, virtually without driver intervention and manipulations thereby improving convenience to a user. Wireless power transfer systems may also eliminate exposed electrical contacts and moving parts minimizing (or eliminating) mechanical breakdown, thereby improving reliability of the wireless power transfer system  100 . Manipulations with cables and connectors may not be needed, and there may be no cables, plugs, or sockets that may be exposed to moisture and water in an outdoor environment, thereby improving safety. There may also be no sockets, cables, and plugs visible or accessible, thereby reducing potential vandalism of power charging devices. Further, since an electric vehicle  105  may be used as distributed storage devices to stabilize a power grid, a docking-to-grid solution may be used to increase availability of vehicles for Vehicle-to-Grid (V2G) operation. 
     The wireless power transfer system  100  as described with reference to  FIG. 1  may also provide aesthetic and non-impedimental advantages. For example, there may be no charge columns and cables that may be impedimental for vehicles and/or pedestrians. 
     As a further explanation of the vehicle-to-grid capability, the wireless power transmit and receive capabilities may be configured to be reciprocal such that the base wireless charging system  102   a  transfers power to the electric vehicle  105  and the electric vehicle  105  transfers power to the base wireless charging system  102   a  e.g., in times of energy shortfall. This capability may be useful to stabilize the power distribution grid by allowing electric vehicles to contribute power to the overall distribution system in times of energy shortfall caused by over demand or shortfall in renewable energy production (e.g., wind or solar). 
       FIG. 2  is a functional block diagram of a wireless power transfer system, in accordance with an exemplary implementation. The system  200  includes a transmitter  204  and a receiver  208 . The transmitter  204  may perform substantially similar functions to the base wireless charging system  102   a . Further, the receiver  208  may perform substantially similar functions as the electric vehicle charging system  114  and the electric vehicle charging induction coil  116  of  FIG. 1 . 
     As shown in  FIG. 2 , the transmitter  204  may include a communication circuit  229  electrically connected to a transmit circuitry  206 . The transmit circuitry  206  may include an oscillator  222 , operationally coupled to a driver circuit  224  and a filter and matching circuit  226 . The oscillator  222  may be configured to generate a signal at a desired frequency that may be adjusted in response to a frequency control signal  223 . The oscillator  222  may provide the oscillator signal to the driver circuit  224 . The driver circuit  224  may be configured to drive the transmit antenna  214  at, for example, a resonant frequency of the transmit antenna  214  based on an input voltage signal (VD)  225 . In one non-limiting example, the driver circuit  224  may be a switching amplifier configured to receive a square wave from the oscillator  222  and output a sine wave. 
     The filter and matching circuit  226  may filter out harmonics or other unwanted frequencies and match the impedance of the transmitter  204  to the transmit antenna  214 . As a result of driving the transmit antenna  214 , the transmit antenna  214  may generate a wireless field  216  to wirelessly output power at a level sufficient for charging a battery  236  of an electric vehicle, for example. 
     The transmitter  204  may further include a controller circuit  228  electrically connected to the communication circuit  229 . The communication circuit  229  may be configured to communicate with the communication circuit  239  within the receiver  208  over a communications link  219 . Communications from the transmitter  204  to the receiver  208  via communications link  219  may comprise information regarding charging processes, including increased or decreased power capabilities of the transmitter  204  and other information associated with the charging capabilities of the transmitter  204 . Unless stated otherwise, each component within the transmit circuitry  206  may have substantially the same functionality as the respective components within any complementary transmit circuitry within the base wireless charging system  102  as previously described in connection with  FIG. 1 . 
     The receiver  208  may comprise a receive coil  218  and a receive circuitry  210 , similar to the electric vehicle charging coil  116  and electric vehicle charging system  118  of  FIG. 1 . The receive circuitry  210  may include a switching circuit  230  operationally connected to a match circuit  232 , and a rectifier circuit  234  operationally connected to the match circuit  232 . The receive coil  218  may be electrically connected to the switching circuit  230 . The switching circuit may selectively connect the receive coil  218  to the match circuit  232  or short circuit terminals of the receive coil  218  together. The match circuit  232  may be electrically connected to the rectifier circuit  234 . The rectifier circuit  234  may provide a DC current to a battery  236 . Unless stated otherwise, each component within the receive circuitry  210  may have substantially the same functionality as the respective components within any complementary receive circuitry within electric vehicle charging system  114  as previously described in connection with  FIG. 1 . 
     The receiver  208  may further include a sensor circuit  235  configured to sense a short circuit current or an open circuit voltage of the receive coil  218 . A controller circuit  238  may be electrically connected to, and receive sensor data from, the sensor circuit  235 . A communication circuit  239  may be connected to the controller circuit  238 . The communication circuit  239  may be configured to communicate with the communication circuit  229  within the transmitter  204  over the communications link  219 , similar to those noted above. Such communications may serve to indicate to the transmitter  204  specific power demands of the receiver  208 , charge state of the battery  236 , or other information related to the power requirements of the receiver  208 . 
     To provide power from the transmitter  204  to the receiver  208 , energy may be transmitted from the transmit coil  214  through a wireless field (e.g., a magnetic or electromagnetic field)  216  to the receive coil  218 . The transmit coil  214  and the transmit circuitry  206  form a resonant circuit having a particular resonant frequency. The receive coil  218  and the receive circuitry  210  form another resonant circuit having a particular resonant frequency. Because electromagnetic losses are minimized between two coupled resonant systems having the same resonant frequency, it is desirable for the resonant frequency associated with the receive coil  218  to be substantially the same as the resonant frequency associated with the transmit coil  214 . Thus, it is further desirable that the tuning topology for one or both of the transmit coil  214  and the receive coil  218  is not significantly affected by inductance or load changes. The embodiments disclosed herein may incorporate resonant or non-resonant architectures. 
     According to the above description, the controller circuit  238  may determine the maximum possible output current or voltage for any position of the receive coil  218  with respect to the transmit coil  214 . The controller circuit  238  may make such a determination before supplying current to the battery  236 . In another implementation, the controller circuit  238  may make such a determination during charging of the battery  236 . Such an implementation may provide a safety mechanism to ensure charging current and/or voltage remain within safe limits during the charging cycle. In yet another implementation the controller circuit  238  may make such a determination while a driver is driving the vehicle  105  ( FIG. 1 ) into a space for charging. 
     As noted above, a matched transmit coil  214  and receive coil  218  of the WEVC system  200  may minimize electromagnetic losses, however some loss remains in the form of leakage fields  212   a ,  212   b  (collectively “leakage fields”  212 ). The movement energy or power through the wireless field  216  (e.g., a magnetic field), or the flux generated by the transmit coil  214  does not typically travel in a straight line to the receive coil  218 . Instead, the wireless field  216  lines may emanate in some or all directions, away from the transmit coil  214  affected by the composition of any surrounding structures (e.g., the ground or the bottom of the electric vehicle  105 ). Accordingly, not all of the transmitted power actually arrives at the receive coil  218 . Some of the transmitted magnetic energy (flux) flows in sub-optimum directions, “leaking” out of the system, becoming “leakage flux,” or creating the leakage fields  212 . The leakage fields  212  may potentially have negative influence on surrounding electronics or creating a safety hazard for people nearby. Accordingly, it may be advantageous to minimize the leakage magnetic field  212  surrounding the transmit coil  214  and the receive coil  218 . 
       FIG. 3  is a functional block diagram of a wireless power transfer system having leakage field collectors, in accordance with an exemplary implementation. A WEVC system  300  is shown having the transmit coil  214  and the receive coil  218  substantially similar to those shown in  FIG. 2 . As shown, the transmit coil  214  may transmit the wireless field  216  in the direction of the receive coil  218 . The portions of the wireless field  216  received by the receive coil  218  may be converted into electrical power for the WEVC system  200  as described above, however not all of the energy of the wireless field  216  is actually received by the receive coil  218 . The wireless field  216  energy (flux) that is not used to transfer power to the receive coil  218  may be referred to as the leakage field  212 , shown flowing in less than optimum directions away from the transmit coil  214  toward the top and bottom of the page as the leakage field  212   a  and the leakage field  212   b . This leakage flux may be detrimental to surrounding electronics or people. 
     In an implementation, one or more leakage field collectors  350   a  and  350   b  (collectively “collectors”  350 ) may be positioned to redirect and/or absorb the respective stray leakage magnetic fields  212   a ,  212   b . The leakage field collectors  350  may be located at a distance  352  from the receive coil  218  or a distance  353  from the transmit coil  214 . The collectors  350  may comprise certain ferrite or other ferromagnetic or ferrimagnetic composites such as soft magnetic composites (SMC), nanocrystalline magnetic materials, or plastic bonded ferrite powder among other materials. Certain ferrous materials such as iron oxides, nickel compositions, among others may also be implemented. Composition, placement, and geometry of the collectors  350  may be selected to allow the collectors  350  to redirect and absorb the leakage magnetic fields  212 . In another implementation, the collectors  350  may be further configured to oppose or negate the leakage magnetic fields  212 . 
     Certain WEVC systems  100 ,  200 ,  300  may exhibit magnetic fields (e.g. the field  216 , the leakage field  212 ) of varying strengths and patterns. Accordingly, selection and composition of the collectors  350  may depend on characteristics of a power transmitter and power receiver pair (e.g., the transmitter  214  and the receiver  218 ) paid. In at least one implementation the collector  350  composition, geometry, and position may consider the position and size of the transmitter/receiver pair. Such a consideration may further include the magnitude and location of the leakage field  212  surrounding the electric vehicle  105 . 
     Similarly, electric vehicles  105  may have various physical dimensions and construction. Thus the electric vehicles  105  may have varying characteristics related to the leakage magnetic field  212 . Accordingly, selection or construction of the collectors  350  may consider a wide variety of physical characteristics of both the vehicle  105  and the collectors  350 . In at least one implementation, the collectors  350  may be selected or formed based on a specific leakage field  212  type and strength. The selection of the collectors  350  may therefore consider that certain leakage fields  212  may be stronger than others or have irregular flux patterns. Such a selection may further consider the presence of people in the vicinity of the vehicle  105  forming or shaping the leakage field  212  as needed. 
     In another implementation, selection of the collectors  350  may further consider position in relation to the receiver/transmitter, a height of the receiver  218  above the ground and above the transmitter  214  (not shown in this figure). 
     In addition to considering the above receiver/transmitter and vehicle  105  characteristics, the collectors  350  may take various shapes, sizes and be placed in various positions. The collectors may further have various cross sectional dimensions or three dimensional geometries. The collectors  350  may be formed in a specific shape or geometry (e.g., rectangular, square, curved, straight, segmented, etc.) to take advantage of the effect of a particular shape on the given leakage flux  212  pattern. 
     The collectors  350  may further be placed in a position that most effectively takes advantage of the selected shape and/or composition. For example, the collectors may be disposed a specific distance from the receiver  218  providing a certain amount of free space between the receiver  218  and the collectors  350 . The collectors may be placed at the front, rear, or the sides of the vehicle  105  (see  FIG. 5A - FIG. 5I ). 
     The orientation of the collectors  350  may further be considered. Certain leakage field  212  flux patterns may react differently to a collector  350  positions in parallel to the lines of flux versus collectors  350  placed orthogonal to them. 
     The collectors  350  may further be selected in varying quantities. For example, a segmented collector  350  (see the collectors  545   a ,  545   b  of  FIG. 5I ) may take advantage of the multiple smaller segments to shape the leakage field  212 . The smaller segments of such an implementation may also reduce the volume of material used in the collectors  350 . 
     In an implementation, the collectors  350  may be formed in one or more of a variety of possible geometries and placements, as discussed in  FIG. 5A - FIG. 6D . As shown in  FIG. 3 , the two collectors  350  are positioned within range of the wireless field  216 , nearest to and flanking the receive coil  218 . In an implementation of the WEVC system  300 , the receive coil  218  may be disposed on or in the bottom of an electric vehicle  105  ( FIG. 1 ) similar to the electric vehicle charging induction coil  116 . Accordingly, the collectors  350  may also be disposed on the bottom of the car, in proximity to the receive coil  218 . The positioning, distance from the transmit/receive coils, and geometry of the collectors  350  may affect the ability of the collectors  350  to redirect or absorb the leakage fields  312 . The geometry and distance between transmit coil  314  or the receive coil  318  and the collectors  350  is further described below with respect to  FIG. 4  and  FIG. 5A - FIG. 5I . 
     In an implementation, the collectors  350  may comprise low-reluctance ferromagnetic materials having a predetermined geometry and composition selected to most effectively direct, capture, collect, or “absorb” the leakage magnetic field  212  to reduce field emissions on the electric vehicle and the surroundings. The collectors  350  may comprise certain ferrite compositions or other ferromagnetic materials. As used herein, magnetic reluctance may be a scalar, expressed in terms of inverse henry (H −1 ). In general, air and vacuum have high reluctance while easily magnetized materials such as iron and most ferrous materials may have low reluctance. 
     Reluctance may be considered to have an inverse relationship with magnetic permeability: R=1/(μ A), where R is the scalar representing reluctance; l is the length of the magnetic circuit in meters; μ is the permeability of the material (dimensionless); and A is the cross sectional area in meters. Thus low reluctance materials are also considered to have “high magnetic permeability.” 
     As used herein, initial magnetic “permeability” generally refers to a measure of the ability of a material to support the formation of a magnetic field within itself (e.g., the collectors  350 ). Permeability is typically indicated by the constant, “μ,” or relative magnetic permeability, “μ r .” As used herein, relative permeability, generally refers to the ratio of the permeability of a specific medium to the permeability of free space (a vacuum), μ 0  (μ r =μ/μ 0 ). As a non-limiting example, ferrite may be said to have a relative magnetic permeability of μ r =2000; SMC: μ r =500; nanocrystalline magnetic material: μ r =1000; and plastic bonded ferrite powder: μ r =30. As a point of reference, iron (Fe) is commonly held to have a relative permeability of μ r =5000. The foregoing examples are provided as reference, as the magnetic permeability of many ferrous/ferromagnetic/ferrimagnetic materials may vary greatly with magnetic field strength (H). For example, the relative permeability of any material in the presence of a sufficiently high field strength may trend toward one (1). 
     Considering the foregoing, a magnetic field causes magnetic flux to follow the path of least magnetic reluctance through a material having high relative permeability. Accordingly, the low reluctance characteristics of the ferromagnetic collectors  350  may provide a path of least magnetic resistance for the leakage magnetic flux. Thus the collectors  350  may be used to influence the path of the magnetic flux, specifically the leakage fields  350 , toward the collectors  350 , thereby reducing magnetic field intensity in the vicinity of the receiver  208 . 
     In an implementation, the low reluctance materials of the collectors  350  placed in proximity to the receive coil  218  may attract magnetic flux, drawing the leakage field  212   a  in direction  356   a  and the leakage field  212   b  in direction  356   b  toward the collectors  350 , as opposed to outward toward external systems and people. Accordingly, the collectors  350  may absorb and influence leakage magnetic flux, and may not opposed or cancel the leakage magnetic fields. 
       FIG. 4  illustrates an electric vehicle charging induction coil housing and leakage field collectors along a lower surface of an electric vehicle, in accordance with an exemplary implementation. The wireless power transfer system  100  ( FIG. 1 ) may be used with a variety of electric vehicles  105  compatible with the wireless power transfer system  100  of  FIG. 1 . 
     As shown in  FIG. 4 , an electric vehicle  405 , similar to the electric vehicle  105 , is receiving wireless power from a WEVC system  400 . The system  400  may be substantially similar to the system  100  and be configured to supply the vehicle  405  with wireless power. The electric vehicle  405  may comprise a vehicle shield  406  disposed on the bottom of the vehicle  405  positioned between the wheels. In an implementation, the vehicle shield  406  may cover an extensive portion of the underside of the car and may comprise a structural portion of the vehicle  405 . In certain implementations where the vehicle shield comprises a structural portion of the vehicle  405 , a separate vehicle shield  406  may not be present. Accordingly, the presence of a specific component referred to as the “vehicle shield  406 ” in  FIG. 4  and in  FIG. 5A - FIG. 6D  may not be present in some implementations. The vehicle shield  406  and other subsequent implementations may, in certain implementations, be illustrative of the magnetic shielding characteristics of the vehicle  405  itself or the chassis as noted below in connection with  FIG. 6A - FIG. 6D . The vehicle shield  406  may also be referred to as a magnetic vehicle shield  406 . 
     The vehicle shield  406  may comprise electromagnetic shielding materials or components. As a non-limiting example, such shielding materials may include certain metallic meshes or solid metal materials configured to negate any incident magnetic energy or otherwise block or prevent such magnetic energy from entering the passenger compartment of the vehicle  405 . The vehicle shield  406  may serve to magnetically shield the interior of the vehicle from the wireless field  216  while not interfering with the functions of the wireless power receiver within the housing  402 . 
     The vehicle  405  may further comprise a housing  402  (shown in dashed lines). As shown, the housing  402  may be disposed or otherwise connected to the bottom of the vehicle shield  406 . As shown, the housing  402  is located approximately midway between the front and rear wheels. In an implementation, the housing  402  may be located anywhere on the vehicle. In some implementations, it may be useful for the housing  402  to be integrated flush (not shown in this figure) with the lower surface of the electric vehicle  405  so that there are no protrusive parts and so that the specified ground-to-vehicle body clearance may be maintained. 
     In some implementations the housing  402  may contain at least wireless vehicle charging components, such as wireless power receiver (e.g., the receiver  208  of  FIG. 2 ), and a receiver coil (e.g., the receiver coil  218 ). The housing  402  may contain all of the components necessary to couple with and receive wireless power from a wireless power transmitter (e.g., the transmitter  204 ). 
     The vehicle  405  is positioned over a transmitter  404  (similar to the transmitter  204  of  FIG. 2 ). The transmitter  404  is shown emitting the wireless field  216  ( FIG. 2 ). The housing  402  may receive wireless power from the wireless field  216  as shown. The wireless field  216  is shown in this figure as a series of continuous arrows flowing from the wireless power transmitter  404  to the housing  402 . The continuous arrows may be generally representative of the circular or continuous flow of magnetic flux within a magnetic field. 
     As shown, a portion of the wireless field  216  is shown flowing away from the housing  402 . While the majority of the continuous arrows comprising the wireless field  216  are shown in the vicinity of the housing  402 , a portion of the arrows are also flowing horizontally away from the power transmitter  404  to the left and right of  FIG. 4 , representing the front and rear of the vehicle  405 . The portion of arrows flowing in sub-optimal directions or away from the housing  402  depict the leakage field  212 , similar to that shown in  FIG. 2 . As noted previously with respect to  FIG. 2 , the leakage field  212  may have negative effects on nearby electronics or possibly present a hazard to people. While not directly represented in this figure, the leakage field  212  of  FIG. 4  also flows to the left and right of the vehicle  405  that is in and out of the page. This is more directly represented below in  FIG. 7A  and  FIG. 7B . 
     The vehicle  405  may further comprise one or more leakage field collectors  450 . The collector  450  may be structurally similar to the collectors  350  ( FIG. 3 ) and may serve to absorb or redirect the leakage magnetic field  212 . The leakage field collector  450  is shown positioned in proximity to the housing  402 , protruding or extending downward from the bottom of the electric vehicle  405  and surrounding the housing  402 . The collector  450  may further be disposed or otherwise mounted to the vehicle shield  406  on the underside of the vehicle  405 . The housing  402  is shown in dashed lines, indicating its position behind and/or within a leakage field collector  450  and below a vehicle shield  406 . The vertical dotted lines near the front and rear edges of the collector  450  indicate a central aperture or opening (discussed with respect to  FIG. 5A - FIG. 5I ) allowing the wireless field  212  to easily flow through the center of the collector  450  to be received at the housing  402 . 
     As shown, the collector  450  may protrude away from the bottom of the vehicle  405  a greater distance than the housing  402 . As noted above, the housing  402  may be integrated into the bottom of the vehicle  405  such that it is flush with the bottom of the vehicle  405 . However, in some implementations, the collector  450  may not protrude from the vehicle  450  than the housing  402 . Accordingly, in such an implementation, the lower portion of the housing  402  may protrude from the bottom of the vehicle  405  further than the collector  450  (not shown in this figure). 
     In some implementations, the leakage field collector  450  may offer a manner to reduce the leakage field  212  by providing a low-reluctance path for the leakage field  212 . As shown in  FIG. 4 , the continuous dotted lines  213  indicate the path of the reduced leakage magnetic field  212  as influenced by the collector  450 . The field lines of leakage field  212  may be induced to, flow toward the collector  450  due to presence of the low-reluctance qualities of the collector  450 . 
       FIG. 5A - FIG. 5I  depict views of the underside of the vehicle  405  in a substantially horizontal plane along the lower surface of the vehicle  405  ( FIG. 4 ). As shown in  FIG. 5A - FIG. 5I , the underside of the vehicle  405  may comprise the vehicle shield  406  disposed along the underside of the vehicle  405 . The housing  402  ( FIG. 4 ) may be disposed in a variety positions incident with the vehicle  405  and the vehicle shield  406 . The vehicle  405  may further comprise leakage collectors similar to the collector  450  ( FIG. 4 ). The leakage collectors may be positioned a distance away from the housing  402  and near the outer edges of the vehicle  405  as described below, but still within the wireless field  216 . Such a distance may vary from a few inches from the housing  402  to the very outer edges of the vehicle  405 . The distance may further be measured in comparison to the separation (distance) between the wireless power receiver, or the housing  402  and the outer edge of the electric vehicle  405 . For example, the collectors described in connection with  FIG. 5A - FIG. 5I  may be placed at a position that is one third or at one half or more of the distance from the housing  402  to the outer edge of the vehicle  405 . Such a separation may not be uniform around the housing  402 . Furthermore, various geometries, shapes (e.g., a line, a square, a rectangle, a circle, a triangle, a polygon, or a semicircle), and other characteristics are shown in  FIG. 5A - FIG. 5H . Different aspects of the designs disclosed below may be mixed and matched to suit different applications to efficiently influence or absorb the leakage fields  212 . 
       FIG. 5A  is an illustration of the bottom of an electric vehicle fitted with a leakage field collector in accordance with an implementation.  FIG. 5A  depicts the vehicle  405  comprising a rectangular leakage field collector  505 . The collector  505  may have a uniform thickness around its perimeter. The collector  505  may further surround the housing  402  in the substantially horizontal plane, leaving a large central aperture through which wireless field such as the wireless field  216 , can flow. In an implementation, the collector  505  may have a generally rectangular shape and dimensions slightly smaller than the vehicle shield  402 . 
       FIG. 5B  is an illustration of the bottom of an electric vehicle fitted with leakage field collectors in accordance with an implementation.  FIG. 5B  depicts a pair of leakage collectors  510   a  and  510   b  disposed on the bottom of the electric vehicle  405 . The collectors  510   a  and  510   b  are positioned within the area shielded by the vehicle shield  406 . In an implementation, the leakage collectors  510   a ,  510   b  may each comprise two separate angled segments disposed on opposite sides of the vehicle  405 . The collectors  510   a ,  510   b  may further substantially surround the housing  402 . As shown, each of the collectors  510   a ,  510   b  each may have three portions. The center portion of each of the collectors  510   a ,  510   b  may be generally parallel with the longitudinal axis of the vehicle  405 . The other two segments of each of the collectors  510  are angled toward the housing  502  and a crude “C” shape. In an implementation, the collectors  510   a ,  510   b  may have a width  512  along their length. In another implementation, the width  512  may not be constant along the entire length of the collectors  510 . 
       FIG. 5C  is an illustration of the bottom of an electric vehicle fitted with leakage field collectors in accordance with an implementation.  FIG. 5C  depicts a pair of leakage collectors  515   a  and  515   b . The leakage collectors  515   a ,  515   b  may comprise two parallel lengths disposed on the underside of the vehicle  405 . The collectors  515   a ,  515   b  may be positioned on opposing sides of the housing  402  within the area shielded by the vehicle shield  406 . The collectors  515   a ,  515   b  may further have a width  517 , similar to the previous implementations. The width  517  as shown is constant along the length of the collectors  515 , but may be varied along the length of the collectors  515   a ,  515   b  as required. In an embodiment, the leakage collectors  515   a ,  515   b  may also be positioned at the front and back (not shown) of the housing  402 , as required. 
       FIG. 5D  is an illustration of the bottom of an electric vehicle fitted with leakage field collectors in accordance with an implementation.  FIG. 5D  depicts a pair of leakage field collectors  520   a ,  520   b  disposed on the bottom of the vehicle  405 . The leakage collectors  520   a ,  520   b  may comprise two parallel lengths disposed on the underside of the sides of the vehicle  405 . The collectors  520   a ,  520   b  may be positioned on opposite sides of the housing  402 , substantially within the area shielded by the vehicle shield  406 . The collectors  520   a ,  520   b  may be configured with a width that varies from a first width  522  to a second width  524 . In another implementation, the first width  522  may be narrower than the second width  524 . As shown, the collectors  520   a ,  520   b  may vary in width from the first width  522  at opposite ends to a wider second width  525  at the middle. In a third implementation, the opposite configuration may be present, having a narrow width at the middle and a wider width at the ends (not shown). 
       FIG. 5E  is an illustration of the bottom of an electric vehicle fitted with leakage field collectors in accordance with an implementation.  FIG. 5E  depicts a pair of leakage field collectors  525   a ,  525   b  disposed on the bottom of the vehicle  405 . The collectors  525   a ,  525   b  may comprise a number of curved, C-shaped portions disposed on the sides of the underside of the vehicle  405 . As shown, the collectors  525   a ,  525   b  may have a width  527  along the entire length. In another implementation, the width  527  may also vary as needed along the length, similar to  FIG. 5D . The C-shaped collectors  525  may flank either side of the housing  402  as shown or be disposed in another geometry around the housing  402  as needed for optimum leakage field absorption. 
       FIG. 5F  is an illustration of the bottom of an electric vehicle fitted with a leakage field collector in accordance with an implementation.  FIG. 5F  depicts a leakage field collector  530  disposed on the bottom of the vehicle  405 . The collector  530  may comprise at least one curved, C-shaped portion of ferromagnetic material. The collector  530  may be disposed on the underside of the rear of the vehicle  406 , adjacent to the housing  402 . In some implementations, the collector  530  may be disposed between the housing  402  and an area where a person may stand, such as the rear of the vehicle  405  as shown. In an implementation, the housing may also be disposed on the front of the vehicle  406  (not shown). Such an implementation may be incorporated where the housing  402  is positioned at the front of the vehicle  405 . Accordingly, the collector  530  may be positioned in to most efficiently influence or absorb leakage field  212  from the housing  402 . 
       FIG. 5G  is an illustration of the bottom of an electric vehicle fitted with a leakage field collector in accordance with an implementation.  FIG. 5G  depicts a leakage field collector  535  disposed on the underside of the rear of the vehicle  405 . The collector  535  is positioned similar to collector  530  of  FIG. 5F . The collector  535  may comprise at least one segment or a bar as shown. The collector  535  may have a uniform thickness along its length as in previous implementations; however a varying thickness may be selected to absorb a desired portion of the leakage field  212 . The collector  535  is shown at the rear of the vehicle  405  in proximity to the housing  402 . In an implementation, the collector  535  may also be disposed under the front of the vehicle to effectively influence or absorb leakage field  212  from the housing  402 . This configuration may be desirable when the housing  402  is positioned at the front of the vehicle  405  (not show in this figure). 
       FIG. 5H  is an illustration of the bottom of an electric vehicle fitted with a leakage field collector in accordance with an implementation.  FIG. 5H  depicts a continuous leakage field collector  540  disposed on the underside of the vehicle  405 . The collector  540  is configured to surround the housing  402 . The collector  540  may have a substantially uniform thickness along its length. However, in some implementations, the width of the collector  540  may vary as required (not shown in this figure). In some implementations the collector  540  may further be segmented, similar to the collector  530  ( FIG. 5E ) or as shown below in  FIG. 5I . As in previous implementations, the collector  540  may have smaller dimensions than the vehicle shield  406 . 
       FIG. 5I  is an illustration of the bottom of an electric vehicle fitted with a leakage field collector in accordance with an implementation.  FIG. 5I  depicts leakage field collectors  545   a  and  545   b  disposed on the underside of the rear of the vehicle  405 . Such a configuration may be similar to  FIG. 5F . The leakage collectors  545   a ,  545   b  may comprise multiple segmented sections along the underside of each side of the vehicle  405 . As shown, two segmented collectors  545   a ,  545   b  are positioned on either side of the housing  402 . While only two collectors  545   a ,  545   b  are show, additional implementations may provide additional collectors. In another implementation, the collectors  545  may be disposed within the area of the vehicle shield  406 , redirecting or absorbing the leakage fields  212  emanating from the sides of the vehicle  405 . 
       FIG. 6A - FIG. 6D  depict internal views along a bottom portion of an electric vehicle, according to certain implementations. As shown, only the bottom portion of an electric vehicle chassis is present. Other components of the electric vehicle, such as wheels and other accessories are omitted from  FIG. 6A - FIG. 6D  figure for simplicity. 
       FIG. 6A  is an internal view along a bottom portion of an electric vehicle according to an implementation. As shown,  FIG. 6A  is depicts an internal view of a chassis  600  taken along the line  6 - 6  of  FIG. 5A . The chassis  600  may be the bottom portion of the vehicle  405  ( FIG. 4 ). The chassis may further comprise the vehicle shield  406  disposed on or otherwise mounted to the bottom of the chassis  600 . As noted above in connection with  FIG. 4 , the vehicle shield  406  may comprise structural portions of the chassis  600 . Accordingly, the vehicle shield  406  may not be a separate component, but may be formed as a portion of the chassis  600 . Thus, for purposes of this description, the vehicle shield  406  is detailed as a separate component for clarity and completeness. 
     The chassis  600  may further comprise the housing  402  positioned on the bottom of the vehicle shield  406 , similar to previous embodiments (e.g.,  FIG. 4 - FIG. 5I ). The chassis  600  may further comprise at least leakage collectors  602   a  and  602   b , similar to the leakage collectors previously described in  FIG. 4 - FIG. 5I . 
     In one implementation, the leakage collectors  602   a ,  602   b  may be cross sectional views of individual segments of a leakage collector (e.g., the leakage collectors  510   a ,  510   b ,  520   a ,  520   b ,  525   a ,  525   b ,  545   a ,  545   b  etc.). In another implementation, the leakage collectors  620   a ,  620   b  may be a cross sectional view of a continuous leakage collector (e.g., the leakage collectors  505 ,  540 , etc.). Accordingly, the leakage collectors  602   a ,  602   b  may depict the shape of any of the leakage collectors described herein. 
     The collectors  602  are disposed on the outer portion of the bottom of the vehicle in an area shielded by the vehicle shield  406 . The collectors  602  may be mounted to, beside, or on the vehicle shield  406  according to a given design. The collectors  602  of  FIG. 6A  have a rectangular cross section. In an implementation, the rectangular cross section of the collectors  602  may be integrated into one of the collector geometries of  FIG. 5A - FIG. 5I . The same is true for the following examples. 
       FIG. 6B  is an internal view of a right hand side of the bottom portion of the electric vehicle of  FIG. 6A , according to an implementation.  FIG. 6B  shows a cross along the bottom of the vehicle  405  taken along the line  6 - 6  of  FIG. 5A .  FIG. 6B - FIG. 6D  show only one side of the internal view for simplicity. In an implementation, a leakage field collector  606  having a rounded or semicircular cross section may be disposed on the bottom of the chassis  600  in proximity to the housing  402 . As in previous implementations, the collectors  606  may be disposed on a portion of the chassis  600  (or the vehicle  405 ) covered by the vehicle shield  406 . 
       FIG. 6C  is an internal view of a right hand side of the bottom portion of the electric vehicle of  FIG. 6A , according to an implementation.  FIG. 6C  shows a cross along the bottom of the vehicle  405  taken along the line  6 - 6  of  FIG. 5A . In an implementation, a leakage field collector  606  having a triangular cross section may be disposed on the bottom of the chassis  600  in proximity to the housing  402 . As in previous implementations, the collectors  608  may be disposed on a portion of the chassis  600  (or the vehicle  405 ) covered by the vehicle shield  406 . 
       FIG. 6D  is an internal view of a right hand side of the bottom portion of the electric vehicle of  FIG. 6A , according to an implementation.  FIG. 6D  shows a cross along the bottom of the vehicle  405  taken along the line  6 - 6  of  FIG. 5A . In an implementation, a leakage field collector  610  having an irregular, rectangular, or composite cross section may be disposed on the bottom of the chassis  600  in proximity to the housing  402 . The collector  610  is depicted having an L-shaped cross section. 
       FIG. 6A - FIG. 6D  depict various cross sectional dimensions and shapes for the leakage field collectors as disclosed herein. It is to be noted that geometry, position, and layout the planar views of the leakage collectors  505 ,  510 ,  515 ,  520 ,  525 ,  530 ,  535 ,  540 ,  545  may be combined in part or in whole with the various cross sections of collectors  602 ,  604 ,  608 ,  610 . Certain implementations may include multiple types and geometries of the field collectors disclosed herein. It should further be noted that implementations described above are not drawn to scale, thus any specific dimensions are not limiting. 
     Additionally, the implementation of various shapes, cross sections, and dimensions of collectors  350  ( FIG. 3 ),  450  ( FIG. 4 ), and those disclosed in  FIG. 5A - FIG. 5I , may have differing effects on the reduction of the leakage fields, further explained with respect to  FIG. 7A - FIG. 7B . It should also be noted that the cross section of the collectors  350  may impact the leakage field  212   a ,  212   b  field distribution. The collectors  350  may have varying or irregular cross sections (see above,  FIG. 6A - FIG. 6D ) which may also affect the overall volume of the collectors  350 . Accordingly, the cross section of the collectors  350  may be selected to optimally adjust the absorption or influence on the leakage field  212 . 
       FIG. 7A  depicts a magnetic field intensity diagram, according to an implementation. As shown,  FIG. 7A , illustrates a field intensity diagram  700 , showing a series of magnetic flux lines depicted in a two-dimensional space relative to a magnetic field source depicted as a transmitter  704 . As shown, each line of magnetic flux represents an equal magnitude of a leakage field  712  in Amperes per meter (A/m) emanating from the transmitter  704 . Each of the vertical (Y) and horizontal axes (X) represents a distance from the transmitter  704 . The vertical axis depicts a height from the ground (0 m) up to 1.5 m from the ground, indicated by a mark on the vertical axis and dotted line. The horizontal axis (X) is also shown in meters, however the horizontal axis indicates an arbitrary distance and is not critical to this description. The 1.5 m mark and a line “g” (shown as a dashed line) are used as references for the following figures,  FIG. 7B  and  FIG. 7C , as described below. 
     As shown, the transmitter  704  is positioned on the bottom of a vehicle  705 . The vehicle  705  is depicted as an outline of an electric vehicle (e.g., the vehicle  105 ). Accordingly, diagram  700  is representative of the electric vehicle  705  as it is receiving wireless power from the transmitter  704 . 
     In some implementations the electric vehicle  705 , substantially similar to the vehicle  405  ( FIG. 4 ), comprises a wireless power receiver  708 , substantially similar to the wireless power receive  208  ( FIG. 2 ). The vehicle  705  is shown positioned over the WEVC transmitter  704  (similar to the transmitter  204  of  FIG. 2 ) in a charging state, receiving wireless power. The series of magnetic flux lines comprised a leakage field  712 , similar to the leakage field  212 . The leakage field  712  is being generated by the transmitter  704  and flowing away from the vehicle  705 . 
     In general, magnetic fields (e.g., leakage field  212 ,  712 ) may decrease in intensity with distance; that is, the farther from the source, the weaker field becomes. This is shown in the diagram  700 . As shown, the leakage field  712  begins at a magnitude of 50.0 A/m, in a space  724 , closest to the transmitter  704 . The leakage field lines are shown having increasing radius and decreasing magnitude with increased distance from the transmitter  704  (and the vehicle  705 ) in the vertical and horizontal axes, to 0.1 A/m at the outer most line of magnetic flux. Various exemplary values are shown in the field depicting the decreasing magnitude of the leakage magnetic field  712 . 
       FIG. 7B  depicts a magnetic field intensity diagram, according to another implementation.  FIG. 7B  illustrates a field intensity diagram  702  showing a series of magnetic flux lines depicted in a two-dimensional space relative to the transmitter  704 . The diagram  702  is substantially similar to the diagram  700  ( FIG. 7A ) depicting magnetic field intensity as a function of distance from the vehicle  705 . Similar to  FIG. 7A , each line of magnetic flux represents an equal magnitude of the leakage field  713  in A/m emanating from the transmitter  704 . As in  FIG. 7A , the 1.5 m line is also shown here, coincident with the line “g” near the top of the vehicle  705 . 
     The diagram  702  further depicts the vehicle  705  having a leakage field collector  750  disposed on the underside of the vehicle  705  in proximity to the receiver  708 . The leakage field collector  750  may be one of the previously described leakage collectors in  FIG. 4 - FIG. 6D . The receiver  708  is shown in dashed lines indicating its position within the leakage collector  750 . 
       FIG. 7B  further shows various values of the magnitude of the leakage field as noted by the numbers adjacent to the flux lines of the leakage field  713 . The field  713  is shown having a maximum magnitude of 50.0 A/m in the space  724  closest to the transmitter  704 . The magnitude of the leakage field  713  decreases with distance in the vertical and horizontal axes, down to a value of 0.1 A/m, similar to  FIG. 7A . However, it should be noted that the intensity of leakage field  713  decreases faster with distance than the leakage field  712 , due to the presence of the leakage collector  750 . 
       FIG. 7C  shows a plot diagram illustrating a comparison of the attenuation of the magnitude of the leakage fields of  FIG. 7A  and  FIG. 7B  as a function of distance. As shown, a chart  760  depicts the relative intensities of the leakage field  712  and the leakage field  713  as a function of the distance in meters. 
     The chart  760  has a vertical (Y) axis depicting a field intensity measured in A/m. The measurements of the leakage field  712 ,  713  intensity comprising the chart  760  are taken from a position relative to the vehicle  705 , common to both diagrams  700 ,  702 , along the line “g.” The line “g” is positioned at an outer edge of the vehicle  705  of  FIG. 7A  and  FIG. 7B . Accordingly, the line “g” is also present in this figure, coincident with the vertical axis of the chart  760 . The line “g” is further representative of a position adjacent to the side of the vehicle  705  where a person might stand. 
     The chart  760  further comprises a horizontal (X) axis depicting a distance from the source (e.g., the transmitter  704 ) in meters (m). The distance shown on the horizontal axis of the chart  760  is measured from zero (0) m on the ground (of  FIG. 7A  and  FIG. 7B ), vertically along the line “g,” to a measurement of 1.5 m high, corresponding the 1.5 m mark of  FIG. 7A  and  FIG. 7 . Specifically, origin of the horizontal (X) axis of the chart  760  represents the measurement of the intensity of the fields  712 ,  713  ( FIG. 7A  and  FIG. 7B ) taken at a point on the line “g” closest to the transmitter  704  at the ground. 
     As shown, the chart  760  depicts a line  762  corresponding to the diagram  700 . The line  762  begins at approximately 1.46 A/m and attenuates with distance from the line “g,” asymptotically approaching zero. The chart  760  further depicts a line  764  corresponding to the diagram  702 . The line  764  begins on the left at a value of approximately 1.08 A/m and attenuates with distance from the transmitter  704 , asymptotically approaching zero at 1.5 m. It is to be appreciated that the line  764  starts at a value less than that of the line  762  and furthermore, attenuates more rapidly than the line  762 , approaching zero at a distance closer to the vehicle  705 . This reduction of initial starting value (e.g., 1.46 A/m versus 1.08 A/m) and more rapid attenuation of the leakage fields with distance may be due to the selected position, geometry, and composition of the leakage collector  750 . 
       FIG. 8  is a flowchart depicting a method according to an implementation. As shown,  FIG. 8  depicts a method  800  describing the process by which a leakage field (e.g., the leakage field  212 ,  712 ) is absorbed or redirected by one or more leakage collectors (e.g., the collector  350 ,  750 , etc.) as described in connection with the foregoing figures. 
     At block  810 , a leakage collector (e.g., the collector  350 ) may couple to a leakage magnetic field (e.g., the leakage field  212 ) of a wireless field (e.g., the wireless field  216 ) generated by a wireless power transmitter (e.g., the transmitter  204 ). 
     At block  820 , the leakage collector  350  may collect at least a portion of the leakage magnetic field (e.g. leakage magnetic flux) generated by the transmitter. As described above in connection with  FIG. 4 - FIG. 7C , the composition, geometry, and position of the leakage collector  350  may be selected to effectively absorb or redirect the leakage flux at block  830 . 
     At block  840  the collector  350  may substantially remove the leakage flux from the wireless power field. In summary, block  840  describes the net effect of process of a leakage collector  350  on the leakage field  212 . Block  840  further describes the process shown by the  FIG. 7C  and the reduction of leakage flux at the line “g.” 
     Information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. 
     The various operations of methods described above may be performed by any suitable means capable of performing the operations, such as various hardware and/or software component(s), circuits, and/or module(s). Generally, any operations illustrated in the Figures may be performed by corresponding functional means capable of performing the operations. 
     The various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the implementations disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. The described functionality may be implemented in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the implementations. 
     The various illustrative blocks, modules, and circuits described in connection with the implementations disclosed herein may be implemented or performed with a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
     The steps of a method or algorithm and functions described in connection with the implementations disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a tangible, non-transitory computer-readable medium. A software module may reside in Random Access Memory (RAM), flash memory, Read Only Memory (ROM), Electrically Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), registers, hard disk, a removable disk, a CD ROM, or any other form of storage medium known in the art. A storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and blu ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer readable media. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal. 
     For purposes of summarizing the disclosure, certain aspects, advantages, and novel features of certain implementations have been described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any particular implementation. Thus, the implementations may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein. 
     Various modifications of the above described implementations will be readily apparent, and the generic principles defined herein may be applied to other implementations without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the implementations shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.