Abstract:
A tunable resonator assembly includes a resonator coil having an inductance, and a tile residing at a position relative to the resonator coil the position selected to produce a desired change in the inductance of the resonator coil.

Description:
BACKGROUND 
     1. Field 
     This disclosure relates to wireless energy transfer and tuning of resonators to accomplish such transfer. 
     2. Description of the Related Art 
     Energy or power may be transferred wirelessly using a variety of known radiative, or far-field, and non-radiative, or near-field, techniques as detailed, for example, in commonly owned U.S. patent application Ser. No. 12/613,686 published on May 6, 2010 as US 2010/010909445 and entitled “Wireless Energy Transfer Systems,” U.S. patent application Ser. No. 12/860,375 published on Dec. 9, 2010 as 2010/0308939 and entitled “Integrated Resonator-Shield Structures,” U.S. patent application Ser. No. 13/222,915 published on Mar. 15, 2012 as 2012/0062345 and entitled “Low Resistance Electrical Conductor,” U.S. patent application Ser. No. 13/283,811 published on Oct. 4, 2012 as 2012/0248981 and entitled “Multi-Resonator Wireless Energy Transfer for Lighting,” the contents of which are incorporated by reference. 
     Magnetic resonators may need to be tuned to achieve desired and/or specified performance metrics. To achieve the desired or specified performance metrics for wireless energy transfer, resonators&#39; parameters may need to be within a specific range. For example, in some embodiments a resonator resonant frequency may need to be within a range of the system resonant frequency for example. In other embodiments the resonator may need to be impedance matched to an amplifier, rectifier or other circuitry. 
     Components used to build and assemble magnetic resonators and power and control circuitry may be specified within a range of tolerances or variability in their component values. Components such as capacitors, inductors, circuit boards, oscillators, resonator coils, transistors, diodes, switches, and the like, may have a rated and/or specified nominal value, but may actually have a value different than the nominal value. In some embodiments for example, variations in the inductance of a resonator coil, or variations in the capacitance of capacitors may result in actual resonant frequencies that are different than the intended and/or designed resonant frequency of the resonator. In other embodiments, variations in inductance of the coil or variations in the capacitance of capacitors may affect the impedance matching between amplifiers, rectifiers, resonators, or any of the circuits. In some embodiments of resonators, the parameters of the resonators may be perturbed by objects in the environment around the resonators. 
     There are thus many ways in which the frequency and/or the impedance matching of the resonator may be outside of the desired or optimum range due to environmental, manufacturing, operating, and the like, uncertainties. What is needed is a simple and way to tune the resonator parameters to compensate for environment perturbations, manufacturing uncertainty, component variability, and the like. 
     SUMMARY 
     A wireless energy transfer system may comprise a resonator coil and a tile. The tile may comprise magnetic material, or electrically conducting material such as copper, or a combination of magnetic material and electrically conducting material. In one aspect, at least one tile of material may be positioned on or near a portion of the resonator coil and the position of the tile of material may be used to change the inductance of the resonator coil. At least one tile of material may be sized to have a desired impact on the inductance. At least one tile of material may be sized to change the inductance by approximately 0.1 μH or more. At least one tile of material may be attached to the coil with tape, adhesives, and/or other fastening methods. The tiles may be movable and may have a common geometric or an irregular shape and may be movable relative to the position of the resonator coil to change the inductance of the resonator. The movement of at least one tile relative to the resonator coil may be adjusted by a person, and/or manually, or it may be adjusted via a mechanical or electromechanical control apparatus, and the tuning of the inductance of the resonator coil may be performed automatically. 
     In another aspect, a magnetic resonator may be tuned using the positioning of at least one tile. In the method, the parameters of a resonator may be measured and the position of at least one tile may be changed near the resonator. The change in positioning may be adjusted to change the portion of the resonator coil that is covered by the at least one tile material. The measured parameters of the resonator may include the inductance of the resonator coil, the resonant frequency of the resonator, and the impedance of the resonator. The positioning may be performed using a microcontroller or manually by a user. 
     In accordance with an exemplary and non-limiting embodiment, a tunable resonator assembly comprises a resonator coil having an inductance, and a tile residing at a position relative to the resonator coil the position selected to produce a desired change in the inductance of the resonator coil. 
     In accordance with another exemplary and non-limiting embodiment, a method for tuning a magnetic resonator comprises measuring a parameter of a resonator comprising a resonator coil, positioning at least one tile to cover an area of the resonator coil and changing the area covered by the at least one tile to change the parameter of the resonator to a desired value. 
    
    
     
       BRIEF DESCRIPTION OF FIGURES 
         FIG. 1  is a block diagram of a system according to an exemplary and non-limiting embodiment; 
         FIG. 2  is an illustration of a resonator coil with a ferrite tuning block according to an exemplary and non-limiting embodiment; 
         FIG. 3  is a graph showing the effect of a ferrite tile on the inductance of a resonator coil according to an exemplary and non-limiting embodiment; 
         FIG. 4  is a flow diagram of a method according to an exemplary and non-limiting embodiment; 
         FIG. 5  is a diagram showing a resonator coil with a triangular ferrite tuning block according to an exemplary and non-limiting embodiment; and 
         FIG. 6  is a diagram showing a resonator coil with a spiral shaped ferrite tuning block according to an exemplary and non-limiting embodiment. 
         FIG. 7  is a block diagram of an embodiment of a system for wireless power transfer. 
     
    
    
     DETAILED DESCRIPTION 
     Magnetic resonators may need to be tuned to achieve desired and/or specified performance metrics. To achieve the desired or specified performance metrics for wireless energy transfer, resonators&#39; parameters may need to be within a specific parameter range. For example, parameters such as the resonant frequency of a magnetic resonator may need to be matched to the wireless energy transfer system resonant frequency. In accordance with some exemplary embodiments a resonator resonant frequency may need to be within approximately 5% of a system resonant frequency and/or within approximately 5 kHz of a fixed frequency such as 145 kHz, 250 kHz, 6.78 MHz and the like. In other exemplary embodiments, an amplifier, rectifier, source electronic circuit, device electronic circuit, matching network, power and control circuitry, and the like may be impedance matched to the impedance of a resonator or resonator coil. Impedance matching may be used to allow an amplifier, a source electronic circuit, a matching network, a power and control circuit, and the like, to more efficiently drive a source resonator coil or for a rectifier, device electronic circuit, impedance matching network, power and control circuitry, and the like, to more efficiently extract energy from a device resonator coil. 
     Components used to build and assemble magnetic resonators and power and control circuitry may be specified within a range of tolerances or variability in their component values. Components such as capacitors, inductors, circuit boards, oscillators, resonator coils, transistors, diodes, switches, and the like, may have a rated and/or specified nominal value, but may actually have a value different than the nominal value, but within a specified range or tolerance of that nominal value. In accordance with some exemplary embodiments, the variability of a part may be +−1%, +−2%, +−5%, +−15%, and the like of its nominal value. A capacitor, for example, with a nominal capacitance rating of 100 pF may in fact have a capacitance value anywhere in the range of 85 pF to 115 pF when the capacitor is specified as having a range or variability of capacitance (or range or tolerance) of +−15%. 
     A variation in the inductance of the resonator coil, or a variation in the capacitance of the resonator may affect the resonant frequency of the resonator. In other embodiments, a variation in the inductance of the coil or a variation in the capacitance of capacitors may affect the impedance matching between amplifiers, rectifiers, or any of the circuits of a wireless power transfer system coupled to the resonators. Such variations may reduce the efficiency of power delivery to or the extraction from, the resonators. The variability of components may mean that for some applications, the parameters of some manufactured resonators or some manufactured wireless power systems may be outside the desired operating range. Some values of the components may need to be tuned or adjusted during manufacture or after manufacture, or additional components may need to be added or existing components removed to compensate for the variability of components placed as part of the resonator or system production process. 
     In some instances involving resonators, the parameters of the resonators may be perturbed by objects in the environment around the resonators. In some instances, metal or lossy objects placed around resonators may load or perturb the parameters of the resonators. For example, a metallic object near a resonator coil may affect the resonant frequency of the resonator and shift the frequency outside a desired operating range. 
     Parameters of magnetic resonators may be adjusted or tuned by adding or removing inductors, capacitors, and the like, from the electronic circuits of the resonators until the desired operating parameters, such as the desired resonant frequency or the desired impedance matching, are reached. Components may be added, subtracted and/or altered using electronically controllable switches to tune the overall circuit parameters. Adjusting the parameters of components such as capacitors and capacitor networks and inductors and inductor networks may require several steps of soldering/de-soldering components, measuring effective circuit parameters and/or system or subsystem operation, and soldering/de-soldering other components until the desired net capacitance and inductance values are achieved. Because the components such as capacitors and/or inductors may each have variability of their individual component values, it may be difficult to predict the number of soldering/de-soldering iterations that will be required to achieve the desired circuit and/or system performance parameters. 
     It therefore may be desirable to allow a user of a wireless power system to perform some tuning of the system after it has been manufactured, purchased, or installed. In such instances, it may be difficult to predict the exact nature or magnitude of perturbations on a resonator due to its environment and hence a user or a consumer may need to tune the parameters at the location and placement that the resonator will be used. In other instances, a wireless power transfer system may comprise resonators that were designed for one environment but are now being operated in a different environment. In yet other instances, tuning the resonators for operation in the different environment may yield system performance improvements. For some products and applications, tuning of the wireless power system components by soldering or unsoldering components such as individual capacitors or inductors may not be desirable, feasible or practical. 
     It may further be preferable to tune resonators during manufacture to reduce the effects of component variability as well as tune resonators after manufacture allowing users to tune resonators to compensate for effects due to perturbations from the environment using a method other than adding or changing or removing electrical components in the resonators, inductive coils, matching networks and the like. A method that enables resonator tuning without changing components on a circuit board could enable faster manufacturing speeds, higher manufacturing yields, post-manufacture system improvements, user-tuned systems, system reuse through re-tuning and the like. 
     As discussed with reference to exemplary and non-limiting embodiments discussed more fully below, magnetic resonators and other components of wireless power transfer systems may be tuned inexpensively and with both coarse and fine precision by locating tiles of materials such as magnetic materials (ferrite) in certain positions in the vicinity of the inductive loops or coils of the magnetic resonators. 
     With reference to  FIG. 1 , there is illustrated a block diagram of various components that may function in a cooperative manner to tune various parameters of a resonator coil or coils  104  as described herein. As illustrated, tile  102  is located within proximity to resonator coil  104  in a manner sufficient to achieve a desired tuning of resonator coil  104 . Actuator  120  operates to position tile  102  in a desired position about resonator coil  104 . As described more fully below in accordance with exemplary embodiments, actuator  120  may linearly translate tile  120  back and forth along a perimeter of resonator coil  104 , forwards and backwards towards and away from resonator coil  104  and up and down above and below resonator coil  104 . In accordance with other exemplary embodiments, actuator  120  may operate to alter a rotational orientation of tile  120  vis-a-vis resonator coil  104 . 
     In accordance with exemplary and non-limiting embodiments, actuator  120  is communicatively coupled to controller  122 . Controller  122  operates to provide actuator  120  with instructions in response to which actuator alters a position of tile  102  with respect to resonator coil  104 . Controller  102  may comprise any and all devices, including, but not limited to, mechanical and computing devices, configured to receive inputs indicative of a desired position and orientation of tile  102  and outputting instructions to actuator  120  to achieve such desired positioning of tile  102 . In accordance with some exemplary embodiments, controller  122  include a computer-readable storage medium encoded with a set of instructions for directing controller to receive user input, such as via a user interface, and to output corresponding instructions to actuator  120 . In accordance with other exemplary embodiments, controller  122  may act in autonomous fashion based, at least in part, upon instructions stored upon and/or accessible to controller  122  to instruct the operation of actuator  120  without direct user input. In such embodiments, controller  122  may receive as input measurements or other feedback indicative of desired attributes of resonator coil  104  as affected by the placement of tile  102 . 
     As used herein, references to “blocks” and/or “tiles” of magnetic materials may be used interchangeably with reference to materials utilized in forming tiles  102  and utilized in tuning the inductance of a resonator or inductor coil  104 . The blocks or tiles may be of any shape, weight, size and material. For example, blocks and tiles may also be referred to as “disks”, “chunks”, “pieces”, “segments”, “chips”, “patches”, “sheets”, “rods”, “cores”, “plates”, and the like. In addition, different tiles  102  may comprise different types of magnetic materials such as ferrites and materials with commercial specifications including, but not limited to, N95, PC95, N49, NLX8, Finemet, Liqualloy, and any other type of magnetic material. Tiles  102  may comprise Ni, Zn, Mg, Fe, and other materials. Tiles  102  may be placed on the resonator coil  104  or any portion of the resonator coil  104 . Tiles  102  may be placed near resonator coil  104  or any portion of resonator coil  104 . Tiles  102  may be touching the copper conductor forming the resonator coil  104  or they may be offset from the copper conductor. Tiles  102  may be fixed in position or may be movable. Tuning may be achieved using any combination of materials and placement positions. The placement or movement of any combination of Tiles  102  may be used to achieve discrete or continuous tuning of the inductance of resonator coil  104 , permanent or adjustable inductance of resonator coil  104 , and coarse or fine tuning of the inductance of resonator coil  104 . 
     In a magnetic resonator, the resonant frequency of the resonator may be in part determined by the inductance value of resonator coil  104 . The frequency of the resonator may be adjusted or tuned by adjusting the inductance of resonator coil  104  by placing at least one tile  102  or near resonator coil  104 . At least one tile  102  placed on or near resonator coil  104  may increase the effective inductance of resonator coil  104  thereby affecting the resonant frequency of the resonator. The change in inductance of the resonator coil  104  may be variably tuned with tiles  102  by varying the size of the magnetic tiles  102 , the tile orientation, the number of tiles  102 , the type of magnetic material used to form tiles  102 , the thickness of tiles  102 , the position of the magnetic tile  102  relative to resonator coil  104 , and the like. In accordance with exemplary embodiments, the inductance of resonator coil  104  may be increased by increasing the size of the tile or tiles  102  of magnetic materials and/or by increasing the area of resonator coil  104  covered by the tile or tiles  102  and/or by varying the position of the tile or tiles  102 . In accordance with exemplary embodiments, the inductance of resonator coil  104  may be increased by moving tiles  102  or a tile  102  of magnetic material closer to resonator coil  104 . Likewise, the inductance of resonator coil  104  may be decreased by reducing the area of resonator coil  104  that is covered by tiles  102  or a tile  102  of magnetic material or by increasing the distance between tiles  102  or tile  102  of magnetic material and the resonator coil  104 . In accordance with exemplary embodiments, tiles  102  or pieces of magnetic material may be added or removed from the vicinity of resonator coil  104  to change its inductance. 
     With reference to  FIG. 2 , there is illustrated an exemplary embodiment of tile  102  and resonator coil  104 . For example, a  20  cm by  20  cm resonator coil  104  comprising  10  turns of Litz wire may be connected to a capacitor network (not shown) such that the resonant frequency of the structure is  250  kHz. The resonant frequency of such a structure may be tuned using at least one tile  102  or piece of magnetic material. In this example, a resonator coil  104  in free space may have an inductance, L, of 40.2 μH. The placement of a 1 mm thick tile  102  of magnetic material on top of the resonator coil  104 , as shown, may affect the inductance of resonator coil  104 . The change in inductance of resonator coil  104  may be varied by changing the tile&#39;s length  106  and/or by adding more tiles  102  and/or by adding or removing pieces of tiles  102  and/or by using tiles  102  composed of a different magnetic material, and the like. By changing the length  106  of tile  102  or tiles  102  of magnetic material and/or by repositioning magnetic tile  102  or tiles  102  so that a different amount of resonator coil  104  is covered and/or contacted by tile  102  or tiles  102 , the inductance of resonator coil  104  may be tuned and the resonant frequency of the resonator may be tuned. 
     With reference to  FIG. 3 , there is illustrated the effect of the length of an exemplary tile  102  of magnetic material on the inductance of an exemplary resonator coil  104 . As illustrated, the length  106  of tile  102  (in millimeters) placed on resonator coil  104  is plotted versus the measured inductance of the resonator coil. As the tile length  106  is increased, the inductance of resonator coil  104  increases as well. 
     In accordance with exemplary embodiments, the change of inductance of a magnetic resonator coil  104  may have a nearly linear relationship with the length of similarly sized and positioned ferrite tiles  102  added to the coil. A known and/or predictable relationship between magnetic tile size (type, shape, position, and the like) and resulting inductance change make it possible to pre-determine the length of tile, or the area of resonator coil  104  that may be covered by a tile  102  of magnetic material, to tune the resonator frequency and/or impedance by a desired amount or to a particular value. 
     Adding or placing magnetic material, such as tile  102 , on resonator coil  104  or near resonator coil  104  may increase the inductance of the coil. In accordance with exemplary embodiments, the desired tuning may be to reduce the inductance of the resonator coil. In such embodiments, a resonator may initially be constructed and tuned with at least one magnetic material tile  102  on or near resonator coil  104  so that inductance may also be reduced by moving, removing or decreasing the size of the at least one tile  102  of magnetic material. In other embodiments, the resonator may be initially constructed and tuned to a lower inductance than the preferred or target inductance of resonator coil  104  thereby ensuring that tuning may require increasing the inductance of resonator coil  104  and thus adding at least one tile  102  of magnetic material. 
     With reference to  FIG. 4 , there is illustrated an exemplary embodiment of a method for tuning a resonator coil  104  via the purposeful positioning of a tile  102 . First, at step  200 , a parameter of a resonator comprising a resonator coil  104  is measured. Next, at step  210 , at least one tile  102  is positioned to cover an area of the resonator coil  104 . Then, at step  220 , the area covered by the at least one tile  102  is altered to change the parameter of the resonator to a desired value. Details associated with these steps are described more fully below. 
     In accordance with exemplary embodiments, tuning of resonator parameters using at least one tile  102  of magnetic material may be performed during the manufacturing of the resonator. For example, the resonant frequency of the resonator may be measured and adjusted by gluing, attaching, sticking, strapping, tying, magnetically attaching, taping, positioning, and the like at least one of various sized tiles  102  of magnetic material to an area of resonator coil  104  or a position sufficiently near resonator coil  104  to achieve a predetermined inductance of resonator coil  104 . During manufacture, a resonator or resonator coil  104  may be manufactured using components whose parameter values may have variability or a specified tolerance. After manufacture, parameters of the resonator or resonator coil  104  may be measured and adjusted with the placement of the at least one tile  102  of magnetic material. For example, a machine or an operator may add one or more tiles  102  or increase the effective size of magnetic tiles  102  added to resonator coil  104  if the inductance is measured to be below a desired value. 
     In accordance with exemplary embodiments, tuning of magnetic resonators and/or wireless power transmission systems may be implemented by a user or a consumer after the resonators and/or systems are manufactured. In accordance with exemplary embodiments, at least one tile  102  of magnetic material may be attached to resonator coil  104  or on the packaging near resonator coil  104 . A product with a magnetic resonator may come with a variety of differently sized adhesive tiles  102  of magnetic material that may be attached to resonator coil  104  or the enclosure of the resonator coil. A person or machine performing tuning may try attaching differently sized tiles  102  and/or combinations of tiles  102  until the desired resonant frequency, or wireless energy transfer performance is achieved. In accordance with exemplary embodiments, a resonator housing  108  may use permanent magnet materials, or other magnetic materials, to attract and hold the differently size tiles and/or combinations of tiles to the desired position on or near the resonator coil. In embodiments, there are many ways to hold differently sized tiles and/or combinations of differently sized tiles  102  on or near resonator coil  104 , either in a temporary or fixed manner, to tune the inductance of magnetic resonator coil  104 . 
     In accordance with exemplary and non-limiting embodiments a resonator or a package for a resonator or a product may include a slide, dial, switch, knob, and the like that allows a user to directly or indirectly change the area of resonator coil  104  that is covered by a tile  102  of a magnetic material thereby tuning the inductance of the resonator coil. 
     With reference to  FIG. 5 , there is illustrated an exemplary embodiment of a configuration of tile  304  for selectively altering the inductance of resonator coil  302 . As illustrated, for example, tile  304  may be shaped or oriented such that when tile  304  is rotated, slid, or moved, tile  304  will span or cover a different area of resonator coil  302 . In this example, the magnetic tile  304  is shaped as a triangle and positioned partially over the resonator coil  302 . Sliding the triangular shaped tile  304  of magnetic material in the direction of the arrow will change the area of resonator coil  302  that is covered by tile  304 . The tile  304  of magnetic material may be moved by hand, and/or by a knob or a slider accessible to a user. The magnetic material may be moved by any type of electro-mechanical or automated actuator  120  such as in response to instructions received from controller  122 . 
     With reference to  FIG. 6 , there is illustrated another exemplary and non-limiting embodiment of tile  402  having a curved shape designed to cover a different area of resonator coil  404  when tile  402  is rotated around a central location  406  as indicated by the arrow. In accordance with some exemplary embodiments, the curved tile  402  may be rotated by hand, a knob or, a slider or the like accessible to a user or actuator  120 . 
     As those skilled in the art will appreciate, the tiles  102  may have a variety of different shapes, cutouts, sizes, and the like depending on the type of movement, amount of tuning range desired, and the like. In some exemplary embodiments, the movement of tiles  102  may be directly controlled by a user with an external knob or slider, such as one providing input to controller  122 , actuator  120  or in physical communication with tie  102 . In other exemplary embodiments, the movement of tile  102  may be controlled electronically by a variety of electromechanical actuators  120  such as servos, motors, piezoelectric materials, electromagnets and the like. In accordance with some exemplary embodiments, the tiles  102  may be continuously moved to sweep the frequency and/or impedance of the magnetic resonator, or the magnetic materials may be moved periodically, intermittently, and/or using a sequence that implements a frequency or impedance hopping scheme. 
     The position of the tile  102  of magnetic material may be controlled by an operator, either directly or via interfacing with controller  122 , or automatically by power and control circuitry, such as may comprise controller  122  and actuator  120 . Power and control circuitry may additionally include components for measuring the parameters of the resonator or the electrical parameters of the resonator during energy transfer and using mechanical or electromechanical actuators  120  or motors to adjust the position of tiles  102  of magnetic material to tune the parameters of magnetic resonator  104 . For example, with reference to  FIG. 7 , when resonator coil  104  of wireless power source  160  is transferring energy (represented schematically by arrow  155 ) to receiving device  151 , controller  122  can receive a measurement feedback signal  153  (represented schematically by arrow  153 ) carrying information about the parameters of resonator coil  104 , which are related to the energy transfer, and can tune the parameters of resonator coil  104  based on the signal. The tiles  102  may thus form part of a feedback circuit or a feedback scheme for controlling magnetic resonators and/or wireless power transmission system performance. Tile  102  may be part of a monitoring method, a communication method, a signaling method and the like utilized in a wireless power transmission system. 
     In accordance with exemplary and non-limiting embodiments, resonator, such as one comprising resonator coil  104 , and/or wireless power transfer system tuning using the position of at least one tile  102  of magnetic material may be performed interactively by a user. For example, the tuning may be performed on a source resonator and the effects of the tuning may be observed on the devices. A device may have a read-out, or an indicator of the power it is receiving, and the power level may vary as the at least one tile  102  of magnetic materials is moved and/or adjusted. A user may adjust the tuning knob that moves the tiles  102  of magnetic material relative to the resonator coil  104  until the power delivered to the device is maximized. As described above, such a knob or other adjusting device may be in physical communication with tile  102  or may be, for example, be a virtual knob or other graphic element comprising a user interface of controller  122  via which the user may adjust the position of tile  102 . The tuning of magnetic resonators using tiles  102  may be implemented on any type of magnetic resonator, including but not limited to source resonators, device resonators, repeater resonators, resonators comprising air core inductors, resonators comprising magnetic material core inductors, resonators comprising tunable and/or fixed components such as capacitors, capacitor banks, inductors, self-structures, switches, and the like. 
     In accordance with exemplary embodiments, tuning using tiles  102  of magnetic material may be used on both source and device resonators. In some embodiments of a wireless energy transfer system only source resonators may have a tuning capability using tiles  102  of magnetic material. In other embodiments of a wireless energy transfer system only the device resonators may have a tuning capability using tiles  102  of magnetic material. In other embodiments of a wireless energy transfer system at least one repeater resonator may have a tuning capability using tiles  102  of magnetic material. In other embodiments of a wireless energy transfer system only one or any combination of resonators may have a tuning capability using tiles  102  of magnetic material 
     In accordance with exemplary embodiments, the effective inductance of resonator coil  104  may also be adjusted by changing the relative distance between resonator coil  104  and at least one tile  102  of magnetic material. The closer tile  102  of magnetic material is to the resonator coil the larger the effective inductance of the coil. In addition to, or instead of adjusting the inductance of the resonator by changing the area of the resonator coil covered by the magnetic material, the inductance of the resonator coil may be adjusted by changing the spacing between the magnetic material and the resonator coil. 
     In accordance with exemplary embodiments, tiles  102  of electrically conducting materials may be used to tune the inductance of resonator coil  104 . Any embodiments, examples, explanations, and the like described herein that include the use of tiles  102  of magnetic material are equally valid and inventive if the tiles  102  comprise good conducting materials in addition to the magnetic materials, or instead of the magnetic materials. Example of good conducting materials include, but are not limited to, copper, silver, aluminum, platinum, gold, conducting paste, gels, inks, paints and the like. 
     In accordance with various exemplary embodiments tiles  102  may comprise a low loss magnetic material such as ferrite and/or appropriately sized and shaped low loss conductors so as to mitigate any undesired effects of tile  102  on other parameters of the resonator such as lowering its quality factor, for example. 
     While the invention has been described in connection with certain preferred embodiments, other embodiments will be understood by one of ordinary skill in the art and are intended to fall within the scope of this disclosure, which is to be interpreted in the broadest sense allowable by law. For example, designs, methods, configurations of components, etc. related to transmitting wireless power have been described above along with various specific applications and examples thereof. Those skilled in the art will appreciate where the designs, components, configurations or components described herein can be used in combination, or interchangeably, and that the above description does not limit such interchangeability or combination of components to only that which is described herein. 
     All documents referenced herein are hereby incorporated by reference.