Methods and apparatus for magnetic field strength measurement

This disclosure provides methods and apparatus for wireless power field testing. An apparatus for sensing magnetic field strength of a wireless charging pad is provided. The apparatus includes a plurality of conductive loops each configured to sense a strength of a magnetic field passing through a respective one of the plurality of conductive loops. The apparatus includes at least one pair of terminals configured to be electrically connected to one or more of the plurality of conductive loops and configured to provide a voltage signal having a magnitude proportional to the strength of the magnetic field passing through the one or more of the plurality of conductive loops. In some implementations, the apparatus further includes a multiplexer circuit configured to individually electrically connect each of at least a subset of the plurality of conductive loops to the at least one pair of terminals.

FIELD

The present disclosure relates generally to wireless power transfer, and more specifically to methods and apparatus for wireless power field testing.

BACKGROUND

When designing wireless power systems, there are several important tasks to be performed during design and testing including measurement of the total magnetic field density (H) and/or magnetic flux density (B), measurement of field evenness in open coil cases, and monitoring magnetic flux density once a chargeable device has been placed. Testing of the magnetic field density or magnetic flux density has traditionally been performed by moving a loop around the transmitter pad. However, it is difficult to move and place a loop accurately over tens or hundreds of locations on the pad to be measured. It is also difficult to insert a coil under an operating device without disturbing it. As such, there is a need for methods and apparatus for wireless power field testing.

SUMMARY

Various implementations of methods and devices within the scope of the appended claims each have several aspects, no single one of which is solely responsible for the desirable attributes described herein. Without limiting the scope of the appended claims, some prominent features are described herein.

One aspect of the disclosure provides an apparatus for sensing magnetic field strength of a wireless charging pad. The apparatus comprises a plurality of conductive loops, each configured to sense a strength of a magnetic field passing through a respective one of the plurality of conductive loops. The apparatus further comprises at least one pair of terminals configured to be electrically connected to one or more of the plurality of conductive loops and configured to provide a voltage signal having a magnitude proportional to the strength of the magnetic field passing through the one or more of the plurality of conductive loops.

Another aspect of the disclosure provides an implementation of a method for sensing magnetic field strength of a wireless charging pad. The method comprises sensing a voltage signal having a magnitude proportional to a strength of a magnetic field passing through each of at least a subset of a plurality of conductive loops. The method further comprises determining the strength of the magnetic field passing through each of at least a subset of the plurality of conductive loops based at least in part on the voltage signal.

Yet another aspect of the disclosure provides apparatus for sensing magnetic field strength of a wireless charging pad. The apparatus comprises a plurality of means for sensing a strength of a magnetic field passing through each of a plurality of predefined spatial areas. The apparatus further comprises means for providing a voltage signal having a magnitude proportional to the strength of the magnetic field passing through one or more of the plurality of means for sensing. The means for providing are configured to be electrically connected to one or more of the plurality of means for sensing.

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 in which the invention 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.

FIG. 1is a functional block diagram of a wireless power transfer system100, in accordance with one exemplary implementation. An input power102may be provided to a transmitter104from a power source (not shown) to generate a wireless (e.g., magnetic or electromagnetic) field105for performing energy transfer. A receiver108may couple to the wireless field105and generate an output power110for storing or consumption by a device (not shown) coupled to the output power110. Both the transmitter104and the receiver108are separated by a distance112.

In one exemplary implementation, the transmitter104and the receiver108are configured according to a mutual resonant relationship. When the resonant frequency of the receiver108and the resonant frequency of the transmitter104are substantially the same or very close, transmission losses between the transmitter104and the receiver108are minimal. As such, wireless power transfer may be provided over a larger distance in contrast to purely inductive solutions that may require large antenna coils which are very close (e.g., sometimes within millimeters). Resonant inductive coupling techniques may thus allow for improved efficiency and power transfer over various distances and with a variety of inductive coil configurations.

The receiver108may receive power when the receiver108is located in the wireless field105produced by the transmitter104. The wireless field105corresponds to a region where energy output by the transmitter104may be captured by the receiver108. The wireless field105may correspond to the “near-field” of the transmitter104as will be further described below. The transmitter104may include a transmit antenna or coil114for transmitting energy to the receiver108. The receiver108may include a receive antenna or coil118for receiving or capturing energy transmitted from the transmitter104. The near-field may correspond to a region in which there are strong reactive fields resulting from the currents and charges in the transmit coil114that minimally radiate power away from the transmit coil114. The near-field may correspond to a region that is within about one wavelength (or a fraction thereof) of the transmit coil114.

As described above, efficient energy transfer may occur by coupling a large portion of the energy in the wireless field105to the receive coil118rather than propagating most of the energy in an electromagnetic wave to the far field. When positioned within the wireless field105, a “coupling mode” may be developed between the transmit coil114and the receive coil118. The area around the transmit antenna114and the receive antenna118where this coupling may occur is referred to herein as a coupling-mode region.

FIG. 2is a functional block diagram of a wireless power transfer system200, in accordance with another exemplary implementation. The system200includes a transmitter204and a receiver208. The transmitter204may include a transmit circuitry206that may include an oscillator222, a driver circuit224, and a filter and matching circuit226. The oscillator222may be configured to generate a signal at a desired frequency that may be adjusted in response to a frequency control signal223. The oscillator222may provide the oscillator signal to the driver circuit224. The driver circuit224may be configured to drive the transmit antenna214at, for example, a resonant frequency of the transmit antenna214based on an input voltage signal (VD)225. The driver circuit224may be a switching amplifier configured to receive a square wave from the oscillator222and output a sine wave. For example, the driver circuit224may be a class E amplifier.

The filter and matching circuit226may filter out harmonics or other unwanted frequencies and match the impedance of the transmitter204to the transmit antenna214. As a result of driving the transmit antenna214, the transmit antenna214may generate a wireless field205to wirelessly output power at a level sufficient for charging a battery236of an electric vehicle, for example.

The receiver208may include a receive circuitry210that may include a matching circuit232and a rectifier circuit234. The matching circuit232may match the impedance of the receive circuitry210to the receive antenna218. The rectifier circuit234may generate a direct current (DC) power output from an alternate current (AC) power input to charge the battery236, as shown inFIG. 2. The receiver208and the transmitter204may additionally communicate on a separate communication channel219(e.g., Bluetooth, Zigbee, cellular, etc). The receiver208and the transmitter204may alternatively communicate via in-band signaling using characteristics of the wireless field205.

The receiver208may be configured to determine whether an amount of power transmitted by the transmitter204and received by the receiver208is appropriate for charging the battery236.

FIG. 3is a schematic diagram of a portion of the transmit circuitry206or the receive circuitry210ofFIG. 2including a transmit or receive antenna, in accordance with exemplary implementations. As illustrated inFIG. 3, a transmit or receive circuitry350may include an antenna352. The antenna352may also be referred to or be configured as a “loop” antenna352. The antenna352may also be referred to herein or be configured as a “magnetic” antenna or an induction coil. The term “antenna” generally refers to a component that may wirelessly output or receive energy for coupling to another “antenna.” The antenna may also be referred to as a coil of a type that is configured to wirelessly output or receive power. As used herein, the antenna352is an example of a “power transfer component” of a type that is configured to wirelessly output and/or receive power.

The antenna352may include an air core or a physical core such as a ferrite core (not shown). Air core loop antennas may be more tolerable to extraneous physical devices placed in the vicinity of the core. Furthermore, an air core loop antenna352allows the placement of other components within the core area. In addition, an air core loop may more readily enable placement of the receive antenna218(FIG. 2) within a plane of the transmit antenna214(FIG. 2) where the coupled-mode region of the transmit antenna214may be more powerful.

As stated, efficient transfer of energy between the transmitter104/204and the receiver108/208may occur during matched or nearly matched resonance between the transmitter104/204and the receiver108/208. However, even when resonance between the transmitter104/204and receiver108/208are not matched, energy may be transferred, although the efficiency may be affected. For example, the efficiency may be less when resonance is not matched. Transfer of energy occurs by coupling energy from the wireless field105/205of the transmit coil114/214to the receive coil118/218, residing in the vicinity of the wireless field105/205, rather than propagating the energy from the transmit coil114/214into free space.

The resonant frequency of the loop or magnetic antennas is based on the inductance and capacitance. Inductance may be simply the inductance created by the antenna352, whereas, capacitance may be added to the antenna's inductance to create a resonant structure at a desired resonant frequency. As a non-limiting example, a capacitor354and a capacitor356may be added to the transmit or receive circuitry350to create a resonant circuit that selects a signal358at a resonant frequency. Accordingly, for larger diameter antennas, the size of capacitance needed to sustain resonance may decrease as the diameter or inductance of the loop increases.

Furthermore, as the diameter of the antenna increases, the efficient energy transfer area of the near-field may increase. Other resonant circuits formed using other components are also possible. As another non-limiting example, a capacitor may be placed in parallel between the two terminals of the circuitry350. For transmit antennas, the signal358, with a frequency that substantially corresponds to the resonant frequency of the antenna352, may be an input to the antenna352.

Referring toFIGS. 1 and 2, the transmitter104/204may output a time varying magnetic (or electromagnetic) field with a frequency corresponding to the resonant frequency of the transmit coil114/214. When the receiver108/208is within the wireless field105/205, the time varying magnetic (or electromagnetic) field may induce a current in the receive coil118/218. As described above, if the receive coil118/218is configured to resonate at the frequency of the transmit coil114/214, energy may be efficiently transferred. The AC signal induced in the receive coil118/218may be rectified as described above to produce a DC signal that may be provided to charge or to power a load.

FIG. 4is a diagram illustrating a side view of an apparatus400for wireless power field testing disposed in, on, or over a base pad402, in accordance with an exemplary implementation. The base pad402may further include a transmit coil214(FIG. 2) and associated circuitry as previously described in connection withFIGS. 1-3. The apparatus400may include an enclosure404(e.g., a plastic enclosure) and may be configured to hold a planar, or non-overlapping sense loop array406. In some implementations, where overlapping loops are utilized, the apparatus400may additionally include a sense loop array408that overlaps sense loop array406. The diagram additionally shows a receiver coil416which may or may not be present during wireless power field testing.

During wireless charging, the total magnetic field (i.e., the H-field) determines the AC voltage induced in the receiver (e.g., the receiver coil416) in accordance with Faraday's Law of Induction. In free space, the H-field equals the magnetic flux (i.e., the B-field). Accordingly, when used without any additional magnetic materials (or receiver416) present, the apparatus400may allow for determination of the H-field present in the vicinity of the apparatus400. By contrast, in the presence of a high permeability magnetic material the B-field is greater than the H-field. Accordingly, where any magnetic material is present on or over the base pad402, the apparatus400may allow for determination of the B-field present. Likewise, if a receiving device having a receive coil present, the apparatus400may allow for determination of the actual B-field present in the vicinity of the receiving device. Designers of wireless power chargers may find it desirable to carefully control the H-field to control the voltage induced at the receiver. In addition, in many systems it is important to have a relatively even H-field over the transmitter (e.g., the base pad402) because it is easier to equalize voltages across several devices placed on the same transmitter coil or base pad in the presence of even H-fields. However, once a power receiving device has been placed on a transmitting coil, the H-field is distorted by any metal or magnetic material within the device and/or by the resonance of the receiving coil. Thus, an apparatus and/or method by which the H-field may be measured over all or a portion of the area of a transmit coil may be desirable. As long as the area of the loop or coil is known, the H-field passing through the loop or coil may be calculated by observing, sensing or measuring the voltage and frequency of a signal induced in the loop or coil utilizing conductive loops or coils disposed in, on or over the transmit coil or base pad.

In some implementations, a large number of inductance sensing coils or loops may be integrated into a flat instrument or apparatus. Exemplary arrangements of such coils or loops are described in more detail in connection withFIGS. 5-7below.

FIG. 5is a diagram illustrating a loop array for wireless power field testing, in accordance with an exemplary implementation. As shown inFIG. 5, a loop array500may include a plurality of sense loops501-508. In general, a sense loop501may be a multi-turn loop or coil of electrically conductive wire. Although 8 sense loops are show inFIG. 5, the present application is not so limited and may include any number of sense loops arranged in an array of any number of rows and columns, according to a particular application. Each of loops501-508in the sense loop array500may be electrically connected to a detection circuit by a lead line (not shown, seeFIG. 8).

The loop array500may completely cover the area of a transmitter for which measurement of the H-field is desired. As described above, by measuring the voltage induced in each of the loops501-508a determination of the H-field intersecting each of the loops501-508may be made. Such induced voltages may accurately simulate a voltage induced in a free space open circuit series-tuned receiver having a loop or coil of similar size. In the alternative, by summing each of these voltages, a determination of the total H-field intersecting all of the loops501-508is possible. Accordingly, in at least some implementations, each of the loops501-508may be electrically separate from one another.

As shown inFIG. 5, the sense loops501-508may not overlap one another. If the sense loops501-508do not overlap one another, any area encompassed by any one of the sense loops501-508will not also be encompassed by any other sense loop of the sense loops501-508. Such a non-overlapping structure may be advantageous for several reasons. A PCB containing the loop array may have a simpler design and a lower cost since fewer layers may be required. In addition, since the loops do not overlap one another the loops may be smaller than in implementations where the loops overlap. Furthermore, a non-overlapping sense loop design may offer greater flexibility for different board arrangements because the PCB may be divided into several subsections and arranged in accordance with a particular application.

The loops501-508may have any suitable dimension or predefined area according to the particular application. For example, in some implementations, each of the sense loops501-508may have a square or rectangular shape. In some other implementations, each of the sense loops501-508may have a circular, a hexagonal, or a triangular shape. For example, densely packed hexagonal loops may provide improved resolution with a non-overlapping structure requiring a lower number of copper layers when implemented in a printed circuit board.

FIG. 6is a diagram illustrating another loop array for wireless power field testing having smaller loops than the loops shown inFIG. 5, in accordance with an exemplary implementation. As shown inFIG. 6, a loop array600may include a plurality of sense loops601-632. The loop array600may have similar dimensions to the loop array500shown inFIG. 5, however, loop array600may have a higher spatial resolution than loop array500due to the increased number of loops, each encompassing a smaller area. Although 32 sense loops are shown in the loop array600(e.g., the loop array600is a 4×8 loop array), the present application is not so limited and may include any number of sense loops arranged in an array of any number of rows and columns, according to a particular application. The loops601-632may also have any suitable dimension according to the particular application. Each of loops601-632may be electrically connected to a detection circuit by a lead line (not shown, seeFIG. 8). The loop array600may completely cover the area of a transmitter for which measurement of the H-field is desired.

As previously described in connection withFIG. 5, by measuring the voltage induced in each of the loops601-632a determination of the H-field intersecting each of the loops601-632may be made. This allows a higher resolution mapping of the H-fields, which may correspond to voltages induced in receive devices having receiving coils of a similar size to the size of the loops601-632. Because the loops601-632each encompass a smaller area than the loops501-508ofFIG. 5, the loops601-632may additionally allow for finer determination of H-field evenness. By summing each of these voltages, a determination of the total H-field intersecting all loops601-632is also possible. Accordingly, in at least some implementations, each of the loops601-632may be electrically separate from one another.

FIG. 7is a diagram illustrating yet another loop array for wireless power field testing having overlapping loops, in accordance with an exemplary implementation. As shown inFIG. 7, the loop array700includes a plurality of sense loops701-708which may be substantially the same as or similar to the sense loops501-508shown inFIG. 5. The loop array700may additionally include sense loops709-711, which overlap the sense loops701-708. Because the sense loops709-711overlap the sense loops701-708, higher spatial resolution may be achieved than with the arrangement shown inFIG. 5without reducing the size of the loops, as previously described in connection withFIG. 6. Although 11 sense loops are show inFIG. 7, the present application is not so limited and may include any number of sense loops arranged in an array of any number of overlapping rows and columns, according to a particular application. The loops701-711may have any suitable dimension according to the particular application. It may be desirable that a thickness of the loop array700be as thin as possible or practical. In addition, loop array700may completely cover the area of a transmitter for which measurement of the H-field is desired. As previously described in connection withFIGS. 5 and 6, by measuring the voltage induced in each of the loops701-711a determination of the H-field intersecting each of the loops701-711may be made.

Because at least a first portion of the loops701-711overlap a second portion of the loops701-711, voltages induced in each of the loops701-711may be measured and processed to extract theoretical voltages, and by extension theoretical H-fields, that would be induced in smaller coils encompassing areas substantially equivalent to the areas of overlap of any two of the loops701-711. For example, the voltage contributions of one or more overlapping loops may be subtracted from a sensed voltage of one or more other loops in order to achieve a higher effective resolution than would be possible with non-overlapping loops of similar size. Each of the loops701-711may be electrically separate from one another. In other words, the loops701-711may not be electrically connected to one another.

In addition to measuring voltage, phase may be measured in one or more implementations if the original phase-accurate signal (e.g., an oscillator signal that drives the wireless power transmitting system) is provided to the tester. In such a case, both H-field strength and phase difference may be measured by sufficiently accurate test equipment. Knowledge of phase may be useful to testers who wish to understand how a given power receiver changes the impedance of the system as a whole. Such knowledge of the phase of the voltage induced by the H-field may be useful to designers of multiple coil transmitter systems where different coils or loops are fed by different phases.

FIG. 8is a functional block diagram of an exemplary circuit configured to measure a voltage induced in one or more loops in a loop array as shown in any ofFIGS. 5-7. As shown inFIG. 8, an apparatus800may include several sense loops801,802,803, and804(hereinafter the sense loops801-804). Although only four sense loops are shown, any number of sense loops may be utilized, in accordance with a particular application. The sense loops801-804may form at least a portion of an array of densely packed wire loops that cover an area within which a wireless power field may be tested. Accordingly, the sense loops801-804may correspond to sense loops in one or more of the sense loop array500ofFIG. 5, the sense loop array600ofFIG. 6, or the sense loop array700ofFIG. 7.

As further shown inFIG. 8, terminals of each of the loops801-804(e.g., the unmarked dots) may be run to more convenient locations in the apparatus800, via a pair of conductors. These terminals may be proximate to a respective loop or may be run to a more convenient location, such as an edge of the apparatus800. In this way, the terminals may be presented to the test operator for measurement. It is desirable that the conductors in a pair be as close as possible to one another to reduce unwanted H-field pickup. Alternatively, a twisted pair of wires or conductors may be used to reduce H-field pickup. In either case, the additional shunt capacitance of the conductors should be taken into account to ensure a resonant condition is not created. The apparatus800includes a multiplexing circuit820(e.g., a multiplexer) that is configured to selectively couple each of the sense loops801-804to a voltage measuring circuit830via a pair of terminals822and824(e.g., a multiplexer port). In one implementation, the voltage measuring circuit830may comprise a hardware processor. The voltage measuring circuit830may alternatively comprise a digital multimeter, an oscilloscope, or any other appropriate circuit configured to measure an AC voltage at a frequency of operation of a transmitter under testing. A voltage impressed across the pair of terminals822and824may be sequentially and periodically measured by the voltage measuring circuit830for each loop801-804selected by the multiplexer820. In this way, a the voltage measuring circuit830may measure the voltage induced in each of the loops801-804in an automated fashion as the multiplexing circuit820selects each of the loops801-804either simultaneously or sequentially. Accordingly, data may be presented in real time to allow a tester to observe the change in magnetic fields when the array of loops (e.g., the array500,600or700ofFIGS. 5-7, respectively) is moved or when a power receiving device (e.g., the receiver coil416ofFIG. 4) is present in the vicinity of the apparatus (e.g., the apparatus400ofFIG. 4or the apparatus800ofFIG. 8). As previously described, sensed H-fields from multiple loops may be summed to determine a total or aggregated H-field in real-time. In some implementations, one or more alarms may be triggered when measured H-fields are detected outside of a safe range, for example, when detected H-fields are strong enough to potentially damage a power receiver.

FIG. 9is a flowchart of an exemplary method900for wireless power field testing, in accordance with an exemplary implementation. The steps or actions described inFIG. 9may be implemented in, or carried out by, either of the circuits and/or devices shown in any ofFIGS. 4-8. Block902may include sensing a voltage signal having a magnitude proportional to a strength of a magnetic field passing through each of at least a subset of a plurality of conductive loops. In one implementation, such sensing may be performed by one or more of the plurality of conductive loops as shown in any ofFIGS. 5-7and or by the voltage measuring circuit830ofFIG. 8. For example, an AC voltage proportional to the total magnetic field passing through the area encompassed by a particular conductive loop will be induced across the terminals of that particular conductive loop. The multiplexer circuit820may then forward the induced AC voltage to the voltage measuring circuit830. In some implementations, the multiplexer circuit820may forward an induced AC voltage from one or more of the loops801-804to the measuring circuit830and simultaneously forward an induced AC voltage from one or more other of the loops801-804to another measuring circuit (not shown inFIG. 8). Block904may include determining the strength of the magnetic field passing through each of at least a subset of a plurality of conductive loops based at least in part on the voltage signal. For example, since the AC voltage induced across the terminals of the particular conductive loop are proportional to the magnetic field passing through the area encompassed by a particular conductive loop, measurement of the induced voltage may be utilized to calculate or determine the strength of the magnetic field.

FIG. 10is a functional block diagram of an apparatus for wireless power field testing, in accordance with an exemplary implementation. Those skilled in the art will appreciate that an apparatus for wireless power field testing may have more components than the simplified apparatus1000shown inFIG. 10. The apparatus1000shown includes only those components useful for describing some prominent features of implementations within the scope of the claims.

The apparatus1000includes a plurality of means1002for sensing a strength of a magnetic field passing through each of a plurality of predefined spatial areas. In an implementation, the means1002can be configured to perform one or more of the functions described above with respect to blocks902and/or904ofFIG. 9. In various implementations, the plurality of means1002can be implemented by one or more of the conductive loop arrays shown in any ofFIGS. 5-7.

The apparatus1000further includes means1004for providing a voltage signal having a magnitude proportional to the strength of the magnetic field passing through one or more of the plurality of means for sensing, wherein the means1004for providing are configured to be electrically connected to one or more of the plurality of means1002for sensing. In an implementation, the means1004can be configured to perform one or more of the functions described above with respect to blocks904and/or906. In various implementations, the means1004can be implemented by one or more of the loops801-804, the multiplexer circuit820, or the voltage measuring circuit830ofFIG. 8, for example.

In some implementations, it may not be possible or practical to place a flat sensor pad on a wireless power transmitter due to shape or size constraints of the wireless power transmitter or the flat sensor pad. In such implementations, it may be desirable to have an instrument or apparatus (e.g., the apparatuses1100and1200ofFIGS. 11 and 12, respectively) that includes one or more sense coils and that may be moved around the wireless power transmitter for testing the wireless power field.

FIG. 11is a diagram illustrating a bottom view of an apparatus1100for wireless power field testing of a base pad, in accordance with an exemplary implementation. As shown byFIG. 11, the apparatus1100may comprise a substantially circular sense loop1101and a location sensor1120. The sense loop1101may be substantially the same as any one of the sense loops as previously described in connection withFIGS. 5-8. Since the sense loop1101may have a substantially circular cross section, the apparatus1100may be rotated in any direction perpendicular to the cross section of the sense loop1101without affecting the field measurement. Accordingly, the apparatus1100may have a single location sensor1120, which may be configured to sense and/or measure a change in relative location of the apparatus1100during H-field measurement. In some implementations, the location sensor1120may comprise an optical sensor having operation similar to that of an optically tracked computer mouse. In some other implementations, the location sensor1120may comprise a mechanical location sensor (e.g., a rollerball as utilized in a computer mouse). However, any sensor type capable of delineating relative movement of the apparatus1100may alternatively be utilized. The apparatus1100may be a handheld apparatus that may be moved around a surface of a wireless power transmitter (seeFIGS. 14A, 14B and 15) and may be configured to map the H-field (as sensed by the sense loop1101) at each of a plurality of locations across the wireless power transmitter (as sensed by the location sensor1120). The apparatus1100may be connected to a volt-meter and a display to allow a field plot to be filled in as the apparatus1100is moved across the surface of the wireless power transmitter. In some implementations, the apparatus1100may be connected to the separate display for guiding a user in scanning the surface of the wireless power transmitter. In some other implementations, a user of the apparatus1100may additionally utilize a printed, flexible guide that allows accurate placement and motion of the apparatus1100. In yet some other implementations, a user of the apparatus1100may additionally utilize some other means for marking a surface of the wireless power transmitter resonator to guide the user in positioning the apparatus1100.

FIG. 12is a diagram illustrating a bottom view of another apparatus1200for wireless power field testing of a base pad, in accordance with another exemplary implementation. As shown byFIG. 12, the apparatus1200may comprise a substantially rectangular sense loop1201and a plurality of location sensors1220,1222,1224. The location sensors1220,1222,1224may be substantially the same as the location sensor1120ofFIG. 11. The sense loop1201may be substantially the same as any one of the sense loops as previously described in connection withFIGS. 5-8. Since the sense loop1201has a substantially rectangular cross section, rotation of the apparatus1200in any direction perpendicular to the cross section of the sense loop1201may affect the field measurement. Accordingly, the apparatus1200may have the plurality of location sensors1220,1222,1224, which may be configured to sense and/or measure a change in relative location, as well as rotation, of the apparatus1200during H-field measurement. The apparatus1200may be utilized by a user as previously described in connection withFIG. 11. A further advantage of the apparatus1200is that the “open” center may allow a line-of-sight viewing down the center of the apparatus1200. This may allow a user to align the apparatus1200more accurately to marks on the surface of the wireless power transmitter even without feedback from the location sensors1220,1222,1224. It may be desirable that both the apparatus1100ofFIG. 11and the apparatus1200ofFIG. 12utilize as little metal as possible in their construction, since metal will interfere with H-field measurements.

FIG. 13is a diagram illustrating a side view1300of either of the apparatuses1100/1200ofFIGS. 11 and 12. As shown inFIG. 13, the apparatus1300may include a sense loop1301, which may correspond to either the sense loop1101ofFIG. 11or the sense loop1201ofFIG. 12. The apparatus1300may additionally include one more location sensors1320, which may correspond to either the location sensor1120ofFIG. 11or the plurality of location sensors1220,1222,1224ofFIG. 12. Although particular positions of the sense loop1301and location sensor1320are shown, such positions are only exemplary and may be located at any position, according to a particular implementation.

FIG. 14Ais a diagram1400illustrating the apparatus1300ofFIG. 13for wireless power field testing of a substantially flat base pad1410, in accordance with an exemplary implementation. As shown inFIG. 14A, the apparatus1300may be moved across the surface of the base pad1410. The user of the apparatus1300may align the apparatus1300to an explicit grid or to “field points” by eye, by utilizing positioning data provided by the one or more location sensors1320, or in a free hand fashion as will be described in connection withFIG. 15.

FIG. 14Bis a diagram1450illustrating the apparatus1300ofFIG. 13for wireless power field testing of a substantially curved base pad, in accordance with an exemplary implementation. As shown inFIG. 14B, the apparatus1300may be moved across the substantially curved surface of the base pad1420. The user of the apparatus1300may align the apparatus1300to an explicit grid or “field points” by eye, by utilizing positioning data provided by the one or more location sensors1320, or in a free hand fashion as will be described in connection withFIG. 15.

FIG. 15is a diagram1500illustrating a scan pattern1504of the apparatus1300ofFIG. 13for wireless power field testing of a base pad1510, in accordance with an exemplary implementation. As shown inFIG. 15, the user may place the apparatus1300at an origin1502of a scanning pattern1504, and then may move the apparatus1300across the surface of the base pad1510in the direction of the scanning pattern1504as shown. In some other implementations, the apparatus1300may be moved automatically by a machine configured to guide the apparatus1300across a predetermined area in a predetermined pattern. The sense loop1301(seeFIG. 13) may sense and capture the H-field either continuously or periodically at each of a plurality of positions along the base pad1510, as determined or sensed by the one or more location sensors1320(seeFIG. 13). Where the H-field is not continuously monitored, the apparatus1300may be further configured to utilize mathematically simulation or analysis to interpolate H-field values at intermediate locations based on one more H-field measurements taken at one or more other proximate locations. Accordingly, a simple scanning pattern1504may be suitable to cover the entire surface of the base pad1510. A display (not shown) may then show the user an H-field intensity plot being generated in real time. The real time display may also allow the user to identify regions missed during the scanning pattern1504and to go back to re-scan any such areas.

The steps of a method and functions described in connection with the implementations disclosed herein may be embodied directly in hardware, in a software module executed by a hardware processor, or in a combination of the two. If implemented in software, the functions may be stored on or transmitted 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 hardware processor such that the hardware processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the hardware 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 hardware processor and the storage medium may reside in an ASIC.

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.