Methods of selectively activating antenna zones of a near-field charging pad to maximize wireless power delivered

Description of equivalent WO 2018111921 A1

0001METHODS OF SELECTIVELY ACTIVATING ANTENNA ZONES OF A NEAR-FIELD CHARGING PAD TO MAXIMIZE WIRELESS POWER DELIVERED

TECHNICAL FIELD

0003[0001] The embodiments herein generally relate to antennas, software, and devices used in wireless power transmission systems and, more specifically, to a near-field RF charging pad with adaptive loading to efficiently charge an electronic device at any position on the pad.

BACKGROUND

0005[0002] Conventional charging pads utilize inductive coils to generate a magnetic field that is used to charge a device. Users typically must place the device at a specific position on the charging pad and are unable to move the device to different positions on the pad, without interrupting or terminating the charging of the device. This results in a frustrating experience for many users as they may be unable to locate the device at the exact right position on the pad in which to start charging their device.

0006[0003] Conventional charging pads also utilize components that are distributed across multiple different integrated circuits. Such a configuration results in processing delays that cause these charging pads to operate slower (e.g., wireless charging and adjustments made during wireless charging takes longer) than is desired by users of such pads.

SUMMARY

0008[0004] Accordingly, there is a need for wireless charging systems (e.g., RF charging pads) that address the problems identified above. To this end, an RF charging pad is described herein that includes components that are efficiently arranged on a single integrated circuit, and that single integrated circuit manages antennas of the RF charging pad by selectively or sequentially activating antenna zones (e.g., one or more antennas or unit cell antennas of the RF charging pad that are grouped together, also referred to herein as an antenna group) to locate an efficient antenna zone to use for transmission of wireless power to a receiver device that is located on a surface of the RF charging pad. Such systems and methods of use thereof help to eliminate user dissatisfaction with conventional charging pads. For example, by monitoring transferred energy while selectively activating the antenna zones, such systems and methods of use thereof help to eliminate wasted RF power transmissions by ensuring that energy transfer is maximized at any point in time and at any position at which a device may be placed on an RF charging pad, thus eliminating wasteful transmissions that may not be efficiently received.

0009[0005] In the description that follows, references are made to an RF charging pad that includes various antenna zones. For the purposes of this description, antenna zones include one or more transmitting antennas of the RF charging pad, and each antenna zone may be individually addressable by a controlling integrated circuit (e.g., RF power transmitter integrated circuit 160, Figures 1 A-1B) to allow for selective activation of each antenna zone in order to determine which antenna zone is able to most efficiently transfer wireless power to a receiver. The RF charging pad is also inter-changeably referred to herein as a near-field charging pad, or, more simply, as a charging pad.

0010[0006] (Al) In some embodiments, a method is performed at a near-field charging pad that includes a wireless communication component (e.g., communication component 204, Figure 1 A), a plurality of antenna zones that each respectively include at least one antenna element (e.g., example antenna zones are shown in Figure IB), and one or more processors (e.g., CPU 202, Figures IB and 2A). The method includes detecting, via the wireless communication component, that a wireless power receiver is within a threshold distance of the near-field charging pad and in response to detecting that the wireless power receiver is within the threshold distance of the near-field charging pad, determining whether the wireless power receiver has been placed on the near-field charging pad. The method further includes, in accordance with determining that the wireless power receiver has been placed on the near- field charging pad, selectively transmitting, by respective antenna elements included in the plurality of antenna zones, respective test power transmission signals with a first set of transmission characteristics until a determination is made that a particular power-delivery parameter associated with transmission of a respective test power transmission signal by at least one particular antenna zone of the plurality of antenna zones satisfies power-delivery criteria. Upon determining, by the one or more processors, that the particular power-delivery parameter satisfies the power-delivery criteria, the method further includes transmitting a plurality of additional power transmission signals to the wireless power receiver using the at least one particular antenna zone, wherein each additional power transmission signal of the plurality is transmitted with a second set of transmission characteristics, distinct from the first set.

0011[0007] (A2) In some embodiments of the method of Al, determining whether the wireless power receiver has been placed on the surface of the near-field charging pad includes: (i) transmitting the test power transmission signals using each of the plurality of antenna zones, (ii) monitoring an amount of reflected power at the near-field charging pad while transmitting the test power transmission signals, and (iii) determining that the wireless power receiver has been placed on the near-field charging pad when the amount of reflected power satisfies a device detection threshold.

0012[0008] (A3) In some embodiments of the method of A2, the amount of reflected power is measured at each antenna zone of the plurality of antenna zones.

0013[0009] (A4) In some embodiments of the method of any of A2-A3, the device detection threshold is established during a calibration process for the near-field charging pad.

0014[0010] (A5) In some embodiments of the method of A4, the device detection threshold is specific to a type of device that is coupled with the wireless power receiver, and the device detection threshold is selected by the one or more processors after detecting the wireless power receiver in proximity to the near-field charging pad (e.g., the wireless power receiver sends a packet of information to the near-field charging pad, and that packet of information includes information that identifies the type of device that is coupled with the wireless power receiver).

0015[0011] (A6) In some embodiments of the method of any of A1-A5, selectively transmitting the respective test power transmission signals is performed using each antenna zone of the plurality of antenna zones. In addition, the method further comprises, before the determination is made that the power-delivery parameter associated with transmission of the respective test power transmission signal by the at least one particular antenna zone of the plurality of antenna zones satisfies the power-delivery criteria: (i) updating a respective power-delivery parameter associated with transmission of a respective test power

0016transmission signal by each respective antenna zone based on the transmission by each antenna zone, and (ii) selecting two or more antenna zones, including the at least one particular antenna zone, based on their associated respective power-delivery parameters, to transmit wireless power to the wireless power receiver. [0012] (A7) In some embodiments of the method of A6, the method further comprises using each of the two or more antenna zones to transmit additional test power transmission signals having the first set of transmission characteristics. Moreover, the determination that the particular power-delivery parameter satisfies the power-delivery criteria includes determining that the particular power-delivery parameter indicates that the particular antenna zone is more efficiently transmitting wireless power to the wireless power receiver as compared to other antenna zones of the two or more antenna zones.

0017[0013] (A8) In some embodiments of the method of any of A6-A7, the determination that the particular power-delivery parameter satisfies the power-delivery criteria also includes determining that the particular power-delivery parameter indicates that a first threshold amount of power is transferred to the wireless power receiver by the at least one particular antenna zone, and the at least one particular antenna zone is the only antenna zone of the two or more antenna zones having a respective power-delivery parameter that indicates that the first threshold amount of power is transferred to the wireless power receiver.

0018[0014] (A9) In some embodiments of the method of any of A6-A8, the determination that the particular power-delivery parameter satisfies the power-delivery criteria also includes determining that (i) no antenna zone is transferring a first threshold amount of power to the wireless power receiver and (ii) an additional power-delivery parameter associated with an additional antenna zone of the two or more antenna zones satisfies the power-delivery criteria. In addition, the particular power-delivery parameter indicates that a first amount of power transferred to the wireless power receiver by the particular antenna zone is above a second threshold amount of power and below the first threshold amount of power, and the additional power-delivery parameter indicates that a second amount of power transferred to the wireless power receiver by the additional antenna zone is above the second threshold amount of power and below the first threshold amount of power.

0019[0015] (A10) In some embodiments of the method of A9, both of the particular antenna group and the additional antenna group are used to simultaneously transmit the additional plurality of power transmission signals to provide power to the wireless power receiver.

0020[0016] (Al 1) In some embodiments of the method of any of A1-A10, information used to determine the power-delivery parameter is provided to the near-field charging pad by the wireless power receiver via the wireless communication component of the near-field charging pad.

0021[0017] (A12) In some embodiments of the method of any of Al-Al 1, the second set of transmission characteristics is determined by adjusting at least one characteristic in the first set of transmission characteristics to increase an amount of power that is transferred by the particular antenna group to the wireless power receiver.

0022[0018] (A13) In some embodiments of the method of A12, the at least one adjusted characteristic is a frequency or impedance value.

0023[0019] (A14) In some embodiments of the method of any of A1-A13, while transmitting the additional plurality of power transmission signals, adjusting at least one characteristic in the second set of transmission characteristics based on information, received from the wireless power receiver, that is used to determine a level of power that is wirelessly delivered to the wireless power receiver by the near-field charging pad.

0024[0020] (A15) In some embodiments of the method of any of A1-A14, the one or more processors are components of a single integrated circuit that is used to control operation of the near-field charging pad. For example, any of the methods described herein are managed by the single integrated circuit, such as an instance of the radio frequency (RF) power transmitter integrated circuit 160 shown in Figure IB.

0025[0021] (A16) In some embodiments of the method of any of Al-Al 5, each respective power-delivery metric corresponds to an amount of power received by the wireless power receiver based on transmission of a respective test power transmission signal by a respective antenna group of the plurality of antenna groups.

0026[0022] (A17) In some embodiments of the method of any of Al-Al 6, the method further includes, before transmitting the test power transmission signals, determining that the wireless power receiver is authorized to receive wirelessly delivered power from the near- field charging pad.

0027[0023] (A18) In another aspect, a near-field charging pad is provided. In some embodiments, the near-field charging pad includes a wireless communication component, a plurality of antenna zones that each respectively include at least one antenna element, one or more processors, and memory storing one or more programs, which when executed by the one or more processors cause the near-field charging pad to perform the method described in any one of A1-A17.

0028[0024] (A19) In yet another aspect, a near-field charging pad is provided and the near-field charging includes means for performing the method described in any one of Al- A17.

0029[0025] (A20) In still another aspect, a non-transitory computer-readable storage medium is provided. The non-transitory computer-readable storage medium stores executable instructions that, when executed by a near-field charging pad (that includes a wireless communication component, a plurality of antenna zones that each respectively include at least one antenna element) with one or more processors/cores, cause the near-field charging pad to perform the method described in any one of A1-A17.

0030[0026] As described above, there is also a need for a transmitter chip that includes components for managing transmission of wireless power that are all integrated on a single integrated circuit. Such a transmitter chip and methods of use thereof help to eliminate user dissatisfaction with conventional charging pads. By including all components on a single chip (as discussed in more detail below in reference to Figures 1 A and IB), such transmitter chips are able to manage operations at the transmitter chips more efficiently and quickly (and with lower latency), thereby helping to improve user satisfaction with the charging pads that are managed by these transmitter chips.

0031[0027] (Bl) In some embodiments, a transmitter chip includes: (i) a processing unit that is configured to control operation of the integrated circuit, (ii) a power converter, operatively coupled to the processing unit, that is configured to convert an input current into radio frequency energy, (iii) a waveform generator, operatively coupled to the processing unit, that is configured to generate a plurality of power transmission signals using the radio frequency energy, (iv) a first interface that couples the integrated circuit with a plurality of power amplifiers that are external to the integrated circuit, and (v) a second interface, distinct from the first interface, that couples the integrated circuit with a wireless communication component. The processing unit is also configured to: (i) receive, via the second interface, an indication that a wireless power receiver is within transmission range of a near-field charging pad controlled by the transmitter chip, and (ii) in response to receiving the indication provide, via the first interface, at least some of the plurality of power transmission signals to at least one of the plurality of power amplifiers. [0028] (B2) In some embodiments of the transmitter chip of Bl, the processing unit includes a CPU, ROM, RAM, and encryption (e.g., CPU subsystem 170, Figure IB).

0032[0029] (B3) In some embodiments of the transmitter chip of any of B1-B2, the input current is direct current. Alternatively, in some embodiments, the input current is alternating current. In these embodiments, the power converter is a radio frequency DC-DC converter or a radio frequency AC-AC converter, respectively.

0033[0030] (B4) In some embodiments of the transmitter chip of any of B1-B3, the wireless communication component is a Bluetooth or Wi-Fi radio that is configured to receive communication signals from a device that is placed on a surface of the near-field charging pad.

0034[0031] To help address the problems described above and to thereby provide charging pads that satisfy user needs, the antenna zones described above may include adaptive antenna elements (e.g., antenna zones 290 of the RF charging pad 100, Figure IB, may each respectively include one or more of the antennas 120 described below in reference to Figures 3 A-6E and 8) that are able to adjust energy transmission characteristics (e.g., impedance and frequency for a conductive line of a respective antenna element) so that the charging pad is capable of charging a device that is placed at any position on the pad.

0035[0032] In accordance with some embodiments, the antenna zones of the radio frequency (RF) charging pads described herein may include: one or more antenna elements that are in communication with the one or more processors for transmitting RF signals to the RF receiver of the electronic device. In some embodiments, each respective antenna element includes: (i) a conductive line forming a meandered line pattern; (ii) a first terminal at a first end of the conductive line for receiving current that flows through the conductive line at a frequency controlled by the one or more processors; and (iii) a second terminal, distinct from the first terminal, at a second end of the conductive line, the second terminal coupled with a component that is controlled by the at least one processor and allows for modifying an impedance value at the second terminal. In some embodiments, the at least one processor is configured to adaptively adjust the frequency and/or the impedance value to optimize the amount of energy that is transferred from the one or more antenna elements to the RF receiver of the electronic device.

0036[0033] There is a need for wireless charging systems (e.g., RF charging pads) that include adaptive antenna elements that are able to adjust energy transmission characteristics (e.g., impedance and frequency for a conductive line of a respective antenna element) so that the charging pad is capable of charging a device that is placed at any position on the pad. In some embodiments, these charging pads include one or more processors that monitor energy transferred from the transmitting antenna elements (also referred to herein as RF antenna elements or antenna elements) and to a receiver of an electronic device to be charged, and the one or more processors optimize the energy transmission characteristics to maximize energy transfer at any position on the charging pad. Some embodiments may also include a feedback loop to report received power at the receiver to the one or more processors.

0037[0034] (CI) In accordance with some embodiments, a radio frequency (RF) charging pad is provided. The RF charging pad includes: at least one processor for monitoring an amount of energy that is transferred from the RF charging pad to an RF receiver of an electronic device. The RF charging pad also includes: one or more antenna elements that are in communication with the one or more processors for transmitting RF signals to the RF receiver of the electronic device. In some embodiments, each respective antenna element includes: (i) a conductive line forming a meandered line pattern; (ii) a first terminal at a first end of the conductive line for receiving current that flows through the conductive line at a frequency controlled by the one or more processors; and (iii) a second terminal, distinct from the first terminal, at a second end of the conductive line, the second terminal coupled with a component that is controlled by the at least one processor and allows for modifying an impedance value at the second terminal. In some embodiments, the at least one processor is configured to adaptively adjust the frequency and/or the impedance value to optimize the amount of energy that is transferred from the one or more antenna elements to the RF receiver of the electronic device.

0038[0035] (C2) In accordance with some embodiments, a method is also provided that is used to charge an electronic device through radio frequency (RF) power transmission. The method includes: providing a transmitter comprising at least one RF antenna. The method also includes: transmitting, via at the least one RF antenna, one or more RF signals and monitoring an amount of energy that is transferred via the one or more RF signals from the at least one RF antenna to an RF receiver. The method additionally includes: adaptively adjusting a characteristic of the transmitter to optimize the amount of energy that is transferred from the at least one RF antenna to the RF receiver. In some embodiments, the characteristic is selected from a group consisting of (i) a frequency of the one or more RF signals, (ii) an impedance of the transmitter, and (iii) a combination of (i) and (ii). In some embodiments, the at least one RF antenna is a part of an array of RF antennas.

0039[0036] (C3) In accordance with some embodiments, a radio frequency (RF) charging pad is provided. The RF charging pad includes: one or more processors for monitoring an amount of energy that is transferred from the RF charging pad to an RF receiver of an electronic device. The RF charging pad also includes: one or more transmitting antenna elements that are configured to communicate with the one or more processors for transmitting RF signals to the RF receiver of the electronic device. In some embodiments, each respective antenna element includes: (i) a conductive line forming a meandered line pattern; (ii) an input terminal at a first end of the conductive line for receiving current that flows through the conductive line at a frequency controlled by the one or more processors; and (iii) a plurality of adaptive load terminals, distinct from the input terminal and distinct from each other, at a plurality of positions of the conductive line, each respective adaptive load terminal of the plurality of adaptive load terminals coupled with a respective component that is configured to be controlled by the one or more processors and is configured to allow modifying a respective impedance value at the respective adaptive load terminal. In some embodiments, the one or more processors are configured to adaptively adjust at least one of the frequency and a respective impedance value at one or more of the plurality of adaptive load terminals to optimize the amount of energy that is transferred from the one or more transmitting antenna elements to the RF receiver of the electronic device.

0040[0037] (C4) In accordance with some embodiments, a method is also provided that is used to charge an electronic device through radio frequency (RF) power transmission. The method includes: providing a charging pad that includes a transmitter comprising one or more RF antennas. In some embodiments, each RF antenna includes: (i) a conductive line forming a meandered line pattern; (ii) an input terminal at a first end of the conductive line for receiving current that flows through the conductive line at a frequency controlled by one or more processors; and (iii) a plurality of adaptive load terminals, distinct from the input terminal and distinct from each other, at a plurality of positions of the conductive line, each respective adaptive load terminal of the plurality of adaptive load terminals coupled with a respective component that is controlled by the one or more processors and allows for modifying a respective impedance value at the respective adaptive load terminal. The method also includes: transmitting, via the one or more RF antennas, one or more RF signals, and monitoring an amount of energy that is transferred via the one or more RF signals from the one or more RF antennas to an RF receiver. The method additionally includes: adaptively adjusting a characteristic of the transmitter using the one or more processors of the transmitter to optimize the amount of energy that is transferred from the one or more RF antennas to the RF receiver. In some embodiments, the characteristic is selected from a group consisting of (i) a frequency of the one or more RF signals, (ii) an impedance of the transmitter, and (iii) a combination of (i) and (ii). In some embodiments, the impedance of the transmitter is adaptively adjusted at a respective one or more of the plurality of adaptive load terminals of the one or more RF antennas using the one or more processors of the transmitter.

0041[0038] (C5) In accordance with some embodiments, a non-transitory computer- readable storage medium is provided. The non-transitory computer-readable storage medium includes executable instructions that, when executed by one or more processors that are coupled with a radio frequency (RF) charging pad that includes one or more transmitting antenna elements, cause the one or more processors to: monitor an amount of energy that is transferred from the RF charging pad to an RF receiver of an electronic device; and communication with the one or more transmitting antenna elements for transmitting RF signals to the RF receiver of the electronic device. In some embodiments, each respective transmitting antenna element includes: a conductive line forming a meandered line pattern; an input terminal at a first end of the conductive line for receiving current that flows through the conductive line at a frequency controlled by the one or more processors; and a plurality of adaptive load terminals, distinct from the input terminal and distinct from each other, at a plurality of positions of the conductive line, each respective adaptive load terminal of the plurality of adaptive load terminals coupled with a respective component that is configured to be controlled by the one or more processors and is configured to allow modifying a respective impedance value at each respective adaptive load terminal. And the one or more processors further adaptively adjust at least one of the frequency and a respective impedance value at one or more of the plurality of adaptive load terminals to optimize the amount of energy that is transferred from the one or more transmitting antenna elements to the RF receiver of the electronic device.

0042[0039] (C6) In some embodiments of any of C1-C5, the frequency is in a first frequency band, and at least one of the one or more transmitting antenna elements is configured to operate at a second frequency band based on adaptive adjustments, by the one or more processors, to respective impedance values at one or more of the plurality of adaptive load terminals of the at least one transmitting antenna element.

0043[0040] (C7) In some embodiments of any of C1-C6, the RF charging pad includes an input circuit that is coupled with the one or more processors and is configured to provide the current to the input terminal at the first end of the conductive line, wherein the one or more processors are configured to adaptively adjust the frequency by instructing the input circuit to generate the current with a new frequency that is distinct from the frequency.

0044[0041] (C8) In some embodiments of any of C1-C7, the one or more processors are configured to adaptively adjust the frequency by instructing the feeding element to generate the current with a plurality of different frequencies that are determined using predetermined increments.

0045[0042] (C9) In some embodiments of any of C1-C8, a respective conductive line for at least one of the one or more transmitting antenna elements has a respective meandered line pattern that allows the at least one transmitting antenna element to efficiently transmit RF signals having the frequency and/or the new frequency, at least two adjacent segments of the respective conductive line having the respective meandered line pattern have different geometric dimensions relative to each other, and the respective conductive line has a length that remains the same when the at least one transmitting antenna element is configured to transmit RF signals having the frequency and/or the new frequency.

0046[0043] (CIO) In some embodiments of any of C1-C9, at least one transmitting antenna element of the one or more transmitting antenna elements has a first segment and a second segment, the first segment including the input terminal, and the at least one transmitting antenna element is configured to: operate at the frequency while the first segment is not coupled with the second segment, and operate at the new frequency while the first segment is coupled with the second segment; and the one or more processors are configured to couple the first segment with the second segment in conjunction with instructing the feeding element to generate the current with the new frequency that is distinct from the frequency.

0047[0044] (CI 1) In some embodiments of any of CI -CIO, the one or more processors are configured to: adaptively adjust the frequency and/or a respective impedance value associated with a first transmitting antenna element of the one or more transmitting antenna elements to cause the first transmitting antenna element to operate in a first frequency band, and adaptively adjust the frequency and/or the respective impedance value associated with a second transmitting antenna element of the one or more transmitting antenna elements to cause the second transmitting antenna element to operate in a second frequency band, wherein the first frequency band is distinct from the second frequency band.

0048[0045] (C12) In some embodiments of any of Cl-Cl 1, the electronic device is placed in contact with or close to a top surface of the RF charging pad.

0049[0046] (C13) In some embodiments of any of C1-C12, the respective component is a mechanical relay coupled with the respective adaptive load terminal for switching the respective adaptive load terminal between open and short states, and the impedance value is adaptively adjusted at the respective adaptive load terminal of the respective transmitting antenna element by opening or closing the mechanical relay to switch between an open or short circuit, respectively.

0050[0047] (C14) In some embodiments of any of C1-C13, the respective component is an application-specific integrated circuit (ASIC), and the respective impedance value is adaptively adjusted by the ASIC to within a range of values.

0051[0048] (CI 5) In some embodiments of any of CI -CI 4, the one or more processors are configured to: adaptively adjust the frequency and/or the respective impedance value by adaptively adjusting the frequency and a respective impedance value at one or more of the plurality of adaptive load terminals to determine a relative maximum amount of energy that is transferred to the RF receiver of the electronic device, and once the maximum amount of energy is determined, cause each of the one or more transmitting antenna elements to respectively transmit the RF signals at a respective frequency and using a respective impedance value that resulted in the maximum amount of energy transferred to the RF receiver.

0052[0049] (CI 6) In some embodiments of any of CI -CI 5, the one or more processors monitor the amount of energy that is transferred to the RF receiver based at least in part on information received from the electronic device, the information identifying energy received at the RF receiver from the RF signals.

0053[0050] (CI 7) In some embodiments of any of CI -CI 6, the information received from the electronic device identifying received energy is sent using a wireless communication protocol. [0051] (CI 8) In some embodiments of any of CI -CI 7, the wireless communication protocol is bluetooth low energy (BLE).

0054[0052] (CI 9) In some embodiments of any of CI -CI 8, the one or more processors monitor the amount of energy transferred based at least in part on an amount of energy that is detected at the respective adaptive load terminal.

0055[0053] Thus, wireless charging systems configured in accordance with the principles described herein are able to charge an electronic device that is placed at any position on the RF charging pad and avoid wasting energy by ensuring that energy transfer is constantly optimized.

0056[0054] In addition, wireless charging systems configured in accordance with the principles described herein are able to charge different electronic devices that are tuned at different frequencies or frequency bands on the same charging transmitter. In some embodiments, a transmitter with a single antenna element can operate at multiple frequencies or frequency bands at the same time or at different times. In some embodiments, a transmitter with multiple antenna elements can operate at multiple frequencies or frequency bands at the same time. That enables more flexibility in the types and sizes of antennas that are included in receiving devices.

0057[0055] Note that the various embodiments described above can be combined with any other embodiments described herein. The features and advantages described in the specification are not all inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and not intended to

0058circumscribe or limit the inventive subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

0060[0056] So that the present disclosure can be understood in greater detail, a more particular description may be had by reference to the features of various embodiments, some of which are illustrated in the appended drawings. The appended drawings, however, merely illustrate pertinent features of the present disclosure and are therefore not to be considered limiting, for the description may admit to other effective features. [0057] Figure 1 A is a block diagram of an RF wireless power transmission system, in accordance with some embodiments.

0061[0058] Figure IB is a block diagram showing components of an example RF charging pad that includes an RF power transmitter integrated circuit and antenna zones, in accordance with some embodiments.

0062[0059] Figure 2A is a block diagram illustrating an example RF charging pad, in accordance with some embodiments.

0063[0060] Figure 2B is a block diagram illustrating an example receiver device, in accordance with some embodiments.

0064[0061] Figure 3 A is a high-level block diagram of an RF charging pad, in accordance with some embodiments.

0065[0062] Figures 3B-3C are high-level block diagrams showing a portion of an RF charging pad, in accordance with some embodiments.

0066[0063] Figure 3D is a block diagram of a simplified circuit that illustrates energy flow within sections of an antenna element that is transmitting an RF signal, in accordance with some embodiments.

0067[0064] Figure 4 is a schematic of a transmitting antenna element with two terminals, in accordance with some embodiments.

0068[0065] Figure 5 is a flow chart of a method of charging an electronic device through radio frequency (RF) power transmission.

0069[0066] Figures 6A-6E are schematics showing various configurations for individual antenna elements within an RF charging pad, in accordance with some embodiments.

0070[0067] Figures 7A-7D are schematics of an antenna element for an RF receiver, in accordance with some embodiments.

0071[0068] Figure 8 is a schematic of an RF charging pad with a plurality of transmitting antenna elements (or unit cells), in accordance with some embodiments.

0072[0069] Figures 9A-9B are flow diagrams showing a method 900 of selectively activating one or more antenna zones in a near-field charging pad, in accordance with some embodiments. [0070] Figure 10 is an overview showing a process of selectively activating one or more antenna zones in a near-field charging pad, in accordance with some embodiments.

0073[0071] Figures 11 A-l IE are flow diagrams showing various aspects of selectively activating one or more antenna zones in a near-field charging pad, in accordance with some embodiments.

0074[0072] Figure 12 is a schematic of a transmitting antenna element with a plurality of adaptive loads of an RF charging pad, in accordance with some embodiments.

0075[0073] Figure 13 is a flow chart of a method of charging an electronic device through radio frequency (RF) power transmission by using at least one RF antenna with a plurality of adaptive loads, in accordance with some embodiments.

0076[0074] Figures 14A-14D are schematics showing various configurations for individual antenna elements that can operate at multiple frequencies or frequency bands within an RF charging pad, in accordance with some embodiments.

0077[0075] Figure 15 is schematic showing an example configuration for an individual antenna element that can operate at multiple frequencies or frequency bands by adjusting the length of the antenna element, in accordance with some embodiments.

0078[0076] In accordance with common practice, 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.

DESCRIPTION OF EMBODIMENTS

0080[0077] Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the various described embodiments. However, it will be apparent to one of ordinary skill in the art that the various described embodiments may be practiced without these specific details. In other instances, well-known methods, procedures, components, circuits, and networks have not been described in detail so as not to unnecessarily obscure aspects of the embodiments. [0078] Figure 1 A is a block diagram of an RF wireless power transmission system in accordance with some embodiments. In some embodiments, the RF wireless power transmission system 150 includes a RF charging pad 100 (also referred to herein as a near- field (NF) charging pad 100 or RF charging pad 100). In some embodiments, the RF charging pad 100 includes an RF power transmitter integrated circuit 160 (described in more detail below). In some embodiments, the RF charging pad 100 includes one or more communications components 204 (e.g., wireless communication components, such as WI-FI or BLUETOOTH radios), discussed in more detail below with reference to Figure 2A. In some embodiments, the RF charging pad 100 also connects to one or more power amplifier units 108-1, ... 108-n to control operation of the one or more power amplifier units when they drive an external TX antenna array 210 (e.g., antennas 210, Figure 2A). In some embodiments, RF power is controlled and modulated at the RF charging pad 100 via switch circuitry as to enable the RF wireless power transmission system to send RF power to one or more wireless receiving devices via the TX antenna array 210. Example power amplifier units are discussed in further detail below with reference to Figure 3 A.

0081[0079] In some embodiments, the communication component(s) 204 enable communication between the RF charging pad 100 and one or more communication networks. In some embodiments, the communication component(s) 204 are capable of data

0082communications using any of a variety of custom or standard wireless protocols (e.g., IEEE 802.15.4, Wi-Fi, ZigBee, 6L0WPAN, Thread, Z-Wave, Bluetooth Smart, ISAlOO. l la, WirelessHART, MiWi, etc.) custom or standard wired protocols (e.g., Ethernet, HomePlug, etc.), and/or any other suitable communication protocol, including communication protocols not yet developed as of the filing date of this document.

0083[0080] Figure IB is a block diagram of the RF power transmitter integrated circuit

0084160 (the "integrated circuit") in accordance with some embodiments. In some embodiments, the integrated circuit 160 includes a CPU subsystem 170, an external device control interface, an RF subsection for DC to RF power conversion, and analog and digital control interfaces interconnected via an interconnection component, such as a bus or interconnection fabric block 171. In some embodiments, the CPU subsystem 170 includes a microprocessor unit (CPU) 202 with related Read-Only-Mem ory (ROM) 172 for device program booting via a digital control interface, e.g. an I²C port, to an external FLASH containing the CPU executable code to be loaded into the CPU Subsystem Random Access Memory (RAM) 174 (e.g., memory 206, Figure 2 A) or executed directly from FLASH. In some embodiments, the CPU subsystem 170 also includes an encryption module or block 176 to authenticate and secure communication exchanges with external devices, such as wireless power receivers that attempt to receive wirelessly delivered power from the RF charging pad 100.

0085[0081] In some embodiments, executable instructions running on the CPU (such as those shown in the memory 206 in Figure 2A and described below) are used to manage operation of the RF charging pad 100 and to control external devices through a control interface, e.g., SPI control interface 175, and the other analog and digital interfaces included in the RF power transmitter integrated circuit 160. In some embodiments, the CPU subsystem also manages operation of the RF subsection of the RF power transmitter integrated circuit 160, which includes an RF local oscillator (LO) 177 and an RF transmitter (TX) 178. In some embodiments, the RF LO 177 is adjusted based on instructions from the CPU subsystem 170 and is thereby set to different desired frequencies of operation, while the RF TX converts, amplifies, modulates the RF output as desired to generate a viable RF power level.

0086[0082] In some embodiments, the RF power transmitter integrated circuit 160 provides the viable RF power level (e.g., via the RF TX 178) to an optional beamforming integrated circuit (IC) 109, which then provides phase-shifted signals to one or more power amplifiers 108. In some embodiments, the beamforming IC 109 is used to ensure that power transmission signals sent using two or more antennas 210 (e.g., each antenna 210 may be associated with a different antenna zones 290 or may each belong to a single antenna zone 290) to a particular wireless power receiver are transmitted with appropriate characteristics (e.g., phases) to ensure that power transmitted to the particular wireless power receiver is maximized (e.g., the power transmission signals arrive in phase at the particular wireless power receiver). In some embodiments, the beamforming IC 109 forms part of the RF power transmitter IC 160.

0087[0083] In some embodiments, the RF power transmitter integrated circuit 160 provides the viable RF power level (e.g., via the RF TX 178) directly to the one or more power amplifiers 108 and does not use the beamforming IC 109 (or bypasses the

0088beamforming IC if phase-shifting is not required, such as when only a single antenna 210 is used to transmit power transmission signals to a wireless power receiver).

0089[0084] In some embodiments, the one or more power amplifiers 108 then provide RF signals to the antenna zones 290 for transmission to wireless power receivers that are authorized to receive wirelessly delivered power from the RF charging pad 100. In some embodiments, each antenna zone 290 is coupled with a respective PA 108 (e.g., antenna zone 290-1 is coupled with PA 108-1 and antenna zone 290-N is coupled with PA 108-N). In some embodiments, multiple antenna zones are each coupled with a same set of PAs 108 (e.g., all PAs 108 are coupled with each antenna zone 290). Various arrangements and couplings of PAs 108 to antenna zones 290 allow the RF charging pad 100 to sequentially or selectively activate different antenna zones in order to determine the most efficient antenna zone 290 to use for transmitting wireless power to a wireless power receiver (as explained in more detail below in reference to Figures 9A-9B, 10, and 11 A-l IE). In some embodiments, the one or more power amplifiers 108 are also in communication with the CPU subsystem 170 to allow the CPU 202 to measure output power provided by the PAs 108 to the antenna zones of the RF charging pad 100.

0090[0085] Figure IB also shows that, in some embodiments, the antenna zones 290 of the

0091RF charging pad 100 may include one or more antennas 210A-N. In some embodiments, each antenna zones of the plurality of antenna zones includes one or more antennas 210 (e.g., antenna zone 290-1 includes one antenna 210- A and antenna zones 290-N includes multiple antennas 210). In some embodiments, a number of antennas included in each of the antenna zones is dynamically defined based on various parameters, such as a location of a wireless power receiver on the RF charging pad 100. In some embodiments, the antenna zones may include one or more of the meandering line antennas described in more detail below. In some embodiments, each antenna zone 290 may include antennas of different types (e.g., a meandering line antenna and a loop antenna), while in other embodiments each antenna zone 290 may include a single antenna of a same type (e.g., all antenna zones 290 include one meandering line antenna), while in still other embodiments, the antennas zones may include some antenna zones that include a single antenna of a same type and some antenna zones that include antennas of different types. Antenna zones are also described in further detail below.

0092[0086] In some embodiments, the RF charging pad 100 may also include a temperature monitoring circuit that is in communication with the CPU subsystem 170 to ensure that the RF charging pad 100 remains within an acceptable temperature range. For example, if a determination is made that the RF charging pad 100 has reached a threshold temperature, then operation of the RF charging pad 100 may be temporarily suspended until the RF charging pad 100 falls below the threshold temperature. [0087] By including the components shown for RF power transmitter circuit 160

0093(Figure IB) on a single chip, such transmitter chips are able to manage operations at the transmitter chips more efficiently and quickly (and with lower latency), thereby helping to improve user satisfaction with the charging pads that are managed by these transmitter chips. For example, the RF power transmitter circuit 160 is cheaper to construct, has a smaller physical footprint, and is simpler to install. Furthermore, and as explained in more detail below in reference to Figure 2A, the RF power transmitter circuit 160 may also include a secure element module 234 (e.g., included in the encryption block 176 shown in Figure IB) that is used in conjunction with a secure element module 282 (Figure 2B) or a receiver 104 to ensure that only authorized receivers are able to receive wirelessly delivered power from the RF charging pad 100 (Figure IB).

0094[0088] Figure 2A is a block diagram illustrating certain components of an RF charging pad 100 in accordance with some embodiments. In some embodiments, the RF charging pad 100 includes an RF power transmitter IC 160 (and the components included therein, such as those described above in reference to Figures 1 A-1B), memory 206 (which may be included as part of the RF power transmitter IC 160, such as nonvolatile memory 206 that is part of the CPU subsystem 170), and one or more communication buses 208 for interconnecting these components (sometimes called a chipset). In some embodiments, the RF charging pad 100 includes one or more sensor(s) 212 (discussed below). In some embodiments, the RF charging pad 100 includes one or more output devices such as one or more indicator lights, a sound card, a speaker, a small display for displaying textual information and error codes, etc. In some embodiments, the RF charging pad 100 includes a location detection device, such as a GPS (global positioning satellite) or other geo-location receiver, for determining the location of the RF charging pad 100.

0095[0089] In some embodiments, the one or more sensor(s) 212 include one or more thermal radiation sensors, ambient temperature sensors, humidity sensors, IR sensors, occupancy sensors (e.g., RFID sensors), ambient light sensors, motion detectors,

0096accelerometers, and/or gyroscopes.

0097[0090] The memory 206 includes high-speed random access memory, such as

0098DRAM, SRAM, DDR SRAM, or other random access solid state memory devices; and, optionally, includes non-volatile memory, such as one or more magnetic disk storage devices, one or more optical disk storage devices, one or more flash memory devices, or one or more other non-volatile solid state storage devices. The memory 206, or alternatively the nonvolatile memory within memory 206, includes a non-transitory computer-readable storage medium. In some embodiments, the memory 206, or the non-transitory computer-readable storage medium of the memory 206, stores the following programs, modules, and data structures, or a subset or superset thereof:

0099• Operating logic 216 including procedures for handling various basic system services and for performing hardware dependent tasks;

0100• Communication module 218 for coupling to and/or communicating with remote

0101devices (e.g., remote sensors, transmitters, receivers, servers, mapping memories, etc.) in conjunction with wireless communication component(s) 204;

0102• Sensor module 220 for obtaining and processing sensor data (e.g., in conjunction with sensor(s) 212) to, for example, determine the presence, velocity, and/or positioning of object in the vicinity of the RF charging pad 100;

0103• Power-wave generating module 222 for generating and transmitting power

0104transmission signals (e.g., in conjunction with antenna zones 290 and the antennas 210 respectively included therein), including but not limited to, forming pocket(s) of energy at given locations. Power-wave generating module 222 may also be used to modify transmission characteristics used to transmit power transmission signals by individual antenna zones; and

0105• Database 224, including but not limited to: o Sensor information 226 for storing and managing data received, detected, and/or transmitted by one or more sensors (e.g., sensors 212 and/or one or more remote sensors); o Device settings 228 for storing operational settings for the RF charging pad 100 and/or one or more remote devices; o Communication protocol information 230 for storing and managing protocol information for one or more protocols (e.g., custom or standard wireless protocols, such as ZigBee, Z-Wave, etc., and/or custom or standard wired protocols, such as Ethernet); and o Mapping data 232 for storing and managing mapping data (e.g., mapping one or more transmission fields); • a secure element module 234 for determining whether a wireless power receiver is authorized to receive wirelessly delivered power from the RF charging pad 100; and

0106• an antenna zone selecting and tuning module 237 for coordinating a process of

0107transmitting test power transmission signals with various antenna zones to determine which antenna zone or zones should be used to wirelessly deliver power to various wireless power receivers (as is explained in more detail below in reference to Figures 9A-9B, 100, and 11A-11E).

0108[0091] Each of the above-identified elements (e.g., modules stored in memory 206 of the RF charging pad 100) is optionally stored in one or more of the previously mentioned memory devices, and corresponds to a set of instructions for performing the function(s) described above. The above identified modules or programs (e.g., sets of instructions) need not be implemented as separate software programs, procedures, or modules, and thus various subsets of these modules are optionally combined or otherwise rearranged in various embodiments. In some embodiments, the memory 206, optionally, stores a subset of the modules and data structures identified above.

0109[0092] Figure 2B is a block diagram illustrating a representative receiver device 104

0110(also sometimes called a receiver, power receiver, or wireless power receiver) in accordance with some embodiments. In some embodiments, the receiver device 104 includes one or more processing units (e.g., CPUs, ASICs, FPGAs, microprocessors, and the like) 252, one or more communication components 254, memory 256, antenna(s) 260, power harvesting circuitry 259, and one or more communication buses 258 for interconnecting these components (sometimes called a chipset). In some embodiments, the receiver device 104 includes one or more sensor(s) 262 such as the one or sensors 212 described above with reference to Figure 2 A. In some embodiments, the receiver device 104 includes an energy storage device 261 for storing energy harvested via the power harvesting circuitry 259. In various embodiments, the energy storage device 261 includes one or more batteries, one or more capacitors, one or more inductors, and the like.

0111[0093] In some embodiments, the power harvesting circuitry 259 includes one or more rectifying circuits and/or one or more power converters. In some embodiments, the power harvesting circuitry 259 includes one or more components (e.g., a power converter) configured to convert energy from power waves and/or energy pockets to electrical energy (e.g., electricity). In some embodiments, the power harvesting circuitry 259 is further configured to supply power to a coupled electronic device, such as a laptop or phone. In some embodiments, supplying power to a coupled electronic device include translating electrical energy from an AC form to a DC form (e.g., usable by the electronic device).

0112[0094] In some embodiments, the antenna(s) 260 include one or more of the meandering line antennas that are described in further detail below.

0113[0095] In some embodiments, the receiver device 104 includes one or more output devices such as one or more indicator lights, a sound card, a speaker, a small display for displaying textual information and error codes, etc. In some embodiments, the receiver device 104 includes a location detection device, such as a GPS (global positioning satellite) or other geo-location receiver, for determining the location of the receiver device 103.

0114[0096] In various embodiments, the one or more sensor(s) 262 include one or more thermal radiation sensors, ambient temperature sensors, humidity sensors, IR sensors, occupancy sensors (e.g., RFID sensors), ambient light sensors, motion detectors,

0115accelerometers, and/or gyroscopes.

0116[0097] The communication component(s) 254 enable communication between the receiver 104 and one or more communication networks. In some embodiments, the communication component(s) 254 are capable of data communications using any of a variety of custom or standard wireless protocols (e.g., IEEE 802.15.4, Wi-Fi, ZigBee, 6L0WPAN, Thread, Z-Wave, Bluetooth Smart, ISAlOO. l la, WirelessHART, MiWi, etc.) custom or standard wired protocols (e.g., Ethernet, HomePlug, etc.), and/or any other suitable communication protocol, including communication protocols not yet developed as of the filing date of this document.

0117[0098] The communication component(s) 254 include, for example, hardware capable of data communications using any of a variety of custom or standard wireless protocols (e.g., IEEE 802.15.4, Wi-Fi, ZigBee, 6L0WPAN, Thread, Z-Wave, Bluetooth Smart, ISAlOO. l la, WirelessHART, MiWi, etc.) and/or any of a variety of custom or standard wired protocols (e.g., Ethernet, HomePlug, etc.), or any other suitable communication protocol, including communication protocols not yet developed as of the filing date of this document.

0118[0099] The memory 256 includes high-speed random access memory, such as

0119DRAM, SRAM, DDR SRAM, or other random access solid state memory devices; and, optionally, includes non-volatile memory, such as one or more magnetic disk storage devices, one or more optical disk storage devices, one or more flash memory devices, or one or more other non-volatile solid state storage devices. The memory 256, or alternatively the nonvolatile memory within memory 256, includes a non-transitory computer-readable storage medium. In some embodiments, the memory 256, or the non-transitory computer-readable storage medium of the memory 256, stores the following programs, modules, and data structures, or a subset or superset thereof:

0120• Operating logic 266 including procedures for handling various basic system services and for performing hardware dependent tasks;

0121• Communication module 268 for coupling to and/or communicating with remote

0122devices (e.g., remote sensors, transmitters, receivers, servers, mapping memories, etc.) in conjunction with communication component(s) 254;

0123• Sensor module 270 for obtaining and processing sensor data (e.g., in conjunction with sensor(s) 262) to, for example, determine the presence, velocity, and/or positioning of the receiver 103, a RF charging pad 100, or an object in the vicinity of the receiver 103;

0124• Wireless power-receiving module 272 for receiving (e.g., in conjunction with

0125antenna(s) 260 and/or power harvesting circuitry 259) energy from power waves and/or energy pockets; optionally converting (e.g., in conjunction with power harvesting circuitry 259) the energy (e.g., to direct current); transferring the energy to a coupled electronic device; and optionally storing the energy (e.g., in conjunction with energy storage device 261); and

0126• Database 274, including but not limited to: o Sensor information 276 for storing and managing data received, detected, and/or transmitted by one or more sensors (e.g., sensors 262 and/or one or more remote sensors); o Device settings 278 for storing operational settings for the receiver 103, a coupled electronic device, and/or one or more remote devices; and o Communication protocol information 280 for storing and managing protocol information for one or more protocols (e.g., custom or standard wireless protocols, such as ZigBee, Z-Wave, etc., and/or custom or standard wired protocols, such as Ethernet); and • a secure element module 282 for providing identification information to the RF charging pad 100 (e.g., the RF charging pad 100 uses the identification information to determine if the wireless power receiver 104 is authorized to receive wirelessly delivered power).

0127[00100] Each of the above-identified elements (e.g., modules stored in memory 256 of the receiver 104) is optionally stored in one or more of the previously mentioned memory devices, and corresponds to a set of instructions for performing the function(s) described above. The above identified modules or programs (e.g., sets of instructions) need not be implemented as separate software programs, procedures, or modules, and thus various subsets of these modules are optionally combined or otherwise rearranged in various embodiments. In some embodiments, the memory 256, optionally, stores a subset of the modules and data structures identified above. Furthermore, the memory 256, optionally, stores additional modules and data structures not described above, such as an identifying module for identifying a device type of a connected device (e.g., a device type for an electronic device that is coupled with the receiver 104).

0128[00101] Turning now to Figures 3 A through 8, embodiments of the RF charging pad

0129100 are shown that include a component for modifying impedance values (e.g., a load pick) at various antennas of the RF charging pad 100, and descriptions of antennas that include a conductive line forming a meandering line pattern are also provided in reference to these figures.

0130[00102] As shown in Figure 3 A, some embodiments include an RF charging pad 100 that includes a load pick 106 to allow for modifying impedance values at various antennas of the RF charging pad 100. In some embodiments, the RF charging pad 100 includes one or more antenna elements that are each powered/ fed by a respective power amplifier switch circuit 103 at a first end and a respective adaptive load terminal 102 at a second end

0131(additional details and descriptions of the one or more antenna elements are provided below in reference to Figures 3B-3C).

0132[00103] In some embodiments, the RF charging pad 100 also includes (or is in communication with) a central processing unit 110 (also referred to here as processor 110). In some embodiments, the processor 110 is a component of a single integrated circuit that is responsible for managing operations of the RF charging pad 100, such as the CPU 202 illustrated in Figure IB and included as a component of the RF power transmitter integrated circuit 160. In some embodiments, the processor 110 is configured to control RF signal frequencies and to control impedance values at each of the adaptive load terminals 102 (e.g., by communicating with the load pick or adaptive load 106, which may be an application- specific integrated circuit (ASIC), or a variable resister, to generate various impedance values). In some embodiments, the load pick 106 is an electromechanical switch that is placed in either an open or shorted state.

0133[00104] In some embodiments, an electronic device (e.g., a device that includes a receiver 104 as an internally or externally connected component, such as a remote that is placed on top of a charging pad 100 that may be integrated within a housing of a streaming media device or a projector) and uses energy transferred from one or more RF antenna elements of the charging pad 100 to the receiver 104 to charge a battery and/or to directly power the electronic device.

0134[00105] In some embodiments, the RF charging pad 100 is configured with more than one input terminal for receiving power (from power amplifier (PA) 108, Figure 3 A) and more than one output or adaptive load terminal 102. In some embodiments, the adaptive load terminals 102 at a particular zone of the RF charging pad 100 (e.g., a zone that includes antenna elements located underneath a position at which an electronic device (with an internally or externally connected RF receiver 104) to be charged is placed on the charging pad) are optimized in order to maximize power received by the receiver 104. For example, the CPU 110 upon receiving an indication that an electronic device with an internally or externally connected RF receiver 104 has been placed on the pad 100 in a particular zone 105 (the zone 105 includes a set of antenna elements) may adapt the set of antenna elements to maximize power transferred to the RF receiver 104. Adapting the set of antenna elements may include the CPU 110 commanding load pick 106 to try various impedance values for adaptive load terminals 102 that are associated with the set of antenna elements. For example, the impedance value for a particular conductive line at an antenna element is given by the complex value of Z = A + jB (where A is the real part of the impedance value and B is the imaginary part, e.g., 0+jO, 1000+jO, 0+50j, or 25+j75, etc.), and the load pick adjusts the impedance value to maximize the amount of energy transferred from the set of antenna elements to the RF receiver 104. In some embodiments, adapting the set of antenna elements also or alternatively includes the CPU 110 causing the set of antenna elements to transmit RF signals at various frequencies until a frequency is found at which a maximum amount of energy is transferred to the RF receiver 104. In some embodiments, adjusting the impedance value and/or the frequencies at which the set of antenna elements transmits causes changes to the amount of energy transferred to the RF receiver 104. In this way, the amount of energy transferred to the RF receiver 104 is maximized (e.g., to transfer at least 75% of the energy transmitted by antenna elements of the pad 100 to the receiver 104, and in some

0135embodiments, adjusting the impedance value and/frequencies may allow up to 98% of the energy transmitted to be received by the receiver 104) may be received at any particular point on the pad 100 at which the RF receiver 104 might be placed.

0136[00106] In some embodiments, the input circuit that includes the power amplifier 108 can additionally include a device that can change frequencies of the input signal, or a device that can operate at multiple frequencies at the same time, such as an oscillator or a frequency modulator.

0137[00107] In some embodiments, the CPU 110 determines that a maximum amount of energy is being transferred to the RF receiver 104 when the amount of energy transferred to the RF receiver 104 crosses a predetermined threshold (e.g., 75% or more of transmitted energy is received, such as up to 98%) or by testing transmissions with a number of impedance and/or frequency values and then selecting the combination of impedance and frequency that results in maximum energy being transferred to the RF receiver 104 (as described in reference to the adaptation scheme below).

0138[00108] In some embodiments, an adaptation scheme is employed to adaptively adjust the impedance values and/or frequencies of the RF signal(s) emitted from the RF antenna(s) 120 of the charging pad 100, in order to determine which combinations of frequency and impedance result in maximum energy transfer to the RF receiver 104. For example, the processor 110 that is connected to the charging pad 100 tries different frequencies (i.e., in the allowed operating frequency range or ranges) at a given location of the RF charging pad 100 (e.g., a zone or area of the RF charging pad 100 that includes one or more RF antenna elements for transmitting RF signals, such as zone 105 of Figure 3 A) to attempt to adaptively optimize for better performance. For example, a simple optimization either

0139opens/disconnects or closes/shorts each load terminal to ground (in embodiments in which a relay is used to switch between these states), and may also cause RF antennas within the zone to transmit at various frequencies. In some embodiments, for each combination of relay state (open or shorted) and frequency, the energy transferred to the receiver 104 is monitored and compared to energy transferred when using other combinations. The combination that results in maximum energy transfer to the receiver 104 is selected and used to continue to transmitting the one or more RF signals to the receiver 104. In some embodiments, the adaptation scheme described above is performed as a part of the methods described below in reference to Figures 9A-9B, 10, and 11 A-l IE to help maximize an amount of energy transferred by the RF charging pad 100 to the receiver 104.

0140[00109] As another example, if five frequencies in the ISM band are utilized by the pad 100 for transmitting radio frequency waves and the load pick 106 is an electromechanical relay for switching between open and shorted states, then employing the adaptation scheme would involve trying 10 combinations of frequencies and impedance values for each antenna element 120 or for a zone of antenna elements 120 and selecting the combination that results in best performance (i.e., results in most power received at receiver 104, or most power transferred from the pad 100 to the RF receiver 104).

0141[00110] The industrial, scientific, and medical radio bands (ISM bands) refers to a group of radio bands or parts of the radio spectrum that are internationally reserved for the use of radio frequency (RF) energy intended for scientific, medical and industrial

0142requirements rather than for communications. In some embodiments, all ISM bands (e.g., 40 MHz, 900 MHz, 2.4 GHz, 5.8 GHz, 24 GHz, 60 GHz, 122 GHz, and 245 GHz) may be employed as part of the adaptation scheme. As one specific example, if the charging pad 100 is operating in the 5.8 GHz band, then employing the adaptation scheme would include transmitting RF signals and then adjusting the frequency at predetermined increments (e.g., 50 MHz increments, so frequencies of 5.75 GHz, 5.755 GHz, 5.76 GHz, and so on). In some embodiments, the predetermined increments may be 5, 10 15, 20, 50 MHz increments, or any other suitable increment.

0143[00111] In some embodiments, the antenna elements 120 of the pad 100 may be configured to operate in two distinct frequency bands, e.g., a first frequency band with a center frequency of 915 MHz and a second frequency band with a center frequency of 5.8 GHz. In these embodiments, employing the adaptation scheme may include transmitting RF signals and then adjusting the frequency at first predetermined increments until a first threshold value is reached for the first frequency band and then adjusting the frequency at second predetermined increments (which may or may not be the same as the first

0144predetermined increments) until a second threshold value is reached for the second frequency band. For example, the antenna elements 120 may be configured to transmit at 902 MHz, 915 MHz, 928 MHZ (in the first frequency band) and then at 5.795 GHz, 5.8 GHz, and 5.805 GHz (in the second frequency band). Additional details regarding antenna elements that are capable of operating at multiple frequencies are provided below in reference to Figures HAND and 15.

0145[00112] Turning now to Figures 3B-3C, high-level block diagrams showing a portion of an RF charging pad are illustrated, in accordance with some embodiments.

0146[00113] Figure 3B shows a schematic of a single TX antenna 120 (which may be a part of an antenna zone that includes one or an array of such antennas 120, all forming the charging pad 100 that is shown in Figure 3A). In some embodiments, the TX antenna 120 is also referred to as a TX antenna element 120. In some circumstances, an RF receiving unit/antenna (RX) (or a device that includes the receiving unit 104 as an internally or externally connected component) is placed on top of a portion of the pad 100 that includes the TX antenna 120 (which includes a conductive line that forms a meandered line arrangement, as shown in Figure 3B).

0147[00114] In some embodiments, the receiver 104 has no direct contact to a metallic conductive line of the single TX antenna 120 and is just coupled (i.e. in near-field zone) to the TX antenna 120.

0148[00115] In some embodiments, the TX antenna 120 has two or more terminals (or ports) that are labeled as 121 (which may be a respective one of the terminals 102 of Figure 3A) and 123 (which may be connected to a respective one of the PA switch circuits 103 of Figure 3A) in Figure 3B. In some embodiments, the source of power (from the power amplifier or PA) is connected to terminal 123 and an adaptive load (e.g., an

0149electromechanical switch or ASIC) is connected to terminal 121. In some embodiments, the adaptive load is formed generally as a complex impedance which may have both real and imaginary parts (i.e., a complex adaptive load can be formed using active devices (e.g., integrated circuits or chips made of transistors) or passive devices formed by

0150inductors/capacitors and resistors). In some embodiments, the complex impedance is given by the formula Z = A + jB (e.g., 0 + jO, 100 + jO, 0 + 50j, and etc.), as discussed above.

0151[00116] In some embodiments, the receiver 104 may also be considered as a third terminal. To eliminate wasted energy, the receiver 104 should be configured to absorb a maximum amount (e.g., 75% or more, such as 98%) of the induced power that travels from terminal 123 and towards terminal 121. In some embodiments, processor 110 is connected to the receiver 104 through a feedback loop (e.g., by exchanging messages using a short-range communication protocol, such by BLUETOOTH low energy (BLE) to exchange messages). In some alternative embodiments, the feedback loop from the receiver back to the CPU at the transmitter may utilize a same frequency band as the power transmission signals transmitted by the pad 100, rather than using a separate communication protocol and/or a different frequency band.

0152[00117] In some embodiments, the feedback loop and messages exchanged may be used to indicate an amount of energy received or alternatively or additionally may indicate an increase or decrease in the amount of energy received as compared to previous

0153measurements. In some embodiments, the processor 110 monitors the amount of energy received by the receiver 104 at certain points in time and control s/optimizes the adaptive load to maximize the power transferred from terminal 123 to terminal 121. In some embodiments, monitoring the amount of energy transferred includes one or both of (i) receiving information from the receiver 104 (or a component of an electronic device in which the receiver 104 is located) that indicates an amount of energy received by the receiver 104 at a certain point in time and (ii) monitoring an amount of energy that remains in the conductive line at terminal 121 (instead of having been absorbed by the receiver 104). In some embodiments, both of these monitoring techniques are utilized while, in other embodiments, one or the other of these monitoring techniques is utilized.

0154[00118] In some embodiments, the receiver 104 (i.e., an electronic device that includes the receiver 104 as an internally or externally connected component) may be placed anywhere on top of the charging pad 100 (i.e., partially or fully covering the conductive line that forms a meandered pattern on a respective antenna element 120) and the processor 110 will continue to monitor the amount of energy transferred and make needed adjustments (e.g., to impedance and/or frequency) to maximize the energy transferred to the receiver 104.

0155[00119] To help illustrate operation of the charging pad 100 and the antenna elements 120 included therein, the transmitting antenna element 120 shown in Figure 3B is divided into two sections: 1) section 125 starts at the terminal 123 of the antenna element 120 and extends to an edge of the receiver 104; and 2) section 127 is formed by the rest of the transmitting antenna element 120 and the terminal 121. The blocks are described in more detail below with respect to Figure 3C. It should be understood that sections 125 and 127 are functional representations used for illustrative purposes, and they are not intended to designate a specific implementation that partitions an antenna element into separate sections.

0156[00120] Turning now to Figure 3C, a block diagram of the TX antenna 120 is shown.

0157In some embodiments, an effective impedance value (Zeffective), starting from a point that divides sections 125 and 127 and ending at the TX antenna 120' s connection to the adaptive load 106 (e.g., terminal 121) will change based on location of the receiver 104 on the TX antenna 120 and based on a selected load provided by adaptive load 106 at the terminal 121. In some embodiments, the selected load is optimized by the adaptive load 106 (in conjunction with the processor 110, Figure 3 A) to tune Zeffective in such a way that the energy transferred between terminal 123 and the receiver 104 reaches a maximum (e.g., 75% or more of energy transmitted by antenna elements of the pad 100 is received by the RF receiver 104, such as 98%), while energy transfer may also stay at a minimum from terminal 123 to terminal 121 (e.g., less than 25% of energy transmitted by antenna elements of the pad 100 is not received by the RF receiver 104 and ends up reaching terminal 121 or ends up being reflected back, including as little as 2%).

0158[00121] In embodiments in which an electromechanical switch (e.g., a mechanical relay) is used to switch between open and shorted states, moving the switch from the open to the shorted state (e.g., shorted to a ground plane) for a particular antenna element 120 causes the impedance value, Zeffective, at a respective terminal 121 for that particular antenna element 120 to drop to a value close to 0 (alternatively, switching from the shorted to the open state causes the impedance value to jump close to a value close to infinity). In some embodiments, the frequency adaptation scheme discussed above in reference to Figure 3 A is employed to test various combinations of impedance values and RF signal frequencies, in order to maximize energy transferred to an RF receiver (e.g., receiver 104, Figures 3A-3C). In some embodiments, an integrated circuit (IC or chip) may be used instead of an electromechanical switch as the adaptive load 106. In such embodiments, the adaptive load 106 is configured to adjust the impedance value along a range of values, such as between 0 and infinity. In some embodiments, the IC may be formed by adaptive/ reconfigurable RF active and/or passive elements (e.g., transistors and transmission lines) that are controlled by firmware of the IC (and/or firmware executing on the CPU 110 that controls operation of the IC). In some embodiments, the impedance produced by the IC, and controlled through firmware and based on information from the feedback loop (discussed above in reference to Figure 3 A), may be changed to cover any load values selected from a Smith Chart (or the IC may be designed to produce certain loads covering a portion of values form the Smith Chart). In some embodiments, this IC is distinct from the RF power transmitter integrated circuit 160 (Figure IB) that is used to manage overall operation of the pad 100, and this other IC is also in communication with the RF power transmitter integrated circuit 160 to allow the circuit 160 to control adjustments to impedance values. A Smith Chart may be sampled and stored in a memory (e.g., as a lookup table) that is accessible by the processor 110, and the processor 110 may perform lookups using the stored Smith Chart to determine various impedance values to test. For example, the integrated circuit may be configured to select a

0159predetermined number of complex values (e.g., 5j to lOj, 100+Oj, or 0+50j, etc.) for the impedance value to test in combination with various RF transmission frequencies, in order to locate a combination of values that optimizes energy transferred to the receiver 104

0160(examples of maximized energy transfer are discussed above).

0161[00122] In some other embodiments, a transmitter or charging pad with more than one antenna elements 120 of Figure IB with one adaptive load 106 may be configured to operate in two or more distinct frequency bands respectively at the same time. For example, a first antenna element operates at a first frequency or frequency band, a second antenna element operates at a second frequency or frequency band, and a third antenna element operates at a third frequency or frequency band, and a fourth antenna element operates at a fourth frequency or frequency band, and the four frequency bands are distinct from each other. A transmitter with two or more antenna elements 120 therefore can be used as a multi-band transmitter.

0162[00123] Figure 3D is a block diagram of a simplified circuit that illustrates energy flow within sections of an antenna element that is transmitting an RF signal, in accordance with some embodiments. The references to parti and part2 in Figure 3D refer to sections illustrated in Figures 3B and 3C, in particular, parti corresponds to section 125 and part2 corresponds to section 127.

0163[00124] As shown in Figure 3D, the effective impedance (Zeffective) for a transmitting antenna element 120 is formed by the portion of the conductive line that is after the receiver 104 (which, in some embodiments, forms a meandered line pattern as discussed in more detail below) and the adaptive load (labelled to as section 127 in Figures 3B and 3C). In some embodiments, by optimizing, the load Zeffective will be tuned so the energy transferred from PA to the receiver 104 is maximized; and, the energy remaining in the conductive line by the time it reaches the adaptive load is minimized (as discussed above).

0164[00125] Figure 4 is a schematic of an antenna element with two terminals, in accordance with some embodiments. As shown in Figure 4, an input or first terminal of the antenna element 120 (also described as terminal 123 in reference to Figures 3B-3D above) is connected with a power amplifier 108 and an output or second terminal (also described as terminal 121 in reference to Figures 3B-3D above) is connected with a load pick 106 that allows for configuring an adaptive load. Stated another way, in some embodiments, the antenna element 120 is fed by the power amplifier 108 from the first terminal and the antenna element 120 is also terminated at a second terminal at an adaptive load (for example, the mechanical relay that switches between shorted and open states).

0165[00126] In some embodiments, the charging pad 100 (Figure 3 A) is made of single- layer or multi-layer copper antenna elements 120 with conductive lines that form a meandered line pattern. In some embodiments, each of these layers has a solid ground plane as one of its layers (e.g., a bottom layer). One example of a solid ground plane is shown and labelled for the transmitting antenna element shown in Figure 4.

0166[00127] In some embodiments, the RF charging pad 100 (and individual antenna elements 120 included therein) is embedded in a consumer electronic device, such as a projector, a laptop, or a digital media player (such as a networked streaming media player, e.g. a ROKU device, that is connected to a television for viewing streaming television shows and other content). For example, by embedding the RF charging pad 100 in a consumer electronic device, a user is able to simply place a peripheral device, such as a remote for a projector or a streaming media player (e.g., the remote for the projector or streaming media player includes a respective receiver 104, such as the example structures for a receiver 104 shown in Figures 7A-7D), on top of the projector or the streaming media player and the charging pad 100 included therein will be able to transmit energy to a receiver 104 that is internally or externally connected to the remote, which energy is then harvested by the receiver 104 for charging of the remote.

0167[00128] In some embodiments, the RF charging pad 100 may be included in a USB dongle as a standalone charging device on which a device to be charged is placed. In some embodiments, the antenna elements 120 may be placed near a top surface, side surfaces, and/or a bottom surface of the USB dongle, so that a device to be charged may be placed at various positions that contact the USB dongle (e.g., a headphone that is being charged might sit on top of, underneath, or hang over the USB dongle and would still be able to receive RF transmissions from the embedded RF charging pad 100).

0168[00129] In some embodiments, the RF charging pad 100 is integrated into furniture, such as desks, chairs, countertops, etc., thus allowing users to easily charge their devices (e.g., devices that includes respective receivers 104 as internally or externally connected components) by simply placing them on top of a surface that includes an integrated RF charging pad 100.

0169[00130] Turning now to Figure 5, a flowchart of a method 500 of charging an electronic device through radio frequency (RF) power transmission is provided. Initially, a transmitter is provided 502 that includes at least one RF antenna (e.g., antenna element 120, Figures 3B-3D and 4) for transmitting one or more RF signals or waves, i.e., an antenna designed to and capable of transmitting RF electromagnetic waves. In some embodiments, an array of RF antenna elements 120 are arranged adjacent to one another in a single plane, in a stack, or in a combination of thereof, thus forming an RF charging pad 100. In some embodiments, the RF antenna elements 120 each include an antenna input terminal (e.g., the first terminal 123 discussed above in reference to Figure 4) and an antenna output terminal (e.g., the second terminal 121 discussed above in reference to Figure 4).

0170[00131] In some embodiments, a receiver (e.g., receiver 104, Figures 3A-3D) is also provided 504. The receiver also includes one or more RF antennas for receiving RF signals 310. In some embodiments, the receiver includes at least one rectenna that converts 318 the one or more RF signals into usable power to charge a device that includes the receiver 104 as an internally or externally connected component. In use, the receiver 104 is placed 506 within a near-field radio frequency distance to the at least one antenna. For example, the receiver may be placed on top of the at least one RF antenna or on top of a surface that is adjacent to the at least one RF antenna, such as a surface of a charging pad 100.

0171[00132] One or more RF signals are then transmitted 508 via at the least one RF antenna. The system is then monitored 512/514 to determine the amount of energy that is transferred via the one or more RF signals from the at least one antenna to a RF receiver (as is also discussed above). In some embodiments, this monitoring 512 occurs at the transmitter, while in other embodiments the monitoring 514 occurs at the receiver which sends data back to the transmitter via a back channel (e.g., over a wireless data connection using WIFI or BLUETOOTH). In some embodiments, the transmitter and the receiver exchange messages via the back channel, and these messages may indicate energy

0172transmitted and/or received, in order to inform the adjustments made at step 516.

0173[00133] In some embodiments, a characteristic of the transmitter is adaptively adjusted at step 516 to attempt to optimize the amount of energy that is transferred from the at least one RF antenna to the receiver. In some embodiments, this characteristic is a frequency of the one or more RF signals and/or an impedance of the transmitter. In some embodiments, the impedance of the transmitter is the impedance of the adjustable load. Also in some embodiments, the at least one processor is also configured to control the impedance of the adaptive load. Additional details and examples regarding impedance and frequency adjustments are provided above.

0174[00134] In some embodiments, the transmitter includes a power input configured to be electrically coupled to a power source, and at least one processor (e.g., processor 110, Figures 3 A-3B) configured to control at least one electrical signal sent to the antenna. In some embodiments, the at least one processor is also configured to control the frequency of the at least one signal sent to the antenna.

0175[00135] In some embodiments, the transmitter further comprises a power amplifier electrically coupled between the power input and the antenna input terminal (e.g., PA 108, Figures 3 A, 3B, 3D, and 4). Some embodiments also include an adaptive load electrically coupled to the antenna output terminal (e.g., terminal 121, Figures 3A-3C and 4). In some embodiments, the at least one processor dynamically adjusts the impedance of the adaptive load based on the monitored amount of energy that is transferred from the at least one antenna to the RF receiver. In some embodiments, the at least one processor simultaneously controls the frequency of the at least one signal sent to the antenna.

0176[00136] In some embodiments, each RF antenna of the transmitter includes: a conductive line forming a meandered line pattern, a first terminal (e.g., terminal 123) at a first end of the conductive line for receiving current that flows through the conductive line at a frequency controlled by one or more processors, and a second terminal (e.g., terminal 121), distinct from the first terminal, at a second end of the conductive line, the second terminal coupled to a component (e.g., adaptive load 106) controlled by the one or more processors and that allows for modifying an impedance value of the conductive line. In some embodiments, the conductive line is disposed on or within a first antenna layer of a multi- layered substrate. Also in some embodiments, a second antenna is disposed on or within a second antenna layer of the multi-layered substrate. Finally, some embodiments also provide a ground plane disposed on or within a ground plane layer of the multi-layered substrate.

0177[00137] In some embodiments, the method described above in reference to Figure 5 is performed in conjunction with the methods described below in reference to Figures 9A-9B, 10, and 11 A-l IE. For example, the operations of modifying/ adjusting impedance values are performed after determining which antenna zones (the "determined antenna zones") to use for transmitting wireless power to a receiver, and then impedance values at the determined antenna zones are adjusted to ensure that a maximum amount of power is transferred wirelessly to the receiver by antennas within the determined antenna zones.

0178[00138] Figures 6A-6E are schematics showing various configurations for individual antenna elements within an RF charging pad, in accordance with some embodiments. As shown in Figures 6A-6E, an RF charging pad 100 (Figure 3 A) may include antenna elements 120 that are made using different structures.

0179[00139] For example, Figures 6A-6B show examples of structures for an antenna element 120 that includes multiple layers that each include conductive lines formed into meandered line patterns. The conductive lines at each respective layer may have the same (Figure 6B) or different (Figure 6A) widths (or lengths, or trace gauges, or patterns, spaces between each trace, etc.) relative to other conductive lines within a multi-layer antenna element 120. In some embodiments, the meandered line patterns may be designed with variable lengths and/or widths at different locations of the pad 100 (or an individual antenna element 120), and the meandered line patterns may be printed on more than one substrate of an individual antenna element 120 or of the pad 100. These configurations of meandered line patterns allow for more degrees of freedom and, therefore, more complex antenna structures may be built that allow for wider operating bandwidths and/or coupling ranges of individual antenna elements 120 and the RF charging pad 100.

0180[00140] Additional example structures are provided in Figures 6C-6E: Figure 6C shows an example of a structure for an antenna element 120 that includes multiple layers of conductive lines forming meandered line patterns that also have sliding coverage (in some embodiments, respective meandered line patterns may be placed in different substrates with just a portion of a first meandered line pattern of a respective substrate overlapping the a second meandered line pattern of a different substrate (i.e., sliding coverage), and this configuration helps to extend coverage throughout width of the antenna structure); Figure 6D shows an example of a structure for an antenna element 120 that includes a conductive line having different lengths at each turn within the meandered line pattern (in some

0181embodiments, using different lengths at each turn helps to extend coupling range of the antenna element 120 and/or helps add to the operating bandwidth of the RF charging pad 100); and Figure 6E shows an example of a structure for an antenna element 120 that includes a conductive line that forms two adjacent meandered line patterns (in some embodiments, having a conductive line that forms two adjacent meandered line patterns helps to extend width of the antenna element 120). All of these examples are non-limiting and any number of combinations and multi-layered structures are possible using the example structures described above.

0182[00141] Figures 7A-7D are schematics of an antenna element for an RF receiver, in accordance with some embodiments. In particular Figures 7A-7D show examples of structures for RF receivers (e.g., receiver 104, Figures 3A-3D and 4), including: (i) a receiver with a conductive line that forms meandered line patterns (the conductive line may or may not be backed by solid ground plane or reflector), as shown in Figures 7A (single-polarity receiver) and 7B (dual-polarity receiver). Figures 7C-7D show additional examples of structures for an RF receiver with dual-polarity and a conductive line that forms a meandered line pattern. Each of the structures shown in Figures 7A-7D may be used to provide different coupling ranges, coupling orientations, and/or bandwidth for a respective RF receiver. As a non-limiting example, when the antenna element shown in Figure 7A is used in a receiver, very small receivers may be designed/ built that only couple to the pad 100 in one direction. As another non-limiting example, when the antenna elements shown in Figures 7B-7D are used in a receiver, the receiver is then able to couple to the pad 100 in any orientation.

0183[00142] Commonly-owned U.S. Patent Application No. 15/269,729 also provides additional examples and descriptions of meandered line patterns for antenna elements (e.g., those shown in Figures 2A-2D, 3, 4, 5, 7, 8, and 9A-9B, and described in the specification) and descriptions of the functioning of power transfer systems that include antenna elements with meandered line patterns (e.g., paragraphs [0022]-[0034] and Figures 1A-1B), and the disclosure of this commonly-owned application thus supplements the descriptions of antenna elements with meandered line patterns provided herein (for both receivers and transmitters, or a combination thereof). [00143] Figure 8 is a schematic of an RF charging pad with a plurality of transmitting antenna elements (unit cells) that form a larger RF charging/ transmitting pad, in accordance with some embodiments. In some embodiments, the RF charging pad 100 is formed as an array of adjacent antenna elements 120 (the distance between cells may be optimized for the best coverage). In some embodiments, when a receiver is placed in an area/ gap that is between adjacent antenna elements 120, attempts to optimize energy transfer (e.g., in accordance with the adaptation scheme discussed above in reference to Figure 3 A) may not result in increased energy transfer above an acceptable threshold level (e.g., 75% or more). As such, in these circumstances, adjacent antenna elements may both be configured to transmit RF waves at full power at the same time to transfer additional energy to a receiver that is placed on a surface of the RF charging pad, and at a location that is between adjacent antenna elements 120.

0184[00144] As one possible configuration in accordance with some embodiments, port (or terminal) group #1 (Figure 8) supplies power, port (or terminal) groups #2 and #3 provide adaptive loads (e.g., an electromechanical relay moving between short-circuit and open- circuit states). As another example of a suitable configuration, port (or terminal) groups #1, #2 and #3 may also be used to supply power via a power amplifier to the charging pad 100 (at the same time or with one group at a time being switched when necessary).

0185[00145] In some embodiments, each transmitting antenna element 120 of the RF charging pad 100 forms a separate antenna zone which is controlled by a feeding (PA) terminal and one or more terminals to support adaptive load(s), as explained in detail above. In some embodiments, feedback from the receiver helps determine the antenna zone on top of which the receiver is placed, and this determination activates that zone. In circumstances in which the receiver is placed between two or more zones (e.g., at an area/ gap that is between adjacent antenna elements 120), additional adjacent zones might be activated to ensure sufficient transfer of energy to the receiver. Additional details regarding determining zones to use for transmitting wireless power to the receiver are provided below in reference to Figures 9A-9B, 10, and 11A-11E.

0186[00146] Figures 9A-9B are flow diagrams showing a method 900 of selectively activating one or more antenna zones (e.g., activating the antennas associated therewith) in a near-field charging pad, in accordance with some embodiments. Operations of the method 900 are performed by a near-field charging pad (e.g. RF charging pad 100, Figures IB and 2A) or by one or more components thereof (e.g., those described above with reference to Figures 1 A-IB and 2A). In some embodiments, the method 900 corresponds to instructions stored in a computer memory or computer-readable storage medium (e.g., memory 206 of the RF charging pad 100, Figure 2 A).

0187[00147] The near-field charging pad includes one or more processors (e.g., CPU 202,

0188Figure IB), a wireless communication component (e.g., communication component(s) 204, Figures 1A and 2A), and a plurality of antenna zones (e.g., antenna zones 290-1 and 290-N, Figure IB) that each respectively include at least one antenna element (e.g., one of antennas 210, Figure 2A, which may be one of the antennas 120 described in reference to Figures 3A- 6E) (902). In some embodiments, the near-field charging pad includes distinct antennas (or unit cells including antennas, also referred to herein as antenna elements) that are each included in respective antenna zones. For example, as shown in Figure IB, an antenna zone 290-1 includes an antenna 210- A. In another example, as is also shown in Figure IB, an antenna zone 290-N includes multiple antennas. The antenna zones may also be referred to as antenna groups, such that the near-field charging pad includes a plurality of antenna zones or groups, and each respective zone/group includes at least one of the distinct antenna elements (e.g., at least one antenna 210). It should be noted that an antenna zone can include any number of antennas, and that the numbers of antennas associated with a particular antenna zone may be modified or adjusted (e.g., the CPU subsystem 170 of RF power transmitter integrated circuit 160 responsible for managing operations of the near-field charging pad 100 dynamically defines each antenna zone at various points in time, as is discussed in more detail below). In some embodiments, each antenna zone includes a same number of antennas.

0189[00148] In some embodiments, the one or more processors are a component of a single integrated circuit (e.g., RF power transmitter integrated circuit 160, Figure IB) that is used to control operation of the near-field charging pad. In some embodiments, the one or more processors and/or the wireless communication component of the near-field charging pad is/are external to the near-field charging pad, such as one or more processors of a device in which the near-field charging pad is embedded. In some embodiments, the wireless communication component is a radio transceiver (e.g., a BLUETOOTH radio, WI-FI radio, or the like for exchanging communication signals with wireless power receivers). [00149] In some embodiments, the method includes establishing (904) one or more device detection thresholds during a calibration process for the near-field charging pad. In some instances, the calibration process is performed after manufacturing the near-field charging pad and includes placing devices of various types (e.g., smartphones, tablets, laptops, connected devices, etc.) on the near-field charging pad and then measuring a minimum amount of reflected power detected at an antenna zone while transmitting test power transmission signals to the devices of various types. In some instances, a first device- specific threshold is established at a value corresponding to 5% or less of the minimum amount of reflected power. In some embodiments, a second device-specific threshold is also established so that if no one antenna zone is able to satisfy the first threshold (e.g., because the wireless power receiver is located at a border between antenna zones), then the second, higher threshold may be used to locate more than one antenna zone to use for transmitting power to the wireless power receiver (as discussed in more detail below). In some embodiments, multiple first and second device-specific detection thresholds are established for each type of device of the various types, and these multiple first and second device- specific detection thresholds may be stored in a memory associated with the RF power transmitter integrated circuit 160 (e.g., memory 206, Figure 2A).

0190[00150] The method 900 also includes detecting (906), via the wireless communication component, that a wireless power receiver is within a threshold distance of the near-field charging pad. In some instances, the detecting may occur after the near-field charging pad is turned on (e.g., powered up). In these instances, the near-field charging pad scans an area around the near-field charging pad (e.g., to scan for wireless power receivers that are located within the threshold distance, e.g., within 1-1.5 meters, away from the F charging pad 100) to determine whether any wireless power receivers are within the threshold distance of the NF charging pad 100. The near-field charging pad may use the wireless communication component (e.g., communication component(s) 204, Figure 2A, such as a Bluetooth radio) to conduct the scanning for signals broadcasted by wireless communication components associated with wireless power receivers (e.g., communication component 254, Figure 2B). In some embodiments, the device detection threshold is selected (from among the multiple first and second device detection threshold discussed above) by the one or more processors after detecting the wireless power receiver within the threshold distance of the near-field charging pad. For example, a wireless communication component of the wireless power receiver is used to provide information to the near-field charging pad that identifies the type of device, such as a BLUETOOTH or BLUETOOTH low energy advertisement signal that includes this information. In some embodiments, to save energy and prolong life of the near- field charging pad and its components, no wireless power is transmitted (and the device detection and antenna selection algorithms discussion herein are not initiated) until a wireless power receiver is detected within the threshold distance of the near-field charging pad.

0191[00151] In some embodiments, the detecting 906 also includes performing an authorization handshake (e.g., using the secure element modules 234 and 282, Figures 2A and 2B) to ensure that the wireless power receiver is authorized to receive wirelessly delivered power from the near-field charging pad and the method only proceeds to operation 908 if it is determined that the wireless power receiver is so authorized. In this way, the near- field charging pad ensures that only authorized wireless power receivers are able to receive wirelessly delivered power and that no device is able to leech power that is transmitted by the near-field charging pad.

0192[00152] The method 900 further includes, in response to detecting that the wireless power receiver is within the threshold distance of the near-field charging pad, determining (912) whether the wireless power receiver has been placed on the near-field charging pad. In some embodiments, this is accomplished by transmitting (908) test power transmission signals using each of the plurality of antenna zones and monitoring (910) an amount of reflected power at the near-field charging pad while transmitting the test power transmission signals.

0193[00153] In some embodiments, if the amount of reflected power does not satisfy the device detection threshold (e.g., the amount of reflected power is greater than 20% of power transmitted with the test power transmission signals), then a determination is made that the wireless power receiver has not been placed on the surface of the near-field charging pad (912-No). In accordance with this determination, the near-field charging pad continues to transmit test power transmission signals using each of the plurality of antenna zones at step 914 (i.e., proceed to step 908). In some embodiments, the operations at 908 and 910 are performed until it is determined that the device detection threshold has been satisfied.

0194[00154] In some embodiments, the amount of reflected power is measured at each antenna zone of the plurality of antenna zones (e.g., each antenna zone may be associated with a respective ADC/DAC/ Power Detector, such as the one shown in Figure IB) while, in other embodiments, the amount of reflected power may be measured using a single component of the RF power transmitter integrated circuit 160 (e.g., the ADC/DAC/ Power Detector). When the amount of reflected power satisfies the device detection threshold (912- Yes), the wireless power receiver is determined to have been placed on the near-field charging pad. For example, the amount of reflected power may satisfy the device detection threshold when the amount of reflected power is 20% or less than amount of power transmitted with the test power transmission signals. Such a result indicates that a sufficient amount of the power transmitted with the test power transmission signals was absorbed/ captured by the wireless power receiver.

0195[00155] In some embodiments, other types of sensors (e.g., sensors 212, Figure 2A) are included in or in communication with the near-field charging pad to help determine when the wireless power receiver has been placed on the near-field charging pad. For example, in some embodiments, one or more optical sensors (e.g., when light is blocked from a part of the pad, then this may provide an indication that the wireless power receiver has been placed on the pad), one or more vibration sensors (e.g., when a vibration is detected at the pad, then this may provide an indication that the wireless power receiver has been placed on the pad), one or more strain gauges (e.g., when a strain level at a surface of the pad increases, this may provide an indication that the wireless power receiver has been placed on the surface), one or more thermal sensors (e.g., when a temperature at a surface of the pad increases, this may provide an indication that the wireless power receiver has been placed on the surface), and/or one or more weighing sensors (e.g., when an amount of weight measured on the surface of the pad increases, then this may provide an indication that the wireless power receiver has been placed on the surface) are utilized to help make this determination.

0196[00156] In some embodiments, before transmitting the test power transmission signals, the method includes determining that the wireless power receiver is authorized to receive wirelessly delivered power from the near-field charging pad. For example, as shown in Figures 2A-2B, the wireless power receiver 104 and the near-field charging pad 100 may include secure element modules 282 and 234, respectively, which are used to perform this authorization process, thereby ensuring that only authorized receivers are able to receive wirelessly delivered power from the near-field charging pad.

0197[00157] The method 900 further includes, in accordance with determining that the wireless power receiver has been placed on the near-field charging pad, selectively transmitting (916), by respective antenna elements included in the plurality of antenna zones, respective test power transmission signals with a first set of transmission characteristics. In some embodiments, the selectively or sequentially transmitting is performed using each antenna zone of the plurality of antenna zones (918). Selectively or sequentially transmitting refers to a process of selectively activating antenna zones one at a time to cause one or more antennas associated with individual antenna zones to transmit test power transmission signals.

0198[00158] Referring now to Figure 9B, the method 900 further includes determining

0199(920) whether a particular power-delivery parameter associated with transmission of a respective test power transmission signal (during the sequential or selective transmission operation at 916 and/or 918) by at least one particular antenna zone of the plurality of antenna zones satisfies power-delivery criteria (e.g., whether the particular power-delivery parameter indicates that more than a threshold amount of power is transferred to the wireless power receiver by the at least one particular antenna zone). In some embodiments, each respective power-delivery parameter corresponds to an amount of power received by the wireless power receiver based on transmission of a respective test power transmission signal by a respective antenna group of the plurality of antenna groups.

0200[00159] Upon determining, by the one or more processors, that the particular power- delivery parameter satisfies the power-delivery criteria (920-Yes), the method further includes transmitting (922) a plurality of additional power transmission signals to the wireless power receiver using the at least one particular antenna zone, where each additional power transmission signal of the plurality is transmitted with a second set of transmission

0201characteristics, distinct from the first set. In some embodiments, the second set of

0202transmission characteristics is determined by adjusting at least one characteristic in the first set of transmission characteristics to increase an amount of power that is transferred by the particular antenna group to the wireless power receiver. Moreover, in some embodiments, the at least one adjusted characteristic is a frequency or impedance value (and the frequency and impedance value may be adjusted using the adaptation scheme discussed above).

0203[00160] The test power transmission signals discussed above are used to help determine which antenna zones to use for delivering wireless power to the wireless power receiver. In some embodiments, these test power transmission signals are not used by the wireless power receiver to provide power or charge to the wireless power receiver, or a device associated therewith. Instead, the plurality of additional power transmission signals is used to provide power or charge to the wireless power receiver. In this way, the near-field charging pad is able to preserve resources during a device detection stage (e.g., while transmitting the test power transmission signals) until a suitable antenna zone is located for transmitting the plurality of additional power transmission signals. As such, the method 900 is able to locate a position of the wireless power receiver using test signals (i.e., the test power transmission signals with the first set of transmission characteristics) and then transmit using antenna from an antenna zone that is best-suited to provide power transmission signals given the position of the wireless power receiver on the near-field charging pad. As discussed in more detail below with reference to Figure 10, this process may include a coarse search for antenna zones (e.g., the coarse search may include the operations 908-918) and a finer search for antenna zones (e.g., the finer search may include operations 920-934).

0204[00161] In some embodiments, a power control process (Figure 1 IE) is also used to help optimize a level of power delivered to the wireless power receiver using the selected antenna zones (e.g., power control may be performed after operations 922, 930, or 934 to tune transmission of wireless power using the antenna zones that were selected during the method 900). As a part of the power control process, the near-field charging pad may, while transmitting the additional plurality of power transmission signals, adjust at least one characteristic in the second set of transmission characteristics based on information, received from the wireless power receiver, which is used to determine a level of power that is wirelessly delivered to the wireless power receiver by the near-field charging pad.

0205[00162] Returning back to operation 920, in response to determining that none of the power-delivery parameters associated with transmission of the test power transmission signals during the sequential or selective transmission operation(s) at 916 (and optionally 918) satisfy the power-delivery criteria (920-No), the method 900 further includes selecting (924) two or more antenna zones (also referred to interchangeably herein as two+ antenna zones) based on their associated respective power-delivery parameters. This may arise when the wireless power receiver is not centered over any particular antenna zone (e.g., the receiver may be over more than one antenna zone). For example, the two or more antenna zones that transferred the highest amount of power to the wireless power receiver during the sequential or selective transmission operation at 916 (and optionally 918) based on their respective power-delivery parameters are selected at operation 924. In this way, in some embodiments, a finer search for the most efficient antenna zone is started by selecting the two or more antenna zones that most efficiently transmitted power to the wireless power receiver during the operations at 916/ 918 based on their respective association with power-delivery parameters that is higher than the power-delivery parameters for other antenna zones. In these embodiments, a respective power-delivery parameter may be monitored (in conjunction with operations 916/918) for each antenna zone and these power-delivery parameters are then compared to determine which of the plurality of antenna zones to select as the two or more antenna zones to use for transmission of wireless power.

0206[00163] After selecting the two or more antenna zones, the method further includes: (i) updating the test power transmission signals by modifying at least one characteristic of the test power transmission signals (e.g., frequency, impedance, amplitude, phase, gain, etc.), based on the previous transmissions (e.g., based on feedback received from the wireless power receiver regarding a level of power receive by the wireless power receiver or based on an amount of reflected power measured at each antenna group after the transmission), and (ii) transmitting (926) the updated test power transmission signals using each of the two or more antenna zones.

0207[00164] The method 900 further includes determining (928) whether a particular power-delivery parameter associated with transmission of an updated respective test power transmission signal by a zone of the two or more antenna zones satisfies power-delivery criteria. In response to determining that the particular power-delivery parameter associated with transmission of the updated respective test power transmission signal by the zone of the two or more antenna zones satisfies the power-delivery criteria (928-Yes), the method 900 further includes transmitting (930) a plurality of additional power transmission signals to the wireless power receiver using the zone of the two or more antenna zones, where each additional power transmission signal of the plurality is transmitted with a second set of transmission characteristics, distinct from the first set. The plurality of additional power transmission signals is used to wirelessly deliver power to the wireless power receiver (or an electronic device coupled with the wireless power receiver).

0208[00165] In some embodiments, the determination that the particular power-delivery parameter satisfies the power-delivery criteria at operations 920 and 928 may include determining that respective power-delivery parameters (associated with the at least one particular zone and/or the zone of the two or more antenna zones) indicates that a first threshold amount of power is transferred to the wireless power receiver. If such a determination is made at operation 928, this indicates that the zone is the only antenna zone of the two or more antenna zones having a respective power-delivery parameter that indicates that the first threshold amount of power is transferred to the wireless power receiver by the zone in conjunction with operation 926.

0209[00166] In some embodiments, the first threshold amount of power corresponds to an amount of power received by the wireless power receiver (in some circumstances, the first threshold amount of power could alternatively correspond to an amount of reflected power detected at the near-field charging pad). As discussed above, in some embodiments, a calibration process is performed after manufacturing the near-field charging pad and includes placing devices of various types (e.g., smartphones, tablets, laptops, connected devices, etc., that are each coupled with wireless power receivers) on the near-field charging pad and then measuring a maximum amount of power received at the receiver (or device coupled thereto) after transmission of the test signal by an antenna group to the devices of various types. In some instances, the first threshold is established at a value corresponding to a percentage of the maximum amount of received power (e.g., approximately 85% or more of power transmitted by a particular antenna zone is received by the receiver).

0210[00167] As explained above, during embodiments of the calibration process, a second threshold is also established so that if no one antenna zone is able to satisfy the first threshold (e.g., because the wireless power receiver may be located at a border between antenna groups) then the second threshold may be utilized to locate more than one antenna zone to transmit wireless power to the wireless power receiver (as discussed below). This second threshold may be another percentage of the maximum amount of reflected power that is measured during the calibration process (e.g., 65%). In some embodiments, the first and second thresholds are determined as respective device-specific first and second thresholds for each of the devices undergoing the calibration process.

0211[00168] In some embodiments, the method 900 includes determining (928-No) that (i) no antenna zone of the two or more antenna zones is transferring the first threshold amount of power to the wireless power receiver and (ii) an additional power-delivery parameter associated with an additional antenna zone of the two or more antenna zones satisfies the power-delivery criteria. For example, a respective power-delivery parameter indicates that a first amount of power transferred to the wireless power receiver by the zone of the two or more zones is above a second threshold amount of power and below the first threshold amount of power, and the additional power-delivery parameter also indicates that a second amount of power transferred to the wireless power receiver by the additional antenna zone is above the second threshold amount of power and below the first threshold amount of power. In other words, if no antenna zones of the two or more antenna zones is able to transfer enough power to the wireless power receiver to satisfy the first threshold amount of power, then the method proceeds to determine whether two of the antenna groups transferred enough power to the wireless power receiver to satisfy a second, lower threshold amount of power. For example, the wireless power receiver may be located at a border between two antenna groups, so no one antenna group is able to satisfy the first threshold, but these two antenna groups may be able to each individually satisfy the second threshold amount of power.

0212[00169] Upon determining, by the one or more processors of the near-field charging pad, that the power-delivery parameters associated with transmission of the updated test power transmission signals by the two or more antennas zones satisfy the power-delivery criteria (932-Yes), the method further includes transmitting (934) a plurality of additional power transmission signals to the wireless power receiver using the two or more antenna zones. Such a situation may arise when the wireless power receiver is placed between two adjacent antenna zones. In some embodiments, the two or more antenna zones each simultaneously transmit the additional plurality of power transmission signals to provide power to the wireless power receiver.

0213[00170] As is also shown in Figure 9B, if the two or more zones do not have power- delivery parameters that satisfy the power-delivery criteria (932-No), then the method 900 returns to operation 906 to start searching for the receiver (or a different receiver again), as no antenna zones were located that could efficiently transfer wireless power to the receiver. In some embodiments, the method 900 may alternatively return to operation 924 to begin transmitting test power transmission signals with different characteristics to determine if those characteristics are able to then allow the two or more antenna zones to deliver enough wireless power to the receiver to satisfy the power-delivery criteria. In some embodiments, the method 900 returns to operation 924 a predetermined number of times (e.g., 2) and, if the two or more zones still do not have power-delivery parameters that satisfy the power-delivery criteria, then the method at that point returns to operation 906 to begin searching for new receivers.

0214[00171] In some embodiments, after the method 900 successfully locates antenna zones to use for wirelessly delivering power to the receiver (e.g., at operations 922, 930, and 934) then the method 900 returns to operation 906 to being search for new receivers. The near-field charging pad, in some embodiments, is capable of simultaneously delivering wireless power to multiple receivers at any particular point in time and, therefore, iterating through the method 900 again allows the near-field charging pad to appropriately determine which antenna zones to use for transmission of wireless power to each of these multiple receivers.

0215[00172] In some embodiments, information used to determine respective power- delivery parameters for each of the antenna zones of the near-field charging pad is provided to the near-field charging pad by the wireless power receiver via the wireless communication component of the near-field charging pad (e.g., the receiver transmits information that is used to determine an amount of power received by the receiver from the test power transmission signals discussed above). In some embodiments, this information is sent via a connection between the wireless communication component of the near-field charging pad and the wireless power receiver, and the connection is established upon determining that the wireless power receiver has been placed on the near-field charging pad.

0216[00173] Additionally, in some embodiments, the near-field charging pad dynamically creates or defines antenna zones. For example, with reference to Figure IB, the near-field charging pad may define a first antenna zone 290-1 to include a single antenna 210-A and may define another antenna zone 290-N to include more than one antenna 210. In some embodiments, at various phases of the method 900 discussed above, antenna zones may be redefined. For example, in accordance with the determination that the two or more antenna zones do not have power-delivery parameters that satisfy the power-delivery criteria (932- No), the near-field charging pad may redefine the antenna zones to each include multiple antennas (instead of having each antenna zone include a single antenna). In this way, the method 900 is able to dynamically define antenna zones to help ensure that an appropriate antenna zone is located that may be used to transmit wireless power to a receiver that has been placed on the near-field charging pad.

0217[00174] Figure 10 is an overview showing a process 1000 of selectively activating one or more antenna groups in a near-field charging pad, in accordance with some embodiments. Some of the operations in process 1000 correspond to or supplement the operations describe above in reference to method 900 of Figures 9A-9B. As shown in Figure 10, the process 1000 begins with a near-field charging pad (e.g., RF charging pad 100, Figures 1A-1B and 2A) detecting (1002) a wireless power receiver (e.g., wireless power receiver 104, Figure 12B) in range and subsequently on the near-field charging pad (operation 1002 corresponds to operations 906 to 912- Yes in Figure 9 A). The process 1000 further includes performing (1004) a coarse search, performing (1006) a fine search, and executing (1008) a power control routine. Each step in the process 1000 is described in further detail below with reference to Figures 1 1 A-l IE. It should be noted that the process 1000, in some

0218embodiments, begins with the near-field charging pad detecting (1002) a wireless power receiver on the near-field charging pad and subsequently in range of the near-field charging pad.

0219[00175] Figure 11 A is a flowchart detailing a process 1002 for detecting a wireless power receiver in range and subsequently on the near-field charging pad (or in some embodiments, on the near-field charging pad and subsequently in range of the near-field charging pad). The process 1002 includes enabling the near-field charging pad (1102), i.e., powering on the near-field charging pad. Thereafter, the near-field charging pad scans (1104) for wireless power receivers and detects (1106) a wireless power receiver in range based, at least in part, on a received signal strength indicator (RSSI). To obtain the RSSI, the near-field charging pad may use a wireless communication component (e.g., communication component(s) 204, Figure 2A, such as a Bluetooth radio) to scan for signals broadcasted by wireless communication components associated with wireless power receivers (e.g., a Bluetooth advertisement signal). Detecting a wireless power receiver in range of the near- field charging pad is discussed in further detail above with reference to operation 906 of the method 900.

0220[00176] Next, the near-field charging pad detects (1108) a wireless power receiver on the near-field charging pad. In some embodiments, the near-field charging pad establishes that the wireless power receiver is on the near-field charging pad using the processes discussed above in reference to operations 908-914 until it is determined that the wireless power receiver has been placed on the near-field charging pad. In some embodiments, operation (1108) occurs before operation (1102).

0221[00177] Continuing, the near-field charging pad establishes (1110) a communication channel with the wireless power receiver in response to detecting the wireless power receiver on the near-field charging pad.

0222[00178] Turning now to Figure 1 IB, the method proceeds to process 1004 in which the near-field charging pad performs a coarse search (1004). In performing the coarse search 1004, the near-field charging pad begins by enabling (1122) power for an antenna zone (e.g., antenna zone 290-1, Figure IB). In some embodiments, enabling power for the antenna zone includes transmitting, by an antenna element included in the antenna zone, test power transmission signals with a first set of transmission characteristics (e.g., phase, gain, direction, amplitude, polarization, and/or frequency). Transmitting test power transmission signals is discussed in further detail above with reference to steps 916-918 of the method 900.

0223[00179] Continuing with the coarse search 1004, the near-field charging pad records

0224(1124) an amount of power received by the wireless power receiver (the "reported power"). In some embodiments, the reported power is communicated to the near-field charging pad by the wireless power receiver via the communication channel that was established at operation 1110.

0225[00180] The near-field charging pad repeats (1126) steps (1122) and (1124) above for all antenna zones that have been defined for the near-field charging pad. Thereafter, in some embodiments, the near-field charging pad selects (1128) a set of antenna zones based on the reported power (e.g., 2 or 3 zones, or some greater or lesser number, depending on the circumstances) and a configured threshold (e.g., power-delivery criteria). For ease of discussion, each antenna zone in the set includes a single antenna 210 (e.g., antenna zone 290-1, Figure IB). However, it should be understood that instead of selecting a set of antenna zones, the near-field charging pad could also select a single antenna zone that includes multiple antennas 210. For example, as shown in Figure IB, the antenna zone 290- N includes multiple antennas 210. In addition, each antenna zone in the set could also include multiple antennas, depending on the circumstances.

0226[00181] Turning now to Figure 11C, after selecting the set of antenna zones based on the reported power, the near-field charging pad performs the fine search process (1006). In some embodiments, the fine search 1006 is used to determine which antenna zone(s) is/are best suited to wirelessly delivery power to the wireless power receiver, based on a location of the wireless power receiver on the near-field charging pad. In performing the fine search (1006), the near-field charging pad selects (1132) at least one antenna zone from the set of antenna zones selected using the coarse search, and for the at least one antenna zone, the near-field charging pad sweeps (1134) across available frequencies and/or impedances (i.e., tunes transmission of power transmission signals by the at least one antenna zone).

0227Thereafter, the near-field charging pad records (1136) those characteristics that result in maximizing an amount of received power reported by the wireless power receiver. In some embodiments, operations 1134 and 1136 are repeated for each antenna zone in the set of antenna zones (1138) and the near-field charging pad selects (1140) an antenna zone (Zl) that delivers a maximum amount of power to the wireless power receiver. In addition, the near- field charging pad also records the frequency (and other transmission characteristics) and a relay position by antenna zone Zl to achieve the delivery of the maximum amount of power to the wireless power receiver.

0228[00182] In some circumstances or situations, the amount of power delivered to the wireless power receiver by the antenna zone Zl does not meet a threshold amount of power. In these circumstances or situations, the near-field charging pad performs an adjacent zone search (1007), which is illustrated in Figure 1 ID. In some embodiments, the adjacent zone search 1007 is used to identify one or more adjacent zones to the selected antenna zone Zl that may be activated in order to increase an amount of power delivered to the wireless power receiver. For example, this may occur when the wireless power receiver is located at a border between adjacent antenna zones of the near-field charging pad (e.g., located at an intersection between two antenna zones, three antenna zones, or four antenna zones). In performing the adjacent zone search 1007, the near-field charging pad identifies (1142) adjacent antenna zones (ZAs) to the selected antenna zone Zl . In some embodiments, identifying adjacent zones (ZAs) includes identifying up to five adjacent zones.

0229[00183] Next, the near-field charging pad pairs (1144) the selected antenna zone Zl with each identified adjacent zone and sweeps (1146) across all antenna tuning combinations and sweeps (1148) across all available frequencies (and perhaps other transmission characteristics). Thereafter, the near-field charging pad selects (1150) a combination of antenna zones from among the adjacent zones (ZAs). For example, the near-field charging pad may determine that the selected antenna zone Zl deliver a higher amount of power to the wireless power receiver than either of these antenna zones is individually able to deliver to the wireless power receiver. In another example, the near-field charging pad may determine that the selected antenna zone Zl and two (or three) other adjacent zones deliver a maximum amount of power to the wireless power receiver. When selecting the desired combination of antenna zones, the near-field charging pad records the transmission characteristics used to produce the maximum amount of power delivered to the wireless power receiver.

0230Performing the fine search and the adjacent zone search are also discussed in more detail above with reference to steps 924-932 of the method 900. [00184] After performing the fine search 1006 (and the adjacent zone search 1007 if needed), the near-field charging pad executes (1008) a power control routine, an example of which is illustrated in Figure 1 IE. In some embodiments, the power control routine allows both the wireless power receiver and the near-field charging pad to continually monitor an amount of power being delivered to the wireless power receiver. In this way, adjustments to the wireless power transmission can be made based on feedback received from the wireless power receiver. For example, if the delivered power is below a configured threshold, then the wireless power receiver may request a power increase from the near-field charging pad. Figure 1 IE illustrates various operations that may be used to allow the receiver to request an increase or a decrease in an amount of wireless power delivered to the receiver, and also illustrates a process executed by the near-field charging pad to determine when to increase or decrease the amount of wireless power delivered to the receiver in response to the receiver's requests for increases or decreases in the amount of wireless power delivered.

0231[00185] The antenna elements 120 described above (e.g., in reference to Figure IB) may also be configured to have multiple adaptive load terminals (e.g., multiple adaptive load terminals 121) that are coupled to at different positions along a respective antenna element 120. An example of an antenna element 120 with multiple adaptive load terminals is provided below in reference to Figure 12. Figure 12 is a schematic showing a transmitting antenna element (unit cell) with a plurality of adaptive loads (which may be a part of an array of such antennas, as described above in reference to Figures 3-8) of an RF charging pad, in accordance with some embodiments. In some embodiments, the RF charging pad 1200 includes one or more antenna elements 1201 (which may be any of the antenna elements as shown in Figures 3B, 4, 6A-6E, 7A-7D, and 8). Each antenna element 1201 is powered/ fed by a respective power amplifier (PA) switch circuit 1208 (which may be a respective one of the PA switch circuits 103 of Figure 3 A) that may be connected to a respective power amplifier 1208 or a source of power at a first end of the antenna element 1201.

0232[00186] In some embodiments, the input circuit that includes the power amplifier 1208 may additionally include a device that can change frequencies of the input signal or a device that can operate at multiple frequencies at the same time, such as an oscillator or a frequency modulator.

0233[00187] In some embodiments, each antenna element 1201 of the RF charging pad

02341200 includes a plurality of respective adaptive load terminals 1202, for example, 1202a, 1202b, 1202c, ... 1202n, at a plurality of positions within a respective antenna element 1201. In some embodiments, the antenna element 1201 includes a conductive line forming a meandered line pattern (as discussed above in reference to Figures 3, 4, and 6-8). In some embodiments, each adaptive load terminals of the plurality of adaptive load terminals 1202 for the antenna element 1201 is located at different positions on the conductive meandered line of the antenna element 1201 as shown in Figure 12.

0235[00188] In some embodiments, a meandered line antenna element 1201 includes a conductive line with multiple turns in one plane. In some embodiments, the multiple turns may be square turns as shown for the antenna element 1201 in Figure 12. In some embodiments, the multiple turns may be round-edged turns. The conductive line may also have segments of varying widths, for example, a segment 1206 having a first width, and short-length segment 1207 that has a second width that is less than the first width. In some embodiments, at least one of the adaptive load terminals 1202a is positioned at one of the short-length segments (e.g., short-length segment 1207) and another adaptive load terminal is positioned anywhere at one of the segments 1206 having the first width. In some

0236embodiments, at least one of the adaptive load terminals 1202 is positioned or connected anywhere on a width segment, for example, at the middle of a width segment of the meandered line antenna element 1201. In some embodiments, the last adaptive load terminal 1202n is positioned at a second end of the conductive line (opposite to a first end at the input terminal 1203 of the antenna element 1201 described above in reference to Figures 3, 4, and 6-8). In some embodiments, in certain design and optimization, an adaptive load terminal is not necessarily positioned at a second end of the meandered line antenna element 1201 but can be positioned at any location of the antenna element 1201.

0237[00189] In some embodiments, the RF charging pad 1200 also includes (or is in communication with) a central processing unit 1210 (also referred to here as processor 1210). In some embodiments, the processor 1210 is configured to control RF signal frequencies and to control impedance values at each of the adaptive load terminals 1202, e.g., by

0238communicating with a plurality of the load picks or adaptive loads 1212, for example, 1212a, 1212b, 1212c, ... 1212n, for each of the adaptive load terminals 1202 (as discussed above in reference to load pick or adaptive load 106 in Figures 3 A and 3B).

0239[00190] In some embodiments, an electronic device (e.g., a device that includes a receiver 1204 as an internally or externally connected component, such as a remote that is placed on top of a charging pad 1200 that may be integrated within a housing of a streaming media device or a projector) and uses energy transferred from one or more RF antenna elements 1201 of the charging pad 1200 to the receiver 1204 to charge a battery and/or to directly power the electronic device.

0240[00191] In some embodiments, the adaptive load terminals 1202 at a particular zone or selected positions of the antenna element 1201 (e.g., a zone on the antenna element 1201 located underneath a position at which an electronic device (with an internally or externally connected RF receiver 1204) to be charged is placed on the charging pad) are optimized in order to maximize power received by the receiver 1204. For example, the CPU 1210 upon receiving an indication that an electronic device with an internally or externally connected RF receiver 1204 has been placed on the pad 1200 in a particular zone on the antenna element 1201 may adapt the plurality of adaptive loads 1212, for example, adaptive loads 1212a, 1212b, 1212c, ... 1212n, that are respectively coupled to the adaptive terminals 1202, in order to maximize power transferred to the RF receiver 1204. Adapting the set of adaptive loads 1212 may include the CPU 1210 commanding one or more of the adaptive loads to try various impedance values for one or more of the adaptive load terminals 1202 that are coupled to different positions of the antenna element 1201. Additional details regarding adapting adaptive loads were provided above, and, for the sake of brevity, are not repeated here.

0241[00192] The effective impedance value (Zeffectve) at a particular position/portion of the conductive line of the antenna element 1201 is affected by a number of variables and may be manipulated by adjusting configurations of the adaptive load terminals 1212 that are coupled to various positions on the antenna element 1201. In some embodiments, an effective impedance value (Zeffective), starting from a point that divides sections 1225 (which starts at the terminal 1203 of the antenna element 1201 and extends to an edge of the receiver 1204) and 1227 (which is formed by the rest of the transmitting antenna element 1201 and the terminal 1202n) and ending at the TX antenna 1201 's connection to the adaptive load 1212n (e.g., terminal 1202n) will change based on location of the receiver 1204 on the TX antenna 1201 and based on a set of selected loads provided by adaptive loads 1212 at various positions within section 1227. In some embodiments, the selected loads are optimized by the adaptive loads 1212 (in conjunction with the processor 1210) to tune Zeffective in such a way that the energy transferred between terminal 1203 and the receiver 1204 reaches a maximum (e.g., 75% or more of energy transmitted by antenna elements of the pad 1200 is received by the RF receiver 1204, such as 98%), while energy transfer may also stay at a minimum from terminal 1203 to terminal 1202n (e.g., less than 25% of energy transmitted by antenna elements of the pad 1200 is not received by the RF receiver 1204 and ends up reaching terminals positioned within section 1227 or ends up being reflected back, including as little as 2%).

0242[00193] In some embodiments, a selected several adaptive loads 1212 of the plurality of adaptive loads 1212 are used (by the processor 1210) on the antenna element 1201 to adjust the impedance and/or frequency of the antenna element 1201. In one example, with reference to Figure 12, only adaptive load terminals 1202a and 1202c are connected at a particular point in time to adaptive loads 1212a and 1212c respectively, while adaptive load terminals 1202b and 1202n are disconnected at the particular point in time. In another example, with reference to Figure 12, only adaptive load terminals 1202a and 1202n are connected at a particular point in time to adaptive loads 1212a and 1212n, respectively, while adaptive load terminals 1202b and 1202c are disconnected at the particular point in time. In some embodiments, all of the adaptive load terminals 1202 are connected at a particular point in time to their respective adaptive loads 1212. In some embodiments, none of the adaptive load terminals 1202 are connected at a particular point in time to their respective adaptive loads 1212. In some embodiments, the impedance value of each of the adaptive loads 1212 connected to a selected adaptive load terminal 1212 is adjusted individually to optimize the energy transfer.

0243[00194] In embodiments in which a meandered line antenna has been optimized for the multi-band operation, the multiple adaptive load configuration within a single antenna element also enables a broader frequency band adjustment compared with a single adaptive load configuration within a single antenna element as described in Figure 3B above. The multiple adaptive load configuration within a single antenna element further enhances multiple frequency band operation on a single antenna element. For example, a single antenna element 1201 with multiple adaptive load terminals is capable of operating at a wider frequency band than a corresponding antenna element that is configured with one adaptive load terminal.

0244[00195] In some embodiments, adapting the set of adaptive loads 1212 also or alternatively includes the CPU 1210 causing the set of antenna elements to transmit RF signals at various frequencies until a frequency is found at which a maximum amount of energy is transferred to the RF receiver 1204. In some embodiments, for example, one of the antenna elements transmits RF signals at a first frequency, and another one of the antenna elements transmits RF signals at a second frequency that is different from the first frequency. In some embodiments, adjusting the impedance value and/or the frequencies at which the set of antenna elements transmits causes changes to the amount of energy transferred to the RF receiver 1204. In this way, the amount of energy transferred to the RF receiver 1204 that is maximized (e.g., to transfer at least 75% of the energy transmitted by antenna elements of the pad 1200 to the receiver 1204, and in some embodiments, adjusting the impedance value and/frequencies may allow up to 98% of the energy transmitted to be received by the receiver 1204) may be received at any particular point on the pad 1200 at which the RF receiver 1204 might be placed.

0245[00196] In some embodiments, the CPU 1210 determines that a maximum amount of energy is being transferred to the RF receiver 1204 when the amount of energy transferred to the RF receiver 1204 crosses a predetermined threshold (e.g., 75% or more of transmitted energy is received, such as up to 98%) or by testing transmissions with a number of impedance and/or frequency values and then selecting the combination of impedance and frequency that results in maximum energy being transferred to the RF receiver 1204 (also as described in reference to the adaptation scheme in Figures 3 A-3D above). In some embodiments, processor 1210 is connected to the receiver 1204 through a feedback loop (e.g. by exchanging messages using a wireless communication protocol, such as BLUETOOTH low energy (BLE), WIFI, ZIGBEE, infrared beam, near-field transmission, etc, to exchange messages). In some embodiments, the adaptation scheme is employed to test various combinations of impedance values of the adaptive impedance loads 1212 and RF frequencies, in order to maximize energy transferred to an RF receiver 1204. In such embodiments, each of the adaptive load 1212 is configured to adjust the impedance value along a range of values, such as between 0 and infinity. In some embodiments, the adaptation scheme is employed when one or more RF receivers are placed on top of one of the antenna element 1201.

0246[00197] In some embodiments, an adaptation scheme is employed to adaptively adjust the impedance values and/or frequencies of the RF signal(s) emitted from the RF antenna(s) 1201 of the charging pad 1200, in order to determine which combinations of frequency and impedance result in maximum energy transfer to the RF receiver 1204. For example, the processor 1210 that is connected to the charging pad 1200 tries different frequencies (i.e., in the allowed operating frequency range or ranges) by using different selected sets of adaptive loads 1212 at different locations of the antenna element 1201, e.g. enabling or disabling certain adaptive loads 1212, to attempt to adaptively optimize for better performance. For example, a simple optimization either opens/disconnects or closes/shorts each load terminal to ground (in embodiments in which a relay is used to switch between these states), and may also cause RF antenna element 1201 to transmit at various frequencies. In some

0247embodiments, for each combination of relay state (open or shorted) and frequency, the energy transferred to the receiver 1204 is monitored and compared to energy transferred when using other combinations. The combination that results in maximum energy transfer to the receiver 1204 is selected and used to continue to transmitting the one or more RF signals using one or more antenna elements 1201 to the receiver 1204.

0248[00198] In some embodiments, the single antenna element 1201 with multiple adaptive loads 1212 of the pad 1200 may be configured to operate in two or more distinct frequency bands (such as the ISM bands described above), e.g., a first frequency band with a center frequency of 915 MHz and a second frequency band with a center frequency of 5.8 GHz. In these embodiments, employing the adaptation scheme may include transmitting RF signals and then adjusting the frequency at first predetermined increments until a first threshold value is reached for the first frequency band and then adjusting the frequency at second

0249predetermined increments (which may or may not be the same as the first predetermined increments) until a second threshold value is reached for the second frequency band. In some embodiments, a single antenna element can operate at multiple different frequencies within one or more frequency bands. For example, the single antenna element 1201 may be configured to transmit at 902 MHz, 915 MHz, 928 MHZ (in the first frequency band) and then at 5.795 GHz, 5.8 GHz, and 5.805 GHz (in the second frequency band). The single antenna element 1201 can operate at more than one frequency bands as a multi-band antenna. A transmitter with at least one antenna element 1201 can be used as a multi-band transmitter.

0250[00199] In some embodiments, multiple antenna elements 1201 each with multiple adaptive loads 1212 may be configured within a particular transmission pad to allow the particular transmission pad to operate in two or more distinct frequency bands respectively at the same time. For example, a first antenna element 1201 of the particular transmission pad operates at a first frequency or frequency band, a second antenna element 1201 of the particular transmission pad operates at a second frequency or frequency band, and a third antenna element 1201 of the particular transmission pad operates at a third frequency or frequency band, and a fourth antenna element 1201 of the particular transmission pad operates at a fourth frequency or frequency band, and the four frequency bands are distinct from each other. In this way, the particular transmission pad is configured to operate at multiple different frequency bands.

0251[00200] In some embodiments, the transmitter described herein can transmit wireless power in one frequency or frequency band, and transmit and exchange data with a receiver in another frequency or frequency band.

0252[00201] Different antenna elements operating at different frequencies can maximize energy transfer efficiency when a smaller device is charged with higher frequencies and a larger device is charged with lower frequencies on the same charging pad. For example, devices that require a higher amount of power, such as mobile phones, may also have more space to include larger antennas, thus making a lower frequency of 900 MHz a suitable frequency band. As a comparison, a smaller device, such as an earbud, may require a small amount of power and may also have less space available for longer antennas, thus making a higher frequency of 2.4 or 5.8 GHz a suitable frequency band. This configuration enables more flexibility in the types and sizes of antennas that are included in receiving devices.

0253[00202] Turning now to Figure 13, in accordance with some embodiments, a flow chart of a method 1300 of charging an electronic device through radio frequency (RF) power transmission by using at least one RF antenna with a plurality of adaptive loads is provided. Initially, a charging pad including a transmitter is provided in step 1302 that includes at least one RF antenna (e.g., antenna element 1201, as described with respect to Figure 12 above which further includes Figures 3-8) for transmitting one or more RF signals or waves, i.e., an antenna designed to and capable of transmitting RF electromagnetic waves. In some embodiments, an array of RF antenna elements 1201 are arranged adjacent to one another in a single plane, in a stack, or in a combination of thereof, thus forming an RF charging pad 1200 (as described in reference to Figures 6A-6E, 7A-7D and 8). In some embodiments, the RF antenna elements 1201 each include an antenna input terminal (e.g., the first terminal 1203 discussed above in reference to Figure 12) and a plurality of antenna output terminals (e.g., the plurality of adaptive load terminals 1202 discussed above in reference to Figure 12). In some embodiments, the antenna element 1201 includes a conductive line that forms a meandered line arrangement (as shown in Figures 3-4, and 6-12). The plurality of adaptive load terminals 1202 are positioned at different locations of the conductive line of the antenna element 1201. [00203] In some embodiments, the transmitter further comprises a power amplifier electrically coupled between the power input and the antenna input terminal (e.g., PA 1208 in Figure 12). Some embodiments also include respective adaptive loads 1212a, 1212b, 1212c, ... 1212n electrically coupled to the plurality of antenna output terminals (e.g., adaptive load terminals 1202 in Figure 12). In some embodiments, the transmitter includes a power input configured to be electrically coupled to a power source, and at least one processor (e.g., processor 1210 in Figure 12, and processor 110 in Figures 3A-3B) configured to control at least one electrical signal sent to the antenna. In some embodiments, the at least one processor is also configured to control the frequency and/or amplitude of the at least one signal sent to the antenna.

0254[00204] In some embodiments, each RF antenna of the transmitter includes: a conductive line forming a meandered line pattern, a first terminal (e.g., terminal 1203) at a first end of the conductive line for receiving current that flows through the conductive line at a frequency controlled by one or more processors, and a plurality of adaptive load terminals (e.g., terminals 1202), distinct from the first terminal, at a plurality of positions of the conductive line, the plurality of adaptive load terminals coupled to a respective component (e.g., adaptive loads 1212 in Figure 12) controlled by the one or more processors and that allows for modifying an impedance value of the conductive line. In some embodiments, the conductive line is disposed on or within a first antenna layer of a multi-layered substrate. Also in some embodiments, a second antenna is disposed on or within a second antenna layer of the multi-layered substrate. Finally, some embodiments also provide a ground plane disposed on or within a ground plane layer of the multi-layered substrate.

0255[00205] In some embodiments, a receiver (e.g., receiver 1204 in reference to Figure

025612) is also provided (also as described in reference to Figure 3). The receiver also includes one or more RF antennas for receiving RF signals. In some embodiments, the receiver includes at least one rectenna that converts the one or more RF signals into usable power to charge a device that includes the receiver 1204 as an internally or externally connected component (see also steps 504, 506, 510, 514 and 518 in reference to Figure 5). In use, the receiver 1204 is placed within a near-field radio frequency distance to the at least one antenna of the transmitter or the charging pad. For example, the receiver may be placed on top of the at least one RF antenna 1201 or on top of a surface that is adjacent to the at least one RF antenna 1201, such as a surface of a charging pad 1200. [00206] In step 1304, one or more RF signals are then transmitted via at the least one

0257RF antenna 1201.

0258[00207] The system is then monitored in step 1306 to determine the amount of energy that is transferred via the one or more RF signals from the at least one antenna 1201 to one or more RF receivers (as is also discussed above). In some embodiments, this monitoring 1306 occurs at the transmitter, while in other embodiments the monitoring 1306 occurs at the receiver which sends data back to the transmitter via a back channel (e.g., over a wireless data connection using WIFI or BLUETOOTH). In some embodiments, the transmitter and the receiver exchange messages via the back channel, and these messages may indicate energy transmitted and/or received, in order to inform the adjustments made at step 1308.

0259[00208] In some embodiments, in step 1308, a characteristic of the transmitter is adaptively adjusted to attempt to optimize the amount of energy that is transferred from the at least one RF antenna 1201 to the receiver. In some embodiments, this characteristic is a frequency of the one or more RF signals and/or an impedance of the transmitter. In some embodiments, the impedance of the transmitter is the impedance of the adjustable loads. Also in some embodiments, the at least one processor is also configured to control the impedance of the selected set of the plurality of adaptive loads 1212. Additional details and examples regarding impedance and frequency adjustments are provided above.

0260[00209] In some embodiments, the at least one processor (e.g. CPU 1210 in Figure 12) dynamically adjusts the impedance of the adaptive load based on the monitored amount of energy that is transferred from the at least one antenna 1201 to the RF receiver. In some embodiments, the at least one processor simultaneously controls the frequency of the at least one signal sent to the antenna.

0261[00210] In some embodiments, the single antenna element 1201 with multiple adaptive loads 1212 of the pad 1200 may be dynamically adjusted by the one or more processors to operate in two or more distinct frequency bands (such as the ISM bands described above) at the same time or at different times, e.g., a first frequency band with a center frequency of 915 MHz and a second frequency band with a center frequency of 5.8 GHz. In these

0262embodiments, employing the adaptation scheme may include transmitting RF signals and then adjusting the frequency at first predetermined increments until a first threshold value is reached for the first frequency band and then adjusting the frequency at second

0263predetermined increments (which may or may not be the same as the first predetermined increments) until a second threshold value is reached for the second frequency band. For example, the single antenna element 1201 may be configured to transmit at 902 MHz, 915 MHz, 928 MHZ (in the first frequency band) and then at 5.795 GHz, 5.8 GHz, and 5.805 GHz (in the second frequency band). The single antenna element 1201 can operate at more than one frequency bands as a multi-band antenna. A transmitter with at least one antenna element 1201 can be used as a multi-band transmitter.

0264[00211] In some embodiments, a charging pad or transmitter may include one or more of the antenna element 1201 with a plurality of adaptive loads as described in Figure 12 and one or more antenna element 120 with one adaptive load as described in Figure 3A-3D.

0265[00212] Figures 14A-14D are schematics showing various configurations for individual antenna elements that can operate at multiple frequencies or frequency bands within an RF charging pad, in accordance with some embodiments. As shown in Figures 14A-14D, an RF charging pad 100 (Figures 3A-3B) or an RF charging pad 1200 (Figure 12) may include antenna elements 120 (Figure 3B) or 1201 (Figure 12) that configured to have conductive line elements that have varying physical dimensions.

0266[00213] For example, Figures 14A-14D show examples of structures for an antenna element that each include a conductive line formed into different meandered line patterns at different portions of the element. The conductive lines at different portions or positions of the element may have different geometric dimensions (such as widths, or lengths, or trace gauges, or patterns, spaces between each trace, etc.) relative to other conductive lines within an antenna element. In some embodiments, the meandered line patterns may be designed with variable lengths and/or widths at different locations of the pad (or an individual antenna element). These configurations of meandered line patterns allow for more degrees of freedom and, therefore, more complex antenna structures may be built that allow for wider operating bandwidths and/or coupling ranges of individual antenna elements and the RF charging pad.

0267[00214] In some embodiments, the antennas elements 120 and 1201 described herein may have any of the shapes illustrated in Figures 14A-14D. In some embodiments, each of the antenna elements shown in Figures 14A-14D has an input terminal (123 in Figure IB or 1203 in Figure 12) at one end of the conductive line and at least one adaptive load terminals (121 in Figure IB or 1202a-n in Figure 12) with adaptive loads (106 in Figure IB or 1212a-n in Figure 12) as described above at another end or a plurality of positions of the conductive line.

0268[00215] In some embodiments, each of the antenna elements shown in Figures 14A-

026914D can operate at two or more different frequencies or two or more different frequency bands. For example, a single antenna element can operate at a first frequency band with a center frequency of 915 MHz at a first point in time and a second frequency band with a center frequency of 5.8 GHz at a second point in time, depending on which frequency is provided at an input terminal of each of the antenna elements. Moreover, the shapes of the meandered line patterns shown in Figures 14A-14D are optimized to allow the antenna elements to operate efficiently at multiple different frequencies.

0270[00216] In some embodiments, each of the antenna elements shown in Figures 14A-

027114D can operate at two or more different frequencies or two or more different frequency bands at the same time when the input terminal is supplied with more than two distinct frequencies that can be superimposed. For example, a single antenna element can operate at a first frequency band with a center frequency of 915 MHz and a second frequency band with a center frequency of 5.8 GHz at the same time when both frequency bands with a first center frequency of 915 MHz and a second center frequency of 5.8 GHz are supplied at the input terminal of the conductive line. In yet another example, a single antenna element can operate at multiple different frequencies within one or more frequency bands.

0272[00217] In some embodiments, the operating frequencies of the antenna elements can be adaptively adjusted by one or more processors (110 in Figures 3A-3B or 1210 in Figure 12) as described above according to the receiver antenna dimension, frequency, or the receiver loads and the adaptive loads on the charging pad.

0273[00218] In some embodiments, each of the antenna elements shown in Figures 14A-

027414D with different meandered patterns at different portions of the conductive line can operate more efficiently at multiple frequencies compared with the more symmetrical meandered line structures (For example, Figure 3B, 4, 6A-6B, or 8). For example, energy transfer efficiency at different operating frequencies of the antenna elements shown in Figures 14A-14D with different meandered patterns at different portions of the conductive line can be improved by about at least 5%, and in some instance at least 60%, more than the more symmetrical meandered line structure elements. For example, the more symmetrical meandered line structure antenna element may be able to transfer no more than 60% of transmitted energy to a receiving device while operating at a new frequency other than a frequency for which the more symmetrical meandered line structure antenna element has been designed (e.g., if the more symmetrical meandered line structure antenna element is designed to operate at 900 MHz, if it then transmits a signal having a frequency of 5.8 GHz it may only be able to achieve an energy transfer efficiency of 60%). In contrast, the antenna element with different meandered patterns (e.g., those shown in Figures 14A-14D) may be able to achieve an energy transfer efficiency of 80% or more while operating at various frequencies. In this way, the designs for antenna elements shown in Figures 14A-14D ensure that a single antenna element is able to achieve a more efficient operation at various different frequencies.

0275[00219] Figure 15 is schematic showing an example configuration for an individual antenna element that can operate at multiple frequencies or frequency bands by adjusting the length of the antenna element, in accordance with some embodiments.

0276[00220] In some embodiments as shown in Figure 15, at least one transmitting antenna element 1502 (as described in Figures 3-8 and 13-14) of the one or more transmitting antenna elements of an RF charging pad 1500 has a first conductive segment 1504 (a first portion of a meandered conductive line, such as any of those described above for antenna elements 120 and 1201) and a second conductive segment 1506 (a second portion of the meandered conductive line, such as any of those described above for antenna elements 120 and 1201). In some embodiments, the first conductive segment includes an input terminal (123 in Figure 3B or 1203 in Figure 12). In some embodiments, the at least one transmitting antenna element 1502 is configured to operate at a first frequency (e.g., 2.4 GHz) while the first conductive segment 1504 is not coupled with the second conductive segment 1506. In some

0277embodiments, the at least one transmitting antenna element 1502 is configured to operate at a second frequency (e.g., 900 MHz) which is different from the first frequency while the first conductive segment is coupled with the second conductive segment.

0278[00221] In some embodiments, one or more processors (110 in Figures 3A-3B or 1210 in Figure 12) are configured to cause coupling of the first segment with the second segment in conjunction with instructing a feeding element (as described as 108 in Figures 3A-3B and 1208 in Figure 12) to generate current with a second frequency (e.g., 900 MHz) that is distinct from the first frequency (e.g., 2.4 GHz), thereby allowing the antenna element 1502 to more efficiently operate at the second frequency. The one or more processor may also be configured to cause de-coupling of the second conductive segment from the first conductive segment in conjunction with instructing the feeding element to generate current with the first frequency instead of the second frequency, thereby allowing the antenna element 1502 to more efficiently operate at the first frequency again. In some embodiments, the one or more processors are configured to determine whether to causing the coupling (or de-coupling) of these conductive segments based on information received from a receiver (e.g., RX 104 or 1204) that identifies a frequency at which the receiver is configured to operate (e.g., for larger devices with longer receiving antennas, this frequency may be 900 MHz, while for smaller devices with small receiving antennas, this frequency may be 2.4 GHz).

0279[00222] In some embodiments, the coupling described here in Figure 15 can be implemented by directly connecting two different segments of a single antenna element 1502 while bypassing the conductive line located in-between the two connection points or the two different segments. In some embodiments, coupling can be implemented between more than two different segments of the antenna element 1502. The coupling of the different portions or segments of a single meandered line antenna element 1502 can effectively change the size or length of the conductive line of the antenna element 1502, and therefore enable the single antenna element 1502 to operate at different frequencies. The single antenna element 1502 may also operate at more than one frequency bands as a multi-band antenna.

0280[00223] All of these examples are non-limiting and any number of combinations and multi-layered structures are possible using the example structures described above.

0281[00224] Further embodiments also include various subsets of the above embodiments including embodiments in Figures 1-15 combined or otherwise re-arranged in various embodiments, as one of skill in the art will readily appreciate while reading this disclosure.

0282[00225] The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the description of the invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. [00226] It will also be understood that, although the terms "first," "second," etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first region could be termed a second region, and, similarly, a second region could be termed a first region, without changing the meaning of the description, so long as all occurrences of the "first region" are renamed consistently and all occurrences of the "second region" are renamed consistently. The first region and the second region are both regions, but they are not the same region.

0283[00227] The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.