Abstract: One embodiment provides a non-contact power transmitter device including a sealed housing provided at least partially within a surface, and a transmitter coil within the sealed housing configured to inductively transfer power to a power receiver device. The power transmitter device also includes a transmitter control unit coupled to the transmitter coil, a transceiver configured to communicate with the power receiver device, and an electronic processor coupled to the transmitter control unit and the transceiver. The electronic processor is configured to establish, using the transceiver, communication with the power receiver device, and negotiate power transfer requirements between the power transmitter device and the power receiver device. The electronic processor is also configured to control the transmitter control unit to transfer power to the power receiver device.

Abstract: Disclosed is a combo antenna module which can improve antenna performance by arranging a radiation pattern for electronic payment such that a portion of the radiation pattern does not overlap a magnetic sheet. The disclosed combo antenna module includes: a radiation pattern for wireless power transmission and a radiation pattern for electronic payment which are formed on a base substrate; and a magnetic sheet arranged to overlap the entire radiation pattern for wireless power transmission and a portion of the radiation pattern for electronic payment.

Abstract: An electrical supply holding circuit includes a primary stage and a secondary stage. The primary stage includes a voltage connector connected to a supply network, and a primary winding connected to a voltage converter. The secondary stage includes a secondary winding facing the primary winding, the primary and secondary windings forming two coupled inductances, and a voltage controller to which the secondary winding is connected, the voltage controller being connected to a load and controlling a voltage across the terminals of the load. Directions of the currents flowing through the primary and secondary windings are the reverse of one another, and the voltage converter stops the supply to the primary winding when the supply voltage is less than a threshold voltage and resumes the supply to the primary winding when the supply voltage is greater than a threshold voltage.

Abstract: At least one component for a wireless power transmitter or a wireless power receiver. The at least one component includes a mechanical structure and/or circuitry configured to maintain and/or adjust a coupling coefficient K between the wireless power transmitter and the wireless power receiver, a loaded quality factor Q of the wireless power receiver, or both, such that K times Q is less than a constant.

Abstract: Wireless power transfer systems, disclosed, include a wireless power transmission system and a wireless power receiver system. The wireless power transmission system includes a transmitter antenna configured to couple with a receiver antenna to transmit alternating current (AC) wireless signals to the receiver antenna. Antenna coupling may be inductive and may operate in conformance to a wireless power and data transfer protocol. A transmission controller drives the transmitter antenna at an operating frequency, and either the wireless power transmission system or the wireless power receiver system may damp the wireless power transmission to create a data signal containing a serial asynchronous data signal.

Abstract: Embodiments of the present disclosure describe systems, methods, and apparatuses for reviving a wireless power receiver client over-the-air. More specifically, dual-mode active/passive wireless power receiver clients are described that can passively harvest RF energy in order to obtain enough energy to rejoin a wireless power network where the client can actively harvest RF energy (the client receives directed or isolated wireless power from a wireless power transmission system). For example, a wireless power receiver client can harvest RF energy while idle or off, e.g., when no beacon or other communications are being sent or received, or, in some instances, asynchronously in order to compliment and/or protect one or more elements of the system such as, for example a radio transceiver.

Abstract: Using inductive currents to wirelessly charge a device via a device connected to a power source. This inductive charging may result when a first mobile device recognizes a second mobile device via a wireless connection (e.g., Bluetooth, Bluetooth Low Energy (BLE), Near-Field Communication (NFC), or the like). An application stored on the first mobile device may recognize a second mobile device by transmitting an advertising packet when the first mobile device is connected to a power source. An advertising packet may be received by the second mobile device and the second mobile device may transmit a response to the advertising packet in order to generate a connection between the first and second mobile devices. The response may include data such as, connection strength, response time, connection preferences, and the like. Upon detection and connection, the second mobile device may be wirelessly charged by the first device via inductive charging.

Abstract: The present disclosure relates to an integrated boost modular multilevel converter, which has particular, but not sole, relevance to a converter for an inductive or capacitive (wireless) power transfer system. More particularly, the present invention according to an embodiment discloses a modular multilevel power converter (MMPC) comprising: at least one submodule stack having an output for connection to a load and an input for connection to an input power source, at least one inductive element provided between the input and the output, the at least one submodule stack including at least two submodules, each submodule comprising at least one capacitor and a plurality of controllable switches, and the submodules being operable to selectively transfer energy from the at least one inductive element to boost a voltage at the output relative to a voltage at the input.

Abstract: The technology described herein relates to wireless power receivers with reconfigurable (or adaptive) antenna configurations for improved wireless power transfer in multipath wireless power delivery environments. In an implementation, a wireless power receiver is described. The wireless power receiver includes one or more radio frequency (RF) antennas, power metering circuitry and control circuitry. The power metering circuitry is adapted to measure at least one characteristic of wireless power received from a wireless power transmission system in a multipath environment. The control circuitry is adapted to monitor the power metering circuitry to determine when the measure of the at least one characteristic of the wireless power fails to meet a preset threshold, and dynamically reconfigure an antenna configuration of the wireless power receiver when the at least one characteristic of the wireless power fails to meet the preset threshold.

Abstract: A multi-power-mode ultra-low-power address detector for Radio Frequency (RF) wakeup receivers is provided herein. The address detector is implemented when combined charging and wake-up of a device is required. The method includes a set of components to process a complex address waveform. This address includes a preamble composed of a pulse with a specific width, followed by a digital Pulse Width Modulation (PWM) modulated bit pattern.

Abstract: Described herein are improved configurations for a wireless power transfer. The parameters of components of the wireless energy transfer system are adjusted to control the power delivered to the load at the device. The power output of the source amplifier is controlled to maintain a substantially 50% duty cycle at the rectifier of the device.

Abstract: A wireless power transmission device for a vehicle and a method are provided. The wireless power transmission device for a vehicle may transmit a signal for detection of a wireless power reception device by using a lower frequency band that is different from an operating frequency band used to control the vehicle. The wireless power transmission device may receive a response signal for the transmitted signal and a power control signal from the wireless power reception device. The wireless power transmission device may control an operating frequency or a voltage (or both) in the wireless power transmission device for the vehicle according to the power control signal. The wireless power transmission device may transmit wireless power to the wireless power reception device.

Abstract: A wireless power feeding system is provided, comprising a power transmission apparatus configured to transmit predetermined transmission power and a power reception apparatus configured to receive the transmission power and generate input voltage according to the transmission power, wherein the power transmission apparatus includes a power transmission control unit configured to control an amount of the transmission power, the power transmission control unit is configured to receive a modulation signal from the power reception apparatus, and to reduce the transmission power in a case where the modulation signal is not received for a predetermined period after receiving the previous modulation signal, and the power transmission apparatus and the power reception apparatus are configured to control the input voltage to be larger than a predetermined first threshold and below a second threshold which is larger than the first threshold.

Abstract: An HMD includes first and second batteries mounted therein, and includes a plurality of power receivers that receive power from the first and second batteries by wireless transmission, a power supply manager that monitors states of the first and second batteries, a communication interface that performs wireless communication with the first and second batteries, and a plurality of limiters that limit the power received by the plurality of power receivers. A controller causes the limiters to limit power, which is supplied to a load, according to a power use state of the load in the device, and the power supply manager acquires information of remaining power storage amounts of the first and second batteries through the communication interface and displays the acquired information on a display. Therefore, since it is possible to supply power required for driving the device while wearing the HMD, the HMD can be continuously used.

Abstract: A wireless power transmitter and a wireless power receiver are discussed. The wireless power transmitter can include a power converter configured to transfer wireless power to a wireless power receiver, and a communicator/controller configured to control the wireless power. The wireless power transmitter can receive a received power (RP) packet which informs a received power value, transmit in response to the RP packet a bit pattern related to requesting permission to communicate, receive a response packet which invites the wireless power transmitter to send a data packet, transmit a specific packet includes a specific power level in response to the response packet, and negotiate a guaranteed power level with the wireless power receiver. The guaranteed power level can be less than or equal to the specific power level.

Abstract: A wireless power transfer holder composed of a receiving space formed by first walling portions to be provided opposite side surfaces, respectively, defining width directions of an electronic device, second walling portions to be provided opposite front and back surfaces, respectively, defining thickness directions of the electronic device, a bottom portion, and an open portion formed opposite the bottom portion, first and second supporting members movable symmetrically forward or backward in the width directions from the first walling portions, respectively, toward the electronic device, to exert bias forces on the side surfaces, respectively, of the electronic device, and an inductive power transferring device mounted on one of the second walling portions to inductively transfer an electric power in a non-contact manner to the electronic device held in the receiving space.

Abstract: Object detection for wireless power transmitters and related systems, methods, and devices are disclosed. A controller for a wireless power transmitter is configured to receive a measurement voltage potential responsive to a tank circuit signal at a tank circuit, provide an alternating current (AC) signal to each of the plurality of transmit coils one at a time, and determine at least one of a resonant frequency and a quality factor (Q-factor) of the tank circuit responsive to each selected transmit coil of the plurality of transmit coils. The controller is also configured to select a transmit coil to use to transmit wireless power to a receive coil of a wireless power receiver responsive to the determined at least one of the resonant frequency and the Q-factor for each transmit coil of the plurality of transmit coils.

Abstract: A temperature-regulating unit includes a base, a thermal element, a contactless sensing assembly, and a controller. The base is configured to support at least one of a pan or a food product. The thermal element is positioned to thermally regulate the at least one of the pan or the food product. The contactless sensing assembly is positioned to acquire sensor data regarding the at least one of the pan or the food product. The controller is configured to receive the sensor data from the contactless sensing assembly and adaptively control the thermal element based on the sensor data.

Abstract: Systems, methods and apparatus for wireless charging are disclosed. A charging device has a plurality of charging cells provided on a charging surface, a charging circuit and a controller. The controller may be configured to detect an object in proximity to a surface of the charging device through a passive ping. The controller is also configured to ping the detected object with an active ping, and determine whether a ping response is received from the object in response to the one or more active pings from the charging device. Additionally, the controller is configured to stop the active pinging of the detected object when no ping response is received in the charging device after a count of successively issued active pings from the at least one coil exceeds a predetermined number. The result is lockout of digital pinging when passive pinging detects an object that is non-responsive to active pings.

Abstract: A power receiving device according to the present disclosure includes a power receiving section that receives power from a power feed device with use of a power receiving coil; and a communication section that transmits coil information to the power feed device, the coil information indicating whether or not a coil is provided near the power receiving coil.

Abstract: A multi-transmitting multi-receiving magnetic-resonance wireless charging system for a medium-power electronic apparatus includes a magnetic-resonance transmitting module and a magnetic-resonance receiving module. The magnetic-resonance transmitting module includes a transmitting-end Bluetooth-communication and control module and at least two magnetic-resonance transmitting channels. Each magnetic-resonance transmitting channel includes a direct current/direct current (DC/DC) regulator module, a radio-frequency power amplifier source, a matching network and a magnetic-resonance transmitting antenna which are connected sequentially. The magnetic-resonance receiving module includes a receiving-end Bluetooth-communication and control module, a power synthesis and protocol module and at least two magnetic-resonance receiving channels.

Abstract: Systems and methods are provided for wireless transmission of power or information. A supplying system include a signal source and a transmitter unit. A consuming system includes an electrical load and a receiver unit. Electrical power or information are transmitted wirelessly from the supplying system to the consuming system. The transmitter unit can include a step up transformer. The receiver unit can include a step down transformer. The transmitter unit and receiver unit are not connected to a common ground, resulting in a truly wireless system for transmitting power or information.

Abstract: Wireless power transfer systems, disclosed, include a wireless power transmission system and a wireless power receiver system. The wireless power transmission system includes a transmitter antenna configured to couple with a receiver antenna to transmit alternating current (AC) wireless signals to the receiver antenna. Antenna coupling may be inductive and may operate in conformance to a wireless power and data transfer protocol. A transmission controller drives the transmitter antenna at an operating frequency, and either the wireless power transmission system or the wireless power receiver system may damp the wireless power transmission to create a data signal containing a serial asynchronous data signal.

Abstract: An electronic device for providing a wireless charging function and a method thereof is provided. The electronic device includes a housing, a touch pad which is disposed in the housing and includes an electrode pattern and multiple openings formed on the electrode pattern, a wireless charging coil, and a processor operationally connected to the touch pad and the wireless charging coil, wherein the processor is configured to perform a touch detection function of detecting a touch by an inputting subject by using at least one electrode pattern of the touch pad, calculate a capacitance variation of the touch pad while the touch detection function is performed, determine whether the inputting subject requires a charging function, based on the calculated capacitance variation, and, in response to determining that the inputting subject requires the charging function, perform a charging function of transmitting power by using the wireless charging coil.

Abstract: A load testing device includes: a resistance unit; a cooling fan that cools the resistance unit; a circuit breaker; a first terminal part that is connected to a test target power source; and a charge/discharge unit that has a charger and a first power storage device. The charge/discharge unit is connected with a test target power source cable being between the first terminal part and the resistance unit, between the first terminal part and the circuit breaker. The first power storage device 45a stores electric power supplied from the test target power source. The cooling fan drives based on electric power from at least the charge/discharge unit.

Abstract: Support of coexistence of wireless transmission equipment in shared wireless medium environments is disclosed, which is applicable to various types of wireless transmission equipment. For instance, a wireless power transmission system (WPTS) delivers power to wireless power receiver clients via transmission of wireless power signals using one or more frequencies and/or channels within shared wireless medium environments in which other wireless equipment is operating, such as access points and stations in wireless local area networks (WLANs). The WPTS is configured to co-exist with the operations of the other wireless equipment within the shared wireless medium environment by adapting its transmission operations to utilize frequencies or channels that do not interfere with other equipment and/or implementing co-channel and shared channels operations under which access to channels is implemented using standardized WLAN protocols such as PHY and MAC protocols used for 802.11 (Wi-Fi™) networks.

Abstract: A drone-based product delivery mechanism in which power is transferred between the drone's battery and a product's battery while the product is in transit to its destination. For a short distance delivery, the drone battery may be used to charge the product battery so that the product is delivered with a fully-charged battery. On the other hand, for long distance deliveries, the power from a fully-charged product battery may be used to charge the drone's battery to extend the flight time/radius of the drone or to supplement the drone battery to conserve its power. The power transfer may be carried out using a wireless connection or a wired connection. The wireless connection may be a Qi interface, whereas the wired connection may be a Universal Serial Bus (USB) connection. The product packaging may be re-designed to allow the desired power transfer between the drone and the product inside the packaging.

Abstract: A device includes a rectifier connected to a receiver coil, a first overvoltage protection apparatus connected between inputs of the rectifier and ground, and a second overvoltage protection apparatus connected between an output of the rectifier and ground, wherein in an overvoltage event, the first overvoltage protection apparatus and the second overvoltage protection apparatus are controlled based upon a comparison between a switching frequency of the device and a predetermine frequency threshold.

Abstract: A multifunctional charging station is provided. The multifunctional charging station includes a housing, an alarm clock, an AC input connector, an AC output interface, a DC output interface, a luminous display screen, a wireless charging system, a controller and a managing circuit. The multifunctional charging station is configured to optimally supply electrical power to AC and DC electric devices, while wirelessly charging electric devices at the same time, and functions as an alarm clock and lighting system (e.g., a nightlight).

Abstract: The present disclosure relates to a device comprising an inductive element and a first capacitive element series connected between a first node and a second node, a first MOS transistor connected between the first node and a third node configured to receive a reference potential, the second node being coupled directly or via a second MOS transistor to the third node, a second capacitive element connected between a fourth node and an interconnection node between the first capacitive element and the inductive element, a current generator configured to provide an AC current to the fourth node, and a switch connected between the fourth node and the third node.

Abstract: A window apparatus of a vehicle includes a removable panel that selectively encloses an exterior opening of the vehicle that includes an electro-optic apparatus. The electro-optic apparatus is configured to adjust a transmittance of the window. A wireless connection interface is in connection with an interface surface of the removable panel, wherein the wireless connection interface communicates power and/or electrical signals from the vehicle to the electro-optic apparatus.

Abstract: A wireless power feeding control apparatus for a vehicle includes a positioning unit and an examination unit. The vehicle is provided with a power receiving coil that wirelessly receives electrical power from a power transmitting coil of a power transmission facility, a parking lock mechanism, and a parking lock sensor that outputs an electrical signal corresponding to a locked state of a wheel established by the parking lock mechanism. The positioning unit positions the power transmitting coil or assists in positioning the power transmitting coil on the basis of a quantity of electricity generated by the power receiving coil receiving a magnetic field from the power transmitting coil subjected to weak excitation weaker than excitation during electrical power transmission. The examination unit checks the locked state of the wheel after the weak excitation is stopped and before the electrical power transmission is started.

Abstract: A wireless power transmission system comprising a wireless power transmitting device and a wireless power receiving device. The wireless power receiving device is configured to regulate power drawn during a power transfer phase to maintain a substantially steady power level that is less than or equal to a power consumption level demanded by an associated load. The wireless power transmitting device is configured to determine the presence of a foreign object by monitoring the power transmitted or the power received and identifying a characteristic change in steady state power indicative of the presence of a foreign object.

Abstract: One general aspect includes methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for fault protection of a bidirectional wireless power transfer system. The method includes the actions of detecting, by control circuitry of a wireless power transfer device, a fault for the bidirectional wireless power transfer system. Identifying an operating personality of the wireless power transfer device and a hardware configuration of the wireless power transfer device. Identifying, in response to detecting the fault and based on the operating personality and the hardware configuration, protection operations for protecting the wireless power transfer device from the fault. Controlling operations of the wireless power transfer device according to the protection operations.

Abstract: An apparatus includes a rectifier having a first input coupled to a first terminal of a receiver coil and a second input coupled to a second terminal of the receiver coil, wherein the rectifier is configured to convert an alternating current voltage into a direct current voltage, a first communication network connected to the first input of the rectifier, and a second communication network connected to the second input of the rectifier, wherein the first communication network and the second communication network are controlled independently to adjust a gain of a wireless power transfer system.

Abstract: A system and method to detect the presence of conductive foreign objects for a multi-coil wireless power system is described. A wireless power receiver resonant circuit quality information may be obtained without any costly hardware or termination of power delivery to the power receiver load. The power receiver free-running coil current or voltage may be measured during a very short time window. In this time window, the measurement may be unaffected by transmitter and receiver load due to the transmitter coil disconnection and because the wireless power receiver has sufficient DC-bus capacitance.

Abstract: A coil arrangement with reduced core losses is provided. The coil arrangement has a first coil and a second coil and a ferrite layer below the coils. A perpendicular recess in the ferrite layer is provided to reduce magnetic flux density in a center conduction path.

Abstract: In certain aspects, an enclosure for a wireless power transfer pad is disclosed. The enclosure includes a cover shell configured to be positioned over a portion of the wireless power transfer pad configured to face a wireless power receiver when wirelessly transferring power, wherein at least a portion of the cover shell is made of a heat resistant material.

Abstract: A charging device, implemented by a first terminal, includes a transceiver, a voltage converter, and a power supply. The voltage converter is connected with the transceiver and the power supply, and is configured to step up a voltage output by the power supply and provide the stepped up voltage for the transceiver when the first terminal supplies power, and to step down a voltage input by the transceiver and supply the stepped down voltage to the power supply when the first terminal is charged. The transceiver is configured to send a wireless charging signal out based on the voltage stepped up by the voltage converter when the first terminal supplies power, and to receive a wireless charging signal and convert the received wireless charging signal into an input voltage to transmit the input voltage to the voltage converter when the first terminal is charged.

Abstract: Provided are an apparatus and method for performing foreign object detection in a wireless power transfer system. The present specification discloses a method comprising receiving a digital ping from the wireless power transmitter; transmitting an identification and configuration packets to the wireless power transmitter; transmitting a foreign object detection (FOD) state packet which indicates a reference Q factor of the wireless power receiver to the wireless power transmitter; and receiving wireless power through magnetic coupling from the wireless power transmitter based on the foreign object detection result of the wireless power transmitter using the reference Q factor. Irrespective of individual characteristics of a wireless power receiver, accuracy and reliability of detecting a foreign object may be improved.

Abstract: A distributed radio frequency (RF) generator for wireless power transfer for wireless power transfer is described. A distributed RF generator can include an electrically-conductive loop having at least a first end and a second end that are adapted to be electrically coupled to one or more direct current (DC) power sources, where the loop comprises a plurality of segments, each of the plurality of segments comprising: a length of wire and at least one active component, wherein the at least one active component has a first terminal and a second terminal that are electrically coupled to the loop, wherein: a DC voltage exists between the first terminal and the second terminal; a DC current flows into the first terminal and out of the second terminal; an oscillating RF voltage is output across the first terminal and the second terminal; and the at least one active component is synchronized in phase.

Abstract: The invention describes a system (100) for transferring electrical power to an electrical load (110), comprising: a direct electrical voltage source (105), and at least one wave generator (145) adapted for converting the direct electric voltage into voltage waves to be transmitted to the electrical load (110); wherein said wave generator (145) comprises at least: an active switch (180) provided with two connection terminals (185, 190) and adapted for being controlled by an electric control signal between a saturation condition, in which it allows the passage of electrical current between said connection terminals (185, 190), and a prevention condition, in which it prevents said passage of electrical current, and a resonant circuit (200) sized to reduce the electrical power applied to said active switch (180) in the moments in which said active switch switches from the saturation condition to the prevention condition and vice-versa; and wherein said resonant circuit (200) comprises at least: a central electric

Abstract: An electronic device having an inductive power transfer system to transfer power to a portable device is disclosed. The electronic device includes a first inductive coil for power transfer using an alternating magnetic field. The electronic device further includes a permanent magnet structure for creating a separable magnetic attachment between the electronic device and the portable device having a second inductive coil for inductive power transfer. The permanent magnet structure is positioned around an outer perimeter of the first inductive coil to align the first inductive coil with the second inductive coil in the portable device for inductive power transfer. The permanent magnet structure includes one or more discontinuous arc-shaped permanent magnets assembled to form a full or partial ring shape that includes a gap to impede eddy current generation in the permanent magnet structure by the alternating magnetic field during inductive power transfer.

Abstract: A wireless charging receiver circuit includes a first bridge arm unit connected to the first node and a common ground node, a second bridge arm unit connected to the second node and the common ground node, a first voltage converter unit connected to the second node and the common ground node, a second voltage converter unit connected to the first node and a common ground node, a filter circuit, a bias power supply circuit, and a control unit configure to control the switch transistors, such that the voltage output terminals of the first voltage converter unit and the second voltage converter unit output a voltage signal.

Abstract: Wireless power transfer systems, disclosed, include a wireless power transmission system and a wireless power receiver system. The wireless power transmission system includes a transmitter antenna configured to couple with a receiver antenna to transmit alternating current (AC) wireless signals to the receiver antenna. Antenna coupling may be inductive and may operate in conformance to a wireless power and data transfer protocol. A transmission controller drives the transmitter antenna at an operating frequency, and either the wireless power transmission system or the wireless power receiver system may damp the wireless power transmission to create a data signal containing a serial asynchronous data signal.

Abstract: The application relates to an electric converter for converting AC or DC input into an electric AC or DC output. A swap circuit with controllable electric switches serves to selectively swap connection of a plurality of DC power banks (DCBs) between an input terminal and an output terminal, thus selectively connecting the DCBs to an electric source or an electric load. The DCBs are formed as series of interconnected submodules (SMs) each having electric energy storage elements (ESEs) and a switching circuit for selectively by-passing or connecting the ESEs. By properly controlling the swap circuit and the switching of the SMs, the converter can be used for DC-AC, DC-DC, AC-DC, or AC-AC conversion, allowing multilevel output.

Abstract: The present disclosure relates to a method and a device for transmitting data in a wireless power transmission system. The method for transmitting data by a wireless power transmitter in a wireless power transmission system may comprise the steps of: receiving from a wireless power receiver, within a first control error interval, a first control error packet containing a control error value with respect to power transmitted from the wireless power transmitter; determining the size of a first data packet on the basis of the length of the first control error interval; and transmitting the first data packet to the wireless power receiver.

Abstract: A system and method are provided for a feed-forward control of an inverter to reduce, and potentially minimize, a DC link capacitor of a wireless power transfer system. The feed-forward control may be utilized to reduce the capacitance of the DC link capacitor in a single-phase series-series compensated WPT system.

Abstract: A wireless charging receiving apparatus includes a wireless charging conversion module, a charging management module, a voltage combination module and at least two wireless charging receiving coils.

Abstract: An electric field-reducing insulating layer is described for an inductive coil. In some examples, a first coil having at least one first winding is arranged for being driven at a first voltage. A solid insulating layer is adjacent the first coil and has a first surface facing the first coil. The first surface of the solid insulating layer has a first groove between the first winding and the insulating layer, having a width that is smaller than a diameter of the electrical wire. The first groove forms a pocket between the first winding and the solid insulating layer.