A wireless power transmission system has a wireless power receiving device that can be charged using multiple different types of wireless power transmitting devices. The different types of wireless power transmitting devices have power transmitting coils that exhibit different levels of magnetic coupling with the power receiving coil of the wireless power receiving device. The wireless power receiving device may include capacitors, resistors, and/or other loading circuits that can be independently switched into use depending on the level of magnetic coupling that is detected, on a rectified voltage level, on the size of the output load, and/or on information conveyed during handshaking operations to present a desired impedance adjustment at the power receiving coil so that data signal can be properly conveyed between the power receiving device and the power transmitting device.

An antenna system can include casing-side antennas and a full wave rectifier. The casing-side antennas can be coupled to a casing string that is positioned in a wellbore for communicatively coupling to a tubing-side antenna positioned in the wellbore. Each of the casing-side antennas can include a conductive wire positioned to carry current that can be induced on the conductive wire in response to an electromagnetic field from the tubing-side antenna. A direction, relative to a common antenna junction point, of the current on the conductive wire can be opposite to the direction, relative to the common antenna junction point, in which an adjacent casing-side antenna is positioned to carry current induced in response to the electromagnetic field. The full-wave rectifier can be conductively coupled to the casing-side antennas for converting alternating current that can be generated on the casing-side antennas into direct current.

One example discloses a near-field device, including: an electric (E-Field) antenna including a first conductive plate and a second conductive plate responsive to non-propagating quasi-static electric near-field signals; wherein the electric antenna is configured to be coupled to a transceiver circuit; a substrate configured to be worn by a user; wherein the first conductive plate is located on a first side of the substrate configured to face away from the user; and wherein the second conductive plate is located on a second side of the substrate configured to face toward the user.

One example discloses a near-field wireless device, including: a near-field antenna; a variable current source; a controller coupled to the near-field antenna and the variable current source; wherein the controller is configured to measure a transmit quality-factor (Qtx) of the near-field antenna; and wherein the controller is configured to increase current sent by the variable current source to the near-field antenna if the measured Qtx is lower than a minimum Qtx.

One example discloses a multi-mode near-field device configured to be coupled to a conductive host surface, including: a conductive antenna surface configured as a near-field electrically inductive (NFEI) antenna; wherein the conductive antenna surface includes a first region and a second region; wherein the first region is configured to be capacitively coupled to the conductive host surface; wherein the second region is configured to be galvanically or capacitively coupled to the conductive host surface; wherein the multi-mode device is configured to operate in, a first mode when the second region is galvanically coupled to the conductive host surface; and a second mode when the second region is capacitively coupled to the conductive host surface.

A passive radio frequency identification (RFID) reader is configured to dynamically vary the Q factor of its resonant antenna coil circuit in order to optimize its performance under different conditions. This RFID reader suitably provides optimal performance for both transponder reading and transponder writing operations, rather than being designed for optimal performance for only one operation or the other, or some fixed compromise between them.

One example discloses a combination near-field and far-field antenna configured to be coupled to a conductive host surface, including: a first feed point configured to be coupled to a far-field transceiver; a second feed point configured to be coupled to a near-field transceiver; a first conductive antenna surface; a first filter having a first interface coupled to both the first feed point and the first conductive antenna surface, and having a second interface coupled to the second feed point; wherein the first filter is configured to attenuate far-field signals passing between the first conductive antenna surface and the far-field transceiver from being received by the near-field transceiver; and wherein the first filter is configured to pass near-field signals between the near-field transceiver and the first conductive antenna surface.

Systems and methods for providing neural stimulation and recording on a subject using flexible complementary CMOS probes are provided. Disclosed systems can include a flexible probe adapted for insertion into a portion of a brain of the subject, the flexible probe comprising a tail portion and a head portion. The tail portion can include a plurality of electrodes configured to be coupled to the brain and a plurality of front-end amplifiers. Each of the plurality of front-end amplifiers can be configured to amplify a signal received from a corresponding electrode of the plurality of electrodes. The head portion can include one or more inductors configured to enable two-way communication with a wireless reader through a near-field inductive link.

A forearm guard compressive sleeve is disclosed which functions as a protective guard in athletic endeavors and as fashion apparel and as an advertising and promotional medium. The sleeve is constructed to mitigate the effects of environmental and mechanical hazards, limit the deleterious effects of an athlete's perspiration and muscle stress and imbue the user with psychological confidence in his or her athletic performance. The inventive forearm guard incorporates Near Field Communication components including one of more NFC tags which enable access via NFC-enabled mobile smart phones or computers to the Internet. A method is disclosed enabling celebrity athletes or personnel using the inventive forearm guard to transfer wireless personalized information to fans and supporters including sending virtual autographs and mementos.

A wireless power receiver can include a magnetic substrate and a coil configured to wirelessly receive power. The coil can be formed as a conductive layer on the magnetic substrate. A connecting unit can be disposed in a receiving space of the magnetic substrate and can be connected to the coil unit.