An antenna device for magnetic field communication may include: a first coil; a second coil; a third coil; a first capacitor connected to a 1-1 terminal of the first coil; a second capacitor connected to a 2-1 terminal of the second coil; a third capacitor connected to a 3-1 terminal of the third coil; and an input port including a first input terminal connected to a 1-2 terminal of the first coil, a 2-2 terminal of the second coil, and a 3-2 terminal of the third coil, and a second input terminal connected to the first capacitor, the second capacitor, and the third capacitor.

A mobile device includes an NFC (Near Field Communication) antenna including a metal coil and a first dielectric substrate, a coupling metal element, and a second dielectric substrate. The metal coil is disposed on the first dielectric substrate. The coupling metal element is adjacent to the metal coil. The coupling metal element does not directly touch the metal coil. The coupling metal element is disposed on the second dielectric substrate. The coupling metal element is configured to adjust the operational frequency of the NFC antenna.

A manhole cover and a manhole management system are provided. A manhole cover according to one embodiment includes: a cover body; an electronic unit including at least one sensing unit configured to sense information inside a manhole and at least one communication module configured to transmit information which is obtained through the sensing unit to the outside, and embedded in the cover body; a battery providing driving power to the electronic unit; and a wireless power reception antenna embedded in the cover body to receive wireless power supplied from the outside and provide the wireless power to the battery.

A hearing device includes first, second, and third antennas oriented respectively along first, second, and third axes that are different from one another. The device includes first channel circuitry coupled to transceive and process antenna signals of each of the antennas. The antennas and the first channel circuitry communicate with another hearing device via a near field magnetic induction (NFMI) signal through a first near field magnetic induction (NFMI) communication channel. Second channel circuitry is coupled to transceive and process the antenna signals of each of the antennas. The antennas and the second channel circuitry communicate with the other device via the NFMI signal through a second NFMI communication channel. Third channel circuitry is coupled to transceive and process the antenna signals of each of the antennas. The antennas and the third channel circuitry communicate with the other device via the NFMI signal through a third NFMI communication channel.

A monaural hearing device includes: a first housing accommodating a first near-field magnetic induction communication unit and a first magnetic field antenna connected to the first near-field magnetic induction communication unit, wherein the first housing is configured for placement behind an ear of a user of the monaural hearing device; and a second housing accommodating a second near-field magnetic induction communication unit and a second magnetic field antenna connected to the second near-field magnetic induction communication unit; wherein the first and second near-field magnetic induction communication units connected to the first and second magnetic field antennas, respectively, are configured to perform near-field wireless data communication with each other.

A non-contact communication medium according to one disclosed embodiment includes a memory unit, a power generation unit, a power monitoring unit, and a capacitance control unit. The power generation unit includes a resonant circuit and a rectification circuit, and generates electric power to be supplied to the memory unit. The resonant circuit includes an antenna coil and resonant capacitance unit having a variable capacitance value, and the rectification circuit rectifies a resonant output of the resonant circuit. The power monitoring unit includes a current adjustment element, a reference voltage generation source, and an operational amplifier. The operational amplifier controls the current adjustment element such that an output voltage of the rectification circuit is equal to a reference voltage from the reference voltage generation source. The capacitance control unit is configured to control the resonant capacitance unit on the basis of an output of the operational amplifier.

Provided are an antenna apparatus and an electronic device. The antenna apparatus includes a radiator, a near-field communication chip and a first non-near-field communication chip. The radiator includes a ground point and a first feeding point that are spaced apart from each other, and the ground point is grounded. The near-field communication chip is configured to provide a differential excitation current. The first non-near-field communication chip is configured to provide a first non-near-field communication excitation current.

Aspects of the present relate to reflection type phase shifters for radio frequency (RF) wireless devices. Reflection type phase structures in accordance with aspects described herein can improve device performance with compact configurations, such as where magnetic and capacitive coupling is integrated into a device design to integrate interactions between elements for improved phase shifting performance in a compact design with wideband performance.

A power transmitter includes: a first switch coupled between a first node and a reference voltage node; a second switch configured to be coupled between a power supply and the first node; a coil and a capacitor coupled in series between the first node and the reference voltage node; a first sample-and-hold (S&H) circuit having an input coupled to the first node; and a timing control circuit configured to generate a first control signal, a second control signal, and a third control signal that have a same frequency, where the first control signal is configured to turn ON and OFF the first switch alternately, the second control signal is configured to turn ON and OFF the second switch alternately, and where the third control signal determines a sampling time of the first S&H circuit and has a first pre-determined delay from a first edge of the first control signal.

A wireless charging device includes a driver unit configured to generate one of a first AC voltage signal having a first frequency and a second AC voltage signal having a second frequency. Also, the wireless charging device includes a transmitting unit having a first coil and a first capacitor and configured to transmit the first AC voltage signal. Further, the transmitting unit includes a second coil and a second capacitor and configured to transmit the second AC voltage signal. Additionally, the wireless charging device includes a control unit configured to detect a first receiver device operating at the first frequency based on a change in a first voltage in the transmitting unit, and detect a second receiver device operating at the second frequency based on a change in a second voltage in the transmitting unit.