A device may include a housing, a wireless transceiver carried by the housing, and an antenna element carried by the housing and having first and second feeds, and a split antenna feed network carried by the housing and providing a phase shift between the first and second feeds. The split antenna feed network may include a first capacitor having a first terminal coupled to the first feed and a second terminal coupled to the wireless transceiver, a second capacitor having a first terminal coupled to the second feed and a second terminal, a first inductor having a first terminal coupled to the second terminal of the first capacitor and a second terminal coupled to the second terminal of the second capacitor, and a second inductor having a first terminal coupled to the second terminal of the second capacitor and a second terminal coupled to a voltage reference.

A device is equipped with one or more communication modules supporting communication on the basis of radio signals and communication on the basis of body-coupled communication signals. Further, the device is equipped with an antenna for transmission of the radio signals. The antenna is further operable to transfer the body-coupled communication signals between the device and a body of a user of the device.

According to one embodiment of the present specification, a user terminal is provided. The user terminal can comprise: a tunable antenna capable of adjusting a band; a diplexer connected to the tunable antenna to synthesize and separate sub-carriers; one or more antenna switches connected to the diplexer to synthesize and separate low-band sub-carriers and middle-band and high-band sub-carriers; and a sub-carrier processing unit connected to the one or more antenna switches to synthesize and separate a plurality of low-band sub-carriers, a plurality of middle-band sub-carriers and a plurality of high-band sub-carriers. A low-noise amplifier can be connected to the sub-carrier processing unit in order to prevent an increase in a reception sensitivity loss and a noise index occurring on a reception path of the diplexer, the one or more antenna switches and the sub-carrier processing unit.

A stray capacitance is generated between an antenna element and a ground electrode. A capacitance detection circuit detects the stray capacitance. An antenna matching circuit, is provided along a wireless communication signal path, which is a transmission path between the antenna element and a feeder circuit. A feedback control circuit transmits a control signal to the variable matching circuit on the basis of a detection result of the capacitance detection circuit in accordance with the stray capacitance. The capacitance detection circuit includes a constant current source and a timing circuit to measure the time taken to charge the antenna from the constant current source and for the voltage to reach a predetermined voltage.

A stray capacitance is generated between an antenna element and a ground electrode. A capacitance detection circuit detects the stray capacitance. An antenna matching circuit, is provided along a wireless communication signal path, which is a transmission path between the antenna element and a feeder circuit. A feedback control circuit transmits a control signal to the variable matching circuit on the basis of a detection result of the capacitance detection circuit in accordance with the stray capacitance. The capacitance detection circuit includes a constant current source and a timing circuit to measure the time taken to charge the antenna from the constant current source and for the voltage to reach a predetermined voltage.

Antenna tuning circuitry includes an antenna tuning node, an antenna tuning switch, and a resonant tuning circuit. The antenna tuning node is coupled to a resonant conduction element of an antenna. The antenna tuning switch and the resonant tuning circuit are coupled in series between the antenna tuning switch and the antenna tuning node, such that the resonant tuning circuit is between the antenna tuning node and the antenna tuning switch. The resonant tuning circuit is configured to resonate at one or more harmonic frequencies generated by the antenna tuning switch such that a high impedance path is formed between the antenna tuning switch and the antenna tuning node at harmonic frequencies generated by the antenna tuning switch. Accordingly, harmonic interference generated by the antenna tuning switch is prevented from reaching the antenna, while simultaneously allowing for tuning of the antenna.

Antenna tuning circuitry includes an antenna tuning node, an antenna tuning switch, and a resonant tuning circuit. The antenna tuning node is coupled to a resonant conduction element of an antenna. The antenna tuning switch and the resonant tuning circuit are coupled in series between the antenna tuning switch and the antenna tuning node, such that the resonant tuning circuit is between the antenna tuning node and the antenna tuning switch. The resonant tuning circuit is configured to resonate at one or more harmonic frequencies generated by the antenna tuning switch such that a high impedance path is formed between the antenna tuning switch and the antenna tuning node at harmonic frequencies generated by the antenna tuning switch. Accordingly, harmonic interference generated by the antenna tuning switch is prevented from reaching the antenna, while simultaneously allowing for tuning of the antenna.

An antenna structure includes an antenna holder, a radiating body, a feed portion, and a grounding portion. The antenna holder includes a plurality of surfaces. The feed portion is positioned on one surface of the antenna holder and electronically connected to a first end of the radiating body. The ground portion is positioned on one surface of the antenna holder and electronically connected to a second end of the radiating body so as to form a loop antenna. An electronic element is surrounded by the loop antenna.

An antenna structure includes an antenna holder, a radiating body, a feed portion, and a grounding portion. The antenna holder includes a plurality of surfaces. The feed portion is positioned on one surface of the antenna holder and electronically connected to a first end of the radiating body. The ground portion is positioned on one surface of the antenna holder and electronically connected to a second end of the radiating body so as to form a loop antenna. An electronic element is surrounded by the loop antenna.

A method for active circuit antenna optimization includes recording a capacitance value at each frequency of a frequency range using one or more tuning capacitors, thereby generating a capacitor value frequency range. The method further includes creating one or more non-linear circuit designs in an RF circuit simulator. The one or more non-linear circuit designs match the capacitance value at each frequency of the frequency range recorded from the one or more tuning capacitors. The method then includes creating one or more non-linear circuits from the non-linear circuit design. Each tuning capacitor has a corresponding non-linear circuit where all the one or more non-linear circuits match the capacitor value frequency range of the one or more tuning capacitors.