A system that incorporates teachings of the present disclosure can include, for example, an apparatus having a matching network adapted to reduce a magnitude of a signal reflection at a port of the matching network. The matching network can have one or more controllable variable reactive elements. A controller can be adapted to determine reflection coefficient information from incident and reflected waves sampled at the port of the matching network, and follow at least one cycle of a coarse tune process for generating one or more control signals to tune one or more reactances of the one or more controllable variable reactive elements. Additional embodiments are disclosed.

An impedance detector includes a sensing circuit with an adjustable impedance. The sensing circuit is coupled to a signal path. Further, an evaluation circuit is coupled to the sensing circuit.

A transceiver arrangement comprising a receiver and a transmitter arranged for frequency-division duplex communication with a communication network, a transmission port for connecting to an antenna, a balancing impedance circuit arranged to provide an adaptive impedance arranged to mimic the impedance at the transmission port, a filtering arrangement connecting the receiver, transmitter, transmission port and balancing impedance circuit, and a common-mode signal reduction circuit is disclosed. The filter arrangement comprises filters of a first type arranged to pass signals at transmitter frequency and attenuate signals at receiver frequency and are connected between the transmitter and the transmission port and between the receiver and the balancing impedance circuit, and filters of a second type arranged to attenuate signals at transmitter frequency and pass signals at receiver frequency and are connected between the transmitter and the balancing impedance circuit and between the receiver and the transmission port. The common-mode signal reduction circuit comprises an inverting amplifier, the input of the inverting amplifier is provided by a voltage division between a first and a second impedance where the first and second impedance have equal impedances, and the output of the amplifier is provided to junction of a third and a fourth impedance where the third and fourth impedances have equal impedances, and the first and second impedances, and the third and fourth impedances, respectively, are connected in series between a filter of the first type and a filter of the second type. A communication device and method are also disclosed.

A semiconductor integrated circuit includes a first transmission power mode configured to transmit by a first power, and a second transmission power mode configured to transmit by a second power smaller than the first power, the semiconductor integrated circuit. The semiconductor integrated circuit includes a first transistor configured to receive and amplify a transmission signal in the second transmission power mode, and an attenuator including a resistor element and a switching element, provided between an output of the first transistor and an output terminal, configured to control attenuation of an output signal of the first transistor.

A radio frequency circuit. In the circuit, a first directional coupler receives a second transmit signal, uses a part of the second transmit signal as a third transmit signal, directly sends the third transmit signal to a first port of a circulator, and obtains a first coupling signal from the second transmit signal; the circulator outputs the third transmit signal through a second port; an impedance tuner transmits the third transmit signal to an antenna port and transmits, to the second port of the circulator, a first input signal from the antenna port; the circulator inputs the first input signal to a second directional coupler through a third port; the second directional coupler obtains a second coupling signal from the first input signal; and a controller adjusts impedance of the impedance tuner according to the first coupling signal and the second coupling signal.

A system includes an antenna, and a contactless component for receiving and/or transmitting information via the antenna according to a contactless communications protocol. An inductive-capacitive network is connected between the antenna and the contactless component and includes a configurable filter for filtering electromagnetic interference. A processor modifies an impedance of the configurable filter for filtering electromagnetic interference to control frequency tuning of the antenna.

An antenna apparatus includes two feeding parts, a filter matching network, and a radiator. The filter matching network includes a first port, a second port, and a third port. A first feeding part is electrically connected to the first port, a second feeding part is electrically connected to the second port, and the radiator is electrically connected to the third port. The first feeding part is configured to feed a low frequency signal and an intermediate frequency signal, the second feeding part is configured to feed a high frequency signal, the low frequency signal, the intermediate frequency signal, and the high frequency signal are respectively fed into the filter matching network by using the first feeding part and the second feeding part, and the filter matching network is configured to improve isolation between the low frequency signal and the intermediate frequency signal, and the high frequency signal.

An antenna device according to an embodiment includes an antenna including a power feeding point, a matching circuit having a variable impedance, a loop type probe being installed near the power feeding point and receiving a radio wave radiated from the antenna, a power detector detecting electric power of the radio wave received by the loop type probe, and a control circuit controlling an impedance of the matching circuit on the basis of power information output from the power detector.

A wireless transmission system includes a first coupler including a plurality of substrates including a signal line and a ground; and a second coupler that transmits a signal with the first coupler. A first substrate is connected to a second substrate by conductors having widths substantially equal to or less than widths of signal lines.

Radio frequency devices and methods are provided where a network like a filter network or impedance matching network comprises a series connection of at least two inductors.