A directional coupler includes a main line through which a first signal in a first frequency band and a second signal in a second frequency band pass from a first port to a second port, a sub-line electromagnetically coupled to the main line and having a third port and a fourth port, the third port outputting a first coupled signal corresponding to the first signal and a second coupled signal corresponding to the second signal, a first termination circuit connected to the fourth port and used in outputting the first coupled signal, a second termination circuit connected to the fourth port and used in outputting the second coupled signal, and a first filter circuit disposed between the fourth port and the first termination circuit, wherein the first filter circuit has frequency characteristics allowing the first coupled signal to pass therethrough and attenuating the second coupled signal.

An electronic device includes a power amplifier that sets the power of a transmit signal that is transmitted via an antenna of the device, and further includes a VSWR detector to identify the VSWR at a signal path between the antenna and the power amplifier. As a person (e.g., a user) moves in close proximity to the antenna, the amount of reflected energy along the signal path increases, thereby increasing the VSWR. A power controller of the electronic device sets a gain of the power amplifier based on the VSWR to ensure that the SAR exposure to the person is maintained below a specified threshold.

To provide a high-voltage output amplifier having a wide bandwidth which can efficiently reduce power consumption and allows employment of relatively low withstand voltage Nch MOS FETs without imbalanced voltage distribution between a Nch MOS FET Q101 and a Nch MOS FET Q102 and imbalanced distribution between a Nch MOS FET Q201 and a Nch MOS FET Q202.

A high-voltage amplifier of a positive-side output stage circuit comprises a Nch MOS FET Q101 and a Nch MOS FET Q 102, while a high-voltage amplifier of a negative-side output stage circuit comprises a Nch MOS FET Q201 and a Nch MOS FET Q 202. The source of the Nch MOS FET Q101 is connected to the drain of the Nch MOS FET Q102, the source of the Nch MOS FET Q201 is connected to the drain of the Nch MOS FET Q202. Current controls at the source of the Nch MOS FET Q102 and the source of the Nch MOS FET Q202 are conducted respectively. The current control at the source of the Nch MOS FET Q202 is conducted by a negative-side photo coupler. The gate of the Nch MOS FET Q101 and the gate of the Nch MOS FET Q201 are connected via a condenser C151.

Doherty power amplifier systems with envelope controlled state are provided herein. In certain embodiments, a Doherty power amplifier system includes a main amplifier, a first auxiliary amplifier, and a second auxiliary amplifier that operate in combination with one another to amplify an RF signal. The Doherty power amplifier system further includes a bias circuit that biases the first and second auxiliary amplifiers based on an envelope of the RF signal to control a state of the Doherty power amplifier system. For example, in certain implementations, the first and second auxiliary amplifiers are selectively activated based on a power level indicating by the envelope.

A multistage linear power amplifier receiving an input signal. The multistage linear power amplifier comprises a plurality of Class-AB amplifiers connected in a cascade configuration. The plurality of Class-AB amplifiers amplifies the input signal to generate an amplified input signal. At least one of the plurality of Class-AB amplifiers is biased such that the multistage linear power amplifier emulates a Class-C amplifier.

A hybrid coupler-based T/R switch for use in a TDM system. An output hybrid coupler of a balanced amplifier is used to selectively switch a transmit or receive path to an antenna. During transmission, power at the output of the balanced amplifier is delivered directly to the antenna. During reception, power from the antenna is reflected through ports of the hybrid coupler connected to respective two amplifiers of the balanced amplifier, to constructively combine at a port of the coupler coupled to the receive path, with a ninety degrees phase shift. A pair of shunting switches coupled to the ports of the hybrid coupler connected to the two amplifiers, and a shunting switch coupled to the port coupled to the receive path, control operation of the hybrid coupler-based T/R switch.

A Doherty power amplifier of a wireless communication system is provided. The Doherty power amplifier includes a first stage including a first power amplifier and a second power amplifier. The Doherty power amplifier includes a second stage including a third power amplifier and a fourth power amplifier. The Doherty power amplifier includes a coupler between the first stage and the second stage. The Doherty power amplifier includes a load impedance connected to the second stage. A bias of the first power amplifier is applied differently from a bias of the second power amplifier. A bias of the third power amplifier is applied in the same manner as a bias of the fourth power amplifier.

According to some aspects, a circuit is provided comprising a plurality of Josephson junctions arranged in series in a loop, at least one magnetic element producing magnetic flux through the loop, a plurality of superconducting resonators, each resonator coupled to the loop between a different neighboring pair of Josephson junctions of the plurality of Josephson junctions, a plurality of ports, each port coupled to at least one of the plurality of resonators at ends of the resonators opposite to ends at which the resonators are coupled to the loop, and at least one controller configured to provide input energy to each of the plurality of ports that causes the circuit to function as a circulator between the plurality of ports.

According to various embodiments, a quadrature hybrid coupler included as part of a phase shifter is used to provide variable phase shift to an input signal. The quadrature hybrid coupler includes an input port, an output port, and two terminated ports. The phase shifter includes one or more static lumped elements connected to the QHC to reduce at least one electrical dimension of the QHC to substantially less than a quarter wavelength. The phase shifter also include one or more variable lumped elements connected to the QHC to provide a variable phase shift to the input signal between the input port and the output port of the QHC.

An amplifier circuit for compensating an output signal provided at an output of the amplifier circuit comprises a cascade of sub-amplifiers. Each sub-amplifier of the cascade contributes to a respective part of the output signal. The cascade of sub-amplifiers comprises an end sub-amplifier and at least one preliminary sub-amplifier. At least one error correction block is coupled to apply feedforward error correction to an output of one of the at least one preliminary sub-amplifier.