An RF frontend IC device includes an RF transceiver to transmit and receive RF signals and a frequency synthesizer to perform frequency synthetization to operate within a predetermined frequency band. The frequency synthesizer generates an LO signal to the RF transceiver to enable the RF transceiver to transmit and receive RF signals within the predetermined frequency band. The frequency synthesizer includes a QPG circuit to generate signals shifted in phases based on the LO signal and a phase shifting circuit to generate quadrant signals based on the signals shifted in phases. Each of the quadrant signals corresponds to one of the four quadrants in phases in the respective quadrant spaces. The phase shifting circuit includes multiple phase switches operable in a collaboration manner to further shift in phase based on the signal shifted in phases to generate the quadrant signals in proper quadrant spaces.

A radio-frequency circuit includes a first power amplifier that amplifies a first transmission signal and outputs the first transmission signal amplified; and a second power amplifier that amplifies a second transmission signal different in frequency from the first transmission signal, and outputs the second transmission signal amplified. At least one of the first power amplifier or the second power amplifier switches from ET mode to APT mode, when (1) both the first power amplifier and the second power amplifier are outputting amplified transmission signals and (2) output power of at least one of the first power amplifier or the second power amplifier is greater than a first threshold power.

In an embodiment, a class-AB amplifier includes: an output stage that includes a pair of half-bridges configured to be coupled to a load; and a current sensing circuit coupled to a first half-bridge of the pair of half-bridges. The current sensing circuit includes a resistive element and is configured to sense a load current flowing through the load by: mirroring a current flowing through a first transistor of the first half-bridge to generate a mirrored current, flowing the mirrored current through the resistive element, and sensing the load current based on a voltage of the resistive element.

A radio frequency (RF) power transistor circuit includes a power transistor and at least one decoupling circuit. The power transistor has a control electrode coupled to an input terminal for receiving an RF input signal, and a current electrode for providing an RF output signal at an output terminal. A decoupling circuit is coupled between the control electrode and a ground terminal, and/or between the current electrode and the ground terminal. The decoupling circuit includes a resistor coupled in series with components of a resonant circuit having a resonance that is lower than an RF frequency (e.g., lower than 20 megahertz). The resistor is for dampening the resonance of the resonant circuit.

An apparatus for detecting difference in operating characteristics of a main circuit by using a replica circuit is presented. In one exemplary case, a sensed difference in operating characteristics of the two circuits is used to drive a tuning control loop to minimize the sensed difference. In another exemplary case, several replica circuits of the main circuit are used, where each is isolated from one or more operating variables that affect the operating characteristic of the main circuit. Each replica circuit can be used for sensing a different operating characteristic, or, two replica circuits can be combined to sense a same operating characteristic.

An amplifier including a signal input terminal, at least one signal output terminal, a first and a second cascode amplifier circuits, a capacitor and a loading circuit. The signal input terminal receives an input signal. The first cascode amplifier circuit includes a first and a second input terminals and a first and a second output terminals. The first input terminal coupled to the signal input terminal receives the input signal. The second cascode amplifier circuit includes a third and a fourth input terminals and a third output terminal. The third input terminal is coupled to the first output terminal, and the third output terminal is coupled to the second input terminal. Two terminals of the capacitor are coupled to the fourth input terminal and the first output terminal respectively. A terminal of the loading circuit is coupled to the third output terminal, and another terminal of the loading circuit is coupled to the second output terminal. At least one of two terminals of the loading circuit is further coupled to the at least one signal output terminal.

An apparatus comprises a plurality of selectable gain stages connected in parallel between a first bias voltage and ground, wherein each selectable gain stage comprises an amplification portion and a current steering portion, and wherein the current steering portion comprises a first selectable signal path connected between an output of the amplification portion and a signal output terminal, and a second selectable signal path connected between the output of the amplification portion and ground through a shunt device.

Disclosed herein are signal amplifiers that provide impedance adjustments for different gain modes. The impedance adjustments are configured to result in a constant real impedance for an input signal at the amplifier. The amplifiers include a scalable impedance adjustment circuit that adjusts inductance and/or a device width to compensate for changes in the total impedance presented to an input signal. By providing impedance adjustments, the amplifiers reduce losses and improve performance by improving impedance matching over a range of gain modes.

A distortion compensation apparatus executes a process including: Performing distortion compensation that compensates in advance for a nonlinear distortion occurring when a transmission signal is amplified by a power amplifier; determining whether power of the transmission signal is smaller than a predetermined threshold; holding a gain relating to the distortion compensation or a result of the distortion compensation when the power of the transmission signal is determined to be smaller than the predetermined threshold; and outputting to the power amplifier, when the power of the transmission signal is determined to be smaller than the predetermined threshold, the result of the distortion compensation, and outputting to the power amplifier, when the power of the transmission signal is determined to be equal to or greater than the predetermined threshold, a result of distortion compensation performed using the held, gain, or the held result of the distortion compensation.

A high-frequency power amplifier is configured to include plural island patterns (28) in which ends thereof are arranged in the vicinity of a transmission line (23) and other ends thereof are arranged in the vicinity of an end line (24a) in a transmission line (24), a wire (30) for connecting an end of an island pattern (28) and the transmission line (23), and a wire (31) for connecting another end of the island pattern (28) and the end line (24a) of the second transmission line (24), so that a mismatch of the impedance component having a resistance component and a reactance component can be compensated for by changing the number of first connecting members and the number of second connecting members, the first and second connecting members configured to connect an island pattern (28) to the transmission lines (23) and (24).