Envelope tracking systems for power amplifiers are provided herein. In certain embodiments, an envelope tracker is provided for a power amplifier that amplifies an RF signal. The envelope tracker includes an error amplifier that controls a voltage level of a power amplifier supply voltage of the power amplifier based on amplifying a difference between a reference signal and an envelope signal indicating an envelope of the RF signal. The envelope tracker further includes a multi-level switching circuit that generates an error amplifier supply voltage based on sensing a current of the error amplifier, and uses the error amplifier supply voltage to power the error amplifier.

A concurrent multi-band linearized transmitter (CMLT) has a concurrent d a multi-band predistortion block (CDMPB) and a concurrent multi-band transmitter (CMT) connected to the CDMPB, The CDMPB can have a plurality of digital baseband signal predistorter blocks (DBSPBs), an analyzing and modeling (A&M) stage, and a signal observation feedback loop. Each DBSPB can have a plurality of inputs, each corresponding to a single frequency band of the multi-band input signal, and its output corresponding to a single frequency band; each output connect corresponding to an input of the CMLT. The A&M stage can have a plurality of outputs connected to and updating the parameters of the DBSPBs, and a plurality of inputs connected to either both outputs of the signal observation loop or the output of the subsampling loop and to outputs of the DBSPBs. The A&M stage can perform signals' time alignment, reconstruction of signals and compute parameters of DBSPBs.

Aspects of this disclosure relate to detecting power associated with an individual carrier of a carrier aggregated signal. In an embodiment, an aggregated carrier including at least a first carrier and a second carrier is provided. An indication of power of the first carrier of the aggregated carrier is detected. Separately from detecting the indication of power of the first carrier, an indication of power of the second carrier of the aggregated carrier is detected. The power associated with a radio frequency (RF) signal provided to an RF source associated with the first carrier can be adjusted based on the indication of power of the first carrier.

A radio frequency amplifying device according to an embodiment includes load impedance calculating circuitry and controlling circuitry. The load impedance calculating circuitry is configured to calculate a load impedance on the basis of information about a voltage standing wave rate and a phase on an output side of radio frequency amplifying circuitry. The controlling circuitry is configured to adjust a gain and a phase of a signal to be input to the radio frequency amplifying circuitry, in accordance with the load impedance calculated by the load impedance calculating circuitry.

A compound semiconductor device includes: a semiconductor laminate structure including an electron transit layer and an electron supply layer that are formed from a compound semiconductor; a gate electrode, a source electrode, and a drain electrode that are provided above the electron supply layer; and an insulating layer that is provided between the source electrode and the drain electrode, over the semiconductor laminate structure, and with a gate recess formed therein, wherein the gate electrode includes: a first portion in the gate recess; and a second portion that is coupled to the first portion and is provided over the insulating layer at a position further on the drain electrode side than the gate recess, wherein the insulating layer includes an aluminum oxide film in direct contact with the semiconductor laminate structure.

Apparatus and methods for power detection with enhanced dynamic range are provided. In certain embodiments, a front end system includes a power amplifier that amplifies a radio frequency (RF) input signal to generate an RF output signal, a directional coupler that generates a sensed RF signal based on sensing the RF output signal from the power amplifier, and a power detector that processes the sensed RF signal to generate a detection signal indicating an output power of the power amplifier. Additionally, the power detector includes two or more detection paths providing different amounts of gain to the sensed RF signal from the directional coupler.

Disclosed are an electronic impedance tuning apparatus for measuring a load-pull of a mobile amplifier and an electronic impedance tuning method therefor. An electronic impedance tuning apparatus according to one embodiment of the present invention comprises: a coupler for transferring, to transmission lines respectively connected to a through port and a coupled port, an input voltage inputted to an input port; a magnitude part for controlling a change in the magnitude of the impedance through a change in length difference of the transmission lines; and a phase part for controlling a change in the phase of the impedance through an equal length change of the transmission lines.

A digital pre-distortion circuit and a digital pre-distortion method are provided. In the method, pre-distortion, digital-to-analog conversion and an amplifying process are performed on an input signal in sequence, to generate an output signal. A first bandwidth of the input signal after the pre-distortion is greater than a second bandwidth of the input signal after the digital-to-analog conversion. Signals outside the second bandwidth are filtered out from the output signal, to generate a second output signal. A third output signal, which is a signal after a pre-distorted signal is amplified, is estimated according to the pre-distorted signal and the second output signal. The pre-distorted signal is a signal after the pre-distortion is performed on the input signal. A third bandwidth of the third output signal is greater than the second bandwidth. Parameters of the pre-distortion can be determined according to the third output signal and the pre-distorted signal.

A balanced-to-Doherty (B2D) mode-reconfigurable power amplifier (PA) has the capability of maintaining high linearity and high efficiency against load mismatch. The reconfigurable PA includes a switch to alternatively connect to a pre-determined resistive load or a pre-determined pure reactive load (jX), i.e., short, open, or finite reactance between an output quadrature coupler and ground. The biasing of Doherty mode is adaptive dependent on the value of reactive loading (jX). The Doherty operation of this PA is based on an architecture configured from a balanced amplifier, e.g., a quasi-balanced amplifier.

Aspects of this disclosure relate to methods of detecting power associated with an individual carrier of a carrier aggregated signal. According to an embodiment, a method can include detecting an indication of power of a first carrier of an aggregated carrier. The method can also include, separately from detecting power of the first carrier, detecting an indication of power of a second carrier of the aggregated carrier. A power associated with a radio frequency source, such as a power amplifier, can be adjusted based on the indication of power of the first carrier.