Aspects of this disclosure relate to a power amplifier system with symbol-based envelope tracking and fault protection. The system can include a power amplifier and a voltage modulator. The voltage modulator can include switches configured to provide the bias voltage and to provide electric circuit breaker protection. The voltage modulator can include a fault detection circuit that can cause a switch of the switches to provide electric circuit breaker protection in response to detecting a circuit fault. Related methods and voltage modulators are disclosed.

Aspects of this disclosure relate to voltage modulators with staged activation of switches. A voltage modulator can receive supply voltages and provide a selected one of the supply voltages as an output voltage. The voltage modulator can include switches in parallel where one of the switches in parallel activates before another switch in parallel in association by transitioning the output voltage between different supply voltages. Embodiments of this disclosure relate to symbol-based envelope tracking. Related systems and methods are disclosed.

An envelope tracking method and device are provided. The envelope tracking method includes: acquiring, by a boost circuit, a target envelope tracking input current signal, and transmitting, by the boost circuit, the target envelope tracking input current signal to an amplifier circuit, where the amplifier circuit includes an operational amplifier and a feedback network, and the operational amplifier operates in a mode of floating ground; and performing, by the amplifier circuit, closed-loop conversion and amplification on the target envelope tracking input current signal and outputting, by the amplifier circuit, an envelope tracking output voltage.

A power amplification system includes: a first power amplifier configured to amplify a first radio-frequency signal; a second power amplifier configured to amplify a second radio-frequency signal; a switched-capacitor circuit configured to generate multiple discrete voltages based on a regulated voltage supplied from a pre-regulator; an output switch circuit configured to selectively output at least one of the multiple discrete voltages as a first power supply of the first power amplifier; and a digital predistortion circuit configured to predistort the first and second radio-frequency signals. The pre-regulator circuit is configured to convert an input voltage to the regulated voltage. The regulated voltage is provided as a second power supply of the second power amplifier without using the switched-capacitor circuit. The digital predistortion circuit predistorts the first radio-frequency signal by using a first mathematical-expression model for digital predistortion. The first mathematical-expression model is not applied on the second radio-frequency signal.

A power amplification system includes: a first power amplifier; an output switch circuit configured to output a power supply to the first power amplifier; a filter circuit that is to connect to a first path in a switchable manner, the first path providing the power supply from the output switch circuit to the first power amplifier; and a digital predistortion circuit configured to generate distortions in a first input signal of the first power amplifier. When the filter circuit is not connected to the first path, the digital predistortion circuit generates the distortions by using a first mathematical-expression model with the first parameter set. When the filter circuit is connected to the first path, the digital predistortion circuit generates the distortions by using a second mathematical-expression model with the second parameter set. The first and second parameter sets are at least partially different from each other.

A Doherty power amplifier and a method therefor are disclosed. According to one aspect, a Doherty power amplifier includes an input having a first signal path and a second signal path. The first signal path receives a first input signal at a first frequency (f1), splits the first input signal into a first main path signal and a first peak path signal according to a first splitter ratio determined in response to a first envelope of the first input signal. The second signal path receives a second input signal at a second frequency (f2), and splits the second input signal into a second main path signal and a second peak path signal according to a second splitter ratio determined in response to a second envelope of the second input signal.

Systems and methods for pulse shaping voltage transitions in envelope tracking systems are provided. In one aspect, a radio frequency module includes a power amplifier configured to receive a radio frequency input signal and a voltage source. The power amplifier further configured to amplify a radio frequency input signal using the voltage source to generate an output radio frequency signal. The radio frequency module further includes a multi-level switch modulator configured to receive an envelope signal indicative of an envelope of the radio frequency input signal and generate the voltage source based on the envelope signal at one of a plurality of discrete voltage levels. The multi-level switch modulator is further configured to generate the voltage source using an analog component during transitions between discrete voltage levels and a digital component following the transitions.

Apparatus and methods for power amplifier distortion networks are disclosed. In one aspect, there is provided a power amplifier system including a power amplifier configured to amplify a radio frequency input signal. The power amplifier including an input configured to receive the radio frequency input signal and an output configured to generate an amplified radio frequency signal. The power amplifier system further includes a distortion network electrically coupled to either the input or the output of the power amplifier. The distortion network including a plurality of channelized resistors. The channelized resistors connected in series to either an input or an output of the power amplifier.

Intra-symbol voltage change acceleration in a wireless transmission circuit is disclosed. The wireless transmission circuit includes a power amplifier circuit that amplifies a radio frequency (RF) signal based on an average power tracking (APT) voltage supplied by a power management integrated circuit (PMIC). The RF signal is modulated in multiple modulation symbols, such as orthogonal frequency division multiplex (OFDM) symbols. To prevent distortion (e.g., amplitude clipping) in the RF signal, the PMIC is configured to increase the APT voltage during each of the modulation symbols whenever the RF signal exceeds a predefined power threshold. Further, the PMIC is configured according to various acceleration embodiments to complete each APT volage change within a defined temporal limit (e.g., <1 s). By supporting intra-symbol voltage change acceleration, the wireless transmission circuit can enable fast APT voltage adaptation to thereby improve operating efficiency of the power amplifier circuit.

Low power radio frequency (RF) receivers and related circuits are described.