Abstract: Envelope tracking systems for power amplifiers are provided herein. In certain embodiments, an envelope tracker supplies power to a power amplifier that amplifies an RF signal. The envelope tracker includes a multi-level switching circuit that generates an output current based on an envelope signal indicating an envelope of the RF signal. The envelope tracker further includes a combiner that combines a DC voltage with the output current of the multi-level switching circuit to generate a power amplifier supply voltage for the power amplifier. Accordingly, the output current of the multi-level switching circuit and a DC voltage are combined to generate the power amplifier supply voltage. Implementing the envelope tracking system in this manner can provide enhanced efficiency and/or higher bandwidth relative to an envelope tracking system in which a multi-level switching circuit directly outputs a power amplifier supply voltage.

Abstract: Multi-level envelope trackers with an analog interface are provided herein. In certain embodiments, an envelope tracking system for generating a power amplifier supply voltage for a power amplifier is provided. The envelope tracking system includes a multi-level supply (MLS) DC-to-DC converter that outputs multiple regulated voltages, and an MLS modulator that controls selection of the regulated voltages over time based on an analog envelope signal corresponding to an envelope of the RF signal amplified by the power amplifier.

Abstract: Apparatus and methods for sounding reference signal (SRS) switching are provided. In certain embodiments, a controller internal to the power amplifier module initiates a sequence of instructions, in response to a single command from UE. The instructions cause a reduction in RF signal amplitude at the power amplifier output and then cause the antenna switch to actuate. Thus ensuring a single command transition and preventing over-power on the power amplifier and antenna switch. The teachings herein can be used to facilitate reduction in gap times between transitions on different antennas and avoid the use of a blank symbol before and after each SRS symbol.

Abstract: 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.

Abstract: Apparatus and methods for power amplifier trimming based on coefficients for digital pre-distortion (DPD) are disclosed. In certain embodiments, a mobile device includes a transmit circuit that generates a plurality of digital transmit signals. The transmit circuit includes a plurality of DPD circuits each operable to provide DPD to a corresponding one of the digital transmit signals, a coefficient comparator circuit that generates a trimming control signal based on a plurality of coefficients of the plurality of DPD circuits, and a plurality of digital to radio frequency (RF) converters that convert the digital transmit signals into a plurality of RF signals. The mobile device further includes a front end system including a plurality of power amplifiers each amplifying a respective one of the RF signals, and a power amplifier trimming circuit that controls trimming of the power amplifiers based on the trimming control signal.

Abstract: 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.

Abstract: Combiners for Doherty power amplifier systems are provided herein. In certain embodiments, a combiner structure includes a first balun combiner for combining an output of a first auxiliary amplifier and a second auxiliary amplifier, and a second balun combiner for combining the output of a main amplifier and an output of the first balun combiner. Each combiner can include a balun having a first conductor connected between a first input port and an output port, a second conductor connected between an isolated node and a second input port and magnetically coupled to the first conductor. An isolation capacitor is connected between the first input port and the isolated node, and an output capacitor is connected between the second input port and the output port. In certain implementations, the balun combiner further includes a termination capacitor between the isolated node and ground.

Abstract: Integrated Doherty power amplifiers are provided herein. In certain implementations, a Doherty power amplifier includes a carrier amplification stage that generates a carrier signal, a peaking amplification stage that generates a peaking signal, and an antenna structure that combines the carrier signal and the peaking signal. The antenna structure radiates a transmit wave in which the carrier signal and the peaking signal are combined with a phase shift.

Abstract: A power amplification system is provided herein. In certain embodiments, the power amplification system comprises: a power amplifier configured to amplify an input radio frequency (RF) signal to generate an output RF signal when powered by a supply voltage and biased by a biasing signal; an envelope tracker configured to generate an envelope signal that changes in relation to an envelope of the input RF signal; a mode controller configured to set an envelope tracking (ET) mode of the power amplification system based on a modulation bandwidth of the input RF signal; a supply voltage controller configured to control the supply voltage based on the envelope signal when the ET mode is set to a first mode; and a bias controller configured to control the biasing signal based on the envelope signal when the operation mode is set to a second mode.

Abstract: Envelope tracking systems for power amplifiers are provided herein. In certain embodiments, an envelope tracker is provided for a power amplifier that amplifies a radio frequency (RF) signal. The envelope tracker controls a power amplifier supply voltage of the power amplifier based on an envelope signal indicating an envelope of the RF signal. The envelope tracker includes a first controllable resistance between a first regulated voltage and the power amplifier supply voltage and a second controllable resistance between a second regulated voltage and the power amplifier supply voltage. The first regulated voltage and the second regulated voltage are of different voltage levels.

Abstract: Envelope tracking systems with modeling for power amplifier supply voltage filtering are provided herein. In certain embodiments, an envelope tracking system includes a supply voltage filter, a power amplifier that receives a power amplifier supply voltage through the supply voltage filter, and an envelope tracker that generates the power amplifier supply voltage. The power amplifier provides amplification to a radio frequency (RF) signal that is generated based on digital signal data, and the envelope tracker generates the power amplifier supply voltage based on an envelope signal corresponding to an envelope of the RF signal. The envelope tracking system further includes digital modeling circuitry that models the supply voltage filter and operates to digitally compensate the digital signal data for effects of the supply voltage filter, such as distortion.

Abstract: Multi-level envelope tracking systems are provided. In certain embodiments, an envelope tracking system includes a first power amplifier that amplifies a first radio frequency (RF) signal and receives power from a first power amplifier supply voltage, a second power amplifier that amplifies a second RF signal and receives power from a second power amplifier supply voltage, and an envelope tracker including a first modulator that controls the first power amplifier supply voltage based on a plurality of regulated voltages and a first envelope signal corresponding to an envelope of the first RF signal, a second modulator that controls the second power amplifier supply voltage based on the regulated voltages and a second envelope signal corresponding to an envelope of the second RF signal, and a switching point adaptation circuit that controls a voltage level of at least one of the regulated voltages based on a radio frequency power level.

Abstract: Envelope tracking systems for power amplifiers are provided herein. In certain embodiments, an envelope tracker supplies power to a power amplifier that amplifies an RF signal. The envelope tracker includes a multi-level switching circuit that generates an output current based on an envelope signal indicating an envelope of the RF signal. The envelope tracker further includes a combiner that combines a DC voltage with the output current of the multi-level switching circuit to generate a power amplifier supply voltage for the power amplifier. Accordingly, the output current of the multi-level switching circuit and a DC voltage are combined to generate the power amplifier supply voltage. Implementing the envelope tracking system in this manner can provide enhanced efficiency and/or higher bandwidth relative to an envelope tracking system in which a multi-level switching circuit directly outputs a power amplifier supply voltage.

Abstract: Integrated Doherty power amplifiers are provided herein. In certain implementations, a Doherty power amplifier includes a carrier amplification stage that generates a carrier signal, a peaking amplification stage that generates a peaking signal, and an antenna structure that combines the carrier signal and the peaking signal. The antenna structure radiates a transmit wave in which the carrier signal and the peaking signal are combined with a phase shift.

Abstract: Apparatus and methods for retraining digital pre-distortion are disclosed. In certain embodiments, a mobile device includes a transmit chain and a front end system. The transmit chain generates a transmit signal and converts the transmit signal to a radio frequency input signal, and includes a digital pre-distortion circuit that provides digital pre-distortion to the transmit signal. The front end system includes a power amplifier that amplifies the radio frequency input signal to generate a radio frequency output signal, and a power detector that generates a detection signal based on detecting an output power of the power amplifier. The detection signal controls initiation of a retraining sequence of the digital pre-distortion circuit.

Abstract: 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 a multi-level switching circuit having an output that provides an output current that changes in relation to an envelope signal indicating an envelope of the RF signal when the envelope tracker is operating in an envelope tracking mode. The multi-level switching circuit includes a multi-level supply (MLS) modulator that receives multiple regulated voltages of different voltage levels, and an MLS control circuit that controls the selection of the MLS modulator over time based on the envelope signal. When transitioning the MLS modulator from selection of one regulated voltage level to another regulated voltage level, the MLS control circuit provides a soft transition to gradually switch the regulated voltage levels.

Abstract: Multi-level envelope trackers with an analog interface are provided herein. In certain embodiments, an envelope tracking system for generating a power amplifier supply voltage for a power amplifier is provided. The envelope tracking system includes a multi-level supply (MLS) DC-to-DC converter that outputs multiple regulated voltages, and an MLS modulator that controls selection of the regulated voltages over time based on an analog envelope signal corresponding to an envelope of the RF signal amplified by the power amplifier.

Abstract: Multi-level envelope tracking systems with adjusted voltage steps are provided. In certain embodiments, an envelope tracking system for generating a power amplifier supply voltage for a power amplifier is provided. The envelope tracking system includes a multi-level supply (MLS) DC-to-DC converter that outputs multiple regulated voltages, an MLS modulator that controls selection of the regulated voltages over time based on an envelope signal corresponding to an envelope of a radio frequency (RF) signal amplified by the power amplifier, and a modulator output filter coupled between an output of the MLS modulator and the power amplifier supply voltage. The envelope tracking system further includes a switching point adaptation circuit configured to control the voltage level of the regulated voltages outputted by the MLS DC-to-DC converter based on a power level of the RF signal.

Abstract: Envelope tracking systems for power amplifiers are provided herein. In certain embodiments, an envelope tracker system includes a first power amplifier that amplifies a first radio frequency (RF) signal and receives power from a first supply voltage, a second power amplifier that amplifies a second RF signal and receives power from a second supply voltage, and an envelope tracker including a first modulator that generates a first output current based on an envelope of the first RF signal and a plurality of regulated voltages, a second modulator that generates a second output current based on an envelope of the second RF signal and the regulated voltages, a first combiner that combines a first DC voltage with the first output current to generate the first supply voltage, and a second combiner that combines a second DC voltage with the second output current to generate the second supply voltage.

Abstract: In some embodiments, an amplifier system can include an amplifier circuit having first and second amplifiers configured to amplify respective first and second portions of an input signal. Each of the first and second amplifiers can include a cascode stage with input and output transistors arranged in a cascode configuration. The amplifier system can further include an envelope tracking bias circuit coupled to the amplifier circuit and configured to provide a bias signal to the output transistor of the cascode stage of at least one of the first and second amplifiers. The amplifier system can further include a supply circuit configured to provide a non-envelope tracking supply voltage to the output transistor of the cascode stage of the at least one of the first and second amplifiers.