A dual-output and dual-mode supply modulator, a two-stage power amplifier using the same, and a supply modulation method therefor are provided. In order to improve the performance of a two-stage power amplifier used in a transmitter of a wireless communication system, the dual-output and dual-mode supply modulator according to the present invention may simultaneously supply an envelope tracking signal to a main amplification stage of the two-stage power amplifier and an average power tracking signal to an auxiliary amplification stage thereof. To this end, the dual-output and dual-mode supply modulator according to the present invention outputs two supply voltages and supports two operation modes. As such, it is possible to improve the efficiency of the two-stage power amplifier over a wide output power range with the use of a single supply modulator by employing envelope tracking on the main amplification stage and average power tracking on the auxiliary amplification stage in high output power regions or employing average power tracking both on the main amplification stage and auxiliary amplification stage in low output power regions.

Envelope tracking can be employed to reduce power consumption of a power amplifier, but envelope tracking can introduce nonlinearities to a power amplifier. These nonlinearities can manifest themselves as noise at the output of the power amplifier. Embodiments described herein provide techniques for characterizing a parameter indicative of power amplifier noise when envelope tracking is employed. Measurement of this parameter can permit power amplifier designers to decide whether to forgo envelope tracking if a power amplifier is too susceptible to such noise, redesign the power amplifier to improve compatibility with envelope tracking, or to employ distortion compensation circuitry to reduce the noise output by the power amplifier. Counterintuitively, this distortion compensation circuitry may involve increasing the power, such as the envelope tracking power supply. However, increasing the power may be a desirable trade-off for increased linearity.

Disclosed herein are circuits, devices and methods that address challenges associated with power amplifier systems. A power amplifier system includes two or more fast error amplifiers coupled to corresponding power amplifiers. The fast error amplifiers are configured to generate envelope tracking signals based on a signal envelope, the envelope tracking signals modifying a DC-DC regulated voltage from a DC-DC converter to more efficiently operate the power amplifiers. By splitting the envelope tracking between two or more fast error amplifiers and amplification between corresponding two or more power amplifiers, the power, frequency or bandwidth, linearity, signal-to-noise ratio, efficiency, or the like of the power amplifier system can be improved. Wireless communications configurations with such power amplifier systems can provide uplink carrier aggregation and/or cellular signals based on standards and protocols that require increased bandwidth and/or power.

Methods of calibrating a power amplifier system to compensate for envelope amplitude misalignment are provided. In certain configurations, a method of calibrating a power amplifier system includes amplifying a radio frequency signal from a transceiver using a power amplifier and generating a supply voltage of the power amplifier using an envelope tracker, including generating a scaled envelope signal based on a power control level signal and an envelope signal, and shaping the scaled envelope signal using a shaping table generated at a target gain compression. The method further includes changing a scaling of the scaled envelope signal using a calibration module, monitoring an output of the power amplifier to determine an amount of scaling of the scaled envelope signal at which a detected gain compression of the power amplifier corresponds to the target gain compression of the shaping table, and calibrating the power amplifier system based on the determination.

An RF transmitter arrangement using analog pre-distortion is disclosed. The arrangement includes lower bandwidth circuitry, an analog pre-distorter, and a non-linear amplifier chain. The lower bandwidth circuitry is configured to generate an analog signal. The analog pre-distorter is configured to apply a non-linear distortion to the analog original signal based on a coupled feedback signal in order to generate an RF output signal. The non-linear amplifier chain is configured to amplify the RF output signal to generate a transmission signal relative to the analog original signal. The coupled feedback signal is derived from the transmission signal.

Apparatus and methods for programmable low dropout regulators for radio frequency (RF) electronics are provided herein. In certain configurations, a power amplifier system includes a multi-stage power amplifier that amplifies a radio frequency signal and includes a driver stage and an output stage. The power amplifier system further includes an envelope tracker that controls a supply voltage of the output stage in relation to an envelope of the radio frequency signal, and a programmable low dropout regulator that includes an output that provides a programmable supply voltage to the driver stage. The programmable low dropout regulator includes an output capacitor electrically connected to the output, a regulation transistor having a drain electrically connected to the output, and an alternative discharge circuit that discharges the output capacitor in response to programming the programmable supply voltage from a high voltage level to a low voltage level.

A system for monitoring the peak power of a telecommunication signal to be transmitted for an RF power amplification, includes a digital processing device with a processing chain having an envelope tracking control logic for generating an envelope tracking control signal at discrete levels. The processing chain further includes a driver logic of the DC-DC converter, which processing chain has a device for calculating peak value over a sliding time window and a supply voltage selection device.

A wide modulation bandwidth radio frequency (RF) circuit is provided. In examples discussed herein, the RF front-end circuit includes a tracker circuit configured to generate a modulated voltage at a wide modulation bandwidth. The modulated voltage can be used by an amplifier circuit(s) for amplifying an RF signal(s). Notably, the tracker circuit may have inherent frequency-dependent impedance that can interact with a load current of the amplifier circuit(s) to cause degradation in the modulated voltage, which can further lead to distortions in an RF offset spectrum. In this regard, a notch circuit is provided and configured to operate at an appropriate notch frequency and a notch bandwidth to filter the modulated voltage in the RF offset spectrum. As a result, it may be possible to reduce the distortions caused by the modulated voltage degradation in the RF offset spectrum, thus helping to improve linearity and efficiency of the amplifier circuit(s).

A tracker circuit configured to provide a variable supply voltage to a power amplifier (PA) circuit is disclosed. The tracker circuit includes a state machine circuit comprising a plurality of states mapped in accordance with transitions associated with a mapping scheme. In some embodiments, the plurality of states of the state machine circuit identify one or more operational modes associated with the tracker circuit, wherein at least one operational mode comprises one or more voltage levels respectively associated therewith. In some embodiments, the one or more operational modes includes at least two active operational modes. In some embodiments, a transition between the one or more operational modes of the tracker circuit is controlled by a digital selection signal received from a digital communication interface associated therewith.

A power amplifier apparatus, includes an envelope tracking (ET) current bias circuit configured to generate a first ET bias current by calculating a direct current DC, based on a reference voltage, and an ET current, based on an ET voltage, according to an envelope of an input signal; and a power amplifier circuit having a bipolar junction transistor supplied with the first ET bias current and a power voltage to amplify the input signal, wherein an average current of the first ET bias current is controlled to be substantially constant.