A tracker circuit is provided that includes a converter circuit configured to convert a battery voltage into a first regulated voltage, and a supply modulator that receives the battery voltage and the first regulated voltage. The supply modulator outputs a modulated voltage to a power amplifier by selectively outputting at least one of a plurality of discrete voltages that includes the battery voltage and the first regulated voltage.

A transmitter and Doherty power amplifier configured for envelope-controlled biasing of an auxiliary transmitter of the Doherty power amplifier are disclosed. According to one aspect, a transmitter having a main amplifier in a main signal path and an auxiliary amplifier in an auxiliary signal path is provided. The auxiliary amplifier is configured to be activated only when an envelope of an input signal of the transmitter exceeds a power threshold. The transmitter also includes at least one component in the auxiliary signal path configured to be deactivated when the auxiliary amplifier is deactivated, the at least one component including at least one of a pre-power amplifier, a mixer and a local oscillator buffer.

A tracker circuit includes a buck boost converter circuit configured to convert an input voltage V.sub.IN to a variable voltage V.sub.1, a buck converter circuit configured to convert the input voltage V.sub.IN to a variable voltage V.sub.2 that is lower than the input voltage V.sub.IN, and a supply modulator configured to selectively supply at least one discrete voltage of a plurality of discrete voltages including the variable voltages V.sub.1 and V.sub.2 to a power amplifier.

A power amplifying circuit includes a splitter connected to an input terminal, a combiner connected to an output terminal, a carrier amplifier group, a peaking amplifier group, a phase shifter, and a bias control circuit. The splitter splits an input signal from the input terminal for two paths. The carrier amplifier group is connected to one of the two paths of the splitter. The phase shifter is connected between the carrier amplifier group and the combiner. The peaking amplifier group is connected between another of the two paths of the splitter and the combiner. The bias control circuit supplies bias signals to each amplifier group. At least one of the amplifier groups includes a plurality of amplifiers. The control circuit changes a quantity of amplifiers to use in each amplifier group by adjusting a level of the bias signal being supplied to each amplifier.

An equalizer circuit in an envelope tracking (ET) integrated circuit (ETIC) is disclosed. The ETIC (26) is configured to generate an ET voltage based on a target voltage (VTGT) for amplifying a radio frequency (RF) signal(s). Since the ETIC has inherent impedance and group delay that can cause distortion in the ET voltage, an equalizer circuit (24) is provided in the ETIC to equalize the target voltage prior to generating the ET voltage. Specifically, the equalizer circuit generates an equalized target voltage to offset the inherent impedance and a modified target voltage to mitigate the group delay. Accordingly, the equalizer circuit can output a processed target voltage, which can include the equalized target voltage and/or the modified target voltage, for generating the ET voltage. As a result, it is possible to reduce distortion resulted from the inherent impedance and group delay, especially when the RF signal(s) is modulated in a wide modulation bandwidth.

Methods and systems for non-uniform discrete envelope tracking. A method includes receiving one or more baseband signals and setting a plurality of initial non-uniform voltage levels. Each of the voltage levels in the plurality of non-uniform voltage levels is non-uniformly spaced from other voltage levels in the plurality of non-uniform voltage levels. The method further includes applying the plurality of initial non-uniform voltage levels to a power amplifier and changing one or more voltage values of the plurality of initial non-uniform voltage levels to generate a plurality of updated non-uniform voltage levels based on the one or more baseband signals.

A tracker circuit is provided that includes a pre-regulator circuit, a switched-capacitor circuit, a supply modulator, and a selector switch circuit. The pre-regulator circuit is configured to convert an input voltage into a regulated voltage. The switched-capacitor circuit includes a plurality of input terminals that receive the input voltage and the regulated voltage. The switched-capacitor circuit generates a plurality of discrete voltages. The supply modulator selectively outputs at least one of the plurality of discrete voltages to a power amplifier. The selector switch circuit selects one of the plurality of input terminals and outputs the input voltage to the selected input terminal. The selector switch circuit also selects an other input terminal and outputs the regulated voltage to the other input terminal.

An amplifier circuit is provided that includes a power amplifier circuit configured to amplify a radio frequency signal by using a power supply voltage V.sub.ET, which can be a discrete voltage, and a variable phase-shift circuit connected to the power amplifier circuit. The variable phase-shift circuit is configured to change the phase-shift amount of a radio frequency signal based on the power supply voltage V.sub.ET.

A tracker system is provided that includes a first integrated circuit disposed in or on a module laminate and a second integrated circuit disposed to be separate from the module laminate. The first integrated circuit includes switches of a switched-capacitor circuit and switches of first and second supply modulators. The second integrated circuit includes switches of a third supply modulator. The switched-capacitor circuit generates multiple discrete voltages. The first supply modulator outputs at least one of the discrete voltages to a first power amplifier. The second supply modulator outputs at least one of the discrete voltages to a second power amplifier. The third supply modulator outputs at least one of the discrete voltages to a third power amplifier. The first and second power amplifiers are connected to a primary antenna. The third power amplifier is connected to a secondary antenna.

A power amplifier comprises a first amplification stage having an input terminal receiving a radio frequency (RF) signal to be amplified and having a first coupling unit, a second amplification stage outputting an amplified radio frequency signal and having a second coupling unit and a third coupling unit providing RF feedback to the input terminal of the first amplification stage through an RF feedback path, the second coupling unit being coupled to the first coupling unit, and the third coupling unit being coupled to the first coupling unit.