Load modulated radio-frequency amplifier with digital predistortion

A method of operating wireless circuitry, comprising:

• receiving a baseband signal from one or more processors;
• upconverting the baseband signal to a radio-frequency signal;
• with a load modulated amplifier circuit, amplifying the radio-frequency signal;
• downconverting a portion of the amplified radio-frequency signal to produce a demodulated signal;
• converting the demodulated signal from an analog domain to a digital domain to produce a measured signal;
• aligning the measured signal and the baseband signal in phase and time;
• with a gain shaping circuit, outputting a control signal based on at least the measured signal to an adjustable load component in the load modulated amplifier circuit;
• keeping the control signal constant when an instantaneous amplitude of the baseband signal is within a first range;
• and
• varying the control signal when the instantaneous amplitude of the baseband signal is within a second range non-overlapping with the first range.

An electronic device comprising:

• one or more processors configured to generate a baseband signal;
• a predistortion circuit configured to selectively predistort the baseband signal to output either the baseband signal or a predistorted signal;
• a modulator configured to convert the baseband signal or the predistorted signal to a radio-frequency signal;
• a load-line modulated amplifier circuit configured to amplify the radio-frequency signal;
• and
• gain shaping circuitry having a first input configured to receive the baseband signal from the one or more processors, a second input configured to receive a portion of the amplified radio-frequency signal via a radio-frequency coupler, a third input configured to receive the baseband signal or the predistorted signal from the predistortion circuit, and an output coupled to an adjustable impedance in the load-line modulated amplifier circuit.