Envelope trackers providing compensation for power amplifier output load variation

A method of envelope tracking in a mobile device, the method comprising:

• amplifying a radio frequency signal using a power amplifier to generate an amplified radio frequency signal for an antenna;
• generating a plurality of detection signals using a plurality of detectors coupled to the power amplifier;
• controlling a supply voltage of the power amplifier based on an envelope of the radio frequency signal using an envelope tracker;
• and
• compensating the power amplifier for output load variation using the envelope tracker, including processing the plurality of detection signals to generate a load variation detection signal indicating a change in an output load of the power amplifier arising from a change in a voltage standing wave ratio of the antenna, and adjusting a gain of the power amplifier based on the load variation detection signal.

A mobile device comprising:

• a front end system including a power amplifier configured to amplify a radio frequency signal to generate an amplified radio frequency signal, and a plurality of detectors coupled to the power amplifier and configured to generate a plurality of detection signals;
• an antenna configured to transmit the amplified radio frequency signal;
• and
• a power management system including an envelope tracker configured to control a supply voltage of the power amplifier based on an envelope of the radio frequency signal, and to process the plurality of detection signals to generate a load variation detection signal indicating a change in an output load of the power amplifier arising from a change in a voltage standing wave ratio of the antenna, the envelope tracker further configured to adjust a gain of the power amplifier based on the load variation detection signal.