APPARATUS AND METHODS FOR ENVELOPE SHAPING IN POWER AMPLIFIER SYSTEMS

摘要

Apparatus and methods for envelope shaping in power amplifier systems are provided. In certain implementations, a power amplifier system includes a modulator for generating a RF signal, a power amplifier for amplifying the RF signal, a gain control circuit for controlling the gain of the power amplifier, and an envelope tracking system for controlling a voltage level of the power amplifier's supply voltage based on an envelope signal corresponding to the RF signal's envelope. The gain control circuit includes a gain adjustment table, and the envelope tracking system includes an envelope shaping circuit including an isodistortion table. The isodistortion table can be used to map the envelope signal to a shaped envelope signal so as to maintain a substantially constant distortion in the system's transmit and/or receive bands across the envelope signal's range.

主权项

1. A power amplifier system comprising:
a modulator configured to generate a radio frequency (RF) signal; a power amplifier configured to amplify the RF signal to generate an amplified RF signal, the power amplifier configured to receive a power amplifier supply voltage for powering the power amplifier; an envelope tracker configured to generate the power amplifier supply voltage, the envelope tracker configured to control a voltage level of the power amplifier supply voltage based on a shaped envelope signal; an envelope shaping circuit configured to generate the shaped envelope signal by shaping an envelope signal corresponding to an envelope of the RF signal, the envelope shaping circuit including a shaping table configured to maintain a substantially constant distortion in at least one of a transmit band or a receive band across voltage changes in the envelope signal, the shaping table calibrated at a first power level; and a gain control circuit including a gain adjustment table configured to boost the gain of the power amplifier for one or more output power levels greater than the first power level, the gain control circuit configured to enhance a combined power efficiency of the modulator and the power amplifier.