Apparatus and methods for calibrating envelope trackers

摘要

Apparatus and methods for envelope tracking calibration are provided. In one embodiment, a power amplifier system includes a power amplifier, an envelope tracker that generates the power amplifier's supply voltage, a power detector, and a calibration module. The envelope tracker includes an envelope shaping table generated at a desired gain compression and a scaling module that scales an amplitude of an envelope signal. The power detector measures the power amplifier's output power, and the calibration module provides calibration data to the scaling module to change the scaling of the envelope signal's amplitude. The calibration module sets the calibration data to a first value corresponding to a supply voltage level associated with substantially no gain compression, and reduces the supply voltage level by changing the calibration data until the power detector indicates that the gain compression of the power amplifier is about equal to the desired gain compression.

主权项

1. A power amplifier system comprising:
a variable gain amplifier (VGA) configured to amplify a radio frequency (RF) input signal to generate an amplified RF input signal, the VGA having a variable gain; a power amplifier configured to amplify the amplified RF input signal to generate an RF output signal, the power amplifier configured to receive power from a supply voltage; an envelope tracker configured to generate the supply voltage, the envelope tracker including a scaling module configured to generate a scaled envelope signal based on a power control level (PCL) signal and an envelope signal that changes in relation to an envelope of the RF input signal, the envelope tracker further including an envelope shaping table including shaping data relating a plurality of scaled envelope signal amplitudes to a plurality of supply voltage levels, the envelope tracker configured to control the voltage level of the supply voltage based on the scaled envelope signal and the envelope shaping table; and a calibration module including calibration data, the calibration module configured to control the variable gain of the VGA with the calibration data to compensate for an envelope amplitude misalignment of the envelope tracker.