Shared Envelope Tracking for MIMO Power Amplifier DPD
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Solution Overview
Problem
In MIMO systems, using separate envelope tracking modulated power supplies for each power amplifier increases overhead and makes it difficult to determine the required DPD pre-correction due to the lack of a one-to-one correspondence between supply voltage and RF input power, especially when multiple power amplifiers receive different input signals.
Innovation Solution
A single envelope tracking modulator generates a common power supply voltage for multiple power amplifiers, with an envelope selector determining the highest envelope signal at any instant to ensure sufficient voltage for pre-distortion, and a moving average filter smooths transitions, while each DPD block receives information on instantaneous supply voltage to correct for distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If separate envelope tracking modulated power supplies are provided for each power amplifier, then amplification efficiency is improved, but device complexity and overhead increase
Solution Approach 1:
The patent merges multiple separate envelope tracking modulators into a single shared envelope tracking modulator that serves multiple power amplifiers. This is achieved by combining the envelope signals from multiple input channels and using one modulator to generate a common modulated power supply voltage for all power amplifiers, thereby reducing device complexity while maintaining amplification efficiency.
Solution Approach 2:
The shared envelope tracking modulator is designed to serve multiple functions by processing envelope signals from multiple different input channels simultaneously. The modulator can handle different envelope characteristics from multiple MIMO channels and provide appropriate power supply modulation for each power amplifier, making a single device perform the work of multiple dedicated modulators.
2Device complexity
If a common power supply voltage is used for multiple power amplifiers, then overhead is reduced, but it becomes difficult to determine required DPD pre-correction due to lack of one-to-one correspondence between supply voltage and RF input power
Solution Approach 1:
The patent applies pre-distortion (DPD) correction to the RF input signals before they are amplified by the power amplifiers. By pre-distorting the input signals in advance based on the known characteristics of the power amplifiers and the common power supply voltage, the system compensates for the lack of one-to-one correspondence between supply voltage and RF input power, enabling accurate distortion correction despite the shared power supply.
Data Source
AI summary
There is disclosed an amplifier arrangement comprising a plurality of amplifiers each arranged to amplify one of a plurality of different input signals, the arrangement comprising an envelope tracking modulator for generating a common power supply voltage for the power amplifiers, and further comprising an envelope selector adapted to receive a plurality of signals representing the envelopes of the plurality of input signals, and adapted to generate an output envelope signal representing the one of the plurality of envelopes having the highest level at a particular time instant as the input signal for the envelope tracking modulator.