MIMO Envelope Tracking Using Peak Envelope Selection
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Solution Overview
Problem
In MIMO systems, the overhead of providing an envelope tracking modulated power supply for each individual power amplifier increases, and existing solutions fail to efficiently manage different input signals across multiple power amplifiers, leading to inefficiencies and distortion.
Innovation Solution
A common envelope tracking modulator generates a power supply voltage for multiple power amplifiers, with an envelope selector determining the highest instantaneous envelope signal, and a moving average filter smoothing transitions, while pre-distortion stages and feedback receivers adaptively correct for distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If an envelope tracking modulated power supply is provided for each individual power amplifier in a MIMO system, then the DC to RF power conversion efficiency is improved, but the overhead and device complexity increase due to requiring separate envelope tracking modulator stages for each power amplifier
Solution Approach 1:
The patent merges multiple envelope tracking modulator functions into a single shared envelope tracking modulator that serves all power amplifiers in the MIMO system. The modulator receives multiple input signals, extracts their envelopes, and generates a composite envelope signal that represents the maximum instantaneous amplitude across all inputs. This single modulator then produces a common envelope-tracking power supply voltage that is distributed to all power amplifiers, thereby maintaining high efficiency while significantly reducing device complexity and overhead.
2Device complexity
If a common envelope tracking modulator is used for multiple power amplifiers, then the overhead is reduced, but the ability to individually optimize each power amplifier's power supply voltage may be compromised
Solution Approach 1:
The patent applies local quality by ensuring that the common envelope-tracking power supply voltage provided to each power amplifier is sufficient for its specific instantaneous signal requirements. The modulator individually processes each input signal to extract its envelope, then combines them to create a composite envelope that reflects the maximum demand at any given time. This allows each power amplifier to receive an appropriately optimized voltage level tailored to its current signal conditions, even though the modulator itself is shared across all amplifiers.
3Use of energy by moving object
If the power supply voltage tracks the envelope of the input signal closely, then the power conversion efficiency is maximized, but distortion may increase due to rapid voltage transitions
Solution Approach 1:
The patent implements beforehand cushioning by introducing smoothing filtering in the power supply voltage generation path. The envelope tracking modulator generates the power supply voltage based on the composite envelope signal, but passes it through a smoothing filter that removes rapid transitions and high-frequency components. This pre-cushions the voltage supply against abrupt changes that could cause distortion in the power amplifier output, while still maintaining the overall envelope-tracking behavior that ensures high power conversion efficiency.
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.