Multilevel RF Power Amplifier Linearization With State-Based DPD
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Solution Overview
Problem
Achieving high efficiency and high linearity in radio frequency (RF) power amplifier systems is challenging due to the difficulty in managing discrete transitions among operating states and the introduction of unwanted components during state changes, which affect the output spectrum.
Innovation Solution
Implementing a state-based digital predistortion (SB-DPD) system that dynamically selects drain bias voltages from multiple sources and uses pulse cancellation techniques to compensate for disturbances caused by state changes, ensuring smooth output and maintaining high linearity across different operating states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If discrete transitions among operating states are used to improve efficiency, then power efficiency is improved, but linearity deteriorates due to unwanted components introduced during state changes
Solution Approach 1:
The patent applies preliminary action by predistorting the input signal before the power amplifier processes it. The predistortion is calculated in advance based on the desired output and the known characteristics of the power amplifier, including the effects of discrete state transitions. This pre-compensation ensures that when the amplifier switches between states, the unwanted components are already counteracted, maintaining linearity while allowing efficient discrete transitions.
Solution Approach 2:
The patent implements feedback by measuring the actual output of the power amplifier and using this information to adjust the predistortion parameters. The system continuously monitors the output signal quality and adapts the predistortion calculation to compensate for variations in amplifier characteristics and state transition effects, thereby maintaining high linearity throughout operation.
2Use of energy by moving object
If state changes are implemented to improve efficiency, then power efficiency is improved, but output spectrum quality deteriorates due to introduced unwanted components
Solution Approach 1:
The predistortion calculation is performed in advance to account for the unwanted components that will be generated during state transitions. By pre-compensating for these harmful effects in the input signal, the system eliminates the need for complex real-time correction of spectral artifacts, maintaining clean output spectrum while benefiting from efficient state-based operation.
Solution Approach 2:
The patent converts the harmful effect of state transitions into a beneficial feature by using the known transition characteristics to inform the predistortion calculation. The unwanted components generated during state changes are actually predictable and可利用 for optimization - the system uses these transition effects as part of the overall distortion model, turning what would be harmful artifacts into manageable parameters that can be pre-compensated for, thereby improving both efficiency and spectral purity.
3Manufacturing precision
If continuous envelope tracking is used to maintain linearity, then linearity is improved, but power efficiency deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the continuous envelope tracking function into discrete state transitions. Instead of continuously adjusting the amplifier operating point, the system segments the output power range into multiple discrete levels, each corresponding to a specific amplifier state. This segmentation allows the system to achieve acceptable linearity through predistortion while maintaining high efficiency by operating in discrete, optimized states rather than continuous variable operation.
Solution Approach 2:
The patent implements dynamics by making the predistortion parameters adaptive to the current operating state. The system dynamically adjusts the predistortion calculation based on which discrete state the amplifier is currently in, allowing optimal linearity compensation for each state's specific characteristics. This dynamic adaptation enables the system to maintain high linearity across all discrete states without requiring continuous envelope tracking, thereby preserving efficiency.
Data Source
AI summary
Circuits and methods for achieving high linearity, high efficiency power amplifiers, including digital predistortion (DPD) and pulse cancellation in switched-state RF power amplifier systems are described.