Multilevel RF Power Amplifier Linearization During Bias Switching
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Solution Overview
Problem
Achieving high efficiency and high linearity in radio frequency (RF) power amplifier systems is a longstanding challenge, as existing systems often face inefficiencies and nonlinearity due to discrete drain bias voltage transitions and the introduction of unwanted components during state changes.
Innovation Solution
Implementing a power amplifier system that dynamically switches among discrete levels for certain conditions and uses continuous envelope tracking for others, combined with digital predistortion (DPD) and pulse cancellation techniques to maintain high linearity and efficiency, particularly through State-Based (or Supply-Based) Digital Pre-Distortion (SB-DPD) and pulse cancellation methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If discrete drain bias voltage switching is used to improve efficiency, then power efficiency is improved, but linearity deteriorates due to unwanted components introduced during state transitions
Solution Approach 1:
The patent applies preliminary action by predistorting the input signal before it reaches the power amplifier. The predistortion is calculated in advance based on the known characteristics of the amplifier and the intended drain bias transitions. This pre-compensation ensures that when the amplifier switches states, the unwanted components are already counteracted, maintaining linearity while allowing efficient discrete voltage switching.
Solution Approach 2:
The patent implements feedback by monitoring the actual output signal and comparing it with the desired output. Based on this comparison, the system adjusts the predistortion parameters to compensate for variations in amplifier behavior during drain bias transitions. This closed-loop approach ensures continuous linearity maintenance while preserving the efficiency benefits of discrete voltage switching.
2Object-generated harmful factors
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 into discrete voltage levels. Instead of continuously adjusting the drain bias voltage, the system switches between a finite set of discrete voltage levels. This segmentation maintains linearity through careful predistortion while improving efficiency by allowing the amplifier to operate at fixed, optimized power levels rather than continuously varying power consumption.
Solution Approach 2:
The patent employs periodic action by using pulsed or periodic predistortion correction signals that are applied in synchronization with the discrete drain bias transitions. Rather than continuous correction, the system applies corrective actions at specific intervals corresponding to state transitions, reducing the energy required for linearity maintenance while preserving output quality.
3Use of energy by moving object
If discrete supply voltage levels are used to improve efficiency, then power efficiency is improved, but output smoothness deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-calculating and applying predistortion corrections that specifically account for the discontinuities introduced by discrete voltage switching. The predistortion signal is designed in advance to smooth out the transitions between discrete supply voltage levels, ensuring that the output remains smooth and continuous despite the discrete nature of the input voltage changes.
Solution Approach 2:
The patent introduces an intermediary predistortion processing stage that mediates between the discrete supply voltage levels and the final output. This intermediary stage transforms the discontinuous input signals into a continuous, smooth output by applying appropriate correction factors and transition management, allowing the system to benefit from discrete voltage efficiency while maintaining output smoothness.
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.