Independent Pre-Distortion for Asymmetric Doherty Amplifiers
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Solution Overview
Problem
Conventional multiple path power amplifiers, such as Doherty amplifiers, face challenges in pre-distorting input signals to achieve optimal efficiency and linearity, especially when using asymmetric configurations, which limits their performance and flexibility in meeting demanding wireless specifications.
Innovation Solution
The method involves splitting the input signal into sub-signals for each branch of the Doherty amplifier and independently pre-distorting them using digital signal processing and feedback mechanisms, allowing for distinct pre-distortion characteristics and coefficients to be calculated for each branch, thereby optimizing performance and reducing the need for symmetry between amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional pre-distortion techniques are applied to multiple path power amplifiers, then the amplifier can operate with improved linearity, but the complexity of the pre-distortion system increases significantly
Solution Approach 1:
The pre-distortion system is segmented into multiple independent pre-distortion units, each associated with a specific path in the multiple path power amplifier. Each unit processes signals for its associated path independently, simplifying the overall system architecture while maintaining linearity across all paths.
Solution Approach 2:
Each pre-distortion unit is configured with specific pre-distortion characteristics tailored to its associated path's performance characteristics. This allows optimization of linearity for each path individually rather than requiring a complex unified pre-distortion system.
2Loss of energy
If asymmetric Doherty amplifier configurations are used to enhance efficiency, then power efficiency improves, but the pre-distortion challenge increases
Solution Approach 1:
The asymmetric Doherty amplifier's main and peaking paths are equipped with separate pre-distortion units, allowing each path to be pre-distorted according to its specific efficiency characteristics without requiring complex cross-path coordination.
Solution Approach 2:
Each pre-distortion unit can independently adjust pre-distortion parameters to match the operating conditions and efficiency characteristics of its associated amplifier path, enabling the asymmetric configuration to maintain both efficiency and linearity.
3Device complexity
If a single pre-distortion unit is used for multiple path amplifiers, then device complexity is reduced, but the ability to meet demanding wireless specifications deteriorates
Solution Approach 1:
The system uses multiple independent pre-distortion units instead of a single unit, with each unit dedicated to a specific path. This segmentation enables each unit to optimize linearity for its path independently, ensuring compliance with demanding wireless specifications while keeping each individual unit relatively simple.
Data Source
AI summary
A method of optimizing performance of a multiple path amplifier includes: splitting an input signal to derive a respective sub-signal for each branch of the multiple path amplifier; independently pre-distorting each sub-signal using a known performance characteristic of its associated branch of the multiple path amplifier; and supplying each pre-distorted sub-signal to its associated branch of the multiple amplifier.