Multistage Digital Predistortion for RF Power Amplifier Linearity
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Solution Overview
Problem
Existing digital predistortion systems face challenges in achieving high accuracy with increased complexity, leading to higher circuit area and power consumption, while maintaining efficient linearity and reducing adjacent channel leakage ratio (ACLR) in power amplifiers.
Innovation Solution
A multistage, multi-rate digital predistortion system with adaptable compensators and a digital predistortion adaptation engine, utilizing a combination of neural networks and adaptive algorithms to optimize distortion compensation, reducing the number of coefficients and improving system linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single high-accuracy compensator is used to improve linearity correction, then manufacturing precision improves, but device complexity increases
Solution Approach 1:
The patent divides a single complex compensator into multiple simpler compensators connected in series. Each compensator handles a specific portion of the distortion correction, with the first compensator processing the input signal and subsequent compensators processing intermediate signals. This segmentation reduces the complexity of each individual compensator while maintaining overall high accuracy through the cascaded structure.
2Manufacturing precision
If more coefficients are used in the compensator to improve accuracy, then manufacturing precision improves, but use of energy increases
Solution Approach 1:
The patent distributes the computational workload across multiple compensators, each using fewer coefficients than a single comprehensive compensator would require. The first compensator uses a first set of coefficients and the second compensator uses a second set of coefficients, reducing the coefficient burden per device and thereby lowering power consumption while achieving equivalent or better overall accuracy.
Solution Approach 2:
Each compensator in the series performs partial correction of the distortion, with the first compensator addressing certain distortion components and subsequent compensators addressing remaining distortion. This partial action approach allows each stage to use fewer coefficients than would be required for complete correction in a single stage, reducing energy usage.
3Manufacturing precision
If a complex compensator structure is used to reduce ACLR, then manufacturing precision improves, but device complexity increases
Solution Approach 1:
The patent implements ACLR reduction through a series of simpler compensators rather than a single complex structure. Each compensator contributes to ACLR improvement through its specific transformation function, and the cascaded arrangement achieves cumulative ACLR reduction while keeping individual compensator structures simple and manageable.
4Manufacturing precision
If processing is done at full signal rate to maintain accuracy, then manufacturing precision improves, but use of energy increases
Solution Approach 1:
The patent processes signals at full rate only when necessary for maintaining accuracy, while allowing intermediate processing at reduced rates when accuracy requirements are met. The multi-stage structure enables selective full-rate processing at critical stages while using lower-rate processing at other stages, optimizing the trade-off between accuracy and power consumption.
Data Source
AI summary
An adaptable, multistage, multi-rate digital predistortion system that can increase the accuracy of the distortion applied to a power amplifier input signal is disclosed. Further, the digital predistortion system can be implemented using a reduced circuit area by reducing a number of coefficients used by the models applied to generate the distortion compensation signal. Further, the system can implement an improved digital predistortion adaptation engine that improves an adjacent channel leakage ratio of the digital predistortion system. Moreover, the system can compensate for non-linear impairments due to analog/RF circuits and systems and improve at least the following metrics: Error vector magnitude (EVM), adjacent channel leakage ratio (ACLR), spectrum emission mask (SEM), and power consumption of the circuits and systems. An example of circuits and systems is radio frequency power amplifier (RF PA).