Multi-PA Digital Predistortion Using Bias Feedback Alignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In RF communication systems, using a single digital predistortion (DPD) circuit for multiple power amplifiers (PAs) is challenging due to differing distortion characteristics among PAs, leading to uneven system performance, as a predistorted signal that results in an acceptably linear output for one PA may not do so for another.
Innovation Solution
Modifying the biasing of PAs to make their distortion characteristics more similar, allowing a single DPD circuit to effectively predistort input signals for multiple PAs, and using a bias feedback circuit to adjust bias currents and voltages individually to align distortion characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single DPD circuit is used for multiple PAs, then device complexity is reduced, but system performance becomes uneven due to differing distortion characteristics
Solution Approach 1:
The patent changes the biasing parameters (bias currents and voltages) of individual PAs to modify their distortion characteristics. By adjusting these electrical parameters, the PAs are transformed to have more similar nonlinear behaviors, enabling a single DPD circuit to effectively linearize multiple PAs with different initial characteristics.
2Adaptability or versatility
If biasing of PAs is modified to align distortion characteristics, then a single DPD circuit can serve multiple PAs, but additional control circuitry is required
Solution Approach 1:
The patent implements feedback circuits that monitor the output of each PA and adjust the biasing parameters accordingly. The feedback mechanism continuously measures performance metrics and modifies bias currents/voltages to maintain optimal distortion characteristics, enabling automatic adaptation without manual intervention.
Solution Approach 2:
The system employs self-adjustment mechanisms where each PA's biasing is automatically tuned based on its own performance characteristics. The bias control circuitry autonomously modifies parameters to align distortion characteristics, reducing the need for external calibration and manual adjustment.
Data Source
AI summary
Various examples are directed to a power amplifier circuit, comprising a digital predistortion circuit, first and second power amplifiers, and a bias feedback circuit. The digital predistortion circuit may be configured to generate a predistorted input signal based at least in part on an input signal. The first power amplifier may be configured to generate a first amplified signal based at least in part on the predistorted input signal. The second power amplifier may be configured to generate a second amplified signal based at least in part on the predistorted input signal. The bias feedback circuit may be configured to adjust at least one of a bias of the first power amplifier or a bias of the second power amplifier to align a first nonlinear behavior of the first power amplifier with a second nonlinear behavior of the second power amplifier.