Shared Digital Predistortion for Multi-Branch AAS Beamforming
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Advanced Antenna Systems (AAS) with multiple active transmitter branches face challenges in digital predistortion due to increased complexity, hardware resource requirements, and the need for separate linearizers for each branch, leading to degraded processing power and efficiency, as well as difficulties in implementing accurate predistortion across varying power amplifier performance and beamforming conditions.
Innovation Solution
A low-complexity digital predistortion (DPD) system that uses a single DPD subsystem for multiple parallel transmitter branches, applying gain and phase adjustments to predistort baseband signals and processing combined receive signals to update an adaptation model, thereby reducing the need for individual couplers and linearizers, and enabling efficient linearization across different non-linear characteristics of power amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate DPD hardware is used for each transmitter branch in AAS, then linearization accuracy is improved, but device complexity and hardware cost increase dramatically
Solution Approach 1:
The patent merges multiple separate DPD hardware units into a single shared DPD subsystem that serves all transmitter branches. The DPD subsystem processes baseband signals and applies predistortion before the signals are distributed to multiple power amplifiers through analog beamforming network, eliminating the need for separate DPD hardware per branch while maintaining linearization performance.
Solution Approach 2:
The DPD subsystem is designed as a universal unit that can linearize multiple power amplifiers simultaneously. It processes the common baseband signal that will be distributed to all transmitter branches, providing multi-functional capability to handle linearization for the entire AAS rather than requiring dedicated hardware for each branch.
2Adaptability or versatility
If the number of active transmitter branches in AAS increases, then antenna system capability is improved, but processing power and capacity for linearization exceed available resources
Solution Approach 1:
The patent combines the linearization processing function into a single shared DPD subsystem that handles all transmitter branches collectively. Instead of allocating separate processing resources to each branch, the system uses one efficient processing unit that operates on the common baseband signal before it is distributed to multiple branches through the analog beamforming network.
3Measurement precision
If individual couplers are added for each transmitter branch to enable feedback, then DPD adaptation accuracy is improved, but hardware space and coupling interference increase
Solution Approach 1:
The patent extracts the feedback function from individual branch-level components and consolidates it into a single receive antenna element. Instead of using individual couplers for each transmitter branch, the system uses one receive antenna to capture the combined radiated signal from all branches, eliminating the need for multiple physical couplers and reducing hardware space requirements.
Solution Approach 2:
The patent introduces the analog beamforming network and antenna radiation channel as an intermediary medium for feedback. Rather than directly coupling each transmitter to a receiver through physical couplers, the system uses the antenna radiation and reception path as a natural feedback channel, where the receive antenna captures the combined signal from all transmitter branches after they have been beamformed and radiated.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Systems and methods are disclosed herein that provide low-complexity Digital Predistortion (DPD) for a transceiver system that uses an Advanced Antenna System (AAS) to provide analog or hybrid beamforming.