5G MIMO DPD Dual-Feedback Loops for Fast Linearization
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Solution Overview
Problem
Current digital predistortion (DPD) devices for 5G broadband MIMO systems face challenges in real-time monitoring and timely response due to high hardware requirements and slow feedback response in multi-channel systems, especially with increased bandwidth and complexity of radio frequency power amplifier nonlinear effects.
Innovation Solution
A dual-feedback loop system is implemented, with a main feedback loop for rapid adjustment and an auxiliary feedback loop for fine-tuning, utilizing multi-path switching and signal combination for real-time monitoring and coefficient updates, along with a dynamic deviation dimension reduction method for improved DPD model accuracy and reduced hardware resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a one-path separate feedback method is used for multi-channel MIMO systems, then real-time monitoring and response can be achieved, but hardware requirements increase significantly requiring separate feedback loops for each RF amplifier
Solution Approach 1:
The patent combines multiple feedback paths into a unified feedback structure where multiple RF amplifier output signals are multiplexed and switched through a single feedback loop. This merging approach maintains real-time monitoring capability while significantly reducing hardware resources by eliminating the need for separate feedback loops, down-conversion circuits, and ADCs for each amplifier.
Solution Approach 2:
The single feedback loop is designed to handle multiple RF amplifier channels universally through time-division multiplexing and switching mechanisms. The same feedback path serves multiple amplifiers by sequentially sampling their outputs, making the feedback system multi-functional rather than dedicated to a single channel.
2Device complexity
If a multi-path switching feedback method is used to reduce hardware resources, then fewer hardware resources are occupied, but the feedback response time increases due to polling manner operation
Solution Approach 1:
The patent implements periodic switching among multiple feedback paths with optimized timing. Each path is sampled in a periodic sequence, and the switching frequency and duty cycle are designed to ensure that the most critical channels receive feedback updates at intervals that maintain system performance while minimizing overall response time.
Solution Approach 2:
The feedback switching mechanism is made dynamic by prioritizing channels based on their current operational state and distortion levels. Channels experiencing higher distortion or more critical operations receive more frequent feedback updates, while stable channels are updated less frequently, optimizing the overall response speed adaptively.
3Loss of time
If DPD models quickly respond to distortion caused by radio frequency power amplifier, then delay requirements are met, but the linearization process becomes more complicated due to wider bandwidth and more serious nonlinear effects
Solution Approach 1:
The patent segments the wideband signal processing into multiple narrower frequency sub-bands. Each sub-band is processed independently through the DPD model, which simplifies the linearization calculations for each segment while collectively covering the entire wide bandwidth. This segmentation reduces the computational complexity of handling wideband nonlinear effects.
Solution Approach 2:
The patent transforms the complex wideband nonlinear compensation problem into a series of simpler narrowband problems by introducing a frequency dimension decomposition. Instead of attempting to compensate for all nonlinear effects across the entire bandwidth simultaneously, the system processes each frequency segment separately and combines the results, effectively reducing the dimensionality of the computational problem.
Data Source
AI summary
The present disclosure relates to the technical field of wireless communications, in particular, a digital predistortion (DPD) apparatus applicable to a 5G broadband multiple-input multiple-output (MIMO) system. The DPD apparatus includes a data processing module, a digital-to-analog conversion module, a signal output module, a signal feedback module, and an analog-to-digital conversion module; the signal feedback module is to ensure that at least two feedback paths are directed to a DPD feedback signal. The first feedback path is a main feedback loop, and the second feedback path is an auxiliary feedback loop. The present disclosure has the advantages of occupying a few of hardware resources, being capable of monitoring a DPD feedback loop signal in real time, and making a response in time.