Adaptive Precoder Mitigating Nonlinear Distortions via Dynamic Filter Coefficients
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Solution Overview
Problem
Conventional precoding methods struggle to effectively mitigate nonlinear distortions and inter-symbol interference (ISI) in communication signals, particularly in direct detection modulation methods like PAM-4, due to bandwidth limitations and the inability to adapt to varying signal levels.
Innovation Solution
A precoding method and precoder system that includes a filter and modulo operator to generate filtering signals based on selected coefficients, using a level detector and delay elements to select and apply filter coefficients, and perform modulo operations to mitigate nonlinear distortions and ISI, allowing for adaptation to signal levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional THP with a linear filter is used to remove post-cursor ISI, then ISI mitigation is achieved, but the system cannot effectively handle nonlinear distortions at different signal levels
Solution Approach 1:
The patent implements dynamic filter coefficient selection by introducing a level detector that identifies signal levels and a selector that chooses appropriate filter coefficients based on the detected level. This transforms the static linear filter into a dynamic adaptive filter that can adjust its characteristics according to the input signal level, thereby resolving the contradiction between maintaining consistent ISI mitigation and adapting to varying nonlinear distortion characteristics at different signal levels.
Solution Approach 2:
The patent changes the filter coefficients based on the detected signal level. Multiple sets of filter coefficients are prepared, each optimized for specific signal levels. The level detector determines the current signal level, and the selector switches between different coefficient sets accordingly. This parameter change approach enables the filter to adapt its behavior to different operating conditions, solving the contradiction between consistent performance and level-specific adaptability.
2Ease of manufacture
If a linear filter with fixed coefficients is used in the precoder, then the filter design is simple, but it cannot compensate for amplitude-dependent nonlinear distortions
Solution Approach 1:
The patent segments the filtering process into multiple operations: level detection, coefficient selection based on the detected level, and filtering with the selected coefficients. This segmentation allows the system to maintain a relatively simple overall structure while achieving precise distortion mitigation through the coordinated operation of multiple functional blocks, each with a specific and manageable complexity.
Solution Approach 2:
The system performs self-adjustment by automatically detecting the signal level and selecting the appropriate filter coefficients without external intervention. The level detector continuously monitors the input signal and triggers the coefficient switch when a level change is detected, enabling the filter to adapt to changing conditions autonomously and maintain high precision across different operating points.
Data Source
AI summary
A method for precoding to mitigate nonlinear distortions and a precoder for performing the same are disclosed. The precoder for mitigating distortions of a communication signal may include a filter configured to generate a filtering signal based on a third signal and filter coefficients corresponding to a selected signal generated based on a first signal, a second signal, and the third signal, and a modulo operator configured to generate the third signal by performing a modulo operation on the second signal, wherein the second signal is generated based on the first signal and the filtering signal.