Receiver Sampling Phase Tracking via Adaptive Equalizer Constraints
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Solution Overview
Problem
In communication systems, the interaction between the clock data recovery (CDR) loop and adaptive equalization can lead to instability, causing the sampling phase to deviate from the optimal sampling phase, resulting in performance degradation due to constrained equalization under changing operating conditions.
Innovation Solution
A method and receiver device that track the sampling phase by determining phase gradient information and updating adaptation constraints of the adaptive equalizer to move the sampling phase towards the optimal sampling phase, allowing the receiver to adapt to changing conditions while preventing instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the adaptive equalizer is allowed to freely adapt to changes in channel response, then the equalizer can compensate for transmission impairments, but the interaction with the CDR loop causes instability and leads the sampling phase away from the optimal sampling phase
Solution Approach 1:
The patent introduces an intermediary mechanism (phase gradient estimator and adaptation constraint controller) that mediates between the adaptive equalizer and the CDR loop. This intermediary estimates the phase gradient and adjusts the equalizer's adaptation constraints dynamically, allowing the equalizer to adapt to channel changes while preventing it from destabilizing the CDR loop and pushing the sampling phase away from optimal values
Solution Approach 2:
The patent makes the equalizer adaptation constraints dynamic rather than static. The adaptation constraints are continuously adjusted based on the estimated phase gradient, allowing the system to adapt to changing channel conditions while maintaining sampling phase stability. This dynamic adjustment enables the equalizer to be more aggressive in adapting to channel changes when the sampling phase is near optimal, and more conservative when the sampling phase is deviating
2Stability of the object's composition
If the adaptive equalizer adaptation is constrained to prevent instability, then the sampling phase remains stable, but the receiver performance degrades under changing operating conditions such as temperature changes
Solution Approach 1:
The patent dynamically adjusts the equalizer adaptation constraints based on the estimated phase gradient. When the phase gradient is small (indicating the sampling phase is near optimal), the constraints are relaxed to allow the equalizer to adapt to changing operating conditions. When the phase gradient is large (indicating the sampling phase is deviating), the constraints are tightened to maintain stability. This dynamic approach resolves the contradiction by making the constraints adaptive rather than fixed
Solution Approach 2:
The patent implements a feedback mechanism where the phase gradient estimator continuously monitors the relationship between the sampling phase and the equalizer adaptation, and this information is fed back to the adaptation constraint controller. This feedback loop allows the system to automatically adjust the equalizer constraints in response to changing operating conditions, maintaining both stability and adaptability without requiring manual intervention
3Productivity
If the sampling phase is allowed to move freely to track the optimal sampling phase, then the receiver can maintain optimal performance, but the interaction with the adaptive equalizer causes the phase to be led away from the optimal sampling phase
Solution Approach 1:
The patent introduces a phase gradient estimator as an intermediary that objectively assesses whether the sampling phase is moving toward or away from the optimal point, independent of the adaptive equalizer's actions. This intermediary provides unbiased phase gradient information to the CDR loop, allowing the sampling phase to be adjusted based on actual performance needs rather than being distorted by the equalizer's adaptation process
Solution Approach 2:
The patent performs preliminary estimation of the phase gradient using the equalized signal before using this information to adjust the sampling phase. By estimating the phase gradient in advance and using it to guide phase adjustments, the system ensures that sampling phase movements are based on predicted performance improvements rather than reactive corrections, preventing the equalizer from leading the phase away from optimal values
Data Source
AI summary
An input signal is sampled at a current sampling phase by a sampler device of a receiver device. The sampled input signal is equalized by an adaptive equalizer of the receiver device. One or more parameters of the adaptive equalizer are adapted, based on the equalized input signal, under one or more adaptation constraints. Phase gradient information indicative of an offset of the current sampling phase from an optimal sampling phase is determined, and the one or more adaptation constraints of the adaptive equalizer are updated based on the phase gradient information to move the current sampling phase towards the optimal sampling phase.