Transition Encoding for DC Balance and Clock Recovery
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Solution Overview
Problem
In data transmission, the absence of transitions over extended intervals can hinder clock recovery at the receiver, and AC-coupled data links face issues with DC wander due to unbalanced DC components in serial data streams.
Innovation Solution
A method and system for DC balanced transition encoding, which generates candidate encoding keys based on disparity contributions and running disparities to encode raw data words, ensuring the maximum run length does not exceed a threshold and minimizing the DC component by selecting an appropriate encoding key that balances the number of ones and zeros.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional encoding is used without DC balancing, then the encoding process is simple, but DC wander occurs in AC-coupled data links and clock recovery fails due to absence of transitions
Solution Approach 1:
The patent applies preliminary action by calculating disparity contributions for each candidate encoding key before selection. The system pre-computes the disparity contribution (difference between number of ones and zeros) for each candidate key, then uses this pre-calculated information to select the key that minimizes running disparity. This preliminary calculation enables proactive DC balancing rather than reactive correction.
Solution Approach 2:
The patent changes the parameter of encoding key selection criteria from simple transition counting to disparity contribution-based selection. By evaluating candidate keys based on their disparity contribution to the running disparity, the system dynamically adjusts the encoded output to maintain DC balance. This parameter change transforms the encoding process into an adaptive DC-balancing mechanism.
2Reliability
If DC balancing is implemented by selecting encoding keys based on disparity contribution, then DC wander is minimized and clock recovery is improved, but the encoding complexity increases due to multiple candidate key evaluation
Solution Approach 1:
The patent segments the encoding key selection process into distinct stages: generating candidate encoding keys, calculating disparity contributions for each candidate, evaluating running disparity, and selecting the optimal key. This segmentation allows the complex task of DC-balanced encoding to be broken down into manageable computational steps, each handling a specific aspect of the problem.
Solution Approach 2:
The patent implements feedback by using the running disparity (accumulated disparity from previously encoded data) as input to the encoding key selection process. The disparity contribution of each candidate key is evaluated in the context of the current running disparity, and the selected key feeds back into updating the running disparity for the next encoding decision. This closed-loop feedback ensures continuous DC balance maintenance.
Data Source
AI summary
A system and method for DC balanced transition encoding. In some embodiments, the method includes: generating a set of candidate encoding keys for a set of raw data words; selecting a first encoding key, of the set of candidate encoding keys, based on a first disparity contribution; and encoding the raw data words with the first encoding key, the first disparity contribution being a difference between the number of ones and the number of zeros in the result of encoding the set of raw data words with the first encoding key.