CTLE Tuning via DFE Tap Values for Link Training
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Solution Overview
Problem
As signaling speeds increase in communications between integrated circuits, signal degradation leads to inter-symbol interference and crosstalk, causing unwanted transmission errors, which existing equalization methods struggle to address efficiently.
Innovation Solution
The method involves tuning a continuous time linear equalizer (CTLE) without performing bit error rate (BER) measurements, reusing decision feedback equalizer (DFE) adaptation circuitry, and selecting CTLE settings based on adapted DFE tap values to optimize equalization efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If bit error rate (BER) measurements are performed for CTLE tuning, then equalization accuracy is improved, but link training time increases significantly
Solution Approach 1:
The patent uses DFE tap values as an intermediary indicator to infer CTLE tuning quality without performing actual BER measurements. The DFE adaptation engine's tap values serve as a proxy metric that correlates with equalization performance, allowing the system to select optimal CTLE settings based on DFE performance rather than direct error rate measurement.
Solution Approach 2:
The patent replaces the time-consuming BER measurement mechanism with a computational approach using DFE adaptation results. Instead of measuring actual bit errors through physical transmission and comparison, the system substitutes this with mathematical analysis of DFE tap values, which can be computed much faster without requiring actual error detection hardware operations.
2Measurement precision
If dedicated CTLE tuning circuitry is implemented, then tuning accuracy is improved, but device complexity and implementation cost increase
Solution Approach 1:
The patent makes the DFE adaptation engine serve multiple functions: it not only performs its primary role of equalization adaptation but also provides the tap values that guide CTLE tuning. This multi-functionality eliminates the need for separate dedicated CTLE tuning circuitry, as the existing DFE engine is repurposed to perform the additional tuning guidance function.
Solution Approach 2:
The system uses its own existing resources (the DFE adaptation engine and its tap values) to perform the CTLE tuning function. Rather than requiring external or dedicated tuning circuitry, the system serves itself by leveraging the information already generated during normal DFE operation to guide CTLE setting selection.
3Reliability
If multiple CTLE settings are evaluated through BER measurements, then optimal equalization is achieved, but productivity and training speed decrease
Solution Approach 1:
The patent skips the time-consuming BER measurement step entirely when evaluating multiple CTLE settings. Instead of measuring actual bit errors for each setting, the system rapidly evaluates settings based on DFE tap values, which can be computed and compared much faster. This allows the system to rush through multiple setting evaluations without the bottleneck of repeated BER measurements.
Solution Approach 2:
The patent uses partial information (DFE tap values) instead of complete information (actual BER measurements) to make tuning decisions. While BER measurements would provide comprehensive error rate data, the system finds that partial information from DFE taps is sufficient to guide CTLE tuning effectively, achieving good enough optimization without the excessive time cost of full BER measurements for each setting.
Data Source
AI summary
The presently-disclosed solution enables continuous time linear equalizer (CTLE) tuning without needing to perform bit error rate (BER) measurements. Because time consuming BER measurements are avoided, the CTLE tuning may be performed more rapidly as to reduce substantially the time required for link training. Furthermore, this solution re-uses decision feedback equalizer (DFE) adaptation circuitry so as to be highly efficient in its implementation. One embodiment relates to a method that tunes the CTLE based on results from the adaptation of the tap values of the DFE. Another embodiment relates to an apparatus that includes an interface for a control module to control a setting of a CTLE and an adaptation engine for a DFE. The value for the setting of the CTLE is selected using the adapted tap 1 value of the DFE as a figure of merit. Other embodiments and features are also disclosed.