Precursor Equalizer Coefficient Selection for SERDES Eye Height
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Solution Overview
Problem
High-speed serial links face challenges in precursor equalization due to difficulties in implementing decision feedback equalizers, particularly at gigabit rates, where analog-to-digital converters and analog delay lines are hard to design, and precursor cancellation at the transmitter makes adaptive derivation of filter coefficients impossible without a feedback mechanism.
Innovation Solution
A system and method for selecting precursor equalizer coefficients using an eye height cost function based on continuous-time channel and crosstalk symbol responses, incorporating a phase-locked loop and a cost evaluator to produce coefficients for a precursor equalizer, which can be applied in a SERDES to improve equalization performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If decision feedback equalizer is implemented at gigabit rates, then equalization effectiveness is improved, but implementation difficulty increases due to challenges with analog-to-digital converters and analog delay lines
Solution Approach 1:
The patent replaces analog delay lines with digital signal processing techniques. Specifically, it uses digital filtering and mathematical operations to achieve the same equalization function that would traditionally require analog delay lines, thereby simplifying implementation at gigabit rates while maintaining equalization effectiveness.
Solution Approach 2:
The patent introduces an intermediary digital processing stage between the analog-to-digital converter and the equalization function. This intermediary layer uses digital signal processing to perform the equalization, avoiding the need for complex high-speed analog components while achieving the same reliability benefits.
2Reliability
If precursor cancellation is applied at the transmitter, then precursor intersymbol interference is reduced, but adaptive derivation of filter coefficients becomes impossible without bidirectional feedback
Solution Approach 1:
The patent implements a feedback mechanism where the receiver evaluates equalization performance and communicates this information back to the transmitter. This allows the transmitter to adaptively adjust its precursor cancellation filter coefficients based on actual channel conditions, enabling adaptive derivation without requiring complex bidirectional training sequences.
Solution Approach 2:
The system enables the transmitter to self-adjust its equalization parameters based on feedback from the receiver. The transmitter uses the received feedback information to automatically optimize its precursor cancellation coefficients, making the system adaptive without requiring external training or complex coordination.
3Ease of manufacture
If fixed precursor equalizer coefficients are used, then implementation simplicity is maintained, but performance degrades when clock recovery phase varies
Solution Approach 1:
The patent transitions from static fixed coefficients to dynamic adaptive coefficients. The precursor equalizer coefficients are made variable and are adjusted based on feedback from the receiver about actual channel conditions and clock recovery phase, thereby maintaining performance consistency across varying operating conditions while keeping implementation relatively simple.
Data Source
AI summary
In one aspect, the present invention provides a system and method for selecting precursor equalizer coefficients and a serializer deserializer (SERDES) incorporating the system or the method. In one embodiment, the system includes: (1) a cost definer configured to generate an eye height cost function based on continuous-time channel and crosstalk symbol responses pertaining to a particular serial link and (2) a cost evaluator associated with the cost definer and configured to evaluate the eye height cost function based on a particular criterion thereby to produce coefficients for a precursor equalizer to be applied with respect to the particular serial link.