SerDes Eye Diagram Capture Using Probability Mapping

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Solution Overview

Problem

Existing high-speed serial interface systems require complex phase alignment and hardware for generating eye diagrams, which increases costs and complexity, especially when analyzing serial connections.

Innovation Solution

A method and circuit that eliminate the need for complex phase alignment by using a probability map generated through fixed phase and voltage stepping, allowing for the creation of an eye diagram without complex processors or multi-bit comparators, leveraging the DC-balanced nature of SerDes protocols to determine signal integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If complex phase alignment and hardware are used to generate eye diagrams, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

Improveeye diagram measurement precisionVSAvoidphase alignment hardware complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent creates a probability map that serves as a statistical copy of the signal behavior across multiple unit intervals. Instead of requiring complex phase-aligned hardware to capture the eye diagram, the system uses multiple unaligned samples and reconstructs the eye diagram information from the probability distribution, thereby achieving accurate measurements without complex alignment hardware

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent replaces the mechanical/physical phase alignment system with a computational probability-based approach. Instead of using hardware to physically align phases, the system uses software algorithms to process unaligned samples and reconstruct eye diagram parameters from probability statistics, eliminating the need for complex phase alignment hardware

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If complex processors and multi-bit comparators are used, then measurement precision is improved, but manufacturing cost increases

Engineering Contradiction:

Improvesignal integrity measurement precisionVSAvoidmanufacturing cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent uses simple, inexpensive single-bit comparators instead of expensive multi-bit comparators. Each sample is processed independently through basic comparison logic, and the cumulative probability information from many such simple operations provides accurate eye diagram measurements, replacing expensive persistent hardware with numerous simple operations

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The system creates a probability map that copies the essential eye diagram information from multiple simple samples. By accumulating probability data from many inexpensive single-bit comparisons rather than using one expensive multi-bit comparator, the system achieves the same measurement precision at lower manufacturing cost

Inventive Principle:

Principle #26Copying

3Device complexity

If fixed phase and voltage stepping is used, then device complexity is reduced, but measurement precision may worsen

Engineering Contradiction:

Improvephase alignment complexityVSAvoideye diagram capture accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent performs preliminary sampling across multiple unit intervals with fixed phase steps, building up a probability map before final eye diagram reconstruction. By pre-collecting statistical data from many fixed-phase samples, the system ensures accurate probability distribution information is available for subsequent eye parameter extraction, maintaining precision without requiring complex real-time phase adjustment

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses periodic sampling at fixed phase intervals across multiple unit intervals. By systematically stepping through fixed phase values and accumulating probability data at each step, the method achieves comprehensive eye diagram coverage through regular periodic measurement cycles, ensuring accuracy through systematic sampling rather than complex continuous adjustment

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS11626934B1Probability-based capture of an eye diagram on a high-speed digital interface

Publication Date: 2023.04.11 AMAZON TECH INC

AI summary

An eye diagram is generated for a digital interface, such as a Serializer/Deserializer (SerDes) interface. A probability map is captured by stepping through a fixed sequence of phase and reference voltage levels and counting a number of highs or lows. The switching of phase includes merely increasing the phase difference rather than performing complex phase/data analysis. The probability map can then be used to generate an eye diagram through simple differentiation. For example, the differentiation between various pixel locations in the probability map can be used to yield the edges of the eye in an eye diagram. The standard Serdes parameters can then be extracted from the eye diagram. The parameters can then be used to determine if the serial connection is problematic.