Pattern-Based Loss of Signal Detection in SerDes Receivers

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Solution Overview

Problem

Existing loss of signal (LOS) detection mechanisms in high-speed communications are inadequate due to variations in signal attenuation across different connection media, making it difficult to set a universally applicable threshold for detecting signal loss.

Innovation Solution

A pattern-based LOS detection system using a decision feedback equalization (DFE) circuit and a slicer circuit, combined with a lookup table and programmable noise threshold, compares the slicer output with an expected signal to determine a loss of signal, accumulating results over a predetermined number of receiver characters to set a pattern-based LOS indicator.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If analog peak detectors with programmable thresholds are used for LOS detection, then LOS detection capability is provided, but the system becomes sensitive to variations in signal attenuation across different connection media, making universal threshold setting difficult

Engineering Contradiction:

ImproveLOS detection capabilityVSAvoidUniversality across connection media

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent replaces the analog peak detector mechanism with a digital pattern-based detection system. Instead of using analog voltage thresholds that are sensitive to attenuation variations, the system uses digital signal processing techniques including decision feedback equalization (DFE), slicer circuits, and pattern recognition to detect LOS conditions. This substitution of analog detection with digital processing eliminates the sensitivity to signal attenuation variations while maintaining LOS detection capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the detection parameter from analog peak amplitude to digital signal patterns. By transforming the detection basis from continuous voltage levels to discrete pattern recognition, the system becomes insensitive to attenuation variations. The pattern-based approach uses the temporal structure and characteristics of digital signals rather than their amplitude, providing universal applicability across different connection media.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If analog peak detectors are used for LOS detection, then signal loss can be detected, but incorrect threshold settings cause false positives or negatives

Engineering Contradiction:

ImproveSignal loss detection accuracyVSAvoidThreshold setting accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent implements self-service through automatic threshold adaptation and self-diagnostic capabilities. The system continuously monitors signal characteristics and automatically adjusts detection parameters without requiring manual threshold configuration. The pattern recognition algorithm inherently adapts to varying signal conditions, eliminating the need for precise manual threshold setting while maintaining high detection accuracy.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent employs feedback mechanisms where the system continuously monitors detection results and adjusts its operation accordingly. The decision feedback equalization (DFE) algorithm uses feedback from previous decisions to refine current detections, and the system incorporates self-diagnostic functions that monitor detection accuracy and adjust thresholds automatically, preventing false positives and negatives.

Inventive Principle:

Principle #23Feedback

3Adaptability or versatility

If pattern-based DFE and slicer circuits are used for LOS detection, then insensitivity to signal attenuation is achieved, but device complexity increases

Engineering Contradiction:

ImproveInsensitivity to signal attenuationVSAvoidDFE and slicer circuit complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent achieves multi-functionality by designing the DFE and slicer circuits to serve multiple purposes: equalization, signal slicing, and LOS detection. Rather than adding separate dedicated LOS detection circuitry, the existing equalization and slicing functions are enhanced to perform detection tasks, reducing overall device complexity while maintaining insensitivity to signal attenuation.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the LOS detection function with the existing signal processing functions. The DFE and slicer circuits that are already present for equalization and data recovery are combined with LOS detection capabilities, eliminating the need for separate detection hardware. This integration reduces device complexity while achieving the desired attenuation insensitivity.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS8953665B2Pattern-based loss of signal detector

Publication Date: 2015.02.10 AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LTD

AI summary

In described embodiments, data pattern-based detection of loss of signal (LOS) is employed for a receive path of serializer/deserializer (SerDes) devices. Pattern-based LOS detection allows for detection of data loss over variety of types of connection media, and is generally insensitive to signal attenuation. More specifically, some described embodiments disclose reliable pattern-based detection of LOS across different connection media for incoming receive data when discreet time decision feedback equalization (DFE) is employed.