Flat Cable LSSL Lay Length Configuration for Crosstalk Reduction

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Solution Overview

Problem

Conventional flat type cables using the Long, Short, Long, Short (LSLS) lay configuration suffer from suboptimal attenuation and crosstalk performance, particularly at higher frequencies, due to increased attenuation in edge twisted pairs and poorer crosstalk performance of central pairs, leading to bottlenecks in electrical and physical performance.

Innovation Solution

A flat type cable design featuring twisted pair conductors with varying lay lengths, where edge conductors have longer lay lengths than central ones, arranged in a Long, Short, Short, Long (LSSL) configuration, improving crosstalk and attenuation performance by minimizing close proximity crosstalk combinations and reducing jacket material surrounding central pairs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the LSLS (Long, Short, Long, Short) lay configuration is used in flat type cables, then the cable structure is simplified and manufacturing is easier, but the attenuation performance deteriorates due to increased attenuation in edge twisted pairs and the crosstalk performance deteriorates due to poor performance of central pairs

Engineering Contradiction:

Improveease of manufactureVSAvoidelectrical performance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies local quality by differentiating the lay lengths of twisted pairs based on their position within the cable. Edge twisted pairs are assigned longer lay lengths to reduce attenuation, while central twisted pairs are assigned shorter lay lengths to improve crosstalk performance. This position-dependent differentiation resolves the contradiction by optimizing each region's electrical characteristics according to its specific requirements rather than using a uniform LSLS configuration.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent introduces asymmetry by breaking the symmetric LSLS pattern and implementing an LSSL (Long, Short, Short, Long) configuration where edge pairs have longer lay lengths and central pairs have shorter lay lengths. This asymmetric arrangement addresses the contradictory requirements by allowing edge pairs to benefit from longer lays (lower attenuation) while central pairs benefit from shorter lays (better crosstalk), thereby improving overall cable reliability without significantly complicating manufacturing.

Inventive Principle:

Principle #4Asymmetry

2Object-affected harmful factors

If shorter lay length twisted pair conductors are used, then crosstalk performance is improved, but attenuation increases particularly in edge twisted pairs

Engineering Contradiction:

ImprovecrosstalkVSAvoidattenuation

Core Design Contradiction:

Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The patent applies local quality by assigning different lay lengths to twisted pairs based on their position. Edge twisted pairs use longer lay lengths to minimize attenuation, while central twisted pairs use shorter lay lengths to minimize crosstalk. This position-specific optimization resolves the contradiction between reducing crosstalk and minimizing attenuation by tailoring the lay length to the specific electrical characteristics and interference patterns experienced at different cable positions.

Inventive Principle:

Principle #3Local quality

3Loss of energy

If longer lay length twisted pair conductors are used, then attenuation is reduced, but crosstalk performance deteriorates

Engineering Contradiction:

ImproveattenuationVSAvoidcrosstalk

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by differentiating lay lengths according to position: edge twisted pairs use longer lay lengths where attenuation is the primary concern, while central twisted pairs use shorter lay lengths where crosstalk is the dominant issue. This spatial differentiation resolves the contradiction by allowing each region to optimize for its primary electrical challenge rather than attempting to simultaneously minimize both attenuation and crosstalk across all pairs.

Inventive Principle:

Principle #3Local quality

4Ease of manufacture

If a round cross section cable is used, then manufacturing is easier, but the number of closely spaced crosstalk combinations increases

Engineering Contradiction:

Improveease of manufactureVSAvoidcrosstalk combinations

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent transitions from the symmetric round cross-section to an asymmetric flat cross-section configuration. This asymmetry reduces the number of closely spaced twisted pair combinations that contribute to crosstalk, particularly by separating edge pairs from central pairs and reducing their interaction. The flat configuration maintains manufacturing feasibility while significantly improving crosstalk performance through geometric separation.

Inventive Principle:

Principle #4Asymmetry

Data Source

PatentUS9099220B2Flat type cable for high frequency applications

Publication Date: 2015.08.04 BELDEN INC

AI summary

A flat-type cable suitable for use in high frequency communications. The cable has a plurality of longitudinally extending and substantially parallel passageways, each housing a twisted pair conductor. The twisted pair conductors are disposed in the cable in a manner that the twisted pair conductors with the longest lay lengths are disposed in the passageways closest to the edges of the cable, and the passageways farther away from the edges of the cable house twisted pair conductors with progressively shorter lay lengths.