Cable Assembly Shield Overlap for EMI Leakage Reduction
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Solution Overview
Problem
Existing cable assemblies face issues with electromagnetic interference leakage, non-linear signal performance, and significant power losses, particularly in low frequency signals, due to gaps in the shield wrapping and improper positioning of conductors relative to the shield, which affects signal integrity and time skew.
Innovation Solution
The cable assembly design includes elongated conductors with primary and secondary dielectric layers, a conductive shield layer, and a drain wire, where the conductors and dielectric layers are twisted within the shield, and the shield is wrapped to overlap itself, reducing gaps and optimizing the distance between conductors and the shield to minimize interference and skew.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the shield is wrapped around the conductors with gaps between adjacent windings, then the cable assembly is easier to manufacture, but electromagnetic interference leakage increases and signal integrity deteriorates
Solution Approach 1:
The shield is wrapped around the conductors such that adjacent windings overlap with one another, creating a continuous shielding effect along the length of the cable assembly. This continuous overlap eliminates gaps between windings, ensuring uninterrupted electromagnetic interference protection while maintaining signal integrity across all frequency bands.
2Volume of moving object
If the conductors are positioned too close to the shield, then the cable assembly structure is more compact, but electrical coupling between conductors and shield increases causing time skew
Solution Approach 1:
A dielectric layer is positioned between the conductors and the shield, creating a localized insulating barrier. This dielectric layer prevents direct electrical coupling between the conductors and the conductive shield, eliminating time skew caused by capacitive coupling while maintaining the compact overall structure of the cable assembly.
3Ease of manufacture
If the drain wire is displaced off-center from the midpoint between conductors, then the cable assembly manufacturing is more flexible, but the effectiveness of the drain wire and shield in shielding conductors from electromagnetic interference is reduced
Solution Approach 1:
The drain wire is intentionally positioned asymmetrically, wrapped around only a portion of the shield rather than being centered. This asymmetric positioning provides manufacturing flexibility while the wrap configuration ensures adequate electromagnetic interference drainage capability is maintained through the conductive path provided by the wrap around the shield.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively reduces electromagnetic interference leakage, enhances signal integrity by minimizing time skew, and reduces power losses across all frequency bands, particularly in low frequency signals, by ensuring continuous shielding and proper signal propagation.
Implementation Method 1
Twisting the conductors about one another may cancel out both external and internal electromagnetic interference in the conductors that is caused by an external source.
Implementation Method 2
The drain wire is electrically joined with the shield and with the ground reference to communicate the electromagnetic interference to the ground reference.
Data Source
AI summary
A cable assembly includes elongated conductors, primary dielectric layers, a secondary dielectric layer, a conductive shield layer and a drain wire. The conductors communicate a signal. The primary dielectric layer is circumferentially disposed around each of the conductors. The secondary dielectric layer surrounds the primary dielectric layers. The conductive shield layer is disposed around the secondary dielectric layer. The drain wire is provided along an outer surface of the conductive shield layer and is electrically coupled with the conductive shield layer. The conductive shield layer communicates electromagnetic interference to an electric ground reference via the drain wire.