Automotive Shielded Cable Resolving Mode Conversion
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Solution Overview
Problem
Conventional shielded communication cables experience significant mode conversion from differential to common mode due to electromagnetic coupling between core wires and metal foil shields, leading to degraded communication properties, especially in high-speed automotive applications.
Innovation Solution
A shielded communication cable design featuring a twisted wire pair with a first sheath between the core wires and a multilayer shield layer comprising a metal foil and resin layer, where the eccentricity ratio of the first sheath is 80% or more, reducing electromagnetic coupling and mode conversion by creating a physical distance between the core wires and the shield layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a metal foil shield is used to cover the twisted wire pair, then electromagnetic shielding is improved, but electromagnetic coupling between core wires and shield increases causing mode conversion
Solution Approach 1:
The patent introduces a resin layer as an intermediary substance between the metal foil shield and the twisted wire pair. This resin layer acts as a mediator that reduces the electromagnetic coupling between the core wires and the metal foil shield, thereby suppressing mode conversion from differential mode to common mode while maintaining the electromagnetic shielding effectiveness of the metal foil.
2Object-affected harmful factors
If the shield layer is placed close to the core wires, then shielding effectiveness is improved, but electromagnetic coupling increases causing mode conversion
Solution Approach 1:
The resin layer serves as a physical and electromagnetic intermediary between the metal foil shield and the core wires. It provides electrical insulation and reduces electromagnetic coupling, allowing the shield to be positioned close to the core wires for effective shielding without causing excessive mode conversion.
3Object-affected harmful factors
If a drain wire is added to connect the metal foil shield, then shield grounding is improved, but common mode impedance decreases increasing mode conversion
Solution Approach 1:
The patent removes the drain wire from the cable structure, extracting this element that was causing the problem. By eliminating the drain wire connection, the patent avoids creating a low-impedance path for common mode currents, thereby preventing mode conversion while still maintaining shielding effectiveness through the metal foil shield and resin layer combination.
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
The design effectively suppresses mode conversion, enhancing communication properties and reducing noise interference, making it suitable for high-speed automotive communications while maintaining a suitable characteristic impedance for Ethernet applications.
Implementation Method 1
electromagnetic coupling occurs not only between the core wires of the twisted wire pair but also between the core wires and the metal foil shield
Implementation Method 2
the shield layer is formed by a multilayer body that includes a metal foil layer and a resin layer disposed on one surface of the metal foil layer
Data Source
AI summary
A shielded communication cable that includes a twisted wire pair formed by a pair of core wires that each include a conductor and an insulator covering the conductor and that are twisted together; a first sheath covering the pair of core wires that are twisted together; a shield layer covering the first sheath; and a second sheath covering the shield layer, wherein: the shielded communication cable does not include a drain wire, the shield layer is formed by a multilayer body that includes a metal foil layer and a resin layer disposed on one surface of the metal foil layer, and the shielded communication cable is used for communications in an automobile.