Coaxial Cable Shield Segmentation for Bending Signal Integrity
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Solution Overview
Problem
Coaxial cables used in electronic devices for high-speed signal transmission, especially in bent states, experience significant signal attenuation due to changes in characteristic impedance and gap formation between the shield layer and insulator when bent.
Innovation Solution
A coaxial cable design featuring a circular cross-sectional inner conductor formed by twisted metal strands and a winding shield layer with strategically placed gaps between second metal strands, along with a shield tape layer, to maintain close contact and prevent signal attenuation when bent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the shield layer is made continuous without gaps, then shielding effectiveness is improved, but the cable becomes rigid and gaps form between shield and insulator when bent
Solution Approach 1:
The shield layer is divided into multiple discrete wound wires instead of being continuous. This segmentation allows the shield to flex and adapt to bending without forming gaps between the shield and insulator, while still maintaining effective shielding through the closely spaced discrete wires.
Solution Approach 2:
The shield layer is designed with dynamic flexibility through the use of multiple wound wires that can move relative to each other during cable bending. This dynamic structure prevents gap formation between the shield and insulator while maintaining shielding effectiveness throughout the bending process.
2Reliability
If the cable is designed for high-speed signal transmission, then transmission quality is improved, but signal attenuation increases when the cable is bent
Solution Approach 1:
The shield layer is segmented into multiple wound wires that maintain close contact with the insulator during bending, preventing characteristic impedance changes that would cause signal attenuation and maintain high-speed signal transmission quality.
Solution Approach 2:
The shield layer structure is optimized by controlling wire diameter, winding pitch, and number of wires to maintain characteristic impedance stability during bending, thereby reducing signal attenuation for high-speed signals while preserving transmission quality.
3Loss of energy
If the shield layer uses closely spaced wires, then signal attenuation is reduced, but manufacturing precision requirements increase
Solution Approach 1:
Optimal parameter ranges are established for wire diameter (0.03-0.08mm), winding pitch (0.5-2.0 times wire diameter), and number of wires (3-10) to achieve low signal attenuation while maintaining manufacturability. These parameter specifications balance performance requirements with manufacturing precision capabilities.
Solution Approach 2:
The design specifies sufficient but not excessive wire density in the shield layer. The winding pitch is controlled to be 0.5-2.0 times the wire diameter, providing adequate shielding and low attenuation without requiring ultra-precise manufacturing, thus balancing performance with manufacturability.
Data Source
AI summary
A coaxial cable includes an inner conductor; an insulator covering a circumference of the inner conductor; a shield layer covering a circumference of the insulator; and a sheath covering a circumference of the shield layer. The inner conductor is composed of first metal strands that are twisted each other in such a manner that a cross-sectional shape of the inner conductor is circular. The shield layer includes a winding shield layer including second metal strands spirally wound around the insulator, and a shield tape layer including a shield tape including a resin tape and a metal layer provided on one side of the resin tape, the shield tape being spirally wound around the winding shield layer with the metal layer being located inwardly radially in such a manner that the metal layer is being in contact with the winding shield layer. The winding shield layer has a gap in at least one location between the second metal strands adjacent to each other in a circumferential direction, and a sum of distances w between the second metal strands adjacent to each other via the gap is not more than an outer diameter d of the second metal strand in a cross-section perpendicular to a longitudinal direction.