Stranded Coaxial Cable Geometry for Low Skew and Bend Resistance
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Solution Overview
Problem
Coaxial cables face challenges in achieving reduced skew variation and excellent bending resistance to accommodate increasing data transfer rates and frequency bands, as conventional designs struggle to meet the required transmission speeds and frequency bands, especially in high-speed applications like Thunderbolt 3, where the skew needs to be less than 10 ps/m.
Innovation Solution
A coaxial cable design featuring an inner conductor with one center wire and six outer wires, an insulator, and a shield conductor, where specific area ratios between the conductor, insulator, and gaps are optimized to reduce electrostatic capacitance and skew variation, along with a silver-plated soft copper wire material and a spiral shield conductor for enhanced flexibility and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional coaxial cable designs are used, then manufacturing is simpler, but skew variation exceeds the required threshold of 10 ps/m for high-speed applications
Solution Approach 1:
The inner conductor is segmented into one center wire and six outer wires arranged in a specific configuration. This segmentation allows precise control of the conductor geometry to achieve the target gap area ratios, thereby controlling electrostatic capacitance and skew variation within the required 10 ps/m threshold while maintaining manufacturability
Solution Approach 2:
The patent applies local quality by specifying different gap area ratios for different regions: the first region (gap between center wire and outer wires) is controlled at 0.5-2.0% and the second region (gap between outer wires and insulator) at 2.0-5.0%. This localized control of geometric parameters enables precise skew variation control without requiring complete redesign of the entire cable structure
2Manufacturing precision
If the cable is made more rigid to reduce skew variation, then transmission precision improves, but bending resistance deteriorates
Solution Approach 1:
The patent changes the geometric parameters of the inner conductor, specifically controlling the gap area ratios between conductor elements and the insulator. By optimizing these parameters to specific ranges (first region: 0.5-2.0%, second region: 2.0-5.0%), the design achieves reduced skew variation while maintaining flexibility for bending, as the optimized geometry allows both precision and flexibility
3Speed
If the gap area between conductor and insulator is reduced to lower electrostatic capacitance, then skew decreases, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies parameter changes by defining specific target ranges for gap area ratios rather than requiring minimal gaps. The first region gap ratio is set at 0.5-2.0% and the second region at 2.0-5.0%, which reduces electrostatic capacitance for high-speed data transfer while establishing achievable manufacturing precision targets that balance performance with manufacturability
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 optimized design achieves a skew variation of 7.5 ps/m or less and demonstrates excellent bending resistance, with the coaxial cables able to withstand multiple bends, addressing the need for improved performance in high-speed data transmission.
Implementation Method 1
a ratio of a total area of first regions which are respectively formed by a gap between the center wire and two adjacent outer wires, with respect to an area of a circumscribed circle of the inner conductor, is 0.5% or higher and 2.0% or lower, and a ratio of a total area of second regions which are respectively formed by a gap between surfaces of the two adjacent outer wires and a surface of the insulator
Data Source
AI summary
A coaxial cable includes an inner conductor having one center wire, and six outer wires stranded around the center wire, an insulator covering an outer periphery of the inner conductor, and a shield conductor covering an outer periphery of the insulator, wherein, in a cross section perpendicular to a longitudinal direction of the coaxial cable, a ratio of a total area of first regions which are respectively formed by a gap between the center wire and two adjacent outer wires, with respect to an area of a circumscribed circle of the inner conductor, is 0.5% or higher and 2.0% or lower, and a ratio of a total area of second regions which are respectively formed by a gap between surfaces of the two adjacent outer wires and a surface of the insulator, with respect to the area of the circumscribed circle of the inner conductor, is 2.0% or higher and 5.0% or lower.