Flat Cable Impedance Stabilization via Asymmetric Ground Openings
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Solution Overview
Problem
Conventional high-frequency signal lines with stripline structures experience fluctuations in characteristic impedance when attached to metallic objects due to capacitance issues between the signal line and ground conductors, leading to instability in signal transmission.
Innovation Solution
A flat cable design featuring a dielectric element assembly with a signal line positioned between two ground conductors, where the first ground conductor is farther from the signal line and has larger openings than the second, creating a triplate stripline structure that alternates between high and low capacitance regions to stabilize impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If openings are provided in both ground conductors to reduce capacitance and thin the cable, then cable thickness is reduced, but characteristic impedance fluctuates when attached to metallic objects
Solution Approach 1:
The patent applies local quality by making the openings in the first and second ground conductors different in size. Specifically, the openings in the first ground conductor are larger than those in the second ground conductor. This creates asymmetric capacitance distribution that compensates for external capacitance variations when attached to metallic objects, thereby stabilizing characteristic impedance while maintaining reduced cable thickness.
Solution Approach 2:
The patent changes the parameter of opening size between the two ground conductors. By varying the opening dimensions (larger in first ground conductor, smaller in second), the capacitance characteristics are modified to achieve impedance stability. This parameter variation allows the cable to maintain consistent electrical performance despite external environmental changes.
2Length of moving object
If openings are provided in ground conductors to reduce capacitance, then distance between signal line and ground conductors can be reduced, but impedance stability deteriorates when attached to metallic objects
Solution Approach 1:
The patent applies local quality by creating asymmetric opening patterns in the two ground conductors. The first ground conductor has larger openings while the second has smaller openings, both at reduced distances from the signal line. This localized differentiation in opening size compensates for the reduced distance effect, maintaining impedance stability even when attached to metallic objects.
3Ease of manufacture
If symmetric openings are provided in both ground conductors, then manufacturing is simplified, but impedance stability worsens when attached to metallic objects
Solution Approach 1:
The patent deliberately introduces asymmetry between the two ground conductors by providing different opening sizes. The first ground conductor has larger openings while the second has smaller openings. This asymmetric design breaks the symmetry that would otherwise cause impedance fluctuations when attached to metallic objects, thereby improving reliability while remaining manufacturable.
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 stabilizes the characteristic impedance of the signal line, reducing fluctuations and maintaining a consistent impedance value, while also allowing for a thinner cable configuration and reduced insertion loss.
Implementation Method 1
there is some capacitance created between the signal line and the battery pack, resulting in fluctuations in the characteristic impedance of the signal line
Data Source
AI summary
A flat cable includes a dielectric element assembly including a plurality of dielectric layers laminated on each other, a linear signal line provided in the dielectric element assembly, a first ground conductor provided on one side in a direction of lamination relative to the signal line and including a plurality of first openings arranged along the signal line, and a second ground conductor provided on the other side in the direction of lamination relative to the signal line and including a plurality of second openings arranged along the signal line. The first ground conductor is more distant from the signal line in the direction of lamination than is the second ground conductor. The first openings are larger than the second openings.