Shielded Cable Ground Return Structure Without Drain Wires
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Solution Overview
Problem
Existing shielded and grounded cables require separate electrical drain wires for grounding, which is inefficient and has drawbacks.
Innovation Solution
A multi-layered, shielded and grounded cable design with overlapping conductive layers forming a direct galvanic contact to create a ground return path, eliminating the need for traditional drain wires, using materials like copper and aluminum for the outer and inner conductive layers, respectively, and applying the shield at an angle exceeding 360 degrees for direct electrical connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate electrical drain wires are used for grounding shielded cables, then grounding is achieved, but cable complexity and manufacturing difficulty increase
Solution Approach 1:
The patent merges the grounding function into the shield structure itself by making the shield layers conductive and overlapping. The outer and inner shield layers are bonded together to form a continuous conductive path that serves both as electromagnetic shielding and as the ground return path, eliminating the need for separate drain wires.
Solution Approach 2:
The shield layers are designed to perform multiple functions simultaneously: they provide electromagnetic shielding against interference and serve as the ground return path for signal currents. This multi-functionality is achieved by making the shield layers conductive and creating direct electrical contact between overlapping layers through bonding or galvanic contact.
2Reliability
If traditional drain wire grounding is used, then grounding path is established, but inductance increases and high frequency performance degrades
Solution Approach 1:
The grounding path is segmented into multiple parallel conductive paths through the overlapping shield layers. This segmentation reduces the overall inductance by providing multiple return paths for the current, thereby improving high-frequency performance and reducing signal loss.
Solution Approach 2:
The patent transitions from a single-wire grounding path to a multi-layered planar grounding structure. The overlapping shield layers create a two-dimensional ground return path that reduces inductance and improves high-frequency performance compared to traditional linear drain wire configurations.
3Reliability
If dissimilar metals are used in shield layers, then galvanic contact is improved, but material complexity increases
Solution Approach 1:
The patent employs composite material construction with dissimilar metals (such as copper and aluminum) in different shield layers. This combination leverages the advantageous properties of each material - copper for excellent conductivity and aluminum for lightweight and corrosion resistance - while achieving reliable galvanic contact through proper bonding or overlapping design.
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 provides effective electromagnetic shielding and grounding without separate drain wires, reducing inductance and preventing grounding path degradation at high frequencies, while allowing direct current flow for efficient signal protection.
Implementation Method 1
The one or more outer conductive layers and one or more inner conductive layers may be configured to make direct galvanic contact over an overlapped portion of the shield to form the ground return path
Implementation Method 2
an electromagnetic shield comprising at least (i) one or more outer conductive shield layers, (ii) one or more inner insulating layers and (iii) one or more inner conductive shield layers
Data Source
AI summary
Assemblies for terminating shielded cables to printed circuit boards are described. An example assembly includes a printed circuit board (PCB), a cable having a signal conductor and a shield layer surrounding the signal conductor, and a conductive strap. The conductive strap includes a top conductive element, a bottom conductive element, and a plurality of legs between the top conductive element and the bottom conductive element. The top conductive element includes a top notch, and the bottom conductive element includes a bottom notch. The assembly also includes a top solder element positioned between the top notch and the shield layer of the cable and a bottom solder element positioned between the bottom notch and the PCB.