Cable Termination Ground Structure for Low-Crosstalk Connectors
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Solution Overview
Problem
Existing cable terminations experience issues with signal integrity due to non-uniformities in signal conductor, dielectric, and conductive layer, leading to increased insertion loss and crosstalk, particularly in high-frequency applications.
Innovation Solution
A conductive structure with tabs is used to provide individual ground paths for each cable, connecting the shield to the PCB ground structure, reducing crosstalk and maintaining signal integrity by minimizing impedance discontinuities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a shared ground path is used for multiple cables, then device complexity is reduced, but crosstalk between cables increases
Solution Approach 1:
The ground path is segmented into individual separate ground paths for each cable, rather than using a shared ground path. Each cable has its own dedicated ground connection that extends from the cable shield along the entire length of the cable to the connector, preventing ground loops and reducing crosstalk between adjacent cables.
2Ease of manufacture
If the conductive layer is removed at the cable end, then ease of termination is improved, but impedance discontinuity increases
Solution Approach 1:
The conductive layer is extended beyond the dielectric material at the cable end before termination. This preliminary extension allows the conductive layer to be properly positioned and connected to the connector ground structure, maintaining impedance continuity and reducing reflections during the termination process.
3Object-generated harmful factors
If individual ground paths are provided for each cable, then crosstalk is reduced, but device complexity and manufacturing difficulty increase
Solution Approach 1:
While individual ground paths are provided for each cable, the ground structure within each connector is merged into a common ground plane that is electrically connected to all individual cable grounds. This combines multiple ground paths at the connector level, simplifying the overall structure while maintaining the benefits of separate ground paths along the cable length.
Data Source
AI summary
A cable assembly comprising a connector with a termination that enables high density and high signal integrity. Shields of cables are terminated to a paddle card via a conductive structure attached to a surface of the paddle card. The signal conductors of the cables are terminated to pads on the paddle card that are exposed within openings of the conductive structure. Such a structure creates a ground structure per cable that provides low insertion loss and low crosstalk, even when multiple cables are aligned side by side and terminated in one or more rows. The cables may be drainless, enabling a large number of cables, such as eight cables, to be packed within the width of a paddle card specified in high density standards such as QSFP-DD or OSFP. The cables may nonetheless have large diameter signal conductors, enabling 2.5 or 3 meter assemblies with less than 17 dB insertion loss.