Controlled-Impedance Cable Termination With Expansion Compensation
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Solution Overview
Problem
Current controlled-impedance cable terminations face issues with impedance mismatches due to cable expansion and contraction, leading to high-frequency attenuation and difficulty in maintaining consistent electrical length, especially under thermal and flexural excursions, which affects the density and precision of connections.
Innovation Solution
The use of compliant electrical contacts and an expansion/contraction compensator (ECC) provides an interface between controlled-impedance cables and devices, accommodating expansion and contraction through adjustable parameters and various coupling methods, ensuring consistent impedance matching and maintaining electrical contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional controlled-impedance connectors (SMA, PCB soldering) are used for cable termination, then impedance matching is achieved, but impedance mismatches cause high-frequency attenuation at the interface between cable and connector/PCB
Solution Approach 1:
The patent introduces an intermediary impedance transformation structure between the cable and the connector/PCB interface. This intermediary structure acts as a mediator that gradually transforms the impedance from the cable characteristic impedance to the connector/PCB impedance, avoiding abrupt impedance discontinuities that cause high-frequency attenuation. The intermediary structure includes tapered sections or transformation layers that smoothly transition the electrical characteristics.
2Strength
If cable terminations require through holes in PCB for mounting, then mechanical connection is achieved, but it becomes difficult to design the best possible controlled impedance environment and decreases connection density
Solution Approach 1:
The patent segments the cable termination function into separate modular components: a cable adapter or transition piece that provides the mechanical connection and impedance transformation, and a separate PCB interface. This segmentation eliminates the need for through-holes in the PCB for cable mounting, as the mechanical connection is established in the cable adapter component. The PCB interface can then be optimized for controlled impedance without the constraints of through-hole mounting, thereby reducing design complexity and increasing connection density.
3Adaptability or versatility
If cables are subjected to temperature excursions and flexure over time, then mechanical flexibility is achieved, but expansion and contraction of the signal conductor and insulator cause inconsistent electrical length
Solution Approach 1:
The patent employs materials and structures with controlled thermal expansion parameters to compensate for cable expansion and contraction. The connector housing or mounting structure is designed with materials having specific thermal expansion coefficients that match or compensate for the cable materials. Additionally, the patent may include compensation mechanisms such as bellows, flexible sections, or adjustable mounting features that maintain consistent electrical length despite thermal excursions and flexure by allowing controlled physical parameter changes in non-critical dimensions.
4Reliability
If compliant contacts are used for cable termination, then electrical connection is achieved, but planarity of the cable center conductor and ground shield becomes difficult to maintain through flexure or thermal excursions
Solution Approach 1:
The patent employs counteracting structural features that compensate for the loss of planarity caused by compliant contact deformation. This may include pre-loaded spring elements, counter-balancing mechanical features, or rigid support structures positioned to offset the deformation of compliant contacts. The counterweight principle here refers to using opposing mechanical forces or structural constraints to balance out the deformation, maintaining the overall planarity and alignment of the center conductor and ground shield despite the compliance of the contact elements.
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
This solution minimizes impedance mismatches, enhances the usability of cables in high-frequency ranges, and improves connection density and precision by compensating for cable expansion and contraction, thereby maintaining consistent electrical length and impedance.
Implementation Method 1
The cables may need to be very precise and have a consistent electrical length in order to be useful in certain applications. The electrical length refers to the amount of time it would take an electrical signal to propagate the entire length of a cable. It is important that the electrical length be held consistent cable to cable through several flexure cycles or thermal excursions.
Implementation Method 2
The present invention employs compliant electrical contacts 12, 14 and an expansion/contraction compensator (ECC) 16 to provide an interface between the controlled-impedance cable and another device. The ECC is installed on the cable and in a cable through hole in the anchor block.
Data Source
AI summary
A controlled-impedance cable termination that minimizes the effects of cable expansion and contraction on impedance matching. The terminator has an anchor block, an expansion/contraction compensator (ECC) attached to the cable, a compliant signal contact for making the electrical connection between the cable center conductor and the electrical device. The ECC has an electrically-conductive ferrule with a bore. The ferrule bore may be formed in the anchor block instead of in a separate ferrule. The cable shield is attached at the bore. A solid dielectric insert fits into the ferrule bore. An electrically-conductive center pin fits into a bore in the dielectric insert and has a bore that accepts the center conductor such that the center conductor can expand and contracting while maintaining electrical contact with the center pin. A plate abuts the anchor block face and holds the compliant contacts through apertures.