PCB Air Openings for Connector Impedance Control
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Solution Overview
Problem
High-speed communications systems face challenges with crosstalk, return loss, and insertion loss due to the design constraints of RJ-45 plugs and jacks, particularly at higher frequencies, where maintaining impedance matching and minimizing crosstalk becomes difficult.
Innovation Solution
The use of printed circuit boards with air-filled openings between conductive paths to adjust the impedance of differential transmission lines, allowing for improved return loss and insertion loss performance without significantly impacting crosstalk, by varying the dielectric constant and modifying the geometry of the transmission lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional RJ-45 plug and jack designs are used, then manufacturing simplicity and standardization are maintained, but return loss and insertion loss performance deteriorate at higher frequencies
Solution Approach 1:
The patent applies local quality by introducing air-filled openings at specific locations between conductive paths on the printed circuit board. These openings are strategically positioned in regions where impedance control is most critical, allowing the dielectric structure to have varying properties (solid dielectric material in most areas, air in specific regions) to optimize return loss performance without requiring complete structural redesign of the entire connector.
Solution Approach 2:
The patent employs parameter changes by modifying the dielectric constant distribution through the introduction of air-filled openings. The air regions (dielectric constant ≈1) create zones of lower effective dielectric constant compared to the solid dielectric material, thereby adjusting the characteristic impedance of transmission lines to achieve better return loss performance at higher frequencies while maintaining standard connector dimensions.
2Reliability
If air-filled openings are added to adjust impedance, then return loss performance improves, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by incorporating the air-filled openings into the printed circuit board fabrication process itself, rather than adding them as separate post-processing steps. The openings are created during the standard PCB manufacturing process (through-hole drilling and plating stages), allowing the dielectric structure to be prepared in advance with the correct impedance characteristics before assembly into the connector.
3Manufacturing precision
If the dielectric structure is modified with openings, then impedance control improves, but structural simplicity deteriorates
Solution Approach 1:
The patent applies composite materials by combining the solid dielectric material with air-filled regions to create a composite dielectric structure. This composite approach allows precise control of effective dielectric constant and characteristic impedance by adjusting the size, shape, and distribution of air openings, achieving superior impedance control precision while maintaining a relatively simple overall structure that integrates with standard PCB fabrication techniques.
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 approach enables communications connectors to meet performance requirements for crosstalk, return loss, and insertion loss, even at higher frequencies, by decoupling these parameters and allowing for individual optimization of each, thus enhancing the overall performance of the connectors.
Implementation Method 1
The dielectric substrate includes an opening that is positioned between the conductive paths of the first pair of conductive paths, the opening containing a second insulative material having a second dielectric constant that is different than the first dielectric constant
Data Source
AI summary
Printed circuit boards for communications connectors are provided that include a dielectric substrate formed of a first insulative material having a first dielectric constant. First and second pairs of input terminals and first and second pairs of output terminals are provided on the dielectric substrate. A first differential transmission line electrically connect the first pair of input terminals to the first pair of output terminals, and a second differential transmission line electrically connect the second pair of input terminals to the second pair of output terminals. The dielectric substrate includes an opening that is positioned between the conductive paths of the first differential transmission line, the opening containing a second insulative material having a second dielectric constant.