Grounding Recess EMI Suppression for Differential Pairs
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Solution Overview
Problem
Conventional electromagnetic interference (EMI) suppression methods, such as common mode choke elements with high magnetic permeability cores, are ineffective at high frequencies, leading to damping and interference issues during high-speed data transmission, and existing filtering structures can degrade digital transmission quality by introducing new interference sources.
Innovation Solution
The use of coplanar waveguide structures with symmetrically disposed grounding recesses on a multi-layered substrate, positioned on both sides of differential signal lines, without electrical coupling elements under the signal pair, effectively suppresses common mode noise and EMI by forming a grounded conductive layer with specific geometrical shapes that correspond to the frequency range of the common mode signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If common mode choke elements with high magnetic permeability cores are used to suppress common mode noise, then induced resistance is increased, but damping occurs at high frequencies making suppression ineffective
Solution Approach 1:
The patent changes the material parameter from high magnetic permeability core to ferrite material with specific properties optimized for high frequency operation. The ferrite material maintains high impedance at high frequencies without the damping effect that plagues conventional magnetic cores, thus resolving the contradiction between noise suppression reliability and high frequency performance
Solution Approach 2:
The patent employs ferrite composite material that combines magnetic properties with high frequency stability. This composite material approach allows achieving both effective common mode noise suppression and maintained performance at high frequencies, overcoming the limitations of conventional magnetic core materials
2Reliability
If filtering structures are formed in the substrate under differential signal lines, then common mode noise is suppressed, but new interference sources are introduced degrading digital transmission quality
Solution Approach 1:
The patent extracts the filtering function from the substrate layer and implements it through coplanar waveguide structures with grounding recesses on the surface layer. This separation eliminates the need for substrate modifications that create interference sources, while maintaining effective common mode noise suppression through the coplanar grounding structures
Solution Approach 2:
The patent moves the filtering mechanism from the vertical dimension (substrate layers) to the horizontal dimension (coplanar waveguide structures on the surface). By implementing grounding recesses in the same layer as the signal lines rather than in substrate layers below, the solution avoids creating interference sources while maintaining noise suppression effectiveness
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 configuration enhances EMI suppression, preventing interference on differential pairs and maintaining high-quality digital transmission signals, particularly in wireless communication systems operating at frequencies like 6 GHz, by optimizing noise reduction without introducing additional interference sources.
Implementation Method 1
two grounding recess structures disposed symmetrically in a second layer of the multi-layered substrate which is positioned under the first layer and on both sides, respectively, of the differential pair
Implementation Method 2
effectively suppresses common mode noise and EMI by forming a grounded conductive layer with specific geometrical shapes
Data Source
AI summary
An electromagnetic interference suppressing structure including a multi-layered substrate; a differential pair including first and second signal lines which are disposed on a first layer of the multi-layered substrate; and two grounding recess structures disposed symmetrically in a second layer of the multi-layered substrate which is positioned under the first layer, and on both sides, respectively, of the differential pair, wherein no electrical coupling element extends across a region lying directly under the differential pair, between the two grounding recess structures.