Defected Ground Structure EMI Suppression in PCB
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Solution Overview
Problem
Existing solutions fail to effectively contain electromagnetic interference (EMI) radiation from circuit boards, particularly at high frequencies, as elements like plated vias and ground vias act as antennas, radiating EMI outward, and current methods like discrete EMI chokes and mechanical shielding are inadequate for modern communication frequencies or increase device heating and production costs.
Innovation Solution
A defected ground structure is fabricated within the circuit board's ground layer, with a specific size, shape, and location relative to EMI-radiating elements to suppress EMI propagation from differential signal lines, minimizing radiation from these elements at selected resonant frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If discrete EMI chokes are used to suppress EMI radiation, then EMI suppression is improved, but frequency suitability deteriorates at high frequencies
Solution Approach 1:
The patent changes the physical parameters of the ground structure by creating defected ground structures with specific geometries (slots, holes, or missing sections) rather than using discrete EMI chokes. This structural modification allows the ground plane itself to suppress EMI across a broad frequency range, including high frequencies where discrete chokes fail to provide effective suppression.
2Reliability
If mechanical shielding is used to contain EMI, then EMI suppression is improved, but device heating increases
Solution Approach 1:
The patent extracts the EMI suppression function from separate mechanical shielding components and integrates it directly into the ground structure itself. The defected ground structures perform both grounding and EMI suppression functions, eliminating the need for additional shielding materials that would trap heat and cause device heating.
3Reliability
If mechanical shielding is used to contain EMI, then EMI suppression is improved, but production costs increase
Solution Approach 1:
The patent merges the EMI suppression function with the existing ground structure of the circuit board. By integrating defected ground structures into the PCB layout during manufacturing, the solution eliminates the need for separate shielding components, assembly steps, and additional materials, thereby reducing production costs while maintaining EMI suppression effectiveness.
4Reliability
If plated vias and ground vias are used to connect layers, then electrical connectivity is improved, but EMI radiation increases
Solution Approach 1:
The patent applies local quality modification by creating defected ground structures at specific locations around plated vias and ground vias. These localized defected regions act as EMI suppression zones that contain and redirect electromagnetic fields, allowing the vias to maintain their electrical connectivity function while preventing them from acting as unintentional antennas that radiate EMI.
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 defected ground structure effectively contains EMI within the circuit board, reducing radiation from vias and other antennas, thereby enhancing EMI suppression without the limitations of existing methods, such as frequency suitability or increased costs.
Implementation Method 1
the defected ground layer has a non-periodic shape to suppress the EMI propagated by the signal lines to minimize the EMI that the element radiates outwards
Data Source
AI summary
A multiple-layer circuit board has a signaling layer, an exterior layer, and a ground layer. A pair of differential signal lines implemented as strip lines are within the signaling layer, and propagate electromagnetic interference (EMI) along the signaling layer. An element conductively extends inwards from the exterior layer, and as an antenna radiates the EMI propagated by the strip lines along the signaling layer outwards from the circuit board. A defected ground structure within the ground layer has a size, shape, and a location in relation to the element to suppress the EMI propagated by the strip lines to minimize the EMI that the element radiates outwards as the antenna.