Via-less Patterned Ground Common-mode Filter for Compact PCBs
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Solution Overview
Problem
Existing common-mode noise filters that use vias consume space on PCBs and are impractical for smaller boards, and surface-mounted filters increase cost and size while having limited bandwidth, making them unsuitable for compact electronic devices.
Innovation Solution
The development of via-less common-mode filters integrated into the PCB structure, which do not require electrical connections to a shield layer and are designed to suppress common-mode noise without affecting differential-mode signal transfer, using patterns etched into the ground plane to provide frequency-selective filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If via-based common-mode filters are used, then common-mode noise suppression is improved, but PCB space consumption increases
Solution Approach 1:
The patent extracts the common-mode filter functionality from the traditional via-based implementation and integrates it directly into the ground plane structure. The filter is formed by etching conductive traces and gaps into the ground plane itself, removing the need for separate via structures while maintaining the noise suppression function.
Solution Approach 2:
The patent merges the common-mode filter with the ground plane structure, combining two previously separate elements (filter and ground plane) into a single integrated structure. The filter traces are formed within the ground plane layer, eliminating the need for additional components and reducing PCB space.
2Object-affected harmful factors
If surface-mounted common-mode filters are used, then common-mode noise suppression is improved, but device size and cost increase
Solution Approach 1:
The ground plane structure serves dual purposes: it provides the reference ground for differential signals and simultaneously functions as the common-mode filter. This self-service approach eliminates the need for separate surface-mounted filter components, reducing device complexity and cost.
Solution Approach 2:
The ground plane is designed to perform multiple functions simultaneously: it serves as the reference ground for differential signaling and as the common-mode filter structure. This multi-functionality eliminates the need for additional dedicated filter components.
3Object-affected harmful factors
If traditional via-based filters are used, then common-mode filtering is achieved, but manufacturing complexity increases
Solution Approach 1:
The patent removes the via structures from the filter implementation, extracting the filtering function and implementing it using only planar etched traces in the ground plane. This eliminates the complex multi-step via formation process while maintaining filtering effectiveness.
Data Source
AI summary
Disclosed herein are multi-layer metal circuits, such as printed circuit boards (PCBs), with single-sided, partially-shielded, or fully-shielded via-less common-mode filters. The multi-layer metal circuits comprise at least one shield layer, at least one signal trace, and at least one reference layer (e.g., ground). The reference layer comprises a pattern of the via-less common-mode filter. The pattern may comprise, for example, a single piece-wise linear segment, or two or more disjoint and non-intersecting segments (which may be strictly linear or piece-wise linear). The reference layer is electrically isolated from the shield layer, and thus the via-less common-mode filters do not require vias. In addition to being used in PCBs, the disclosed multi-layer metal circuits may also be used in other applications, such as integrated circuits (e.g., implemented in semiconductor chips).