PCB Ground Plane Pattern for Signal Trace Impedance Control
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Solution Overview
Problem
Printed circuit boards with patterned ground planes face impedance variations and signal reflections due to directional changes in circuit traces, which existing technologies fail to consistently manage, leading to unwanted signal distortions.
Innovation Solution
Varying characteristics of the ground plane pattern, such as shape, material, and thickness, in regions where circuit traces change direction to maintain consistent impedance along the trace, including using a rectangular grid pattern that adjusts its orientation and density to match the trace's geometry, and varying the circuit trace's width and material to compensate for impedance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If a patterned ground plane is used in PCB, then weight and complexity are reduced, but impedance variations and signal reflections occur due to directional changes in circuit traces
Solution Approach 1:
The ground plane pattern transitions from a uniform structure to a non-uniform structure where the pattern characteristics (such as grid density, shape, or orientation) are locally adjusted in regions where circuit traces change direction. This local modification maintains consistent impedance along the trace while still using a patterned ground plane, thus reducing weight compared to solid ground planes while preventing signal reflections.
2Reliability
If the ground plane pattern is varied to maintain consistent impedance, then signal transmission reliability improves, but manufacturing complexity increases
Solution Approach 1:
The ground plane is divided into multiple regions with different pattern characteristics. Each region is segmented according to the directional changes of circuit traces, allowing impedance consistency to be maintained through discrete pattern variations rather than continuous complex patterns. This segmentation approach manages manufacturing complexity by creating distinct, manageable zones.
3Reliability
If circuit trace width and material are varied to compensate for impedance changes, then impedance consistency is maintained, but manufacturing precision requirements increase
Solution Approach 1:
Instead of varying circuit trace width and material throughout the board, the invention applies local quality changes to the ground plane pattern while keeping the circuit traces relatively uniform. This approach maintains impedance consistency through ground plane modifications rather than trace modifications, thereby reducing the manufacturing precision requirements for trace dimensions while still achieving reliable signal transmission.
Data Source
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AI summary
Embodiments are disclosed for a printed circuit board 200. An example printed circuit board includes a ground plane 202 comprising a pattern of an electrically conductive material. The example printed circuit board further includes a circuit trace 204 disposed adjacent to the ground plane, where one or more characteristics of one or more of the pattern of the electrically conductive material in the ground plane and the circuit trace vary based upon a directional change of the circuit trace.