Substrate Slot Ground Plane Impedance Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-frequency strip lines in miniaturized components face limitations in achieving desired impedance due to constraints in signal conductor width and distance from ground planes, especially when using symmetric strip lines for isolation, which restricts the ability to reach standard impedances like 50 Ω.
Innovation Solution
A substrate with a multiple-layer construction featuring a signal conductor between two ground planes, where at least one ground plane has a slot following the signal conductor's profile, allowing for adjustable capacitance and increased impedance without significantly reducing isolation, with the slot width setting the capacitance and maintaining constant impedance across the line's length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the width of the strip-shaped signal conductor is reduced or the distance from the closest ground plane is increased to raise impedance, then the impedance increases, but the substrate thickness limits the maximum distance and technology limits the minimum conductor width
Solution Approach 1:
The ground plane is segmented by introducing slots that divide the continuous ground plane into separate regions. This segmentation reduces the capacitive coupling between the signal conductor and the ground plane, thereby increasing the characteristic impedance of the strip line without requiring changes to the conductor width or substrate thickness.
Solution Approach 2:
The slot width is specifically optimized to achieve the desired impedance value. By controlling the local geometry of the slot (its width and position), the capacitive constant is adjusted locally, enabling precise impedance control while maintaining the overall substrate dimensions and conductor width within technological limits.
2Object-affected harmful factors
If symmetric strip lines are used to improve isolation, then isolation improves, but the ability to achieve desired standard impedance values deteriorates
Solution Approach 1:
The symmetric strip line structure is modified by introducing asymmetric slots in the ground planes. This creates an asymmetric field distribution that reduces capacitive coupling while maintaining the isolation benefits of the symmetric configuration. The slots break the symmetry in a controlled manner to achieve the desired impedance without compromising isolation.
Solution Approach 2:
Instead of adjusting impedance by changing the conductor width (one dimension) or distance to ground plane (another dimension), the invention introduces slots that affect the electromagnetic field distribution in a different dimensional aspect, providing an additional degree of freedom for impedance control while preserving the isolation characteristics.
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 the achievement of desired impedance values while maintaining isolation, allowing for efficient high-frequency signal transmission in miniaturized components, with the slot width and conductor width optimized to match the characteristic impedance of 50 Ω, and supports complex wiring and component integration in high-frequency modules.
Implementation Method 1
The impedance of each strip line is determined by a capacitive and an inductive transmission-line constant. The capacitance can be set in a simple way by means of the width of the slot.
Data Source
AI summary
A substrate with an HF-compatible line arranged in this substrate will be proposed that is formed similar to a tri-plate strip line in which, however, at least one of the ground planes has a slot that follows the profile of the signal line arranged between two ground planes. With the aid of this slot, the capacitive constant of the line can be lowered and thus the impedance of the line can be increased.