High-Frequency Signal Transmission Line Impedance Control
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Solution Overview
Problem
Conventional high-frequency signal transmission lines experience significant low-frequency noise due to impedance mismatches at the ends, leading to reflection and standing waves, which affect signal integrity and noise radiation.
Innovation Solution
A high-frequency signal transmission line design featuring alternating line portions with different impedances and strategically positioned ground conductors, where the line portions are alternately connected across layers and overlaid in a specific pattern to minimize capacitance and impedance mismatches, thereby reducing low-frequency noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the property impedance at end portions is made equal to the line portion, then low-frequency noise is reduced, but the structure becomes more complex with multiple ground conductors and alternating line portions
Solution Approach 1:
The signal line is divided into alternating first line portions and second line portions with different property impedances. This segmentation allows the line to interact with ground conductors at specific intervals, creating impedance transformation effects that reduce low-frequency noise without requiring the entire line structure to be modified.
Solution Approach 2:
Different portions of the signal line are given different local properties (different property impedances). The first line portions have one impedance characteristic while the second line portions have another, allowing localized impedance control to achieve overall noise reduction while maintaining structural feasibility.
2Reliability
If ground conductors are positioned to overlay second line portions but not first line portions, then capacitance is minimized and impedance is stabilized, but manufacturing precision requirements increase
Solution Approach 1:
The arrangement of ground conductors relative to the signal line is intentionally asymmetric. Ground conductors are positioned to overlay only the second line portions in planar view, creating an asymmetric capacitance distribution that stabilizes the overall property impedance by compensating for end-effect variations.
Solution Approach 2:
The alternating second line portions act as intermediaries between the signal source and the ground conductors. These portions are specifically designed to face the ground conductors, mediating the electromagnetic field interaction and providing a controlled capacitance effect that stabilizes impedance without requiring precise alignment of all components.
3Ease of manufacture
If the transmission line structure is simplified, then manufacturing is easier, but low-frequency noise increases due to impedance mismatches at the ends
Solution Approach 1:
The signal line employs a periodic structure with alternating first and second line portions. This periodic arrangement creates a patterned distribution of property impedances that interacts with the ground conductors to reduce low-frequency noise, while the regularity of the pattern maintains manufacturing feasibility through standardized fabrication processes.
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 design effectively reduces low-frequency noise by ensuring consistent impedance across the transmission line, minimizing standing waves, and preventing signal reflection, thus enhancing signal integrity and reducing electromagnetic interference.
Implementation Method 1
capacitance is generated between the first ground conductor and the first line portion, and capacitance is generated between the first ground conductor and the second line portion
Data Source
AI summary
A high-frequency signal transmission line includes a body; a signal line including a first line portion provided to a first layer of the body, a second line portion provided to a second layer of the body alternately being connected; and a first ground conductor provided to the first layer or a third layer positioned on an opposite side of the second layer relative to the first layer, and also overlaid with a plurality of second line portions in planar view from a normal direction of a principal surface of the body, and also not overlaid with a plurality of the first line portions. A property impedance of the first line portion and a property impedance of the second line portion are different from each other.