Stair-Like High-Speed Feedthrough for Resonance-Free 3D Signal Transmission
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Solution Overview
Problem
Existing high-speed feedthroughs face challenges in providing compact, broadband, resonance-free transmission with minimal inter-channel cross-talk and small reflection when accommodating vertical and horizontal displacements between terminals that are comparable to or longer than half of the shortest wavelength, especially in high-frequency applications above 10 GHz.
Innovation Solution
A compact broadband multi-layer non-coplanar high-speed feedthrough design featuring a stairs-like sequence of alternating horizontal and vertical conductors spanning the displacement between terminals, optimized as a 3-dimensional structure, allowing for lengths and heights of conductors that deviate from standard impedance requirements, thereby accommodating significant vertical and horizontal displacements without resonance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single vertical via is used to span the displacement, then the structure is simplified, but resonance and excessive cross-talk occur when the vertical length is comparable with or longer than half of the effective wavelength
Solution Approach 1:
The single vertical via is segmented into multiple shorter vertical vias separated by horizontal conductors. Each vertical via has a height less than one quarter of the effective wavelength, preventing resonance. The horizontal conductors connect these vertical segments, forming a stairs-like transmission line that maintains signal integrity while accommodating large vertical displacements.
Solution Approach 2:
The transmission line transitions from a purely vertical path to a three-dimensional stairs-like structure with both vertical and horizontal segments. This dimensional change allows the transmission line to span large vertical displacements while keeping each individual vertical segment electrically short, avoiding resonance issues.
2Ease of manufacture
If coplanar transmission lines are used, then manufacturing is simplified, but vertical displacement between terminals cannot be accommodated
Solution Approach 1:
The transmission line extends from the coplanar two-dimensional plane into the third vertical dimension, creating a non-coplanar stairs-like structure. This allows the transmission line to accommodate both horizontal and vertical displacements between terminals while maintaining manufacturability through standardized multi-layer substrate fabrication processes.
Solution Approach 2:
The transmission path is segmented into alternating horizontal and vertical conductors distributed across multiple substrate layers. Each segment is electrically short, and the segments are connected through vias, creating a modular structure that is easier to manufacture than a single long via while accommodating three-dimensional displacements.
3Length of stationary object
If the vertical length of the via is made comparable with or longer than half of the effective wavelength, then the displacement is accommodated, but resonance and excessive cross-talk occur
Solution Approach 1:
The total vertical displacement is accommodated by multiple shorter vertical via segments rather than a single long via. Each vertical via has a height less than one quarter of the effective wavelength, ensuring that no single vertical segment is long enough to resonate, while the cumulative effect of multiple segments spans the required vertical distance.
Solution Approach 2:
The transmission line uses a combination of vertical and horizontal segments in a stairs-like configuration. This allows the overall vertical displacement to be large while each individual vertical segment remains electrically short, preventing resonance while still accommodating the required displacement.
4Length of stationary object
If many ceramic layers are used to span horizontal displacement with small via diameter, then vertical displacement is accommodated, but the structure becomes non-compact and manufacturing complexity increases
Solution Approach 1:
The transmission line uses a moderate number of substrate layers with alternating horizontal and vertical conductors. The horizontal conductors provide lateral displacement accommodation within each layer, reducing the need for excessive layer stacking. This segmented approach achieves the required vertical displacement with fewer layers and less stringent positioning requirements.
Solution Approach 2:
The transmission line utilizes both horizontal and vertical dimensions in a stairs-like configuration. Horizontal conductors accommodate lateral displacement within layers, while vertical vias provide vertical connectivity between layers. This three-dimensional approach reduces the number of layers needed compared to purely vertical via stacking, simplifying manufacturing.
Data Source
AI summary
A high-speed feedthrough (HSFT) is disclosed for transmitting a signal having a highest frequency of at least 10 GHz between first and second locations separated by a vertical distance of at least approximately half of the shortest transmitted wavelength, and separated by a horizontal distance. A substrate structure includes multiple stacked layers. An RF transmission line is connected through the structure between the first and second locations for transmitting the signal. The RF transmission line comprises a series of sequentially connected horizontal conductors having lengths less than half of the effective wavelength and vertical conductors having heights less than one quarter of the effective wavelength, thereby spanning the horizontal and vertical distance between the two locations in a stairs-like shape through the structure's layers. Each conductor's geometry may deviate from standard 50 ohm buried strip lines and is optimized for complete 3-dimensional structure.