RF Multilayer Substrate Via Design for VSWR Reduction
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Solution Overview
Problem
The existing radio frequency multilayer substrates face issues with high VSWR due to unnecessary stray capacitance caused by conductor stubs in through-holes connecting strip lines and microstrip lines, which degrades the connection efficiency.
Innovation Solution
A radio frequency multilayer substrate design that includes a through-hole with a conductor connecting the central conductors of strip and microstrip lines, accompanied by an insulating hole formed by cutting and removing the conductor from the surface, ensuring the tip of the insulating hole does not reach the central conductor of the strip line, thereby reducing stray capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a through-hole with conductor is used to connect strip line and microstrip line, then electrical connection is achieved, but unnecessary stray capacitance is generated degrading VSWR
Solution Approach 1:
The patent extracts and removes the harmful portion of the conductor from the through-hole, keeping only the necessary conducting portion that connects the strip line and microstrip line. The unnecessary conductor that extends beyond the dielectric layers and creates stray capacitance is completely removed, while the essential electrical connection function is maintained through the controlled conducting portion within the dielectric layers.
Solution Approach 2:
The through-hole structure is segmented into distinct functional zones: a conducting portion within the dielectric layers that provides electrical connection, and an insulating portion that extends to the surface but contains no conductor. This segmentation separates the useful function (electrical connection) from the harmful function (stray capacitance generation), allowing independent optimization of each zone.
2Reliability
If through-hole penetrates all dielectric layers to connect conductors, then electrical connection is established, but conductor stub is formed causing standing wave
Solution Approach 1:
The patent converts the potentially harmful through-hole structure into a beneficial configuration by carefully controlling where the conductor exists and where it does not. The through-hole itself is not eliminated, but the conductor is strategically placed only where needed for connection, transforming the structure from a source of standing waves into an effective connection mechanism that maintains signal integrity.
Data Source
AI summary
A radio frequency multilayer substrate which has a connection portion connecting a strip line and a microstrip line, of which connection portion improves VSWR, is provided. The high frequency multilayer substrate has a through-hole which electrically connects a central conductor of the strip line and a central conductor of the microstrip line. The high frequency multilayer substrate also has an insulating hole which does not have a conductor inside. The through-hole is connected with the insulating hole. A length of the conductor layer of the through-hole from the central conductor to an insulating hole is smaller than one half the distance from the central conductor to a 2nd ground conductor. The insulating hole can be formed by cutting the through-hole.