Multilayer Substrate Feed Structure for Patch Antenna Impedance Matching
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Solution Overview
Problem
The mismatch in characteristic impedance between the patch antenna and the feed line in existing multilayer substrates leads to inefficiencies.
Innovation Solution
A multilayer substrate design with specific conductor layer configurations, including a radiation conductor layer, signal conductor layer, and inter-layer connection conductors, which are arranged to minimize impedance mismatch through strategic use of connection portions, intermediate portions, and ground conductor layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple feed line structure is used to connect the patch antenna, then the device complexity is reduced, but the characteristic impedance mismatch between the patch antenna and feed line occurs
Solution Approach 1:
The feed line is segmented into multiple functional portions: a first connection portion connected to the patch antenna, a second connection portion connected to the signal line, a transmission line portion connecting the two, and first and second intermediate portions. This segmentation allows each portion to be optimized for its specific function, achieving impedance matching while maintaining a manageable structure.
Solution Approach 2:
Different portions of the feed line are designed with different local characteristics. The first intermediate portion has a width greater than the transmission line portion to provide impedance transformation, while the second intermediate portion has a width greater than the transmission line portion for similar purposes. This local variation in geometry enables impedance matching without requiring a completely different structure.
2Manufacturing precision
If the connection conductor layer uses uniform width throughout, then the manufacturing precision is simplified, but the characteristic impedance mismatch between signal conductor layer and radiation conductor layer occurs
Solution Approach 1:
The connection conductor layer features local variations in width at specific portions. The first intermediate portion has a width greater than the transmission line portion, and the second intermediate portion also has a width greater than the transmission line portion. These localized dimensional changes are designed to transform impedance while the rest of the structure maintains consistent dimensions for ease of manufacturing.
Solution Approach 2:
The width parameter of the connection conductor layer is changed at specific locations to achieve impedance transformation. By varying the width of the intermediate portions relative to the transmission line portion, the characteristic impedance is adjusted to match between the patch antenna and the signal line, while other parameters remain constant.
3Device complexity
If a direct connection between radiation conductor layer and signal conductor layer is made, then the device complexity is reduced, but the bandwidth is limited due to impedance mismatch
Solution Approach 1:
The connection structure is divided into multiple segments including connection portions, intermediate portions, and a transmission line portion. This segmentation enables gradual impedance transformation across the connection path, which broadens the bandwidth by reducing reflections and improving signal transmission across a wider frequency range.
Solution Approach 2:
The feed line connection is extended into the Z-axis dimension by routing it through multiple layers. The first inter-layer connection conductor pierces through the intermediate insulator layer to connect the radiation conductor layer and signal conductor layer, creating a three-dimensional connection path that enables impedance matching while maintaining a compact planar footprint.
Data Source
AI summary
A maximum width of a second connection portion in a line width direction is smaller than a maximum width of a first connection portion in the line width direction. A first intermediate portion includes a first thick-line portion of which the width is greater than that of a transmission line portion in the line width direction. A second intermediate portion includes a second thick-line portion of which the width is greater than that of a transmission line portion in the line width direction. The first thick-line portion and the second thick-line portion adjoin the transmission line portion.