Pseudo-Coaxial Package Transition for Impedance-Matched RF Routing
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Solution Overview
Problem
Conventional high-frequency signal packages experience mismatched characteristic impedance and signal leakage at the connecting portion between differential coplanar and pseudo coaxial lines, leading to reflection and radiation of high-frequency signals.
Innovation Solution
Forming concave portions in the insulator layer at the connecting points between coplanar and pseudo coaxial lines to reduce electrical capacitance and maintain impedance matching, thereby preventing signal leakage and reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pseudo coaxial line is used to connect differential coplanar lines through the substrate, then high-frequency signal transmission is enabled, but characteristic impedance mismatching occurs at the connecting portion causing signal reflection and radiation
Solution Approach 1:
The patent applies local quality by forming a concave portion specifically at the connecting portion between the coplanar line and pseudo coaxial line. This local structural modification changes the electrical capacitance distribution only where needed (at the connection interface) without altering the overall line structure, thereby achieving impedance matching at the critical interface while maintaining the integrity of the entire signal transmission path
Solution Approach 2:
The patent changes the physical parameter of the insulator layer by forming a concave portion that reduces the insulator thickness at the connecting portion. This parameter change (reducing insulator thickness) directly modifies the electrical capacitance at the connection interface, enabling characteristic impedance matching between the coplanar line and pseudo coaxial line, thereby reducing signal reflection and radiation
2Ease of manufacture
If the coplanar line and pseudo coaxial line are connected at almost right angles, then substrate routing is simplified, but high-frequency signal leakage occurs because the signal cannot be completely bent
Solution Approach 1:
The patent applies local quality by forming a concave portion specifically at the connecting portion where the coplanar line and pseudo coaxial line meet at almost right angles. This local modification contains the signal confinement effect precisely where the bending occurs, preventing signal leakage to the outside while maintaining the advantageous almost right-angle routing configuration for ease of manufacture
Solution Approach 2:
The concave portion acts as an intermediary structure at the connecting portion between the coplanar line and pseudo coaxial line. It provides a transition zone that mediates the abrupt direction change, allowing the signal to bend from the coplanar line to the pseudo coaxial line without complete bending, thereby preventing signal leakage while maintaining the simple almost right-angle routing
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
Ensures smooth propagation of high-frequency signals without loss by maintaining characteristic impedance and reducing radiation, enhancing signal transmission quality.
Implementation Method 1
a concave portion in a depth direction of the insulator layer in the connecting portion between the coplanar line and the pseudo coaxial line
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 1E(a)~1F(b)
AI summary
A pseudo coaxial line (104) is connected to a first coplanar line (102) at a first connecting portion (105) and connected to a second coplanar line (103) at a second connecting portion (106). The first coplanar line (102) and the second coplanar line (103) are, for example, differential coplanar lines. Also, a back surface concave portion (107) in which the second connecting portion (106) of the pseudo coaxial line (104) is exposed is provided. The back surface concave portion (107) is formed into an almost semicircular shape, an almost semielliptical shape, or a rectangular shape in a planar view.