High-Frequency Line Connection Structure for Wideband Impedance Matching
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Solution Overview
Problem
The existing high-frequency line connecting structures on printed circuit boards face challenges in suppressing impedance mismatch and achieving low reflection and passage loss characteristics across a wide bandwidth of DC to 70 GHz, particularly due to the presence of open stubs and the need for high-precision machining, which increases costs and complicates the integration of bridge substrates with coplanar lines and microstrip lines.
Innovation Solution
A high-frequency line connecting structure is designed where the ground lead pins are made taller than the signal lead pins, ensuring they surround the signal lead pins, thereby maintaining capacitance and preventing impedance increases, and allowing for impedance matching between the bridge substrate and the printed circuit board, while also reducing crosstalk by enclosing the signal lead pins' electric field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the length of open stub is shortened by maximizing machining accuracy, then stub resonance frequency shifts to high region, but manufacturing cost increases and economic efficiency deteriorates
Solution Approach 1:
The invention accepts the presence of open stubs and their resonance effects rather than trying to eliminate them through precision machining. Instead, it converts the harmful resonance into a manageable characteristic by designing the ground lead pin structure to surround the signal lead pin, creating a capacitive effect that compensates for the stub resonance. This approach transforms the problem of open stubs from a defect to be eliminated into a factor that can be worked with through structural design.
Solution Approach 2:
The invention changes the geometric parameters of the lead pins, specifically making the ground lead pin taller than the signal lead pin. This parameter change creates a capacitive coupling effect between the ground lead pin and signal lead pin, which compensates for the impedance increase caused by air exposure and mitigates the impact of open stub resonance. By adjusting the height parameter, the invention achieves impedance matching without requiring high-precision machining of the stub length.
2Reliability
If ground lead pins are made taller to surround signal lead pins, then capacitance is maintained and impedance increase is prevented, but manufacturing complexity increases
Solution Approach 1:
The invention introduces asymmetry in the lead pin structure by making the ground lead pin taller than the signal lead pin. This asymmetric design creates a capacitive effect between the two lead pins, which helps maintain capacitance and prevent impedance increase at the connection portion. The asymmetric height difference is a simple geometric modification that achieves the desired electrical characteristic without requiring complex structures or additional components.
Solution Approach 2:
The invention applies a localized structural modification only at the connection portion between the bridge substrate and printed circuit board. The ground lead pin is made taller specifically at this critical interface to create the necessary capacitive effect, while the rest of the substrate structure remains unchanged. This local quality change focuses the design effort where it is most needed, minimizing overall device complexity.
3Object-affected harmful factors
If high-frequency lines are bypassed to inner layer line, then spatial interference is prevented, but open stubs are generated causing resonance
Solution Approach 1:
The invention accepts the inevitable presence of open stubs created by back drilling and instead of trying to eliminate them through precision machining, it uses the ground lead pin structure to create a capacitive effect that compensates for the stub resonance. This converts the harmful resonance effect into a manageable characteristic through structural design rather than dimensional control.
Solution Approach 2:
The ground lead pin acts as an intermediary element between the signal lead pin and the ground plane. By making the ground lead pin taller, it creates a capacitive coupling that serves as a mediator to compensate for the impedance changes and resonance effects caused by the open stubs. This intermediary structure bridges the gap between the signal path and ground, mitigating the harmful effects of the stubs.
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
This configuration achieves low reflection loss, passage loss, and crosstalk characteristics across a wide bandwidth, ensuring effective signal propagation and reducing the need for high-precision machining, thus maintaining economic efficiency.
Implementation Method 1
the height of the ground lead pins from the first main surface of the first substrate is greater than that of the signal lead pins... not only is it possible to prevent a decrease in capacitance between the signal lead pins and the ground lead pins
Implementation Method 2
reducing crosstalk by enclosing the signal lead pins' electric field
Data Source
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AI summary
A high-frequency line substrate (2-1) is mounted on a printed circuit board (2-2). The printed circuit board (2-2) includes a first high-frequency line. The high-frequency line substrate (2-1) includes a second high-frequency line, and lead pins (2-1-2a, 2-1-2b, 2-1-3a, 2-1-3b) that connect the first high-frequency line and the second high-frequency line. At the contact portions between the signal lead pins (2-1-3a, 2-1-3b) and the second high-frequency line of the high-frequency line substrate (2-1), and the contact portions between the ground lead pins (2-1-2a, 2-1-2b) and the second high-frequency line of the high-frequency line substrate (2-1), the height of the ground lead pins (2-1-2a, 2-1-2b) from an upper surface of the printed circuit board (2-2) is greater than the height of the signal lead pins (2-1-3a, 2-1-3b).