High Frequency Connection Device Impedance Matching
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Solution Overview
Problem
The connection between a printed circuit and a coaxial connector for high-frequency signals, particularly in the X band, experiences spurious electrical effects due to the intrinsic capacitive nature of the bump contact, leading to mismatching and increased insertion losses, which degrades transparency and is sensitive to production and positioning tolerances, resulting in a narrow-band correction.
Innovation Solution
The introduction of a resist on the internal ground plane facing the bump contact reduces the impedance added by the bump contact, and the inclusion of inductive and capacitive line sections near the bump contact forms a low-pass filtering element to enhance transparency, while a second ground plane provides shielding and electromagnetic closure, allowing for broader bandwidth and improved reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a bump contact is used to connect the transmission line to the connector, then the connection is simplified and surface-mounting is enabled, but spurious electrical effects occur due to the intrinsic capacitive nature of the bump contact, leading to mismatching and increased insertion losses
Solution Approach 1:
A resist is introduced as an intermediary element on the internal ground plane facing the bump contact. This resist mediates the capacitive coupling between the bump contact and the ground plane, reducing the spurious electrical effects while maintaining the surface-mounting advantage. The resist acts as a controlled impedance element that mitigates the harmful capacitive effect without requiring metallized holes or complex internal structures.
2Object-affected harmful factors
If the ground plane is positioned close to the transmission line for shielding, then grounding is improved and shielding is enhanced, but the interaction with the transmission line modifies the impedance and degrades signal transparency
Solution Approach 1:
The ground plane is selectively positioned at a distance from the transmission line in the critical area where the bump contact interfaces with the connector. This local modification allows the ground plane to provide shielding and grounding benefits while avoiding harmful interactions with the transmission line's electromagnetic field. The ground plane is still present for overall shielding but is strategically recessed to maintain impedance matching.
3Measurement precision
If correction elements are added to improve transparency at a specific frequency, then matching is improved at that frequency, but the solution becomes sensitive to production and positioning tolerances and only works for a narrow bandwidth
Solution Approach 1:
The resist value is carefully selected and optimized to provide broadband impedance transformation that compensates for the bump contact's capacitive effect across a wide frequency range. By changing the parameter of the resist (its resistance value) rather than adding complex frequency-specific correction elements, the solution achieves robust matching that is insensitive to small variations in production and positioning tolerances while maintaining effectiveness across a significant bandwidth including the X band and adjacent frequencies.
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 solution significantly improves the matching level and reduces insertion losses over a wide frequency band, making the connection more robust to production and positioning variations, with matching levels around -26 dB and insertion losses of 0.15 dB at 9.3 GHz, achieving excellent performance across a significant bandwidth.
Implementation Method 1
The introduction of a resist on the internal ground plane facing the bump contact reduces the impedance added by the bump contact
Implementation Method 2
the inclusion of inductive and capacitive line sections near the bump contact forms a low-pass filtering element to enhance transparency
Implementation Method 3
a second ground plane provides shielding and electromagnetic closure
Data Source
AI summary
A connection device for high frequency signals is disclosed. The connection device includes a printed circuit having an external face and a transmission line printed on the external face, and a coaxial connector surface mounted on the external face of the printed circuit. The transmission line is connected to the connector by means of a bump contact belonging to the transmission line. A central core of the connector is connected to the bump contact. The printed circuit has at least one internal ground plane disposed parallel to the external face and contributing to the matching of the transmission line. The internal ground plane defines a perforation therethrough that faces the bump contact.