Coaxial Protective Device Impedance Stability
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Solution Overview
Problem
Existing coaxial protective devices for RF transmission lines suffer from disturbances and impedance variations due to voltage suppression components, which can lead to reduced operational frequency and poor protection, especially in lower frequency ranges and against transient high voltage signals.
Innovation Solution
A coaxial protective device with an inner conductor and outer conductor, featuring a voltage suppression component with opposing contact terminals and a resilient conductive band to maintain a consistent impedance and accommodate manufacturing and environmental tolerances, while minimizing the overall size and parts count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gas discharge tubes are used as voltage suppression components in coaxial protective devices, then over-voltage protection is provided, but transmission line disturbance increases due to the wide diameter and inherent capacitance of the tubes
Solution Approach 1:
The patent changes the physical parameters of the voltage suppression component by using a pin geometry with diameter significantly smaller than traditional gas discharge tubes (approximately 3mm vs 8mm). This parameter change reduces the capacitance and transverse cross-section, thereby minimizing transmission line disturbance while maintaining protection functionality.
Solution Approach 2:
The patent introduces an intermediary structure - a dielectric member with a cavity - that houses the voltage suppression component. This intermediary allows the small-diameter pin to be positioned within the larger coaxial structure without directly contacting the inner conductor, thereby isolating the disturbance-causing elements from the transmission line while maintaining electrical connection for protection.
2Reliability
If the inner conductor pin is widened to ensure adequate conductive path contact with gas discharge tubes, then reliable electrical connection is achieved, but the overall size of the protective device increases
Solution Approach 1:
The dielectric member acts as an intermediary that provides mechanical support and electrical connection without requiring widening of the inner conductor pin. The pin remains small in diameter while the dielectric member's cavity and structure ensure adequate contact area and mechanical stability, preventing the pin from needing to be enlarged.
Solution Approach 2:
The patent replaces the traditional mechanical connection method (direct contact between wide pin and tube electrodes) with a system where the dielectric member provides both mechanical support and electrical connection pathways, allowing the use of smaller pins without compromising connection reliability.
3Volume of moving object
If voltage suppression components are incorporated into the inner conductor to minimize device size, then compact design is achieved, but impedance variance increases due to contact area limitations
Solution Approach 1:
The dielectric member serves as an intermediary that maintains consistent impedance by providing uniform electrical connection between the small-diameter pin and the voltage suppression component. The dielectric's structured cavity and material properties ensure stable electromagnetic field distribution, preventing impedance variance despite the reduced pin diameter.
4Reliability
If traditional coaxial protective devices are designed for lower frequency ranges, then protection against lightning strikes is improved, but upper operational frequency is reduced
Solution Approach 1:
The patent changes critical parameters including the voltage suppression component diameter (smaller pin), dielectric material properties, and overall device geometry. These parameter changes reduce the device's electrical length and capacitance, enabling it to operate effectively at higher frequencies while maintaining lightning protection capability through the same voltage suppression mechanism.
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
The solution effectively suppresses transient high voltage signals, maintains a consistent impedance, and allows for extended frequency operation without significant disturbance to the transmission line, ensuring reliable protection across a broader frequency range.
Implementation Method 1
a resilient conductive band to maintain a consistent impedance and accommodate manufacturing and environmental tolerances
Implementation Method 2
excessive voltage (e.g., as a result of a lightning strike) transmitted along the inner conductor is diverted from the inner conductor and treated by the voltage suppression device
Data Source
AI summary
A protective device for transmitting electromagnetic signals includes an inner conductor that extends coaxially within an outer conductor. To compensate for dimensional tolerances without compromising performance, inner conductor is constructed to include a center pin with a conical end, a plunger pin slidably disposed within an axial bore in the center pin, the plunger pin including a conical end located outside the center pin, and a resilient, expandable, conductive band coaxially mounted onto the conical ends of the center and plunger pins. A gas discharge tube is conductively coupled between the inner and outer conductors to discharge transient voltages transmitted along the inner conductor. To minimize disturbance to the transmission line, the width of the gas discharge tube in the region of contact with the inner conductor is preferably equal to the diameter of the inner conductor. Additionally, the gas discharge tube is preferably greater in length than in width.