Radiating Coaxial Cable Jacket Layout for Clamp-Induced Return Loss
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Solution Overview
Problem
Radiating coaxial cables experience increased return loss and attenuation when metal objects, such as fire-resistant clamps, come into contact with or near their radiating side, due to the metal objects acting as resonating elements, which can exceed the maximum acceptable threshold of -18 dB.
Innovation Solution
A radiating coaxial cable design with a conductive shield featuring radiating and non-radiating longitudinal portions, where the jacket thickness is varied to maintain a greater distance between the radiating shield and external metal objects, reducing the detrimental effects of metal clamps by increasing the thickness of the jacket portion facing the radiating shield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal fire-resistant clamps are used to secure the cable, then cable fixation reliability is improved, but return loss increases beyond acceptable thresholds
Solution Approach 1:
A non-conductive tube is introduced as an intermediary element between the metal clamp and the radiating shield. This tube acts as a mediator that allows the metal clamp to secure the cable while preventing direct contact between the conductive clamp and the radiating shield, thereby eliminating the harmful resonating effect that causes excessive return loss.
Solution Approach 2:
The space between the metal clamp and the radiating shield is segmented by inserting a non-conductive tube. This segmentation separates the conductive elements from the radiating elements, breaking the direct electromagnetic interaction that causes resonance and high return loss, while still maintaining mechanical fixation.
2Object-affected harmful factors
If plastic clamps are used to avoid return loss issues, then return loss remains below threshold, but cable fixation security is insufficient
Solution Approach 1:
The solution merges the advantages of both plastic and metal clamps by combining a non-conductive tube (which prevents return loss) with a metal clamp (which provides secure fixation). The non-conductive tube allows the metal clamp to be used while eliminating its harmful electromagnetic effects, achieving both secure fixation and acceptable return loss.
3Reliability
If metal clamps are placed closer together to improve fixation, then cable security is enhanced, but attenuation increases due to resonating effects
Solution Approach 1:
The non-conductive tube serves as a mediator that allows metal clamps to be placed closer together for enhanced security without increasing attenuation. By preventing direct contact between the metal clamp and radiating shield, the tube eliminates the resonating effects that would otherwise cause energy loss, enabling closer clamp spacing.
4Object-affected harmful factors
If the jacket thickness is increased to reduce the effect of metal objects, then return loss is reduced, but cable flexibility and installation ease are compromised
Solution Approach 1:
Instead of uniformly increasing the jacket thickness throughout the entire cable, the solution applies a non-conductive tube only at specific locations where metal clamps contact the cable. This localized approach provides the necessary protection against return loss only where needed, while maintaining the original cable flexibility and installation ease in other areas.
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 design reduces return loss below the maximum threshold of -18 dB over the entire operative frequency range, allowing for reduced installation spacing of metal clamps from 8-10 meters to 2-3 meters, simplifying installation, lowering costs, and enhancing safety in fire events.
Implementation Method 1
A metal object placed near a radiating coaxial cable on a radiating side thereof may affect its performance in terms of return loss and attenuation. A metal object near the cable on its radiating side indeed acts as a resonating element which reflects the radiofrequency signal and ultimately increases its return loss and attenuation.
Data Source
Figure 1
Figure 2a~3b
Figure 4a~4b
AI summary
Disclosed is a radiating coaxial cable comprising an inner conductor, an insulating layer surrounding the inner conductor, a conductive shield surrounding the insulating layer and a jacket surrounding the shield. The conductive shield comprises a radiating longitudinal shield portion with radiating apertures and a non-radiating longitudinal shield portion with no radiating apertures. The jacket comprises a first jacket portion facing the radiating shield portion and a second jacket portion facing the non-radiating shield portion. The first jacket portion is thicker than the second jacket portion. This way, the cable is more protected against detrimental effects of metal objects brought near to or in contact with its radiating side.