Leaky Coaxial Antenna Two-Layer Shield Design
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Solution Overview
Problem
Existing leaky and radiating coaxial cables are heavy, inflexible, and do not meet the specific requirements for aerospace applications, such as flexibility, high bandwidth, low longitudinal loss, and lightweight design, which are necessary for use in airplanes for wireless communication standards like WLAN and GSM.
Innovation Solution
A leaky coaxial antenna design featuring a two-layer shield structure, where the first shield conductor has openings for electromagnetic energy transmission and a second shield conductor covers or masks these openings to reduce longitudinal loss, allowing for flexible and lightweight construction with controlled bandwidth and radiation patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a continuous braided shield or ridged outer conductor is used in leaky coaxial cables, then the cable provides good shielding and structural integrity, but the cable becomes heavy and inflexible
Solution Approach 1:
The continuous shield is segmented into discrete shield sections separated by gaps. Each shield section is individually supported by insulator segments, allowing the shield to be discontinuous rather than continuous. This segmentation reduces material usage and weight while maintaining shielding effectiveness through the distributed configuration of multiple shield sections along the cable length.
Solution Approach 2:
The patent employs thin film dielectric layers and flexible insulator segments to support the shield structure. These thin film structures provide the necessary mechanical support and electrical insulation without adding significant weight, enabling the cable to achieve both shielding performance and flexibility suitable for aerial deployment.
2Adaptability or versatility
If openings are created in the shield conductor for electromagnetic energy transmission, then the cable can function as a leaky antenna, but longitudinal loss increases
Solution Approach 1:
The shield conductor has different properties in different locations: in shield sections, the shield is continuous for low loss transmission, while in gap sections, the shield is discontinuous to allow controlled electromagnetic energy leakage. This local variation in shield continuity enables the cable to provide both low longitudinal loss in certain regions and antenna functionality in other regions.
Solution Approach 2:
The cable structure alternates periodically between shield sections with continuous shielding and gap sections with discontinuous shielding. This periodic configuration creates a distributed antenna system where energy is leaked at regular intervals along the cable, providing omnidirectional radiation patterns while maintaining acceptable transmission efficiency over long distances.
3Ease of operation
If the cable is made flexible with a small bend radius for airplane installation, then the cable can be routed around obstacles, but the structural integrity and shielding performance may deteriorate
Solution Approach 1:
The patent uses thin film dielectric layers and flexible insulator segments that can bend without compromising the integrity of the shield sections. These flexible components allow the cable to achieve a small bend radius suitable for airplane installation while maintaining the continuous shield structure in shield sections for effective electromagnetic shielding.
Solution Approach 2:
The discontinuous shield structure with individual shield sections supported by separate insulator segments allows each section to move independently during bending. This segmentation prevents stress concentration that would occur in a continuous rigid shield, enabling the cable to flex repeatedly without damaging the shielding performance or structural integrity.
4Weight of moving object
If the cable is made lightweight for airplane weight constraints, then the cable meets airline specifications, but the structural strength and shielding effectiveness may be reduced
Solution Approach 1:
By segmenting the shield into discrete sections rather than using a continuous heavy shield, the cable achieves weight reduction while maintaining shielding effectiveness. The distributed arrangement of multiple lightweight shield sections provides omnidirectional radiation patterns and adequate shielding performance without the weight penalty of a continuous heavy-duty shield.
Solution Approach 2:
The patent employs composite structures combining lightweight conductive materials for the shield sections with thin film dielectric materials for insulation and support. This composite construction achieves the necessary mechanical strength and electromagnetic shielding performance while minimizing the overall cable weight to meet airplane payload constraints.
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 two-layer shield design enables a flexible coaxial cable with low longitudinal loss, high bandwidth, and wideband performance, meeting the requirements for aerospace applications by reducing attenuation and maintaining noise immunity, while allowing for bending and long reach lengths.
Implementation Method 1
the first shield conductor having openings distributed in longitudinal direction of the inner conductor and being adapted in that electromagnetic energy passes through the openings
Implementation Method 2
the second shield conductor is adapted to cover or mask at least a number of the openings of the first shield conductor in a shielded section for preventing the electromagnetic energy from passing to the outside of the antenna within the shielded section
Implementation Method 3
Leaky coaxial cables support surface waves, were a fraction of the power is radiated radially
Data Source
AI summary
The invention relates to a leaky coaxial antenna (10) comprising an inner conductor (1), a dielectric (2) around the inner conductor (1), and a first shield conductor (4) disposed around the dielectric (2), the first shield conductor having openings (41) distributed in longitudinal direction of the inner conductor (1) and being adapted in that electromagnetic energy passes through the openings (41). A second shield conductor (5) is disposed around or underneath the first shield conductor (4), the second shield conductor (5) being adapted to cover or mask at least a number of the openings (41) of the first shield conductor in a shielded section (S1-S12). The second shield conductor (5) is arranged discontinuously In the longitudinal direction of the antenna (10) defining uncovered or unmasked portions (AS1-AS12) of the first shield conductor (4) in the longitudinal direction of the antenna which are adapted in that electromagnetic energy passes through the uncovered portions (AS1-AS12). Thus, the present invention suggests a two-layer shield for improving the properties of a leaky coaxial antenna with respect to e.g. aerospace applications.