Embedded Armor Antenna Parasitic Coupling
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Solution Overview
Problem
Designing an antenna system for armored vehicles that is embedded within the armor panel without piercing it, while maintaining performance and protecting against explosive and ballistic attacks, is challenging due to the close proximity of the conductive armor surface to the radiating element, which typically requires a ground plane spaced at least a quarter wavelength away.
Innovation Solution
A thin, embedded antenna system utilizing a bowtie dipole as both the directly driven and parasitically-driven element, with the parasitic element on the outside of the armor plate, allowing for electromagnetic characterization of armor materials to tailor dielectric constants and reduce VSWR, achieving efficient radiating structure performance without aperturing the armor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the antenna is embedded close to the armor surface, then the armor protection is maintained, but the ground plane spacing requirement (quarter wavelength) cannot be met
Solution Approach 1:
The patent transitions from a traditional single-dimension ground plane spacing problem to a three-dimensional stacked element configuration. By placing one dipole element in front of the armor and another behind the armor at the same location, the system creates a spatial arrangement where the elements are separated along the depth dimension (perpendicular to the armor surface) rather than requiring lateral spacing. This dimensional transformation allows the antenna to achieve proper element spacing while maintaining close proximity to the armor surface for protection.
Solution Approach 2:
The patent implements a nested configuration where one dipole element is positioned within the armor structure and another dipole element is positioned outside the armor, both at the same lateral location. This nesting approach allows the antenna system to be embedded within the armor thickness while maintaining the required electrical spacing between elements, effectively solving the spacing constraint without compromising armor protection.
2Reliability
If traditional whip antennas are used on armored vehicles, then communication coverage is achieved, but the antennas are susceptible to damage and attack
Solution Approach 1:
The patent merges the antenna structure with the armor panel by embedding the dipole elements within the armor thickness. Instead of having separate whip antennas mounted on the vehicle surface, the communication antenna becomes an integral part of the armor panel itself. This integration provides the communication function while the armor structure naturally protects the antenna elements from damage and attack.
Solution Approach 2:
The patent uses a parasitic element that is electrically coupled to the driven element through the armor structure. The parasitic element replicates the radiating function without requiring direct feedline connection, allowing the antenna system to maintain communication coverage while being protected within the armor. The parasitic element acts as an electromagnetic copy of the driven element, achieving the same radiation pattern and coverage.
3Ease of operation
If the armor panel is apertured to feed the antenna, then the antenna can be fed, but the armor integrity and protection are degraded
Solution Approach 1:
The patent introduces the armor panel itself as an intermediary medium to couple the driven dipole element (behind the armor) to the parasitic dipole element (in front of the armor). Instead of creating apertures to feed the antenna, the feedline connects to the driven element behind the armor, and the electromagnetic energy is coupled through the armor structure to the parasitic element on the outside. The armor acts as the coupling medium, eliminating the need for apertures while maintaining armor integrity.
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 provides a conformal, ultra-wideband antenna with increased gain and reduced VSWR, maintaining armor integrity and achieving 180° coverage without penetrating the armor, with gain improving from -7 dBi to over 12 dBi across the 30 MHz to 150 MHz range and maintaining VSWR under 3:1 across 225-450 MHz.
Implementation Method 1
a first dipole element to the inside of an armor layer with a second, parasitic dipole element to the outside of the armor layer such that the second dipole element is electromagnetically coupled to the first dipole element
Implementation Method 2
it has been found that one can establish the permittivity and loss of each piece of the armor recipe that affects the effective electrical length and efficiency of the radiating structure
Data Source
AI summary
An extremely thin embedded antenna for an armor-carrying vehicle utilizes a dipole driven element to the inside of the armor plate and a parasitically-driven dipole element on top of the armor plate, with the parasitic element providing appropriate forward gain and antenna matching characteristics such that there need be no aperturing of the armor plate in order to feed the antenna. In one embodiment, the bowtie antenna elements are elongated, extended or expanded by outboard antenna sections which are spaced from the distal ends of the corresponding bowties, with a meanderline choke bridging the gap between a bowtie element and its extended portion.