Embedded Armor Antenna Using Meanderline Choke
Solution Overview
Problem
Existing armor-embedded antenna systems face challenges in achieving wideband performance without compromising the armor's integrity, as the close proximity of the conductive armor surface to the radiating element creates a ground plane that is too close, limiting antenna design and making it difficult to extend the frequency range beyond 225-450 MHz.
Innovation Solution
A bowtie dipole antenna system is used with outboard extensions and a meanderline choke to operate in both VHF and UHF bands, where the meanderline acts as a choke above 225 MHz, allowing the antenna to resonate from 30 MHz to 455 MHz without piercing the armor, and utilizing a variable impedance transmission line to disconnect VHF and UHF portions, enabling wideband operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a driven dipole antenna is embedded close to the conductive armor surface, then the antenna structure is thin and protected, but the ground plane is too close creating poor antenna performance
Solution Approach 1:
A dielectric layer is introduced between the driven dipole antenna and the conductive armor surface to act as an intermediary. This dielectric spacer increases the effective distance between the radiating element and the ground plane, improving antenna performance while maintaining the thin embedded structure. The dielectric material with specific permittivity values (e.g., 2.25, 4.5, 9.0) serves as the mediator that resolves the contradiction between proximity and performance.
2Reliability
If traditional whip antennas are used on armored vehicles, then communication is reliable, but the antennas are susceptible to damage and attack
Solution Approach 1:
The antenna system is nested within the armor panel structure itself. The driven dipole is embedded in the interior surface of the armor panel, with the dielectric layer and parasitic elements contained within the panel thickness. This nesting approach protects the antenna from external damage while maintaining communication functionality, eliminating the need for exposed whip antennas.
3Volume of moving object
If the armor panel is made thin for vehicle integration, then the vehicle profile is reduced, but the spacing between ground plane and driven element is insufficient
Solution Approach 1:
The dielectric constant (permittivity) of the spacer material is varied to change the electrical spacing between the driven element and ground plane. By selecting dielectric materials with different permittivity values (2.25, 4.5, 9.0), the effective electrical length is adjusted without changing the physical thickness of the armor panel. This parameter change allows sufficient electrical spacing to be achieved within thin physical constraints.
4Adaptability or versatility
If a single wideband antenna is embedded to cover 30-455 MHz, then the number of antennas is reduced and vulnerability is decreased, but achieving wideband performance with thin structure is challenging
Solution Approach 1:
The embedded dipole antenna system is designed to perform multiple functions across a wide frequency range (30-455 MHz). By using a parasitically-fed configuration with multiple parasitic elements of different lengths and orientations, the single antenna structure achieves broadband coverage including VHF, UHF, and L-band frequencies, replacing what would traditionally require multiple separate antennas of different thicknesses and configurations.
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 achieves unity gain across 225-450 MHz with a VSWR of 3:1 or less, providing 360° coverage and matching the performance of standard whip antennas, while maintaining the armor's protective integrity by avoiding apertures and extending the antenna's range to 30 MHz to 455 MHz.
Implementation Method 1
a variable impedance transmission line, or VITL, commonly a 4 pole photonic band gap device called a meanderline. This choke is used to cut off frequencies below 225 MHz such that the dipole without extensions resonates in the 225 MHz to 455 MHz UHF band.
Implementation Method 2
a bowtie dipole antenna system is used with outboard extensions and a meanderline choke to operate in both VHF and UHF bands, where the meanderline acts as a choke above 225 MHz, allowing the antenna to resonate from 30 MHz to 455 MHz
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.