Multi-Height eLoran Antenna Elements for Bandwidth and Radiation Resistance
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Solution Overview
Problem
Conventional eLoran antennas are limited by the Chu Bandwidth Limit, resulting in restricted bandwidth and radiation resistance, necessitating large physical sizes and additional components like transformers for signal transmission, particularly at low frequencies like 100 kHz.
Innovation Solution
The proposed antenna configuration includes a vertically extending tower with two sets of elongate antenna elements at different heights, electrically coupled to the ground via buried conductors, allowing for increased tuning order and impedance matching without the need for base transformers, using ground return cables to enhance radiation resistance and bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional eLoran antenna configuration is used, then the antenna can transmit low frequency signals, but the bandwidth is limited by the Chu Bandwidth Limit
Solution Approach 1:
The antenna is divided into multiple discrete elongate elements arranged in conical and planar patterns at different heights, rather than using a continuous top-loading structure. This segmentation allows independent optimization of each element's contribution to radiation resistance and bandwidth, overcoming the Chu limit by creating multiple resonant paths.
Solution Approach 2:
The patent introduces vertical dimensionality by placing antenna elements at multiple heights (first height and second height) along the tower, creating a three-dimensional antenna structure. This multi-level configuration increases the effective electrical size of the antenna without increasing the horizontal footprint, thereby improving bandwidth and radiation resistance simultaneously.
2Use of energy by moving object
If large physical size antenna is used to overcome Chu limit, then bandwidth may be improved, but the antenna requires large tower height and physical footprint
Solution Approach 1:
The patent utilizes the vertical dimension efficiently by distributing antenna elements across multiple heights on a relatively compact tower structure. The conical and planar arrangements at different levels create an electrically large antenna structure within a physically compact footprint, achieving enhanced bandwidth without requiring excessive tower height.
Solution Approach 2:
The antenna elements are nested in a hierarchical structure with conical patterns at outer radii and planar patterns at inner radii, with elements at different heights nested vertically. This nested configuration maximizes the use of available space, creating an electrically large antenna within a compact physical envelope.
3Ease of operation
If base transformer is used for impedance matching, then signal transmission can be achieved, but the device complexity increases
Solution Approach 1:
The antenna structure itself provides the impedance matching function through its geometric configuration. The specific arrangement of elongate elements in conical and planar patterns at defined heights creates inherent impedance transformation, eliminating the need for external base transformers and associated complex impedance matching circuitry.
Solution Approach 2:
The patent extracts the impedance matching function from separate transformer components and integrates it directly into the antenna structure itself. The geometric configuration of the antenna elements performs the impedance transformation that would otherwise require external devices, simplifying the overall system.
4Ease of operation
If top loading elements are used to increase radiation resistance, then the antenna structure becomes more complex with many upper wires connecting to tower top
Solution Approach 1:
Instead of using a dense network of radial wires forming a continuous top-loading structure, the patent segments the top-loading function into discrete elongate elements arranged in conical and planar patterns. This segmentation reduces the total number of wires required while maintaining or enhancing radiation resistance through optimized element placement and grounding.
Solution Approach 2:
The patent inverts the conventional top-loading approach by selectively grounding certain elements while leaving others ungrounded. Rather than connecting all radial wires to the tower top, specific elements are grounded at different heights, creating a more efficient radiation structure with fewer wires.
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 configuration achieves a wider bandwidth and higher radiation resistance, enabling sharper eLoran pulses with reduced antenna size and eliminating the need for transformers, while maintaining stability across varying soil conditions and frequencies.
Implementation Method 1
For communications in the Very Low Frequency (VLF), Low Frequency (LF), and Medium Frequency (MF) ranges, for example, relatively large ground-based antenna towers are used for transmitting such signals
Implementation Method 2
Low frequency eLoran transmissions can propagate by ground wave, a type of surface wave that hugs the earth
Data Source
AI summary
An antenna may include a tower extending vertically upward from a ground location, a first set of elongate antenna elements extending outwardly from the tower at a first height above the ground location, and a second set of elongate antenna elements extending outwardly from the tower at a second height above the ground location and below the first height. In some embodiments, at least one elongate antenna element of the first and second sets of elongate antenna elements may be electrically coupled to the ground location. A radio frequency (RF) feed may be electrically coupled to the first and second sets of elongate antenna elements.