Directional NVIS Antenna Array with Reduced Side Lobes
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Solution Overview
Problem
Conventional high-frequency communication monopoles have a vertical null in their antenna pattern, preventing significant HF reflections from the ionosphere to the region close to the antenna, and placing a horizontal dipole closer to ground increases ground loss, necessitating an improved near vertical incidence skywave antenna with reduced side lobes.
Innovation Solution
An antenna array comprising four dipole antennas, each with two conductive elements and a feed point between them, positioned in an x-y plane parallel to a ground plane, with the conductive elements parallel to the x-axis and feed points at specific coordinates, forming a directional near vertical incidence skywave antenna with reduced side lobes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a horizontal dipole is placed closer to ground to achieve practical height, then the antenna becomes more practical to implement, but ground loss increases
Solution Approach 1:
The patent divides a single dipole antenna into four separate dipole elements arranged in a specific geometric configuration (square or rectangular pattern). This segmentation allows the antenna to achieve directional radiation patterns with reduced ground wave loss while maintaining practical heights above ground. Each dipole element contributes to the overall radiation pattern, creating constructive interference in desired directions and destructive interference in others.
Solution Approach 2:
The patent employs asymmetric feed point positioning and dipole orientation to create a unidirectional radiation pattern. By strategically placing feed points at specific coordinates and orienting dipoles at different angles, the antenna achieves asymmetric radiation characteristics that direct energy away from the ground while maintaining practical installation heights.
2Device complexity
If a conventional monopole antenna is used, then the antenna structure is simple, but the vertical null in the antenna pattern prevents significant HF reflections to the region close to the antenna
Solution Approach 1:
The patent segments the conventional monopole into four dipole elements arranged in a planar configuration. This segmentation transforms the omnidirectional radiation pattern with a vertical null into a directional pattern with enhanced vertical gain. The multiple elements work together to eliminate the null region and create constructive interference in the vertical direction, improving reliability for near-vertical incidence skywave communication.
Solution Approach 2:
The patent transitions from a vertical monopole structure to a horizontal planar array of dipoles. This dimensional change from vertical to horizontal arrangement, combined with specific spacing and orientation, creates a radiation pattern that maintains vertical gain while eliminating the vertical null. The planar configuration allows the antenna to achieve three-dimensional radiation control that a simple vertical monopole cannot provide.
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 enhances the efficiency and directivity of the antenna, increasing peak gain and reducing ground wave loss, while maintaining high vertical gain and minimizing side lobes, thus improving communication effectiveness.
Implementation Method 1
An antenna array comprising four dipole antennas configured to function together as a directional, near vertical incidence skywave (NVIS) antenna
Data Source
AI summary
An antenna array comprising: four dipole antennas configured to function together as a directional, near vertical incidence skywave (NVIS) antenna with reduced side lobes, wherein each dipole antenna comprises two conductive elements and a feed point disposed between the two conductive elements, wherein the conductive elements of each of the four dipole antennas are disposed in an x-y plane of an x-y-z mutually orthogonal axes coordinate system, and wherein the conductive elements are substantially parallel with the x-axis and the x-y plane is substantially parallel with a ground plane; and wherein the feed points of the four dipole antennas are positioned on the x-y plane at approximately (x, 0), (−x, 0), (0, y), and (0, −y), and wherein the x-y plane is separated from the ground plane by a distance h that is less than or equal to 1/10 the wavelength (λ) of an operating frequency.