Low-Profile Planar Antenna for Unattended Ground Sensor
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Solution Overview
Problem
Unattended ground sensors face challenges with whip antennas, including visibility, vulnerability to damage, and false alarms due to wind-induced movements, which affect their covert operation and reliability.
Innovation Solution
A low-profile omnidirectional planar antenna with vertical polarization using two in-phase elements, a solid dielectric, and shorting pins, integrated within the sensor housing to enhance camouflage, robustness, and efficiency, while minimizing mechanical stress and false alarms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a whip antenna is used, then the antenna can provide omnidirectional radiation pattern, but the antenna becomes visible and difficult to camouflage
Solution Approach 1:
The patent transitions from a traditional vertical whip antenna to a planar antenna structure that lies substantially flat against the ground. This dimensional change allows the antenna to maintain omnidirectional radiation characteristics while achieving a low-profile configuration that is difficult to detect visually and can be effectively camouflaged with the terrain.
Solution Approach 2:
The planar antenna elements are integrated within or against the housing structure of the unattended ground sensor. By nesting the antenna within the existing sensor housing or positioning it flush against the housing surface, the antenna becomes part of the overall sensor unit, reducing its visual profile and improving camouflage capabilities.
2Device complexity
If a whip antenna is used, then the antenna can be simple in design, but the antenna becomes vulnerable to damage in hazardous environments
Solution Approach 1:
By changing from a vertical whip structure to a horizontal planar structure, the antenna becomes more resistant to damage from vehicles or equipment passing over the sensor location. The low-profile design prevents the antenna from protruding upward where it could be struck or damaged by external objects.
Solution Approach 2:
The antenna structure is merged with the housing structure of the unattended ground sensor. The planar antenna elements are positioned against or integrated into the housing, creating a unified structure that strengthens both the antenna and the overall sensor unit, making the system more robust in hazardous environments.
3Reliability
If a whip antenna extends vertically, then the antenna can provide omnidirectional radiation, but wind causes movements that create false alarms
Solution Approach 1:
The patent reorients the antenna from a vertical configuration to a horizontal planar configuration that lies flat against the ground. This eliminates the vertical element that would otherwise be susceptible to wind-induced movement, thereby preventing false seismic detections while maintaining omnidirectional radiation capability through the planar geometry.
Solution Approach 2:
The planar antenna structure makes contact with or is positioned against the ground surface at multiple points along its edges. This local contact with the ground provides stabilization and damping, preventing the antenna from moving in response to wind while still allowing it to function as an effective omnidirectional radiator.
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 covert, robust, and efficient antenna configuration that reduces false alarms and enhances the reliability of unattended ground sensors by minimizing mechanical stress and improving antenna efficiency, allowing for effective communication without external exposure.
Implementation Method 1
an antenna as defined in claim 1. The solid dielectric can allow a top-loaded antenna to be produced with a reduced size for a given volume and efficiency. The solid dielectric can minimise antenna de-tuning, and it can also improve the robustness of the antenna by resisting any mechanical forces
Implementation Method 2
The clamp can be provided to resist any movement of the solid dielectric in a vertical direction (i.e. in a direction that is substantially perpendicular to the first and second planar surfaces). The clamp may also be arranged to lock together all of the components of the antenna
Implementation Method 3
The antenna may comprise one or more shorting pins connected to the first conductor and extending between the first and second conductors, wherein the one of more shorting pins are electrically connected to both the first and second conductors
Implementation Method 4
transmission means for transmitting signals away from the unit in dependence on the output of the sensor
Data Source
Figure 1
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AI summary
An unattended ground sensor unit (30) is disclosed comprising an antenna (2) which is accommodated mainly in a head portion (5) of the unit. The antenna (2) comprises a base conductor (100) and a top conductor (102), both of which are circular plates arranged in a horizontal plane. An antenna rod (204) is electrically connected to the top conductor (102). A hole is provided in the base conductor (100) and the antenna rod (204) extends through the hole to be connected to antenna control circuitry on a printed circuit board (104) on the reverse side of the base conductor (100). An insulating ring (106) is provided around the antenna rod (204) where it extends through the base conductor (100) so that the antenna (rod 204) is electrically insulated from the base conductor (100). Two shorting pins (205) are provided between the top conductor (102) and the base conductor (100). The shorting pins (20) are provided on diametrically opposite sides of the antenna rod (204). A dielectric spacer (202) is provided having a keying cut-out (112) that can be engaged to resist its rotation.