Offset Array Antenna Shaped Beam Toll Zone Illumination
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Solution Overview
Problem
Automated toll-road collection systems face issues with unintentional interrogation of vehicles outside the toll collection zone due to shadowing effects, leading to incorrect toll charging, as existing systems struggle to provide precise illumination patterns that avoid illuminating areas where no tolls should be charged.
Innovation Solution
An array antenna with a shaped beam pattern is mounted on a gantry, offset from the center, generating a tailored RF illumination pattern that ensures vehicles within the collection zone receive sufficient illumination while maintaining low RF levels outside the zone, using a linear array antenna with a passive corporate feed and adjustable phases and amplitudes to create a specific antenna pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the RF antenna is center-mounted on an overhead gantry, then the illumination coverage is maximized, but shadowing effects occur causing vehicles behind tall vehicles to be inadequately illuminated
Solution Approach 1:
The patent divides the single center-mounted antenna into multiple antenna elements arranged in an array configuration. Each element contributes to the overall illumination pattern, creating a composite beam that covers the toll collection zone while reducing shadowing through spatial distribution of radiation sources.
Solution Approach 2:
The patent employs asymmetric amplitude and phase distribution across the antenna elements to shape the radiation pattern. By applying different weights and phases to individual elements, the system creates a tailored illumination pattern that extends coverage behind tall vehicles while maintaining control over the illuminated area.
2Reliability
If the RF antenna is positioned to one side of the road, then shadowing effects are mitigated, but areas outside the toll collection zone are illuminated causing incorrect toll charging
Solution Approach 1:
The patent applies local quality by creating a non-uniform radiation pattern where different spatial regions receive different illumination intensities. The shaped beam pattern provides enhanced illumination within the toll collection zone while deliberately reducing illumination in adjacent areas, achieving spatially selective interrogation.
Solution Approach 2:
The patent changes the radiation pattern parameters (amplitude distribution and phase distribution) across the antenna array to achieve the desired beam shaping. By adjusting these parameters, the system controls the illumination footprint to match the toll collection zone boundaries, preventing interrogation of vehicles outside the zone.
3Measurement precision
If a directional RF antenna is used to focus illumination, then the illumination precision is improved, but the coverage area is reduced
Solution Approach 1:
The patent transitions from a single-directional antenna approach to a multi-element array that controls radiation in multiple dimensions simultaneously. By manipulating phase and amplitude across the array, the system achieves precise beam shaping in both azimuth and elevation, maintaining focus while expanding the effective coverage through controlled beam patterns.
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 effectively illuminates vehicles within the toll collection zone while avoiding unnecessary interrogation of vehicles outside, reducing errors in toll charging and enhancing the system's accuracy by using a tailored antenna pattern that minimizes shadowing effects.
Implementation Method 1
an array of antenna elements... radiating electromagnetic energy
Implementation Method 2
shaped beam pattern... creating a tailored illumination pattern
Data Source
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AI summary
A system for properly illuminating a toll collection zone without illuminating any areas outside the toll collection zone in which vehicles may be found, while minimizing lost tolls due to shadowing of shorter vehicles by taller vehicles. In one embodiment, a linear array antenna is configured to illuminate a rectangular collection zone from a point offset from the center of the roadway. The linear array antenna is configured to produce an asymmetric antenna pattern providing RF illumination over the rectangular collection zone sufficient for reliable reading of vehicle RF tags in the collection zone, and which also minimizes spillover of RF power outside the collection zone.