Passive Repeater Pit Lid With Coupled Patch Antennas
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Solution Overview
Problem
Radio signals from underground water meters experience significant attenuation due to small antennas and limited power, requiring proximity to a base station, which is not cost-effective to expand, and existing solutions for improving signal strength are either expensive or vulnerable to damage.
Innovation Solution
A pit lid with coupled patch antennas, where the top antenna is excited in higher modes for directional beam patterns and the bottom antenna operates in fundamental mode, providing improved signal propagation by reducing ground transmission and increasing air-based signal strength, with interchangeable lids for different elevation angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If antennas are incorporated in the meter itself at the bottom of the cavity, then the meter can operate autonomously without external power or connections, but radio signal strength is severely attenuated due to the small antenna size and underground position
Solution Approach 1:
A passive repeater antenna system is introduced as an intermediary between the underground meter antenna and the base station. The repeater receives signals from the meter and retransmits them at ground level, effectively mediating the signal transfer without requiring power or active electronics in the lid.
Solution Approach 2:
The solution moves the antenna system from a single point (meter at bottom) to a distributed system involving both bottom and top antennas. By creating a two-dimensional antenna arrangement across the lid, the system improves signal propagation without requiring increased transmit power from the meter.
2Power
If base stations are placed in close proximity to improve signal coverage, then radio signal strength is improved, but the cost increases due to the need for multiple base stations
Solution Approach 1:
The passive repeater lid acts as an intermediary that extends the effective range of existing base stations. By placing the repeater at ground level, signals can travel further without requiring additional base stations, thus reducing the quantity needed while maintaining signal strength.
3Power
If active electronics and microprocessors are mounted in the pit lid to improve signal, then radio signal strength is improved, but the lid becomes expensive and vulnerable to damage from mishandling or dropped objects
Solution Approach 1:
The passive repeater lid uses simple, inexpensive antenna elements without delicate electronics. If damaged, the entire lid can be replaced as a single unit without concern for protecting sensitive components, making it robust against mishandling and suitable for disposable or easy-replacement applications.
Solution Approach 2:
The active electronics and microprocessors are extracted from the pit lid design. By removing these vulnerable components, the lid becomes purely passive and mechanically robust, eliminating the risk of damage to sensitive electronic parts while maintaining the signal improvement function through the passive antenna system.
4Ease of manufacture
If a passive repeater with simple antennas is used in the lid, then installation is easier and cost is reduced, but signal improvement is limited due to radiation patterns extending at right-angles to the lid plane
Solution Approach 1:
The radiation pattern is made asymmetric by orienting the antenna elements to extend parallel to the lid plane rather than perpendicular. This asymmetric configuration directs the majority of the radiation pattern downward into the pit where the meter is located, improving signal strength while maintaining the passive, easy-to-install design.
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
Enhances signal strength and quality for underground water meters, reducing the need for multiple base stations and ensuring robustness against damage, while allowing for easy replacement of damaged lids.
Implementation Method 1
a first patch antenna (42) arranged to face an upper surface (41) of the lid and configured to transmit or receive a radio signal from a base station remote from the pit, and a second patch antenna (48) arranged to face a lower surface (49) of the lid and configured to transmit or receive a radio signal
Implementation Method 2
The stripline may be coupled to a ground plane and separated from the upper antenna by a dielectric, the dielectric having a plurality of apertures, and one or more via posts pass through the apertures to couple the ground plane to the upper antenna to induce the higher modes in the antenna
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A passive radio repeater is built into a cover for a pit, in order to relay radio signals between a base station and a wireless communications device such as a water meter at the bottom of the pit. Within the external surface (41, 48) of the lid are provided upper and lower patch antennas (42, 47). The lower antenna (47) has a radiation pattern that extends downwards at right-angles to the plane of the lid, so that it communicates with the device at the bottom of the pit. The top antenna (42) has a directional beam pattern in the elevation plane, achieved achieved by exciting the top antenna in a mode that is higher than fundamental. The two antennas are coupled by a stripline printed circuit board (45) provided with feeds (92, 98) to generate the required beam patterns.