RFID Tag Distance Locator Using Impedance Supervision
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Solution Overview
Problem
Existing methods for locating buried or submerged RFID tags, such as those on pipes, suffer from inaccuracy in horizontal positioning and depth determination due to interference from external magnetic disturbances and the complexity of electromagnetic field patterns in moist media, leading to unreliable location data.
Innovation Solution
A locating device that evaluates the distance of an RFID tag from an interface between two media by determining minimum electromagnetic field values, using an inductive coupling mechanism and a reader with a supervision circuit to detect and respond to the tag's impedance changes, allowing for precise positioning and depth measurement independent of tag performance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inductive coupling is used for RFID communication, then reliability is improved, but measurement precision deteriorates due to external magnetic disturbances
Solution Approach 1:
The patent extracts the useful signal (RFID tag response) from the background of external magnetic disturbances by using a supervision circuit that specifically monitors impedance changes in the antenna circuit. This selective extraction of the tag's impedance modulation signal allows reliable detection independent of external magnetic field variations.
Solution Approach 2:
The supervision circuit provides feedback by continuously monitoring the antenna circuit's impedance and detecting changes caused by the RFID tag. This feedback mechanism enables the system to distinguish tag-induced impedance changes from external magnetic disturbances, thereby improving measurement precision while maintaining reliable communication.
2Length of stationary object
If electromagnetic field patterns are used in moist media, then communication range is extended, but measurement precision deteriorates due to complex field patterns and wave absorption
Solution Approach 1:
The patent replaces direct electromagnetic field measurement with an indirect electrical measurement approach. Instead of measuring complex electromagnetic field patterns in moist media, the system measures electrical impedance changes in the antenna circuit, which are easier to interpret and less affected by media complexity, thereby improving depth determination accuracy while maintaining communication range.
Solution Approach 2:
The patent introduces impedance change as an intermediary parameter between the RFID tag and the measurement system. Rather than directly measuring electromagnetic field patterns in moist media, the system detects impedance changes in the antenna circuit caused by the tag, providing a more reliable and precise measurement that is less affected by media absorption and field pattern complexity.
3Adaptability or versatility
If RFID tags are used on buried pipes, then location capability is enabled, but ease of operation deteriorates due to inability to directly access tags
Solution Approach 1:
The RFID tags on buried pipes perform self-service by automatically responding to reader queries through inductive coupling without requiring physical access or manual intervention. The tags autonomously modulate their impedance to communicate their presence and location information, enabling easy operation despite being buried and inaccessible.
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 high-accuracy location of RFID tags with ease, distinguishing them from other sources and allowing operation in restricted spaces, even with ground obstacles, and is less dependent on tag performance over time.
Implementation Method 1
The communication between a reader and RFID tags is for example defined in the standards ISO15693 and ISO18000-3 for the frequency of 13.56 MHz. In the case of inductive antennas, the interactions between the antenna of the reader and the antenna of the tag can be described by equations of inductive coupling (with a quasi-static approach and the use of the calculation of mutual inductances). The inductive coupling induces the transfer of energy between the reader and the tag by mutual inductance.
Implementation Method 2
The inductive coupling induces the transfer of energy between the reader and the tag by mutual inductance.
Implementation Method 3
Across its surface, a coiled conducting circuit of the tag taps off the flux of the magnetic field produced by the antenna of the reader. The temporal variation of this flux creates an induced voltage termed the e.m.f (for electromotive force) within this coiled circuit. This voltage is rectified and generally used to power the functions of the tag.
Data Source
AI summary
A locating device for determining a distance of an RFID tag with respect to an interface between two media comprising an inductive coupling antenna and a sensor for determining a distance between the antenna and the interface. There is an energizing circuit configured to energize the antenna to generate an electromagnetic field with various successive amplitude values and a detection device for detecting an electromagnetic field response from the RFID tag. There is a processing circuit configured to determine several pairs of information, each pair including: a distance between the antenna and the interface and a minimum electromagnetic field value detected by the detection device from the RFID tag at the determined distance between the antenna and the interface. The processing circuit also evaluates the distance between the RFID tag and the interface as a function of the several pairs.