RFID Tag Resonant Coupling for Focused B-Field Readout
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Solution Overview
Problem
Traditional RFID systems face challenges in accurately tracking multiple gaming tokens on a table due to cross-talk errors, limited read range, and poor discrimination between adjacent spots, especially in densely stacked configurations, which are exacerbated by the interaction of tags changing their resonant frequency when in close proximity.
Innovation Solution
The use of resonant inductive coupling between RFID tags, tuned to a higher frequency than the excitation frequency, creates a 'lensing effect' that collimates the B-field, allowing precise determination of spatial coordinates and efficient energy transfer without the need for high-permeability materials like ferrite cores.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If traditional RFID systems use omnidirectional excitation antennas, then the read range is extended in all directions, but cross-talk errors occur when multiple antennas are in close proximity
Solution Approach 1:
The patent applies local quality by shaping the B-field to concentrate magnetic flux density in specific local regions corresponding to individual betting spots, rather than uniformly in all directions. This is achieved through ferrite core elements in the tags that collimate the B-field, creating localized high-density regions that enable reliable reading at each spot without cross-talk interference from adjacent spots.
2Quantity of substance
If multiple RFID tags are placed in close proximity on a gaming table, then tracking of multiple tokens is enabled, but tags interact and change their resonant frequency, causing read errors
Solution Approach 1:
The patent applies parameter changes by tuning each tag's resonant frequency to be higher than the excitation frequency. This frequency offset creates a resonant coupling effect that stabilizes the system's magnetic flux density distribution, preventing the resonant frequency shifts that would otherwise occur due to tag interactions in close proximity.
3Measurement precision
If ferrite core elements are used in each RFID tag, then the B-field is collimated and magnetic flux density is focused, but manufacturing costs and device complexity increase
Solution Approach 1:
The patent applies parameter changes by operating tags at a resonant frequency higher than the excitation frequency. This frequency parameter change creates a resonant coupling effect that produces a lensing phenomenon, focusing the B-field and collimating magnetic flux density without requiring ferrite core elements, thereby reducing manufacturing complexity while maintaining spatial precision.
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
This approach enhances read range and reduces errors by focusing the magnetic flux density, enabling accurate tracking of multiple tags with improved efficiency and reduced manufacturing costs, while maintaining aesthetic flexibility.
Implementation Method 1
The grouping of RFID tags has a resonant frequency that is lower than the resonant frequency of each of the RFID tags considered individually due to resonant coupling
Implementation Method 2
the grouping of RFID tags shapes a magnetic flux density field of the transmission generated by the RFID reader through the grouping of RFID tags
Implementation Method 3
The first concept is the presence of a coupling capacitor that extracts only the energy needed from the excitation field sufficient to power the RFID tag
Data Source
AI summary
A radio-frequency identification (RFID) tag includes circuit elements that result in a resonant frequency that differs from the excitation frequency of an RFID reader. The RFID tag, when stacked with other similar RFID tags, channels the magnetic flux density field (B-field) through the stack to power each of the tags in the stack. As a result, the B-Field is collimated in a manner that increases the sensitivity (read range) in one dimension (up a stack of chips) while simultaneously limiting the sensitivity in the two lateral dimensions, thereby providing precise spatial resolution of each tag as to its location on a gaming table.