RFID Lateral Discrimination via Asymmetric Magnetic Field
Solution Overview
Problem
Existing RFID technologies face challenges in providing precise lateral discrimination and accurate location determination of RFID tags in close proximity, particularly in casino gaming environments with multiple betting areas, due to limitations in spatial resolution and interference from human presence and metal objects.
Innovation Solution
The method involves creating an asymmetry in the magnetic field strength between the inside and outside of a coil by adjusting the energization of the coil to differentiate between tags inside and outside, allowing for unique identification of transponders even when coils are closely adjacent, without requiring changes to the reader coil design and maintaining system performance with ISO18000-3 Mode 2 RFID systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If RFID technology operates at approved frequencies such as 433 MHz, 915 MHz, 2.4 GHz, then communication range is extended, but spatial resolution deteriorates and precision is lost
Solution Approach 1:
The patent applies asymmetry by creating an asymmetric magnetic field distribution using multiple coils with different field strengths. The system establishes a strong field region and a weak field region, allowing tags to be uniquely identified based on which region they are in. This asymmetric field configuration enables precise lateral discrimination (improving spatial resolution) while maintaining extended communication range through the use of multiple coils operating at approved RFID frequencies.
2Area of stationary object
If multiple coils are placed closely adjacent to cover multiple betting areas, then coverage area is increased, but cross-talk between coils increases
Solution Approach 1:
The patent applies local quality by assigning different field strength characteristics to different spatial regions. Each coil creates a localized magnetic field with specific strength characteristics, and the system uses the combination of these localized fields to uniquely identify tag positions. This allows multiple coils to operate closely adjacent (increasing coverage area) while minimizing cross-talk, as each coil's local field dominates in its specific region.
Solution Approach 2:
The system dynamically adjusts the field strength of individual coils based on the detection needs. By controlling the energization of each coil independently, the system can create dynamic field patterns that reduce interference between adjacent coils while maintaining comprehensive coverage of multiple betting areas.
3Measurement precision
If field strength is increased to read tags at the top of chip stacks, then reading capability is improved, but cross-read of neighbouring betting spots increases
Solution Approach 1:
The patent applies segmentation by dividing the detection space into multiple distinct regions, each associated with a specific coil. By segmenting the field coverage and using multiple coils with controlled field strengths, the system can read tags at the top of chip stacks (improving reading capability) while ensuring that each tag is primarily detected by the coil corresponding to its betting spot, thereby reducing cross-read of neighboring areas.
4Power
If antennas are placed above the table top for better signal reception, then signal strength is improved, but visibility to players and system complexity increases
Solution Approach 1:
The patent applies merging by integrating the coil system within the existing table structure, combining the RFID detection function with the table's architectural elements. This allows signal strength to be maintained through optimized coil placement and configuration while keeping the system visually unobtrusive and structurally integrated, rather than adding separate above-table antenna components.
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 enables accurate location determination of RFID tags, reduces cross-talk, and allows for efficient communication with tags in stacked configurations, enhancing the precision and reliability of RFID systems in crowded and complex environments like casino gaming tables.
Implementation Method 1
energising a coil to provide a magnetic field having an internal flux of a first strength and an external flux of a second strength, the internal flux having a greater strength than the external flux
Data Source
Figure 1
Figure 2~3
Figure 4a~4d
AI summary
The present invention relates to the field of radio frequency identification (RFID). In one form, the invention relates to a method and / or device adapted to provide at least some level of providing lateral discrimination within a given area. The invention has been developed primarily for interrogating multiple passive transponders which are attached to objects to be identified by those respective transponders and will be described hereinafter with reference to that application. A typical application is the identification of RFID transponders or other RFID devices, such as those embedded in plastic tokens or cards within a selected area and which may be provided near each other or stacked on each other.