RFID Tag Subset Selection via Light-Induced Persistence
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Solution Overview
Problem
Passive RFID tags are susceptible to light, which reduces their persistence time and makes them unreliable for subset selection and identification in environments with ambient light, and conventional readers require complex anti-collision software to distinguish between multiple tags.
Innovation Solution
The use of light to intentionally reduce persistence times in specific RFID tags by illuminating them, allowing for subset selection based on logic value changes, and incorporating light-insensitive circuit structures and transistor-based voltage multipliers to maintain functionality under varying light conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive RFID tags are used in environments with ambient light, then the tags can operate autonomously without power supply, but the persistence time of the tags is reduced making them unreliable for subset selection and identification
Solution Approach 1:
The patent applies preliminary action by pre-setting persistent nodes to a first logic value before the actual selection process. This allows the system to establish a known initial state that can be reliably distinguished after light exposure, enabling subset selection even in environments with ambient light that would otherwise reduce persistence time
Solution Approach 2:
The patent converts the harmful effect of ambient light reducing persistence time into a beneficial selection mechanism. By intentionally illuminating specific tags during a power interruption period, the system creates a distinguishable state change in persistent nodes, transforming light-induced persistence reduction from a reliability problem into a useful subset selection tool
2Measurement precision
If conventional readers use complex anti-collision software to distinguish between multiple tags, then accurate tag identification is achieved, but system complexity increases
Solution Approach 1:
The patent replaces complex software-based anti-collision mechanisms with a simpler optical differentiation approach. By using light to create distinct logic states in persistent nodes of illuminated versus non-illuminated tags, the system achieves accurate tag identification through physical state differentiation rather than complex computational algorithms
Solution Approach 2:
The patent changes the operational parameter of persistent node logic values based on light exposure. Tags that are illuminated during power interruption transition their persistent nodes to a second logic value, while non-illuminated tags maintain the first logic value, creating a simple binary distinction that enables accurate identification without complex software
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
Enables efficient subset selection and identification of RFID tags by utilizing light to differentiate illuminated from non-illuminated tags, reducing the need for complex anti-collision software and improving tag reliability in light-exposed environments.
Implementation Method 1
a subset of the plurality of tags is illuminated with light during at least a portion of the second time period. As a result, the persistent nodes of the subset change into a second logic value
Data Source
AI summary
Methods and apparatuses for selecting a subset of RFID tags are provided in some embodiments. These methods and apparatuses utilize the susceptibility to light by persistent nodes found in passive tags. Light can be used to intentionally reduce persistence times in a particular subset tags or even an individual tag. Then, persistent nodes can be used as a selection criterion to distinguish previously illuminated tags from non-illuminated tags. In other embodiments, a power circuit receives a RF input source and generates a direct current (DC) output voltage. The circuit includes a bias circuit to supply a gate to source bias, which is independent of the DC output voltage. The circuit further includes a voltage multiplier circuit that is coupled to the bias circuit. The voltage multiplier circuit has MOS transistors with one transistor to receive the gate to source bias.