Passive RFID Tag Selection Using Light-Sensitive Persistent Nodes
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Solution Overview
Problem
Passive RFID tags are susceptible to light, which reduces their persistence time and complicates subset selection and identification, especially in environments with ambient light, and conventional readers require complex anti-collision software to distinguish multiple tags.
Innovation Solution
Utilizing 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 to mitigate light-induced photocurrents, while employing temperature-varying properties for tag identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive RFID tags are exposed to ambient light, then the persistent node values change due to light-induced photocurrents, but this reduces measurement precision and complicates subset selection
Solution Approach 1:
The patent applies preliminary anti-action by using light to intentionally alter persistent node values before the reading process. By exposing selected tags to light during a specific time window, the system proactively changes their persistent node states to distinguish them from non-illuminated tags, thereby enabling reliable subset selection without ambiguity
Solution Approach 2:
The patent utilizes parameter changes by exploiting the light-sensitive property of persistent nodes to change their logic values (0 or 1) based on light exposure. This parameter change mechanism allows the system to encode selection information into the persistent node states, enabling precise tag identification and subset selection through simple logic value comparison
2Difficulty of detecting and measuring
If conventional readers use complex anti-collision software to distinguish multiple tags, then tag identification capability is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex software-based anti-collision mechanisms with a simpler optical control approach. Instead of using sophisticated algorithms to distinguish and identify individual tags among multiple tags, the system uses light to selectively alter persistent node values, enabling tag differentiation through simple optical exposure and basic logic value comparison
Solution Approach 2:
The patent applies self-service by using the tags' inherent light-sensitive persistent nodes to automatically encode identification information. The tags themselves perform the differentiation function through their light-responsive persistent node behavior, eliminating the need for complex reader software to actively manage and distinguish multiple tag identities
3Productivity
If light is used to alter persistent node values for subset selection, then productivity is improved, but loss of information occurs due to unintended light exposure effects
Solution Approach 1:
The patent applies preliminary action by setting all persistent nodes to a known initial logic value before the light-based selection process begins. This preliminary initialization ensures that subsequent light-induced changes can be reliably detected and interpreted, preventing information loss by establishing a clear baseline state for all tags
Solution Approach 2:
The patent uses periodic action by controlling light exposure in specific time windows during the tag selection process. By illuminating selected tags only during predetermined time intervals and keeping others in darkness, the system ensures that only intended tags experience persistent node value changes, preserving information integrity while maintaining high selection productivity
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 leveraging light susceptibility and temperature variations, reducing the need for complex anti-collision software and improving tag performance in light-exposed environments.
Implementation Method 1
Passive backscatter tags use voltage multipliers to convert RF signals into DC power to power the chips circuitry. The range of a passive RFID tag is limited by its ability to convert low amplitude RF signals into sufficient DC power to power the tag's circuits.
Implementation Method 2
A passive tag is a beam powered device which rectifies energy required for operation from radio waves generated by a reader.
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.