RFID Tag Distance Determination via Signal Modulation Depth
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Solution Overview
Problem
Current RFID systems lack an effective method for accurately determining the distance between passive RFID tags without requiring external power sources or complex infrastructure, which is essential for applications like robotic sensing, assembly systems, and wearable technology.
Innovation Solution
The method involves establishing communication between two RFID tags, transmitting a series of signals with progressively reduced amplitude modulation, and identifying the minimum detectable signal to determine the distance, utilizing the tags' ability to harvest energy from an RF field for powering operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If passive RFID tags are used without external power sources, then the system simplicity and ease of deployment are improved, but the ability to perform active measurements and determine distance accurately deteriorates
Solution Approach 1:
The passive RFID tag performs self-service by harvesting energy from the RF field to power its own operations including distance determination. The tag autonomously executes signal transmission, reception, and processing without external power sources, enabling it to serve itself while maintaining system simplicity.
Solution Approach 2:
The system changes the parameter of energy availability by harvesting RF energy dynamically. By varying the depth of amplitude modulation and signal transmission parameters based on harvested energy levels, the system achieves accurate distance determination while maintaining passive operation.
2Measurement precision
If signal strength is reduced to determine minimum detectable signal, then distance measurement capability is improved, but the reliability of signal detection deteriorates
Solution Approach 1:
The system implements feedback by having the second tag confirm receipt of signals at different amplitude modulation depths. This feedback mechanism allows the first tag to adjust transmission parameters and reliably identify the minimum detectable signal threshold, balancing measurement precision with detection reliability.
Solution Approach 2:
The system uses partial action by transmitting signals at progressively reduced amplitude modulation depths rather than continuous full-power transmission. This approach identifies the minimum necessary signal level for detection, achieving accurate distance measurement while maintaining sufficient detection reliability through incremental reduction.
3Measurement precision
If multiple signals are transmitted sequentially at reduced amplitude modulation, then distance determination accuracy is improved, but the time required for measurement increases
Solution Approach 1:
The system applies periodic action by transmitting signals at regular intervals with progressively reduced amplitude modulation. This structured periodic transmission allows accurate distance determination through multiple measurements while managing time consumption through systematic signal reduction sequences.
Solution Approach 2:
The system uses preliminary action by establishing communication and testing signal detection before final distance determination. Initial signals at higher amplitude modulation confirm tag functionality and communication viability, allowing subsequent reduced-power measurements to proceed efficiently with known parameters.
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 allows for accurate distance determination between RFID tags without external power, enabling applications in robotic sensing, assembly systems, and wearable technology by leveraging the tags' energy harvesting capabilities.
Implementation Method 1
the RFID tags may harvest energy from electromagnetic radiation provided by an external field generator, such as the RFID reader, to power tag operations
Implementation Method 2
An RFID tag may include an antenna configured to receive a RF field generated by an external field generator
Data Source
AI summary
Technologies are generally described for distance determination between two or more RFID tags based on a minimum detectable signal. In some examples, a first RFID tag may establish communication with a second RFID tag, and modulate an irradiating electromagnetic field to generate backscatter signals for sequential transmission to the second RFID tag. A depth of amplitude modulation of each transmitted signal may be progressively reduced until the second RFID tag can no longer detect the modulation. The particular distance between the first and second RFID tags may then be determined based on a minimum detectable signal by the second RFID tag, which may be identified as a last transmitted signal detected by the second RFID tag. In some embodiments, distance determination between two or more RFID tags as described above may be implemented for robotic sensing, assembly systems, security, and wearable technology to track motion and/or position of objects.