Passive RFID Ranging Using Wideband Time-of-Flight
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Solution Overview
Problem
Existing radio frequency identification (RFID) systems using narrowband signals struggle to provide accurate ranging for passive RFID tags, especially in environments larger than 100 feet, due to issues with multipath nulls and errors, making it difficult to accurately locate tags and distinguish between adjacent portals.
Innovation Solution
The integration of wideband RFID transceivers with existing narrowband RFID systems, using synchronized narrowband and wideband RF signals to enhance location accuracy, where wideband transceivers determine time-of-flight or time-of-arrival data for reflected signals from passive RFID tags, allowing for more precise location measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If narrowband RFID signals are used for communication, then compatibility with existing RFID infrastructure is maintained, but location accuracy deteriorates in environments larger than 100 feet
Solution Approach 1:
The patent combines narrowband RFID communication signals with wideband ranging signals into a unified system. The narrowband signals maintain compatibility with existing RFID infrastructure for tag identification and data communication, while wideband signals are simultaneously transmitted to provide precise time-of-flight measurements for accurate ranging, thus merging the advantages of both signal types.
Solution Approach 2:
The RFID system is enhanced to perform multiple functions: traditional narrowband RFID communication for tag identification and data exchange, plus wideband signal transmission for precision ranging and location determination. This multi-functional approach allows the same system to serve both legacy RFID applications and new high-precision location requirements.
2Device complexity
If narrowband RFID signals are used for ranging, then system simplicity is maintained, but measurement accuracy deteriorates due to multipath nulls and errors
Solution Approach 1:
Wideband signals act as an intermediary mechanism to overcome the limitations of narrowband signals for ranging. The wideband component provides the temporal resolution needed for accurate time-of-flight measurements, serving as a mediator that enables precise ranging without requiring complete replacement of the existing narrowband RFID system.
Solution Approach 2:
The system transitions from using only narrowband frequency parameters to incorporating wideband frequency parameters for ranging measurements. By changing the frequency bandwidth parameter from narrow to wide, the system achieves better resolution for time-of-flight measurements while maintaining the original narrowband communication functionality.
3Measurement precision
If wideband RF signals are added to enhance location accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The system segments the functionality into distinct signal processing paths: narrowband processing for RFID communication and tag identification, and wideband processing for ranging and location determination. This segmentation allows each path to be optimized independently while sharing common hardware resources, reducing overall system complexity.
Solution Approach 2:
The system dynamically switches between narrowband and wideband signal modes depending on the operational requirement. During RFID communication phases, narrowband signals are used; during ranging phases, wideband signals are activated. This dynamic operation allows the system to achieve high precision when needed while maintaining simplicity during standard communication operations.
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 and reliable location determination of passive RFID tags within larger environments, improving portal discrimination and reducing errors, while maintaining compatibility with existing infrastructure.
Implementation Method 1
In the case of a passive tag, the RF electromagnetic field, sometimes called an interrogation signal, energizes the tag, thereby enabling the tag to respond by modulating the interrogation signal using a technique called backscattering.
Implementation Method 2
providing timing-based distance measurement to a passive RFID tag by using one or more wideband RF signals
Data Source
AI summary
An example system for locating passive RFID tags includes a narrowband RFID reader configured to transmit a narrowband RF signal to energize a passive RFID tag, thereby causing the passive RFID tag to create a backscatter reflection target; a first wideband transceiver configured to transmit a wideband RF signal; a second wideband transceiver configured to: receive the wideband RF signal reflected from the backscatter reflection target; and record time-of-arrival data for the reflected wideband signal; and processing circuitry configured to determine a location measurement of the passive tag based on the time-of-arrival data.