RFID Tag Tracking via Phase Likelihood and Monte Carlo Simulation
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Solution Overview
Problem
Current RFID systems face challenges in accurately tracking the position and velocity of backscatter RFID tags with high precision without using expensive phased array antennas, which are time-consuming and costly.
Innovation Solution
The use of multiple antennas and a computationally efficient recursive procedure that updates the RFID tag state estimate based on phase and receive signal strength, incorporating a Monte Carlo simulation and bootstrap sampling to improve spatial diversity and accuracy of tag position and velocity estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phased array antennas are used to improve tag position tracking accuracy, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces expensive phased array antennas with multiple inexpensive omnidirectional or diversity antennas. These simple antennas provide sufficient tracking accuracy when used with the proposed signal processing methods, eliminating the need for complex and costly phased array systems while maintaining measurement precision.
Solution Approach 2:
The patent substitutes the mechanical/physical complexity of phased array antenna systems with computational methods. By using signal processing techniques including phase difference analysis, amplitude ratio methods, and probabilistic data association filters, the system achieves accurate tracking without requiring complex antenna hardware.
2Measurement precision
If phased array antennas with steerable beams are used to estimate tag position, then measurement precision is improved, but productivity decreases due to narrow beam scanning time
Solution Approach 1:
The patent employs periodic transmission of RFID signals from multiple antennas and uses the phase and amplitude information from these periodic signals to continuously estimate tag position. This eliminates the need for slow mechanical beam scanning while maintaining precision through mathematical processing of periodic measurements.
Solution Approach 2:
The patent replaces the mechanical beam steering mechanism with computational signal processing. By analyzing phase differences and amplitude ratios from simultaneously received signals at multiple antenna elements, the system achieves rapid position estimation without mechanical movement or sequential scanning.
3Measurement precision
If multiple antennas are used to improve spatial diversity and tracking accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent makes simple omnidirectional antennas multi-functional by using them for both signal reception and position/velocity estimation. The same antenna elements that provide spatial diversity also provide the phase and amplitude information needed for tracking, eliminating the need for specialized phased array structures and reducing overall system complexity.
Solution Approach 2:
The patent changes the approach from using antenna physical structure (phased array geometry) to using signal parameters (phase difference, amplitude ratio) for position estimation. This parameter-based approach allows simple antennas to provide accurate tracking by exploiting the information content of received signals rather than relying on complex antenna configurations.
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 enhances the accuracy of tag position and velocity tracking without the need for specialized antennas, providing precise location and movement data efficiently and cost-effectively.
Implementation Method 1
UHF backscatter RFID the read range can be 10 meters or more
Data Source
AI summary
RFID tag tracking according to embodiments of the invention uses apparatus and methods for tracking backscatter RFID tags using the phase and receive signal strength of the tag signal. The tag tracking in some embodiments is accomplished with a computationally efficient recursive procedure to update a tag state estimate on each new response of the tag based on the previous tag state estimate and the measured phase of the tag signal. Some embodiments use a Monte Carlo simulation based on the previous tracking algorithm state and a statistical model of the forces acting on the tag. A system according to example embodiments of the invention can include a processor connected to a quadrature mixer. The processor is operable, for example through the use of firmware or software, to estimate a tag state of an RFID tag.