RFID Antenna Array Phase Steering for Multipath Tag Localization
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Solution Overview
Problem
Existing RFID technologies face challenges in accurately locating tags due to multipath interference, which causes signal overlap and ghosting, leading to inaccurate positioning and increased interference.
Innovation Solution
An array of antennas is used to distinguish between line-of-sight and non-line-of-sight paths by digitally controlling phase differences, allowing for precise angle-of-arrival measurements and triangulation to determine the location of RFID tags.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional RFID signal reception is used, then the system can detect RFID tags, but multipath interference causes signal overlap and ghosting leading to inaccurate positioning
Solution Approach 1:
The patent segments the received RFID signal into multiple candidate signals, each representing a potential propagation path (LOS or NLOS). By dividing the signal analysis into discrete path candidates with associated metrics, the system can evaluate and select the most accurate path, resolving the positioning accuracy issue caused by multipath interference
Solution Approach 2:
The patent changes the parameter of signal evaluation by introducing multiple metrics (signal strength, time of flight, angle of arrival) to characterize each candidate signal path. This multi-parameter approach allows the system to distinguish between LOS and NLOS paths more effectively, improving positioning accuracy despite multipath interference
2Quantity of substance
If multiple signal paths are received, then more signal copies are available for processing, but signal overlap causes destructive interference and fading
Solution Approach 1:
The patent extracts individual candidate signals from the composite received signal, separating them into distinct path representations. By taking out each candidate signal and evaluating it independently with associated metrics, the system avoids the destructive interference that occurs when multiple signals are processed together, while still utilizing the information from all signal copies
3Measurement precision
If signal copies are processed separately, then ghosting may occur deceiving the receiver, but selective processing can improve accuracy
Solution Approach 1:
The patent implements feedback by calculating metrics for each candidate signal path and using these metrics to select the most reliable path for positioning. The system feeds back the evaluation results to determine which signal copy to trust, preventing ghosting from deceiving the receiver while maintaining accurate signal interpretation through metric-based selection
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 RFID tag localization within 50 cm to 2.5 cm, facilitating real-time tracking and inventory management with improved precision and speed, and can be applied to various indoor environments.
Implementation Method 1
The reader includes an antenna to transmit radio frequency (RF) signals as well as to receive RF signals reflected or emitted by the tag
Implementation Method 2
A processor coupled to the antenna(s) estimates an angle-of-arrival, a phase difference, and a frequency difference of the first LOS signal
Implementation Method 3
allows for precise angle-of-arrival measurements and triangulation to determine the location of RFID tags
Data Source
AI summary
A radio frequency identification (RFID) system includes an array of antennas to distinguish line-of-sight (LOS) paths from non-line-of-sight (NLOS) paths. The distance between adjacent antennas in the array of antennas is less than half the wavelength of the radio frequency (RF) signal of the system. Each antenna in the antenna array is also digitally controlled to change relative phase difference among the antennas, thereby allowing digital steering of the array of antennas across angles of arrival (AOAs) between 0 and π. The digital steering generates a plot of signal amplitudes as a function of AOAs. LOS paths are distinguished from NLOS paths based on the shapes (e.g., depth, gradient, etc.) of local extremes (e.g., maxima or minima) in the plot.