RFID Tag Detection for Accurate FHSS Location Tracking
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Solution Overview
Problem
Conventional passive RFID readers are limited in tracking locations and movements of RFID tags due to their inability to operate with frequency hopping spread spectrum (FHSS) and face interference issues, leading to large size, high cost, and reduced accuracy.
Innovation Solution
An RFID detector that operates separately from the reader, receives a combined signal of the CW RF signal transmitted by the reader and the backscattered signal from the tag, and uses an indication of the CW RF signal characteristic, such as frequency or phase, to determine position-related parameters for accurate tag location, even in FHSS environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional passive RFID readers are used for tag location tracking, then the system can operate with standard RFID infrastructure, but the tracking accuracy is reduced and the device size and cost increase due to inability to handle FHSS and interference issues
Solution Approach 1:
The system separates the RFID reader functionality from the detection functionality. The reader transmits CW RF signals while separate detectors receive and process the backscattered signals for location determination, allowing each component to be optimized independently for its specific function
Solution Approach 2:
The patent introduces an intermediary detection system that receives signals from both the reader and the tag. This intermediary detector processes the combined signals to extract location information, resolving the conflict between using standard RFID infrastructure and achieving high tracking accuracy
2Reliability
If the RFID detector receives the combined signal of CW RF signal and backscattered signal, then the receive sensitivity is improved and interference is reduced, but the signal processing complexity increases
Solution Approach 1:
The detector performs preliminary signal processing by obtaining an indication of the CW RF signal characteristics (frequency, phase) before processing the combined signal. This preliminary action allows the detector to prepare appropriate reference signals and processing parameters in advance, simplifying the subsequent extraction of backscattered signal information
Solution Approach 2:
The system uses feedback from the obtained CW RF signal characteristics to adjust the signal processing parameters. The detector uses the frequency and phase information of the CW signal to properly demodulate and extract the backscattered signal, creating a closed-loop processing system that improves reliability while managing complexity
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 accurate and efficient tracking of RFID tags in FHSS systems by improving receive sensitivity and reducing interference, allowing for smaller and less costly RFID readers with enhanced location precision.
Implementation Method 1
A passive RFID tag receives both information and operating energy from an RF signal transmitted by a reader
Implementation Method 2
A BAP RFID tag, such as an ISO/IEC18000-6 Type D tag, transmits information to a reader using backscattering in a manner similar to that employed by a passive tag
Data Source
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AI summary
An RFID detector suitable for use in a passive RFID tag system that employs frequency hopping spread spectrum (FHSS) operation obtains an indication of at least one characteristic of a CW RF signal employing a hopped-to-carrier frequency that is being transmitted from an RFID tag reader, e.g., for use in activating the RFID tag to be located, the indication of the characteristic being obtained based on a signal that is received from a source other than the RFID detector. The RFID detector may use the obtained indication of the characteristic of the CW RF signal to determine at least one position related parameter for the RFID tag. A location, e.g., of the tag, of a group of tags, of the RFID detector, or of another RFID detector, may be determined based on the position parameter.