Passive RFID Tag Ranging with Phase-Based Distance Confidence
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Solution Overview
Problem
Existing RFID systems struggle with low accuracy in measuring distances between RFID tags and readers, particularly in densely populated environments like retail stores, leading to unreliable inventory estimation and difficulty in isolating specific RFID tags.
Innovation Solution
Implementing phase-based ranging (PBR) and PBR-based distance estimation to accurately measure distances between RFID tags and readers, combined with confidence metrics derived from phase variance, to identify the closest RFID tag with high precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If traditional RFID systems are used in densely populated environments, then the system can cover a large area, but the measurement precision of distance between RFID tags and readers deteriorates
Solution Approach 1:
The patent changes the measurement parameter from traditional signal strength-based distance estimation to phase-based ranging. By measuring the phase difference of the signal reflected from the RFID tag and comparing it with the transmitted signal phase, the system achieves centimeter-level distance measurement accuracy even in densely populated environments with multiple tags.
2Quantity of substance
If traditional RFID reading methods are used, then all RFID tags within range can be read, but the ability to isolate specific RFID tags deteriorates
Solution Approach 1:
The patent replaces traditional signal strength-based tag identification with phase-based distance measurement. By calculating the precise distance to each RFID tag using phase difference, the system can identify and isolate the closest tag with high accuracy, enabling selective reading even when multiple tags are within communication range.
3Measurement precision
If phase-based ranging is implemented, then the distance measurement precision is improved, but the device complexity increases
Solution Approach 1:
The system uses the existing RFID communication infrastructure and signal reflections to perform phase-based ranging. The RFID tags themselves serve as the measurement targets and reflectors, eliminating the need for additional active transponders or complex external measurement equipment. The wireless communication device performs both RFID communication and distance measurement using the same hardware.
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
Enhances the ability to accurately isolate and provide contextual information about the closest RFID tag, improving inventory management and user interaction by ensuring high confidence in distance measurements.
Implementation Method 1
determine, based on a difference between a phase of the transmit signal and the respective phase of the response signal, a plurality of distances for the plurality of passive devices
Implementation Method 2
receive, from each passive device of the plurality of passive devices, a respective response signal based on the transmit signal
Data Source
AI summary
Techniques are described for wireless communications. For example, a device can transmit, to passive devices, a transmit signal with a first phase. The device can receive, from each passive device, a respective response signal based on the transmit signal and determine, based on a difference between the first phase and a respective phase of each respective response signal, distances for the passive devices. The device can determine a respective confidence level for each respective distance of each passive device to the device based on a variance of the respective phase of each respective response signal. The device can compare the respective distance of each passive device with each other distance to determine a passive device with a smallest distance. The device can output contextual information based on the passive devices first having the smallest distance, with a confidence level determined for a distance from the passive device to the device.