RF Tag Location via Phase Shift Triangulation
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Solution Overview
Problem
Current RF-tag location systems face challenges in achieving high positional accuracy while being inexpensive and low-power, particularly due to limitations in bandwidth and power consumption, which hinder effective use of time-of-flight or time-difference-of-arrival methods.
Innovation Solution
The system employs angle-of-arrival estimation using multiple strategically located antennas in beacon nodes, which cyclically switch symbols to determine phase shifts, enabling accurate RF-tag location through extended radio frequency triangulation, and calibrates beacon node positions and orientations using both forward and reverse signal directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If time-of-flight or time-difference-of-arrival methods are used to achieve high positional accuracy, then measurement precision is improved, but bandwidth and power consumption increase
Solution Approach 1:
The patent replaces time-based localization methods (time-of-flight, time-difference-of-arrival) with angle-of-arrival estimation using phase shifts. Instead of measuring time delays which require high bandwidth and power, the system uses phase information from cyclically switched antennas to determine angular positions, achieving accurate localization with lower resource consumption
Solution Approach 2:
The patent changes the measurement parameter from time-based metrics (time-of-flight, time-difference-of-arrival) to phase-based angle-of-arrival estimation. By using phase shifts introduced by cyclically switching between multiple antennas, the system achieves positional accuracy without the high bandwidth and power requirements of time-based methods
2Measurement precision
If multiple antennas with cyclical switching are used for angle-of-arrival estimation, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent divides the localization task into segments: multiple antennas are used to capture phase information from different spatial positions, and cyclical switching segments the transmission of different symbols through different antennas. This segmentation allows angle-of-arrival estimation without requiring complex simultaneous multi-antenna reception systems
Solution Approach 2:
The patent employs periodic cyclical switching of antennas during symbol transmission. Each antenna transmits a sequence of symbols in a cyclic pattern, creating periodic phase variations that encode angular position information. This periodic action simplifies the receiver design compared to continuous multi-antenna operation
3Measurement precision
If angle-of-arrival estimation with multiple beacon nodes is used, then measurement precision is improved, but loss of time increases due to calibration requirements
Solution Approach 1:
The patent implements self-calibration where beacon nodes automatically determine their own positions and orientations by measuring angle-of-arrival of signals from other beacon nodes. This self-service calibration eliminates the need for external calibration equipment or manual positioning, reducing calibration time while maintaining high measurement precision
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 provides superior positional accuracy with reduced resource intensity, maintaining low bandwidth and power consumption, and is robust against multi-path effects, offering a better trade-off between accuracy and resource usage compared to conventional methods.
Implementation Method 1
The symbols transmitted through the different antennas result in phase shifts within the frame received by the RF-tag
Implementation Method 2
From the phase shifts and the known arrangements of the antennas, the angle at which the RF-tag is RF visible from the specific beacon node can be estimated
Data Source
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AI summary
Determination of the location and bearing of an RF-tag is accomplished through extended radio frequency triangulation. A beacon arrangement determines the direction of an RF tag from a specially designed beacon node. RF-tag localization is achieved by performing this measurement from multiple spatially displaced beacon nodes. The beacon nodes are equipped with multiple antennas and transmit frames with each symbol cyclically switched to a different antenna. The symbols traveling different distances result in phase shifts within the frame received by the RF-tag. From the phase shifts and the known arrangements of the antennas the angle at which the RF-tag is RF visible from the specific beacon node can be estimated.