RFID Phase Detection for Accurate Distance Measurement
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Solution Overview
Problem
Existing RFID technology faces challenges in accurately detecting the distance to RFID tags due to limited frequency differences between reader and tag, leading to inaccurate distance detection.
Innovation Solution
A storage medium location detection system that uses a phase detection unit to identify phases of signals from RFID tags at multiple antenna positions, combined with a parameter acquisition section to calculate distance using a predetermined distance detection parameter, allowing for high-accuracy distance detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple signals with different fundamental frequencies are transmitted to detect distance, then distance detection accuracy is improved, but sufficient frequency differences cannot be assured due to limited frequency range assigned for RFID communications
Solution Approach 1:
The patent changes the detection parameter from frequency-based phase rate of change to spatial-based phase difference measurement. Instead of transmitting multiple signals at different frequencies and measuring phase rate of change, the system transmits a single frequency signal and measures phase differences at multiple spatial positions of the antenna, thereby achieving distance detection without requiring multiple frequency channels.
Solution Approach 2:
The patent replaces the frequency-domain measurement approach with a spatial-domain measurement approach. Instead of varying frequency to extract distance information, the system varies the antenna position in space and measures phase differences at each position, substituting mechanical movement for frequency modulation.
2Device complexity
If signal strength is used to detect distance, then the detection process is simplified, but distance detection accuracy is insufficient
Solution Approach 1:
The patent introduces phase information as an intermediary parameter between signal transmission and distance calculation. Instead of directly using signal strength, the system measures the phase of received signals at multiple antenna positions and uses phase differences as an intermediate step to calculate distance, thereby improving accuracy while maintaining reasonable system complexity.
3Measurement precision
If bearing detection using phase of tag signals is used, then the bearing location is improved, but distance to the RFID tag cannot be detected
Solution Approach 1:
The patent adds a spatial dimension to the phase measurement process. Instead of measuring phase at a single antenna position, the system measures phase at multiple antenna positions along a movement path, thereby extracting both bearing information (from phase at any position) and distance information (from phase differences between positions).
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 precise detection of RFID tag location in three-dimensional space with high accuracy, overcoming limitations of limited frequency differences and improving distance detection accuracy.
Implementation Method 1
a phase detection unit that detects phases of signals received from the storage medium
Implementation Method 2
a storage medium-compatible communications unit that communicates with a storage medium by wireless using electromagnetic waves at a predetermined frequency
Data Source
AI summary
A storage medium-compatible communications unit, a phase detection unit, a parameter acquisition section and a location detection section are provided. The storage medium-compatible communications unit communicates with a storage medium by wireless using electromagnetic waves at a predetermined frequency. The phase detection unit detects phases of signals received from the storage medium. The parameter acquisition section acquires a distance detection parameter to be used in detecting a storage medium distance from a first position of an antenna to the storage medium. The first position is a position in a range of positions of the antenna from which the distance to the storage medium is shortest. The distance detection parameter is a value set in accordance with a positional relationship between the first position and a second position. The second position is a position of the antenna in the range of positions of the antenna that is different from the first position. The location detection section detects the storage medium distance, using a first phase detected by the phase detection unit at the first position, a second phase detected by the phase detection unit at the second position, and the distance detection parameter acquired by the parameter acquisition section. The location detection section identifies the first position at a time at which a trend of changes of phase detected by the phase detection unit in association with movement of the antenna reverses.