RFID Finger Input Sensing via Transmission Line Analysis
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Solution Overview
Problem
Existing RFID-based finger input sensing devices face challenges in detecting multiple gesture inputs robustly without requiring frequent calibration and retraining, especially in changing environments and device positions, and are often limited by the need for multiple tags or complex setups.
Innovation Solution
A method and apparatus using two RFID tags connected by a transmission line, where the received signal strength (RSS) changes are analyzed to detect finger sliding gestures independently of tag location and RF environment, allowing for robust detection of ten finger input gestures without calibration or retraining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple RFID tags are used to detect multiple gesture inputs, then the gesture detection capability is improved, but the device complexity and cost increase
Solution Approach 1:
The patent merges multiple RFID tags into a single integrated tag structure where multiple antennas are combined within one tag. This allows the system to detect multiple gesture inputs (improving versatility) while maintaining a simple single-tag configuration (reducing device complexity). The multiple antennas within the single tag are excited differently to detect different finger gestures at various positions.
Solution Approach 2:
The single RFID tag is designed with multi-functional capability by incorporating multiple antennas that can detect various finger gestures (tap, slide, click) at different positions. This universal tag can handle multiple gesture types without requiring separate tags for each gesture, thus improving gesture detection capability while keeping the device simple.
2Adaptability or versatility
If RFID tags are used in changing RF environments, then the sensing capability is maintained, but the reliability decreases due to environment sensitivity
Solution Approach 1:
The patent uses parameter changes by analyzing variations in RFID signal characteristics (phase, amplitude, impedance) when fingers interact with different parts of the transmission line. By monitoring these parameter changes and comparing them against predefined patterns, the system can reliably distinguish between different gestures even in changing RF environments, maintaining both sensing capability and reliability.
3Measurement precision
If frequent calibration and retraining are performed to maintain accuracy, then the measurement precision is improved, but the loss of time increases
Solution Approach 1:
The system implements self-service by automatically adapting to environmental changes and device position variations without requiring user calibration. The RFID tag and reader work together to automatically adjust to the current configuration, eliminating the need for manual calibration and retraining processes, thus maintaining high measurement precision while minimizing time loss.
4Adaptability or versatility
If additional RFID tags are added to expand gesture input options, then the adaptability is improved, but the device complexity increases
Solution Approach 1:
The patent combines multiple RFID tag functions into a single tag by integrating multiple antennas within one tag structure. This allows the system to provide expanded gesture input options (improving adaptability) without increasing the quantity of RFID tags, as all gesture detection capabilities are achieved through the multi-antenna single tag configuration.
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 reliable and robust detection of finger input gestures, allowing for versatile applications such as remote control or integration into everyday objects, with the ability to adjust smart device properties without the need for calibration or additional tags.
Implementation Method 1
two RFID tags, each including a microchip and an antenna... each RFID tag returns a characteristic received signal strength (RSS) and pattern of RSS changes for different sliding finger gestures
Implementation Method 2
When a finger slides between different positions along the transmission line, the finger movement continuously changes the impedance matching between each RFID chip and its antenna
Data Source
AI summary
A method and apparatus are provided for effecting an RFID-based finger input sensing system using a transmission line connected to at least two RFID tags, by analyzing a plurality of features relating to the number of spikes in the derivatives of the RSS, timing of maximum RSS and the spikes of the RSS derivatives, relative RSS magnitude between the at least two RFID tags, and increase/decrease trend of the RSS, thereby eliminating the need for calibration and training.