Capacitive RFID Tag Electrodes for Miniaturized Power Transfer
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Solution Overview
Problem
Conventional RFID tags face limitations in miniaturization due to the need for large electrodes for capacitive coupling, which are required to transfer sufficient power, and this restricts their application in miniaturized devices.
Innovation Solution
Integrating electrodes into the IC of RFID tags and readers, eliminating the need for separate external antennas or electrodes, and using resonant circuits and voltage amplification to increase power transfer, while allowing flexible placement and reduced size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If relatively large capacitor electrodes are used to transfer sufficient power from the RFID reader to the RFID tag, then power transfer capability is improved, but the size of the RFID tag increases
Solution Approach 1:
The patent merges the capacitor electrodes with the RFID tag's antenna structure, forming an integrated capacitive coupling system. The antenna serves dual purposes: as the RFID communication element and as one of the capacitor electrodes for power transfer. This integration eliminates the need for separate large capacitor electrodes, thereby maintaining power transfer capability while reducing overall tag size.
Solution Approach 2:
The antenna structure is designed to perform multiple functions simultaneously: it acts as the RFID communication antenna and as a capacitor electrode for capacitive power transfer. This multi-functionality allows the system to achieve both communication and power transfer objectives without requiring additional dedicated components, thus avoiding the size penalty of separate electrodes.
2Reliability
If conventional inductive coupling antennas are used for RFID communication, then communication capability is achieved, but the antenna size becomes significantly larger than the RFID circuitry
Solution Approach 1:
The patent replaces the conventional inductive coupling mechanism with a capacitive coupling mechanism. Instead of using large inductive antennas that rely on magnetic field coupling, the system uses capacitive coupling through integrated electrodes that can be much smaller. This substitution of the coupling mechanism allows for significant size reduction while maintaining communication capability.
Solution Approach 2:
The patent changes the fundamental operating parameters of the RFID system by transitioning from inductive coupling (magnetic field-based) to capacitive coupling (electric field-based). This parameter change enables the use of smaller electrode structures instead of large antennas, as capacitive coupling can achieve effective power transfer with smaller dimensions at the operating frequencies specified.
3Power
If separate external antennas or electrodes are used for capacitively coupled RFID, then power transfer is achieved, but device complexity and manufacturing complexity increase
Solution Approach 1:
The patent combines the capacitor electrodes directly into the RFID tag's antenna structure and integrated circuit assembly. Rather than using separate external electrodes that would require additional mounting, alignment, and connection steps, the electrodes are formed as part of the tag's existing structure. This integration significantly reduces device complexity and simplifies manufacturing processes.
Solution Approach 2:
The RFID tag structure serves its own dual purpose: the antenna structure automatically functions as both the communication element and the capacitive electrode. This self-service approach eliminates the need for separate dedicated electrodes and reduces the number of components that need to be assembled and managed, thereby reducing overall device 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
This approach enables smaller RFID tags and readers with increased power transfer capabilities, facilitating wider applications and improved reading distances.
Implementation Method 1
power transfer and/or communication may be performed via capacitive coupling
Implementation Method 2
forming first and second capacitors with the electrodes of the RFID reader
Implementation Method 3
using resonant circuits and voltage amplification to increase power transfer
Data Source
Figure 1~2
Figure 3a~3b
Figure 4a~5c
AI summary
An RFID tag for capacitively coupled RFID communication with an RFID reader. The RFID tag comprising an integrated circuit (IC), the IC including a first RFID tag electrode arranged to capacitively couple with a first electrode of the RFID reader to form a first capacitor, and a second RFID tag electrode arranged to capacitively couple with a second electrode of the RFID reader to form a second capacitor when the RFID tag is in a first position relative to the RFID reader; power supply circuitry configured to extract power from a first time-varying signal received from the RFID reader via at least one of the first RFID tag electrode and the second RFID tag electrode, and supply the extracted power to circuitry of the RFID tag; and data transmission circuitry configured to receive the extracted power from the power supply circuitry, and transmit data to the RFID reader via at least one of the first RFID tag electrode and the second RFID tag electrode.