Hybrid RFID Tag With Optical Clock Extraction
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Solution Overview
Problem
Conventional RFID tags face challenges in achieving a small footprint due to the need for separate antennas for transmit and receive modes, complex circuitry, and battery power, making them impractical for very small integration areas and prone to mutual coupling and interference.
Innovation Solution
A hybrid framework incorporating an optical transmitter/receiver system and an RF transmitter/receiver system, where the RFID tag extracts clock signals from optical signals and generates a regulated supply voltage, eliminating the need for on-chip batteries and complex circuitry like VCOs and PLLs, and using magnetic coupling for wireless communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional RFID tags use separate antennas for transmit and receive modes, then communication functionality is achieved, but the footprint area increases significantly
Solution Approach 1:
The patent merges the transmit and receive antenna functions into a single antenna structure. The antenna can operate in transmit mode by receiving RF energy from the reader and converting it to optical signals, and in receive mode by detecting optical signals from the reader. This consolidation eliminates the need for separate transmit and receive antennas, significantly reducing the footprint area while maintaining full communication functionality.
Solution Approach 2:
The patent introduces an optical signal as an intermediary to transfer information between the RFID tag and reader. Instead of using traditional RF bidirectional communication requiring separate antennas, the tag receives RF energy, converts it to optical signals for data transmission, and the reader converts optical signals back to RF for reception. This optical intermediary enables full-duplex communication with a single antenna.
2Area of stationary object
If RFID tags operate at higher frequencies with smaller antennas, then footprint is reduced, but mutual coupling and interference occur between antennas
Solution Approach 1:
The patent uses optical signals as an intermediary to eliminate RF mutual coupling between antennas. By converting RF signals to optical signals for data transmission, the system avoids the harmful electromagnetic interference and mutual coupling that occur when multiple RF antennas are placed close together, even at higher frequencies.
3Area of stationary object
If RFID tags decrease in size, then integration area is reduced, but complex circuitry like VCOs and PLLs becomes impractical
Solution Approach 1:
The patent extracts the clock signal generation functionality from the tag by receiving clock signals from the reader via optical signals. This eliminates the need for on-chip VCOs and PLLs, which are complex and area-consuming, while still providing accurate timing control for the tag's operations.
Solution Approach 2:
The tag uses the optical signals received from the reader to generate its own supply voltage and clock signals through on-chip circuitry. This self-service approach eliminates the need for external batteries and complex clock generation circuits, reducing both area and complexity while enabling autonomous operation.
4Use of energy by moving object
If RFID tags use batteries or power generating circuitry, then power supply is achieved, but area consumption increases
Solution Approach 1:
The patent implements self-service power generation where the tag uses optical signals received from the reader to generate its own supply voltage through on-chip voltage regulator circuitry. This eliminates the need for separate batteries or power generating circuits, providing continuous power supply while minimizing area consumption.
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 the development of very small footprint RFID tags with high integration density, operating autonomously without batteries and complex clock signal generation, reducing mutual interference and area consumption while maintaining effective communication.
Implementation Method 1
The optical receiver circuitry is configured to receive an optical signal having an embedded clock signal from an interrogator device, and convert the optical signal into an electrical signal comprising the embedded clock signal
Implementation Method 2
The receiver circuitry is configured to (i) apply an unmodulated radio frequency carrier signal to the antenna, (ii) detect changes in amplitude of an amplitude modulated backscattered radio frequency carrier signal which is reflected from the tag device and captured on the antenna
Data Source
AI summary
RFID (radio frequency identification) systems are provided in which tag and interrogator devices implement a hybrid framework for signaling including an optical transmitter/receiver system and an RF transmitter/receiver system. For instance, an RFID tag device includes: optical receiver circuitry configured to receive an optical signal having an embedded clock signal from an interrogator device, and convert the optical signal into an electrical signal comprising the embedded clock signal; clock extraction circuitry configured to extract the embedded clock signal from the electrical signal, and output the extracted clock signal as a clock signal for controlling clocking functions of the tag device; voltage regulator circuitry configured to generate a regulated supply voltage from the electrical signal, wherein the regulated supply voltage is utilized as a bias voltage for components of the tag device; and data transmitter circuitry configured to wirelessly transmit tag data to the interrogator device.