Self-Adaptive RFID Resonator for High-Q Power and Communication
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Solution Overview
Problem
RFID tags face challenges in achieving high Q operation for efficient energy transfer and communication, as high Q values result in narrow frequency bands, making them susceptible to environmental detuning and limiting communication bandwidth.
Innovation Solution
The implementation of a self-adaptive resonator with a MOSFET and capacitive paths that auto-tune to the reader's frequency, combined with a feedback circuit to manage resonance amplitude and facilitate fast communication, allowing for high Q operation during power transfer and rapid response during communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the tag Q is increased to achieve high voltage step up for efficient energy transfer, then the resonance width drops proportionally, making the system susceptible to environmental detuning and limiting communication bandwidth
Solution Approach 1:
The patent applies dynamics by making the resonant frequency of the tag adjustable through a tuning circuit. The resonant frequency can be dynamically changed to match the reader's operating frequency, allowing the system to maintain high Q operation while adapting to different frequency conditions. This resolves the contradiction by enabling the tag to operate at optimal resonance when needed while retaining the ability to shift frequency to avoid detuning.
Solution Approach 2:
The patent changes the resonant frequency parameter of the tag through the tuning circuit, which adjusts the operating parameters of the resonator. By modifying the resonant frequency parameter, the system can maintain high voltage step-up efficiency while adapting to different communication bandwidth requirements and environmental conditions, thus resolving the trade-off between energy efficiency and frequency adaptability.
2Loss of energy
If the tag Q is increased to achieve high voltage step up, then the amplitude of load modulation is attenuated, limiting communication capability
Solution Approach 1:
The tuning circuit dynamically adjusts the resonant frequency to match the reader's frequency, ensuring that the tag operates at peak resonance during power transfer while maintaining the ability to modulate the resonance for communication. This dynamic adjustment allows the system to optimize voltage step-up while preserving communication capability through coordinated control of the resonant frequency.
Solution Approach 2:
The system uses feedback from the reader to detect the tag's resonant frequency and adjusts the tuning circuit accordingly. This feedback mechanism ensures that the tag maintains optimal resonance for voltage step-up while the reader can still detect load modulation signals for communication, resolving the contradiction between energy efficiency and information transfer.
3Length of stationary object
If a high Q resonator is used to extend the range of the RFID tag, then the tag becomes more susceptible to environmental detuning and manufacturing variations
Solution Approach 1:
The tuning circuit provides dynamic frequency adjustment that allows the tag to track and follow the reader's operating frequency. This dynamic tracking capability enables the tag to maintain high Q operation for extended range while compensating for environmental detuning and manufacturing variations, thus resolving the contradiction between range and reliability.
Solution Approach 2:
The system changes the resonant frequency parameter in real-time to match the reader's frequency, allowing the tag to maintain optimal performance across varying environmental conditions. This parameter adjustment capability enables the tag to achieve extended operating range while maintaining reliability through adaptive frequency tuning.
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 solution extends the range of the RFID tag, enhances tolerance to environmental detuning, and enables efficient communication over a wide frequency range, combining long-range capabilities with fast response times.
Implementation Method 1
Radio frequency identification (RFID) generally employs resonance in order to increase the efficiency of energy transfer from the reader to the tag. This is achieved through the resonant recycling of energy that results in voltage step up in the tag when subject to the reader powering field.
Implementation Method 2
a nonlinear resonator that self-adapts to the driving frequency of a reader... the tag has an auto tuning behaviour to the stimulus frequency, provided it is within a designed frequency band
Implementation Method 3
the use of an antenna and two capacitive paths that are coupled into the resonance with a variable duty cycle; the duty cycle is controlled by the waveform amplitude and the gate voltage on a MOSFET
Implementation Method 4
the induced voltage is used to control the mosfet gate voltage and ramp up the amplitude in tag
Implementation Method 5
A method is disclosed in PCT/GB2006/050440 whereby feedback is employed in a reader to reduce the variation in resonance amplitude in response to tag load modulation.
Data Source
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Figure 2A~2B
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AI summary
We describe RFID tag embodiments that incorporate a nonlinear resonator that self-adapts to the driving frequency of a reader. More particularly we describe RF tag comprising: an adaptive resonator configured to receive energy from an electromagnetic field produced by an RF reader; an energy store to store energy received by said adaptive resonator; a transmitter and configured to communicate with an RF reader; and a switch to switch said tag between an energy receiving mode during which said adaptive resonator receives energy from said electromagnetic field and stores energy in said energy store; and a communication mode during which said transmitter communicates with an RF reader.