Passive RFID Sensor Tag Harmonic Oscillator Design
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Solution Overview
Problem
Passive RFID sensors face limitations in sensitivity and read-out distance due to the constraints of existing oscillators, which are often sized and powered for specific sensor elements, leading to reduced sensitivity and increased power consumption, especially when incorporating generic sensor elements like MEMS sensors.
Innovation Solution
A passive RFID transponder design featuring an oscillator with a harmonic multiple modulation frequency, utilizing a frequency divider to enhance sensitivity, allowing the oscillation frequency to be dependent on sensed values without additional power-consuming components, and enabling multiple sensing elements to be integrated with digitally controlled switches for optimal sensitivity across various capacitance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an oscillator is sized and powered for specific sensor elements, then sensitivity is improved, but power consumption increases and adaptability decreases
Solution Approach 1:
The oscillator is designed to operate with multiple different sensor elements (capacitive, inductive, resistive) rather than being dedicated to a single sensor type. The system can adapt the oscillator parameters based on which sensor element is connected, allowing one oscillator circuit to serve multiple sensing functions without requiring separate oscillators for each sensor type.
Solution Approach 2:
The oscillator parameters (frequency, amplitude, duty cycle) are dynamically adjusted based on the detected sensor element type and the desired sensitivity level. By changing operational parameters rather than hardware configuration, the system achieves high sensitivity for different sensors without increasing power consumption through additional dedicated circuits.
2Measurement precision
If an oscillator is sized and powered for specific sensor elements, then sensitivity is improved, but device complexity increases
Solution Approach 1:
A single oscillator circuit replaces what would traditionally require multiple dedicated oscillators for different sensor types. The universal oscillator can be configured through software or control logic to work with capacitive sensors, inductive sensors, resistive sensors, and other sensor elements, eliminating the need for multiple physical oscillator circuits and reducing overall device complexity.
Solution Approach 2:
The patent combines multiple sensing capabilities into a single integrated oscillator-based sensing system. Different sensor elements are connected to the same oscillator, which modulates its operation based on the sensor feedback, merging what would be separate sensing circuits into one unified design.
3Measurement precision
If additional power-consuming components are added to enhance sensitivity, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The sensor element itself is used to modulate the oscillator operation rather than requiring separate signal conditioning circuits. The sensor's natural electrical characteristics (capacitance, inductance, resistance) directly influence the oscillator frequency or amplitude, eliminating the need for additional power-consuming signal amplification or conversion components.
Solution Approach 2:
The patent replaces traditional electronic signal conditioning circuits with a direct electro-mechanical coupling approach where the sensor element physically interacts with the oscillator circuit. This substitution eliminates intermediate electronic components that would consume power, using the sensor's inherent electrical properties to directly control oscillator behavior.
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 design achieves high sensitivity and extended read-out distance for passive RFID sensors, allowing small changes in sensed properties to be detected without increasing power consumption or component size, and is compatible with existing RFID systems, enabling efficient measurement of external quantities.
Implementation Method 1
an oscillator providing a modulation frequency for the modulator, a sensing element connected to the oscillator such that an oscillation frequency of the oscillator is dependent on a value of a predetermined variable sensed by the sensing element, wherein the oscillation frequency is a harmonic multiple N of the modulation frequency
Implementation Method 2
a passive wireless transponder comprising an antenna, a rectifier, and a modulator for communication with a backscattering principle to provide radio frequency identification (RFID) features
Data Source
AI summary
In a RFID sensor tag, a sensing element is connected to an oscillator such that an oscillation frequency of the oscillator is dependent on a value of a predetermined variable sensed by the sensing element. The oscillation frequency of the oscillator is a harmonic multiple N of a modulation frequency required for a backscattering modulator. A frequency divider is arranged at the output of the oscillator to produce the modulation frequency from the oscillation frequency. The oscillator can be designed and dimensioned such that a high sensitivity is obtained with all sensor values, and the desired modulation frequency is derived resulting oscillation frequency by selecting a suitable division ratio N.