Passive RFID Tag Temperature Measurement via Capacitor Discharge
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Solution Overview
Problem
Traditional temperature measurement methods using passive RFID tags are costly, energy-intensive, and not suitable for non-line-of-sight scenarios, as they require additional sensors and are sensitive to environmental changes.
Innovation Solution
A method that utilizes the maximum discharging duration of a passive RFID tag's circuit to estimate environmental temperature without additional equipment or hardware changes, by acquiring and analyzing the circuit's temperature features through the tag's de-energized persistence time, which is independent of environmental factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated temperature sensor is embedded in the passive RFID tag, then temperature measurement capability is achieved, but manufacturing cost increases significantly
Solution Approach 1:
The patent makes the passive RFID tag multi-functional by enabling it to perform both identification and temperature measurement functions. The tag uses its existing circuit components (capacitor, resistor, diode) for temperature sensing without adding dedicated temperature sensor hardware, allowing a single device to serve multiple purposes.
Solution Approach 2:
The passive RFID tag measures temperature using its own internal circuit components rather than requiring external sensors or additional hardware. The tag's capacitor discharge characteristics are exploited to infer temperature, allowing the system to self-diagnose environmental conditions without external assistance.
2Measurement precision
If a dedicated temperature sensor is embedded in the passive RFID tag, then temperature measurement capability is achieved, but communication distance and computing capability are reduced
Solution Approach 1:
The patent enables the passive RFID tag to perform temperature measurement using its existing communication and circuit components, avoiding the need for additional sensors that would consume power and reduce communication range. The same transceiver circuitry used for identification also facilitates temperature data transmission.
Solution Approach 2:
The tag uses its own operational characteristics (capacitor discharge time) to measure temperature, rather than relying on separate sensing mechanisms. This self-service approach maintains the tag's original power consumption profile and communication capabilities while adding temperature sensing functionality.
3Ease of manufacture
If physical layer information of the tag signal is used for temperature detection, then unmodified general passive tags can be used, but expensive radio wave analysis equipment is required
Solution Approach 1:
The patent introduces a standard RFID reader as an intermediary device that can extract temperature information from the tag's capacitor discharge characteristics during normal communication. This mediator translates the physical layer signal variations into usable temperature data without requiring specialized expensive analysis equipment.
Solution Approach 2:
The patent exploits changes in the tag's capacitor discharge time constant as a temperature-dependent parameter. By measuring how the discharge characteristics change with temperature, the system can infer temperature information from standard RFID communication signals using conventional readers.
4Ease of manufacture
If physical layer information methods are used for temperature detection, then unmodified tags can be utilized, but the methods are very sensitive to environmental changes and tag position cannot be changed
Solution Approach 1:
The patent replaces sensitive physical layer signal analysis with a more robust electrical measurement approach based on capacitor discharge characteristics. This electrical measurement method is less susceptible to environmental interference and signal propagation effects that plague radio wave analysis methods.
Solution Approach 2:
The patent uses the tag's internal capacitor discharge time constant as a temperature indicator, which is an intrinsic electrical property less affected by external environmental factors compared to radio signal characteristics. This allows for more reliable temperature measurement across different positions and environmental conditions.
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 provides robust, accurate, and non-line-of-sight temperature sensing with high robustness against environmental changes, compatible with existing commercial RFID devices, and does not require modifications to tags or readers.
Implementation Method 1
the circuit temperature feature of the tag is the maximum discharging duration within which a passive RFID tag can operate normally during a discharging process after the tag is fully charged and then powered off
Implementation Method 2
temperature will change the resistance of the tag circuit, thereby affecting the radio signal emitted by the tag
Data Source
AI summary
A temperature measurement method based on a passive RFID tag. The method comprises: acquiring a circuit temperature feature of a tag multiple times, and establishing a tag temperature-feature correspondence; and estimating, by using the tag temperature-feature correspondence and the current circuit temperature feature of the tag, the temperature of an environment where the tag is located, wherein the circuit temperature feature of the tag is the persistence time within which a passive RFID tag can operate normally during a discharging process after the tag is fully charged. By means of the method, a robust and accurate temperature measurement is achieved, and a tag can be directly deployed on an existing commercial RFID device without modifying the hardware of the tag and a reader.