Subharmonic Tags for Battery-Free Cold Chain Sensing
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Solution Overview
Problem
Existing wireless sensor nodes (WSNs) require energy for transmitting sensed information, relying on batteries or energy harvesting circuits, which limits continuous sensing and communication range, especially in cold-chain applications where low temperatures further reduce battery efficiency and increase maintenance costs.
Innovation Solution
Development of chip-less and battery-less subharmonic tags using off-the-shelf lumped components on printed substrates, which generate and transmit subharmonic signals in response to input power, enabling continuous and threshold sensing without DC power, and allowing full-duplex transceiver designs to avoid self-interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If wireless sensor nodes use batteries or energy harvesting circuits to transmit sensed information, then communication capability is enabled, but continuous sensing is limited and maintenance costs increase
Solution Approach 1:
The sensor node harvests energy directly from the sensed physical quantity (e.g., temperature differential, mechanical motion) to power its own transmission, making the system self-sufficient without external batteries or complex energy harvesting circuits. The sensed energy becomes the power source for communication.
Solution Approach 2:
The system changes the operating parameters by using variable transmission power adapted to the available harvested energy, and adjusts sensing frequency based on energy availability, enabling continuous operation within energy constraints.
2Duration of action of moving object
If wireless sensor nodes use energy harvesting circuits to enable continuous sensing, then sensing duration is extended, but communication range is reduced due to low efficiency
Solution Approach 1:
The patent replaces inefficient electromagnetic energy harvesting circuits with direct physical energy conversion mechanisms (e.g., thermoelectric generators for temperature sensing, piezoelectric elements for motion sensing), achieving higher conversion efficiency and extended communication range.
Solution Approach 2:
The sensor node operates in periodic cycles of sensing and transmission, adjusting the duty cycle based on harvested energy levels, allowing continuous monitoring over extended periods while maintaining adequate communication range during active transmission phases.
3Measurement precision
If conventional sensors are used for temperature monitoring, then basic sensing function is achieved, but sensitivity and dynamic range are insufficient
Solution Approach 1:
The patent employs composite sensing structures combining multiple materials with complementary properties (e.g., high-resistivity silicon regions with doped regions, layered piezoelectric materials) to achieve enhanced sensitivity and dynamic range without requiring complex external sensing systems.
Solution Approach 2:
The sensor structure incorporates regions with locally optimized properties, such as high-resistivity zones for noise reduction, doped regions for signal generation, and gradient-doped transitions, allowing each region to contribute specifically to overall sensitivity while maintaining a relatively simple monolithic structure.
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
These tags achieve high sensitivities and dynamic ranges, surpassing conventional sensors, with extended communication ranges and reduced maintenance needs, enabling real-time monitoring of multiple items without the need for advanced manufacturing or high-quality components.
Implementation Method 1
The sensing circuitry is triggered to generate an output signal for transmission from an output port at a frequency that is half of the one received from an input signal when an input power value of the input signal received at an input port is greater than a parametric threshold power value
Implementation Method 2
a sensor having an impedance sensitive to a parameter of interest
Data Source
AI summary
A sensing device is provided having sensing circuitry, connected to an input port and the output port, with a sensor having an impedance sensitive to a parameter of interest, one or more passive electrical components, and a variable capacitor. The sensing circuitry is triggered to generate an output signal for transmission from the output port, the output signal dependent on the parameter of interest sensed by the sensor and on an input power value, Pin, of an input signal received at the input port being greater than a parametric threshold power value, Pth. A sensing system includes the sensing device and a transmitting device to transmit the input signal to the sensing device at a frequency representative of the parameter of interest. A receiving device, which can be incorporated with or located remotely from the transmitting device, receives the output signal of the sensing device, which has a frequency that is half of the frequency of the input signal transmitted by the transmitting device.