Differential SAW Sensor Design for Temperature Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing temperature measurement systems using single resonators are limited by maximum interrogation distance and are sensitive to frequency pulling effects due to antenna impedance variations, leading to aberrant temperature measurements, especially in metal environments.
Innovation Solution
A method for optimizing the design of a device with differential passive sensors comprising two resonators, involving the determination and selection of curves representing the received power/transmitted power ratio to achieve two frequency peaks with a narrow mid-height width, optimizing sensor antenna impedance to minimize frequency pulling and maximize interrogation distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single resonator is used for temperature measurement, then the device complexity is reduced, but the measurement precision deteriorates due to frequency pulling effects and limited interrogation distance
Solution Approach 1:
The patent divides a single resonator into two separate resonators with different center frequencies. This segmentation allows the system to measure temperature based on the frequency difference between the two resonators, which is immune to frequency pulling effects caused by antenna impedance variations, thereby improving measurement precision while maintaining relatively simple device structure
Solution Approach 2:
The patent introduces an intermediary calculation method where the temperature is determined from the frequency difference between two resonators rather than from absolute frequency values. This intermediary approach eliminates the impact of antenna impedance variations on measurement accuracy and extends the effective interrogation distance
2Length of stationary object
If the antenna impedance is optimized for maximum power transfer, then the interrogation distance is increased, but the frequency pulling effect worsens leading to aberrant temperature measurements
Solution Approach 1:
The patent extracts the temperature measurement information from the frequency difference between two resonators, separating it from the absolute frequency values that are affected by antenna impedance. This extraction allows the system to maintain maximum power transfer for extended interrogation distance while eliminating frequency pulling effects on measurement accuracy
Solution Approach 2:
The patent changes the measurement parameter from absolute resonator frequency to frequency difference between two resonators. This parameter transformation makes the measurement immune to antenna impedance variations, allowing optimization of antenna impedance for maximum interrogation distance without compromising temperature measurement accuracy
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 enhances temperature measurement accuracy by reducing aberrant readings and increasing the interrogation distance, while maintaining a high signal level, thereby improving the reliability of temperature measurements in various environments.
Implementation Method 1
surface wave resonator is composed of metal electrodes, deposited by standard photolithography methods in microelectronics, on the surface of a piezoelectric substrate
Implementation Method 2
surface wave resonator is composed of metal electrodes, deposited by standard photolithography methods in microelectronics, on the surface of a piezoelectric substrate
Implementation Method 3
interdigital combs surrounded on either side by Bragg mirrors M1 and M2. At the resonance frequency, the condition of synchronism between the reflectors is satisfied making it possible to obtain a coherent addition of the different reflections which occur under the reflectors
Implementation Method 4
the resonator is discharged into the antenna which is connected to it, transmitting a decreasing exponential at its natural oscillation frequency Fr, that is to say at the resonance frequency
Data Source
AI summary
A method for optimizing the design of a device includes interrogation means and a differential passive sensor, including a generator connected directly or indirectly to a reader antenna, a passive sensor including at least two resonators, a sensor antenna connected to the sensor. The method includes determining a set of curves PSAW as a function of the frequency of interrogation of the sensor, each curve being defined for a given impedance ZT representing the impedance of the Thevenin equivalent generator dependent on the impedance of the reader antenna, on the impedance of the sensor antenna and on the coupling between the two antennas, for a given sensor impedance ZSAW; selecting at least one curve PSAW from the set of predefined curves meeting two criteria: exhibiting two frequency peaks representative of a coherent differential sensor behavior; having a width at mid-height of the two the peaks below a threshold value; and determining the sensor antenna exhibiting the sensor antenna impedance correlated to the curve PSAW selected for the predefined SAW sensor.