Surface Acoustic Wave Temperature Sensor Research Articles

Wireless Temperature Measurement for Curved Surfaces Based on AlN Surface Acoustic Wave Resonators.

In this paper, we propose a novel method for temperature measurement using surface acoustic wave (SAW) temperature sensors on curved or irregular surfaces. We integrate SAW resonators onto flexible printed circuit boards (FPCBs) to ensure better conformity of the temperature sensor with the surface of the object under test. Compared to traditional rigid PCBs, FPCBs offer greater dynamic flexibility, lighter weight, and thinner thickness, which make them an ideal choice for making SAW devices working for temperature measurements under curved surfaces. We design a temperature sensor array consisting of three devices with different operating frequencies to measure the temperature at multiple points on the surface of the object. To distinguish between different target points in the sensor array, each sensor operates at a different frequency, and the operating frequency bands do not overlap. This differentiation is achieved using Frequency Division Multiple Access (FDMA) technology. Experimental results indicate that the frequency temperature coefficients of these sensors are -30.248 ppm/°C, -30.195 ppm/°C, and -30.115 ppm/°C, respectively. In addition, the sensor array enables wireless communication via antenna and transceiver circuits. This innovation heralds enhanced adaptability and applicability for SAW temperature sensor applications.

Rational Design of a Surface Acoustic Wave Device for Wearable Body Temperature Monitoring.

Continuous monitoring of vital signs based on advanced sensing technologies has attracted extensive attention due to the ravages of COVID-19. A maintenance-free and low-cost passive wireless sensing system based on surface acoustic wave (SAW) device can be used to continuously monitor temperature. However, the current SAW-based passive sensing system is mostly designed at a low frequency around 433 MHz, which leads to the relatively large size of SAW devices and antenna, hindering their application in wearable devices. In this paper, SAW devices with a resonant frequency distributed in the 870 MHz to 960 MHz range are rationally designed and fabricated. Based on the finite-element method (FEM) and coupling-of-modes (COM) model, the device parameters, including interdigital transducer (IDT) pairs, aperture size, and reflector pairs, are systematically optimized, and the theoretical and experimental results show high consistency. Finally, SAW temperature sensors with a quality factor greater than 2200 are obtained for real-time temperature monitoring ranging from 20 to 50 °C. Benefitting from the higher operating frequency, the size of the sensing system can be reduced for human body temperature monitoring, showing its potential to be used as a wearable monitoring device in the future.

Design and Characterization of Surface Acoustic Wave-Based Wireless and Passive Temperature Sensing System.

The surface acoustic wave (SAW) temperature sensor has received significant attention due to its wirelessly powered, battery-free, and chipless capabilities. This paper proposes a wireless sensing system comprising a one-port SAW resonator, helix antenna, and transceiver circuit. The SAW resonator used in this system is based on aluminum nitride (AlN) thin film, which exhibits high velocity and excellent piezoelectric properties. Simulations and experiments were conducted to investigate the performance of the designed SAW resonator. A helix antenna was also designed using finite element simulation to facilitate signal transmission between the SAW temperature sensor and the transceiver. An impedance-matching network was introduced between the helix antenna and the SAW resonator to optimize signal transmission. When the wireless SAW temperature sensor was placed within a certain distance of the mother antenna, the reflection peak of the SAW resonator was observed in the spectrum of the return signal. The frequency of the echo signal increased almost linearly as the temperature increased during the temperature tests. The fitted temperature coefficient of frequency (TCF) was -31.34 ppm/°C, indicating that the wireless temperature sensing system has high-temperature sensitivity.

High-Resolution and High-Precision Demodulation Method for Surface Acoustic Wave Temperature Sensor Based on PRONY Algorithm

High-Resolution and High-Precision Demodulation Method for Surface Acoustic Wave Temperature Sensor Based on PRONY Algorithm

Research and experiment the wireless passive surface acoustic wave technology for conductor temperature monitoring of high voltage equipment

This paper presents the research and design of a passive thermal monitoring system using wireless temperature sensors based on the principle of surface acoustic wave (SAW). The monitoring system is employed on components that need to be monitored for heat generation, including switch contacts, busbars, and cable connections at switchgears or ring main units (RMUs). The basic impulse insulation level (BIL), or voltage spike tolerance, of the wireless SAW temperature sensor utilised in this study, means that it is not necessary to power it with sensors that meet the high criteria for equipment installed in closed cabinets or medium voltage cabinets. The research team’s activities in this study included software development, data transmission design and manufacture, and sensor selection. The system functions steadily, with a temperature error of no more than 2oC, according to the test findings under laboratory settings.

Development of Temperature Sensor Based on AlN/ScAlN SAW Resonators

Temperature monitoring in extreme environments presents new challenges for MEMS sensors. Since aluminum nitride (AlN)/scandium aluminum nitride (ScAlN)-based surface acoustic wave (SAW) devices have a high Q-value, good temperature drift characteristics, and the ability to be compatible with CMOS, they have become some of the preferred devices for wireless passive temperature measurement. This paper presents the development of AlN/ScAlN SAW-based temperature sensors. Three methods were used to characterize the temperature characteristics of a thin-film SAW resonator, including direct measurement by GSG probe station, and indirect measurement by oscillation circuit and antenna. The temperature characteristics of the three methods in the range of 30–100 °C were studied. The experimental results show that the sensitivities obtained with the three schemes were −28.9 ppm/K, −33.6 ppm/K, and −29.3 ppm/K. The temperature sensor using the direct measurement method had the best linearity, with a value of 0.0019%, and highest accuracy at ±0.70 °C. Although there were differences in performance, the characteristics of the three SAW temperature sensors make them suitable for sensing in various complex environments.

Surface acoustic wave temperature sensor based on Pt/AlN/4 H-SiC structure for high-temperature environments

Surface acoustic wave temperature sensor based on Pt/AlN/4 H-SiC structure for high-temperature environments

Influence of electrode apodization weighted structure on the performance of SAW temperature sensors

In order to improve the comprehensive performance of the surface acoustic wave (SAW) temperature sensors and reduce clutter interference, the optimized Chebyshev window function, Blackman window function and Hamming window function are used to carry out the apodization weighting design for interdigital transducer (IDT) and reflective grating respectively. The influence of electrode apodization weighted structure on the performance of SAW temperature sensors is systematically studied through experiments. The results show that the apodization weighted design of IDT and reflective gate can effectively improve the resonance peak intensity and reduce the side lobe interference; the IDT and the reflection grating are designed with apodization weighting at the same time, compared with the single reflection grating weighting, the volatility of the side lobe of the Chebyshev window function and the Hamming window function increases, the volatility of the side lobe of the Blackman window function decreases; after electrode apodization optimization, the resonance frequency, Q value of the SAW sensor and the sensitivity to temperature increases; using a hamming window optimized electrode structure, the peak value of S11 is −36.73 dB and the Q value is 15 030. In order to ensure the signal processing ability and comprehensive performance of the sensor, an optimized Hamming window should be used for the electrode design of the SAW sensors.

Real-Time Monitoring of Tire Condition with Fast Detection Passive and Wireless TPMS

<div class="section abstract"><div class="htmlview paragraph">Accurate tire pressure monitoring system (TPMS) is of great practical importance and the reliability and safety of its power supply module has great concern. The piezoelectric-based surface acoustic wave (SAW) sensor is considered to have great potential in this field because of its passive, wireless and small size advantages. This paper presents the application of passive and wireless SAW sensors for real-time tire condition monitoring. The pressure sensitive structure is optimized and a three-resonator structure is also designed sensing temperature and pressure. Furthermore, a fast detection system is developed to realize high-speed signal acquisition. At last, experiments are executed and the SAW temperature and pressure sensor property is measured. The results show that the designed SAW sensor can realize real-time monitoring of tire condition; the temperature measurement range can reach -40~120°C with an accuracy of ±1°C; the pressure measurement range can reach 0~2MPa with an accuracy of 0.2MPa. This paper indicates the wireless and passive SAW temperature and pressure sensor system has the potential for application in real-time monitoring of tire condition.</div></div>

4.74-GHz Harmonically Operated SAW Temperature and Strain Sensors

This paper presents the development of surface acoustic wave (SAW) temperature and strain sensors that can operate at high frequencies up to 4.74 GHz. The third harmonic response of the SAW device was utilized to enable operation at higher frequencies, which helped overcome the limitations of the contact photolithography process used in fabrication. Specifically, a design of an orthogonal frequency coding (OFC) SAW device provided by Pegasense LLC and originally designed for use with lithium niobate YZ was implemented on lithium niobate YX 128 cut, which increased the device’s operating frequency from 4.3 GHz to 4.74 GHz. The SAW device demonstrated wireless temperature sensing capabilities with a standard deviation of 0.044C after signal processing using a thousand averages and a matched filter. Additionally, initial measurements of a strain sensor at 4.74 GHz showed good correlation with commercial strain sensor measurements, with a standard deviation of 2.278μstrains using 1000 averages and a frequency sensitivity of -1.260lstrains approximately. The potential of SAW technology to impact super high frequencies (SHF) and its practical application in wireless temperature and strain sensing will be highlighted.

High-Performance SAW Low Temperature Sensors with Double Electrode Transducers Based on 128° YX LiNbO3.

Low temperature measurement is crucial in deep space exploration. Surface acoustic wave (SAW) sensors can measure temperature wirelessly, making them ideal in extreme situations when wired sensors are not applicable. In this study, 128° YX LiNbO3 was first introduced into low temperature measurements for its little creep or hysteresis in cryogenic environments and affordable price. The finite element method was utilized to raise the design efficiency and optimize the performance of SAW sensors by comparing the performance with different interdigital transducer (IDT) structure parameters, including the height of electrodes, pairs of IDTs, reflecting grid logarithm and acoustic aperture. Once the parameters were changed, a novel design of high-performance SAW temperature sensors based on 128° YX LiNbO3 with double electrode transducers was obtained, of which the Q value could reach up to 5757.18, 4.2-times higher than originally reported. Low temperature tests were conducted, and the frequency responsiveness of SAW sensors was almost linear from -100 °C to 150 °C, which is in good agreement with the simulation results. All results demonstrate that double electrode transducers are considerably efficient for performance enhancement, especially for high-Q SAW sensors, and indicate that LiNbO3 substrate can be a potential high-performance substitute for cryogenic temperature measurements.

High-temperature Pt–Al2O3 composite nano-thick interdigital electrodes for surface acoustic wave sensors

High-temperature stability of ultra-thin film electrodes is vital for surface acoustic wave (SAW) devices in harsh environments. This paper proposed the Pt–Al2O3 composite Nano-thick interdigital electrodes (IDEs) for langasite-based high-temperature SAW sensors. The sandwich structure of the IDEs was composed of Pt layers and Al2O3 armors. The armor consisting of barrier and coating layers was introduced to reduce the agglomeration, oxidation, and interdiffusion of IDEs at high temperatures. Capacitive bonding pads were proposed to transmit radiofrequency signals through the closed armor. The composite IDEs (226 nm thickness) had good structural stability and impurities concentration less than 1% at 1000 °C (3 h, air condition). Improved quality factors of 8805, and matched electrical impedance of 51 Ω and −16° were achieved through the electroacoustic optimized IDEs. Finally, multiple SAW temperature sensors using the composite IDEs presented fitting errors less than 1% and hysteresis errors below 4% in 80–1000 °C exceeded 9 h, which was 150 °C higher than existing ones. The proposed composite IDEs enable SAW devices to be applicated in 80–1000 °C.

The development of a smart additively manufactured part with an embedded surface acoustic wave sensor

• The embedding of a temperature SAW sensor in an additively manufactured component results in a wireless and passive smart device. • The adopted embedding strategy did not cause any damage to the structure of the part. • The embedded SAW temperature sensor shows full functionality after the embedding process, confirming that the strategy used was successful in protecting it from the AM process temperatures. This paper presents the embedding of a temperature Surface Acoustic Wave (SAW) sensor in an additively manufactured 316L stainless steel part during the Laser Powder Bed Fusion (L-PBF) process. The embedding of sensors and integrated circuits in additively manufactured (AM) parts is an important step towards the development of smart components; however, there are still some barriers to overcome for this to become an established technology. The L-PBF process is paused to embed a SAW sensor in an AM part to produce a wireless and passive smart component. The effect of the pausing of the L-PBF process to embed sensors on the microstructure and hardness of the manufactured parts is investigated and the embedded sensor is also tested to verify its functionality. These results act as a proof-of-concept for the embedding of SAW sensors during the L-PBF process and will lead to the development of passive wireless smart components manufactured by additive manufacturing.

Anti-irradiation SAW temperature sensor based on 128° YX LiNbO3 single crystal

The ferroelectric materials own the natural anti-irradiation property, paving great potentials and applications regarding the aerospace fields. Benefiting from this property, LiNbO3-based surface acoustic wave (SAW) devices can be used for high accuracy sensing signal test under extreme circumstances. In this work, the 128° YX cut LiNbO3 substrate was adopted for SAW resonator temperature sensor application, and the response frequency varied from 180.44 MHz to 177.628 MHz with temperature from 21.9 ℃ to 199.9 ℃. Subsequently, the device irradiated by 100 Krad Gamma ray was tested with vector network analyzer (VNA). A maximum frequency shift of ~ 0.38% was found under γ-ray irradiation with a dose of 100 Krad on account of slight irradiation effect. The results verify the radiation resistance ability of SAW for development of highly reliable temperature sensor in the irradiation environment.

Wireless Multifunctional Surface Acoustic Wave Sensor for Magnetic Field and Temperature Monitoring

AbstractA one‐port surface acoustic wave (SAW) resonator based on Co40–Fe40–B20/SiO2/ZnO/quartz multilayer structure and exhibiting a dual mode, Rayleigh and Love wave modes, is investigated to achieve a multifunctional sensor measuring both temperatures and magnetic fields. The Rayleigh wave mode of the resonator is used for temperature measurement with a temperature sensitivity of −37.9 ppm/°C, and the Love wave mode is used for magnetic field measurement. Co40‐Fe40‐B20 is the magnetic sensitive layer, and quartz crystal is the piezoelectric substrate. ZnO film is also a piezoelectric but considered here in combination with SiO2 as insulating layers and serves to control impedance matching and temperature dependence of the sensor. ZnO and SiO2 thicknesses are selected to realize temperature compensation for the Love wave mode and making this mode highly sensitive to magnetic fields and insensitive to temperatures. The magnetic field sensitivities of −170.4 kHz m−1 T−1 and −621.6 kHz m−1 T−1 are obtained respectively for the fundamental and the third harmonic of the Love wave mode. The proposed structure is beneficial to design reliable hybrid SAW magnetic field and temperature sensors.

Development of Wireless and Passive SAW Temperature Sensor with Very High Accuracy

A surface acoustic wave (SAW) temperature sensor with high accuracy was developed and wirelessly characterized in this work. The sensing chip with reflective delay line pattern was simulated using typical coupling of modes (COM) model and prepared by the standard photolithographic technique. Sharp reflection peaks with high signal-to-noise (SNR) were observed from the developed sensing chip operating at 433 MHz. Referring to the frequency-stepped continuous wave (FSCW)-based transceiver, planar antennas, and the developed SAW chip, the wireless and passive temperature sensor system was built. Adaptive Least Mean Square (LMS) algorithm was used for the first time in the SAW sensor signal processing to significantly improve the system SNR, and the corresponding phase fluctuation is down to only 3°. High temperature sensitivity of 36.5 °C and very high accuracy of ±0.2 °C in the range of −30 °C∼100 °C were achieved successfully by wireless measurement.

Novel Multilayer SAW Temperature Sensor for Ultra-High Temperature Environments

Performing high-temperature measurements on the rotating parts of aero-engine systems requires wireless passive sensors. Surface acoustic wave (SAW) sensors can measure high temperatures wirelessly, making them ideal for extreme situations where wired sensors are not applicable. This study reports a new SAW temperature sensor based on a langasite (LGS) substrate that can perform measurements in environments with temperatures as high as 1300 °C. The Pt electrode and LGS substrate were protected by an AlN passivation layer deposited via a pulsed laser, thereby improving the crystallization quality of the Pt film, with the function and stability of the SAW device guaranteed at 1100 °C. The linear relationship between the resonant frequency and temperature is verified by various high-temperature radio-frequency (RF) tests. Changes in sample microstructure before and after high-temperature exposure are analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The analysis confirms that the proposed AlN/Pt/Cr thin-film electrode has great application potential in high-temperature SAW sensors.

Development of Inplantable Surface Acoustic Wave Sensor for High Voltage Cable Core Temperature Monitoring in Intermediate Joint

In this paper, a kind of implantble passive wireless surface acoustic wave (SAW) sensor and its reader are developed to measure the operation temperature of high voltage crossed-linked cable core. A small type SAW temperature sensor is embedded into cable intermediate joint. A radio frequecny transceiver of the reader based on discrete devices is optimally designed to achieve high signal-to-noise ratio and receiving sensitivity. The characteristic of resonant frequency and temperature of SAW sensor is determined by frequency scan method. Through AC withstand voltage and temperature rise test of 110kV cable, it proves that the prototype can accurately measure the operation temperature of 110kV cable core in intermediate joint under high operation temperature and strong electromagnetic environment.

GHz AlN-based multiple mode SAW temperature sensor fabricated on PEN substrate

Polymeric based surface acoustic wave (SAW) devices represent one of the most interesting platform for the development of wireless passive sensors for IoT and smart packaging applications. An important feature to be addressed in order to develop a compact and conformable wireless SAW sensor is the increase of the working frequency which allows an easy antenna integration and miniaturization.In this work, we present a disposable polymeric SAW temperature sensor device working in the GHz range, based on aluminum nitride (AlN) and built on a 125 μm thick film of polyethylene naphthalate. The flexible device has been compared to the same SAW device fabricated onto silicon substrates. The polymeric based SAW device shows three operating wave modes corresponding to the Rayleigh, Love, and Lamb, highlighting that the Lamb mode exhibits a resonance frequency as high as 1.325 GHz, corresponding to a phase wave velocity of 10,600 m/s, an electromechanical coupling of 2.91 % and Q factor of 109. Temperature coefficient of frequency (TCF) values of 149, 109, 53 ppm/°C have been calculated for the Rayleigh, Love and Lamb waves, respectively.The different behavior of the three SAW modes let us envision the development of a multiple sensing platforms based on different modes in the same device (e.g. temperature, microbiological contamination, light exposure).

Surface Acoustic Wave Resonator Echo Signal Frequency Estimation

Surface Acoustic Wave (SAW) resonator measuring technology can be used in high temperature and high pressure, strong electromagnetic radiation and strong electromagnetic interference to realize wireless passive parameter detection. Based on the the non-stationary characteristics of the SAW signal, a kind of echo signal frequency estimation method, Digital Frequency Significant Place Tracking (DFSPT) method is put forward. Compared with the existing methods based on Fast Fourier Transform (FFT) and Singular Value Decomposition (SVD), the simulation results show that the method can determine the number of significant digits of digital frequency according to the difference of signal-to-noise ratio. Thus, it can increases stability and accuracy. The experiment of wireless SAW temperature sensor shows that the frequency estimation standard deviation of this method is small and the robustness is high.