Passive Surface Acoustic Wave Sensors Research Articles

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>

Special Issue on Wireless and Passive Surface Acoustic Wave Sensor

The surface acoustic wave (SAW) generated by the so-called piezoelectric effect was confined to the piezoelectric substrate surface at a depth of one or two wavelengths; hence, it was very sensitive towards the external perturbations [...]

Passive Surface Acoustic Wave Sensors for Early Corrosion Onset Detection

Corrosion creates serious safety concerns and economic burden in fuel processing and transportation. Being able to monitor the infrastructures in real time and detect corrosion onset may prevent potential consequences resulting from their failure. Passive wireless surface acoustic wave (SAW) devices are promising passive devices to detect the presence of water and corrosion onset amongst other parameters in natural gas pipelines and wellbore tubes. Here, we present on the possibility of using shear horizontal (SH-) SAW devices for monitoring metal film dissolution in hydrochloric acid of varied pH. 520 MHz SH-SAW reflective delay lines with two reflectors were fabricated on 36°Y-X LiTaO3, of which a channel was coated with 60 nm thick iron film by magnetron sputtering. With the film, the sensor had a center frequency of 529.8 MHz when measured in air. The sensor showed a slight attenuation and small frequency shift in DI water. In HCl solution with pH 2.01, the sensor’s center frequency first decreased with time for the first six minutes to reach down to 521 MHz and then remained almost unchanged. The S11 magnitude also showed similar behavior. After ten minutes immersion into the corrosive solution, no iron film was left under a visual inspection. The decrease in the frequency and attenuation is probably due to the changes in the mass and elasticity and the film surface roughening, respectively. Observed initial results are promising towards the implementation of SAW devices for monitoring corrosion in metallic structures in real time.

Wireless passive surface acoustic wave (SAW) technology in gas sensing

PurposeThis paper aims to give an overview about the state of wireless passive surface acoustic wave (SAW) gas sensor used in the detection of chemical vapor. It also discusses a variety of different architectures including delay line and array sensor for gas detection, and it is considered that this technology has a good application prospect.Design/methodology/approachThe authors state the most of the wireless passive SAW methods used in gas sensing, such as CO2, CO, CH4, C2H4, NH3, NO2, et al., the sensor principles, design procedures and technological issues are discussed in detail; their advantages and disadvantages are also summarized. In conclusion, it gives a prospect of wireless passive SAW sensor applications and proposes the future research field might lie in the studying of many kinds of harmful gases.FindingsIn this paper, the authors will try to cover most of the important methods used in gas sensing and their recent developments. Although wireless passive SAW sensors have been used successfully in harsh environments for the monitoring of temperature or pressure, the using in chemical gases are seldom reported. This review paper gives a survey of the present state of wireless passive SAW sensor in gas detection and suggests new and exciting perspectives of wireless passive SAW gas sensor technology.Research limitations/implicationsThe authors will review most of the methods used in wireless passive SAW sensor and discuss the current research status and development trend; the potential application in future is also forecasted.Originality/valueThe authors will review most of the methods used in wireless passive SAW sensor and discuss the current research status and development trend; the potential application in future is also forecasted.

Passive wireless UV SAW sensor

This paper presents studies of a passive wireless ultraviolet (UV) surface acoustic wave (SAW) sensor operating in the frequency range 436–440 MHz. The sensor contains two SAW delay lines (DLs). The first DL is measuring, and the second is the reference. In the measuring DL, receiving–transmitting inter-digital transducer (IDT) is connected to the antenna and the sensing element zinc oxide film. In the reference DL, the receiving–transmitting IDT is connected to another antenna and does not contain a UV-sensitive element. Two methods of information reading from the sensor are proposed: based on the Fourier transform of the frequency dependence of the parameter S11 of the reader antenna and using reading pulses of 1.5-μs duration, which have carrier frequencies corresponding to the central frequencies of the measuring and reference channels. The sensor can measure UV intensities from 10 to 40,000 μW/cm2 with a maximum sensitivity of 6000 ppm/(μW/cm2) at low intensities, and which rapidly decreases as the UV intensity increases (less than 100 ppm at the UV intensity of 40,0000 µw/cm2).

Efficient data delivery in dense reader environment of passive sensor network

Wireless Sensor Network (WSN) is a self-organizing network which is mostly employed in industrial scale. In this network, there is random dispersion of nodes in order to sense diverse range of parameters. The main objective of this research paper is to scrutinize the design of Wireless Surface Acoustic Wave (SAW) Sensor Network (WSSN). Passive SAW sensor is a ridged sensor which is best suited to monitor harsh environmental condition. It works in a dense reader environment for stable communication because it has a narrow connectivity radius. In this research paper, the viability analysis has been performed, utilizing WirelessHART (WH) connectivity protocol, by gauging the operation of WSSN with simulator and emulator in aggregation, in order to support the practicality of WSSN. The results have shown that WH can be relied upon and implemented in a Dense Reader Environment (DRE) for commercial applications. The analysis has also showed the efficiency of WH in rugged and harsh environments. However, WH is not built to operate particularly in DRE. Through our study, a distinctive anti-collision algorithm, NFRA-C is proposed, which is in line with protocols of the WSSN and WH. NFRA-C provides noise free connectivity in WSSN as compared to other protocols. A power proficient standard (GREEN protocol) with capabilities of network coding is analyzed for WSSN. GREEN protocol even works in DRE producing high packet transmission percentage because the protocol arrangement is used with the network coding and retransmission request capabilities.

Development of a Wireless Surface Acoustic Wave Methane Sensor Using a Metal-Organic Framework As a Sensing Layer for Natural Gas Pipelines

Methane emission from the processing and transportation of fossil fuels can create serious environmental and safety issues as well as a financial burden. The need to monitor the energy infrastructure creates an opportunity for developing low-cost and robust sensors with wireless options. Wireless surface acoustic wave (SAW) devices, which are highly sensitive, cost-efficient, and passive, are a potential candidate for these applications. Nanoporous metal-organic frameworks (MOFs), which can selectively adsorb large amounts of gases in engineered pores at ambient conditions, are potential sensing layers. Here, we present on the development of a wireless and passive SAW sensor using the MOF zeolitic imidazolate framework-8 (ZIF-8) as the sensing layer for methane detection at ambient conditions. The SAW delay lines (nominal operating frequency = 436 MHz) were custom fabricated on Y-Z LiNbO3 piezoelectric substrates and coated with a 500 nm thick ZIF-8 layer using a dip coating method. The devices were excited by 428 MHz RF pulses to test for various concentrations of CO2 and CH4 in N2 background at a constant gas flow rate. Wireless measurements were performed via dipole antennas of nominal resonant frequency 433 MHz. When the sensor was exposed to the gases, surface acoustic wave phase shifted in a negative direction relative to the N2 baseline. This shift was attributed to the decrease in SAW velocity due to the increased mass of the MOF film upon gas adsorption. The CO2 and CH4 sensitivities extracted as the slopes of the respective calibration curves were 1.26 deg/vol-% and 0.03 deg/vol-%, respectively. It is important to note that currently tested minimum concentrations of CO2 and CH4 were 1% and 20%, respectively. Also, the wireless measurements were highly affected by the housing and metal reflectors around it. The demonstration on wireless methane sensing is of great importance for remote monitoring of methane emission sites and transmission pipelines. Our current investigations are focused in advancing the detection limit for leak detection and addressing the electromagnetic interferences in wireless measurement caused by the housing.

Fast and Accurate Finite Transducer Analysis Method for Wireless Passive Impedance-Loaded SAW Sensors.

An accurate and fast simulation tool plays an important role in the design of wireless passive impedance-loaded surface acoustic wave (SAW) sensors which have received much attention recently. This paper presents a finite transducer analysis method for wireless passive impedance-loaded SAW sensors. The finite transducer analysis method uses a numerically combined finite element method-boundary element method (FEM/BEM) model to analyze non-periodic transducers. In non-periodic transducers, FEM/BEM was the most accurate analysis method until now, however this method consumes central processing unit (CPU) time. This paper presents a faster algorithm to calculate the bulk wave part of the equation coefficient which usually requires a long time. A complete non-periodic FEM/BEM model of the impedance sensors was constructed. Modifications were made to the final equations in the FEM/BEM model to adjust for the impedance variation of the sensors. Compared with the conventional method, the proposed method reduces the computation time efficiently while maintaining the same high degree of accuracy. Simulations and their comparisons with experimental results for test devices are shown to prove the effectiveness of the analysis method.

A context-aware frequency estimation method for wireless passive resonant SAW sensors

PurposeThis paper aims to present an context evaluation and frequency measurement method for surface acoustic wave (SAW) resonant sensor.Design/methodology/approachThis method is based on a signal subspace construction, which, along with assembling optional value set, provides the results.FindingsThe method can assess the application context and improve the resolution and accuracy of the passive wireless SAW resonator sensor system.Originality/valuePassive wireless SAW resonators have been used as sensor elements for different physical parameters such as temperature, pressure and force in a number of industrial and medical applications. Various wireless channel environments introduce different application contexts.

Research on transmission performance of a surface acoustic wave sensing system used in manufacturing environment monitoring

Surface acoustic wave (SAW) sensors show great promise in monitoring fast-rotating or moving machinery in manufacturing environments, and have several advantages in the measurement of temperature, torque, pressure, and strain because of their passive and wireless capability. However, very few studies have systematically attempted to evaluate the characteristics of SAW sensors in a metal environment and rotating structures, both of which are common in machine tools. Simulation of the influence of the metal using CST software and a series of experiments with an SAW temperature sensor in real environments were designed to investigate the factors that affect transmission performance, including antenna angles, orientations, rotation speeds, and a metallic plate, along with the interrogator antenna–SAW sensor antenna separation distance. Our experimental measurements show that the sensor’s optimal placement in manufacturing environments should take into account all these factors in order to maintain system measurement and data transmission capability. As the first attempt to systematically investigate the transmission characteristics of the SAW sensor used in manufacturing environment, this study aims to guide users of SAW sensor applications and encourage more research in the field of wireless passive SAW sensors in monitoring applications.

RF energy powered wireless temperature sensor for monitoring electrical equipment

In this work, a radio frequency (RF) energy powered temperature sensor (RFEH) is presented. The aim of this work is to assess whether RFEH is a real alternative to passive surface acoustic wave (SAW) for a high voltage equipment sensing. The RFEH system consists of a dual channel reader and several sensor nodes. The sensor nodes are powered by RF energy transmitted from the reader. The transmitted RF energy is also used as a wake up message for turning on a desired sensor avoiding data clashing. The experiments have successfully demonstrated reliable data transmissions between the sensor nodes and reader. The RF energy harvesting modules are also able to withstand a short burst of electrical discharge at 25kV for 60s. When the sensor nodes are placed on top of the hotplate, the measured temperature is linearly related to the variations of actual temperature with a maximum error of 3.2°C. According to our analysis, RFEH can be considered as a low cost alternative to passive SAW sensor.

A noise-robust method for passive wireless resonant SAW sensor

Purpose This paper aims to propose a noise-robust method to estimate the frequency of the reflective echo to reduce the negative effects of noise and improve the accuracy and resolution of a resonant surface acoustic wave (SAW) sensor. Design/methodology/approach The proposed approach exploits the singular value decomposition to obtain the frequency information of a SAW response signal and overcome the noise influences. Findings Compared with the commonly used Fourier transform (FT) method, the accuracy and resolution improvement of the proposed method used in the SAW sensor is validated. Originality/value The system using the proposed method delivers lesser standard deviation, that is, delivers higher performance than the conventional system using the fast FT method.

Uncertainty-aware frequency estimation algorithm for passive wireless resonant SAW sensor measurement

Passive wireless surface acoustic wave (SAW) resonators have been used as sensor elements for different physical parameters such as temperature, pressure, and force in a number of industrial and medical applications. Their operation is based on measuring the variation of the SAW resonant frequency with a physical parameter. The good measurement practice requires that the measurement uncertainty is estimated and provided together with the measurement result. This paper presents an uncertainty-aware frequency estimation approach, based on representation of the measurement uncertainty with a confidence probability of 95%, which, along with accurately calculating the frequency of the received echo signal, provides a quality evaluation for each measured SAW resonant frequency. The method has been validated by experiments.

Water Pressure Sensingbased on Wireless Passive SAW Technology

The conventional water pressure measurement method requiresbatteries as power sources for pressure sensors. This methodis unreliable because the risk of damaging batteries is high especially in harsh environment. This paper provides a novel method that wireless passive surface acoustic wave (SAW) pressure sensoris introduced for water pressure measurement. Wireless passive SAW sensors do not need direct power supply. Therefore, batteries are not requiredby using this new technology. The main types of wireless passive SAW sensors are reviewed. The performance of wireless passive SAW sensor is tested. The water pressure sensing framework is proposed.

Wireless SAW Sensor Temperature Extraction Precision

Surface acoustic wave (SAW) devices are suitable for use in harsh environments because of their ruggedness under radiation and extreme temperatures and ability to be configured as passive wireless sensors. This orthogonal frequency coded (OFC) sensor system consists of a transceiver that wirelessly interrogates the passive SAW sensor, which can be used in several types of environments. A modified radar equation is presented that can be used to estimate the signal power from the returned sensor signal as a function of practical parameters. The precision performance of the OFC passive wireless sensor, not previously investigated, is shown to be a function of signal-to-noise ratio as expected from an analog sensor; extracted temperature precision better than 0.001 °C is reported. Signal integration is an effective means to increase the precision and/or range of the wireless temperature extraction scheme when deciding if the OFC passive wireless sensing scheme will fit a particular application.

Wireless Passive Sensors for Remote Sensing of Temperature on Aerospace Platforms

This paper is devoted to the feasibility study of a wireless sensing system, mainly based on passive surface acoustic wave sensors, for remote measurement of temperature aboard space platforms. The use of passive sensors is particularly attractive since they need no battery and are robust in extreme environments, as they contain no active electronic circuits. The main objective of this paper is the complete characterization of the wireless system environment, in order to determine the main fundamental limits of this technology from a communication theory point of view. Preliminary experimental measurements are used for defining the main environment parameters, validating some of the theoretical limit computations, and proving the space application feasibility.

Analysis of passive surface acoustic wave sensors using coupling of modes theory

Passive surface acoustic wave (SAW) sensors, which are a combination of a SAW device and a classical sensor, have attracted recent interest. These sensors can detect physical quantities without a power supply and does not require maintenance. In this study, passive SAW sensors are modeled using coupling of modes (COM) theory. To optimize the COM parameters, Brent’s method is adopted. The simulated and measured results are in good agreement. Then, the model is applied as a novel identification method for SAW devices using a characteristic of a passive SAW sensor. The simulated results indicate the applicability of the new identification method for SAW sensors.

Tire Pressure Monitoring System and Wireless Passive Surface Acoustic Wave Sensor

The TPMS can not only save fuel and protect the tire, but also make the driver more safety. Tire safety is attracting the driver's attention, the United States had developed laws to enforce the TPMS installation in the car and the deadline is in 2008. In this paper, the basic structure and the implement method of TPMS are introduced. The active sensors are already used in most of the TPMS applications. The SAW theory and some wireless passive SAW pressure and temperature sensors which suit for the TPMS application are illustrated, because the passive sensor is becoming the focus in the TPMS research field. Passive SAW sensor is the good choice for TPMS, according to its wireless, passive, zero age rate, small size etc. The wireless passive SAW TPMS is one of the most important research direction. In this paper, some kinds of passive SAW sensor are introduced, which are used in TPMS.

Accurate FEM/BEM Simulation of Wireless Passive Surface Acoustic Wave Sensors

The wireless passive surface acoustic wave (SAW) impedance-loaded sensors offer new and exciting perspectives for remote monitoring and controlling of moving parts, even in harsh environments. However, the classical simulation models such as equivalent circuit model (ECM) and coupling of modes (COM) model are not rigorous enough for these sensors since these sensors usually work in the RF band. We try to make it more accurate by using FEM/BEM (combined finite element method and boundary element method) model to determine some key parameters used in the COM model of impedance-loaded SAW sensors. In this paper, we use periodic Green function which is the basis of FEM/BEM model to determine the key parameters. The result of measurements on real SAW is nearly in accordance with that of simulations.

Design and Fabrication of Passive Wireless SAW Sensor for Pressure Measurement

This paper mainly presents the design and fabrication of a TDMA (time division multiple access) passive wireless pressure sensor using 2.45 GHz surface acoustic wave (SAW) delay lines. The SAW pressure sensor consists of two LiNbO3 substrates. The first layer is a pressure-detective thin substrate, on which an interdigital transducer (IDT) and reflectors are fabricated. The second layer is a support substrate, in which a reference pressure cavity is etched. These two substrates are directly bonded. The pressure measurement was successfully demonstrated in a pressure range of 20∼280 kPa with good repeatability. In addition, the influence of a tire on the wireless interrogation of the sensor was investigated. Automobile tires have little negative influence on wireless communication, at least if they do not rotate.