Showing papers in "IEEE Sensors Journal in 2002"

Multisensor fusion and integration: approaches, applications, and future research directions

Abstract: Multisensor fusion and integration is a rapidly evolving research area and requires interdisciplinary knowledge in control theory, signal processing, artificial intelligence, probability and statistics, etc. The advantages gained through the use of redundant, complementary, or more timely information in a system can provide more reliable and accurate information. This paper provides an overview of current sensor technologies and describes the paradigm of multisensor fusion and integration as well as fusion techniques at different fusion levels. Applications of multisensor fusion in robotics, biomedical system, equipment monitoring, remote sensing, and transportation system are also discussed. Finally, future research directions of multisensor fusion technology including microsensors, smart sensors, and adaptive fusion techniques are presented.

Pattern analysis for machine olfaction: a review

Abstract: Pattern analysis constitutes a critical building block in the development of gas sensor array instruments capable of detecting, identifying, and measuring volatile compounds, a technology that has been proposed as an artificial substitute for the human olfactory system. The successful design of a pattern analysis system for machine olfaction requires a careful consideration of the various issues involved in processing multivariate data: signal-preprocessing, feature extraction, feature selection, classification, regression, clustering, and validation. A considerable number of methods from statistical pattern recognition, neural networks, chemometrics, machine learning, and biological cybernetics have been used to process electronic nose data. The objective of this review paper is to provide a summary and guidelines for using the most widely used pattern analysis techniques, as well as to identify research directions that are at the frontier of sensor-based machine olfaction.

Distributed odor source localization

Abstract: This paper presents an investigation of odor localization by groups of autonomous mobile robots. First, we describe a distributed algorithm by which groups of agents can solve the full odor localization task. Next, we establish that conducting polymer-based odor sensors possess the combination of speed and sensitivity necessary to enable real world odor plume tracing and we demonstrate that simple local position, odor, and flow information, tightly coupled with robot behavior, is sufficient to allow a robot to localize the source of an odor plume. Finally, we show that elementary communication among a group of agents can increase the efficiency of the odor localization system performance.

A wireless, passive carbon nanotube-based gas sensor

Abstract: A gas sensor, comprised of a gas-responsive multiwall carbon nanotube (MWNT)-silicon dioxide (SiO/sub 2/) composite layer deposited on a planar inductor-capacitor resonant circuit is presented here for the monitoring of carbon dioxide (CO/sub 2/), oxygen (O/sub 2/), and ammonia (NH/sub 3/). The absorption of different gases in the MWNT-SiO/sub 2/ layer changes the permittivity and conductivity of the material and consequently alters the resonant frequency of the sensor. By tracking the frequency spectrum of the sensor with a loop antenna, humidity, temperature, as well as CO/sub 2/, O/sub 2/ and NH/sub 3/ concentrations can be determined, enabling applications such as remotely monitoring conditions inside opaque, sealed containers. Experimental results show the sensor response to CO/sub 2/ and O/sub 2/ is both linear and reversible. Both irreversible and reversible responses are observed in response to NH/sub 3/, indicating both physisorption and chemisorption of NH/sub 3/ by the carbon nanotubes. A sensor array, comprised of an uncoated, SiO/sub 2/ coated, and MWNT-SiO/sub 2/ coated sensor, enables CO/sub 2/ measurement to be automatically calibrated for operation in a variable humidity and temperature environment.

Polarization imaging: principles and integrated polarimeters

Abstract: Polarization is a general descriptor of light and contains information about reflecting objects that traditional intensity-based sensors ignore. Difficult computer vision tasks such as image segmentation and object orientation are made tractable with polarization vision techniques. Specularities, occluding contours, and material properties can be readily extracted if the Stokes polarization parameters are available. Astrophysicists employ polarization information to measure the spatial distribution of magnetic fields on the surface of the Sun. In the medical field, analysis of the polarization allows the diagnose of disease in the eyes. The retinae of most insect and certain vertebrate species are sensitive to polarization in their environment, but humans are blind to this property of light. Biologists use polarimeters to investigate behaviors of animals-vis-a-vis polarization-in their natural habitats. In this paper, we first present the basics of polarization sensing and then discuss integrated polarization imaging sensors developed in our laboratory.

A monolithic CMOS microhotplate-based gas sensor system

Abstract: A monolithic CMOS microhotplate-based conductance-type gas sensor system is described. A bulk micromachining technique is used to create suspended microhotplate structures that serve as sensing film platforms. The thermal properties of the microhotplates include a 1-ms thermal time constant and a 10/spl deg/C/mW thermal efficiency. The polysilicon used for the microhotplate heater exhibits a temperature coefficient of resistance of 1.067/spl times/10/sup -3///spl deg/C. Tin(IV) oxide and titanium(IV) oxide (SnO/sub 2/,TiO/sub 2/) sensing films are grown over postpatterned gold sensing electrodes on the microhotplate using low-pressure chemical vapor deposition (LPCVD). An array of microhotplate gas sensors with different sensing film properties is fabricated by using a different temperature for each microhotplate during the LPCVD film growth process. Interface circuits are designed and implemented monolithically with the array of microhotplate gas sensors. Bipolar transistors are found to be a good choice for the heater drivers, and MOSFET switches are suitable for addressing the sensing films. An on-chip operational amplifier improves the signal-to-noise ratio and produces a robust output signal. Isothermal responses demonstrate the ability of the sensors to detect different gas molecules over a wide range of concentrations including detection below 100 nanomoles/mole.

State of the art in sensor technologies for sewer inspection

Abstract: This paper reviews the state of the art in sensors and automated inspection devices for enhanced sewer inspection. Efficiency, safety, environmental, and legislative concerns have made inspection and assessment of communal sewers a central issue to water and sewerage companies. Nowadays, the standard sewer inspection system is based on a wheeled platform on which a closed circuit television (CCTV) camera is mounted. One of the disadvantages of camera inspection systems is that they can only detect a small proportion of all possible damage in a sewer. The inspection outcome of such systems relies not only on the quality of the acquired images, but also on the off-line. recognition and classification conducted by human operators. In consequence, CCTV-based platforms are frequently not effective. Infrared, microwave, optical, and ultrasonic-based sensors have been proposed to complement the existing CCTV-based approach and to improve inspection results. New inspection devices employing multiple sensors and being capable of carrying out remote sewer inspection tasks are under research.

Signal processing techniques for landmine detection using impulse ground penetrating radar

Abstract: Landmines are affecting the lives and livelihoods of millions of people around the world. A number of detection techniques, developed for use with impulse ground penetrating radar, are described, with emphasis on a Kalman filter based approach. Comparison of results from real data show that the Kalman filter algorithm provides the best detection performance, although its computational burden is also the highest.

GaN metal-semiconductor-metal ultraviolet sensors with various contact electrodes

Abstract: Indium-tin-oxide (ITO), Au, Ni, and Pt layers were deposited onto n-GaN films and/or glass substrates by electron-beam evaporation. With proper annealing, it was found that we could improve the optical properties of the ITO layers and achieve a maximum transmittance of 98% at 360 nm. GaN-based MSM UV sensors with ITO, Au, Ni, and Pt as contact electrodes were also fabricated. It was found that we could achieve a maximum 0.12 A photocurrent and a photocurrent to dark current contrast higher than five orders of magnitude for the 600/spl deg/C-annealed ITO/n-GaN MSM UV sensor at a 5-V bias voltage. We also found that the maximum responsivity at 345 nm was 7.2 A/W and 0.9 A/W when the 600/spl deg/C-annealed ITO/n-GaN MSM UV sensor was biased at 5 V and 0.5 V, respectively. These values were much larger than those observed from other metal/n-GaN MSM UV sensors. However, the existence of photoconductive gain in the 600/spl deg/C-annealed ITO/n-GaN MSM UV sensor also results in a slower operation speed and a smaller 3-dB bandwidth as compared with the metal/n-GaN MSM UV sensors.

Toward a miniature wireless integrated multisensor microsystem for industrial and biomedical applications

Abstract: This paper presents our work toward the integration of a multisensor microsystem with wireless communication, using system-on-chip (SoC) methodology. Four different forms of microelectronic sensors have been fabricated on two separate 5/spl times/5 mm/sup 2/ silicon chips measuring pH, conductivity, dissolved oxygen concentration, and temperature. The sensors are integrated with a sensor fusion chip comprising analog circuitry for sensor operation and signal amplification prior to digital decoding and transmission. The microsystem prototype will be packaged in a miniature capsule, which measures 16 mm /spl times/55 mm including batteries and dissipates 6.3 mW for a minimal life cycle of 12 h.

Air quality monitoring and fire detection with the Karlsruhe electronic micronose KAMINA

Abstract: An indoor air monitoring device is one of the most prominent consumer applications of an electronic nose (EN). Integral gas analysis similar to biogenic odor perception can be a versatile tool to obtain continuous information about pollutants, odors, and air compositions indicating gaseous precursors of dangers such as fires. However, an EN to be used as a common household device has to combine high sensitivity and excellent gas discrimination power with inexpensiveness, small size, and low power consumption. A special gas sensor microarray of thumbnail size has been developed at the Forschungszentrum Karlsruhe based on metal-oxide technology to meet these requirements. The microarray is produced by simply partitioning a monolithic metal-oxide layer with parallel electrode strips allowing low cost fabrication. A temperature gradient and a membrane thickness gradient (on metal-oxide layer) are responsible for differentiation between the individual sensor segments and thus for the conductivity patterns that are accordingly produced. The two membranes form the basis of gas discrimination power, reliability self checks, and online noise reduction. Model gas exposures usually show detection limits lower than 1 ppm. Successful practical tests are reported on the detection of overheated wire insulation for fire prevention as well as on air quality analysis for air conditioning purposes (e.g., air quality control during a meeting).

Simultaneous measurement of humidity and temperature by combining a reflective intensity-based optical fiber sensor and a fiber Bragg grating

Abstract: A novel sensor capable of simultaneously measuring temperature and humidity has been fabricated and demonstrated using optical fiber waveguides. The sensor head is composed of a fiber Bragg grating and a low-finesse Fabry-Perot interferometric cavity. The Fabry-Perot cavity was fabricated using the electrostatic self-assembled monolayer process for the molecular-level deposition of materials of different thicknesses that form a humidity-sensitive coating on the end of the fiber, while the in-line Bragg grating fiber element is used to monitor temperature. Experimental results for a humidity range from 11% to 97% RH and for a temperature range from 10/spl deg/C to 85/spl deg/C are shown.

Response mechanism of SiC-based MOS field-effect gas sensors

Abstract: SiC-based field-effect gas sensors with catalytic platinum electrodes (Pt-MOSiC) have been subjected to a series of gas response measurements. Structural analysis of the Pt electrodes revealed that the gas sensitivity and the selectivity of Pt-MOSiC gas sensors depend on two major parameters: the porosity and the catalytic activity of the Pt electrodes. Pt-MOSiC gas sensors with thick, dense Pt electrodes only exhibit hydrogen sensitivity, whereas Pt-MOSiCs with thin porous gates exhibit a broad range of gas sensitivities similar to resistive metal-oxide gas sensors. A model is put forward that explains the nonhydrogen gas response of Pt-MOSiC devices and of conventional polycrystalline metal-oxide materials on a common basis.

A vision-based DSP embedded navigation sensor

Abstract: Spacecraft missions such as spacecraft docking and formation flying require high-precision relative position and attitude data. Deep space missions require the use of alternative technologies. One such technology is the vision-based navigation (VISNAV) sensor system developed at Texas A&M University. VISNAV comprises an electro-optical sensor combined with light sources or beacons. This patented sensor has an analog detector in the focal plane with a rise time of a few microseconds. Accuracies better than one part in 2000 of the field of view have been obtained. Simultaneous activation of beacons with frequency division multiplexing is given as part of the VISNAV sensor system. The synchronous demodulation process uses digital heterodyning and decimating filter banks on a low-power fixed point digital signal processor, which improves the accuracy of the sensor measurements and the reliability of the system. This paper also presents an optimal and computationally efficient six-degree-of-freedom estimation algorithm using a new measurement model based on the attitude representation of modified Rodrigues parameters.

Learning from data: a tutorial with emphasis on modern pattern recognition methods

Abstract: The purposes of this tutorial are twofold. First, it reviews the classical statistical learning scenario by highlighting its fundamental taxonomies and its key aspects. The second aim of the paper is to introduce some modern (ensembles) methods developed inside the machine learning field. The tutorial starts by putting the topic of supervised learning into the broader context of data analysis and by reviewing the classical pattern recognition methods: those based on class-conditional density estimation and the use of the Bayes theorem and those based on discriminant functions. The fundamental topic of complexity control is treated in some detail. Ensembles techniques have drawn considerable attention in recent years: a set of learning machines increases classification accuracy with respect to a single machine. Here, we introduce boosting, in which classifiers adaptively concentrate on the harder examples located near to the classification boundary and output coding, where a set of independent two-class machines solves a multiclass problem. The first successful applications of these methods to data produced by the Pico-2 electronic nose (EN), developed at the University of Brescia, Brescia, Italy, are also briefly shown.

Characterization of a silicon thermal gas-flow sensor with porous silicon thermal isolation

Abstract: In this paper, the results of full characterization of a micromachined-silicon thermal gas flow sensor will be presented. The sensor is composed of two series of thermocouples on the right and left side of a polysilicon resistor, used as heater. The resistor and the hot contacts of the thermocouples lie on a thick porous silicon layer, which assures local thermal isolation, while the thermopile cold contacts lie on bulk silicon. Gas flow is parallel to the surface of the sensor and perpendicular to the resistor, which is heated at constant temperature. The power of the heater is stabilized by an external circuit, which provides a feedback current to compensate changes in the resistance of the heater under flow. Characterization of the sensor both under static conditions and under flow of different gases will be presented. The sensor shows high sensitivity [of the order of 175 /spl times/ 10/sup -3/ mV/(m/s)/sup 1/2/ per thermocouple] and very rapid response, below 1 ms, which makes it appropriate for use both under laminar and under turbulent flows.

Comparison of three humidity sensors for a pulmonary function diagnosis microsystem

Abstract: Three capacitive humidity sensors developed for a portable clinical application are presented and compared. The first structures consist of interdigitated electrodes covered by a polyimide sensitive layer. The second structures have the same geometry but include a benzocyclobutene sensitive layer and a heating. resistor. The third structure has been developed with a new geometry, with the electrodes being stacked. Humidity measurement results are presented, in particular sensor response time in absorption that must be very small (less than 500 ms). The influence of the heating on the response time is described. In conclusion, the three sensors are compared and the most suitable structure for our application is indicated. Although polyimide has been widely used for realization of capacitive humidity sensors, we demonstrate here that it is not the best sensitive material for our application.

A novel logarithmic response CMOS image sensor with high output voltage swing and in-pixel fixed pattern noise reduction

Abstract: A novel logarithmic response 0.25 /spl mu/m CMOS image sensor technology for high output swing and low noise error is proposed. The experimental results show that the new cell has 4 times higher output voltage swing. Optimized simulation results show 6.5 times larger output voltage swing, which is achievable for an input signal range of 0.01 lux to 100,000 lux. With this wider swing, the effect of fixed pattern noise (FPN) reflecting on the digital output can be reduced significantly. In addition, after adding a correlated double sampling (CDS) control transistor, the output voltage difference variation due to FPN is greatly reduced from 73 mV to 15 mV.

SnO/sub 2/ gas sensing array for combustible and explosive gas leakage recognition

Abstract: A gas-sensing array with ten different SnO/sub 2/ sensors was fabricated on a substrate for the purpose of recognizing various kinds and quantities of indoor combustible gas leakages, such as methane, propane, butane, LPG, and carbon monoxide, within their respective threshold limit value (TLV) and lower explosion limit (LEL) range. Nano-sized sensing materials with high surface areas were prepared by coprecipitating SnCl/sub 4/ with Ca and Pt, while the sensing patterns of the SnO/sub 2/-based sensors were differentiated by utilizing different additives. The sensors in the sensor array were designed to produce a uniform thermal distribution along with a high and differentiated sensitivity and reproducibility for low concentrations below 100 ppm. Using the sensing signals of the array, an electronic nose system was then applied to classify and identify simple/mixed explosive gas leakages. A gas pattern recognizer was implemented using a neuro-fuzzy network and multi-layer neural network, including an error-back-propagation learning algorithm. Simulation and experimental results confirmed that the proposed gas recognition system was effective in identifying explosive and hazardous gas leakages. The electronic nose in conjunction with a neuro-fuzzy network was also implemented using a digital signal processor (DSP).

Classification of bacteria responsible for ENT and eye infections using the Cyranose system

Abstract: The Cyranose 320 (Cyrano Sciences Inc., USA), comprising an array of 32 polymer carbon black composite sensors, has been used to identify species of bacteria commonly associated with medical conditions. Results from two experiments are presented: one on bacteria causing eye infections and one on a new series of tests on bacteria responsible for some ear, nose, and throat (ENT) diseases. For the eye bacteria tests, pure lab cultures were used and the electronic nose (EN) was used to sample the headspace of sterile glass vials containing a fixed volume of bacteria in suspension. For the ENT bacteria, the system was taken a step closer toward medical application, as readings were taken from the headspace of the same blood agar plates used to culture real samples collected from patients. After preprocessing, principal component analysis (PCA) was used as an exploratory technique to investigate the clustering of vectors in multi-sensor space. Artificial neural networks (ANNs) were then used as predictors, and a multilayer perceptron (MLP) trained with back-propagation (BP) and with Levenberg-Marquardt was used to identify the different bacteria. The optimal MLP was found to correctly classify 97.3% of the six eye bacteria of interest and 97.6% of the four ENT bacteria including two sub-species. A radial basis function (RBF) network was able to discriminate between the six eye bacteria species, even in the lowest state of concentration, with 92.8% accuracy. These results show the potential application of the Cyranose together with neural network-based predictors, for rapid screening and early detection of bacteria associated with these medical conditions, and the possible development of this EN system as a near-patient tool in primary medical healthcare.

Biomimetic sound-source localization

Abstract: Sound-source localization systems typically comprise free-field microphone arrays. In nature, directional acoustic sensing evolved to rely on diffraction about the head with only two ears. For localization, the brain uses the resultant frequency-dependent acoustic phase and intensity differences between the two ears. We conceive a biomimetic artificial head with microphones placed on its surface. The interaural functions can be computed analytically by modeling the head as a sphere. We define a suitable metric between interaural functions, whose global minimum provides the true source direction. The natural configuration in which the two sensors are placed antipodally on the sphere has intrinsic rotational symmetry: it allows localization only up to a circle around the interaural axis. We describe two methods for breaking the detrimental symmetry in order to achieve full spherical localization capability. First, we consider rotation of the apparatus relative to the source and the information it adds to the localization metric. We derive analytically the gradient of the pressure field under rotation and compute the induced acoustic flow on the interaural localization functions. Second, we explore placing the sensors in configurations differing from antipodal. We show the efficacy of these methods through simulations.

Ion-sensitive field-effect transistors in standard CMOS fabricated by post processing

Abstract: Highly integrated ion-sensitive field-effect transistor (ISFET) microsystems require the monolithic implementation of ISFETs, CMOS electronics, and additional sensors on the same chip. This paper presents new ISFETs in standard CMOS, fabricated by post-processing of a standard CMOS VLSI chip. Unlike CMOS compatible ISFETs fabricated in a dedicated process, the new sensors are directly combined with state-of-the-art CMOS electronics and are subject to continuous technology upgrading. The ISFETs presented include an intermediate gate formed by one or more conducting layers placed between the gate oxide and the sensing layer. The combination of the highly isolating gate oxide of the MOS with a leaky or conducting sensing layer allows the use of low temperature materials that do not damage the CMOS chip. The operation of ISFETs with an intermediate gate and sensing layers fabricated at low temperature is modeled. ISFETs with a linear pH response and drift as low as 0.3 mV/h are reported.

Optical-fiber finger photo-plethysmograph using digital techniques

Abstract: This paper presents digital techniques to design an optical-fiber photo-plethysmograph. This noninvasive method is based on the measurement of the intensity of an infrared-light beam, which penetrates the index finger. Sinusoidal modulation of the light-beam by driving an infrared LED is proposed. The method of direct digital synthesis is used to produce a very stable sinusoidal waveform. Optical fibers are used to transfer the light to and from the sampling point. Synchronous amplitude demodulation is used here instead of using analog low-pass filters, so the information concerning the amplitude is almost noiseless. Off-line frequency analysis of the peripheral volume pulse-wave signal is performed. The power content in the harmonics of this pulse wave may be a useful measure of aging and vascular disease.

A biologically inspired modular VLSI system for visual measurement of self-motion

Abstract: We introduce a biologically inspired computational architecture for small-field detection and wide-field spatial integration of visual motion based on the general organizing principles of visual motion processing common to organisms from insects to primates. This highly parallel architecture begins with two-dimensional (2-D) image transduction and signal conditioning, performs small-field motion detection with a number of parallel motion arrays, and then spatially integrates the small-field motion units to synthesize units sensitive to complex wide-field patterns of visual motion. We present a theoretical analysis demonstrating the architecture's potential in discrimination of wide-field motion patterns such as those which might be generated by self-motion. A custom VLSI hardware implementation of this architecture is also described, incorporating both analog and digital circuitry. The individual custom VLSI elements are analyzed and characterized, and system-level test results demonstrate the ability of the system to selectively respond to certain motion patterns, such as those that might be encountered in self-motion, at the exclusion of others.

A novel ultrasonic sensing system for autonomous mobile systems

Abstract: This paper presents a novel ultrasonic sensing system for autonomous mobile systems. We describe how wide-angled ultrasonic transducers can be used to obtain substantial information from the environment. This can be achieved by exploiting the overlapping of detection cones from neighbor sensors and by receiving cross echoes between them. The ultrasonic sensing system also allows the detection of multiple echoes from different echo paths for each sensor. In this way, a significantly higher number of echoes can be obtained in comparison to conventional ultrasonic sensing systems for mobile robots. In order to benefit from the increased sensor information, algorithms for adequate data post-processing are required. In this context, we describe how an environment model can be created from ultrasonic sensor data.

Coaxial range measurement - current trends for mobile robotic applications

Abstract: The useful environmental interaction of a mobile robot is completely dependent on the reliable extraction of information from its immediate surroundings. A review of some of the most commonly used coaxial, active sensing methods in robotics is presented. A coaxial sensor results if the transmitter and receiver are geometrically arranged in a coaxial manner. Certain advantages of such configurations are discussed. First, optical sensors, in which a controlled light signal is transmitted, are reviewed with respect to their applicability to mobile robotics. An overview of the literature describing light detection and ranging (LIDAR) systems for range measurement in robotics is given. A review of mobile robot research using sound navigation and ranging (SONAR) is presented where processing algorithms are demonstrated for the correct interpretation of ultrasonic data recorded in indoor environments. Ultrasonic wave reflection is generally dominated by specular reflections. Methods for the interpretation of SONAR data, for correct target classification, and, hence, range estimation are given, based on the acoustic reflection mechanism.

A portable electronic nose based on embedded PC technology and GNU/Linux: hardware, software and applications

Abstract: This paper describes a portable electronic nose based on embedded PC technology. The instrument combines a small footprint with the versatility offered by embedded technology in terms of software development and digital communications services. A summary of the proposed hardware and software solutions is provided with an emphasis on data processing. Data evaluation procedures available in the instrument include automatic feature selection by means of SFFS, feature extraction with linear discriminant analysis (LDA) and principal component analysis (PCA), multi-component analysis with partial least squares (PLS) and classification through k-NN and Gaussian mixture models. In terms of instrumentation, the instrument makes use of temperature modulation to improve the selectivity of commercial metal oxide gas sensors. Field applications of the instrument, including experimental results, are also presented.

Hydrogen catalytic oxidation reaction on Pd-doped porous silicon

Abstract: The efficiency of Pd-doped porous silicon (PS) as a catalytic material for hydrogen sensing is studied. Pd is deposited by an electroless process on the internal surface of porous silicon. The catalytic behavior of Pd-doped PS samples is estimated and the parameters that influence the kinetics of the chemical reaction are evaluated. The catalytic activity is examined through the kinetics of the chemical reaction, which occurs in low hydrogen content mixtures with air (up to 1% v/v in air), far below the mixture flammability limit. It was found that the catalytic activity of Pd-doped porous silicon at 160/spl deg/C is significantly higher than that of a planar surface covered with Pd. The dependence of the catalytic activity on processing conditions was also evaluated. These results open important new possibilities for applications in gas sensors.

Ultra-high frame rate focal plane image sensor and processor

Abstract: Application examples of a fully-programmable analogic focal plane array processor are introduced. One mixed-signal sensory/processing chip is presented, which is capable of capturing, processing, and evaluating over 10,000 images in a second. Morphological analysis of silhouettes and sparks were carried out and real-time decision making was performed running at this extraordinary high frame-rate.

The potential of microacoustic SAW- and BAW-based sensors for automotive applications - a review

Abstract: In recent years, sensors and sensor systems have gained increasing importance for automotive electronics. In this paper, the suitability and the perspectives in the application of microacoustic surface- and bulk-acoustic-wave sensors in the fields of angular rate sensors, pressure sensors, wireless sensor readout, and liquid sensors are discussed.