Showing papers in "IEEE Transactions on Instrumentation and Measurement in 2005"
TL;DR: Simple but effective step detection and step length estimation methods are implemented in order to reduce computation, memory, and communication requirements on the Motes and show that satisfactory tracking performance with relatively long operational time is achieved.
Abstract: In this paper, we combine inertial sensing and sensor network technology to create a pedestrian dead reckoning system. The core of the system is a lightweight sensor-and-wireless-embedded device called NavMote that is carried by a pedestrian. The NavMote gathers information about pedestrian motion from an integrated magnetic compass and accelerometers. When the NavMote comes within range of a sensor network (composed of NetMotes), it downloads the compressed data to the network. The network relays the data via a RelayMote to an information center where the data are processed into an estimate of the pedestrian trajectory based on a dead reckoning algorithm. System details including the NavMote hardware/software, sensor network middleware services, and the dead reckoning algorithm are provided. In particular, simple but effective step detection and step length estimation methods are implemented in order to reduce computation, memory, and communication requirements on the Motes. Static and dynamic calibrations of the compass data are crucial to compensate the heading errors. The dead reckoning performance is further enhanced by wireless telemetry and map matching. Extensive testing results show that satisfactory tracking performance with relatively long operational time is achieved. The paper also serves as a brief survey on pedestrian navigation systems, sensors, and techniques.
352 citations
TL;DR: This paper considers the dependency of the signal-to-noise-and-distortion ratio (SINAD) on the combination of several different channel mismatch effects and derives closed-form equations for calculating the explicit or the expected SINAD for an arbitrary number of channels.
Abstract: A time-interleaved multichannel analog-to-digital converter (ADC) achieves high sampling rates with the drawback of additional distortions caused by channel mismatches. In this paper, we consider the dependency of the signal-to-noise-and-distortion ratio (SINAD) on the combination of several different channel mismatch effects. By using either explicitly given mismatch parameters or given parameter distributions, we derive closed-form equations for calculating the explicit or the expected SINAD for an arbitrary number of channels. Furthermore, we extend the explicit SINAD by the impact of timing jitter. We clarify how channel mismatches interact and perform a worst case analysis of the explicit SINAD for individual mismatch errors. We also show that equations describing the expected SINAD of individual mismatch errors are special cases of our general formulation. We indicate how to use the expected SINAD for finding efficient optimization priorities and demonstrate the importance of worst case analyses.
225 citations
TL;DR: A new high-resolution reflectometry technique that operates simultaneously in both the time and frequency domains, which rests upon time-frequency signal analysis and utilizes a chirp signal multiplied by a Gaussian time envelope.
Abstract: In this paper, we introduce a new high-resolution reflectometry technique that operates simultaneously in both the time and frequency domains. The approach rests upon time-frequency signal analysis and utilizes a chirp signal multiplied by a Gaussian time envelope. The Gaussian envelope provides time localization, while the chirp allows one to excite the system under test with a swept sinewave covering a frequency band of interest. This latter capability is of particular interest when testing communication cables and systems. Sensitivity in detecting the reflected signal is provided by a time-frequency cross-correlation function. The approach is verified by experimentally locating various types of faults, located at various distances, in RG 142 and RG 400 coaxial cables.
219 citations
TL;DR: The feasibility of designing an accelerometer-based (or gyroscope-free) inertial navigation system that uses only accelerometer measurements to compute the linear and angular motions of a rigid body relative to a fixed inertial frame is examined.
Abstract: We examine the feasibility of designing an accelerometer-based (or gyroscope-free) inertial navigation system that uses only accelerometer measurements to compute the linear and angular motions of a rigid body. The accelerometer output equation is derived to relate the linear and angular motions of a rigid body relative to a fixed inertial frame. A sufficient condition is given to determine if a configuration of accelerometers is feasible. If the condition is satisfied, the angular and linear motions can be computed separately using two decoupled equations of an input-output dynamical system: a state equation for angular velocity and an output equation for linear acceleration. This simple computation scheme is derived from the corresponding dynamical system equations for a special cube configuration for which the angular acceleration is expressed as a linear combination of the accelerometer outputs. The effects of accelerometer location and orientation errors are analyzed. Algorithms that identify and compensate these errors are developed.
186 citations
TL;DR: This approach provides an enabling technology for cost-effective full-code testing of high precision ADCs in production test and for potential cost- effective chip-level implementation of a built-in self-test capability.
Abstract: Linearity testing of analog-to-digital converters (ADCs) can be very challenging because it requires a signal generator substantially more linear than the ADC under test. This paper introduces the stimulus error identification and removal (SEIR) method for accurately testing ADC linearity using signal generators that may be significantly less linear than the device under test. In the SEIR approach, two imprecise nonlinear but functionally related excitations are applied to the ADC input to obtain two sets of ADC output data. The SEIR algorithm then uses the redundant information from the two sets of data to accurately identify the nonlinearity errors in the stimuli. The algorithm then removes the stimulus error from the ADC output data, allowing the ADC nonlinearity to be accurately measured. For a high resolution ADC, the total computation time of the SEIR algorithm is significantly less than the data acquisition time and therefore does not contribute to testing time. The new approach was experimentally validated on production test hardware with a commercial 16-bit successive approximation ADC. Integral nonlinearity test results that are well within the device specification of /spl plusmn/2 least significant bits were obtained by using 7-bit linear input signals. This approach provides an enabling technology for cost-effective full-code testing of high precision ADCs in production test and for potential cost-effective chip-level implementation of a built-in self-test capability.
123 citations
TL;DR: A miniature implantable and dynamically configurable potentiostat and galvanostat for two- and three-electrode biosensor with a telemetry electronics package was developed to provide remote monitoring of implantable amperometric and voltametric biosensors such as for glucose.
Abstract: A miniature implantable and dynamically configurable potentiostat and galvanostat for two- and three-electrode biosensors with a telemetry electronics package was developed to provide remote monitoring of implantable amperometric and voltametric biosensors such as for glucose. Included are circuitry for sensor biasing, a transimpedance amplifier to produce the sensor proportional output signal, and a transceiver (transmitter and receiver) which can both receive setup parameter values and transmit the biosensor concentration data to a corresponding remote transceiver and computer for monitoring. Remotely configurable features included in the in vivo implanted unit include: sensor excitation changes; filter frequency cutoff values, amplifier gain; and transmission intervals utilizing 303.825-MHz UHF RF telemetry for end-to-end remote data monitoring. The developed mP/Gstat printed circuit board measures about 51/spl times/22/spl times/1mm thick, and is suitable for bench top or encapsulated use. Instrumentation developed in this paper will allow other researchers to develop implantable units. Evaluation in two- and three-electrode mPstat and two electrode mGstat modes with simulated biosensors showed overall average theoretical to actual recorded value differences of only 0.5859% reading (RDG) with a standard deviation (SD) of 0.5376% indicating excellent design performance. System testing in two-electrode mPstat mode with actual glucose sensors showed excellent stability and correlation to standard biosensor calibrations with an average difference of only 7.33% full scale (FS) with 3.65% SD, which is minimal considering two totally independent calibration instrument configurations.
119 citations
TL;DR: This work proposes a generalization to combine multiple LMS filters with different steps that provides the combination with better tracking capabilities and uses a different mixing parameter for each weight of the filter in order to make independent their adaption speeds.
Abstract: Among all adaptive filtering algorithms, Widrow and Hoff's least mean square (LMS) has probably become the most popular because of its robustness, good tracking properties and simplicity. A drawback of LMS is that the step size implies a compromise between speed of convergence and final misadjustment. To combine different speed LMS filters serves to alleviate this compromise, as it was demonstrated by our studies on a two filter combination that we call combination of LMS filters (CLMS). Here, we extend this scheme in two directions. First, we propose a generalization to combine multiple LMS filters with different steps that provides the combination with better tracking capabilities. Second, we use a different mixing parameter for each weight of the filter in order to make independent their adaption speeds. Some simulation examples in plant identification and noise cancellation applications show the validity of the new schemes when compared to the CLMS filter and to other previous variable step approaches.
109 citations
TL;DR: Results of testing linear extrapolation techniques and dielectric mixture equations on pulverized coal, limestone, plastics, and granular wheat and flour are presented and recommendations are provided for reliable estimation of solid material permittivities.
Abstract: Relationships between the permittivities of powdered or granular solid materials and their bulk densities (density of the air-particle mixture) are discussed. Linear relationships between functions of the permittivity and bulk density are identified that are useful in determining permittivity of solids from measurements of the permittivity of pulverized samples. The usefulness of several dielectric mixture equations for calculating solid material permittivity from measured permittivity of pulverized samples is also discussed. Results of testing linear extrapolation techniques and dielectric mixture equations on pulverized coal, limestone, plastics, and granular wheat and flour are presented. Recommendations are provided for reliable estimation of solid material permittivities or changes in permittivities of powdered and granular materials as a result of changes in their bulk densities.
108 citations
TL;DR: A new compressed video watermarking procedure that embeds several binary images, decomposed from a single watermark image, into different scenes of a video sequence and incorporates a visual mask based on local image characteristics into the compressed bit streams.
Abstract: Digital watermarking is becoming more and more important for protecting the authenticity of multimedia objects as they become easier to copy, exchange, and modify. Several watermarking schemes have been proposed in recent years, but most of them deal with still images, only some being extended over to the temporal domain for video watermarking. But again most of those approaches are applied to uncompressed video processing domain. In the subject paper, a new compressed video watermarking procedure is proposed. The developed method embeds several binary images, decomposed from a single watermark image, into different scenes of a video sequence. The spatial spread spectrum watermark is embedded directly into the compressed bit streams by modifying discrete cosine transform (DCT) coefficients. In order to embed the watermark with minimum loss in image fidelity, a visual mask based on local image characteristics is incorporated. Extensive experimental simulations demonstrate that the proposed watermarking scheme is substantially more effective and robust against spatial attacks such as scaling, rotation, frame averaging, and filtering, besides temporal attacks like frame dropping and temporal shifting.
107 citations
TL;DR: A triangular/square-wave generator with current-controllable frequency and amplitude and the application of the circuit to a current- Controllable saw-tooth waveform generator is presented.
Abstract: A triangular/square-wave generator with current-controllable frequency and amplitude is presented. The generator utilizes operational transconductance amplifiers as switching elements. A prototype circuit built with commercially available components exhibits less than 2% nonlinearity in its current-to-frequency transfer characteristic from 1 to 10 kHz and -150 ppm//spl deg/C temperature coefficient of frequency over 15/spl deg/C to 35/spl deg/C. The circuit also displays wide sweep capability and good linearity of current to amplitude. The application of the circuit to a current-controllable saw-tooth waveform generator is also presented.
98 citations
TL;DR: In the paper, some ADC error compensation methods are briefly introduced according to a classification criterion based on the main research trends.
Abstract: Analog-to-digital converters (ADCs) are critical components of signal-processing systems. ADC errors can compromise the overall accuracy and the effectiveness of the whole system. This leads researchers to direct increasing attention to error correction topics. In this paper, some ADC error compensation methods are briefly introduced according to a classification criterion based on the main research trends.
TL;DR: Issues important to further development of health-enabled networks are identified, which should be of interest to others working with smart sensors and intelligent health management systems.
Abstract: Based on requirements for a next-generation rocket test facility, elements of a prototype intelligent rocket test facility (IRTF) have been implemented. The preliminary results provide the basis for future advanced development and validation using rocket test stand facilities at Stennis Space Center (SSC). Key components include distributed smart sensor elements integrated using a knowledge-driven environment. One of the specific goals is to imbue sensors with the intelligence needed to perform self-diagnosis of health and to participate in a hierarchy of health determination at sensor, process, and system levels. We have identified issues important to further development of health-enabled networks, which should be of interest to others working with smart sensors and intelligent health management systems.
TL;DR: Precise behavioral modeling of switched-capacitor /spl Delta//spl Sigma/ modulators is presented and it is shown that neglecting the DCG nonlinearity of the integrators would lead to a significant underestimation of the modulators' behavior and increase the noise floor as well as the harmonic distortion at the output of themodulator.
Abstract: Precise behavioral modeling of switched-capacitor /spl Delta//spl Sigma/ modulators is presented. Considering noise (switches' and op-amps' thermal noise), clock jitter, nonidealities of integrators and op-amps including finite dc-gain (DCG) and unity gain bandwidth, slew-limiting, DCG nonlinearities and the input parasitic capacitance, quantizer hysteresis, switches' clock-feedthrough, and charge injection, exhaustive behavioral simulations that are close models of the transistor-level ones can be performed. The DCG nonlinearity of the integrators, which is not considered in many /spl Delta//spl Sigma/ modulators' modeling attempts, is analyzed, estimated, and modeled. It is shown that neglecting this parameter would lead to a significant underestimation of the modulators' behavior and increase the noise floor as well as the harmonic distortion at the output of the modulator. Evaluation and validation of the models were done via behavioral and transistor-level simulations for a second-order modulator using SIMULINK and HSPICE with a generic 0.35-/spl mu/m CMOS technology. The effects of the nonidealities and nonlinearities are clearly seen when compared to the ideal modulator in the behavioral and actual modulator in the circuit-level environment.
TL;DR: A newly developed resolver converter, providing a pseudolinear voltage proportional to the shaft angle, is presented, based on a new concept involving the absolute values of the demodulated sine and cosine resolver signals together with a dedicated linearization technique.
Abstract: A newly developed resolver converter, providing a pseudolinear voltage proportional to the shaft angle, is presented. This converter is based on a new concept involving the absolute values of the demodulated sine and cosine resolver signals together with a dedicated linearization technique. The converter enables instantaneous determination of the mechanical angle with a theoretical error of nonlinearity below 0.011/spl deg/ over the 360/spl deg/ range. The practical performance of this converter is compared to that of a 10/sup 5/ pulses per revolution optical encoder arrangement. The theory of operation, computer simulation, full circuit details, and experimental results are given.
TL;DR: A novel automatic target tracking (ATT) algorithm for tracking targets in forward-looking infrared (FLIR) image sequences is proposed and experimental results using real-life long-wave and medium-wave infrared image sequences are shown to validate the robustness of the proposed technique.
Abstract: A novel automatic target tracking (ATT) algorithm for tracking targets in forward-looking infrared (FLIR) image sequences is proposed in this paper. The proposed algorithm efficiently utilizes the target intensity feature, surrounding background, and shape information for tracking purposes. This algorithm involves the selection of a suitable subframe and a target window based on the intensity and shape of the known reference target. The subframe size is determined from the region of interest and is constrained by target size, target motion, and camera movement. Then, an intensity variation function (IVF) is developed to model the target intensity profile. The IVF model generates the maximum peak value where the reference target intensity variation is similar to the candidate target intensity variation. In the proposed algorithm, a control module has been incorporated to evaluate IVF results and to detect a false alarm (missed target). Upon detecting a false alarm, the controller triggers another algorithm, called template model (TM), which is based on the shape knowledge of the reference target. By evaluating the outputs from the IVF and TM techniques, the tracker determines the real coordinates of one or more targets. The proposed technique also alleviates the detrimental effects of camera motion, by appropriately adjusting the subframe size. Experimental results using real-life long-wave and medium-wave infrared image sequences are shown to validate the robustness of the proposed technique.
TL;DR: Modified AIC and MDL rules with improved finite sample behavior are proposed, useful in those measurement applications where gathering a sample is very time consuming and/or expensive.
Abstract: The classical model selection rules such as Akaike information criterion (AIC) and minimum description length (MDL) have been derived assuming that the number of samples (measurements) is much larger than the number of estimated model parameters. For short data records, AIC and MDL have the tendency to select overly complex models. This paper proposes modified AIC and MDL rules with improved finite sample behavior. They are useful in those measurement applications where gathering a sample is very time consuming and/or expensive.
TL;DR: A novel current-mode instrumentation amplifier that utilizes an operational floating current conveyor (OFCC) as a basic building block that outperforms existing CMIAs in terms of the number of basic building blocks used, differential gain, and CMRR.
Abstract: This paper presents a novel current-mode instrumentation amplifier (CMIA) that utilizes an operational floating current conveyor (OFCC) as a basic building block. The OFCC, as a current-mode device, shows flexible properties with respect to other current- or voltage-mode circuits. The advantages of the proposed CMIA are threefold. First, it offers a higher differential gain and a bandwidth that is independent of gain, unlike a traditional voltage-mode instrumentation amplifier. Second, it maintains a high common-mode rejection ratio (CMRR) without requiring matched resistors, and finally, the proposed CMIA circuit offers a significant improvement in accuracy compared to other current-mode instrumentation amplifiers based on the current conveyor. The proposed CMIA has been analyzed, simulated, and experimentally tested. The experimental results verify that the proposed CMIA outperforms existing CMIAs in terms of the number of basic building blocks used, differential gain, and CMRR.
TL;DR: This paper presents a wide-bandwidth, high dynamic range, BiCMOS RF rms detector based on the dynamic translinear principle, suitable for embedded on-chip testing, particularly for "alternative test" of RF circuits.
Abstract: This paper presents a wide-bandwidth, high dynamic range, BiCMOS RF rms detector based on the dynamic translinear principle. A current-domain circuit carries out the main computation, and a circuit compensates for errors due to finite transistor gain. Wide-bandwidth input and output circuits allow connecting voltage-mode signals to the internal current-mode circuitry. Measurements on a prototype chip demonstrate that the circuit is suitable for embedded on-chip testing, particularly for "alternative test" of RF circuits.
TL;DR: An algorithm to detect the fundamental frequency is proposed, based on the chirp-z transform (CZT) spectral analysis, which is able to observe all standards in force because of its accuracy and working characteristics.
Abstract: In the last few years, increased interest in power and voltage quality has forced international working groups to standardize testing and measurement techniques. IEC 61000-4-30, which defines the characteristics of instrumentation for the measurement of power quality, refers to IEC 61000-4-7 for the evaluation of harmonics and interharmonics. This standard, revised in 2002, requires a synchronous sampling of voltage or current signal, in order to limit errors and to ensure reproducible results even in the presence of nonstationary signals. Therefore, an accurate estimation of the fundamental frequency is required, even in the presence of disturbances. In this paper, an algorithm to detect the fundamental frequency is proposed; it is based on the chirp-z transform (CZT) spectral analysis and is able to observe all standards in force because of its accuracy and working characteristics. Theoretical aspects are discussed and various experimental tests are reported, comparing the proposed method with a similar well-known one based on interpolated fast Fourier transform (FFT) analysis. Finally, a complete characterization of the proposed system was performed, and its accuracy was evaluated by means of a calibrator.
TL;DR: The random fuzzy variables are considered in order to express the result of a measurement together with its uncertainty, and a significant application is considered to prove the practical utility of the proposed approach.
Abstract: This paper analyzes the result of a measurement in the mathematical model of incomplete knowledge and shows how it can be treated in the framework of the theory of evidence. The random fuzzy variables are considered in order to express the result of a measurement together with its uncertainty, and a significant application is considered to prove the practical utility of the proposed approach
TL;DR: The presented discussion confirms that, with the proper signal processing, 1-s-long system observations are quite sufficient to describe the system with an accuracy to satisfy practical demands.
Abstract: In this paper, the principal problems of distribution system identification and accurate measurements of distribution system impedance frequency contour are discussed. Some new results of field identification are presented. The focus of this paper is on the effective method of signal processing adapted to real signals which appear in the power systems. The principal problem of accurate identification is in the system nonstationariness. Its influence on accuracy is discussed and illustrated with experimental results. The proposed method of impedance identification based on short 40-ms system observations is relatively insensitive to power system nonstationariness. The presented discussion confirms that, with the proper signal processing, 1-s-long system observations are quite sufficient to describe the system with an accuracy to satisfy practical demands.
TL;DR: A loopback circuit that can be applied to transceiver loopback measurements is demonstrated and is a first attempt at a new on-chip RF test technique.
Abstract: This paper explores the use of on-chip or on-wafer loopback implementations for verifying performance of 5-GHz wireless local area network (WLAN) IC circuits. The loopback test diagram, the test-circuit design, and the characterization data are reported for subcircuits (attenuators, and switches) necessary to implement 5-GHz transceiver loopback. A loopback circuit that can be applied to transceiver loopback measurements is demonstrated. This research is exploratory in nature and is a first attempt at a new on-chip RF test technique.
TL;DR: This paper describes the investigation into the effects of signal cables on the operating frequencies, radiation patterns, and gains of handset antennas under test by using a proposed testing scheme.
Abstract: This paper describes the investigation into the effects of signal cables on the operating frequencies, radiation patterns, and gains of handset antennas under test by using a proposed testing scheme. In this simple testing method, a coaxial signal cable feeds the handset antenna under test through a microstrip transmission-line etched onto a printed circuit board. The studies of the influences of different feeding schemes and cable arrangements on two commonly used handset antennas are carried out experimentally and numerically. Also, the distributions of the fields close to the antenna, handset chassis, and the cable are measured and simulated to explore the cable-related influences.
TL;DR: An intelligent multimodal sensor system developed to enhance the haptic control of robotic manipulations of small three-dimensional (3-D) objects and is able to recognize small-size objects that cannot be accurately differentiated through range measurements and provides an estimate of the objects orientation.
Abstract: Controlling robotic interventions on small devices creates important challenges on the sensing stage as resolution limitations of noncontact sensors are rapidly reached. The integration of haptic sensors to refine information provided by vision sensors appears as a very promising approach in the development of autonomous robotic systems because it reproduces the multiplicity of sensing sources used by humans. This paper discusses an intelligent multimodal sensor system developed to enhance the haptic control of robotic manipulations of small three-dimensional (3-D) objects. The proposed system combines a 16 /spl times/16 array of force sensing resistor (FSR) elements to refine 3-D shape measurements in selected areas previously monitored with a laser range finder. Using the integrated technologies, the sensor system is able to recognize small-size objects that cannot be accurately differentiated through range measurements and provides an estimate of the objects orientation. Characteristics of the system are demonstrated in the context of a robotic intervention that requires fine objects to be localized and identified for their shape and orientation.
TL;DR: Simulation results show that the proposed BIST technique is an effective BIST solution for various capacitive MEMS devices and the combination of both BIST modes covers a larger defect set, thus a robust testing for the device can be expected.
Abstract: A dual-mode built-in self-test (BIST) scheme which partitions the fixed (instead of movable) capacitance plates of a capacitive microelectromechanical system (MEMS) device is proposed. The BIST technique divides the fixed capacitance plate(s) at each side of the movable microstructure into three portions: one for electrostatic activation and the other two equal portions for capacitance sensing. Due to such a partitioning method, the BIST technique can be applied to surface- and bulk-micromachined MEMS devices and other technologies. Further, the sensitivity and symmetry dual BIST modes based on this partitioning can also be developed. The combination of both BIST modes covers a larger defect set, so a more robust testing result for the device can be expected. The BIST technique is verified by three typical capacitive MEMS devices. Simulation results show that the proposed technique is an effective BIST solution for various capacitive MEMS devices.
TL;DR: A novel second-generation current conveyor (CCII)-based resistance-capacitance (RC) sinusoidal oscillator operating over a wide dynamic range is described, and experimental results are given, showing close agreement with the theoretical conclusions.
Abstract: A novel second-generation current conveyor (CCII)-based resistance-capacitance (RC) sinusoidal oscillator operating over a wide dynamic range is described. The oscillation condition and the oscillation frequency can be adjusted independently by two control resistors. The circuit proposed makes use of grounded capacitors and is suitable for implementation with the commercially available integrated circuit chip AD844 from Analog Devices which implements a CCII+. The circuit enjoys low sensitivities and is suitable for integration. Experimental results are given, showing close agreement with the theoretical conclusions.
TL;DR: For the 7-term TRL calibration of a four-sampler vector network analyzer (VNA), expressions for the deviations of the S-parameters of two-port test objects are presented as functions of the deviations from the ideal values of the TRL standards used.
Abstract: For the 7-term TRL calibration of a four-sampler vector network analyzer (VNA), expressions for the deviations of the S-parameters of two-port test objects are presented as functions of the deviations from the ideal values of the S-parameters of the TRL standards used. The sensitivity coefficients obtained are suitable for establishing the Type-B uncertainty budget for the S-parameter measurement.
TL;DR: In this paper, an easy and reliable method is discussed for accurate determination of the properties of small-sized samples for cavity perturbation measurements of dielectric materials.
Abstract: The cavity perturbation method has been used to measure the permittivity of various dielectric materials such as Teflon, alumina, silica fiber, single crystal potassium chloride, bakelite, and p-type silicon at X-band frequencies. Normally, the samples required for measurements in a rectangular cavity are in the form of thin slabs/rods of height at least equal to the height of the cavity. When available samples are smaller (smaller than the height of the cavity), accurate measurements are often difficult. In this paper, an easy and reliable method is discussed for accurate determination of the properties of small-sized samples.
TL;DR: In this paper, a comparison between several different millimeter-wave open-ended rectangular waveguide-based probes is made for the detection and evaluation of corrosion precursor pitting at Ka-band (26.5-40 GHz) and V-band(50-75 GHz).
Abstract: Aircraft structural components such as wings and fuselages are constantly exposed to harsh environments, which make them susceptible to corrosion initiation and growth. To complicate matters, corrosion is normally hidden under paint and primer and cannot be visually detected until significant corrosion has occurred, causing the paint to blister. Corrosion of this type is usually preceded by the presence of corrosion precursor pitting. Hence, early detection of pitting is a critical issue in the maintenance of an aircraft and its structural components. Near-field microwave nondestructive testing techniques have been successfully used for detection of corrosion under paint, including very small laser machined pits. However, it is desirable to improve the spatial resolution associated with these techniques so that pits with dimensions in the range of a few hundreds of micrometers can be effectively detected. In this paper, a comparison between several different millimeter-wave open-ended rectangular waveguide-based probes is made for the detection and evaluation of corrosion precursor pitting at Ka-band (26.5-40 GHz) and V-band (50-75 GHz). A number of laser machined pits with dimensions varying between 150 to 500 /spl mu/m were produced for this investigation. Using these probes, millimeter-wave images of these pits were produced, indicating that the modified open-ended rectangular waveguide probes, namely, single and double tapered and dielectric slab-loaded waveguide probes, were successful in detecting small pits. The results of this investigation, along with a complete discussion of the results, are presented.
TL;DR: A new methodology to experimentally determine fundamental temperature-dependent parameters of a thermoelectric module from observable variables obtained from temperature, voltage, and electric current measurements made on a working TE device is presented.
Abstract: The fundamental temperature-dependent parameters of a thermoelectric module (TEM), such as Seebeck coefficient, electrical resistance, thermal conductance, and figure-of-merit are necessary, among other factors, for conception of models for this type of devices. This paper presents a new methodology to experimentally determine these parameters from observable variables obtained from temperature, voltage, and electric current measurements made on a working TE device. Calculated parameters are plotted against the module's average temperature. Results are verified by inserting the average-value parameters into an electrothermal SPICE model of a TEM and comparing simulation and measured results for a given test configuration.