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Moment representations have been proposed to facilitate the interpretation of geophysical time domain electromagnetic responses. We present a new methodology for estimating these moments from field data for different system waveforms when on-time and off-time measurements are available. Quadrature impulse response moments are estimated by a recursive relation involving moments of the input waveform and moments of the observed response. After adapting this method to time domain electromagnetic applications—in particular, MEGATEM and AeroTEM (AirTEM) airborne electromagnetic systems—we present the results from applying this method on synthetic and real data collected over the Reid–Mahaffy test site in northern Ontario, Canada. [ABSTRACT FROM AUTHOR]

Terahertz (THz) plasmonic metamaterial, based on a metal-wire-woven hole array (MWW-HA), is investigated for the distinct power depletion in the transmittance spectrum of 0.1–2 THz, including the reflected waves from metal holes and woven metal wires. Woven metal wires have four orders of power depletion, which perform sharp dips in a transmittance spectrum. However, only the first-order dip at the metal–hole–reflection band dominates specular reflection with a phase retardation of approximately π. The optical path length and metal surface conductivity are modified to study MWW-HA specular reflection. This experimental modification shows that the first order of MWW-HA power depletion is sustainable and sensitively correlated with a bending angle of the woven metal wire. Specularly reflected THz waves are successfully presented in hollow-core pipe wave guidance specified from MWW-HA pipe wall reflectivity. [ABSTRACT FROM AUTHOR]

We present a multiwavelength, multichannel, time-domain near-infrared spectroscopy system named MAESTROS. This instrument can measure absorption and scattering coefficients and can quantify the concentrations of oxy- and deoxy-haemoglobin ([HbO2], [HHb]), and oxidation state of cytochrome-c-oxidase ([oxCCO]). This system is composed of a supercontinuum laser source coupled with two acousto-optic tuneable filters. The light is collected by four photomultipliers tubes, connected to a router to redirect the signal to a single time-correlated single-photon counting card. The interface between the system and the tissue is based on optical fibres. This arrangement allows us to resolve up to 16 wavelengths, within the range of 650–900 nm, at a sampling rate compatible with the physiology (from 0.5 to 2 Hz). In this paper, we describe the system and assess its performance based on two specifically designed protocols for photon migration instruments, the basic instrument protocol and nEUROPt protocols, and on a well characterized liquid phantom based on Intralipid and water. Then, the ability to resolve [HbO2 ], [HHb], and [oxCCO] is demonstrated on a homogeneous liquid phantom, based on blood for [HbO2], [HHb], and yeast for [oxCCO]. In the future, the system could be used to monitor brain tissue physiology. [ABSTRACT FROM AUTHOR]

Aging sensitive parameters like dissipation factor, oil and paper conductivity and paper moisture can be estimated from insulation model parameterized using polarization current to assess the condition of transformer insulation. However, polarization current measurement is a time-consuming offline technique. During measurement, variation of environmental conditions (especially temperature) affects the monotonically decreasing nature of recorded data. Analysis of such affected data lead to incorrect conclusion regarding insulation condition. Power transformer being a crucial equipment, utility prefer to reduce its shut down time to minimum amount. In this paper a technique is discussed through which the polarization current measurement time can be reduced significantly. Several transformer data are used for verification of developed method. Presented results show that measurement data corresponding to only 10 minutes is sufficient to estimate the remaining data through the application of discussed method. [ABSTRACT FROM AUTHOR]

Power system is witnessing change to become smarter due to recent interconnection/grid connections. Even small spike in voltages need to be notice for reliable smart power system. One of the important phenomenons is proximity effect which need to investigate specially for conductor system as now offshore wind farm and solar farms are the trend for modern power supplies. The proximity effect is very significant to investigate transient spurs or spikes voltages of a conductor system. Because of proximity effect, there is an increase in conductor resistance or uneven current distribution causing increase in series impedance. Proximity effect is significant for pipe-type cables with touching formation. Therefore, for investigation simplicity, circuit is formed consisting of an energized single covered conductor placed in an Al pipe. In this paper, effect on impedance of covered conductor is investigated as a function of height from ground as aluminium plate. The analysis involves frequency domain measurements and time domain measurements. [ABSTRACT FROM AUTHOR]

High frequency current transformers (HFCTs) are widely employed to detect partial discharge (PD) induced currents in high voltage equipment. This paper describes measurements of the wideband transfer functions of HFCTs so that their influence on the detected pulse shape in advanced PD measurement applications can be characterized. The time-domain method based on the pulse response is a useful way to represent HFCT transfer functions as it allows numerical determination of the forward and reverse transfer functions of the sensor. However, while the method is accurate at high frequencies it can have limited resolution at low frequencies. In this paper, a composite time-domain method is presented to allow accurate characterization of the HFCT transfer functions at both low and high frequencies. The composite method was tested on two different HFCTs and the results indicate that the method can characterize their transfer functions ranging from several kHz to tens of MHz. Results are found to be in good agreement with frequency-domain measurements up to 50 MHz. Measurement procedures for using the method are summarized to facilitate further applications. [ABSTRACT FROM PUBLISHER]

The performance of ultra-high frequency (UHF) sensors has a significant impact on the accuracy of UHF partial discharge (PD) detection. In this paper, a method is presented for the time-domain characterization of UHF sensors to provide a comprehensive evaluation of their performance in the time domain. The peak envelope value and the envelope width are adopted in the method as two characterization parameters for predicting the output waveforms of UHF sensors. However, due to the ill-posedness of deconvolution, the measurement of these parameters is highly sensitive to noise. Therefore, an automated optimization scheme is devised based on the multi-parameter filter technique to solve the problem. Two UHF sensors are then investigated using the proposed method. The measured characterization parameters are found to be dependent on the orientation of the sensors, which is discussed from the perspective of sensor geometry. Further, PD experiments are carried out using the same UHF sensors to validate the method. The actual performances of the sensors are in good agreement with their time-domain characterization parameters. The proposed method would be complementary to existing frequency-domain characterization methods and is useful for the comparison of different UHF sensors, especially when their output waveforms are utilized for PD detection. [ABSTRACT FROM AUTHOR]

To take effective measures for the interference problem between electronic devices, it is important to estimate the equivalent current distribution that is equivalent to the radiation source of unnecessary electromagnetic waves inside the electronic devices. Information of the equivalent current distribution could provide us some important knowledge to analyze the radiation source which could be the source of the EM interference. Previously, most of the researches have focused on estimating the location of CW electromagnetic radiation source in frequency domain. In this paper, a method including near field measurement in time domain and matrix inversion is proposed to estimate the equivalent current distribution of incoherent radiation source. The validity of this method is demonstrated using numerical simulations and experiments. [ABSTRACT FROM AUTHOR]

The resistive switching phenomenon is analyzed using a purposely developed setup which allows fast ramped voltages and measurements in the time domain. Taking advantage of these capabilities, the Set and Reset processes in Ni/HfO 2 structures have been studied for a large range of voltage ramp speeds. The results obtained show that Set and Reset voltages increase with voltage ramp speed. The use of time domain measurements has allowed concluding that a critical energy is needed to trigger the Set and Reset processes, independently of the biasing conditions. [ABSTRACT FROM AUTHOR]

Smart grid users and standardization committees require that utilities and third parties collecting metering data employ techniques for limiting the level of precision of the gathered household measurements to a granularity no finer than what is required for providing the expected service. Data aggregation and data perturbation are two such techniques. This paper provides quantitative means to identify a tradeoff between the aggregation set size, the precision on the aggregated measurements, and the privacy level. This is achieved by formally defining an attack to the privacy of an individual user and calculating how much its success probability is reduced by applying data perturbation. Under the assumption of time-correlation of the measurements, colored noise can be used to even further reduce the success probability. The tightness of the analytical results is evaluated by comparing them to experimental data. [ABSTRACT FROM PUBLISHER]

Partial discharge (PD) analysis has been widely used to detect premature degradation of power cables. Although there are recognized techniques for PD analysis, there is still lack of knowledge about measuring and modeling this phenomenon. This paper proposes a new model based on time domain parameters of the PD signal envelope. The proposed variables (time duration, and rising and falling slopes of the envelopes), together with conventional PD analyses focused on PD amplitude and phase resolved patterns, will provide a better understanding of this phenomenon. Based on this model, a new technique to reshape the PD signal envelope is also proposed that compensates the negative effect of dispersion in the location techniques that estimate the time of arrival (TOA). Experimental results were obtained in the lab, where a power cable has been artificially damaged in order to produce PD. To this end, a specific PD on-line acquisition system has been developed. In the first set of experiments, we illustrate how the cable attenuates and disperses the PD signal envelope. In the second one, we show how the proposed variables are useful to distinguish among different types of PD sources. Finally, an accurate estimation of the PD source location is achieved by measuring the time of arrival of the PD signal envelopes at both cable ends, and reshaping one of the signals captured. This technique improves the accuracy of the estimated location of the PD sources, both in simulation and in experimental results. [ABSTRACT FROM AUTHOR]

A high precision and high resolution time-to-digital converter (TDC) based on multichain measurements averaging method is implemented in a 40 nm fabrication process Virtex-6 FPGA. The results of the detailed theoretical analysis and the simulation with the MATLAB tool based on a complete TDC module show that the resolution limitation determined by the intrinsic cell delay of plain tapped-delay chain can be overcame, which results in an improvement on both resolution and precision without increasing the dead time. The test results agree with the simulation results quite well. In such a TDC, the input signal is connected to multiple tapped-delay chains simultaneously (the number of the chains is M), and each chain is just a plain TDC and generates a timestamp for a hit signal. Therefore, M timestamps should be obtained in total, which, after averaging, give the final timestamp. A TDC with 1.7 ps equivalent bin size, 1.5 ps averaged bin size and 4.2 ps RMS has been implemented with M being 16, which performs much better than the plain TDC constructed of a single tapped delay chain having 42.3 ps equivalent bin size, 24.0 ps averaged bin size resolution and 13.2 ps RMS precision. The comparisons of equivalent bin size and averaged bin size show that the nonlinearity is improved with a larger M. Due to the real time integral nonlinearity (INL) calibration and averaging calculation, the multichain TDC is almost insensitive to the process voltage and temperature (PVT) variations. [ABSTRACT FROM PUBLISHER]

In this paper, a time-domain system dedicated to medical diagnostics has been designed, a prototype has been built and its performance has been evaluated. Measurements show that the system has a 3-dB bandwith of about 3.5 GHz and a signal to noise ratio over 40 dB in the frequency range about 800 MHz to 3.8 GHz. The system has been used to perform a microwave tomographic image reconstruction test. The same target was reconstructed based on data measured with a network analyzer. A comparison between the images shows very small differences, and proves the functionality of the time domain system. [ABSTRACT FROM AUTHOR]

Estimating the input-output behavior of low voltage powerline channels for indoor high speed data communications requires the availability of proper wideband channel sounding tools. In fact, the properties of real world powerline channels are substantially different from those commonly exhibited by their wireless counterparts, so that standard methods for wireless channel sounding cannot be adapted to a powerline scenario. In this paper, after providing some general design guidelines for powerline channel sounding, a detailed description of a FPGA-based implementation of a wideband powerline channel sounder is provided. Such a tool is based on low cost hardware and is flexible, since it can be easily customized to user needs using a set of simple graphical user interfaces. Some of its specific applications, namely the estimation of the time-varying transfer function of an indoor powerline channel and the evaluation of the power spectral density of the noise affecting it, are illustrated to show the potentialities of the developed equipment. [ABSTRACT FROM PUBLISHER]

A novel approach for analyzing signal reflections on transmission lines terminated on non-linear impedances is presented. The starting point of this new method is the Bergeron diagram method. The results obtained by the well-known method are used as input data for the new approach. This new method is implemented in MatLab and is suitable for both linear and non-linear impedances, and also for driving signals having rise/fall times of any value. This is the novelty of this approach compared to the Bergeron method which is valid only for fast command signals. The results are compared and they show good agreement with the ones obtained by experimental measurements performed with a high-performance digital oscilloscope. [ABSTRACT FROM AUTHOR]

Miniaturized monopole and dipole antenna designs are reported with performances optimized for ultrawideband pulsed radio applications. The geometries are created using Bézier spline shapes, which have been refined with a genetic algorithm to simultaneously take account of both frequency- and time-domain criteria. Time-domain measurements of ultra wideband antennas with uniformly distributed energy across the full 3.1–10.6 GHz mask are reported for the first time and validate a new approach to minimization of pulse dispersion effects in the antenna designs. [ABSTRACT FROM PUBLISHER]

We perform a theoretical analysis of the measurement accuracy of ultrawideband time domain systems. The theory is tested on a specific ultrawideband system and the analytical estimates of measurement uncertainty are in good agreements with those obtained by means of simulations. The influence of the antennas and propagation effects on the measurement accuracy of time domain near field microwave imaging systems is discussed. As an interesting application, the required measurement accuracy for a breast cancer detection system is estimated by studying the effect of noise on the image reconstructions. The results suggest that the effects of measurement errors on the reconstructed images are small when the amplitude uncertainty and phase uncertainty of measured data are less than 1.5 dB and 15 degrees, respectively. [ABSTRACT FROM AUTHOR]

This paper deals with finding appropriate hysteresis models that predict the behavior of electro-magnetic lenses used with electron microscopy. The iterative selection procedure consists of experiment design and mathematical analysis of hysteresis models. We will show two examples of pitfalls when the suitability of models is assessed by means of curve-fitting to observations. The first example illustrates the inability of models with local memory to describe the magnetic hysteresis in our application. The second deals with accommodation. With both, the experiments carried out on an off-line setup of a magnetic lens are compared to hysteresis models. [ABSTRACT FROM AUTHOR]

This work presents the creation of a coupled analysis engine and experimental system capable of fully characterizing the thermal behavior of complex, 3-D, active, submicron, electronic devices. First, the surface temperature field of an activated device is non-invasively measured with submicron spatial resolution. Next, the thermal conductivity of each thin-film layer composing the device is measured and a numerical model is built using these values. The measured temperature distribution map is then used as input for an ultra-fast inverse computational solution to fully characterize the thermal behavior of the complex 3-D device. By bringing together measurement and computation, it becomes possible for the first time to non-invasively extract the 3-D thermal behavior of nanoscale embedded features that cannot otherwise be accessed. The power of the method was demonstrated by verifying that it can extract details of interest of a representative MOSFET device. [ABSTRACT FROM AUTHOR]

We propose an algorithm for inverting time domain induced polarization data to a relaxation time distribution. The algorithm is based on the (Tikhonov) regularized solution of the 1st kind Fredholm integral equation. We test the algorithm on synthetic data, and show its robustness for a noise level, typical of laboratory time domain measurements. We also show that, for the inversion purpose, the time domain data must be obtained with the different current wavelengths. We then test the algorithm on the experimental data recently obtained on brine-saturated medium-grained quartz sand (average grain diameter of 4 × 10−4 m), and on sand mixtures. For the medium-grained sand, relaxation time distribution contains a main peak at 25 s. Different amounts (3%, 8% and 12%) of fine-grained quartz sand (average grain diameter of 1.12 × 10−4 m) were added to the medium-grained quartz sand. For the sand mixture, an additional peak is observed in the relaxation time distributions, in the time range from 1.0 to 2.5 s. The magnitude of the second peak increases with the increase of the fine-grained sand content. Therefore, the experimental data show that peaks in the relaxation time distributions are related to the grain size. On the basis of the known peak location, and of the known grain size value, we obtained the values of the diffusion coefficient, which were found to be of the same order of magnitude as those in the bulk solution. [ABSTRACT FROM AUTHOR]

A phase-locked-loop (PLL) concept for the generation of two extremely stable RF-signals with a small frequency difference is presented. The system is based on only one PLL and comprises two crystal oscillators. One is fixed frequency acting as the reference while the other one is tuneable being controlled by the PLL-system. A special PLL-concept allows us to achieve a very small frequency difference of only some 100 Hz between the two oscillators while maintaining a short settling lime below 2 ms as well as a very good phase-noise performance. These features mainly rely on low division factors in the feedback of the PLL and a high reference frequency at the phase-frequency-detector. [ABSTRACT FROM AUTHOR]

The method of normal-mode expansion has been extended for time domain simulation of a piezoelectric bimorph, for arbitrary voltage excitations. An experimental method for time domain measurements is proposed and the logarithmic decrement technique is used for the estimation of the damping factor near the first resonance. The experimental setup consists of an auto-balancing bridge circuit and requires only an oscilloscope for measuring the input and output voltages. Resonant frequencies of the bimorph were also obtained by taking the FFT of the measured output voltage. For comparison purposes the method of normal-mode expansion in frequency domain was applied to obtain the driving point impedance of the bimorph near the first resonance. The value of the damping factor, computed through impedance measurements, was in agreement with the value computed using the logarithmic decrement technique. [Copyright &y& Elsevier]

In this paper, we investigate the mutual power-spectra distributions in the azimuth, elevation, and time-delay domains in different urban environments with randomly distributed arrays of buildings placed on rough terrain. This is done for various orientations of street guiding structures in the urban scene, and for different elevations of the terminal antenna, the base station, and the subscriber, whether mobile or not, and with respect to the buildings' overlay profile. A combination of the stochastic multi-parametric and crossing-street waveguide models, created earlier, is used to describe a total probability-density function (PDF) of mutual azimuth time-delay, elevation time-delay, and azimuth-elevation distribution of multiply reflected signals arriving at the receiver after multiple reflection, diffraction, and scattering from the numerous obstructions surrounding both terminal antennas. Comparisons with some high-resolution three-dimensional measurements, as well as with the corresponding three-dimensional numerical ray-tracing model, are done to describe directional and spatial-temporal urban channel characteristics, and to predict propagation situations in the urban scene for various locations and directional properties of the terminal antennas. [ABSTRACT FROM AUTHOR]

Nonlinear models of microwave subsystems are identified from time domain measurements. Scattering functions in the form of nonlinear time domain functions are used to derive a system identification model instead of an equivalent circuit. The advantage being the simplicity of the measurement and the developed models and the speed and accuracy of the simulation of the entire system. [ABSTRACT FROM AUTHOR]

A breast cancer imaging system with time‐domain measurements is proposed. This system is based on complementary metal‐oxide semiconductor circuits such that it is very cost‐effective and the image is acquired in a very short time. It consists of ultra‐wideband transceivers and a master controller for system control and data collection. Simulation results with a 3D FDTD hemi‐spherical breast model show the proposed system can reconstruct the breast image in the presence of possible disturbances such as clock skew, clock jitter, and white noise. [ABSTRACT FROM AUTHOR]

We propose a novel electromagnetic bandgap (EBG) structure with a significantly extended noise isolation bandwidth, called a double-stacked EBG (DS-EBG) structure, fabricated on a low-temperature co-fired ceramic (LTCC) multilayer substrate. The DS-EBG structure was devised for wideband suppression of simultaneous switching noise (SSN) coupling in system-in-package (SiP) applications. Our design approach was enabled by combining two EBG layers embedded between the power and ground planes. The two EBG layers had different bandgaps from using different cell sizes. Enhanced wideband suppression of the SSN coupling was validated using a 11.4-GHz noise stop bandwidth with 30-dB isolation in time and frequency domain measurements up to 20GHz [ABSTRACT FROM PUBLISHER]

We present a multiwavelength, multichannel, time-domain near-infrared spectroscopy system named MAESTROS. This instrument can measure absorption and scattering coefficients and can quantify the concentrations of oxy- and deoxy-haemoglobin ([HbO 2 ], [HHb]), and oxidation state of cytochrome-c-oxidase ([oxCCO]). This system is composed of a supercontinuum laser source coupled with two acousto-optic tuneable filters. The light is collected by four photomultipliers tubes, connected to a router to redirect the signal to a single time-correlated single-photon counting card. The interface between the system and the tissue is based on optical fibres. This arrangement allows us to resolve up to 16 wavelengths, within the range of 650-900 nm, at a sampling rate compatible with the physiology (from 0.5 to 2 Hz). In this paper, we describe the system and assess its performance based on two specifically designed protocols for photon migration instruments, the basic instrument protocol and nEUROPt protocols, and on a well characterized liquid phantom based on Intralipid and water. Then, the ability to resolve [HbO 2 ], [HHb], and [oxCCO] is demonstrated on a homogeneous liquid phantom, based on blood for [HbO 2 ], [HHb], and yeast for [oxCCO]. In the future, the system could be used to monitor brain tissue physiology.