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This study proposes the first estimator in the open literature (to the present authors' best knowledge) to nonparametrically estimate a Hammerstein system's nonlinear static subsystem when excited by an input that is temporally self‐correlated with an unknown spectrum, an unknown variance and an unknown mean (instead of the input as commonly presumed to be white and zero‐mean). This proposed nonparametric estimator is analytically proved here to be asymptotically unbiased and pointwise consistent. The proposed estimate's associated finite‐sample convergence rate is also derived analytically.

Azimuthal centrosymmetry in an array grid is typically associated with arrays that are circular, concentric, cylindrical, spherical, or hemispherical. However, a recently proposed alternative combines an azimuthal circular array with a linear vertical array. For this elegantly simple new array grid's use in the direction-of-arrival estimation, this article advances array-design insights to meet a given estimation–precision threshold, by examining the tradeoff between the azimuth-angle Cramer–Rao bound vis-a-vis the polar-angle Cramer–Rao bound in a proposed two-step design procedure.

For a Hammerstein system subject to a stochastic input that is spectrally coloured, this study is first in the open literature (to the present authors' best knowledge) to estimate its linear dynamic subsystem. This estimation is achieved without any prior knowledge nor any prior/simultaneous estimation of the preceding non‐linear static subsystem. This proposed estimator can handle any temporally self‐correlated input despite its potentially unknown spectrum, unknown variance and unknown mean—unlike the common assumption that the input is white and zero‐mean. This proposed estimator needs observations only of the Hammerstein system's overall input and consequential output, but not any observation of any intrasubsystem signal. Furthermore, this proposed estimator can handle a linear subsystem whose input and/or output are each corrupted additively by stationary (and possibly coloured) noises of unknown probability distributions, of unknown non‐zero means and of unknown autocovariances. The proposed estimate is analytically proved herein as asymptotically unbiased and as pointwise consistent; and the estimate's finite‐sample convergence rate is also derived analytically.

An “electromagnetic vector sensor” (EMVS) comprises three orthogonal dipoles and three orthogonal loops, all in spatial collocation. The former triplet aims to directly measure the $3 \times 1$ electric-field vector ${\mathbf{e}} $ , whereas the latter triplet aims to directly measure the $3 \times 1$ magnetic-field vector ${\mathbf{h}} $ . Their vector cross product $ {\mathbf{e}} \times {\mathbf{h}} $ would yield the incident source’s Poynting vector, which specifies the incident wavefield’s propagation direction. In reality, all these are only an idealization. Instead, a real-world dipole triad’s measurement could equal the incident ${\mathbf{e}} $ , only if the dipoles were electrically short (i.e., with an electrical length of $({L}/{\lambda }) ). Likewise, a practical loop triad’s measurement could equal the incident ${\mathbf{h}} $ , only if the loops were electrically small (i.e., with an electrical circumference of $2 \pi ({R}/{\lambda }) ). However, such short dipoles and small loops would be electromagnetically inefficient receivers. For a practical dipole that is electrically long , its measurement equals not the incident wavefield’s ${\mathbf{e}} $ but a vector dot product between: 1) the incident wave’s ${\mathbf{e}}$ and 2) that dipole antenna’s “effective length” vector (which depends on that dipole’s $({L}/{\lambda })$ and orientation). An analogous complexity exists for a practical loop that is electrically large . For such practical dipoles and loops, the aforementioned vector-cross-product would fail to yield the Poynting vector, hence it would inaccurately estimate the direction-of-arrival. Instead, this article will advance a new closed-form algorithm to simultaneously estimate an incident source’s direction-of-arrival and polarization, despite the practical dipoles’/ loops’ mathematically complicated gain/phase responses as described earlier, but without any prior knowledge of the dipoles’ electric length $({L}/{\lambda })$ nor the loops’ electric radius $({R}/{\lambda })$ .

High-frequency power converters enabled by wide bandgap (WBG) and silicon semiconductor devices offer distinct advantages in power density and dynamic performance. However, switching oscillations are commonly observed in these circuits with undesirable consequences. This paper reviews the impacts, root causes, and mitigation techniques of switching oscillations through literature survey, modeling analysis, and experimental investigation. We categorize the following root causes for oscillations during switching transients: 1) damped oscillation triggered by high di/dt and/or dv/dt coupled with parasitic elements; 2) undamped oscillation of WBG devices as part of a negative resistance oscillator; and 3) semiconductor device physical mechanisms such as the negative capacitance phenomenon due to conductivity modulation in insulated gate bipolar transistors or impact ionization in MOSFETs, the plasma extraction transit-time effect in bipolar power devices, and the reverse conduction property of GaN HEMTs. Furthermore, this paper discusses various circuit techniques to suppress switching oscillations, and techniques of extracting parasitic inductances of power devices.

The use of additive manufacturing and different metallization techniques for prototyping radio frequency components such as antennas and waveguides are rising owing to their high precision and low costs. Over time, additive manufacturing has improved so that its utilization is accepted in satellite payloads and military applications. However, there is no record of the frequency response in the millimeter-wave band for inductive 3D frequency selective structures implemented by different metallization techniques. For this reason, three different prototypes of dielectric 3D frequency selective structures working in the millimeter-wave band are designed, simulated, and manufactured using VAT photopolymerization. These prototypes are subsequently metallized using metallic paint atomization and electroplating. The manufactured prototypes have been carefully selected, considering their design complexity, starting with the simplest, the square aperture, the medium complexity, the woodpile structure, and the most complex, the torus structure. Then, each structure is measured before and after the metallization process using a measurement bench. The metallization used for the measurement is nickel spray flowed by the copper electroplating. For the electroplating, a detailed table showing the total area to be metallized and the current applied is also provided. Finally, the effectiveness of both metallization techniques is compared with the simulations performed using CST Microwave Studio. Results indicate that a shifted and reduced band-pass is obtained in some structures. On the other hand, for very complex structures, as in the torus case, band-pass with lower loss is obtained using copper electroplating, thus allowing the manufacturing of inductive 3D frequency selective structures in the millimeter-wave band at a low cost.

Efficient first-principle simulation with self-consistence of the feedback-interferometric fiber laser sensor has been studied. The feedback-interferometric fiber laser sensor consists of a Distributed Bragg Reflectors/Distributed Feedback (DBR/DFB) fiber laser and an external feedback sensing element. The approach is self-consistent in that it effectively integrates the inter-dependence of the 980-nm pump/1550-nm laser powers and the rate equations of the Er/Yb co-doped fiber laser medium. The 1550-nm laser field is efficiently solved by Coupled Modes Theory (CMT) method while the solutions of the rate equations are obtained with the iterative Newton-Raphson method. Four types of external reflection schemes have been simulated: 1) without reflection at either side; 2) reflection at the pump side; 3) reflection at the remote side; and 4) reflections at both sides of the fiber laser. With the self-consistent simulation, the lasing wavelength and lasing signal power for various reflection schemes are obtained. In this investigation, the procedure to optimize the reflections to achieve optimal sensor sensitivity is demonstrated.

A rectangular array of sensors is often used in direction finding, due to the geometric regularity in its spatial rectangular grid. The sensor positions may be confined to the rectangle's perimeter (as in a “rim” array), or may span over the rectangle's entire interior as well (as in a “filled” array). This paper compares these two array grids by their precision in direction finding, by pioneering Cramer-Rao bound expressions for both array grids above, in closed forms and explicitly in terms of the array parameters.

Using two electrically long dipoles to estimate the polarizations of impinging sources, this paper pioneers signal-processing algorithms in closed forms. The existing literature on crossed-dipoles polarimetry are restricted to electrically short dipoles with an electrical length of $(L/\lambda) \le (1/10)$ , which have subpar efficiency in radiation and in reception. In contrast, this paper allows electrically long dipoles—two of them here are perpendicularly oriented but may be collocated or may be separated by a known displacement. Using such a pair of electrically long dipoles for polarization estimation, this paper proposes new closed-form formulas and derives the associated Cramer–Rao bounds.

An eight-element broadband wide-beam circularly polarized (CP) antenna array is developed for mobile wireless communications. The CP antenna element consists of two rectangular loops with gaps for circular polarization and parasitic elements for bandwidth enhancement. A wide beamwidth is achieved in the horizontal plane because the CP antenna elements have a narrow cross section in the plane. The CP antenna array also has higher isolation between antenna elements than a linear polarized (LP) array with the same element space, which is due to the polarization mismatch caused by the currents in the CP antenna elements. The eight-element CP antenna array achieves a bandwidth of 40% (1.7–2.55 GHz) for return loss >15 dB and a bandwidth of 47% (1.67–2.7 GHz) for axial ratio (AR) < 3 dB. The half-power beamwidth and the 3 dB AR beamwidth in the horizontal plane are ~65° ± 8° and approximately 100°, respectively. The antenna gain for the array is about 17 dBi. The CP antenna array is suitable for applications in urban macrocell base stations.

We evaluate the micromagnetic energy of a domain wall contained in a thin, horn-shaped nanostructure and propose a method to extract the strength of the interfacial Dzyaloshinskii-Moriya interaction based on the equilibrium position of the wall. An inplane magnetic field coupled with the interfacial DMI balances a competing driving force related to the "nanohorn" tapering and consequent variation in length. It is evident that the strength of the the DMI is directly correlated to the equilibrium position of the DW. Moreover, the range of measurable DMI values can be controlled by varying the degree of tapering in the nanohorn. Numerical and semi-analytical calculations were separately performed and show broad agreement. The calculations provided here offer an alternative framework for future measurement of DMI, which has been notoriously difficult to do experimentally., 3 pages, 3 figures, submitted to IEEE Transactions on Magnetics

The parasitic inductances of silicon carbide (SiC) power mosfet s have a major influence on their operation and circuit performance. They incur negative effects such as switching oscillations, power losses, and electromagnetic interference noise. This paper introduces a new technique to accurately characterize the parasitic inductances of SiC power mosfet s in both discrete packages and power modules based on two-port S-parameters measurement. By treating a power mosfet as a two-port network, we obtain the scattering (S) and impedance (Z) parameters from network analyzer measurement. These parameters, through detailed network analysis, provide more accurate values of the internal parasitic inductances than the commonly used single-port impedance measurement technique. The new approach is first verified with high-frequency circuit simulation and then applied in the case study of SiC power mosfet s in a TO-247 discrete package and a half-bridge power module. In addition, a number of silicon power mosfet s and IGBTs in TO-247, TO-220, D2PAK, DPAK, and SO-8 packages are also characterized for comparison. A comparison between the characterization results from the new two-port and the prior art one-port methods reveals a significant difference ranging from 12.6% to 93.9%.

Electric polarizations in metallic nanoparticles have enabled them to be employed in a variety of applications such as sensors, light trapping, polarizer, filter, and wave guiding at optical frequencies. Semiconductor nanoparticles, with a lower carrier concentration and hence plasma frequency, can be expected to find applications in the terahertz frequency range. The effect of a dielectric shell on the charge-field interaction in a semiconductor nanoparticle in the terahertz frequency range is investigated. The presence of a nonconductive layer on the surface of a conductive particle results in a modification in its polarization properties. Employing a formulation based on carrier transport in the semiconductor, the space charge dynamics is revealed, along with the electric field inside and outside the core-shell structure. From the polarizations, in the semiconductor and the dielectric, the total induced dipole moment is obtained. Building upon an equivalent circuit developed for the bare semiconductor nanoparticle, the equivalent circuit for the core-shell particle is arrived at. It provides a direct correspondence of the polarizability of the structure to the circuit elements, whose values are given in closed-form expressions in terms of the material parameters in the two regions. The process in the development of the equivalent circuit provides physical insight to the polarization within the structure, while the circuit obtained enables models for a cluster of interacting particles to be built by employing network theory.

Electrically small loops have been the focus of the research literature on loop-antenna signal processing, but such electrically small loop-antennas are electromagnetically inefficient. Electrically large loop-antennas will instead be analyzed here in this paper, in the context of estimating an incident source's direction-of-arrival or polarization. Specifically, three large loop-antennas here are collocated and are oriented orthogonally, in order to measure all three Cartesian components of the incident magnetic field simultaneously all at one specific spatial position. This orthogonal triad offers azimuth-elevation bivariate directivity despite the three loops' spatial collocation. For such a triad of electrically large loops, this paper (first in the open literature) formulates the array manifold, develops the corresponding algorithms in closed form to estimate an incident source's azimuth-elevation direction-of-arrival or polarization, and demonstrates these proposed estimators' precision as close to the Cramér-Rao bounds. Accepted version

This paper proposes a new configuration of acoustic sensors—the collocation of three cardioid sensors in perpendicular orientation, in order to increase the mainlobe-to-sidelobe height ratio (possibly to $\infty$ ). This paper will analyze such a proposed triad's “spatial matched filter” beam-pattern that is independent of the frequency/spectrum of the incident signals. Specifically, this paper will analytically derive the mainlobe's pointing error in azimuth-elevation, the mainlobe's two-dimensional beam “width,” the necessary and sufficient conditions for a sidelobe to exist, the mainlobe-to-sidelobe height ratio, and the array gain. These above characteristics depend on the cardioids’ “cardiodicity parameter” and on the beam's nominal “look direction.”

If a nominally L-shaped sensor-array's two legs are not exactly perpendicular, its azimuth-polar direction-of-arrival estimation would be degraded. This paper quantifies this degradation via a deterministic Cramer–Rao bound analysis of the direction-finding error variance.

In dipole-antenna array signal-processing algorithm development, research has focused on “short dipoles” whose physical length ( $L$ ) is under (1/10) of a wavelength $\lambda $ . Such electrically “short” dipoles have very small input impedances, rendering such “short” dipoles to be inefficient radiators. Practical dipoles, with an electrical length of $({L}/{\lambda }) \in [{0.1, 1}]$ , have notably larger input impedance, hence making them better radiators. Of such practical dipoles, this paper investigates their use for azimuth-polar direction finding and for polarization estimation. This paper will first present the measurement model (i.e., array manifold) of a triad of such practical dipoles, collocated in space and orthogonally oriented. This paper will then develop the corresponding closed-form algorithms to estimate the bivariate azimuth–elevation direction-of-arrival or the bivariate polarization. Such closed-form algorithms previously have been unavailable in the existing literature for such a triad of electrically “long” dipoles of pragmatic radiation efficiency.

An electromagnetic vector-sensor consists of a triad of electric dipoles in orthogonal orientation, plus another triad of similarly arranged magnetic loops, all in spatial collocation. This electromagnetic vector-sensor has been used in a series of algorithms to estimate the incident sources' directions-of-arrival (DOA) and polarizations. However, these algorithms have presumed the dipole-triads and the loop-triads of perfect ideality in their gain/phase responses, their orientations, and locations. Such idealization is rarely (if ever) attained in actual field deployment. Instead, the non-idealities need to be calibrated, often blindly with no training signal impinging from any prior known direction-of-arrival at any prior known polarization. For such a scenario, this work proposes a new algorithm for direction finding, for polarization estimation, and for “blind” calibration (a.k.a. “self-calibration”, “auto-calibration”, or “unaided calibration”) of all above non-idealities. This new algorithm is orders-of-magnitude computationally simpler than maximum-likelihood estimation. This reduction in complexity is achieved here by exploiting the electromagnetic vector-sensor's quintessential array manifold, and by a judicious breakdown of the originally high-dimensional problem (of estimating the directions-of-arrival, polarizations, and the antenna non-idealities) into suitably chosen/sequenced low-dimensional sub-problems. This proposed algorithm is first in the open literature to exploit the electromagnetic vector-sensor's quintessential array manifold for “blind” calibration of all abovementioned non-idealities simultaneously. Monte Carlo simulations verify this proposed algorithm's effectiveness in “blind” calibration and this algorithm's orders-of-magnitude computational efficiency over the maximum-likelihood approach.

For a triad of short dipoles (or of small loops), in perpendicular orientation relative to each other but collocated in space, this study derives a lower bound for their error in direction-of-arrival estimation and polarisation estimation, accounting for the possibility of failure in any individual dipoles (or loops).

The paper analyzes how a sensor array's direction-finding accuracy may be degraded by any stochastic uncertainty in the sensors’ complex value gains, modeled here as complex value Gaussian random variables. This analysis is via the derivation of the hybrid Cramer-Rao bound (HCRB) of the azimuth-elevation direction-of-arrival estimates. This HCRB is analytically shown to be inversely proportional to a multiplicative factor equal to one plus the variance of the sensors' gain uncertainty. This finding applies to any array grid geometry. The maximum a posteriori (MAP) estimator corresponding to this uncertain gain data model is also derived. Monte Carlo simulations demonstrate that this estimator approaches the lower bound derived.

A Wiener system consists of two sequential sub-systems: (i) a linear, dynamic, time-invariant, asymptotically stable sub-system, followed by (ii) a nonlinear, static (i.e. memoryless), invertible sub-system. Both sub-systems will be identified non-parametrically in this paper, based on observations at only the overall Wiener system's input and output, without any observation of any internal signal inter-connecting the two sub-systems, and without any prior parametric assumption on either sub-system. This proposed estimation allows the input to be temporally correlated, with a mean/variance/spectrum that are a priori unknown (instead of being white and zero-mean, as in much of the relevant literature). Moreover, the nonlinear sub-system's input and output may be corrupted additively by Gaussian noises of non-zero means and unknown variances. For the above-described set-up, this paper is first in the open literature (to the best of the present authors' knowledge) to estimate the linear dynamic sub-system non-parametrically. This presently proposed linear system estimator is analytically proved as asymptotically unbiased and consistent. Moreover, the proposed nonlinear sub-system's estimate is assured of invertibility (unlike earlier methods), asymptotic unbiasedness, and pointwise consistence. Furthermore, both sub-systems' estimates' finite-sample convergence is also derived analytically. Monte Carlo simulations verify the efficacy of the proposed estimators and the correctness of the derived convergence rates.

This study introduces the mathematical paradigm of ‘copula’ to the technical field of channel modelling. Copula-based modelling allows each sensor of its distinct set of fading parameters, and allows cross-correlation among various sensors’ parameter sets. Hence, the branch statistics may be non-identical over various branches, yet cross-correlated between branches. This scenario is realistic especially for sensors of different polarisations/constructions and/or for sensors at widely separate locations – as increasingly common for wireless transceivers. Despite such versatility in modelling, this copula-based multivariate fading distribution may yet be so simple in mathematical form that the system's outage probability can be analytically derived in a closed form, free of any infinite-term summation and free of any unsolved integration.

One isotropic pressure sensor and one uniaxial particle velocity sensor is used in order to estimate the azimuth-elevation angle of arrival of a source impinging from the far field. This work introduces new estimation formulas in closed forms applicable to estimators based on an eigen-decomposition of the data covariance matrix. The validity region for unambiguous estimation is also identified, and the corresponding Cramer-Rao bound is derived as well.

This paper proposes a new radar/sonar processing architecture that enables a low-rate time-sampling rate while still producing a high-resolution range profile over a narrow range-window. This new architecture generalizes the conventional “stretch processing” architecture (which employs linear frequency modulated (LFM) waveforms that suffer from high range-sidelobes), to nonlinear frequency modulated (NLFM) waveforms, which can lower the range-sidelobes without tapering. Computational results demonstrate both the estimation efficacy and the time-sampling efficiency of the proposed scheme.

International audience; In this paper, we introduce a novel direction finding (DF) algorithm for a multi-scale sensor-array, that is, an array presenting multiple scales of spatial invariance. We show that the collected data can be represented as a Candecomp/Parafac (CP) model, for which we analyze the identifiability properties. A two-stage algorithm for direction-of-arrival (DOA) estimation with such an array is also proposed. This approach generalizes the results given in \cite{SidiSPT0800} to an array that presents an arbitrary number of spatial invariances. We illustrate, on two particular array geometries, that our method outperforms, in some difficult scenarios, the ESPRIT-based approach introduced Wong and Zoltowski in 1998, the ESPRIT-MUSIC of Zoltowski and Wong and the Tensor-ESPRIT. Moreover, we show that the single-snapshot case and the fully cross-correlated sources case can be handled by our method without any spatial smoothing procedure, provided that the array includes at least three scale-levels.

This paper shows how a triad of orthogonally oriented uniaxial velocity sensors may be spatially separated, yet facilitate direction finding of incident emitters via closed-form subspace-based parameter estimation algorithms, while extending the triad’s spatial aperture in three-dimensional space to enhance the resolution of the azimuth/elevation direction of arrival estimates.

This paper analyzes the noise statistics of a tri-axial velocity sensor. This tri-axial sensing system comprises three orthogonal axes. Along each axis, a uni-axial velocity sensor is realized through two isotropic pressure sensors displaced along that axis. Hence, a tri-axial velocity sensor may be implemented with as few as four isotropic sensors: one at the Cartesian origin and one at each Cartesian axis. Each isotropic sensor’s noise would contribute to its axis’ effective noise. As the three axes share one isotropic sensor in common, the three axes’ effective noises would be cross-correlated, but how? This is answered in this paper, through rigorous mathematics that analytically derive the statistical codifference across the three axes’ effective noises. This analysis models the noises accommodatingly as α-stable distributed, which includes the special cases of the Gaussian distribution, the Cauchy distribution, and many other heavy-tailed probability distributions. This finding is then generalized from the aforementioned velocity sensors (i.e., differential sensors of the first order) to differential sensors of arbitrarily high orders.

An electrically small antenna (ESA) designed for portable communication device applications is described. The antenna structure is based on the introduction of parasitic element to the transverse bilateral helical (TBH) antenna to enhance the bandwidth, leading to the TBH antenna with parasitic elements (TBHP). By insertion of a second helix into the core of the host helix, the overall dimensions of the antenna structure are kept the same as the original TBH antenna. A first-order analytical model is developed to gain insight to the design process. Performance of the TBHP antenna is evaluated using finite element method (FEM) electromagnetic simulation. The experimental and simulation data showed that the TBHP antenna has 105% wider bandwidth in a $50-\Omega $ reference system and 74% higher radiation efficiency around the 621-MHz operating frequency compared with the original TBH antenna. Simulation and measurement results are found to be in good agreement.

This paper proposes a new way to realize a maximum-SINR beamformer for block-based cyclically prefixed single-carrier modulation. Here, SINR stands for ‘signal to interference plus noise’ ratio, at the beamformer output. This spatial beamformer will ‘blindly’ pass the signal-of-interest; and this beamformer will ‘blindly’ null any co-channel interference, any adjacent-channel interference, any out-of-system interference, and/or any spatio-temporally correlated additive noises. This proposed scheme is made possible by zero-padding an insufficient guard interval, which may be shorter than the temporally spreading channel's order. The proposed receiver will first undergo frequency-domain equalization, to ‘clear’ the data of any signal-of-interest's energy in the zero-padded guard interval, in order to facilitate the estimation of the interference and noise. This interference-and-noise estimate will then be eigen-subtracted from the signal-and-interference-and-noise dataset by the aforementioned ‘blind’ beamformer in the spatial dimension.

This paper advances a new “quasi-blind” calibration algorithm to calibrate a multi-array network (MAN) of acoustic-vector-sensors, whose component-sensors may have non-ideal gain/phase responses, incorrect orientations, and imprecise locations. This proposed calibration is “quasi-blind” in not requiring any prior knowledge/estimation of any training signal's arrival-angle. This proposed algorithm is computationally orders-of-magnitude more efficient than maximum-likelihood estimation. These advantages are achieved here by exploiting the acoustic vector-sensor's quintessential characters, to interplay between two complementary approaches of direction-finding: (1) customary interferometry between vector-sensors, and (2) “acoustic particle-velocity-field normalization” DOA-estimation within each individual vector-sensor. Monte Carlo simulations verify the proposed algorithm's efficacy in “quasi-blind” calibration and its aforementioned computational efficacy.

An “acoustic vector sensor” (also known as a “vector hydrophone” in underwater or sea-surface applications) is composed of three orthogonally oriented uni-axial particle-velocity sensors, plus a “pressure-sensor” (i.e., a microphone or a hydrophone) - all collocated in a point-like spatial geometry. (This collocated setup is versatile for direction finding, because its azimuth-elevation spatial response is independent of frequency.) This paper investigates how the acoustic vector sensor's direction finding accuracy would be degraded by random deviations from its nominal gain response and/or phase response. Each type of deviation is statistically modeled herein as a random variable with a small variance, reasonably so for a well-built acoustic vector sensor. The resulting hybrid Cramer-Rao bound (HCRB) is derived exactly in open form for azimuth-elevation arrival-angle estimation, but also approximated to produce a closed form that is simple enough to yield qualitative observations. This closed-form hybrid Cramer-Rao lower bound's tightness is illustrated by a new estimator developed in this paper.

An acoustic "particle velocity sensor" (a.k.a. a geophone) exhibits a gain-response with a cosine-like directivity. The particle velocity sensor may be realized in hardware by two "pressure sensors" (of isotropic directivity) displaced in space, and by computing the spatial first-order finite difference between the data of the two isotropic component-sensors. As each component-sensor's data are degraded by additive noises (modeled here with much generality as stochastically distributed as "stable" (a.k.a. "alpha stable" or "$\alpha$ stable"), and not restricted to being Gaussian), the particle velocity sensor as a whole would also experience noise, the statistics of which is analytically derived here. Furthermore, beyond this particle velocity sensor involving a first-order finite difference, the work presented here also derives the composite noise statistics of higher order difference realizations of sensors of higher order directivity in their gain responses.

This study extends an algorithm, previously proposed by the present authors, for ‘linear minimum-mean-squared error’ estimation of phase noise of (possibly) temporal non-stationarity, large magnitude, ‘non’-identical increments that have a Levy distribution, of which the Wiener distribution represents a special case. This estimator-taps may be pre-set to any number, may be pre-computed offline with no matrix inversion, based on the prior knowledge of only the signal-to-(additive)-noise ratio and the phase-noise's characteristic function. That estimator may be set to various degrees of latency. This is here generalised to allow observables at irregular time-instants (e.g. because of the irregular placement of pilot symbols in the transmitted waveform), under which the phase-noise increments become non-identically distributed. This study handles this more complicated scenario.

An investigation of the interaction of a conductive sphere with an electromagnetic wave with attention given to space-charge effects would appear timely, as there is much current interest in the electromagnetic properties of mesoscopic structures. In this study, the polarization of a small semiconductor sphere immersed in a dynamic electric field is explored analytically and numerically. In one approach, suitable for a sphere with low to moderate charge carrier concentration, the Poisson's equation is coupled with the transport equations of the carriers, leading to a quasi-static formulation under the weak-field approximation. Screening effects of the charges on the interior field are revealed, along with a current distribution that is essentially uniform over much of the volume of the sphere. Frequency dependence of the total induced dipole moment of the sphere displays strong dispersion and absorption near the bulk plasma frequency. Validity of the quasi-static assumption is assessed by comparison to results of calculations based on a full-wave formulation. As the nominal carrier concentration exceeds 1020 cm-3, the quasi-static solutions for interior field and current distribution begin to deviate from the full-wave solution and the latter must be employed to provide a realistic account of the charge-wave interaction within the sphere.

In biomedical applications, the similarity between a signal measured from an injured subject and a reference signal measured from a normal subject can be used to quantify the injury severity. This paper proposes a generalization of the adaptive signed correlation index (ASCI) to account for specific signal features of interest and extend the trichotomization of conventional ASCI to an arbitrary number of levels. In the context of spinal cord injury assessment, a computational example is presented to illustrate the enhanced resolution of the proposed measure and its ability to offer a more refined measure of the level of injury., 2 two-column pages, 3 figures

The work presented here derives an approximate lower bound (ALB) for the error variance of direction-finding using a single acoustic vector sensor subject to random breakdown in its sensors. This ALB equals a weighted sum of Cramer-Rao bounds (CRBs), conditioned on disjoint events of sensor breakdown, that together define the overall phenomenon of random sensor breakdown. Its tightness is verified by Monte Carlo simulation of a maximum likelihood estimator.

An acoustic vector-sensor (a.k.a. vector-hydrophone) is composed of three acoustic velocity-sensors, plus a collocated pressure-sensor, all collocated in space. The velocity-sensors are identical, but orthogonally oriented, each measuring a different Cartesian component of the three-dimensional particle-velocity field. This acoustic vector-sensor offers an azimuth-elevation response that is invariant with respect to the source's center frequency or bandwidth. This acoustic vector-sensor is adopted here for recursive least-squares (RLS) adaptation, to track a single mobile source, in the absence of any multipath fading and any directional interference. A formula is derived to preset the RLS forgetting factor, based on the prior knowledge of only the incident signal power, the incident source's spatial random walk variance, and the additive noise power. The work presented here further advances a multiple-forgetting-factor (MFF) version of the RLS adaptive tracking algorithm, that requires no prior knowledge of these aforementioned source statistics or noise statistics. Monte Carlo simulations demonstrate the tracking performance and computational load of the proposed algorithms.

This paper introduces new closed-form formulas to estimate an incident source's azimuth-elevation angle-of-arrival, for various combinations of higher order directional acoustic sensors, that are orthogonally oriented in a collocated triad. Also identified are the validity regions for un ambiguous estimation of the azimuth-elevation arrival-angle. These new direction-finding formulas may be used in the open literature's eigen-structure-based direction-finding algorithms, originally designed for (first-order) acoustic particle-velocity sensors.

To form a collocated triad of orthogonally oriented dipole(s) and/or loop(s), 20 different compositions are possible. For each such composition: 1) closed-form formulas are produced here to estimate the azimuth-elevation direction-of-arrival and the polarization-parameters from an ambiguous steering vector subject to an unknown complex-value multiplicative coefficient; or 2) reasoning is given why such estimation is inviable.

For radiowave landmobile cellular wireless communication in ‘bad urban’ environments dominated by high rises, this paper analytically derives closed-form expressions for the trivariate and bivariate joint distributions of the time-of-arrival and two-dimensional azimuth-elevation direction-of-arrival of the uplink multipaths. These expressions are explicitly in terms of the parameters of a ‘geometrical’ model of the three-dimensional spatial relationships among the mobile station, the scatterers and the base station. This present ‘geometric model’ idealises the scatterers as uniformly located within the volume of a three-dimensional vertical above-ground cylinder whose flat bottom circular base centres at the mobile. Copyright © 2012 John Wiley & Sons, Ltd.