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In this paper, we study flash light sintering of inkjet-printed silver nanoink and show its application in printed and flexible thin film transistors. Flash method, which uses pulsed light to sinter metal nanoparticles, is a very fast and low-temperature sintering method. Hence, it facilitates in quick fabrication of low cost, flexible electronic devices. In the current work, various silver patterns were obtained by inkjet printing of silver nanoink on flexible substrate and then the patterns were sintered by flashmethod. Several flash sintering parameters were carefully optimized to achieve high electrical conductivity. In next stage, such printed and flash sintered silver patterns were used as source and drain contacts in thin-film transistor. Indium tin oxide coated polyethylene terephthalate sheet was used as substrate as well as bottom gate contact in transistor structure. On the other hand, polystyrene and pentacene were used in gate dielectric and channel layer, respectively. Such printed transistor with channel length of 28 mu m and width of 68 mu m exhibited field effect mobility of 0.09 cm(2)V(-1)s(-1) and ON/ OFF ratio on the order of 106. Finally, a comparative study was made between transistor performance with printed silver contacts and vacuum deposited silver contacts to ensure printing and sintering steps do not cause any notable degradation to the organic semiconducting layer.

This paper presents the development of a doubly fed induction machine (DFIG) harmonic model in matlab/Simulink, which is used to examine the spectral content of DFIG controller signals and improve the understanding of their behavior and spectral nature. The reported DFIG harmonic model has the capability of representing the effects of higher order time and space harmonics and thus, allows detailed analysis of the controller signals embedded spectral effects. The model consists of a wound rotor induction machine (WRIM) harmonic model coupled with a stator flux oriented controller model. The WRIM space harmonic effects are represented using the conductor distribution function approach to enable the calculation of winding inductances as a harmonic series. In addition, analytical expressions are derived to define the possible spectral content in the controller signals of DFIGs. Both the reported DFIG harmonic model and the analytical expressions are validated by comparison with measurements taken from a purpose built vector-controlled DFIG laboratory test rig. The findings confirm the capability of the developed DFIG harmonic model in representing the controller signals embedded spectral effects, as well as the accuracy of the reported analytical expressions, and enables a much improved understanding of the spectral nature of the DFIG controller signals. [EP/L014106/1] This work was supported by theUKEPSRC SUPERGENWind Hub under Grant EP/L014106/1. Paper no. TSTE-00333-2018. WOS:000522438600015 2-s2.0-85082589664

Many applications that use high-energy plasma are realized using microwave tubes (MWT) that operate at peak power in the range of hundreds of MW and frequency in GHz. One failure mode of the MWT is due to the excess energy in the tube during internal arcing events. Crowbar is used to protect the MWT by diverting the energy during fault. To compute the energy released into the MWT, the dc fault current model and the MWT model are essential. An equivalent fuse wire model is utilized for the MWT for the crowbar applications. The paper proposes a model for the dc fault current, the analysis for which is based on Joules Integral energy concept. The model provides flexibility to choose a range of practically observed reactance to resistance ratio ( $X{/}R$ ) of transformer and also allows the use of a range of dc current-limiting resistances that are utilized in the high-voltage (HV) power supply circuits in microwave applications. The nonlinearity of the system due to the multipulse diode rectifier is also considered by introducing a correction factor in the model. This paper shows that the same correction factor can be applied for both dc side parallel- and series-connected rectifier circuits. Both dc fault current and MWT models are verified experimentally. Using the model, a 10 kV, 1 kA crowbar is built to limit the energy in MWT below 10 J.

This paper presents a novel single-stage soft-switched high-frequency-link three-phase dc–ac converter topology. The topology supports unidirectional dc to ac power flow and is targeted for applications like grid integration of photovoltaic sources, fuel cell, etc. The high frequency magnetic isolation results in reduction of system volume, weight, and cost. Sine-wave pulsewidth modulation is implemented in dc-side converter. Though high-frequency switched, dc-side converter is soft switched for most part of the line cycle. The ac-side converter active switches are line frequency switched incurring negligible switching loss. The line frequency switching of ac-side converter facilitates use of high voltage blocking inherently slow semiconductor devices to generate high voltage ac output. In addition, a cascaded multilevel structure is presented in this paper for direct medium-voltage ac grid integration. A detailed circuit analysis considering nonidealities like transformer leakage and switch capacitances, is presented in this paper. A 6-kW three-phase laboratory prototype is built. The presented simulation and experimental results verify the operation of the proposed topologies.

In this paper, a dual-transformer-based asymmetrical triple-port active bridge converter (DT-ATAB) is proposed to interface two different dc-sources and a load. DT-ATAB consists of three active power electronic converters and two high-frequency transformers. All switches of these converters can be turned on with zero-voltage switching to reduce the switching losses. The bidirectional power flow operation is possible between the ports. The DT-ATAB also reduces the circulating powers between the ports for well-matched transformer turns ratios as compared to those in the other existing triple-port active bridge converters (TAB). Furthermore, the magnetic short-circuit conditions arising in the three-winding transformer of the TAB are mitigated in DT-ATAB. The principle of operation, steady-state analysis, various modes of operation (three-port and two-port modes), and a closed loop controller of DT-ATAB are presented. The theoretical analysis of this paper is verified using both simulation and experimental studies. The illustrated results show that DT-ATAB can be used as a promising multiport converter to interface the multiple sources and load to achieve wide-ranging outputs with the minimal losses.

This paper reveals an early quasi-saturation (QS) effect attributed to the geometrical parameters in shallow trench isolation-type drain-extended MOS (STI-DeMOS) transistors in advanced CMOS technologies. The quasi-saturation effect leads to serious $g_{m}$ reduction in STI-DeMOS. This paper investigates the nonlinear resistive behavior of the drain-extended region and its impact on the particular behavior of the STI-DeMOS transistor. In difference to vertical DMOS or lateral DMOS structures, STI-DeMOS exhibits three distinct regions of the drain extension. A complete understanding of the physics in these regions and their impact on the QS behavior are developed in this paper. An optimization strategy is shown for an improved $g_{m}$ device in a state-of-the-art 28-nm CMOS technology node.

This paper proposes a technique to build SPICE micromodels of integrated circuits in bipolar technology appropriate to simulate single event transients. First of all, we will show how to obtain SPICE models of the internal transistors from texts in the scientific and academic literature. Next, several strategies to figure out the internal structure of the integrated circuits and bias point will be shown. Finally, simulation results will be compared to data issue from experiments, either performed by the authors or by other researchers. As the simulations do not require expensive software or hardware, this paper can be a start point for research groups with small budget or for academic purposes at universities.

Remote sensing of physiological parameters could be a cost effective approach to improving health care, and low-power sensors are essential for remote sensing because these sensors are often energy constrained. This paper presents a power optimized photoplethysmographic sensor interface to sense arterial oxygen saturation, a technique to dynamically trade off SNR for power during sensor operation, and a simple algorithm to choose when to acquire samples in photoplethysmography. A prototype of the proposed pulse oximeter built using commercial-off-the-shelf (COTS) components is tested on 10 adults. The dynamic adaptation techniques described reduce power consumption considerably compared to our reference implementation, and our approach is competitive to state-of-the-art implementations. The techniques presented in this paper may be applied to low-power sensor interface designs where acquiring samples is expensive in terms of power as epitomized by pulse oximetry.

The sensing of relative humidity (RH) at room temperature has potential applications in several areas ranging from biomedical to horticulture, paper, and textile industries. In this paper, a highly sensitive humidity sensor based on carbon nanotubes (CNTs) coated on the surface of an etched fiber Bragg grating (EFBG) sensor has been demonstrated, for detecting RH over a wide range of 20%-90% at room temperature. When water molecules interact with the CNT coated EFBG, the effective refractive index of the fiber core changes, resulting in a shift in the Bragg wavelength. It has been possible to achieve a high sensitivity of similar to 31 pm/% RH, which is the highest compared with many of the existing FBG-based humidity sensors. The limit of detection in the CNT coated EFBG has been found to be similar to 0.03 RH. The experimental data shows a linear response of Bragg wavelength shift with increase in humidity. This novel method of incorporating CNTs on to the FBG sensor for humidity sensing has not been reported before.

This paper describes the temporal characteristics of surface charging on a cylindrical insulator made of polymethylmethacrylate (PMMA) resin or alumina ceramic. The insulator is subjected to a dc voltage step or to a trapezoidal voltage in vacuum. The charging is observed by using an electrostatic probe located at the surface of the cathode close to the triple junction where the insulator, cathode and vacuum meet. The probe signal shows a step increase associated with the charging. The interval between the voltage rise and the charging, which is defined as the delay time of charging in this paper, ranges from 10/sup -5/ s to 10 s depending on the material and the applied voltage. It also depends on the condition of the insulator-cathode interface, the electrical prestress and the surface roughness of the insulator. Among these factors, the surface roughness has the largest effect on the delay time. Two-dimensional Monte Carlo simulation based on the secondary emission electron avalanche model has been performed to analyze the charging progress. During the delay period, positive charge accumulates on the surface of the insulator near the cathode, which further accelerates the charging.

[EN] Failures in damper windings of synchronous machines operating in real facilities have been recently reported by several authors and companies. These windings are crucial elements of synchronous motors and generators, playing an important role in the asynchronous startup of these machines as well as in their stability during load transients. However, the diagnosis of failures in such elements has barely been studied in the literature. This paper presents a method to diagnose the condition of damper bars in synchronous motors. It is based on the capture of the stator current of the machine during a direct startup and its further analysis in order to track the characteristic transient evolution of a particular fault-related component in the time-frequency map. The fact that the damper only carries significant current during the startup and little or no current, when the machine operates in steady state, makes this transient-based approach specially suited for the detection of such failure. The Hilbert-Huang transform (based on the empirical mode decomposition method) is proposed as a signal-processing tool. Simulation and experimental results on laboratory synchronous machines prove the validity of the approach for condition monitoring of such windings. © 2012 IEEE., This work was supported by the Spanish Ministerio de Ciencia e Innovacion (MICINN) in the framework of the VI Plan Nacional de Investigacion Cientifica, Desarrollo e Innovacion Tecnologica 2008-2011. (Programa Nacional de proyectos de Investigacion Fundamental, project reference DPI2011-23740). Paper no. TEC-00443-2011.

Matrix Converters (MCs) have some advantages when compared to conventional back-to-back PWM voltage source converters. The converter may be considered more reliable and it can be smaller because the bulky dc capacitors are eliminated from the topology. For ac to ac power conversion, the size and weight of the whole generation system can be much reduced when back-to-back converters are replaced by MCs. To supply electrical energy to an unbalanced 3Φ stand-alone load, a fourth leg is required to provide a path for the zero-sequence load current. To regulate the load voltage, closed-loop control is required. In this paper, the application of d -q controllers and resonant controllers to four-leg MCs is addressed. The design and performance issues of the controllers, for operation with balanced, highly unbalanced loads and nonlinear loads are discussed in this paper. Experimental results obtained from a small prototype are presented and analysed in detail.

Multilevel converters have become an interesting alternative for medium- and high-voltage drives over the last decade. Among the existing alternatives, multicell structures offer advantages due to their modularity and scalability. This paper presents experimental results of a recently introduced multilevel topology. The converter is based on the mixture of the two most popular multicell topologies, namely, flying capacitor and cascaded multicell inverter. The new cell provides a high number of output levels, a low number of components, high modularity, and low losses. The results presented in this paper confirm that this new medium-voltage inverter topology is able to reach high-quality output voltages, allowing further advances in modulation techniques and other issues.

Recently a new CMOS current-mode pseudo-exponential function generator circuit was reported by Popa. The entire analysis and exponential function generator circuit, given in Popa's paper, is based on a current-squaring circuit module. In this comment paper we show that the current-squarer circuit, presented in Popa's paper, does not work as a current squarer. Consequently the pseudo-exponential generator also does not work as described in Popa's paper. We present a detailed mathematical analysis in this paper to derive its actual operation. Simulation results of the circuit module using Mentor Graphics custom IC design tool set, in a TSMC 0.18-mu m CMOS process, are also shown in this paper. Simulation results match the behavior predicted by mathematical analysis.

The objective of this paper is to provide suitable approximations of effective permeability for magnetic concentration cores. This core has a dumbbell shape so that the magnetic flux is concentrated to the coil winding part of the core. It is well known that the demagnetizing factor strongly depends on the core shape, which defines the effective permeability. Although several researchers have already proposed an approximation for a dumbbell-shaped core, they did not take into account the flange part length. In this paper, a novel approximation for a dumbbell-shaped core is proposed. It is based on the demagnetizing factor and correction terms related to the aspect ratio of both the flange and coil winding part. From experimental results, the validity of the approximation is confirmed., Article, IEEE TRANSACTIONS ON MAGNETICS. 51(1):4000304 (2015)

A long transmission line needs controllable series as well as shunt compensation for power flow control and voltage regulation. This can be achieved by suitable combination of passive elements and active FACTS controllers. In this paper, series passive compensation and shunt active compensation provided by a static synchronous compensator (STATCOM) connected at the electrical center of the transmission line are considered. It is possible to damp subsynchronous resonance (SSR) caused by series capacitors with the help of an auxiliary subsynchronous damping controller (SSDC) on STATCOM. The objective of this paper is to investigate the SSR characteristics of the system and propose a new design procedure for SSDC based on nonlinear optimization to meet the specifications on the damping torque in the range of critical torsional frequencies. The SSDC uses the Thevenin voltage signal to modulate the reactive current reference of STATCOM. The Thevenin voltage signal is derived from the locally available STATCOM bus voltage and reactive current signals. The STATCOM configurations considered in this paper are 12 pulse, two- and three-level voltage source converter with Type-2 and Type-1 control, respectively. The controller regulates either reactive current (supplied by the STATCOM) or the bus voltage. The 3-phase model of the STATCOM is based on switching functions. By neglecting harmonics in the switching function, D-Q model is derived which is combined with similar models of the other system components for linear analysis. The results of the linear analysis are validated by carrying out transient simulation based on the detailed nonlinear models. The study is performed on the system adapted from the IEEE First Benchmark Model.

Multilevel inverters with a large number of steps (more than 50 levels) can generate high quality voltage waveforms, good enough to be considered as suitable voltage template generators. Many levels or steps can follow a voltage reference with accuracy, and with the advantage that the generated voltage can be modulated in amplitude instead of pulse-width modulation. The main disadvantage of this type of topology is the large number of power supplies and semiconductors required to obtain these multistep voltage waveforms. This paper is focussed on minimizing the number of power supplies and semiconductors for a given number of levels. Different combinations of topologies are presented, and the corresponding mathematical relations have been derived. This paper shows optimized curves to obtain the relation between a minimum number of power semiconductors required for a given number of levels. Experimental results obtained from an optimized prototype, capable of generatng 81 levels of voltage with only four power supplies and 16 transistors per phase, are shown.

Thanks to their many merits such as high power density and fast dynamic response, the high-speed permanent magnet machines (HSPMMs) have attracted increasing industrial and domestic applications. However, the iron loss may become significantly higher at higher operating speed and frequency and it should be carefully considered in the machine design and analysis. In this paper, an advanced iron loss analytical calculation method is applied for HSPMMs in which the influences of rotating magnetic field and thermal field are both considered. A 30 kW, 45000 r/min HSPMM is studied to demonstrate that the proposed model is feasible and advantageous. Analysis results reveal that the predicted iron loss by using the proposed method has satisfactory accuracy with small errors (maximum error of 3.73% and absolute average error of 3.03%) under different operating conditions. The proposed method can also be applied in other electromagnetic devices such as superconducting electrical machines.

Thanks to the merits of superior dynamic response capability and current tracking performance, the deadbeat predictive current control (DPCC) has become a research hotspot for the permanent magnet synchronous motor (PMSM) drive system. However, DPCC is a model parameter sensitive control method. If there is a motor parameter mismatch, the performance of the DPCC drive system in terms of expected voltage vector, current harmonics, and torque ripple would be influenced. In this paper, firstly, a novel power sliding mode reaching law is proposed, which shortens the convergence time of the system state no matter what the initial state is. Then, an improved non-homogeneous disturbance observer (NHDO) with the proposed power sliding mode reaching law is established, which guarantees d-q axis current errors converge to zero when the PMSM drive system suffers uncertain disturbances, such as motor parameter mismatch. Finally, an improved DPCC using the novel stator current and disturbance observer, which includes the proposed power sliding mode reaching law and NHDO, is established. Hence the accuracy of the predicted current increases significantly, and voltage vectors can be immediately compensated once disturbances occur. Both simulation and platform experiments verify that the improved DPCC can maintain the current tracking performance with lower current ripples than the traditional DPCC when the major motor parameters mismatch. The proposed novel stator current and disturbance observer may also enhance the PMSM’s drive performance under other control strategies.

This paper presents a novel study of the wide-band spectral signatures in the controller signals of doubly fed induction generators (DFIGs) for the identification of rotor electrical faults. The aim is to advance the understanding of diagnostic information obtainable from the readily available DFIG controller signals. Analytical equations defining the controller signals possible spectral contents are derived to enable characterization of spectral signatures and their correlation to operating conditions and rotor faults. The equations are verified in a DFIG harmonic model study and also validated by undertaking a range of experiments on a laboratory DFIG test-rig. It is shown that the calculated, simulated and experimental results are in good agreement with regards to representing fault induced signatures in the examined DFIG controller signals spectra. Furthermore, it is shown that wide-band rotor electrical fault related spectral signatures in the controller signals carry considerable diagnostic potential for recognition of rotor electrical faults. UK Engineering and Physical Sciences Research Council HOME-Offshore: Holistic Operation and Maintenance for Energy from Offshore Wind Farms Consortium [EP/P009743/1] This work was supported by the UK Engineering and Physical Sciences Research Council HOME-Offshore: Holistic Operation and Maintenance for Energy from Offshore Wind Farms Consortium under Grant EP/P009743/1. WOS:000599507600057 2-s2.0-85098276892

This article presents a novel study of stator electrical faults detection using the wide-band spectral signatures in the controller signals of doubly fed induction generators (DFIGs). The possible wide-band spectral content of the controller signals are first defined with a set of analytical equations in order to characterize the wide-band spectral signatures and their correlation to operating conditions including stator electrical faults. A DFIG harmonic model and laboratory test-rig are used to validate the derived equations. The calculated, simulated and experimental results are in good agreement. Furthermore, it is shown that the wide-band stator electrical fault related spectral signatures carry considerable diagnostic potential for recognition of stator electrical faults, and therefore, can potentially be used to advance controller embedded fault detection techniques. U.K. Engineering and Physical Sciences Research Council (EPSRC) HOME-Offshore: Holistic Operation and Maintenance for Energy from Offshore Wind Farms ConsortiumUK Research & Innovation (UKRI)Engineering & Physical Sciences Research Council (EPSRC) [EP/P009743/1] This work was supported by the U.K. Engineering and Physical Sciences Research Council (EPSRC) HOME-Offshore: Holistic Operation and Maintenance for Energy from Offshore Wind Farms Consortium under Grant EP/P009743/1. Paper no. TEC-00044-2020. WOS:000652806800022 2-s2.0-85107015224

Recent research treats radar emitter classification (REC) problems as typical closed-set classification problems, i.e., assuming all radar emitters are cooperative and their pulses can be pre-obtained for training the classifiers. However, such overly ideal assumptions have made it difficult to fit real-world REC problems into such restricted models. In this paper, to achieve online REC in a more realistic way, we convert the online REC problem into dynamically performing subspace clustering on pulse streams. Meanwhile, the pulse streams have evolving and imbalanced properties which are mainly caused by the existence of the non-cooperative emitters. Specifically, a novel data stream clustering (DSC) algorithm, called dynamic improved exemplar-based subspace clustering (DI-ESC), is proposed, which consists of two phases, i.e., initialization and online clustering. First, to achieve subspace clustering on subspace-imbalanced data, a static clustering approach called the improved ESC algorithm (I-ESC) is proposed. Second, based on the subspace clustering results obtained, DI-ESC can process the pulse stream in real-time and can further detect the emitter evolution by the proposed evolution detection strategy. The typically dynamic behavior of emitters such as appearing, disappearing and recurring can be detected and adapted by the DI-ESC. Extinct experiments on real-world emitter data show the sensitivity, effectiveness, and superiority of the proposed I-ESC and DI-ESC algorithms.

© 1982-2012 IEEE. All the existing linear generators used for oceanic wave energy conversions are basically single-port linear electrical generators (SPLEGs). The conventional SPLEG transfers electrical power to the load/grid discontinuously due to its working principle and the intermittent nature of oceanic waves. This paper proposes a new dual-port linear electrical generator (DPLEG) topology, which is capable to transfer electrical power with an adequate voltage even at zero vertical velocity of the oceanic wave. The analysis shows that the efficiency and the performance of the DPLEG depend greatly on the stator tooth design. For this reason, the proposed DPLEG is optimized using the genetic algorithm for successful operation. The shape optimization method is implemented to determine the stator tooth shape of the DPLEG. By optimizing the stator tooth shape, the force ripples of the proposed DPLEG is further reduced by 40.89%. The analysis is carried out using multiphysics simulation, and the electromagnetic performance is determined by the finite-element analysis. Simulation results show that the shape optimization of the stator tooth not only minimizes the force ripples of the translator but also increases the power generation of the DPLEG. A laboratory prototype of the proposed DPLEG is built to test the concept of the proposed DPLEG topology. The experimental results verify its unique advantage by showing that it can generate an adequate voltage even at zero vertical velocity of the oceanic wave which cannot be achieved using the existing SPLEGs.

© 1967-2012 IEEE. Wide deployment of radar sensors on automotive vehicles can potentially lead to a severe interference problem. Such interference has been characterized without considering directional antenna patterns, which could lead to results significantly larger than the actual ones. In this paper, we study the mean power of effective echo signals and interference, by considering both front- and side- mounted radars equipped with directional antennas. We employ the stochastic geometry method to characterize the randomness of vehicles and hence radars in both two-lane and multi-lane scenarios, and derive closed-form expressions for the mean interference by approximating the radiation pattern by Gaussian waveforms. Simulation results are shown to match the analytical results very well, and insights are obtained for the impact of radar parameters on interference. Based on the interference analysis, we aim to minimize the total transmission power of each vehicle with constraints on the required signal to interference and noise ratio. An optimal solution is obtained based on linear programming techniques and corroborated by simulation results.

Millimeter-wave (mm-wave) spectrum unravels the humongous and accelerating demand for wireless data rates and, therefore, it will be a fundamental ingredient of the fifthgeneration (5G) wireless technology. In case of mm-wave access links, humans are the most noticeable blockers of electromagnetic waves from access points to mobile stations and hence cause temporal variation in the radio channel. This paper presents human blockage measurements in the anechoic chamber at 15, 28 and 60GHz frequencies employing 15 human subjects of different sizes and weights. An effective three-dimensional human blockage model as a double-truncated and absorbing multiple knife-edge (DTMKE) scheme is also proposed. By calculating diffraction from the DTMKE, the frequency, body orientation and antenna height dependency of the blockage are most accurately reproduced compared to the existing models, such as absorbing double knife-edge model and third generation partnership project (3GPP) human blockage model. The results demonstrate that the losses are proportional to the cross-section of the human body with respect to the radio link. Furthermore, the blockage loss decreases as the height of the transmitting antenna increases.

© 2019 IEEE. This paper considers wireless-powered relaying multiple-input-multiple-output (MIMO) communication, where all four nodes (information source, energy source, relay, and destination) are equipped with multiple antennas. Orthogonal frequency division multiplexing (OFDM) is applied for information processing to compensate the frequency selectivity of communication channels between the information source and the relay and between the relay and the destination as these nodes are assumed to be located far apart from each. The relay is equipped with a full-duplexing interface for harvesting energy not only from the wireless transmission of the dedicated energy source but also from its own transmission while relaying the source information to the destination. The problem of designing the optimal power allocation over OFDM subcarriers and transmit antennas to maximize the overall spectral efficiency is addressed. Due to a very large number of subcarriers, this design problem poses a large-scale nonconvex optimization problem involving a few thousand variables of power allocation, which is very computationally challenging. A novel path-following algorithm is proposed for computation. Based on the developed closed-form calculation of linear computational complexity at each iteration, the proposed algorithm rapidly converges to an optimal solution. Compared to the best existing solvers, the computational complexity of the proposed algorithm is reduced at least 105 times, making it very efficient and practical for online computation while existing solvers are ineffective. Numerical results for a practical simulation setting show promising results by achieving high spectral efficiency.

This paper presents the design and experimental evaluation of a micromachined Lorentz force magnetometer with a dual-resonator structure, interfaced with an electromechanical sigma-delta modulation (EM- $\Sigma \Delta {\text {M}}$ ) force rebalancing control loop. The magnetometer chip comprises a matched pair of resonators on the same silicon die. The closed-loop control circuit relies on a self-oscillating architecture; the frequency of which is determined by first resonator. It is used to generate a drive current injected to the second resonator, and also generates all internal circuit clocks based on a self-clocking scheme. System level simulation indicate a signal-to-noise ratio (SNR) larger than 100dB in a bandwidth of 64Hz with a 10mT, 32Hz magnetic field input ( ${B}$ ). The system was implemented in hardware based on a dual quantization technique, which has the advantage of reduced quantization error of multi-bit quantization in a single sigma-delta modulator. Experimental results demonstrate that proposed dual-resonator magnetometer achieved a 7-fold improvement in bias instability (increasing the averaging time to reach the bias instability from 1s to 8s) and the bandwidth (BW) is increased to ~80Hz, 16-fold higher compared to an open-loop magnetometer with a single resonator. With a 1mA bias current, the output noise is less than $1\mu \text{T}/\surd $ Hz for the z-axis magnetic field.

Hybrid precoding has emerged as a promising technique to reduce the hardware cost and complexity in millimeter wave (mmWave) massive multiple-input multiple-output (MIMO) systems. However, due to the drastic increase in the number of user devices and higher data rate demand, new frequency bands (i.e., terahertz (THz) communications) are needed to explore. At THz frequencies, the precoding technique can provide a large beamforming gain, but still, the blockage and high path-loss remain a significant problem. To overcome the blockage problem, in this paper, we introduce the two-way relay design where the well-known two-way amplify-and-forward (AF) relay in THz-MIMO orthogonal frequency-division multiplexing (OFDM) systems is employed. The optimal two-way relay hybrid precoding problem is non-convex due to the practical hardware constraints (i.e., unit-modulus and block-diagonal constraints). To solve this problem, we first propose to use mathematical manipulations to remove the block-diagonal constraints from its analog part and then reformulate the original two-way relay hybrid precoding problem into a quadratic-convex problem with only power constraint. Finally, we obtain the closed-form solution for the two-way relay hybrid precoding problem. Simulation results reveal that our proposed solution can achieve better sum-rate and energy efficiency than existing hybrid schemes. China National Key Research and Development Program [2018YFB0803600]; Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [61801008]; Scientific Research Common Program of Beijing Municipal Commission of EducationBeijing Municipal Commission of Education [KM201910005025]; Chinese Postdoctoral Science FoundationChina Postdoctoral Science Foundation [2020M670074] This work was supported in parts by the China National Key Research and Development Program under Grant 2018YFB0803600, the Natural Science Foundation of China under Grant 61801008, the Scientific Research Common Program of Beijing Municipal Commission of Education under Grant KM201910005025, and the Chinese Postdoctoral Science Foundation under Grant 2020M670074. WOS:000603715900001 2-s2.0-85098334509

This paper presents structural optimization based on sensitivity analysis exploiting a bi-directional beam propagation method (Bi-BPM) to design efficiently passive components in high-index-contrast optical waveguides. In this study, the Bi-BPM based on scaled-version Denman-Beavers iteration (S-DBI) with branch-cut technique, and scattering operator formulation (SO-Bi-BPM) is employed to execute stable, accurate wave-propagation analysis. Comparing three computation approaches of sensitivity with respect to design variables, efficient way of sensitivity analysis is revealed when the SO-Bi-BPM is used. The application range of the presented design approach is studied by designing a wavelength filter with waveguide grating, and a polarizer based on 1D photonic crystal (1D-PhC).

This paper presents a general theory of time-dependent single-event effects in CMOS LC -oscillators. The analysis employs the oscillator’s impulse-sensitive function (ISF) to calculate the effect of a transient current due to an ionizing particle. A discussion is made on the dependence of the maximum junction collection current and the modulation of this current with the voltage-controlled oscillator (VCO) signal waveform, supported by TCAD simulations. An experimental study using a two-photon absorption (TPA) laser setup is performed to obtain accurate measurements of the time-dependent charge-to-phase transfer function of the oscillator.

Recently, the present authors’ research group derived an analytical expression to link the harmonic sum of the squares of short circuit natural frequencies (SCNFs) of a single, isolated winding to its elementary inductances and capacitances. Also, it was demonstrated how this expression could be practically used for locating radial and axial displacements, along with assessing its severity on a single, isolated, actual transformer winding. The next logical task was to extend the derived expression to multi-phase windings, viz., star/delta connections and for any terminal condition of the neutral. Actually, it would be desirable to have a similar expression for open circuit natural frequency (OCNF) as well. A major highlight of this paper is that it presents a single, unified approach (using salient features of coefficients of the numerator and denominator polynomial of driving-point impedance) by which compact analytical expressions can be simultaneously derived for both SCNF and OCNF, for any multi-phase transformer configuration, and for any condition of the neutral terminal. Complete derivation details of the proposed method are presented, and then, the expressions for SCNF and OCNF are derived for 1- $\Phi$ isolated windings as well as 3- $\Phi$ (Y, $\Delta$ ) configurations. Finally, simulation results for all the cases are reported.

This paper presents a 400-GHz CMOS TX and RX chip with two different chip-to-waveguide transitions. The first design is based on a coupled microstrip to waveguide coupler and is integrated together with a 400-GHz oscillator in 28-nm bulk CMOS. When this transmitter is combined with a micromachined horn antenna, it is capable of providing an equivalent isotropic radiated power of 1.26 dBm. In the second design, a folded dipole based coupler is utilized to make the transition between a waveguide and a 400-GHz mixer first receiver. This receiver fully integrates an on-chip local oscillator, mixer, and baseband circuits and achieves an effective conversion gain of 39 dB and a noise figure of 45 dB. Both chips are combined into a lensless active imaging setup with a spatial resolution of 2 mm.

© 1986-2012 IEEE. The voltage ratings for dc transmission and distribution are not currently standardized because cable technology is advancing rapidly and therefore a low step-ratio dc-dc converter at multi-megawatt scale is a crucial technology for combining point-to-point dc links into multi-terminal networks. This paper presents a modular multilevel dc-dc converter configuration with only a single stack of half-bridge sub-modules (SM) and a resonant tank. The power processed through the stack is a small fraction of the throughput power if the step ratio is small (1 - boldsymbolv_boldsymbolL/boldsymbolv_boldsymbolH). Detailed analysis shows the required semiconductor ratings are much smaller compared to the front-to-front MMC and modular converters derived from standard dc-dc topologies. Further, the requirement for SM capacitive energy storage is also significantly less than those converters. The theoretical analysis and the operating principles have been verified by full-scale simulation examples and experiments with a down-scaled prototype. The SMs are operated with an adjustable phase shift to create a high frequency excitation across the resonant tank for further volume reduction. The SM capacitors self-balance without the need for switching pattern adjustments and the resonant operation provides soft switching for all power switches to increase efficiency. ispartof: IEEE TRANSACTIONS ON POWER DELIVERY vol:34 issue:1 pages:312-323 status: published

Today, the use of Ethernet-based protocols in industrial control systems (ICS) communications has led to the emergence of attacks based on information technology (IT) on supervisory control and data acquisition systems. In addition, the familiarity of Ethernet and TCP/IP protocols and the diversity and success of attacks on them raises security risks and cyber threats for ICS. This issue is compounded by the absence of encryption, authorization, and authentication mechanisms due to the development of industrial communications protocols only for performance purposes. Recent zero-day attacks, such as Triton, Stuxnet, Havex, Dragonfly, and Blackenergy, as well as the Ukraine cyber-attack, are possible because of the vulnerabilities of the systems; these attacksare carried by the protocols used in communication between PLC and I/O units or HMI and engineering stations. It is evident that there is a need for robust solutions that detect and prevent protocol-based cyber threats. In this paper, machine learning methods are evaluated for anomaly detection, particularly for EtherCAT-based ICS. To the best of the author's knowledge, there has been no research focusing on machine learning algorithms for anomaly detection of EtherCAT. Before testing anomaly detection, an EtherCAT-based water level control system testbed was developed. Then, a total of 16 events were generated in four categories and applied on the testbed. The dataset created was used for anomaly detection. The results showed that the k-nearest neighbors (k-NN) and support vector machine with genetic algorithm (SVM GA) models perform best among the 18 techniques applied. In addition to detecting anomalies, the methods are able to flag the attack types better than other techniques and are applicable in EtherCAT networks. Also, the dataset and events can be used for further studies since it is difficult to obtain data for ICS due to its critical infrastructure and continuous real-time operation.

© 2018 IEEE. This paper presents a very thorough analysis of the potential of Schottky diodes as photodetectors for fully integrated optical receivers in bulk CMOS. By absorbing photons in the metal, these devices can detect the 1310/1550 nm telecommunication wavelengths, unlike silicon PN-diodes. Moreover, besides being sensitive to a broader range of wavelengths, Schottky photodiodes in CMOS have a very high intrinsic bandwidth. Schottky photodiodes of various types and sizes were fabricated in several bulk CMOS processes. As a case study, the photodiodes in 40 nm CMOS have been extensively characterized. By enabling 1310/1550 nm detection in CMOS, we envision that optical receivers for these applications will become significantly cheaper, smaller, lower power, and more densely integrated. ispartof: IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS vol:24 issue:6 status: published

Recently, transformerless (TL) inverters are being extensively used in small-scale photovoltaic (PV) systems due to their compact-size, lighter-weight, lower-cost and higher-efficiency compared to their counterpart with transformer. However, the growing penetration of these small-scale based PV systems and low-inertia induction motor (IM) loads in low-voltage distribution networks (DNs) make the grid more vulnerable to short-term voltage stability (STVS). Hence, this paper thoroughly examines the STVS of DN with high-penetration of TL-PV units, and provides countermeasures by TL-PV systems to mitigate any short-term voltage instability. The detailed dynamic model of the TL inverter is developed first. Next, three control strategies: (1) constant peak current (CPC), (2) constant active current (CAC), and (3) constant active power (CAP) with low voltage ride through (LVRT) and dynamic voltage support (DVS) capabilities are proposed to improve STVS. The impacts of different level of PV penetrations and LVRT capability of TL-PV inverters on the STVS are explored. Moreover, countermeasures, such as LVRT with CAC and CAP controls and DVS by the TL-PV systems are designed and implemented. Several case studies are carried out on an IEEE 4 bus system first, and later extended to IEEE 13 node test feeder. The results show that DVS can further improve STVS in residential DNs. In addition, CAP and CAC control strategies can speed-up the postdisturbance voltage recovery compared with the conventional CPC control.

A single phase grid connected transformerless photovoltaic (PV) inverter, which can operate either in buck or in boost mode, and can extract maximum power simultaneously from two serially connected subarrays while each of the subarray is facing different environmental conditions, is presented in this paper. As the inverter can operate in buck as well as in boost mode, depending on the requirement, the constraint on the minimum number of serially connected solar PV modules that is required to form a subarray is greatly reduced. As a result, power yield from each of the subarray increases when they are exposed to different environmental conditions. The topological configuration of the inverter and its control strategy are designed so that the high-frequency components are not present in the common mode voltage, thereby restricting the magnitude of the leakage current associated with the PV arrays within the specified limit. Further, high operating efficiency is achieved throughout its operating range. A detailed analysis of the system leading to the development of its mathematical model is carried out. The viability of the scheme is confirmed by performing detailed simulation studies. A 1.5 kW laboratory prototype is developed, and detailed experimental studies are carried out to corroborate the validity of the scheme.

Contemporary surveillance systems mainly use video cameras as their primary sensor. However, video cameras possess fundamental deficiencies, such as the inability to handle low-light environments, poor weather conditions, and concealing clothing. In contrast, radar devices are able to sense in pitch-dark environments and to see through walls. In this paper, we investigate the use of micro-Doppler (MD) signatures retrieved from a low-power radar device to identify a set of persons based on their gait characteristics. To that end, we propose a robust feature learning approach based on deep convolutional neural networks. Given that we aim at providing a solution for a real-world problem, people are allowed to walk around freely in two different rooms. In this setting, the IDentification with Radar data data set is constructed and published, consisting of 150 min of annotated MD data equally spread over five targets. Through experiments, we investigate the effectiveness of both the Doppler and time dimension, showing that our approach achieves a classification error rate of 24.70% on the validation set and 21.54% on the test set for the five targets used. When experimenting with larger time windows, we are able to further lower the error rate.

This paper for the first time presents design and theoretical model for a fiber-optic pressure sensor based on a highly sensitive phenomenon of lossy mode resonance (LMR). Unlike transmission-based sensors, the proposed LMR-based pressure sensor works in reflection mode where sensing signal is measured in terms of the retro-reflection spectra. A detailed analysis of zinc oxide (ZnO) coated reflection-based LMR pressure sensor has been carried out. Also to improve sensitivity of the proposed sensor, an additional film of halfnium dioxide (HfO2) is considered, and the combined effect of ZnO and oxide thickness ratio on the sensitivity has been investigated. Maximum sensitivity of the proposed pressure sensor is $2~\mu \text {m}/\text {MPa}$ , which is higher than the previously reported popular fiber Bragg grating, interference and surface plasmon resonance-based pressure sensors. Additional feature of the proposed sensor is that one can achieve a tunable sensitivity and operating range only by changing the thickness ratio of ZnO and oxide overlay.

This paper presents an optimized topology of 3- $\phi$ , multilevel inverter (MLI) configuration for five or higher level operation with reduced switch count. The proposed solution consists of two basic units (BUs) of multilevel converter and a T-structured 3-level inverter (3-LI). Both BUs are equally shared by the three phases maintaining symmetry among the phases. Moreover, for a higher level operation of the proposed MLI, the modifications required are at two BUs only and not at three legs of the inverter. It further helps in reducing the requirement of extra components for higher level operation compared to the conventional solutions. Furthermore, the topology also has the benefits of reduced switching and conduction loss. An algorithm is also devised to generate the switching pulses for the BUs and the 3-LI, using a carrier-based space vector modulation technique. Presented topology is compared with other existing topologies to prove its advantage. All the details regarding the operating modes and pulse width modulation techniques employed for the proposed system are given and supported by the simulation and experimental results.

Silicon photonics is widely acknowledged as a game-changing technology, driven by the needs of datacom and telecom. Silicon photonics builds on highly capital-intensive manufacturing infrastructure, and mature open-access silicon photonics platforms are translating the technology from research fabs to industrial manufacturing levels. To meet the current market demands for silicon photonics manufacturing, a variety of open-access platforms is offered by CMOS pilot lines, R&D institutes, and commercial foundries. This paper presents an overview of existing and upcoming commercial and noncommercial open-access silicon photonics technology platforms. We also discuss the diversity in these open-access platforms and their key differentiators.

The classification of urban areas in polarimetric synthetic aperture radar (PolSAR) data is a challenging task. Moreover, urban structures oriented away from the radar line of sight pose an additional complexity in the classification process. The characterization of such areas is important for disaster relief and urban sprawl monitoring applications. In this paper, a novel technique based on deep learning is proposed, which leverages a synthetic target database for data augmentation. The PolSAR dataset is rotated by uniform steps and collated to form a reference database. A stacked autoencoder network is used to transform the information in the augmented dataset into a compact representation. This significantly improves the generalization capabilities of the network. Finally, the classification is performed by a multilayer perceptron network. The modular architecture allows for easy optimization of the hyperparameters. The synthetic target database is created and the classification performance is evaluated on an L-band airborne UAVSAR dataset and L-band space-borne ALOS-2 dataset acquired over San Francisco, USA. The proposed technique shows an overall accuracy of $91.3{\%}$ . An improvement over state-of-the-art techniques is achieved, especially in urban areas rotated away from the radar line of sight.

This paper presents a CMOS-based $32\times 32$ ion-sensitive field-effect transistor (ISFET) system-on-chip for real-time ion imaging. Fabricated in an unmodified 0.35- $\mu \text{m}$ CMOS technology, the ISFET sensor array is based on a pixel topology, which uses capacitive feedback to improve signal attenuation due to passivation capacitance and a low-leakage floating-gate reset followed by a digital correlated double sampling to robustly remove unwanted trapped charge-induced dc offset. An automatic gain calibration (AGC) is used to perform real-time calibration and guarantee all sensors that have the same gain with a 99% accuracy, and combining all these mechanisms guarantees an average pixel voltage variation of 14.3 mV after gain is applied when measured over multiple dies. The full array is experimentally shown to be capable of real-time ion imaging of pH, with an intrinsic sensitivity of 39.6mV/pH and a scan rate of 9.3 frames/s when running the AGC, with a total power consumption of 10.2 mW.

This paper presents a comparison of two of the most sensitive methods to detect low-level turn-to-turn faults in the windings of three-phase transformers. The performance of the negative sequence component and of the space-vector protection algorithms is tested under several internal and/or external fault conditions. The results indicate that the space-vector approach is slightly more sensitive for detecting low-level turn-to-turn winding faults. For more severe defects, the fault detection sensitivity of both methods is similar. info:eu-repo/semantics/publishedVersion

This paper presents dual copolarized (PP) (VV and HH) Ka-band sea surface backscattering measurements taken from the Black Sea research platform at incidence angles ranging from 25 degrees to 65 degrees and in the wind speed range from 3 to 18 m/s. These measurements are corrected for radar antenna pattern and geometry of observations. The resulting normalized radar cross section (NRCS) is parameterized in a form of truncated azimuthal Fourier series with coefficients dependent on the incidence angle and wind speed. This dual PP empirical model (KaDPMod) is consistent with the Ku-band NSCAT-4 model. However, some remarkable differences are revealed. They are apparent when analyzed using a decomposition of VV and HH measurements into polarized Bragg backscattering (polarization difference, PD = VV-HH) and nonpolarized (NP) backscattering from breaking waves. The polarization difference (PD) has strong azimuth and wind dependencies, with the wind exponent ranging from 2.5 to 3. The saturation wave spectra derived from multifrequency PD (based on KaDPMod and Ku- and C-band empirical models) have a notable peak in the capillary-gravity range. The relative contribution of NP radar return to the Ka-band NRCS is significant. In the upwind direction, it reaches up to 60%-80% and 25%-50% for HH and VV, respectively. It is found that the NP wind exponent is lower than that for Bragg backscattering. Therefore, the relative contribution of the NP to Ka-band NRCS decreases with increasing wind speed at both polarizations. Such a behavior is the opposite of that observed in the Ku-band.

This paper presents an effective and efficient method to fabricate novel fiber optic sensing probes. The new, simple, and low cost approach is based on a 3-D photonic crystal dielectric structure directly deposited on the tip of a multimode optical fiber through the self-assembly of colloidal crystals (CCs) via a vertical deposition technique. Here, the CC is made of polystyrene nanospheres with 200 nm diameter, and the optical fiber is a UV-vis fiber with a core diameter of 200 μm. The obtained fiber probes exhibit a resonant peak at 480 nm and an amplitude enhancement of 3.7 with respect to the bare fiber; these results are highly repeatable. A numerical tool based on a finite element method analysis has been developed to study and analyze the 3-D subwavelength structures. Numerical results are in good agreement with the observed experimental spectra. Moreover, refractive index measurements have been carried out, revealing a sensitivity of up to 445 nm/RIU in the 1.33-1.36 values range. The achieved performances, which have been obtained by using very small active areas and an easy and reliable fabrication procedure, demonstrate the future perspectives of these fiber-optic probes for chemical and biological sensing applications.

This paper presents an optimized, 3-phi, multilevel inverter (MLI) topology. The proposed system is derived by cascading the level generation part with the phase sequence generation part. Further, it can be operated at any required level depending upon the configuration of the level generation part. Thus, for higher level operation extra components are required at the level generation part only. Therefore, number of components required for the proposed MLI is lower than the conventional 3-phi MLI topologies for higher level operation. Further, the level generation part is shared by the three phases equally. This eliminates the possibility of phase unbalance. The working principle and the operation of the proposed MLI are supported with the simulation and experimental validations. Further, the proposed optimized MLI is also compared with theconventional 3-phi MLIs to prove its advantage.

This paper discusses in detail the effects of transistor width, layout, and technological parameters like gate dielectric and Lanthanum capping layer thickness on positive bias temperature instability (PBTI) of nMOS transistors fabricated using 28-nm gate-first High- ${K}$ metal gate CMOS technology. It is shown that the PBTI reduces with decrease in width ( ${W}$ ), increase in capping layer thickness and decrease in high- ${K}$ dielectric thickness. The physical mechanisms responsible for these dependencies are investigated and attributed to the modulation of preexisting traps in the high- ${K}$ dielectric and the modulation of electron injection into these traps. It is also shown that the PBTI of the devices could be improved by dividing a single active into multiple actives, by increasing active-to-active spacing and gate pitch.

For the safe operation of transformerless grid connected photovoltaic (PV) inverters, the issue of common mode (CM) leakage current needs to be addressed carefully. In this paper, a novel multilevel transformerless inverter topology is proposed, which completely eliminates CM leakage current by connecting grid neutral point directly to the PV negative terminal, thereby bypassing the PV stray capacitance. It provides a low-cost solution consisting of only four power switches, two capacitors, and a single filter inductor. As compared to half-bridge topologies, with this inverter a minimum of 27% and maximum of 100% more output voltage is obtained for the same dc-link voltage. The proposed inverter is analyzed in detail and its switching pattern to generate multilevel output while maintaining the capacitor voltage is discussed. Simulations and experiments results confirm the feasibility and good performance of the proposed inverter.

Vural, Bulent/0000-0001-8018-5495 WOS: 000425280900017 Using multi-input converters (MICs) in hybrid energy storage systems (HESSs) presents several advantages, such as low component count, control simplicity, and fully control of source energies. The power levels of sources in these systems need to be determined wisely by an energy management strategy (EMS). This paper presents an EMS for a battery/ ultracapacitor (UC) HESS including a bidirectional MIC for electric vehicles (EVs). Thanks to the fact that energy flow between battery and UC is free in this MIC, the proposed EMS not only regulates the state-of-charge of UC but also smooths the battery power profile by using a fuzzy logic controller and a rate limiter. Therefore, it results in a sustainable HESS with longer battery life. Through a simulation study and an experimental setup including a real EV, the performance of the proposed system is evaluated comprehensively. Then, based on experimental results, battery cycle-life improvement due to the battery/UC hybridization is explored. Scientific and Technological Research Council of Turkey-TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [113M088] This work was supported by The Scientific and Technological Research Council of Turkey-TUBITAK under Grant 113M088. (Corresponding author: Furkan Akar.)