An efficient finite-element domain decomposition method based on the multilevel compressed block decomposition (MLCBD) algorithm is presented. The dual-primal finite element tearing and interconnecting (FETI-DP) method is first introduced to generate a nonoverlapping domain decomposition method with good convergence properties. A second-order transmission condition is adopted to further accelerate the convergence rate of the FETI-DP. With the MLCBD algorithm, the computational complexity for the direct solution of FETI-DP subdomain equations can be reduced to be almost logarithmic linear. The accuracy of the MLCBD algorithm is highly adjustable according to practical requirements. Exploiting the repetitiveness of finite periodic structures, the proposed method can significantly reduce the computational costs. Numerical examples demonstrate the effectiveness of the proposed method for the electromagnetic simulation of finite periodic structures.

This paper deals with the effect of structural, doping, and work function parameter variations on the Radio-Frequency metrics, unity gain cutoff frequency (f_{t}), non-quasi static delay, intrinsic gain, and noise figure in double-gate Fin Field Effect Transistor (FinFET), junctionless FinFETs, and conventional and junctionless gate-all-around devices using Technology Computer-Aided Design simulations. This is done quantitatively by performing a simple sensitivity study experiment and screening analysis through Plackett-Burman's design of experiment approach. The individual and overall rankings of the input parameters for the devices considered are given. Gate length affects FinFETs significantly, whereas it does not affect junctionless devices. The impact of work function on the output responses is more in junctionless devices compared with that of FinFET and gate-all-around devices. Ovality in gate-all-around devices has no impact on all the output responses.

This Special Issue reviews the state-of-the-art and new trends in modeling of Gallium Nitride transistors. Aspects of transistor characterization, simulation, and design all receive significant attention, highlighting the potential of this disruptive technology in the development of future communication systems.

This study aims to demonstrate the effects of the different boundary conditions on triangular split ring resonator (TSRR)-shaped metamaterials in X band frequency regime. Three different TSSR-shaped metamaterials are designed and simulated in a certain frequency range. TSSR-shaped metamaterials are utilized to show that the use of different boundary conditions may result in completely different electromagnetic responses. Characterization is explained by applying 5 different boundary conditions. To verify simulation results, an experimental study is realized for the unit cell boundary condition. Both experimental and simulation results are complying with each other. For further investigation, electrical energy density and surface current distributions are simulated and discussed.

In this paper, the bias-dependent current–voltage (I–V) characteristics and their high-order derivatives of GaAs pseudomorphic high electron mobility transistors (pHEMTs) have been modeled over a wide temperature range. To simulate these characteristics at different temperatures, the model is developed considering the dependence on the ambient temperature. It is the first time that the temperature-dependent high-order derivatives of I–V characteristics of pHEMT are predicted, which can guarantee their accuracy under different bias conditions. The artificial neural networks are employed with the temperature as one of the input variables. The validity of this model has been demonstrated by comparing the measured and modeled *I _{ds}* and its derivatives (

By using network theory, a wireless power transfer network based on coupled capacitance, that is, on electric field coupling, is numerically investigated. Three possible solutions of interest are considered: one that maximizes efficiency, one that maximizes the power delivered to the load and one that realizes power matching (conjugate matching). In each case, at a selected frequency, the optimal source/load impedances are derived in closed form. It is shown that maximum efficiency solution has the possibility of achieving almost unitary efficiency. It is also shown that, as the efficiency is increased, the power delivered to the load is decreased. Copyright © 2016 John Wiley & Sons, Ltd.

In this paper, the analog/radio frequency (RF) and linearity performance of an InAs-based nanowire (NW) tunnel field-effect transistor (TFET) is studied and compared with InAs-based NW MSFET of identical dimension. InAs-based NW TFETs shows a great promise for high performance digital application because of its superior subthreshold behavior. Different analog/RF and linearity key figure-of-merits like cut-off frequency (f_{t}) and 1-dB compression point are extracted and the effect of gate length down scaling on those parameters has been studied. The results reveal that down scaled InAs-based NW TFET shows a significant improvement in its RF and linearity performance. However, this advantage diminishes in terms of poor analog performance with gate-length downscaling. This clearly indicates the necessity of a trade-off between analog and RF performance. Moreover, an in-depth comparison between InAs-based NW TFET and conventional MOSFET has also been provided in order to demonstrate the superiority of InAs-based NW TFET to become a competitive contender by replacing conventional MOSFET for Analog/Mixed signal System-on-Chip (SOC) applications. Copyright © 2016 John Wiley & Sons, Ltd.

In this paper, we report the numerical analysis of a nanostructured photonic crystal fiber for making an efficient dispersion-compensating medium. For our computational studies, the core of the proposed structure is made up of As_{2}Se_{3}, and the cladding structure is a mixture of air holes and holes filled with silica. Our simulations indicate that the chromatic dispersion and the confinement loss at the wavelength of 1.55 µm is −3280 ps/nm/km and 1.71 × 10^{−6} dB/m respectively. Moreover, the relative dispersion slope at the wavelength of 1.55 µm is computed to be 0.00357 nm^{−1} that closely matches that of the conventional fibers at the third window. The effect of changing the dimensions of the holes in the first ring and also the distance between the adjacent holes (*Λ*) in the same ring on chromatic dispersion are also studied. The presented structure is an efficient dispersion-compensating medium. Copyright © 2016 John Wiley & Sons, Ltd.

The conventional non-uniform rational B-spline (NURBS)-based isogeometric analysis (IGA) preserves the exact description of geometrical shapes and significantly improves the computational accuracy, but suffers from the topological limitations of a single intact NURBS patch in the parameter space, which renders IGA to be applied in complex topology like the ridged structure inconvenient. In this present work, trimming technique which is the isogeometric approach for handling two-dimensional topologically complicated geometry with a single patch is employed to demonstrate how this issue can be resolved, and further extended to analyze the quadruple arch-cut ridged circular waveguide. The main benefit of the proposed approach is that only one patch is sufficient to represent the complex two-dimensional topology such as circular or any degrees of polygonal shapes. Because the finite element constituents of the trimmed elements are calculated and mapped into underlying global control variables by remodeling the trimmed elements as a single patch, various properties of conventional IGA are maintained. Numerical example illustrates the flexibility for describing complicated two-dimensional domain, and high computational accuracy and efficiency of present method with much less degree of freedom compared to commercial finite-element software package. Effects of arch-cut ridge dimensions on the cut-off wave numbers of modes are investigated in details. Copyright © 2016 John Wiley & Sons, Ltd.

In this paper, we propose a flexible memristive model with simplex basis function. In the memristive model, a piecewise window function is applied to limit the physical range of the state variable, and a piecewise linear model (called simplex basis function model) is applied to describe the integral function of the current and charge. The expression of the state variable and the memristance can be almost analytically obtained. Thus, some serious errors occurring in the simulations of some existing memristive models can be avoided. The proposed memristive model shows great flexibility due to the good approximation capability of the simplex basis function model. Copyright © 2016 John Wiley & Sons, Ltd.

In this paper, empirical mode decomposition is applied to decompose the non-stationary power signals that results in a set of maximum and minimum points while satisfying the properties of the sifting process. Further, the empirical mode decomposition method is implemented to extract various intrinsic mode functions from the non-stationary signal disturbance waveforms that are already superimposed by various undulating modes. A novel short-time modified Hilbert transform with an equivalent window is applied on all the intrinsic mode functions to extract the modified Hilbert energy spectrum and instantaneous magnitude response. Distinct features are derived from the short-time modified Hilbert energy spectrum for automatic classification of non-stationary power signals. The features obtained from the short-time modified Hilbert transform are found to be different, understandable, and immune to noise. These features are then applied to the modified fuzzy C-means based improved bacterial foraging optimization algorithm for improving the classification accuracy of the disturbances. Extensive simulation results yield excellent visual detection, localization, and classification of the different types of non-stationary power signal disturbances. Copyright © 2016 John Wiley & Sons, Ltd.

A simple small-signal equivalent circuit based on the physical structure of silicon-on-insulator metal–oxide–semiconductor field-effect transistor varactor for substrate loss effects is presented in this paper. The model includes a BSIMSOI charge formulation and physical geometry and process parameter based on parasitic modeling. Key device performances of capacitance and quality factor are validated over voltage, frequency, and geometry. The model, implemented in Verilog-A, provides robust and accurate radiofrequency simulation of metal–oxide–semiconductor varactor. Copyright © 2016 John Wiley & Sons, Ltd.

This article deals with the large problem of interferometric synthetic aperture. Our analysis begins with the study of transverse distance influence and the orientation of the interferometric baseline. The processing of elevation problem solving relative to the horizontal resolution of conventional synthetic aperture radar has been carried out, including its ambiguity to choose the optimum parameters of the interferometer and thus improve the surface topography. We found out indeed that when we take a picture of the earth's surface at an angle of inclination of the baseline *α* = *π* / 4, the best results are obtained. Copyright © 2016 John Wiley & Sons, Ltd.

We propose a compressed non-local surface-impedance-type boundary condition for the efficient numerical modeling of large geometrically persistent parts in multi-scale electromagnetic simulations. The underlying compressed model is an approximate Schur complement of finite element Galerkin matrix. Our approach relies on local low-rank representation in the framework of the -matrix storage format. We discuss two ways to build -matrix approximations of Schur-complement matrices: adaptive cross approximation and -arithmetics. Profound numerical tests and studies of accuracy are carried out for an axisymmetric setting, employing the open source library AHMED by M. Bebendorf. To demonstrate the use of our method, we build the compressed model for an axisymmetric scanning near-field optical microscopy tip. The model can be embedded in three-dimensional tip-sample simulations. Copyright © 2016 John Wiley & Sons, Ltd.

Current characteristic has not been detailed, analyzed, and modeled in conventional High-electron-mobility transistor field-effect transistor model, which is not accuracy enough because the current has different variation rules under different gate voltages. A novel approach for the modeling of high-electron-mobility transistor high power amplifier is proposed in this paper. In order to obtain a more accuracy nonlinear model, drain current database are divided into three different regions, including the high gate bias region, the middle gate bias region, and the approximate pinch-off regions. The three nonlinear current regions are modeled separately and implemented in final high-electron-mobility transistor field-effect transistor model based on support vector regression algorithm. The proposed model is validated with high accuracy by comparing the simulated data with the tested data of a high power gallium nitride high-electron-mobility transistor amplifier, which the modeling is based on fewer samples compared with conventional methods based on the integrated current model. Copyright © 2016 John Wiley & Sons, Ltd.

Radial junction nanorods (nanowires) are mainly used to improve the carrier collection efficiency and accordingly the conversion efficiency of solar cells. In this work, a numerical simulator has been produced for a cylindrical p–n junction solar cell based on a finite difference discretization of semiconductor, Poisson's, drift–diffusion transport and charge continuity equations. It can be applied to estimate the photogenerated current density, open circuit voltage, fill factor and conversion efficiency of inorganic radial p–n and p–i–n junction nanowires. Additionally, the simulator can produce the spatial distribution of the carriers' densities, electric field and energy bands of the nanowires. The simulator results show a good matching with previously published ones. Finally, the simulator is used in a parametric study to optimize the geometry and the junction depth of cylindrical silicon solar cells. Copyright © 2016 John Wiley & Sons, Ltd.

Fast and complex model-based computations are often needed during the controller design process; therefore, a hot cathode electron source simulator was designed and implemented. The simulator uses the static model of electron source and is based on the LabView environment. It is developed for different materials and dimensions of filaments popular in vacuum instruments. The simulator is able to calculate the maximum temperature of the hot filament, its resistance, voltage drop and temperature and distribution of the electron emission current along the filament length in a steady state. Also, a new method was proposed and implemented for approximate calculations of distributions of the temperature and the electron emission current without measurements of the filament temperature. Copyright © 2016 John Wiley & Sons, Ltd.

Stress effects in semiconductor devices have gained significant attention in semiconductor industry in recent years, and numerical modeling is often used as a powerful tool for stress analysis in semiconductor devices. Here, we present a nontraditional 1D model for fast stress analysis in bipolar junction transistors. Because bipolar transistors are operationally 1D devices, it is possible to speed up the simulation with a 1D numerical model and get results that are comparable with 2D and 3D simulation outcomes. This model consists of a complete numerical algorithm that can be used for stress analysis of bipolar transistors on any plane. Existing 1D simulators take more time as they solve all device equations throughout the device. In contrast, our model optimizes the solutions for different regions with the development and inclusion of specific algorithms. A fractional starting point is introduced for the depletion region to speed up the process further. This way, faster computing time and much higher accuracy can be reached. At the same time, popular 2D and 3D simulators, which are using finite element methods, are naturally much slower, especially if high accuracy is needed. Simulation results of this 1D model match well with the simulation results of a 2D model developed with a commercial technology computer aided design (TCAD) tool. The validity of our model was verified with experimental results and theoretical expectations as well. Copyright © 2016 John Wiley & Sons, Ltd.

Significant down-scaling of device dimension has made cylindrical gate MOSFET (CG-MOS), a cutting edge device for low power applications. But in order to sustain the competition for real-time devices, it should have improved RF performances as well. In this paper, an analytical model of dual material cylindrical gate MOSFET (DMCG-MOS) with underlap engineering has been developed using the solution of 2-D Poisson's equation. The electrical parameters such as surface potential, threshold voltage and drain current are determined and compared with that of conventional CG-MOS. The effect of the variation of underlap length on the DC/RF performance of the model has been extensively discussed. The results show improvement in the performance of threshold voltage, leakage current and transconductance generation factor (TGF) with the introduction of underlap at the drain end. On the contrary, the model with source underlap exhibits better drain current and higher cut-off frequency. The analytical results are validated using Sentaurus TCAD device simulator. The improvement in DC and RF performance of this model would address emerging challenges posed by high frequency and low power applications. Copyright © 2016 John Wiley & Sons, Ltd.

This work addresses the problem of expedited design optimization of decomposable compact microwave structures, particularly impedance matching transformers. The approach proposed here exploits structure decomposition and a bottom-up technique where the elementary building blocks of the transformer circuit of interest are first optimized with respect to specifications extracted from a conventional circuit design, and subsequently, the entire circuit is optimized using the previously obtained building-block dimensions as a starting point. The optimization engine for each stage of the process is adjoint-based gradient search embedded in the trust region framework. The bottom-up approach turns out to be critical from the reliability standpoint: As the initial dimensions obtained from the optimized building blocks already result in reasonably good characteristics of the entire circuit, no global search is required to find a satisfactory design. This is in contrast to direct adjoint-based optimization of the entire circuit which leads to a local optimum, which may not satisfy the imposed requirements. At the same time, computational cost of the design process is reduced compared with direct optimization of the entire circuit, because building block optimization is carried out in low-dimensional search spaces and using simpler (i.e., less expensive) electromagnetic models. Our technique is demonstrated using a three-section impedance matching transformer. Copyright © 2016 John Wiley & Sons, Ltd.

A methodology based on the support vector machine (SVM) combined with a hybrid kernel function (HKF) for accurately modeling the resonant frequencies of the compact microstrip antenna (MSA) is presented and dedicated to reduce the number of samples and simplify the structure when predicting the resonant frequency of the compact MSA by artificial neural network. The parameters of the SVMs and weight coefficients of the HKF are optimized by means of particle swarm optimization algorithm. In addition, two different kernel functions (KFs), namely polynomial KF (a kind of global KF) and Cauchy KF (a kind of local KF), are employed to overcome the disadvantages of traditional KF. The proposed method is validated by the UCI database. The evaluation results show that the HKF can improve the learning ability and generalization ability of the SVM. Furthermore, the resonant frequencies of a planar inverted F-shaped antenna and an L-shaped MSA are modeled by the proposed method. Predictive results with high accuracy demonstrate that the particle swarm optimization-based SVM with the HKF can improve the prediction accuracy for a small dataset. Copyright © 2016 John Wiley & Sons, Ltd.

In this work, a self-contained numerical simulation tool for nanoscale Ion-Sensitive Field-Effect Transistor (ISFET) is developed. The tool is based on merging nanoscale ballistic MOSFET analytical equations with the Gouy–Chapman–Stern model equations of ISFET to form a system of nonlinear equations that can be solved iteratively to yield ISFET output current. The numerical solution is accomplished using Newton–Raphson method with efficient trust-region-dogleg algorithm using MATLAB software coding. The tool is used to optimize the sensitivity and linearity of nanoscale ISFETs, and to study their dependence on reference voltage, drain current level, and gate-insulator thickness. Moreover, a comparison between three types of insulators, SiO_{2}, Si_{3}N_{4}, and Al_{2}O_{3}, has been made. The tool is given the name: NIST (Nanoscale ISFET Simulation Tool). It can be used as a guide for design and optimization of nanoscale ISFETs and can be applied for both single-gate and double-gate structures. Copyright © 2016 John Wiley & Sons, Ltd.

In this paper, an efficient encoding and decoding algorithm is developed for tracking circulation of commodity. We take a discrete and optimized approach to construct the encoding and decoding method by using a matrix as an information carrier. This method is more durable against the damage of outer packages and can obtain a high recovery rate of commodity's information. Generally, it is very diffcult to track the original information in the circulation of commodity. We use the optimized encoding method to link the original information of commodity with a database so that the commodity can be pinpointed in the whole circulation. Also, the original information can be restored by an efficient decoding algorithm whenever necessary. The optimized method is designed based on two traditional encoding and decoding methods, and these methods are compared by running certain simulations with a large number of testing data. The results show that the improved and optimized method can obtain a much higher recovery rate of commodity's information and is more durable against the damage of outer packages. Copyright © 2016 John Wiley & Sons, Ltd.

Since the introduction of SPICE non-linear controlled voltage and current sources, they have become a central feature in the interactive development of behavioural device models and circuit macromodels. The current generation of SPICE-based open source general public license circuit simulators, including Qucs, Ngspice and Xyce©, implements a range of mathematical operators and functions for modelling physical phenomena and system performance. The Qucs equation-defined device is an extension of the SPICE style non-linear B type controlled source which adds dynamic charge properties to behavioural sources, allowing for example, voltage and current dependent capacitance to be easily modelled. Following, the standardization of Verilog-A, it has become a preferred hardware description language where analogue models are written in a netlist format combined with more general computer programming features for sequencing and controlling model operation. In traditional circuit simulation, the generation of a Verilog-A model from a schematic, with embedded non-linear behavioural sources, is not automatic but is normally undertaken manually. This paper introduces a new approach to the generation of Verilog-A compact device models from Qucs circuit schematics using a purpose built analogue module synthesizer. To illustrate the properties and use of the Qucs Verilog-A module synthesiser, the text includes a number of semiconductor device modelling examples and in some cases compares their simulation performance with conventional behavioural device models. Copyright © 2016 John Wiley & Sons, Ltd.

This paper studies the sliding mode control (SMC) and terminal SMC (TSMC) techniques of output voltage regulation in dc–dc buck converters. In this paper, the conventional terminal sliding manifold (TSM), fast terminal sliding manifold, and adaptive terminal sliding manifold are investigated by using hysteresis-modulated control. In addition, proportional-integral-derivative-shaped TSM, PI-shaped TSM, and proportional-integral-derivative-integral-shaped TSM are proposed in order to overcome the problems of conventional TSMs. Furthermore, a new continuous controller based on control Lyapunov function (CLF), with pre-settable-fixed switching frequency, is suggested. CLF-based controller (CLF-bC) is also adapted to the discontinuous digital input of the buck converter. In the proposed CLF-bC, the switching frequency is completely independent and pre-settable. Stabilization, reference tracking, high performance dynamic response, robustness against parameter uncertainties, and rejection of disturbances (e.g., input voltage changes and load variations) are some advantages of the proposed controllers. Impact of the controllers' parameters on the performance of the system is also summarized. Finite-time stability of TSMs and proposed CLF-bC, and the robustness of CLF-bC against parameter variations and disturbances are mathematically proved. Performance of the proposed Adaptive TSMC (ATSMC), proportional-integral-derivative-TSMC, and CLF-bC has been verified through matlab simulations and compared with the conventional SMC and TSMC strategies. Copyright © 2016 John Wiley & Sons, Ltd.

A novel extrinsic resistance extraction method of MOSFET at *V*_{gs} = *V*_{ds} = 0 V from S-parameter measurements is presented in this paper. Simulated and measured results of 90-nm gatelength MOSFET device with a 8 × 0.6 × 12 µm gatewidth (number of gate finger × unit gate width × cells) are compared, and good agreement has been obtained up to 50 GHz. Furthermore, comparisons between the proposed approach and other three methods published are also made in this paper. Copyright © 2016 John Wiley & Sons, Ltd.

The purpose of this paper is to develop the element-free Galerkin method for a numerical simulation of the second-order elliptic equation with discontinuous coefficients. Discontinuities in the solution and in its normal derivatives are prescribed on an interface inside the domain. The proposed method is one of the powerful meshless methods based on moving least squares approximation. The element-free Galerkin method uses only a set of nodal points to discretize the governing equation. No mesh in the classical sense is needed, but a background mesh is used for integration purpose. A quadrilateral mesh unfitted with the interface is used for integration objective. The Lagrange multipliers are used to enforce both Dirichlet boundary condition and Dirichlet jump condition. The presented numerical experiments confirm the efficiency of the proposed method in comparison with some existing methods for interface problems. Copyright © 2016 John Wiley & Sons, Ltd.

A novel GaN high-electron mobility transistor (HEMT) nonlinear large-signal statistical model based on empirical equivalent circuit is proposed in this paper. Thirty-four GaN HEMTs from 10 batches are measured, and all the parameters of the large-signal model are extracted by in-house parameter extraction program. We choose six most sensitive parameters of the drain-source current model and the gate charge model. The statistical method is modeled by using a symbolic processing method to change the range of the six parameters. The statistical model is implemented in Agilent ADS software for validation. A S-band GaN HEMT power amplifier is designed by using the established statistical model for demonstration purpose. The results show that good accuracy has been achieved by comparing measured and simulated output power (Pout) and power added efficiency (PAE). So it has been proven that this method is suitable for GaN HEMT power amplifier design and yield estimation. Copyright © 2016 John Wiley & Sons, Ltd.

This paper presents physics based analytical model for center potential, electric field and subthreshold drain current of Junctionless Accumulation Mode Cylindrical Surrounding Gate MOSFET (JAM-CSG). The expressions are derived from Poisson's equation in cylindrical co-ordinate system based on parabolic potential approximation (PPA). The influence of technology parameter variations such as gate length, silicon pillar diameter and oxide thickness on electrical characteristics is studied in detail. Developed analytical model results are validated through the good agreement with simulated data obtained from ATLAS 3D simulator. Copyright © 2016 John Wiley & Sons, Ltd.

In this paper, we describe an extraction procedure of nonlinear models for microwave field-effect transistor (FET). We use a nonlinear model available in commercial CAD tools, and we extract the parameters by combining direct extraction and numerical optimization. We determine a first estimate of the model parameters by few DC and S-parameter measurements. Next, we refine the parameters by optimization against low-frequency and high-frequency vector-calibrated large-signal measurements gathered with a Large-Signal-Network Analyzer (LSNA). As case study we consider a 0.25 × 200 µm^{2} GaN FET on SiC for power amplifier applications. Ultimately, we want to show that a good accuracy level can be achieved while minimizing the extraction effort and that an accurate model can be built and suitably tailored depending on the final application. Copyright © 2016 John Wiley & Sons, Ltd.

Artificial neural network (ANN) provides an efficient modeling technique based on input–output data obtained from an engineering problem. Highly nonlinear and complex relationships can be formed by ANN because of its nonlinear nature and representing knowledge at interconnection weights. If an ANN model is not sufficient in respect to the accuracy and time consumption, the knowledge based on design experience can be embedded into the modeling process. This knowledge reduces the complexity of the nonlinear input–output relationships; therefore, the knowledge embedded ANN can be formed easily compared with the conventional ANN model. Three-step modeling strategy generates the initial knowledge via the conventional ANN modeling and consists of three sequential and also discrete training processes exploiting the knowledge-based methods such as prior knowledge input and prior knowledge input with difference. The latter step improves the accuracy of the former step, and three-step modeling provides more accuracy than conventional ANN modeling. The efficiency of three-step modeling strategy is demonstrated on two data sets, which are obtained by the reconfigurable microstrip patch antenna design problem. The different number of neurons and ANN structures is handled for the comparison as well. In addition, ANN modeling is formed by MATLAB m-file through neural network toolbox to reveal the efficiency of knowledge-based three-step modeling strategy. Copyright © 2016 John Wiley & Sons, Ltd.

One of the important prerequisites for efficient design optimization of microwave structures is availability of fast yet reliable replacement models (surrogates) so that multiple evaluations of the structure at hand can be executed in reasonable timeframe. Direct utilization of full-wave electromagnetic (EM) simulations for handling optimization-related tasks is often prohibitive. A popular approach to construction of fast surrogates is data-driven modeling. Unfortunately, it normally requires a large number of training samples, and it is virtually infeasible for structures that exhibit highly nonlinear responses (e.g. filters or couplers). In this work, a design-oriented modeling technique is proposed where good accuracy is achieved by careful non-uniform design space sampling that accounts for nonlinear relationship between the operating frequency of the structure and its geometry parameters, as well as carrying out the modeling process only for selected characteristic points of the structure responses (those that determine satisfaction/violation of given design specifications). Our approach is demonstrated using a miniaturized microstrip rat-race coupler modeled in a wide range of geometry parameters and compared to conventional data-driven modeling using kriging interpolation. Design optimization examples are also provided. Copyright © 2016 John Wiley & Sons, Ltd.

As wireless cellular communication keeps expanding toward higher bandwidth, multiband signals, and high frequencies of operation, the design of power efficient radio frequency power amplifiers (PAs) for cellular phone basestations is submitted to more stringent requirements. This paper discusses the promising technique of nonlinear embedding, which may help stream line the design of such PAs. To this order, the design of a GaN radio frequency PA from device modeling to circuit design is presented. The large signal modeling of GaN high-electron-mobility transistors including thermal and trapping memory effects is discussed first. The nonlinear embedding device model is then introduced using the concept of an anti-circuit transfer network. This embedding device model is then applied to the design of a Chireix amplifier. New Chireix design equations are developed to work with the memoryless inner core of the embedding device model, and their validity is confirmed in circuit simulations. The Chireix amplifier is then designed using the multi-harmonic impedance terminations predicted by the embedding device model for the package reference planes. Finally, the resulting Chireix amplifier is implemented in a circuit simulator with the original GaN high-electron-mobility transistors device model and verified in simulations to have a performance approaching that of the originally targeted Chireix at the current reference planes. These theoretical and simulation results demonstrate the potential of the nonlinear embedding PA design technique in the design of Chireix power amplifiers. Copyright © 2016 John Wiley & Sons, Ltd.

In this work, a new multi-objective population-based optimization algorithm is presented and tested. In this contribution, the concepts of fast non-dominating sorting and density estimation using the crowding distance are used to create a multi-objective optimization algorithm based on previous work, which is a single objective evolutionary optimization algorithm based on self-organizing maps (SOMs). The SOMs paradigm introduces a strong collaboration between neighbors solutions that improves exploitation. Furthermore, the representative power of the SOMs enhances the exploration and diversification. A state of the art benchmark approach is used to evaluate the performance of the proposed algorithm, obtaining positive results. The test problem uses an analytical model of an inductively coupled wireless power transfer system (WPT). The objective is to optimize the WPT model characteristics in order to allow simultaneous data and power transfer between the coils. The WPT design approach uses more degrees of freedom than existing techniques leading to a number of solutions where both the power signals and the data signal can coexist on the same physical channel achieving good figures of merit. Copyright © 2016 John Wiley & Sons, Ltd.

In this work, the broadband capability of composite right/left-handed transmission lines (CRLH TLs) in the balanced condition is exploited for ultra-wideband matching of a compact single transistor front-end amplifier. For this purpose, the LC element values and the number of identical asymmetric CRLH TL cells are taken as optimization variables. The minimum noise and maximum power delivery at each operation frequency of the chosen high technology transistor are considered as the feasible design target provided that the stability of the transistor is ensured. This feasible design target is expressed simply by a single objective function in terms of the port impedances of the input and output matching circuits together with the realization conditions of the CRLH TLs. Thus, human efforts for the design optimization process are reduced as much as possible. A novel metaheuristic algorithm ‘modified cuckoo search’ is used as a fast and accurate tool to find out ‘the global optimum’ within the feasible design variable space in the design procedure. In the study case, BPF640 is chosen as a high performance low-noise microwave transistor. The design optimization results in a low-noise amplifier using a single CRLH TL cell input and output matching circuits provided that a good agreement is obtained with the targetted performance and verified by Applied Wave Research, Inc. (AWR) simulation software. Thus, it can be concluded that CRLH TLs enable a designer to design high-performance miniaturized low-noise amplifiers. Copyright © 2016 John Wiley & Sons, Ltd.

An improved linear modeling technique for gallium nitride high electron mobility transistor small-signal equivalent circuit under different bias conditions is presented in this paper. The method is a combination of the test structure and sensitivity analytical method to improve the precision of the intrinsic elements in the small-signal model. The analytical expressions for the relative sensitivities with respect to deviations in the measured scattering (*S*) parameters are also given here. The derived relationships have universal validity, but they have been verified by the good agreement between the measured *S*-parameters and simulated ones over the frequency range up to 40 GHz. Copyright © 2016 John Wiley & Sons, Ltd.

The wave approach has appeared as a very efficient tool for modeling as well as for measurements of noise parameters of microwave transistors. Having in mind the attractiveness of transistors in gallium nitride technology in modern communication systems, where it is very important to keep the noise on a low level and, thus, to have accurate transistor noise models, in this paper, the wave approach is applied for the noise modeling of high electron-mobility transistor in gallium nitride technology. The noise wave representation of the transistor intrinsic circuit noise is used, where the noise wave parameters are modeled by exploiting the artificial neural networks. The modeling results, compared with the measured data and with those obtained by the conventional noise equivalent circuit model, provide a verification of the developed model accuracy. Copyright © 2015 John Wiley & Sons, Ltd.

This paper presents an analytical parameter extraction method for empirical large-signal model of GaN high electron mobility transistors (HEMTs) including self-heating and trapping effects. Every parameter in the model is extracted in an analytic way. An improved Angelov I–V model specific for GaN HEMTs with 53 parameters is employed. The I–V model parameters are divided into blocks according to their physical meaning, and different blocks are extracted separately by fitting the pulsed I–V transfer characteristic curves of the device at different quiescent bias points. The capacitance model is extracted through mathematical analysis. This method has been implemented in MATLAB (MathWorks, Natick, MA, USA) programming, and good accuracy is obtained between model predictions and experimental results. Copyright © 2015 John Wiley & Sons, Ltd.

Artificial neural networks (ANNs) have been often used for engineering design problems. In this work, an inverse model of a reconfigurable N-shaped microstrip patch antenna which is formed by ANN is considered to find design parameters. For this task, knowledge-based response correction consists of two steps, which include generating response using multilayer perceptron as a first step and correcting this response using knowledge based methods such as source difference, prior knowledge input, and prior knowledge input with difference as a second step. The proposed antenna has four states of operation controlled by two Positive-Intrinsic-Negative (PIN) diodes with ON/OFF states. The two-step ANN models are inversely trained using the optimum of the resonant frequency parameter as the input and the physical dimensions of the proposed antenna as outputs of the multilayer perceptron. The outputs and, in some methods, the input parameters of the multilayer perceptron are sent as input to the knowledge-based models while the obtained outputs from the two steps are the results of the new physical dimensions of the redesigned reconfigurable antenna that will be compared and analyzed. This input/output complexity of the proposed reconfigurable antenna allows an accurate and fast inverse model to be developed with less training data. Users may use this antenna and its ANN models to develop new products in the market where any frequency in the operating region can be given to the input to result an appropriate form of the new reconfigurable antenna. Copyright © 2015 John Wiley & Sons, Ltd.

In this work, the sensitivities of the Gain *G _{T}*, noise figure

An optimization-based method allowing a straightforward extraction of scalable small-signal equivalent-circuit models for high-frequency active devices is proposed. The approach only requires a set of devices with a fixed number of fingers and scaling unit gate widths: no dummy structures or bias conditions potentially harmful for the devices are needed. The extraction method is then demonstrated by presenting in full a sample extraction, carried out on a 0.25 GaN-on-SiC HEMT technology provided by Selex-ES. The example also includes the extraction of a noise model, by means of a well-known noise-temperature approach. Both the small-signal and noise models agree well with the experimental data. Copyright © 2015 John Wiley & Sons, Ltd.

This paper is focused on the design of bandpass filters based on open complementary split ring resonators (OCSRRs) in microstrip technology. The filters are obtained by coupling the corresponding shunt resonators (OCSRRs) through admittance inverters (quarter wavelength transmission line sections). Different undesirable effects derived from the chosen topology are taken into account and are compensated at the design level. These effects include the reduction in bandwidth (caused by the narrowband functionality of the line sections acting as admittance inverters), and the presence of a spurious band above the filter passband. The proposed technique is based on the well-known aggressive space mapping algorithm, which is a powerful tool for the synthesis and design of microwave components. The design of the OCSRR-based filter is provided in a fully automated way as the main result of this paper. Copyright © 2015 John Wiley & Sons, Ltd.

A design method for microwave GaN high-electron mobility transistor (HEMT) power amplifier based on equivalent circuit parameters multi-bias statistical models is presented. The statistical modeling method includes principal component analysis, factor analysis, and multiple regressions modeling techniques. The statistical model is validated by comparing original and Monte Carlo-simulated means, standard deviations, correlation matrix, and S-parameters. A Ku-band GaN HEMT power amplifier is designed with high drain efficiency by using the established statistical model for demonstration purpose. The simulated results are statistically indistinguishable from the measured results. This method is suitable for GaN HEMT power amplifier design and yield analysis. Copyright © 2015 John Wiley & Sons, Ltd.

This paper proposes an efficient parameter extraction algorithm for GaN high electron mobility transistors small-signal equivalent circuit model. The algorithm combines parameter scanning and iteration methods to solve the problem of error accumulation in conventional methods and is implemented in matlab programming. By using the iteration method, the algorithm each time uses more accurate element values thus makes the results converge to the optimal value faster. A 20-element small-signal equivalent circuit model of GaN high electron mobility transistors is used to validate the proposed algorithm, and the results show that the calculated *S*-parameters agree well with the measured *S*-parameters within the frequency range of 0.1 to 40 GHz. Copyright © 2015 John Wiley & Sons, Ltd.

Gallium nitride high electron mobility transistors (GaN HEMTs) have been accused of suffering from soft-compression, a recognized form of nonlinearity. Recently published works showed that this phenomenon – explained with the devices' charge-trapping effects – is only observed under CW operation, which has little in common with generally used communication signals. In real operation, those effects (modeled as a self-biasing phenomenon visible as a threshold voltage variation) are also observable, but in an apparently different way. Several nonlinear models already take into account this variation and, more recently, the authors presented an extraction methodology for such complicated systems. Based on that information, this paper presents the trapping behavior of GaN HEMTs and a physically based way of adjusting the quiescent point of a desired class B GaN HEMT-based PA, designed to operate under dynamically varying signals. Copyright © 2015 John Wiley & Sons, Ltd.

The purpose of this invited paper is to give readers a comprehensive and critical overview on how to extract equivalent-circuit models for GaN HEMTs, which are the preferred devices for high-power high-frequency applications. This overview is meant to provide a practical modeling know-how for this advanced type of transistor, in order to support its development for improving device technology and circuit design. With the aim to broaden knowledge to empower models, experimental results are presented as illustrative examples of the most crucial challenges faced by the microwave engineers in modeling high-power GaN HEMTs. All the relevant aspects are covered, going from linear (also noise) to nonlinear models. The analysis is mainly focused on the modeling of distinctive peculiarities of GaN HEMTs. Particular attention is paid to study the importance of accurately modeling the kink effect in the output reflection coefficient, because of the relatively high transconductance, the peak in the magnitude of the short circuit current-gain, because of the relatively large intrinsic capacitances, and the low-frequency dispersion, because of trapping and thermal effects. Furthermore, to emphasize the key role of accurate device models for a successful circuit design, a practical example of power amplifier is discussed. Copyright © 2015 John Wiley & Sons, Ltd.

In this paper, a physics-based analytical model for threshold voltage, two-dimensional electron gas (2DEG) sheet charge density and DC characteristics of the proposed spacer layer-based Al_{x}In_{1−x}N/AlN/GaN metal-oxide-semiconductor high electron mobility transistor is presented by considering the quasi-triangular quantum well. 2DEG sheet charge density (*n*_{s}) is obtained by the variation of Fermi level (*E _{f}*) with supply voltage and the formation of energy subbands

An ad hoc setup for complete on-chip large-signal characterization of both series and parallel high-power GaN high-electron-mobility transistor switches has been developed. Thanks to its characteristics, arbitrary loads at both switch terminals (i.e., drain and source) for power levels up to tens of watts can be applied. The setup is suitable for extraction and validation of equivalent circuit and behavioral models. The potentiality of the presented solution is demonstrated by model validation and measurements of series and shunt C-band high-power GaN high-electron-mobility transistor switches from two commercial foundries. Copyright © 2015 John Wiley & Sons, Ltd.

Design centering is an optimal design process that seeks for the values of system parameters which maximize the probability of satisfying the design specifications (yield function). In this article, a derivative-free trust region (TR) optimization approach is combined with the generalized space mapping technique to develop a new space mapping (SM) surrogate-based statistical technique for design centering of computationally expensive microwave circuits. The TR optimization approach is well suited for expensive objective functions that have some uncertainty in their values or subject to statistical variations. The principal operation relies on building and successively updating quadratic surrogate models to be optimized instead of the objective function over TRs employing the truncated conjugate gradients. The approach constructs the initial quadratic surrogate model using fewer data points, then updates the surrogate model using a weighted least squares fitting that gives more emphasis to points close to the current center point. Integrating the TR optimization approach with the generalized space mapping technique results in a novel statistical design centering technique for the microwave circuits with a great reduction in computations and simulations needed for the yield optimization process. Design of practical microwave circuits is presented to indicate the effectiveness of the new design centering technique. Copyright © 2015 John Wiley & Sons, Ltd.

In this paper, a nonlinear modeling approach for gallium nitride high-electron mobility transistor (GaN HEMT) on Si substrate is proposed. A reliable method has been developed to extract the extrinsic elements of the model. Its main advantage is its accuracy and dependency on only pinched-off and unbiased *S*-parameter measurements. The extrinsic elements are de-embedded from multi-bias *S*-parameters to characterize the transistor intrinsic and construct a large-signal model. The validity of the developed modeling approach is verified by comparing its small-signal and large-signal (single-tone and two-tone) simulations with measured data of a 2-mm GaN HEMT on Si substrate. The model has been employed for designing a class-AB power amplifier. A very good agreement between the amplifier simulation and measurement shows the validity of the model. Copyright © 2015 John Wiley & Sons, Ltd.

A practical formulation for EM-based design optimization of high-frequency circuits using simple polynomial surrogate functionals is proposed in this paper. Our approach starts from a careful selection of design variables and is based on a closed-form formulation that yields global optimal values for the surrogate model weighting factors, avoiding a large set of expensive EM model data, and resulting in accurate low-order low-dimension polynomials interpolants that are used as vehicles for efficient design optimization. Our formulation is especially suitable for EM-based design problems with no equivalent circuital models available. The proposed technique is illustrated by the EM-based design optimization of a Ka-band substrate integrated waveguide (SIW) interconnect with conductor-backed coplanar waveguide (CBCPW) transitions, a low crosstalk PCB microstrip interconnect structure with guard traces, and a 10–40-GHz SIW interconnect with microstrip transitions on a standard FR4-based substrate. Three commercially available full-wave EM solvers are used in our examples: CST, Sonnet, and COMSOL. Copyright © 2015 John Wiley & Sons, Ltd.

In this article, a simple, accurate, fast, and reliable black-box modeling is proposed for the scattering (S)-parameters and noise (N)-parameters of microwave transistors using the general regression neural network (GRNN) with the substantially reduced measurements and computational cost. In this modeling method, GRNN is employed as a nonlinear extrapolator to generalize the S-data and N-data belonging to only a single bias voltage in the middle region into the entire device operation domain of the bias condition (V_{DS}/V_{CE}, I_{DS}/I_{C}, *f*) within the shortened human effort. The proposed method is implemented to the modeling of the two transistors BFP640 and ATF-551 M4 as study cases. Thus, comparisons are made with the multilayer perceptrons, trained by the two standard backward propagation algorithms, which are the Levenberg–Marquardt, Bayesian regularization and the 10 data mining methods recently published in the literature using the chosen training data sets in both ınterpolation and extrapolation types of generalization. All the comparisons are achieved using four criteria commonly used in the literature. It can be concluded that GRNN is found to be a fast and accurate modeling method that extrapolates the reduced amount of training data consisting of measured S-parameters and N-parameters at the typical currents of the middle bias voltage to the wide operating range. Copyright © 2015 John Wiley & Sons, Ltd.

In this paper, optimal designs of non-uniform single-ring circular antenna array (CAA) and non-uniform three-ring concentric circular antenna array (CCAA) have been dealt with, which gives rise to optimal improvement of far-field radiation characteristics. An evolutionary optimization technique based on opposition-based bat algorithm (OBA) is applied to determine an optimum set of current excitation weights and antenna inter-element spacing for CAA of 8, 10, and 12 elements and optimal current excitation weights for CCAA, respectively. Two three-ring CCAAs, one having the set of 4, 6, and 8 elements and the other having 8, 10, and 12 elements with and without center element, are considered. The results show a considerable reduction of side lobe level, 3-dB beamwidth, and improved directivity of CAA and better side lobe level of CCAA, with respect to the results of some recent literature reported in this paper. The BAT is a metaheuristic algorithm, based on the echolocation behavior of bats. The capability of echolocation of microbats is fascinating as the bats can find their prey and discriminate different types of insects even in complete darkness. By idealizing the echolocation behavior of bats, BAT is recently introduced in the literature. In the present paper, opposition-based learning is employed for population initialization and also for the generation jumping along with the original BAT for further improving the convergence performance of BAT. This new variant of BAT is termed as opposition-based BAT. Copyright © 2015 John Wiley & Sons, Ltd.

In this paper, simultaneous improvement of array factor directivity and side lobe level of time-modulated linear antenna arrays using opposition-based harmony search algorithm has been dealt with. Because of the periodic function of switching time, the same antenna array will radiate at fundamental (center) frequency as well as its harmonic frequencies. The first two harmonic frequencies are (*f*_{0} + *F*_{p}) and (*f*_{0} + 2*F*_{p}), where *f*_{0} and *F*_{p} are operating frequency and pulse repetition frequency, respectively. Four case studies have been adapted; Case-1: optimal switching time sequence of each element; Case-2: optimal switching time sequence of each element and optimal non-uniform inter-element spacing; Case-3: optimal switching time sequence of each element, optimal excitation phase of each element, and optimal uniform inter-element spacing; Case-4 refers to optimal switching time sequence of each element and optimal uniform inter-element spacing. Simulation results reflect that Case-4 outperforms Case-1, Case-2, and Case-3. The objective function was judiciously chosen in such a way that it can simultaneously improve the array factor directivity as well as side lobe level. Considered for the analysis was 16-element linear antenna array. Various simulation results are presented showing better side lobe performance, better side band performance, and improved array factor directivity with respect to the uniform array having the same number of elements. The numerical results show the power radiated by any harmonic frequency is less as compared with the power radiated at the center frequency called the fundamental frequency. It has also been observed that as the harmonic frequency increases, sideband level and power radiated by the antenna at its harmonic frequency decrease. Copyright © 2015 John Wiley & Sons, Ltd.

In this paper, computationally efficient simulation-driven design optimization of integrated photonic couplers is discussed. The design process is conducted using variable-fidelity electromagnetic (EM) simulations and surrogate-based optimization (SBO) techniques. Two design case studies are considered: conventional directional coupler and a curved coupler. A particular choice of the SBO approach relies on a visual inspection of the low- and high-fidelity coupler model responses as well as their correlations. The first structure is optimized using adaptively adjusted design specifications technique. Because of limited correlations between the high- and low-fidelity EM models of the second structure, its optimal design is obtained using the additive response correction method. Subsequently, the design is fine-tuned using local response surface approximations. As demonstrated through numerical results, utilization of the SBO techniques allows for considerable reduction of the design optimization time compared with direct handling of the high-fidelity model. The total optimization cost of conventional and curved coupler corresponds to only 13.5 and 23.7 high-fidelity model simulations, respectively. Copyright © 2015 John Wiley & Sons, Ltd.

A general model that combines the effect of controllable reflectivity resulting from semi-periodic gratings with the transfer function of a single ring resonator add/drop filter is derived. An optimization approach based on minimizing the least squared error is performed to calculate parameters that increase the crosstalk suppression bandwidth of a rough-walled ring resonator. The resulting design has a 28-GHz crosstalk suppression bandwidth. Copyright © 2015 John Wiley & Sons, Ltd.

In recent years, the electronic industries tend to offer products with smaller scales, lower cost, larger storage space and integration of various functions. The development of redistributed chip package (RCP) technology is facilitated to reduce package size for three-dimensional integration and to enhance packaging capability for miniature requirements. Meanwhile, the logic unit is required to be combined with the memory unit to achieve miniaturization and system integration.The RCP with package on package (PoP) is constructed by stacking the RCP for the very fine pitch ball grid array at topside and the stack package ball grid array (SPBGA) at bottom side. The finite element software ANSYS is adopted in this study using the Global/Local modeling approach. The reliability of the RCP with PoP is subjected to a thermal cycle test of -40-125 °C based on JEDEC specification. The Coffin-Manson strain-based model and the Morrow energy-based model are employed for prediction of package fatigue life, in which the SAC387 (95.5Sn3.8Ag0.7Cu) solder joints are treated as viscoplastic behavior according to the Anand constitutive model. The other materials are modeled as elastic behavior.To investigate the solder joint reliability for the stacked package design, a numerical experiment by means of the single factor analysis is first conducted for investigation. The material factors such as Young's Modulus and coefficient of thermal expansion, the geometric factors such as component thickness are evaluated. Accordingly, the significant factors are filtered and analyzed by the Taguchi method to obtain the optimal combination. As a result, the optimal design increases package fatigue life, which contributes a significant improvement by up to 86.5% when comparing with the original model.Copyright © 2014 John Wiley & Sons, Ltd.

No abstract is available for this article.

]]>In this paper, a coherent perfect absorption-type NOR gate based on plasmonic nano particles is proposed. It consists of two plasmonic nanorod arrays on top of two serial arms with quartz substrate. The operation principle is based on the absorbable formation of a conductive path in the dielectric layer of a plasmonic nanoparticle waveguide. Because the coherent perfect absorption efficiency depends strongly on the number of plasmonic nanorods and the locations of nanorods, an efficient binary optimization method based the Particle Swarm Optimization algorithm is used to design an optimized array of the plasmonic nanorods in order to achieve the maximum absorption coefficient in the ‘off’ state and the minimum absorption coefficient in the ‘on’ state. In Binary Particle Swarm Optimization, a group of birds consists a matrix with binary entries, control the presence (‘1’) or the absence (‘0’) of nanorods in the array. Copyright © 2016 John Wiley & Sons, Ltd.

Channel allocation in the wireless sensor networks is one of the important issues, and these networks must allocate shared channels between sensor nodes in the transmission phase. This paper proposes a novel protocol for channel allocation, so it focuses on energy efficiency and collisions avoidance. The main idea of this protocol is based on the Guaranteed Time Slot approach by using novel high-rate collaborative codes. The sum rate of the proposed collaborative codes is double than the conventional codes, thus increasing the capacity of codes and allowing more nodes to simultaneously transmit at a given time slot. The proposed protocol has a cluster-based structure, so the sensor nodes of each cluster can communicate together only inside of the any cluster. The protocol performs clustering (grouping) of the nodes based on the geometric distance from the coordinator node and hence allocating different transmission power to each cluster. Because of the difference in transmission power among the groups, the same codes can be reused in the adjacent groups increasing the overall sum rate of the codes. The performance of a proposed protocol is evaluated through extensive simulation and analysis. It is shown from the results that the proposed scheme outperforms significantly the existing ZigBee Guaranteed Time Slot allocation schemes as well as the conventional collaborative codes. Copyright © 2016 John Wiley & Sons, Ltd.

A promising time domain electromagnetics numerical method for treating the highly nonlinear problem of charge transport in electronic devices called Delaunay–Voronoi surface integration is presented. This method couples the rotational electric and magnetic fields governed by Ampere's and Faraday's laws with the electrostatic potential dictated by Poisson's equation in a simultaneous solution. Discretization of the governing equations using dual meshes and the relevant boundary conditions are presented. The engineering application details specific to electronic device simulation are treated, and an example calculation is shown to compare with an analytical solution for propagation in a waveguide. Benchmark results are presented for the rotational equations, Poisson's equation, and the complete set of electromagnetic equations. Copyright © 2016 John Wiley & Sons, Ltd.

This paper incorporates the compensated Mitzner boundary conditions (CMBC) into the hybrid finite element- boundary integral-multilevel fast multipole algorithm (FE-BI-MLFMA) for fast and accurate computation of scattering by three-dimensional inhomogeneous objects with thin dielectric structures. In this CMBC-FE-BI-MLFMA, each thin dielectric layer is reduced to an interface with zero thickness; then CMBC is applied to establish the relation of electromagnetic fields across the interfaces. This approach can reduce the amount of computation and remain the advantages of versatility, accuracy, and efficiency of the conventional FE-BI-MLFMA algorithm. The formulation of this CMBC-FE-BI-MLFMA is presented in this paper. An efficient preconditioner based on the sparse approximate inverse is employed and further parallelized on memory-distributed platforms. Numerical results are presented to demonstrate the accuracy, efficiency, and capability of the parallel CMBC-FE-BI-MLFMA. Copyright © 2016 John Wiley & Sons, Ltd.

Lab-on-a-chip (LOC) integrated microfluidics has been a powerful tool for new developments in analytical chemistry. These microfluidic systems enable the miniaturization, integration and automation of complex biochemical assays through the reduction of reagent use and enabling portability. Electroosmotic micropumps could be employed as powerful tools to generate required flow in point of care (POC) devices. In the present study, parallel electroosmotic micropumps are investigated to improve the efficiency of simple micropumps. According to the results, parallel micropumps generate higher flow rate in comparison with conventional electroosmotic pump. In the last decade, a large variety of non-Newtonian fluids have been utilized in biomedical application but requirements for a POC device such as high efficient driving flow, miniaturization and simple handling of POC devices remain unmet. As a consequence, in this study, power law model as non-Newtonian fluids that flow through the parallel micropumps are investigated in order to enhance fluid pumping and decreasing voltage requirement.. It is found that as the power law index increases the mass flow rate decreases. Also, the flow rate is almost constant for the higher power law index. Obtained results, demonstrated that parallel micropump could enhance pumping of non-Newtonian fluid (blood) up to 30%. Copyright © 2016 John Wiley & Sons, Ltd.

In the presented work, influence of magnet shaping on cogging torque of surface-mounted Permanent Magnet (PM) machines is investigated. The considered PM shape for the magnet shaping is the loaf-shape PM with off-set arcs. For the first time, based on the solution of the Poissons's equation, an analytical model is provided to predict the magnetic flux density of the slotted-armature and surface-mounted PM machines with the loaf-shape PM. The influence of the slotted armature on the magnetic flux density is taken into account by considering the slot virtual surface currents. The geometry of the loaf-shape PM is formulated and optimized to reach a design with a low value of the cogging torque. The machine cogging torque is computed by the Maxwell stress tensor. The obtained analytical model is used as the computational tool to find the dependence of the machine cogging torque on the PM geometry. Finally, the validity of the obtained results is verified by finite element analysis. Copyright © 2016 John Wiley & Sons, Ltd.

This paper presents an efficient approach for the optimal designs of two analog circuits, namely complementary metal oxide semiconductor) two-stage comparator with p-channel metal oxide semiconductor input driver and n-channel input and folded-cascode operational amplifier using a recently proposed meta-heuristic-based optimization algorithm named as colliding bodies optimization (CBO). It is a multi-agent algorithm that does not depend upon any internal control parameter, making the algorithm extremely simple. The main objective of this paper is to optimize the metal oxide semiconductor (MOS) transistors' sizes using CBO in order to reduce the areas occupied by the circuits and to get better performance parameters of the circuits. Simulation Program with Integrated Circuit Emphasis simulation has been carried out by using the optimal values of MOS transistors' sizes and other design parameters to validate that CBO-based design is satisfying the desired specifications. Simulation results demonstrate that the design specifications are closely met and the required functionalities are achieved. The simulation results also confirm that the CBO-based approach is superior to the other algorithms in terms of MOS area and performance parameters like gain, power dissipation, etc., for the examples considered. Copyright © 2016 John Wiley & Sons, Ltd.

An efficient parallelization of the dual-primal finite-element tearing and interconnecting (FETI-DP) algorithm is presented for large-scale electromagnetic simulations. As a nonoverlapping domain decomposition method, the FETI-DP algorithm formulates a global interface problem, whose iterative solution is accelerated with a solution of a global corner problem. To achieve a good load balance for parallel computation, the original computational domain is decomposed into subdomains with similar sizes and shapes. The subdomains are then distributed to processors based on their close proximity to minimize inter-processor communication. The parallel generalized minimal residual method, enhanced with the iterative classical Gram-Schmidt orthogonalization scheme to reduce global communication, is adopted to solve the global interface problem with a fast convergence rate. The global corner-related coarse problem is solved iteratively with a parallel communication-avoiding biconjugate gradient stabilized method to minimize global communication, and its convergence is accelerated by a diagonal preconditioner constructed from the coarse system matrix. To alleviate neighboring communication overhead, the non-blocking communication approach is employed in both generalized minimal residual and communication-avoiding biconjugate gradient stabilized iterative solutions. Three numerical examples are presented to demonstrate the accuracy, scalability, and capability of the proposed parallel FETI-DP algorithm for electromagnetic modeling of general objects and antenna arrays. Copyright © 2016 John Wiley & Sons, Ltd.

Because the nonlinear and time-varying characteristics of the continuously variable transmission system operated using a six-phase copper rotor induction motor are unknown, improving the control performance of the linear control design is time-consuming. To capture the nonlinear and dynamic behaviour of the six-phase copper rotor induction motor servo-driven continuously variable transmission system, a blend modified recurrent Gegenbauer orthogonal polynomial neural network (NN) control system, which has the online learning capability to return to the nonlinear time-varying system, was developed. The blend modified recurrent Gegenbauer orthogonal polynomial NN control system can perform overseer control, modified recurrent Gegenbauer orthogonal polynomial NN control, and recompensed control. Moreover, the adaptation law of online parameters in the modified recurrent Gegenbauer orthogonal polynomial NN is based on the Lyapunov stability theorem. The use of amended artificial bee colony optimization yielded two optimal learning rates for the parameters, which helped improve convergence. Finally, comparison of the experimental results of the present study with those of previous studies demonstrated the high control performance of the proposed control scheme. Copyright © 2016 John Wiley & Sons, Ltd.

This paper presents the optimal designs of two analogue complementary metal–oxide–semiconductor (CMOS) amplifier circuits, namely differential amplifier with current mirror load and two-stage operational amplifier. A modified Particle Swarm Optimization (PSO), called Craziness-based Particle Swarm Optimization (CRPSO) technique is applied to minimize the total MOS area of the designed circuits. CRPSO is a highly modified version of conventional PSO, which adopts a number of random variables and has a better and faster exploration and exploitation capability in the multidimensional search space. Integration of craziness factor in the fundamental velocity term of PSO not only brings diversity in particles but also pledges convergence close to global best solution. The proposed CRPSO-based circuit optimization technique is reassured to be free from the intrinsic disadvantages of premature convergence and stagnation, unlike Differential Evolution (DE), Harmony Search (HS), Artificial Bee Colony (ABC) and Particle Swarm Optimization (PSO). The simulation results achieved for the two analogue CMOS amplifier circuits establish the efficacy of the proposed CRPSO-based approach over those of DE, HS, ABC and PSO in terms of convergence haste, design conditions and design goals. The optimally designed analogue CMOS amplifier circuits occupy the least MOS area and show the best performance parameters like gain and power dissipation, in compared with the other reported literature. Copyright © 2016 John Wiley & Sons, Ltd.

The iterative Fourier technique (IFT) is applied to design monopulse radar tracking system using time-modulated linear antenna array (TMLA). IFT is used to modify the time sequences of the radio-frequency switches connected to the antennas to generate sum and difference patterns with suppressed interference-plus-noise signal while constraining the power losses associated with side-band radiation (SBR). The time modulation allows quick and precise control of the excitation distribution, which increases the tracking accuracy. To obtain best angle sensitivity, the article computes the tradeoff among side-lobe level (SLL), half power beam width, directivity, and dynamic efficiency. The approach is proved successful to handle several design constraints through adaption in radiation domain as well as in aperture domain. Authors illustrate additional representative TMLA examples where the time sequences of the selected elements are prefixed to enhance the dynamic efficiency and directivity for different SLL and side-band level (SBL). Application of IFT saves the computational cost significantly with respect to existing state-of-the-art optimization techniques. Introduction of the symmetric switching sequences simplifies the feed network greatly. The proposed design solution is validated with a fabricated TMLA prototype consisting of two time-switched printed dipoles with microstrip via-hole balun at 2.45 GHz. Copyright © 2016 John Wiley & Sons, Ltd.

In recent years, several papers have dealt with eccentricity fault diagnosis considering the cage-induction machine while wound machine type has not been studied as a case. In this paper, eccentricity fault is studied based on the current/torque signature considering modified winding function approach (MWFA). A novel discrete model is introduced, and eccentricity fault is evaluated in both static and dynamic cases. To reach this aim, a numerical model is presented for slot openings, distributed windings and air-gap, thereby computing the machine's inductances using MWFA. Power spectral density (PSD) of stator's current and machine's vibration are analyzed for static and dynamic eccentricity diagnosis and the finite element method (FEM) is utilized to precisely verify the proposed method. Mathematical-based model with consideration of both slot openings and non-sinusoidal winding function effects are the advantages of the proposed method over the previous researches in this field. Moreover, proposed method, which is based on mathematical modeling, could be easily applied to other types of electrical machines, and this feature is regarded as another key point of this paper. Copyright © 2016 John Wiley & Sons, Ltd.

Three-phase power distribution transformer banks (DTrBs) are widely applied to serve single-phase lighting loads and three-phase power loads in a medium-voltage three-phase four-wire (3Φ4W) power distribution systems simultaneously. Furthermore, the growing small-scale wind turbine generator (WTG) systems are directly connected to the secondary side of DTrBs. It has been found that the system imbalance of a power distribution system might be significantly enlarged when WTGs are operated in parallel. Because of the determination the system imbalances of these systems are extremely complicated. In this paper, we introduce an effective method to develop the mathematical models of asymmetrical DTrBs, rigorously. These models can be easily applied in an unbalanced 3Φ4W power distribution system for more detailed analyses. In addition, such a kind of unbalanced system will be solved with an aid of the computer program, Matlab^{®}/Simulink^{®}, to analyze the effects of system imbalances when an asymmetrical DTrB serves the single- and three-phase loads and the WTG system in parallel operation simultaneously. The simulation results and conclusion are of value to power distribution engineers for better planning, operating, and promoting their distribution system. Copyright © 2016 John Wiley & Sons, Ltd.

In this paper, Monte Carlo (MC) simulation has been applied for the analysis and stochastic calculus of far-field radiation from the small, large, and infinite open-ended waveguide arrays. Elements of the arrays are excited by the fundamental TE_{10} mode and with equal amplitude and linear phase. The simulated results from MC are compared closely with the finite element method (FEM). Numerical analysis based on FEM is performed using Ansoft High Frequency Structural Simulator to calculate the far-field radiation characteristics of the arrays. The accuracy and the effectiveness of the aforesaid method, which is based on Monte Carlo integration technique, are also demonstrated in uniformly and nonuniformly spaced waveguide arrays for pattern synthesis or achieving side lobe level reduction. The arrays with arbitrary shapes are simply evaluated by MC method in equal spacing array. It is found that by applying MC simulation, the open-ended waveguide arrays have the ability to produce the desired radiation pattern and could satisfy requirements for many applications. Copyright © 2016 John Wiley & Sons, Ltd.