Due to the increasing number of applications in engineering design and optimization, more and more atention has been paid to full-wave simulations based on computational electromagnetics. In particular, the finite-element method (FEM) is well suited for problems involving inhomogeneous and arbitrary shaped objects. Unfortunately, solving large-scale electromagnetic problems with FEM may be time consuming. A numerical scheme, called the dual-primal finite element tearing and interconnecting method (FETI-DPEM2), distinguishes itself through the partioning on the computation domain into non-overlapping subdomains where incomplete solutions of the electrical field are evaluated independently. Next, all the subdomains are ``glued'' together using a modified Robintype transmission condition along each common internal interface, apart from the corner points where a simple Neumann-type boundary condition is imposed. We propose an extension of the FETI-DPEM2 method where we impose a Robin type boundary conditions at each interface point, even at the corner points. We have implemented this Extended FETI-DPEM2 method in a bidimensional configuration while computing the field scattered by a set of heterogeneous, eventually anistropic, scatterers. The results presented here will assert the efficiency of the proposed method with respect to the classical FETI-DPEM2 method, whatever the mesh partition is arbitrary defined.

In this paper, a new numerical method of calculating rectangular busbar impedance is proposed. This method is based on integral equation method and partial inductance theory. In particular, impedances of shielded and unshielded three-phase systems with rectangular phase and neutral busbars, conductive enclosure, and use of the method are described. Results for resistances and reactances for these systems of multiple rectangular conductors have been obtained, and skin and proximity effects have also been taken into consideration. The impact of the enclosure on impedances is also presented. Finally, two applications to three-phase shielded and unshielded systems busbars are described. The validation of the proposed method is carried out through FEM and laboratory measurements, and a reasonable level of accuracy is demonstrated.

For the coaxial outer corrugated resonator, dispersion equations of TE and TM modes are derived by the surface impedance theory, and the first order transmission line equations with mode coupling coefficients are deduced by means of the transmission line and coupling wave theory. According to them, resonant frequency, diffractive quality factor and field profile of geometry of the eigen-mode about the coaxial outer corrugated resonator can be calculated. The effect of outer slot depth, tooth width as well as asymptotic angle of outer conductor and slope angle of inner conductor on resonant frequency and quality factor can be researched. Results show that changes of the outer slot depth and tooth width slightly affect the field frequency and quality factor and that the changes of the asymptotic angle of outer conductor and slope angle of inner conductor almost do not affect field frequency, but greatly affect quality factor.

The theory of even/odd mode based dual composite right/left handed (D-CRLH) unit cells is developed, and a unified modeling approach based on stubs is presented. The theory shows that these unit cells will have left-handed behavior if the even and odd mode corresponding stubs have dual behavior. Several unit cells are investigated. The proposed models agree with EM simulations. Experimental results confirm the presented theory.

An ultra-wideband (UWB) bandpass filter (BPF) with application oriented triple notches and simultaneously suppressed stopband is proposed. Implementing complementary split ring resonator (CSRR) and novel complementary meandered folded split ring resonators (CMFSRR) shaped defected ground structures (DGS) in the ground of proposed structure generates the triple notch in the UWB passband. The notch positions are functions of CSRR/CMFSRR profile dimensions. Stopband is suppressed using the dual attenuation poles generated by the double equilateral-U (DEU) shaped DGS. An approximate lumped equivalent circuit model of the proposed filter is presented. Measured results obtained are in good agreement with the equivalent circuit model and full wave electromagnetic (EM) simulation. The filter is small in size with an overall area of 26.06 mm × 11 mm.

In this paper, a novel circular-hexagonal fractal antenna is investigated for super wide band applications. The proposed antenna is made of iterations of a hexagonal slot inside a circular metallic patch with a transmission line. A partial ground plane and asymmetrical patch toward the substrate are used for designing the antenna to achieve a super wide bandwidth ranging from 2.18 GHz to 44.5 GHz with bandwidth ratio 20.4 : 1. The impedance bandwidth and gain of the proposed antenna are improved than the recently reported antennas which make it appropriate for many wireless communications systems such as ISM, Wi-Fi, GPS, Bluetooth, WLAN and UWB. Details of the proposed antenna design are presented and discussed.

In this paper, some optimal programs have been proposed through the analyses of transient grounding resistance (TGR) to reduce the grounding resistance using the finite-difference time-domain method. First, the TGR of various electrode types, lengths and sectional programs is studied, and it is found that a flat bar is the most financially efficient conductor to be used as grounding electrode. Enlarging grounding electrode length can reduce grounding resistance when it is shorter than the effective length, but the reduction effect declines as the length increases. Additionally, a series of small electrodes would lead to a much lower resistance than a single large one. Second, it is demonstrated that locally improving the soil near the grounding system is an efficient way of reducing the grounding resistance. Improving a limited area soil surrounding the lifting line would reduce the peak resistance significantly, while local enlarging electrodes surrounded soil conductivity can reduce the grounding system steady resistance obviously.

Electromagnetic interference (EMI) of the power supply system in electric vehicles will seriously affect the safety of the vehicle and passengers' health. So a model of power supply system is presented to analyze its conducted EMI in the paper. This model shows the effects of paralleled interleaving DC/DC converter, which contains the new circular current EMI characteristics. Also, a novel power battery model is established considering both the energy dynamic processes and the high frequency features. Firstly, the power electronics devices are studied as the most important part of the DC/DC converter. Then, the equivalent model of the paralleled interleaving DC/DC converter is set up to express the interference source features. Also, the power battery, which is the main energy storage equipment in electric vehicles, is modeled as EMI propagation paths. Furthermore, loads of the power supply system, such as lead acid battery and low voltage devices, are investigated to evaluate their immunity. Finally, the system model is established. The system EMI is analyzed to get their generating causes, time domain and frequency domain characteristics based on both simulations and experiments.

Simulations based on electromagnetic topology (EMT) have been carried out to analyze an external electromagnetic pulse interaction with a shielded coaxial cable linking two systems together. The proposed EMT approach, combined with the SPICE model of the shielded cable, can be applied in the transient simulation directly and used for the electromagnetic interference analysis of systems including nonlinear devices. The effects of the outer terminators, cable length, and connection of the voltage limiter on the induced voltages at the systems are studied by using the proposed EMT approach. It has been found that adding a resistance between the system's shielding enclosure and the ground can effectively reduce the coupling through the shielded cable. The cable length affects the pulse-widths rather than the magnitudes of the induced voltages. The results also show that the voltage limiter can reduce the induced voltages but at the same time result in mismatch at the source or load.

Passive millimeter (MMW) imaging can penetrate clothing to create interpretable imagery of concealed objects. However, the image quality is often restricted by low signal to noise ratio and temperature contrast as well as low spatial resolution. In this paper, we explore a four-channel passive MMW imaging system operating in the 8 and 3 mm wavelength regimes with linear vertical and horizontal polarization directions. Both registration between different channel images and segmentation of concealed objects are addressed. Multi-channel image registration is performed by geometric feature matching and affine transform, and then multi-level segmentation separates the human body region from the background, and concealed objects from the body region, sequentially. In the experiments, several metallic and non-metallic objects concealed under clothing are captured in indoors. It will be shown that our method can separate objects with higher accuracy than the conventional method.

A novel design of decoupling network for a compact three-element array is presented. The proposed decoupling network has simple and compact structure that can be implemented easily with microstrip lines. The conventional microstrip open stubs can be used to match the decoupled ports of the array. The proposed decoupling and matching network is applied to a compact three-monopole array operating at 2.4 GHz. Both the simulated and the measured results show that the ports of the array are well matched and decoupled at the operating frequency.

The utility of slotted waveguide antennas would be maximized if the bandwidth of the radiating elements matched that available in the waveguide. This was achieved using a spiral shaped slot cut through the broad-wall of a rectangular waveguide. The predicted total efficiency and peak realized gain were relatively uniform across the entire bandwidth. The current distribution around the slot was predicted to be similar to that around a conventional, center fed, slot spiral antenna, indicating similarity of radiation mechanisms. Finally, the antenna patterns for spiral shaped slots in waveguides manufactured from copper and carbon fibre reinforced polymer (CFRP) were shown to be similar to that predicted.

Tape-helix transmission lines and helical coils have important applications in communication technology, signal measurement, pulse delay, pulse forming and antenna technology. In this paper, a set of fully dispersive propagation theory based on matrix method is firstly introduced to explain the propagation characteristics of travelling electromagnetic waves in multiple stages of helical Blumlein transmission lines with finite lengths. The different stages of helical transmission lines are filled with different propagation dielectrics, and the effects of dispersion and dielectrics on the propagation matrix and S-parameter matrix of the travelling waves are analyzed in detail. Relations of the exciting current waves in the series-connected helical Blumlein transmission lines are studied, and the dispersive transmission coefficients and reflection coefficients of electromagnetic waves at different dielectric ports are also initially analyzed. As an innovation, the proposed fully dispersive propagation theory which was demonstrated by simulation and experiments can substitute the non-propagating tape-helix dispersion theory and the non-dispersive telegraphers' equation to analyze the helical transmission lines.

An analytical method based on combination of Fourier transform and Taylor's series expansion is presented for analyzing interaction of electromagnetic cylindrical waves with inhomogeneous planar media. In the proposed method, constitutive parameters and Fourier transformed electric and magnetic fields of the inhomogeneous layer are expressed using Taylor's series expansion. Then, the unknown coefficients of the fields are obtained based on Maxwell's equations and boundary conditions. The validity of the method is verified by considering some special types of inhomogeneous media and comparing the obtained results by this method with those of other reported methods. The results show that when Fourier transform is combined with Taylor's series expansion, a powerful and quick approach is provided for solving such problems.

In this paper, we propose a new antenna structure that can be adjusted for narrow band as well as UWB applications. The proposed antenna is of very simple geometry and easy to manufacture. It is monopole type antenna and made of copper. We present antennas with the same geometrical concept and different dimensions. Antenna designed for narrow band operation exhibits 3.7% bandwidth at 800 MHz frequency (S₁₁ < -10 dB). Two UWB antenna designs exhibit 77% bandwidth (from 2 to 4.5 GHz) and 54% bandwidth (from 2.6 to 4.5 GHz) and are of smaller size compared to the dielectric resonator antennas (DRA). Furthermore, it can be easily shown that using the proposed geometry broad family of antennas (for operation in various frequency bands) can be designed.

We present numerical time-domain modeling and validation framework for impulse-driven near-field thermoacoustics imaging. It has been recently demonstrated that this new imaging approach comprises a viable alternative for high performance and low-cost imaging using the thermoacoustic phenomenon. Placement of the imaged object in a close vicinity (near field) of an antenna elements along with generation of ultrashort (nanosecond) duration high-voltage excitation impulses further provide high imaging resolution and ensure that sufficient level of electromagnetic energy reaches the object under investigation. In order to analyze the measured results and also provide a design and optimization framework, this work presents a full-wave computational electromagnetic framework which couples the near-field electromagnetic field to the acoustic signal generation. The numerical method comprises a finite integral time domain method (FITD) based on the industry standard CST 2010 software package. The results can be further utilized for normalization and quantification of the generated images.

In this paper, a new technique is proposed to optimize the conflicting parameters like low value of maximum side lobe level (SLL), narrow beam-width of the main beam and low value of maximum sideband radiation level (SRL) of time-modulated linear antenna arrays (TMLAAs). The method is based on minimizing a multi-objective fitness function by using single-objective differential evolution algorithm (DEA) technique. The method is applied to both uniformly excited TMLAA (UE-TMLAA) and non-uniformly excited TMLAA (NUE-TMLAA) to synthesize low side lobe optimum pattern at operating frequency by suppressing the sideband radiation level to a sufficiently low value. For UE-TMLAA only the switch-on time durations of the array elements and for NUE-TMLAA the switch-on time durations and the static amplitudes with predetermined dynamic range ratio (DRR) of static amplitudes are taken as the optimization parameters for the DEA. To show effectiveness of the proposed approach, the single-objective DEA optimized results are compared with those obtained by other single objective and multi-objective techniques that has been reported previously. Also, first null beam width (FNBW) and half power beam width (HPBW) of the DEA optimized patterns at fundamental radiation are compared with those of the Dolph-Chebyshev (D-C) pattern of same SLL.

The practically important case of a dielectric-loaded tape helix enclosed in a coaxial perfectly conducting cylindrical shell is analysed in this paper. The dielectric-loaded tape helix for guided electromagnetic wave propagation considered here has infinitesimal tape thickness and infinite tape- material conductivity. The homogeneous boundary value problem is solved taking into account the exact boundary conditions similar to the case of anisotropically conducting open tape helix model [1,2]. The boundary value problem is solved to yield the dispersion equation which takes the form of the solvability condition for an infinite system of linear homogeneous algebraic equations viz., the determinant of the infinite-order coefficient matrix is zero. For the numerical computation of the approximate dispersion characteristic, all the entries of the symmetrically truncated version of the coefficient matrix are estimated by summing an adequate number of the rapidly converging series for them. The tape-current distribution is estimated from the null-space vector of the truncated coefficient matrix corresponding to a specified root of the dispersion equation.

With the renewed application of millimeter technology in remote sensing, radio astronomy, and meteorological satellite, millimeter wave antennas of electrically large aperture are frequently deployed. Shaping techniques are accordingly developed to meet different requirements. In this paper, a shaping technique for the scanning reflector antenna system of a remote sensing spacecraft is presented. The shaping technique is based on Fourier optical theory to control the maximal radiating direction of the antenna system. To implement such functionality, a new shaping technique of the sub-reflector has been developed. In addition, rotation of the shaped sub-reflector can achieve scanning purpose with identical footprints in all scanning angles. Case studies have been performed to verify the shaping technique.

This paper presents a novel quasi-elliptic function lowpass filter (LPF) by using quasi-lumped elements. The proposed LPF is firstly based on a seven-order Chebyshev response lowpass prototype. Then, a series branches of shunt resonant LC circuit is introduced in the filter design to provide a transmission zero close to the transition band, which can improve the roll-off rate of proposed LPF significantly. To implement the lumped elements of lowpass prototype, the high-impedance meander lines are employed to realized the inductors while inter-digital microstrip lines and the microstrip parallel-plate structures are used to realize the capacitors. To validate the proposed method, a LPF with 3 dB cutoff frequency fc at 1.9 GHz is designed and fabricated. The measured results show that the fabricated LPF has a sharp roll-off rate up to -142 dB/octave and -15 dB harmonic suppression from 1.1f_c to 9.7f_c. Moreover, the fabricated LPF also has a compact size of 0.1λ_gc × 0.11λ_gc. Good agreement can observed between the simulation and measurement.