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This paper presents an accurate design technique for a low-pass filter (LPF) with a dumbbell-shaped slot (DSS) in the ground plane. In the proposed technique, a new simplified DSS inductance equation is suggested and modified to account for the stub parasitic inductance of the LPF. The compensated inductance of the DSS is determined from the modified DSS inductance equation. As a result, additional tuning is not required to achieve the desired LPF cutoff frequency. The stub section of the LPF is analyzed by transmission line theory to derive the stub parasitic inductance equation. 3-D electromagnetic field and circuit simulation validate the theoretical analysis. Two LPFs are designed, simulated, measured, and compared for further validation. One LPF is designed through a conventional method and the other through the proposed method. Both simulated and measured results show very good agreement in the proposed design. Index Terms--Circuit simulation, electromagnetic bandgap (EBG), electromagnetic (EM) field analysis, low-pass filter (LPF), microstrip, parasitic effect.

A numerical method for the analysis of the fields in highly oversized waveguides is proposed in this paper. This method allows the simulation of the fields on waveguide walls with arbitrary surface deformations in the case that the waveguide is highly oversized, and the wall deformations are shallow and smooth. Combined with the analysis method, an algorithm has been developed for synthesizing the waveguide wall to provide a desired field distribution. As an example, a 309.6-mm-long waveguide launcher has been designed for a 170-GHz coaxial-cavity gyrotron to transform the [TE.sub.34,19] cavity mode to a fundamental Gaussian distribution. An efficiency of transformation to the desired fundamental Gaussian mode of 96.3% has been obtained at the launcher aperture, whereas the transformation efficiency is just 86% using a conventional dimpled-wall launcher with a length of 660 mm. Index Terms--Cylindrical waveguides, gyrotrons, mode conversion, waveguide antennas.

The scattering by an arbitrary collection of perfectly conducting connected strips is analyzed for TE incidence. The studied configurations include both closed and open polygonal cross-section cylinders, as well as more complicated structures in which more than two strips are connected at a point. The proposed method is very efficient as few expansion functions are needed in a Galerkin scheme. This is achieved by means of expansion functions factorizing the correct edge singularity of the electromagnetic field, and ensuring the continuity of the current at connecting points. Index Terms--Conducting cylinder, electromagnetic scattering, Galerkin method.

In this paper, we introduce an approach to analyze the interaction between antennas and the propagation channel. We study both the antennas and the propagation channel by means of the spherical vector wave mode expansion of the electromagnetic field. Then we use the expansion coefficients to study some properties of general antennas in those fields by means of the antenna scattering matrix. The focus is on the spatio-polar characterization of antennas, channels and their interactions. We provide closed form expressions for the covariance of the field multimodes as function of the power angle spectrum (PAS) and the channel cross-polarization ratio (XPR). A new interpretation of the mean effective gains (MEG) of antennas is also provided. The maximum MEG is obtained by conjugate mode matching between the antennas and the channel; we also prove the (intuitive) results that the optimum decorrelation of the antenna signals is obtained by the excitation of orthogonal spherical vector modes. Index Terms--Channel modeling, cross-polarization ratio, mean effective gain, scattering matrix, spherical vector wave expansion.

Interfacing of disparate simulation programs is increasingly undertaken to gain a deeper understanding of their functionality and exploit their merits for modeling complex systems. In this paper, techniques for interfacing field and circuit equations of low-frequency electromagnetic apparatus are reviewed, analyzed, and classified into two main categories of direct and indirect methods according to the coupling method. Each category includes a vast array of techniques employing different methods for circuit modeling. The field analysis is restricted to 2-D finite-element method, which is a widely used numerical technique for modeling magnetic behavior of power apparatus. The main features and problems associated with each technique are summarized. Methods for coupling of mechanical equations are addressed in a separate section. A comprehensive list of references is also included at the end of this paper to provide further information to the readers. Index Terms--Circuit simulation, electromagnetic (EM) fields, finite-element methods (FEMs), interfacing.

The paper deals with detailed investigation of the electromagnetic forces in the end zone of turbine generator. The electromagnetic field is analyzed using 3-D FEM computation. The regions of interest are the stator and rotor end cores including the zone of the teeth and the end windings. The dynamic behavior of the local electromagnetic force densities is studied in accordance with the working mode. Two modes at the leading and at the lagging power factor are considered. Comparison between the ratio of the local electromechanical loads under considered modes and the relevant loads at the rated mode is discussed and appropriate conclusions are drawn. Calculations are implemented on a 200 MW turbine generator. Index Terms--Force densities, turbo-generator end zone.

Electromagnetic launch (EML) system has such advantages as high thrust, good controllability, reusable, etc., and so it will be widely used in the future. As a launching motor, a double-side plate Permanent Magnet Linear Synchronous Motor (PMLSM) can provide high instantaneous thrust. According to the characteristics of the EML, this paper studies the thrust characteristics of double-side plate PMLSM. Analyzes the thrust and thrust ripple characteristics in different conditions including: phase current, length of air-gap, height of secondary permanent magnet and pole arc efficient. The analysis results provide a foundation for the optimum design of electromagnetic launcher. Index Terms--EML, PMLSM, thrust, thrust ripple.

The free space time domain coupled electric and magnetic field integral equation solution for Maxwell's differential equations is derived. The coupled field integral equation solution is expressed as a vector containing the electric and magnetic fields found in terms of a surface integral over the equivalent surface currents on a boundary, an integral over the electric and magnetic current sources in the region enclosed by the boundary, and a volume integral over the initial field in the bounded region. Because of the irreversibility of the vector differential equation and the lack of spatial symmetry in the corresponding free space dyadic Green function, as a starting point the Green differential equation is replaced by the reciprocal (adjoint) equation and the dyadic Green function is replaced by its transpose. These replacements plus identities that relate the components of the Green function to its transpose lead in a straightforward way to the coupled field solution. The general dyadic expression derived here provides a framework for developing source current, boundary integral, and propagator methods that are based on the interaction between the electric and magnetic vector field components in the time domain. Index Terms--Coupled field, dyadic Green function, dyadic Green's function, integral equations, Maxwell equations, propagator.

This paper promotes the use of numerical methods as an alternative tool in order to evaluate and manage electromagnetic compatibility in health care facilities. Numerical analysis is performed employing the Transmission Line Modeling (TLM) Method and Kriging, which are supported by measurement tests, providing a reliable assessment of the electromagnetic profile established in clinical environments. Index Terms--Electric field measurement, health care facilities, numerical analysis, transmission line modeling method.

In this contribution, we present a proper extension of the finite-element method based on a variational formulation which is able to take into account the effects of nonconventional materials in the evaluation of the electromagnetic field inside a cavity bounded by both closed and open boundary conditions. As a numerical application, we show how nonconventional materials like, for instance, metamaterials can be used in the design of integrated circuits, in order to reduce the proximity effects among planar transmission lines. Index Terms--Anisotropic media, crosstalk, finite-element method (FEM), microstrip couplers.

In the course of designing and analyzing electromagnetic devices, open boundary field problems often need to be solved. The mapping of the infinite exterior of a finite circular region onto the interior of that closed circular region has emerged and established itself as one of the best methods. However, as a result of the work done in the past in solving homogenous exterior regions, this paper shows that this mapping method has been mistakenly taken to apply only when the exterior consists of air or, at best, some other homogeneous medium. This paper validates the method for problems with uniformly inhomogeneous exterior regions and makes possible the solution of a new class of problems by this powerful method. Index Terms--Computational theory, computer-aided analysis, design automation, electromagnetic fields, finite elements.

Accurate and reliable evaluation of the electromagnetic field scattered by dielectric objects is a canonical problem in the electromagnetic community. In the framework of integral equation formulations, iterative techniques, and in particular conjugate gradient (CG) schemes, are widely used. However, when the number of parameters grows, CG techniques may become too demanding from a computational point of view. In this paper, we show that many forward scattering problems can be conveniently solved by means of very simple series expansions, which allow a lower computational complexity and memory storage with respect to other iterative schemes. In particular, we consider three different series expansions, namely: 1) the traditional Born series; 2) the contrast source-extended Born series, which is recently introduced by rewriting the traditional source-type integral equations; and 3) a new series, which is a hybridization of the previous ones. Theoretical conditions for the applicability of the series expansions are discussed, and practical tools to foresee that a problem can be solved by means of these simple iterative schemes are provided. Numerical examples are reported for the sake of comparison and to assess performance. Index Terms--Contrast source extend Born model, electric field integral equation, electromagnetic scattering, integral equations.

Experimental data showing the transient behavior Of tall objects struck by lightning are reviewed. The influence of this transient behavior, illustrated by simple calculations, on measured lightning current and measured remote electromagnetic fields is discussed. The estimated equivalent impedance of the lightning channel at the time of the initial current peak is appreciably higher than the characteristic impedance of an ordinary tall object (a factor of 3 or so for both the Ostankino and Peissenberg towers and about a factor of 2 for the CN tower). The grounding impedance of a tower is typically lower than its characteristic impedance. Thus, the current reflection coefficient is negative at the top and positive at the bottom of the tower. The similarity of the statistical distributions of subsequent-return-stroke peak currents in: 1) natural downward lightning; 2) natural upward (object-initiated) lightning; and 3) rocket-triggered lightning measured at objects with heights ranging from 4.5 to 540 m suggests that current peaks are not significantly influenced by the presence of a tall object, provided that measurements are taken at the top of the object. This inference is consistent with modeling results of Melander who showed that the current peaks measured in Switzerland and Italy at the top of 70-m and 40-m towers, respectively, are essentially unaffected by the presence of the towers. If lightning current could be represented by an ideal current source, current at the top of the object would be equal to the source current at all times. The peak current measured at the bottom of a tall object is usually more strongly influenced by the transient process in the object than the peak current at the top. For example, peak currents measured in the lower part of the 540-m Ostankino tower are about a factor of two higher than the peak currents measured near the tower top because the current reflection coefficient at the bottom of the tower is near +1. Observations and modeling suggest that a tall metallic strike object replacing the lower part of lightning channel serves to enhance the lightning-radiated electromagnetic fields relative to the fields due to similar lightning discharges attached directly to ground, this effect being more pronounced for the sharper lightning current pulses. Index Terms--Lightning, lightning current, lightning electromagnetic field, tall objects, transients, traveling waves.

We discuss the design, construction, and performance of an all-electric rifle-caliber railgun. The railgun, pulsed power supply, and injector weigh approximately 38 kg. The barrel is 0.5 m in length and has a 5 x 10 mm rectangular bore. Neodymium--iron--boron permanent magnets provide the augmentation field. Projectiles ranging in mass from 0.5 to 1 g were fitted with both sliding and plasma contacts and were tested in the railgun. The sliding contact projectiles proved to be the most efficient. The pulsed power supply consisted of ten electrolytic capacitors arranged in a type B Guillemin network that were charged to a maximum of 450 V. The maximum railgun current was approximately 15 kA over a 1- to 4-ms time period. The maximum measured projectile velocity was 450 m/s with a 0.5-g projectile. Projectile materials were brass, tungsten, aluminum, titanium, stainless steel, copper, graphite, and copper-impregnated graphite and the rail materials were brass, copper, copper-chromium, and copper-impregnated graphite. The copper-impregnated graphite was the best material for both the rail and the projectile because of its low erosion rate and relatively low electrical resistivity. The results show that the highest measured railgun efficiency was slightly less than 1%. Index Terms--Electromagnetic forces, electromagnetic guns, propulsion, railguns.

A new algorithm for calculating HVDC fields in the presence of corona and strong wind based on boundary element method is presented. The new algorithm uses an auxiliary Poisson's equation for updating the space charge density during the iteration. The iteration process is convergent for wind velocities tested up to 12m/s.

Microwave electric fields of an X-band H-plane tapered iris are calculated and plotted using the moment method for the first time. The moment method results are compared with previously obtained experimental measurements and numerical results based on an equivalent circuit approach, giving confirmation that the tapered iris is both a reciprocal and asymmetrical network. The moment method results now reveal that the asymmetry stems from the asymmetry in the phase of the input and output voltage reflection coefficients, their magnitudes being equal.

The analysis of a double-clamped graphene device positioned over a planar waveguide in which propagate electronic fields up to 60 GHZ is presented. Many double-clamped graphene flakes have displayed good characteristics in enabling and disabling the propagation of high-frequency electromagnetic fields and these characteristics are retrieved in a graphene switch based on the rapid change in the resistivity due to an applied gate voltage.

The problem of evaluation of the electromagnetic emissions from large power electrical rotating machinery is considered. The results of three measurement campaigns are reported: emissions are correlated with the operating conditions and the characteristics of the machine under test. The measured electric and magnetic field spectra are treated so that they may be used as a reference for preliminary evaluation on similar machines.

This paper deals with the broad-band modeling of a realistic power converter shield used in an electric vehicle. To validate such a model, comparisons between computation and measurements are required. As it is not practical to characterize experimentally the true radiation of a power converter through its enclosure, a reciprocal approach has been defined in which the enclosure is illuminated by a plane wave (receiving configuration). The associated experimental setup has been carefully defined and tested. At low frequency, the model is based on radiation through apertures in a simple cavity. At higher frequency, the Aseris-BE code, which is based on the boundary integral equations technique, has been used for computation. An optimal and realistic mesh of the enclosure suitable for the Aseris-BE code has been built by making numerous comparisons between computation and measurements, which have shown how to improve the mesh. Index Terms--Aseris-BE code, boundary integral equation, electric vehicle, electromagnetic (EM) field simulator, power converter shield, shielding effectiveness.

A novel particle simulation code is described that self-consistently models certain classes of laser--plasma interactions without resolving the optical cycles of the laser. This is accomplished by separating the electromagnetic field into a laser component and a wake component. Although the wake component is treated as in a fully explicit particle-in-cell (PIC) code, the laser component is treated in the high-frequency limit, which allows the optical cycles to be averaged out. This leads to enormous reductions in computer time when the laser frequency is much greater than all other frequencies of interest. This work is an extension of the work of Mora and Antonsen, Jr. [1], [2], who derived the time-averaged equations coupling the laser with the particles and developed a code to solve these equations in the quasi-static limit. The code presented here is distinguished by the fact that it is useful when the plasma length is much less than the laser pulse length. Also, it is already parallelized and should be straightforward to extend to three dimensions. Index Terms--Particle code, plasma simulation.

The problem of predicting the voltages and currents induced on a printed circuit multiconductor transmission line (MTL) network by an impinging transient plane wave electromagnetic field is considered. The MTL network contains nonlinear circuit elements and test cases with various dielectric substrates are examined. Numerical predictions based on quasi-TEM models of the MTL's and modified nodal analysis (MNA) models of the lumped element junctions are compared to experimental results obtained in the time domain using a GTEM cell. As has been done in the past, the effect of the incident plane wave is introduced as forcing functions in the MTL equations. The primary goal of this paper is to quantify the accuracy of the various commonly used quasi-TEM mathematical time-domain models. It is shown that when modeling the forcing function terms, it is important to take into account the perturbation of the incident plane wave due to the dielectric substrate. (The experimental-numerical comparisons herein are shown for the case of end-fire illumination since it best demonstrates this point.) Neglecting the dielectric effect on the incident transient pulse, even for substrates with low dielectric constant, produces poor results. Index Terms--Experimental validation, field coupling, measurements, modified nodal analysis, modeling, MNA, MTL, MTL network, nonlinear circuits, printed circuit board, surface wave, transient.

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A new approach based on QR compression of the off diagonal blocks of the impedance matrix arising in integral equations solutions of electromagnetic (EM) scattering problems, previously implemented for finite and irregular gratings, is extended here to an arbitrarily shaped obstacle. The main tool consists in dividing the entire surface scatterer into subdomains and in assembling the global impedance matrix as a combination of the macromatrices associated to each interaction of any patch on the other. Correlation between compression rate and accuracy of field computation is drawn up. An experimental study is performed to optimize the method relatively to the two competing parameters: accuracy and cost. Finally, it is shown that this method works equally well in both the high and the low frequency domain and also with an inclusion of a small detail in a large object. Index Terms--Electromagnetic (EM) scattering, large size problems, matrix compression, method of moments (MoM).

An analytical solution for the bi-static electromagnetic (EM) scattering from an acoustically excited vibrating dielectric circular cylinder is presented. The incident acoustic wave causes a boundary deformation as well as a dielectric inhomogeneity within the dielectric cylinder. First, a perturbation method is developed to calculate the EM scattering from a slightly deformed and inhomogeneous dielectric cylinder. Then, assuming the vibration frequency is much smaller than the frequency of the incident EM wave, a closed form expression for the time-frequency response of the bi-static scattered field is obtained. The solution for acoustic scattering from an elastic cylinder is applied to give the displacement on the surface as well as the compression and dilation within the cylinder. Both the surface displacement and the variation in material density (dielectric constant fluctuation) within the cylinder contribute to the Doppler component of the EM scattered field. Results indicate that the Doppler frequencies correspond to the mechanical vibration frequencies of the cylinder and that the Doppler components only become sizeable near frequencies corresponding to the natural modes of free vibration in the cylinder. These resonances depend only on the object properties and are independent of the surrounding medium. Thus, utilizing the information in the Doppler spectrum scattered by an acoustically excited object vibrating at resonance could provide a means for buried object identification. Index Terms--Acoustics, Doppler spectra, electromagnetic scattering, perturbation techniques.