Features of spatial power spectrum (SPS) of scattered radiation in a randomly inhomogeneous medium with strongly prolated anisotropic inhomogeneities of dielectric permittivity are investigated. In single scattering approximation, it has been shown that a pronounced gap along a direction of prolate inhomogeneities appears in SPS. Features of SPS of multiple scattered waves at oblique illumination of a boundary of randomly-inhomogeneous medium with prolate irregularities have been analytically studied using smooth perturbation method taking into account diffraction effects. Numerical calculations have shown that with an increase of a distance passing by the wave in random media, SPS has a double-peaked shape and a gap substantially increases. Its maximum is slightly changed and the width is broadening. The results have been obtained analytically for the first time and could find extensive practical application in optics and be useful in development of principles of remote sensing of random media.

Numerical analysis of a generalized form of the recently developed electric and magnetic current combined field integral equation (JM-CFIE) for electromagnetic scattering by homogeneous dielectric and composite objects is presented. This new formulation contains a similar coupling parameter α as CFIE contains in the case of perfectly conducting objects. Two alternative JM-CFIE(α) formulations are introduced and their numerical properties (solution accuracy and convergence of iterative Krylov subspace methods) are investigated. The properties of these formulations are found to be very sensitive to the choice of α and to the permittivity of the object. By using normalized fields and currents the optimal value of α minimizing the number of iterations becomes only weakly dependent on the permittivity object. Using linear-linear basis functions instead of the more conventional constant-linear (RWG) basis functions the solution accuracy can be made less dependent on the choice of α.

A method based on adaptive neuro-fuzzy inference system (ANFIS) for computing the effective permittivity and the characteristic impedance of the micro-coplanar strip (MCS) line is presented. The ANFIS is a class of adaptive networks which are functionally equivalent to fuzzy inference systems (FISs). A hybrid learning algorithm, which combines the least square method and the backpropagation algorithm, is used to identify the parameters of ANFIS. The effective permittivity and the characteristic impedance results obtained by using ANFIS are in good agreement with the theoretical and experimental results reported elsewhere.

In this paper, planar multilayered antireflection coatings composed of isotropic and dispersive common materials and metamaterials (DPS, DNG, ENG, and MNG) are designed and optimized at Ku band under circularly polarized oblique plane wave incidence by a full-wave method and combination of the method of least squares (MLS), genetic algorithm (GA) and conjugate gradients (CG). The body on which the coating is applied may be selected as PEC, plexiglas, or any other material. As a result a new class of radar absorbing materials (RAM) are obtained, which may be effectively used for antireflection coatings. Furthermore, guidelines are presented for the selection of correct signs for the real and imaginary parts of propagation constant k and intrinsic impedance η.

This paper presents a computational approach to the two-dimensional time domain inverse scattering problem of a dielectric cylinder based on the finite difference time domain (FDTD) method and the particle swarm optimization (PSO) to determine the shape, location and permittivity of a dielectric cylinder. A pulse is incident upon a homogeneous dielectric cylinder with unknown shape and dielectric constant in free space andthe scattered fieldis recorded outside. By using the scattered field, the shape and permittivity of the dielectric cylinder are reconstructed. The subgridding technique is implemented in the FDTD code for modeling the shape of the cylinder more closely. In order to describe an unknown cylinder with arbitrary shape more effectively, the shape function is expandedb y closedcubicspline function insteadof frequently used trigonometric series. The inverse problem is resolved by an optimization approach, and the global searching scheme PSO is then employedto search the parameter space. Numerical results demonstrate that, even when the initial guess is far away from the exact one, good reconstruction can be obtained. In addition, the effects of Gaussian noise on the reconstruction results are investigated. Numerical results show that even the measured scattered E fields are contaminated with some Gaussian noise, PSO can still yield good reconstructed quality.

This paper focuses on a tutorial overview of defected ground structure (DGS). The basic conceptions and transmission characteristics of DGS are introduced and the equivalent circuit models of varieties of DGS units are also presented. Finally, the main applications of DGS in microwave technology field are summarized and the evolution trend of DGS is given.

A set of scalar differential equations for treating scattering by rotationally symmetric radially inhomogeneous anisotropic sphere is presented. These equations may easily be treated by applying the integral equation method that has been developed. Besides a possible different expansion in a Neumann series is also discussed.

The sum and difference multiple channels were usually applied to the monopulse system only in a receiver. But this paper presents a technique of multiple beam modulation transmitted by the sum and difference multiple channels. The modulated field is designed as three chip signal vectors whose sum and whose differences are controlled by the gains of antennas,and the angle between the sum vector and the differential vector depends on the phase error between the channels so that the different microwave signals can be transmitted in the different directions. A receiver with single-antenna can extract azimuth and elevation with respect to the transmitter. Simulation results show that the proposed modulation system has been successfully designed to integrate digital communication with direction-finding in the way of the reverse monopulse.

A theoretical analysis of the lateral shift for an electromagnetic beam reflected from an uniaxial anisotropic slab coated with perfect conductor is presented. The analytic expression for the lateral shift is derived by using the stationary-phase approach, and the conditions for negative and positive lateral shifts are discussed. It is shown that the lateral shift depends not only on the slabthic kness and the incident angle, but also on the constitutive parameters of the uniaxial medium. Enhancement and suppression of lateral shift are observed and are attributed to the interference between the reflected waves from the two interfaces of the slab. By tuning the thickness of the slaband material parameters, large negative and positive shifts can be attained. In particular, when total reflection occurs at the upper interface, the lateral shift will saturate with increasing slabthic kness.

A new full-wave Parabolic --- Integral Equation Method (PE-IEM) for the simulation of wave propagation in realistic, highly complex indoor communication environments is proposed, together with an extensive validation via measurements. The method is based on a wide-angle parabolic equation, further enhanced by an integral equation correction and is capable of providing good approximations of the electromagnetic fields and the received power, incorp orating all fundamental propagation mechanisms in a single simulation. For a rigorous validation, it has been applied in a complex twelve-room office space and compared with measurements at the two different frequencies of 1 GHz and 2.5 GHz. The accuracy of the approximation is within reasonably expected margins, while the method retains all the advantages of full wave methods and it also has moderate requirements of computational resources.

In this paper an improved particle swarm optimization algorithm (IPSO) for electromagnetic applications is proposed. In order to overcome the drawbacks of standard PSO, some improved mechanisms for velocity updating, the exceeding boundary control, global best perturbation and the simplified quadratic interpolation (SQI) operator are adopted. To show the effectiveness of the proposed algorithm, a selected set of numerical examples, concerned with linear as well as planar array, is presented. Simulation results show that the refined pinpointing search ability and the global search ability of the proposed algorithm are significantly improved when compared to the particle swarm optimization (PSO) and Genetic Algorithm (GA).

The societal and technological priorities of the world have been continuously changing because of complex computer and technology-driven developments in everywhere like communications, health, defense, economy, etc. Electromagnetic (EM) systems have become more and more complex however the explosive growth of computer capabilities has revolutionized the design and analysis of such complex systems. This has made interdisciplinary exposure necessary in modern EM engineering, also has brought up discussions of educational challenges and novel teaching approaches that confront wave-oriented EM engineering in the 21st century. This paper reviews EM computer simulation strategies and summarizes novel virtual tools that may be used in connection with classical EM lectures as well as with a newly proposed EM Engineering Program.

Excitation of the electromagnetic fields by a wide-band current surge, which has a beginning in time, is studied in a cavity bounded by a closed perfectly conducting surface. The cavity is filled with Debye or Lorentz dispersive medium. The fields are presented as the modal expansion in terms of the solenoidal and irrotational cavity modes with the time-dependent modal amplitudes, which should be found. Completeness of this form of solution has been proved earlier. The systems of ordinary differential equations with time derivative for the modal amplitudes are derived and solved explicitly under the initial conditions and in compliance with the causality principle. The solutions are obtained in the form of simple convolution (with respect to time variable) integrals. Numerical examples are exhibited as well.

A novel compact Archimedean spiral antenna with gaploading is investigated in this paper. A circular frame sharing the same centre with the spiral elements introduces a capacitive gap. By adjusting the width of the gap and the width of the circular frame, the initial resonant frequency of the proposed antenna is shifted from 2.79 to 1.93 GHz. Compared with the traditional Archimedean spiral antenna with the same lowest operation frequency, the area of the proposed antenna can be reduced by more than 30simulated radiation pattern results.

The effect of cold plasma beam on electromagnetic whistler wave with perpendicular AC electric field has been studied by using the unperturbed Lorentzian (Kappa) distribution in the Earth's atmosphere for relativistic plasma. The cold plasma has been described by a simple Maxwellian distribution where as Lorentzian (Kappa) distribution function has been derived for relativistic plasma with temperature anisotropy in the presence of a perpendicular AC electric field to form a hot/warm background. The dispersion relation is obtained by using the method of characteristic solutions and kinetic approach. An expression for the growth rate of a system with added cold plasma injection has been calculated. Results for representative values of parameters suited to the Earth's magnetosphere has been obtained. It is inferred that in addition to the other factors, the relativistic plasma modifies the growth rate and it also shifts the wave band significantly. The relativistic electrons by increasing the growth rate and widening the bandwidth may explain a wide frequency range of whistler emissions in the Earth's magnetosphere.

Forward scattering from a finite, right-circular cylinder is analyzed as a function of size. Both axial and broadside incidence are treated. Predictions based upon combinations of Physical Optics, Wu's series, and empirical formulas are compared with numerical results from the moment method. The analysis examines cylinders that vary between 1 to 20 wavelengths in radius and 0 to 20 wavelengths in length. Approximate formulas accurately model the RCS of cylinders as small as one wavelength in radius. Accuracy of predictions improves with increase in cylinder size.

In this paper two-dimensional problem of plane-wave diffraction by a "fractional strip" is studied. "Fractional strip" is introduced as a strip with fractional boundary conditions (FBC) involving fractional derivatives of the field components. FBC describe intermediate boundary between perfect electric conductor (PEC) and perfect magnetic conductor (PMC). It is shown that "fractional strip" has scattering properties similar to the well-known impedance strip. For one important case of fractional order equal to 0.5 the solution of the wave diffraction problem by a "fractional strip" can be found analytically. Detailed comparison analysis of the physical characteristics of the scattered fields for both fractional and impedance strips is presented. The relation between the fractional order and the value of impedance is derived. It is shown that in a wide range of input parameters the physical characteristics of the "fractional strip" are similar to the strip with pure imaginary impedance.

In this paper we evaluate the potential of a 5-element monopole array incorporated into a handheld device for beamforming in the 5.0-GHz band. The geometry of the handset consists of a 5-element array: four elements located at the handset corners and the fifth-element located at the center. Also, the interaction of the antenna array, mounted on a mobile handset, with a human head phantom is investigated. Firstly, the spatial peak specific absorption rate (SAR) values of 5-element array antennas for mobile handsets in the vicinity of a spherical phantom of a human head are evaluated numerically as a function of the distance between the handset and the head phantom for two different scenarios. Next, the effect of the human head on the handset radiation pattern is studied. The effect of different handset positions on the radiation pattern is also considered. The particle swarm optimization (PSO) algorithm is used to optimize the complex excitations of the adaptive arrays elements in a mutual coupling environment for beamforming synthesis. All numerical simulations are performed using the FEKO Suite 5.3 software. To validate the numerical simulations, we first perform two validation tests and compare the numerical results with published simulated and measurement results.