Propagation of waves in circular waveguide withth e boundary condition of hard surface is considered. The waveguide is filled with uniaxial chiral material. This study is a generalization of previously studied cases withisotropic chiral or anisotropic material filling. The eigenvalue equation is formed and the corresponding eigenmodes are presented. It is seen that the hard surface boundary condition simplifies the field analysis remarkable. While the eigenwaves in anisotropic waveguide were TE and TM fields in this more general case the eigenwaves are elliptically polarized hybrid fields. Since the eigenwaves are certain combinations of TE and TM fields and propagate withdifferen t propagation factors, uniaxial chiral medium can be used for polarization transformation. Reflection and transmission from a uniaxial chiral section of a waveguide is analyzed withn umerical examples.

An analytical model of a grid composed of small S-shaped conducting particles located on the surface of a dielectric slab is presented. This approach replaces the original one-layer structure with metallic particles printed on the interface by a multilayered structure with homogenized permittivities for each layers. This way one can homogenize the arrays of small resonant particles. The analytical model is verified by numerical simulations for the case of normal incidence of the plane wave. The homogenization is possible due to the small sizes of S-particles compared to the resonant wavelength in the substrate and due to the small thickness of the whole structure.

We consider oscillations in cylindrical slotted resonators formed by combinations of rectangular domains with several slots cut in the walls using the methods of approximate semi-inversion of integral operator-valued functions with a logarithmic singularity of the kernel. The initial boundary value problems for the Helmholtz equation are reduced to Fredholm integral equations and systems of integral equations of the first kind with a logarithmic singularity. In the case of narrow slots, the dispersion equations are obtained and evaluated using perturbations and the small-parameter method. Eigenfrequencies and eigenfields are calculated explicitly. The values of geometrical and material parameters are determined that lead to the interaction of oscillations. The results obtained are used for improving the design of filters and switches on the basis of simple model prototype structures.

A Combined Genetic Algorithm and Method of Moments design methods is presented for the design of unusual near-field antennas for use in Magnetic Resonance Imaging systems. The method is successfully applied to the design of an asymmetric coil structure for use at 190 MHz and demonstrates excellent radiofrequency field homogeneity.

This paper presents an improved variant of timedomain method for predicting crosstalk on parallel-coupled matched terminated microstrip lines. This method derives simple near-end and far-end time-domain crosstalk expressions which are applicable to lossless case with significant harmonic frequency < 1 GHz. The expressions are in polynomial form with geometrical dimensions of the structure and stimulus information as the only required entry parameters. They are simpler as compared to other methods because the difficult-to-determine distributed RLCG electrical parameters of the coupled lines are not needed. A look-up table for the polynomial coefficients is generated for easy application of this technique. The expressions are applicable for board thickness of 4-63 mils, 30-70Ω line characteristic impedance, 0.5W-4.0W (where W is the line width) inner edge to edge separation, and 3-5 dielectric constant. For significant harmonic frequency > 1 GHz, the effect of both losses and dispersion on the crosstalk levels is accounted for by investigating the gradient of the distorted driving signal. The peak crosstalk levels are then predicted by modifying the time derivative term in the lossless expressions. In addition, the far-end crosstalk is proved to saturate at half of the magnitude of the driving signal entering the active line. The saturation phenomenon is studied from the viewpoint of difference in odd-mode and even-mode propagation velocities.

The paper deals with proposition and evaluation of new and specific methods to represent vector radar data acquired by means a side-looking measurement in order to use compression process of Lind, Buzo, Gray (LBG), and Kohonen's self organizing feature maps of topology. The aim is to enable after coding, transmission, and decoding a high-resolution reconstruction image using the Synthetic Aperture Radar (SAR) methods. The approach proposed for compression uses the statistical properties of the signals to be compressed in order to perform the vector quantification in an optimal way.

A new synthesis algorithm for shaped, double-reflector antennas with complex array feed is presented. The approach presented here aims to improve the efficiency of synthesis techniques without missing the required accuracy. The algorithm is based on a convenient splitting of the original problem into two phases, each one involving a sub-problem significantly simpler than the original one. A double reflector synthesis problem involving only Fourier Transform (FT) operators is of concern during the first phase. The subre- flector surface and a first estimate of the main reflector geometry are obtained in this step. A single reflector synthesis problem is considered during the second phase wherein the final main reflector surface and the excitation coefficients of the primary feed array are obtained. While in the first phase only approximate relationships between the unknowns and the secondary radiated field are exploited, in the second phase accurate radiation operators are involved. Despite this accuracy, the second phase is still numerically effective since it involves a single reflector synthesis problem and exploits, as "good" starting point, the main reflector estimate obtained during the first phase. The effectiveness of the approach is due to the fact that the necessity of dealing simultaneously with two reflector surfaces, the key of the synthesis difficulties, is afforded only during the first phase where efficient computational tools are allowed. A numerical example shows the effectiveness of the proposed approach.

Dyadic Green's functions for inhomogeneous parallel-plate waveguides are considered. The usual residue series form of the Green's function is examined in the case of modal degeneracies, where secondorder poles are encountered. The corresponding second-order residue contributions are properly interpreted as representing "associated functions" of the structure by constructing a new dyadic root function representation of the Hertzian potential Green's dyadic. The dyadic root functions include both eigenfunctions (corresponding to first-order residues) and associated functions, analogous to the idea of Jordan chains in finite-dimensional spaces. Numerical results are presented for the case of a two-layer parallel-plate waveguide.

The field conditions inside a vibrating intrinsic reverberation chamber (VIRC) are examined. By the use of the Finite Difference Time Domain (FDTD) method,the field strength in the VIRC is calculated,and an investigation of the field uniformity and the field distribution is performed. The modes inside the cavity are excited by applying an appropriately modulated waveform on a dipoles gap. The use of this kind of waveform enables the study of the field conditions over a wide frequency range. On the contrary,an implementation of the field excitation with an unmodulated carrier would require a simulation of the FDTD method at each frequency of interest. Thus,a considerable reduction in the simulation time is achieved. The results presented,describing the field behavior inside the enclosure,agree with theory to a high degree.

In this paper, we present time-domain integral equation (TDIE) formulations for analyzing transient electromagnetic responses from three-dimensional (3-D) arbitrary shaped closed conducting bodies using the time-domain electric field integral equation (TDEFIE), the time-domain magnetic field integral equation (TD-MFIE), and the time-domain combined field integral equation (TD-CFIE). Instead of the conventional marching-on in time (MOT) technique, the solution methods in this paper are based on the Galerkin's method that involves separate spatial and temporal testing procedure. Triangular patch basis functions are used for spatial expansion and testing functions for arbitrarily shaped 3-D structures. The timedomain unknown coefficient is approximated by using an orthonormal basis function set that is derived from the Laguerre functions. These basis functions are also used as temporal testing. Using these Laguerre functions it is possible to evaluate the time derivatives in an analytic fashion. We also propose a second alternative formulation to solve the TDIE. The methods to be described result in very accurate and stable transient responses from conducting objects. Detailed mathematical steps are included and representative numerical results are presented and compared.

This paper is a theoretical study of solitons in multidimensions, also known as optical bullets, that is governed by the nonlinear Schrodinger's equation in 1 + 3 dimensions. The parameter dynamics of such multidimensional solitons has been obtained. The study is extended to obtain the adiabatic evolution of soliton parameters in presence of the perturbation terms. Furthermore, the parameter dynamics for the vector multidimensional solitons and including the presence of the perturbation terms has been obtained.

An analytic solution to the problem of plane wave scattering by an achiral multilayered sphere in a host chiral medium is obtained in this paper. By applying the radiation-to-scattering transform, the scattering problem can be considered as the specific radiation problems where the radiated source equivalent to the electromagnetic plane wave is located at infinity. The volumetric currents which generate right circular polarization (RCP) and left circular polarization (LCP) plane waves,resp ectively, are found. An integral equation consisting the volumetric current distributions and the dyadic Green's functions is formulated to obtain both the equivalent incident wave fields and the scattered fields. Two-layered lossless and lossy dielectric spheres and a conducting sphere with a dielectric coated layer buried in an infinitely extended host chiral medium are considered and the expressions for the scattered fields in far-zone are found in explicit analytic form. The characteristics of scattered fields are illustrated and discussed in terms of the circular polarization degree and linear polarization degree against different chiral admittances and sizes.

In this paper, the problem of scattering from sea surface with and without oil slicks is investigated taking the finite size of the illuminated area into account. A model of an inhomogeneous random rough surface with finite size of the scattering area is considered. To apply the results for a broad range of the random surface spectrum, an approach is developed which extends the range of validity beyond that of small perturbation theory. The general expression obtained for the scattering cross section takes into account a modulation of the rough surface by long surface waves. Analytical and numerical studies of the scattering cross section are provided to investigate the role of different mechanisms of scattering from various parts of the surface spectrum, and of diffraction caused by the finite size of the area. It is shown that the area size may affect the normalized scattering cross section in the case of the surface with a slick. Possibilities to explain the features of the suppression of the backscattering by oil slicks 238 Timchenko, Serebryannikov, and Schünemann are discussed. Furthermore, a way to distinguish between different scattering mechanisms is suggested.

The purpose of this paper is to use the analytical asymptotic extraction technique to analyze the bend discontinuity. We show that the derived analytical techniques significantly reduce the computational time while improving the accuracy compared to the conventional method. Especially, the advantage of the proposed method can eliminate the truncation error for evaluating the asymptotic part of impedance matrix. The proposed method has applied for solving the bend discontinuity, and verified with measurement results.

This paper shows the scattering cross sections of a random medium which is a simple model of moist soil by analyzing a dense medium radiative transfer equation (DMRT). The parameters in the DMRT, the extinction rate and the scattering coefficient, are calculated by a multiple scattering method called our method in this paper. Our method is valid for particles with high dielectric constant like water drops. Characteristics of the scattering cross section are made clear by changing the fractional volume of water and the incident angle, polarization of incident waves. We discuss the possibility of detection of a water content in this approach by using the characteristics of the scattering cross section.

We generalize to scalar pulses with finite duration a previous work [1] in which a new approach to diffraction at plane apertures is developed for scalar harmonic waves. A particular attention is given to rectangular pulse modulated signals for which an exact solution to the diffraction problem is obtained. As an example, the diffraction of a truncated harmonic pulse is investigated and the numerical problems to be solved are discussed with an important simplification when one is only interested in the diffraction pattern far from the aperture. More works are needed for apertures with no simple geometrical form.

Auseful and flexible method based on the tabu search algorithm for the pattern synthesis of linear antenna arrays with the prescribed nulls is presented. Nulling of the pattern is achieved by controlling the amplitude-only and both the amplitude and phase of each array element. To show the versatility of the present method, some design specifications such as the sidelobe level, the null depth and the dynamic range ratio are considered by introducing a set of weighting factors in the cost function constructed for the tabu search algorithm. Several illustrative examples of Chebyshev pattern with the imposed single, multiple and broad nulls are given.

A complete set of three dimensional multilayered media Green's functions is presentedfor general electric andmagnetic sources. The Green's functions are derived in the mixed potential form, which is identical with the Michalski-Zheng C-formulation. The approach appliedin this paper is basedon the classical Hertz potential representation. A special emphasis is on the formulation of the dyadic Green's functions G^HJ and G^EM. In these functions the derivatives due to the curl operator are taken in the spectral domain. This avoids the needof the numerical differentiation. Furthermore, it is foundthat the Hertzian potentials satisfy several useful duality and reciprocity relations. By these relations the computational efficiency of the Hertz potential approach can be significantly improvedandthe number of requiredSommerfeldin tegrals can be essentially reduced. We show that all spectral domain Green's functions can be obtained from only two spectral domain Hertzian potentials, which correspond to the TE component of a vertical magnetic dipole and the TM component of a vertical electric dipole. The derived formulas are verified by numerical examples.

The variational principle is employed to obtain the parameters dynamics of Gaussian and super-Gaussian chirped solitons which propagates through birefringent optical fibers that is governed by the dispersion-managed vector nonlinear Schrödinger's equation. The waveform deviates from that of a classical soliton. The periodically changing strong chirp of such a soliton reduces the effective nonlinearity that is necessary for balancing the local dispersion. This study is extended to obtain the adiabatic evolution of the parameters of such a soliton in presence of perturbation terms.

A numerical study of split cylindrical dielectric resonator antennas on a conducting ground plane excited by a coaxial probe is presented. The numerical solution is based on the method of moments for a body of revolution coupled to a wire. We consider in this study bandwidth enhancement for dielectric resonators excited in the HEM₁₁ and HEM₁₂ modes for the split dielectric cylinder. A wideband performance of about 35% has been achieved for the antenna and experimental measurements have verified this finding.