The accurate analysis of scattering from ob jects with dimensions large compared to the wavelength using rigorous methods (finite element, FDTD, method of moments) with a personal computer is almost impractical. In asymptotic methods, physical optics (PO), geometrical theory of diffraction (GTD), the accurate modeling of the object's boundary is too cumbersome. The parabolic equation method gives accurate results in calculation of scattering from objects with dimensions ranging from one to tens of wavelengths. Solving parabolic equation with the marching method needs limited computer storage even for scattering calculations of large targets. In this paper, first the calculation procedure of radar cross section using parabolic equation is studied and the necessary equations are derived. The parabolic equation and the model of reflecting facet is utilized for calculation of the scattered fields in the forward and backward directions. In order to model the lossy background, the impedance boundary condition is utilized in lower boundary. Finally the scattered fields and RCS of a ship and a tank are calculated as two examples of targets with lossy background.

In this paper the analysis of radiation from known current distributions placed on a dielectric coated elliptic conducting cylinder has been effected. The analysis is carried out considering the expansion of the field as a series of Mathieu functions. The presence of the current is taken into account in the boundary conditions at the air-dielectric interface. The behavior of the radiated field as a function of the minor over ma jor axis ratio of the elliptic conducting cylinder has been investigated and discussed.

Based on the asymptotic method of averaging, an approximate analytical solution of the integral equation concerning a magnetic current in slot-hole coupling apertures of electrodynamic volumes, which differ profitably from the known ones in literature, has been obtained. The formulas for the currents and characteristics scattering of transverse and longitudinal slots in common broad and narrow walls of rectangular waveguides are given. The comparison to results obtained by other methods and experimental data has been done.

In this paper, the parabolic approximation of wave equation will be solved by the method of least squares. At first, the radio wave propagation in homogeneous media will be considered. The electromagnetic field will be expanded by proper expansion functions, which satisfy the parabolic equation in homogeneous media. The expansion coefficients will be derived by the least square method through enforcing initial and boundary conditions. The least square functionals satisfy the initial and boundary conditions. Similar to the split step method, the field in the inhomogeneous media with known profile of refractive index can be obtained by proper phase shifting of the field in homogeneous media. The proposed method is more reliable than the split step method and can be applied over rough boundary without any excess computations. In comparison with the finite difference method, the proposed method is very fast.

The paper presents the Scattering Operator Method, which is devoted to the problem of scattering from a set of N cylindrical ob jects. By contrast with the Scattering Matrix Method, which has been used by many groups in the last twenty years, it applies to any kind of cylinder shape, regardless of the relative location of the cylinders. The theory is based on a mathematical result: it is possible to define in the vicinity of the surface of each cylinder two complementary parts of the field: the total incident field and the field scattered by this cylinder. These two parts are the Calderon projectors of the values of the total fields on the surface of the cylinder. The validity of the method is checked on two examples. It is shown that the theory avoids some problems encountered in integral method like evaluations of singular or hypersingular integrals, or instabilities due to internal resonance of ob jects.

Field structures of waveguide Y-junction circulators containing irregular shaped ferrite material, such as Y-junction with partial-height cylinder/triangle ferrite posts and metal step impedance transformer, Y-junction with a ferrite sphere, and dual higher order modes circulator, which are classified as different junction resonance modes, are depicted to illustrate the circulating process. The analysis method used is a combination of the mode expansion method and finite element method, which is based on the weak form of Helmholtz equation. Calculated results (return loss, insertion loss and isolation) of these structures are shown and compared respectively to those in literatures. Consistencies have been observed.

This paper presents a hybrid technique, which combines the desirable features of two different numerical methods, finite difference frequency domain (FDFD) and the method of moments (MoM), to analyze large-scale electromagnetic problems. This is done by dividing the computational domain into smaller sub-regions and solving each sub-region using the appropriate numerical method. Once each sub-region is analyzed, independently, an iterative approach takes place to combine the sub-region solutions to obtain a solution for the complete domain. As a result, a considerable reduction in the computation time and required computer memory is achieved.

Representation of electromagnetic expressions in terms of the four-dimensional differential-form formalism has been recently shown to allow simple analysis to problems involving general classes of linear electromagnetic media. In the present paper, another class of media is defined by expressing the medium dyadic representing the mapping between the electromagnetic two-forms in terms of one dyadic representing mapping between two four-vectors. Thus, the class, labeled as that of IB-media, is represented by 16 parameters instead of the 36 of the most general bi-anisotropic medium. Condition for the medium dyadic is derived and and properties of fields in the IB-medium are discussed.

In this paper a study is presented to handle the behavior of radar cross section (RCS) of partially convex targets of large sizes up to five wavelengths in free space. The nature of incident wave is an important factor in the remote sensing and radar detection applications. To investigate the effects of incident wave nature on the RCS, scattering problems of plane and beam wave incidences are considered. Targets are taking large sizes to be bigger enough than the beam width with putting into consideration a horizontal incident wave polarization (E-wave incidence). The effects of the target configuration together with the beam width on the laser RCS compared to the case with the plane wave incidence are numerically analyzed. Therefore, we will be able to have some sort of control on radar detection using beam wave incidence.

Spectral domain approach for continuous spectrum of wide class of microwave integrated circuit (MIC) lines is proposed. The continuous spectrum is treated as a continuum of so called hybrid radiation modes. They are the limits of volume modes of line in which lower and/or upper shieldings are moved to infinity. In the preliminary part of analysis a convenient classification of MIC lines into one-side opened and two-sides opened lines is introduced. The spectral domain representation of hybrid radiation modes is discussed in detail and boundary conditions for visible and invisible parts of spectrum are formulated. The normalization conditions in spectral domain are also proposed for both classes of lines. In the next part of paper an iterative approach in spectral domain is proposed for hr modes of one-side opened line. The boundary conditions for hybrid radiation modes are combined with spectral domain approach and the second order equation is formulated for unknown spectral amplitudes of electric or magnetic fields in visible part of spectrum. Two schemes of iteration are presented and they both lead to solutions classified as hybrid EH^(y) and HE^(y) modes. In the case of two-sides opened lines the solution is a sum of two partial solutions corresponding to symmetrical and unsymmetrical sources distributions. Each partial solution can be found by the iterative procedure proposed for one-side opened lines. The efficiency of proposed procedure was verified for the case of hybrid radiation modes of microstrip line. The results of calculations of amplitudes and phases of spectral amplitudes in visible spectrum part for examplary hybrid radiation modes are shown. As an example of an application of the hybrid radiation modes concept, the advanced cavity model of rectangular patch antenna is proposed. This model allows to calculate the parameters with acceptable precision nearly ten times faster than professional full-wave design tools. In the conclusion other possible applications of this approach are proposed e.g., in modal analysis of discontinuities including the radiation effect or 3D rectangular patch analysis.

Observations of L- and C-band backscatter from snow cover are presented at all polarizations. Airborne passive-microwave data was collected in Northern Finland during EMAC'95 (European Multi-sensor Airborne Campaign-95). The measurements cover the 6.8-18.7 GHz frequency range with both verticaland horizontal polarizations. The empirical SAR data were acquired by EMISAR of TechnicalUniv ersity of Denmark over the city of Oulu in Northern Finland during EMAC'95. Airborne measurements were conducted on 22-23 March, and on 2-3 May 1995. The land-use map of the test sites was obtained from the NationalLand Survey of Finland. This study combines the semi-empirical and empirical models that were developed. Applicability of the forest transmissivity formulas developed by using the different data sets of passive and active sensors is shown. Because of the effect of dry snow at C-band is more visible than at L-band. A C-band semi-empiricalbac kscattering modelis developed for the forest-snow-ground system.

A parallel implementation of an automatic CAD tool based on the parallel virtual machine software package, genetic algorithms and finite element simulators is presented. It is shown that the parallel implementation can be obtained by developing just a few hundred lines of code and a pseudocode description is provided. Finally, selected numerical results are provided in order to show the effectiveness and the reliability of the proposed approach.

The paper presents the application of the hybrid global optimization algorithm, introduced in the companion paper Part I, to reflector antenna power pattern synthesis and reflector antenna surface diagnosis from only amplitude data. The synthesis algorithm determines both the reflector surface and the excitation coefficients of the array of primary feeds to meet the designing specification on the far-field pattern expressed by means of two couple of masks bounding the squared amplitude of both the copolar and crosspolar components. The diagnosis technique allows to find the reflector surface profile from the measurement of the far field power pattern by a proper formulation of the corresponding inverse problem. In both cases we take advantage of the exploring capability of an evolutionary algorithm and of the solution refinement capability of an efficient, quasi-Newton based, local search procedure. The numerical analysis shows that Global Optimization can outperform the standard local approach, by significantly improving the performance of the synthesized antenna in the first case and by enhancing the reliability of the diagnosis procedure in the second one.

This is the first of two companion papers on global optimization and antenna analysis and synthesis. In Part I, an analysis of the problems involved in Global Optimization is presented by critically discussing the basic concepts and tools, the performances to be expected, the required computational complexity and the guidelines to select algorithms solving efficiently the problem at hand. The relevance of stochastic techniques is enhanced and the role of double phase algorithms is stressed. The proof of the convergence property of an idealized version of a simplified evolutionary algorithm is provided. In Part II, the selected algorithm, a hybrid evolutionary algorithm, is tested against two real world problems relevant in electromagnetics, the power synthesis of contoured beam hybrid reflector antennas and the reflector antenna diagnosis from only amplitude data. The results of an extensive numerical analysis are presented.

Wideband printed rectangular slot antennas backed with reflectors for unidirectional radiation patterns are investigated. A U- shaped tuning stub is used to improve the matching. Two different feeding mechanisms are introduced. A rectangular slot excited by microstrip line feed with a U-shaped tuning stub gives an impedance bandwidth of 110% ( |S11| < −10 dB). When the rectangular slot is excited by a coplanar waveguide (CPW), it gives an impedance bandwidth of 120%. Both slot antennas radiate broadside across the matching band, with front-to-back ratios of 20 dB.

This paper presents a novel broadband, low-profile dielectric resonator antenna using relatively low dielectric constant substrate material. The rectangular DRA is fed with a stepped microstrip feed to ensure efficient coupling. Bandwidths in excess of 17% are obtained. In addition, the paper investigates methods to miniaturize the antenna using metallic strips or patches. Substantial size reduction is demonstrated while maintaining a reasonable bandwidth. Simulations as well as experimental results are presented.

The inverse problem of using an unshielded multiconductor transmission line (MTL) as an distributed sensor is considered. The MTL is analyzed by means of the quasi-TEM mode theory and a propagator formalism. In the inverse problem, the focus is on the problem with intermodal dispersion, due to the possibility of more than one propagating mode. Reconstruction results, from both measured and simulated reflection data, are presented for a three conductor MTL that has been used for diagnosing soil and snow. Both the case when one mode propagates, and the case when two modes propagate are considered. For the latter case it is demonstrated that intermodal dispersion deteriorates the resolution in the reconstruction, due to corruption of the high frequency part of the spectrum.

A radiated susceptibility problem has been identified and solved by means of simulations for a wearable computer system in the frequency range 30 MHz-1 GHz. Simulation strategy is presented for analyzing the effects induced by an electromagnetic plane wave within the system comprising infra-red sensors connected by coaxial cables. A procedure of creating a TLM model of the coaxial cable with controlled electromagnetic coupling characteristics on a coarse grid is proposed. Results are verified by means of theoretical calculations. Different sensor enclosures and filtering circuits are analyzed and implemented to meet the hard electromagnetic compatibility requirements while not interfering with the functionality of the wearable application.

Multiple-scale analysis is employed for the analysis of plane wave refraction at a nonlinear slab. It will be demonstrated that the perturbation method will lead to a nonuniformly valid approximation to the solution of the nonlinear wave equation. To construct a uniformly valid approximation, we will exploit multiplescale analysis. Using this method, we will derive the zerothorder approximation to the solution of the nonlinear wave equation analytically. This approximate solution clearly shows the effects of self-phase modulation (SPM) and cross-phase modulation (XPM) on plane wave refraction at the nonlinear slab. In fact, the obtained zeroth-order approximation is very accurate and there is not any need for derivation of higher-order approximations. As will be shown, the proposed method can be generalized to the rigorous study of nonlinear wave propagation in one-dimensional photonic band-gap structures.