Plane wave scattering by slots on a ground plane loaded withsemicircular dielectric cylinders in case of oblique incidence andarbitrary polarization

Plane wave scattering by single or double slots loaded with semicircular dielectric cylinders is investigated in the most general case of oblique incidence and arbitrary polarization. To this end, systems of singular integral-integrodifferential equations of the first kind are constructed and discretized on the basis of recently developed algorithms. Several internal tests and extensive comparisons with available results were made in order to validate the numerical codes. Plotted results both for the surface magnetic current densities and the radar cross sections reveal how the scattering properties may be controlled by changing several physical and geometrical parameters of the structure     

Radiation properties of microstrip dipoles

The fundamental problem of printed antennas is addressed. The printed or microstrip dipole is considered, and its radiation characteristics are investigated. The Green's function to the problem is obtained in dyadic form by solving the problem of a Hertzian dipole printed on a grounded substrate. Input impedance computations are presented, and the numerical solution for the Sommerfeld integrals is discussed.     

Scattering of E-polarized waves from conducting strips inthe presence of a magnetically uniaxial half-space-a singular integralequation approach

A method based on the theory of singular integral equations (SIE) is presented for treating analytically scattering by perfectly conducting infinitely long strips in the presence of a magnetically uniaxial half-space. A uniform plane wave, polarized parallel to the strip axis, is incident from the isotropic region. As a prerequisite to this approach, the E-mode scalar Green's function of the structure is developed. Use of the reciprocity theorem then leads to a SIE for the current density induced on the scatterer's surface. The solution of the SIE is carried out in the case of a strip parallel or perpendicular to the interface, either located above or embedded in the anisotropic space. Numerical results for the induced current density and for the scattered far field in a variety of cases are presented in graphical form     

TM scattering by conducting strips right on the planar interface ofa three-layered medium

Combining the Fourier transform with powerful singular integral equation methods, the authors investigate the scattering properties of a variety of two-dimensional, three-layered planar structures loaded by a strip or a couple of coplanar strips right on an interface. The primary excitation is the lowest-order incident TM (to strip axis) surface wave mode or an incident E-polarized plane wave. In the practical case where the entire space is magnetically homogeneous, the kernel of the integral equations is most conveniently decomposed into a singular closed-form term added to an exponentially convergent inverse Fourier integral. An efficient, accurate, and stable numerical code is obtained and used to determine the strip-induced current densities as well as any quantity of practical interest. Plotted results reveal that by a proper choice of certain geometrical parameters the structures may become very efficient radiators, which can be designed to exhibit either very wideband and high directivity or considerable frequency scanning     

Strongly convergent Green's function expansions for rectangularlyshielded microstrip lines

The exact analytical treatment of the quasi-TEM mode in various cross-sectional configurations of microstrip lines may be used on Carleman-type singular integral equations (SIEs). Their kernel is a Laplacian Green's function G with source point limited on the interface separating the dielectric media. Strongly convergent expansion for G, particularly suited for the subsequent solution of the SIE and for exact field-point evaluations in rectangularly shielded microstrip configurations, are developed. Extraction of the singular logarithmic term leads to rapidly converging series expansions for the nonsingular part. The convergence of certain of these series is further improved when the field point lies also on the interface or when the source point approaches the shielding boundaries     

Exact solutions for rectangularly shielded lines by theCarleman-Vekua method

Exact solutions for the field of the TEM mode of rectangularly shaped round (or strip) conductors are obtained by solving linear, singular integral equations. There are no limitations on the dimensions or the proximity of the conductors to the shield. The authors consider only round conductors. The kernel of the integral equation in such problems is the Green's function G of a line source inside the shield, possessing a logarithmic singularity near the source point     

TE and TM modes in circularly shielded slot waveguides

Cutoff wavenumbers and the field of TE and TM modes are evaluated in circularly shielded, single- or double-slot waveguides in the case of infinitely thin fins. The formulation, based on field equivalence principles, is exact and leads to Carleman-type singular integral or integrodifferential equations for the equivalent surface magnetic current across the slot(s). The solution of these equations is based on Neumann's expansion of the Hankel kernels and leads to numerically stable and efficient algorithms regardless of the slot widths. Numerical results for the cutoff wavenumbers, both TE and TM, are presented. By lowering the cutoff frequencies of the TE modes and by raising the corresponding ones of the TM modes, considerable increase in the operating frequency bandwidth may be achieved after suitably selecting the various geometrical parameters of the configuration     

Rapidly converging spectral-domain analysis of rectangularly shielded layered microstrip lines

A moment-method-oriented direct integral-equation technique is presented for the exact analysis of rectangularly shielded layered microstrip lines. This technique retains the simplicity of conventional moment methods while optimizing them by recasting all matrix elements into rapidly converging series. Filling up the matrix requires no numerical integration. The proposed algorithms yield highly accurate results both for the modal currents and propagation constants.     

The use of the frill generator in thin-wire integral equations

For a frill-generator feed, certain fundamental mathematical properties of Hallen's and Pocklington's equations with the approximate kernel are stated and derived. For a particular moment-method procedure (Galerkin's method with pulse functions applied to Hallen's equation), the consequences to the numerical solutions are carefully examined. Generalizations to other numerical methods with subsectional basis functions are discussed. Many of our results come from studying the simpler problem of the infinite dipole analytically and applying the understanding thus obtained to the case of the finite dipole.     

Scattering From Axisymmetric Dielectric Scatterers: A Hybrid Method of Solving the Surface Integral Equations

Scattering of EM waves from homogeneous dielectric scatterers is formulated in terms of two surface integral equations, for the components of the total electric and magnetic fields that are tangential to the surface of the scatterer. Two equivalent systems of such equations may be used, corresponding to the two types of Maue's integral equations for perfectly conducting scatterers. The appearance of surface divergence terms of both components in the dielectric case, in addition to the unknowns themselves, causes serious complications when the method of solution is based on some kind of division of the scatterer surface into patches; these complications become particularly apparent in the process of evaluating the locally dominant self-patch contribution to the surface integrals. They can be effectively avoided if a third equivalent system of surface integral equations is used, arising from a proper summation of the original two systems; then, the two singular Green functions that appear in the surface divergence terms are replaced by their non-singular difference and this, followed by a further transformation of these critical terms, results in the complete elimination of the surface divergence terms. The self-patch contribution can then be evaluated analytically and this helps reduce the size of the matrix, via which the values of the tangential field components at the patch centers are calculated. Scatterers of considerable electrical size, for instance spheres with ka of the order of 10 or 15, can then be treated with moderate size matrices. Numerical results for spheres, sphere-cone-spheres and other shapes are obtained and compared with results from other methods. Apart from spheres, results for other shapes are very rare and limited to small sizes in the literature.