J.L. Tsalamengas

Interaction of electromagnetic waves with general bianisotropic slabs

An efficient, elegant, and systematic formulation technique which, combining Fourier transform with matrix analysis methods, is suitable for problems related to radiation by dipole or other sources in the presence of an arbitrarily general stratified anisotropic medium has been recently developed. This technique is adapted further extended to allow the presence of general bianisotropic media described by four tensors with no limitations on their elements. Two specific applications pertaining to some canonical problems of fundamental importance are included to exemplify the method and demonstrate its usefulness: radiation by an arbitrarily oriented elementary electric dipole source located in the vicinity of a general bianisotropic slab, either grounded or ungrounded, leading to the expressions of the dyadic Greens function of the structure, and reflection and transmission of an arbitrarily polarized plane wave incident upon such a slab, leading to closed-form concise expressions for the reflection and transmission coefficient matrices. >

Electromagnetic fields of elementary dipole antennas embedded in stratified general gyrotropic media

Using matrix methods in conjunction with Fourier transformation techniques, the field excited by arbitrarily oriented elementary electric or magnetic dipole sources in the presence of a uniaxial or biaxial stratified gyrotropic medium is obtained in the form of a full dyadic Greens function. Both the permittivity and permeability tensors, being completely unrestricted, assume their most general forms in each layer separately. The singular behavior of the solution in the close vicinity of the source-point is properly taken into account by separate, suitably selected dyadic delta function terms. Using suitably selected upward or downward wave amplitude matrices, the field inside any of the layers is determined. >

Exponentially converging Nystro/spl uml/m's methods for systems of singular Integral equations with applications to open/closed strip- or slot-loaded 2-D structures

This paper concerns the fast, highly accurate, and exponentially convergent solution of three sets of integral equations pertaining to two-dimensional generalized microstrip or microslot structures. The analysis relies on Nystroumlms method with due regard to all singular integrals and slowly converging series that appear in the kernels; the sophisticated treatment and efficient computation of such series and integrals is of paramount importance, entailing the use of advanced techniques. As a result of our specialized treatment, the discretization procedures developed herein: a) fully account for both the singular nature of the kernels and the singularities of the solution at the edges; b) obviate the need for taking inner products with testing functions; c) appear to converge exponentially versus matrix size; and d) enable expressing all matrix elements via single, finite sums. Detailed numerical examples and case studies illustrate the simplicity, flexibility, and remarkable efficiency of the algorithms

Direct singular integral equation methods in scattering and propagation in strip- or slot-loaded structures

Problems of three-dimensional (3-D) scattering/hybrid-wave propagation for strip- or slot-loaded structures are often formulated in terms of systems of singular integral-integrodifferential equations (SIE-SIDE) of the first kind. Proper handling of the singular part of the kernels constitutes a major difficulty in carrying out method of moments (MoM). Three powerful techniques explored in the present paper provide efficient solutions by direct recourse to the theory of singular integral equations. In contrast to low-frequency methods wherein similar concepts are utilized for electrically narrow strips/slots, the proposed procedures are applicable uniformly to the whole range of widths from very narrow to very wide scatterers with remarkable accuracy. Numerical results are presented to validate and compare to one another the various numerical codes.

Radiation from a dipole near a general anisotropic layer

The radiation properties of a dipole source located near a gyrotropic layer are investigated analytically. Both electric and magnetic anisotropy of the most general form are assumed. Fourier-transform domain field representations in conjunction with matrix analysis techniques are used to facilitate the analysis. Transmission phenomena through the general anisotropic layer are investigated by examining the radiation patterns at the far-field region. The analysis is also used to derive the response of the anisotropic layer to an incident plane wave. In this case, the transmission and reflection coefficient matrices are obtained. >

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.

Exact solutions for shielded printed microstrip lines by the Carleman-Vekua method

Exact analytical solutions for the field of the quasi-TEM (transverse electromagnetic) mode in various cross-sectional configurations of rectangularly shielded printed microstrip lines are obtained on the basis of Carleman-type singular integral equations (SIEs). For the kernel of the SIE, strongly and uniformly convergent series expansions have recently been developed that are suitable for the exact solution of the equation by the Carleman-Vekua regularization method, which proceeds by first solving the so-called dominant equation. The procedure leads to rapidly convergent series solutions for the field of the quasi-TEM mode even when the conductors are large or very near the shield, i.e. in situations for which numerical techniques becomes inadequate. Characteristic values of the shielded microstrip lines are evaluated by summing a few terms, while field plots, requiring more terms, are shown for various configurations including the case of close proximity. >

Exponentially Converging NystrÖm Methods Applied to the Integral-Integrodifferential Equations of Oblique Scattering/Hybrid Wave Propagation in Presence of Composite Dielectric Cylinders of Arbitrary Cross Section

Systems of singular integral-integrodifferential equations are studied that pertain to 2-D oblique scattering and to hybrid-wave propagation in presence of a dielectric cylinder with arbitrarily shaped smooth boundary. These systems, having the tangential to the surface of the cylinder components of the electric and magnetic fields as the unknowns, are solved via fast, highly accurate algorithms that rely on the Nystrom method (NM). Because of our specialized treatment, the present solution technique has the following characteristics: (1) it fully accounts for the singular nature of the kernels, (2) it appears to converge exponentially, and (3) it yields simple closed-form expressions for all matrix elements. In addition, an extension of the analysis is presented to account for composite dielectric cylinders that contain arbitrarily shaped dielectric or conducting cylindrical inclusions. Numerical examples and case studies illustrate the simplicity, flexibility, and efficiency of the algorithms. Exhaustive comparisons with available results for several special cases serve to test the correctness of the implementation and bring to light the extremely high accuracy of our algorithms.

Rapidly converging direct singular integral-equation techniques in the analysis of open microstrip lines on layered substrates

In this paper, moment-method-oriented direct singular integral-equation techniques are used for the exact analysis of planar layered microstrip lines. While these techniques retain the simplicity of the conventional method of moments, they optimize them by evaluating all matrix elements via rapidly converging real-axis spectral integrals. The proposed algorithms yield highly accurate results for the dispersion characteristics and for the modal currents both of the fundamental and higher order modes.

Plane-wave scattering by strip-loaded circular dielectric cylinders in the case of oblique incidence and arbitrary polarization

Plane-wave scattering by strip-loaded circular, multilayered dielectric cylinders is investigated in the most general case of oblique incidence and arbitrary polarization. The problem is formulated via systems of singular integral-integrodifferential equations of the first kind which are most efficiently discretized on the basis of previously developed analytical algorithms. Several internal tests along with extended comparisons with available results have been completed to validate the numerical codes. Plotted results for both the induced surface current densities and the total radar cross section reveal how the scattering properties may be controlled by changing several physical and geometrical parameters of the structure. >