Edge condition of a perfectly conducting wedge with its exterior region divided by a resistive sheet

The edge condition for a perfectly conducting wedge which has its exterior region divided by a resistive sheet is derived. It is shown that the behavior of an electromagnetic field at the edge is altered as a result of the appearance of the resistive sheet but is independent of the resistance value. In particular, the singularities in the electric field components transverse to the edge in the absence of the resistive sheet have been eliminated. This assures the finiteness of the energy dissipated on the resistive sheet in the vicinity of the edge.     

Reflection from a periodically perforated plane using a subsectional current approximation

The scattering from a zero thickness plane having finite sheet resistance and perforated periodically with apertures is calculated for arbitrary plane wave illumination. The surface current density within the unit cell is approximated by a finite number of current elements having rooftop spatial dependence. The transverse electric field is expressed in terms of the current, and the electric field boundary condition is satisfied in an integral sense over the conductor, generating a finite dimension matrix equation whose solution is the current density. Since the conductor shape is defined through the locations of subsectional current elements, arbitrary shaped apertures can be handled. The reflection coefficient and current distribution are calculated for square apertures in both perfectly conducting and resistive sheets, and for cross-shaped apertures. Finite resistivity is shown to cause the magnitude of the transverse magnetic (TM) reflection coefficient to decrease more rapidly and its phase to decrease less rapidly, as the angle of incidence approaches glancing. Through detailed plots of the current density, the current crowding around the apertures is made clearly evident.     

Convergence tests of several moment-method solutions

Matrix elements used in previously published two- and three-dimensional moment-method solutions are here used for arrays of large numbers of cells arranged to approximate a thin dielectric slab. Richmond's two-dimensional solutions for both transverse magnetic (TM) and transverse electric (TE) excitation and the three-dimensional solutions considered appear to approach the analytical solution in the limit of zero slab thickness.     

TM scattering by an impedance sheet extension of a paraboliccylinder

An integral equation and method of moments (MM) solution are presented for the two-dimensional (2-D) problem of transverse magnetic (TM) scattering by an impedance-sheet extension of a perfectly conducting parabolic cylinder. An integral equation is formulated for a dielectric cylinder of general cross section in the presence of a perfectly conducting parabolic cylinder. It is then shown that the solution for a general dielectric cylinder considerably simplifies for the special case of TM scattering by a thin multilayered dielectric strip that can be represented as an impedance sheet. The solution is termed an MM/Green's function solution, where the unknowns in the integral equation are the electric surface currents flowing in the impedance sheet; the presence of the parabolic cylinder is accounted for by including its Green's function in the kernel of the integral equation. The MM solution is briefly reviewed, and expressions for the elements in the matrix equation and the scattered fields are given. Sample numerical results are provided     

Oblique scattering from lossy strip structures with one-dimensionalperiodicity

The intentional addition of loss to a periodic structure can be used as a technique to alter its scattering characteristics. The problem of an oblique plane wave incident on an array with one-dimensional periodicity is examined. The unit cell of the array is composed of a number of thin resistive strips. The obliqueness of the incident plane wave combined with the lossy nature of the structure causes the transverse electric (TE) to zˆ and the transverse magnetic (TM) to zˆ fields to couple. To analyze the described problem, two coupled electric field integral equations that have as unknowns the equivalent surface currents on the strips in the unit cell are derived. The integral equations are discretized and solved approximately using the method of moments with subdomain basis and testing functions. The periodic Green's function is efficiently calculated using the Poisson summation formula. The interaction of the structure with the surrounding environment is described in terms of a generalized scattering matrix. Results are presented showing the TE/TM coupling behavior as strip resistance is increased for representative structures     

TM scattering by a general sheet impedance discontinuity

An integral equation and spectral-domain method of moments (MM) solution to the two-dimensional problem of transverse magnetic (TM) scattering by a general sheet impedance discontinuity in a plane multilayered medium is presented. The MM solution uses a combination of pulse and traveling-wave physical basis functions to efficiently analyze discontinuities that extend to infinity. Numerical results that illustrate the use and accuracy of the method are presented     

Electromagnetic fields of buried sources in stratified anisotropic media

A general formulation to the problem of the radiation of arbitrary distribution of buried sources within a horizontally stratified anisotropic medium is presented. The fields are obtained in terms of appropriately defined electric and magnetic types of dyadic Green's functions which are dual to each other. The formulation is considerably simplified by the resolution of these dyadic Green's functions into transverse electric (TE) and transverse magnetic (TM) waves and by the existing duality between them. A systematic procedure for deriving the fields in an arbitrary layer in terms of the primary source excitation and appropriately defined wave amplitude matrices is described.     

Oblique scattering from inhomogeneous cylinders using a coupledintegral equation formulation with triangular cells

A novel method of moments formulation for scattering from penetrable two-dimensional cylinders illuminated by an obliquely incident excitation is presented. The permittivity and permeability profiles may have arbitrary piecewise-constant dependence on the transverse variables. Regardless of the polarization of the incident field, the response of the scatterer is a combination of transverse electric (TE) and transverse magnetic (TM) waves. Coupled integral equations for the longitudinal electric and magnetic fields are used in conjunction with a triangular-cell discretization, a piecewise linear representation for E_z and H_z, and point-matching. Numerical results for the internal fields and scattering cross-section are presented to illustrate the accuracy of the approach     

Galerkin solution for the thin circular iris in aTE11-mode circular waveguide

An integral equation for the transverse electric (TE) field in the aperture of a concentric circular iris in a transverse plane of a circular waveguide is approximately solved using Galerkin's method. The aperture field is represented by a finite sum of normal TE and TM (transverse magnetic) circular waveguide modes that fit the circular aperture. The numerical convergence of the Galerkin solution is demonstrated using the resultant aperture field distributions and equivalent shunt susceptance for the case of dominant TE₁₁-mode excitation. The resultant aperture electric field distribution closely resembles that of the TE₁₁ aperture mode alone, except for edge contribution behavior at the edge of the iris. A resonant or capacitive iris is possible over a restricted range of frequencies     

Excitation of electromagnetic waves in a gyroelectric cylinder

The coupling of electromagnetic waves originating from a dipole to an infinite gyroelectric cylinder is treated analytically. The anisotropy axis of the gyrotropic medium is assumed to coincide with the cylinder axis. An electric dipole type primary excitation, with an arbitrary axis of orientation, is considered and the dyadic Green's function is derived for the gyroelectric cylinder. The field inside the anisotropic medium is expressed as a superposition of transverse magnetic (TM) and transverse electric (TE) type waves and a purely longitudinal wave. Excitation of guided modes along the gyroelectric guide and radiation patterns of dipoles radiating in the proximity of the gyroelectric cylinder are analyzed and computed for several cases.     

Surface waves on a grounded dielectric slab covered by a resistivesheet

Surface wave propagation in a grounded dielectric slab covered with a resistive sheet is examined. Transcendental equations are derived for each polarization and are solved using iterative techniques. Attenuation and phase velocity are shown for a representative geometry. The results are applicable to both a grounded slab covered with a resistive sheet and an ungrounded slab covered on each side with a resistive sheet     

Modeling of resistive sheets in finite element solutions [EMscattering]

A variational formulation is presented for modeling a resistive card in the context of the finite-element method (FEM). To validate this formulation, results based on a physical modeling of the resistive sheet are also presented. In this case, the resistive sheet is equivalently replaced by a thin dielectric layer. The modeling of such a layer in the usual manner leads to larger and consequently inefficient linear systems, which is the primary reason for resorting to a mathematical modeling of the resistive sheet. Results based on the mathematical and physical modeling are presented in connection with the scattering by a metal-backed cavity in a ground plane. These are used to validate the proposed mathematical model     

Radiation properties of a flanged parallel-plate waveguide loadedwith an ε-μ general anisotropic slab

In this analysis, the excitation is taken to be either (1) the lowest-order transverse electric (TE) or the lowest-order transverse magnetic (TM) (i.e. transverse electromagnetic) waves, or (2) a uniform, E- or H-polarized, incident plane wave. As a result of the anisotropy, cross-polarization effects are observed. The formulation of the boundary-value problem is carried out in the Fourier transform domain. Considerable contraction results by using previously developed matrix analysis techniques. In this way, a fruitful integral representation of the tangential components of the magnetic field is first derived in terms of the tangential components of the electric field at the excitation aperture. Next, and after imposing the boundary conditions at the aperture boundary surface, this representation is used as the starting point for a solution on the basis of a moment method (MM) approach using the eigenmodes as basis and weighting functions. Numerical results related to the reflection and coupling coefficients as well as the directive diagrams of the structure are presented in graphical form for various cases     

TM electromagnetic scattering by a transparent wedge with resistivefaces

The Sommerfeld-Maliuzhinets (1958) method is used to calculate the total fields in the interior and exterior regions of an arbitrarily angled resistive wedge. A E-plane wave (TM mode) normally illuminates the two-dimensional resistive wedge. Two spectral functions are introduced to represent the fields in both regions. By imposing the resistive boundary conditions on the wedge faces, a system of coupled functional equations is obtained for the two unknown spectral functions. The functional equations are reduced to singular integral equations for the auxiliary functions. The predictions for a right-angled resistive wedge are shown to be in good agreement with measurements     

Admittance-voltage characteristic of an MOS capacitor formed over p-on-n semiconductor structure

A distributed RC transmission line analysis is extended to facilitate numerical computations and to include the device configuration where a resistive sheet is located between an oxide capacitance and a junction capacitance. General expressions of gate admittance for arbitrary electrode shape are given. The results of calculations for a square electrode explain well the anomalous experimental result. The sheet conductance of the resistive sheet is obtained as a function of gate bias.     

The Efficiency of Excitation of a Surface Wave on a Dielectric Cylinder

This paper presents a theoretical and experimental study of the excitation of the lowest order TM surface wave on an infinite dielectric cylinder. The source is a circular filament of magnetic current within the dielectric rod. The integral solution for the field is evaluated as a contour integral by applying Cauchy's theorem. The far zone radiation field is obtained by means of a saddle pointintegration. Curves are presented which show excitation efficiency as a function of k/sub 0/a, the normalized circumferential length of the filament. A filament 0.83 wavelength in diameter will launch the TM mode with an efficiency of 95 per cent. A narrow annular slot in a large metal sheet was used to approximate the magnetic current filament and efficiency was measured using Deschamps' method for a two-port junction. The experimental measurements verify the theoretical analysis. In addition, it was found that the slot launching efficiency was essentially independent of the ground plane dimensions.     

Liquid-crystal polarization stabilizers on fiber arrays

We have built polarization stabilizer arrays of ultrathin liquid-crystal (LC) polarization controller (PC) arrays and a tap-type photodetector array on a fiber array. The ultrathin (35-/spl mu/m-thick) LC cells are inserted into trenches cut across the fiber array, which is affixed to V grooves in a glass plate and are used to change the phase of 1.55-/spl mu/m lights from 0.5 to 3.9/spl pi/ with the application of less than 3 Vrms. Two cascaded ultrathin LC cells, where the directions of alignment of the LCs are rotated by 45/spl deg/ relative to each other, are capable of converting light with an arbitrary input polarization to the transverse electric (TE) or transverse magnetic (TM) polarization. We fabricated a multichannel TE- and TM-polarization stabilizer of the previously mentioned 16-channel LC PC array and a feedback system made up of a multichannel tap-type photodetector array, sheet polarizer, and a computer and analog-to-digital converters. Feedback control was applied to maximize and minimize the tapped light, to convert an arbitrary input polarization to TM or TE output polarization, and stabilize it in the given state.     

Smith chart approach to the design of multilayer resistive sheet

The design of the multilayer resistive sheet is often given in some formulae or in some tabulated forms. The electrical engineer or material scientist often cannot visualize how the design really works or the achievable bandwidth. In this paper, we attempt to give a good understanding of the design of the multilayer resistive sheet by using the Smith Chart approach. The Smith Chart approach offers more flexibility to the design of the multilayer resistive sheet, as compared to published formulae or tables.     

Electromagnetic scattering by an inhomogeneous penetrable material with an embedded resistive sheet

This paper presents the method of moments (mom) formulation for the electromagnetic scattering by an inhomogeneous penetrable material with an embedded resistive sheet. Triangular surface facets and tetrahedral volume cells are used to discretize the scatterer allowing for greater flexibility in the geometric modeling of the material body. The formulation is very general in that it allows for a variety of material configurations : open or closed conducting surfaces, open or closed resistive (thin dielectric) surfaces, solid dielectric/ferrite material volumes, embedded conducting/resistive surfaces in material volumes, and partially embedded conducting/resistive surfaces (cladded materials). Results for a material coated resistive spherical shell and a material propeller blade are presented.     

V-conical antenna

A new angular antenna called the V-conical antenna was investigated. The characteristics of the antenna are frequency-independent, and the electromagnetic fields are pure spherical waves (transverse electromagnetic mode) even in the near region. The theoretical analysis makes use of conformal mapping. Closed-form solutions for the fields, currents, and characteristic parameters are obtained. The formulas are simple and precise. An experimental study of the antenna was conducted under pulse excitation. The shape of the measured electric-field pulses is the same as that of the source pulse from a picosecond pulse generator. The measured field patterns are very close to those predicted by the theory. Such a structure with a tapered resistive termination is an ideal directional pulse antenna or electromagnetic pulse simulator