Browsing by Subject "Scattering pattern"

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Open Access
Resonances in the electromagnetic scattering by very large finite-periodic grids of circular dielectric wires
(IEEE, 2010-06) Natarov, D. M.; Benson, T. M.; Altıntaş, Ayhan; Sauleau, R.; Nosich, I.
Diffraction of plane waves by infinite gratings is a classical research topic in the scattering theory. Using the Floquet theorem, one can reduce the infinite grating problem to the one-period problem. A characteristic feature of infinite-grating scattering is the drastic transformation of the scattering pattern and reflectance intensity if, in the process of changing the frequency or the angle of incidence, one of the Floquet harmonics is "passing over horizon." This phenomenon was first explained by Rayleigh [1] who studied theoretically the "anomalies" discovered experimentally by Wood [2]. In the simplest case of the normal incidence, these Rayleigh-Wood anomalies are observed if the period of the grating is multiple to the wavelength. © 2010 IEEE.
Open Access
Spherical wave representation of the dyadic Green's function for a spherical impedance boss at the edge of a perfectly conducting wedge
(Electromagnetics Academy, 2012) Ghassemiparvin, Behnam; Altıntaş, Ayhan
In this work, canonical problem of a scatterer at the edge of a wedge is considered and eigenfunction solution is developed. Initially, a dyadic Green's function for a spherical impedance boss at the edge of a perfect electrically conducting (PEC) wedge is obtained. Since scattering from objects at the edge is of interest, a three-dimensional Green's function is formulated in terms of spherical vector wave functions. First, an incomplete dyadic Green's function is expanded in terms of solenoidal vector wave functions with unknown coefficients, which is not valid in the source region. Unknown coefficients are calculated by utilizing the Green's second identity and orthogonality of the vector wave functions. Then, the solution is completed by adding general source correction term. Resulting Green's function is decomposed into two parts. First part is the dyadic Green's function of the wedge in the absence of the sphere and the second part represents the effects of the spherical boss and the interaction between the wedge and the scatterer. In contrast to cylindrical vector wave function expansions and asymptotic solutions which fail to converge in the paraxial region, proposed solution exhibits good convergence everywhere in space. Using the developed Green's function scattered field patterns are obtained for several impedance values and results are compared with those of a PEC spherical boss. Effects of the incident angle and surface impedance of the boss on the scattering pattern are also examined.