Alinur Büyükaksoy

High-frequency surface currents induced on a perfectly conducting cylindrical reflector

An explicit expression for the surface current induced by sources on a perfectly conducting cylindrical reflector is obtained by taking into account the locality of the high-frequency diffraction phenomenon. The results show that the component previously conjectured by Ufimtsev involves several components having different propagation behaviors that can be separated into three main groups. When the reflector becomes infinitely large, the currents excited by edge diffraction are shown to reduce to those for the classical half-plane problem. The results are independent of the actual source configuration and may thus be useful in more complicated situations.

Plane wave diffraction by a thick-walled parallel-plate impedance waveguide

The diffraction of E-polarized plane waves by a thick-walled parallel-plate impedance waveguide is investigated rigorously by using the Fourier transform technique in conjunction with the mode-matching method. This mixed method of formulation gives rise to a scalar Wiener-Hopf equation of the second kind, the solution of which contains infinitely many constants satisfying an infinite system of linear algebraic equations. A numerical solution of this system is obtained for various values of the plate impedances, plate thickness, and the distance between the plates through which the effect of these parameters on the diffraction phenomenon are studied.

Scattering of electromagnetic waves by a rectangular impedance cylinder

Abstract A uniformly valid asymptotic solution is developed for the diffraction of a high-frequency wave by an infinitely long rectangular cylinder having different impedance walls. The incident wave is generated by a line source located parallel to the cylinder. The problem is reduced first to a system of modified Wiener–Hopf equations involving infinitely many unknown constants and then to a couple of infinite system of linear algebraic equations which are solved numerically. Explicit expressions of the dominant wave components existing in different regions are found. Some illustrative examples show the capability of the approach.

Plane wave diffraction by an impedance step

Plane wave diffraction by two half-planes joined by a step is studied in the case where the half-planes and the step are characterized by different surface impedances. The diffraction problem is first reduced to a modified Wiener-Hopf equation of the second kind whose solution contains an infinite set of constants satisfying an infinite system of linear algebraic equations. A numerical solution of this system is obtained for various values of the surface impedances and the height of the step, through which the effect of these parameters on the diffraction phenomenon is studied. >

Radiation of Sound from a Semi-Infinite Rigid Duct Inserted Axially into a Larger Infinite Tube with Wall Impedance Discontinuity

In the present work the radiation of sound from a bifurcated circular waveguide formed by a semi-infinite rigid duct inserted axially into a larger infinite tube with discontinous wall impedance is analyzed. The formulation of the boundary-value problem in terms of Fourier integrals leads to a matrix Wiener-Hopf equation which is uncoupled by the introduction of infinite sum of poles. The exact solution is then obtained in terms of the coefficients of the poles, where these coefficients are shown to satisfy infinite system of linear algebraic equations. This system is solved numerically and the influence of the parameters such as the outer cylinder radius and the discontinuity of the surface impedances on the radiation phenomenon is shown graphically.

A HYBRID METHOD FOR THE SOLUTION OF PLANE WAVE DIFFRACTION BY AN IMPEDANCE LOADED PARALLEL PLATE WAVEGUIDE

The diffraction of E-polarized plane waves by an impedance loaded parallel plate waveguide formed by a two-part impedance plane and a parallel half plane with different face impedances is investigated rigorously by using the Fourier transform technique in conjunction with the Mode Matching Method. This mixed method of formulation gives rise to a scalar Modified WienerHopf equation, the solution of which contains infinitely many constants satisfying an infinite system of linear algebraic equations. A numerical solution of this system is obtained for various values of the surface impedances and waveguide height.

Diffraction of an obliquely incident plane wave by the discontinuity of a two part thin dielectric plane

Abstract The problem of diffraction of an obliquely incident plane wave by the discontinuity occuring in the permittivity of a thin dielectric layer is investigated. The structure is simulated by a set of boundary conditions involving the normal components of the field and their normal derivatives. The related boundary value problem is then reduced to three scalar Wiener-Hopf equations and solved by standard techniques. Some numerical results are presented in the case of normal incidence.

Influence of the junction of perfectly conducting and impedance parallel plate semi-infinite waveguides to the dominant mode propagation

The Wiener-Hopf technique is used to compute the reflection and transmission coefficients related to the junction of perfectly conducting and impedance parallel plate waveguides in the case where the surface impedances of the upper and lower semi infinite plates are different from each other.

Multiple diffraction of plane waves by a soft/hard strip

A uniform asymptotic high-frequency solution is developed for the problem of diffraction of plane waves by a strip which is soft at one side and hard on the other. The related three-part boundary value problem is formulated into a “modified matrix Wiener-Hopf equation”. By using the known factorization of the kernel matrix through the Daniele-Khrapkov method, the modified matrix Wiener-Hopf equation is first reduced to a pair of coupled Fredholm integral equations of the second kind and then solved by iterations. An interesting feature of the present solution is that the classical Wiener-Hopf arguments yield unknown constants which can be determined by means of the edge conditions.

Plane wave diffraction by a pair of parallel soft and hard overlapped half-planes

Abstract The diffraction of plane waves by a pair of parallel, overlapped half-planes characterized by Dirichlet and Neumann boundary conditions, respectively, is investigated. The corresponding boundary value problem is formulated as a matrix Weiner-Hopf equation whose solution is obtained through the “weak factorization” method. This method reduces the problems to an infinite system of linear algebraic equations which are solved numerically. An analysis of the scattered field, which depends on the solution obtained numerically, is also performed in some detail.