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A Uniform Geometrical Theory of Diffraction (UTD) is developed for modeling realistic small antennas placed on large, smooth, convex metallic surfaces with a uniform material coating which is extremely thin (with respect to the convex surface radii of curvatures). The very thin uniform material coating on a convex metallic surface is approximated here by a linear surface impedance boundary condition...
A numerical analytic problem solution of a diffraction radiation of a narrow rectilinear slot into space over an infinite impedance screen is presented. An asymptotic solution for the magnetic current in the slot was obtained by a generalized method of induced magnetomotive forces (MMF) applying the Green's functions for the space above the impedance plane. Influence of the screen impedance coating...
On the base of the uniform geometric diffraction theory method, using the asymptotical expression for a current of an impedance wire dipole located over a perfectly conducting plane, the fast active algorithms and programs are developed for computations of the directional and polarization characteristics of radiation produced by two synphasely excited crossed dipoles placed in parallel to a square...
This paper studies diffraction of a plane electromagnetic wave by a uniformly moving, anisotropic impedance wedge and presents an exact solution in closed form to a class of impedance wedges based on frame hopping [1] and earlier results for diffraction by such obstacles at rest [2, 3].
Gradient metasurfaces have received significant attention in the past few years, due to their potential for advanced wave manipulation over a thin surface. Following the first, largely inefficient proposals to pattern the impinging wavefront by nanostructuring a plasmonic metasurface, to date there are several elegant approaches to design metasurfaces that can imprint a pattern of choice to the impinging...
The problem of diffraction of a plane electromagnetic wave of p- and s- polarizations incident at an arbitrary angle on a plane-structure is considered in terms of connection with the spread of plasmon-polaritons in the structure. It is shown that the dispersion equation arises from the condition of equality to zero of the reflection coefficient from the structure, i.e. the coincidence of the impedance...
This note deals with a concise description of the approach enabling one to study diffraction of an acoustic plane wave by a semi-infinite angular sector with impedance boundary conditions on its faces.
A radiation field of a radially oriented dipole located on a sphere was studied using an electric Green's function for the space outside of an impedance sphere. The directivity of the spherical antenna in wave zone was determined depending upon variations of the sphere diffraction radius and reactive impedance magnitudes.
The 3D vector problem of diffraction of the field of the system of synphasely excited crossed half-wave wire dipoles of similar geometrical sizes, but with different surface impedances, and located parallel to the perfectly conducting rectangular screen, has been solved. On the base of the uniform geometric diffraction theory method with using the asymptotical expression for a current of an impedance...
The necessary conditions which provide the circularly polarized radiation with maximum directive gain for the in-phase crossed impedance wire dipoles system located over a perfectly conducting square screen have been investigated in the normal direction to the screen. On the base of the uniform geometric diffraction theory method with using the asymptotical expression for a current of an impedance...
The scattering of high-frequency waves by two-part impedance strips is an important topic in diffraction theory because it can provide usefull information concerning the radiation of electromagnetic waves in the presence of discontinuity in the material properties of a surface of finite width, as well as of composite structures on aircrafts, satellites etc. According to the Geometrical Theory of Diffraction...
In this paper, the total far-field pattern around a finite width strip in presence of an electric line source using perfect electric conductor (PEC) and impedance strip equations are presented. We used two dimensional uniform geometrical theory of diffraction (UTD) in both analysis for soft (TM) polarization. For finite PEC strip, we used PEC strip equations and for finite impedance strip we used...
Analysis of the wave propagation modes produced by Ground Wave Radar (GWR) antennas requires the calculation of the diffraction field and its addition to the Geometrical optics (GO) fields in order to determine the total radiation field. In coastal based GWR systems operating in the HF band, diffraction fields are produced by the edges of two non-perfectly conducting wedges; ground wire grid to soil,...
The 3D radiation patterns of the tilted impedance wire dipole located over a perfectly conducting infinitely thin finite size screen are investigated by the uniform geometric diffraction theory method. The technique is developed for definition of a slope angle of the wire dipole taking into account the diffraction effects on the screen edges at which the circularly polarized wave in the set directions...
The high-frequency asymptotic approach to diffraction by strongly elongated bodies is generalized to the case of the impedance boundary conditions. However, this is done only in the limiting case of infinitely flat elliptic cylinder. The representations for the field in the boundary layer near the surface of the strip and for the radar cross section in the case of small scattering angles are derived...
This paper deals with the asymptotic description of the diffraction pattern which is analogous to the classical Weyl-Van der Pol phenomenon (the Weyl-Van der Pol formula). The latter arises in the problem of diffraction of waves generated by a source located near an impedance plane. The incident wave illuminates a circular impedance cone. The singular point of the cone's boundary (the vertex of the...
The changes induced in the near- and far-field scattering by rounding the corners of an illuminated obstacle are discussed as a function of the radius of curvature near such corners. Dirichlet, Neumann or impedance boundary conditions are imposed on the surface. An integral equation formulation is employed; it is found that a graded mesh is necessary to obtain accurate results as well as to enable...
Radar cross section (RCS) reduction using binary structures with non-equidistant matrix arrangement of modules and anisotropic impedance metasurface is presented. The block principle of construction of the binary structures is proposed. Monostatic RCS is reduced on co-polarizations on 15…20 dB in the band 8…16 GHz. Bistatic RCS patterns have no diffraction lobes on co-polarizations. The diffraction...
The rigorous solution of the problem of axially-symmetric TM-wave diffraction by the open end of the bi-cone, which consists of finite and semi-infinite shoulders, is obtained. The structure is irradiated by the ring source of the magnetic current. The mode matching method and regularization technique are applied to obtain the problem solution. The transition from the bi-conical scatterer to the disc-cone...
The interaction of the elastic SH-wave with the defect on the boundary joint of an elastic layer with half-space is investigated. The defect is modelled by the impedance tape on the boundary of a joint. The solution of the diffraction problem is obtained as the infinite system of linear algebraic equations by using the Wiener-Hopf technique. The corresponding characteristic equation is derived for...
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