Vector Problem Of Diffraction Research Articles

Quasi-Vector Model of Propagation of Polarized Light in a Thin-Film Waveguide Lens

Maxwell equations describe the propagation with diffraction of waveguide modes through a thin-film waveguide lens. If the radius of the thin-film lens is large, then the thickness of the lens varies slowly in the yz plane. For this case we propose the model, which is based on the assumption of a small change in the electromagnetic field in a direction y. Under this assumption the vector diffraction problem is reduced to a number of scalar diffraction problems. The solutions demonstrate the vector nature of the electromagnetic field, which allows us to call the proposed model a quasi-vector model.

ФОРМИРОВАНИЕ ВОЛНЫ С КРУГОВОЙ ПОЛЯРИЗАЦИЕЙ НАКЛОННЫМ ИМПЕДАНСНЫМ ВИБРАТОРОМ, РАСПОЛОЖЕННЫМ НАД ПРЯМОУГОЛЬНЫМ ЭКРАНОМ

PACS number: 07.57.-c Purpose: The conditions for formation of a wave with circular polarization and extremely achievable field density amplitude in the set directions of the main observation planes in the far zone, radiated by the oblique impedance wire dipole located over the rectangular perfectly conducting screen are determined. Design/methodology/approach: To solve the 3-D vector problem of diffraction of a field of arbitrarily oriented impedance thin wire dipole on the perfectly conducting rectangular screen the uniform geometric theory diffraction method is applied, and the asymptotic expressions for an electric current of the horizontal impedance wire dipole with electrical length 0.4 ≤ 2 l /λ ≤ 0.6 are used. Findings: The dipole’s slope angles at which the wave with equal amplitudes of orthogonal components of the electric field vector is radiated, and also the corresponding to them ellipticity coefficients and normalized squared absolute values of the electric field vector as functions of the observation angles and the distance between dipole and screen are calculated accounting for the diffraction effects on screen edges. Conclusions: The technique is developed for determination of an impedance wire dipole slope angle with account for the diffraction effects on screen edges at which the circularly polarized wave is radiated. It is shown that by the choice of an appropriate slope angle and distance of the resonant impedance wire dipole from the screen, the circularly polarized radiation with extremely achievable intensity in the given direction in one of the main observation planes can be realized. Key words: rectangular screen, surface impedance, resonant wire dipole, wave, circular polarization, ellipticity coefficient, field amplitude Manuscript submitted 31.03.2016 Radio phys. radio astron. 2016, 21(3): 216-230 REFERENCES 1. WOODWARD, O. W., 1957. A Circularly Polarized Corner Reflector Antenna. IRE Trans. Antennas Propag. vol. 5, is. 1, pp. 290–297. DOI: https://doi.org/10.1109/TAP.1957.1144512 2. NG, T. S. and LEE, K. F., 1982. Theory of Corner Reflector Antenna with Tilted Dipole. IEE Proc. vol. 129. is. 1, pp. 11–17. DOI: https://doi.org/10.1049/ip-h-1.1982.0003 3. Eliseeva, N. P., 2001. Optimizing the Directivity Factor of a Finite Corner Antenna with a Circularly PolarizedRadiation Field. J. Commun. Technol. Electron. vol. 46, no. 8, pp. 891–900. 4. GOROBETS, N. N. and YELISEYEVA, N. P., 2008. Synthesis of a Circular Polarized Field Radiated by an Electric Dipole Located over a Rectangular Screen. J. Commun.Technol. Electron. vol. 53, no. 1, pp. 26–33. 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GOROBETS, N. N., YELISEYEVA, N. P. and ANTONENKO, YE. A., 2012. Optimization of Radiation Characteristics of Wire-Screened Antennas. Telecommunications and Radio Engineering. vol. 71, is. 1, pp. 59–69. DOI: https://doi.org/10.1615/TelecomRadEng.v71.i1.60 10. Yeliseyeva, N. P. and Gorobets, N. N., 2009. Diffraction of radiation of the wire antenna on the rectangular and corner screen. Kharkiv: V. N. Karazin Kharkiv National University Publ. (in Russian). 11. Nesterenko, M. V., 2010. Analytical methods in the theory of thin impedance vibrators. Prog. Electromagn. Res. B. vol. 21, pp. 299–328. 12. NESTERENKO, M. V., KATRICH, V. A., PENKIN, Y. M., DAKHOV, V. M. and BERDNIK, S. L., 2011. Thin Impedance Vibrators. Theory and Applications. New York: Springer Science+Business Media Publ. DOI: https://doi.org/10.1007/978-1-4419-7850-9_1 13. YELISEYEVA, N. P., BERDNIK, S. L., KATRICH, V. A. and NESTERENKO, M. V., 2015. Electrodynamic characteristics of horizontal impedance vibrator located over a finite-dimensional perfectly conducting screen. Prog. Electromagn. Res. B. vol. 63. pp. 275–288. DOI: https://doi.org/10.2528/PIERB15043003 14. YELISEYEVA, N. P., BERDNIK, S. L., KATRICH, V. A. and NESTERENKO, M. V., 2016. Directional and polarization radiation characteristics of a horizontal impedance vibrator located above a rectangular screen. J. Commun. Technol. Electron. vol. 61, no. 2. pp. 99–111. DOI: https://doi.org/10.1134/S1064226908010038

On the Fredholm property of the electric field equation in the vector diffraction problem for a partially screened solid

We consider a vector problem of diffraction of an electromagnetic wave on a partially screened anisotropic inhomogeneous dielectric body. The boundary conditions and the matching conditions are posed on the boundary of the inhomogeneity domain, and under passage through it, the medium parameters have jump changes. A boundary value problem for the system of Maxwell equations in unbounded space is studied in a semiclassical statement and is reduced to a system of integro-differential equations on the body domain and the screen surfaces. We show that the quadratic form of the problem operator is coercive and the operator itself is Fredholm with zero index.

The modified auxiliary current method applied for the problem of diffraction by a body of revolution with a kinked boundary

A new version of the modified auxiliary current method is proposed for the solution of the vector problem of diffraction by an impedance body of revolution. It is shown that the proposed approach makes it possible to develop efficient algorithms for the solution of this problem for bodies of revolution of various shapes, including scatterers with kinked boundaries. Numerical results for bodies of various geometries are reported, and the high accuracy of the results is demonstrated.

The radiation characteristics of two parallel electric dipoles with a finite screen

The 3D vector problem of diffraction of the fields of two coupled parallel electric dipoles located in parallel to an infinitely thin rectangular perfectly conducting screen is considered. On the basis of the asymptotic solution to this problem, fast algorithms and programs are developed for computation of patterns, the directive gain, and the radiation resistance as functions of the geometric parameters and electric dimensions of the radiating structure. It is shown that, when the distance between a dipole and the screen is fixed, the appropriately chosen distance between the dipoles and the appropriately chosen dimensions of the screen provide for axially symmetric patterns and the maximum maximorum directive gain.

The mixed finite element method as applied to waveguide diffraction problems

A mixed finite element algorithm for solving the vector problem of diffraction by an inhomogeneity in a waveguide is constructed and implemented. Partial radiation conditions are used to proceed to a bounded domain.

Vector diffraction problem of focusing a category 1 aberrated wavefront through a multilayered lossless medium

In optical storage and other imaging applications, a laser beam is focused through a transparent lossless medium of different refractive index. Applications include optical and magneto-optical recording. It is highly likely that, in the near future, conventional magnetic recording will transition to optically/thermally assisted magnetic recording technology. In all these applications, it is necessary to ascertain the quality of the image formed by the focusing apparatus on an imaging surface when in the neighbourhood of the focus, the focused beam of light passes through a stratified lossless medium. This paper examines the vector diffraction problem of focusing radiation through a multilayered medium. The solution is accomplished by first deriving a general solution of the focusing problem in any homogenous medium. This solution is then used to obtain the solution in the multilayered medium by applying continuity of the electric and magnetic fields at the interfaces. The technique used here allows one to calculate the field quantities in the entire image space. Furthermore, the focusing lens may have Seidel aberrations of the fourth order. The salient feature of this method is that the vector diffraction problem is solved only once - for the zeroth layer, immediately next to the exit pupil. In the remaining layers, the results are obtained by solving linear algebraic equations. The solution of the algebraic equations is obtained in closed form.

Vector diffraction problem of focusing a category 1 aberrated wavefront through a multilayered lossless medium

Vector diffraction problem of focusing a category 1 aberrated wavefront through a multilayered lossless medium

Scattering from a slit in a biisotropic medium

An analytical solution is developed for spherical wave scattering by a slit in an infinitely perfectly conducting sheet in a homogeneous biisotropic medium. Interestingly, the vector diffraction problem is reduced to the scattering of a single scalar field, this scalar field being the normal component of either a left-handed or a right-handed Beltrami field. The point source is assumed to be far from the slit so that the incident spherical wave is locally plane. The slit is wide and the sheet thin, both with respect to wavelength. By using the Fourier transform technique the boundary-value problem is transformed into Wiener–Hopf equation that is solved approximately. The diffracted wave field is studied in the far field of the slit. The diffracted field is the sum of the wave fields produced by the two edges of the slit and an interaction wave field.PACS Nos.: 41.20.q, 41.20.Jb, 52.35.Hr

Electromagnetic-Wave Diffraction by a Grating with a Chiral Layer

We consider the vector problem of diffraction of an obliquely incident, elliptically polarized wave by a one-dimensional periodic grating located in a layered medium with a chiral layer. The use of analytical regularization based on the Riemann-Hilbert problem allows us to obtain a rigorous and efficient method for solving such diffraction problems. The performed numerical study reveals certain features of diffraction in the presence of a chiral medium.

Field of a point source within perfectly conducting parallel-plates in a homogeneous biisotropic medium

The spherical wave scattering response by a perfectly conducting open–ended waveguide in a biisotropic medium is obtained. Interestingly, the vector diffraction problem is reduced to the scattering of a single scalar field, this scalar field being the normal component of either a left–handed or a right–handed Beltrami field. Here, we explicitly consider the scattering of the left–handed field component, that of the other scalar field being analogously tractable. The solution is constructed with the aid of the Wiener–Hopf technique.

Diffraction of a spherical electromagnetic wave by a perfectly conducting strip in a biisotropic medium

The diffraction of an electromagnetic spherical wave (emanating from a point source) by a perfectly conducting strip in a biisotropic medium is investigated. This consideration is important because the point source is regarded as a fundamental radiating device. The vector diffraction problem is reduced to the scattering of a single scalar field, this scalar field being the normal component of either a left-handed or a right-handed Beltrami field. The diffraction problem of the left-handed field component is explicitly analyzed, that of the right-handed field component being analogously tractable. The problem is solved using the Wiener–Hopf technique and asymptotic methods. The diffracted field is shown to be sum of fields produced by the two edges of the strip and an interaction field. Finally, physical interpretation of the result is discussed.