Structure of an edge-diffraction wave over a wide angular range

1999 ◽  
Author(s):  
Galina V. Bogatiryova ◽  
Peter V. Polyanskii
2017 ◽  
Vol 9 (4) ◽  
pp. 125 ◽  
Author(s):  
Ugur Yalcin ◽  
Can Altingoz

The uniform scattered fields of the cylindrical wave from a parabolic surface are obtained with the theory of the boundary diffraction wave (TBDW). The non-uniform diffracted field is calculated with the regenerated vector potential and rearranged by considering the Fresnel function to obtain the uniform solution. The uniform scattered fields are calculated as the sum of the diffracted and the geometrical optic fields. The numerical analyses of the diffracted and scattered fields in both uniform and non-uniform solutions are in harmony with the literature. Full Text: PDF ReferencesBaker, B. B., Copson, E. T., The mathematical theory of the Huygens' principles, 2nd Edition, Oxford Press, (1950). DirectLink Lit, J. W. Y. "Boundary Diffraction Waves due to a General Point Source and Their Applications to Aperture Systems" J. Modern Opt., 19, 1007 (1972). CrossRef Otis, G., "Application of the Boundary Diffraction Wave Theory to Gaussian Beams", J. Opt. Soc. Am., 64, 1545 (1974). CrossRef Ganci, S., "Boundary Diffraction Wave Theory for Rectilinear Apertures", Eur. J. Phys., 18, 229 (1997). CrossRef Longhurst, R. S., Geometrical and Physical Optics, 2nd Edition, Longmans [London], (1968). DirectLink Maggi, G. A., "Sulla Propagazione Libra e Perturbata delle Onde Luminose in un Mezzo Izotropo", Ann. di Mat. IIa, 16, 21 (1888).Rubinowicz, A., "Die Beugungswelle in der Kirchoffschen Theorie der Beugungsercheinungen", Ann. Physik, 4, 257 (1917). CrossRef Miyamoto, K. and Wolf, E., "Generalization of the Maggi-Rubinowicz Theory of the Boundary Diffraction Wave Part I", J. Opt. Soc. Am., 52, 615 (1962). CrossRef Miyamoto, K., Wolf, E., "Generalization of the Maggi-Rubinowicz Theory of the Boundary Diffraction Wave Part II", J. Opt. Soc. Am., 52, 626 (1962). CrossRef Born, M. and Wolf, E. Principles of Optics Seventh edition, Cambridge Univ. Press, (1999). CrossRef Alt?ngöz, C., Yalç?n, U. "Calculation of the Diffracted Waves from the Edge of an Opaque Cut Cylinder by the Boundary Diffraction Wave Theory", Journal of the Faculty of Eng. and Arch. of Gazi University, 28, 85, (2013). CrossRef Yalç?n, U. "Yutucu Yar?m Düzlemin Kenar?ndan K?r?nan Üniform Alanlar?n S?n?r K?r?n?m Dalgas? Teorisi ile Hesab?", Çankaya Üniversitesi 2.Müh. ve Tek. Sempozyumu, (2009). (In national language) CrossRef Lee, S. W. and G. A. Deschamps, \A uniform asymptotic theory CrossRef Lee, S. W., "Comparison of uniform asymptotic theory and Ufimtsev's theory of electromagnetic edge diffraction," IEEE Trans. Antennas & Propagat., Vol. 25, 162-170, 1977. CrossRef Yalç?n, U., "Uniform Scattered Fields of the Extended Theory of Boundary Diffraction Wave for PEC Surfaces", PIER M, 7, 29, (2009) DirectLink Yalç?n, U., "Analysis of Diffracted Fields with the Extended Theory of the Boundary Diffraction Wave for Impedance Surfaces", Appl. Opt., 50, 296 (2011). CrossRef Sarn?k, M., Yalç?n, U., "Uniform scattered fields from a perfectly conducting parabolic reflector with modified theory of physical optics", Optik-International J. for Light and Electron Opt., 135, 320 (2017). CrossRef Sarn?k, M., Yalç?n, U., "Modified theory of physical optics and solution for scattering fields from a perfectly conducting parabolic reflector", 16th Int. Conference on Math. Met. in Electromagnetic T. (MMET), July 5-7, Ukraine, 349 (2016). CrossRef Umul, Y. Z., Yalç?n, U. "Asymptotic Evaluation of The Edge Diffraction In Cylindric Paraboloidal Surface Antennas", Mathematical & Computational App., 8, 143 (2003). CrossRef Yalç?n, U., "Scattering from a cylindrical reflector: modified theory of physical optics solution", J. Opt. Soc. Am. A, 24, 502 (2007). CrossRef


Author(s):  
Yu Liu

The image obtained in a transmission electron microscope is the two-dimensional projection of a three-dimensional (3D) object. The 3D reconstruction of the object can be calculated from a series of projections by back-projection, but this algorithm assumes that the image is linearly related to a line integral of the object function. However, there are two kinds of contrast in electron microscopy, scattering and phase contrast, of which only the latter is linear with the optical density (OD) in the micrograph. Therefore the OD can be used as a measure of the projection only for thin specimens where phase contrast dominates the image. For thick specimens, where scattering contrast predominates, an exponential absorption law holds, and a logarithm of OD must be used. However, for large thicknesses, the simple exponential law might break down due to multiple and inelastic scattering.


Author(s):  
J.D. Geller ◽  
C.R. Herrington

The minimum magnification for which an image can be acquired is determined by the design and implementation of the electron optical column and the scanning and display electronics. It is also a function of the working distance and, possibly, the accelerating voltage. For secondary and backscattered electron images there are usually no other limiting factors. However, for x-ray maps there are further considerations. The energy-dispersive x-ray spectrometers (EDS) have a much larger solid angle of detection that for WDS. They also do not suffer from Bragg’s Law focusing effects which limit the angular range and focusing distance from the diffracting crystal. In practical terms EDS maps can be acquired at the lowest magnification of the SEM, assuming the collimator does not cutoff the x-ray signal. For WDS the focusing properties of the crystal limits the angular range of acceptance of the incident x-radiation. The range is dependent upon the 2d spacing of the crystal, with the acceptance angle increasing with 2d spacing. The natural line width of the x-ray also plays a role. For the metal layered crystals used to diffract soft x-rays, such as Be - O, the minimum magnification is approximately 100X. In the worst case, for the LEF crystal which diffracts Ti - Zn, ˜1000X is the minimum.


1995 ◽  
Vol 17 (4) ◽  
pp. 6-12
Author(s):  
Nguyen Tien Dat ◽  
Dinh Van Manh ◽  
Nguyen Minh Son

A mathematical model on linear wave propagation toward shore is chosen and corresponding software is built. The wave transformation outside and inside the surf zone is considered including the diffraction effect. The model is tested by laboratory and field data and gave reasonables results.


2011 ◽  
Vol 57 (1) ◽  
pp. 115-120 ◽  
Author(s):  
Mariusz Zamłyński ◽  
Piotr Słobodzian

Influence of the Aperture Edge Diffraction Effects on the Mutual Coupling Compensation Technique in Small Planar Antenna Arrays In this paper the quality of a technique to compensate for mutual coupling (and other phenomena) in small linear antenna arrays is investigated. The technique consists in calculation of a coupling matrix, which is than used to determine corrected antenna array excitation coefficients. Although the technique is known for more than 20 years, there is still very little information about how different phenomena existing in a real antenna arrays influence its performance. In this paper two models of antenna arrays are used. In the first model the effect of mutual coupling is separated from the aperture edge diffraction. In the second model antenna both mutual coupling and aperture edge diffraction effects are included. It is shown that mutual coupling itself can be compensated very well and an ultralow sidelobe level (i.e. -50 dB) could be achieved in practice. In the presence of diffraction effects -46.3 dB sidelobe level has been attained, but radiation pattern can be controled only in narrow angle range (i.e. up to ±60°).


1974 ◽  
Vol 10 (10) ◽  
pp. 167 ◽  
Author(s):  
G.L. James
Keyword(s):  

1968 ◽  
Vol 6 (3) ◽  
pp. 207-212 ◽  
Author(s):  
G. Meyerhoff ◽  
U. Moritz ◽  
R. L. Darskus

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