Spelling suggestions: "subject:"[een] SCALAR THEORY OF DIFFRACTION"" "subject:"[enn] SCALAR THEORY OF DIFFRACTION""
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[en] SCANNING OF GREGORIAN OFF-SET ANTENNAS BY DISPLACEMENT OF FEEDER / [pt] VARREDURA DE ANTENAS GREGORIANAS OFF-SET POR DESLOCAMENTOS DO ALIMENTADORHELIO FRANCISCO DA SILVA 03 January 2007 (has links)
[pt] Este trabalho tem por objetivo um estudo da viabilidade de
se fazer varreduras com uma antena gregoriana off-set com
deslocamentos apenas do alimentador.
São localizadas as regiões focais para a antena receptora
de modo a posicionar o alimentador de uma maneira simples.
Também são apresentados os diagramas de radiação
correspondentes a estes deslocamentos calculados segundo a
Teoria Escalar da Difração; e as limitações de varreduras
para a antena particular que serviu para testar a
eficiência do método. / [en] This work is related to the study of the pattern of
Gregorian off-set antennas, by displacement of the feeder.
The position of the feeder is obtained, in a simple way,
by determining the focal regions of the antennas, working
in reception.
The radiation patterns corresponding to different position
of the feeder are also presented. Such patterns are
calculated according to the scalar theory of diffraction.
The useful range of scanning, for a given antenna, used to
check the efficiency of the method, is determined.
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Difrakce na prostorových a/nebo hlubokých objektech / Diffraction on Spatial and/or Deep ObjectsHrabec, Aleš January 2008 (has links)
This discourse deals with a theoretical study of the radiation passage through a diffraction screen with non-zero size in the propagation direction of the radiation, i.e. the radiation passage through a three-dimensional object. Without any loss of generality, we solve the problem for cylindrical cavity in metal. The task exceeds evidently standard scalar theory of diffraction, thus we solve the problem using a waveguiding theory. Following the principles of the electromagnetic theory, we derive required formulae to determine mode distribution at the entry of the cavity. Further, we solve numerically the radiation propagation through the cavity, then we actually seek for radiation distribution at the very end of the cavity. This yields, with a help of the discrete Fourier transform, an intensity distribution of Fraunhofer diffraction pattern, consequently compared with an intesity distribution of the radiation pattern of Fraunhofer diffraction on infinitely thin circular opening having the radius of the cylinder cavity under study. A comparison of such patterns results to a conclusion, that the cavity length has a significatn influence on the diffraction pattern and more importantly, that the scalar diffraction theory appears incorrect for a coherent light passage through cavities longer than their radius squared. Similarly, the same conclusion is inversely proportional to a wavelength of the interacting radiation. Finally, we mention an existence of the so called "focal regime", when the radiation repeatedly exhibits roughly one order increased intensity on the symmetry axis of the cavity.
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