




Aperture Antennas and Diffraction Theory
The Institution of Engineering and Technology, 1981 eISBN: 9781849193733  Cloth: 9780906048528 Library of Congress Classification TK7871.6.J85 1981 Dewey Decimal Classification 621.380283
ABOUT THIS BOOK  TOC
ABOUT THIS BOOK
Two powerful techniques for the analysis of aperture antennas are now used. One is based on the convenient Fourier transform relationship between aperture field and farfield radiation pattern. Here this relationship is derived from the plane wave spectrum representation of the aperture fields. In the near field of the aperture, Fourier transforms become Fresnel transforms. Farfield patterns may be predicted from nearfield measurements by treating the near field as the aperture plane. In its application this method is basically the Kirchhoff approximation of diffraction theory. It is accurate for the forward fields of large antennas but cannot provide the lateral and back radiation. The other method is based on aperture edge diffraction and called the geometrical theory of diffraction. It is developed from an asymptotic approximation to rigorous diffraction theory. Inherently more accurate and more widely applicable, it is especially useful in the calculation of antenna radiation in the lateral and rear directions. However, at present it fails in some situations where the Kirchhoff method succeeds, for example the axial fields of paraboloidal reflectors. In this sense the two methods are complementary and often both are required in antenna analysis. Application of the two methods to the calculation of the pattern, gain and reflection coefficient of some common antenna types is shown and comparisons are made with experiment. See other books on: Diffraction  Electronics  Radio waves  Technology & Engineering See other titles from The Institution of Engineering and Technology 
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