Accession Number : ADA186399
Title : Overestimation of On-Axis Power Density by the Fraunhofer ('Far-Field') Approximation.
Descriptive Note : Final rept.,
Corporate Author : MITRE CORP BEDFORD MA
Personal Author(s) : Weiner, Melvin M
PDF Url : ADA186399
Report Date : Apr 1987
Pagination or Media Count : 25
Abstract : The overestimation of power density by the Fraunhofer (far-field) approximation to the more exact Fresnel (near-field) diffraction integral is determined as a function of Fresnel number at arbitrary on-axis field points for rectangular and circular aperture illuminations of uniform amplitude and phase. For square and circular apertures, the overestimation is 2.8 percent and 1.3 percent, respectively, at a Fresnel number of 1/8 (corresponding to the far field boundary distance D-sq/ lambda) and 518 percent and 147 percent, respectively, at a Fresnel number of 1. Keywords: Antenna aperture; Aperture distribution of uniform intensity and phase circular aperture; Constructive interference; Destructive interference; Diffraction; Fresnel kirchhoff integral; Fresnel number; Optical aperture; Rectangular aperture.
Descriptors : *DIFFRACTION, *ELECTROMAGNETIC WAVE PROPAGATION, *ANTENNA APERTURES, AXES, DENSITY, DESTRUCTION, DISTRIBUTION, FRESNEL INTEGRALS, INTENSITY, INTERFERENCE, POWER, FAR FIELD, ESTIMATES, SHAPE, CIRCLES
Subject Categories : Electricity and Magnetism
Distribution Statement : APPROVED FOR PUBLIC RELEASE