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