Overestimation of On-Axis Power Density by the Fraunhofer ('Far-Field') Approximation.

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.

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Document Details

Document Type
Technical Report
Publication Date
Apr 01, 1987
Accession Number
ADA186399

Entities

People

  • Melvin M. Weiner

Organizations

  • MITRE Corporation

Tags

Communities of Interest

  • Air Platforms
  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Air Force
  • Amplitude
  • Antenna Apertures
  • Antennas
  • Applied Mathematics
  • Boundaries
  • Diffraction
  • Equations
  • Far Field
  • Fresnel Zones
  • Governments
  • Illumination
  • Integrals
  • Intensity
  • Magnetic Fields
  • Mathematics
  • Near Field

Fields of Study

  • Physics

Readers

  • Electromagnetic Wave Scattering and Antenna Radiation Engineering