Where Does the Far Field of an Antenna Start? [Stand on Standards]

Mohammad N. Abdallah, Tapan K. Sarkar, Magdalena Salazar-Palma, Vikass Monebhurrun

Research output: Contribution to journalArticle

9 Scopus citations

Abstract

The far field of an antenna is generally considered to be the region where the outgoing wavefront is planar and the antenna radiation pattern has a polar variation and is independent of the distance from the antenna. Hence, to generate a local plane wave in the far field, the radial component of the electric field must be negligible compared to the transverse component. Also, the ratio of the electric and the magnetic far fields should equal the intrinsic impedance of the medium. These two requirements-that the radial component of the field should be negligible when compared with the transverse component and the ratio of the electric and the magnetic fields equal the intrinsic impedance of the medium-must hold in all angular directions from the antenna. So to determine the starting distance for the far field, we need to examine the simultaneous satisfaction of these two properties for all θ and φ angular directions, where θ is the angle measured from the z-axis and φ is the angle measured from the x-axis. It is widely stated in the antenna literature that the far field of an antenna operating in free space, where all the aforementioned properties must hold, starts from a distance of 2D2/λ, where D is the maximum dimension of the antenna and λ is the operating wavelength.

Original languageEnglish (US)
Article number7590187
Pages (from-to)115-124
Number of pages10
JournalIEEE Antennas and Propagation Magazine
Volume58
Issue number5
DOIs
StatePublished - Oct 2016

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electrical and Electronic Engineering

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    Abdallah, M. N., Sarkar, T. K., Salazar-Palma, M., & Monebhurrun, V. (2016). Where Does the Far Field of an Antenna Start? [Stand on Standards]. IEEE Antennas and Propagation Magazine, 58(5), 115-124. [7590187]. https://doi.org/10.1109/MAP.2016.2594002