Field regions

Field regions.

Picture showing the three regions of an antenna

Enter the frequency f, the dimension d, and click the "Calculate" button to compute the two radii r₁ and r₂.

The space surrounding an antenna is usually subdivided into three regions: the reactive near-field, the radiating near-field (Fresnell) and the far-field (Fraunhofer) regions. These regions are so designed to identify the field structure in each, but no abrupt changes in the field configurations are noted.

Reactive near-field region: That portion of the near-field region immediately surrounding the antenna wherein the reactive field predominates.

Radiating near-field (Fresnel) region: That region of the field of an antenna between the reactive near-field region and the far-field region wherein radiation fields predominate and wherein the angular field distribution is dependent upon the distance from the antenna.

Far-field (Fraunhofer) region: That region of the field of an antenna where the angular field distribution is essentially independent of the distance from the antenna.

Bibliography:

C.-A. Balanis, Antenna theory, analysis and design Wiley, 1997, Chapter 2.

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Frequency:	f =	Hz
Maximum dimension of the antenna:	d =	m

Reactive region radius:	r₁ =	m
Radiating region radius:	r₂ =	m

Reactive near-field region:	That portion of the near-field region immediately surrounding the antenna wherein the reactive field predominates.
Radiating near-field (Fresnel) region:	That region of the field of an antenna between the reactive near-field region and the far-field region wherein radiation fields predominate and wherein the angular field distribution is dependent upon the distance from the antenna.
Far-field (Fraunhofer) region:	That region of the field of an antenna where the angular field distribution is essentially independent of the distance from the antenna.