Antenna Field Regions

Antenna radiation is made up of several different regions. Read on.

Antenna Field Regions

Antenna Field Regions

The transitions between these regions are not distinct and changes between them are gradual. The reactive near-field region is the region close to the antenna and up to about 1 wavelength away from any radiating surface. In the reactive region, the energy decays very rapidly with distance.

In the radiating near-field region, the average energy density remains fairly constant at different distances from the antenna, although there are localized energy fluctuations.

The radiating near-field region extends from the reactive region boundary out to a distance defined as, 2D2/l with D being the largest dimension of the antenna aperture, and l (lambda) being the wavelength.

Beyond this distance is the far-field region where the angular distribution of the energy does not vary with distance, and the power level decays according to the inverse square law with distance.

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