Antenna Near Field Distance Calculator
This CalcTown calculator calculates the near field ranges of an antenna. It determines the cross-over distance between the near and far field of an antenna and the limiting distances of the reactive near field, reactive radiating near field and radiating near field regions.
Antenna Near Field Distance Calculator
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Where,
D = Largest dimension of the antenna
f = Operating signal frequency
λ = Wavelength of the signal
Rff = Near field crossover distance (Fraunhoffer distance)
Rrn = Reactive near field limiting distance
Understanding the Antenna Near Field & Far Field Distances
The fields surrounding an antenna are divided into 3 main regions:
Reactive Near Field
The reactive near field ad the radiating near field. The reactive near field is the region where the fields are reactive i.e the E and H fields are out of phase by 90 degrees to each other. For propagating or radiating fields, the fields must be orthogonal to each other but in phase.
Radiating Near Field (Fresnel region)
The radiating near field or Fresnel region is the region between the reactive near and far field. The reactive fields do not dominate in this region. However unlike the far field region, the shape of the radiation pattern varies significantly with distance.
Far Field
When talking about antennas the far field is the region that is at a large distance from the antenna. In the far field the radiation pattern does not change shape as the distance increases. There are three conditions which must be satisfied to ensure that the antenna is at a distance which qualifies as the far field.
