Antenna Near Field & Far Field Distance Calculator

This calculator calculates the reactive near field distance, radiating near field distance (Fresnel region) and the far field distance. Just enter the frequency of operation and the dimension of the antenna.

Calculate the Reactive, Radiating Near Field Distance & Far Field Distance

  • Antenna Length or Diameter (D)
  • Frequency (f)
  • Calculate Reset

Result

  • Wavelength
    m
  • Reactive Near Field Distance
    m
  • Radiating Near Field Distance
    m
  • Far Field (Greater than this distance)
    m
Click here to view image

Where,

D = Antenna dimensions (Can be the length or diameter of the antenna)

f = Signal Frequency

λ = Wavelength

 

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.