Near Field and Far Field from the Antenna Calculator

Posted by Dinesh on

The radiation pattern in the region close to the antenna is not exactly the same as the pattern at large distances. The term near-field refers to the field pattern existing close to the antenna. The term far-field refers to the field pattern at large distances. The far-field is also called the radiation field, and is what is most commonly of interest. The nearfield is called the induction field (although it also has a radiation component).

Ordinarily, it is the radiated power that is of interest so antenna patterns are usually measured in the far-field region. For pattern measurement, it is important to choose a distance sufficiently large to be in the far-field, well out of the near-field. The minimum permissible distance depends on the dimensions of the antenna in relation to the wavelength.

Formula:

rmin = 2D2 / ?

Where:
rmin is the minimum distance from the antenna
D is the largest dimension of the antenna
? is the wavelength