Directivity
Directivity is the ratio of the radiation intensity in a given direction from the antenna in relation to the radiation intensity averaged over all directions.
If the main direction of radiation is known, the directivity can be calculated for each antenna pattern with the following equation:
indicates the maximum radiated power density and indicates the power density radiated by the isotropic radiator.
It is also possible to determine from the directional characteristic with:
If the antenna pattern consists of a discrete number of values, the integrals in the equations must be substituted with a summation with increments and :
Often the directivity of an antenna is given in dB. The logarithmic value in dB can be obtained from the linear value of the directivity with the following equation: