Isotropic Radiator

An isotropic radiator is an ideal (theoretical) antenna operating without losses and having equal radiation in all directions.

This antenna is not available in the real world – but is used as a reference for all real-world antenna patterns.

The power density S i radiated from an isotropic radiator is homogeneously distributed over a spherical surface (with the radiator in the center of the spherical surface). With the power P t 0 fed to the antenna, this leads to the following power density S i in a distance d :

S i = P t 0 4 π d 2