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 $d$ :

(1)

S_{i} = \frac{P_{t 0}}{4 π d^{2}}