Antenna Factor is defined by the ratio of the electromagnetic field received by an antenna to the voltage produced at the output terminal of the antenna.

Antenna Factor is an important parameter for EMI/EMC testing (electric field strength (E-field) measurements), where the Antenna Factor specification defines the relationship between the electric field strength (E) around the antenna and the voltage induced by the antenna (V).

Antenna Factor is expressed in dB/m and the equation used to calculate it can be seen below:

Where,

At any specific frequency, the antenna factor always has a linear relationship with the electric field received by the antenna. So the antenna factor can be used to determine the value of an incident electric field, by simply adding the antenna factor value (expressed in dB) to the value of voltage measured (expressed in V). This is one of the main advantages of using antenna factor while taking the emissions measurements for EMI-EMC testing.