What is EIRP?

Effective Isotropic Radiated Power or Equivalent Isotropically Radiated Power (EIRP) is a measurement of radiated output power from an ideal isotropic antenna in a single direction.

An isotropic antenna is meant to distribute power equally in all directions – When we channel that power into a single direction and calculate the power it is known as EIRP. It will be the maximum power emitted by the antenna in the direction with highest antenna gain. When calculating EIRP we must take in to account the losses in the transmission line and the loss of power due to the connectors.

EIRP can be used to compare any two emitters regardless of type, size or form. Its unit is dBi.

EIRP is calculated using the following formula.

Click here to view the EIRP Calculator developed by everything RF.

Effective, or Equivalent, Isotropically Radiated Power (EIRP) is the maximum amount of power that could be radiated from an antenna, given its antenna gain and the transmitter power of the RF system. EIRP is most commonly given in decibels over isotropic, dBi.

The IEEE definition for effective radiated power (ERP), which is similar to EIRP, is used to measure RF frequency sources, such as transmitters, and indicate the power of the mainlobe of the antenna that the system would radiate transmitting over a half-wave dipole antenna. The ERP measurement is equivalent to the input power of the antenna multiplied by the antenna gain. EIRP and ERP are different, in that EIRP is based on a hypothetical isotropic antenna, for which a half-wave dipole antenna has an antenna gain 1.64 times, or 2.15 decibels, that of an isotropic antenna.