Basic Concepts of EIRP/ERP

What is EIRP ?

EIRP: Effective Isotropic Radiated Power, the product of the power supplied to the antenna by the radio transmitter and the absolute gain of the antenna in a given direction. An ideal omnidirectional antenna with the same unit gain in all directions is usually used as a reference antenna for wireless communication systems. EIRP is defined as: EIRP=Pt*Gt, which represents the transmission power that can be obtained by the transmitter in the direction of maximum antenna gain compared to an omnidirectional antenna. Pt represents the transmission power of the transmitter, and Gt represents the antenna gain of the transmitting antenna. In wireless communication engineering, it is usually used to measure the intensity of interference and the ability of the transmitter to transmit strong signals.

What is ERP ?

ERP: Effective radiated power. The product of the power supplied to the antenna by the radio transmitter and the gain of the antenna relative to a half-wave dipole in a given direction. In fact, the effective transmission power ERP is used instead of EIRP to represent the maximum transmission power compared to a half-wave dipole antenna. Note: The dipole antenna has a gain of 1.64 (2.15dB), so ERP is 2.15dB lower than EIRP.

dBm: It is a value that measures the absolute value of power. The calculation formula is: 10lgP (power value/1mw). For example, if the transmission power P is 1mw, it is 0dBm after conversion to dBm.

dBi and dBd: dBi and dBd are values that measure gain (power gain). Both are relative values, but the reference standards are different. The reference standard of dBi is omnidirectional antenna, and the reference standard of dBd is dipole, so the two are slightly different. It is generally believed that the same gain is 2.15 greater when expressed in dBi than in dBd. For an antenna with a gain of 16dBd, when its gain is converted into dBi, it is 18.15dBi (generally ignoring the decimal place, it is 18dBi). 0dBd=2.15dBi. The GSM900 antenna gain can be 13dBd (15dBi), and the GSM1800 antenna gain can be 15dBd (17dBi).