Equivalent isotropic radiation power

The equivalent isotropic radiation power ( English equivalent isotropically radiated power , eirp, EIRP ) is a calculation variable which, in the field of antenna technology, expresses the power fed into a transmitting antenna multiplied by its antenna gain . The EIRP uses the isotropic radiator as a reference for the antenna gain , an antenna that theoretically radiates spherically equally on all sides. The power value determined in this way does not occur physically with antennas with directional effect. For antennas with directional effect and if no direction is specified explicitly, the main beam direction of the transmitting antenna is assumed. The antenna gain is maximum in this direction.

If the half-wave dipole is used instead of the isotropic radiator when defining the antenna gain , one speaks of the effective radiated power (erp, ERP).

calculation

{\ displaystyle EIRP = {P_ {s} \ cdot G_ {i}}}

${\ displaystyle P_ {s}}$ : power fed into the antenna (in watts),
${\ displaystyle G_ {i}}$ : Antenna gain compared to an isotropic radiator (dimensionless)

The isotropic radiator is used here as the reference antenna for the antenna gain. In order to identify the reference antenna for antenna gain, this is given in dBi , with the "i" appended to the unit dB standing for the reference antenna "isotropic radiator".

Since ERP and EIRP only differ in the reference antenna for the antenna gain (a half-wave dipole has an antenna gain of 1.64 compared to an isotropic radiator - corresponding to 2.15 dBi), the following relationship exists:

{\ displaystyle EIRP = ERP \ cdot 1 {,} 64}

Or, for example, in logarithmic units:

{\ displaystyle {\ frac {EIRP} {\ mathrm {dBm}}} = {\ frac {ERP} {\ mathrm {dBm}}} + {\ frac {2 {,} 15} {\ mathrm {dBi}} }}

The German term for the EIRP is relatively unusual. For example, the phrase radiated power (EIRP) is often used.

EIRP is often treated as a physical quantity , even if this value does not physically occur in an antenna with directional effect. A unit (watt) is assigned to the calculated variable. Another possibility is to put EIRP after the unit of measurement in brackets, e.g. B. Watt (EIRP) .

Practical calculation

The calculation of the equivalent isotropic radiated power (EIRP) of a WLAN device with exactly one antenna is given below as an example:

+ electrical transmission power ( dBm )

+ Gain of an additional amplifier ( dB ) (if available)

- Attenuation of the cables (dB / m × length)

- Attenuation of the connector (dB) (mostly negligible)

- Attenuation of a lightning protection adapter (dB) (if available)

+ Gain of the antenna (dBi)

________________________________________________________

= EIRP in the unit dBm.

Individual evidence

↑ ITU, Radio Regulations, ARTICLE 1 Terms and definitions, Section VI - Characteristics of emissions and radio equipment, § 1.161: Product of the power supplied to the antenna and its gain in a given direction, based on an isotropic antenna ( isotropic or absolute gain).
^ Hans Heinrich Meinke , Friedrich-Wilhelm Gundlach : Pocket book of high frequency technology , 4th edition 1985, Springer-Verlag: page H4
^ ITU, Recommendation ITU-R V.574-4: USE OF THE DECIBEL AND THE NEPER IN TELECOMMUNICATIONS
↑ ITU, Recommendation ITU-R BS.1195: TRANSMITTING ANTENNA CHARACTERISTICS AT VHF AND UHF

[ITU_RR-1] ITU, Radio Regulations, ARTICLE 1 Terms and definitions, Section VI - Characteristics of emissions and radio equipment, § 1.161: Product of the power supplied to the antenna and its gain in a given direction, based on an isotropic antenna ( isotropic or absolute gain).

[Meinke-Gundlach-2] Hans Heinrich Meinke , Friedrich-Wilhelm Gundlach : Pocket book of high frequency technology , 4th edition 1985, Springer-Verlag: page H4

[ITU-R_V.574-3] ITU, Recommendation ITU-R V.574-4: USE OF THE DECIBEL AND THE NEPER IN TELECOMMUNICATIONS

[ITU-R_BS.1195-4] ITU, Recommendation ITU-R BS.1195: TRANSMITTING ANTENNA CHARACTERISTICS AT VHF AND UHF