effective isotropically radiated power
In radio communication systems, Effective isotropically-radiated power (EIRP) is the amount of power that would have to be emitted by an isotropic antenna (that evenly distributes power in all directions) to produce the peak power density observed in the direction of maximum antenna gain. EIRP takes into account the losses in transmission line and connectors and effective isotropically radiated power the gain of the antenna. The EIRP is often stated in terms of decibels over a reference power level, that would be the power emitted by an isotropic radiator with an equivalent signal strength.
- EIRP(dBm) = (power of transmitter (dBm)) – (losses in transmission line (dB)) + (antenna gain(dB))
where antenna gain is expressed relative to a (theoretical) isotropic reference antenna.
This example uses dBm, although it is also common to see dBw.
Decibels are a convenient way to express the ratio between two quantities. dBm uses a reference of 1mW and dBw uses a reference of 1W.
- dBm = 10 log(power out / 1mW)
and
- dBw = 10 log(power out / 1W)
A transmitter with a 50W output can be expressed as a 16dBw output
- 16.9897 = 10 * log(50/1)
The EIRP is used to estimate the service area of the transmitter, and to co-ordinate transmitters on the same frequency so that their coverage areas do not overlap.
In built-up areas, regulations may restrict the EIRP of a transmitter to prevent exposure of personnel to high power electromagnetic fields.
See also
- Effective radiated power
Electronics Topics
The field of electronics is the study and use of systems that operate by controlling the flow of electrons or other electrically charged particles in devices such as thermionic valves and semiconductors. The design and construction of electronic circuits to solve practical problems is part of the fields of electronic engineering, and the hardware design side of computer engineering. The study of new semiconductor devices and their technology is sometimes considered as a branch of physics.
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