EIRP - effective
isotropic radiated power (EIRP) The resulting signal power level, measured in dBm,
of the combination of a transmitter, cable, and an antenna, as measured at the
antenna
Once you know the complete combination of transmitter power
level, the length of cable, and the antenna gain, you can figure out the actual
power level that will be radiated from the antenna. This is known as the
effective isotropic radiated power (EIRP), measured in dBm.
EIRP is a very important parameter because it is regulated
by governmental agencies in most countries. In those cases, a system cannot
radiate signals higher than a maximum allowable EIRP. To find the EIRP of a
system, simply add the transmitter power level to the antenna gain and subtract
the cable loss.
When you work with wireless LAN devices, the EIRP levels
leaving the transmitter’s antenna normally range from 100 mW down to 1 mW. This
corresponds to the range +20 dBm down to 0 dBm.
FCC
Band
|
Allowed Use
|
Transmitter Max
|
EIRP Max
|
|
2.4Ghz ISM
|
Indoor or outdoor
|
30 dBm (1 W)
|
36 dBm
|
|
U-NII-1
|
Indoor only
|
17 dBm (50 mW)
|
23 dBm
|
|
U-NII-2
|
Indoor or outdoor
|
24 dBm (250 mW)
|
30 dBm
|
|
U-NII-2
|
Extended Indoor or outdoor
|
24 dBm (250 mW)
|
30 dBm
|
|
U-NII-3
|
Indoor or outdoor
|
30 dBm (1 W)
|
36 dBm
|
ETSI
|
Band
|
Allowed Use
|
EIRP Max
|
|
2.4 GHz ISM
|
Indoor or outdoor
|
20 dBm
|
|
U-NII-1
|
Indoor only
|
23 dBm
|
|
U-NII-2
|
Indoor only
|
23 dBm
|
|
U-NII-2
|
Extended Indoor or outdoor
|
30 dBm
|
|
U-NII-3
|
Licensed
|
N/A
|
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