18
Decibel formula
X dB [10log (Pout/Pin)] Power ratio (Pout/Pin)
60
1 000 000
50
100 000
40
10 000
30
1 000
20
100
10
10
3
2
0
1
-3
0.5
-10
0.1
-20
0.01
-30
0.001
-40
0.0001
-50
0.00001
-60
0.000001
The notation of the Decibel typically follows the form dBx, where ‘x’ is the reference unit.
Common dBx terms are shown below:
•
Decibels relative to 1 milliwatt (dBm)
•
Decibels relative to 1 Watt (dBW)
•
Decibels relative to 1 microvolt (dBµV)
•
dBi and dBd
dBi is the gain of an antenna relative to an isotropic antenna.
dBd is the gain of an antenna relative to a dipole antenna.
These are related by dBi=dBd + 2.15
