Specific Units

Voltage Units

Due to the wide dynamic range of signals in EMC, we use decibel instead of linear units. In other words, we replace µV, mV, kV and mega-volt by corresponding values. Both currents and voltage are described in dB.

Radio frequency integrated circuits such as the ones used in mobile phones are sensitive to very small amplitudes of signal. Consequently, the dBµV unit is also commonly used. 0dBµV is equal to 1µV.

Wide dynamic range of signals
in EMC → use of dB (decibel)

We use dBV, dBA.

dBV = 20 log (V)
dBA = 20 log (A)

We also use dBµV

V_dBµV = 20 log (V/1µV)

Power Units

For power, we use the dBm unit, where m (very simply) means milli-watts. Fill the dBm/Watt scale according to this formulation.

The most common power unit is the "dBmW"
(dB milli-Watt)

P_dBmW = 10 log (P/ 1mW) = 10 log (P) + 30

We can also have the equivalence between V_dBµV
and P_dBmW with P = V ² / Z :

Exercise: Specific units

1 mV = ___ dBµV
1 W = ___ dBmW
0dBm in 50 Ω = ___ dBµV