> 6.3.1 | Calculating dB

> dBm0 is a measure of digital telecommunication signals. It relates to the digital coded signal on the digital side of the network. It should not be confused with any electrical unit. For example, 3.15dBm0 corresponds to a fully scaled digital coded sine wave. For Siemens GSM modules, the correlation between the digital value and the amplitude of the analog signal at 1kHz is given in [1].

> • | dBm0p is the psophometric weighted dBm0 value.

> • | dBV relates to 1Vrms and dBm relates to 1mWrms while you can convert each other assuming a telecom typical nominal resistance of 600Ohms as

> 1Veff = 0dBV ~ + 2.2dBm.

> • | dB is just a gain (G) or attenuation (negative gain). It can be used for both RF and AF, while for RF you usually compare power (P) at a constant impedance and for AF you compare voltages (V).

> G = 10*log(P1/P2) = 20*log(V1/V2)
> Some common values / samples:
> V1/V2 = 10 → G = 20dB P1/P2 = 10 → G = 10dB
> V1/V2 = 2 → G ≈ 6dB P1/P2 = 2 → G ≈ 3dB
> V1/V2 = 20 → G ≈ 26dB P1/P2 = 20 → G ≈ 13dB