Here is what I promised from my AI on dBmV, etc.. I
have copied the reflector to solicit review, as well, in case I’ve missed
something.
Definitions:
- dBmV (dB millivolts): The
decibel ratio of an RMS voltage value relative to one millivolt.
Hence 20 mV(rms) is equal to 20*log10(20mV/1mV) = 26 dBmV.
Note that this does not depend on the impedance level.
- dBm (dB milliwatts): The decibel ratio of a
power value relative to one milliwatt. Hence, 20mW is equal to 10*log10(20mW/1mW)
= 13dBm. If this power were measured at a 50 ohm impedance level,
20mW would be equivalent to sqrt(0.02W*50ohms) = 1V (equal to 60dBmV).
However, at a 25 ohm impedance level (the ref impedance for common mode
measurements), the same 20mW would be equivalent to sqrt(0.02W*25ohms) =
0.707V (equal to 57dBmV).
Below is the proposed Vcm spec with dBmV values on the left
y-axis and dBm values on the right y-axis:
Regards,
Mike