I've been playing with the NCD/DCD with excel, and there's something I can't seem to work in there.
Granted, I'm relying on 30 year old memories from when I was working on microwave radios in the air force. But if memory serves me right, then a change of 3 db is double the power, and -3 db is half the power. And since the impedance is constant, it also means the voltage is either doubled or halved.
So let's assume the signal is scaled so that the (maximum A/D reading +1) corresponds to +7 dbm. Then half of that would be 512 or +4 dbm.
If you keep dividing that down, since there's only 10 bit's, you end up with a minimum of -23 dbm with an A/D input of 1.
And it appears that it would take a resolution of 16-bits to be able to get down to -40 dbm.
I think this applies to however you do it. Lookup, calculate, ...
ADDED: And any noise or offset voltages will Obliterate the low end.
But then, maybe I've got it all wrong? ??
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