db is a generic term basically meaning: Decibel. A unit for measuring the
relative strength of a signal. Usually expressed as the logarithmic ratio of
the strength of a transmitted signal to the strength of the original signal.
A decibel is one tenth of a "bel".

the key is that it is a ratio... without a reference a ratio is essentially
meaningless. that is why you often hear that station a is 10db louder than
station b... saying that station a was 10db wouldn't mean anything.

dbm has a built in reference. by definition: Decibels referred to 1
milliwatt.
so the reference is 1 mw. do you can say that the power of a source is 0dbm
meaning that it is 1mw, 10dbm is 10mw, 20dbm is 100mw, -10dbm is .1mw, -20db
is .01mw, etc.

i don't know an ip3, but maybe that will give you a start to know what you
are looking for.



"jason" wrote in message
ups.com...
Hello All

I am beginner in RF
I may ask about some silly question and please pardon me
May I know what actually the unit of dbm and db is different from one
another?
If they are different how can we minus the gain in unit of db from a
IP3 in unit of dbm?
Kindly enlighthen
Thank you all


rgds and thanks
Jason