I assume that you need a relationship between ACPR
and IP3, so when you test the device, you don´t
have to use a digital transmitter generator to know
if you are meeting with the ACPR specs, and you
want to meas the ACPR indirectly using the IP3.
What I can recommend is to always polish the
designs with the digital signal and be sure to meet
with the specs. Once you have this, you can characterize
the amplifier measuring many points of it´s IP3
from the P1db to the point of your average power.
This way, you will know the linearity of the peak
to av zone of your amp, this zone is where the digital
modulated signal will be and this is what will define
your ACPR, you can´t predict an ACPR of a peaking
signal with one IP3 point.
An Other way
I never did any simulation, but i
know it can be done (not in a easy way), knowing
the CCDF curve of your signal, the IP3 vs power
characteristic of your amp and your desired avg
output power, you will be able to simulate the ACPR
responce... But it is very slow.. every change you
do on the amplifier you will have to extract all
the IP3 vs power data and enter it again on the
Hope this helps..