IIP3 calculation using SpectreRF in command line

Dear all,

I use spectreRF in order to calculate circuit performances in a linux command line (i do not use virtuoso).

I am currently using a pss+pac analysis and a rapid IP3, in order to get the IP3 value. When I do so, spectreRF writes a file named pac.ip3.pac, however, the IP3 value is not available there!

The only values available are:

VALUE
"RF dBm" "Pwr" -2.000000000000000e+01
"IM1 output V" "Pwr" 1.250615786982958e+00
"IM3 output V" "Pwr" 4.664492147525044e-01
END

How can I calculate the IIP3 value in dBm from this values?
I have seen a few threads here, but no one solved my problem!
Thank you in advance!

Pin=-20dBm
IM1=10*log10(1.25**2/50/2)+30=12dBm
IM3=10*log10(0.46**2/50/2)+30=3.3dBm

Gain=32dB

IIP3=Pin + (IM1-IM3)/2=-15.7dBm

BTW, Rapid IP3 is not reliable at all.
No one use these projection pertubation method.

Thank you pancho_hideboo!

By some other thread here, I saw those formulas and reached that value. The problem is that if I perform a qpss+qpac with a power sweep (from -60 to 10dBm) and calculate the ip3 with this method I get the value of IIP3=1.85dBm.

Of course this changes if I change the input interpolation power to (e.g., between -60dbm and -20dbm). However, for the same circuit this does not happen for the rapid IP3. By the way, what does this input power extrapolation point mean exactly? is it the input power of my system?

So from your experience I should never trust rapid IP3 ?

PS: I am considering qpss+qpac because i am simulating an rf front-end.

It is very natural result.
Study and understand projection perturbation method used in rapid IP3.

I can not understand what you want to mean at all.

Yes.
Don't use and believe rapid IP3.

These order reduction methods were introduced in Spectre-6.0, almost 15 years ago.
However no one use these, since they are not useful at all.
Currently even Cadence don't refer them at all.

See https://www.edaboard.com/showthread.php?t=125073

What algorithm do you use as QPSS, shooting-newton or HB ?
Show me analysis statement of QPSS and QPAC.

in QPSS I use harmonic balance because from my experience it is much faster, and the results are relatively similar.

I send you the analysis statements

.