First of all, you have to understand difference between one large signal drive and two large signal drive correctly.
True P1dBin is defined for one large signal drive.
So P1dBin defined under two large signal drive has to be corrected.
True P1dBin will be 3~6dB larger than P1dBin defined under two large signal drive.
I usually use following relation.
P1dBin_One_Input=P1dBin_Two_Inputs+4.5dB
Some people set "Pin_dBm-3dB" for each tone's power in two large signal drive.
This is appropriate if you evaluate correct P1dBin from two large signal drive.
But this is never appropraite if you evaluate IM3 or IP3.
In evaluation of IM3 or IP3, you have to set "Pin_dBm" not "Pin_dBm-3dB".
For example, starter of the following thread are misunderstanding.
http://www.designers-guide.org/Forum/YaBB.pl?num=1262828862/26#26The followings are summary of my simulation results of Class-B Amplifier.
(1) One Large Tone HB Analysis
P1dBin=24dBm
This P1dBin is true value.
If I roughly estimate P1dBin as Class-A operation from P1dB as Class-B Operation, it will be P1dBin=24-6=
18dBm.
(2) Two Large Tone HB Analysis
P1dBin=19dBm
IIP3in=28.275dBmHere this P1dBin is defined under two large signal drive, so this is not correct value.
So we have to correct this P1dBin value.
In this case, P1dBin_One_Input=P1dBin_Two_Inputs+4.5=19+4.5=23.5dBm.
This corrected value is well matched to result of (1).
(3) One Large Tone + One Small Signal HB Analysis
P1dBin=24dBm
IIP3=27.114dBm
The followings are conclusion for analysis of nonlinear amplifier such as Class-B and Class-C Amplifiers.
(1) IP3 can be defined for only linear system essentially.
You have to use IM3[dBc] for characterization for nonlinear amplifier such as Class-B and Class-C Amplifiers.
(2) IM3 output is not subjected to gradient of 3dB/dB line except for some region of input power level.
(3) IM3 characteristics of nonlinear amplifier such as Class-B and Class-C Amplifiers is affected by not only AM/AM but also AM/PM characteristics.
On the other hand, P1dBin is pure AM/AM characteristics.
Well-known relation of "IIP3=P1dBin+9.6dB" is derived under only AM/AM characteristics.
(4) Null of IM3 is true phenomena which is also observed in actual measurement.
This extremely small IM3 is a result of exquisite balance of AM/AM and AM/PM characteristics.
(5) You can not apply slave Small Signal Analysis subjected to master Large signal Analysis such as HBSS, PSS/PAC, QPSS/QPAC for nonlinear amplifier such as Class-B and Class-C Amplifiers.
Especially you must not apply them for evaluation of IM3.
Again see
http://www.designers-guide.org/Forum/YaBB.pl?num=1277203226/3#3(6) If you use estimated P1dBin as Class-A operation and IIP3 where IM3 is relative subjected to gradient of 3dB/dB line,
IIP3=P1dBin+9.6dB can be satisfied.
In this case, P1dBin=18dBm and IIP3=28.275dBm.
P1dBin+9.6dB=27.6dBm is close to IIP3=28.275dBm.