Rfsurfer, thank you very much.
I have almost understood. at first, sorry for my enlish, i speak little. it presents some difficulties for me and other people. That's why i have some questions? Could you advice me?
I read the paper which attached here. And i don't understand why the intermodulation distortion are converted to voltages distortion and after added.
Assume two cascaded stages.
IM3_1 - output distortion power generated in stage 1,
IM3_2 - output distortion power generated in stage 2,
IM3 - overall distortion (watts or milliwats).
Can i add the ditstortion power due to stage 1 and stage 2 referred to output all system as
IM3=IM3_1*G2+IM3_2 (watts or milliwats) ?
where G2 - power gain of stage 2.