Mixer's IIP3 in upconvertion mode

Hello to everyone!

I have designed an double balanced mixer in Ka band. When I count an mixer's IIP3 in downconvertion mode, I have a result about 16-18 dBm in my band. But... When I do the same count, but in upconvertion mode, I have a lower value IIP3, about 11-12 dBm.

I found the same situation in Avago AMMP-6545, but I don't understaind it... Could some one tell me a physical cause for lowering IIP3 in upconvertion mode? Or, may be, could some one tell me the name of a book, or a paper, where I could find a reason for my problem?

Thanks a lot

It might be due to lower Power Gain of the Mixer and worse non-linearity due to its nature.
The difference is not huge, seems normal.

Usually mixers are dedicated for down-conversion, or for up-conversion, and rarely for both.
Mainly due to their output port frequency characteristics (IF for down-conversion, and RF for up-conversion) there is a challenge to make a mixer working for both, down-conversion and up-conversion.
And for this reason their IP3 will be slightly different.