What is the reference plane of S parameters measurement of ATF36077?

What is the reference plane of S parameters measurement of ATF36077?
Is it measured at the red line in the picture?

PS: the red line is add by myself, not by Avago

It tells the model is accurate without accounting the the lead inductance/para cities.

Hi, Kspalla,

Although there are many para cities, I think Avago test the S para of the ATF36077 with package. So I guess that the red line is the reference plane, am I right?

there are a lot of papers decribes the S para measurement fixtures, but I haven't seen one paper clearly define the reference plane.

Yes and correct.