Import models in hfss, help on the format

I have to study a 3d model, in hfss or cst, scanned by a 3d laser scanner.
My problems are on the choice of the model format (.sat, .dxf, .stl, .step, ...).
Ah, the model is a closed surface of 400,000 faces.

Thanks.

.sat is catia/CAD file
I think DXF should work.
But what is the format you have? I am not sure that laser scanner output file will be opened in HFSS.
It it opens tell us too.

I think DXF is not good for this problem

Try STL format (it describes 3D object by mesh that is spread on object surface .. so if you have scanned object by 3d laser scanner the STL format describe your object with no problem). Originally, this format is developed to this task (STereoLithography).
400 000 faces are quite good. Sometimes, I import geometry with several milions of faces to CST and everything is OK.
If you have chance to import such geometry in CST in SAT, try it (it is "native and best supported format" for this software).

Advice: don't forget to proper representation in EM environment (check if imported geometry suits with reality (volumes vs sheets))