# Getting Extinction cross section from Radar cross section using HFSS

1. Sep 2, 2010

### El Flea

Hi, Has anyone tried using the HFSS software to get the extinction cross section of a particle?

I've been told that the extinction cross section of a particle is the imaginary part of the radar cross section in forward direction, so I did exactly what the RCS tutorial from HFSS did, except using my own model and frequencies, and getting just the 0deg im(ComplexRCS).
Where, I'm supposed to get results around 1 point something, I got results around 1e-13 and some negative numbers. And it gets even smaller if I divide it by the wavenumber. Was I wrong to just take the imaginary part of the radar cross section in 0deg as the extinction cross section?