what is the Floquet Port deembed distance mean in HFSS

simulating a FSS unit with Floquet Port,
when setting Floquet Port ,post processing, deembed distance
how can i set the value of deembed distance


need your help ,and thank you

i know it now
it is a way to calcullate the phase of S parameter

So would you please enlighten me about how to set these parameters? My email is nseagull at gmail dot com.