question about modelling EBG to get the reflection phase

hello
i'm now trying to get the reflection phase properties of EBG stuctures with CST
unfortunately, i have no idea about the first step--------the modelling .
The main problems are :
1 which solver to choose? (The model is only one unit cell with periodic boundaries on xmin xmax ymin and ymax)
2 how can i get the reflection phase ?( use a probe? )

many thanks for your reply