EBG Reflection phase Using Waveguide method_HFSS

Hi all,

I have simulated mushroom EBG using HFSS for the attached paper in order to get the reflection phase. I used waveguide method to do that ( 2 PMC & 2PEC walls) as in the attached HFSS file. The rsulted phase of the reflected waves was shifted from that in the paper. My question:

1- When i use this WG method can i consider the reflected phase as the real EBG phase ?

2- Do i need to compare it to PEC sheet phase with the same hight of the top face of EBG ? Why ? and How ? Add pi ? subtract pi ?

3- Is the using of WG model gives good results ? is it better than using PBC ?

Please I need to some help

Mustafa

Please upload the full version of the above paper.
Thank you.