hfss periodic structures

I am trying to use HFSS to get the dispersion diagram for periodic structures, say, UCPBG. I used PML boundary ended with nothing and master/slave boundary to simulate periodicity. However, I can not get right dispersion diagram. I don't know if there's something that I need to specify to get right results. Can anybody send me a tuitorial for that type of simulation?

Thanks in advance!

I think this tutorial may help, it is on generating the dispersion diagram of a parallel plate waveguide treated as a periodic structure:

http://emtalk.com/tut_2.htm

Thanks a lot!