I will collect my all literature and answer ur questions, since i have not touched microwave since june 2005, for dielectric variation of PBGs i have used this in antennas superstrate, this gives concentration of lobes. i will be back soon. mean while search for antenna superstrate and pbg.
which software you are using in your labs, i have worked with ADS-2004, and Sonnet 9.53
both have given be good results.
In software u can test this by making a patch antenna and then putting your pbg dielectric slab with variations on it and then see the effects you will learn lot from this.
I am in stating level of studying of PBG structure and I have not any simulation, But, I will simulate my structures by matlab, bacause of its flexibility.
regard