ebg antenna

I m designing the microstrip antenna (3.1-10.6Ghz). The bandwidth of the antenna was degraded seriously (in low frequency range) because of the ground reflector effect. I want to design the simple ebg substrate (square metalic patch array over the dielectric substrate) to replace the ground.
Does anyone have some suggestions for this ebg structure. I get difficult with this structure in the frequence range (3 - 10GHz) especially in the low freq range.

Please help me.
Thanks in advance

remained me later about your post,
I have to look at home, I think that I have an article which may help you

Thanks for your reply.

Do u have any suggestion about this problem.

I send you two articles, if you have any questions feel free to ask.

Thanks for your reply.

My antenna is microstrip type (spiral on dielectric substrate). I want to make it radiate unidirectionally so the antenna is backed by ground on the backside of the substrate. But with ground, the bandwidth is degraded seriously. As I know, the reason for this phenomena is multi-reflections in the substrate (knowned as ground effect). I wonder that it relate to the problems in these article (harmonic supress) or not.
I posted here the s11 (even with ebg substrate replaced ground). The ebg is designed to act as AMC at 5Ghz. Can u give me some suggestion for this.

its quite interesting problem:)

EBG add to the equivalent circuit some capacity and induction it is more useful for miniaturization of the antenna.
Maybe it will be better to look at structures called FSS - frequency selective surface or ferrite loops (you will find for ex. in Pozar).

In the next week I will tray to find something.