need HElp: semi passive microstrip antenna for Rfid at 8GHz

Hi,

I'm a student and I have to design a project.

I need to design an microstrip antenna at 8 Ghz for rfid application . from my survey i can't find any chip on that frequency.

so I decided to design semi-passive RFID tag. I need some advices. Where should I start to design this.? what requirement that i need ? can anyone give me some idea on this?