rfid antenna design, pcb antenna

hi,

I am doing a project on rfid and i want to design a tag antenna for 13.56mhz. am using the software eznec, which basically means am designing the antenna in the form of wires initially.

does anyone know how to get the correct dimensions for the antenna, because i can get it to resonate at that frequency but the dimensions are tooo large like 8 by 4 m p.s am trying to design a spiral rectangular antenna

i have only managed to do one loop of the antenna on eznec, but i cant seem to get it in spiral form.

Even a multiturn loop for 13MHz will be 2 meters across. Are you sure you want to pay for a circuit board that big. Your only hope is an aircore coil or a coil on a ferrite rod.