A Miniature Antenna for 2.45 GHz RFID Tag

On the basic of fractal theory and folded technique, a miniature antenna for 2.45 GHz radio frequency identification (RFID) tag applications is designed and analyzed in the present paper. In order to realize the miniaturization of tag antenna, a Hilbert fractal structure is used. Impedance matching between antenna and IC chip is of great importance for improving tag performances. A folded technique is employed to achieve impedance matching flexibly. The value of input impedance of tag antenna can be varied readily only by tuning the high of folded line. The dimensions for the designed tag antenna at 2.45GHz are 23.32mm×7.66mm, and its return loss, bandwidth, and gain are analyzed by HFSS. The detection distance is estimated by Friis transfer theory. Analysis results demonstrate that the tag antenna designed in this paper may satisfy the requirements of RFID tag applications.