An impedance matching technique of a UHF-band RFID tag on a high-impedance surface with parasite elements

In this paper, an impedance matching technique of a UHF RFID tag inlet antenna on a high impedance surface (HIS) with parasite elements is studied experimentally. It is shown that, regardless of the fact that the input impedance of the inlet antenna is affected by a vicinal HIS, parasite elements on the HIS can successfully recover the original input impedance and lead to a good matching to the IC chip without any modification to the tag antenna itself. A reading range of 4 m, which is almost the same as that in free space, is demonstrated with a 953 MHz band RFID tag inlet on a HIS with optimized parasite elements, and the validity and usefulness of the technique is confirmed experimentally using a commercial RFID system.