Phased Array Antenna for UHF RFID applications Using Artificial Transmission Lines

In recent years, ultra-high-frequency (UHF) radio frequency identification (RFID) systems have drawn more and more attentions in a wide variety of applications such as retail item management, access control system, electronic toll collection, and etc. By incorporating with a commercial RFID reader, it has been noted that the phased array antenna can be implemented in a RFID system to either control the interrogation region or to improve the successful tag identification rate. The switch-beam antenna, which is capable of sequentially steering the radiation beam to certain pre-defined spatial directions for given periods of time, can be applied to improve the successful tag identification rate since the tags to be interrogated in such an arrangement can be illuminated by higher transient RF power. By utilizing the switch-beam antenna array, it is believed that the carrier-to-interference (C/I) ratio of a RFID system can be substantially improved along the direction to which the mainbeam of the antenna array illuminated.