Passive Tag for Multi-carrier RFID Systems

A passive RFID tag derives its power from RF signal emitted by a RFID reader and responds its modulated backscatter signals to the reader. Because of the large propagation loss, the accessible range of a passive RFID tag is hence limited. In addition, the readability of a passive RFID tag is often influenced by multipath fading problems. In order to mitigate the problems, a multi-carrier UHF passive RFID system utilizes isolated power sources which provide additional power to passive RFID tags via a carrier frequency different with the RFID reader operating frequencies. This approach however affects reader command demodulation circuit of a passive RFID tag. This work proposes a new passive tag demodulation circuit design which is more suitable for multi-carrier RFID systems.