Broadband Notching Mask for Immunity Improvement of Onshelf UHF RFID Tag

Broadband design (860 MHz–960 MHz) of ultra high frequency (UHF) radio frequency identification (RFID) tag significantly propelled its worldwide application, however also make RFID system suffering interference with other wireless systems severely. A broadband notching mask which is consisted of a pair of split ring printed on flexible 0.3 mm polyethylene terephthalate (PET) is proposed in this paper. A wide band notching effect would be caused by attaching the mask on top face of RFID tag, which turned the wide band tag into a narrow band tag. Thus the immunity of the system can be greatly enhanced. Different notch frequency and bandwidth can be obtained by adjusting the size and geometry of the split ring. The simulations show that after attaching the mask on the tag, the original bandwidth of 750 MHz–1.14 GHz is changed to 670 MHz–890 MHz without any distortion on the radiation pattern of the tag except –1.18 dB gain reduction. The scheme proposed in this paper provides a simple way to avoid interference among RFID and other wireless systems, thus further lowered the threshold of the deployment of UHF RFID system applications.