B9. Simple Microstrip Bandstop Resonators for Chipless RFID Tag

This paper presents a new radio frequency identification (RFID) chipless tag operating in the frequency span 3.5-4.3 GHz. This frequency band can be used for chipless RFID systems in the case of car-to-infrastructure (C2I) communication and may be used in automatic reading of road signs. It focuses on the integration of the antenna and multiresonator structures to form the chipless RFID tag. The tag consists of triangle microstrip filter. A 6-bit chipless tag is designed. The bits are encoded into the spectrum hence the tag has a unique spectral signature. The chipless tag is comprised of a vertically polarized circular UWB microstrip monopole receiving tag antenna, a multiresonating circuit and a horizontally polariz ed circular UWB microstrip monopole transmitting tag antenna. The multiresonating circuit is designed by cascading triangle resonators next to the microstrip line with different positions of cutting slot in the triangle side so that a multiple resonances occur. The simple opening of the triangle side shifts the resonant frequency of the triangle resonator to an insignificant frequency, which is not used in the band. Each resonance is separated by approximately 100 MHz from each other. A commercial based soft ware, the finite-element method and the finite-integration technique are used to investigate the characteristics of the chipless RFID tag.