Flexible microwave chipless tag system based on DGS resonators

In this paper, a flexible microwave tag system using a frequency-scanning type RFID is proposed with multi-resonators based on defected ground structures. While a conventional chip-based tag stores time-sequential codes, the proposed one achieves pure passive tags by using multiresonant bit over a wide frequency range. Moreover, the resonator of the spiral-shaped defected ground structure implemented on the back side of transmission lines has advantages of the excellent band notch characteristics as well as the bit-error avoidance by the re-radiation occurred on normal resonators. The proposed microwave tag is designed and implemented with UWB antennas at 3-7 GHz on the thick FR4 and thin flexible polyimide substrates, respectively. From the experimental results in an anechoic chamber, it has been verified of the excellent recognitions for various 5-bits identification codes.