A Depolarizing Chipless RFID Tag with Quasi-Loop Resonators

A novel depolarizing chipless RFID tag with quasi-loop resonators is presented. A set of resonators, similar to the concentric loops, are employed in the structure of the proposed chipless tag. Each resonator is composed of a pair of inverted L-shaped microstrips with short horizontal stubs at one end. Due to the layout of resonant elements, a compact dimension of 2.1 cm x 2.2 cm with four resonant peaks in the frequency band from 4 to 9.5 GHz is obtained. A reliable frequency shift encoding (FSE) is realized even though the coupling effect exists between the resonators. The frequency shift encoding enables each resonant element to represent 3.9-bit digital information. Furthermore, the designed chipless tag possesses depolarizing characteristic, increasing the reliability of detection in a harsh environment full of multi-path reflections.