A miniaturized low-profile two-bit QPSK metamaterial inspired phase modulated chipless RFID tag
Date of Issue2018
School of Electrical and Electronic Engineering
RFID is a non-contact automatic identification technology, which automatically identifies target objects and obtains relevant data by radio frequency (RF) signals without manual intervention. However, the high cost and difficulty to fabricate comparing with barcodes limits RFID tags to replace barcodes. Chipless RFID tags refer to RFID tags that do not contain silicon chips which mainly have advantages of low cost and ease to fabricate. In this thesis a vialess passive two-bit metamaterial based Quadrature Phase Shift Keying (QPSK） modulated Chipless RFID tag operating at 2.4 GHz is presented. Based on QPSK modulation, there are four different phase changes of the tag backscattered signal over a period of time. These four phase changes correspond four QPSK symbols by using four independent phase modulating sections which have unique reflection coefficients. The compact CRLH based vialess antenna is an open end zeroth order resonating antenna which is an open end CRLH transmission line(TL) structure with a 0.286λ0*0.168λ0*0.0065λ0 size at 2.4GHz. The time delay of vialess structure is realized by CRLH delay lines which proved to be very useful in reducing the overall size of the circuit while offering significantly longer delays at lower frequencies  comparing with conventional right hand true time delay lines. The composed CRLH delay line provides a 3ns time delay. SRRs and CSRRS are used as discontinuities to achieve abrupt phase changes of backscattered signals. The dimensions of the Chipless tag is 0.32λ0*0.546λ0*0.0065λ0. This Chipless RFID can be used by connected with temperature sensor as well  . Measurement and simulation results show that the proposed Chipless RFID tag is compact and delivers the desired performance.
DRNTU::Engineering::Electrical and electronic engineering