DESIGN,FABRICATION,AND MEASUREMENTOF TAGAND READER ANTENNASFOR RFID APPLICATIONS

Abstract

Radio Frequency Identification (RFID) system used to monitor data included in object through radio waves between reader and tag automatically without need of direct connection. RFIDsystemconsists of tag which carries objects identifying data, reader that demodulates the received signal from tag to exclude the identified data then send it back to computer, and host computer which manages the data sent by the tag. The tag separated from reader by distance called reading range. This range depends on IC chip used, performance of antenna, frequency range,etc. Manufacturing of RFID system receives a great attention in the recent years. It reduces inventory control, reduce time and cost, control goods properties like: temperature, humidity,etc. In this thesis two proposed methods of input impedance calculation for Bow-Tie antenna are introduced. The proposed methods show input impedance calculation with high accuracy. Also, design curves for input impedance values were developed depending on the geometry of antenna. The proposed design curves are used to design a conventional and modified bow-tie RFID tag antennas. The input impedance of the tag antenna is calculated using proposed methods and compared with that obtained using CST studio suite 2014 and IE3D Zeland version 12.0 software packages. The results are investigated and discussed. A modified bow-tie antenna was designed so as to achieve a better conjugate matching to complex chip impedance and also to increase the bandwidth than conventional one. The antenna results demonstrate that it has maximum reading range which extends to 6m. The tag antennas are fabricated, measured using vector network analyzer and the obtained input impedance is compared with the simulation and the proposed methods. Then uncertainty budget is calculated for both antennas. A UHF RFID patch tag antenna was also designed and simulated. This antenna is suitable to be attached on metallic objects as it gives a high performance. It has a thin substrate thickness which is flexible so as to be curved to be mounted on metallic cylinder with a good performance. The results of simulated reading range indicates that it is larger in free space than on metal surface , on metallic cylinder is . RFID reader circularly polarized slot antenna with microstrip linecircular disk end is designed, fabricated and measured using vector network analyzer. This antenna achieves a good matching to impedance of 50Ω, wide impedance bandwidth, axial ratio covers 2.3% of universal frequency band. Also, two modified shapes of CP patch antenna with stacked three slot- rings was implemented and simulated using CST simulation tool. The first modified shape achieved a good matching to 50Ω impedance ,wide impedance bandwidth, increase in gain, while the second one performance degrades, its 3-dB axial ratio bandwidth decreased.