UHF RFID uygulamaları için yeni bir anten çoklayıcı sistemi

UHF passive RFID is an emerging technology that is increasingly being used in many fields of industry where the identification and tracking is required. One of the major challenges in passive RFID is to increasing the tag reading zone. The most common method for increasing the tag reading zone is to use multi antenna systems which are placed at different locations. This method requires setting up a system with antenna multiplexers to increase the number of antenna outputs of UHF RFID reader. However, there are certain limitations when multiple antennas connected to a single RFID reader by using multiplexers such as insertion losses of ICs and number of antenna outputs. In this thesis, design, implementation, and test results of a CAN based antenna multiplexing system for UHF RFID applications has been presented. Designed system has novel features that provide flexible configuration based on application requirements such as cascade connection up to three stages and reliable communication between multiplexers with reduced number of wires. The system is implemented with three major subsystems; the main controller node, which converts digital input signals to CAN messages and controls other CAN nodes, the multiplexer node which is responsible for switching the antenna channels and the RF switching unit that consists RF switch ICs that multiplex antenna channels. Performance results of the embedded system showed that each of the CAN based multiplexer node could be controlled simultaneously and the time delay due to the command processing operations is insignificantly low. Insertion loss of the RF switching unit is measured as -1.342 dB at 865MHz, which is better than expected. The system was also tested with an RFID reader and antennas to demostrate antenna switching, cascade connection and tag reading performance. This thesis is a part of Smart Shelf Design project funded by the Scientific and Technological Research Council of Turkey. Within the scope of this thesis, antenna multiplexing system of this project has been succesfully prototyped. Currently, the project is still under development and the large-scale testing with more antennas (near field) is scheduled in winter 2015.