| This project presents a design method for Ultra High Frequency (UHF) Radio Frequency Identification Device (RFID) transponder antenna, which can be used in various tracking applications including assets and personnel. The frequency band of interest is 860 to 960 megahertz (MHz).;The factors that influence the overall performance of an RFID system are studied. They include size and shape of antenna, materials selected for fabrication and proximity of objects from the transponder. They are important design parameters and need to be addressed in the design process.;Ansoft High Frequency Simulation Software (HFSS), a Finite Element Method (FEM) simulation software, is used to compute three-dimensional (3D) electromagnetic fields generated by the antenna model. The results are visualized on a Smith Chart for antenna impedance and on a 3D plot for antenna radiation pattern. The antenna parameters are then optimized, seeking good matching between the antenna and Application Specific Integrated Circuit (ASIC) impedance.;Prototype antennas are developed and tested. Parameters such as antenna input impedance and gain are measured. The results of these measurements are used to compute a reflection coefficient and an estimated range of operation for transponders as variation of frequency. The prototype transponders are built and the operation range tested inside the anechoic chamber. The results verify the design method proposed in this project.;A significant portion of this project is dedicated to the analysis of error sources affecting the measurements. The overall approach is to progress in small steps and ensure verification after each stage of the design. In such a way, understanding and accounting for unpredictable effects can be carried out. |
