A Link Analysis for Passive UHF RFID System in LOS Indoor Environment

A link analysis model for passive UHF RFID system in LOS indoor environment is developed and demonstrated. Using this model, the power received by tag and the read performance are investigated. The multipath fading and RMS delay spread for UHF RFID system are analyzed by a 5-ray model with different polarization, e.g., horizontal polarization, vertical polarization, and circular polarization. A practical test is developed on an indoor balcony of an office building. In addition, the electric field environment is simulated using the tool of Ansoft HFSS for the analysis of multipath degradation. The results of theoretical analysis, simulation and test are almost conformable, and the small scale fading and the field nulls are observed. Multipath degradation affects the UHF RFID system so much on read performance, and it is still a key limitation on system performance. More research on anti-multipath interference should be developed, e.g., high gain antenna, high sensitivity tag and reader receiver, and more effective protocols, and so on.