Characterisation of a UHF fading channel for an RFID-based EVI system
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On the request of government's transport authority, SANRAL, the North-west University was requested to investigate the applicability of using passive ultra-high frequency (UHF) radio-frequency identification (RFID) for vehicle identification. This work focuses on the characterisation of the physical channel of passive UHF RFID for the purposes of electronic vehicle identification (EVI). A literature study was done on the principles of RFID, radio-wave propagation, fading, elctro-magnetic (EM) modelling, and simulation. An EM modelling package, SuperNEC, was used to resolve static frames of EM environments. An addition to the SuperNEC package was created for analysis of moving vehicles. Models of an RFID reader antenna assembly, tag and discrete vehicle classes were developed, which resulted in five main classes of vehicle models. The orientation angle of the reader antennas, the length of the interrogation zone, and the magnitude of reflected power from metal surfaces were determined from simulations. From the simulations, it was possible to draw profiles of the power received by tags, as well as the energy reflected from metal surfaces on vehicles. Results from simulations were analysed and the optimum reader orientation was found, interrogation zone lengths were found, and bench-marks for reflected energy were found. An alternative placement of tags on bus and truck windscreens was also a result. The initial goal was achieve, namely to address the risk of unknowns in the UHF environment. This work thus serves to support the use of UHF RFID in EVI applications.
- Engineering