Dispersion Effects at High Bandwidth Localization for UHF RFID Tags

Position estimation of UHF RFID tags is a feature, which brings new applications to the fore, e.g. indoor navigation, object localization, etc. This paper proposes a wide-band signal architecture for UHF RFID systems, estimating the distance between reader and tags on basis of signal propagation delay evaluation. However, the main focus is on dispersion effects, which arise if high bandwidth signals are utilized to estimate the range in the UHF RFID band. Therefore, this paper will shortly present the hardware used and the signals within the system, which result in distance measurements. It will be shown, that the reader's non-constant frequency-dependent impedance over the whole bandwidth causes dispersion effects, which will distort the wide-band signals in a way, that negatively influences the resolution error. A comparison between experimental signals and derived signals including the distortion effects shows, that the large part of this distorting effect is owed to the reader's impedance mismatching.