An Enhanced Range Estimation Algorithm based on Trimmed WPD for Passive UHF RFID Systems

As recent RFID interrogators perform coherent detection and allow coherent signal processing, techniques based on the tag phase information are widely concerned for the range estimation. It has a problem of having ambiguities from which the measured phase alone does not interpret the distance since it is periodic. In this paper, we focus on the range estimation with ambiguous wrapped phase for indoor multipath environment. The range estimation algorithm based on trimmed wrapped phase differences(WPD) is presented to improve accuracy. We adopt the alpha-trimmed mean method on multiple frequencies to mitigate the error of wrapped phase differences. Based on the modeling of phase difference error in multipath environment, simulation results show that our algorithm has higher accuracy than classical algorithms.