Spatial Statistics of Received UHF RFID Phase in Indoor Environment Using Distributed Reader Antenna System

We report on Ultra High Frequency (UHF) Radio Frequency Identification (RFID) received phase and signal strength measurements in an experimental lab. The lab consists of a UHF RFID reader connected to a distributed antenna system installed in a lab room at TU Wien. The antennas are multiplexed in time by phase-stable coaxial switches. Precise tag positioning is realized by motorized linear axes. The lab provides detailed maps of received phase and signal strength for all tag positions in a rectangular area in the lab. Key measurement statistics are reported forming the basis for tag localization: maps of signal strength and phase, their mean and standard deviation for individual antennas, and numbers of antennas providing coverage for each position. For 11 installed reader antennas, 99.96 percent of tag positions are covered by at least four reader antennas indicating the feasibility of high precision localization at 0.04 percent outage.