SHF RFID based Localization: Combining Time-of-Flight and Angle-of-Arrival

In this work, we combine time-of-flight (ToF) and angle-of-arrival (AoA) measurements to determine the position of a radio-frequency identification (RFID) transponder. This enables precise tracking of the use and location of tools, for example. A super high frequency (SHF) frequency-modulated continuous wave (FMCW) radar at 24 GHz is used to determine the ToF. The modulated backscatter from the transponder allows for clutter suppression. Two receiving antennas are employed in the radar for AoA determination. The investigation shows that localization of a transponder is possible in a realistic environment. The range is limited to a few meters due to the low signal-to-noise ratio in this implementation. It becomes evident that tracking tagged objects is feasible with the presented approach using a commercial automotive radar as a reader.