Method for determining the location of a moving RFID tag

摘要

There is provided a method for determining the location of an RFID tag moving along a known path with known speed. The phases of the tag response signals from successive interrogations are stored. For a given location of the tag at the time of the first reading, the phase relative to the first response changes in a characteristic way for a given distance. The set of obtained phase values (phase history) is correlated to nominal phase trend curves, each representing the phases for successive readings where the distance between the reader and the tag at the first reading had a respective particular value, i.e. a particular distance is associated with a predetermined phase change pattern. Since the trajectory and speed are known, the position at a given time is implicitly known, i.e. it can be extrapolated from the position determined for the first reading.