Device and method for detecting movement of radio tag

A radio tag movement detection device for detecting a movement state of a radio tag, comprising:

• a phase measurement part configured to measure a phase of a response wave from the radio tag;
• a memory configured to sequentially store a phase measured by the phase measurement part together with a measurement time at which the phase is measured;
• a first calculation part configured to calculate a difference from a previous phase and a difference from a previous measurement time with respect to each phase stored in the memory as a phase difference and a time difference;
• a second calculation part configured to calculate a phase addition value obtained by cumulatively adding a plurality of the phase differences so as to correct a phase difference in which the corresponding time difference among the plurality of the phase differences calculated by the first calculation part exceeds a predetermined threshold;
• and
• a detection part configured to detect the movement state of the radio tag based upon the phase addition value calculated by the second calculation part, wherein
• a required time when a phase measured by the phase measurement part is changed by n is obtained by a movement distance and a movement average speed of the radio tag, and the predetermined threshold is set to become equal to or less than half of the required time.