| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a wireless tag distance calculation system in which each of a plurality of wireless tag readers can calculate a distance from a wireless tag while suppressing battery consumption of the wireless tag. <P>SOLUTION: A wireless tag reader 1A counts up a time TA from a transmission completion time t3 of a tag command up to a reception completion time t10 of an ACK signal transmitted from a wireless tag 2 and performs broadcast transmission of the counted time TA. A wireless tag reader 1B receives (intercepts) the tag command and the ACK signal, counts up a time TB from a reception completion time t4 of the tag command up to a reception completion time t11 of the ACK, and receives time data (TA) transmitted from the wireless tag reader 1A. The wireless tag reader 1B calculates a distance D2 from the wireless tag 2 by using the times TA, TB, previously stored Ttag, Tres and a distance D3 between the wireless tag reader 1A and the wireless tag reader 1B. Consequently, the wireless tag reader 1B can calculate the distance D2 without communicating with the wireless tag 2. <P>COPYRIGHT: (C)2012,JPO&INPIT |
