| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a noncontact communication system capable of preventing an operable distance of a wireless tag for a reader from being shorten regardless of use environments. <P>SOLUTION: A reader/writer transmits a received power monitor start command with an initial transmission frequency, sets a frequency channel 1 corresponding to a slot 1, and then transmits a transmission carrier frequency change completion code. An RFID tag detects and stores the received power when the reader-writer receives the received power monitor start command. The reader/writer transmits the transmission carrier frequency change completion code while sequentially changing frequency channels. The RFID tag sequentially detects the received power at that time. Further, when receiving the received power corresponding to the frequency channel of the last slot n, the RFID obtains maximum received power and returns a slot X at that time to the reader/writer. The reader/writer executes subsequent data communication with the RFID tag at the frequency channel corresponding to the slot X. <P>COPYRIGHT: (C)2007,JPO&INPIT |
