| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a reliable radio tag configured to perform carrier sense free from an error even when a strong radio wave is inputted from another radio tag reader communicating by a frequency in another channel, and to secure stable carrier sense sensitivity in the channel band of the communication. <P>SOLUTION: The radio tag reader comprises: a modulator 22 which modulates a high-frequency signal sent by an oscillator oscillating the high-frequency signal; a frequency converter 10 which converts a reception signal into a baseband signal based upon the high-frequency signal modulated by the modulator 22; a carrier sense unit 34 which executes the carrier sense where the baseband signal is received and passed through band-stop filters 32 and 34, whether there is the same frequency component with a transmission frequency of transmission is detected before the transmission from baseband signals having passed through the band-stop filters 32 and 34, and when the component is not detected, transmission of the radio tag reader is allowed; and a modulated signal control unit 50 which alternates and inputs f1 and f2 to the modulator at intervals of predetermined time. <P>COPYRIGHT: (C)2009,JPO&INPIT |
