| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent responders existing upstairs or downstairs, or at a side opposite to a wall from being detected erroneously even if an antenna where a symmetrical radiation pattern to a radiation surface is formed is used in a radio authentication system for allowing an interrogator to detect the responder by using the radio authentication system for the entering/leaving management in a room, the stock control of products, or the like, by allowing the interrogator to transmit a question signal, and by allowing the responder to return a response signal in response to the question signal. <P>SOLUTION: When a detection area 35 can be set to the question signal relatively accurately and the responders 16A, 16B use an LF band for easily receiving the question signal, the radiation pattern symmetrical to the radiation surface is forcedly formed from the LF antenna 34. Accordingly, another LF antenna 41 is provided in the interrogator 31 for generating feeble interfering waves to the question signal, thus detecting only the responder 16A on an installation floor accurately without detecting the responder 16B on a lower floor erroneously. <P>COPYRIGHT: (C)2009,JPO&INPIT |
