| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve communication efficiency, even in the system of a single antenna and to perform communication in the case when a responder is moving at a high speed by making the responder specified from an interrogator not to return a response even though a command is received from the interrogator. SOLUTION: The responder 12 provided with an ID code for identification and attached to a mobile object, such as a vehicle or the like, is called from a fixedly installed interrogator 11, and carrier waves are generated in an oscillator 1 first, then switched to a right-handed circularly polarized waves by a polarization plane-switching device 3, for instance, and radiated from a transmission antenna 4. In the responder 12 which receives the radio waves by a reception antenna 5, received carrier waves are modulated in a modulator 6 and radiated from the transmission antenna 7 to the interrogator 11. In this case, the responder 12 specified by the interrogator 11 does not return a response. Thus, the number of the responders which responds to the interrogator is reduced, the communication efficiency is improved, and the communication is made possible, even when the responder is moving at a high speed.</p> |
