| 摘要 |
<p>PROBLEM TO BE SOLVED: To attain improvement in S/N ratio in SAW-ID-TAG which utilizes a surface acoustic wave(SAW) element. SOLUTION: A SAW converting electrode is formed from a chirp electrode. In place of a single RF pulse, this chirp signal SAW-ID-TAG is transmitted. Then, the chirp signal is converted into a SAW of a single RF pulse stream at the SAW converting electrode. This SAW is converted into an RF pulse stream at an encoding electrode 68. On the side of a receiver, this RF pulse stream is detected by a detection circuit 28, and its code is detected by a code detector 30 so that the code can be read out. As a result, since the pulse stream compressed by a compression gain corresponding to a BT as a product of distribution time T and distribution band width B for the chirp signal can be transmitted by the chirp signal, the S/N ratio can be improved only for this compression gain. Further, a third person, who does not know that this is a chirp signal, is unable to read the code, and the privacy of the code can be kept.</p> |
