| 摘要 |
A method and a transponder for measurement of distance to and identification of living creatures and/or objects/articles. Prior to reception of an interrogating signal (14-16) a transponder (23m; 38m) is listening intermittently. Upon reception of correct interrogation signal frequency (fo), the transponder will listen continuously over a time space related to the duration of the interrogation signal (14-16) in order to detect a correct enabling code (15) therein, and upon reception thereof, it will respond with a transponder identifying receipt signal (17) of duration equal to a terminal part (16) of the interrogating signal (14-16) and with a second carrier frequency (n x fo). A time-limited activation signal (18; fo) is sent to the transponder which in turn transmits a response signal (19-21; n x fo) having a duration equal to that of the activation signal (18) and may contain encoded information/status (20). The time (ts) between transmission of the activation signal and reception of said response signal is measured in order to calculate the distance between the transponder and interrogating station. Upon repeated measurement of distance from at least two locations, and accurate position of the transponder is determined through intersection point of the measured distances. |
