抄録
Datacarrier technology is used in a remote readable ID tag system composed of tags, an encoder, and a writer. In previous papers, the authors presented the results of a study of the characteristics of a tag composed of an amorphous strip and a magnetic tape from the viewpoint of its practical application. Several problems have remained unsolved, particularly concerning the reader, such as how to reduce its power consumption and size, how to eliminate external noise, and how to improve the reading distance. In this paper, we propose a portable reader with a superheterodyne detection system. The antenna of the reader is controlled in such a way as to resonate at the resonant frequencies of a tag. By studying the relationship between the reading distance and the characteristics of the tag, we proved experimentally that the reading distance is proportional to the square root of the product of the coupling factor K and the Q-value. The information on a tag could be read at a distance of 0.7 m by the reader with an antenna 0.3 m in diameter.
