Identifying system for overlapped tags

摘要

A system for identifying overlapped tags (11 to 13; 51; 61) comprises an interrogator (85) and a plurality of tags, each tag being appended to an article (1 7) and each having a resonance circuit (24) comprising an antenna coil (14; 54) and connected to the antenna coil a RFID device (16). Each resonance circuit (24) includes a switching element (26; 27; 66) for interrupting the connection between the RFID device (16) and the antenna coil (14; 54) if an electric current beyond a predetermined value flows in the resonance circuit (24). The interrogator (85) oscillates a radio wave from a transceiver antenna (25 a) to tags (11 to 13; 61) and identifies the tags (11 to 13; 61). An oscillation circuit (85i) is able to sweep the radio wave oscillated from the transceiver antenna (25 a) within a predetermined frequency range. The predetermined frequency range being defined so that it includes all of the resonance frequencies of one or more tags (11 to 13; 61), the resonance frequencies change due to the overlapping of one or more tags (11 to 13; 61) and/or one or more metal plates (91).