METHOD OF IDENTIFYING OVERLAPPING TAGS

摘要

A number of tags are identified individually even if they overlap one another or overlap a metal plate. Tags (11-13) attached to an article have an antenna coil (14) and a RFID element (16) connected to the antenna coil (14). The antenna coil (14) and the RFID element (16) form a resonant circuit (24), which is provided with a normally closed switch (26) capable for opening the resonant circuit (24). The switch (26) is connected with a time constant circuit (27) that operates the switch (26) at predetermined time intervals while current flows in the resonant circuit (24). The time constant circuit (27) opens the switch (26) for different periods of time for different tags (11-13).