Antenna device of interrogator

摘要

An antenna device of an interrogator which constitutes an automatic identification system by exchanging information with an IC tag attached to an object to be identified by electromagnetic coupling is disclosed. The antenna device comprises an antenna element, and a capacitor connected in series to the antenna element and having a variable capacitance to maintain a predetermined resonance frequency. The predetermined resonance frequency is maintained by switching taps on an antenna coil. Alternatively, the predetermined resonance frequency is maintained by switching taps on a tapped inductor or by a variable inductor. <IMAGE>