Antenna device and wireless IC device

摘要

To constitute an antenna device in which characteristic fluctuations due to changes in the distance between a wireless IC device and a reader/writer are suppressed, and the wireless IC device which can perform communication with high reliability. In order to send/receive a wireless communication signal to/from an external device such as a reader/writer, an antenna resonant circuit (AR) is constituted by an antenna coil (La) and a capacitor (Ca), and an additional resonant circuit (LC1) is constituted by an inductor (L1) and a capacitor (C1). The additional resonant circuit (LC1) is connected to the antenna resonant circuit (AR), thereby constituting an antenna device (101). The antenna device (101) and a wireless IC (21) constitute a wireless IC device (201).