| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent the generation of a null region within a communicable distance after a frequency shift in a noncontact IC card system. <P>SOLUTION: A noncontact IC card system 102 in the embodiment includes an antenna 801 and, as lower stage circuits of a frequency shift circuit 802, a voltage detection circuit 901, an IC card function circuit 904, and a control circuit 805. The voltage detection circuit 901 is provided with, as voltage detection circuits, a frequency shift ON voltage detection 902 (circuit) and a frequency shift OFF voltage detection 903 (circuit). The voltage detection circuit 901 controls the frequency shift circuit 802 based on the output results of the frequency shift ON voltage detection 902 (circuit) as first voltage detection means and the frequency shift OFF voltage detection 903 (circuit) as second voltage detection means and changes antenna resonance frequencies of the antenna 801. <P>COPYRIGHT: (C)2012,JPO&INPIT |
