To provide a non-contact data carrier for monitoring a direct current voltage from a rectifying circuit to select an appropriate resonance frequency and shape of a coiled antenna, efficiently receiving electric power when a distance from a reader-writer is far, capable of avoiding malfunction due to heating or damage caused by overvoltage impression when the reader-writer is near and excessive electric power is received, and capable of providing a favorable communication state by stabilizing a power supply voltage to an internal circuit.
Switches 12a-12f are connected to a plurality of portions of the coiled antenna 1, and by changing the switches and changing connection portions of the coiled antenna 1 connected in parallel to a tuning capacitor 2 and the rectifying circuit 3, adjustment of the resonance frequency and the antenna shape capable of efficiently receiving electric power can be provided. The resonance frequency is adjusted by changing inductance, and an amount of a magnetic flux interlinking with the coiled antenna 1 is adjusted by changing the shape of the coiled antenna 1.
Yoshihiro Morimoto
Toshiji Sasahara
Yohei Harada
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