| 摘要 |
PROBLEM TO BE SOLVED: To maximize communication efficiency at all times irrelevantly to a communication distance by using as a data-carrier side matching circuit a varactor diode which varies the impedance matching of a coil by varying capacity in response to the application of a voltage corresponding to the distance to a reader writer. SOLUTION: An amplifier 31 shifts the level of a variable control voltage outputted from the matching circuit within the control voltage of the varactor diode. A varactor diode 40d regarding variation of the impedance matching of the coil by variation in the capacity in response to the application of the voltage corresponding to the distance to the reader writer 10 is added to the matching circuit on the side of a data carrier 20 and the potential obtained by rectifying electric power generated at a coil for power reception is used as a control signal to vary the impedance matching corresponding to variation in impedance by coil coupling with the reader write side coil of a coil 26 for communication. Therefore, the communication efficiency can be always maximized irrelevantly to the communication distance. |
