| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide an automatic tuning circuit and the like which is automatically tuned properly to secure a communication distance. <P>SOLUTION: When an RFID operates, a control circuit 41 determines, based on a comparison result of a comparator 65, that a tuning frequency is set low when a DC output voltage of a rectifying circuit 50 when a tuning frequency increasing circuit 20-2 operates is higher than the DC output voltage of the rectifying circuit 50 when a tuning frequency decreasing circuit 20-3 operates. On the other hand, it determines that the tuning frequency is set high when the DC output voltage of the rectifying circuit 50 when the tuning frequency increasing circuit 20-2 operates is lower than the DC output voltage of the rectifying circuit 50 when the tuning frequency decreasing circuit 20-3 operates and controls a capacitance adjustment circuit 20 by control signals CS1 to CS3 to set a direction to be properly tuned. As a result, when an RFID 10 operates, proper tuning is automatically attained, thereby securing the communication distance. <P>COPYRIGHT: (C)2010,JPO&INPIT</p> |
