| 摘要 |
<p>PROBLEM TO BE SOLVED: To realize a data carrier system by inserting an attenuation section into a signal transmission system to vary high frequency power to vary a communication distance with an ID card thereby revising a read range. SOLUTION: A high frequency transmission reception circuit 2 uses a PLL section 6 to set a transmission frequency for a GHz band, a transmission amplifier 7b amplifies the transmission signal, and the result is inputted to an ASK modulation section 9 via a transmission attenuation section 8. The ASK modulation section 9 applies ASK modulation to a prescribed data signal and a high frequency component is attenuated by a low pass filter 10 and the result is sent from a transmission antenna 3. Then the transmission range of a radio wave sent from the transmission antenna 3 is varied by controlling the attenuation of high frequency power by the transmission attenuation section 8 to be ON/OF, then a communication distance with an ID card 5 is made variable and a read range of identification information of the ID card 5 is adjusted in response to the application of the data carrier system.</p> |
