| 摘要 |
<p>PROBLEM TO BE SOLVED: To realize distance detection between a transponder and a terminal, which is executed on a terminal side and which does not require transmission from the transponder for the evaluation of the distance, by measuring a variable decided by a load formed on the oscillation circuit of the terminal through the means of the transponder. SOLUTION: A terminal 1' is located between the output terminal 2p of an amplifier, namely, an antenna coupler 3 and a prescribed terminal 2m in a reference potential, and it comprises an oscillation circuit formed of a capacitive part 24 and an inductance connected to a resistor R1 in series, namely an antenna L1. Voltage between the connection point 30 of the resistor R1 in the oscillation circuit and the inductance L1 and a ground 2m is measured. A measuring device comprises a capacitor storing voltage measured at a node 30. Voltage between both ends of the capacitor is dropped, as the distance between the terminal and a transponder increases. Voltage stored in the capacitor is sent to the processor of the terminal 1'.</p> |
