| 摘要 |
[Object] To provide a passive keyless entry system which prevents control ICs from being damaged during its normal detecting operation in presence of high-level signal. [Solving Means] The portable device 2 is provided with a control IC 3, an antenna 4 having both ends thereof connected to input and output terminals of the control IC 3 for wirelessly transmitting or receiving signals, a level detector 5 for detecting the receiving level of the antenna 4, a Qdump circuit 6 that operates only when the level detector 5 detects the receiving level which exceeds an allowable value of the control IC 3 and that varies the quantity of Qdump in accordance with the receiving level of the antenna 4, and a time constant circuit 7 or a latch circuit 8 for holding the Qdump circuit 6 in its operational state in an OFF period of an LF modulation signal. |
