Passive keyless entry device

摘要

A passive keyless entry device includes an in-vehicle transceiver and a portable transceiver. The in-vehicle transceiver has a clock signal generating circuit, a control signal generating signal that outputs a binary control signal having positive and negative values, a modulation circuit that forms a pulse modulation signal by modulating the clock signals by the control signal, and a transmission circuit that has half-bridge circuits, a low-frequency antenna being connected to output ends of the half-bridge circuits. The change time of the control signal from the positive value to the negative value is set to be slightly later than the usual change time from the positive value to the negative value. During a period from the usual change time of the control signal from the positive value to the negative value up to the change time slightly later than the usual change time, the clock signals modulated by the control signal are inverted clock signals that are shifted by half wavelength with respect to the usual clock signals.