| 摘要 |
<P>PROBLEM TO BE SOLVED: To achieve a device to monitor around a vehicle using a novel principle. <P>SOLUTION: A vehicle monitoring device comprises: a transmission device which excites a body of a vehicle with an excitation signal; and a receiving device which receives an electromagnetic wave in proximity to the body of the vehicle. The receiving device has: a demodulator 30; a target frequency setting resistor; a target phase setting resistor; a pulse oscillator which outputs a reference signal with frequency as well as a phase coinciding with target frequency as well as a target phase; a phase comparison device 32 which outputs a phase difference signal indicating a phase difference between the reference signal and a transmission monitoring signal; a frequency control device which controls the target frequency of the pulse oscillator by obtaining the phase difference between the reference signal and the transmission monitoring signal from a temporal change in the phase difference signal; and a phase control device which controls the target phase of the pulse oscillator on the basis of the phase difference indicated by the phase difference signal. The vehicle monitoring device detects the target phase at different times, determines whether a variation is equal to or larger than a predetermined value and issues a warning that abnormality occurs around the vehicle when determining that the variable is equal to or larger than the predetermined value. <P>COPYRIGHT: (C)2013,JPO&INPIT |
