Patent ID: 7376493

Claim:
A vehicle-surroundings monitor apparatus having: a sensor comprising: a transmission/reception means for transmitting an ultrasonic wave to surroundings of a vehicle and receiving a reflected ultrasonic wave from the surroundings; a transmission circuit for generating an ultrasonic wave to be transmitted from the transmission/reception means; a reception-processing means for processing an ultrasonic wave received by the transmission/reception means; a regulator configured to supply the transmission circuit and the reception-processing means with substantially constant voltage; and a filter; and a control means for supplying a power-supply voltage to the sensor, wherein the vehicle-surroundings monitor apparatus is used for measuring a distance to a body existing in the vicinity of a vehicle employing the vehicle-surroundings monitor apparatus based on a period of time between transmission of the ultrasonic wave from the transmission/reception means and reception of the reflected ultrasonic wave by the transmission/reception means and is characterized in that a power-supply voltage supplied by the control means to the sensor is split into a power-supply voltage to be supplied to the transmission circuit and a power-supply voltage to be supplied to the reception-processing means, and the power-supply voltage to be supplied to the transmission circuit and the power-supply voltage to be supplied to the reception-processing means are supplied to the transmission circuit and the reception-processing means respectively, wherein the transmission circuit converts the power-supply voltage to be supplied to the transmission circuit into a pulse voltage of a predetermined frequency, wherein the filter is configured to absorb voltage variations arising when the transmission circuit outputs the pulse voltage such that the power-supply voltage to be supplied to the reception-processing means is substantially constant, wherein the filter is a low-pass filter configured to pass therethrough the power supply voltage supplied from the regulator and block high frequency components arising in the transmission circuit from the reception-processing means.