Abstract: In an ultrasonic transceiver, an inner housing has a bottom portion, a first tubular side wall extending from one end surface of the bottom portion and a first flange portion formed on an outer peripheral portion of the first tubular side wall. The bottom portion and first tubular side wall provide a tubular cavity formed therebetween, and the piezoelectric member is mounted on the one end surface of the bottom portion in the tubular cavity. An outer housing has a second tubular side wall coaxially arranged around the outer peripheral portion of the first tubular side wall with a predetermined gap therebetween. The second tubular side wall is provided with one end portion which is opposite to one end surface of the first flange portion and contacted thereto. A first absorption member is inserted in the gap between the first tubular side wall and the second tubular side wall.

Abstract: An ultrasonic sonar has a transceiver equipped with an ultrasonic oscillator. An ultrasonic wave is transmitted from the transceiver. The ultrasonic wave reflected from an obstacle is received by the ultrasonic oscillator to detect the obstacle. The transmission frequency of the ultrasonic wave is set to be different from the reverberation frequency. When the obstacle is detected, a microcomputer converts the analog signal received by the ultrasonic oscillator into a digital signal, performs a frequency transform of this signal by Fourier transform to extract only the transmission frequency component, and performs an inverse transform.

Abstract: An ultrasonic sensor has a sensor body, a diaphragm, and a vibrator for generating ultrasonic and attached to the diaphragm. The diaphragm has a thinnest portion. The thinnest portion has a predetermined thickness by which reverberation of the diaphragm is restrained. The reflected ultrasonic can be detected correctly by this construction of the sensor.

Abstract: An ultrasonic sonar has a transceiver equipped with an ultrasonic oscillator. An ultrasonic wave is transmitted from the transceiver. The ultrasonic wave reflected from an obstacle is received by the ultrasonic oscillator to detect the obstacle. The transmission frequency of the ultrasonic wave is set to be different from the reverberation frequency. When the obstacle is detected, a microcomputer converts the analog signal received by the ultrasonic oscillator into a digital signal, performs a frequency transform of this signal by Fourier transform to extract only the transmission frequency component, and performs an inverse transform.

Abstract: In an entering detecting system for vehicles, a received ultrasonic signal is amplified by an amplifier circuit so that a Doppler signal may be generated from an amplified signal and a transmission signal for detecting an entering of unauthorized person into a vehicle compartment. An operational amplifier circuit of the amplifier circuit has an output limiter circuit. The output limiter circuit has diode series circuits which are connected to a feedback resistor of an operational amplifier.

Abstract: An intrusion detecting apparatus for a vehicle comprises: a doppler shift signal outputting unit for outputting a doppler shift signal in response to a reflected and received ultrasonic signal from an ultrasonic receiver and a transmitted ultrasonic signal from a transmitter, an envelope detecting circuit for detecting the level of the received ultrasonic signal, and a detecting means for detecting an illegal intrusion by a person only when it is determined that the doppler shift signal is within a predetermined amount corresponding to the movement of a person intruding into the passenger compartment and it is also determined that the detected level of the received ultrasonic signal is out of a range of a disturbance, whereby an erroneous detection due to a disturbance caused by some reason other than an intrusion can be prevented.

Abstract: An intrusion detecting apparatus for a vehicle comprising an ultrasonic transmitting/receiving sensor, an intrusion detecting unit for detecting whether or not a person intrudes into a passenger compartment, based on the received signal, a stopping unit for intermittently stopping the transmission from the transmitter, and a cover detecting unit for detecting whether or not the sensor is covered, based on the signal received after stopping the transmission of the signal and, in response to a predetermined condition representing that the sensor is covered, whereby it can correctly determine whether or not the sensor is covered, improving the accuracy of the detection of an illegal intrusion of a person. At least one of a transmitter and a receiver in the sensor and the intrusion detecting unit is also intermittently operated to reduce the power consumption.