Ultrasonic ground speedometer utilizing doppler effect of ultrasonic waves

摘要

An ultrasonic ground speedometer utilizing Doppler effect of ultrasonic waves comprises an ultrasonic transmitter for outputting an ultrasonic wave at an emitting angle against a road surface, an ultrasonic receiver for receiving a reflected ultrasonic wave caused by reflection of the output ultrasonic wave from the road surface, a signal processor for deriving a Doppler shift frequency between the frequencies of the output ultrasonic wave from the ultrasonic transmitter and the reflected ultrasonic wave received by the ultrasonic receiver, a first arithmetic circuit for deriving the angle difference between the emitting angle and the reception angle defined between the road surface and the propagation direction of the reflected ultrasonic wave received by the receiver, on the basis of the Doppler shift frequency, and a calculating circuit for calculating a ground speed of the vehicle, on the basis of both the Doppler shift frequency and the angle difference.