| 摘要 |
<p>An ultrasonic ground speedometer utilizing Doppler effect comprises an ultrasonic transmitter (1,2,3) for outputting an ultrasonic wave (4) having a particular wavelength ( theta ) at a predetermined angle against a road surface (5), an ultrasonic receiver (6,7,8) for receiving a reflected ultrasonic wave caused by reflection of the output ultrasonic wave from the road surface, and a signal processor (10,11,12) for deriving ground speed from Doppler shift between the output ultrasonic wave and the reflected ultrasonic wave. The particular wavelength is set to a value within a range of 2.6 mm through 3.4 mm to assure the highest possible S/N ratio for the Doppler shift signal obtained from the signal processor.</p> |
