2001 Volume 63 Issue 2 Pages 53-59
Usually, a narrow beam of high-frequency ultrasonic wave is used for ultrasonic Doppler ground speed sensors. However, serious errors may be caused especially on smooth ground surfaces, because the received signal will be weak due to the high attenuation ratio and the small insonified area of the narrow sonic beam. In order to solve the problem, an ultrasonic Doppler speed sensor was developed using transducers operating at a relatively low frequency of 40kHz. The transmitted sonic wave had a high intensity and a broad directivity. An offset parabolic reflector was used to control the traveling directions of sonic waves instead of a narrow beam. The experimental results demonstrated the effect of the reflector. Even for a smooth ground such as a concrete surface, the sensor showed almost the same performance as that for rough ground surfaces.
