| 摘要 |
<p>GROUND SPEED SENSOR An ultrasonic ground speed sensor has a vehicle-mounted transmitter and a receiver for receiving signals reflected from the transmitter to the receiver by terrain over which the vehicle travels. An attenuated and phase-shifted transmit frequency is superimposed upon an output of the receiver to cancel cross talk, thus providing a substantially pure reflected frequency. A phase-locked loop converts the reflected frequency to a voltage which represents the direction and speed of the vehicle.</p> |
