| 摘要 |
PURPOSE:To accurately set a tracking gate at all times by catching a lost reflection echo again and using it as a reference for subsequent tracking gate setting. CONSTITUTION:A tracking gate signal generating means finds a predicted arrival distance by using the distance from a pier to a shift, a speed, and an ultrasonic wave transmission period which are found from measured values obtain so far. A wave reception off detecting means detects a reflected wave not being received in a set tracking gate and outputs a wave reception off signal. A gate setting means receives a tracking gate signal and sets a gate for the received signal. Further, the gate setting means receives the reception off signal and closes the gate for the received signal in a receivable time area wherein tracking gate signal can not be received in next measuring operation. Then a reflected wave echo which is caught newly is used as a reference thereafter to set a tracking gate.
|
