| 摘要 |
<p>PURPOSE:To measure a ground speed of a ship by catching effectively, appropriately and usefully a reflected wave coming back from the sea bottom of a wide range, which is obtained by an ultrasonic wave having a directivity, and extracting a Doppler component. CONSTITUTION:When the transmitting pulse from a transmitter 4 is transmitted to a transmitter and receiver 6 through a transmission and reception coupling circuit 5 and an ultrasonic wave is sent out into the water, the reflected wave coming back to the transmitter and receiver 6 is amplified by a receiving part 7 through the transmission and reception coupling circuit 5. It is applied to an operating part 9, DELTAt2 is calculated from the expression, and when its output is applied to a t0 operating part 14 for determining a transmitting pulse width, on the other hand, the output of a DELTAt setting part 13 which has set a sampling time is applied to this operating part 14, therefore, the transmitting pulse width having a relation of t0>=DELTAt2+DELTAt is calculated from both data, and the transmitting part 4 is driven by its output signal. Subsequently, a gate generating part 10 opens the gate of a gate circuit 11, and the signal is sent to a Doppler counter 12 of the post-stage.</p> |
