| 摘要 |
PROBLEM TO BE SOLVED: To suppress reduction in a S/N ratio of a display signal so as to display a high level signal by mutually comparing an echo stored in a memory with an echo detected in this time on a time base and extracting an echo having a level other than a maximum or minimum level. SOLUTION: A main processor 11 intensively controls an underwater detector. A controller 12 feeds a predetermined control signal to each circuit according to a command from the main processor 11. A transmission pulse oscillation circuit 13 generates a transmission pulse with a period T and modulates a ultrasonic wave signal into a transmission pulse via a transmission signal forming circuit 14 for forming a transmission signal. A signal processing circuit 19 displays an echo of the ultrasonic waves transmitted by a fixed period, stores echoes based on transmitted waves in several times in the past into a memory, and compares the echo stored in the memory with the echo detected in this time mutually on a time base for extracting an echo having a level other than a maximum/minimum level. Because an echo generated irregularly is not used, unnecessary waves can be removed.
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