ULTRASONIC DETECTING DEVICE

PURPOSE:To improve the SN ratio of a signal after composition by reception processing by providing one transmitter receiver, oscillation means which send out sent signals of plural frequencies, a discriminating and converting means, and an adding means. CONSTITUTION:Oscillation signals f1 - f3 of three waves oscillated by oscillators 32a - 32c are added by an adder 34 and supplied to a transmission/reception switching circuit 40 through a buffer power amplifier 36. Then the signal is radiated into the sea through the transmitter receiver 42. A received signal Sg from a reflecting body is inputted to an input and addition part 50 through the circuit 40. The signal Sg is branched and supplied to mixers 52a - 52c at the input and addition part 50 and the mixers 52a - 52c are supplied with local oscillation signals fa - fc from local oscillators 54a - 54c and output converted signals Sh - Sj. Noise components, etc., are removed from the signals Sh - Sj, envelopes are detected, and the signals are added by an adder 60 to output an output signal Sr. The signal Sr is supplied to a signal processing part which displays an image of the state of the reflecting body, etc., as a hard copy, etc.