| 摘要 |
PURPOSE:To enable the display of shoal information at a proper level combined with a topographic change of the sea bottom, by controlling the amplification factor of an amplifier for amplifying the output of a limiter circuit and the degree of attenuation of an attenuator for attenuating a signal received. CONSTITUTION:A wave receiver 1 receives a coming wave moving a receiver mechanically or electronically toward the incoming from a wide ranging direction. The signal received outputted from the unit 1 is attenuated with an attenuator 2 to restrict the amplitude of the output signal to a fixed range with a limiter circuit 4. After pulse is compressed with a matched film 6, the output of the circuit 4 is amplified with an amplifier 8. Then, a control circuit 10 controls the amplification factor of the amplifier 8 and the degree of attenuation of the attenuator 2 and in the control, the amplification factor of the amplifier 8 is set to correct the attenuation of the attenuator 2.
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