| 摘要 |
1507177 Sonar KLEIN ASSOCIATES Inc 14 April 1975 [4 Nov 1974] 15207/75 Heading. G1G The Specification describes a system for enhancing the quality of received sonar or similar signals which are to be displayed and recorded in a recording means having a dynamic range capability substantially less than that of the received signals. A logarithmically compressed, amplified form of the sonar echo signal is smoothed and the derivative thereof is obtained which signal is applied to the recording means to substantially match the dynamic range thereof. As described, pulses are transmitted from a transducer (8), Fig.1 (not shown) and received echoes are filtered and amplified and transmitted back to a ship via a tow cable which is towing the sonar TX/RX apparatus. The echo signals are applied to an amplifier 14' Fig. 3 which comprises an operational amplifier A1 having back-to-back diodes CR1 CR2 in the feedback loop thereof whereby logarithmic compression of the echo signals is obtained. The signals are then full wave rectified by circuit 5 and integrated by capacitors C1 and C2. The resulting smoothed absolute value signal which represents the envelope of the received signals is then differentiated at 7 and applied to print amplifier 22 which drives the recording mechanism 10 which may be a drum recorder. It is stated that the aforementioned circuitry matches the dynamic range of the echo signal, e. g. 120dB to that of the recording mechanism e. g. 20-40dB. Modifications are described wherein the rectifier output is made to be negative going whereupon increasing, echo signal magnitude will be recorded as a whiter signal; a diode CR5 may be included in differentiator 7 to allow output signals therefrom of one polarity only.
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