Underwater acoustic detection system
First Claim
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1. An underwater acoustic detection system comprising:
- hydrophone means for detecting an acoustic signal from an object in the water medium and converting said acoustic signal into an electrical signal;
low pass filter means for filtering said electrical output signal to provide a bandwidth limited electrical signal;
a full wave rectifier for providing a rectified electrical signal from said bandwidth limited electrical signal;
a Threshold switch sensitive to the level of said rectified electrical signal that closes when the amplitude of said rectified electrical signal is above a certain threshold level;
an acoustic pinger for transmitting an acoustic detection signal through the water medium in response to the closing of said threshold switch, said acoustic detection signal having a frequency substantially higher than the cutoff frequency of said low pass filter; and
means remotely located from said hydrophone for receiving said transmitted signal.
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Abstract
An underwater acoustic detection system having remotely located passive detection field units submerged underwater and a centrally located receiving station having an underwater receiver. The field units passively detect the presence of surface or submerged objects by the objects'"'"''"'"' acoustic noise and transmit an acoustic detection signal in response thereto. The transmitted acoustic detection signal is detected by the receiving station'"'"''"'"'s underwater receiver and converted into a utilizable form in the receiving station.
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Citations
4 Claims
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1. An underwater acoustic detection system comprising:
- hydrophone means for detecting an acoustic signal from an object in the water medium and converting said acoustic signal into an electrical signal;
low pass filter means for filtering said electrical output signal to provide a bandwidth limited electrical signal;
a full wave rectifier for providing a rectified electrical signal from said bandwidth limited electrical signal;
a Threshold switch sensitive to the level of said rectified electrical signal that closes when the amplitude of said rectified electrical signal is above a certain threshold level;
an acoustic pinger for transmitting an acoustic detection signal through the water medium in response to the closing of said threshold switch, said acoustic detection signal having a frequency substantially higher than the cutoff frequency of said low pass filter; and
means remotely located from said hydrophone for receiving said transmitted signal.
- hydrophone means for detecting an acoustic signal from an object in the water medium and converting said acoustic signal into an electrical signal;
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2. An underwater acoustic detection system as recited in claim 1, wherein said certain threshold level represents the ambient background noise in said water medium.
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3. An underwater acoustic detection system as recited in claim 2, wherein said remotely located means comprises:
- means for receiving said transmitted acoustic detection signal; and
means for converting said transmitted acoustic detection signal into a utilizable form.
- means for receiving said transmitted acoustic detection signal; and
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4. An underwater acoustic detection system as recited in claim 3 wherein said detecting and transmitting means are separately located.
Specification