Communications – electrical: acoustic wave systems and devices – Underwater system – Telemetering
Patent
1990-04-27
1992-03-24
Pihulic, Daniel T.
Communications, electrical: acoustic wave systems and devices
Underwater system
Telemetering
367110, H04B 1100
Patent
active
050994581
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF INVENTION
The present invention relates to an underwater detection system which radiates ultrasonic wave search signals and receives echo signals resulting from the search signals at a first position in the water to detect underwater conditions and transmits information representative of the underwater conditions to a second position spaced from the first position and displays the underwater conditions at the second position.
TECHNICAL BACKGROUND OF INVENTION
Conventionally, for example, with a bottom trawl fishing method, the obtaining of information relating to a fishing net "a" being dragged by a ship "d" such as a range from the fishing net "a" to the sea-bottom "b", a range from the net "a" to the water surface "c" and fish schools moving around the net, is shown in FIG. 4. In order to obtain the information, conventionally, a fish school detecting apparatus has been used as shown in FIG. 5.
With a conventional fish school detecting apparatus, a transmitter "g" is fixed at an upper portion of the mouth of the fishing net "a"; a receiver "h" is installed on the ship "d"; and further, the transmitter "g" is provided with two transmitting and receiving transducers "i1" and "i2" to produce echo signals obtained by radiating ultrasonic wave signals in up and down directions and to receive resultant echo signals therefrom respectively. The fishing net "a" is being dragged by the ship "d", and at the same time ultrasonic wave signals are emitted and echo signals are received alternately at time intervals by the transmitting and receiving transducers "i1" and "i2" at a fishing net side. Echo signals coming from the up and down directions with respect to the fishing net "a" and received thereby are supplied through an amplifier "j" to an AM modulator "k" (or an FM modulator) which modulates in amplitude the echo signals (or in frequency). The modulated echo signals are amplified by a power amplifier "m" and then are converted by means of a transmission transducer "n" to ultrasonic wave signals which propagate to a ship side. The signals transmitted from the net are received by a receiving transducer "p" of a receiver "h" installed on the ship "d". The echo signals received thereby are amplified by an amplifier "q" and then recorded by a recorder or displayed by a color monitor. The recorder and the color monitor are not shown.
The frequency bandwidth in relation to ultrasonic wave signals transmitted from a transmitter to a receiver is generally of a narrow frequency bandwidth determined by characteristics of an ultrasonic transducer. In addition, another limitation is imposed by a requirement that there has to be avoided mutual interferences with signals used by other ships and hence the frequency bandwidth can not be too broad.
With a bottom trawl fishing method, information in association with areas above and below of the net and in the neighborhood of the fishing net is most important. The farther a position goes away from the fishing net, the less the importance of information associating the point becomes. In other words, there is desired to obtain detailed information in association with narrow areas in the neighborhood of the fishing net (for example, bandlike areas above and below the fishing net, each having a vertical length of about 5 meter). There is not desired to obtain information in association with positions considerably far away from the ship, which is, however, desired to be obtained by scanning sonars and the like.
With prior art underwater detection apparatii, information produced in the neighborhood of the fishing net and obtained and other information produced in areas farther away therefrom are transmitted at the same information density. From a viewpoint of information quality, the necessary information is inadequate and poor in association with the neighborhood of the transmitting and receiving transducer, and information produced in areas farther away from the transducers is excessive.
Thus, prior art apparatii have presented such drawbacks that record or disp
REFERENCES:
patent: 4104609 (1978-08-01), Minegishi et al.
patent: 4644511 (1987-02-01), Asakura
Furuno Electric Co. Ltd.
Pihulic Daniel T.
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