Communications – electrical: acoustic wave systems and devices – Echo systems – Speed determination
Patent
1992-04-09
1994-07-05
Pihulic, Daniel T.
Communications, electrical: acoustic wave systems and devices
Echo systems
Speed determination
367 87, 367 94, G01S 1550, G01S 1504
Patent
active
053273966
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an underwater detection system for searching the water in a wide range of directions. Particularly, it relates to an underwater detection system which is capable of detecting angular carrier frequencies (or carrier frequencies) of ultrasonic signals coming from search areas extending in a wide range of directions. Further, it relates to an apparatus for displaying moving targets in predetermined colors corresponding to angular carrier frequencies based on the detected angular carrier frequencies (or carrier frequencies) of incoming ultrasonic signals.
Hereinafter, the present invention will be explained as embodied in an underwater detection system which finds moving targets, for example, fish schools, detects angular carrier frequencies of ultrasonic signals reflected by the fish schools, and displays the fish schools in different colors corresponding to speeds of the fish schools based on the detected angular frequencies.
BACKGROUND ART
When a fish school is moving, the frequency of an ultrasonic signal reflected by the school of fish is shifted in frequency (Doppler frequency shift) due to the Doppler effect. Due to detection of the Doppler frequency shift ultrasonic echoes from a moving fish school can be distinguished from ultrasonic echoes reflected by a fixed target such as the seabed. Also, a fast or slow speed or the like of the moving fish school can be detected.
A prior art underwater detection system has been provided which detects a Doppler frequency shift (refer to, for example Japanese Unexamined Patent Application Publication No. 29975/1982).
However, the prior art apparatus was merely capable of detecting Doppler frequency shifts of ultrasonic signals coming from one specific direction, but was not capable of detecting Doppler frequency shifts of ultrasonic signals coming from the whole range of directions. Thus, information such as a fast or slow speed or the like of moving fish schools in a wide range of directions can not be obtained in a short time duration.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide an underwater detection system which receives ultrasonic signals coming from a wide range of directions and is capable of obtaining information relating to speeds of targets producing the ultrasonic signals in a short time duration.
Another object of the present invention is to provide an underwater detection system which receives ultrasonic signals coming from a wide range of directions and displays targets having produced the ultrasonic signals in different colors depending on speeds of the targets based on the received ultrasonic signals.
Another object of the present invention is to provide an underwater detection system which receives ultrasonic signals coming from a wide range of directions and detects angular frequencies of the carriers included in the received ultrasonic signals.
Another object of the present invention is to provide an underwater detection system which receives ultrasonic signals having a known carrier frequency coming from a wide range of directions and displays targets having produced the ultrasonic signals in different colors depending on speeds of the targets based on the received ultrasonic signals.
Another object of the present invention is to provide an underwater detection system which emits ultrasonic search signals in a wide range of directions and catches echo signals coming from the wide range of directions and displays targets having reflected the search signals in different colors depending of speeds of the targets based on the received echo signals.
Another object of the present invention is to provide an underwater detection system which emits ultrasonic search signals in a wide range of directions and detects angular frequencies (or frequencies) of the carriers included in echo signals coming from the wide range of directions and received.
Another object of the present invention is to provide an apparatus which detects angular carrier frequencies included in u
REFERENCES:
patent: 4069468 (1978-01-01), Bartram
patent: 4425634 (1984-01-01), Iino et al.
patent: 4573477 (1986-03-01), Namekawa et al.
patent: 4680739 (1987-07-01), Lannuzel
Furuno Electric Company Limited
Pihulic Daniel T.
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