4,425,634

43.30.Vh DETECTION SYSTEM

Hiroshi Iino and Toyoki Sasakura, assignors to Furuno Electric Com- pany, Limited

10 January 1984 (Class 367/120); filed in Japan 26 August 1980

A most unusual sonar receiving system is described in which a circular array of hydrophones is rotated mechanically in order to generate Doppler shifts that are exploited in beam forming. At any given time, the hydro- phones within q- 45 ø of the receiving direction are utilized. In this sector, the Doppler shifts vary almost linearly with the angular position of the hydrophones. The hydrophones are shifted by gates that are controlled by triangular voltage waves so that one signal is faded in as another is faded out. The Doppler-shifted signals are fed to a matched filter which com- presses them in time, and transmits them to a cathode-ray-tube indicator. It is a pity that the patent does not give a fuller explanation.--LB

4,439,844

43.30.Vh SALMON COUNTER WITH SEPARATE KING SALMON TABULATOR

Arthur S. Menin, assignor to The Bendix Corporation 27 March 1984 (Class 367/87); filed 5 October 1981

A boom 80 is installed across a river with a screen 90 extending from it to the bottom, so that every fish swimming up the river must swim over the boom. An ultrasonic projector 20 has an acoustic beam that just fills the angle between the boom and the water surface. In the other direction, paral- lel to the stream, the acoustic beam is 2 ø wide. A fish swims upstream at about 1.75 ft per second, and is in the beam long enough to return four to eight echoes, depending on its range. The river flows at 4 ft per second, so debris carried with it is in the beam for a shorter time, and returns fewer echoes. There are no echoes from the river bottom because the beam is

above it. Therefore, any echoes that recur four to eight times, depending on their range, are presumed to come from fish, and are counted. The system transmits !00-/as bursts of 5 ! 5 kHz ultrasound, which penetrate the fish to some extent, so that returning echoes are stretched in time by an amount dependent on the thickness of the fish. Echoes shorter than 275/as come from ordinary salmon, but those longer than that are presumed to come from king salmon, which are a larger species. The system makes a count of all fish and also a supplemental count of the king salmon. Moreover, for some reason that is not stated, the system divides the river into ! 6 sectors, and provides separate counts of the fish swimming in each interval of range.--LB

4,425,635

43.30.Vh FISH SONAR

Shigeo Yamamoto and Kazuto Kobayashi, assignors to Keisuke Honda

10 January 1984 (Class 367/125); filed in Japan 30 May 1980

This patent describes the receiving portion of an active sonar designed for finding fish. Two adjacent hydrophones are used with means for delay- ing the signal in one channel only, and means to deliver an output signal only when the delayed and undelayed signals coincide in phase. Preferably, there are a number of channels, each with a progressively different delay corresponding to a set of adjacent receiving beams. The width of each beam depends on the precision of phase coincidence that the circuits require to produce an output signal.--LB

4,436,049

43.30.Vh SIMULATOR FOR TESTING SONOBUOYS

Louis E. Ante, Richard A. Lindquist, and Eugene R. Roeschlein, as- signors to the United States of America

13 March 1984 (Class 114/254); filed 20 May 1982

This apparatus enables a sonobuoy to be tested in the calm water of a lake while simulating the motions it would have in a rough sea. The appara- tus is mounted on a floating platform that is towed toward the shore to simulate a water current. The sonobuoy is supported by a winch that is repeatedly wound u• and unwound to simulate the vertical motion that would be imparted by the waves. The device is designed to simulate sea states 3, 4, and 5, which represent wave heights of 4, 8, and 12 ft, respective- ly. The apparatus simulates the motions that the sonobuoy would undergo in service, and the resulting noise of turbulence, but it does not simulate the ambient noise which would prevail under real conditions.•LB

4,439,845 43.30.Vh SONAR SYSTEM

Kenneth P. Geohegan and Henry M. Gruen, assignors to Westing- house Electric Corporation

27 March 1984 (Class 367/87); filed 3 December 1981

This mine-hunting sonar exploits the resonant quality of a mine casing, which, unlike a rock, adds a ringing to the trailing portion of its echo. The sonar transmits composite signals, comprising two slightly different fre- quencies in close succession. If the target is a rock, the two parts of the echo will be substantially alike. But if it is a mine, the two trailing portions of the echo will have noticeably different envelopes, even though the two frequen- cies are far from any resonance of the mine casing. By comparing the two envelopes of a composite echo, it is possible to classify the echo as coming from a mine or from a rock.--LB

1281 J. Acaust. Sac. Am. 76(4), Oct. 1984; 0001-4966/84/101281-01500.80; ¸ 1984 Acaust. Sac. Am.; Patent Reviews 1281

Redistribution subject to ASA license or copyright; see http://acousticalsociety.org/content/terms. Download to IP: 128.42.202.150 On: Mon, 24 Nov 2014 05:03:59