JPH0886866A - Underwater-target detection apparatus - Google Patents

Abstract

PURPOSE: To provide an underwater-target detection apparatus by which an underwater target can be detected over a wide range. CONSTITUTION: A sound-generating bullet which uses gunpowder is used as a sound source. A plane arrangement-type wave-receiver array 8 in which a plurality of wave receivers are arranged in a plane shape on a plurality of horizontally and radially arranged arms is used as a wave-reception device. The interval between the sound-generating bullet 1 and the plane arrangement- type wave-receiver array 8 is separated at a maximum detection distance or larger at a time when the sound source and the wave-reception device are situated in the same position so as to be monostatic, and an underwater-target detection apparatus is formed to be of a bistatic type.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underwater target detecting apparatus which emits sound waves into water to detect an underwater target from the echo of the sound.

[0002]

2. Description of the Related Art Conventionally, this type of device is composed of a sound source that emits a sound wave into the water and a wave receiving device that receives a reverberant sound that is reflected by the sound wave and returns from the target. It is called monostatic when it is located at the same position, and bistatic when it is located apart from the sound source and the wave receiving device. FIG. 9 is an explanatory view showing the principle of a bistatic type underwater target detection device. As for the sound wave emitted from the sound source 101, both a direct wave (solid line) and a reverberant sound from the target 102 (dashed line) are received devices. Although it reaches 103, the reverberant sound has a time delay of the path length difference from the direct wave. Therefore, the direct wave and the reverberant sound are detected by the wave receiving device 103, and if the time delay is multiplied by the underwater sound velocity (about 1500 m / sec), the path length difference is obtained, and the target 102 is the constant path length difference. It exists on an ellipse (dotted line).

[0003]

However, the sound waves emitted from the sound source are reflected and scattered from the surface of the water, the bottom of the water, and foreign substances (fish, water mass, etc.) in the water, and arrive at the wave receiving device as reverberation. . Therefore, there was a problem that the echo sound was buried in this reverberation, making it difficult to detect the target. The present invention has been made to solve this problem, and an object of the present invention is to provide an underwater target detection device capable of detecting an underwater target over a wide range.

[0004]

In order to achieve this object, the present invention uses, as a sound source, a sounding bullet using gunpowder capable of obtaining a large output at a low frequency, and as a wave receiving device,
Using a planar array type receiver array in which a plurality of wave receivers are arranged in a horizontal plane, the maximum distance between the sound source and the wave receiving device when the sound source and the wave receiving device are at the same position in monostatic It is a bistatic type that is separated from the detection distance. Further, the present invention is an array in which a plurality of wave receivers are respectively arranged on nine arms that horizontally expand the planar array type wave receiver array at an equal angle from the center, and near the center. The interval between a plurality of wave receivers adjacent to each other is ½ of the underwater wavelength of the highest acoustic frequency, and this is the minimum wave receiver interval. They are arranged at the same expansion intervals.

[0005]

According to the present invention having the above-described structure, the sound wave emitted from the sound source reaches the wave receiving device at a long distance, but the sound source is set to a large output and the distance between the sound source and the wave receiving device is increased. As a result, the reverberant sound at the point of the receiving device has a horizontal directional property, so the multiple horizontal standby pencil beams formed by the planar array type receiver array suppress reverberation and the reverberant sound detection capability is reduced. improves. Further, the beam pattern formed by the planar array type receiver array is uniform in the entire circumferential direction, and it is possible to suppress the generation of a large auxiliary pole and efficiently form a beam in the frequency band of the reverberant sound.

[0006]

Embodiments Embodiments will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of an underwater target detection apparatus showing an embodiment of the present invention. In the figure, 1 is a sounding bullet as a sound source that is generated by being dropped in water and exploding, and 2 is stored in a buoy floating on the water, and the sounding bullet is released by a command via radio waves. It is a sounding buoy device that is released into the water. FIG. 2 is an external perspective view of the sounding bullet 1. The sounding bullet 1 sinks under its own weight when it is put into water, and when it reaches a predetermined depth, the built-in explosive explodes, and this explosion Since sound is used as a sound source, it is possible to obtain a large acoustic output despite being small and economical.

FIG. 3 is a partial sectional view showing the structure of the sound buoy device 2. Reference numeral 3 denotes a float. The float 3 functions as a buoyant body, and houses the antenna 4 inside, and the air chamber 5 also houses the receiver 6 connected to the antenna 4. Further, a column 7 is provided in the lower portion of the float 3, and a plurality of columns, here 2 columns, are provided in the column 7.
The individual sound bullets 1 are respectively held by the release mechanism 7a. In the above structure, when the radio wave of the release command arrives, the receiver 6 decodes the radio wave and operates the release mechanism 7a to discharge the sounding bullet 1 stored in the column 7 into the water from the lower part.

Then, when the sound bullet 1 sinks in water,
Gunpowder explodes at a predetermined depth and sounds. In this embodiment,
Since the two sounding bullets 1 and the two releasing mechanisms 7a corresponding thereto are provided, it is possible to command sounding twice by radio waves. Accordingly, if the sounding buoy device having the above configuration is floated on water in advance, it is possible to sound at a desired point at a desired time from a remote place. Here, the sound source using this kind of explosive is not only able to obtain a large acoustic output, but also contains abundant low-frequency spectrum components, so the distance between the sound source and the receiving device is set to a long distance. In the case of the bistatic type, there is an advantage that a low frequency with little sound wave absorption loss can be used.

As the device for dropping the sounding bullet 1 into the sea, the sounding buoy device described in FIG. 3 may be used, or the sounding bullet 1 may be dropped directly from an aircraft or the like. Returning to FIG. 1, reference numeral 8 denotes a planar array type receiver array as a wave receiving device for receiving the sound wave generated by the sounding bullet 1. FIG. 4 is a plan view showing the structure of the planar array type receiver array. In the figure, 9 to 17 are nine arms that are radially deployed from the center point O, and each arm 9 to 17 has the same length and is horizontally arranged at equal angular intervals, that is, at 40 ° intervals. It is being deployed.

9a to 9e are five wave receivers arranged on the arm 9, and 12a to 12e are 120 ° with respect to the arm 9.
Five wave receivers 15a to 15e arranged on the arm 12 in the open position, one for each of the arms 9 and 12
5 wave receivers arranged on the arm 15 in a 20 ° open position. Reference numerals 10a to 10d denote four wave receivers 11a arranged between the arms 9 and 12 and arranged on the arm 10 in a position opened by 40 ° with respect to the arm 9.
˜11d are four wave receivers 13a to 1d arranged between the arms 9 and 12 and arranged on the arm 11 in a position opened by 40 ° with respect to the arms 10 and 12.
3d is between the arms 12 and 15, and four wave receivers are arranged on the arm 13 in a position opened by 40 ° with respect to the arm 12, and 14a to 14d are the arm 12
Between the arm and the arm 15, and the arm 13 and the arm 1
The four wave receivers 16a to 16d arranged on the arm 14 in the position opened by 40 ° with respect to 5 are located between the arms 15 and 9 and are in the position opened by 40 ° with respect to the arm 15. 4 wave receivers arranged on a certain arm 16,
17a to 17d are four wave receivers arranged between the arm 15 and the arm 9 and on the arm 17 in a position opened by 40 ° with respect to the arm 16 and the arm 9, and as described above, Arms 9 and 1 at 120 ° intervals
Five wave receivers on 2, 15 and the other arms 10,
Four wave receivers are arranged on 11, 13, 14, 16 and 17.

Then, the arrangement of the five wave receivers on the arms 9, 12, 15 is made identical to each other, and the other arms 10,
The arrangement of the four wave receivers on 11, 13, 14, 16 and 17 is the same as each other, and when this wave receiver array is viewed from the angle direction, the entire circumference 360 ° is divided into three and arranged uniformly. The arrangement of the receiver on each arm is first near the center,
Innermost wave receivers 9a, 12 on the arms 9, 12, 15
a, 15a are located closest to the center point O, and the arm 1
Innermost wave receivers 10a, 11a, 13a, 14a, 16a and 1 on 0, 11, 13, 14, 16 and 17
7a is arranged outside this to make the distribution of receivers near the center uniform. For the outside, the wave receivers on the arms are arranged at intervals that widen toward the outside, and the wave receivers are arranged so that the distribution is uniform even outside the circular plane.

A specific procedure for determining the position of the receiver will be described below with reference to FIG. 4, taking the arms 9, 10 and 11 as an example. In the arms 9, 10, 11, the wave receiver that occupies the most important position near the center is the wave receiver 9a that is the innermost position on the arm 9, and the distance from the center point O to the wave receiver 9a is used as a reference. Put a value of 1. The next most important receiver is the arm 9
The second upper receiver 9b and the arm 10 next to the arm 9
This is the innermost wave receiver 10a, but this type of 40
° With uniform arm structure, when arranging the receivers so that the uniformity of the arrangement is maintained near the center, when the receivers are on the same arm and on the adjacent arm, The minimum receiver spacing is between the receivers 9a-9b and 9a-10.
Since the distances are a and 10a to 11a, the positions of the wave receivers 9b and 10a are determined so that the three receiver intervals are equal. When this position is obtained from the plot, the distance between the wave receivers 9a and 9b is about 1.3 with respect to the reference value 1, and the wave receiver 10a is
The distance from the center point O of ≈1.9. By this procedure, the arrangement of the wave receivers 9a, 9b, 10a and 11a forming the vicinity of the center on the arms 9, 10, 11 can be determined,
When the distance from the center point O to the wave receiver 9a is set to the reference value 1, the minimum wave receiver interval of 1.3 is set to 1/2 of the underwater wavelength of the highest frequency of the target acoustic frequency.

Regarding the positions of the wave receivers outside this on each arm, first, the outermost wave receivers 9e and 10d are placed at the positions of the maximum radii which are limited by the restrictions on the hardware.
At this time, the distance from the center point O to the wave receiver 9e and the center point O
From the receiver 10d is assumed to be equal. Next, based on 1.3 which is the minimum receiver spacing when the distance from the center point O to the receiver 9a is set to a reference value 1, the receivers outside this are set to have the same magnification on the same arm. The distance between the wave receivers is increased as it goes to the outside. This magnification is determined so that the distance from the center point O to the wave receivers 9e and 10d becomes the maximum radius value. Here, FIG. 4 shows the maximum radius when the distance from the center point O to the wave receiver 9a is set to a reference value 1 (the distance from the center point O to the wave receiver 9e and from the center point O to the wave receiver 10d). Distance) = 8, and at this time, the magnification on the arm 9 is ≈1.20 and the magnification on the arm 10 is ≈1.24 by the above procedure, and the reception on the arm 9 and the arm 10 is performed. The distance from the center point O of the wave machine is as shown in Table 1 below.

[0014]

[Table 1]

Although the arms 9, 10, 11 have been described as an example here, the arrangement of the receivers on the arms 12, 15 is the same as that on the arm 9, and the arms 13, 14, 16 are the same.
The arrangement of the receivers on and 17 is the same as on the arms 10, 11. Next, the reason why the wave receiver is arranged as described above will be described. In this embodiment, the sound wave emitted from the sounding bullet 1 serving as the sound source is omnidirectional, and the sound wave traveling upward and downward from the sound source propagates while being reflected and scattered by the water surface and the water bottom. In order to propagate from the sound source to the wave receiving device located at a long distance, a large number of reflections and scatterings occur, so that the sound wave propagating while traveling in the vertical direction is greatly attenuated. Therefore, the reverberation and the reverberant sound at the point of the wave receiving device placed at a long distance from the sound source disappear in the vertical directionality and become horizontal directionality.

In such a sound field composed of reverberation and reverberation, the beam pattern to be formed by the receiver array is a horizontal pencil beam. And, an efficient array that forms a beam uniformly in the 360 ° direction around the entire circumference in a limited size is a horizontal circular plane receiver array. Furthermore, a simple method of realizing a circular plane with a small wave receiving device is an arm deployment type planar array type receiver array in which a plurality of arms are provided radially from the center and the wave receivers are arranged on the arms. . N received by the receiver array (N = 39 in FIG. 4)
The signal of 1 is phased by the wave receiving device or a signal processing device connected to the wave receiving device, and a plurality of standby beams are formed.

FIG. 5 is an explanatory view showing the principle of the phasing process for forming a beam. In addition, here, the arms 9, 12, 1
Taking the wave receiver on 5 as an example, the phasing direction is from the arm 9 clockwise by 10 °. A straight line (shown by a broken line) that passes through the center point 0 and is orthogonal to the phasing direction (shown by a one-dot chain line) is taken as a phasing line A, and on this phasing line A, the output signals of the respective wave receivers are made into the same phase. By adding them, a beam whose main axis is oriented in the direction of 10 ° is obtained. That is, the output signals of the wave receivers 9a to 9e are delayed by the length of the line (dotted line) drawn from the wave receivers on the phasing line A at a right angle.
The output signals of 2a to 12e are time-advanced by the length of the line (dotted line) drawn from the respective wave receivers onto the phasing line A at a right angle, and the same time is applied to the wave receivers 15a to 15e. If the signal is advanced and all the signals are added, the beam output is in the phasing direction of 10 °. The output signals of the wave receivers on each arm not shown here are also output from each wave receiver by the phasing line A.
Draw a line at a right angle to the top and give a time delay or time advance for the distance according to the relationship between the phasing line and the position of the wave receiver, and by adding this, the beam output in the desired phasing direction is obtained. can get.

On the side of the wave receiving device, the entire circumference is 360 ° on a horizontal plane.
Since a plurality of stand-by beams in the phasing direction are generated and received, each stand-by beam output suppresses reverberation coming from directions other than the phasing direction. Therefore, in the beam output where the phasing direction matches the arrival direction of the echo,
The reverberation-to-reverberation level ratio is improved and the reverberation detection capability is improved. The target azimuth can also be measured from the echo sound level ratio of each beam. The configuration shown in FIG. 4 is an example of a planar array type receiver array for achieving this object, and since an odd number of arms are used, the number of receivers arranged in a straight line is halved, Since the distance between the receivers is widened toward the outside on each arm, the receivers are not arranged on a straight line at equal intervals, and a large auxiliary pole is not generated in the beam pattern.

Further, since the arrangement is such that the entire circumference 360 ° direction is equally divided when viewed from the angle direction, the beam pattern is also uniform regardless of the phasing direction. Furthermore, the receivers are evenly distributed near the center, and the minimum value of the spacing between adjacent receivers is set to 1/2 of the underwater wavelength of the highest acoustic frequency, and the outer receivers are placed on the arm. Since the light beams are arranged at the intervals that are expanded at the same magnification toward the outside, the beam can be efficiently formed within the limited size with respect to the frequency band of the reverberant sound. The planar array type receiver array having the above-mentioned configuration is such that each arm is telescopically expandable and contractible.
Also, as a support that can be folded near the center point 0, each of the nine arms is shortened shortly before being put into the water and folded at a fulcrum on the circumference near the center point O for compact storage. After the insertion, the arm automatically opens its umbrella, deploys horizontally, and then extends it into a telescope shape.
The state shown in FIG. 2 is adopted, and such a structure is within the scope of the existing technology and can be applied to a small wave receiving device.

Further, in the wave receivers on the adjacent arms, the wave receivers having the same distance from the center point O, when the arms are folded and housed as described above, they are mutually incompatible.
It will be arranged by shifting the inside and outside by the size of the wave receiver. In the procedure for determining the wave receiver position described above, the case where the maximum radius = 8 when the distance from the center point O to the innermost wave receiver 9a on the arm 9 is set to the reference value 1 is shown. Five wave receivers are arranged on each of 9, 12, 15 and four wave receivers are arranged on each of the remaining arms 10, 11, 13, 14, 16 and 17, but the maximum When the radius is smaller than this, the magnification that determines the receiver interval on the arm becomes smaller with this number of receivers, and the uniformity in the outer direction becomes weaker. Therefore, when the maximum radius is made smaller, first, the number of outside receivers on the arms 9, 12, 15 is reduced by one to make the total number of receivers 36, and when the maximum radius is further made smaller. Is arm 1
The number of outside receivers on 0, 11, 13, 14, 16 and 17 is also reduced by one, and the total number of receivers is 30. By maintaining the value of, the uniformity of the arrangement of the receivers can be maintained even in the outward direction, and the efficiency of beam forming can be maintained.

FIG. 6 is a plan view of the compact planar array type receiver array as described above, and shows a case where the total number of receivers is 30. At this time, the position of the wave receiver near the center is the same as that shown in FIG. 4 according to the above-mentioned determination procedure. Taking the arms 9 and 10 as an example for explanation, the wave receivers on the outer side of the arm 9 will be described.
Place c and 9d at a magnification of 1.2. Therefore, the positions of the wave receivers 9c and 9d in FIG. 6 are also the same as the positions of the wave receivers 9c and 9d shown in FIG. 4, and the maximum radius is 5.73. As a result, the position of the outermost wave receiver 10c on the arm 10 becomes 5.73, and the position of the wave receiver 10b changes to the arm 10.
The upper magnification is 1.288, which is determined to be 3.57. The distances from the center point O of the wave receiver on the arms 9 and 10 in FIG. 6 are summarized in Table 2 below.

[0022]

[Table 2]

Although the arms 9 and 10 have been described as an example here, the arrangement of the wave receivers on the arms 12 and 15 is the same as that on the arm 9, and the arms 11, 13, 14, 16 are arranged.
The receiver placement on and 17 is the same as on arm 10. Next, the distance between the sound source, here the sounding bullet 1, and the wave receiving device, here, the planar array type receiver array 8 as described in FIGS. 4 and 6 will be described. The detection ability of this kind of underwater target detection device is the sound source level of the sound bullet used,
Predetermined by device parameters such as reflection coefficient from target (called target strength), directivity of receiving device and ability to detect echo sound, and minimum signal-to-noise ratio (called signal excess) due to sound wave propagation loss ) Becomes zero, it can be expressed as the maximum detection distance. The most basic propagation loss is spherical diffusion,
The spherical diffusion propagation loss expressed in decibels is expressed by the following equation (1) at a certain distance (meter).

[0024]

[Equation 1]

Assuming that the maximum detection distance during monostatic is R, the propagation loss is doubled on the outward path and the return path, so the detection ability of this type of device can be expressed by the following equation (2).

[0026]

[Equation 2]

FIG. 7 is a plan view showing the respective components of the bistatic type underwater target detection apparatus according to the present invention on the coordinates. The straight line connecting the sound source and the wave receiving device is the x-axis, and the straight line connecting the sound source and the wave receiving device is the same. Coordinates are set with the y-axis as the axis that intersects at the midpoint and is perpendicular to the x-axis, the target position coordinates are (x, y), and the distance between the sound source and the receiving device is αR, that is, maximum detection during monostatic. It is expressed as α times the distance. Note that FIG. 7 shows the case where the target is in the first quadrant. As a result, the forward and backward spherical diffusion propagation losses at the position coordinates (x, y) are as shown in equations (3) and (4) below.

[0028]

(Equation 3)

Here, the propagation loss at the time of bistatic is the sum of the above two equations, and when the position coordinate (x, y) is at the maximum detection distance point at the time of bistatic, the combination of (x, y) is the device. It is uniquely determined by the detection ability of. In the case of a device with the same parameters, the propagation loss on the maximum detection distance point is the same for monostatic and bistatic conditions, so the following equation (5) is established.

[0030]

[Equation 4]

Solving this for y, in the first quadrant,
The following equation (6) is obtained.

[0032]

(Equation 5)

The above equation (6) expresses the maximum detection distance point at the time of bistatic where the distance between the sound source and the wave receiving device is separated by αR when the maximum detection distance at the monostatic time is R on the x and y coordinates. It becomes the function that did. For generalization, the distance x, y
Is standardized by the maximum detection distance R during monostatic,
Putting x = mR and y = Rf (m), the following (7)
The formula is obtained.

[0034]

(Equation 6)

FIG. 8 is a graph showing changes in the maximum detection distance in the bistatic type underwater target detection device obtained from the equation (7), where m is the horizontal axis and f (m) is the vertical axis. It is a curve in which the equation (7) is calculated in the first quadrant with α as a coefficient. Here, α = 0 represents a monostatic time, and at this time, the origin O has both the sound source and the wave receiving device, and the circle with the radius R centering on the origin O is the maximum detection distance. As a bistatic type, for example, α =
When set to 1.6, the wave receiving device has a position of m = 0.8 on the horizontal axis, and the sound source has a position on the horizontal axis symmetrical with the wave receiving device with respect to the origin O (m = −0.8). It can be seen that the maximum detection distance on the y-axis is 0.6R and the maximum detection distance on the x-axis is 1.28R. Further, it can be seen that when the distance between the sound source and the wave receiving device is 2R or more, an undetectable region occurs on the straight line connecting the sound source and the wave receiving device. The maximum detection distance is a graph symmetrical with respect to the horizontal axis of FIG. 8 in the second quadrant, a graph in which the graph of the second quadrant is symmetrical with respect to the vertical axis in the third quadrant, and a graph in the fourth quadrant. The graph is symmetrical with respect to the vertical axis of 8.

From this, it can be seen that, in the axial direction connecting the sound source and the wave receiving device, it is possible to detect at a longer distance than the monostatic type, and the reverberation level decreases as the distance from the sound source increases. It can be seen that the appropriate distance between the receiving device and the wave receiving device is between 1 and 2 times the maximum detection distance in monostatic mode. Also,
If a plurality of wave receiving devices are set in a plurality of desired axial directions and the multi-static operation is performed in which the sound of the sound source is received at the same time, the effect is further enhanced. Here, in the planar array type receiver array having the above-mentioned configuration, all the receivers are arranged on the arms that are deployed radially from the center, so that it can be easily applied to a compact small-sized receiver device, and the bistatic device by an aircraft can be used. Alternatively, when a plurality of sounding buoy devices and wave receiving devices are dropped and laid in a wide range by multi-static operation to detect an underwater target, it is also applicable to a drop type wave receiving device. The wave receiving device in this case transmits the received N acoustic signals to the aircraft by radio waves, and the signal processing device in the aircraft forms a beam to detect the echo sound.

[0037]

As described above, the present invention uses, as a sound source, a sounding bullet using gunpowder capable of obtaining a large output at a low frequency, and uses a plurality of horizontal wave receivers as a wave receiving device. Using a planar array type receiver array that is arranged in a plane,
Since the distance between the sound source and the wave receiving device is separated by more than the maximum detection distance when the sound source and the wave receiving device are at the same position when monostatic, the reverberation that reaches the wave receiver array is horizontal. It becomes directional, and the multiple horizontal standby pencil beams formed by the planar array type receiver array have the effect of suppressing reverberation, improving the reverberation-to-reverberation level ratio, and improving the ability to detect reverberation. .

Further, according to the present invention, the planar array type receiver array is an array in which a plurality of receivers are respectively arranged on nine arms which are horizontally developed at equal angles from the center, and The intervals between the adjacent wave receivers near the center are set to ½ of the underwater wavelength of the highest acoustic frequency, and this is set as the minimum wave receiver interval. Since they are arranged at the same magnification and at intervals that spread, a uniform beam pattern can be formed in the entire circumferential direction, and since the wave receivers do not line up at equal intervals on a straight line, it is possible to suppress the occurrence of sub-poles. Yes, for the reverberant frequency band,
There is an effect that a beam can be efficiently formed within a limited size.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an underwater target detection apparatus showing an embodiment of the present invention.

FIG. 2 is an external perspective view of a sounding bullet.

FIG. 3 is a partial cross-sectional view showing the structure of a sound producing buoy device.

FIG. 4 is a plan view showing the structure of a planar array type receiver array.

FIG. 5 is an explanatory diagram showing the principle of a phasing process for forming a beam.

FIG. 6 is a plan view of a compact planar array type receiver array.

FIG. 7 is a plan view showing each component of a bistatic type underwater target detection device on coordinates.

FIG. 8 is a graph showing changes in maximum detection distance in a bistatic underwater target detection device.

FIG. 9 is an explanatory diagram showing the principle of a bistatic underwater target detection device.

[Explanation of symbols]

 1 pronunciation bullet 8 plane array type receiver array 9 to 17 arm 9a to 9e receiver 10a to 10d receiver 11a to 11d receiver 12a to 12e receiver 13a to 13d receiver 14a to 14d receiver Receivers 15a to 15e Wave receivers 16a to 16d Wave receivers 17a to 17d Wave receivers

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number for FI Technical indication location G01S 7/54 8907-2F (72) Inventor Katsushi Okubo 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd.

Claims (2)

[Claims] 1. A sound standby bullet capable of obtaining a large output at a low frequency is used as a sound source, and a plurality of wave receivers are arranged in a horizontal plane as a wave receiving device to form a horizontal standby pencil beam. Using a planar array type receiver array capable of performing the above, the distance between the sound source and the wave receiving device is separated by more than the maximum detection distance when the sound source and the wave receiving device are in the same position when monostatic, An underwater target detection device characterized by being a bistatic type with horizontal directionality. 2. A horizontal standby pencil beam is formed by using a sounding bullet capable of obtaining a large output at a low frequency as a sound source and arranging a plurality of wave receivers in a horizontal plane as a wave receiving device. Using a planar array type receiver array capable of performing the above, the distance between the sound source and the wave receiving device is separated by more than the maximum detection distance when the sound source and the wave receiving device are in the same position when monostatic, In addition to being a bistatic type whose directionality is horizontal, the planar array type receiver array is provided with a plurality of wave receivers on nine arms that are horizontally deployed at equal angles from the center. The array is arranged, and the interval between a plurality of adjacent wave receivers near the center is set to ½ of the underwater wavelength of the highest acoustic frequency, and this is set as the minimum wave receiver interval. , Going to the outside on the arm Underwater target detection apparatus characterized by being arranged at intervals spread at the same magnification.