JPH0441312B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a hydrophone suitable for receiving sound waves generated from a ship or the like and detecting their presence and measuring their direction.

(Prior art) This type of conventional equipment has a surface parallel to the water surface (hereinafter referred to as
It is called the horizontal plane. ) has a figure-8 directivity with zero sensitivity on the surface, suppresses traffic-induced underwater noise, receives multipath waves from the sea surface and the seabed, and improves the signal-to-noise (S/N) ratio. I was listening to music with a heightened sense of well-being. In general, in the propagation of sound waves in the deep sea, multipath waves are dominant up to a medium distance (10 to 20 miles) between the sound source and the listening device, but at long distances of about 30 miles, there is a convergence zone (convergence zone). ) waves are generated, and this focused band wave is the most effective for listening. However, the focused band wave is based on, for example, Robert J. Urick's "principles of underwater
sound” (McGraw-Hill Book Company,
From slightly below (approximately -10 degrees) or above (approximately +10 degrees) from the direction parallel to the water surface (hereinafter referred to as the horizontal direction), as described in Since the waves arrive from a direction close to zero directional sensitivity, the device cannot receive the focused band waves with a good S/N ratio, and is therefore effective up to medium distances, but has the disadvantage of being disadvantageous at long distances. Ta.

(Object of the Invention) An object of the present invention is to eliminate the above-mentioned conventional drawbacks and to realize a hydrophone that is effective over a range from medium to long distances.

(Structure of the Invention) In order to achieve the above object, the present invention places an odd number of omnidirectional receivers underwater on a straight line perpendicular to the water surface and on both sides of the central receiver. The receivers are arranged symmetrically, and two dipole-type directional receivers are placed near the center of the array of omnidirectional receivers, each with its maximum sensitivity axis parallel to the water surface. A first beamformer is arranged so as to be shifted by 90 degrees from each other in the directions, and each output of the omnidirectional receiver creates a figure-eight directivity with zero sensitivity on a plane parallel to the water surface. The beamformer is supplied to a second beamformer that creates blowside directivity directed slightly downward or upward from the normal direction, and one of these two outputs is frequency-converted at a predetermined reference frequency and added to the output of the other. The first output is defined as the first output, and the second and third outputs are obtained by adding each output of the dipole type directional receiver to the output obtained by frequency-converting the output with the reference frequency. This is a characteristic feature.

(Embodiment) Fig. 1 shows an embodiment of the present invention, in which 1 to 7 are omnidirectional receivers, 8 and 9 are dipole type directional receivers, and 10 to 14 are amplifiers. ,15,
16, 19, 28, 29, 32, 39, 46, 5
1 is an adder, 17, 30, 36, 40, 43, 4
8 is a low pass filter (LPF), 18, 31 is a high pass filter (HPF), 21, 22, 23, 24, 2
5, 26, 27 are phase shifters (PSC), 37, 44,
49 is a balanced modulation circuit (BM); 38, 45, 50 are bandpass filters (BPF); 41 is an oscillator (OSC);
42, 47, 52 are output terminals, 53 is the water surface, 54
is at the bottom of the water, and 55 is underwater.

The omnidirectional receivers 1 to 7 are arranged in the water 55 on a straight line perpendicular to the water surface, with the receiver 1 at the center, and the receivers 2 and 3 are arranged at a distance d1 on both sides thereof, Receivers 4 and 5 are placed at a distance d2, and receivers 6 and 7 are placed at a distance d3. Further, the dipole type directional receivers 8 and 9 are arranged near the center position of the array of the omnidirectional receivers 1 to 7 so that their maximum sensitivity axes are both in the horizontal direction and are shifted by 90 degrees from each other. .

Amplifiers 10 to 14, adders 15, 16, 19,
The low-pass filter 17 and the high-pass filter 18 constitute the first beamformer 20, and the amplifier 1
0 multiplies the output of receiver 1 by -α, and also the output of amplifier 1
1, 12, 13, and 14 are receivers 2, 3, and 14, respectively.
Multiply the outputs of 4 and 5 by 1/2α. An adder 15 adds the outputs of the amplifiers 10, 13 and 14 and calculates the distance d.
2 in the lower frequency region
As shown in the figure, a figure-of-eight directivity output with zero sensitivity is obtained on the horizontal plane. Further, the adder 16 is connected to the amplifier 1.
The outputs of 0, 11, and 12 are added to obtain a figure-8-shaped directivity output in a higher frequency region determined by the distance d1. The outputs of the adders 15 and 16 are added and combined by an adder 19 via a low-pass filter 17 and a high-pass filter 18, respectively.
Obtain an output corresponding to the square-shaped directivity.

Phase shifters 21 to 27, adders 28, 29, 32,
The low-pass filter 30 and the high-pass filter 31 constitute a second beamformer 33, and the phase shifter 2
1 to 27 add the amount of time advance or delay as shown in Fig. 3 to each output of the receivers 1 to 7 according to distances d1, d2, and d3, and
The signals are aligned in phase at 10 degrees. The adder 28 adds the outputs of the phase shifters 21, 24, 25, 26, and 27, and the distance is determined by distances d2 and d3, which is about 10 degrees below the horizontal direction as shown in FIG. 4 at a lower frequency.
Obtains broadside directional output with tilted beam. Additionally, the adder 29 includes phase shifters 21, 22, 2.
Add the outputs of 3, 24 and 25 and get the distances d1 and d
Obtain a broadside directivity output tilted approximately 10 degrees downward from the horizontal direction at higher frequencies determined by 2. The outputs of the adders 28 and 29 are added and combined by an adder 32 via a low-pass filter 30 and a high-pass filter 31, respectively, to produce an output corresponding to the broadside type directivity tilted approximately 10 degrees downward from the horizontal direction as described above. get.

The output of the first beamformer 20 is sent to an adder 39 via a low-pass filter 40, and the output of the second beamformer 33 is sent to a balanced modulation circuit 37 via a low-pass filter 36. Here, the pass band of the low pass filters 36 and 40 is different from that of the low pass filters 17 and 30, and the pass band of the high pass filter 18 is different from that of the low pass filters 17 and 30.
and adders 16 and 29 output through 31
The signal is also considered to be a pass band. The output of the low-pass filter 36 is frequency-converted by the balanced modulation circuit 37 by the reference frequency fo generated by the oscillator 41, and is sent to the bandpass filter 38. The output a1 of the band filter 38 is added to the output a2 of the low-pass filter 40 in an adder 39 and outputted from a terminal 42 as a signal (first output) having the frequency distribution shown in FIG.

On the other hand, the output of the dipole-type directional receiver 8 is sent to a low-pass filter 43 that is the same as the low-pass filter 36 (or 40), and its output is sent to a balanced modulation circuit 44 and an adder 46. be done. The signal input to the balanced modulation circuit 44 is frequency-converted by the reference frequency fo and sent to the band filter 45. The output of the band filter 45 is added to the signal directly input from the low-pass filter 43 in an adder 46, and is output from a terminal 47 as a signal (second output) having a frequency distribution similar to that shown in FIG. Output.

Further, the output of the dipole type directional receiver 9 is similarly sent to a low pass filter 48 which is the same as the low pass filter 36 (or 40), and is sent to a balanced modulation circuit 49.
, the frequency is converted by the reference frequency fo, sent to the band filter 50, and added to the direct output from the low-pass filter 48 in the adder 51, resulting in a signal with a frequency distribution similar to that shown in FIG. 5 (third output). ) is output from the terminal 52.

With this configuration, it is possible to simultaneously obtain a figure-8 directional output and a broadside directional output tilted approximately 10 degrees downward from the horizontal direction, making it ideal for ships, etc. from medium to long distances. The target sound can be detected with a good S/N ratio, and the receivers 8 and 9
The output is also obtained according to the frequency distribution of the figure-8-shaped directional output and the broadside-type directional output tilted approximately 10 degrees below the horizontal direction (both are omnidirectional on the horizontal plane). Therefore, it can be used to detect the direction of targets from medium to long distances.

In the above embodiment, the output of the second beamformer is a broadside type directivity that is tilted approximately 10 degrees downward from the horizontal direction. Directional output may also be obtained, and similar effects can be obtained in that case as well. Further, in the above embodiment, the total number of omnidirectional receivers is seven, the total number of amplifiers of the first beamformer 20 is five, and the total number of amplifiers of the first beamformer 20 is five, and the second
The case is shown in which the total number of phase shifters in the beamformer 33 is seven, but if the number of receivers is increased and the number of amplifiers, phase shifters, etc. is increased correspondingly, the band can be further widened. In particular, the beam width of the second beam former can be narrowed. Also, the low-pass filter 36 (or 43,
48) and balanced modulation circuit 37 (or 44, 49)
The frequency conversion by the bandpass filter 38 (or 45, 50) uses the subcarrier of the reference frequency fo.
It is the same technology as SSB amplitude modulation, and other circuit systems can also be used.

FIG. 6 shows a hydrophone system to which the present invention is applied, and in the figure, 60 is the hydrophone described above;
61 is a transmitter, 62 is a transmission line, 63 is a receiver, 6
4 is a signal processing device. The first, second and third outputs obtained from the hydrophone 60 were modulated by a transmitter 61, with the first output unchanged and the second and third outputs each modulated with subcarriers having a phase difference of 90 degrees. The signals are then mixed and sent to the transmission line 62 as one signal. The receiver 63 reproduces the first output through a low-pass filter, creates two synchronous subcarriers with a 90 degree phase difference from the simultaneously sent phase reference signal, and performs synchronous demodulation to reproduce the second, The third outputs are regenerated and sent to signal processing device 64 . This transmission system is explained in detail in, for example, Japanese Patent Publication No. 53-22038.
In the signal processing device 64, from the Fourier transforms Z1, Z2 and Z3 of the first, second and third outputs, Z
Find the real part and imaginary part of the cross periodogram of 1, Z2, and Z3, multiply them by the real part and imaginary part of the characteristics of receivers 8 and 9, add them, and accumulate these values. The added values A and B are determined, and the direction of the arriving wave is determined from the sign and the value of the quotient between A and B, and the presence of the target and its direction are shown on the display. The method for measuring the orientation is described in detail in, for example, Japanese Patent Publication No. 55-28514. In addition, here, the reference frequency fo of the hydrophone 60 is
If is set in the middle of the conventional frequency band, the conventional signal processing device 64 can be used as is.

(Effect of the invention) As explained above, according to the present invention, underwater,
An odd number of omnidirectional receivers are arranged on a straight line perpendicular to the water surface and the receivers on both sides are symmetrical to the center receiver, and the omnidirectional receivers are Two dipole-type directional wave receivers are arranged near the center position of the array of wave devices so that their respective maximum sensitivity axes are parallel to the water surface and deviated from each other by 90 degrees. A first beamformer that creates a figure-eight directivity with each output of the transducer having zero sensitivity on a plane parallel to the water surface, and a broadside type directivity that directs the beam slightly below or above the direction parallel to the water surface. one of these two outputs is frequency-converted at a predetermined reference frequency and added to the other output to form the first output, and the dipole-type directional receiver Since the respective outputs and the outputs obtained by frequency-converting the outputs using the reference frequency are added together to obtain the second and third outputs, it is possible to detect ships, etc. from medium to long distances compared to the first output. The sound of the target can be detected with a good S/N ratio, its presence can be detected, and the direction of the target from medium to long distances can be measured using a single signal processing device using the first, second, and third signals. There are advantages such as being able to

[Brief explanation of drawings]

The drawings serve to explain the present invention; Fig. 1 is a block diagram showing an embodiment of the hydrophone of the present invention, and Fig. 2 is an explanatory diagram of the figure-8 directivity with zero sensitivity on the horizontal plane. , FIG. 3 is an explanatory diagram showing the state of phasing of the receiver output in the second beamformer,
Figure 4 is an explanatory diagram of broadside type directivity with the beam directed slightly below the horizontal, and Figure 5 is an illustration of the 1st beam.
FIG. 6 is an explanatory diagram showing the frequency distribution of the hydroacoustic system to which the present invention is applied. 1 to 7... Omnidirectional receiver, 8, 9... Dipole directional receiver, 20... First beam former, 33... Second beam former, 37, 4
4, 49... Balanced modulation circuit, 41... Oscillator, 3
6, 46, 51... Adder, 42, 47, 52...
...Output terminal.

Claims (1)

[Claims] 1. An odd number of omnidirectional receivers are placed underwater on a straight line perpendicular to the water surface, and the receivers on both sides are symmetrical with respect to the central receiver. In addition, near the center of the array of omnidirectional receivers, two dipole-type directional receivers were placed so that their maximum sensitivity axes were parallel to the water surface and 90 degrees apart from each other. and a first beamformer that creates a figure-eight directivity with each output of the omnidirectional receiver having zero sensitivity on a plane parallel to the water surface, and a first beamformer slightly below or slightly below the direction parallel to the water surface. It is supplied to a second beamformer that creates broadside directivity with the beam directed upward, and one of these two outputs is frequency-converted at a predetermined reference frequency and added to the output of the other to become the first output. Further, the hydrophone is characterized in that each output of the dipole type directional receiver is added to a frequency-converted output using the reference frequency to obtain second and third outputs. .