JP5659851B2 - SONER DEVICE AND DIRECTIONAL SYNTHESIS METHOD THEREOF - Google Patents

Description

  The present invention relates to a sonar device, and in particular, a sonar device having a plurality of receivers and combining the outputs of the receivers to obtain a directivity gain, and a directivity synthesis method in such a sonar device, and About.

  In a sonar device used in water, a plurality of acoustic receivers are used to detect acoustic signals from all directions in a horizontal plane and determine the arrival method of acoustic signals. The desired directivity is obtained by synthesizing the output from the waver. As a typical receiver, an Omni type having a uniform sensitivity (isotropic sensitivity) in any direction, that is, having an omnidirectional characteristic, and a dipole having a dipole directional characteristic The type is known.

  For example, as a configuration for detecting an acoustic signal arriving from a desired direction θ in a plane parallel to the water surface or the sea surface, there is a technique of horizontal directivity synthesis by cardioid processing (for example, Patent Document 1, Patent) Reference 2). In the cardioid processing method, as shown in FIG. 1, an omni-type receiver 11 and two dipole-type receivers 12 and 13 are used. In the figure, each of the receivers 11 to 13 is indicated by the directivity pattern of the receiver. The dipole receivers 12 and 13 are arranged so that their maximum sensitivity axes are orthogonal to each other and parallel to the water surface or the sea surface. Here, for convenience, the maximum sensitivity axis of the receiver 12 faces the N (north) -S (south) direction, and the maximum sensitivity axis of the receiver 13 faces the E (east) -W (west) direction. Therefore, the received signal at the receiver 12 is called an NS signal, and the received signal at the receiver 13 is called an EW signal. Of course, the directions of the maximum sensitivity axes of the receivers 12 and 13 do not have to coincide with the north-south direction and the east-west direction, respectively, and these receivers are incorporated in a portable sonar device such as Sonobui. In general, the north-south and east-west directions do not coincide with the direction of the maximum sensitivity axis of the receivers 12 and 13. In any case, if the relationship between the direction of the maximum sensitivity axis of the receiver and the true direction is clear, the arrival method of the acoustic signal can be accurately determined.

  In the cardioid process, the received signal (referred to as NS signal) at the receiver 12 is multiplied by sin θ, and the received signal (referred to as EW signal) at the receiver 13 is multiplied by cos θ. Then, the reception signal (referred to as an omni signal) at the receiver 11 is added to the NS signal multiplied by sin θ and the EW signal multiplied by cos θ, and the signal obtained by the addition is squared. The detection signal. As a result, the sonar device shown in FIG. 1 has a directivity pattern in which the directivity in the horizontal plane is a cardioid type, and outputs a detection signal corresponding to such a directivity pattern. The directivity is maximum with respect to the direction of θ. None of the dipole receivers 12 and 13 have sensitivity in the vertical direction (up and down direction), but since the omni signal from the omni receiver 11 is added, the entire sonar apparatus As such, it has some sensitivity in the vertical direction, and the directivity pattern in the vertical plane including the maximum sensitivity axis is also a cardioid type. In the cardioid processing, a directivity gain (DI) of 4.2 dB can be expected.

  Since sin θ multiplication, cos θ multiplication, addition, and square processing can be performed as digital signal processing, once an omni signal, NS signal, and EW signal are acquired, detection signals for a plurality of azimuth angles can be obtained simultaneously. Can be obtained, that is, an acoustic signal can be received by a plurality of directivity patterns.

  On the other hand, there is a synthetic omni process as a process for receiving an acoustic signal with the same intensity (horizontal omnidirectionality) in any direction in a plane parallel to the water surface or the sea surface. In the synthetic omni processing, it is assumed that the same receivers 11 to 13 as those shown in FIG. 1 are provided, and among these, two dipole receivers 12 and 13 are used. Here, the receivers 12 and 13 are arranged so that their maximum sensitivity axes are orthogonal to each other and parallel to the water surface or the sea surface, and the NS signal and the EW signal are respectively transmitted in the same manner as described above. Shall be output. The omni signal from the omni-type receiver 11 is not used in the synthetic omni processing.

  In the synthetic omni process, as shown in FIG. 2, each of the NS signal and the EW signal is squared, the squared signals are added, and then the square of the added signal is calculated to be a detection signal. The omni signal is omnidirectional and shows a spherical directional pattern, whereas the detection signal by synthetic omni processing, that is, the synthetic omni signal, shows a donut-shaped directional pattern, especially in the vertical direction upward and downward. The sensitivity is zero. As shown below, the sensitivity is uniform in all directions in the horizontal plane.

Assuming that the intensity of the NS signal is represented by S _NS and the intensity of the EW signal is represented by S _EW , an acoustic signal having a strength P from the azimuth θ in the horizontal plane enters the receivers 12 and 13. Since the waver has a dipole type directivity, S _NS = P × sin θ and S _EW = P × cos θ. As a result, the synthetic omni signal S _SO is obtained by the fact that cos ² θ + sin ² θ = 1 is an identity.

And P regardless of θ (see FIG. 3). Therefore, the synthetic omni signal has the same sensitivity regardless of the direction in the horizontal plane, and becomes omnidirectional in the horizontal plane.

  Considering the case where the sonar device is constructed as a sonobuoy placed in the sea, the use of synthetic omni treatment as shown in FIG. 3 suppresses the sensitivity to the vertical direction, that is, the sea surface direction and the sea bottom direction. The influence of noise from the direction and noise from the seafloor direction can be suppressed, and the influence of components reflected from the sea surface and the seabed (sea surface reverberation and seafloor reverberation) can be suppressed. Therefore, according to the synthetic omni process, it is possible to accurately detect only the acoustic signal that has traveled straight from the target to the sea.

In the synthetic omni processing, the signals from the two receivers 12 and 13 are combined, so that a maximum directivity gain of log ₁₀ 2 = 3 dB is obtained with respect to isotropic noise, and a goodness index (FOM; From the relationship between the figure of merit and the detection distance, the detection distance can be extended by about 1.2 times. Further, since the signals of the two receivers are combined, the standard deviation σ of the noise level is reduced to 2 ^−1/2 times (≈0.7 times), and the probability of erroneous detection can be reduced.

JP 2009-150662 A JP 2010-169644 A

  As a method of processing signals received by a plurality of receivers for acoustic signals, the cardioid processing described above can know the direction of arrival of acoustic signals, but in order to have sensitivity even in the vertical direction, for example, There is a problem that it is susceptible to noise and reverberation from the sea surface and the sea floor. On the other hand, the synthetic omni processing described above is not sensitive in principle in the vertical direction, so it has the advantage of being less susceptible to noise and reverberation from the sea surface and sea floor, but is non-directional in the horizontal plane. There is a problem that it is impossible to know the direction of arrival of the acoustic signal.

  In the sonar device, in order to increase the directivity gain and reduce the influence of signals coming from unnecessary directions, it is conceivable to increase the number of receivers, for example, to have a phased array configuration. . However, in a portable sonar device such as Sonobuoy, the number of receivers cannot be increased due to restrictions on the size of the device.

  An object of the present invention is a sonar device capable of setting a directivity in a desired direction so that the arrival direction of an acoustic signal can be known while suppressing an increase in the number of receivers, for example, suppressing sensitivity in the vertical direction. It is to provide a directivity synthesis method.

  The first directivity synthesis method of the present invention includes a first receiver having an omni-directional characteristic, and second and third receivers having a dipole directivity, and the maximum of the second receiver A directivity synthesis method in a sonar device in which a sensitivity axis and a maximum sensitivity axis of a third receiver are orthogonal to each other, wherein received signals from the first to third receivers are first to third, respectively. The first received signal, the signal obtained by multiplying the second received signal by sin θ, and the third received signal are cos. The signal multiplied by θ is added to obtain a first added signal, the first added signal is squared to obtain a cardioid signal, the square of the second received signal and the third received signal Is added to the square of the second sum signal to obtain a second sum signal. With the method comprising the items, and generating a signal representing a detection result by performing multiplication processing of the cardioid signal and the synthetic omni signal.

  The second directivity synthesis method of the present invention comprises a first receiver having an omni-directional characteristic, and second and third receivers having a dipole directivity, and the maximum of the second receiver A directivity synthesis method in a sonar device in which a sensitivity axis and a maximum sensitivity axis of a third receiver are in a reference plane and are orthogonal to each other, and received by first to third receivers The signals are first to third received signals, respectively, and the first to third received signals have the maximum sensitivity with respect to a predetermined direction in the reference plane, and are opposite to the predetermined direction in the reference plane. The first signal is formed by the first directivity pattern having sensitivity to the direction perpendicular to the reference plane, and the maximum sensitivity direction is determined by the second and third received signals. It is in the plane and has a uniform sensitivity to each direction in the reference plane, and in a direction perpendicular to the reference plane To form a second signal according to a second directivity pattern becomes null sensitivity, the first signal and the multiplication result or a signal representing a detection result with the square root of the multiplication result of the second signal.

  The sonar device of the present invention includes a first receiver having an omni directional characteristic, a second receiver having a dipole directional characteristic, and a maximum sensitivity axis orthogonal to the maximum sensitivity axis of the second receiver. A third receiver having a dipole directivity characteristic, a first received signal that is a received signal by the first receiver, where θ is an azimuth angle of the direction in which directivity is to be directed, and a second A signal obtained by multiplying the second received signal, which is a received signal by the receiver, and sin θ, and a signal obtained by multiplying the third received signal, which is the received signal by the third receiver, by cos θ. Are added to form a first added signal, and the first added signal is squared to obtain a cardioid signal, and the second received signal square and third received signal are squared. The square of the wave signal is added to obtain a second addition signal, and a signal that is the square root of the second addition signal is obtained to obtain a synthetic signal. A second directivity synthesis processing unit to two signals, and the third directivity synthesis processing unit for outputting a result detected by performing multiplication processing of the cardioid signal and the synthetic omni signal.

  The present invention includes a first receiver having an omni directional characteristic and second and third receivers having a dipole directional characteristic, and the maximum sensitivity axis of the second receiver and the third received wave. When directivity synthesis is performed in a sonar device in which the maximum sensitivity axis of the detector is orthogonal, the plane stretched by the maximum sensitivity axes of the second and third receivers is used as a reference plane, such as a cardioid signal. The first directivity having maximum sensitivity with respect to a predetermined direction in the reference plane, null sensitivity with respect to a direction opposite to the predetermined direction within the reference plane, and sensitivity with respect to a direction perpendicular to the reference plane. The first signal according to the pattern and the maximum sensitivity direction in the reference plane, such as a synthetic omni signal, have uniform sensitivity in each direction, and null sensitivity in the direction perpendicular to the reference plane. And a second signal with a second directivity pattern . Then, the first signal or cardioid signal is multiplied by the second signal or synthetic omni signal. As a result, as will be apparent from the following description, null sensitivity is obtained in a direction perpendicular to the reference plane while having directivity so as to have the maximum sensitivity in a predetermined direction in the reference plane. Become. According to the present invention, directivity can be set in a desired direction so that the arrival direction of an acoustic signal can be known while suppressing an increase in the number of receivers in the sonar device, for example, while suppressing sensitivity in the vertical direction. The effect of becoming is obtained.

It is a figure explaining horizontal directivity composition by cardioid processing. It is a figure explaining a synthetic omni process. It is a figure explaining the directivity by synthetic omni processing. It is a figure which shows the principle of the synthetic cardioid process in the sonar apparatus of one Embodiment of this invention. It is a block diagram which shows the structure of the sonar apparatus of another embodiment of this invention.

In the most principle of the directivity synthesis method according to the present invention, the sonar device has a first receiver having an omni directional characteristic and second and third receivers having a dipole directional characteristic. Is used. The maximum sensitivity axes of the second and third receivers having the dipole directivity are orthogonal to each other, and a plane stretched by these two maximum sensitivity axes is called a reference plane. Moreover, the received signals of the first receivers of omni directional characteristic and received signal S _OM, second and third respectively received signals and received signals by receivers S _NS dipole directivity characteristics, S It will be expressed as _EW .

In the most basic processing, the received signals S _OM , S _NS , and S _EW provide the maximum sensitivity for a predetermined direction in the reference plane (the azimuth angle in this direction is θ). A first signal is formed by a first directivity pattern having null sensitivity in a direction opposite to the predetermined direction and sensitivity in a direction perpendicular to the reference plane. The predetermined direction θ is a direction in which directivity is desired. At the same time, with the received signals S _NS and S _EW , the maximum sensitivity direction is in the reference plane, the sensitivity is uniform in each direction in the reference plane, and the direction perpendicular to the reference plane is null. A second signal based on a second directivity pattern serving as sensitivity is formed. Then, a detection result is represented by the multiplication result of the first signal and the second signal or the square root of the multiplication result.

If the reference surface was a plane parallel to the water surface or sea surface, such first signal representative ones are detection signals i.e. cardioid signal S _CD by cardioid process described by Figure 1, representative of the second signal is the detection signal or synthetic Omni signal S _SO by synthetic Omni process described by FIGS.

Therefore, one form of sonar apparatus of the present invention shown in FIG. 4 is configured to perform the multiplication process seeking the cardioid signal S _CD and synthetic Omni signal S _SO. The sonar apparatus comprises a wave receiver 11 with omni directional characteristic, the two receivers 12, 13 having a dipole directivity characteristics, the first directivity synthesis processing unit 31 for obtaining the cardioid signal S _CD, Synthetic Omni signal S and the second directivity synthesis processing unit 32 for determining the _SO, cardioid signal S _CD and synthetic omni signal S third directivity synthesis processing unit 33 for outputting a detection result by performing multiplication processing of the _SO And. The maximum sensitivity axes of the receivers 12 and 13 having the dipole directivity are within a reference plane that is parallel to the water surface or the sea surface, for example, and are orthogonal to each other. The first directivity synthesis processing unit 32 receives the received signal S _OM of the receiver 11, a signal obtained by multiplying the received signal S _NS of the receiver 12 by sin θ, and the received signal of the receiver 13. a first addition signal by adding a signal obtained by multiplying cos theta in S _EW, the cardioid signal S _CD by squaring the first sum signal. θ is an azimuth in the reference plane and is an azimuth angle in a direction in which directivity is to be maximized. The second directivity synthesis processing unit 34 adds the square of the received signal S _{NS and} the square of the received signal S _EW to obtain a second added signal, and obtains a signal that is the square root of the second added signal. and synthetic omni signal S _SO Te. The third directivity synthesis processing unit 35 preferably obtains the square root of the value obtained by calculating S _CD × S _SO and outputs this as the synthetic cardioid signal S _SC .

After all, the sonar device shown in FIG.
S _CD = (S _OM + S _NS × sin θ + S _EW × cos θ) ²
And S _SO = (S _NS ² + S _EW ² ) ^1/2
As
S _D = S _CD × S _SO
In other words, the process equivalent to the above is executed, and the process of making the signal representing the detection result by the square root of S _D or S _D is performed.

By the way, when two signals of different directivity patterns are multiplied, the null sensitivity should also be in the directivity pattern of the signal after multiplication in the direction of null sensitivity in the original directivity pattern. The directivity pattern of the synthetic Omni processed signal S _SO, does not have the sensitivity in a direction perpendicular to the reference plane, also the directivity pattern of the signal S _D is a result of multiplying, a direction perpendicular to the reference plane For example, it has no sensitivity to the sea surface direction and the sea floor direction. Since car directivity pattern geoid signal S _CD has a null sensitivity in the opposite direction has a maximum sensitivity (in the direction of the azimuth angle theta) a specific direction in the reference plane, signal is the result of multiplying S The directivity pattern _D has maximum sensitivity in the direction of the angle θ and null sensitivity in the opposite direction. For even signal S _D signal obtained by the square root of (this is referred to as synthetic cardioid signal S _SC), so that the direction of maximum sensitivity direction and a null sensitivity similarly to the signal S _D is determined. In FIG. 4, the directivity patterns of the cardioid signal S _CD , the synthetic omni signal S _SO and the synthetic cardioid processing signal S _SC are shown.

According to the signal S _D or synthetic cardioid signals S _SC, lobe azimuth is emphasized, the detection result of the null direction has been removed is obtained, for example, in water or sea, being affected by noise and reverberation Therefore, an acoustic signal from a desired direction can be reliably detected. In this embodiment, by multiplying the cardioid signal S _CD and synthetic Omni signal S _SO as a linear (linear) amount, i.e., by calculating the cross spectrum, the vertical plane directivity in conformity with synthetic Omni processing While having the characteristics, it is possible to have a horizontal plane directivity characteristic according to the cardioid treatment, and to obtain a directivity gain. The directivity gain of the synthetic cardioid signal S _SC is slightly lower than +4.2 dB of the directivity gain by the cardioid processing, but is sufficiently larger than +3.0 dB of the directivity gain in the synthetic omni processing. Since three receivers are used, the standard deviation σ of the noise level is also smaller than in the case of synthetic omni processing.

  FIG. 5 shows the configuration of a sonar device according to another embodiment of the present invention. The sonar device shown in FIG. 5 is suitable for receiving a modulated acoustic signal by the receivers 11 to 13, and obtains a detection result according to a frequency component in the acoustic signal. In addition, it is possible to perform azimuth calculation and target detection. Therefore, the sonar device shown in FIG. 5 further includes a demodulation processing unit 34, an FFT processing unit 35, a normalization processing unit 36, a signal detection processing unit 37, and an azimuth calculation processing unit 38, compared to the sonar device shown in FIG. In addition, a display unit 39 is added.

The receivers 11 to 13 all receive the modulated acoustic signal, and the demodulation processing unit 34 demodulates each received acoustic signal to receive the received signals S _OM , S _NS and S _EW. And What is described as a modulation signal in FIG. 5 is a signal output from each of the receivers 11 to 13 when the receivers 11 to 13 receive the acoustic signals. From the demodulation processing unit 34, the signals S _OM , S _NS and S _EW are sent to the first directivity synthesis processing unit 31, and the signals S _NS and S _EW are sent to the FFT processing unit 35. The FFT processing unit 35 performs fast Fourier transform (FFT) on the signals S _NS and S _EW and sends the result to the second directivity synthesis processing unit 32, and the first directivity. performing fast Fourier transform to the cardioid signal S _CD from the combining processing unit 31 and sends the result to the third directivity synthesis processing unit 33. In this configuration, the first directivity synthesis processing unit 31 processes the time domain signal, and the second directivity synthesis processing unit 32 processes the frequency domain signal and outputs a frequency domain synthetic omni signal. To do. Third directivity synthesis processing unit 33, a synthetic omni signal S _SO of the frequency domain from cardioid signal S _CD and the second directivity synthesis processing unit 32 is converted into those in the frequency domain by the FFT processing unit 35 And a synthetic cardioid signal S _SC is output.

The normalization processing unit 36 normalizes the signal level in the synthetic cardioid signal S _SC and sends the normalized signal to the signal detection processing unit 37. The signal detection processing unit 37 performs threshold processing at the signal level, etc. To determine whether the signal is significant. On the other hand, the azimuth calculation processing unit 38 calculates from which azimuth the detected acoustic signal is based on the synthetic cardioid signal S _SC . When the signal detection processing unit 37 determines that the signal is a significant signal, the display unit 39 displays information such as signal strength and direction on the screen based on the calculation result of the direction calculation processing unit 38.

  In the configuration shown in FIG. 5, the preprocessing block 21 is configured by the demodulation processing unit 34 and the first directivity synthesis processing unit 31, and the FFT processing unit 35, the second and third directivity synthesis processing units 32, 33, the normalization processing unit 36 and the azimuth calculation processing unit 38 constitute a signal processing block 22, and the signal detection processing unit 37 constitutes a signal detection block 23. The first directivity synthesis processing unit 31 may be arranged in the signal processing block 22.

Further, when the acoustic signals to be received by the receivers 11 to 13 are unmodulated signals or when the receivers 11 to 13 are operated by a passive sonar method, the demodulation processing unit 34 is not required. The position where the FFT processing unit 35 is provided is not limited to the position shown in FIG. For example, the FFT processing unit 33 may be provided immediately before the third directivity synthesis processing unit 33, or the high-speed operation with respect to the synthetic cardioid signal S _SC output from the third directivity synthesis processing unit 33. An FFT processing unit 35 may be provided after the third directivity synthesis processing unit 33 so as to perform Fourier transform.

  The sonar device and the directivity synthesis method of each embodiment of the present invention described above can be applied to both an active sonar device and a passive sonar device.

11 to 13 Receiver 21 Preprocessing block 22 Signal processing block 23 Signal detection block 31 to 33 Directivity synthesis processing unit 34 Demodulation processing unit 35 FFT processing unit 36 Normalization processing unit 37 Signal detection processing unit 38 Direction calculation processing unit 39 Display section

Claims (9)

A first receiver having an omni-directional characteristic, and second and third receivers having a dipole directional characteristic, wherein the maximum sensitivity axis of the second receiver and the third receiver A directivity synthesis method in a sonar device in which the maximum sensitivity axis is orthogonal,
The received signals from the first to third receivers are first to third received signals, respectively, and the azimuth angle of the direction in which directivity is to be directed is θ,
The first received signal, the signal obtained by multiplying the second received signal by sin θ, and the signal obtained by multiplying the third received signal by cos θ are added to form a first added signal. , Squaring the first addition signal to obtain a cardioid signal;
The square of the second received signal and the square of the third received signal are added to obtain a second added signal, and a signal that is a square root of the second added signal is obtained to obtain a synthetic omni signal. And
Performing a multiplication process of the cardioid signal and the synthetic omni signal to generate a signal representing a detection result;
I have a,
The maximum sensitivity axis of the second receiver and the maximum sensitivity axis of the third receiver are set to be parallel to the water surface or the sea surface .   2. The method according to claim 1, wherein the multiplication process includes multiplying the cardioid signal and the synthetic omni signal to obtain a square root as a signal representing the detection result. Further comprising the method of claim 1 or 2 to perform a fast Fourier transform to represent the detection result according to the frequency of the respective received signal. A first receiver having an omni-directional characteristic, and second and third receivers having a dipole directional characteristic, wherein the maximum sensitivity axis of the second receiver and the third receiver A directivity synthesis method in a sonar device in which the maximum sensitivity axis is in a reference plane set to be parallel to the water surface or the sea surface and orthogonal to each other,
The received signals by the first to third receivers are first to third received signals, respectively.
The first to third received signals have maximum sensitivity in a predetermined direction in the reference plane, null sensitivity in a direction opposite to the predetermined direction in the reference plane, and the reference plane Forming a first signal with a first directivity pattern having sensitivity to a direction perpendicular to
According to the second and third received signals, the maximum sensitivity direction is in the reference plane and has a uniform sensitivity to each direction in the reference plane, and with respect to the direction orthogonal to the reference plane. Forming a second signal with a second directivity pattern resulting in null sensitivity;
A method of obtaining a detection result with a multiplication result of the first signal and the second signal or a square root of the multiplication result. A first receiver having an omni-directional characteristic;
A second receiver having a dipole directional characteristic;
A third receiver having a dipole directional characteristic having a maximum sensitivity axis orthogonal to the maximum sensitivity axis of the second receiver;
A first reception signal that is a reception signal by the first receiver and a second reception signal that is a reception signal by the second receiver, where θ is the azimuth angle of the direction in which directivity is to be directed. A signal obtained by multiplying the received signal by sin θ and a signal obtained by multiplying the third received signal, which is a received signal by the third receiver, by cos θ, are added as a first added signal. A first directivity synthesis processing unit that squares the first addition signal to obtain a cardioid signal;
The square of the second received signal and the square of the third received signal are added to obtain a second added signal, and a signal that is a square root of the second added signal is obtained to obtain a synthetic omni signal. A second directivity synthesis processing unit;
A third directivity synthesis processing unit that performs a multiplication process of the cardioid signal and the synthetic omni signal and outputs a detection result;
I have a,
The sonar device , wherein the maximum sensitivity axis of the second receiver and the maximum sensitivity axis of the third receiver are set to be parallel to the water surface or the sea surface . 6. The apparatus according to claim 5 , wherein the third directivity synthesis processing unit multiplies the cardioid signal and the synthetic omni signal, calculates a square root of the multiplication result, and uses the result as the detection result. The apparatus according to claim 5 , further comprising a fast Fourier transform processing unit that performs fast Fourier transform on a signal to be supplied to the third directivity synthesis processing unit. The apparatus according to claim 5 , further comprising a fast Fourier transform processing unit that performs fast Fourier transform on a signal output from the third directivity synthesis processing unit. Each of the first to third receivers receives a modulated acoustic signal and demodulates each received acoustic signal to obtain the first to third received signals. The apparatus according to claim 5 , further comprising a unit.

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