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JPH11215583

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JPH11215583
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sonar system which receives an acoustic signal by means of a hydrophone and acquires
information in the water of the sea or the like.
[0002]
2. Description of the Related Art FIG. 2 is a block diagram showing a receiver of a conventional
sonar system, and FIGS. 3 (a) to 3 (d) are frequency characteristics of the signals S0 to S3 in FIG.
The receiver of this sonar system receives a hydrophone 1 for receiving and outputting an
acoustic signal S0 propagating in the sea, an equalizer (EQL) 2 connected to the hydrophone 1,
and a phase shifter connected to the equalizer 2. And a vessel 3. Conventionally, there was no
type of hydrophone attached directly to a hull such as a ship body, so the hydrophone 1 of FIG. 2
is provided in a place dedicated to the ship and is disposed at the dedicated place.
[0003]
The acoustic signal S0 propagates in the sea with a frequency characteristic of -6 dB / oct, as
shown in FIG. 3 (a). The hydrophone 1 having received the acoustic signal S0 outputs a reception
signal S1 having the same frequency characteristic as the acoustic signal S0 as shown in FIG. 3
(b). The equalizer 2 has a characteristic of 6 dB / oct opposite to that of the acoustic signal S0,
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and corrects the received signal S1. As a result of this correction, as shown in FIG. 3C, a
correction signal S2 whose level is flat with respect to the frequency is obtained. The phasing
device 3 performs phasing on the correction signal S2, and outputs a hearing signal S3 having a
flat frequency-to-level characteristic to an analysis unit (not shown) or the like in the subsequent
stage.
[0004]
However, the conventional sonar system has the following problems. In recent years, a hull
mounted hydrophone 11 has been developed that can be directly attached to a ship without
providing a dedicated place on a ship such as a ship. Therefore, it is not necessary to add a
dedicated place, and the receiving unit of FIG. 2 using the hydrophone 1 and the receiving unit
using, for example, the hull mounting type hydrophone 11 are used in combination. FIG. 4 is a
block diagram showing a receiving unit using a conventional ship-mounted hydrophone, and FIG.
5 is a frequency characteristic diagram of the signals S11 to S13 in FIG.
[0005]
This receiving unit is used in combination with the receiving unit shown in FIG. 2, and includes a
hull mounted hydrophone 11 for receiving the acoustic signal S0, an equalizer 12 connected to
the hull mounted hydrophone 11, and the equalizer 12 And a phase shifter 13 connected to the
The acoustic signal S0 propagates in the sea with a frequency characteristic of -6 dB / oct as in
FIG. 3A, but the frequency vs. sensitivity characteristic of the hydrophone 11 receiving the
acoustic signal S0 is different from that of the hydrophone 1 . That is, the reception sensitivity in
the low frequency region is degraded, and the frequency characteristic of the reception signal
S11 output by the hydrophone 11 is distorted as shown in FIG. 5A. The equalizer 12 corrects the
reception signal S11 by 6 dB / oct, which is the reverse of the acoustic signal S0, and outputs a
correction signal S12. Even if this correction is performed, the frequency characteristic of the
correction signal S12 does not become flat as shown in FIG. 5 (b). Therefore, the level of the
audio signal S13 output from the phasing device 13 that performs phasing on the correction
signal S12 to the analysis unit at the subsequent stage does not become flat as shown in FIG. This
is different from the listening signal S3. Therefore, there has been an adverse effect such as the
necessity of distinguishing the processing in the analysis unit in the latter stage with the
hydrophone 1 or 11.
[0006]
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SUMMARY OF THE INVENTION In order to solve the above problems, according to the present
invention, there is provided a hydrophone directly attached to a ship, receiving an acoustic signal
propagated in water and outputting a received signal; A receiver that corrects the received signal
output from the hydrophone with a frequency characteristic reverse to the frequency
characteristic of the propagation of the acoustic signal, and an equalizer that outputs the
corrected signal, and an audio signal with phasing the corrected signal. In the sonar system for
acquiring underwater information from the audio signal, the following configuration is adopted.
That is, there is provided a filter connected to the output side of the equalizer or the phasor to
remove the correction signal or the listening signal from the influence of the frequency vs.
sensitivity characteristic at the reception of the hydrophone.
[0007]
As described above, according to the present invention, the sonar system is configured, so that
the received signal output from the hydrophone directly attached to the ship is corrected by the
equalizer and becomes a listening 0 signal by phasing by the phasing device. Here, since the
reception signal includes the frequency vs. sensitivity characteristic 0 influence at the reception
of the hydrophone, the influence remains on the correction signal and the audio listening signal
output from the equalizer. The influence of the frequency-sensitivity characteristic on the
reception of the hydrophone is removed by the filter and the correction signal or the listening
signal is corrected. Therefore, the problem can be solved.
[0008]
DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the main
part of a sonar system showing an embodiment of the present invention. The sonar system
includes two systems of receiving units 20 and 30, and a selector 40 connected to the output
side of the receiving units 20 and 30. The receiving unit 20 includes a hydrophone 21 that
receives the acoustic signal S0 propagated in the water, such as in the sea, and outputs a
received signal S21. The hydrophone 21 is not a hull mounting type, and is disposed at a
dedicated installation place provided on, for example, a bow of a ship such as a ship. The output
side of the hydrophone 21 is connected to an equalizer (EQL) 22 that corrects the reception
signal S21 to generate a correction signal S22. At the output side of the equalizer 22, a phasing
device 23 is connected which generates the listening signal S23 by phasing the correction signal
S22.
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[0009]
The receiving unit 30 has a hull mounted hydrophone 31 that receives the acoustic signal S0 and
outputs a received signal S31. The hydrophone 31 is an extension of the hydrophone 21 at the
bow, and is directly attached, for example, to the stern's hull. The output side of the hydrophone
31 is connected to an equalizer 32 that corrects the reception signal S31 to generate a correction
signal S32. The output side of the equalizer 32 is connected to a phasing device 33 that
generates a listening signal S33 by phasing the correction signal S32, and the output side of the
phasing device 33 is connected to a frequency characteristic correction filter 34. The output
terminal of the frequency characteristic correction filter 34 of the reception unit 30 and the
output terminal of the phasor 23 of the reception unit 20 are connected to the selector 40. The
selector 40 selects the output signal of the frequency characteristic correction filter 34 or the
output signal of the phasor 23 and outputs it as an audio listening signal S40 to an analysis unit
in the subsequent stage (not shown).
[0010]
FIG. 6 is a circuit diagram showing a configuration example of the frequency characteristic
correction filter 34 in FIG. The frequency characteristic correction filter 34 corrects the sound
reception signal S33 by removing the influence of the frequency vs. sensitivity characteristic at
the reception of the hull mounted type hydrophone 31, and is made of, for example, an active
filter. The input terminal In of the frequency characteristic correction filter 34 is connected to the
inverting input terminal (-) of the operational amplifier 34b via the resistor 34a. A power supply
voltage of 15 V is applied to the operational amplifier 34 b via the resistor 34 c, and a power
supply voltage of −15 V is applied to the operational amplifier 34 b via the resistor 34 d. The
noninverting input terminal (+) of the operational amplifier 34b is grounded via the offset
compensating resistor 34e. The output terminal of the operational amplifier 34b is connected to
the output terminal Out of the frequency characteristic correction filter 34, and is connected to
one end of the resistor 34f and one end of the resistor 34g. The other end of the resistor 34f is
directly feedback-connected to the inverting input terminal (-) of the operational amplifier 34b,
and the other end of the resistor 34g is feedback-connected to the inverting input terminal (-) via
a capacitor 34h.
[0011]
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FIG. 7 is an explanatory diagram of frequency characteristics of the signals S0 and S21 to S34 in
FIG. 1. The operation of the sonar system of FIG. 1 will be described with reference to FIG. The
acoustic signal S0 propagates in the water of the sea and the like to reach the hydrophones 21
and 31, but the frequency-to-level relationship is a relationship of -6 dB / oct. The hydrophone
21 outputs a reception signal S21 having the same frequency-to-level relationship as the acoustic
signal S0 and supplies the reception signal S21 to the equalizer 22. The equalizer 22 corrects the
received signal S21 with a characteristic of 6 dB / oct which is opposite to the frequency
characteristic of propagation in the sea, and generates a correction signal S22. The frequency to
level relationship in the correction signal S22 becomes flat due to the correction. The phasing
device phases the correction signal S22 to generate a listening signal S23. The relationship
between the frequency and the level in the listening signal 23 is also flat as in the correction
signal S22.
[0012]
On the other hand, the hull mounted hydrophone 31 is different from the hydrophone 21 in
frequency-to-reception sensitivity characteristic due to reflection and absorption of the acoustic
signal S0, and is deteriorated in a low frequency region. Therefore, in the frequency-to-level
characteristic of the reception signal S31 output from the hydrophone 31, the level at the low
frequency becomes low as shown in FIG. The equalizer 32 corrects the reception signal S31 with
a characteristic of 6 dB / oct which is opposite to the frequency characteristic of propagation in
the sea to generate a correction signal S32, and the phasing device 33 performs phasing on the
correction signal S32 Then, a listening signal S33 is generated. The frequency-to-level
relationship in the correction signal S32 or the listening signal S33 has a low level at the low
frequency due to the reception sensitivity of the hydrophone 31. Here, considering the case
where the listening signal S33 is directly input to the selector 40, the frequency-to-level
relationship of the listening signal S33 is different from that of the listening signal S23. For
example, different signals S40 correspond to the same acoustic signal S0. It will be given to the
latter stage, which is inconvenient. Therefore, the listening signal S33 is corrected through the
frequency characteristic correction filter 34.
[0013]
The frequency characteristic correction filter 34 amplifies the audio listening signal S33 input
from the input terminal In using the operational amplifier 34b. At the inverting input terminal (-)
of the operational amplifier recorder 34b, a negative feedback rope from the output terminal side
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formed of a resistor 34f, a resistor 34g and a capacitor 34h is formed. The capacitor 34h
increases the impedance in the negative feedback loop at low frequencies, so the negative
feedback voltage at low frequencies is reduced. Therefore, the frequency characteristic correction
filter 34 is a low pass filter having a transfer characteristic reverse to the frequency-to-level
relationship in the audio signal S33, and the influence of the frequency-sensitivity characteristic
of the hydrophone 31 in the audio signal S33 is removed and corrected. It will be done. As a
result of this correction, a listening signal S34 having a flat frequency-to-level relationship is
generated, and is provided to the selector 40 via the output terminal Out. The selector 40 selects
the audio listening signal S23 or S34 based on the selection signal or the like, and provides the
audio listening signal S23 or S34 to an analysis unit (not shown) at the subsequent stage.
[0014]
As described above, in the present embodiment, the frequency characteristic correction filter 34
configured by the active filter using the operational amplifier 34 b in the reception unit 30
including the hull mounted hydrophone 31, the equalizer 32, and the phasing device 33. Since
the characteristics of the frequency to reception sensitivity of the hydrophone 31 deteriorate in
the low frequency region, and the influence on the audio signal S33 remains, the influence can be
eliminated. Therefore, the characteristics of the audio listening signal S23 obtained by the
receiving unit 20 and the audio listening signal S34 output from the frequency characteristic
correction filter 34 become the same, and even if the signals S23 and S34 are switched and given
to the subsequent stage, There is no need to distinguish between treatments.
[0015]
The present invention is not limited to the above embodiment, and various modifications are
possible. As a modification, for example, there are the following. (1) Although the frequency
characteristic correction filter 34 is connected to the output side of the phasing device 33 in the
above embodiment, the same effect can be obtained by connecting it to the output side of the
equalizer 32. (2) The frequency characteristic correction filter 34 may have a configuration other
than that shown in FIG. 6, and may be, for example, a band pass filter that matches the reception
sensitivity of the hydrophone 31. (3) When the audio signal S33 is not an analog signal but a
digital signal, the frequency characteristic correction filter 34 uses a digital filter instead of an
active filter.
[0016]
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As described above in detail, according to the present invention, in the sonar system having the
hydrophone directly attached to the hull, the equalizer and the phasor, the filter on the output
side of the equalizer or phasor Can be generated to generate an audio signal in which the
influence of the frequency vs. sensitivity characteristic at the reception of the hydrophone is
removed. Therefore, even if it is used together with, for example, a type of hydrophone that can
not be attached directly to the hull, it is not necessary to distinguish and process the processing
of the audio signal.
[0017]
Brief description of the drawings
[0018]
1 is a configuration diagram showing a main part of a sonar system showing an embodiment of
the present invention.
[0019]
2 is a block diagram showing a receiving unit of the conventional sonar system.
[0020]
3 is a frequency characteristic diagram of the signals S0 to S3 in FIG. .
[0021]
4 is a block diagram showing a receiving unit using a conventional ship-mounted hydrophone.
[0022]
5 is a frequency characteristic diagram of the signals S11 to S13 in FIG.
[0023]
6 is a circuit diagram showing a configuration example of the frequency characteristic correction
filter 34 in FIG.
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[0024]
7 is an explanatory view of the frequency characteristics of the signals S0 and S21 to S34 in FIG.
[0025]
Explanation of sign
[0026]
Reference Signs List 20, 30 receiver 21 hydrophone 31 hull mounted hydrophone 22, 32
equalizer 23, 33 phasor 34 frequency characteristic correction filter 40 selector S0 acoustic
signal S21, S31 reception signal S22, S32 correction signal S23, S33 listening signal
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