JPH08152467A - Direction detection apparatus for underwater sound source - Google Patents

Abstract

PURPOSE: To obtain a direction detection apparatus by which the direction of a true object can be detected even when a grading globe is generated in the directivity of a linear array. CONSTITUTION: While an LFM-type sound transmitter 2 and a linear array 1 are being towed, sound waves are radiated from the LFM-type sound transmitter 2, and the linear array 1 receives the transmitted sound waves. When the sound waves are at a high frequency, their directivity is set so as to comprise grading globes 16. When they are at a low frequency, their directivity is set so as to comprise only main poles 14 without the grading globes. Integrators 4a to 4n in an integral part 4 remove a received signal which is generated in an instant by the grading globes 16 in such a way that the reception time of the received signal in every direction due to change in the directivity is stored when the reception time is longer than the modulation time of a linear frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underwater sound source direction detecting device, and more particularly to an underwater sound source direction detecting device for preventing erroneous detection due to a grading lobe.

[0002]

2. Description of the Related Art A horizontal linear array receiver (hereinafter, referred to as a linear array) is one type of sonar for detecting the position of a sound source in water. This linear array is generally formed by disposing passive type receivers for low frequency sound reception at equal intervals and imposing a phase or delay time distribution on each receiver to form the desired directivity. For example, when the distribution of these phases or delay times is random, a wavefront pointing in a specific direction does not occur, but a linear function-like delay distribution such that the wavefront aligns with a certain azimuth angle. Gives a uniform wavefront. That is, if the delay distribution is changed into a linear function, the main pole of directivity can be obtained in an arbitrary direction. Then, for example, considering a wavefront in which a target sound source is synthesized at a low level, the interval between each of the receivers is the most important in order to determine them unambiguously, and they have been manufactured with the highest possible accuracy.

[0003]

However, when a transmitter and a linear array are combined to use a bistatic method of detecting a target position, a linear array in which receivers at equal intervals are arranged is called a linear array. When the relationship between the wavelength λ of the transmitted sound and the arrangement interval d satisfies d / λ> １ ／, some sub-components (hereinafter referred to as grading lobes)
Occurs. For example, the target sound source has a low frequency (d / λ <1).
Grading lobes do not occur during the generation of / 2), but high frequency sounds (d / λ> 1 /
Grading lobes are inevitably generated during the generation of 2). That is, when a high-frequency sound (d / λ> 1/2) is emitted from the target sound source, there are sub-poles in addition to the main pole, and the target is moved in the sub-pole and main pole directions. That means you can't specify your goals. Therefore, it is desirable to be able to detect the true target direction even if a high frequency sound is generated from the target sound source or a low frequency sound.

[0004]

An underwater sound source direction detecting apparatus according to the present invention places a linear array and a sound transmitter in water, and the sound transmitter linearly outputs a reference signal for a predetermined time interval. Frequency modulation is performed and a sound wave corresponding to the modulation is transmitted into the water. A plurality of receivers arranged linearly at equal intervals in a linear array receive the transmitted sound waves. The phase adjuster inputs a plurality of reception signals from a plurality of receivers in a linear array, and phasing each of the reception signals for each of the received directions. Each accumulator of the accumulator group accumulates the received signal when the received signal corresponding to the azimuth is input and the reception time of the received signal is the same as the linear frequency modulation time. The detector informs the accumulator that there is a target in the direction of the accumulator when the received signal is accumulated.

[0005]

According to the present invention, the linear array and the sound transmitter are placed in water, the sound transmitter linearly frequency-modulates the reference signal for a predetermined time interval, and a sound wave corresponding to the modulation is submerged in the water. Send towards. A plurality of receivers arranged linearly at equal intervals in a linear array receive the transmitted sound waves, and when the transmitted sound waves have a high frequency, the directivity has a grading lobe, and the frequency is low. In some cases, the directivity has only the main pole without the grading lobe. Even if a received signal is input by each accumulator in the accumulator group and the received signal for each direction due to such a change in directivity is phased by the phase adjuster, the reception time of the received signal is linear frequency. It is stored only at the same time as the modulation time. And
The detector informs the accumulator that there is a target in the direction of the accumulator when the received signal is accumulated.

[0006]

【Example】

First Embodiment FIG. 1 is a schematic configuration diagram of a first embodiment. In the figure, 1 is a horizontal linear array (hereinafter referred to as a linear array) in which omnidirectional wave receivers are linearly arranged at equal intervals. When each of the wave receivers of the linear array 1 receives a sound, it converts the sound into an electric signal (hereinafter referred to as a wave reception signal) and outputs the electric signal. 2 is an LFM type sound transmitter. The LFM-type sound transmitter 2 changes the transmission frequency to a higher frequency at predetermined intervals as time elapses in the interval, thereby setting an LFM (Liner Frequency Modulation).
system is adopted, and at least the frequency of sound is set such that the ratio between the arrangement interval d and the wavelength of sound is 0.5 or less or 0.5 or more. 3 is a phase adjuster. The phasing device 3 controls a delay device provided corresponding to each of the receivers of the linear array 1 to form a desired directivity, and receives the received signals a to
Each time the received signal i is input, the phase is phased by a delay unit, combined, and output. This output signal is a function signal in which the reception intensity and the azimuth (90 degrees to -90 degrees) are associated.

Reference numeral 4 denotes a storage unit (hereinafter, referred to as an integration unit).
The integrator 4 is a storage (hereinafter, referred to as an integrator) corresponding to the direction.
And each input an output signal corresponding to an azimuth, and each integrator 4a to integrator 4b integrates and accumulates each time an output signal of the corresponding azimuth is input, and accompanies an input of a control signal. Output the accumulated value. At the time of this integration, the time constant τ is in the range of the time constant for removing the received signal of the frequency generated by the grading lobe. That is, when the reception time of the reception signal is longer than the linear frequency modulation time, the reception signal is accumulated. 5 is a detector. The detector 5 is connected to each integrator 4 at predetermined time intervals.
a to a control signal for outputting the accumulated data from the integrator 4n to the integrator 4, and if the accumulated data is accumulated, it is determined that there is a signal. The determination of the presence or absence of this signal
Since there is noise or the like, it is determined that there is a signal when the accumulated value exceeds a predetermined level. Reference numeral 6 denotes a display for displaying a target in a direction based on the determination result from the detector 5.

The underwater sound source direction detecting device having the above-described configuration will be described below. FIG. 2 is an explanatory diagram of directivity when the frequency of the sound from the target sound source is low. FIG.
This is the directivity of the linear array when the FM sound transmitter 2 is generating a low frequency sound (d / λ = 0.5). As shown in FIG. Only the portion designated as 14 has directivity. FIG. 2B shows the sound level from the target sound source when the linear array 1 is as shown in FIG. 2A, and only one peak is obtained. For example, if the main pole 14 is located at the center of the linear array 1,
There is a target sound source in the 0 degree direction. FIG. 3 is an explanatory diagram of directivity when the sound from the target sound source has a high frequency.
In the figure, reference numeral 16 denotes a grading lobe. The figure shows that the LFM type sound transmitter 2 has a high frequency sound (d / λ =
1.5) is the directivity of the linear array 1 when (1) is generated, and has a grading lobe in addition to the main pole 14 as shown in FIG. It has become. FIG. 3B shows the sound level from the target sound source when the linear array 1 is as shown in FIG. 3A, and three peaks are obtained.

For example, when the linear array 1 is towed while driving the LFM type sound transmitter 2, the sound transmitted from the LFM type sound transmitter 2 changes in frequency from low to high with the passage of time. Produces a sound. That is, since the sound is a low-frequency sound at first, the directivity is as shown in FIG. Therefore, when the target is below and the sound wave transmitted from the LFM type sound transmitter 2 is reflected on the target, the target can be detected. Next, when the transmission sound from the LFM type sound transmitter 2 has a high frequency, the directivity of the linear array 1 is as shown in FIG. Sound is detectable,
Since the grading lobe occurs, the direction cannot be specified. However, even if the transmission sound from the LFM type sound transmitter 2 has a high frequency, the time is instantaneous. Therefore, even if the sound receiving signal is output to the integrator corresponding to the direction in which the grading lobe has occurred, the integrators 4a to 4n
Since the time constant is set, the sound will not be accumulated unless a sound is generated from that direction for a time longer than this time constant.

That is, if no sound is actually generated from that direction, the sound is removed as a sound due to the grading lobe. Therefore, the target sound source has a low frequency sound (d / λ >＞) or a high frequency sound (d / λ <1/1).
Since detection is possible even when 2) occurs, the detection range becomes wide. That is, when the main pole is oriented in a certain direction, the direction in which the grading lobe occurs is determined by the transmission frequency to be phased because the receiver interval is constant. Frequency to be phased, that is, LFM
Since the transmission frequency of the sound source changes with time, the direction of the grading lobe changes with time. On the other hand, the direction of the LFM sound source is constant and does not change with time. Therefore, the time when the direction of the grading lobe matches the direction of the LFM sound source is only a moment. For this reason, LF
If the frequency sweep time of the M sound source is made sufficiently fast so that the integrator output is not affected by the received signal level due to the grading lobe, the output of the integrator will be from the main pole direction.

Accordingly, the main pole 14 of the linear array 1 is oriented in a certain direction, and d transmitted from the LFM type sound transmitter 2 is transmitted.
/ Λ> 1/2 or more wideband LFM signal is converted into a linear array 1
As described above, the signal output from the integrator 4 is not affected by the grading lobe, so that the detector 5 determines that the signal is present, and the direction in which the signal arrival direction is displayed on the display 6 is the sound source. Direction. In the first embodiment, the frequency of the LFM type sound generator is set lower or higher, but may be reversed.

Second Embodiment In the first embodiment, the vessel is towed, but the linear array may be arranged near the water surface without towing the vessel. FIG. 4 is a schematic configuration diagram of the second embodiment. In the figure, 1 to 5 are the same as above. 22 is a detector 5
Is a buoy that amplifies the detected azimuth and converts it into radio waves. 24 is a float. As shown in the figure, since the direction from the detector 5 is transmitted as radio waves, even if the vehicle is not towed,
When the LFM type sound transmitter 2 is driven, the sound transmitted from the LFM type sound transmitter 2 generates a sound having a frequency changed from a lower frequency to a higher frequency as time passes. That is, the sound receiving level cannot be expected because the sound is low frequency sound at first, but the directivity is as shown in FIG. Therefore, if the target sound source is below and the target sound source is generating a low sound tuned to the frequency of the transmission sound from the LFM sound transmitter 2,
It can be detected sufficiently without error.

Next, when the transmission sound from the LFM type sound transmitter 2 has a high frequency, the directivity of the linear array 1 is as shown in FIG. The sound from the sound source can be detected, but the azimuth cannot be specified because a grading lobe is generated. However, even if the transmission sound from the LFM type sound transmitter 2 has a high frequency, the time is instantaneous. Therefore, even if the sound receiving signal is output to the integrator corresponding to the direction in which the grading lobe is generated, the time constant is set in the integrators 4a to 4n, and the sound from that direction is output for a time longer than this time constant. If is not generated, it will not be accumulated. In other words, if no sound is generated from that direction, the sound is removed as a sound due to the grading lobe. Therefore, the sound can be detected even in a water area where a ship or the like cannot travel, and the sound of a target in a narrow water area can be detected.

[0014]

As described above, according to the present invention, a linear array and a sound transmitter for transmitting a linear frequency-modulated sound wave are placed close to each other in water, and the linear array receives the transmitted sound wave. Sometimes, when the sound wave has a high frequency, the directivity has a grading lobe, and when the frequency is low, the directivity has only a main pole having no grading lobe. Since the reception signal is stored only when the reception time is longer than the linear frequency modulation time, the reception signal generated momentarily by the grading lobe is removed. Even if the target generates high-frequency sound even if it is a linear array in which receivers are arranged for low frequencies, it is detected as a result. Since the frequency band of the waves is enlarged, and the effect is obtained that can detect the direction of the true target.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment.

FIG. 2 is an explanatory diagram of directivity when the frequency of a sound from a target sound source is low.

FIG. 3 is an explanatory diagram of directivity when a sound from a target sound source has a high frequency.

FIG. 4 is a schematic configuration diagram of a second embodiment.

[Explanation of symbols]

 1 linear array 2 LFM type sound transmitter 3 phaser 4 integration part 5 detector 6 indicator 16 grading lobe 22 buoy

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigekazu Matsunaga 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (72) Shinichi Sayama 1-12-12 Toranomon, Minato-ku, Tokyo No. Oki Electric Industry Co., Ltd.

Claims (3)

[Claims] 1. A sound transmitter that linearly frequency-modulates a reference signal at a predetermined time interval for a predetermined period of time, and emits a sound wave corresponding to the modulation toward the water, and a sound transmitter near the sound transmitter, A linear array in which a plurality of wave receivers are linearly arranged at equal intervals, and a plurality of received signals from a plurality of wave receivers of the linear array are input, and each received signal is received in the received direction. A phasing device for phasing for each azimuth, and when a reception signal corresponding to the azimuth is input, when the reception time of the reception signal is longer than the linear frequency modulation time, the reception Underwater sound source direction detection, characterized by having a group of accumulators for accumulating signals and a detector for notifying that there is a target in the direction of the accumulator when received signals are accumulated in the accumulator. apparatus. 2. A time longer than the linear frequency modulation time is a time when a ratio between an arrangement interval of the receivers and a wavelength of a sound wave from the sound transmitter is 0.5 or more. The underwater sound source direction detecting device according to claim 1. 3. The underwater sound source direction detecting apparatus according to claim 1, wherein a transmitter for transmitting a detection result is connected to the detector.