JPH0366628B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a forward-looking sonar, and in particular to a ghost display when it is mounted on a navigation vehicle that is slid on the seabed by a mother ship and used to monitor obstacles in front of the runway. This article relates to a forward auditing sonar designed to eliminate

[Conventional technology]

As a navigation vehicle that is glided along the seabed by a mother ship, it is used for many operational purposes, including collecting and surveying seabed resources such as manganese nodules. In this case, such a mobile vehicle is usually equipped with a forward-looking sonar for detecting obstacles in front, and searches a predetermined distance and range ahead with a predetermined resolution.

[Problem that the invention seeks to solve]

In the conventional forward monitoring sonar described above, when trying to widen the forward monitoring range, ghosts occur due to the side ropes of the transducer, or ghosts occur when the phase information repeats the same state every 360 degrees, which deteriorates the quality of the displayed information. However, if the transmitting and receiving wave directivity is made sharp in an attempt to avoid this problem, the monitoring range becomes extremely narrow.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a forward-looking sonar that can fundamentally eliminate ghost components from the luminance signal to be displayed by using azimuth information obtained from transmitted and received signals.

[Means for solving problems]

The forward-looking sonar of the present invention is a forward-looking sonar mounted on a mobile vehicle that glides on the seabed, in which a received signal is input separately into a brightness information signal and a phase information signal, and azimuth information is detected from the phase information signal. Based on the above, the present invention includes a ghost component removing means for removing a ghost component due to a side lobe of receiver directivity or a ghost component due to repetition of phase information every 360 degrees from the luminance information signal.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. The embodiment shown in FIG. 1 includes a transducer 1, a phaser 2, an amplifier 3, a display controller 4, a phase detector 5,
It is configured to include a phase comparator 6 and a display 7. Among these components, only the display 7 is mounted on the mother ship, and the other transducers 1 to phase comparators 6 are mounted on the navigation body.

The transducer 1 has a so-called line array configuration in which transducer elements are linearly arranged, and in the case of wave transmission, a part of the transducer elements is used to widen the directivity width. In the case of wave reception, in order to input luminance information, shading is applied using all transducer/receiver elements to suppress sidelobes, and when inputting phase (azimuth) information, luminance information is input. In order to provide a larger directivity width including the directivity width at , fewer than the total number of transducer elements are used for this purpose.

The details and purpose of how the transducer 1 is used in each operation mode are as follows.
FIG. 2a is a transmission directivity characteristic diagram of the embodiment of FIG. 1. Out of the total number b of transducer elements of the transducer 1, a pieces are used to form a wave transmission directivity pattern 101 with a wide directivity angle. P ₀ indicates the center direction of the main rope, and P ₁ and P ₂ indicate directions 3 dB lower than the P ₀ direction. The purpose of increasing the directivity angle without using all the transducers 1 is to expand the monitoring range.

FIG. 2b is a diagram showing the basic receiving directivity characteristic of the transducer in the embodiment of FIG. 1. In this case, the reception directivity pattern 102 is formed by using a total number of b transducer elements in parallel, and therefore there are -13 dB first side lobes on the left and right sides of the main lobe.
Furthermore, adjacent to this, second, third, . . . n side lobes appear. In this embodiment, the angle determined by the first zero pole position interposed between the main lobe and the first left and right side lobes corresponds to the transmitting directivity pattern 10.
It is set to almost match the directivity angle of 1.

By the way, the phase information of the main lobe and side lobe in the center direction is 2π (360 degrees).
Different. Therefore, for example, the input S ₁ becomes a ghost captured in the direction of S ₀ at the same declination from the direction of P ₀ as a ghost for the input S ₀ . Suppress this
In order to improve (Signal)/N (Noise), this embodiment performs shading as follows.

FIG. 2c is a receiving directivity characteristic diagram when luminance information is input to the transducer in the embodiment of FIG. 1.

The reception directivity pattern 103 shown in FIG. 2c is obtained by applying predetermined shading to the outputs of the total number b of transducer elements.

As is well known, this shading is a so-called phasing process in which the output of each receiver element that forms the receiving directivity is multiplied by a weighting coefficient, and then added to effectively obtain the desired directivity. This shading process is also used in this embodiment to significantly suppress sidelobes.

The received wave directivity pattern 103 is a pattern formed based on such shading,
Care has been taken to ensure that the directivity width with a 13dB drop is approximately the same. Obviously, the directions of P ₁ and P ₂ are +π (180 degrees) and −π phase shifted, respectively, with respect to the direction of P ₀ , and there is a 2π difference between them. That is, −π<<
+π. This type of shading not only eliminates ghosts by lowering side lobes, but also
It is also clear from a comparison with the received wave directivity pattern 102 in FIG. 2b that signal detection in the vicinity of the P ₁ and P ₂ directions is also possible.

In this embodiment, all the transducer elements are subjected to shading, but instead of this, each b/2 transducer element forms the wave reception directivity pattern shown in Fig. 2c. Of course, it is also possible to use a format in which the outputs of the received wave directivity patterns are added and synthesized.

Returning again to FIG. 1, the explanation of the embodiment will be continued. The outputs of the transducer 1 are supplied to the phaser 2 as the outputs of all b transducer elements as luminance information input. The phaser 2 performs shading on these b received wave outputs using a predetermined shading function, in the case of this embodiment, a Hanning function, and
It is converted into an output having the reception directivity characteristic shown in the figure and is supplied to the amplifier 3.

The amplifier 3 amplifies the input to a predetermined level and supplies the amplified signal to the display controller 3.

The display controller 3 attempts to eliminate ghosts that may occur from the input output of the amplifier 3 based on the repetition of phase information every 360 degrees. This ghost occurs under the following conditions.

In FIG. 2c, the input shown at S ₁ in FIG. 2b is included in the received wave directivity pattern 103 and displayed in the vicinity of direction P ₂ . Now, let β be the angle between the directions P ₀ and S ₁ , and δ be the angle between the directions P ₂ and S ₁ . The ghost of S ₁ considered in this state is S ₀ , and the angle between S ₀ and P ₀ is (β
−2δ). This is based on the fact that the phase difference between the P ₁ and P ₂ directions is 2π. In order to eliminate this ghost, phase information is used in the following manner.

During the received wave output of the transducer 1, the output of two channels of c/2 each is supplied to the phase detector 5 as phase information. Here, c<b and is determined under the following conditions.

FIG. 3 is a receiving directivity characteristic diagram when phase information is input to the transducer in the embodiment of FIG. 1.

The receiving directivity pattern 104 formed using c/2 transducer elements has a larger angle φ between the first zero poles, and in this embodiment, the angle φ between the first zero poles in FIG. It is made equal to the angle.

Of the output reception signals of the transducer 1, the output reception signals of c/2 channels each are converted to BDI via the reception characteristics of the reception directivity pattern 104.
(Bearing Deviation Indication) Phase information input is supplied to the phase detector 5 using a reception method.

FIG. 4 is a diagram showing the principle of the BDI reception method. It is assumed that an incoming sound wave Q shown by an arrow is received by two channels, channel CH1 and channel CH2. These two channels output received signals having a phase difference corresponding to the path length difference d, but this d also obviously changes in response to the azimuth angle θ. Therefore, the azimuth angle θ of the incoming sound wave is determined from the phase difference between the outputs of the two channels, and this is normally expressed as the azimuth angle on the X axis and the distance on the Y axis.
Use as a B scope display to display the axis. This embodiment also utilizes this BDI reception and B scope display method.

Returning again to the embodiment shown in FIG. 1, the explanation will be continued.
The phase detector 5 detects the azimuth angle θ as phase information based on the BDI reception method shown in FIG.

This azimuth angle θ is then supplied to a phase comparator 6, where the phase is compared with a reference azimuth angle. This reference azimuth is −/2 and +/2, i.e. the azimuth P ₁
and _P2, and when the azimuth of the input signal exceeds this ±/2, a display control signal is generated to remove the display of that input signal. Specifically, this display control signal is provided in a format that suppresses the output of the luminance signal, and while the display control unit 4 is receiving the display control signal and the amplifier 3 is outputting, the display control signal is output in an azimuth range exceeding ±/2. Control the display so that it is not output.

In this way, the azimuth object displayed on the display 7 is −
It is only in the range of /2 to +/2, therefore, inputs such as S ₁ that are included in the received wave directivity pattern 103 and may be displayed as ghosts are fundamentally removed from display. . Furthermore, as for ghosts due to the first side lobe exceeding ±/2, the level thereof is significantly suppressed due to the shading effect in the reception directivity pattern of FIG. 2c formed by the phaser 2. , the brightness level that should be displayed will not be reached.

To explain the selection of C here, as a general matter, the beam width and array length are in an inversely proportional relationship (the larger the array length, the narrower the beam width;
(The smaller the array length, the wider the beam width.) In the embodiment, the beam width φ is realized with the array length b, and the target _S1 outside the beam width becomes a ghost. On the other hand, array length C
(<b) widens the beam width and allows accurate confirmation of S ₁ . Therefore, C should be made small enough to ensure the beam width necessary to confirm _S1 .

In this way, it is possible to perform received signal processing that simultaneously expands the monitoring area and improves the S/N ratio by suppressing ghosts.

〔Effect of the invention〕

As explained above, according to the present invention, in a forward monitoring sonar, a received signal is divided into a brightness information signal and a phase information signal, and a ghost component is suppressed by suppressing the brightness signal using azimuth information detected by the phase information signal. By providing a means for erasing the information in a formal manner, it is possible to fundamentally eliminate ghost display, significantly improve the reliability of displayed information, and realize a forward-looking sonar that can significantly expand the monitoring range.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention;
Fig. 2a is a transmitting directivity characteristic diagram of the embodiment shown in Fig. 1, Fig. 2b is a basic receiving directivity characteristic diagram of the transducer in the embodiment shown in Fig. 1, and Fig. 2c is a diagram of the embodiment shown in Fig. 1. Fig. 3 shows the receiving directivity characteristics when luminance information is input to the transducer in the embodiment shown in Fig. 1, and Fig. 4 shows the receiving directivity characteristics when phase information is input to the transducer in the embodiment shown in Fig. 1. It is a principle diagram. DESCRIPTION OF SYMBOLS 1... Transducer/receiver, 2... Phaser, 3... Amplifier, 4... Display controller, 5... Phase detector, 6...
...Phase comparator.

Claims (1)

[Scope of Claims] 1. In a forward monitoring sonar using a transducer having a line array configuration of a plurality of transducer elements mounted on a mobile vehicle sliding on the seabed, a received signal from the transducer is determined by luminance. The information signal and the phase information signal are input separately, and based on the azimuth information detected from the phase information signal, the ghost component due to the side lobe of the receiver directivity or the ghost component due to repetition of phase information every 360 degrees is calculated from the luminance. comprising a ghost component removing means for removing from the information signal, applying shading using all of the plurality of wave transmitting/receiving elements when inputting the luminance information signal, and applying shading to the plurality of wave transmitting/receiving elements when inputting the phase information signal; A forward monitoring sonar characterized by providing a large pointing width by using a smaller number of.