JPH0479548B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an apparatus for performing underwater detection by transmitting and receiving ultrasonic pulses underwater, and particularly relates to an apparatus for detecting underwater by arbitrarily switching a wide range of directions. (Prior art) When transmitting and receiving ultrasonic waves to detect a wide range of angles underwater, the ultrasonic waves are transmitted in a specific direction within a wide range,
Alternatively, it is necessary to receive ultrasonic waves from a specific direction. When transmitting or receiving ultrasonic signals in a specific direction, the combined directivity of a plurality of ultrasonic transducers is generally used. For example, if a plurality of ultrasonic transducers are arranged on a plane and an appropriate phase relationship is given to each transducer signal or received signal, a directional characteristic corresponding to the phase relationship is formed. This directional characteristic is formed by a main pole beam having the strongest wave transmission/reception sensitivity in a specific direction determined by the above-mentioned phase relationship and a sub-pole beam having very low wave transmission/reception sensitivity in other directions. When performing underwater detection using such a directional transmitting/receiving beam, if the reflected waves returning from each direction underwater arrive at the same level, it is due to the inherent level difference between the main pole beam and the sub pole beam. Only reflected waves arriving from the direction of the main pole beam can be detected. However, if the level of the sound waves arriving from unnecessary directions is extremely high, for example, if the ultrasonic waves arriving from the directional envelope θ ₀ of the main pole beam M are extremely strong in FIG. and the received wave output by the sub-pole beam _S2 are output at almost the same level. Therefore, it is not possible to determine whether the received signal is an ultrasound signal in the desired direction θ ₀ or an ultrasound signal in the unnecessary direction θ _i . This phenomenon is most noticeable when receiving ultrasonic signals from the ocean floor. For example, the third
In the figure, when an ultrasonic pulse is transmitted in the wide angle α direction of the ocean floor and the reflected waves returning from each direction are received, the reflected waves with a relatively high level return from the direction of the ocean floor immediately below. Therefore, when a reflected wave in the Χθ direction is received by the main pole beam M directed in the θ direction, the reflected wave from the direction of the seabed immediately below becomes the sub-pole beam.
As a result of the waves being received by S ₁ and S ₂ , it is not possible to distinguish between the reflected waves in the θ direction and the reflected waves in the direction of the ocean floor directly below. In order to remove unnecessary waves such as the waves reflected from the seabed just below, it is desirable to make the level difference between the main pole beams as large as possible. That is, it is desirable to suppress the sub-pole beam. Means for suppressing sub-pole beams are known. For example, as is clear from "Magnetostrictive Vibrators and Ultrasonics P291, published by Colora Publishing, written by Yoshimitsu Kikuchi," it is clear that This is possible by adjusting. Here, it is conceivable to suppress the sub-pole beam in all directions in which the sub-pole beam is generated, but in practice, it is not necessarily necessary to suppress the sub-pole beam in all directions. For example, as described above, when strong unnecessary waves arrive from the direction of the ocean floor directly below, it is sufficient to suppress the sub-pole beam that has wave transmission/reception sensitivity characteristics in the direction of the ocean floor immediately below. When suppressing only the sub-pole beam in a specific direction, it can be suppressed by adjusting the phase of the transmitted and received signals of each of the arrayed ultrasonic transducers. FIG. 4 shows an example of characteristics in which the directivity direction of the main pole beam is set in the 60° direction and the transmission/reception sensitivity of the sub-pole beam in the 90° direction is suppressed. The directional characteristics in Figure 4 are based on 64 ultrasonic transducers.
Arranged at 0.67λ intervals (λ is the wavelength of the ultrasonic wave), the phase of the excitation signal of each transducer is adjusted so that the combined pointing direction of each transducer, that is, the main pole beam direction is 60°. After regulating, the phase of the excitation signal of each vibrator is further shifted by the amount shown in Table 1.

【table】

【table】

[Table] In (Table-1), No. indicates the transducer arrangement number, and φ indicates the phase amount of the excitation signal. The amount of phase shift is shown in the unit of "RAD", and the "-" sign indicates the amount of phase lag. Therefore, if the phase amount of the array oscillator is set as shown in Table 1, as is clear from Fig. 4,
It can be seen that while the main pole beam is formed in the 60° direction, the sub-pole beam in the 90° direction is significantly suppressed. The azimuth scale in the fourth characteristic is based on the transducer array plane. Therefore, since the 90° direction in which the sub-pole beam is suppressed corresponds to the front direction of the transducer array, by using a transducer with this characteristic, unnecessary reflected waves from the seabed directly below can be removed. I can do it. The amount of phase shift of each vibrator excitation signal shown above (Table 1) can be calculated using, for example, Lagrange's slope method. That is, in the case of the characteristic diagram of FIG. 4, first, the phase arrangement given to the excitation signal of each vibrator is calculated so that 64 vibrators are arranged and a main pole beam is formed in the 60° direction. Calculation of this phase array is well known. For example, when arranging Z ₁ to Z ₆₄ ultrasonic transducers at intervals d to form reception directivity in the θ direction as shown in Figure 1, the phase of the reception signal of each transducer is It is sufficient to shift the phase by φ=2π/λd sinθ in the order of arrangement. Then, after giving a phase arrangement so that the main pole beam is generated in the 60° direction, when the phase of each vibrator excitation signal is variously adjusted, a phase arrangement is created such that the sub-pole beam in the 90° direction is suppressed the most. Calculate convergence. It is effective to use the well-known Lagrange gradient method for this convergence calculation. (Problems to be Solved by the Invention) This invention solves the problem of how to realize the directional characteristics described in FIG. 4 for actual underwater detection. That is, the underwater detection device needs to detect any direction underwater. However, since the phase array shown in Table 1 is effective only for forming the directivity characteristics shown in Figure 4, the directivity direction of the main beam is set in a direction different from that shown in Figure 4, and it is necessary to set the direction of the main beam in a direction different from that shown in Figure 4, and to In order to suppress the receiving sensitivity to the reflected waves returning from the
1) must be set to a different phase arrangement. Therefore, it is necessary to change the phase amount of each vibrator signal every time the detection direction is changed. For example,
When changing the detection direction every 5° within a 120° range, 24
The purpose is to perform switching times. When switching the amount of phase shift using commonly used phase control, for example, a delay circuit, it is expected that the phase control switching circuit will become very complex. The present invention can easily realize a phase arrangement for forming the directional characteristics shown in FIG. 4, and
A method is provided that can easily realize a phased array for changing the directivity in any direction. (Means and effects for solving the problem) The device of Japanese Patent Application No. 1983-121439 (Japanese Patent Publication No. 01-016392) previously provided by the applicant as a means for solving the problem. is used. As will be described later with reference to FIG. 1, this device reads out stored data written in a storage circuit, generates a multiphase rectangular wave train, and changes the phase relationship of each broken rectangular wave train to a desired phase relationship. By setting this, the directivity direction of the received beam can be set to an arbitrary direction. Since the phase relationship between each rectangular wave train is determined by the data stored in the memory circuit, the phase relationship can be arbitrarily set by changing the writing of the stored data. For example, when forming a directional characteristic as shown in FIG. 4, the present invention generates a rectangular wave train having a phase arrangement as shown in Table 1 by reading data stored in a storage circuit. A directional characteristic is formed in which the wave transmitting and receiving sensitivity is maximum in the direction, and the wave transmitting and receiving sensitivity in unnecessary directions is suppressed as much as possible. (Example) First, to explain the operation shown in Fig. 1, Z ₁ to
_Z64 indicates ultrasonic receivers, which are arranged in a straight line at regular intervals d. The received signals of the ultrasonic receivers Z ₁ to Z ₆₄ are mixed with the rectangular wave trains output from the latch circuits 5 ₁ to 5 ₆₄ in mixing circuits M ₁ to M ₆₄ via preamplifiers P ₁ to P ₆₄ . be done. The mixed outputs of the mixing circuits M ₁ to M ₆₄ are added to the adder circuit Σ
After addition, a specific frequency component is extracted from the added signal by a filter circuit F. The extracted output of the filter circuit F is amplified by an amplifier 6 and then guided to a display 7. For example, a cathode ray tube display is used as the display 7. In the display device 7, a scanning circuit 8 performs pixel scanning based on the output of a sweep circuit 9. Reference numeral 10 denotes a transmitter, which causes an ultrasonic wave transmitter 11 to transmit an ultrasonic panel at fixed time intervals. The ultrasonic transmitter 11 transmits ultrasonic pulses in a wide range of directions, and the reflected waves returning from each direction are extracted by the ultrasonic wave transducers Z ₁ to Z ₆₄ after identifying the return direction. Ru. The transmitter 10 transmits the ultrasonic pulse and at the same time resets the coefficient value of the counter 3. The counter 3 counts the pulse train output from the frequency circuit 2 and reads out the stored data at the storage address of the storage circuit 4 corresponding to the counted value. Further, the frequency divider circuit 2 divides the frequency of the pulse train of the clock pulse source 1 and sends it out. The memory circuit 4 stores 64 bits each time each memory address is designated.
Outputs the binary value of the digit, and each digit output is the latch circuit 5
₁ to ₅₆₄ , respectively. Latch circuit 5 ₁
Each of ₅₆₄ outputs a high level or a low level corresponding to the numerical output of each digit, and a rectangular wave output is sent by repeating the high level output and the low level output. In addition, the latch circuits 5 ₁ to 5
₆₄ performs a latch operation using the latch pulse output from the latch pulse generating circuit 5, and the latch pulse generating circuit 5 generates a pulse train of the clock pulse source 1. The memory output generated in synchronization with the counting operation of the latch pulse counter 3 and read from the memory circuit 4 is held until the next memory output is read. In the above, the phases of the mixed outputs of the mixing circuits M ₁ to M ₆₄ are influenced by the phase of each mixed signal. That is, by changing the phase of the rectangular wave train output from the latch circuits ₅₁ to ₅₆₄ , the phase of the mixed output can be changed, and equivalently, the phase of the mixed output can be changed by changing the phase of the rectangular wave train output from the latch circuits ₅₁ to ₅₆₄ . Wave signals can be phase shifted. Therefore, the ultrasonic receiver Z ₁ to
_The mixing _{circuit M} It is possible to obtain phase-shifted signals obtained by equivalently shifting the phase of each received signal by a desired amount at each output of _M1 to _M64 . Then, after adding the mixed outputs of the mixing circuits M ₁ to M ₆₄ in the adding circuit Σ,
When a specific frequency signal is extracted by filter F,
A directional reception signal in a specific direction can be obtained from the output of the filter F. The phase of the rectangular wave train output from the latch circuits ₅₁ to ₅₆₄ is disclosed in Japanese Patent Application No. 121439/1983
As explained in No. 016392), as the stored data at each storage address is read out by the counter 3, the phase changes to a predetermined phase. As the phase of each rectangular wave train changes variously, the phase of the mixed outputs of the mixing circuits M ₁ to M ₆₄ also changes, and as a result, the directivity of the directional beam formed by the adder circuit Σ and the filter F varies. Changes to Therefore, by appropriately writing the stored data in the memory circuit 4, the directional characteristics of the directional reception beam outputted by the filter F can be arbitrarily formed.
By writing so that the phase arrangement of the rectangular wave trains output from the latch circuits ₅₁ to ₅₆₄ corresponds to the above (Table 1), the directivity characteristics shown in FIG. 4 can be formed. The above (Table 1) is the phase data when the main pole beam is formed in the 60° direction, so when changing the directivity direction of the main pole beam, the phase data corresponding to each directivity direction can be changed as described above. After calculating and finding it, the phase shift data is written to another memory address in the memory circuit 4. When the main pole beam is directed in that direction, the stored data at that storage address may be read. Therefore, when changing the directivity direction of the main pole beam sequentially within a predetermined range angle, the phase shift data corresponding to each directivity direction is written to the corresponding memory address, and the stored data at the memory address is sequentially changed. By reading out and shifting the phases of the rectangular wave trains, it is possible to suppress reception sensitivity to a specific direction and sequentially change the directivity direction of the main pole beam. The reception signal of the directional reception beam extracted by the filter F is guided to the display 7 and displayed, and the display device on the display screen is determined by the feedback circuit 9. Based on the transmitter 10, the return circuit 9 is linked to the counting operation of the counter 3, and
The scanning circuit 8 is caused to perform pixel scanning. That is, when the readout address of the memory circuit 4 sequentially changes in response to the counting operation of the counter 3 and the directivity direction of the directional reception beam sequentially changes, the pixel scanning position on the display screen of the display device 7 becomes directional. It changes in response to changes in the direction of the receiving beam. FIG. 5 shows another embodiment, in which the same numbers as in FIG. 1 perform the same operations. In FIG. 1, as the memory addresses of the memory circuit 4 are sequentially read out in response to changes in the count value of the counter 3, the directional direction of the received beam also changes. On the other hand, in FIG. 5, the counter 3' stores data stored at storage addresses within a certain range based on the storage address of the storage circuit 4 determined by the scanning direction setting device 12 and the disturbance direction setting device 13. is read out. Therefore, in FIG. 5, the counter 3' repeatedly specifies the memory address necessary to generate at least one week period of the rectangular wave train output from the latch circuits ₅₁ to ₅₆₄ , and reads the stored data. put out. The scanning direction setter 12 determines the reception direction of the reception beam, and the interference direction setter 13 determines the direction in which the reception sensitivity is suppressed. Therefore, for example, if the scanning direction setting device 12 specifies the storage address with a 6-digit binary number and the disturbance direction setting device 13 specifies the storage address with a 3-digit binary number, then 2 ⁶ × 2 ³ = 512, so (Table 1 ), 512 types of phase shift data are stored in the storage circuit 4'. FIG. 6 shows an embodiment in which the present invention is applied to forming the directional direction of a transmission beam. That is, when forming the directional direction of the transmission beam, the latch circuits 5 ₁ to 5
Ultrasonic transmitter using rectangular wave train output from ₆₄
It is sufficient to excite Z ₁ to Z ₆₄ . Therefore, the frequency of the rectangular wave train generated by reading the data stored in the memory circuit 4'' matches the resonance frequency of the ultrasonic transmitters _Z1 to _Z64 , and the phase arrangement of each rectangular wave train is as follows. As explained with reference to FIG. 1 or FIG. 5, the data stored in the memory circuit 4'' may be written so that the transmitted wave output in the desired direction is maximized and the transmitted wave output in unnecessary directions is suppressed. (Effects of the Invention) As explained above, the present invention sets the composite directivity of the ultrasonic transducer in a desired direction based on the data stored in the storage circuit, and at the same time suppresses the sensitivity of the transmission and reception to unnecessary directions. It is. Therefore,
Since the phase of the transmitted and received signals can be easily controlled arbitrarily, it becomes possible to easily control the direction of the transmitted and received waves and the direction of suppressing the sensitivity of the transmitted and received waves. It is suitable for use in a device that changes arbitrarily.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the present invention, Fig. 2 shows an example of the directivity characteristics of a conventional transmitting/receiving beam, Fig. 3 is a diagram for explaining an overview of underwater detection, and Fig. 4 shows an example of the directional characteristics of a conventional transmitting/receiving beam. An example of the directivity characteristics of the transmitted and received beams to be implemented is shown, and FIGS. 5 and 6 show other embodiments. 1... Clock pulse source, 2... Frequency divider circuit, 3
... Counter, 4 ... Memory circuit, 5 ... Latch pulse generation circuit, 5 ₁ to 5 ₆₄ ... Latch circuit,
6...Amplifier, 7...Display device, 8...Scanning circuit,
9...Sweep circuit, 10...Transmitter, 11...Transmitter, _Z1 to _Z64 ...Ultrasonic receiver, _P1 to _P64 ...
Preamplifier, M ₁ to M ₆₄ ... Mixed circuit, Σ...
Addition circuit, F...filter.

Claims (1)

[Claims] 1. By sequentially reading stored data consisting of n-digit binary numbers from each memory address and generating a rectangular wave train for each digit from the binary value change of each digit of the stored data. An n-phase rectangular wave train is generated, and the phase relationship between the n-phase rectangular wave train and the n-phase rectangular wave train is changed by changing the read range of the memory address of the memory circuit. A specific frequency signal is extracted from the synthesized signal by mixing corresponding received signals of n ultrasonic transducers and adding the mixed signals to each other to have directivity in a specific direction. When receiving ultrasonic waves, the n-phase rectangular wave generated by reading the stored data in a predetermined read range of the memory address of the memory circuit has a directional characteristic of the extracted signal that is set to receive the ultrasonic signal. The ultrasonic signal has directivity in one specific direction in which the wave should be transmitted, and the receiving sensitivity in a predetermined specific direction is suppressed the most, and furthermore, each time the readout range of the memory address of the memory circuit is changed, the ultrasonic signal A directional beam forming method used in a wide-angle underwater detection device in which memory data at each memory address is written so that the phase relationship of n-phase rectangular waves is maintained so that the directional direction in which the waves are received changes. 2. An n-phase rectangular wave train is generated by sequentially reading the stored data consisting of n-digit binary numbers from each memory address and generating a rectangular wave train for each digit from the binary value change of each digit of the stored data. Furthermore, the phase relationship of the n-phase rectangular wave train is changed by changing the read range of the memory address of the memory circuit, and n ultrasonic vibrations are generated using the n-phase rectangular wave train. In transmitting ultrasonic waves having directivity in a specific direction by exciting the n ultrasonic transducers and using the combined output of the n ultrasonic transducers, The n-phase rectangular wave generated by reading the stored data has a composite directional characteristic for transmitting the ultrasonic wave having directivity in one specific direction in which the ultrasonic signal should be transmitted, and a predetermined direction. The phase relationship of the n-phase rectangular waves is such that the transmitted wave output in a specific direction is suppressed the most, and furthermore, the directional direction in which the ultrasonic signal should be transmitted changes every time the readout range of the memory address of the memory circuit is changed. A method for forming a directional beam used in a wide-angle underwater detection device in which memory data at each memory address is written so as to maintain the same.