JPS5932746B2 - underwater detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an underwater detection device suitable for performing underwater detection using multi-frequency waves.

When performing underwater detection using multi-frequency ultrasonic waves, separate ultrasonic transducers must be provided for each frequency.

Therefore, it is expected that the structure of the ultrasonic transducer will be relatively large.

As a means of making such an ultrasonic transducer relatively compact, it is conceivable to arrange the ultrasonic transducers for each frequency in a concentric circle.

For example, in FIG. 1, Zl, , Z2 . Z3 is a group of vibrators arranged concentrically in an annular manner, the vibrator group z1 resonates at the frequency f1, and the vibrator group Z2 resonates at the frequency f2.

Further, the vibrator group Z3 resonates at the frequency f3.

When the oscillators are arranged in a ring in this way and the individual oscillators are combined to form a composite directional beam, its directional characteristics are
It will look like Figure A.

That is, at the same time that the main pole BO is generated in the direction of the central axis of the annular arrangement, the angle θ1. θ2 subpoles Bl, B2 in different directions
or occur in a circular pattern.

In this case, the sub-poles B1 and B2 generate relatively stronger beams than the main pole BO.

Therefore, when underwater detection is performed using such an annular vibrator, accurate underwater detection cannot be performed because detection signals from unnecessary directions are mixed in.

The present invention provides an underwater detection device that can accurately perform underwater detection in a desired direction by suppressing the sub-pole beam as much as possible using the annular vibrator as described above.

First, to explain the principle, FIG. 2A shows a group of vibrators Z1, Z2 . This is the characteristic when Z3 (Fig. 1) is synthesized in the same phase.

That is, a main pole beam BO is formed in the main direction, and a sub-pole beam B1 is formed in a direction different from the main pole beam BO by an angle of 01.
Or, the sub-pole beam B2 is formed in a direction that differs by an angle θ2.

However, if individual oscillators are synthesized with different phases, for example, m oscillators may be arranged circularly on the circumference of a radius r, and the received signals of each oscillator may be phase-shifted separately. And,
Each phase shift amount is m
When the oscillators are set to change in the order of arrangement of the vibrators by equal amounts of phase shift and are synthesized, the synthesized directional characteristic becomes as shown in FIG. 2B.

That is, the sensitivity in the central axis direction of the annular arrangement is "zero", the first beam B'1 is annularly generated in the direction of the angle θ11, and the second beam B'2 is annularly generated in the direction of the angle θ12.

And beam B'1. Directional direction θ11 of B'2. θ1
2 changes depending on how many periods of the received signal the maximum phase shift amount by the circularly arranged vibrators is set to be an integer value of the period which is an integer multiple divided into m equal parts.

Alternatively, the beam B' can also be
The orientation direction θ/l and θ12 of 1°B'2 change.

In this case, the vibrators arranged in a circular manner have eight cylindrical shapes forming a circular shape, and it is desirable to arrange at least eight or more vibrators.

Figures 6 to 9 show eight oscillators with a radius of 5CIrL.
The composite directional characteristics are shown when 50kHz ultrasonic signals are received by each transducer arranged at 45° intervals on the circumference, and the received signals are synthesized by changing the phase of each received signal by 45°.

Figures 6 to 9 all show the directional characteristics of a cross section that includes the center of the circular array, and the directional characteristics that are obtained by changing this cross section by 7.5 degrees on the array plane from any vibrator position. show.

In other words, when eight transducers are arranged circularly at 45° intervals, the cross-sectional directivity in all directions including the center is the cross-sectional directivity between 22.5°, which is 1 of the 45° arrangement angle of the transducers. It is expressed as a repetition of characteristics.

Therefore, the directivity characteristics of the cross section in all directions can be seen from FIGS. 6 to 9, and it can be seen that they have almost the same characteristics in all directions.

The above characteristics are obtained by calculating the reception sensitivity of sound waves arriving from any direction for each transducer, and applying a predetermined phase shift to the reception signal of each transducer as described above. It can be obtained by adding .

In the above, when the phase of the received signal of each vibrator is changed by 45 degrees, the corresponding phase shift amount of each vibrator is shown in Table 1.

In Table 1, the phase shift amount of the 8th oscillator is 360°
Since this corresponds to one period of the received signal, the same result can be obtained even if the received signal is used directly without phase shifting.

Table 1 is an example of a case where one period of the received signal is phase-shifted using eight oscillators, or when two periods of the received signal are phase-shifted, the amount of phase shift of each oscillator is shown in Table 1. −2.

In Table 2, the phase shift amount of the fifth oscillator is “450°”
is expressed as 450° - 360° + 90°, so this means that the received signal is in phase with the received signal of the first transducer by shifting the phase of the received signal by 90°.

Therefore, the amount of phase shift of each oscillator is given in Table-2.
It is possible to obtain the same results as in Table 2 even if the settings are as follows.

Therefore, as is clear from the above, if the maximum phase shift amount by the circular array vibrator or the array radius is set appropriately,
Beam B'1. The orientation direction σ'1°θ'2 of B'2 is set as the second
Directional direction θ1 of sub-pole beams Bl and B2 in Figure A. Is it possible to make it match θ2?

After the directivity directions match, if the directivity characteristic shown in FIG. 2B is subtracted from the directivity characteristic shown in FIG. 2A, the directivity characteristic shown in FIG. 2C can be obtained.

Therefore, as a result of subtracting the sub-pole beam, it can be seen that in FIG. 2C, the sub-pole beam B3 is largely suppressed compared to the main station beam BO.

FIG. 3 shows an embodiment based on the above principle.

In FIG. 3, T1 is a group of transducers arranged in a ring with an array radius r1 as shown in FIG.

Further, T2 is also a group of transducers, and is arranged in a ring shape concentrically with the group of transducers T1 with an array radius r2.

The transducer group T1 is guided through the transmission pulse of the transmitter 1 through the switching circuit 2 and is simultaneously excited by the transmission pulse.

The reflected waves returning to each vibrator from the water are combined in phase and then sent to the amplifier 3.

Therefore, the composite signal guided to the amplifier 3 has the directivity characteristic shown in FIG. 2A.

On the other hand, in the same way for the transducer group T2, the transmission pulse of the transmitter 1 is guided through the switching circuit 4, and each transducer is simultaneously excited by the transmission pulse.

At this time, the transmitted pulses are guided to each vibrator through bypass circuits 51 to 5m.

The bypass circuit is composed of two diodes DI and D2 connected in parallel in opposite directions, for example, as shown in FIG.

The reflected waves returning to each of the transducer group T2 are delayed by delay circuits 61 to 6m connected to each, and then combined.

The delay circuits 61 to 6m are, for example, as shown in FIG.
, C circuit.

Since the pulse voltage of the transmitter's transmission pulse is relatively large, it must be guided to each vibrator through a diode bypass circuit.

However, since the reflected waves returning to each vibrator are very weak signals, the impedance effect of the diodes DI and D2 becomes large, so that a signal delayed by the delay circuit is sent out.

Each delay time of the delay circuits 61 to 6m is the maximum delay time TM.
It is set to change in order of - of AX.

And, as explained above, the maximum delay time TMAX is
The period is set to an integral multiple of the received signal.

The received signals of the transducer group T2 are delayed as described above, combined, and sent from the switching circuit 4 to the amplifier 7.

Therefore, the composite signal introduced to the amplifier 7 has the directivity characteristics as shown in FIG. 2B.

In the above, the transducer group T1. T2 array radius r1. r
2 and the maximum delay time TMA due to delay circuits 61 to 6m
X is the sub-pole B1゜B2 and sub-pole B in the directional characteristics in Figure 2.
When subtracting '1, , B'2, sub-pole B1.

Set each sub-pole position so that B2 can be reduced to the maximum extent possible.

The composite beam signals amplified by the amplifiers 3 and 7 are individually subjected to envelope detection in the detection circuits 8 and 9, and then sent to the subtraction circuit 10.

Since the received signals of the transducer group T2 are delayed and combined, the combined signal and the combined signal of the transducer group T1 do not necessarily match in phase.

Therefore, even if the respective composite signals are directly combined, it is not possible to obtain the characteristics shown in FIG. 2C.

Therefore, after envelope-detecting each composite signal, by subtracting the detected voltages from each other, it is possible to obtain a characteristic voltage as shown in FIG. 2C.

Therefore, in order to display the output voltage of the subtraction circuit 10 on the display 10, reflected waves returning from unnecessary directions are suppressed as much as possible.
Since only reflected waves in the desired direction are displayed, accurate underwater detection can be performed.

As described above, according to the present invention, underwater detection can be performed by suppressing the sub-pole beam as much as possible using the vibrator arranged in an annular manner as shown in FIG.

Therefore, since the ultrasonic transducers for each frequency can be arranged concentrically in an annular manner, the structure of the transducer can be extremely miniaturized, which is suitable for multi-frequency applications.

By arranging the transducers for each frequency concentrically, it is possible to easily make the pointing directions of the transducers coincide in the same direction.

[Brief explanation of the drawing]

Fig. 1 shows an example of a transducer array, Fig. 2 shows a diagram for explaining the directional characteristics of an ultrasonic beam, Fig. 3 shows an embodiment of the present invention, and Fig. 4 shows the transducer. FIG. 5, which is a diagram for explaining the group arrangement, shows a specific example of the bypass circuit and delay circuit. FIGS. 6 to 9 show examples of directivity characteristics in specific examples of vibrator arrays. T1 and T2...Circular array transducer group, 1...
...Transmitter, 2...Switching circuit, 3...
・Amplifier, 4...Switching circuit, 51 to 5m...
...Bypass circuit, 61 to 6m...Delay circuit, 7...Amplifier, 8 and 9...Detection circuit, 10...Subtraction Circuit, 11...
display.

Claims (1)

[Claims] 1. A first ultrasonic transducer group in which at least eight or more transducers are arranged circularly at equal angular intervals on a circumference with a radius r1; and the first ultrasonic transducer group. At least eight or more transducers are arranged circularly at equal angular intervals on the circumference of a radius r2 concentric with the second ultrasonic transducer group and the first ultrasonic transducer group. After synthesizing the signals in the same phase, a first synthesizing circuit transmits an envelope detection output of the synthesized signal, and separately phase-shifting each received signal of the second ultrasonic transducer group, and The phase shift amount is set to vary in the order of arrangement of the transducer groups by the amount of phase shift, which is equal to the period of the integer multiple of the ultrasonic reception signal divided by the number of arranged ultrasonic transducer groups. a second synthesis circuit that synthesizes each phase shift output sent out from the phase shift circuit group and sends out an envelope detection output of the synthesized signal; and synthesis of the first synthesis circuit. It is equipped with a subtraction circuit that subtracts the output and the combined output of the second combining circuit from each other, and a display that displays the subtracted output as an underwater detection signal. The arrangement radius r1 of the first ultrasonic transducer group and the arrangement radius r2 of the second ultrasonic transducer group are set so that the azimuth coincides with the azimuth of the sub-pole beam output from the second synthesis circuit. An underwater detection device characterized by being set with.