JPS6226429B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an underwater object detection device, and particularly to a scanning sonar receiving device.

As is well known, scanning sonar sets an appropriate exploration range, such as a 180 degree range around the own ship, and simultaneously sends out sound waves or ultrasonic waves to the exploration area in order to obtain information within that range. For reception, a reception beam with narrow directivity is formed by a plurality of adjacent reception elements, and then the reception beam is changed by switching the reception elements one by one in the direction of rotation of the reception beam. It rotates sequentially at high speed and displays the direction and distance of the detected object as a planar figure on the cathode ray tube.

However, when transitioning from one receiving beam to the next, an angle θ is created between the central axes of the receiving beams, but this angle θ is limited by the dimensions of the receiving element forming the receiver. Also, due to the high cost, it is not possible to selectively set the angle to a small enough angle to receive the echo signal without any apparent problem.

Therefore, in the range of angle θ, the receiving sensitivity is lower than in the direction of the central directivity axis, and the echo signal appears weak, which is a problem.As a solution, it is necessary to look at the directivity in the range of angle θ. Although interpolation means for overlapping correction is used, the present invention is also concerned with solving the same problem, and the present invention is applied to reliably correct the receiving sensitivity by a simple means.
Care was taken to ensure that echo signals of sufficient strength could be received in any direction. A detailed explanation will be given below with reference to the drawings.

To make it easier to understand, we will first give an overview of the reception system used in current scanning sonar.
Next, we will move on to examples of the present invention.

Figure 1 shows _the main parts _of a current _{receiving system .} The receiving elements are the same shape and size, and the beam width of each receiving element itself is the same as that of a detection receiving beam formed via a phase shift circuit (described later), as in the case of general scanning sonar. They are sufficiently wide for the beam width of , and are arranged at equal intervals around the periphery of the cylinder.

The SW is a switch that sequentially switches the receiving elements in groups of 5 (for convenience of explanation, 5 elements are used) in the direction of φ _s in the figure, one by one each time it is switched.
Although it is actually a high-speed electronic switch using an electronic circuit, it is shown as a mechanical switch for convenience.

Next, PS is the phase difference of the wave receiving element output (φ
₁ and φ ₂ ).

Figure 2 is an explanatory diagram of the phase of the receiving element, where the central receiving element is set as V _o and the wavefront of the arriving signal is
The case of WF is shown.

Since the opening angle of each receiving element is constant at φ ₀ (see Figure 1), the interval between V _o and V _o1 ' (or V _o1 ) is set as l ₁ (the phase difference is φ ₁ ), and the distance between V _o and V _o2 ' (or V _o2 ) interval is l ₂ (phase difference is φ ₂ ), R is the radius of the receiving surface,
If λ is the wavelength, φ ₁ = l ₁ 2π/λ=2πR/λ (1−cosφ ₀ ) (1) φ ₂ = l ₂ 2π/λ=2πR/λ (1−cos2φ ₀ ) (2) From this, the phase shift circuit PS converts the receiving elements V _o1 and V _o1 ′
By shifting the phase of φ ₁ and the phases of the receiving elements V _o2 and V _o2 ′ by φ ₂ , we obtain V _o2 ′・V _o1 ′・V _o・
The combined output OP of V _o1 and V _o2 is equivalent to the output obtained by receiving the wavefront WF in phase. Therefore, these five receiving elements provide a narrow directivity R (φ _o ).
A receiving beam is created.

Therefore, if you move the receiving elements one by one and form directivity in five groups, for example, V _o1 ', V _o , V _o1 , V _o2 , and V _o3 , you can cover the entire exploration area. It is possible to search with narrow directivity over a wide range of areas.

In this case, as mentioned earlier, when one directivity moves to the next, there is an angle φ ₀ difference between the center lines, so the reception sensitivity in the direction between them decreases, so it is practical to avoid this decrease in sensitivity. A measure to interpolate the upward directivity is required.

FIG. 3 shows the configuration of an embodiment of the present invention proposed as a countermeasure against this problem, and EL is V _o , V _o1 , V _o2 ... and V _o
A wave receiving element group composed of oscillators of ₁ ′・V _o2 ′...
The SW is a changeover switch for a wave receiving element group consisting of six lines _S1 , _S2 ... _S6 , and is operated to sequentially switch the wave receiving elements one by one every _T0 .

GATT is an interlocking variable attenuator (hereinafter abbreviated as attenuator). ATT1A...ATT5A is used for output A and operates to attenuate from 100% to 0%, while ATT2B...ATT6B is used for output B. It operates to increase from 0% to 100%. That is, two wave receiving elements are combined, and the output of one is attenuated from 100% to 0%, and the output of the other is increased from 0% to 100%.

MIX-1 is a mixer composed of M1, M2..., and the outputs of the attenuators _E1A , _E2B , _E2A , _E3B ...
Mix each of E _6B .

FS is a phase shift circuit that shifts the phase φ ₁ and φ ₂ of the outputs of the mixers M1...M5, and MIX-
2 is a mixer that mixes the outputs of the wave receiving element groups.

Next, Figure 4 shows the continuously variable attenuator GATT in Figure 3.
For example, FIG. 5 is a vector explanatory diagram of the combined output of GATT.

In Figure 4, R1A1, R1A2 and R1A3 are attenuators
Resistance elements forming ATT1A, R2B1 and R
2B2 and R2B3 are resistance elements that constitute the attenuator ATT2B, and these resistance elements are connected to the switch _S1 and
The outputs E _1S and E _2S of the wave receiving element taken out at S ₂ are applied.

K1A1, K1A2...K2B4 are electronic switches for switching attenuation amount, and attenuator ATT1
The output taken out from A is E _1A and the output taken out from attenuator ATT2B is E _2B , and these outputs are mixed in mixer M1 to become output E _1M .

In order to extract the outputs E _1A and E _2B , the time T ₀ for rotating and scanning the receiving beam by the opening angle φ ₀ between the receiving elements is set to an appropriate time width, for example, when n is an arbitrary integer. In the example shown in the figure, with n=3, control voltages E _T1 , E _T2 , E _T3 and E _T4 are generated every T ₀ /3 by a pulse generation circuit not shown in the figure, and with these control voltages, electronic switches K1A1,
When K1A2,... are driven sequentially, the resistor R1
The voltage division ratio of A1, R1A2, ... changes, and E _1A attenuates from the maximum value to the minimum value, that is, from 100% to 0%, and E _2B , on the other hand, decreases from the minimum value to the maximum value, that is, from 0% to 100. %.

Note that the attenuation amount of this attenuator is preset as follows. That is, for example, as shown in FIGS. 4 and 5, t ₁
Attenuators ATT1A and ATT2 in the time period ~t ₂
Assuming that the respective attenuation amounts of B are α ₂ and β ₂ , the respective output voltages of attenuators ATT1A and ATT2B are E〓 _1
A2 and E〓 _2B2 are combined in mixer M1, resulting in voltage E〓 _1M2
is E〓 _1A2 = α ₂ E〓 _1S , E〓 _2B2 = β ₂ E〓 _2S , and E
〓 _1M2
=E〓 _1A2 +E〓 _2B2 =α ₂ E〓 _1S +β ₂ E〓 _2S , but
The absolute value of E〓 _1M2 is ｜E〓 _1M2 ｜=｜E〓 _1S ｜=｜E
〓 _2
S | and the phase angle of E〓 _1M2 with respect to E〓 _1S is
The attenuation amount α 2 is set so that the phase angle is advanced by 1/3 (φ ₂ −φ ₁ ) of 1/3 of _the phase difference (φ ₂ −φ ₁ ) between |E〓 _1S | and |E〓 _2S | β ₂ is set.

Similarly, the attenuation amounts α ₃ and β in the time period t ₂ to _{t 3
3} is the sum of the outputs of ATT1A and ATT2B E = _1M3
The absolute value of |E〓 _1M3 |=|E〓 _1S |=|E〓 _2S |, and the phase angle of E〓 _1M3 is set to be 2/3 (φ ₂ −φ ₁ ).

Note that from t ₀ to _{t 1} , α ₁ = 1, β ₁ = 0, and from t ₃ to _{t 4}
Then α ₄ =0 and β ₄ =1.

In this way, the output voltages E _1S and E _2S from the receiving elements V _o2 ' and V _o1 ' are applied to the attenuators ATT1A and
Mixer M1 after receiving attenuation via ATT2B
The amplitude of the synthesized output voltage E〓 _1M is always constant, but its phase advances by 1/3 (φ ₂ - φ ₁ ) from φ ₂ every time T ₀ /3 elapses, and after 3/3T ₀ reaches _φ1 .

That is, the output appears to have a phase shifted from _φ2 to _φ1 in three steps from _E1S to _E2S .

In this way, the output of each wave receiving element V _o2 ', V _o1 '...V _o2 is changed to V _o2 after three steps of switching.
₁ '·V _o ...The phase is shifted to the output of V _o3 .

Also, during the 3-step switching, the output of each receiving element is set to be phased with the output of the adjacent receiving element by 1/3 of the phase angle between them.
E _1M・E _2M ...E _5M is always φ ₂ - φ ₁ , φ ₁ , 0,
It is extracted with a phase difference of φ ₁ and φ ₂ −φ ₁ .

Therefore, the phases of E _1M ...E _5M are respectively φ ₂ and
By phasing φ ₁ , 0, φ ₁ , and φ ₂ and then combining them, a receive beam with the same shape and same size as the direction for each φ ₀ will be sequentially generated for each step (that is, every φ ₀ /3 directions). can be obtained. In other words, it has turned by an angle φ ₀ in three steps of φ ₀ /3.

Therefore, the overall result is that within the opening angle φ ₀ between adjacent wave receiving elements, there is a shape and shape that is the same as the direction for each φ ₀ .
Since receiving beams of the same size are inserted, the exploration within the angle φ ₀ becomes more precise, information is more accurately grasped, and the accuracy of observation is improved.

Note that a phase shift circuit is provided corresponding to each of the mixers M1 to M5, and the respective phase shift amounts are φ ₂ φ ₁・
0, φ ₁ , and φ ₂ , but as an alternative method, M1 and M5 and M2 and M3 are replaced with a 4-channel input mixing circuit, and the phase shifters that input the respective outputs are replaced with φ ₂ , φ ₁ , and 0. The same effect can be obtained even with 3 pieces.

Also, the phase shift amount of the phase shift circuit is φ ₂・φ ₁・0・φ
Although we have explained that the phase advances as ₁・φ ₂ , it goes without saying that the phase shift may be delayed as 0・φ ₂ -φ ₁・φ ₂・φ ₂ -φ ₁・0 instead. .

Note that the variable attenuator circuit can be easily constructed by using elements such as a resistor and a semiconductor switch, a resistor and a capacitor, and the like. Therefore, using inexpensive component materials, it is possible to easily configure a large number of inserted receiving beams and perform high-speed rotational scanning, and the practical effects are extremely large.

[Brief explanation of the drawing]

Figure 1 shows the main parts of the reception system of a current scanning sonar. V _o・V _o1 ... vibrator, SW ... switch. FIG. 2 is an explanatory diagram of the phase of the wave receiving element. Third
The figure shows an example of the present invention GATT: interlocking variable attenuator, MIX: mixer,
PS...Phase shift circuit. Figure 4 is an example of an interlocking variable attenuator. FIG. 5 is a vector diagram of the composite output.

Claims (1)

[Claims] 1. Selecting a plurality of adjacent wave receiving element groups (m = an integer of 3 or more), and sequentially switching the combination of these element groups in the rotating scanning direction of the receiving beam at regular intervals. At the same time, the phases of the reception outputs of each receiving element are shifted so that they are in the same phase.
In a scanning sonar that forms a receiving beam by adding signals to each other and performs rotational scanning, the time period when multiple (m) receiving elements are connected.
At T ₀ , m-1 pairs of outputs taken out from two adjacent wave receiving elements, respectively, are set as an integer of 2 or more where n is set appropriately, and at every time T ₀ /n, m-1 pairs of outputs are extracted from two adjacent wave receiving elements. Among the wave receiving elements, the output of the wave receiving element on the side in the rotating scanning direction is gradually increased from 0% to 100%, and the output of the wave receiving element on the side opposite to the rotating scanning direction is gradually attenuated from 100% to 0%. , the absolute value of the composite value of two outputs that increase and decrease, respectively, is equal to the absolute value of the output of one wave receiving element, and the phase of the composite value is 1/ of the phase difference between the outputs of the two wave receiving elements.
Through m-1 pairs of variable attenuators each having an attenuation amount set such that the phase is shifted in the turning direction every time T ₀ /n in accordance with the step of the variable attenuator by n,
means for taking out the m-1 pairs of outputs, and then synthesizing the two outputs of each of the m-1 pairs taken out from each variable attenuator to output m-1 combined outputs; One composite output, time period T ₀
At the switching time, the signals are extracted through a phase shift circuit that compensates for the phase difference between the outputs of each of the m-1 wave receiving elements determined by the geometrical arrangement of each of the wave receiving elements, and then combined to form a received signal. A scanning sonar receiving device comprising: