JPS63303501A - Wide band antenna for underground searching - Google Patents

Abstract

PURPOSE:To hold narrow directional characteristics and to increase the detecting accuracy of an underground buried body by forming a pair of antenna elements, bending in an obtuse angle the flat plate of approximately the isosceles triangle shape and arranging it approximately symmetrically while a triangle part is inside. CONSTITUTION:An antenna bends in an obtuse angle a pair of flat plates of the same shape and same dimension of an obtuse isosceles triangle shape with a line parallel to a base as a fold, a pair of antenna elements 1 and 2 are formed, the elements 1 and 2 are arranged with both trapezoidal parts 1a and 2a in the same plane and while triangular parts 1b and 2b are inside, the elements are arranged symmetrically. Peak parts 1e and 2e of the triangular parts 1b and 2b of the elements 1 and 2 are made into a feeding point, an output impedance connects a transmitter through a balance 13 of 200OMEGA to peak parts 1e and 2e and a single pulse-shaped output from the transmitter is radiated as an electric wave from the elements 1 and 2.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a radar-type underground exploration device for detecting the presence or absence of an underground object such as an underground gas pipe and its position without excavation. This invention relates to a broadband antenna for underground exploration used for transmitting and receiving radio waves.

[Conventional technology]

Exploration of objects buried underground uses a radar-type underground exploration device that transmits vehicle-pulsed radio waves in the microwave SW range from the ground surface to the ground using a transmitting antenna placed parallel to the ground surface. The radio waves reflected by underground objects are captured by a receiving antenna placed parallel to the ground surface.
The antenna used for this purpose detects the presence or absence of an underground object based on the presence or absence of a peak in the received radio waves, and further detects the depth of the object based on the time from when the transmitted radio wave is emitted to the peak of the received radio wave. is 10
A return loss characteristic that is approximately flat in the range of MHz to 400 MHz and that does not cause ringing is required.

The conventional broadband antenna for underground exploration used as a transmitting antenna (or receiving antenna) in the above-mentioned radar-type underground exploration equipment is an isomorphic antenna in the shape of an acute isosceles triangle, as shown in Figure 5. A pair of antenna elements 31 and 32 each made of a flat plate with a diameter of
They are arranged symmetrically with 32a facing inside.

In addition, strip-shaped conductors 37 and 38 are arranged on both sides of the antenna element 31, with one edge spaced apart by about 11 points from the bottom side edges 31b and 31c of the antenna element 31, and on both sides of the antenna element 32, respectively. A strip-shaped conductor 39, 40 is connected so that one end edge is leached from the bottom side edges 32b, 32c of the antenna element 32.
The conductor 37.38 is arranged with a distance of about 11 degrees from the other end of the conductor 37.
and between the bottom side edges 32b, 32C of the antenna element 32 and one end edge of the conductor 39.40, and between the other end edge of the conductor 37.39 and the conductor 38.40.
Loading resistors 33 to 36.41° 42 each having a resistance value of about 1000 are connected between the other edges.

and the top 3 of the pair of antenna elements 31, 32.
18.32a are respectively the power feeding points, and the top portions 31a, 32
Transmitter (baseband pulser) via balun 43 to a
are connected, and the single pulse output from the transmitter is radiated as radio waves from a pair of antenna elements 31 and 32.

In this broadband antenna for underground exploration, as shown in FIG. 6, both apexes 31a and 32a of a pair of antenna elements 31 and 32 are fixed in an insulating balun case 44 containing a balun 43. It is housed in an aluminum box 45 lined with ferrite and open at the bottom. In this case, a pair of antenna elements 31.32
Align the arrangement plane of the connector 46. with the opening surface of the box body 45, and connect the connector 46. Coaxial cable 47. Connector 48. A pair of antenna elements 31 and 32 are connected to a transmitter 51 attached to the back side of the box body 45 via a coaxial cable 49 and a connector 50, and the transmission output from the transmitter 51 is transmitted to the connector 50. Coaxial cable 49. Connector 4
8. Coaxial cable 47° connector 46 and balun 43
The radio waves are supplied to the pair of antenna elements 31 and 32 via the antenna elements 31 and 32, and the radio waves are radiated from the pair of antenna elements 31 and 32. - [Problems to be solved by the invention] The conventional broadband antenna for underground exploration described above has wide directional characteristics in all directions, which makes it undesirable for exploring underground objects. . In other words, when used as a transmitting antenna, there is a large amount of radio waves leaking into the air (and radio waves cannot be effectively radiated underground). returns to the receiving antenna, making it impossible to increase the accuracy of detecting objects buried underground.Furthermore, when used as a receiving antenna, it receives noise from the air and reflected radio waves from objects buried underground over a wide range of areas. As a result, it is not possible to increase the accuracy of detecting objects buried underground.

Therefore, an object of the present invention is to provide a wideband antenna for underground exploration that has narrow directivity characteristics and can improve detection accuracy of underground objects.

[Means for solving problems]

The broadband antenna for underground exploration of the present invention is made by bending a pair of substantially isosceles triangular flat plates at an obtuse angle with a line substantially parallel to the base as a crease, and the two trapezoidal portions are arranged in substantially the same plane. and a pair of antenna elements arranged substantially symmetrically with both triangular portions facing inside, and first and second mountings each having one end connected to both sides of the lower bottom of the trapezoidal portion of one of the pair of antenna elements. a resistor, third and fourth loading resistors each having one end connected to both sides of the lower bottom of the other trapezoidal part of the i pair of antenna elements, and the other ends of the first and second loading resistors, respectively. first and second conductors whose one ends are connected to each other; third and fourth conductors whose one ends are connected to the other ends of the third and fourth loading resistors; and the other ends of the first and third conductors. A fifth loading resistor is connected between the ends, and a sixth loading resistor is connected between the second and fourth conductors.

[Effect]

According to the configuration of the present invention, the pair of antenna elements are formed by bending a substantially isosceles triangular flat plate at an obtuse angle, and the pair of antenna elements are arranged substantially symmetrically with the triangular portion facing inside. The directional characteristics of the pair of antenna elements in the longitudinal direction can be made narrow directional characteristics, and the detection accuracy of underground objects can be improved by performing detection operations while moving the pair of antenna elements in the longitudinal direction. It is possible to further improve radio wave radiation efficiency.

In addition, since the directional characteristics of the pair of antenna elements in the direction orthogonal to the longitudinal direction remain as wide directional characteristics, by performing the detection operation while moving the pair of antenna elements in the direction orthogonal to the longitudinal direction, The presence or absence of an underground object and its location can be detected over a wide area in a relatively short time, albeit roughly. By combining the detection operation for underground objects and the detection operation while moving the pair of antenna elements in the longitudinal direction, it is possible to search for a wide range of underground objects in a short time and with high precision.

〔Example〕

A practical example of this invention will be explained based on FIG. 1A, FIG. 1B, FIG. 2, FIG. 3, and FIG. 4. As shown in Figures 1A and 1B, this broadband antenna for underground exploration is constructed by bending a pair of flat plates of the same shape and size in the shape of an acute isosceles triangle at an obtuse angle with a line parallel to the base as the crease. to form a pair of antenna elements 1.2, and the pair of antenna elements 1.2 are arranged symmetrically with the lily-shaped portions 1a and 2a disposed in the same plane and the triangular portions lb and 2b facing inside. There is.

Furthermore, the trapezoidal portion 1a of the pair of antenna elements 1.2
, 2a on each side of the trapezoidal portions 1a.

Plate-shaped conductors 7 to 1 are arranged symmetrically in the same plane as 2a.
0 is placed in each.

The conductor 7.8 has one end edge facing the trapezoidal portion 1a of the antenna element 1 on both sides alc and 1d of the upper base with a predetermined width, and the conductors 9 and 10 also have one end edge facing the trapezoidal portion 2a of the antenna element 2. They are closely opposed to the lower bottom side edges 2c and 2d of the , respectively, with a predetermined width. In addition, the conductor 7,
9, the other edges thereof face each other with a predetermined width, and the conductor 8
．． Similarly, the other edges of IO face each other with a predetermined width. Further, the conductor 7.9 has both side edges curved into an arc shape, so that the both side edges are smoothly continuous at the other end. Similarly, both edges of the conductor 8 and 10 are curved into an arc shape, so that the edges are smoothly continuous at the other end.

Furthermore, the trapezoidal portion 1a of the pair of antenna elements 1.2
, 2a, lower bottom side edges 1c, ld, 2c.

Between 2d and conductors 7 to 10, conductor 7.9 and conductor 8
．． Loading resistor 3~ having a resistance value of about 150Ω between 10 and 10
6, 11 and 12 are connected respectively.

Then, the top portions 1e and 2e of the triangular portions lb and 2b of the pair of antenna elements 1.2 are used as feeding points, and the top portions 1s,
A transmitter (baseband pulser) is connected to 2e via a balun 13 with an output impedance of 200Ω, and a single pulse output from the transmitter is transmitted to a pair of antenna elements 1.
．． 2, it is now radiated as radio waves.

As shown in Figure 2, this broadband antenna for underground exploration has an insulating balun case 1 with a built-in balun 13.
4, a pair of antenna elements 1°2 triangular part lb
, 2b are identified and housed in this state in an aluminum box 15 lined with ferrite. In this case, a pair of antenna elements 1
．． Align the arrangement plane of connector 16.2 with the opening surface of the box body 15, and connect the connector 16. A pair of antenna elements 1.2 are connected to a transmitter 19 provided on the back side of the box body 15 via a coaxial cable 17 and a connector 18, and the transmission output from the transmitter 19 is connected to the connector 18° coaxial cable 1.
7. The signal is supplied to the pair of antenna elements 1.2 via the connector 16 and the balun 13, and the radio waves are radiated from the pair of antenna elements 1.2.

Here, the dimensional relationship of each part in FIGS. 1 and 2 will be explained. First, the trapezoidal portions 1a and 2a of the pair of antenna elements 1 and 2 have lower bottom side edges 1c and ld.
, 2c, 2d and one end edge of the conductors 7 to 10, the distance d1 is:
For example, it is set to 0.5 tm, the opposing width W1 is set to 33 tns, and the distance d8 between the other ends of conductor 7.9 and conductor 8.10 is set to 0.5 tm, for example. Width W! is set to, for example, 10 m, and these dimensions are not limited to the above values, and some increase or decrease in the values is allowed.

Further, the pair of antenna elements 1.2 are arranged in the trapezoidal portion 1.
The height hl from a, 2a to the tops 1e, 2e of the triangular parts lb, 2b is set to 101, and the triangular parts lb, 2b
The distance d between the tops 1e and 2e of.

is set to 4 points in accordance with the spacing between the baluns 13, and the distance d4 between the bottoms of the triangular portions lb and 2b is set to 45 points. In this case, the triangular portion lb.

The opening angle θ of 2b is about 20 degrees. In addition, trapezoidal part 1
The height hl from a, 2a to the tops le, 2e of the triangular portions lb, 2b is preferably 101 or more, but 10
It may be less than or equal to Cs, and the triangular parts lb, 2b
Sufficient performance can be obtained if the distance between the bottoms is in the range of 30 to 50 squares.

Further, the width W of the bottom of the triangular portion lb, 2b is 1/1.5 with respect to the distance d4 between the bottom of the triangular portion lb, 2b.
It is preferable to set it to ~1/2, and good results were obtained in the range of 30 to 36 m. Also, the triangular parts lb, 2b
Since the output impedance of the balun 13 is 200Ω with respect to the distance d between the tops 1e and 2e of the triangular portions lb and 2b, the convergence w4 of the tops 1e and 2e of the triangular portions lb and 2b is 1/1. It is set to 3rd and 2nd which is 24. A slight deviation is allowed for this value as well.

Further, it is preferable that the radius of curvature of the bent portions of the pair of antenna elements 1.2 is as small as possible.

Note that even if the radius of curvature is somewhat thick (ie, the pair of antenna elements 1.2 is curved in an arc shape), the output will decrease somewhat, but a satisfactory directivity characteristic can be obtained.

Here, the difference in directivity characteristics between the wideband antenna for underground exploration according to the embodiment and the wideband antenna for underground exploration according to the conventional example will be explained.

In order to investigate the directivity characteristics, a receiving antenna consisting of a small dipole was placed at a depth of 50 (J) from the ground surface, and a straight line on the ground surface passing through a point on the ground surface directly above the receiving antenna was used for underground exploration. The radio waves were radiated from the ground surface to the ground while moving the broadband antenna in the longitudinal direction of the pair of antenna elements 1.2, and the received signal level by the receiving antenna was measured. While moving the broadband antenna for underground exploration of the embodiment in a direction orthogonal to the longitudinal direction of the pair of antenna elements 1.2 on a straight line on the ground surface that passes through the point, radiate radio waves from the ground surface to the ground. , the received signal level by the receiving antenna was measured.For comparison, a receiving antenna consisting of a small dipole was placed at a depth of 50 cm from the ground surface, and a straight line on the ground surface passing through a point on the ground surface directly above the receiving antenna. A pair of conventional broadband antennas for underground exploration (see above) 31.While moving in the longitudinal direction of 32, radio waves were radiated from the ground surface to the ground, and the received signal level by the receiving antenna was measured. . In addition, while moving the conventional broadband antenna for underground exploration in a direction perpendicular to the longitudinal direction of the pair of antenna elements 31 and 32 on a straight line on the ground surface passing through a point on the ground surface directly above the receiving antenna, We radiated radio waves underground and measured the signal level received by the receiving antenna. The results are shown in the table below, Figures 3 and 4.
The broadband antenna for underground exploration according to the embodiment and the conventional example shown in the figure has a width of 60 cn, a depth of 50 cII, and a height of l0.
Radio waves were emitted while housed in a CII box 15.45 with the bottom open.

The following table shows the radio waves at the ground surface position directly above the underground receiving antenna, that is, at the distance Ocs from the ground surface point directly above the receiving antenna, for the broadband antenna for underground exploration of the embodiment and the conventional example. The received signal levels at distances of 5 cm and 10 cm are shown, respectively, with the received signal levels when emitted as a reference (1, 0). In addition, in the following table, the column ``■'' shows how to transmit radio waves from the ground surface to the ground while moving the broadband antenna for underground exploration according to the example in a direction perpendicular to the longitudinal direction of the pair of antenna elements) 1.2. The results of measuring the received signal level by the receiving antenna are shown in the column (■). The results of emitting radio waves toward the target and measuring the received signal level by the receiving antenna are shown. The results show the results of measuring the signal level received by the receiving antenna by emitting radio waves from the ground surface to the ground while moving the antenna. The figure shows the results of measuring the received signal level by the receiving antenna by emitting radio waves from the ground surface to the ground while moving in the longitudinal direction of the antenna.

Figure 3 of Table 1 shows the data in Table 1 in a graph, with the horizontal axis representing the distance from the point on the ground directly above the receiving antenna and the vertical axis representing the received signal level. Codes in Figure 3: ■～
■ corresponds to ■ to ■ in Table 1, respectively.

From FIG. 3, it can be seen that in the broadband antenna for underground exploration according to the embodiment, the slope of decrease in the received signal level with respect to the distance is the same when the received signal level is measured while moving the pair of antenna elements 1.2 in the longitudinal direction (■ It can be seen that the received signal level is smaller in case 1) than when the received signal level is measured while moving in a direction perpendicular to the longitudinal direction of the pair of antenna elements 1.degree.2. This means that in the broadband antenna for underground exploration according to the embodiment, the directional characteristics in the longitudinal direction of the pair of antenna elements 1.2 are narrower than the directional characteristics in the direction orthogonal to the longitudinal direction of the pair of antenna elements 1.2. This means that it has directional characteristics.

In addition, in the conventional broadband antenna for underground exploration, the slope of decrease of the received signal level with respect to distance is different from that when the received signal level is measured while moving the pair of antenna elements 32° 32 in the longitudinal direction (case ◯). When the received signal level is measured while moving the pair of antenna elements 31 and 32 in a direction perpendicular to the longitudinal direction (in case of ■)
It can be seen that they are almost the same. This means that in the conventional broadband antenna for underground exploration, the directional characteristics in the direction perpendicular to the longitudinal direction of the pair of antenna elements 31 and 32 are approximately the same as the directional characteristics in the longitudinal direction of the pair of antenna elements 31 and 32. That is to say.

In addition, in Fig. 3, the line connecting the point 101 at a distance of 5 cm on the ground surface and the receiving antenna at a depth of 501 makes an angle of approximately 5.7 degrees and 11.3 degrees, respectively, with respect to the perpendicular. become.

FIG. 4 shows that the broadband antenna for underground exploration according to the embodiment emits radio waves at a position on the ground surface directly above the underground receiving antenna, that is, at a distance of Ocs from a point on the ground surface directly above the receiving antenna. The received signal level when
dB), the received signal level at a distance of 5011.10 cm in the wideband antenna for underground exploration of the example, and the 0 value, 5 am, 10 cm, . . . shows the received signal level at the distance. In Fig. 4, the curve ■ indicates that radio waves are radiated from the ground surface to the ground while moving the broadband antenna for underground exploration according to the embodiment in the longitudinal direction of the pair of antenna elements 1.2, and the receiving antenna is used to emit radio waves. The curve ■ shows the results of measuring the received signal level, and the curve ■ shows that a conventional broadband antenna for underground exploration is moved in the longitudinal direction of the pair of antenna elements 31 and 32 while emitting radio waves from the ground surface to the ground. It shows the results of measuring the received signal level by the receiving antenna.

From FIG. 4, it can be seen that the received signal level when emitting radio waves while moving the broadband antenna for underground exploration of the embodiment in the longitudinal direction of the pair of antenna elements 1.2 is higher than that of the conventional example in the area where the distance is small. It can be seen that the received signal level is higher than the received signal level when radio waves are emitted while moving the broadband antenna for underground exploration in the longitudinal direction of the pair of antenna elements 31 and 32. This indicates that the broadband antenna for underground exploration of the example has higher radio wave radiation efficiency than the broadband antenna for underground exploration of the conventional example.

This broadband antenna for underground exploration is constructed by forming a pair of antenna elements 1.2 by bending a flat plate in the shape of an acute isosceles triangle at an obtuse angle. Since the pair of antenna elements 1.2 is arranged symmetrically in the state of By performing this, it is possible to improve the detection accuracy of underground objects and further improve the radiation efficiency of radio waves.

In addition, since the directivity characteristics in the direction perpendicular to the longitudinal direction of the pair of antenna elements 1.2 remain the wide direction characteristics,
By performing the detection operation while moving the pair of antenna elements 1.2 in a direction perpendicular to their longitudinal direction,
The presence or absence of an underground object and its position can be roughly detected over a wide area in a relatively short time. By combining the detection operation of underground objects while moving and the detection operation while moving a pair of antenna elements 1゜2 in the longitudinal direction, a wide range of underground objects can be searched with high precision in a short time. can be set.

In addition, this broadband antenna for underground exploration has a pair of antenna elements 1.2 formed by bending a pair of acute isosceles triangular flat plates at an obtuse angle.
Since the pair of antenna elements 1.2 are arranged symmetrically with the antenna facing inside, the pair of antenna elements 1.2 becomes three-dimensional, and when configured to radiate radio waves while housed in the box body 15,
Top 1 of trapezoidal part la, 2a to triangular part lb, 2b
e.

By setting the height hl up to 2e to be approximately the same as the height of the box 15, the balun case 14 identified at the triangular portion lb, the top le of 2b, and 2e can be made to protrude from the back side of the box 15. When connecting the transmitter 19 attached to the back side of the body 15 and the balun 14, the balun case 1
5 and the transmitter 19 can be reduced (therefore, the number of connectors can be reduced compared to the conventional example, the structure can be simplified, and unnecessary reflections by the connectors can be reduced to reduce ringing. Can be done.

Note that in the above embodiment, the pair of antenna elements 1.
Although No. 2 is formed by bending an acute triangular flat plate at an obtuse angle, the shape of the flat plate does not have to be an exact acute isosceles triangular shape, but may be a shape close to this.

〔Effect of the invention〕

According to the broadband antenna for underground exploration of the present invention, the pair of antenna elements are formed by bending a substantially isosceles triangular flat plate at an obtuse angle. Because they are arranged symmetrically, the directional characteristics of the pair of antenna elements in the longitudinal direction can be made narrow directional characteristics, and by performing the detection operation while moving the pair of antenna elements in the longitudinal direction, it is possible to detect objects buried underground. Detection accuracy can be improved, and radio wave radiation efficiency can also be improved.

In addition, since the directional characteristics of the pair of antenna elements in the direction orthogonal to the longitudinal direction remain as wide directional characteristics, by performing the detection operation while moving the pair of antenna elements in the direction orthogonal to the longitudinal direction, The presence or absence of an underground object and its location can be detected over a wide area in a relatively short time, albeit roughly. By combining the detection operation for underground objects and the detection operation while moving the pair of antenna elements in the longitudinal direction, it is possible to search for a wide range of underground objects in a short time and with high precision.

[Brief explanation of the drawing]

Fig. 1A is a perspective view showing the configuration of a broadband antenna for underground exploration according to an embodiment of the present invention, Fig. 1B is an enlarged perspective view of the main part of Fig. 1A, and Fig. 2 is a state in which the antenna is housed in the same box. 3 is a characteristic diagram showing the directivity characteristics of the broadband antenna for underground exploration according to the embodiment and the conventional example. FIG. 4 is a characteristic diagram showing the radiation efficiency of the broadband antenna for underground exploration according to the embodiment and the conventional example. 5 is a plan view showing the configuration of a conventional broadband antenna for underground exploration, and FIG. 6 is a sectional view of the antenna housed in a box. 1.2... Antenna element, la, 2a trapezoidal part, Ib, 2b... triangular part, 3-6... loading resistance, 7-10... conductor, 11.12... loading resistance 1
．． 2-...7) 8 navigation 1a, 2a-Isshiki false parts 7-10...-4 bodies 1ca d Figure 1A Old figure Figure 2 Figure 3 Figure □ Miyabi (cm) M4 figure Figure 6

Claims (1)

[Claims] It is made by bending a pair of approximately isosceles triangular flat plates at an obtuse angle with a line approximately parallel to the base as the crease, and both trapezoidal portions are placed in approximately the same plane and both triangular portions are placed on the inside. a pair of antenna elements arranged symmetrically; first and second loading resistors each having one end connected to both sides of the lower bottom of a trapezoidal portion of one of the pair of antenna elements; and the other trapezoidal portion of the pair of antenna elements. third and fourth loading resistors each having one end connected to both sides of the lower bottom of the first and second conductors; a third and fourth conductor having one end connected to the other ends of the third and fourth loading resistors, a fifth loading resistor connected between the other ends of the first and third conductors; 2
and a sixth loading resistor connected between the fourth conductors.