JPH028413Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Field of the Invention> This invention relates to an underground radar antenna used to detect the presence or absence of a buried object.

<Technical background of the invention> Underground radar is used as a means to detect various targets buried underground. Ground penetrating radar emits radio waves underground, measures the time from the time the radio waves are emitted until the reflected waves return, and measures the distance to the target.

In the case of ground penetrating radar, as mentioned earlier, the antenna is placed near the ground surface and has a structure that emits radio waves underground, so the reflected waves from the ground surface are returned with an extremely short time delay. I'll come. Therefore, in order to distinguish between radiated radio waves and reflected radio waves, the emission time of the radiated radio waves must be shortened. For this reason, generally, radio waves are emitted for half a cycle to one cycle to shorten the wave transmission time.

On the other hand, underground radar generally uses a dipole antenna. The sharpness Q of a dipole antenna is relatively high, so when half a cycle to one cycle of radio waves is transmitted, several cycles to several tens of cycles are transmitted.
A cycle of damped oscillations occurs, which interferes with the reception of the reflected wave. Therefore, the sharpness of the antenna must be reduced.

<Prior art and its disadvantages> Conventionally, in order to reduce the sharpness Q of the antenna, the antenna conductor constituting the dipole antenna was formed into a triangular shape, and the area of the antenna conductor was increased to lower the sharpness Q of the antenna. I have to.

However, even if the Q is lowered, the dipole antenna has a bidirectional directional characteristic, so it receives radio waves arriving from the ground and the reflecting side, which has the disadvantage of interfering with the reception of reflected waves. Furthermore, when emitting radio waves, radio waves that should be directed underground are also emitted into the air, which also has the disadvantage of radiating unnecessary radio waves.

<Purpose of the invention> This invention lowers the sharpness and absorbs and reduces radio waves arriving from the surface opposite to the ground using a resistor electrically connected to the end of the shielding plate, making it unnecessary. It is an object of the present invention to provide an antenna for underground radar that does not radiate radio waves to the outside and does not interfere with the reception of reflected waves by radio waves from the outside.

<Structure of the invention> The underground radar antenna according to this invention includes a pair of antenna conductors forming a dipole antenna,
A semi-cylindrical shielding plate made of a relatively thin conductive plate that shields one side of the dipole antenna constituted by this antenna conductor, and a space between this shielding plate and the end of the antenna conductor. It consists of a connected resistor.

According to this structure, one surface of the dipole antenna is shielded by the semi-cylindrical shielding plate, and unnecessary radio waves are not radiated to the outside. Furthermore, the semi-cylindrical shielding plate blocks radio waves from outside, and the reception of reflected waves reflected from underground is not interfered with. Furthermore, by connecting a resistor between the end of the antenna conductor and the end of the shielding plate constituting the dipole antenna, the dipole antenna functions as a resistance-loaded type. Therefore, the sharpness Q of the antenna can be lowered.

<Example of the invention> An example of the invention is shown in FIG. 1 and below. 1st
The figure is a partially sectional perspective view showing the whole of the underground radar antenna according to this invention, and FIG. 2 is a cross-sectional view taken along line A--A in FIG. 1. In the figure, 1 indicates an insulating plate provided as a bottom plate. As shown in FIG. 3, a pair of triangular antenna conductors 2A and 2B are attached to the upper surface of this insulating plate 1. Antenna conductor 2A, 2B
can be formed, for example, by cutting a copper plate into a triangular shape, and by adhering the triangularly cut copper plate to the insulating plate 1 with an adhesive or attaching it with screws or the like, a dipole antenna can be constructed.

3 indicates a semi-cylindrical shielding plate. This shielding plate 3 is attached to the insulating plate 1 so that the axis of its semi-cylindrical surface coincides with the direction in which the antenna conductors 2A and 2B are arranged. In other words, the structure for attaching the shielding plate 3 to the insulating plate 1 is to install reinforcing plates 4A and 4B formed by semicircular insulating plates at both free ends of the antenna conductors 2A and 2B.
The shielding plate 3 is supported along the arcs of the reinforcing plates 4A and 4B. As shown in FIG. 4, the reinforcing plates 4A and 4B have conductive plates 5 and 6 attached along the straight sides and arcuate portions that contact the antenna conductors 2A and 2B. The free ends are soldered and the reinforcing plates 4A and 4B are planted on the insulating plate 1. At the same time, the shielding plate 3 is soldered to the arc-shaped conductive plate 6, and the shielding plate 3 is attached to the insulating plate 1 by this soldering.

On the other hand, on the reinforcing plates 4A and 4B, for example, a carbon film 7 is applied between the conductive plates 5 and 6 as shown in FIG.
The end of B and the shielding plate 3 are electrically connected. In this way, the antenna conductor 2 is
By electrically connecting the ends of A and 2B and the end of the shielding plate 3, the shielding plate 3 will equivalently work as a resistance-loaded conductor 8 of a dipole antenna, as shown in FIG. . Resistor 7 shown in FIG.
A and 7B indicate resistors constituted by the carbon film 7 shown in FIG.

The shielding plate 3 is required to function as a resistance-loaded conductor of the dipole antenna, and at the same time to function as a radio wave absorber and a shielding plate. In other words, it is required that the antenna conductors 2A, 2B absorb radio waves radiated from the antenna conductors 2A, 2B, and do not emit reflected waves toward the ground, and that radio waves from the outside do not reach the antenna conductors 2A, 2B.

To meet this requirement, the shielding plate 3 may be a thin conductive plate to increase current loss. When a conductive plate with a thin plate thickness is used, if the shielding plate 3 moves wobbling due to vibration or the like, there is a risk that the characteristics of the antenna will change.

Therefore, in this embodiment, both ends of the shielding plate 3 are supported and reinforced by the reinforcing plates 4A and 4B, and at the same time, a material such as styrofoam is placed inside the cavity surrounded by the shielding plate 3 and the reinforcing plates 4A and 4B. The reinforcing bodies 11A and 11B formed by the above are press-fitted.

A waterproof cover 12 can be placed over the shielding plate 3.
This waterproof cover 12 can be made of a resin material such as reinforced plastic, for example. The shape is a semi-cylindrical part 12B similar to the semi-cylindrical shielding plate 3.
and a closing part 12C that closes both ends of the semi-cylindrical part 12B, and a flange part 12A formed to protrude outward from the opening edge formed by the semi-cylindrical part 12B and the closing part 12C, This flange part 1
2A are overlapped on the periphery of the insulating plate 1 and connected with screws. Further, a waterproof insulating plate 13 is laminated on the back side of the insulating plate 1, that is, on the ground side for reinforcement.

Reference numeral 14 shown in FIG. 1 indicates an equipment storage case that houses a transmitter or a receiver. This equipment storage case 1
4 is inserted into a case storage hole 17 formed in the center of the waterproof cover 12. The rear end of the equipment storage case 14 has a flange portion 14A, and this flange portion 1
A screw 15 passing through 4A is screwed into a screw hole 16 formed in the center of the waterproof cover 12 and fixed. The cylindrical body 14 and the flange portion 14A are all made of an insulating material.

A cylindrical guide 18 is installed between the case storage hole 17 and the insulating plate 1 as shown in FIGS. 1 and 2. As shown in FIGS. Reference numeral 19 indicates a flange for fixing the tip of this cylindrical guide 18 to the insulating plate 1. The cylindrical guide 18 and flange 19 are also made of an insulating material such as Bakelite.

A pair of male connectors 21 are provided at the lower end of the cylindrical guide 18.
will be established. In this example, a banana chip is used as the male connector 21. The male connectors 21 are connected to the antenna conductors 2A and 2B, respectively, and are supported by an insulating plate 22 fitted inside the cylindrical guide 18.

A pair of female connectors 23 are provided at the lower end of the equipment storage case 14, as shown in FIG. This female connector 23 is connected to the output terminal of the transmitter when the transmitter is stored in the equipment storage case 14. In the case of a receiver, it is connected to the antenna input terminal of the receiver. With this structure, when the device storage case 14 is inserted into the cylindrical guide 18, the female connector 23 provided at the tip fits into the male connector 21, and the antenna conductor 2
A, 2B can be connected to a transmitter or receiver inside the equipment storage case 14. The connected state is fixed by tightening the screw 15.

A connector 24 is provided at the center of a flange portion 14A provided at the rear end of the equipment storage case 14. This connector 24 connects a cable for pulling out a power supply line and a transmission timing signal or reception signal line to the transmitter or receiver provided inside the equipment storage case 14 to the outside.

<Operations and Effects of the Invention> In a practical form of the above-mentioned underground radar antenna according to this invention, two antennas are installed in parallel, and one is used as a transmitting antenna and the other as a receiving antenna. When the antenna conductors 2A and 2B are used as transmitting antennas, the presence of the shielding plate 3 causes the radiated radio waves to be radiated only to the surface side of the insulating plate 1. That is, the radio waves radiated toward the shielding plate 3 are shielded by the shielding plate 3 and are not radiated toward the upper surface side. Also, since the antenna conductors 2A, 2B and the shielding plate 3 are connected by the resistors 7A, 7B, the antenna conductors 2A, 2B and the shielding plate 3 are connected by the resistors 7A, 7B.
A and 2B operate as dipole antennas with low sharpness Q.

As a result, when radio waves are emitted for only half a cycle or one cycle, no damped vibration occurs thereafter. Therefore, even if a reflected wave returns within a short time after the radio wave is emitted, the reflected wave can be identified and received. As a result, the minimum measurable distance becomes smaller, and an excellent underground radar antenna can be provided.

Furthermore, since a thin conductive plate is used as the shielding plate 3, current loss increases when receiving radio waves. Therefore, there is an advantage that the amount of secondary radio waves, that is, reflected waves generated by this current can be reduced.

Also, when used as a receiving antenna, the shielding plate 3
Due to the presence of the antenna conductor 2, radio waves from the outside are
It is prevented from reaching A and 2B. Therefore, reception of reflected waves is not interfered with by external radio waves.

On the other hand, since the underground radar antenna of this invention has a structure in which both the transmitting antenna and the receiving antenna are covered with a waterproof cover 12, it can be used even in the rain.

Furthermore, since the equipment storage case 14 is detachably attached, the transmitter and receiver can be freely replaced.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing a part of an embodiment of this invention in cross section, Fig. 2 is a sectional view taken along line A-A in Fig. 1, and Fig. 3 shows the antenna conductor used in this invention and its FIG. 4 is a plan view for explaining the shape of the antenna conductors 2A and 2B, FIG. 4 is a front view for explaining the shape of the reinforcing plate used in this invention, and FIG. 5 is an equivalent of the underground radar antenna according to this invention. It is a connection diagram for explaining a circuit. 1: Insulating plate, 2A, 2B: Antenna conductor, 3:
Shielding plate, 4A, 4B: reinforcing plate, 5, 6: conductive plate,
7: carbon film, 7A, 7B: resistor, 8: folded conductor, 11A, 11B: reinforcing body, 12: waterproof cover, 13: insulating plate, 14: equipment storage case,
14A: Flange part, 15: Screw, 16: Screw hole, 17: Equipment storage hole, 18: Cylindrical guide, 1
9: Insulating flange, 21: Male connector, 22: Insulating plate, 23: Female connector.

Claims (1)

[Scope of Claim for Utility Model Registration] A: A pair of antenna conductors provided on an insulating plate and forming a dipole antenna; B: A thin conductive plate bent into a semi-cylindrical shape;
a semi-cylindrical shielding plate that is attached to the insulating plate so that the semi-cylindrical axis coincides with the arrangement direction of the pair of antenna conductors, and that shields one surface of the dipole antenna; a cylindrical case that penetrates from approximately the center of the plate toward the insulating plate, has a connector at its tip that is connected to the opposite ends of the pair of antenna conductors, and has a transmitting means or a receiving means built therein; D. A semicircular insulation reinforcing plate inserted between the insulating plate and the end of the semicylindrical shielding plate; a resistor connected to F, a semi-cylindrical part that covers the upper surface of the semi-cylindrical shielding plate, a closing part that closes both ends of the semi-cylindrical part, and the semi-cylindrical part and the closing part. a waterproof cover that protrudes from the opening edge of the insulating plate and protects the semi-cylindrical shielding plate and the insulating reinforcing plate by joining with the periphery of the insulating plate; An antenna for underground radar comprising: a case storage hole for storing a shaped case;