JP2845334B2 - Invisible object detection antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention non-destructively detects buried pipes, cavities, reinforcing bars, scratches, etc. existing in the ground or in an invisible medium such as concrete. The present invention relates to an antenna for detecting invisible objects.

(Prior Art) In an invisible object detection device using electromagnetic waves,
Conventionally, an impulse or a monocycle-shaped electric signal is supplied to a pair of triangular antenna elements, and electromagnetic waves converted by the antenna elements are propagated in an invisible medium, and the electromagnetic waves have different electrical properties from the invisible medium. A reflected wave reflected at a location such as a buried pipe in the soil is received by a pair of triangular antenna elements, converted into an electric signal, and an invisible object is detected by the converted electric signal.

FIG. 6 is a diagram showing an antenna element 11 used in a conventional antenna for detecting an invisible object. The antenna element 11 shown in FIG. 1 is composed of a pair of triangular metal flat plates 1 and is disposed on the same plane so that the vertices of the two metal flat plates 1 are separated from each other by a predetermined distance and face each other. The vertices facing each other are the feed points of the antenna, the length of the base opposite to the vertices is the open end length Lb, the shortest distance from the feed point to the open point is the axial length Lax, and the distance between the two vertices Let Lc be the distance.

FIGS. 7 (a), (b) and (c) are respectively a sectional view from above, a sectional view from one end, and the other of the invisible object detecting antenna incorporating the antenna element 11 shown in FIG. A sectional view from the side, that is, a sectional view along line BB 'in FIG. 3C, a sectional view along line CC' in FIG. It is sectional drawing along A '.

In the antenna for detecting an invisible object shown in FIG. 7, a space on one side of a plane on which the antenna element 11 of FIG. 6 is provided is covered with a chassis 2 made of a metal box. Both ends of the open end of each metal plate 1 are electrically connected by a resistor 3. A radio wave absorber 4 is inserted in the space between the chassis 2 and the antenna element 11 to suppress unnecessary reflection of electromagnetic waves. Further, a feed circuit 6 for supplying an electric signal to the antenna element 11 is directly connected to a feed point of the antenna element 11. The antenna element 11 itself is disposed on the radio wave transmitting plate 7.

In addition, this invisible object detection antenna can be used as two antennas, an electromagnetic wave transmitting antenna for transmitting electromagnetic waves and an electromagnetic wave receiving antenna for receiving electromagnetic waves, but when used as an electromagnetic wave transmitting antenna,
As described above, the opposing apex of the antenna element 11 becomes a feeding point, and the feeding circuit 6 is connected to this feeding point, and when used as an electromagnetic wave receiving antenna,
The opposite vertex of the antenna element 11 is the receiving point,
A receiving circuit for receiving the reflected signal is connected to this receiving point.

When the invisible object detecting antenna configured as described above is used for actual measurement, as shown in FIG. 8, an electromagnetic wave transmitting antenna 8 including an invisible object detecting antenna in which a feeder circuit is incorporated and a receiving antenna. An electromagnetic wave receiving antenna 9 comprising an invisible object detecting antenna in which a circuit is incorporated is arranged side by side, and is provided above an invisible medium, for example, soil.
Detect two metal tubes, each buried at a depth of cm.

FIG. 9 is a diagram showing signals observed in the situation shown in FIG. 8 for each reception level. In this observation signal,
The waveform 10 observed at the earliest position is a composite wave of a wave directly propagated from the transmitting antenna 8 to the receiving antenna 9 through the atmosphere and a reflected wave on the ground surface. Hereinafter, this wave is referred to as a direct coupling component 10.

On the other hand, since the underground radio wave propagation speed here is 7.15 cm / nesc, the propagation time T (nsec) from a metal pipe with a buried depth of 15 cm or 50 cm is calculated using the following formula, where the buried depth is L (cm). T = 2L / 7.15 (1) 4.2 nsec and 14 nsec, respectively.

(Problem to be Solved by the Invention) In the above-described measuring method, the reflected wave 20 from the metal tube buried at 15 cm is superimposed on the direct coupling component 10 having an extremely large amplitude value. It is necessary to reduce the reception level as shown in). In addition, since the electromagnetic waves that have entered the ground are rapidly reduced in water, the amplitude of the waves 30 reflected by the metal tube buried 50 cm is much smaller than the direct coupling component. Therefore, if the reception level is low as shown in FIG.
The reflected wave 30 from the metal tube buried in the can not be observed. Conversely, when the reception level is increased as shown in FIG. 9 (b), the reflected wave 30 from the metal tube buried at 50 cm is
Can be observed, but the reflected wave 20 from the metal tube buried 15 cm cannot be observed. As a result, it is not possible to observe the reflected wave from the tube buried relatively near the ground surface affected by the direct coupling component and the reflected wave from the tube at the buried depth that is not affected by the same reception level, There is a problem that either of them cannot be detected.

In addition, the invisible object detection antenna is required to be small, light, and portable, and in particular, to be small in the measurement plane direction. In order to reduce the size, it is necessary to reduce the antenna element, that is, to shorten the axial length Lax of the antenna element or the open end length Lb of the antenna element. There is a problem that a decrease in the detectable depth and a decrease in the open end length Lb cause a decrease in resolution and an extremely low detection capability.

The present invention has been made in view of the above, and it is an object of the present invention to reduce the direct coupling component and detect all invisible objects at the same reception level without impairing the detection ability, and to reduce the size. It is an object of the present invention to provide a gantena for detecting an invisible object.

[Configuration of the invention]

(Means for Solving the Problems) In order to achieve the above object, an antenna for detecting an invisible object according to the present invention includes a pair of triangular-shaped metal members which are arranged so that one vertex is separated by a predetermined distance and are opposed to each other on the same plane. A predetermined angle with respect to the open side from two points located at a predetermined distance on the open side from each vertex at both ends of one open side facing the vertex of each metal plate. An antenna element formed by bending each metal plate at a predetermined angle with respect to a metal plane along a line having, without contacting the antenna element, the antenna element with respect to the plane on which the antenna element is disposed. A chassis that covers a space facing the bent portion; a resistor that electrically connects the two bent vertexes of the antenna element to the chassis; It consists of a radio wave absorber disposed in the space between the chassis and the antenna element so as to absorb the reflected wave, and a pair of opposed vertices of a pair of metal plates constituting the antenna element disposed in the same plane. Connected to the feeding or receiving point,
The gist of the invention is to have circuit means for performing a power supply or reception operation and a radio wave transmitting plate on which the antenna element is provided.

(Operation) The antenna for detecting an invisible object of the present invention has an antenna element formed by bending a triangular region including vertices at both ends of an open side of a pair of triangular metal plates by a predetermined angle. The transmitting and receiving invisible object detecting antennas each having an element are arranged side by side and disposed near the invisible medium, and the reflected wave of the electromagnetic wave radiated from the transmitting invisible object detecting antenna is received by the receiving invisible object detecting antenna. Receiving and detecting invisible objects.

(Example) Hereinafter, an example of the present invention is described using a drawing.

FIG. 1 is a diagram showing an antenna element 110 used for an invisible object detecting antenna according to one embodiment of the present invention, and FIG. 2 is an embodiment of the present invention using the antenna element 110 of FIG. FIG. 2 is a diagram showing an invisible object detection antenna according to the first embodiment. In FIG. 1, FIG. 1A is a development view before the antenna element 110 is completed, FIG. 1B is a perspective view of the completed antenna element 110, and FIG. FIG. 4B is a side view of the antenna element 110 viewed from the direction of the arrow in FIG. 2, (a), (b), and (c) are cross-sectional views from above of the invisible object detection antenna, cross-sectional views from one end, and cross-sections from the other side, respectively. The figure, that is, a cross-sectional view along the line BB 'in FIG.
FIG. 4 is a cross-sectional view taken along a line C-C ′ and a cross-sectional view taken along a line AA ′ of FIG.

The antenna element 110 shown in FIG.
A pair of triangular metal plates 12 shown in FIG.
The vertices 12a are arranged on the same plane facing each other at a predetermined distance Lc, and the sides 12b facing the vertices 12a,
That is, two vertices 12c and 12d existing at both ends of the open side 12b
Are bent as shown in FIGS. 1 (b) and 1 (c). More specifically, the vertex
The triangular area bent including 12c and 12d has vertices 12c and 1
2d along the open side 12b along a dotted line forming a predetermined angle φ ₁ , φ ₂ with respect to the open side 12b from a point separated by a predetermined distance L ₁ , L ₂ with respect to the plane of the metal plate 12 respectively. The metal plate 12 is bent at angles θ ₁ and θ ₂ . In the antenna element 110 configured as described above, the length Lb of the open side is the length of the open end, the shortest distance from the vertex 12a to the open side 12b is the axial length Lax, and the two vertices 12a The distance therebetween is the vertex distance Lc, the distances L ₁ and L ₂ are the bending lengths, and the angles φ ₁ , φ ₂ , θ ₁ and θ ₂ are the bending angles.

The invisible object detection antenna shown in FIG. 2 is configured using the antenna element 110 configured as shown in FIG. 1, and the space on one side where the bent portion of the antenna element 110 faces is used. Both ends of the open end of each metal plate 12 of the chassis 2 and the antenna element 110 are covered with, for example, 100 to 30.
They are electrically connected by a 0 ohm resistor 3.
In addition, the space between the chassis 2 and the antenna element 110 is provided with a radio wave absorber 4 in order to suppress unnecessary reflection of electromagnetic waves.
Is inserted. Further, the power supply circuit 6 for supplying an impulse or a monocycle signal having a width of several nsec to the antenna element 110 is connected to the top 1 of the antenna element 110.
It is directly connected to the feed point consisting of 2a. The antenna element 110 itself is disposed on the radio wave transmitting plate 7 having a thickness of about 2 cm. As described above, the invisible object detecting antenna shown in FIG. 2 can be used as two antennas, an electromagnetic wave transmitting antenna for transmitting electromagnetic waves and an electromagnetic wave receiving antenna for receiving electromagnetic waves. In this case, the opposing apex of the antenna element 11 is a feed point as described above, and the feed circuit 6 is connected to this feed point, and when used as an electromagnetic wave receiving antenna, the antenna element 11 Is a receiving point, and a receiving circuit for receiving the reflected signal is connected to the receiving point.

FIG. 3 is a view showing an antenna element 120 used for an invisible object detecting antenna according to another embodiment of the present invention, and FIG. 4 is another view of the present invention using the antenna element 120 of FIG. It is a figure showing the antenna for invisible object detection concerning an example. In FIG. 3, FIG.
FIG. 4 is a development view before completing the antenna element 120, FIG. 4B is a perspective view of the completed antenna element 120, and FIG. 4C is an antenna viewed from the direction of the arrow in FIG. FIG. 4 is a side view of the element 110. 2, (a), (b), and (c) are cross-sectional views from the upper side, a cross-sectional view from one side, and a cross-section from the other side of the invisible object detection antenna, respectively. FIG. 3C is a sectional view taken along the line BB ′ in FIG. 3C, a sectional view taken along the line CC ′ in FIG. 3A, and is a sectional view taken along the line AA ′ in FIG. It is sectional drawing.

The antenna element 120 shown in FIG. 3 is composed of a pair of triangular metal plates 12 like the antenna element 110 shown in FIG.
While being spaced apart and opposed to each other and arranged on the same plane,
The open sides 12b facing the apex 12a apart a predetermined distance L _3,
As shown in FIGS. 3B and 3C, a predetermined angle θ ₃ is set in parallel.
It is formed by bending.

The invisible object detecting antenna shown in FIG. 4 is configured by using the antenna element 120 of FIG. 3, and has the same configuration as the invisible object detecting antenna of FIG. 2 described above. In the invisible object detection antenna shown in FIG. 4, the same components as those shown in FIG. 2 are denoted by the same reference numerals, and the configuration is omitted.

When the antenna for detecting an invisible object, which is configured as shown in FIGS. 2 and 4, respectively, is used for actual measurement, the antenna for detecting an invisible object, in which a feeder circuit is incorporated as in FIG. An electromagnetic wave transmitting antenna consisting of an antenna and an electromagnetic wave receiving antenna consisting of an invisible object detecting antenna with a built-in receiving circuit are arranged side by side, and provided near the invisible medium in which the invisible object is embedded. Radiates electromagnetic waves inward,
A reflected wave from an invisible object or the like embedded in an invisible medium is received by a receiving antenna to detect the invisible object.

An antenna element 11 using the two invisible object detecting antennas shown in FIGS. 2 and 4 respectively.
0 and 120 are type A and type B, respectively, and the sizes of the actually created antenna elements are shown in Tables 1 and 2 below.
Shown in

FIGS. 5 (a) and (b) show the metal pipes buried underground shown in FIG.
FIG. 5 is a diagram showing a signal waveform when observed by the invisible object detecting antenna of FIGS. 2 and 4 using the type A and B antenna elements of the actual dimensions shown in FIG. In the observation signals shown in FIGS. 5 (a) and 5 (b), at the earliest position, a wave directly propagated from the transmitting antenna 8 to the receiving antenna 9 through the atmosphere and a reflected wave on the ground surface are combined. A direct coupling component 10 as a wave is observed, and thereafter, reflected waves 20 and 30 from two metal tubes having an embedded depth of 15 cm and 50 cm are simultaneously observed at the same reception level. The waveform of the reflected wave is also the same as the waveform observed in the prior art shown in FIG. 9 described above, and the detection ability is not reduced.

As described above, it is possible to simultaneously detect a plurality of buried pipes having different depths at the same reception level without reducing the detection capability of the invisible object detection antenna and reducing only the direct coupling component of the observation signal.

Table 3 below shows the reduction ratios of the antenna elements having the dimensions shown in Tables 1 and 2 with respect to the conventional antenna elements in three items of the horizontal open end length, the horizontal axial length, and the horizontal area reduction ratio. It shows the results of the comparison.

Here, the horizontal direction indicates a plane on which the antenna element is arranged, that is, the same plane of the radio wave transmitting plate 7. The numerical value in parentheses () is a reduction ratio in comparison with the conventional type.

As described above, the observed signal waveform is the same as the signal observed with the conventional antenna except for the reduction of the direct coupling component, and it is possible to achieve the miniaturization of the antenna without impairing the detection capability of the antenna. .

It should be noted that the dimensions shown in Tables 1 and 2 are not definitive, and slight deviations do not affect the effects of the present invention. However, in the type A antenna element,
The bending distance is desirably not more than one-third of the length of the open end, and in the type B antenna element, it is desirably that the bending length is not more than one-half of the axial length.

Further, in the above embodiment, the case where the metal pipe buried underground is detected has been described.However, the present invention is not limited to this. It is also effective in detecting watersheds. Further, the present invention is not limited to the underground, and can be applied to detection of an object existing in an electromagnetic wave transmitting medium such as concrete or water, for example, a reinforcing bar, a cavity, or a scratch.

〔The invention's effect〕

As described above, according to the present invention, there is provided an antenna element formed by bending a triangular region including each terminating point present at both ends of an open side of a pair of triangular metal plates by a predetermined angle. The transmitting and receiving invisible object detecting antennas each having an element are arranged side by side and disposed near the invisible medium, and the reflected wave of the electromagnetic wave radiated from the transmitting invisible object detecting antenna is received by the receiving invisible object detecting antenna. Because it detects and detects invisible objects, it can reduce the direct coupling component of the observed signal and reduce the horizontal area of the antenna without compromising the detection capability, making compact and efficient invisible object detection possible. Antenna can be provided.

[Brief description of the drawings]

FIG. 1 is a view showing an antenna element used for an invisible object detection antenna according to one embodiment of the present invention, and FIG. 2 is a diagram showing an invisible object detection according to one embodiment of the present invention using the antenna element of FIG. FIG.
FIG. 4 shows an antenna element used for an invisible object detecting antenna according to another embodiment of the present invention. FIG. 4 shows an invisible object detecting apparatus according to an embodiment of the present invention using the antenna element of FIG. FIG. 5 is a diagram showing a signal obtained by observing an invisible object by the invisible object detection antenna of FIGS. 2 and 4, FIG. 6 is a diagram showing a conventional antenna element, and FIG. FIG. 6 is a diagram showing an invisible object detecting antenna using the conventional antenna element of FIG. 6, FIG. 8 is an explanatory diagram showing a measurement state of an invisible object by the invisible object detecting antenna, and FIG. 9 is a conventional diagram of FIG. FIG. 4 is a diagram illustrating a signal obtained by observing an invisible object with the invisible object detection antenna. 12 Metal plate, 2 Chassis, 3 Resistor, 4,5 Radio wave absorber, 6 Feeding circuit (receiving circuit), 7 Radio wave transmitting plate, 8 Antenna for electromagnetic wave transmission , 9 ... an electromagnetic wave receiving antenna, 110, 120 ... ... an antenna element.

Continuation of front page (72) Inventor Junichi Masuda 1-1-6 Uchisaiwai-cho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (56) References JP-A-3-3503 (JP, A) JP-A-59-196607 (JP, A) JP-A-63-303501 (JP, A) JP-A-61-85915 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01S 7/03 G01S 13 / 88 H01Q 1/04

Claims (1)

(57) [Claims] An apex is separated by a predetermined distance and is constituted by a pair of triangular metal plates arranged opposite to each other on the same plane, and is provided at both ends of one open side opposed to the apex of each metal plate. Each metal plate is formed by bending a predetermined angle with respect to a metal plane along a line having a predetermined angle with respect to the open side from two points located at a predetermined distance on the open side from each existing vertex. An antenna element, a chassis for covering a space opposed to a bent portion of the antenna element with respect to a plane on which the antenna element is disposed without contacting the antenna element, and a bent 2 of the antenna element. A resistor for electrically connecting one of the vertices to the chassis; and a resistor disposed in a space between the chassis and the antenna element to absorb unnecessary reflected waves. A radio wave absorber, circuit means connected to a feeding point or a receiving point consisting of opposing vertices of a pair of metal plates constituting an antenna element disposed in the same plane, and a circuit means for performing a feeding or receiving operation, An antenna for detecting an invisible object, comprising: a radio wave transmitting plate provided with an antenna element.