JPH0371670B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is directed to a detector that uses radio waves to detect targets, etc., which is equipped with a deflection means that improves the isolation between a transmitting antenna and a receiving antenna. The present invention relates to an antenna device.

(Background of the Invention) A detector is known that detects a target object by emitting radio waves from a transmitter, reflecting the radio waves from the target object, and receiving the reflected waves with a receiver.

In such a detector, as shown in FIG. 4, a transmitting antenna 1 and a receiving antenna 2 are installed side by side with a distance L between them, and radio waves radiated from the transmitting antenna 1 are transmitted to a target 6 buried underground 5. The receiving antenna 2 is configured to receive the reflected wave that is reflected back.

The radio waves incident on the receiving antenna 2 are reflected waves from the target object 6, which serve the original purpose, as well as reflected waves from the ground surface 4, and wetted radio waves that directly reach the receiving antenna from the transmitting antenna 1. There is,
A signal is obtained at the receiving antenna 2 as a composite vector of these three types of radio waves.

(Problem to be Solved by the Invention) By the way, not only is the above-mentioned wetting radio wave C completely unnecessary for target object detection, but if its amount becomes excessive, its vector component will be The vector components of the reflected wave A and the reflected wave B from the ground surface 4 are greatly exceeded, and the reception detection diode and reception circuit on the receiving side are saturated, and the detection function is impaired or detection becomes impossible.

This problem also occurs in CW radars of the same type, but in CW radars, the detection target is generally far away from the transmitting and receiving antennas, so the distance L between the transmitting antenna 1 and the receiving antenna 2 is set to be long. Therefore, this problem can be solved by improving the isolation between the transmitting antenna and the receiving antenna (that is, by reducing the amount of wetted radio waves). However, if the distance between the detection target and the transmitting/receiving antenna is short, if the distance L between the transmitting antenna 1 and the receiving antenna 2 is increased, the beam A of the transmitted radio wave and the beam H of the received radio wave will no longer intersect, and the target will be detected. The reflected wave A at 6 and the reflected wave B at the ground surface 4 no longer enter the receiving antenna 2, making it impossible to detect the target.

(Means for Solving the Problems) The present invention is proposed to solve the above problems. The purpose is to obtain an antenna device.

In the antenna device with deflection means of the present invention, in a configuration in which a receiving antenna receives reflected waves of radio waves radiated from a transmitting antenna by a target object, the planes of polarization of the radio waves of the transmitting antenna and the receiving antenna are 90 degrees to each other. The polarization plane of the radio wave is placed in the same container, and the plane of polarization of the radio wave is placed on the opening surface of the container, which is a plane located in front of the transmitting antenna and the receiving antenna and parallel to the plane containing both antennas.
It is equipped with a deflection means that deflects the light by 45 degrees, and furthermore,
The deflection means has a plurality of straight metal bars or patterns arranged in the same plane at an angle of 45 degrees with respect to the polarization plane of the radio waves of the transmitting antenna, and The interval T between the metal bars or patterns is λ/20≦T≦λ/10 (where λ is the wavelength of the transmitted radio wave in the atmosphere), and the width R of the metal bars or patterns in the same polarization plane direction is
By setting R≦λ/100, the radio waves radiated from the transmitting antenna are deflected by 45 degrees by the deflection means and radiated toward the target, and the radio waves reflected by the target are returned to the deflection means. The problem of the prior art described above is solved by deflecting the signal by 45 degrees at the angle of 45° to reach the receiving antenna.

(Function) In the antenna device with deflection means of the present invention, by arranging the transmitting antenna and the receiving antenna so that the planes of polarization of radio waves are at 90 degrees to each other,
Even when both antennas are housed in the same container, the level of the wetting radio waves input from the transmitting antenna to the receiving antenna is kept very low;
Moreover, by disposing deflection means for deflecting the polarization plane of radio waves by 45 degrees on the opening surface of the container located in front of the receiving antenna of the transmitting antenna, the radio waves radiated from the transmitting antenna are deflected by the deflecting means.
The isolator between the transmitting antenna and the receiving antenna is configured so that the radio waves deflected by 45 degrees and radiated toward the target object and reflected by the target object are again deflected by the deflecting means by 45 degrees and reach the receiving antenna. It is possible to improve the performance. Therefore, it is particularly effective when applied to devices such as underground target detectors in which the transmitting antenna and receiving antenna must be close to each other.

(Example) Hereinafter, an example of the antenna device with deflection means according to the present invention will be described with reference to the drawings.

Fig. 1 is a bottom view showing the structure of the first embodiment of the present invention suitable as an antenna section of a detector, Fig. 2 is a front sectional view of the same, and Fig. 3 shows the state of radio wave transmission in the first embodiment. FIG.

As shown in these figures, in the first embodiment, a transmitting antenna (such as a dipole antenna) 1a
and receiving antenna (e.g. dipole antenna)
2a are arranged in the container 10 so that the plane of polarization of the radio waves is 90 degrees to each other, and arranged at equal intervals to deflect the plane of polarization of the radio waves by 45 degrees with respect to the transmitting antenna 1a and the receiving antenna 2a. multiple metal rods 3
A deflection means 3a consisting of b is provided on the opening surface of the container 10.

Here, the deflection means 3a tilts a plurality of metal rods 3b at 45 degrees with respect to the polarization plane of the radio waves of the transmitting antenna 1a, and aligns the plurality of metal rods 3b in the same plane (parallel to the plane containing both the transmitting antenna and the receiving antenna). Experimentally, the spacing T (in the direction of the polarization plane of the radio waves of the transmitting antenna) in Fig. 2 is λ/20≦T≦λ/10 (where λ: in the atmosphere). It has been found that the width R of the metal rod 3b is preferably in the range R≦λ/100.

Note that the transmitting antenna 1a and the receiving antenna 2a
Alternatively, a microstrip antenna (an antenna element made of a metal pattern on a printed circuit board) may be used. Further, in order to support the metal rod 3b in the deflecting means 3a, a frame made of resin or the like or a plate made of resin or the like may be used in combination. Furthermore, instead of the metal rod 3b, the deflecting means can be constructed by forming linear metal patterns on the printed circuit board at equal intervals.

By setting the arrangement of each antenna and deflection means as described above, the polarization planes of the transmitting antenna 1a and the receiving antenna 2a form an angle of 90 degrees to each other, so that the wetting radio waves are transmitted from the transmitting antenna 1a to the receiving antenna 2a. level will be very low.

Next, the transmission of radio waves when detecting a target in the first embodiment will be explained with reference to FIG.

The radio waves radiated from the transmitting antenna 1a pass through the deflection means 3a made up of a plurality of metal rods 3b, so that the plane of polarization is deflected by 45° and becomes a radio wave.

The above radio wave is a target 6 buried underground 5a.
The above radio waves are reflected by the ground surface 4a and become radio waves.

The radio waves L and N pass through the deflection means 3a again, so that the plane of polarization is deflected by 45 degrees, and the radio waves A and W are received by the receiving antenna 2a. That is, the planes of polarization of the radio waves O and W that have reached the receiving antenna 2a differ by 90 degrees from the plane of polarization of the radio waves H and T radiated from the transmitting antenna 1a. Therefore, since the transmitting antenna 1a and the receiving antenna 2a are arranged so that their polarization planes differ from each other by 90 degrees, the level of the wetting radio waves from the transmitting antenna 1a to the receiving antenna 2a is extremely low, and the target object 6a is
Since the radio waves reflected from the ground surface 4a become very strong, implementing the present invention will greatly improve the isolation between the transmitting antenna and the receiving antenna. Furthermore, when used as an antenna section of a detector, detection performance can be improved.

In the embodiments of the present invention, a case has been described in which a set includes one transmitting antenna and one receiving antenna, but the present invention can also be implemented as a set including one transmitting antenna and a plurality of receiving antennas. This case is the fifth
The figure shows a second embodiment of the present invention. Also in this FIG.
Deflection means 3a that is arranged within 0a and deflects the plane of polarization by 45° toward the container opening surface, that is, in front of each antenna.
is located.

Furthermore, the configuration of the first embodiment of the present invention may be installed side by side as shown in FIG. 6, and radio waves of different frequencies may be radiated from the respective transmitting antennas 1a.

(Effects of the Invention) As explained above, the antenna device with a deflection means of the present invention arranges the transmitting antenna and the receiving antenna so that the polarization planes of radio waves are 90 degrees to each other, and By installing a deflection means that deflects the polarization plane of radio waves by 45 degrees,
It is designed to extremely reduce the amount of radio waves that penetrate from the transmitting antenna to the receiving antenna, and relatively increase the amount of radio waves that are reflected from the target. Therefore, the distance between the transmitting antenna and the receiving antenna can be set short, and the present invention has an extremely large effect on equipment such as buried object detectors in which the transmitting antenna and the receiving antenna are installed close to each other. It is something that plays.

[Brief explanation of drawings]

FIG. 1 is a bottom view showing the structure of a first embodiment of the antenna device with deflection means according to the present invention, FIG. 2 is a front sectional view of the same, and FIG. 3 is a detection of a target by the first embodiment. Explanatory diagram showing the transmission state of radio waves when
The figure is an explanatory diagram showing the transmission state of radio waves when detecting a target using conventional technology, FIG. 5 is a bottom view showing the second embodiment of the present invention, and FIG. 6 is the configuration of the first embodiment. FIG. 2 is a bottom view showing an application example of the present invention in which two devices are installed together. 1, 1a... Transmitting antenna, 2, 2a... Receiving antenna, 3a... Deflection means, 3b... Metal rod,
4, 4a...ground surface, 5,5a...underground, 6,6
a...Target, 10, 10a...Container.

Claims (1)

[Claims] 1. In an antenna device in which a receiving antenna receives reflected waves of radio waves radiated from a transmitting antenna by a target object, the transmitting antenna and the receiving antenna are arranged such that the planes of polarization of the radio waves are 90 degrees to each other. The polarization plane of the radio wave is deflected by 45 degrees to an opening plane of the container, which is placed in the same container, and is located in front of the transmitting antenna and the receiving antenna, and is a plane parallel to the plane containing both antennas. A configuration is provided in which a deflection means is arranged, and the deflection means is a plurality of straight metal bars or patterns arranged in the same plane at an angle of 45 degrees with respect to the polarization plane of the radio waves of the transmitting antenna. , the interval T between the metal bars or patterns in the polarization plane direction of the radio waves of the transmitting antenna is λ/20≦T≦λ/10 (where λ is the wavelength of the transmitted radio waves in the atmosphere), and the metal bar or pattern spacing T in the polarization plane direction of the radio waves of the transmission antenna is λ/20≦T≦λ/10 (where λ is the wavelength of the transmitted radio waves in the atmosphere). Width R of bar or pattern
By setting R≦λ/100, the radio waves radiated from the transmitting antenna are deflected by 45 degrees by the deflection means and radiated toward the target,
The radio waves reflected by the target object are deflected again at 45° by the deflection means.
An antenna device with deflection means, characterized in that the antenna device is deflected to reach the receiving antenna.