JP5271784B2 - Search radar antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance a resolution of a probe image in probing a relatively shallow region. <P>SOLUTION: A probe radar antenna 10 provided for a buried object detector 1 has: circular antennas comprising two each of circular element conductors arranged on a substrate 17; and a circular antenna being a reception antenna B arranged in parallel with a transmission antenna A. A pulser 23 generates a pulsed radar wave, and the pulsed radar wave is sent to the two circular element conductors (11, 12) forming the transmission antenna A and radiated to a floor or a wall surface. The reflected wave from the wall or the floor is received by the circular element conductors (13, 14), and the buried object detector 1 discriminates a state of a buried object, based on a time between radiation of the radar wave and reception of the reflected wave, and a phase of a reception signal. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an exploration radar antenna of a buried object exploration device, and more particularly to an exploration radar antenna having a transmission antenna that transmits a radar wave and a reception antenna that receives a reflected wave.

  In construction sites and the like, buried object exploration devices using electromagnetic induction, X-rays, or radar are used for exploring reinforcing bars and gas pipes buried in the ground, walls and floors. In particular, a buried object exploration apparatus using a radar radiates a pulsed radar wave generated at a predetermined repetition period from a transmitting antenna to a wall or floor and receives a reflected wave returned from the wall or floor by a receiving antenna. To do. This buried object searching device displays internal information of walls and floors on a display by processing a reflected wave received by a receiving antenna by a signal processing unit.

  FIG. 6 shows a configuration of a conventional exploration radar antenna 30, and FIG. 7 shows a circuit configuration of a transmission antenna. 6 includes a transmitting antenna A and a receiving antenna B, and two triangular element conductors (31 to 34) each having a feeding point (A1, A2, B1, B2) arranged at the center. And is generally called a bow-tie antenna. The element conductors (31 to 34) of each antenna are arranged on a substrate 37 having a predetermined dielectric constant with feeding points adjacent to each other. Further, baluns 38 and 39 having coils L1 to L6 in FIG. 7 are provided at the feeding point in order to balance the coaxial cable and the antenna. Further, each antenna shown in FIG. 6 is provided with conductive shield cases 35 and 36 and a radio wave absorber (not shown) to prevent unnecessary radiation from the element conductor to the direction other than the object to be measured and to prevent external noise from entering. It has a structure.

  In recent years, further improvements have been made in order to increase the resolution of the internal information obtained by the buried object search apparatus. For example, Patent Document 1 discloses a technique for easily identifying a target such as a reinforcing bar or a gas pipe that is close to the inside of a wall or floor by improving the return loss characteristic of an antenna for an exploration radar.

  In the radar type underground exploration device described in Patent Document 2, a transmission antenna and a reception antenna are combined, a transmission / reception integrated transmission / reception unit is used, and signal processing with amplification is performed in the reception signal processing unit. Even in the case of performing this technique, a technique for improving the resolution of internal information by performing good signal processing without causing saturation is shown.

  In addition, the electromagnetic wave radar device described in Patent Document 3 includes a shield case that covers the transmission antenna and the reception antenna, and a radio wave absorber that absorbs unnecessary radar waves, and is directly incident on the reception antenna from the transmission antenna. Techniques have been shown to improve target identification by reducing direct wave ringing, reflections from walls and floor surfaces, and other unwanted incident waves. Further, Non-Patent Document 1 discloses a tree-shaped antenna of GSSI, USA, and Non-Patent Document 2 discloses a technique related to a circular antenna.

Japanese Patent Laid-Open No. 6-18650 JP-A-11-64510 JP 2003-107146 A

QF75101 ANTENNA ASSEMBLY Internal Photos (see photo), [online], [March 24, 2009 search], Internet <URL: https://fjallfoss.fcc.gov/oetcf/eas/reports/ViewExhibitReport.cfm?mode= Exhibits & RequestTimeout = 500 & calledFromFrame = N & application # id = 890868 & fcc # id =% 27QF75101% 27> S. Honda, M .; Ito, H .; seki and Y. Jimbo: “A disc monopole antenna with 1: 8 impedance bandwidth and omnidirectional radiation pattern” Proc. 1992 Int. Symp. , Antennas and Propag. , ISAP'92 pp. 1145-1148, Sapporo, Japan, 1992.2.8.

  In order to improve the resolution of the exploration image by the above-described technique, it is possible to increase the bandwidth by impulse response by further shortening the pulse width of the radar wave to be transmitted, and to increase the frequency on the reception side as well. Necessary. In order to search for a relatively shallow region, a transmission / reception integrated antenna as in Patent Document 2 is desirable, but there is a technical problem with a transmission / reception circuit, which is difficult to realize.

  Therefore, the exploration radar antenna according to the present invention increases the frequency by shortening the pulse width of the transmitted radar wave (widens the impulse response) and transmits / receives that affect the exploration of a relatively shallow region. An object of the present invention is to provide an antenna for an exploration radar in which the resolution of the exploration image is improved by reviewing the antenna shape and positional relationship.

  In order to achieve the above object, an exploration radar antenna according to the present invention is an exploration radar antenna having a transmission antenna and a reception antenna. The transmission antenna and the reception antenna have a predetermined dielectric constant. An endless circular antenna having a connector connected to a circular element conductor provided on an antenna substrate and arranged side by side. Adjacent transmitting antennas and receiving antennas are surfaces of the object to be measured to be probed. In order to improve the resolution in a region close to, the distance between the transmitting antenna and the receiving antenna is narrowed and arranged on the antenna substrate.

  Further, in the exploration radar antenna according to the present invention, the feeding point provided on the circular element conductors arranged in a line is constituted by a balunless.

  Further, the exploration radar antenna according to the present invention is characterized in that the polarities of the signals connected to the transmitting antenna and the receiving antenna each constituted by two circular element conductors are connected in the same polarity or inverted.

  Further, in the exploration radar antenna according to the present invention, the transmitting antenna and the receiving antenna constituted by two circular element conductors arranged side by side are endless antennas.

  The exploration radar antenna according to the present invention has a transmission pulse width that is shorter than that of the conventional antenna, and also increases the reception frequency and improves the resolution due to a high frequency, and the shape and positional relationship of the transmission and reception antennas that affect the exploration of a relatively shallow region. By reviewing, it is possible to obtain a high-resolution exploration image.

It is explanatory drawing explaining the outline | summary of the antenna for search radar which concerns on embodiment of this invention. It is the conventional structure which becomes a reference in understanding the antenna for search radars concerning the present invention. It is explanatory drawing explaining the positional relationship of the antenna for search radars concerning embodiment of this invention, and the antenna for search radars of a conventional structure. It is explanatory drawing explaining the measurement characteristic important in setting the space | interval of the transmission antenna of a search radar antenna and the receiving antenna which concern on embodiment of this invention. It is explanatory drawing explaining the comparison result of the measurement image by the conventional antenna and the circular antenna of this embodiment. It is a perspective view of the conventional antenna for search radars. It is a circuit diagram of the conventional antenna for search radars. It is the front view and partial enlarged view of the antenna for search radars concerning the embodiment of the present invention. It is the right view and partial enlarged view of the antenna for search radars concerning the embodiment of the present invention. It is the bottom view and back view of the antenna for search radars concerning the embodiment of the present invention.

  Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described with reference to the drawings.

  FIG. 1 shows an exploration radar antenna 10 and its peripheral configuration in the buried object exploration device 1. The search radar antenna 10 comprises a circular antenna in which two circular element conductors are arranged on a substrate having a predetermined dielectric constant, and has a transmission antenna A and a reception antenna B arranged in parallel. Further, the transmitting antenna A and the receiving antenna B are shielded by the shield cases 21 and 22, and the radar waves are transmitted and received from the back surface of the substrate 17 that is not shielded.

  The pulsar 23 is connected to the delay line 15, and the delay line 15 is connected to the transmission antenna A. The pulsar 23 generates a pulsed radar wave generated at a predetermined repetition period and outputs it to the delay line 15. Radar waves from the delay line 15 are sent to the two circular element conductors (11, 12) forming the transmission antenna A, and are radiated to the floor or wall surface.

  Similarly, the receiving antenna B is connected to the delay line 16, and the delay line 16 is connected to the sampler 24. The reflected wave returned from the wall or floor is received by the circular element conductors (13, 14) forming the receiving antenna B, received by the sampler 24 via the delay line 16, and from the radar wave emission to the reception of the reflected wave. The state of the buried object is determined by the time and the phase of the received signal.

  FIG. 2 shows an exploration radar antenna 30 that is helpful in understanding the exploration radar antenna 10 of the present embodiment. The exploration radar antenna 30 of FIG. 2 includes a transmission antenna A and a reception antenna B formed on a substrate 37 having a predetermined dielectric constant, and a shield case (35, 36) that covers the transmission / reception antenna. Each antenna feed point A1, A2, B1, B2 is provided at the apex of the triangular element conductor, and the other apex is connected to the other apex of the other triangular element conductor via resistors R1 to R8. Termination is connected.

  In this embodiment, in order to improve the resolution of the exploration image, the pulse width of the pulsar is further shortened from, for example, the conventional 1 ns (half-value width), and the frequency band of the sampler is made higher than, for example, 1 GHz. In particular, in a handy type buried object search apparatus, it is desired to improve the resolution in a relatively shallow region having a depth of about 10 cm. For this reason, one way to improve the resolution in shallow regions is to narrow the apparent angle between the transmitting and receiving antennas and the target to be probed from the usual angle, and even in shallow regions, the transmission and reflected waves of radar waves are acute. There is a method that is realized by the reception of.

  FIG. 3 shows the positional relationship between the exploration radar antenna 10 of the present embodiment and the conventional exploration radar antenna 30. Since the radio field intensity of the transmission / reception antenna is proportional to the area of the element conductor, in order to obtain a predetermined radio field intensity, the area of the triangular element conductor such as the exploration radar antenna 30 as in the conventional configuration is required. The distance between the centers of the antennas was the distance LA shown in FIG.

  Therefore, in order to place the transmitting and receiving antennas close to each other, the conventional bow-tie type antenna is changed to an endless round antenna, and the diameter is about 4 cm in order to obtain a radio wave intensity equivalent to the conventional level, The distance LB shown in FIG. 3 can be set. By using such an endless round antenna, an antenna with few components including a circular antenna and a connector for connecting to the antenna is obtained.

  The balun used for balanced connection between the antenna and the coaxial cable has a function of smoothing a sharp pulse due to the integration effect. Therefore, the search radar antenna 10 of the present embodiment has a search resolution due to the sharp pulse. In order to increase this, the connector 18 was directly connected to the connector 18 as a balunless. In addition, because it is balunless, depending on the target, the exploration image can be clearly displayed by switching the form of connecting the positive and negative electrodes to the transmitting and receiving antennas facing each other on the same side or connecting them differently. It is also possible to do.

  FIG. 4 shows measurement characteristics that are important in setting the interval between the transmitting antenna and the receiving antenna of the exploration radar antenna 10 of the present embodiment. In FIG. 4A, the horizontal axis indicates the distance between the transmitting antenna and the receiving antenna, and the vertical axis indicates the width of the dead zone, the size of the direct coupling, and the required measurement characteristics. Since the transmission antenna and the reception antenna generally have a predetermined spread, the dead zone increases as the distance between the transmission antenna and the reception antenna increases as shown in FIG.

  The measurement characteristics required in the present embodiment are good characteristics when the dead zone is reduced in the shallow region of the measurement target and the resolution of the search image is improved. In FIG. 4, the smaller the distance LB between the transmission antenna and the reception antenna, the better. However, when the distance between the transmission antenna and the reception antenna is narrowed, the radio wave generated by the reception antenna directly receiving the radar wave emitted from the transmission antenna. The intensity increases (direct coupling phenomenon), and reflection near the surface increases.

  Therefore, in this embodiment, each of the transmission antenna and the reception antenna is composed of two circular antennas, and the best point of the effect and resolution of the direct coupling phenomenon that is directly transmitted from the transmission antenna to the reception antenna is experimentally determined. The resolution of the exploration image was ensured, and the transmitting antenna and the receiving antenna were arranged close to each other (for example, with an interval of about 1 cm) so that direct coupling would not adversely affect the measurement. In addition, by using an endless circular antenna, it is possible to arrange a transmitting / receiving antenna closer than a conventional bow-tie antenna.

  FIG. 5 shows a comparison result of the search images by the conventional antenna (A) and the circular antenna (B) of the present embodiment. The exploration images were compared using a test specimen in which five reinforcing bars were embedded in concrete with a depth of about 8 cm, an interval of about 8 cm, about 5 cm, about 4 cm, and about 3 cm. This test body evaluates the resolution in the horizontal direction based on the distance in the horizontal direction with reference to the depth.

  In the figure, with the conventional antenna (A), the horizontal resolution was difficult to identify the reinforcing bars with an interval of about 8 cm, but with the circular antenna (B) of the present embodiment, the chevron echoes were separated and displayed. Reinforcing bars with a spacing of 5 cm could be identified, and it was confirmed that they had higher horizontal resolution than conventional antennas.

  As described above, the search radar antenna according to the present embodiment makes it possible to acquire a high-resolution search image in search of a relatively shallow area. Although the circular antenna is used in this embodiment, only the feeding point side may be a semicircular shape or an elliptical shape, a snowman shape or a rice ball shape combining a plurality of large and small circles, a circular and triangular combination type, and a circular shape. Relatively good results can be obtained even with a square and a combined type.

  The exploration radar antenna, which is an article of this embodiment, is characterized by the shape, pattern, color, etc. of the circular element conductor. FIG. 8 is a front view of a survey radar antenna according to the present embodiment and a partially enlarged view of a connector. This article is a planar antenna feeding element mounted on the bottom of a handy type buried object exploration device having wheels, for example, for exploring the interior along the floor or wall surface in order to measure the internal situation of the floor or wall surface. is there. The circular antenna of this embodiment is mounted on the bottom surface of the handy type buried object searching device, and the size of the antenna substrate is about 12 cm wide, about 15 cm long, and about 2 mm thick.

  FIG. 9 is a right side view of the exploration radar antenna of this embodiment and a partially enlarged view of the connector. Note that the right side view is omitted because it appears symmetrically with the left side view.

  FIG. 10 is a bottom view and a rear view of the exploration radar antenna of this embodiment. The back surface of the radar for exploration radar may come into contact with the floor, wall surface, etc., and black silk printing or black coating is applied to protect the surface.

  The exploration radar antenna according to the present invention can be used in a buried object exploration device as a transmitting antenna and a receiving antenna, which are endless circular antennas.

  DESCRIPTION OF SYMBOLS 1 Embedded object exploration device, 10, 30 Search radar antenna, 11, 12, 13, 14 Circular element conductor, 15, 16 Delay line, 17, 37 Substrate, 18 Connector, 21, 22, 35, 36 Shield case, 23 Pulsar, 24 sampler, 38,39 balun.

Claims (4)

In an exploration radar antenna having a transmission antenna and a reception antenna,
The transmitting antenna and the receiving antenna are endless circular antennas each having a connector connected to a circular element conductor that is provided on an antenna substrate having a predetermined dielectric constant and arranged side by side,
An adjacent transmitting antenna and a receiving antenna are arranged on an antenna substrate with a small distance between the transmitting antenna and the receiving antenna in order to improve the resolution in a portion near the surface of the measurement target to be searched. Radar antenna. The survey radar antenna according to claim 1,
2. An exploration radar antenna characterized in that a feed point provided on two circular element conductors arranged side by side is constituted by a balunless. In the exploration radar antenna according to claim 2,
An exploration radar antenna characterized in that the polarities of signals connected to a transmitting antenna and a receiving antenna each composed of two circular element conductors are connected in the same polarity or inversion. In the exploration radar antenna according to claim 2,
An exploration radar antenna characterized in that a transmitting antenna and a receiving antenna constituted by two circular element conductors arranged side by side are endless antennas.

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