JP2008252789A - Pressure-resistant and explosion-proof directional antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accommodate a directional antenna effective for a long-distance communication in a robust and thick dielectric container that is small in capacity, proof against explosion without deteriorating the original antenna directional characteristics. <P>SOLUTION: A Yagi or helical directional antenna 4 or 5 is accommodated along a long length direction of a cylindrical dielectric container 3 with the thickness of 3 mm or more. In the antenna, a radio wave reflection plate 7 whose diameter D2 is 1.1-10 times the outer diameter D1 of the container is disposed to be projected from the outer periphery of the container 3 in a direction perpendicular to the long length direction of the container 3 at a rear position of the directional antenna 4 or 5. This results in combining a travelling wave and a wave reflected by a reflection plate 7 disposed to be projected from the outer periphery of the container 3, so that the directional antenna is adjusted and the original directional antenna characteristic not in the dielectric container is obtained. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a flameproof directional antenna that can be installed in an explosion-hazardous atmosphere where flammable gas or flammable dust exists.

  In explosion-proof areas such as refineries, petrochemical factories, chemical factories, and smelters that handle hazardous materials, the manufacturing and management facilities installed here are designed to be explosion-proof so as not to ignite explosive gases. However, wired communication is generally used for communication such as operation data, error report data, and other audio and video data between these facilities or management equipment installed in non-explosion-proof areas. .

However, the wired communication system has a drawback that the cost burden associated with the construction of facilities such as laying cables increases. A wireless communication system is considered to be effective as a means of eliminating this drawback, and as a means of adopting this system, the flat antenna is housed in a robust container that can withstand radio wave-permeable explosion pressure, and the relay station has an explosion-proof structure. What is considered.
JP 2006-197402 A

However, the planar antenna has a problem that it is difficult to arrange it in a vast explosion-proof area with a short communication distance. In order to solve this problem, it is conceivable to use a Yagi type or helical type antenna having excellent directivity effective for remote communication. Therefore, such a directional antenna was housed in a robust dielectric container (made of glass) having a thickness of 3 mm or more that can withstand an explosion pressure having a small volume and thickness, and the directivity with respect to a frequency of 2400 to 2500 MHz was measured. The result is shown in FIG. 4 expressed on the dB scale. FIG. 3 is a directional characteristic diagram showing the results of measuring the directivity of the Yagi antenna and the helical antenna when not stored in the dielectric container on a dB scale. From the comparison of the characteristics shown in FIG. 3 and FIG. 4, the antenna housed in the dielectric container clearly has a problem that the directional characteristics deteriorate and the characteristics of the directional antenna cannot be secured.

  The problem to be solved by the present invention is to provide a directional antenna effective for remote communication, a robust dielectric that can withstand a large explosion pressure with a small volume and a thickness of 3 mm or more without deteriorating the inherent characteristics of the antenna. It is possible to store in a container and to solve such a problem.

  The present invention is a Yagi-type or helical-type directional antenna housed in a cylindrical dielectric container having a thickness of 3 mm or more along the longitudinal direction of the container, and has a predetermined size larger than that of the container. A radio wave reflecting plate having a diameter is provided so as to protrude from the outer periphery of the container in a direction perpendicular to the longitudinal direction of the container at the rear position of the directional antenna.

  The phase change of the traveling wave occurred due to the influence of the dielectric container having a wall thickness of 3 mm or more, and the directional antenna could not be adjusted. In the present invention, a radio wave reflector having a predetermined diameter larger than a cylindrical dielectric container having a wall thickness of 3 mm or more is disposed at the rear position of the directional antenna in the direction perpendicular to the longitudinal direction of the container. Because the projecting wave is arranged from the outer side of the container, the traveling wave and the reflected wave from the reflector that is projected from the outer periphery of the container are combined, and the directional antenna can be adjusted, and the directivity when there is no dielectric container The directivity characteristic of the antenna can be obtained.

  The purpose of enabling a directional antenna effective for remote communication to be housed in a robust dielectric container that can withstand an explosion pressure with a small volume and a thickness of 3 mm or more without deteriorating the characteristics inherent to the antenna. Is a Yagi-type or helical-type directional antenna that is stored along the longitudinal direction of the cylindrical dielectric container, and has a radio wave reflector having a predetermined diameter larger than that of the dielectric container that stores the directional antenna. This is realized by projecting from the outer periphery of the container in a direction orthogonal to the longitudinal direction of the container at the rear position of the directional antenna.

Embodiments of the present invention will be described below with reference to the drawings. 1 is an external perspective view of a pressure-proof explosion-proof directional antenna according to an embodiment, FIG. 2 is a cross-sectional view of the pressure-proof explosion-proof directional antenna shown in FIG. b) shows a case where a helical antenna element is used. 1 and 2, 1 is a metal container having an open surface, 2 is a metal lid that closes the opening surface of the metal container, and 3 is one end made of glass (may be made of resin or ceramic). Cylindrical dielectric container, 4 is a Yagi type antenna element, 5 is a helical type antenna element, 6 is a support for supporting the antenna and the Yagi type or helical type antenna element, 7 is a reflector, 8 is a fixing of the dielectric container It is a board.

In this embodiment, a radio wave having a frequency of 2450 MHz is received and transmitted. The dielectric container 3 is made of glass, has a thickness T of about 3 mm, an outer diameter D1 of about 70 mm, a length of about 400 mm, and includes the metal container 1. The overall length is about 530 mm. Moreover, the diameter D2 of the reflecting plate 5 is about 200 mm.

On the side surface of the metal container 1, a through-hole 1 a is formed that hermetically fixes a power cable 9 extending from the antenna element and a cable gland through which a power supply line drawn outside (not shown) passes. One end of the column 6 is fixed to the bottom surface of the metal container 1, and the other end protrudes outside from the opening of the metal container 1, and a portion led out to the outside is as shown in FIG. A Yagi-type antenna element 4 (may be a helical antenna element 5 shown in FIG. 2B) is fixed. That is, the antenna element 4 or 5 is accommodated along the longitudinal direction of the cylindrical dielectric container 3.

The metal lid 2 is formed with a through hole 2a having a large diameter on the container side at the center, and the opening end of the dielectric container 3 is thick on the outside so as to be fitted to the wide diameter portion of the through hole 2a. The outer diameter is increased by increasing the thickness. Then, the dielectric container 3 is inserted into the through hole 2a of the metal lid 2 from the closed end, and the end having the larger outer diameter is fitted into the wide diameter portion of the through hole 2a, so that the ring-shaped fixing plate 8 is abutted. The metal lid 2 is fixed in contact therewith. By this fixing, the through hole 2 a of the metal lid 2 is closed by the dielectric container 3.

The metal lid 2 to which the dielectric container 3 is attached is covered with the antenna element 4 or 5 fixed to the support column 6 with the dielectric container 3, and abuts on the opening edge of the metal container 1 and is fixed by bolting. Thereafter, the reflecting plate 7 formed in a ring shape is inserted into the dielectric container 3 and fixed to the outer surface of the metal lid 2 with screws.

FIG. 5 shows the reception result of the antenna having the explosion-proof structure as described above measured at a frequency of 2400 MHz to 2500 MHz. As is clear from comparison between FIG. 3 and FIG. 5, the rear position of the antenna in which a radio wave reflector having a diameter of about 200 mm larger than a cylindrical dielectric container having a thickness of about 3 mm is accommodated in the container. Thus, it can be seen that the original characteristics of the directional antenna are secured by projecting from the outer periphery of the container in a direction perpendicular to the longitudinal direction of the container.

Although the above description is about the receiving antenna, the present invention is also applied to the transmitting antenna. Further, the thickness of the dielectric container was suitably T3 mm to 50 mm, and the diameter D2 of the reflecting plate was suitably adapted to 1.1 to 10 times, particularly 2 to 3 times the outer diameter D1 of the dielectric container. Further, in the embodiment, the opening at one end of the dielectric container is closed with a metal container. However, the dielectric container is not limited to the metal container, but may be other materials or plates.

1 is an external perspective view of an explosion-proof directional antenna according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the explosion-proof directional antenna shown in FIG. 1. It is a characteristic view of a Yagi type and a helical type directional antenna. It is a characteristic view of an antenna when a Yagi type and a helical type directional antenna are stored in a thick dielectric container. It is a characteristic view of the explosion-proof directional antenna according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal container 2 Metal lid of metal container 3 Thick dielectric container 4 Yagi type antenna element 5 Helical type antenna element 6 Strut 7 Reflecting plate 8 Fixing plate 9 Feeding line

Claims (1)

A Yagi-type or helical-type directional antenna housed in a cylindrical dielectric container having a thickness of 3 mm or more along the longitudinal direction of the container, and having a predetermined diameter larger than that of the container A flameproof explosion-proof directional antenna, characterized in that a reflecting plate is disposed so as to protrude from the outer periphery of the container in a direction orthogonal to the longitudinal direction of the container at a rear position of the directional antenna.

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