JPS63155806A - Direction finding antenna system of turning radio wave absorbing body type - Google Patents

Abstract

PURPOSE:To obtain satisfactory unidirectional directivity group and input/output matching characteristic and to simplify the system by arranging a radio wave absorbing body on the rear face of an antenna to form a unidirectional beam and turning the radio wave absorbing body to rotate this beam. CONSTITUTION:A radio wave absorbing body 2 is attached to rotation fulcrums provided upper and lower positions in the expansion direction of a dipole antenna 1D, for example, rotating pieces 12A and 12B rotated around a shaft 11, which is pierced in the center by the output cable of the antenna and consists of an insulating material, in a plastic dome 10 of less radio loss and is turned around the antenna 1D, and the lower rotating piece 12B is rotated by a rotating mechanism consisting of a motor 13, a belt pulley mechanism 14, etc., to rotate the unidirectional beam. Thus, a satisfactory input/output matching characteristic is obtained because the radiation characteristic on the rear side is erased by the absorbing body 2, and the whole of the system is made small-sized and lightweight because the directional beam is rotated by only turning the absorbing body.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a radio direction finding antenna device that detects the arrival direction of radio waves by rotating an antenna having a unidirectional directional beam. be.

[Conventional technology]

Conventionally, as a unidirectional 7-antenna used in such an antenna device, for example, for UHF/VHF bands, a 7-rector (reflector) is placed on the back side of the antenna, and an antenna with a 7-rector (Reference: Shortwave antenna” 1955
(1st edition published by Corona Publishing Co., Ltd., 1987), logarithmically periodic Gouibor array (commonly known as LP antenna) (Reference: [Antenna Engineering Handbook] published by Ohm Publishing Co., Ltd., October 1980), etc.

In addition, in ultra-short-range radar, an antenna device in which a concave radio wave absorber is placed on the back side of the antenna for the purpose of removing unnecessary echoes from nearby utility poles, buildings, workers, etc. was developed by U.S. Patent Application Publication No. 55-157307. It is well known.

[Problem that the invention seeks to solve]

The above-mentioned antenna with a 7-rector has the advantage that the directivity can be varied by changing the distance between the antenna and the 7-rector and the opening angle of the 7-rector. If the size is increased, an extra sub-pole is generated, and the VSWR (voltage standing wave ratio) value changes significantly, resulting in poor input/output matching. For applications such as wide frequency band direction detection that require input/output characteristics, it is necessary to prepare antennas with several types of structures, select the appropriate one, and rearrange them. It is not practical for this purpose due to the space it occupies and the workability.

On the other hand, LP antennas do not have such problems due to the wide frequency band, but because they have a shape with many antenna elements arranged in tandem, they are inevitably large and cannot be constructed compactly. It is unsuitable for use in vehicles.

Therefore, there is a problem in that an antenna that replaces these is expected to emerge.

[Means for solving problems]

This invention forms a unidirectional directional beam by arranging a radio wave absorber in place of the above-mentioned 7-rector, and rotates the directional beam by rotating this radio wave absorber around the antenna. This invention provides a radio direction-finding antenna device having a small and convenient configuration and having a mutually good unidirectional directivity characteristic group and input/output matching characteristics in a wide frequency band at a low cost by a simple means designed to In this way, the above-mentioned problems can be solved.

[For production]

In contrast to the conventional reflection synthesis means using a reflector, the radiation resistance characteristics on the back side are canceled by an absorption and cancellation means, which is the exact opposite, so that effects such as combination and interference between the radiation resistance characteristics of the antenna itself and the waves reflected by the reflector are eliminated. Therefore, there is no effect of deterioration of input/output matching characteristics due to the distance/frequency conditions between the antenna and the reflector.9 [Embodiment] Hereinafter, an embodiment will be described with reference to the drawings.

In FIG. tJ&1, the antenna 1 is a ball-shaped antenna such as a monopole or a dipole, and is arranged in a direction perpendicular to the plane of the paper.

The radio wave absorber 2 is a radio wave absorbing layer made of, for example, a tile-shaped ferrite plate or a foamed plastic plate mixed with carbon powder or carbon powder and 7-elite powder, and is arranged parallel to the direction in which the antenna 1 is arranged. .

The distance d between the antenna 1 and the radio wave absorber 2 is selected as appropriate depending on the size of the radio wave absorber 2 relative to the required degree of unidirectionality, as described below, but in general, it is It is set to half the wavelength of the highest frequency radio wave, that is, λ/2 or less.

In this figure, the opening angle a of the radio wave absorber 2 is 180° and is formed in a flat plate shape, but in FIG. 2, the opening angle a is set to 90°, for example.

The above is shown in terms of a planar arrangement, but from an elevational perspective, the above ball-shaped antenna is made into a multi-stage mower ball IA as shown in Fig. 3, or it is made into a goo ball IA, as shown in Fig. 4. When the length of the radio wave absorber 2 is shorter than the antenna 1 (dipole antenna ID) as shown in the figure, the radio wave absorber 2A for the end face is also installed at the upper and lower open ends.
, an isosceles triangular monopole IB with an isosceles triangular plate as an antenna element as shown in Figure 5, or a Guiball version of this, and a cone-shaped monopole IC or a Guiball version of this as shown in Figure 6. Configurations such as those shown below are possible.

The antenna body configured as described above forms a unidirectional directional beam through the intervention of the radio wave absorber 2, as will be described later. Rotation fulcrums are provided in the dome 10 made of a small amount of plastic, and are provided at the upper and lower positions in the direction of extension of the antenna 1 (dipole antenna ID), for example, a pongee of insulating material with the antenna output cable passed through the center 11A・
11B and the rotating pieces 12A and 12B that rotate this in a ring, the radio wave absorber 2 is attached to the lower rotating piece 1 so as to rotate around the antenna 1 (dipole antenna ID).
2B is rotated by a rotating mechanism such as a motor 13 and a belt pulley mechanism 14, as shown in FIG.
It is designed to rotate a unidirectional directional beam.

The rotation m structure of this radio wave absorber 2 is shown in Figs. 3, 5, and 7.
In the case of a configuration using a monopole and a ground plane (ground plate 3) as shown in the figure, by replacing the part of the support plate 15 in Fig. 4 with the part of the ground plane, the structure can be similarly constructed using conventional mechanism construction techniques. It is possible to configure
Further, for the sake of stable rotation of the radio wave absorber 2, the provision of a balancing weight to eliminate the unbalance of the center of gravity is the same, so no explanation is necessary.

The radio wave absorber 2 theoretically exhibits an absorption effect by itself, but due to the relationship between its thickness and absorption effect, it generally has a thin good conductor layer 2B (commonly known as a shield) on its back side. The electromagnetic wave absorber layer) is formed of, for example, a copper plate or an aluminum plate and attached thereto, so that a sufficient effect can be obtained with a relatively thin radio wave absorber layer.

In the above configuration, the opening angle α is appropriately selected depending on the directional beam width to be obtained, for example, the degree of its half-value angle, and the distance d is determined based on the relationship with the width of the radio wave absorber 2. In addition, the radio wave absorber 2
In addition to the planar shape shown in Figure 1 and the ■-shaped shape shown in Figure 2,
An appropriate concave shape such as a U-shape or C-shape may be selected depending on the beam shape to be obtained (the ground plane may be a conductive surface such as a plate or net shape).

Among the above examples, regarding the ms diagram, there are two antenna configurations with the dimensions shown in the same figure, and an antenna configuration with the same dimensions and arrangement but with seven rectors located on the surface of the radio wave absorber 2. Figures 7 and 8 show measurement data when comparing the two for a wide frequency band of 200 to 100100O.

In the figure, the output of the antenna 1 is taken out below the ground plate 3, and for the highest frequency of 100100O, the distance d and the height hl of the antenna 1 are less than half the wavelength, and the width of the radio wave absorber 2 is The height h2 of the radio wave absorber 2 is selected to be at least 2 to 3 times the distance d, and the height h2 of the radio wave absorber 2 is selected to be at least 1.4 times the height hl of the antenna 1.

Each horizontal directivity pattern shown in the characteristic comparison diagram of FIG.
This was measured at 00100O, and in the case of the antenna with the 7-rector, there is a small sub-pole left at the rear due to leakage, but apart from this, it is clearly two beams divided into left and right. .

As stated in Chapter 11 of the above-mentioned document "Very Short Wave Antenna", this is the case when the opening angle α is 180°, the horizontal direction angle is θ, the directional sensitivity is E(θ), and the electric field strength is Eo. Then, E(θ) = E osin(2!-d cosθ)
, , , , (1) λ is represented by °, and the interval d is (0,1 to 0.3)
Since it exceeds λ, the beam is divided into two, indicating that the directivity pattern is as per theory.

On the other hand, the antenna with a radio wave absorber according to the present invention similarly leaves a small sub-pole at the rear due to leakage, but apart from this, the beam is clearly one unidirectional beam.

The radio wave absorber 2 absorbs and eliminates radio waves arriving from the rear direction, and also does not reflect, combine or interfere with radio waves arriving from the front direction, so E. (θ) = E0 (cos θ - (cos θ))...
...(2) However, only the range of 90" to 270° is substituted in the brackets.

This results in a unidirectional directivity pattern that is expressed bluntly.

1. If the opening angle α is narrow as shown in Fig. 2, for example, α
= 90° configuration, E(θ) = E 0(cos 2θ-(cos2θ), as can be easily estimated from the above data.
)-(3) However, only the range of 45° to 315° is substituted in [ ].

This results in a unidirectional directivity pattern expressed by .

Next, each data shown in the characteristic comparison diagram of FIG. 8 shows that the antenna with a radio wave absorber of the present invention, the antenna alone and the antenna with a reflector, and the distance d between them are conditions under which the input/output matching characteristics are likely to be affected. Distance, i.e. set to 1001III11 shown outside parentheses, 200 to 10010
This is data of impedance Z, its resistance component R, reactance component j, and VSWR (voltage standing wave ratio) measured in the range of 0O. VSW in this data
Looking at the change in R value with respect to frequency, the value of the antenna with a radio wave absorber according to the present invention shows the smallest change, and it can be seen that its input/output matching characteristics are more or less constant compared to others. .

〔Effect of the invention〕

According to this invention, as described above, by simply arranging the radio wave absorber on the back side of the antenna, one antenna configuration for a wide frequency band can achieve unidirectional directivity and good input/output matching characteristics. In addition, the directional beam can be rotated simply by rotating the radio wave absorber, which eliminates the need for the space required to prepare several types of antennas as in the past. In addition, since the directional beam can be rotated simply by rotating the radio wave absorber, the entire structure can be made smaller and lighter, making it suitable for use in mobile or vehicle-mounted applications that require a lightweight design. It has the advantage that it can be easily provided at low cost.

[Brief explanation of the drawing]

The drawings show examples, and Figures 1, 2, and 9 are plan layout diagrams, Figures 3, 5, and 6 are elevational layout perspective views, and Figure 4 is a plan layout diagram.
The figure is a perspective half-sectional view of an elevational arrangement, and FIGS. 7 and 8 are characteristic comparison diagrams. 1... Antenna, IA... Multi-stage monopole antenna, IB... Isosceles triangular monopole antenna, IC.
... Cone-shaped mower ball antenna 2 ... Radio wave absorber,
2B...Good conductor layer 3...Grounding plate

Claims (1)

[Claims] 1. A planar or concave radio wave absorber is arranged on the back side of the antenna to form a unidirectional directional beam, and the directional beam is formed by rotating the radio wave absorber. An antenna device for wireless direction finding, characterized in that the antenna rotates. 2. An antenna device for radio direction finding according to claim 1, characterized in that the monopole antenna and the radio wave absorber are arranged on a ground plane.