JPS63149906A - Antenna system for searching direction of radio wave with radio wave absorbing body - Google Patents

Abstract

PURPOSE:To prevent an input/output matching characteristic from being deteriorated over a wide frequency band by arranging a radio wave absorbing body at the rear side of the antenna. CONSTITUTION:Plural unidirectional beams are arranged by arranging unidirectional antennas whose unidirectional directivity is formed through the arrangement of a flat or recessed radio wave absorbing body 2 at the rear face of the antenna 1 in a ring or a sector shape. Since the radiation characteristic at the rear face side is erased, the action such as synthesis/ interference with the reflected wave by a reflector and the radiation characteristic of the antenna 1 itself does not exist at all. Thus, the deterioration in the input/output matching characteristic due to the frequency condition/distance between the antenna and reflecting plate is not caused.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an antenna device for radio direction finding in which a plurality of antenna groups having unidirectional directivity are arranged in a circumferential ring.

[Conventional technology]

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For example, a unidirectional antenna used for 1-15 dte + is a UHF/VHF HF equipment with 7 rectors (reflectors) placed on the back side of the antenna. ” [first edition published by Corona Publishing, July 1955], and in this way.
An antenna with a rectifier formed for wireless direction finding, for example, an antenna in which the antennas are arranged in a circular pattern to form a plurality of unidirectional beams, and each antenna is sequentially switched and scanned to obtain a direction finding signal. equipment, i.e.
The one with "lLLENWEBER type" is rlRE C0N.
VENTION RECORD, PART 5 VO
L, 3J Magazine C, published in 1955].

Mainly, 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. It is well known by

[Problem that the invention seeks to solve]

The above-mentioned antenna with a 7-reflector has the advantage of being able to vary the directivity depending on the distance between the antenna and the 7-rector and the opening angle of the reflector. In addition to creating an extra sub-pole by increasing the size, the SWR (voltage standing wave ratio) value changes significantly and the input/output matching characteristics deteriorate, making it difficult to maintain good unidirectionality across a wide frequency band. In the case of wide frequency band direction finding applications that require input/output characteristics, it is necessary to prepare antennas with several types of structures, select the appropriate one, and rearrange them. The problem with this is that it is not suitable for practical use in terms of the space it occupies and the workability, and it is hoped that an alternative antenna will emerge.

[Means for solving problems]

The present invention uses an extremely simple method of arranging unidirectional antennas in a ring shape by arranging radio wave absorbers in place of the above-mentioned 7-rector. The above-mentioned problems can be solved by providing a radio direction finding antenna device having a directional beam group and input/output matching characteristics.

[For production]

Unlike the conventional reflection synthesis means that goes up to the 7-rector, the absorption and canceling means on the back side is used to eliminate the radiation resistance characteristics of the antenna itself, which is the exact opposite, so the combination and interference with the waves reflected by the 7-rector and the radiation resistance characteristics of the antenna itself are eliminated. Therefore, there is no effect such as deterioration of input/output matching characteristics due to distance/frequency conditions between the antenna and the reflector.

〔Example〕

Examples will be described below with reference to the drawings.

In FIG. 1, an antenna 1 is, for example, a ball-shaped antenna such as a monoball 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 ferrite powder, and is arranged parallel to the direction in which the antenna 1 is arranged.

The spacing d between the antenna 1 and the radio wave absorber 2 is appropriately selected depending on the size of the radio wave absorber 2 relative to the required degree of unidirectionality, as described later, but in general, 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.

In addition, the single unidirectional antenna shown in FIGS.
Figures 3 and 4 show antenna devices for wireless direction finding in which antennas arranged at intervals are configured, and the signals obtained by sequentially switching and scanning the outputs of each antenna have directional components. The detection signal is configured to be obtained as a detection signal.

Further, FIG. 5 shows a configuration using a common radio wave absorber 2C in which the rear distances D1 and D2 of the radio wave absorber 2 shown in FIG. 4 are eliminated, and each adjacent radio wave absorber is formed in common. The above is
This is shown as a planar arrangement, but from an elevational perspective, the above ball-shaped antenna is made into a multi-stage monoball IA as shown in Fig. 6, and radio waves are transmitted to antenna 1 (dipole antenna ID) as shown in the figure. For cases where the length of the absorber 2 is short, end face radio wave absorbers 2A are added to the upper and lower open ends of the absorber 2, and as shown in Figure 8, an isosceles triangle plate is used as an antenna element. Monoball IB or its Guiball version, or cone-shaped Monoball IC or its Guigor version as shown in Figure 9, can be used as shown in Figures 3 and 4 or Figure 10 below. Thus, it is possible to arrange the antennas in a circumferential ring shape or a fan shape to form a wireless direction finding antenna device.

In FIG. 10, a part of the circumferential annular arrangement of FIGS. 3 to 5 is removed to form a fan-shaped arrangement.

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. For example, the electromagnetic wave absorber layer is formed of a copper plate or an aluminum plate and is attached to the electromagnetic wave absorber layer, so that a sufficient effect can be obtained with a relatively thin radio wave absorber layer. The beam width of the beam, for example, should be selected appropriately depending on the degree of its half-value angle. It may be selected appropriately depending on the beam formation. 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 a C-shape may be selected depending on the beam shape to be obtained, and the ground plane may be a conductive surface such as a plate or net shape.

Among the above embodiments, the one in FIG. 8 has an antenna configuration 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. Figure 11 shows the measurement data when comparing the 200~100100O wide frequency band.
This is shown in FIG.

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.

For each horizontal directivity pattern shown in the characteristic comparison diagram of FIG.
This was measured at 0100O, 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 separated into left and right. .

As stated in Chapter 11 of the above-mentioned document ``Very Short Wave Antenna'', this is the case where the opening angle α is 180°, the horizontal direction angle is θ, the directional sensitivity is E(θ), and the electric field strength is E. Then, E(θ)-E osin(2!-d cosθ)...
...(1) λ, and the opening distance d is (0,1~0.3)λ
Since it exceeds , the beam is divided into two, indicating that the directivity pattern is in accordance with the 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) = E o (cos θ - (: cos θ)
) −・・−・−(2) However, numbers in [ ] are 90'
Substitute only the ~270° range.

This results in a unidirectional directivity pattern expressed by .

Also, if the opening angle is narrow as shown in Figure 2, for example, α=9
In the 0° configuration, as can be easily deduced from the above data, E(θ) = E 0(cos 2θ−Ccos2θ))
-(3) However, only the range of 45° to 315° should be substituted in [ ].

This results in a unidirectional directivity pattern expressed by .

Next, each data shown in the characteristic comparison diagram of FIG.
The distance d between the antenna with a rectifier and the antenna is set to a distance where the input/output matching characteristics are easily affected, that is, 100 ma+ shown outside the parentheses.
This is data of impedance Z, its resistance component R, reactance component j, and VSWR (voltage standing wave ratio) measured in the range of . V SW 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 the pond. .

〔Effect of the invention〕

According to the present invention, as described above, a directional antenna has unidirectionality and good input/output matching characteristics with one antenna configuration over a wide frequency band by simply placing a radio wave absorber on the back side of the antenna. Because it can be configured as a conventional antenna, there is no need to take up space to prepare several types of antennas, and the antenna is small and lightweight, so it needs to be portable or can be mounted on a car. In addition to being able to easily and inexpensively provide a radio direction finding antenna device that is suitable for various applications, in the case of a circularly arranged antenna device, the radio wave absorber on the back side of one antenna and the radio wave absorber on the opposite side of the antenna can be easily and inexpensively provided. Since the absorber is arranged as a double radio wave absorber, it has the advantage of being able to effectively eliminate the generation of a sub-pole beam due to leakage from the rear side.

[Brief explanation of the drawing]

The drawings show examples, and FIGS. 1 to 5 and 10 are plan layout diagrams, FIGS. 6 to 9 are elevational layout diagrams, and FIGS. 11 and 10 are plan layout diagrams.
FIG. 12 is a characteristic comparison diagram. 1... Antenna, IA... Multi-stage monoball antenna, IB... Isosceles triangular monoball antenna, IC.
... Cone-shaped monoball antenna 2 ... Radio wave absorber,
2B...Good conductor layer 3...Ground plate 1 time i Threat 2 Figure 6 Figure extension Waguchi Blue 8 times Paralysis qw3 Small 10 times Naka H times

Claims (1)

[Claims] 1. By arranging unidirectional antennas in which a planar or concave radio wave absorber is arranged on the back side of the antenna to form unidirectional directivity in a circular or fan shape. An antenna device for wireless direction finding characterized by arranging a plurality of unidirectional beams. 2. The antenna device according to claim 1, characterized in that the antenna made of a monoball and the radio wave absorber are arranged on a ground plane.