RU2371820C2 - Wideband omnidirectional antenna with varied polarisation - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: antenna comprises the following components located in cylindrical fairing - exciter of TEM-wave, disk and cone that create a truncated conical opening. Fairing has a cavity, in which replaceable multi-layer polariser may be installed. Layers of polariser consist of inclined parallel conductors with period of inclination angle variation of 22.5 degrees in each subsequent layer. Position of cone relative to disk is aligned by dielectric ring installed in opening and dielectric thrust of fairing cover introduced in cone. On both sides of conical opening along perimetre of edges there are absorbing screens with height of 2λ_c and 3λ_c near disk and cone accordingly.

EFFECT: provision of antenna operation in wide frequency band at any polarisation without variation of antenna structure.

4 cl, 4 dwg

Description

The invention relates to the field of radio engineering, in particular to microwave antennas, and can be used in broadband communication systems.

Known omnidirectional microwave antennas (R. Kuhn. Microwave antennas. L., Shipbuilding, 1967, p. 257-258).

These include biconical horns and discus antennas. They are excited by TEM or H ₀₁ waves, and, accordingly, the antenna operates on vertical or horizontal polarization. With simultaneous excitation of the TEM antenna and H ₀₁ waves with an appropriate phase shift, it is possible to obtain an elliptical polarization.

In the described antennas, in order to be able to work at different polarizations, it is necessary to change the design of the antenna. In addition, in a disk-cone antenna, where the disk is smaller than the diameter of the base of the cone, with increasing frequency, the maximum radiation pattern deviates towards the generatrix of the cone, and in the biconical horn it is directed horizontally, which can lead to deformation of the radiation pattern during ground use. When the antenna turns the cone up, the feeder obscures the opening due to the fact that the antenna is supplied from the cone side.

Omnidirectional biconical horn antennas are known (M.S. Zhuk, Yu.B. Molochkov. Design of antenna-feeder devices. M., L., Energia, 1966, p. 525-528). They are excited by a circular waveguide with a wave of H ₀₁ (vertical polarization) or with a wave of H ₀₁ (horizontal polarization). When using round waveguides as pathogens, the operating frequency range of the antenna is limited. The maximum antenna pattern is also directed horizontally. In addition, the antenna needs protection from environmental influences.

Known biconical horn antenna excited by a circular waveguide with the wave ₁₁ of TE (Uenakada Katsuaki, Yasunaga Keiichi An omni -.. Directional biconical horn antenna excited by the TE ₁₁ mode in a circular waveguide «HXK gidzyutsu Kenko, NHK Techn J..», 1972 , 24, No. 3, p.149-159 (Japanese; res. Eng.). - RJ Radiotehnika, 24B, 1972, No. 11, p.6, 11B48), adopted as a prototype, as the closest in technical essence to the claimed object.

, a горизонтальная выбором расстояния

, а также благодаря размещению в радиальной линии проводящих штырей. Экспериментальное значение коэффициента стоячей волны по напряжению (КСВН) в диапазоне частот не превышает 1,5, а при размещении на верхней пластине радиальной линии настроечного контура, состоящего из фторопластовой пластинки и металлического кольца, КСВН снижается до 1,2.The antenna can operate on vertical and horizontal polarization in the microwave range. Vertical polarization is provided by the choice of distance between parallel conductive plates

, a horizontal choice of distance

, and also due to the placement of conductive pins in the radial line. The experimental value of the standing wave coefficient by voltage (VSWR) in the frequency range does not exceed 1.5, and when placed on the upper plate of the radial line of the tuning circuit, consisting of a fluoroplastic plate and a metal ring, the VSWR decreases to 1.2.

The antenna does not provide the ability to work in a wide frequency band due to the presence of resonant elements, such as pins, as well as a waveguide exciter, and works in the frequency range with an overlap of no more than 1.1 (11.5 ÷ 12.5 GHz). In addition, when changing polarization, the design of the antenna is changed.

The objective of the invention is the operation of the antenna in a wide frequency band at any polarization without changing the design.

The solution to this problem is achieved by the fact that in an omnidirectional antenna containing a TEM wave exciter located in a cylindrical cowl, a disk and a cone forming a truncated conical opening, the antenna exciter is located on the side of the disk whose diameter is (4 ÷ 5) λ _s , where λ _c is the average wavelength of the range, and exceeds 1.2–1.25 times the diameter of the base of the cone, the angle at the apex of which is 100–110 degrees, and the wall of a cowl made of a dielectric with a dielectric constant ε≤1,4 has cavity in which m Jet be positioned removable multilayered polarizer.

The polarizer layers consist of inclined parallel conductors with a period of change of the inclination angle of 22.5 degrees in each subsequent layer from the first layer on the pathogen side, the conductors of which are perpendicular to the vector E. The layers are arranged concentrically and fixed at a distance of 0.15λ _from each other by the same dielectric material from which the fairing is made.

и введенным в конус диэлектрическим упором крышки обтекателя.The position of the cone relative to the disk is centered by a thick dielectric ring installed in the aperture

and inserted into the cone dielectric focus of the cowl cover.

On both sides of the conical aperture along the perimeter of the edges, absorbing screens with a height of 2λ _s and 3λ _s at the disk and base of the cone, respectively, are introduced.

The invention is illustrated by drawings:

figure 1 shows a General view of the antenna;

figure 2 shows a General view of a five-layer polarizer;

figure 3 shows the experimental radiation patterns in the horizontal plane in the frequency range f _n ÷ 2.25 f _n (f _n - the lower frequency of the range);

figure 4 shows the experimental radiation patterns in the vertical plane in the frequency range f _n ÷ 2.25 f _n

Broadband omnidirectional antenna with variable polarization (figure 1) contains a coaxial pathogen 1, disk 2, cone 3 installed in the dielectric fairing 4.

Coaxial pathogen 1 is made on a coaxial cable RK 50-2-29 or RK 50-2-27 with connector 13, SR 50-726 FV (VRO 364.049 TU). The outer sheath of the cable is installed in the hole of the disk 2 and soldered to it along the perimeter of the hole, and the central conductor is soldered to the top of the cone 3 so that the gap between the disk and the top of the cone is not more than 0.02λ _s .

The disk 2 is made with a diameter (4 ÷ 5) λ _s of metal or a metallized dielectric and is mounted on the base 11. In front of the disk 2, an absorbing screen 10 of a cylindrical shape that has a reflection coefficient of not more than 10%, for example, from material B2 ( F3) TU 38-105.486-79.

The cone 3 is made of the same sheet metal as the disk 2, and has an angle at the apex of 106 degrees, and the diameter of the base of the cone 3 is 1.2-1.25 times smaller than the diameter of the disk 2.

Fairing 4 is installed on the base 11 and is fixed by flange 12 and screws. The outer diameter of the fairing is 6.0 λ _s . The wall of the fairing consists of two layers with a thickness of 0.2-0.25 λ _s , forming a cavity (Fig. 1) into which a multilayer polarizer can be inserted 5. The width of the cavity should be at least the thickness of the polarizer 5. The implementation of the wall of the fairing with a two-layer increases rigidity design when using an antenna without a polarizer. The dielectric fairing 4 is made of a foamed dielectric with ε≤1,4, for example PEN-I-0.2 TU 6-05-88. The material of the fairing and the thickness of the layers of its wall are selected from the conditions of the necessary structural strength and minimal reflections with minimal losses in energy absorption.

существенного искажения диаграммы направленности слабонаправленной антенны не происходит. Расчетное значение коэффициента отражения определялось по формуле [1]It was experimentally established on wall samples that with a reflection coefficient

Significant distortion of the radiation pattern of a weakly directed antenna does not occur. The calculated value of the reflection coefficient was determined by the formula [1]

, где

where

;

, d_c - толщина слоев стенки обтекателя, образующих полость.

;

, d _c is the thickness of the layers of the wall of the fairing forming the cavity.

The upper part of the fairing (cover 8) can be performed separately or as a unit with a radiolucent wall. The cover 8 can be made with a conical emphasis 7 having a conical and cylindrical part. An absorbing screen 9, similar to the screen 10 mentioned above, is fixed on the cylindrical part.

. Диаметр кольца 6 может быть подобран экспериментально для улучшения согласования антенны [2]. Кольцо может быть вклеено в рупорном коническом раскрыве антенны эпоксидным клеем для обеспечения жесткости конструкции.The dielectric stop 7 enters the cone 3 and together with the ring 6 fixes the concentric position of the cone 3 relative to the disk 2. The ring 6 is made of the same foamy dielectric as the cowl and has a wall thickness

. The diameter of the ring 6 can be experimentally selected to improve antenna matching [2]. The ring can be glued into the horn conical aperture of the antenna with epoxy glue to provide structural rigidity.

The outer surface of the fairing is covered with one layer of fabric with ε≤3.5 and a thickness of not more than 0.01λ _s , which protects the fairing from moisture absorption in the foam structure, for example, AzTS TU-17-21-3-3-3-79 or type F4-D-E01- And TU301-05-422-89 (fiberglass E01 GOST 8481-57, coated with fluoroplastic from the outside). The fabric is fixed on the outer surface of the fairing during foaming by the method described in A.S. No. 1053691 (USSR), without the use of an adhesive layer.

The multilayer polarizer 5 is installed in the cavity of the wall of the fairing 4 if necessary, change the polarization of the antenna.

Figure 2 shows the five-layer horizontal polarizer applied in the antenna. The polarizer consists of five layers of concentrically arranged wire structures 15, separated by a dielectric 16 of the same type as the fairing wall. The structures can also be made on a fluoroplastic reinforced film F4 MBSF-2, TU 6-05-041-649-83. Each structure is etched and represents parallel metallized strips with a width of (0.015-0.02) λ _s , the distance between which is 0.1 λ _s , and the distance between the concentric layers is 0.15 λ _s .

The first structure from the side of the pathogen 1 has strips parallel to the disk 2, the second is rotated by 22.5 degrees, the third is 45 degrees, the fourth is 67.5 degrees, and the fifth structure has strips perpendicular to the disk 2. Ring structures at the bases the cylinders can be additionally fixed with flat textolite rings using epoxy glue, and lap glued over the forming after processing. As strips in the polarizers, as already mentioned, wire conductors can be used, and concentric structures can be separated not by a solid dielectric, but by separate strips along the generatrices of the cylinders.

Shown in figure 2, the polarizer is used to convert vertical polarization to horizontal.

To obtain an oblique polarization of the antenna, a three-layer polarizer is used, ending with a structure of conductive strips inclined at an angle of 45 degrees.

In both cases, the outer diameters of the polarizers must be equal to the inner diameter of the outer layer of the wall of the fairing for its unambiguous fixation in the cavity of the wall.

The antenna works as follows.

The formation of a diagram with vertical polarization is realized without a polarizer.

When microwave energy is applied to the pathogen 1, the conical horn opening formed by the disk 2 and the cone 3 forms an omnidirectional pattern in the horizontal plane, and a directivity pattern in the vertical plane, which is determined by the size of the generatrix of the truncated cone of the annular aperture. A dielectric ring 6 is installed in the path of the energy emitted by the pathogen, which reflects part of the energy, approximately 0.5%, and the rest of the energy, passing through the dielectric wall of the fairing, is formed in the form of a circular radiation pattern in the horizontal plane and a directional diagram in the vertical plane. Since the pathogen 1 forms a TEM wave, the polarization of the antenna is vertical. Broadband is provided by coaxial washing of the antenna, which does not have a critical wavelength, and an increased angle at the apex of the cone 3 to 100 or more degrees.

When forming the antenna radiation pattern in the vertical plane, especially with small openings, the radiation pattern is distorted due to the annular and conical aperture [3]. These distortions are eliminated by an absorbing screen 9, which reduces the mutual influence of diametric radiation patterns in elevation, and the screen 10 absorbs reflected energy from the wall of the fairing and structural elements.

Due to the conical aperture, the maximum of the radiation pattern is rejected, since it is directed approximately normal to the generatrix of the truncated conical aperture.

If necessary, change the polarization of the antenna in the cavity of the fairing 4 is installed polarizer 5.

The operation of the antenna on horizontal polarization provides a five-layer polarizer (figure 2). The conductors of the first layer of the polarizer are normal to the vector E, and therefore cross-polarization component is filtered. After passing through the second polarizer layer, the normal component of the vector E rotates by 22.5 degrees. After passing through the third layer of parallel conductors, the normal component of the vector E rotates another 22.5 degrees and the vector E is deflected 45 degrees relative to the vertical polarization. After microwave energy passes through the fourth layer, the normal component of the vector E to the conductors rotates by 67.5 degrees, and then after the vertical conductors of the fifth layer pass, the vector E is horizontal, and the antenna operates on horizontal polarization.

When installing a polarizer with three layers, the antenna operates on an inclined polarization with an angle of inclination of the vector E of 45 degrees.

An antenna layout was made at the enterprise and design documentation was developed. An experimental model of the antenna in the frequency band with an overlap of 2.25 was studied.

Figure 3 shows the experimental radiation patterns of the antenna, measured in the horizontal plane at frequencies f _n , 1.5 f _n , 2f _n , 2.25 f _n - without a polarizer (dashed line — vertical polarization) and with a five-layer polarizer (solid line - horizontal polarization). As a result of measurements, it was found that the maximum irregularity of the radiation pattern in the horizontal plane at individual frequencies is not more than 3.0 dB.

Figure 4 shows the experimental radiation patterns of the antenna in one of the sections of the vertical plane at frequencies f _n , 1.5 f _n , 2.25 f _n without a polarizer (dashed line — vertical polarization) and with a five-layer polarizer (solid line — horizontal polarization) ) It was found that the maximum radiation pattern is deviated from the horizon by approximately 20-25 degrees.

The measured gain at the maximum of the azimuthal radiation pattern was in the range from 3 to 6.3 dB with the width of the radiation pattern in the vertical plane from 30 to 57 degrees at minus 3 dB in the frequency range with an overlap of 2.25.

The measured standing wave coefficient is not more than 2.0 at individual frequencies of the range with an overlap of 2.25.

The proposed technical solution ensures the operation of the antenna in the frequency band with an overlap of more than 2 times compared with the prototype, allows you to change the polarization of the antenna without changing its design, and also protects the antenna from the effects of climatic factors on its parameters.

Literature

1. G.T. Markov, A.F. Chaplin. Microwave Scanning Antenna Systems. T.1, M., Soviet Radio, 1966, p. 494.

2. V.A. Kaplun. Microwave Fairings M., Soviet Radio, 1974, p. 62-69.

3. J.D. Feld, L.S. Benenson. Antenna feeder devices. Part 2, t.2, M., VVIA them. Zhukovsky, 1959, p. 154.

Claims (4)

1. Broadband omnidirectional antenna with variable polarization, characterized in that it has a TEM wave exciter located in the protective cowl, a disk and a cone forming a truncated conical opening, while the TEM wave exciter is located on the side of the disk, the diameter of which is (4 ÷ 5) λ _s , where λ _s is the average wavelength of the range and exceeds 1.2–1.25 times the diameter of the base of the cone, the angle at the apex of the cone is 100–110 °, and the wall of a cowl made of a dielectric with a dielectric constant of the material ε≤1,4, has n a cavity with the possibility of placing a replaceable multilayer polarizer in it. 2. The antenna according to claim 1, characterized in that the polarizer layers are made of inclined parallel conductors with a period of change of the inclination angle of 22.5 ° in each subsequent layer from the first layer on the pathogen side, the conductors of which are perpendicular to the vector E, the layers being arranged concentrically and fixed at a distance of 0.15 λ _from each other by the same dielectric material from which the fairing is made. 3. The antenna according to claim 1, characterized in that the position of the cone relative to the disk is centered by a thick dielectric ring installed in the aperture

and inserted into the cone dielectric focus of the cowl cover. 4. The antenna according to claim 1, characterized in that on both sides of the conical aperture of the antenna along the perimeter of the edges, absorbing screens are introduced with a height of 2λ _s and 3λ _s at the disk and base of the cone, respectively.

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