RU2426203C1 - Axysymmetric mirror antenna (versions) - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: unclosed cylindrical screen is arranged along axysymmetric mirror to shield thermal noises received by irradiator from earth surface. Screen with coaxial taper geometry may be used, cone vertex being located behind mirror.

EFFECT: lower weight and dimensions, higher-Q-factor.

2 cl, 3 dwg

Description

The invention is intended for use in the composition of radio devices for satellite radio systems in the microwave ranges.

To increase the noise immunity, a cylindrical screen located at the edge of the mirror is used for an axisymmetric antenna made according to a single-mirror scheme or a two-mirror scheme [1]. Such screens reduce the level of the side lobes of the radiation pattern, thereby reducing the noise temperature of the mirror antennas [2]. The profile of the mirror represents a paraboloid of revolution with a coaxial irradiating device. As an irradiating device, either a separate irradiator or an irradiator with a counter-reflector can be used.

The technical result of the invention is to reduce the overall dimensions of the screen while maintaining a low noise temperature and increased noise figure of merit of the axisymmetric mirror antenna.

According to the first variant, a cylindrical screen 2-3-7-6 is mounted on an axisymmetric mirror along the edge 1-3-7 around the edge of the mirror edge so as to shield the irradiating device, for example, in the form of a horn 4 from receiving thermal radiation from the earth's surface 8- 11 (figure 1). The length of the perimeter of the edge of the mirror, along which the screen is installed with a length (L _e ), curve 12-15-13 (figure 2), is determined by the expression

where R _a is the radius of the main mirror 14-15 (figure 2), f is the focal length of the main mirror 4-5 (figure 1), r is the depth of the main mirror and α is the angle of inclination of the antenna to the horizon 3-4-5 ( figure 1). The depth of the screen 6-7 is selected depending on the required level of reduction in noise temperature by shielding the irradiating device from the thermal radiation of the earth's surface 9-10 (figure 1).

An open cylindrical screen 2-3-7-6, mounted on the upper edge of the mirror 1-3, for example, on a single-mirror axisymmetric antenna, has lower weight and size parameters compared to a closed one, nevertheless it also effectively reduces the reception of thermal radiation of the earth’s surface 8 -11 while maintaining a screening angle of 9-4-10 (figure 1). The part of the screen that complements it to a closed screen shields the antenna from thermal noise of the atmosphere, which is significantly less than the thermal noise of the earth’s surface, and therefore does not make a significant contribution to the reduction of noise temperature. Thus, metal consumption, wind load and open screen weight are reduced compared to a cylindrical screen closed at the edge of the mirror while maintaining a low total noise temperature of the antenna.

According to the second variant, a coaxial conical screen 17-18-21-22 with an apex of the cone 20 located behind the mirror can also be used open in the upper part of the mirror 16-18 (Fig. 3). The angle of the conical surface of the screen 16-20-22 (2θ) is determined from the formula for calculating the screening angle 21-19-22 (β)

- угол раскрыва основного зеркала 16-19-21, R_э - глубина экрана 22-21 (фиг.3). Выбираемый угол раствора конической поверхности экрана 16-20-22 (2θ) соответствует максимальному углу экранирования теплового излучения 21-19-22 (β) земной поверхности 23-24 при фиксированной глубине экрана 22-21 (R_э) (фиг.3). Применение такого экрана позволяет уменьшить массогабаритные параметры и ветровую нагрузку на антенну.Where

- the opening angle of the main mirror 16-19-21, R _e - the depth of the screen 22-21 (figure 3). The selected angle of the conical surface of the screen 16-20-22 (2θ) corresponds to the maximum screening angle of thermal radiation 21-19-22 (β) of the earth's surface 23-24 at a fixed screen depth 22-21 (R _e ) (Fig.3). The use of such a screen allows to reduce weight and size parameters and the wind load on the antenna.

The invention is illustrated by drawings, in which:

figure 1 - open cylindrical screen mounted on the edge of the mirror of a single-mirror antenna in a vertical plane of section;

figure 2 - open cylindrical screen mounted along the edge of the mirror, view from the side of the focus of the mirror;

figure 3 - open coaxial conical screen in the vertical plane of the section.

LITERATURE

1. Eisenberg G.Z. and other VHF antennas. Ed. G.Z. Eisenberg. In 2 hours, part 1. M., "Communication", 1977, p.353.

2. Somov A.M. The effect of cylindrical screens on the noise temperature of mirror antennas. "Radio Engineering", 1983, No. 3 p. 74-76.

Claims (2)

1. Mirror antenna, consisting of an axisymmetric mirror, an irradiating device, its fastening elements and a cylindrical screen, a coaxial mirror located along its edge, characterized in that the screen is not closed on the part of the perimeter of the edge. 2. A mirror antenna consisting of an axisymmetric mirror, an irradiating device, its mounting elements and a screen, a coaxial mirror located along its edge, characterized in that the screen has a coaxial conical shape with a cone apex located behind the mirror and is not closed on the part of the perimeter the edges of the mirror.

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