RU2346365C1 - Anechoic chamber - Google Patents

Abstract

FIELD: physics; radio.

SUBSTANCE: invention relates to radio engineering and may be used to measure radar cross-section diagrams for radar target simulators. Anechoic chamber is a room with walls, floor and ceiling covered inside with radar absorbent material sheets. Anechoic chamber transverse section is a parallelogram, two sides of which form acute angle φ with vertical plane, and the other two with the horizontal one. Anechoic chamber longitudinal section is a horizontal-base trapezoid. φ angles are equal to ratio of anechoic zone diameter D to four distances from anechoic zone outer surface to the closest inner surface of anechoic chamber L or exceed this value (φ≥D/4L).

EFFECT: reduced diagram measurement error and reduced chamber cost.

3 dwg

Description

The invention relates to anechoic chambers (BEC), which are designed to measure the patterns of the effective scattering surface (EPR) of radar targets on models and antenna patterns. The primary purpose of the invention is the measurement of EPR diagrams of models of radar targets.

Known BEC, which is made in the form of a rectangular parallelepiped, the inner surface of which is covered with awl-shaped radar absorbing material (M.Yu. Mintsmakher, V.A. Torgovanov. Anechoic chambers Microwave. Radio and Communications, 1982, p. 39 , Fig. 2.3).

When measuring the EPR diagrams of target models (MCs) in such a chamber and rotating them in the horizontal plane, at observation angles of ± 45 ° from their longitudinal axis, large measurement errors arise. The side lobes of the EPR diagram of cylindrical objects, at viewing angles of ± 45 ° to their longitudinal axis of the objects, are less by 20-30 dB EPR of the ends and side surface. The radiation of the measuring antenna (IA) is reflected specularly from the generatrix of the cylindrical surface at angles of 45 ° in the direction of the perpendicular to the side wall of the BEC. After that, the radiation returns to the side surface of the cylinder and is reflected from it towards the receiving antenna in the form of interference, where it is added to the reflection of the edges of the cylinder, which leads to errors in the measurement of side radiation.

A camera with longitudinal corrugations on the side walls and transverse at the end walls was adopted as a prototype of the invention (M.Yu. Mintsmakher, V.A. Torgovanov, Anechoic chambers Microwave. M., "Radio and communications", 1982, p. 40, Fig. .2.5). It is known that corrugations made in the form of a blunt wedge reflect in the opposite direction the first Fresnel zone, which reflects like a strip. Corrugations, in comparison with a flat wall, in the opposite direction reflect less by 5-10 dB. Such a decrease in wall reflections reduces the EPR measurement errors of the side lobes of the EPR diagrams of the cylinders, but not enough when the dimensions of the cylinder are commensurate with the diameter of the anechoic zone (BZ) of the BEC.

The technical result of the invention is to reduce the measurement errors of the EPR diagrams of models of radar targets at angles of ± 45 ° to their longitudinal axis and to reduce the cost of the camera through the use of low-quality RPM with a reflection coefficient of minus 10-15 dB.

The invention is illustrated by drawings of figures 1, 2 and 3.

Figure 1 shows the cross section of the camera, in the plane of which is the center of the anechoic zone BEC, which is made in the form of a parallelogram, the opposite sides of the parallelogram are at an acute angle to the vertical and horizontal plane, and the measured target model (MC) located in the horizontal plane under angle of 45 ° to the electrical axis of the IA.

Figure 2 shows the axial longitudinal section of the camera in the horizontal plane with a measuring antenna (IA) and the measured MC, the longitudinal axis of which is at an angle of 45 ° to the longitudinal axis of the BEC.

Figure 3 shows the axial longitudinal section of the camera in a vertical plane, made in the form of a trapezoid with horizontal bases, the sides of the trapezoid are at an acute angle to the vertical plane;

φ is the acute angle formed by the surfaces of the walls, ceiling and floor of the BEC and similar surfaces of the rectangular parallelepiped described around the camera;

D is the diameter of the anechoic zone (BS) or the maximum size of the measured model;

L is the distance from the BS to the nearest inner surface of the chamber, to which the MC reflects the radiation of the IA;

BZ - anechoic zone BEC;

IA - measuring antenna;

MC - a model of the goal.

Positions 1, 2, 3, and 4 denote radiation beams that are specularly reflected from the MC and the inner surface of the BEC. Beam 1 - re-reflection of IA emissions from the MC to the side wall. Beam 2 - reflection from the first side wall to the second side wall. Beam 3 - reflection from the second side wall to the first. Beam 4 - second reflection from the first side wall to the ceiling.

An anechoic chamber (BEC) is made in the form of a closed room, the internal walls, the floor and ceiling of which are flat and covered with a flat radar absorbing material.

The BEC cross section is made in the form of a parallelogram, one parallel side of which is at an acute angle φ to the vertical plane, and the other two to the horizontal plane. The longitudinal section of the BEC is made in the form of a trapezoid with a horizontal base. BEC is inscribed in a rectangular box. The angles φ are equal to or greater than the ratio of the diameter D of the anechoic zone to four distances L from the outer surface of the anechoic zone to the nearest inner surface of the BEC (φ≥D / 4L).

In one end wall of the chamber along the longitudinal axis of the BEC there is a window designed for a measuring antenna (IA).

The proposed camera was made in the form of a desktop BEC, 2 m long and 1 m wide. The cross section was made in the form of a rhombus, and the longitudinal section in the form of an equal-sided trapezoid (Figs. 1 and 3). The diameter of the base zone is 0.2 m. The camera was irradiated with a 2 cm IA wavelength range. The walls, ceiling, floor of the BEC are covered with a multilayer plane-layered RPM with a reflection coefficient of minus 15 dB.

The chamber was tested using a cylinder 0.2 m long and 0.1 m in diameter. For multiple measurements of the same cylinder with a shift of its center of mass by a quarter wavelength along and across the electrical axis of the antenna, the side lobes of the EPR diagram, with the cylinder axis at an angle of 45 °, reproduced exactly the same. This fact indicates the absence of interference reflections caused by reflections from the walls of the chamber and cylinder.

With this position of the cylinder in the BZ BEC, beam 1, which is mirrored from the lateral cylindrical surface, hits one side wall of the chamber (beam 2) and is mirrored from it towards the opposite side wall (beam 3), after reflection of beam 3 from the second side wall beam 3 is again reflected from the first side wall, reflected from it (beam 4) and hits the BEC ceiling. One can trace the further fate of the rays that do not fall into the BR. At each reflection, the rays are attenuated by 15 dB, repeatedly reflected from the walls, floor and ceiling of the BEC and absorbed by them (figure 1).

The technical result of the invention is to reduce the measurement errors of the EPR diagrams of models of radar targets at angles of ± 45 ° to their longitudinal axis and to reduce the cost of the camera through the use of RPM with a reflection coefficient of minus 10-15 dB.

Claims (1)

An anechoic chamber (BEC) made in the form of an enclosed space, the inner walls, the floor and ceiling of which are flat and covered with radar absorbing material (RPM), characterized in that the BEC walls are covered with flat RPM, and the BEC cross-section is made in the form of a parallelogram, one parallel side which are at an acute angle φ to the vertical plane, and the other two to the horizontal plane, the longitudinal section is made in the form of a trapezoid with a horizontal base, and the BEC is inscribed in a rectangular parallelepiped, the angles φ are equal or more, the ratio of the diameter D of the anechoic zone to four distances L from the outer surface of the anechoic zone to the nearest inner surface of the BEC (φ≥D / 4L).

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