RU2772671C1 - Radiotransparent fairing - Google Patents

Abstract

FIELD: antennas.

SUBSTANCE: invention relates to antenna equipment, in particular, to radiotransparent fairings of antenna equipment. The technical result is achieved by the fact that in a radiotransparent fairing made with a single-layer structure of a curvilinear wall made of a dielectric material, the optimal thickness d of the wall of the fairing intended for work in a wide range of values of the angle of incidence θ in various areas of the fairing from the minimum value θ_min to the maximum value θ_max is calculated by the equation:

wherein n=1, 2, … is an integer, the order of the half-wave wall; λ is the length of the radio wave in free space (air); ε is the permittivity of the material; r_min and r_max are Fresnel coefficients.

EFFECT: improvement in the radio technical characteristics of a fairing with a single-layer wall structure in a wide range of values of the angle of incidence of radio waves on the wall of the fairing.

1 cl, 2 dwg, 1 tbl

Description

Technical field

The invention relates to radio-transparent radomes of antenna devices and can be used in the field of mainly aviation and rocket technology, in relation to the construction of antenna radomes with radio-transparent shells.

State of the art

An antenna radome is known (RF patent No. 2697516, class H01Q 1/42, publ. 2019), including a single-layer cone-shaped shell made of fiberglass with a dielectric constant of 3.2-4.2. The wall size is based on the average value of the angle of incidence of radio waves on the fairing wall.

The disadvantage of this solution is the fact that to optimize the wall, the average value of the angle of incidence ϑ _cp and the corresponding wall thickness are used, which does not accurately determine the optimal wall thickness that provides the best radio performance of the fairing over the entire operating range of angle of incidence from the minimum value ϑ _min to the maximum ϑ value _max .

It is known (Antenna fairings. Edited by A.N. Shpuntov, M.: Soviet radio, 1950. 264 s) that the best conditions for the passage of radio waves through the fairing wall, the best radio performance of the "antenna-radome" system are observed for half-wave walls as a result electrodynamic matching of the parameters of the incident radio wave and the characteristics of the fairing wall. For such walls, the formula for the electrical wall thickness ϕ is valid:

where d is the wall thickness; λ is the length of the radio wave in free space (air); ε is the dielectric constant of the material.

For half-wave walls, in the case of using an ideal dielectric as the fairing material (dielectric loss tangent tan δ=0), the losses and reflection of the electromagnetic energy of radio waves are equal to 0, which ensures the best radio performance of the fairing. For real materials (dielectric loss tangent tan δ>0), the losses and reflection of electromagnetic energy of radio waves increase somewhat due to thermal losses in the wall material and the impossibility, in this case, of complete suppression of reflection.

The variable angle of incidence of radio waves on the fairing wall in its different zones requires, according to formula (1), a corresponding change in the wall thickness. However, this is extremely difficult in practice and even impossible in the case of scanning antenna devices, since for the case of scanning, the same area of the fairing is exposed to radiation at different angles.

In such a situation, there is a mismatch between the electrodynamic characteristics of the fairing and the parameters of the wall in various local zones, which can lead to a deterioration in the radio performance of real "antenna-radome" systems.

In connection with the inevitable deterioration of the radio performance of a fairing operating in a wide range of angles of incidence, it is relevant to develop technical proposals that ensure minimal deterioration of its radio performance.

Radiotransparent fairings with a single-layer wall structure are known, designed to operate at variable angles of incidence of radio waves on the fairing wall (RF patent 2647563, class H01Q 1/42, 2006; RF patent No. 2653185 class H01Q 1/42, 2006; RF patent No. 2697516 , class H01Q 1/42, 2006).

Optimization of the structures and dimensions of the wall in known solutions is based on the average value of the angle of incidence of radio waves on the wall of the fairing ϑ _cf between the minimum ϑ _min and maximum ϑ _max values. The disadvantage of the known solutions is the fact that the average value of the angle of incidence ϑ _cf and the corresponding wall thickness (according to equation (1)) are used to optimize the wall, which does not accurately determine the optimal wall thickness that provides the best radio performance of the fairing in the entire operating range of the angle of incidence from the minimum value ϑ _min to the maximum value ϑ _max .

The closest technical solution is an antenna radome (V.A. Kaplun. Microwave antenna radomes. M.: Soviet radio, 1974. 240 p.), containing a cap-shaped wall made of dielectric material, equipped with an attachment to an aircraft, with a dielectric stack , corresponding to the half-wave electrical thickness at the operating frequency. The structure of the fairing wall consists of one or more layers of material with known frequency-independent values of the permittivity in the operating frequency band. The geometric wall thickness is selected to be equivalent to the half-wave electrical thickness at the average frequency over the range. The wall thickness of the dielectric material is calculated by the equation

The disadvantages of this technical solution include the impossibility of directly using formula (2) to calculate the optimal wall thickness, which provides the best radio performance for variable angles of incidence. The use in formula (2) of the average value of the angle of incidence ϑ is not a sufficiently accurate result.

The technical result of the proposed invention is to improve the radio performance of a fairing with a single-layer wall structure in a wide range of angles of incidence of radio waves on the wall of the fairing.

The technical result of the proposed invention is achieved due to the fact that in a radio-transparent fairing made with a single-layer curvilinear wall structure made of a dielectric material, the optimal thickness d of the fairing wall is designed to operate in a wide range of angles of incidence ϑ in different areas of the fairing from the minimum value ϑ _min up to the maximum value ϑ _max , is calculated by the equation:

where n=1, 2 ... is an integer, the order of the half-wave wall; λ is the length of the radio wave in free space (air); ε is the dielectric constant of the material; r _min and r _max Fresnel coefficients;

DISCLOSURE OF THE INVENTION

The change in the values of the angle of incidence is due to both the curvilinear shape of the fairing, and the design of the antenna, and scanning conditions.

The angle of incidence of radio waves on the wall of the fairing is defined as the angle between the direction of propagation of radio waves 1 (Fig. 1, 2) emitted by antenna 2 (Fig. 1, 2) and the normal 3 to the surface of the fairing (Fig. 1, 2) at the point of intersection of the radio wave with a wall of a radio-transparent fairing 4 (Fig. 1, 2).

The values of the angle of incidence in modern electronic systems vary over a fairly wide range. Particularly difficult conditions for the passage of radio waves are typical for radio-transparent fairings of aircraft, since such fairings, in addition to radio engineering, also have requirements for aerodynamic flow around. So, for example, for high-speed aircraft, pointed nose cones are used, with a shape close to conical, in which the angle at the top in some cases is 30 - 40 °. The angle of incidence of radio waves on the wall in such nose cones reaches 70 - 75°.

One of the most important indicators of the fairing, characterizing its perfection, is such an indicator as the loss of electromagnetic energy (EME) during the passage of radio waves through the wall of the fairing. Low values of EME losses contribute to increasing the range of radar, communication reliability, and the least distortion of the antenna pattern.

EME reflection is also a very important characteristic of the radome, since low reflection values provide reduced EME losses, a decrease in the radio technical visibility of radio-electronic antenna equipment, and a decrease in the level of internal re-reflections of radio waves in the "antenna - radome" system, which have a negative impact on the electrical parameters of the system.

The authors of this invention carried out computational experiments, which made it possible to establish that the use of this invention leads to a significant improvement in the radio performance of the fairing - table 1. The given illustrative calculations are performed for the following conditions: radio wave frequency f=10 GHz, dielectric constant of the fairing material ε=4.5 , dielectric loss tangent tg δ=0.015. The case of a perpendicular orientation of the plane of polarization of radio waves to the plane of incidence is considered.

The analysis of the given data shows the absolute advantages of the fairing made according to the invention compared to the fairing made according to the prototype in terms of such characteristics as EME losses, EME reflection, distortion of the phase front of radio waves after passing through the fairing wall.

In the vast majority of cases, radiotransparent fairings are made in the form of three-dimensional shells. In these cases, the angle of incidence of radio waves on the fairing wall is variable even for the simplest systems, including fixed, non-scanning antennas - FIG. one.

Scheme of the passage of radio beams through the curvilinear wall of the radio-transparent fairing:

1. radio wave;

2. antenna;

3. normal to the fairing surface;

4. Fragment of the radio-transparent fairing wall.

In the case of using scanning, rotary antennas, PAA type antennas, the angles of incidence are variable and in the case of flat radome shapes at different angles of electronic scanning - fig. 2.

The scheme of passage through the flat wall of the fairing of radio waves emitted by the antenna type FAR:

1. radio wave;

2. antenna;

3. normal to the fairing surface;

4. Fragment of the radio-transparent fairing wall.

Thus, the proposed technical solution provides an advantage over known methods.

Claims (4)

A radio-transparent fairing made with a single-layer curvilinear wall structure made of a dielectric material, characterized in that the optimal wall thickness d of the fairing designed to operate in a wide range of angles of incidence ϑ in different areas of the fairing from the minimum value ϑ _min to the maximum value ϑ _max , is calculated according to the equation:

where n=1, 2, … is an integer, the order of the half-wave wall; λ is the length of the radio wave in free space (air); ε is the dielectric constant of the material; r _min and r _max - Fresnel coefficients;

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