RU2435262C1 - Multi-beam mirror antenna - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: multi-beam mirror antenna includes asymmetrical parabolic reflector and group of feeds located in focal area not in focus. Absorbent with inverse proportion of reflection coefficient and working range frequency is applied to working surface of reflector. In central part of reflector throughout its surface there installed is metal strip with height of

where λ_min - minimum wave length of working range of frequencies,

- beam width of antenna direction pattern, which is offset by λ_min towards focus. Feeds are identical and made in the form of combined horns with combs providing the operation in ninefold frequency band. Absorbent reflection coefficient has been chosen in the range of 0.8 to 0.1.

EFFECT: reducing the distortion of direction pattern, increasing crossover level and reducing the lateral radiation background of direction patterns in wide frequency band by using reflector with absorbent on its surface.

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Description

The invention relates to the field of radio engineering, namely to the field of antennas, and can be used to detect and direction finding objects.

Known multi-beam reflector antenna three-coordinate radar (Handbook on radar, t.4, "Soviet radio", M, 1978, p. 71).

The antenna contains a section of a parabolic reflector, which is irradiated by a group of stationary horns located in the vertical plane. During transmission, a group of irradiators is excited in phase and the shape of the radiation pattern corresponds approximately to the distribution law cosec ² θ. At reception, each horn is connected to the corresponding receiver and is formed in the vertical plane "fan" from the intersecting partial radiation patterns (PDN).

The antenna cannot provide a high level of PDN intersection in a wide frequency band with a low background level of side lobes, since with increasing frequency the PDN width decreases in proportion to the frequency and the level of intersection drops to an unacceptable level.

When horns with openings close to the open ends of the waveguides are used as irradiators in order to increase the level of intersection, the reflector aperture is re-irradiated, as a result, the level of lateral radiation increases and the directivity coefficient (LPC) of the antenna decreases. In addition, in the antenna, the longitudinal axes of the horn irradiators are parallel to each other and irradiate different sections of the reflector, which leads to the expansion and distortion of the PD shape in the horizontal plane.

Known multi-beam mirror antenna (Russian patent No. 2234774 from 2004.08.20, H01Q 15/14), providing the formation of a "fan" of several PDN in a wide frequency band with a stable level of intersection.

до

, где λ_мин и λ_макс - минимальная и максимальная длина волны рабочего диапазона. В антенне повышена стабилизация уровня пересечения за счет уменьшения зависимости ширины диаграмм направленности от частоты, которая происходит за счет изменения локальных отражающих поверхностей.The antenna contains an asymmetric parabolic reflector and four remote from the focus of the irradiator, the longitudinal axes of which are parallel to each other. The stabilization of the level of intersection is ensured due to the fact that the reflector is made of conductive plates, the edges of which are mounted in such a way that they form local parabolic reflective surfaces. The plates are placed at a distance that varies linearly from

before

where λ _min and λ _max - the minimum and maximum wavelength of the operating range. In the antenna, stabilization of the level of intersection is increased by reducing the dependence of the width of radiation patterns on the frequency, which occurs due to changes in local reflective surfaces.

However, due to the non-uniformity of the reflector surface, diffraction edge effects appear in the antenna, leading to the deformation of the main lobe of the PDD with a change in frequency, as a result of which the level of intersection of the PDN decreases and becomes unstable, and the background of the back and side radiation increases. Due to the parallelism of the irradiator axes, the PDD is distorted in the orthogonal plane. The design and manufacturing technology of the reflector are complex and require significant implementation costs.

Known multi-beam reflector antenna (Russian patent No. 2336615 dated 2006.12.15, H01Q 15/14), which is adopted as a prototype as the closest to the claimed object in technical essence.

The antenna contains a reflector made of parallel conductive plates, the edges of which form a parabolic surface and irradiators removed from the focus with a linear dependence of their radiation pattern width on wavelength. The antenna forms a “fan” of five PDNs intersecting each other. The antenna has increased stabilization of the width of partial radiation patterns due to the use of irradiators with the dependence of the width of their patterns on the frequency, for example log-periodic.

In the antenna, the main PDN petals are distorted, the low level of intersection between individual beams is about minus 8-9 dB, and this leads to dips in the envelope of the beam of partial radiation patterns, especially in the high-frequency part of the range. In addition, the antenna has a significant background of lateral radiation due to inhomogeneities in the form of plate edges and energy leakage into the back space. The level of the side lobes reaches minus 5-7 dB. The use of log-periodic irradiators leads to a re-irradiation of the aperture of the reflector and an additional increase in the background of side radiation, as well as to a decrease in the directivity of the antenna. The use of a lattice in the form of irradiators leads to the problem of their placement to ensure the necessary level of PDN intersection. The design and manufacturing technology of the antenna are complex and require significant implementation costs.

The objective of the invention is to reduce the distortion of partial radiation patterns, increase their level of intersection in a wide frequency band and reduce the background of the side lobes with a simplified design of the reflector.

, где λ_мин - минимальная длина волны,

- ширина луча диаграммы направленности антенны, причем металлическая полоса по профилю одинакова с центральной частью несимметричной параболической поверхности отражателя и смещена на величину λ_мин в сторону фокуса, а идентичные облучатели размещены по дуге радиуса R=(1,05-1,1)f, где f - фокусное расстояние, от ближней кромки отражателя через

градуса относительно друг друга и направлены продольными осями в центр параболической полосы, причем коэффициент отражения поглотителя выбран величиной, изменяющейся от 0,8 до 0,1 в диапазоне от максимальной до минимальной длины волны соответственно.The solution to this problem is achieved by the fact that in a multi-beam reflector antenna containing an asymmetric parabolic reflector and a group of irradiators placed in the focus placed in the focal region, an absorber is applied to the working surface of the reflector, which is characterized by an inversely proportional dependence of the reflection coefficient on the frequency of the operating range, and in the central part a reflector with a height of not covered by the absorber is installed over its entire surface

where λ _min is the minimum wavelength,

- the beam width of the antenna pattern, and the metal strip along the profile is the same as the central part of the asymmetric parabolic surface of the reflector and is shifted by λ _min towards the focus, and identical irradiators are placed along an arc of radius R = (1.05-1.1) f, where f is the focal length from the proximal edge of the reflector through

degrees relative to each other and are directed by the longitudinal axes to the center of the parabolic strip, and the reflection coefficient of the absorber is selected as a value varying from 0.8 to 0.1 in the range from maximum to minimum wavelength, respectively.

Figure 1 shows a diagram of the construction of the antenna.

Figure 2 shows the design of the irradiator.

Figure 3 shows a General view of the antenna.

Figure 4 shows the experimental radiation patterns in the elevation plane in the frequency range from f _n to 9f _n , where f _n is the lower frequency of the range.

The multi-beam reflector antenna (Fig. 1) consists of an asymmetric parabolic reflector 1 with a ratio of focal length f to aperture size in the vertical plane equal to 0.795, and combined horn irradiators 2 in the amount of 5 pieces mounted on top of each other.

, равные ширине луча диаграммы направленности антенны в вертикальной плоскости (Зеркальные сканирующие антенны. Л.Д.Бахлах, Г.К.Галимов, М., «Наука», 1981, с.53-54).The irradiators 2 with their openings are directed to the center of the reflector 1 and placed along an arc MN of radius R = 1.05f drawn from the lower edge of the reflector 1 through the corners

equal to the beam width of the antenna pattern in the vertical plane (Mirror scanning antennas. L.D. Bahlakh, G.K. Galimov, M., "Science", 1981, p.53-54).

The second irradiator 2 'from above is directed by the longitudinal axis through the focus F (FK), like all others, to the point "K" - the center of the reflector 1. The near edge of the reflector 1 is 20λ _min from the focal axis OF.

In the horizontal plane, the reflector 1 has a symmetrical parabola profile and its size is 110λ _min , and the ratio of its focal length f to the opening is 0.575.

In the central part of the reflective surface of the reflector 1, a metal parabolic strip 3 is installed with a width of the entire horizontal dimension of the symmetric parabolic part of the reflector and a height h of 15λ _min . The parabolic metal strip has the same focal length as the reflector and the size to the lateral edges of the central part of the asymmetric reflector. The metal strip 3 is offset in the direction of the OZ axis by λ _min . The role of the reflective strip can be performed by a pedestal made by stamping in the manufacture of the reflector. The remaining surface of the reflector 1 is covered with an absorbing material 4, which has a reflection coefficient increasing from 0.1 to 0.8 in the range of lowering the frequency of electromagnetic energy incident on its surface, from maximum to minimum, respectively. As the absorber in the proposed technical solution, two layers of absorbing material were used: the first XB-10.6 and the second layer B2-F3, which are fixed to the surface of the reflector 1.

The irradiator (figure 2) is made in the form of a combined horn (Antenna-feeder devices, A.L. Drabkin, V.L. Zuzenko, A.G. Kislov, "Soviet Radio", M., 1974, p.272).

The irradiator consists of a coaxial connector 5, pin 6, insulator 7, ridges 8, horn walls 9, combi nozzle 10, bracket 11, plug 12, and radiolucent wall 13.

The coaxial connector 5 is made standard, which includes the pin 6 and the insulator 7. The ridges 8 have an exponential profile, start from the insulator 7 and end at the combined nozzle 10, the ridges must have electrical contact over the entire surface of the walls of the horn 9. The horn 9 is made with the opening size from the end of the ridges 4.8λ _min (E-plane) and in the orthogonal plane (H-plane) 6.0λ _min . The nozzle of the combined part of the horn has dimensions in the E-plane of 10λ _min , and in the H-plane of 7.5λ _min . The total length of the horn feed is 15λ _min .

As part of the antenna design (Fig. 3), the irradiators are protected by a fairing 14 with a radiotransparent window 15 from the influence of the external environment. The entire antenna design is placed on an azimuth slewing ring 16.

Multi-beam mirror antenna operates as follows.

, выдвинутая от основной на λ_мин, чем исключаются фазовые искажения диаграммы направленности в области высоких частот из-за дефокусировки облучателей. Кроме того, с повышением частоты при уменьшении эффективной отражающей поверхности расширяется диаграмма направленности и тем самым стабилизируется ее ширина, увеличивается отношение f к размеру апертуры и становятся меньше искажения ПДН из-за выноса облучателей из фокуса. В области высоких частот ширина диаграммы направленности определяется, в основном, размером h дополнительной поверхности. Уменьшается также зависимость ширины ДН от частоты. В области высоких частот работает в большей степени рупорная часть облучателя, а в области низких частот больший вклад в формирование диаграммы направленности облучателя вносит комбинированная часть увеличенного раскрыва рупора, уменьшающая уровень «переливания» энергии за кромки отражателя, снижая тем самым уровень фона боковых лепестков. Поглотитель исключает краевые дифракционные эффекты, что также способствует снижению фона боковых лепестков и повышению стабильности уровня пересечения парциальных диаграмм направленности.At the lower frequencies of the operating range, where the absorbing properties of the absorber are minimal, the entire surface of the reflector works, and with increasing frequency, the absorbing properties of the material increase and thereby the effective opening decreases. In the high-frequency region, an additional reflective surface with a height of mainly works.

, extended from the main one by λ _min , which eliminates phase distortion of the radiation pattern in the high frequency region due to defocusing of the irradiators. In addition, with an increase in the frequency with a decrease in the effective reflective surface, the radiation pattern expands and its width stabilizes, the ratio f to the aperture size increases, and the distortion of the PDD becomes smaller due to the removal of the irradiators from the focus. At high frequencies, the width of the radiation pattern is determined mainly by the size h of the additional surface. The dependence of the width of the beam on the frequency also decreases. In the high-frequency region, the horn part of the irradiator works to a greater extent, and in the low-frequency region, the combined part of the enlarged aperture of the horn makes a greater contribution to the formation of the radiation pattern of the horn, which reduces the level of “transfusion” of energy beyond the edges of the reflector, thereby reducing the background level of the side lobes. The absorber eliminates edge diffraction effects, which also helps to reduce the background of the side lobes and increase the stability of the level of intersection of the partial radiation patterns.

Experimental studies of the operation of a multi-beam mirror antenna showed (Fig. 4) that, in comparison with the prototype, PDN distortions are reduced, the level of intersection of partial radiation patterns is increased by an average of 3-4 dB in the ninefold frequency band, the background level of side lobes in the PD sector is reduced to 12 dB, behind the sector - up to 20 dB, and in the back sector - up to 35 dB. Simplified design and manufacturing technology of the antenna with the same energy parameters as the prototype.

Claims (2)

1. A multi-beam reflector antenna containing an asymmetric parabolic reflector and irradiators placed out of focus placed in the focal region, characterized in that an absorber is applied to the working surface of the reflector, which has an inversely proportional dependence of the reflection coefficient on the frequency of the operating range, and the length of the central part is asymmetric parabolic reflector with an offset by an amount λ _m in the direction of focus is a metal band which coincides with the reflector profile, h that

where λ _min is the minimum wavelength of the working frequency range,

- the beam width of the antenna pattern, while the irradiators, made in the form of identical combined horns, are placed along an arc of radius R = (1.05-1.1) f from the proximal edge of the reflector through an angle

degrees relative to each other and are directed by the longitudinal axes to the center of the parabolic metal strip, where f is the focal length. 2. The antenna according to claim 1, characterized in that the reflectance of the absorber is selected to be a value that varies from 0.8 to 0.1 in the range from maximum to minimum wavelength, respectively.

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