RU154066U1 - MICROWAVE ANTENNA WITH FOCUSING ZONE PLATE - Google Patents

Abstract

Microwave antenna with a focusing zone plate, containing a flat radiolucent plate with conductive regions deposited on its front side located in the same plane, and also an irradiator located in front of it, characterized in that the antenna is made according to the offset circuit with the deviation of the incident wave direction from the normal to the surface plates at an arbitrary angle, a continuous conductive coating is applied to the back of the plate, the electric thickness of the plate is chosen equal to a quarter of the working wavelength, and the boundaries of the leading regions in Cartesian coordinates (x, y) are given by the relation where f is the focal length, n = 1, 2, 3 ...

Description

h01Q19 / 00

Microwave antenna with a focusing zone plate

The invention relates to antennas with a primary radiating element and a flat reflecting surface and can be used for directional transmission and reception of microwave signals.

In microwave technology for directional transmission and reception of signals, mirror antennas with reflectors in the form of segments of rotation paraboloids are widely used. A spherical wave emanating from the primary radiating element (irradiator), placed in the focus of the paraboloid, is transformed into a plane wave propagating over a considerable distance with a small divergence. The implementation of paraboloids is a complex technical process, and the parabolic segment itself, due to its bulge, is a bulky structure, difficult to transport and prone to deformation. In this regard, it is of interest to switch from the three-dimensional structure of the microwave antenna to a flat structure. A number of variants of such structures are known, one of which is a phased antenna array (Voskresensky D. I., Gostyukhin V. L., Maksimov V. M., Ponomarev L. I. Antennas and microwave devices / Ed. By D. I. Voskresensky Textbook. - 2nd ed. - Moscow: MAI, 1993), the other is a zoned antenna in which a parabolic segment is divided into fragments attached to one plane (A.I. Amosova Band properties of a zoned reflector. - Journal of Radio Electronics No. 1 , 2008. - URL http://jre.cplire.ru/jre/jan08/2/text.html).

The disadvantages of the PAR include the complexity of the equiphase branching of the signal supplied to the elements making up the grating, as well as the additional losses caused by attenuation in the branching system and nonzero phase errors. The disadvantages of zoned antennas include increased technical complexity and preservation of the volumetric nature of the fragments of the parabolic segment.

To a large extent, these shortcomings have been overcome in antennas based on a zone plate, which was originally used to focus optical waves. The optical zone plate is a flat structure with the boundaries of alternating Fresnel zones highlighted, with all even (or, on the contrary, odd) zones being blackened. The addition of waves emanating only from even (or odd) zones occurs predominantly in phase, which gives the plate focusing properties.

With the development of microwave technology, in particular, the principles of creating focusing antennas based on zone plates have been successfully transferred to it. At the same time, along with transmissive working plates, reflection working plates were also used. A typical example is a microwave antenna based on a focusing zone plate used to receive satellite television signals (V.A. Nikitin, V.V. Pyasetskiy. Fresnel zone antenna. Http://www.telesputnik.ru/archive/32.html , p. 68). Selected as a prototype utility model.

The known microwave antenna with a focusing zone plate contains a flat radiotransparent plate with conductive regions deposited on its front side located in the same plane, as well as an irradiator located in front of the plate. According to the Fresnel concept, the boundaries of the conducting regions are determined so that the waves reflected from the indicated regions are added in phase to the irradiator with a phase error within ± π / 2. Under these conditions, the zone plate is equivalent to a focusing mirror. The implementation of the focusing mirror of the microwave antenna in the form of a zone plate increases the manufacturability and compactness of the product. Known microwave antennas based on the zone plate, in particular, the prototype, perform in the form of direct focus reflector antennas. In them, the focus and, accordingly, the irradiator are on a perpendicular axis passing through the center of the reflector. The boundaries of the conductive regions (Fresnel zones) are circles whose radii r _{n are} determined in accordance with the formula

(1),

(one),

where λ is the wavelength, f is the focal length, n = 1, 2, 3 ...

In Cartesian coordinates (x, y), the boundaries of the regions are determined from the relation

(2).

(2).

The disadvantage of the prototype is the low coefficient of directional action (KND), due to the fact that half of the plate area is not used. In addition, the disadvantage is the inconvenience of use associated with the need to orient the plate perpendicular to the direction of the radiation source. For example, to receive satellite signals, the antenna must be installed with an elevation angle depending on the coordinates of the installation site, and therefore it is almost as cumbersome as a direct-focus antenna with a parabolic reflector.

, на обратную сторону пластины нанесено сплошное проводящее покрытие, электрическая толщина пластины выбрана равной четверти рабочей длины волны

, а границы проводящих областей в декартовых координатах (x,y) заданы соотношением The technical result of the utility model is to increase the efficiency and ease of use compared with the prototype. This result is achieved by the fact that in the known microwave antenna with a focusing zone plate containing a flat radiolucent plate with conductive regions deposited on its front side located in the same plane, as well as an irradiator located in front of it, the difference is that the antenna is made according to the offset circuit with a deviation of the direction of the incident wave from the normal to the surface of the plate at an arbitrary angle

, a continuous conductive coating is applied to the back of the plate, the electric thickness of the plate is chosen equal to a quarter of the working wavelength

, and the boundaries of the conducting regions in Cartesian coordinates (x, y) are given by

,\tab\tab(3)

, \ tab \ tab (3)

where f is the focal length, n = 1, 2, 3 ...

The achievement of the technical result is illustrated by the following.

The implementation of the antenna according to the offset scheme with an arbitrary angle of deviation of the incident wave direction from the normal makes it possible to orient the radiolucent plate in an arbitrary plane convenient for fixing, for example, on the surface of a wall or roof, so that it does not make changes to the exterior of the object on which it is located. Under these circumstances, the antenna does not experience wind loads and, in addition, can be painted in the background color. Thus, the offset circuit provides the maximum usability of the antenna.

The application of a continuous conductive coating to the back of the radiolucent plate provides an increase in the directivity gain by summing the reflections from the specified coating with reflections from the conductive regions on the front side of the plate. Due to this, the utilization of the plate area increases. The choice of the plate thickness equal to a quarter of the wavelength provides in-phase addition of the waves reflected by the conductive regions on the front side and the conductive coating on the reverse side of the plate, thereby increasing the antenna directivity in this configuration to a maximum value.

The determination of the boundaries of the conducting regions from relation (3) ensures that their shape corresponds to Fresnel zones, thereby achieving the focusing effect of the zone plate.

The utility model is illustrated by the illustrations of FIG. 1-3. In FIG. 1 shows a typical appearance of a known direct focus microwave antenna with a focusing zone plate. In FIG. 2 shows the proposed microwave antenna with a focusing zone plate, made according to the offset circuit. In FIG. Figure 3 shows the boundaries of the Fresnel zones constructed for a focusing zone plate with an angle of deviation of the incident wave direction from the normal to the surface of 30 °.

. На обратную сторону пластины 1 нанесено сплошное проводящее покрытие. Электрическая толщина пластины 1 выбрана равной четверти рабочей длины волны

. Границы проводящих областей в декартовых координатах (x,y) определены из соотношенияMicrowave antenna with a focusing zone plate (Fig. 2) contains a flat radiolucent plate 1 with deposited on its front side conductive regions 2 located in the same plane. An irradiator 3 is located in front of the plate 1. The antenna is made according to the offset scheme with a deviation of the incident wave direction AO from the normal OB to the surface of the plate 1 at an arbitrary angle

. A continuous conductive coating is applied to the back of the plate 1. The electrical thickness of the plate 1 is chosen equal to a quarter of the working wavelength

. The boundaries of the conducting regions in Cartesian coordinates (x, y) are determined from the relation

,

,

where f is the focal length. The phase center of the irradiator 3 is aligned with the focus of the zone plate F.

. При этих условиях вторичные волны в пределах каждой зоны различаются по фазе не более чем на половину периода, что соответствует максимуму их суммарной амплитуды. Геометрически границы имеют эллиптическую форму. В частности при

=0 эллипсы вырождаются в окружности, формула (3) переходит в формулу (2), антенна становится прямофокусной. Возможность произвольного выбора угла

позволяет ориентировать пластину 1 наиболее удобным образом, например, монтировать ее вплотную на вертикальную, горизонтальную или наклонную поверхность (стену, крышу и т.п.), что в значительной степени повышает удобство применения: снижает ветровую нагрузку, сохраняет внешний вид, особенно при окрашивании под фон.The antenna works as follows. The wave arriving in the AO direction undergoes diffraction on the conducting regions 2 and the conducting coating 4, which, according to the Fresnel concept, serve as sources of secondary waves. The conductive regions 2 and sections of the conductive coating 4 in the gaps between the conductive regions 2 correspond to even and odd Fresnel zones. Due to the fact that the electric thickness of the plate 1 is a quarter of the wavelength, the total wave delay in it when reflected from the conductive coating 4 is half the period. This ensures the in-phase addition in the focus F of the secondary waves from even and odd Fresnel zones, and, consequently, an increase in the directivity gain due to the full use of the area of the plate 1. The electric thickness of the plate 1 is equal to the product of the physical thickness by the square root of the dielectric constant of the radiolucent material from which plate. The boundaries of the Fresnel zones by formula (3) are determined from the conditions of the multiplicity of phase distances between the focus and the front of the incident wave to

. Under these conditions, the secondary waves within each zone differ in phase by no more than half the period, which corresponds to the maximum of their total amplitude. Geometrically, the borders are elliptical in shape. In particular, when

= 0, the ellipses degenerate in a circle, formula (3) goes into formula (2), the antenna becomes direct focus. Possibility of arbitrary choice of angle

allows you to orient the plate 1 in the most convenient way, for example, mount it closely on a vertical, horizontal or inclined surface (wall, roof, etc.), which greatly increases the usability: reduces wind load, maintains its appearance, especially when painting under the background.

составлял 30°, размеры пластины 200х160 мм. Границы зон определялись по формуле (3) для фокусного расстояния 100 мм. Эскиз лицевой стороны зонной пластинки с границами проводящих областей приведен на фиг. 3. Металлизация на четных зонах удаляется. Координатная ось «y» располагается в плоскости AOF фиг. 2. Облучатель 3, помещаемый в фокусе F, представляет собой волноводный раскрыв конической формы, плавно переходящий в прямоугольный волновод. Измерение КНД офсетной СВЧ антенны с фокусирующей зонной пластинкой проводилось методом сравнения с коническим рупором диаметром 80 мм и длиной образующей 180 мм, а также с прямофокусной зеркальной параболической антенной диаметром 160 мм. Для этих антенн существуют достоверные методики расчета КНД [Родионов В. М. Линии передач и антенны СВЧ. Сборник номограмм. М.: Сов. радио, 1965. - 119 с.]. Согласно этим методикам конический рупор вышеуказанных размеров имеет КНД порядка 24 дБ, а параболическая антенна - порядка 30 дБ. Полученные сравнительные результаты свидетельствуют, что предложенная антенна имеет КНД порядка 28 дБ при ширине диаграммы направленности порядка 3°. При практически равных размерах апертуры с параболической антенной предложенная антенна проигрывает ей в КНД не более чем на 2 дБ. Для сравнения можно упомянуть пирамидальный рупор с таким же раскрывом, который при той же величине КНД 28 дБ должен иметь длину 600 мм. Полоса пропускания предложенной антенны по уровню -1 дБ составила 10%. Это свидетельствует об относительно малой критичности к точности выполнения антенны для конкретной частоты, как в отношении геометрии проводящих областей, так и в отношении толщины радиопрозрачной пластины.Tests confirmed the industrial applicability of the utility model in accordance with the claims. An experimental sample of a microwave antenna with a focusing zone plate was tested in the wavelength range of 12.5 mm (frequency 25 GHz). As the material for the radiolucent plate, FLAN-10 metallized on both sides with dielectric constant ε = 10 was chosen. The material thickness was 1 mm, which corresponded to an electric plate thickness of the order of a quarter wavelength for a range of 25 GHz. Angle

was 30 °, plate dimensions 200x160 mm. The boundaries of the zones were determined by formula (3) for a focal length of 100 mm. A sketch of the front side of the zone plate with the boundaries of the conductive regions is shown in FIG. 3. Metallization on even zones is removed. The y axis is located in the AOF plane of FIG. 2. The irradiator 3, placed in focus F, is a waveguide opening of a conical shape, smoothly transitioning into a rectangular waveguide. The directivity measurement of the microwave offset antenna with a focusing zone plate was carried out by comparison with a conical horn with a diameter of 80 mm and a generatrix length of 180 mm, as well as with a direct-focus reflective parabolic antenna with a diameter of 160 mm. For these antennas there are reliable methods for calculating the directivity gain [Rodionov V.M. Transmission lines and microwave antennas. Collection of nomograms. M .: Sov. Radio, 1965. - 119 p.]. According to these techniques, the conical horn of the above sizes has a gain of about 24 dB and a parabolic antenna of about 30 dB. The obtained comparative results indicate that the proposed antenna has a gain of about 28 dB with a beam width of about 3 °. With almost equal sizes of the aperture with a parabolic antenna, the proposed antenna loses to it in KND by no more than 2 dB. For comparison, we can mention the pyramidal horn with the same opening, which with the same magnitude of the directivity gain of 28 dB should have a length of 600 mm. The bandwidth of the proposed antenna at a level of -1 dB was 10%. This indicates a relatively low criticality to the accuracy of the antenna for a particular frequency, both in terms of the geometry of the conductive regions and the thickness of the radiolucent plate.

. В этом случае проводящими поверхностями могут служить металлические сетки или металлизированные пленки, натянутые на каркас типа обруча или рамы.The proposed utility model can find application in radio systems with increased requirements for reliability and mechanical stability, in particular, in the long-wave part of the range. Unlike parabolic reflectors, a zoned offset reflector can be attached to the bearing surface over its entire area. A special case of radiolucent material can be considered air

. In this case, the conductive surfaces may be metal meshes or metallized films stretched over a frame such as a hoop or frame.

Claims (1)

Microwave antenna with a focusing zone plate, containing a flat radiolucent plate with conductive regions deposited on the front side located in the same plane, as well as an irradiator located in front of it, characterized in that the antenna is made according to the offset circuit with the deviation of the incident wave direction from the normal to the surface plates at an arbitrary angle

, a continuous conductive coating is applied to the back of the plate, the electric thickness of the plate is chosen equal to a quarter of the working wavelength

, and the boundaries of the conducting regions in Cartesian coordinates (x, y) are given by

where f is the focal length, n = 1, 2, 3 ...

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