RU2723909C1 - Method of constructing bead conical antenna arrays - Google Patents

Abstract

FIELD: antenna equipment.SUBSTANCE: invention relates to superhigh-frequency equipment, specifically to antenna arrays (AA) used in onboard radar systems of ground-to-air missiles, air-to-air and other types of rockets and aircrafts (AC) located directly on conical or generalized conic surface of missile or aircraft nose part. Implementation of the proposed method of constructing a conic AA consists in solving a diffraction problem on the drop of an arbitrarily polarized plane wave on the cone conducting surface along its longitudinal axis, determining the electric currentat an arbitrary point P on the surface of the cone, determining amplitude-phase and polarization excitation of emitters, which satisfies condition, where c is some arbitrary constant; "*" is a sign of complex conjugation and realization by means of slot (or other type) radiators of calculated amplitude-phase and polarization excitation.EFFECT: technical result consists in formation of total-difference directive patterns in the direction of the axis of the cone with the maximum antenna directive gain on the total channel due to establishment of the optimum amplitude-phase and polarization excitation of the emitters, wherein the directional characteristics of antenna directive gain significantly exceed similar characteristics of the equivalent flat antenna and provide a level of cross-polarization radiation is substantially lower than the level of cross polarization in known analogues of conical AA and AA with ogival shape of surface.4 cl, 13 dwg

Description

The invention relates to techniques for microwave frequencies, namely, to antenna arrays (AR) used in airborne radar systems (radar) of missiles of the class "ground-to-air", "air-to-air" and other types of missiles and aircraft (LA).

Based on the requirements for airborne ARs of this class, the AR must form a sharply directed sum-difference directivity pattern (LH) with a maximum total LH and a minimum difference LH in the direction of the rocket axis, have high mechanical strength, not exceed the specified weight and size parameters, work stably in conditions of high and low temperatures, do not violate aerodynamic performance of the aircraft, have high directivity characteristics (directional coefficient (KND), gain (KU) and slope of the difference characteristic μ) and have a low cost.

It is known that in order to ensure good aerodynamics and to exclude the radar antennas in the design of airborne antennas, AR emitters can be located directly on the conical surface of the nose of a rocket or aircraft [1-6]. It is also possible to arrange AR emitters on an arbitrary surface of an animated shape. In this case, the surface of the animated shape is understood to mean the surface of rotation with a generatrix in the form of a hyperbola, parabola or with an arbitrary generatrix of a smooth shape. In what follows, we will call this surface “generalized conic”.

The emitters in such ARs can be longitudinal, transverse, or inclined slots located along the generatrix of the animated surface or cone [1, 2, 4-6], emitters in the form of open ends of the waveguide, or strip emitters located on this surface [3] (Fig. 1).

However, the significant drawbacks of conical ARs and ARs with a lively shape considered in [1-6] are the possibility of forming a narrow pencil beam that scans only in a limited sector of angles relative to the normal to the generatrix of the cone, [1] or an axisymmetric funnel-shaped ray [2] with a minimum of DN along the axis of the cone. In addition, such antennas have a low gain along the axis of the cone, not exceeding the gain of the equivalent planar aperture [1], and a high level of cross-polarization radiation [4-6]. Possible optimization algorithms for the total characteristics do not give a sufficiently convincing answer to the relationship between the directivity characteristics of the antenna with its geometry. These reasons do not allow the use of conical ARs given in [1-6] in small-sized missiles of the type indicated above.

In addition, in such ARs, the law of optimal excitation and the geometry of slotted or other type of emitters are unknown and there is no data on the effect of the conductive conical surface on the characteristics of the AR. Existing methods of numerical optimization to minimize the level of the side lobes of the pattern, in particular, according to the genetic algorithm [7], do not give a clear answer to the influence of the geometry of the cone and the characteristics of individual emitters on the directivity characteristics of the generalized conical antenna, since the optimization is performed using the directivity factor of the AR and does not take into account real characteristics of individual emitters.

Closest to the proposed invention is a method of placing emitters on a generalized conical surface and the optimal excitation of each emitter, which implements the formation of the maximum radiation pattern of a conical antenna in a given direction [8]. The disadvantages of this method include the lack of initial data on the amplitude-phase distribution required for the formation of MDs with the maximum directivity gain in a given direction, the maximum directivity gain (LPC), the determination of the optimal polarization structure of the emitters, the impossibility of generating differential patterns and the absence of data on the influence of diffraction effects on the surface of the cone for the total-difference characteristics of the conical antenna array according to the main and cross-polarization components of the emitted field.

The aim of the invention is to establish a method for placing emitters on a conductive conical surface, a method for forming total-differential DNs in the direction of the cone axis with maximum KND (KU) along the total channel, establishing the optimal amplitude-phase and polarization excitation of emitters for which directivity characteristics (KND, KU ) significantly exceed the similar characteristics of an equivalent planar antenna and the level of cross-polarization radiation is ensured significantly lower than the level of cross-polarization in the known analogues of conical AR and AR with a lively surface shape.

Implementation of the proposed method for constructing a conical AR is as follows.

в произвольной точке Р на поверхности конуса [9].At the first stage, the diffraction problem of the incident of an arbitrarily polarized plane wave on the conducting surface of the cone along its longitudinal axis and determining the electric current is solved

at an arbitrary point P on the surface of the cone [9].

, удовлетворяющее условию

, где с - некоторая произвольная константа; «*» - знак комплексного сопряжения.At the second stage, in the transmission mode, the amplitude-phase and polarization excitation of the emitters is determined

satisfying the condition

where c is some arbitrary constant; "*" - a sign of complex pairing.

At the third stage, the calculated amplitude-phase and polarization excitation is realized using gap (or other type) emitters.

(например,

, как показано на фиг. 2, где Е_пад - комплексная амплитуда падающего поля при z=0). Под действием падающего поля на проводящей поверхности возбуждаются электрические токи, поверхностная плотность которых

в приближении физической оптики может быть определена по соотношениюLet us explain this in more detail. Let a linearly polarized (in the general case, arbitrarily polarized) plane wave with a frequency ω and a certain orientation of the electric field intensity vector be incident on a conical or rotation surface with an arbitrary generator of an animated shape

(eg,

as shown in FIG. 2, where E _pad is the complex amplitude of the incident field at z = 0). Under the influence of the incident field, electric currents are excited on the conductive surface, the surface density of which

in the approximation of physical optics can be determined by the ratio

- напряженность падающего магнитного поля в точке Р;

- вектор единичной нормали к поверхности в точке Р.where P is an arbitrary point on a conductive surface;

- the intensity of the incident magnetic field at point P;

is the vector of the unit normal to the surface at point P.

по законуIn accordance with the principle of reciprocity, if now in the transmission mode we create surface current sources on some part S of the conducting generalized conical surface of the antenna

according to law

и с основанием конуса а_осн (фиг. 3).where c is some arbitrary constant; “*” Is the sign of complex conjugation, then in the direction of the Oz axis, such sources will form a beam with a maximum directed along the Oz axis and with a maximum directivity gain (SLC) for the selected source location surface S and with a polarized radiated field that matches the polarization of the transmitting antenna. As a surface S for the problem under consideration, it is advisable to choose a part of the upper surface of rotation of the “generalized cone" with a finite generatrix length

and with the base of the cone a _osn (Fig. 3).

в видеImagine

as

, фазовое распределение Ф_прд(Р) и поляризационное распределение

для обеспечения максимального КУ в направлении оси Oz должно подчиняться следующим закономерностям:Then, in accordance with (2), the optimal amplitude distribution

, phase distribution Ф _prd (P) and polarization distribution

To ensure maximum KU in the direction of the Oz axis, it must obey the following laws:

In FIG. Figure 4 shows the calculated dependences of the amplitude and orientation of the induced current upon the incidence of a plane wave with linear polarization (E _y component) on the surface of the conducting cone with an angle at the apex of α = 11.3 °. The amplitude distribution is presented as a gradation of color dependence and is a concentric circle. The polarization distribution (orientation of surface currents) is presented more clearly in FIG. 4, d - the dashed line indicates the direction of flow of surface currents. The phase distribution of surface currents along the generatrix of the cone in the yOz plane is shown in FIG. 4, d.

It was found that the required amplitude distribution of radiation sources rather weakly depends on the longitudinal coordinate of the radiation source and to a greater extent depends on the azimuthal coordinate. The polarization distribution of the radiation sources represented by the dashed curve in FIG. 4d, also substantially depends on the azimuthal coordinate along the cone.

The required amplitude, phase, and polarization distributions can be realized using slot emitters. To achieve the required amplitude-phase and polarization distribution in slot radiators on a cone, the latter must be located in p waveguides (p = 1, 2, ..., p _max , where p _max is the maximum number of waveguides in each sublattice of the cone) formed as a result of the cross section two coaxial conical surfaces by segments p (p = 1, 2, ..., p _max +1) of metal plane-parallel surfaces (Figs. 5 and 6). The system of waveguides can also be formed by a similar external surface of the nth quasi-rectangular waveguide and segments of metal surfaces passing through the lateral lines of the nth waveguide on the outer surface of the cone orthogonally to the surface of both coaxial metal cones forming the side and lower walls of the nth waveguide. Quasi-rectangular waveguides can be formed as a result of pairs of rows of closely spaced point contacts extending parallel to the longitudinal axes of the p-waveguides and connecting two conical metal surfaces embedded in each other (Fig. 5).

In order to form the total-difference directivity characteristics, the conical antenna array is made of four sublattices, each of which consists of a system of curved quasi-rectangular waveguides placed along hyperbolic curves on the surface of the cone (or curves on an arbitrary animated surface) formed as a result of the section of the surfaces of two coaxial cones (or an arbitrary animated surface) by a system of plane-parallel metal planes (Figs. 2 and 3) located relative to each other at a distance from the lower wide wall of the waveguide.

The configuration of the lines on the outer surface of the “generalized cone" at the intersection of this surface by a system of plane-parallel planes is shown by solid lines in FIG. 2 and 3. In particular, if instead of a “generalized cone" we use a regular cone with an angle at the vertex α, then the equation for the nth curve has the form of a hyperbola:

where x _p - coordinate of the flat p-th. the surface described by the equation

This can be either the coordinate of each side (narrow) wall of the quasi-rectangular waveguide (the wall shown by solid lines with p = 1, 2, ..., p _max +1), or the coordinate of the midline on the upper wide wall of the waveguide, shown by the dotted line with p = 1, 2, ..., p _max .

и радиусом основания а_осн, определяется выражениемIf the distance d _p between adjacent planes defined by the circumferential base of the cone with base radius as _DOS, the same and equal to d (FIG. 3), the greatest number of parallel planes p _max which intersect at a predetermined half cone generatrix

and the radius of the base and _DOS is determined by the expression

where] ... [means taking the nearest integer, and x _pcr is the average coordinate of a surface on a cone between adjacent p-th planes. Therefore, the equation of the midline of a surface area on a cone between adjacent planes in the coordinate system (x, y, z) has the form

and the curves themselves are shown by dashed lines in FIG. 2, 3 and 5.

между соседними m_p, m_p+1 излучателями в р-м волноводе, а также размера широкой стенки волновода или дополнительного диэлектрического заполнения, обеспечивающего требуемую разность фаз между соседними щелями.Narrow gaps are located in each rth curved VShCHAR (Fig. 6), the orientation of the axis of each gap is selected by the orthogonal orientation of the surface current density vector arising on the upper conductive conical surface when a plane-polarized electromagnetic wave with an electric field vector is incident on this surface along the longitudinal axis of the cone parallel to the system p (p = 1, 2, ..., p _max ) of plane-parallel surfaces (the current orientation is in accordance with (6) orthogonal to the longitudinal axis of the upper wide wall of the curved waveguide described by equation (10)). The phase centers of slot emitters for ensuring a single-beam mode are located at a minimum distance from each other, providing in-phase addition of fields from these emitters in the direction of the Oz axis, i.e. the phase excitation of gap emitters E _n is selected in accordance with (5) the complex conjugate phase of the surface current. The law of amplitude excitation m _p = 1, 2, ..., m _{p max of} gaps is ensured by the choice of the displacement of the gap along the transverse axis of the _pth waveguide, and the law of phase distribution by the choice of the corresponding distance

between adjacent m _p , m _p +1 emitters in the r-th waveguide, as well as the size of the wide wall of the waveguide or additional dielectric filling, which provides the required phase difference between adjacent slots.

, угол поворота излучателя (продольной оси щели) β₂ зависит от угла конуса α и угла образующей 0°<β₁<180°, на которой находится фазовый центр излучателя (фиг. 7) следующим образом:

. При этом углу образующей β₁=0° соответствует положение излучателя с β₂=90°.In the case of ensuring an arbitrarily specified polarization of the emitted field, the emitters should be oriented so that in the direction of the cone axis the polarization of each emitter coincides with the desired polarization of the antenna, i.e. each emitter must have the required polarization structure of the radiation field in the direction of the cone axis, and its position is determined from the condition that the required polarization field is provided in the direction of the cone axis. In particular, for slot radiators with polarization of the radiated antenna field in the direction of the cone axis, which coincides with the direction

, the angle of rotation of the emitter (longitudinal axis of the slit) β ₂ depends on the angle of the cone α and the angle of the generatrix 0 ° <β ₁ <180 °, which is the phase center of the emitter (Fig. 7) as follows:

. In this case, the angle of the generatrix β ₁ = 0 ° corresponds to the position of the emitter with β ₂ = 90 °.

(фиг. 8) можно определить из следующих рассуждений. Так, при питании каждого волновода полем бегущей волны, идущей сверху вниз, требуемая разность фаз между соседними излучателями для р=1 волновода линейной формы с координатой х≈0 определяется из соотношенияPossible required phase difference between adjacent slots with distance

(Fig. 8) can be determined from the following reasoning. So, when each waveguide is supplied with a traveling wave field going from top to bottom, the required phase difference between adjacent emitters for p = 1 linear waveguide with coordinate x≈0 is determined from the relation

where λ _B is a wavelength of type H ₁₀ in a quasi-rectangular waveguide, or

- угол между направлением оси Oz и средней линией р-го волновода, проходящего через данную точку.

- the angle between the direction of the Oz axis and the middle line of the p-th waveguide passing through this point.

Accordingly, for n = 1

. В частности, при а_В=0,7λ,

получаем

где

- максимальное число щелей в первом волноводе.From relation (13) for a known value of γ, we can choose the ratio

. In particular, with a _B = 0.7λ,

we get

Where

- the maximum number of slots in the first waveguide.

между соседними излучателями из условияFor cases when the middle line of the upper wide wall of the nth quasi-rectangular waveguide, formed as a result of a section by a system of plane-parallel metal planes, is described by the relation (10), the phase matching of two adjacent emitters can be achieved either by choosing the distance

between adjacent emitters from the condition

обозначена длина

между двумя соседними излучателями вдоль средней линии р-й образующей, а через

- продольные координаты точек

и

(фиг. 8), или выбором замедления в локальном участке между соседними излучателями, или за счет изменения локального расстояния между широкими стенками с помощью локального диэлектрического заполнения соответствующих участков волноводов.where through

marked length

between two adjacent emitters along the midline of the rth generatrix, and through

- longitudinal coordinates of points

and

(Fig. 8), or by the choice of deceleration in the local area between adjacent emitters, or by changing the local distance between the wide walls using local dielectric filling of the corresponding sections of the waveguides.

от общего входа до р-го коаксиально-волноводного возбудителя. Схема коаксиально-волноводного питания представлена на фиг. 9.To provide in-phase power in the direction of the Oz axis of the power supply of adjacent waveguides, a sequential waveguide power supply circuit is used, as shown in FIG. 6c and 6d, with the appropriate choice of the position of the first slot in the rth VCHAR from the condition that the fields of the first slots are in phase in the rth and (p-1) -th waveguide in the direction of the Oz axis or when choosing the dimensions of this waveguide with additional phasing with using phase shifters installed at the input of each rth waveguide. Along with the waveguide power supply circuit in the supply waveguides, it is possible to use a coaxial power supply circuit with the further use of coaxial-pin waveguide pathogens in each VCHAR. The advantages of this power supply circuit are its small overall dimensions and the possibility of ensuring the common-mode addition of the fields of individual VCHAR in the direction of the Oz axis by choosing the length of the power cables

from the common entrance to the rth coaxial waveguide pathogen. The coaxial waveguide power supply circuit is shown in FIG. nine.

The desired law of amplitude excitation is provided both along each waveguide and between waveguides by selecting the coupling coefficients of each slot with the supply waveguide (Fig. 6, b). To ensure the traveling wave regime in the waveguides with slots and the waveguides feeding them, coordinated loads are used at the end of each waveguide.

Slit emitters are excited by a quasi-H ₁₀ wave field in a quasi-rectangular waveguide, each of these quasi-rectangular waveguides is excited from the supply waveguide (Fig. 6, c and d) through the communication holes between these waveguides, and the phase excitation of each rectangular waveguide is such that The radiation of the grating is directed along the Oz axis.

The conical AR is composed of four sublattices, each of which is located on 1/4 of the conical surface and has its own input (output), which is connected to a system of four hybrid nodes (Fig. 10), forming two total (for receiving and transmitting) and two differential outputs in mutually orthogonal planes.

The proposed method for constructing a conical AR makes it possible to provide directivity characteristics that exceed the characteristics of an equivalent planar AR. In FIG. 11 as an example, a comparative calculated dependence (compared with the corresponding dependence for 1/4 of the aperture of the equivalent flat aperture) of the gain in KND (KU) of the proposed AR compared with the KND (KU) of the equivalent flat aperture on the size x / R for a cone with the angle at the apex is 11.3 ° (base radius 2.5λ, height 12.5λ), which show that the directivity gain of the conical AR at x / R = 1 is more than 3 times higher than that of the equivalent flat aperture. The smaller the angle at the apex of the cone α, the greater the gain in the directivity gain of the conical antenna.

In FIG. 12 and 13 show the calculated MDs for the total and difference channels in two orthogonal planes, as well as the MDs for the cross-polarization component. From the given DN it follows that the level of cross-polarization does not exceed -50 dB from the main radiation level.

Thus, the proposed method allows you to develop antennas that provide the formation of total-differential DN, with low aerodynamic drag and not requiring an additional fairing. Based on the totality of the claimed features, the proposed method for constructing on-board conical antenna arrays is new, which allows developing antennas with higher directivity compared to prototypes.

List of sources

1. Resurrection D.I., Ponomarev L.I., Filippov B.C. Convex scanning antennas (basics of analysis and calculation methods). M .: Sov. radio. 1978.

2. Reznikov G.B. Aerials of aircraft. M .: Sov. radio. 1967.

3. Josefsson L., Persson P. Conformal array antenna theory and design. IEEE Press. 2006.

4. Munger A.D., Guy V., Provencher J.H., Gladman B.R. Conical array studies // IEEE Trans. on Antennas and Propagation. 1974. V. 22. No. 1. P. 35-43.

5. Villeneuve A., Behnke M., Kummer W. Wide-angle scanning of linear arrays located on cones // IEEE Trans. on Antennas and Propagation. 1974. V. 22. No. 1. p. 97-103.

6. Gobert J.F., Yang R.F.H. A theory of antenna array conformal to surfaces of revolution // IEEE Trans. on Antennas and Propagation. 1974. V. 22. No. 1. P. 87-91.

7. Aboul-Seoud A.K., Hafez A.-D.S., Hamed A.M., Abd-El-Latif M. A conformal conical phased array antenna for modern radars // 2014 IEEE Aerospace Conference. Big Sky, MT. 2014.P. 1-7.

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Claims (12)

1. The method of constructing waveguide-slot antenna arrays in the form of a system of emitters located on a generalized conical (animated) surface, which consists in the fact that the excitation of each emitter is selected in the process of enumerating various discrete values of the amplitude, phase and polarization of the emitter, characterized in that the problem of diffraction of a plane wave incident along the axis of the cone with a certain polarization on the conductive surface of the cone is previously solved, and the current distribution over the cone surface is determined

P is an arbitrary point on the surface of the cone, then the AR is constructed from slot emitters located on a generalized conical surface, excited in the mode of transmission by the excitation current

from the condition

where c is an arbitrary constant, * is the sign of complex conjugation, and oriented in such a way that the polarization of the radiation field of each emitter coincides in the direction of the cone axis with the polarization of the incident field, Slit emitters are excited using a system of curved waveguides formed by sections of coaxial conical surfaces and segments of parallel metal planes passing parallel to the axes of the cones at some distance d from each other, the middle lines of the outer walls of which coincide with the curves formed by the intersection of the external conical surface parallel to the axis cone by planes having in the coordinate system (x, y, z) with a linear generator of the cone the form of hyperbolas

where α is the angle at the apex of the cone; p is the number of the plane having the average coordinate x _pcr ; p _max - the maximum possible number of planes intersecting the surface of the cone with the length of the generatrix

and a base as _DOS, the longitudinal axis of the radiating slots with the E _y polarization of the radiated field are oriented orthogonally to the longitudinal middle axis on the upper surface of the waveguide in accordance with the formula

where α is the angle at the apex of the cone, β ₂ is the angle of rotation of the emitter (transverse axis of the slit), β ₁ is the angle of the generatrix, The excitation of slot emitters in each of the four sublattices of a monopulse conical antenna is carried out by a field of a traveling wave of the quasi-H _{10 type} in waveguides, which in turn are excited by a traveling wave through a feeding rectangular waveguide through a system of holes (slots) in a linear waveguide having a common wall with radiating waveguides, the distance between adjacent emitters within each VCHAR and the distance between individual VCHAR are selected from the condition of ensuring the phase-in-phase of the emitted fields in the direction of the Oz axis in accordance with the ratio

Where

- distance

between two adjacent emitters along the midline of the rth generatrix;

- the difference in the longitudinal coordinates of the points

the supply waveguide of each of the four sublattices is connected to a power distribution circuit for the formation of two total MDs (for transmission and reception) and two differential MDs (in azimuth and elevation). 2. The method of constructing a conical AR according to claim 1, characterized in that the external surface of the pth waveguide is formed as a result of the intersection of the surface of the external cone with a system of plane-parallel surfaces, and the side walls of each curved rth waveguide are formed by segments of metal surfaces passing through the profile of the external the side wall is orthogonal to the surface of both coaxial metal cones. 3. The method of constructing a conical AR according to claim 1, characterized in that in order to reduce the weight and size parameters of the power supply system from the common input of each sublattice to the VCHAR and to ensure the common-mode addition of the fields of the individual VARs in the direction of the Oz axis, a coaxial scheme for dividing the power from the general input to p is used th coaxial-waveguide pathogen in each rth VCHAR with a choice of length

r-th coaxial cable, providing in-phase addition of the fields of all VCHAR in the direction of the Oz axis. 4. The method of constructing a conical AR according to claim 1, characterized in that the narrow side walls of the waveguides can be formed by rows of closely spaced point contacts extending parallel to the longitudinal axes of the p-waveguides and connecting two metallic conical surfaces embedded in each other.

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