RU2742287C1 - Method for generation of expanded beams of phased antenna array - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to antenna engineering, particularly to methods of controlling the beamform of a phased antenna array. Technical result is achieved by the fact, that in the method for formation of expanded beams of phased antenna array, based on determination of amplitude-phase distribution in its opening, at which predetermined beam pattern is oriented in direction u₀, formation of expanded beam pattern by partial beams, selection of spatial positions of partial beams only in region of main beam of preset beam pattern, in contrast to prototype in phased antenna array with initial cophased distribution, radiators of which have coordinates x_i with corresponding consecutive numbering from 1 to M, partial beams are formed by pairs of adjacent emitters, numbered in the same sequence from 1 to (M-1), amplitudes of the first F₁ and the last F M-1 partial beams are formed respectively by the sum of the amplitude of the signal of the first radiator and the half-value of the amplitude of the second and the sum of the half-value of the amplitude of the signal of the penultimate emitter and amplitude of the latter, amplitudes of the remaining partial beams are formed by sums of half-values of amplitudes of signals of the respective neighbouring emitters, each partial beam successively in accordance with the number of the partial ray m is selected angular interval Δu_m in generalized coordinates u = sin (θ), where θ is the angle relative to the normal to the opening, determining the coordinates u_m of the middle of the angular interval allocated to each partial beam with the current number m, in which corresponding partial beams are directed, by adding to the initial phase of the signal passing through each radiator, such that the phase of the first radiator does not change, and the phases of all subsequent radiators change simultaneously by the corresponding value.

EFFECT: technical result of the invention is to increase energy efficiency when generating an extended beam pattern.

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Description

The invention relates to the field of antenna technology, in particular to methods for controlling the shape of the directional pattern (DP) of a phased antenna array (PAR).

When forming radiation patterns of a special shape, beams widened in one of the main planes are often used. In passive PAA, the amplitude distribution is strictly limited by the parameters of the distribution system. Therefore, all transformations of the beam shape can be performed only by controlling the phase distribution in the PAA aperture. Under such conditions, the problem of forming extended beams is solved by phase synthesis methods.

There is a known method of beam expansion based on the introduction of the initial phase distribution, when to the law of control of the phases of the signals in the emitters, which is necessary for controlling the beam, add phase biases having a spherical, parabolic or generalized polynomial form [1 - VI Samoilenko, Yu.A. Shishov. Phased array control. M .: Radio and communication, 1983, p. 129-142]. So in a multifunctional antenna array with the implementation of the quadratic phase control law, the width of the directional pattern changes several times [2 - Bibarsov MR, Voloshina VA, Zemlyansky SV, Manuilov BD. et al. Study of the characteristics of a multifunctional antenna array // News of higher educational institutions of Russia. Radioelectronics, 2012, issue. 2, p. 3-9]. The disadvantage of the method based on the introduction of a phase bias is that the rays formed on its basis have insufficiently high energy efficiency, and the side lobes grow with the expansion of the beam.

The closest in technical essence to the proposed one is "A method of forming an extended directional pattern of a phased antenna array" (RU 2644456 C1, application No. 2016152832 dated 12/30/2016, published on 02/12/2018, IPC H01Q 3/26). It is based on the determination of the amplitude-phase distribution in the aperture of the phased antenna array, in which the given radiation pattern is oriented in the direction u ₀ , the choice of the spatial positions of the partial rays only in the region of the main beam of the given radiation pattern. The extended radiation pattern is formed by three partial beams, with the central partial beam oriented in a given direction u ₀ , and two side partial beams are displaced in directions opposite to the central beam by an angle u ₁ The value of the angle u _{1 is} chosen from the solution of the optimization problem by the criterion of minimum

where ƒ (u - u ₀ ), ƒ (u - u ₀ + u ₁ ), ƒ (u - u ₀ - u ₁ ) are the directional patterns of the central partial and two lateral partial rays, respectively;

u ₀ = 0.5kLsinθ ₀ - the direction of the maximum of the generated radiation pattern and the central partial beam in generalized coordinates;

u ₁ = 0.5kLsinθ ₁ is the displacement of the side partial rays relative to the maximum of the generated radiation pattern in generalized coordinates;

a - the amplitudes of the deflected lateral partial rays;

u = 0.5kLsinθ - generalized coordinate;

L is the size of the aperture of the phased antenna array in the plane of the extended radiation pattern being formed;

k is the wavenumber,

determine the amplitudes of the side partial rays in accordance with the expression

a = (ƒ (Δ) - 0.707) (0.707 (ƒ (u ₁ ) + ƒ (-u ₁ )) - (ƒ (Δ + u ₁ ) + ƒ (Δ - u ₁ ))) ^-1 ,

Where

Δ is the half-width of the total beam directional pattern at the half-power level,

and the resulting amplitude-phase distribution in the aperture of the phased antenna array is calculated by the formula

A (x) = A ₀ (x) (1 + a (exp (ikx sinθ ₁ ) + exp (-ikx sinθ ₁ ))) = A ₀ (x) (1 + 2 a cos (kx sinθ ₁ )),

where A ₀ (x) is the amplitude-phase distribution in the aperture, which ensures the formation of a central partial ray in the direction u ₀ .

The main disadvantages of the "Method of forming an extended directional pattern of a phased array antenna", selected as a prototype, are:

- an extended directional pattern is formed by only three partial beams, as a result of which the formed beam does not have good energy efficiency, since its shape is not rectangular, especially at high expansion coefficients;

- for the formation of an expanded beam, it is required to change both the phase and amplitude distributions in the aperture of the HEADLIGHTS, which limits the use of the method only by active HEADLIGHTS;

- to determine the angles of the direction of partial rays, it is required to solve optimization problems, which complicates the algorithm for finding a solution.

The object of the invention is to control the phase distribution in the aperture of the phased array for the formation of extended beams of the directional pattern of the phased array antenna.

The technical result of the proposed method is to increase energy efficiency while forming an extended directional pattern.

The essence of the proposed method consists in determining the amplitude-phase distribution in the aperture of the phased antenna array, in which the given radiation pattern is oriented in the direction u ₀ , the formation of an extended radiation pattern by partial rays, and the choice of the spatial positions of the partial rays only in the region of the main beam of the given radiation pattern. The new features that ensure the achievement of the claimed technical effect are as follows: in a phased array antenna with an initial in-phase distribution, the emitters of which have coordinates x _i with the corresponding sequential numbering from 1 to M, the partial rays are formed by containers of neighboring emitters numbered in the same sequence from 1 House number 1). The amplitudes of the first F ₁ and the last F _M-1 partial rays are formed, respectively, by the sum of the signal amplitude of the first emitter and the half value of the amplitude of the second, and the sum of the half value of the signal amplitude of the penultimate emitter and the amplitude of the latter. The amplitudes of the remaining partial rays are formed by the sums of the half values of the signal amplitudes of the corresponding neighboring emitters. Each partial ray sequentially, in accordance with the number of the partial ray m, is allocated an angular interval Δu _m in generalized coordinates u = sin (θ), where θ is the angle relative to the normal to the aperture, in accordance with the expression:

Where:

m is the number of the partial beam;

n is the current number of the partial beam;

ΔU is the half-width of the expanded beam at half-power,

F _n is the current amplitude of the partial beam;

F _m is the amplitude of the partial beam,

the coordinates u _{m of the} middle of the angular interval allocated to each partial ray with the number m are determined in accordance with the expression:

Where

Δu _n is the current number of the angular interval into which the corresponding partial rays are directed, by adding to the initial phase of the signal passing through each radiator, so that the phase of the first radiator does not change, and the phases of all subsequent radiators change simultaneously by the value determined by the expression:

Where:

k = 2π / λ is the wave number;

Δx _i-1 ⁼ (x _i - x _i-1 ) is the distance between the coordinates of adjacent radiators with numbers i and (i-1).

FIG. 1 shows the division of the linear PAR into paired sublattices with allowance for the virtual splitting of the amplitudes included in the neighboring sublattices.

FIG. 2 shows the operation of forming an expanded beam by superposition of partial beams formed by pairs of adjacent emitters.

FIG. 3 shows the process of determining the location of the n-th corner zone and its dimensions, which can be visually displayed using the corresponding integral functions P (x) and Ρ (u), expressing the energy balance of the energy distribution in the PAA aperture on the one hand and the angular space on the other.

FIG. 4 shows a uniform phase distribution and, corresponding to it, the initial pattern with an unexpanded beam.

FIG. 5 shows a modified phase distribution along the aperture, forming a corresponding expanded beam.

The formation of an expanded beam by a phased antenna array by the proposed method is carried out as follows:

- taking into account the given amplitude distribution in the aperture of the HEADLIGHTS calculate the levels of partial rays {F _m } formed by pairs of adjacent emitters (Fig. 1). Numerically, these levels are equal to the sum of the contributions from the amplitudes of neighboring radiators that form partial beams;

- are set by the values of half the width of the expanded beam at the level of half power ΔU and the direction to the center of the expanded beam u ₀ ;

- determine the angular intervals {Δu _m } corresponding to each partial ray using expression (1);

- determine the coordinates of the middle of each angular interval {u _m } allocated to each partial ray using expression (2);

- determine the phase distribution {Δϕ _m } forming a sector beam using expression (3).

The required beam shape is ensured by the correct positioning of the partial beams, taking into account their level. The energy emitted by each m-th element of the aperture located in the interval Δx _m should be directed to the corresponding m-th corner zone, and it is this that should determine the energy density in the zone Δu _n . The process of determining the location of the m-th corner zone and its dimensions can be visually displayed using the corresponding integral functions P (x) and P (u), expressing the energy balance of the energy distribution in the PAR aperture on the one hand and the angular space on the other (Fig. 3) ...

The level of the maxima of the partial RPs F _m (0) is determined by the type of amplitude distribution in the aperture and the location of a pair of corresponding emitters:

The width of the angular interval allocated to each partial ray (Fig. 3) is proportional to the level of the partial ray and is determined by the expression

The maxima of the partial rays should be directed to the centers of the corresponding intervals, therefore they will be determined in an expression that takes into account the beginning of the expanded ray (u _min = u ₀ -ΔU) and the sizes of the previous angular intervals

So, in the case of equidistant arrangement of elements, to set the partial rays in the direction {u _m }, it is necessary to provide a phase shift on the right radiators of the sublattices by the value

Δφ _{m + 1} = -kdu _m .

It is obvious that the phases of the common emitters of neighboring sublattices should be the same (Fig. 1). Taking into account that the phase of the first (leftmost) radiator can be left unchanged, the desired phase of the radiator with number m (m> 1) will be determined by a formula that takes into account the phase shifts on the previous sublattices

The resulting phase distribution {Δϕ _m } will form an expanded beam.

Since the amplitude component of the PAA pattern does not depend on the sign of the additional phase distribution in the aperture, then the same expanded beam will form the phase distribution taken with the opposite sign. Therefore, there are two phase distributions with different phase signs, forming the same extended beam

A comparative analysis of the claimed method and the prototype shows that the claimed method has the following distinctive properties:

- a larger number of partial beams is used, the number of which is equal to (M-1), where Μ is the number of HEADLIGHTS emitters, which allows for greater energy efficiency (rectangularity) of the expanded beam shape;

- for the formation of the beam, it is necessary to change only the phase distribution in the aperture of the HEADLIGHTS, which makes it possible to use the claimed method in both active and passive HEADLIGHTS;

- to determine the angles of the direction of partial rays {u _m } it is not required to solve optimization problems.

The comparative analysis of the claimed method and the prototype shows that the claimed method offers significant advantages in the use of phase synthesis of sector rays, the most important of which are:

- the ability to unambiguously determine the phase distribution based on the known amplitude distribution in the aperture and the required beam shape on the basis of simple algebraic operations;

- sector beams obtained using this method have high energy efficiency;

- the considered approach eliminates the need to solve the optimization problem by the minimum criterion; instead, it is proposed to use simple formulas that do not require complex calculations;

- the possibility of realizing a beam with the required expansion coefficients directly during the operation of the radar.

Claims (16)

A method of forming extended beams of a phased antenna array, based on determining the amplitude-phase distribution in its aperture, in which a given radiation pattern is oriented in the direction u ₀ , forming an extended radiation pattern by partial beams, and choosing the spatial positions of partial beams only in the region of the main beam of a given radiation pattern , characterized in that in a phased antenna array with an initial in-phase distribution, the emitters of which have coordinates x _i with the corresponding sequential numbering from 1 to M, the partial beams are formed by pairs of adjacent emitters, numbered in the same sequence from 1 to (M-1), the amplitudes of the first F ₁ and the last F _M-1 partial rays are formed, respectively, by the sum of the signal amplitude of the first emitter and the half value of the amplitude of the second and the sum of the half value of the signal amplitude of the penultimate emitter and the amplitude of the latter, the amplitude of the partial rays are formed by the sums of half values of the signal amplitudes of the corresponding neighboring emitters, each partial ray is sequentially allocated in accordance with the number of the partial ray m an angular interval Δu _m in generalized coordinates u = sin (θ), where θ is the angle relative to the normal to the aperture, in accordance with with expression

Where m is the number of the partial beam; n is the current number of the partial beam; ΔU is the half-width of the expanded beam at half-power, F _n is the current amplitude of the partial beam; F _m is the amplitude of the partial beam, coordinates u _{m of the} middle of the angular interval allocated to each partial ray with the current number m are determined in accordance with the expression

where Δu _n is the current number of the angular interval, into which the corresponding partial rays are directed, by adding to the initial phase of the signal passing through each radiator, so that the phase of the first radiator does not change, and the phases of all subsequent radiators change simultaneously by the amount determined by the expression

Where k = 2π / λ is the wave number; Δx _i-1 = (x _i - x _i-1 ) is the distance between the coordinates of adjacent radiators with numbers i and (i-1).

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