RU2760976C1 - Method for tomographic registration of inclined range and azimuth of position of surface objects and objects above underlying surface - Google Patents

Abstract

FIELD: radar technology.

SUBSTANCE: invention relates to the field of radar technology, namely to methods for determining the coordinates of the inclined range and azimuth of overwater objects and objects above the underlying surface. The claimed method uses a digital ring multi-element equidistant phased array antenna. Due to the use of a grid that consistently generates the same radiation patterns, circular probing of the radar scene with an acutely directed beam is carried out. With a time delay proportional to the length of the trajectory formed by multiple reflections from objects inside the radar scene, the response signals returned at different angles, the so-called trajectories-sums representing the initial projection data of the tomographic method, are recorded. According to the projection data, as a result of digital reconstruction on a discrete hexagonal grid, the trajectory estimation is selected. For each unknown initial trajectory, a set of all possible estimates of it is selected with the corresponding lengths satisfying the condition of comparing the modulus of the length difference with the systematic sampling error. In addition, the projection data, if a response is received, is assigned the status of reliable events with a probability equal to one, if there is no response, impossible events with a probability equal to zero. For each received (i.e. come off) or missing event, the restoration of the original function of the radar scene is carried out using the theorems of multiplying the probabilities of independent events: finding reflecting objects at the vertices of the trajectory estimate, and then adding up all trajectory estimates satisfying the condition, from which a system of nonlinear equations with unknowns is formed. The solution by the method for successive Gauss exceptions of a system of nonlinear equations is a vector column of unknowns of the reconstructed probabilistic estimation of the radar scene with an estimate of the inclined range and an estimate of the azimuth of the position of objects inside the scene.

EFFECT: detection of hidden objects that are out of direct radio visibility or, due to design features, do not reflect, but scatter radio waves.

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Description

The invention relates to the field of radar technology, namely to methods for determining the coordinates of the slant range and azimuth:

- surface objects;

- objects above the underlying surface.

In traditional active radar with a passive response, there are four variants of the trajectory along which the electromagnetic wave reflected from the object and from another surface returns to the receiver:

- the signal directly reflected from the object with the "emitter - object - receiver" trajectory;

- signal with the "emitter - surface - object - receiver" trajectory;

- a signal with a "emitter - object - surface - receiver" trajectory, such as a single specular reflection;

- a signal with a trajectory "emitter - object - surface - receiver", which describes the diffuse scattering of the signal reflected from the object. It is generally accepted that the first two versions of the above list are a useful signal from which the coordinates are determined; the last two variants of the given list - there is a false signal that needs to be excluded.

A known method for determining the elevation coordinate of a low-flying target (NLC), containing the reception of the total signal reflected from the target and the underlying surface at the outputs of four antennas, the formation of discriminatory characteristics (DC) of the coordinate meter in two orthogonal planes S _x and S _y and positioning the maximum of the main lobe of the total directional pattern (DP) of the antenna system of the coordinate meter in the direction of the point of projection of the target onto the underlying surface, characterized in that the centers of the four antennas of the coordinate meter are arranged symmetrically in pairs in the horizontal and vertical planes, an additional signal is formed at one of their outputs of the coordinate meter, which is the difference of the total signals of pairs of elements of the antenna system located in the horizontal and vertical planes, which is used to form an additional DH, and the elevation coordinate and (with a known slant range) the height of the NLC are determined from the ratio using the HHs found in this way. The achieved technical result is an increase in the accuracy of determining the coordinates of the target [1]. The known method does not allow you to accurately determine the angular coordinates of even two closely spaced targets. The algorithm based on the known method is quite sensitive to discrepancies with the real situation and can give significant statistical errors even in a two-beam model of electromagnetic wave propagation.

и вектор 2N сигналов столбцевых диаграмм,

и

- векторы сигналов строковой диаграммы с номером n и столбцевой диаграммы с номером k, θ_j - угол места цели и β_j - азимут цели с номером j относительно нормали к антенне, η_n и ζ_k - помехи - внутренние шумы строковой диаграммы с номером n и столбцевой диаграммы с номером k, описывающиеся комплексным «белым» шумом с нулевым средним и известной дисперсией:The closest analogue is a method for measuring the angular coordinates of a group of N closely spaced targets, possibly under conditions of active interference, which consists in the fact that true and false signals reflected from targets are received by means of a digital linear equidistant phased antenna array, which is a matrix consisting of 2N × 2N beams, 4N ² beams in total, and representing an equidistant line of radiation patterns, with the same total radiation patterns and phase centers located at the same distance from each other, from the received total signals, a vector of 2N signals of line diagrams is formed

and a 2N vector of bar graph signals,

and

are the signal vectors of the line diagram with number n and the bar diagram with number k, θ _j is the elevation angle of the target and β _j is the azimuth of the target with number j relative to the normal to the antenna, η _n and ζ _k are interference - internal noise of the line diagram with number n and a bar chart with number k, described by complex "white" noise with zero mean and known variance:

a F (θ) is the function of the amplitude-phase distribution of the total radiation pattern, common for all line and bar diagrams, k _j and ρ _j are the complex reflection coefficients of targets in the vertical and horizontal planes, μ _j and γ _j are the generalized angles of the target with the number j in horizontal and vertical planes:

обозначено комплексно сопряженное число с числом х; далее осуществляют цифровую обработку вектора сигналов

и

для формирования вектора измерений целей по углу места и курсовому углу, по которым определяют обобщенные углы целей, корреляционную матрицу ошибок измерений и корреляционную матрицу векторного шума и, используя матрицу Вандермонда, определяют угловые координаты близкорасположенных целей [2]. В силу того, что известный метод полноценно не учитывает полезную информацию, содержащуюся в сигналах, порожденных зеркальным отражением и диффузным рассеянием, сводя их информативность к ложному проявлению, определить угловые координаты скрытых объектов не представляется возможным.D is the distance between the phase centers of the receiving diagrams, λ is the wavelength, through

denoted a complex conjugate number with the number x; then carry out digital processing of the signal vector

and

to form a vector of measurements of targets in elevation and heading, which determine the generalized angles of targets, the correlation matrix of measurement errors and the correlation matrix of vector noise and, using the Vandermonde matrix, determine the angular coordinates of closely spaced targets [2]. Due to the fact that the known method does not fully take into account the useful information contained in the signals generated by specular reflection and diffuse scattering, reducing their information content to a false manifestation, it is not possible to determine the angular coordinates of hidden objects.

The task is to develop a method that makes it possible to fix the coordinates of the slant range and azimuth of the position of scattering objects from a variety of objects of the radar scene, allowing the possible absence of a reflected echo signal, which is characteristic of traditional active monostatic radar with a passive response, but does not exclude the return of radio echo as a result of multiple reflections of the scanning signal inside Radar scene, including from other objects and at a different azimuth angle. In the traditional way - active radar with passive response - this is impossible to achieve.

The technical result consists in the detection of hidden objects that are out of direct radio visibility or, due to design features, not reflecting, but scattering radio waves.

и азимута ϕ положения надводных объектов и объектов над подстилающей поверхностью, описываемого радиус-вектором

, благодаря использованию цифровой кольцевой многоэлементной эквидистантной фазированной антенной решетки, последовательно генерирующей одинаковые диаграммы направленности, тем самым осуществляющей остронаправленным лучом с азимутальным углом α круговое зондирование радиолокационной сцены, описываемой исходной функцией р, с задержкой по времени τ пропорциональной длине

образованной многократными отражениями от объектов внутри радиолокационной сцены траектории L, регистрируются возвращенные под разными углами β сигналы отклика, так называемые траектории-суммы, представляющие собой исходные проекционные данные

томографического метода, по которым, в результате цифровой реконструкции на дискретной пространственной сетке {(R_j, α_j)}, состоящей из гексагональных элементов, представленных в обратном перспективном сокращении к центру, с построениями звеньев

оценки траектории

схожими с фрактальными, осуществляется подбор для каждой неизвестной исходной траектории L_t ее оценки в виде множества K всех возможных оценок траекторий

с соответствующими длинами

, удовлетворяющими условию сравнения модуля разности длин со систематической погрешностью дискретизации

, кроме того проекционным данным если отклик получен, присваивается статус достоверных событий с вероятностью равной единице, если отклик отсутствует, - невозможных событий с вероятностью равной нулюThis result is achieved due to the fact that in the method of tomographic recording of the slant range

and azimuth ϕ of the position of surface objects and objects above the underlying surface, described by the radius vector

, thanks to the use of a digital ring multielement equidistant phased antenna array, which sequentially generates the same directional patterns, thereby carrying out a circular sounding of the radar scene described by the original function p, with a time delay τ proportional to the length

formed by multiple reflections from objects inside the radar scene of the trajectory L, the response signals returned at different angles β are recorded, the so-called sum trajectories, which are the initial projection data

tomographic method, according to which, as a result of digital reconstruction on a discrete spatial grid {(R _j , α _j )}, consisting of hexagonal elements, presented in reverse perspective reduction to the center, with constructions of links

trajectory estimates

similar to fractal ones, for each unknown initial trajectory L _t its estimates are selected in the form of a set K of all possible estimates of trajectories

with corresponding lengths

satisfying the condition for comparing the modulus of the difference in lengths with a systematic sampling error

, in addition, the projection data, if a response is received, is assigned the status of reliable events with a probability equal to one, if there is no response, - impossible events with a probability equal to zero

осуществляется с помощью теорем умножения вероятностей независимых событий - нахождения отражающих объектов в вершинах оценки траектории

и последующего сложения всех удовлетворяющих условию оценок траекторий

, из которых формируется система Т нелинейных уравнений с J неизвестными, записываемая в матричном виде:for each received (i.e., taken place) or absent event l _t filling the function P (l _t ) with estimates of the original function

is carried out using the theorems of multiplying the probabilities of independent events - finding the reflecting objects at the vertices of the trajectory estimate

and the subsequent addition of all trajectory estimates satisfying the condition

, from which a system of T nonlinear equations with J unknowns is formed, written in matrix form:

where is the column vector of unknowns

восстановленной вероятностной оценки радиолокационной сцены, с оценкой R_j наклонной дальности

и оценкой α_j азимута ϕ_j положения объектов внутри сцены.the solution by the method of successive Gaussian elimination which is the column vector

reconstructed probabilistic assessment of the radar scene, with the estimate R _{j of the} slant range

and an estimate α _{j of the} azimuth ϕ _{j of the} position of the objects within the scene.

FIG. 1 shows a radar scene.

FIG. 2 shows the principles of active monostatic radar with passive response.

Fig. 3 shows specular reflection and diffuse scattering of a signal reflected from an object.

FIG. 4 shows the paths of the return of the radio echo as a result of multiple reflections of the probing signal inside the radar scene.

FIG. 5 shows the trajectories of the radio echo as a result of multiple reflections of the probing signal inside the radar scene.

FIG. 6 shows the sampling of the space of the radar scene with a grid.

FIG. 7. shows the fractal construction of the links of the trajectory estimates on the hexagonal elements.

FIG. 8. shows many estimates of trajectories from projection data.

FIG. 9. shows the emitting antenna and the probing directional beam.

FIG. 10. shows a diagram for determining the coordinates of the slant range and azimuth of surface objects and objects above the underlying surface.

FIG. 1-10 indicate: 1 - surface objects and objects located above the underlying surface, 2 - emitting antenna, 3 - probing directional beam, 4 - scattering of the signal reflected from the object, 5 - object that does not return reflected radio echo in the direction of the receiving antenna, 6 - receiving antenna, 7 - radio echo return paths, 8 - trajectories, 9 - hexagonal elements presented in reverse (to the center) perspective reduction, 10 - trajectory estimates, 11 - block of initial projection data registration, 12 - block of digital reconstruction of the radar scene.

It is assumed that in a given coordinate system there is a radar scene containing surface objects and objects located above the underlying surface (Fig. 1).

с наклонной дальностью R и азимутальным углом α, трасса зондирующего сигнала имеет азимутальный угол α=ϕ₁.The principles of active monostatic radar are widely known, based on the effect of scattering of the radiated radio wave on objects located on the path of the probing signal, and the subsequent registration of part of the wave energy reflected in the direction of the emitter (Fig. 2). When describing the coordinates of the polar system by the radius vector

with a slant range R and an azimuth angle α, the path of the sounding signal has an azimuth angle α = ϕ ₁ .

координат положения некоторого рассеивающего объекта из множества объектов

радиолокационной сцены, допускается возможное отсутствие отраженного эхосигнала, характерного для традиционной активной радиолокации с пассивным ответом. Хотя при этом не исключается возвращение радиоэха в результате многократного отражения зондирующего сигнала внутри радиолокационной сцены, в том числе от других объектов и по другим трассам с азимутальным углом β (фиг. 4).In the present invention, to the known principles of radar, it is proposed to add the registration of objects that do not return the reflected radio echo in the direction of the emitter (Fig. 3). In other words, take into account that, when fixing those described by the radius vector

coordinates of the position of some scattering object from a set of objects

radar scene, the possible absence of the reflected echo signal characteristic of traditional active radar with a passive response is allowed. Although this does not exclude the return of radio echo as a result of multiple reflections of the probing signal inside the radar scene, including from other objects and along other paths with an azimuthal angle β (Fig. 4).

, описывающая радиолокационную сцену:To solve the problem of formalizing the direct tomographic transformation, the original function was introduced

describing the radar scene:

which at points in space where a reflecting (scattering) object is present, takes on a value equal to one, and at other points zero.

.In addition, a certain trajectory has been introduced along which the probing signal and repeatedly reflected from the objects moves. Trajectory L is one of the set {L} of trajectories - in the general case, a broken line (closed with a finite length / or open) in space, which has kinks at the points of presence of objects

...

In the selected coordinate system, the trajectory is a set of points (Fig. 5). Let the trajectory L be a polyline given parametrically:

разбиение отрезка параметризации [ϕ₁, β] то разбиение ломаной L точками:if

the partition of the interval of parametrization [ϕ ₁ , β] then the partition of the broken line L by points:

, где индекс t=(1…T) - уникален и указывает на комбинацию аргументов (ϕ, β, τ). Наличие замкнутых и незамкнутых траекторий

являют собой анализируемые события. Замкнутые траектории на фиг. 5 представлены ломаными L₁ и L₂, а незамкнутые представлены ломаной L₅.Closed trajectories with the time delay of the response signal τ are recorded by the receiver, since they have a finite length l (ϕ, β, τ) = l _t and

, where the index t = (1… T) is unique and indicates a combination of arguments (ϕ, β, τ). The presence of closed and non-closed trajectories

are analyzed events. The closed paths in FIG. 5 are represented by broken lines L ₁ and L ₂ , and open ones are represented by broken line L ₅ .

The connection of the broken trajectory L _t with the reflecting objects forming it is defined:

указывает на соответствующую i-ую вершину ломаной L_t.where δ is the Dirac function, and each vector of the set

points to the corresponding i-th vertex of the broken line L _t .

The analogy of the proposed method with tomography requires the presence of the so-called initial projection data obtained during the scanning (sensing) procedure of the space. The initial data in the proposed method of reflection tomography is the length l _t proportional to the delay time τ _t spent by the signal to pass the broken path L _t .

Since direct tomographic transformation is a procedure for obtaining initial projection data, or as they are also called integral sums (trajectory-sums), the initial projection data, which is a summation procedure along a closed broken line of a trajectory, are described by the expression:

numerically equal

- есть звенья ломаной L_t, и конкретное включение

в указанной разности определяется из выражения (1).where the difference vector of coordinates of objects participating in the reflection,

- there are links of the broken line L _t , and a specific inclusion

in the specified difference is determined from expression (1).

разбиение наклонной дальности, а

разбиение отрезка параметризации полного азимутального угла [0,2π), то изначально непрерывный радиус-вектор

принимает одно из множества конкретных дискретных состояний:To solve the problem of inverse tomographic transformation, preliminary constructions have been carried out. The original investigated space of the radar scene was discretized by a grid consisting of hexagonal elements. In polar coordinates, the grid is shown in reverse (to the center) perspective reduction (Fig. 6). Moreover, if

splitting of the slant range, and

splitting the segment of the parameterization of the total azimuthal angle [0,2π), then the initially continuous radius vector

takes one of many specific discrete states:

и мелкость разбиения отрезка параметризации наклонной дальности

where the index j = (1 ... J) -unique and indicates a combination of arguments (m, n), respectively, the fineness of the partition of the segment of the parameterization of the total azimuthal angle

and the fineness of the partition of the slant range parameterization segment

радиолокационной сцены.It is known that the problem of the inverse tomographic transformation is to search for the _{set of reflecting objects from the initial projection data {l t} } from (2)

radar scene.

. Такой оценкой радиус-вектора

положения отражающего объекта является дискретный радиус-вектор

из (3) с рассчитанной вероятностью

его наличия в радиолокационной сцене.The declared search required the introduction of the concept of assessing the position of an object, i.e. radius vector estimates

... Such an estimate of the radius vector

the position of the reflecting object is a discrete radius vector

from (3) with the calculated probability

its presence in the radar scene.

в свою очередь также является оценкой ранее введенной исходной функцией

, описывающей радиолокационную сцену.It should be noted that the calculated stochastic function

in turn is also an estimate of the previously introduced original function

describing a radar scene.

, восстановленная функция

приобретает свойства дискретной стохастической (вероятностной), область значений которой находится уже в интервале от 0 до 1.Thus, during the reconstruction of the deterministic original original

, restored function

acquires the properties of a discrete stochastic (probabilistic), the range of values of which is already in the range from 0 to 1.

. Множество оценок

известно заранее еще до реконструкции и задается построениями звеньев схожими с фрактальными на гексагональных элементах в обратном перспективном сокращении к центру:An estimate of a specific trajectory L _{t of} length l _t is the set

... Lots of ratings

is known in advance even before the reconstruction and is given by the constructions of links similar to fractal ones on hexagonal elements in reverse perspective reduction to the center:

These constructions are shown in Fig. 7.

описывается суммой длин звеньев:

где разностный вектор

- есть звенья оценки ломаной

The length of the closed path estimation polyline

is described by the sum of the lengths of the links:

where the difference vector

- there are links in the evaluation of the broken line

с соответствующими длинами

, удовлетворяющими условию:The search begins with a match (Fig. 8). For each unknown initial trajectory L _t , but with a known length l _t ~ τ proportional to the signal response delay time τ, an estimate is selected in the form of a set K of all possible estimates of trajectories

with corresponding lengths

satisfying the condition:

where Δ is the systematic error in the discretization of space, given by the fineness of the partition by the hexagonal grid.

Projection data (2), if a response is received, is assigned the status of reliable events with a probability equal to one, if there is no response, - impossible events with a probability equal to zero:

осуществляется с помощью теорем умножения вероятностей независимых событий - нахождения отражающих объектов в вершинах оценки

и последующего сложения всех удовлетворяющих (4) оценок траекторий

For each received (i.e., taken place) or absent event l _t, filling the function P (l _t ) with estimates

is carried out using the theorems of multiplying the probabilities of independent events - finding the reflecting objects at the vertices of the estimate

and the subsequent addition of all trajectory estimates satisfying (4)

where

Let the projection data (2) be represented by the set:

where

then the probabilities of finding an object (at least one) in discrete hexagonal grid elements of the radar scene are represented by the set:

where

From (5), a system of T nonlinear equations with J unknowns is formed, written in matrix form:

а соответственно и координат (R_j - как оценки наклонной дальности

объекта, a_j - как оценки азимута ϕ объекта), которые при подстановке в систему (6), превращает каждое уравнение в верное числовое равенство осуществляется методом последовательных исключений (методом Гаусса).Column Vector Search

and, accordingly, coordinates (R _j - as estimates of the slant range

object, a _j - as estimates of the azimuth ϕ of the object), which, when substituted into system (6), turns each equation into a true numerical equality is carried out by the method of successive elimination (Gauss method).

Literature

1. Patent No. 2444750 RF, IPC G01S 5/08. Method for determining the elevation coordinate of a low-flying target / Balagurovsky V.A., Kondratyev A.S., Polishchuk N.P. - Publ. 03/10/2012.

2. Patent No. 2649899 RF, IPC G01S 13/20. Method for measuring the angular coordinates of group low-flying targets / Korobochkin Yu.B. - Publ. 04/05/2018.

Claims (7)

Method for tomographic recording of slant range

and azimuth ϕ of the position of surface objects and objects above the underlying surface, described by the radius vector

, in which, thanks to the use of a digital ring multielement equidistant phased antenna array, which sequentially generates the same directional patterns, thereby carrying out a circular sounding of the radar scene described by the original function p with a time delay τ proportional to the length

formed by multiple reflections from objects inside the radar scene of the trajectory L, characterized in that the response signals returned at different angles β are recorded, the so-called sum trajectories, which are the initial projection data

tomographic method, according to which, as a result of digital reconstruction on a discrete spatial grid {(R _j , α _j )}, consisting of hexagonal elements, presented in reverse perspective reduction to the center, with constructions of links

trajectory estimates

similar to fractal ones, for each unknown initial trajectory L _t its estimates are selected in the form of a set K of all possible estimates of trajectories

with corresponding lengths

satisfying the condition for comparing the modulus of the difference in lengths with a systematic sampling error

, in addition, the projection data l _t , if a response is received, is assigned the status of valid events with a probability equal to one, if there is no response, - impossible events with a probability equal to zero

for each received (i.e., taken place) or absent event l _t filling the function P {l _t ) with estimates of the original function

is carried out using the theorems of multiplying the probabilities of independent events - finding the reflecting objects at the vertices of the trajectory estimate

, and the subsequent addition of all trajectory estimates satisfying the condition

from which a system of T nonlinear equations with J unknowns is formed, written in matrix form:

where is the column vector of unknowns

the solution by the method of successive Gaussian elimination which is the column vector

the reconstructed probabilistic assessment of the radar scene with the estimate R _{j of the} slant range

and an estimate α _{j of the} azimuth ϕ _{j of the} position of the objects within the scene.

Images