RU2730182C1 - Method of multiple-rundown signal accumulation in radar station when detecting aerial targets in pulse-doppler mode - Google Patents

Abstract

FIELD: physics.SUBSTANCE: method of multiple-rundown signal accumulation in a radar station when detecting aerial targets in pulse-Doppler mode relates to radar ranging and specifically to methods of detecting moving targets. Method can be used in ground-based radars for detecting aerial targets which perform a sequential survey of a given sector of space and operating in a high-pulse repetition mode. Method includes coherent-Doppler filtering of signals in each element of resolution on range and radial velocity and generation of matrix range - radial velocity, containing amplitudes of signals, for several recent space surveys, generation of sufficient statistics as a function of maximum signal values for several consecutive spatial surveys based on hypothesis on target motion parameters, checking of private hypotheses on presence of target in current view for each channel of radial speed by comparison of sufficient statistics with threshold value. Sufficient statistics are formed as sum of amplitude-limited modules of maximum values of signal amplitudes from samples of radial velocity channel obtained in adjacent surveys of one angular direction.EFFECT: technical result of the invention is reducing the number of false marks when observing powerful signals of targets, as well as when the radar unit is exposed to single pulse interference.1 cl, 4 dwg

Description

The method of multi-view accumulation of the signal in the radar when detecting air targets in the pulse-Doppler (ID) mode relates to the field of radar and, in particular, to methods of detecting moving targets. The method can be used in ground and aviation radars for detecting air targets, carrying out a sequential survey of space, and operating in a high pulse repetition rate mode [1, p. 178].

The known method of incoherent extreme accumulation-detection of a signal in the ID of the radar [2]. The essence of the known method is as follows.

The known method consists in the coherent-Doppler filtering of signals in each element of the resolution in terms of range and radial velocity and the formation of a distance-radial velocity matrix containing the signal amplitudes. The hypothesis of the presence of a target in the current survey for each radial velocity channel is accepted if at least one of the particular hypotheses is accepted. A particular hypothesis is accepted if sufficient statistics exceed a threshold value. Sufficient statistics are formed by summing the modules of the maximum values of the signal amplitudes from the samples of the radial velocity channel obtained in adjacent surveys of the same angular direction. The volume of samples is limited by range gates, which are formed by inverse extrapolation of the range relative to the range resolution element with the maximum signal amplitude in the current survey based on estimates of its range, radial velocity and its measurement error, the period of the survey, and the adopted target motion hypothesis. For the current view, the range strobe coincides with the entire analyzed range. Private hypotheses are hypotheses about the presence of a target signal only in the current survey, the current and previous surveys, the current and two previous surveys, and so on, the number of tested partial hypotheses is determined to be equal to the detector order.

или отсутствии

сигнала цели в одном (H¹ ₁, Н¹ ₀), двух (Н² ₁, Н² ₀) и т.д. смежных, включая текущий, обзорах одного углового направления, что позволяет производить обнаружение как вновь появляющихся в анализируемой выборке сигналов, так и сигналов, присутствующих в выборках текущего и предыдущих обзоров. Гипотеза о присутствии цели в текущем обзоре принимается в случае принятия хотя бы одной из частных гипотез присутствия сигнала целиIn the known method, a simultaneous (parallel) verification of particular two-alternative hypotheses about the presence

or absence

target signal in one (H ¹ ₁ , H ¹ ₀ ), two (H ² ₁ , H ² ₀ ), etc. adjacent, including current, surveys of the same angular direction, which allows detecting both newly appearing signals in the analyzed sample and signals present in the samples of the current and previous views. The hypothesis of the presence of a target in the current survey is accepted if at least one of the particular hypotheses of the presence of a target signal is accepted

In the opposite case, the hypothesis of the absence of a goal is accepted - H ₀ .

The disadvantage of this method, which significantly reduces its practical applicability, is the appearance of false marks when observing powerful target signals, as well as when the radar receiver is exposed to single impulse interference.

The reason for the disadvantage of the known method is the use of signals with a large amplitude during the entire time of multispectral accumulation and the appearance of false marks in several consecutive surveys due to a single appearance of a signal with a large amplitude, as well as the emergence and false confirmation of several hypotheses, at the appearance of which one and the same the same signal with a large amplitude.

As the closest analogue, the considered method of incoherent extreme accumulation-detection of the signal in the radar ID was chosen [2].

The technical result of the invention is to reduce the number of false marks when observing powerful target signals, as well as when the radar receiver is exposed to single pulse interference.

The technical result is achieved by limiting the amplitude of signals used in multi-view accumulation.

The claimed method consists in the coherent-Doppler filtering of signals in each element of the resolution in terms of range and radial velocity and the formation of a distance-radial velocity matrix containing signal amplitudes. Saving (memorizing) the range - radial velocity matrix for the last several surveys of space. The hypothesis of the presence of a target in the current survey for each radial velocity channel is accepted if at least one of the particular hypotheses is accepted. Each of the particular hypotheses of which is accepted if sufficient statistics exceed a threshold value. Sufficient statistics are formed as the sum of the maximum values of the signal amplitudes, limited by the amplitude of the modules, from the samples of the radial velocity channel obtained in the adjacent surveys of the same angular direction. The volume of samples is limited by range gates, which are formed taking into account the hypothesis about the parameters of the target movement by inverse extrapolation of the range, relative to the range resolution element with the maximum signal amplitude in the current survey based on estimates of its range, radial velocity and its measurement error, the survey period and the accepted hypothesis target movement. For the current view, the range strobe coincides with the entire analyzed range. Private hypotheses are hypotheses about the presence of a target signal only in the current survey, the current and previous surveys, the current and two previous surveys, and so on, the number of tested partial hypotheses is determined to be equal to the detector order.

или отсутствии

сигнала цели в одном (Н¹ ₁ Н¹ ₀), двух (Н² ₁ Н² ₀) и т.д. смежных, включая текущий, обзорах одного углового направления, что позволяет производить обнаружение как вновь появляющихся в анализируемой выборке сигналов, так и сигналов, присутствующих в выборках текущего и предыдущих обзоров. Гипотеза о присутствии цели в текущем обзоре принимается в случае принятия хотя бы одной из частных гипотез присутствия сигнала целиThe claimed method consists in the simultaneous (parallel) testing of private two-alternative hypotheses about the presence

or absence

target signal in one (H ¹ ₁ H ¹ ₀ ), two (H ² ₁ H ² ₀ ), etc. adjacent, including current, surveys of the same angular direction, which allows detecting both newly appearing signals in the analyzed sample and signals present in the samples of the current and previous views. The hypothesis of the presence of a target in the current survey is accepted if at least one of the particular hypotheses of the presence of a target signal is accepted

In the opposite case, the hypothesis of the absence of a goal is accepted - H ₀ .

The number of simultaneously considered hypotheses is equal to the number of adjacent surveys, the results of which are processed jointly, is called the order of the detector and is denoted by M. As in the method selected as a prototype, the detected marks are characterized by an ambiguously measured range.

The implementation of the claimed method is identical for each angular direction and each radial velocity channel (Doppler filter), and therefore it is considered in relation to one angular direction, determined by the angular dimensions of the radar receiving beam, and one radial velocity channel (Doppler filter).

The claimed method requires joint processing of M matrix range-radial velocity obtained as a result of correlation-filter processing of the echo signal received from the same angular direction in the current and M-1 past surveys. Matrix rows range - radial velocity correspond to radial velocity channels (Doppler filters), columns - to channels of range (ambiguously measured).

Sufficient statistics used to test the hypothesis of the presence of a target signal only in the current k-th survey are the modules of values of the elements of the range - radial velocity matrix, limited in amplitude, obtained in the current survey.

FIG. 1 and 2 schematically show an example of the selection of signal values for the formation of sufficient statistics for three adjacent surveys.

Sufficient statistics to test a particular hypothesis about the presence of a target signal from the current k-th to k-u-th surveys, inclusive, for the case of linear summation [3, p. 165], is formed by the formula

where b ' _k is the amplitude-limited value of the signal b _k

- порог ограничения амплитуды сигнала;Where

- signal amplitude limitation threshold;

b _k - maximum signal value from the sample

where s _k is a row vector of complex signals (one of the rows of the range-radial velocity matrix) containing n elements;

z _k is a binary diagonal matrix defined by the strobe mask w _k defining the range strobe

The sample size specified by the strobe mask for the ku-th survey is equal to the number of nonzero elements w _ku

where w _{ku, i} is the i-th element of the column vector w _ku .

An estimate of the ambiguous range of the mark r _k corresponding to the center of the range resolution element at which the extremum is located in the current k-th survey

where Δ _r - range resolution;

m is the number of the range channel with the extremum.

For the current k-th survey, all elements of the sample are analyzed, therefore v _k = n, az _k = I, where I is the identity matrix.

производится при условии Z_u>h_u, где h_u - пороговое значение. В противном случае принимается гипотеза

.Acceptance of a particular hypothesis about the presence of a goal

is performed under the condition Z _u > h _u , where h _u is the threshold value. Otherwise, the hypothesis is accepted

...

For the ku-th survey, the gating mask w _ku is defined as follows.

в котором сигнал цели находился и обзоров назад с вероятностью близкой 1 в случае принятой модели движения цели. Нижняя и верхняя границы строба дальностиRange strobe is calculated

in which the target signal was located and reviews backward with a probability close to 1 in the case of the adopted target movement model. Lower and upper limits of the range strobe

where υ _k is the estimate of the radial velocity of the target corresponding to the center of the analyzed channel (filter) of the Doppler frequency;

- ошибка измерения радиальной скорости цели, задаваемая шириной фильтра доплеровской частоты

и длиной волны λ;

- error in measuring the radial velocity of the target, specified by the width of the Doppler filter

and wavelength λ;

T _ki is the time between the current k-th and ki-th views of the analyzed angular direction (the period of the view).

и верхнего

индексов элементов, определяющих w_k-u.The calculation of the lower

and top

indices of elements defining w _ku .

рассчитанный по (9), не меньше интервала однозначного измерения дальности год, определяемого частотой повторения импульсов РЛС,

тогда

If the size of the range strobe

calculated according to (9), not less than the interval of unambiguous measurement of the range year, determined by the pulse repetition rate of the radar,

then

и (или)

, тогдаOtherwise, due to ambiguous range measurement, it is possible

and / or

then

where mod ( a , b) is the function of calculating the remainder of dividing a by b;

floor - rounding function to the smallest integer;

ceil is a rounding function.

Elements of the strobe mask w _ku

The principle of formation and application of strobe masks is shown in Fig. 2.

The decision on particular hypotheses is made from the conditions

используемые для принятия решения по достаточной статистике Z_u, задаются по критерию обеспечения заданной вероятности ложной тревоги F в элементе разрешения, и определяются из уравненийThreshold values h _u ,

used to make a decision on sufficient statistics Z _u , are set according to the criterion for providing a given false alarm probability F in the resolution element, and are determined from the equations

at

where ƒ ₀ (s) is the probability density of the amplitude-limited modulus of the noise amplitude at the detector input.

- характеристическая функция усеченного справа по α распределения случайной величины.

is the characteristic function of the distribution of a random variable truncated from the right in α.

Characteristic distribution function of the maximum value of a random variable on a sample of size n

where ƒ _ext (x, n) is the probability density of the distribution of the maximum value of the random variable [4, p. 99] on a sample of size n.

выбирается равным порогу, обеспечивающему заданный уровень ложных тревог F по критерию Неймана-Пирсона для обнаружителя без многообзорного накопления сигнала.Signal amplitude limiting threshold

is selected equal to the threshold providing the specified level of false alarms F according to the Neumann-Pearson criterion for the detector without multi-scan signal accumulation.

The invention is illustrated by the following drawings:

FIG. 1 - the principle of inverse extrapolation of the range strobe.

FIG. 1 shows three realizations of the signal module at the output of the same Doppler filter for one position of the radar antenna radiation pattern obtained in three consecutive surveys.

FIG. 2 - the principle of applying gating masks and generating sufficient statistics.

FIG. 2 shows three samples of the signal of one radial velocity channel obtained in three adjacent surveys of the same angular direction. Parts of the samples used to generate sufficient statistics are highlighted with oblique shading, elements containing extrema are highlighted with solid fill.

FIG. 2 are marked:

- выборка, являющаяся транспонированной вектор-строкой, содержащая n комплексных сигналов в элементах дальности одного канала радиальной скорости;

- a sample that is a transposed row vector containing n complex signals in the range elements of one radial velocity channel;

s ₁ , s ₂ , ..., s _n - complex signal values in resolution elements;

w _k - strobe mask;

R - range axis;

- интервал однозначного измерения дальности ИД РЛС;

- the interval of unambiguous measurement of the radar ID range;

r _k - number of the sample element obtained in the current survey and having the maximum value;

Δr is the size of the range resolution element;

T _k - survey period.

FIG. 3 is an example of elimination of false marks when observing a strong target signal. On the left - when the signal is accumulated in a known way, chosen as an analog, on the right - by the proposed method.

FIG. 3 in the coordinate system azimuth - slant range shows the results of detecting a moving air target when using multi-view accumulation for 4 surveys during 260 surveys. Dots indicate true and false marks, arrows - the direction of the target.

FIG. 4 is an example of the elimination of false marks when observing a powerful target signal under conditions of exposure to the radar receiver of impulse noise with an intensity of 5 pulses per survey. On the left - when the signal is accumulated in a known way, chosen as an analogue, on the right - the proposed method.

Used in FIG. 4, the legend is the same as in FIG. 3.

FIG. 5 - Curves of detection (dependence of the probability of correct detection D on SNR, with a fixed probability of false alarm F) of a signal that does not fluctuate in amplitude at F = 5⋅10 ^-6 when evaluating three hypotheses (M = 3).

FIG. 3 are indicated:

KO - detection curve for the classical detection method;

"1 of 3" - the curves of detection for the proposed method in the presence of a target signal only in the current survey;

"1 and 2 of 3" - detection curves for the proposed method in the presence of a target signal only in the current and past surveys;

"1, 2 and 3 of 3" - the curves of detection for the proposed method in the presence of a target signal in the last three reviews;

{v _k , v _k-1 , v _k-2 } - sample sizes set by gating masks for k-th, k-1-th and k-2 surveys, respectively.

FIG. 6 - Curves of detection of a signal fluctuating in amplitude at F = 10 ^-6 when evaluating three hypotheses (M = 3).

The designations in FIG. 4 correspond to the designations in FIG. 2.

The claimed method includes:

Extraction of the range from the matrix - the radial velocity obtained as a result of sounding the current, k-th angular direction, and containing the complex values of the signal, the rows corresponding to the radial velocity channels.

For each line of the current survey s _k , consisting of n elements corresponding to the range channels, at w _k = I according to (6), z _{k is} calculated.

, в которых сигнал цели с высокой вероятностью находился u обзоров назад.Calculation according to (9) M-1 range strobes

, in which the target signal with a high probability was u backward.

и верхнего

индексов по (10); определение стробирующей маски w_k-u по (11) и z_k-u по (6).Calculation according to (4) of the values b ' _k of the sample elements, limited by the range gates of the current and past surveys, including: estimation of the ambiguous range of the mark r _k according to (8); lower calculation

and top

indices according to (10); determination of the gating mask w _ku according to (11) and z _ku according to (6).

Calculation of sufficient statistics Z _u according to (3-5).

по (13).Calculation of threshold values h _u ,

according to (13).

Decision making based on particular hypotheses by comparing the sufficient statistics Z _u with the corresponding threshold statistics according to (12).

Making a decision on the presence or absence of a target in the row sk of the matrix range - radial velocity according to (2).

The efficiency of the proposed method, in terms of target detection range, is similar to the efficiency of the method selected as the closest analogue.

The claimed technical result is confirmed by the results obtained by the method of computer simulation of the detection system that implements the proposed method.

Modeling was performed with the following initial data

Detection of a moving air target by a 2-coordinate radar in the azimuth sector of 90 ° in the range of slant ranges from 20 to 150 km. The accumulation time of the detected marks is 260 review cycles. Detector order - 4. Number of resolution elements in azimuth - 90, in range - 500. Rate of view - 6 s. Target speed - from 10 to 500 m / s. The probability of a false alarm is 2⋅10 ^-3 . The signal-to-noise ratio for a target at a distance of 100 km is 5.5 dB.

The simulation results of the known and proposed methods for the case of observing a target with a speed of 200 m / s are shown in Fig. 3 and 4. The above simulation results demonstrate the achievement of the claimed technical result, which consists in reducing the number of false marks when observing powerful target signals, as well as when the radar receiver is exposed to single pulse interference.

Literature

1. Handbook on radar, ed. M.I. Skolnik. Per. from English. Ed. B.C. Willows. Book 2.M .: Technosphere, 2014.

2. Pat. 2694809 Russian Federation, IPC G01S 3/02. Method of incoherent extreme accumulation-signal detection in a pulse-Doppler radar / Kolbasko I.V. - No. 2019101558, app. 01.21.19, publ. 07/17/19, Bul. No. 20.

3. Theoretical foundations of radar. Ed. Shirman Y.D. - M .: "Soviet radio", 1970.

4. Gumbel E. Statistics of extreme values. Translated from English, Moscow: Mir, 1965, p.

Claims (1)

A method for multi-view accumulation of a signal in a radar when detecting air targets in a pulse-Doppler mode, which provides for coherent-Doppler filtering of signals in each element of the resolution in terms of range and radial velocity and the formation of a range-radial velocity matrix containing signal amplitudes, preserving the range-radial velocity matrix for several recent surveys of space, the formation of sufficient statistics as a function of the maximum values of the signal for several consecutive surveys of space, taking into account the hypothesis about the parameters of the target movement, verification of particular hypotheses about the presence of a target in the current survey for each radial velocity channel by comparing sufficient statistics with a threshold value, which differs that sufficient statistics are formed as the sum of the maximum values of the signal amplitudes, limited by the amplitude of the modules, from the samples of the radial velocity channel obtained in adjacent surveys of the same angular direction.

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