RU184465U9 - False target selection device - Google Patents

Abstract

The utility model relates to radar and can be used in surveillance coherent-pulse reconnaissance radars (RLS) of the reconnaissance, providing monitoring of the air situation, and in coherent-pulse tracking radars to select false targets from true targets. Achievable technical result - the ability to select single false and / or true targets in the channels in range and speed, increasing the radar noise immunity. The specified technical result is achieved by the fact that in the known device containing a complex compression filter connected in series, the input of which receives a complex signal of the intermediate frequency of the radar receiver, a sampler, a compressed signal envelope detector, a storage device and a detector, a random access memory (RAM1) for storing complex samples compressed signal, the input of which is connected to the output of the sampler, a random-access memory (RAM2) for storing samples of the signal detected the input of which is connected to the output of the detector, as well as a calculator and a threshold device (PU), at the second input of which a fixed threshold is supplied, the calculator is configured to calculate a signal coherence measure, containing a series-connected unit for generating an estimated (selective) correlation matrix (CM) , a unit for calculating the eigenvalues of the CM and a block for calculating the entropy, while the first and second inputs of the unit for forming the estimated CM are connected to the outputs of RAM1 and RAM2, respectively, and the control unit is made with the possibility of a comparison of entropy values with a fixed threshold, the first input of which is connected to the output of the entropy calculation unit, in addition, a decoding device is added that contains a logic unit and (n-1) delay units for the review period, and the output of the control unit is connected to the input of the first of the chain consecutively connected (n-1) delay blocks for the review period and the first input of the logic block, while the output of each of (n-1) delay blocks for the review period is connected to the inputs of the logic block, the output of which is the output of the device. 2 ill.

Description

The utility model relates to radar and can be used in surveillance coherent-pulse reconnaissance radars (RLS) of the reconnaissance, providing monitoring of the air situation, and in coherent-pulse tracking radars to select false targets from true targets.

The problem of protection against response simulation interference is extremely urgent, because these interferences lead to the most significant disruption of the functioning of radar systems and disorientation by forming marks from false targets on the radar indicator. The result of such interference is, for example, non-detection of echo signals from an air target or overload of the radar computing system due to the processing of a large amount of false information about the air situation.

Known devices for protection against active imitating interference -purpose, similar in purpose [1]. The effectiveness of these devices largely depends on the introduction of additional hardware and a priori knowledge of the signal-noise environment. The disadvantages of these devices are the impossibility of simultaneous protection against interference that leads away in range and speed, the use of additional watchdog strobes in the protection systems, and the adjustment of the operating frequency. Also, the current trend of deploying repeaters on board an airplane or helicopter type mini / micro unmanned aerial vehicle, on MALD and TALD cruise missiles [2] does not allow the radar to detect the true signal due to secondary radiation from a small target (the effective reflective surface of such targets is of the order of (0.1 ÷ 0.001 m ² )). This feature makes the protection devices against relay interference, based on a comparison of signals from false and true targets, in view of the absence of the latter, inoperative.

The closest analogue (prototype) to the proposed utility model according to the technical solution is a device for selecting false targets in the radar range channel with a complex pulse signal [3] (the block diagram of which is shown in Fig. 1) containing a typical receiving path including a compression filter ( SF), a discretizer, an envelope detector, a drive and a detector, and an additional device that includes random-access memory devices (RAM1, RAM2), the calculator of the modules of the correlation coefficients between the samples of the complex is compressed a signal device and a threshold comparison module correlation coefficients with a fixed threshold.

The work of the known device is based on the selection of true and false targets, carried out on the basis of estimates of the correlation coefficients between the samples of the complex signal at the output of the SF receiver of the radar. The calculation of these coefficients is carried out for those samples in the range in which the detection of signals. If in two or more samples the detection occurred under the influence of one interference signal (as in the case of amplitude-modulated interference of the repeater), then the fluctuations of the corresponding samples of the compressed signal should be significantly correlated. In this case, fluctuations in the samples of the compressed signal corresponding to the positions of true targets are weakly correlated with fluctuations in the samples corresponding to false targets. To make a decision on whether the detected targets belong to true or false targets, the modules of the obtained correlation coefficient estimates are compared with a given threshold. If the threshold is exceeded for any pair of samples, both targets are considered false.

The disadvantage of the above devices are:

- protection against active simulating interference exists only in the channel in range;

- a necessary condition for making decisions for the selector regarding the numbers of samples (channels) in range is the presence of a pair of false or true targets;

- the inability to determine the ownership of signals from an active simulating interference at the output of the radar receiver detector when the interference signal is detected ahead, or after the true target signal, when the true target signal does not exceed the detector threshold (for example, a signal from a small target);

- the impossibility of determining the belonging of the signals at the output of the radar receiver detector (selection of true and false targets), in the case when in the channel in range there is one signal of false and true targets.

Achievable technical result - the ability to select single false and / or true targets in the channels in range and speed, increasing the radar noise immunity.

An additional technical result is to increase the likelihood of correct recognition of false and true targets based on the processing results for several periods of the review (sensing) performed by the deciding device.

The specified technical result is achieved by the fact that in the known device containing a complex compression filter connected in series, the input of which receives a complex signal of the intermediate frequency of the radar receiver, a sampler, a compressed signal envelope detector, a storage device and a detector, a random access memory (RAM1) for storing complex samples compressed signal, the input of which is connected to the output of the sampler, a random-access memory (RAM2) for storing samples of the signal detected the input of which is connected to the detector output, as well as a calculator and a threshold device (PU), at the second input of which a fixed threshold is supplied, the calculator is configured to calculate a signal coherence measure, containing a series-connected unit for generating an estimated (selective) correlation matrix (CM), a unit for calculating the eigenvalues of the CM and a unit for calculating the entropy, while the first and second inputs of the unit for forming the estimated CM are connected to the outputs of RAM1 and RAM2, respectively, and the control unit is configured to comparing entropy values with a fixed threshold, the first input of which is connected to the output of the entropy calculation unit, in addition, a decoding device is added that contains the logic block “m of n” and (n-1) delay units for the review period, and the output of the control unit is connected with the input of the first from the chain of series-connected (n-1) delay blocks for the review period and the first input of the logic block “t from p”, while the output of each of (n-1) delay blocks for the review period is connected to the inputs of the logic block “m from n ", the output of which is the output of the device oystva.

m is the number of excesses of a given threshold h.

n is the number of inputs of the logic block, corresponding to the total number of review periods, on which the sign of the goal is formed.

m, n - 1, 2, 3, ...

In FIG. 2 presents a structural diagram of the proposed device, where it is indicated:

1 - SF;

2 - discretizer;

3 - detector;

4 - drive;

5 - detector;

6 - RAM1;

7 - RAM2;

8 - calculator measures the coherence of the signal;

9 - PU;

10 - a decisive device;

11 - block forming the estimated CM;

12 - block calculating the eigenvalues of the CM;

13 — entropy calculation unit;

14 - block delay;

15 is a logic block.

The device for selecting false targets contains a complex SF 1 connected in series, to the input of which a complex signal of the intermediate frequency of the radar receiver, a sampler 2, a compressed signal envelope detector 3, a drive 4 and a detector 5, as well as a random access memory (RAM1) 6 for memorizing complex a compressed signal, the input of which is connected to the output of the sampler 2, random access memory (RAM2) 7 for storing the samples of the detection signal, the input of which is connected to the detection output 5, the calculator of the measure of coherence of the signal 8, PU 9 for comparing the values of the entropy with a fixed threshold and a solver 10. Moreover, the calculator of the measure of coherence of the signal 8 contains a series-connected unit for the formation of the estimated (selective) KM 11, a unit for calculating the eigenvalues KM 12 and a block computing entropy 13, and the output of RAM1 6 is connected to the first input of the evaluation unit KM 11, the second input of which is connected to the output of RAM2 7. The structure of the deciding device 10 includes (n-1) delay units 14 for the review period and a logic block 15 “m of n”. In this case, the first input of the control unit 9 is connected to the output of the entropy calculation unit 13, and a fixed threshold is supplied to the second input, and the output of the control unit 9 is connected to the input of the first from the chain of series-connected (n-1) delay units 14 for the review period and the first input of the logic unit 15 "m of n". In addition, the output of each of the (n-1) delay units 14 for the review period is connected to the inputs of the logic unit 15 “m from n”, the output of which is the output of the device.

SF 1, sampler 2, detector 3 of the envelope of the compressed signal, drive 4 and detector 5 form a typical receiving path.

RAM1 6, RAM2 7, the calculator measures the coherence of the signal 8, PU 9 and the deciding device 10 form an additional device.

The delay unit 14 for the review period can be implemented, for example, on the delay lines.

The logic block 15 “m of n” is a configurable logic block based on logic gates.

The device operates as follows.

A description of the operation of a typical receiving path, comprising a complex SF 1, a sampler 2, a compressed signal envelope detector 3, a drive 4 and a detector 5, connected in series, is the same as in the prototype [3].

The operation of the inventive device is based on an assessment of the coherence measure of radar signals as the entropy of the signal energy distribution over the eigensubspaces of its correlation matrix [4, 5] to identify an additional sign of the selection of false targets, namely, the difference in the values of the energy distribution of signals reflected from true and false targets when fixed signal-to-noise ratio (SNR).

The principle of operation of the proposed device is based on the analysis of "rigidity" of the temporal structure of the received signal and operates with the concept of signal coherence [6].

When signals are detected in the detector 5 and the channel numbers are stored in range in RAM2 7, from RAM2 7 a target designation (CC) is issued on channels (for example, in range) to the calculator of signal coherence measure 8, namely, to the unit for estimating CM 11. In addition, , all the vector columns of S signals after sampler 2 are recorded in RAM1 6. The evaluation unit KM 11 generates from RAM 1 6 only those channels that are received from the RAM with RAM2 7.

The unit for forming the estimated CM 11 F is formed by a column vector S of a fixed dimension N of its samples and is described by formula (1):

where ^H is the sign of Hermitian conjugation.

Next, the KM F from the output of the formation unit of the estimated KM 11 is fed to the input of the eigenvalue calculation unit KM 12, where the spectral decomposition of the KM F, the calculation of the eigenvalues and their normalization takes place.

The coherence measure is based on the estimation of the QM of an arbitrary signal [4]. Being Hermitian and non-negative definite, the CMF by formula (1) has an orthonormal system of eigenvectors U ₁ , ..., U _N and a collection of non-negative eigenvalues λ ₁ , ..., λ _N corresponding to these vectors. Moreover, the number of nonzero eigenvalues (taken taking into account their algebraic multiplicity) coincides with the rank r of the CMF, and the multiplicity of the zero eigenvalue is N - r. We consider that all eigenvalues, except zero, have unit multiplicity, and number them in decreasing order λ ₁ > λ ₂ >...> λ _r > λ _{r + 1} = ... = λ _N = 0.

The spectral decomposition of the Hermitian CMF is described by the formula (2):

where i = 1, 2, 3, ..., N.

является матрицей-проектором на i-е собственное подпространство матрицы Ф, величина λ_i определяет собой среднее значение энергии сигнала, приходящейся на это подпространство. Отсюда следует, что вектор-столбец S сигнала полностью принадлежит r-мерному подпространству с базисом U₁,...,U_r, и верхний предел суммирования в формуле (2) равен r. Since the product

is a projector matrix onto the ith eigensubspace of the matrix Φ; the quantity λ _i determines the average value of the signal energy per this subspace. It follows that the column vector S of the signal completely belongs to the r-dimensional subspace with the basis U ₁ , ..., U _r , and the upper limit of summation in formula (2) is r.

Normalization of the eigenvalues λ _0i ; in the block of calculation of eigenvalues KM 12 is carried out according to the formula (3):

where SрФ is the trace (the sum of the diagonal elements) of the CMF, which characterizes the average signal energy. The set of normalized eigenvalues A ₀ i can be interpreted as the law of the statistical distribution of the signal energy over the eigenspaces of its CM F. Moreover, each normalized eigenvalue λ _0i determines the probability of the distribution of the signal energy over ie, the eigenspace of the QM F. The coherence measure with this statistical approach can be postulated as the degree of disorder (chaos), that is, the entropy of H in the distribution of the signal energy over the eigenspaces of its CM F.

The set of normalized eigenvalues λ _0i goes to the input of the entropy calculation unit 13. In this case, the entropy H is calculated by the formula (4):

where the base of the logarithm is any number greater than one.

A quantitative measure in the form of entropy H gives an exact meaning to the coherent properties of the signals. So, for a given dimension N, signals with zero entropy should be considered coherent (or completely coherent), and entropy log N should be considered completely incoherent. All other signals whose energy distribution entropy is enclosed between these two values are partially coherent. Moreover, the greater the value of entropy, the greater the disorder of the distribution and, accordingly, the less coherent the signal.

распределения энергии сигнала, полученная с одного обзора, и далее поступает в ПУ 9, где выполняется операция сравнения выражения

- Н_эт с заданным порогом h, где Н_эт - табличное значениеэнтропии распределения энергии сигнала, хранящееся в банке данных и восстановленное по эмпирическим данным от сигналов реальных воздушных целей. Так как характеристики распределений значений энтропии от ложных целей при фиксированных ОСШ располагаются выше по сравнению с характеристиками истинных целей, то на выходе ПУ 9 разность

- Н_эт будет превышать h (заданный порог).From the output of the entropy calculation unit 13, a current estimate of the entropy value is formed

the energy distribution of the signal obtained from one review, and then goes to PU 9, where the operation of comparing the expression

- H _et with a given threshold h, where H _et is the tabular value of the entropy of the signal energy distribution stored in the data bank and reconstructed from empirical data from signals from real air targets. Since the characteristics of the distributions of entropy values from false targets for fixed SNRs are higher than the characteristics of true targets, at the output of PU 9 the difference

- H _et will exceed h (given threshold).

The issuance of a sign about the presence / absence of a false target occurs using a deciding device 10, operating in accordance with the logic “m of n”. From the output of the control unit 9 to the input of the logic unit 15 receives n signals, (n-1) of which are delayed relative to the previous one for the period of review. When identifying in PU 9 m excesses of a given threshold h, the decisive device 10 issues a decision on the sign of a false target.

The device allows you to uniquely select the target in the channels in range and speed, regardless of the presence or absence of other targets in the processing channels.

The technical result stated in this utility model is confirmed by field experiments, the results of which are given in [7].

Thus, due to the fact that in the known device containing a comprehensive compression filter, a sampler, a envelope detector of a compressed signal, a drive and a detector, RAM 1 for storing samples of a complex compressed signal, RAM 2 for storing samples of a detection signal, as well as a calculator and a control unit, the calculator with the possibility of calculating a measure of coherence of a signal, comprising a unit for generating an estimated CM, a unit for calculating eigenvalues of a CM, and an entropy calculation unit, wherein of entropy values with a fixed threshold, and a solver is additionally introduced that contains the logic block “m of n” and (n-1) delay blocks for the period of the review, with corresponding links, it is possible to select single false and / or true targets in the channels in range and speed, increasing the radar noise immunity from false targets, using only algorithmic methods of primary signal processing on modern microprocessors, without changing the station's hardware parameters.

Information sources:

1. Protection of radar systems from interference. Status and development trends / Ed. A.I. Kanaschenkova and V.I. Merkulova, M .: Radio engineering, 2003, S. 109-136;

2. Aviation Group Aids of EW of the US Armed Forces / S. Yashin, Foreign Military Review, 2016, No. 9, P. 64-68;

3. RF patent No. 120237 for utility model “Device for the selection of false targets in the range channel of a radar with a complex pulse signal”, publ. 09/10/2012, application No. 2012115359 dated 04/17/2012, IPC G01S7 / 36 - prototype;

4. A method for assessing the coherent properties of radar signals / P.V. Mikheev, University News. Radiophysics, 2006, T. XLIX, No. 1, P. 82-87;

5. Assessment of the coherence of radar signals in antenna arrays based on the analysis of signal energy distributions by eigenvalues of the correlation matrix / Orlov I.Ya., Fitasov ES, Ivlev DN, Kozlov SA, Antennas, No. 3, 2017, S. 31-36;

6. Theoretical foundations of radar. Under. ed. Shirmana Y.D. Textbook for universities. M., publishing house "Soviet Radio", 1970, S. 560;

7. Experimental studies of the possibility of recognition of false targets based on the assessment of the coherence of radar signals / Kozlov SA, Fitasov ES, Sorokina AV, Zharkov Yu.A., Nasonov VV, Proceedings of the XX scientific conference on radiophysics dedicated to the 110th anniversary of the birth of G.S. Burner / Ed. S.V. Obolensky, V.V. Matrosova, Nizhny Novgorod: NNSU, 2016, S. 138-139.

Claims (1)

A device for selecting false targets, containing a complex compression filter connected in series, to the input of which a complex signal of the intermediate frequency of the radar receiver, a sampler, an envelope detector of a compressed signal, a drive and a detector, a random access memory (RAM1) for memorizing the samples of a complex compressed signal, the input of which is connected to the output of the sampler, random access memory (RAM2) for storing samples of the detection signal, the input of which is connected to the output resident, as well as a calculator and a threshold device (PU), at the second input of which a fixed threshold is applied, characterized in that the calculator is configured to calculate a signal coherence measure, comprising in series a unit for estimating the correlation matrix (CM), a unit for calculating the eigenvalues of the CM and an entropy calculation unit, wherein the first and second inputs of the estimating CM formation unit are connected to the outputs of RAM1 and RAM2, respectively, and the control unit is configured to compare the values of entropy with a fixed threshold, the first input of which is connected to the output of the entropy calculation unit, in addition, a decoding device is added that contains a logic unit and (n-1) delay units for the review period, and the output of the control unit is connected to the input of the first of the chain of series-connected (n- 1) delay blocks for the review period and the first input of the logic block, while the output of each of the (n-1) delay blocks for the review period is connected to the inputs of the logic block, the output of which is the output of the device.

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