RU184465U1 - Device selection of false targets - Google Patents

Abstract

The utility model relates to radar and can be used in survey coherent-pulse radar stations (radar) reconnaissance, providing monitoring of the air situation, and in coherent-pulse radar tracking for selecting false targets from true targets. Achievable technical result - the possibility of selecting a single false and / or true targets in the channels in range and speed, increasing the noise immunity of the radar. This technical result is achieved by the fact that in a known device comprising a complex compression filter connected in series, the complex intermediate frequency signal of the radar receiver, sampler, compressed signal envelope detector, accumulator and detector, operational memory (RAM1) for storing complex compressed signal, the input of which is connected to the output of the sampler, a random access memory (OZU2) for storing the detected signal samples which input is connected to the detector output, as well as a calculator and a threshold device (PU), to the second input of which a fixed threshold is fed, the calculator is configured to calculate a measure of coherence of the signal containing the serially connected evaluation unit (sample) correlation matrix (KM) , the unit for calculating the eigenvalues of the CM and the unit for calculating the entropy, the first and second inputs of the unit for forming the estimated CM are connected to the outputs ОЗУ1 and ОЗУ2, respectively, and the control panel is made with 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 solver device is added that contains a logic block and (n-1) delay blocks for the period of review, and the output PU is connected to the input of the first of the chain serially 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 whose output is the output of the device. 2 Il.

Description

The utility model relates to radar and can be used in survey coherent-pulse radar stations (radar) reconnaissance, providing monitoring of the air situation, and in coherent-pulse radar tracking for selecting false targets from true targets.

The problem of protection against response imitation interference is extremely important, since This interference leads 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, the non-detection of echoes from an air target or an overload of the radar computer system due to the processing of a large amount of false information about the air situation.

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

The closest analogue (prototype) of the technical solution to the proposed utility model is a device for selecting spurious targets in a radar channel with a complex pulse signal [3] (block diagram of which is shown in Fig. 1) containing a typical receiving path including a compression filter ( SF), sampler, envelope detector, drive and detector, and an additional device, including operational storage devices (OZU1, OZU2), calculator of the modules of the correlation coefficients between the samples of the complex compressed a signal device and a threshold comparison module correlation coefficients with a fixed threshold.

The operation 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 of the radar receiver. The calculation of these factors is carried out for those samples in range, in which the detection of signals occurred. If, in two or more samples, the detection occurred under the influence of a single 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. At the same time, fluctuations of samples of a compressed signal corresponding to the provisions of true targets are weakly correlated with fluctuations of samples corresponding to false targets. To decide whether the detected targets belong to the true or false targets, the modules of the obtained estimates of the correlation coefficients are compared with a predetermined 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 imitation interference exists only in the channel in range;

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

- the impossibility of determining the belonging of signals from an active simulating interference at the output of a 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, the signal from a small target);

- the impossibility of determining the affiliation of signals at the output of a radar receiver detector (selection of a true and false target), in the case when in the channel in range there are one signal of a false and true target.

Achievable technical result - the possibility of selecting a single false and / or true targets in the channels in range and speed, increasing the noise immunity of the radar.

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

This technical result is achieved by the fact that in a known device comprising a complex compression filter connected in series, the complex intermediate frequency signal of the radar receiver, sampler, compressed signal envelope detector, accumulator and detector, operational memory (RAM1) for storing complex compressed signal, the input of which is connected to the output of the sampler, a random access memory (OZU2) for storing the detected signal samples input, which is connected to the detector output, as well as a calculator and a threshold device (PU), to the second input of which a fixed threshold is fed, the calculator is designed to calculate the coherence measure of the signal containing the serially connected estimator (sample) correlation matrix (KM), a unit for calculating eigenvalues KM and a unit for calculating entropy, with the first and second inputs of the unit for forming the estimated KM connected to the outputs OZU1 and OZU2, respectively, and the control panel is configured as possible 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 solver has been added that contains a logic block "m from n" and (n-1) delay blocks for the review period, and the output PU is connected with the input of the first of the chain of series-connected (n-1) delay blocks for the period of review and the first input of the logic block "t of p", the output of each of the (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 exceedances of a given threshold h.

n is the number of inputs of the logic block corresponding to the total number of periods of the review on which the target attribute is formed.

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

FIG. 2 shows a block diagram of the proposed device, where indicated:

1 - SF;

2 - sampler;

3 - detector;

4 - drive;

5 - detector;

6 - OZU1;

7 - OZU2;

8 - calculator measures the coherence of the signal;

9 - PU;

10 - solver;

11 - unit for the formation of the estimated KM;

12 is a block for calculating eigenvalues of the CM;

13 — entropy calculation unit;

14 - delay unit;

15 - logic block.

The device for selecting false targets contains a series-connected complex SF 1, the input of which receives a complex intermediate frequency signal from a radar receiver, a sampler 2, a compressed signal envelope detector 3, a drive 4 and a detector 5, as well as an on-line memory (OZU1) 6 for storing complex samples compressed signal, the input of which is connected to the output of the sampler 2, a random access memory (RAM2) 7 for storing samples of the detection signal, the input of which is connected to the output of the detection itel 5, calculator of coherence measure signal 8, PU 9 for comparing entropy values with a fixed threshold and resolver 10. At that, calculator of coherence measure of signal 8 contains serially connected evaluation unit (sample) КМ 11, calculator of own numbers КМ 12 and block entropy calculation 13, and the output of OSU1 6 is connected to the first input of the estimator CM 11, to the second input of which the output of OSU2 7 is connected. Solver 10 includes (n-1) delay blocks 14 for the period of review and logic block 15 "m from n". The first input of PU 9 is connected to the output of the entropy calculation unit 13, and a second threshold is fed to the second input, and the output of PU 9 is connected to the input of the first of a chain of series-connected (n-1) delay blocks 14 for the review period and the first input of the logic block 15 "m from n". In addition, the output of each of (n-1) delay blocks 14 for the period of the review is connected to the inputs of the logic block 15 "m from n", the output of which is the output of the device.

The SF 1, sampler 2, detector 3 of the compressed signal envelope, accumulator 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 resolver 10 form an additional device.

The delay unit 14 for the period of review 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 works as follows.

The description of the operation of a typical receiving path containing sequentially connected complex SF 1, discretization 2, detector 3 of the compressed signal envelope, drive 4 and detector 5, is the same as in the prototype [3].

The operation of the claimed device is based on evaluating the coherence measure of radar signals as the entropy of the signal energy distribution over its own subspaces of its correlation matrix [4, 5] to reveal an additional feature of selecting false targets, namely, the difference of the values of the energy distribution of signals reflected from true and false targets fixed signal-to-noise ratio (SNR).

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

When detecting signals in the detector 5 and memorizing channel numbers by range in OZU2 7, OZU2 7 is given target designation (DD) via channels (for example, by range) to the calculator of the coherence measure of signal 8, namely to the evaluation unit of the CM 11. , all the column vectors of the S signals after the sampler 2 are recorded in RAM1 6. The evaluation unit for evaluating CM 11 reads from RAM 1 6 only those channels that are received from the DD with RAM 2 7.

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

where ^H is the sign of Hermitian conjugation.

Then KM F from the output of the unit for forming the estimated KM 11 enters the input of the eigenvalue calculator KM 12, where the spectral decomposition of KM F takes place, the calculation of the eigenvalues and their normalization.

The coherence measure is based on the QM F estimate of an arbitrary signal [4]. Being Hermitian and nonnegatively defined, KMF by formula (1) has an orthonormal system of eigenvectors U ₁ , ..., U _N and the set of corresponding non-negative eigenvalues λ ₁ , ..., λ _N corresponding to these vectors. Moreover, the number of nonzero eigenvalues (taken with regard to their algebraic multiplicity) coincides with the rank r KM F, and the multiplicity of the zero eigenvalue is N - r. We assume that all eigenvalues, except for 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 KM F 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 work

is the projector matrix on the i-th eigenspace of the matrix Ф, the value 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 equal to r.

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

where SрФ is the trace (the sum of the diagonal elements) KM F, which characterizes the average signal energy. The set of normalized eigenvalues A ₀ i can be interpreted as the law of statistical distribution of a signal's energy over its own subspaces KM F. Moreover, each normalized eigenvalue λ _0i determines the probability of the signal energy distribution to ie its own subspace KM F. With this statistical approach, the measure of coherence as the degree of disorder (chaos), that is, the entropy H in the distribution of the signal energy over its own subspaces KM F.

The set of normalized eigenvalues λ _{0i is} fed 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.

Quantitative measure in the form of entropy H gives the exact meaning of the coherent properties of signals. So, for a given dimension N, signals with zero entropy should be considered coherent (or fully coherent), and signals with entropy log N should be considered completely incoherent. All other signals whose entropy of energy distribution lies between these two values are partially coherent. Moreover, the greater the value of entropy, the greater the distribution disorder 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, the current estimate of the entropy value is formed

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

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

- N _at will exceed h (preset threshold).

The issuance of a sign about the presence / absence of a false target occurs with the use of a resolver 10 operating in accordance with the logic “m from n”. From the output of PU 9 to the input of the logic block 15 receives n signals, (n-1) of which are delayed relative to the previous one for the period of review. When detecting in PU 9 m exceeding a predetermined threshold h, the decisive device 10 makes a decision about the sign of a false target.

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

The technical result stated in the present 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 complex compressing filter, a sampler, a compressed signal envelope detector, a drive and a detector, an OS1 for storing samples of the complex compressed signal, an AR2 for storing the counts of the detection signal, as well as a calculator and a PU, the calculator is executed with the possibility of calculating the measure of coherence of the signal, containing the unit for the formation of the estimated KM, the unit for calculating the eigenvalues of the CM and the unit for calculating the entropy, while PU is made with the ability to compare entropy values with a fixed threshold, and a solver additionally introduced, containing a logic block “m of n” and (n-1) delay blocks for the period of review, with corresponding links, it is possible to select single false or / and true targets in channels in range and speeds that increase the noise immunity of the radar from spurious targets, using only algorithmic methods of preprocessing signals on modern microprocessors, without changing the hardware parameters of the station.

Information sources:

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

2. Aviation group means of electronic warfare of the US armed forces / S. Yashin, Foreign Military Review, 2016, No. 9, p. 64-68;

3. RF patent №120237 for a useful model “Device for selecting false targets in a radar channel with a complex pulse signal”, publ. September 10, 2012, application no. 2012115359 of 04/17/2012, IPC G01S7 / 36 - a prototype;

4. Method for assessing the coherent properties of radar signals / P.V. Mikheev, Izvestiya VUZ. Radiofizika, 2006, T. XLIX, №1, p. 82-87;

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

6. Theoretical foundations of radar. Under. ed. Shirman Ya.D. Textbook for universities. M., publishing house "Soviet Radio", 1970, p. 560;

7. Experimental studies of the possibility of detecting 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 radiophysics dedicated to the 110th anniversary of the birth of G.S. Gorelika / Ed. S.V. Obolensky, V.V. Matrosova, Nizhny Novgorod: UNN, 2016, p. 138-139.

Claims (1)

A device for selecting spurious targets containing a series-connected complex compression filter, the input of which receives a complex intermediate-frequency signal from a radar receiver, a sampler, a compressed signal envelope detector, a drive and a detector, a memory device operatively (RAM1) for storing samples of the complex-compressed signal whose input is connected to the output of the sampler, an operative storage device (RAM2) for storing samples of the detection signal, the input of which is connected to the output of the detection a resident, as well as a calculator and a threshold device (PU), to the second input of which a fixed threshold is supplied, characterized in that the calculator is configured to calculate a measure of signal coherence, which contains series-connected unit for forming an estimated correlation matrix (KM), a unit for calculating eigenvalues KM and an entropy calculation unit, with the first and second inputs of the estimator CM generating unit connected to the outputs OSU1 and OSU2, respectively, and the control unit is configured to compare the entropy values with a fixed threshold, the first input of which is connected to the output of the entropy calculation unit, in addition, a solver is additionally introduced, containing a logic block and (n-1) delay blocks for the review period, with the PU output connected to the input of the first of the series connected in series (n- 1) the 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 whose output is the output of the device.