RU2540951C1 - Method of determining number of targets in group - Google Patents

Abstract

FIELD: radio, communication.

SUBSTANCE: when making decision on correspondence of the local maximum to two targets, that is, when the value of the interval width is greater than the threshold width or quadratic residual of readings of complex correlation sums of the received signal and the readings of the reference correlation sums of the signal of one target greater than the residual threshold, the magnitude of the radial acceleration of the target a_r is determined, if a_r=0, then the decision is made on correspondence of the local maximum to two targets, and if a_r≠0, when determining the residual the readings of the reference correlation sums of the signal of one target is used, moving with the radial acceleration a_r, if the residual is less than the threshold of the residual, then the decision is made on correspondence of the local maximum of one accelerating target, otherwise - two targets.

EFFECT: increased probability of correct identification of the number of targets in the group with radar observation of manoeuvring targets.

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Description

The invention relates to the field of radar and can be used in radar technology to estimate the number of targets in a group.

A known analogue method of detecting a group target, which allows you to establish the fact of the presence of a group target in the pulsed volume by analyzing the quadrature envelopes of the received antenna signal in the frequency of the region [Guskov Yu.I., Zhiburtovich N.Yu., Abramenkov VV et al. Method for detecting a group target / Yu.N. Guskov, N.Yu. Zhiburtovich, V.V. Abramenkov et al. - RF Patent No. 2293349 C1].

Closest to the proposed invention (prototype) is a method for determining the number of targets in a group, based on the calculation of the minimum quadratic discrepancy of samples of complex correlation sums of a sample of a received signal and samples of reference correlation sums of a signal of one target and comparing it with a threshold [AGANIN, Bely Yu.I., Novichenok A.B. et al. A method for determining the number of goals in a group / A.G. Aganin, Yu.I. White, A.B. Novichok et al. RF Patent No. 2260196 C2]. The disadvantage of the above technical solutions is that during radar observation of a maneuvering target moving with radial acceleration a , the structure of the reflected signal at the output of the primary processing device in the frequency and time domain is distorted, which leads to the false acceptance of one accelerating target as a group [see, for example , Merkulov V.I. The dynamism of aviation systems and on-board electronic systems. // Radio engineering, 2010, No. 1].

The technical result, the achievement of which the claimed invention is directed, is to increase the likelihood of correctly determining the number of targets in a group during radar observation of maneuvering targets.

The specified technical result is achieved by the fact that in the known method for determining the number of targets in a group, which consists in analog-to-digital conversion of the reflected signal from the target and the received signal, calculating the complex correlation sums of the sample of the received signal and reference quadrature signals with the values of the resolution parameter of the reference signals taken on a uniform grid, determining the maximum width of the intervals of the resolution parameter values, inside which all modules of the correlation sums exceed the detection threshold I, determining the local maxima of the modules of the correlation sums, deciding on the correspondence of each local maximum of one target in those intervals within which the number of local maxima is more than one, calculating the width of the interval within which there is one local maximum, if the width of the interval is less than the threshold width, then calculating the minimum quadratic residual of the samples of complex correlation sums and samples of the reference correlation sums of the signal of one target, if the residual is less than the residual threshold, then uu solutions of the corresponding local maximum within the range of a single target, if the interval value width greater than the threshold width or discrepancy greater than a threshold discrepancy, then determine the magnitude of radial acceleration target a _r, and if a _r = 0, then decide according to the local maximum two purposes within the interval, and if a _r ≠ 0, when determining the least square residuals using standard samples of the correlation sum signal one target moving at a certain radial acceleration a _r, and if the discrepancy is less than the pore and residuals, then decide according to a local maximum within a range of one accelerating target, otherwise - two purposes.

The specified technical result is achieved in that the radial acceleration of the target can be determined by the formula

,

,

where λ is the wavelength, T _c is the duration of the probe signal, Δω is the position of the maximum of the signal spectrum S _Δ (ω) obtained by the formula

,

,

where signals S ₁ (t) and S ₂ (t) of duration T _c / 2 are obtained by dividing the received signal S (t) into two equal parts by sampling time, the symbol ∗ denotes the complex pairing operation.

The essence of the proposed method is as follows. The prototype method for determining the number of targets in a group shows satisfactory results in radar observation of targets moving with zero radial acceleration relative to the radar. In accordance with it, the processing of the signal reflected from the target begins with its digitalization and the implementation of the target detection procedure, which consists in the formation of complex correlation sums (KKS) samples of the received signal and reference quadrature signals, calculation of the KKS modules and comparing them with the detection threshold. Nearby readings of the KKS, exceeding the detection threshold, are combined into intervals within which local maxima are determined. If there are several local maxima inside the interval, then a decision is made on the number of observed targets equal to the number of local maxima. Provided that there is one local maximum within the interval, it can be a reflection both from one target and from two simultaneously located in the pulsed volume of the radar. The decision to observe one or two goals in the prototype method is carried out in two stages. At the first stage, the width of the interval containing the local maximum is compared with the threshold value, and if it exceeds it, then a decision is made to observe two targets. At the second stage, if the interval width corresponds to one target, then the envelope shape of the KKS samples within the interval is analyzed by calculating the quadratic residual of the KKS samples of the received signal and the samples of the reference KKS of one target. If the residual exceeds a threshold, then this indicates a significant difference between the received signal and the reference signal of one target, i.e. about the presence of two targets in the pulse volume.

The radial acceleration that occurs when maneuvering a target leads to the appearance of linear frequency modulation in the reflected signal. In this case, both the width of the interval and the shape of the envelope of the KKS signal are distorted, which leads to a significant increase in the probability of mistaken acceptance of one accelerating target for two targets. The simulation results confirm this hypothesis. The figure 1 shows the dependence of the erroneous decision on the presence of a group of targets in the pulse volume of the radar under the condition of observing one accelerating target P _gr1 on the signal-to-noise ratio q. Characteristics 1, 2, 3, 4 correspond to the target’s radial acceleration of 0.2 g, 4 g and 10 g, where g is the gravitational acceleration of 9.81 m / s ² at a wavelength of 4 cm [see, for example, Filonenko V.V., Novichenok A.B. The application of the theory of pattern recognition to determine the presence of a group of air targets in the resolved volume of the radar. Materials of the XVIII International Scientific and Technical Conference "Radar, Navigation, Communication - 2012". Part 3. - Voronezh: NPO Sakvoee, 2012. - S.1708-1715].

To eliminate this phenomenon in cases when in the prototype method a decision is made on whether the local maximum corresponds to two goals, the correspondence of its single accelerating target is checked. For this, the implementation of the input sample determines the magnitude of the radial acceleration of the target. If the target is not accelerating ( a _r = 0), then the solution of the prototype method remains to observe two goals. If an acceleration value equal to a _r ≠ 0 is determined, then the minimum quadratic residual of the samples of the KKS of the received signal and the samples of the reference KKS of the signal of one target moving with a certain radial acceleration a _{r is} calculated. If the discrepancy is less than the threshold value, then a decision is made on the correspondence of the local maximum of one accelerating target, if more than two. Samples of reference KKS of one target moving with different values of a _r must be predetermined.

The claimed invention proposes to determine the magnitude of the radial acceleration of the target by the phase-difference method [see, for example, Likhachev V.P., Ryazantsev L.B. Probabilistic characteristics of an air target’s maneuver indicator based on a phase-difference estimate of approach acceleration. // Achievements of modern radio electronics, 2010, No. 11], characterized by a lack of energy and low computational costs. The essence of the method is as follows. The signal from the output of the receiver of duration T _c is divided in time into two signals S ₁ (t) and S ₂ (t) of duration T _c / 2, the signal S ₂ (t) is complexly conjugated, and then both signals are shifted in time by T _c / 4 and are multiplied by each other:

Having carried out the Fourier transform of the signal S _Δ (t) by the formula

and estimating the position of the maximum Δω of the spectrum S _Δ (ω) by the expression

you can determine the magnitude of the radial acceleration by the formula

The sequence of operations that implements the proposed method for determining the number of goals is shown in figure 2. Operations 1-5 completely coincide with the operations of the prototype method. Operations 6-8 are new significant features of the invention, the use of which eliminates the specified disadvantage of the prototype method.

The method can be implemented, for example, using the device, the circuit of which is shown in Fig. 3, consisting of an ADC block 1, a correlation sum calculator 2, a switch 3, a residual calculator 4, an amplitude calculator 5, a local maximum calculator 6, an interval calculator 7, calculator of the number of targets 8, scheme "or" 9, calculator of radial acceleration 10.

The radial acceleration calculator 10 is designed to determine the value of the radial acceleration of the target relative to the radar from the input sample of the received signal and solves the following problems:

- separation of the input sample S (t) of duration T _c in time into two signals S ₁ (t) and S ₂ (t) each of duration T _c / 2;

- complex conjugation of the signal S ₂ (t);

;- time shift by T _c / 4 in opposite directions of the signals S ₁ (t) and $${\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="00000011.png,00000012.png"\; state="\{\{state\}\}">S</figure-callout>}}_2^{*}\left(t\right)$$

;

- elementwise multiplication of shifted signals;

- Fourier transform of the product of the signals;

- determination of the maximum position of the result of the Fourier transform;

- calculation of the radial acceleration of the target according to the formula (4).

The operation of the device does not differ from the operation of the device of the prototype method, except when in the calculator of the number of targets 8, the calculated interval width exceeds the threshold width or the residual value exceeds the residual threshold. In these cases, the target number calculator 8 forms a unit at the outputs 6 or 7, which, through the "or" 9 circuit, is fed to the first input of the radial acceleration calculator 10 for its inclusion. Samples of the received signal from ADC 1 are fed to the second input. In the radial acceleration calculator 10, the samples of the received signal S (t) are divided in time into two samples: the first corresponds to the first half of the samples (S ₁ (t)), and the second to the second half (S ₂ (t)). Next, with samples S ₁ (t) and S ₂ (t), actions are performed in accordance with formulas (1-4). The calculated value of the radial acceleration of the target is fed to the fifth input of the calculator of the number of targets 8 and the second input of the calculator of the residual 4. When the condition a _r = 0 is fulfilled, the calculator of the number of targets continues to work in the same way as in the device of the prototype method. If a _r ≠ 0, then residual computer 4 calculates the minimum quadratic residual of samples of the KKS of the received signal arriving at its first input and of samples of the reference KKS of the signal of one target moving with radial acceleration a _r . For this, in contrast to the prototype method device, in the read-only memory of the residual calculator 4 of the proposed device, pre-calculated reference samples of the CCF of one target moving with different values of radial acceleration should be stored. The calculated residual is fed to the fourth input of the calculator of the number of targets 8, there it is compared with the threshold value of the residual. If the discrepancy is less than the threshold value, then the value of the target number register increases by one, if more, then by two.

Thus, the proposed method for determining the number of targets in a group can increase the likelihood of a correct estimate of the number of targets in a group under conditions of radar surveillance of maneuvering targets.

Claims (2)

1. A method for determining the number of targets in a group, which consists in analog-to-digital conversion of the reflected signal from the targets and the received signal, calculating the complex correlation sums of the sample of the received signal and reference quadrature signals with the values of the resolution parameter of the reference signals taken on a uniform grid, determining maximum intervals in width values of the resolution parameter, inside which all the modules of the correlation sums exceed the detection threshold, determining the local maxima of the modules of the correlation sums, deciding on the correspondence of each local maximum of one target in those intervals within which the number of local maximums is more than one, calculating the width of the interval within which there is one local maximum, if the interval width is less than the threshold width, then calculating the minimum quadratic residual of samples of complex correlation sums and samples reference correlation sums of the signal of one target, if the residual is less than the residual threshold, then deciding on the correspondence of the local maximum within the interval one target, characterized in that if the value of the width of the interval is greater than the threshold width or the residual is greater than the residual threshold, then determine the value of the radial acceleration of the target a _r, and if a _r = 0, then decide whether the local maximum inside the interval corresponds to two goals, and if a _r ≠ 0, then when determining the minimum quadratic residual, samples of the reference correlation sums of the signal of one target moving with a certain radial acceleration a _{r are used} , and if the residual is less than the residual threshold, then the decision on the locale l maximum within the interval of one accelerating target, otherwise - two goals. 2. The method for determining the number of targets in a group according to claim 1, characterized in that the radial acceleration of the target is determined by the formula
$$a_r=\frac{\Delta \omega \lambda }{2\pi T_c}$$

,
where λ is the wavelength, T _c is the duration of the probe signal, Δω is the position of the maximum of the signal spectrum S _Δ (ω) obtained by the formula
$$S_{\Delta }\left(t\right)=S_{\mathrm{one}}\left(t+T_c/\mathrm{four}\right)S_2^{*}\left(t-T_c/\mathrm{four}\right)$$

,
where signals S ₁ (t) and S ₂ (t) of duration T _c / 2 are obtained by dividing the received signal S (t) into two equal parts by sampling time, the symbol * denotes the operation of complex pairing.

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