RU2492502C9 - Method of resolving group target - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: quadrature components of the complex envelope of a signal received by an antenna are selected; in each quadrature component, the signal is converted to digital form, within intervals (gates) equal to duration of the probing pulse; summation of digital readings is performed; a sequence of N readings is augmented with zeros to a sequence of M readings, where, where M=2ⁿ>N (n is an integer); the obtained M readings undergo amplitude weighing; filter processing is carried out according to an M-point fast Fourier transform (FFT); the modulus of the complex signal envelope at the output of Doppler filters is determined; the number of range gate kmax and the number of the frequency filter jmax, corresponding to the maximum signal amplitude, are determined; an analysis region with a centre (kmax, jmax), made of complex amplitude values of signals in the analysis region is formed; vector Z is multiplied by a pre-calculated inverse matrix of signal mismatch Q^-1; moduli of elements of the resultant vector E are compared with threshold values which are set based on the required spurious solution probability values; the i-th element of the vector E exceeding the threshold indicates a signal from a separate target in a group target with a range which corresponds to the k-th gate and radial velocity which corresponds to the j-th frequency filter.

EFFECT: determining quality, range and Doppler frequencies of separate targets in a group target.

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Description

The invention relates to radar and can be used in airborne, ground and ship radar stations (radar) to resolve individual targets from the group in the pulse volume.

A known method for detecting a group target [RF patent No. 2106653 of 03/10/1998, IPC G01S 7/292]. In this method, the task of detecting a group target is solved based on the phenomenon of mutual suppression of overlapping signals when they are compressed after limitation. The specified result is achieved by the fact that in the known method of processing a radar signal based on the weight processing of the received oscillation and comparing it with the threshold U ₀ , additionally carry out the weight processing of the oscillation after its limitation. The decision to detect a group target is made if the signal level after the main processing reaches the value U _0i , and after the additional one — below the level U _di corresponding to the value U _0i .

The disadvantage of this method is that in order to make a decision on the detection of a group target, an additional processing channel is necessary, which complicates the technical implementation of the method. In addition, it provides for signal processing in a limited mode, which leads to additional losses, distortion of the phase structure of the received signal and a decrease in the probability of detecting a group target.

A known method for detecting a group target [US patent No. 4536764 from 08.20.85, IPC G01S 7/28, 13/52]. The essence of the method lies in the fact that within the intervals equal to the duration of the probe pulse (range gates), the digital samples are added up, the results obtained from the summation of N samples are subjected to amplitude weighting, filter processing is performed according to the N-point fast Fourier transform (FFT) algorithm, in the range strobe, a plurality of adjacent Doppler filters is selected, the first Doppler frequency f ₁ is determined from the named set of adjacent Doppler filters, as the filter frequency jm ax1 with the maximum signal amplitude, select the first subset of the set of adjacent Doppler filters R ₁ centered around the selected first Doppler frequency f ₁ , obtain the value of the first threshold by multiplying the amplitude of the signal of the first Doppler frequency f ₁ with the first factor less than unity in the first subset of the set of adjacent Doppler filters R ₁ , determine the group of amplitudes of the signals exceeding the first threshold, divide the obtained group of amplitudes of the signals into clusters, the width of which is three Doppler filter, count the number of clusters to obtain the first count C ₁ , attenuate by blanking the amplitudes of the signals of the first Doppler frequency f ₁ and the group of Doppler frequencies located close to, determine the second Doppler frequency f ₂ , as the filter frequency jmax2 with the maximum signal amplitude among the unstimulated signals from the first subset adjacent Doppler filters R _1, selecting a second subset of adjacent Doppler filters R ₂ centered about the selected second Doppler frequency f ₂ are prepared ve second threshold Ichin by multiplying the signal amplitude of the second Doppler frequency f ₂ to the second multiplier if the first score of ₁ is less than or equal to one, or by multiplying the signal amplitude of the second Doppler frequency f ₂ to the first multiplier when the first tab C ₁ greater than unity, then in second subset of the plurality of adjacent Doppler filters R ₂ group is determined signal amplitudes that exceed the second threshold, the separated received signal amplitudes group into clusters, the width of which is three Doppler filter Calc vayut number of clusters to obtain a second score with ₂ intermediate score is calculated according to the mathematical expression

C = C ₁ - | C ₂ -C ₁ | +1,

Further, the final score is equated to the interim account C, if the received interim account C is greater than or equal to one, or the final score is equal to one, if the received interim account C is less than one, a decision is made to detect a group target in the range gate if the received final count is more than one .

The disadvantage of this method is the low probability of detecting a group target, for which the Doppler frequencies of the signals of individual targets coincide. This is due to the fact that the resolution of the method is determined by the width of the group of adjacent Doppler filters, which in principle cannot be less than the width of one or three Doppler filters. Thus, if the Doppler frequencies of the signals of individual targets from the group target are the same, then when performing the operation of blanking the amplitudes of the signals of a group of adjacent Doppler frequencies, the information that the target is a group can be lost. This is the reason for the low probability of detecting a group target, the Doppler frequencies of the signals of which practically coincide.

к амплитуде сигнала в фильтре jmax1 строба $$k\max \left|{\dot{U}}_{j\max \mathrm{1,}k\max }\right|$$

:A known method for detecting a group target [RF patent No. 2298806 (priority from 10.10.2005), IPC G01S 13/04, 13/56]. The essence of the method is that the quadrature components of the complex envelope of the received signal antenna are extracted, the signal is converted into digital form in each quadrature component, within the interval equal to the duration of the probe pulse, digital samples are added up, N samples obtained from the summation are subjected to amplitude weighting filtering is performed according to the N-point FFT algorithm, the modulus of the complex envelope of the signal at the output of the doppler is calculated ovskih filters in the gate range is selected plurality of adjacent Doppler filters, determining a first Doppler frequency f ₁ of said plurality of adjacent Doppler filters as filter frequency jmax1 with maximum signal amplitude for all the other range gates determining the ratio of signal amplitudes b _k in the filter jmax1 k- th gate $$\left|{\dot{U}}_{j\max \mathrm{one,}k}\right|$$

to the signal amplitude in the filter jmax1 strobe $$k\max \left|{\dot{U}}_{j\max \mathrm{one,}k\max }\right|$$

:

, $$b_k=\frac{\left|{\dot{U}}_{j\max \mathrm{one,}k}\right|}{\left|{\dot{U}}_{j\max \mathrm{one,}k\max }\right|}$$

,

, $${\rho }_k^s$$

, равные разностям модулей соответствующих квадратурных составляющих сигнала в фильтре jmax1 k-го строба и произведений найденных отношений амплитуд сигналов b_k на модули соответствующих квадратурных составляющих сигнала в фильтре jmax1 строба kmax:find the quadrature components of the voltage $${\rho }_k^c$$

, $${\rho }_k^s$$

equal to the differences of the modules of the corresponding quadrature components of the signal in the filter jmax1 of the kth gate and the products of the found ratios of the amplitudes of the signals b _k by the modules of the corresponding quadrature components of the signal in the filter jmax1 of the strobe kmax:

$${\rho }_k^c=\left|U_{j\max \mathrm{one,}k}^c\right|-b_k\left|U_{j\max \mathrm{one,}k\max }^c\right|,\left(2\right)$$

$${\rho }_k^s=\left|U_{j\max \mathrm{one,}k}^s\right|-b_k\left|U_{j\max \mathrm{one,}k\max }^s\right|,\left(3\right)$$

, величина которой характеризует состав цели (одиночная или групповая) какget voltage amplitude $$\left|{\dot{\rho }}_k\right|$$

, the value of which characterizes the composition of the target (single or group) as

$$\left|{\dot{\rho }}_k\right|=\sqrt{{\left({\rho }_k^c\right)}^2+{\left({\rho }_k^s\right)}^2},\left(\mathrm{four}\right)$$

с амплитудой напряжения η, характеризующей порог обнаружения, который устанавливают, исходя из требуемого значения вероятности ложного обнаружения групповой цели, при превышении порога принимают решение об обнаружении групповой цели в стробе дальности.compare the obtained voltage amplitude $$\left|{\dot{\rho }}_k\right|$$

with a voltage amplitude η characterizing the detection threshold, which is set based on the required value of the probability of false detection of the group target, when the threshold is exceeded, a decision is made to detect the group target in the range gate.

The disadvantages of the method are the impossibility of detecting a group target in the range gate, determining the number of individual targets in the group and their Doppler frequencies in the case when the Doppler frequencies of the echo signals of individual targets from the group are located within the width of the Doppler filter, and their ranges and angular coordinates coincide.

, вычисляют модуль комплексной огибающей сигнала на выходе доплеровских фильтров, выбирают множество смежных доплеровских фильтров, определяют доплеровскую частоту f₁ из названного множества смежных доплеровских фильтров, как частоту фильтра jmax1 с максимальной амплитудой сигнала, выбирают подмножество множества смежных доплеровских фильтров R₁ с центром около выбранной доплеровской частоты f₁, для всех фильтров подмножества R₁ вычисляют коэффициент b_j, равный отношению амплитуды сигнала j-го фильтра $$\left|{\dot{U}}_j\right|$$

к найденной максимальной амплитуде сигнала в фильтре $$j\max 1\left|{\dot{U}}_{j\max 1}\right|$$

:There is also a method of detecting a group target [RF patent No. 2293349 (priority from 05/18/2005), IPC G01S 13/04, 13/56]. The essence of the method is that the quadrature components of the complex envelope of the received signal antenna are extracted, the signal is converted into digital form in each quadrature component, within the interval equal to the duration of the probe pulse, digital samples are added up, N samples obtained from the summation are subjected to amplitude weighting filtering is performed according to the N-point FFT algorithm; for all Doppler filters, the signal in the jth filter is multiplied by value $$e^{i\pi \frac{N-\mathrm{one}}{N}j}$$

the module of the complex envelope of the signal at the output of the Doppler filters is calculated, the set of adjacent Doppler filters is selected, the Doppler frequency f ₁ is determined from the above set of adjacent Doppler filters, as the filter frequency jmax1 with the maximum signal amplitude, a subset of the set of adjacent Doppler filters R ₁ with a center near the selected Doppler frequency f ₁ , for all filters of the subset R ₁ calculate the coefficient b _j equal to the ratio of the amplitude of the signal of the j-th filter $$\left|{\dot{U}}_j\right|$$

to the found maximum signal amplitude in the filter $$j\max \mathrm{one}\left|{\dot{U}}_{j\max \mathrm{one}}\right|$$

:

$$b_j=\frac{\left|{\dot{U}}_j\right|}{\left|{\dot{U}}_{j\max \mathrm{one}}\right|},$$

, $${\rho }_j^s$$

, равные разностям модулей соответствующих квадратурных составляющих сигнала j-го фильтра и произведений найденных коэффициентов b_j на модули соответствующих квадратурных составляющих сигнала фильтра с максимальной амплитудой:calculate values $${\rho }_j^c$$

, $${\rho }_j^s$$

equal to the differences between the modules of the corresponding quadrature components of the jth filter signal and the products of the found coefficients b _j by the modules of the corresponding quadrature components of the filter signal with the maximum amplitude:

, $${\rho }_j^c=\left|U_j^c\right|-b_j\left|U_{j\max \mathrm{one}}^c\right|$$

,

, $${\rho }_j^s=\left|U_j^s\right|-b_j\left|U_{j\max \mathrm{one}}^s\right|$$

,

какcalculate indicator $$\left|{\dot{\rho }}_j\right|$$

as

, $$\left|{\dot{\rho }}_j\right|=\sqrt{{\left({\rho }_j^c\right)}^2+{\left({\rho }_j^s\right)}^2}$$

,

с порогом обнаружения η, который устанавливают, исходя из требуемого значения вероятности ложного обнаружения групповой цели, при превышении порога хотя бы в одном фильтре принимают решение об обнаружении групповой цели.compare the result $$\left|{\dot{\rho }}_j\right|$$

with a detection threshold η, which is set based on the desired probability of false detection of a group target, when a threshold is exceeded, at least one filter decides to detect a group target.

The disadvantages of the method are the inability to detect the echo of the group target in the Doppler filter, to determine the number of individual targets in the group and their ranges in the case when the ranges of individual targets from the group are located within the range gate width, and their Doppler frequencies and angular coordinates coincide.

The closest technical solution is a method for resolving a group target [RF patent No. 2379704 (priority from 06/09/2008), IPC G01S 13/00], which consists in isolating the quadrature components of the complex envelope of the received antenna signal, in each quadrature component converting the signal to digital form, within an interval equal to the duration of the probe pulse, sum the digital samples, supplement the sequence of N samples obtained by summing with zeros to the next telnosti of M samples, where M = 2 ^{n> N (n} - an integer) is subjected received M samples of amplitude weighting is carried out The filter processing by the algorithm M-point FFT, calculate the complex envelope of the signal unit at the output of the FFT algorithm, selecting a plurality of adjacent Doppler filters, determine the Doppler frequency f ₁ from the named set of adjacent Doppler filters, as the filter frequency jmax1 with the maximum signal amplitude, select a subset of the set of adjacent Doppler filters R ₁ centered around the Pleler frequency f ₁ , composed of the complex amplitudes of the filter signals of the subset R _{1, the} vector Z is multiplied by a pre-calculated inverse autocorrelation matrix, the modules of the elements obtained by multiplying the vector E are compared with threshold values that are set based on the required values of the probabilities of false decisions if threshold of the i-th element of the vector E decide on the presence of a signal of an individual target in the group with a Doppler frequency corresponding to the i-th filter of the subset R ₁ .

The disadvantage of the prototype method is the inability to detect the echo of a group target, the number of individual targets in the group and their ranges in the case when the ranges of individual targets from the group are located within the range gate width, and their Doppler frequencies and angular coordinates coincide.

The invention solves the problem: to provide the ability to determine the number, ranges and Doppler frequencies of individual targets in the group when the ranges of individual targets from the group are located within the range gate width, and their Doppler frequencies coincide and there is no resolution in angular coordinates, or in the case when the Doppler frequencies of individual targets from the group are located within the width of the Doppler filter, and their ranges coincide and there is no resolution in angular coordinates and there.

The solution to the problem is that after calculating the module of the complex envelope of the signal at the output of the FFT algorithm, select the range gate number kmax and the filter number jmax corresponding to the maximum signal amplitude, form the analysis area with the center (kmax, jmax). the vector Z composed of the complex amplitudes of the signals from the analysis domain is multiplied by a pre-calculated inverse mismatch matrix of signals Q ^-1 , the modules of the elements obtained by multiplying the vector E are compared with threshold values, which are set based on the required values of the probability of false decisions, when the threshold i- m element of vector E decide on the presence of a signal of an individual target in the group with a range corresponding to the k-th strobe and radial velocity corresponding to the j-th part to the filter.

, где Δ_f - рассогласование сигналов отдельных целей из состава групповой по частоте Доплера, Δf - ширина доплеровского фильтра. На фиг.4, 5 представлены результаты обработки для ситуаций, когда дальности отдельных целей из состава групповой расположены в пределах строба дальности, а их частоты Доплера практически совпадают (отличаются на одну десятую $$\frac{{\Delta }_f}{\Delta f}=\mathrm{0,1}$$

и одну двадцатую $$\frac{{\Delta }_f}{\Delta f}=\mathrm{0,05}$$

ширины фильтра М-точечного БПФ соответственно). Истинные значения частот Доплера эхосигналов целей на фиг.3-5 обозначены вертикальными стрелками, а их оценки вертикальными линиями.The invention is illustrated by drawings. Figure 1 shows a structural diagram of a device that implements the proposed method for resolving a group target, where 1 is a phase detector, 2 is a low-pass filter, 3 is an analog-to-digital converter, 4 is an adder, 5 is an antenna, 6 is a receiver, 7 is a local oscillator , 8 - signal processing processor. Figure 2 presents a diagram explaining the sequence of signal conversion in the signal processing processor 8. Figure 3-5 shows diagrams showing a decrease in the resolution efficiency of a group target by the prototype method in the case when the ranges of individual targets from the group are located within the range gate , their Doppler frequencies are close and there is no resolution in angular coordinates. Figure 3 presents the processing results for a situation where the ranges of individual targets from the group are located within the range gate, and their Doppler frequencies differ by a quarter of the filter width of the M-point FFT $$\frac{{\Delta }_f}{\Delta f}=0.25$$

where Δ _f is the mismatch of the signals of individual targets from the group Doppler frequency group, Δf is the width of the Doppler filter. Figures 4 and 5 show the results of processing for situations when the ranges of individual targets from the group are located within the range gate, and their Doppler frequencies practically coincide (differ by one tenth $$\frac{{\Delta }_f}{\Delta f}=0.1$$

and one twentieth $$\frac{{\Delta }_f}{\Delta f}=0.05$$

filter width M-point FFT, respectively). The true values of the Doppler frequencies of the target echoes in Figs. 3-5 are indicated by vertical arrows, and their estimates by vertical lines.

и $$\frac{{\Delta }_f}{\Delta f}=0$$

, на фиг.7, а, б для ситуации, когда $$\frac{{\Delta }_d}{\Delta D}=0$$

и $$\frac{{\Delta }_f}{\Delta f}=\mathrm{0,125}$$

, на фиг.8, а, б для ситуации, когда $$\frac{{\Delta }_d}{\Delta D}=\mathrm{0,3}$$

и $$\frac{{\Delta }_f}{\Delta f}=\mathrm{0,125}$$

.Figures 6-8 are diagrams that demonstrate the possibility of determining the proposed method, the number, ranges and frequencies of Doppler of individual targets in the group in cases: the echo signals of individual targets from the group are within the same range gate, their Doppler frequencies coincide and there is no angular resolution coordinates; echoes of individual targets from the group are within the same Doppler filter, their ranges coincide and there is no resolution in angular coordinates; echoes of individual targets from the group are within the same range gate and Doppler filter and there is no resolution in angular coordinates. On figa-8a presents the analysis area formed after the correlation-filter processing, and on figb-8b the results of signal processing according to the proposed method, where Δ _d is the distance between single targets from the group in range, ΔD is the value of the range gate. On figa, b presents the results of signal processing for the situation when $$\frac{{\Delta }_d}{\Delta D}=0.25$$

and $$\frac{{\Delta }_f}{\Delta f}=0$$

, Fig.7, a, b for the situation when $$\frac{{\Delta }_d}{\Delta D}=0$$

and $$\frac{{\Delta }_f}{\Delta f}=0.125$$

, in Fig.8, a, b for the situation when $$\frac{{\Delta }_d}{\Delta D}=0.3$$

and $$\frac{{\Delta }_f}{\Delta f}=0.125$$

.

The essence of the invention is as follows. It is known that the response to the sum of the input actions for linear systems is a superposition of the responses to each effect. That is, the response of the correlation filter processing scheme to a mixture of echoes of individual targets from a group is nothing more than the sum of the responses to the echo of each individual target. The response in the range gates and frequency filters of the correlation-filter processing circuit to the echo of an individual target is the function of the mismatch of the probe signal, shifted by the delay time and the Doppler frequency, multiplied by the complex amplitude of the echo signal.

Having performed the inverse linear transformation of the output signal of the range gates and frequency filters of the selected analysis area, the values of the complex amplitudes of the echo signals of individual targets from the group are determined. The lag times and frequency shifts of the echo signals of real individual targets correspond to certain range gates and frequency filters of the processing system. In the remaining gates and filters of the analysis area, zeros are formed, since there are no echo signals of real targets with corresponding ranges and radial velocities.

If there are observation noises in those range gates and frequency filters where there are no real echo signals, values close to zero will be obtained. By comparing the modules of the obtained estimates of the amplitudes with the thresholds established on the basis of the required values of the probabilities of false decisions, the number, ranges and radial velocities of individual targets from the group are estimated. To obtain a specific relationship linking the amplitudes of the echo signals of individual targets from the group to the output signal, we introduce a number of notation.

Let τ ₁ , τ ₂ , τ ₃ , ..., τ _{n be} the delay times and F ₁ , F ₂ , F ₃ , ..., F _n the Doppler frequencies of the echo signals of individual targets from the group, corresponding to the analysis area with the center (kmax, jmax). Assume that (τ ₂ -τ ₁ = ... = τ _n -τ _n-1 = Δτ and F ₂ -F ₁ = ... = F _n -F _n-1 = ΔF). From the complex amplitudes of the signals at the output of the range gates and frequency filters corresponding to the analysis area with the center (kmax, jmax), the vector Z = [Z ₁ Z ₂ ... Z _n ] ^{T is formed} , T is the transpose operator.

By associating with each pair the range gate — the frequency filter of the analysis area — some amplitude of the echo of an individual target from the group, that is, formally assuming that the processed signal contains echoes of individual targets with ranges and radial velocities corresponding to the analysis region, we write the vector of complex amplitudes of these echo signals: E = [E ₁ E ₂ ... E _n ] ^T. Since the composition of a real group goal may contain a different number of single goals, the individual elements of the vector E are actually zero.

If in the processed implementation there is only a target echo with a delay time τ ₁ , Doppler frequency F ₁ and complex amplitude E ₁ , and the amplitudes of the other targets are zero (E ₂ = E ₃ = ... = E _n = 0), then the vector Z in the absence observation noise takes the form

Z = [1 q (τ ₂ -τ ₁ , F ₂ -F ₁ ) ... q (τ _n -τ ₁ , F _n -F ₁ )] ^T E ₁ =

= [1 q (Δτ, ΔF) ... q ((n-1) Δτ, (n-1) ΔF)] ^T E ₁ ,

where q (τ, F) is the mismatch function of the probe signal.

Similarly, in the case when in the processed implementation there are all n goals corresponding to the analysis area with the center (kmax, jmax), then:

$$Z=\left[\begin{array}{cccc}\mathrm{one}& q*\left(\Delta \tau ,\Delta F\right)& ...& q*\left(\left(n-\mathrm{one}\right)\Delta \tau ,\left(n-\mathrm{one}\right)\Delta F\right)\\ q\left(\Delta \tau ,\Delta F\right)& \mathrm{one}& ...& q*\left(\left(n-2\right)\Delta \tau ,\left(n-2\right)\Delta F\right)\\ ...& ...& ...& ...\\ q\left(\left(n-\mathrm{one}\right)\Delta \tau ,\left(n-\mathrm{one}\right)\Delta F\right)& q\left(\left(n-2\right)\Delta \tau ,\left(n-2\right)\Delta F\right)& ...& \mathrm{one}\end{array}\right]E,\left(\mathrm{one}\right)$$

Formula (1) takes into account the fact that the value of the mismatch function for the negative value of the argument is complex conjugate (operator (*)).

Denoting by the variable Q the matrix of values of the mismatch function (signal mismatch matrix):

$$Q=\left[\begin{array}{cccc}\mathrm{one}& q*\left(\Delta \tau ,\Delta F\right)& ...& q*\left(\left(n-\mathrm{one}\right)\Delta \tau ,\left(n-\mathrm{one}\right)\Delta F\right)\\ q\left(\Delta \tau ,\Delta F\right)& \mathrm{one}& ...& q*\left(\left(n-2\right)\Delta \tau ,\left(n-2\right)\Delta F\right)\\ ...& ...& ...& ...\\ q\left(\left(n-\mathrm{one}\right)\Delta \tau ,\left(n-\mathrm{one}\right)\Delta F\right)& q\left(\left(n-2\right)\Delta \tau ,\left(n-2\right)\Delta F\right)& ...& \mathrm{one}\end{array}\right],\left(2\right)$$

we write formula (1) in the form of a linear matrix equation with an unknown vector E:

$$QE=Z.\left(3\right)$$

To find E from equation (3), we multiply both its parts on the left by the matrix Q ^-1 , the inverse of Q:

$$E=Q^{-\mathrm{one}}Z.\left(\mathrm{four}\right)$$

In the absence of observation noises, as a result of calculating E according to (4), complex amplitudes of echo signals of real targets are formed in frequency filters and gates corresponding to their radial speeds and ranges. The remaining elements of the vector E are equal to zero. In real radar systems, there are observation noises, which means that the vector Z in (1) will be somewhat distorted, and the elements of the vector E are also calculated with some error. Therefore, to make a decision about the number and ranges to individual targets from the group, it is necessary to compare the modules of the elements of the vector E with threshold values. The latter are selected based on the required values of the probabilities of false decisions.

The potential resolution of the radar in the implementation of the proposed method and a sufficiently high signal to noise ratio depends on the mutual distance of the range gates from the delay time Δτ and the distance from the frequency ΔF of the FFT points, i.e. may be significantly smaller than the classical (Rayleigh) interval of joint resolution in range and frequency.

The proposed method of processing in a pulse-Doppler radar. One of the variants of the structural diagram of a device that implements the proposed method for detecting a group target, is presented in figure 1. The signal received by antenna 5 is fed to the input of receiver 6. To ensure coherent processing, the signal from the output of receiver 6 using two phase detectors 1, a local oscillator 7, a 90 ° 9 phase shifter, and two low-pass filters 2 is divided into quadrature components. In analog-to-digital converters 3 the formation of a sequence of digital samples of the quadrature components of the signal. Further, in the adders 4, the summation of the digital samples of the quadrature components of the signal. Summation is carried out within intervals equal to the duration of the probe pulse (range gates).

All further signal processing occurs in the signal processing processor 8. FIG. 2 is a diagram explaining the signal conversion sequence in the signal processing processor 8. The sequences of N samples obtained by summing in each gate are supplemented with zeros to the sequence of M samples, where M = 2 ⁿ > N (n is an integer), the obtained M samples are subjected to amplitude weighing, filter processing is performed according to the M-point FFT algorithm in each range gate. Then calculate the module of the complex envelope of the signal at the output of the Doppler filters. Next, select the range gate number kmax and the number of the Doppler filter jmax corresponding to the maximum signal amplitude, and form the analysis area with the center (kmax, jmax). Then, from the complex amplitudes of the signals at the outputs of the gates and filters, the analysis areas compose the vector Z and multiply it by the inverse signal mismatch matrix Q ^-1 previously calculated according to formula (2). The modules of the elements obtained by multiplying the vector E are compared with threshold values, which are set based on the required values of the probabilities of false decisions. If the threshold is exceeded by the ith element of the vector E, they decide on the presence of a signal of an individual target in the group with a range corresponding to the kth gate and a radial velocity corresponding to the jth filter.

Confirmation of the receipt of the above technical result in the implementation of the proposed method was carried out using mathematical modeling. A group target was simulated, consisting of two separate targets with different parameters for their relative position in range and Doppler frequency.

и одну двадцатую $$\frac{{\Delta }_f}{\Delta f}=\mathrm{0,05}$$

ширины фильтра М-точечного БПФ) в способе-прототипе становится невозможным обнаружение эхосигнала групповой цели, определение количества отдельных целей в составе групповой и их доплеровских частот, что следует из фиг.4 и 5 соответственно.Figures 3-5 show diagrams demonstrating a decrease in the resolution efficiency of a group target using the prototype method in the case when the ranges of individual targets from the group are located within the range gate, their Doppler frequencies are close and there is no resolution in angular coordinates. Figure 3 shows that if the echoes of the targets are in the same range gate and their Doppler frequencies differ by a quarter of the filter of the M-point FFT, the prototype method, although it determines the quantitative composition of the group target, but the estimates of the Doppler frequencies of individual targets from the group are very far from their true meanings. With further approximation of the Doppler frequencies of the echo signals of individual targets from the group to a fairly small amount (one tenth $$\frac{{\Delta }_f}{\Delta f}=0.1$$

and one twentieth $$\frac{{\Delta }_f}{\Delta f}=0.05$$

the filter width of the M-point FFT) in the prototype method, it becomes impossible to detect the echo of the group target, determining the number of individual targets in the group and their Doppler frequencies, which follows from figure 4 and 5, respectively.

Figures 6-8 are diagrams that demonstrate the possibility of determining the proposed method, the number, ranges and frequencies of Doppler of individual targets in the group in cases: the echo signals of individual targets from the group are within the same range gate, their Doppler frequencies coincide and there is no angular resolution coordinates; echoes of individual targets from the group are within the same Doppler filter, their ranges coincide and there is no resolution in angular coordinates; echoes of individual targets from the group are within the same range gate and Doppler filter and there is no resolution in angular coordinates. From Fig.6b-8b it is seen that the comparison of the modules of the elements of the vector E with threshold values in the cases: the echo signals of individual targets from the group are within the same range gate, their Doppler frequencies coincide and there is no resolution in angular coordinates (see Fig.6b) ; echoes of individual targets from the group are within the same Doppler filter, their ranges coincide and there is no resolution in angular coordinates (see figb); the echoes of individual targets from the group are within the same range gate and the Doppler filter and there is no resolution on the angular coordinates (see figb) provides the ability to determine the number, ranges and Doppler frequencies of individual targets in the group.

The use of the invention in airborne, ground and ship radars will not require a change in their construction principles, operating modes, significant computational costs and will allow high resolution to resolve individual targets in a group in the absence of resolution in angular coordinates, range and radial speed.

Claims (1)

A method for resolving a group target, which consists in isolating the quadrature components of the complex envelope of the received antenna signal, in each quadrature component, the signal is converted to digital form, within the interval equal to the duration of the probe pulse, the digital samples are added up, the sequence of N samples is supplemented with zeros to the sequence of M samples, where M = 2 ⁿ > N (n is an integer), the obtained M samples are subjected to amplitude weighting, a filter is carried out processing using the M-point FFT algorithm, the module of the complex envelope of the signal at the output of the FFT algorithm is calculated, characterized in that they select the range gate number kmax and filter number jmax corresponding to the maximum signal amplitude, form the analysis area with the center (kmax, jmax), composed from the complex amplitudes of the signals of the analysis region, the vector Z is multiplied by a pre-calculated inverse signal mismatch matrix Q ^-1 , the modules of the elements obtained by multiplying the vector E with threshold values are compared, which They establish, based on the required values of the probability of false decisions, when the threshold is exceeded by the i-th element of the vector E, they decide on the presence of an individual target signal in the group with a range corresponding to the k-th gate and radial speed corresponding to the j-th frequency filter.

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