RU2298806C9 - Mode of detection of a group target - Google Patents

Abstract

FIELD: the invention refers to radiolocation and may be used in airborne, surface and shipboard radar stations.

SUBSTANCE: the technical result is in increasing possibility of detection a group target whose signals are not resolvable on distance, speed and angular coordinates. For this they separate quadrature components of an enveloping line of the received signal, in each quadrature component transformation of the signal into a digital form is executed, in the limits of an interval equal to the duration of a sounding impulse summing of digital readings are carried out, the results received in the summing of N readings are subjected to an amplitude weighing , the filter processing on the algorithm of N- dot Fourier rapid transformation is executed, a module of a complex enveloping line of the signal is calculated at the output of Doppler filters of Fourier rapid transformation, in the distance strobe many adjacent Doppler filters are selected, the first Doppler frequency of the mentioned adjacent Doppler filters is determined as a frequency of the filter with maximum amplitude of the signal. At that the coefficient of weakening of the amplitude of the signal on strobes is defined for all distance strobes, quadrature components of tension are found out, the amplitude of tension is received, the received amplitude of tension is compared with the threshold of detection, decision about detection of a group target is taken in case of exceeding the threshold at least in one distance strobe.

EFFECT: increases possibility of detection of 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 establish the fact of the presence of a group target 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. This 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 _∂i 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.

The closest technical solution is a 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 the quadrature components of the complex envelope of the received signal antenna are isolated, in each quadrature component, the signal is converted into digital form within an interval equal to the duration of the probe pulse, the digital samples are added up, N samples obtained from the summation are subjected to amplitude weighting, carry out filtering according to the N-point fast Fourier transform (FFT) algorithm, calculate the complex og modulus bayuschey signal at the output of the Doppler FFT filter, a gate kmax range selected plurality of adjacent Doppler filters, determining a first Doppler frequency f ₁ from said plurality of adjacent Doppler filters as the filter frequency jmax1 with maximum signal amplitude is selected first subset of plurality of adjacent Doppler filters R ₁ centered near the selected first Doppler frequency f ₁ , the value of the first threshold is obtained by multiplying the amplitude of the signal of the first Doppler frequency f ₁ with the first factor, less m units, in the first subset of the set of adjacent Doppler filters R ₁ , the signal amplitude groups exceeding the first threshold are determined, the signal amplitude groups obtained are divided into clusters whose width is limited by a predetermined number of signal amplitudes of adjacent Doppler frequencies, the number of clusters is calculated to obtain the first count C _1, weaken by blanking a first Doppler frequency signals f ₁ and the amplitude of the Doppler frequencies band, located near define a second Doppler frequency f ₂ as the filter frequency jmax2 maximum amplitude signal among the non-weakened signal from the first subset of the plurality of adjacent Doppler filters R _1, selecting a second subset of adjacent Doppler filters R ₂ centered about the selected second Doppler frequency f ₂ gave a second threshold value by multiplying the amplitude the signal of the second Doppler frequency f ₂ with a second factor, if the first count C _{1 is} less than or equal to unity, or by multiplying the amplitude of the signal of the second Doppler frequency f ₂ s the first factor, if the first count C _{1 is} greater than one, then in the second subset of the set of adjacent Doppler filters R ₂ determine the group of amplitudes of the signals that exceed the second threshold, divide the resulting group of signal amplitudes into clusters whose width is limited by a predetermined number of amplitudes of the signals of adjacent Doppler frequencies, count the number of clusters to obtain a second account With ₂ , calculate the intermediate account in accordance with 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 the prototype method is the low probability of detecting a group target in the range gate, the Doppler signal frequencies of which coincide. This is due to the fact that the resolution of the prototype method is determined by the width of the cluster (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 group target signals coincide, then when performing the blanking operation (zeroing) of the amplitudes of the signals of the first Doppler frequency and the group of Doppler frequencies located nearby, the information that the target is group can be lost. This is the reason for the low probability of detecting a group target whose Doppler signal frequencies coincide.

The objective of the invention is: to increase the likelihood of detecting a group target in a range gate whose Doppler frequencies coincide, and there is no resolution in angular coordinates.

к амплитуде сигнала в фильтре jmax1 строба kmax

The solution to the problem is that after determining the Doppler frequency f ₁ in the range gate kmax as the filter frequency jmax1 with the maximum signal amplitude, for all range gates, the attenuation coefficient of the signal amplitude across the gates b _k is equal to the ratio of the signal amplitude in the filter jmax1 of the kth strobe

to the signal amplitude in the filter jmax1 strobe kmax

равные разностям модулей соответствующих квадратурных составляющих сигнала в фильтре jmax1 k-го строба и произведений, найденных коэффициентов ослабления амплитуды сигнала по стробам b_k, на модули соответствующих квадратурных составляющих сигнала в фильтре jmax1 строба kmax:find quadrature stress components

equal to the differences between the modules of the corresponding quadrature components of the signal in the filter jmax1 of the kth gate and the products of the found attenuation coefficients of the signal amplitude across the strobes b _k , by the modules of the corresponding quadrature components of the signal in the filter jmax1 of the strobe kmax:

какget voltage amplitude

as

с порогом обнаружения η, который устанавливают, исходя из требуемого значения вероятности ложного обнаружения групповой цели, принимают решение об обнаружении групповой цели при превышении порога хотя бы в одном стробе дальности.compare the obtained voltage amplitude

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

и относительном рассогласований сигналов целей по частоте

The invention is illustrated by drawings. Figure 1 shows a structural diagram of a device that implements the proposed method for detecting 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, 9 - phase shifter 90 °. Figure 2 presents a diagram explaining the sequence of signal conversion in the signal processing processor 8. Figure 3 shows diagrams showing changes in the detection efficiency of a group target when using the proposed method compared to the prototype method, where P ₁₁ is the probability of correct detection of a single targets ₁₂ P - probability of false detection target group, R ₂₁ - group target probability of missing, P ₂₂ - the probability of correct detection of multiple target, Δ _d - the distance between each GOVERNMENTAL targets from the group of ranges, ΔD - value range gate, Δ _f - mismatch signal frequency purposes, ΔF - the width of the Doppler filter. Figure 3 presents the dependence of performance indicators on the signal-to-noise ratio at a relative distance of single targets from the group range

and relative frequency mismatches of target signals

The essence of the invention is as follows. For the single-target option, the attenuation coefficients of the signal amplitude over the gates b _k calculated according to (1) are equal to:

- комплексная амплитуда сигнала цели;Where

- the complex amplitude of the target signal;

- комплексная частотная характеристика доплеровского фильтра с номером jmax;

- complex frequency response of the Doppler filter with jmax number;

f is the Doppler frequency of the target signal;

F _k (t) is the value of the correlation function of the law of amplitude modulation of the target signal with the weight function of the adder in the kth range gate;

F _kmax (t) is the value of the correlation function of the law of amplitude modulation of the target signal with the weight function of the adder in the range gate kmax;

t is the delay time of the target signal.

The quadrature components of the signals at the outputs of the range gates in this case are described by the following expressions:

Substitution (5) - (9) in (2) and (3) allows to obtain the quadrature components of the signals at the outputs of the range gates in the form

в случае одиночной цели равна нулю. Для варианта групповой (например, парной) цели коэффициент ослабления амплитуды сигнала по стробам b_k зависит не только от корреляционных функций F_k(t), F_kmax(t), но и от комплексных амплитуд

:As follows from (4), (10), (11), the magnitude of the voltage amplitude

in the case of a single target is zero. For a group (e.g., paired) target, the attenuation coefficient of the signal amplitude over the gates b _k depends not only on the correlation functions F _k (t), F _kmax (t), but also on complex amplitudes

:

и

отличны от нуля:Accordingly, the quadrature stress components

and

nonzero:

характеризует состав цели (одиночная или групповая) и является показателем обнаружения групповой цели. При наличии внутреннего шума приемника для принятия решения необходимо амплитуду напряжения

сравнить с порогом обнаружения η, который устанавливают, исходя из требуемого значения вероятности ложного обнаружения групповой цели, например, в соответствии с выражениемThus, the magnitude of the voltage amplitude

characterizes the composition of the target (single or group) and is an indicator of the detection of a group target. If there is internal receiver noise, a voltage amplitude is required to make a decision.

compare with the detection threshold η, which is set based on the desired value of the probability of false detection of a group target, for example, in accordance with the expression

where μ is a constant coefficient;

μ ₀ - detection threshold of a single target.

Implement the proposed method of processing is possible in a pulse-Doppler radar. One of the possible structural diagrams of a device that implements the proposed method for detecting a group target is shown in FIG. 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 performed within an interval equal to the duration of the probe pulse.

и рассчитывают амплитуду напряжения

величина которой характеризует состав цели (одиночная или групповая), согласно (4). Затем амплитуду напряжения

сравнивают с порогом обнаружения η. При превышении порога хотя бы в одном стробе дальности принимают решение об обнаружении групповой цели.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 samples obtained as a result of summation are subjected to amplitude weighting and are filtered by the FFT algorithm. Then calculate the module of the complex envelope of the signal at the output of the Doppler filters. Next, in the kmax range gate, a plurality of adjacent Doppler filters are selected. From the selected set of adjacent Doppler filters, the Doppler frequency f ₁ is determined as the filter frequency jmax1 with a maximum signal amplitude. For all range gates, the attenuation coefficient of the signal amplitude over the gates b _{k is} calculated according to relation (1). Next, in the signal processing processor 8, in accordance with expressions (2) and (3), the quadrature components of the voltages are calculated

and calculate the amplitude of the voltage

the value of which characterizes the composition of the target (single or group), according to (4). Then voltage amplitude

compared with the detection threshold η. If the threshold is exceeded in at least one range gate, a decision is made to detect a group target.

Confirmation of the possibility of obtaining the above technical result in the implementation of the proposed method was carried out using mathematical modeling.

As an indicator of the effectiveness of the proposed method, a matrix P of the probabilities of the outcomes of signal processing is introduced. The element P _{nm of the} matrix P is the probability that in the presence of a single (n = 1) or group (n = 2) target, a decision will be made whether there is a single (m = 1) or group (m = 2) target. The probabilities P ₁₁ and P ₂₂ are the probabilities of making the right decisions, and P ₁₂ and P ₂₁ are the wrong decisions.

Figure 3 shows the estimates of the values of the elements of the matrix P when using the proposed processing method and the prototype method for single and dual-purpose situations and various signal-to-noise ratios.

и относительное рассогласований сигналов целей по частоте

вероятность правильного обнаружения Р₂₂ для предлагаемого способа в зависимости от отношения сигнал/шум составляет 0,2-0,9, а для способа-прототипа - не превышает 0,1.Analysis of the graphical dependencies shown in figure 3, allows us to conclude that the probability of correct detection of the group target P ₂₂ when using the proposed method is 2-10 times higher than the prototype method depending on the signal-to-noise ratio. The greater the gain, the higher the signal-to-noise ratio. For example, in the most difficult conditions for detecting a group target, when the relative distance between targets in range

and relative mismatches of target frequency signals

the probability of correct detection of P ₂₂ for the proposed method, depending on the signal-to-noise ratio, is 0.2-0.9, and for the prototype method it does not exceed 0.1.

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 make it possible to detect with high reliability a group target whose signals are within the same range gate in the absence of resolution of individual targets in the group by angular coordinates and speed.

Claims (1)

A method for detecting a group target, which consists in isolating the quadrature components of the complex envelope of the received antenna signal, converting the signal into digital form in each quadrature component, within the interval equal to the duration of the probe pulse, summing up the digital samples, subjecting the resulting N summation to N samples of amplitude weighing, carry out filtering according to the algorithm of N-point fast Fourier transform (FFT), calculate m modulus of the complex envelope of the signal at the output of the Doppler FFT filter, a gate kmax range selected plurality of adjacent Doppler filters, determining a first Doppler frequency f ₁ from said plurality of adjacent Doppler filters as the filter frequency jmax1 maximum amplitude signal, characterized in that for all strobes range determined the attenuation coefficient of the signal amplitude along the strobe b _k equal to the ratio of the signal amplitude in the filter j _{max1 of the} kth gate

to the signal amplitude in the filter j _max1 strobe kmax

:

find quadrature stress components

equal to the differences between the modules of the corresponding quadrature components of the signal in the filter j _{max1 of the} kth gate and the products of the found attenuation coefficients of the signal amplitude in the gates b _k , by the modules of the corresponding quadrature components of the signal in the filter j _{max1 of the} gate k _max :

get voltage amplitude

as

, compare the obtained voltage amplitude

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

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