Method for determining number of targets in a group

FIELD: radiolocation.

SUBSTANCE: method includes analog-digital conversion of reflected from targets and received signal, calculating complex correlation sums of selection of received signal and support quadrature signals with values of parameter of resolution of support signal, taken on e even mesh, maximal by width intervals of values of resolution parameter, inside which all modules of correlation sums exceed threshold of detection, decision is taken about match of each local maximum to one target in the ranges, in which number of local maximums is more than one, width of range is calculated, inside which one local maximum is placed, decision about match of one local maximum to two targets is taken in case, if width of range is more than threshold width, in opposite case minimal non-square non-match of counts of complex correlation sums and count s of standard correlation sums of signal of one target are calculated, and decision is taken about match of local maximum inside range of one target in case, if non-match is less than non-match threshold, and two targets - in opposite case.

EFFECT: higher efficiency.

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The invention relates to radar systems and can be used in radar technology to determine the number of targets in the group in terms of when the targets are close by allow coordinates so that hampered their individual detection.

There is a method of determining the number of targets in the group consisting in testing composite hypotheses on the criterion likelihood ratio [1]. However, this method having characteristics close to the optimum, requires considerable computational effort, nonlinear, increasing with an increase in the detection area so that hampered its implementation.

Closest to the proposed invention is a method for determining the number of targets in the group, namely, that perform analog to digital conversion reflected from targets and the received signal, calculates a complex correlation sum Y(fn) sampling the received signal and the reference quadrature signals at values resolution reference signals f, taken on a uniform grid

where N is the number of grid points, δf is the grid spacing, δf<Δf, Δf - element size resolution [f1fN] the detection area. Determine the maximum width of the intervals of values of the parameter resolution [aibi], in which all modules correl the operating amounts exceed the detection threshold V where i=1...I, I is the number of intervals. So that for fn∈[aibi] is the ratio |Y(fn)|>V, and from the condition fn∉[aibi], i=1...I, |Y(fn)|≤V. Determine local maximamodules correlation sums inside the intervals [aibi], i=1...I, where j=1...J, J is the number of local maxima, which are defined as those values of fnwhich satisfy the conditions:

Decide whether each local maximum of one goal in those intervals in which the number of local maxima more than one. Calculate the width of the interval [aibi]inside one local maximum, and decide according to one local maximumtwo purposes if

where- threshold interval width, depending on the value of local maximum above the threshold. Decide according to one local maximumone purpose in the event of failure of conditions (3) [2].

The disadvantage of this method is the low probability of a correct estimation of the number of goals in g is the SCP in terms when the values of parameters resolution corresponding to the signals from targets that differ by a value smaller feature size resolution.

The purpose of the invention is the increased likelihood of a correct estimation of the number of targets in the group in the conditions, when the values of the resolution corresponding to the signals from targets that differ by a value smaller feature size resolution.

The proposed method of determining the number of goals in the group is as follows.

Perform analog to digital conversion reflected from targets and the received signal, calculates a complex correlation sum Y(fn) sampling the received signal and the reference quadrature signals at values resolution reference signals, taken on a uniform grid fndefined by formula (1). Determine the maximum width of the intervals of values of the parameter resolution [aibi], i=1...I, in which all modules of the correlation sums exceed the detection threshold V. Determine local maximaj=1...J, modules correlation sums within intervals by the formula (2). Decide whether each local maximum of one goal in those intervals in which the number of local maxima more than one. Calculate the width of the interval inside which is one locallymade, decide according to one local maximum two purposes in condition (3). Otherwise (when the interval width is less than the threshold width) calculate the minimum quadratic error D samples of the complex correlation sums and counts the reference correlation sums signal to one goal by the formula

where [fafb]=[aibi] for some i;

σ - standard deviation of the quadrature components of the correlation sums due to the presence of noise;

Ym=Y(fm+n);

M=1...M, M is even;

when

when

Sm(f) values of the reference correlation sums signal to one goal with a resolution equal to f, computed at the same points as the value of Ym, m=1...M

Decide on the conformity of local maximum inside the interval [aibi] one purpose if D<Vdand two purposes - if - D≥Vdwhere Vd- threshold residuals that are selected based on the probability of making a single goal for the group.

The new sign, with significant differences is the following.

In the case when the interval width is less than the threshold width in chislet minimum quadratic error D samples of the complex correlation sums and counts the reference correlation sums signal to one goal by the formula (4), decide on the conformity of local maximum inside the interval [aibi] one purpose if D<Vdand two purposes - if D≥Vdwhere Vd- threshold residuals that are selected based on the probability of making a single goal for the group.

This characteristic has significant differences, as in the known methods are not found. Applying a new sign will increase the probability of correct estimation of the number of targets in the conditions, when the values of the resolution corresponding to the signals from targets that differ by a value smaller feature size resolution.

Example evaluate the impact of the distinctive features on the technical result.

In pulse-Doppler radar stations in the same channel range reference are harmonic signals, the quadrature components are shifted in phase by 90° [3]. The resolution setting is the Doppler frequency f. Items resolution Doppler frequency determined by the values of the frequencies of the reference signals, are placed uniformly in increments Δf=1/T, where T is the coherent accumulation time of the signal. To suppress the side lobes of the spectrum of the signal sample values of the reference signals is additionally multiplied by the weight coefficients of the window. Sample value of the complex correlation sums Y(fn) meet the t discrete Fourier transform on the grid frequency f nn=1...N. the Values of the reference correlation sums signal to one goal Sm(f) in the case of the weight Hamming window is calculated by the formula

where Nx- the size of the signal sample.

The detection threshold V is exposed on the probability of false alarm equal to 10-4. The threshold width for the window Hamming and this value V is calculated by the formula

In the simulation determined that the selected thresholds width provides the probability of making a single goal for the group at the level of 10-4. Quadratic discrepancy D is defined with the following parameter values: δf=Δf/2, M=4. The residual threshold Vdequal to 15, which also provides the probability of making a single goal for the group at the level of 10-4.

Figure 1 and 2 shows the dependence of the probability of correct determination of two goals P22from the frequency separation between the signal df in the case where the signal amplitude is constant and is distributed according to the Rayleigh law, respectively, for values of the signal-to-noise ratio q=20, 25 and 30 dB. Graphs 1 and 2 refer to the prototype and the proposed method respectively. The dependencies obtained by the method of mathematical modeling, and to build a single point of the graph the imp is the proof 1000 realizations. As can be seen from the graphs, when df/Δf<1.2...1.4 the effectiveness of the proposed method relative to the prototype above 20...60% by probability P22.

Figure 3 shows a variant of the technical " of the proposed method. The device consists of a CPU unit 1, the transmitter correlation sums 2, switch 3, the transmitter residuals 4, transmitter amplitude 5, the transmitter local maximum 6, evaluator interval 7, the transmitter number of targets 8.

The device operates as follows. To the input of the CPU unit 1 receives an analog signal. Digital samples of the signal received at the transmitter correlation sums 2, N outputs which are formed integrated value of the correlation sums, corresponding to a uniform grid of values resolution fnn=1...N. the Outputs of the transmitter correlation sums 2 is fed to the input of the switch 3. The operation of the switch 3 is controlled by the clock pulses so that in each cycle to the first output of the switch 3 receives a comprehensive reference correlation sums Y(fn), n=1...N. the first output switch 3 data fed to the input of transmitter amplitude 5, the output of which is formed the magnitude |Y(fn)|. From the output of the transmitter amplitude 5 data arrives at the input of the transmitter local maximum 6, evaluator interval 7 and evaluator amount of CE is her 8. The transmitter local maximum 6 output forms the unit in the condition (2) and zero otherwise. The evaluator interval 7 output unit generates, if the reference fnbelongs to the interval [aibi] (i=1...I), and zero otherwise. With outputs of the transmitter local maximum 6, transmitter amplitude 5 and evaluator interval 7, the data arrives at the first, second and third inputs of the transmitter number of targets 8.

The transmitter number of targets 8 contains the register number of targets, the register number of targets in the interval, the register position of the local maximum and register the position of the interval. At the beginning of the work in the registers are written to a zero value.

When switching to the third input of the transmitter number of targets 8 from scratch in the unit is reset register number of targets on the range, and in case the position of the interval is filled in with the number n of the current position. When it arrives at the first input of the transmitter number of targets 8 units, the value of the register number of targets on the interval is incremented.

When switching to the third input of the transmitter number of targets with 8 units to zero the following actions are performed. If the value of the register number of targets on the interval is greater than one, the value of the register number of targets is increased by the value of the register quantities of the goals at the interval. If the value of the register number of targets in the interval is equal to one, then the width of the interval and compared with a threshold width. If the relation (3), the value of register number of targets is increased by two. Otherwise, the second group of outputs of the switch 3 are formed integrated value Ym, m=l...M, in accordance with formula (4). Data from the second group of outputs of the switch 3 receives the inputs of the transmitter residuals 4, which performs calculation of residuals D by the formula (4). Minimum values of the residuals are defined for discrete values of the parameter resolution f with a small step, equal to 0.005Δf, and the values of Sm(f), m=l...M, is precalculated and stored in a permanent storage device. From the output of the transmitter residuals 4 the value of D is supplied to the fourth input of the transmitter number of targets 8. If D<Vdthen the value of the register number of targets is increased by one. If D≥Vdthen the value of the register number of targets is increased by two.

Thus, the proposed method of determining the number of goals in the group can improve the probability of correct estimates of the number of targets in the group in the conditions, when the values of the resolution corresponding to the signals from targets that differ by a value smaller feature size resolution.

SOURCES of INFORMATION THE PURPOSE

1. Konovalov LN. Determining the number of signals, the method of testing composite hypotheses on the criterion likelihood ratio/Izv. University. Electronics, 1988, volume 31, N 7, p.18...25 (similar).

2. Kobasew I.N. A measure of the resolution of radar signals on one parameter.// Foreign electronics, 1992, No. 10 (prototype).

3. Multi-function radio-electronic complexes fighters./ Under. edit Gascondensate. - M.: Military publishing house, 1994.

The method of determining the number of targets in the group, namely, that perform analog to digital conversion reflected from targets and the received signal, calculates a complex correlation sum sampling the received signal and the reference quadrature signals at values resolution reference signals, taken on a uniform grid fnn=1...N, where N is the number of grid points in the field of detection with a constant pitch, the smaller the element size resolution, determine the maximum width of the intervals of values of the parameter resolution, in which all modules of the correlation sums exceed the detection threshold, determine local maxima of the correlation modules amounts

where J is the number inside the interval, decide on the compliance of each local maximum of one goal in those intervals, within which the number of local maxima more than one, calculate the width of the interval inside of which there is one local maximum, decide according to one local maximum two purposes in case, if the width of the interval is more than the threshold width, depending on the value of local maximum above the threshold, wherein if the width of the interval is less than the threshold width, calculate the minimum quadratic error D samples of the complex correlation sums and counts the reference correlation sums signal to one goal by the formula

where f is the permissions option;

[fafb] - interval parameter resolution;

σ - standard deviation of the quadrature components of the correlation sums due to the presence of noise;

Ym=Y(fm+n);

m=1...M, M is even;

when

when

Sm(f) values of the reference correlation sums signal to one goal with a resolution equal to f, computed at the same points as the value of Ym, m=1...M,

decide according locally is about the maximum inside the interval [f afb] one purpose if D<Vdand two purposes - if D≥Vdwhere Vdthe threshold of the residual is selected as the level of probability of making a single goal for the group.



 

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