RU209015U1 - SUPPRESSION FILTER - Google Patents

Abstract

The utility model relates to radar technology and is designed to isolate signals from moving targets against the background of passive interference with unknown correlation properties. Achievable technical result - improving the efficiency of the selection of signals from moving targets against the background of passive interference with a priori unknown correlation properties. This result is achieved by the fact that the noise suppression filter contains a weight block, the first and second complex adders, the first, second, third and fourth delay blocks, a weight coefficient calculator and a clock generator, connected in a certain way and performing adaptive coherent processing of the original digital samples. 6 ill.

Description

The utility model relates to radar technology and can be used in coherent-pulse radar systems to isolate signals from moving targets against a background of passive interference with unknown correlation properties.

Known radar device for detecting a moving target [1], containing series-connected delay blocks, a multiplier of complex numbers and a subtractor. However, this device has a low signal separation efficiency of a moving target.

Another well-known device is a correlation autocompensator [2], which contains a number of delay blocks, two multipliers, an adder, and a block for estimating correlated interference parameters. The disadvantage of this device is the poor suppression of the edges of extended interference due to the large time constant of the adaptive feedback loop.

Closest to this utility model, a digital device for suppressing passive interference [3], selected as a prototype, contains a weight block, a complex adder and delay blocks. However, this device has a loss in interference suppression performance.

The task to be solved in the utility model is to increase the efficiency of suppressing passive interference and separating signals from moving targets when processing signals from the target against the background of passive interference with a priori unknown correlation properties.

To solve the problem, the noise suppression filter, containing the weight block, the first delay block, the first and second complex adders, the second delay block and the clock generator, includes the third and fourth delay blocks and the weight coefficient calculator connected to each other in a certain way.

The essence of the utility model as a technical solution is characterized by a set of essential features set forth in the formula of the utility model and providing a solution to the problem by optimal and coordinated processing of incoming pulses.

The technical result of the utility model is to increase the efficiency of passive interference suppression with a priori unknown correlation properties and the separation of signals from moving targets.

In FIG. 1 is a block diagram of an interference suppression filter; in fig. 2 - weight block; in fig. 3 - block delay; in fig. 4 - complex adder; in fig. 5 - weight calculator; in fig. 6 - drive.

The noise suppression filter (Fig. 1) contains a weight block 1, delay blocks 2, 4, 7, 8, complex adders 3, 5, a clock generator 6 and a weight calculator 9.

Weight block 1 (Fig. 2) contains two multipliers 10; blocks 2, 4, 7, 8 delay (Fig. 3) contain two delay lines 11; complex adders 3, 5 (Fig. 4) contain two adders 12; the weight calculator 9 (Fig. 5) contains four multipliers 13, an adder 14, two accumulators 15, a divider 16, a combining unit 17, a delay line 18, a square root extraction unit 19, and a memory unit 20; the drive 15 (Fig. 6) contain n delay elements 21 for the interval t _d and n adders 22.

The noise suppression filter can be implemented as follows.

входных квадратурных проекций, следующих через период повторения Т в каждом

элементе разрешения по дальности (кольце дальности) каждого (j-го) периода повторения.The initial sequence of coherent radio pulses, consisting of a signal from a moving target and passive interference, significantly exceeding the signal, is represented by digital readings

input quadrature projections following through the repetition period T in each

the range element (range ring) of each (j-th) repetition period.

Digital readings in the proposed device (Fig. 1) are fed to the connected inputs of the third delay block 7 (Fig. 3) for the interval τ and the first inputs of the calculator 9 of the weight coefficient (Fig. 5). The second inputs of the weight calculator 9 receives samples from the output of the first delay block 2 for the interval T-τ. The readings on the first and second inputs of the calculator 9 of the weight coefficient are divided into interval T.

In the calculator 9, the delayed and undelayed projections of the same name are multiplied, followed by the summation of the obtained products in the adder 15. In the unit 17 of the union, the sum of the squares of the projections is calculated. In the drives 15 (Fig. 6) with the help of delay elements 21 and adders 22, sliding along the range in each repetition period, the summation of incoming samples from n + 1 adjacent resolution elements in terms of the range of the time gate, except for the element with the number n / 2 + 1, is carried out, for whereby the output values of the delay element 21 with the number n/2 are fed only to the subsequent delay element 21. As a result of accumulation at the first input of the divider 16, the value

- номер текущего кольца дальности, n - объем обучающей выборки, определяемый числом отсчетов со смежных элементов разрешения по дальности, за исключением среднего отсчета с номером

where j is the number of the current period,

- the number of the current range ring, n - the size of the training sample, determined by the number of samples from adjacent elements of resolution in range, with the exception of the middle sample with the number

In block 19 of extracting the square root, taking into account the previous operations in blocks 17, 15, 18 and 13, the value arriving at the second input of the divider 16 is calculated

b=(c ₁ c ₂ ) ^1/2 ,

where

в видеAt the output of the divider 16, an estimate of the real part of the complex interference correlation coefficient is formed

as

- оценка коэффициента межпериодной корреляции,

- оценка доплеровского сдвига фазы за период повторения Т.where

- estimation of interperiod correlation coefficient,

- assessment of the Doppler phase shift for the repetition period T.

с хранимым в блоке 20 памяти множителем «-2 » образуется весовой коэффициентAs a result of multiplying the score

with the multiplier "-2" stored in the memory block 20, a weighting coefficient is formed

coming to the second input of the weight block 1 (Fig. 2).

The fourth delay block 8 for the interval t together with the first delay block 2 for the interval T-τ form the resulting delay for an interval equal to the repetition period T. In the second delay block 4, there is a delay for the interval T. As a result, the inputs of complex adders 3 and 5 samples arrive synchronously, forming at the output of the complex adder 5 the readings of the residuals of the compensated interference in the form

where

учитывает коэффициент корреляции помехи

и ее доплеровский сдвиг фазы

, что повышает эффективность подавления помехи.Weight coefficient

takes into account the interference correlation coefficient

and its Doppler phase shift

, which improves the efficiency of interference suppression.

для среднего элемента обучающей выборки, исключенному в накопителях 15 (фиг. 6). Величина τ определяется выражениемThe introduction of the third block 7 of the delay of input samples for the interval τ provides the calculation of estimates and a weighting coefficient

for the middle element of the training sample, excluded in the accumulators 15 (Fig. 6). The value of τ is determined by the expression

τ=t _in +nt _d /2,

n - количество элементов обучающей выборки, t_д - интервал (период) временной дискретизации.where t _in - the time of calculating the weighting factor

n is the number of elements of the training sample, t _d is the interval (period) of time sampling.

среднему элементу, исключенному из обучающей выборки. Тогда в случае сигнала, соизмеримого по величине с помехой, или разрывной помехи при компенсации отсчетов помехи с элемента разрешения, содержащего сигнал, исключается возможность ослабления или подавления сигнала за счет его влияния на используемые оценки. Кроме того, уменьшаются ошибки за счет рассогласования оцениваемых и действительных корреляционных свойств помехи.In this case, the compliance of the weight coefficient entered into the weight block 1 is achieved

the middle element excluded from the training sample. Then, in the case of a signal commensurate in magnitude with the interference, or discontinuous interference, when compensating for interference samples from the resolution element containing the signal, the possibility of weakening or suppressing the signal due to its influence on the estimates used is excluded. In addition, errors are reduced due to the mismatch between the estimated and actual correlation properties of the interference.

и не влияющего на получаемую оценку

.Adaptive processing is carried out for the average element of the training sample, excluded in the accumulators 15 (Fig. 6) in accordance with the algorithms for calculating the estimate

and does not affect the resulting score.

.

Synchronization of the noise suppression filter is carried out by applying to all blocks of the proposed device a sequence of clock pulses from the clock generator 6 (Fig. 1). The repetition period of the clock pulses is equal to the time sampling interval t _d selected from the condition of the required range resolution.

Achievable technical result consists in the following. The calculated estimates of the noise parameters are used when weighing its samples corresponding to the average element of the training sample, which reduces the discrepancies between the estimates obtained by averaging the samples of the training sample and the real properties of the noise. The exclusion of the middle element from the training sample makes it possible to eliminate the possible influence of the signal on the effectiveness of noise suppression.

Thus, the interference suppression filter makes it possible to increase the efficiency of suppressing passive interference and isolating signals from moving targets against the background of passive interference with a priori unknown correlation properties.

Bibliography

1. Patent No. 63-49193 (Japan), IPC G01S 13/52. Radar device for detecting a moving target / K.K. Toshiba. Published 03.10.1988. - Inventions of the countries of the world. - 1989. - Issue 109. - No. 15. - S. 52.

2. Radioelectronic systems: fundamentals of construction and theory. Directory / Ya.D. Shirman, S.T. Bagdasaryan, A.S. Malyarenko, D.I. Lekhovitsky [and others]; under the editorship of Ya.D. Shirman. - 2nd ed., revised. and additional - M.: Radio engineering, 2007; With. 439, fig. 25.22.

3. A.s. 743208 USSR, IPC G01S 7/36. Digital device for passive interference suppression / D.I. Popov. - No. 2540079/09; dec. 03.11.1977; publ. 06/25/1980, Bull. No. 23. - 4 s.

Claims (1)

An interference suppression filter containing a weight block, containing the first and second multipliers, the first delay block, the first complex adder, the second delay block, the second complex adder, the third delay block, the fourth delay block, the weight coefficient calculator and the clock generator, while the inputs of the first delay block connected, respectively, to the first inputs of the first and second multipliers and the first inputs of the second complex adder, the outputs of the first and second multipliers are connected, respectively, to the first inputs of the first complex adder, the outputs of which are connected to the inputs of the second delay block, the outputs of which are connected to the second inputs of the second complex adder, the inputs of the third delay block are connected to the first inputs of the weight coefficient calculator, the outputs of the third delay block are connected to the inputs of the first delay block, the outputs of which are connected to the inputs of the fourth delay block and the second inputs of the weight coefficient calculator, in the output of which is connected to the second inputs of the first and second multipliers, the outputs of the fourth delay block are connected to the second inputs of the first complex adder, the output of the sync generator is connected to the sync inputs of the first delay block, the first complex adder, the second delay block, the second complex adder, the third delay block, the fourth delay block and the weight coefficient calculator, characterized in that the output of the clock generator is connected to the clock inputs of the first multiplier and the second multiplier, and the inputs of the noise suppression filter are the inputs of the third delay block, and the outputs are the outputs of the second complex adder.

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