RU2765852C1 - Passive interference rejection filter - Google Patents

Abstract

FIELD: radio location.

SUBSTANCE: invention relates to radio location equipment and is intended for isolating signals of moving targets against the background of passive interference with unknown correlation properties. In the passive interference rejection filter, estimates of the interference parameters are calculated, used in weighing of the counts thereof corresponding to the average element of the training sample, reducing the misalignment between the estimates obtained by averaging the counts of the training sample and the actual properties of the interference. The exclusion of the median element from the training sample allows for elimination of the possible influence of the signal on the interference compensation efficiency.

EFFECT: increase in the efficiency of isolation of signals of moving targets against the background of passive interference with a priori unknown correlation properties.

1 cl, 6 dwg

Description

SUBSTANCE: invention relates to radar engineering and can be used in coherent-pulse radar systems for extracting signals from moving targets against the 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 invention, 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 losses in the rejection of passive interference.

The problem solved in the invention is to increase the efficiency of passive interference rejection and signal separation of moving targets when processing signals from the target against the background of passive interference with a priori unknown correlation properties.

To solve the problem set, the passive noise rejection 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 invention as a technical solution is characterized by a set of essential features set forth in the claims and providing a solution to the problem by optimal and consistent processing of incoming pulses.

The technical result of the invention is to increase the efficiency of rejection of passive interference with a priori unknown correlation properties and the selection of signals from moving targets.

In FIG. 1 shows a structural electrical diagram of the passive interference rejection 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 passive noise rejection 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 delays (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 passive interference rejection filter can be implemented as follows.

A sequence of coherent radio pulses, consisting of a signal from a moving target and passive interference, significantly exceeding the signal, is represented by digital codes (x _jl ,y _jl ) of input quadrature projections following through a repetition period T in each (l-th) element of resolution in range (ring range) 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 receive samples from the output of the first delay block 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.

строба, кроме элемента с номером n/2+1, для чего выходные величины элемента 21 задержки с номером n/2 поступают только на последующий элемент 21 задержки. В результате накопления на первом входе делителя 16 образуется величинаIn 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) using the delay elements 21 and the adders 22, the summation of the incoming samples from n + 1 adjacent elements of resolution in range is carried out sliding along the range in each repetition period

strobe, except for the element with the number n/2+1, for which the output values of the delay element 21 with the number n/2 are supplied only to the subsequent delay element 21. As a result of accumulation at the first input of the divider 16, the value

where j is the number of the current period, l is the number of the current range ring, n is the volume of the training sample, determined by the number of samples from adjacent elements of resolution in range, except for the average sample with the number l=n/2+1.

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 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 weight coefficient is formed

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

The fourth delay block 8 for the interval τ 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, a delay for the interval T is carried out. 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 rejected interference in the form

where

учитывает коэффициент корреляции помехи

и ее доплеровский сдвиг фазы

, что повышает эффективность режекции помехи.Weight coefficient

takes into account the interference correlation coefficient

and its Doppler phase shift

, which increases the efficiency of interference rejection.

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)

дискретизации.where t _in - the time of calculating the weighting factor

, n - the number of elements of the training sample, t _d - interval (period)

discretization.

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 set. 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 passive interference rejection 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 compensation.

Thus, the passive interference rejection 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. - P.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)

Passive noise rejection filter containing a weight block, a first delay block, a first complex adder, a second delay block, a second complex adder, a third delay block, a fourth delay block, a synchronizer and a weight coefficient calculator containing the first, second, third and fourth multipliers, an adder , the first and second accumulators, a divider, a combining block, a delay line, a square root block and a memory block, while the first input of the first multiplier is connected to the first input of the combining block, the output of which is connected to the input of the first accumulator, the output of which is connected to the first input of the divider , the output of the combining unit is connected to the input of the second accumulator, the output of which is connected to the input of the delay line and the first input of the third multiplier, the output of the delay line is connected to the second input of the third multiplier, the output of which is connected to the input of the square root extraction unit, the output of which is connected to the second input of the divider , the output of the divider line with the first input of the fourth multiplier, the second input of which is connected to the output of the memory block, the inputs of the first delay block are connected to the first inputs of the weight block and the first inputs of the second complex adder, the outputs of the weight block are connected 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 inputs of the combining block, 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, respectively, to the second inputs of the first and second multipliers, the output of the fourth multiplier is connected to the second input of the weight block, the outputs of the fourth delay block are connected to the second inputs of the first complex adder, the output of the clock generator is connected to the clock inputs of the weight block, the first delay block, the first complex adder ora, the second delay block, the second complex adder, the third delay block and the fourth delay block, characterized in that the output of the clock generator is connected to the clock inputs of the first multiplier, second multiplier, third multiplier, fourth multiplier, adder, first accumulator, second accumulator, divider, block combining, a delay line, a square root extraction unit and a memory unit, wherein the inputs of the passive noise rejection filter are the inputs of the third delay unit, and the outputs are the outputs of the second complex adder.

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