RU2816701C1 - Noise suppression filter - Google Patents

Abstract

FIELD: radar equipment.

SUBSTANCE: invention can be used in coherent-pulse radar systems for separation of signals of moving targets against background of passive interference with unknown Doppler phase. In the noise suppression filter, the output of the synchronous generator is additionally connected to the synchronous inputs of the delay lines of the third delay unit. Inputs of the noise suppression filter are inputs of the third delay unit, and outputs of the second complex adder.

EFFECT: high efficiency of suppressing passive interference with a priori unknown Doppler phase and selecting signals from moving targets.

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Description

The invention relates to radar technology and can be used in coherent-pulse radar systems to isolate signals from moving targets against the background of passive interference with an unknown Doppler phase.

A radar device for detecting a moving target is known [Japanese patent No. 63-49193, IPC G01S 13/52], containing sequentially connected delay units, a complex number multiplier and a subtractor. However, this device has low efficiency in isolating a moving target signal.

The noise compensation filter closest to this invention [patent RU No. 2758877, IPC G01S 13/524], selected as a prototype, contains a weighting unit, delay units and complex adders. However, this device suffers from losses in interference suppression efficiency.

The problem solved by the invention is to increase the efficiency of suppressing passive interference and isolating signals from moving targets when processing signals from a target against the background of passive interference with an a priori unknown Doppler phase.

To solve the problem, the first and second complex multipliers and a Doppler phase meter, connected to each other in a certain way, are introduced into the interference suppression filter, which contains a weight block, the first, second, third and fourth delay blocks, the first and second complex adders and a clock generator.

The essence of the invention as a technical solution is characterized by a set of essential features set out in the claims and providing a solution to the problem through optimal and coordinated processing of incoming pulses.

The technical result of the invention is to increase the efficiency of suppressing passive interference with an a priori unknown Doppler phase and identifying signals from moving targets.

Figure 1 shows a block diagram of an interference suppression filter; figure 2 - weight block; figure 3 - delay block; figure 4 - complex adder; figure 5 - complex multiplier; Fig.6 - Doppler phase meter; Fig.7 - complex interface block; Fig.8 - drive; Fig.9 - module calculation block.

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, complex multipliers 9, 10 and a Doppler phase meter 11.

Weight block 1 (Fig. 2) contains a memory block 12 and first and second multipliers 13; delay blocks 2, 4, 7, 8 (Fig. 3) contain first and second delay lines 14; the first and second complex adders 3, 5 (Fig. 4) contain the first and second adders 15; the first, second and third complex multipliers 9, 10, 20 (Fig. 5) contain two channels (I, II), each of which contains the first and second multipliers 16, 17 and an adder 18; Doppler phase meter 11 (Fig. 6) contains a complex conjugation unit 19, a third complex multiplier 20 (Fig. 5), first and second accumulators 21, module calculation unit 22 and first and second dividers 23; complex interface block 19 (Fig. 7) contains a sign inverter 24; the first and second drives 21 (Fig. 8) contain n delay elements 25 for the interval t _d and n adders 26, module calculation unit 22 (Fig. 9) contains the first and second quadrators 27, an adder 28 and a square root extraction unit 29.

The interference suppression filter can be implemented as follows.

The digital samples (x _kl , y _kl ) arriving at the input of the proposed device (Fig. 1) follow through a repetition period T and in each range resolution element (range ring) of each repetition period they form a sequence of complex numbers

where k is the number of the current period, l is the number of the current range ring, ϕ _l is the Doppler phase shift over the repetition period (Doppler phase), usually interference, due to its significant excess over the signal.

Digital samples in the inventive device (Fig. 1) are supplied to the connected inputs of the third delay block 7 (Fig. 3) for the interval τ and the second inputs of the Doppler phase meter 11 (Fig. 6). The first inputs of the Doppler phase meter 11 receive samples from the output of the first delay block 2 for the T-τ interval. The readings at the first and second inputs of the Doppler phase meter 11 are divided into the T interval.

Samples from the output of the third delay block 7 are supplied to the inputs of the weight block 1, the first inputs of the second complex adder 5 and to the inputs of the first delay block 2, from the outputs of which the samples are supplied to the cascaded fourth delay block 8, the first complex multiplier 9, the first complex adder 3 , a second delay block 4, a second complex multiplier 10 and a second complex adder 5, the outputs of which are the outputs of the inventive device. Readings from the outputs of weight block 1 are sent to the first inputs of the first complex adder 3.

In the sign inverter 24 (Fig. 7) of the block 19 of the complex interface of the meter 11 (Fig. 6), the sign of the imaginary projections of the delayed samples is inverted. In the third complex multiplier 20, the corresponding complex numbers are multiplied, implemented by operations with the projections of these numbers in accordance with Fig. 5 and leading to the formation of the quantities

In drives 21 (Fig. 6), with the help of delay elements 25 and adders 26 (Fig. 8), the summation of the projections Re X _kl and ImX _kl with n+1 adjacent resolution elements along the range of the time strobe is carried out sliding along the range in each repetition period, except element with number n/2+1, for which the output values of delay element 25 with number n/2 are supplied only to the subsequent delay element 25 (Fig. 8). As a result of accumulation, quantities are formed

Where - estimate of the Doppler phase shift of the interference over the repetition period, averaged over n adjacent range resolution elements.

In module calculation block 22 (Fig.9) the values are determined and then at the outputs of dividers 23 (Fig. 6) - the values arriving at the second inputs of the first and second complex multipliers 9, 10. The accumulation of n samples provides a highly accurate measurement of the quantity

In weight block 1 (Fig. 2), incoming samples are weighed by a weight coefficient g=-2, stored in memory block 12.

The fourth delay block 8 for the interval x together with the first delay block 2 for the interval T-τ form the resulting delay for the interval T. In the second delay block 4 there is a delay for the interval T.

As a result, samples are received synchronously at the inputs of complex adders 3 and 5. Taking into account complex multiplication with the quantity delayed samples and in-phase summations in complex adders 3, 5, at the output of complex adder 5, samples of the remaining interference have the form

Two-dimensional rotation of delayed samples in the first and second complex multipliers 9, 10 by angle provides the in-phase consistency of the summed samples necessary to compensate for interference. Signal samples from a moving target are not suppressed due to the preservation of Doppler phase shifts.

The introduction of the third delay block 7 for the interval τ ensures consistency of estimates the average element of the training set excluded in accumulators 21 (Fig. 8). The value of m is determined by the expression where t _in is the time of calculating the estimate n is the number of elements of the training sample, t _d is the interval (period) of time sampling.

In this case, the correspondence of the estimates entered into the first and second complex factors 9, 10 is achieved the middle element excluded from the training set. Then, in the case of a signal comparable in magnitude to the interference, or discontinuous interference, when compensating for interference samples from the resolution element containing the signal, the possibility of attenuation or suppression of the signal due to its influence on the estimates used is eliminated. In addition, errors are reduced due to the mismatch between the estimated and actual values of the Doppler phase of the interference.

Synchronization of the noise suppression filter is carried out by supplying all blocks of the inventive device with a sequence of synchronizing pulses from the clock generator 6 (Fig. 1).

The achieved technical result consists in increasing the efficiency of compensation for passive interference with an a priori unknown Doppler phase and isolating signals from moving targets, which is ensured by the in-phase of the summed samples, increasing the accuracy of estimating the Doppler phase of interference and reducing the mismatch between the estimates obtained by averaging the samples of the training sample and the samples corresponding to the average element of the training sample. samples.

Thus, the interference suppression filter makes it possible to increase the efficiency of compensation for passive interference and the selection of signals from moving targets against the background of passive interference with an a priori unknown Doppler phase.

Claims (1)

An interference suppression filter comprising a weighting block, a first delay block, a first complex adder, a second delay block, a second complex adder, a clock generator, a third delay block containing delay lines, a fourth delay block, a first complex multiplier, a second complex multiplier and a Doppler phase meter, in this case, the inputs of the first delay block are connected to the 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 the third delay block are connected to the inputs of the first delay block, the outputs which are connected to the inputs of the fourth delay block, the outputs of the fourth delay block are connected to the first inputs of the first complex multiplier, the outputs of which are connected to the second inputs of the first complex adder, the outputs of the second delay block are connected to the first inputs of the second complex multiplier, the outputs of which are connected to the second inputs of the second complex adder, the outputs of the first delay block are connected to the first inputs of the Doppler phase meter, the inputs of the third delay block are connected to the second inputs of the Doppler phase meter, the outputs of which are connected to the second inputs of the first and second complex multipliers, the output of the clock generator is connected to the clock inputs of the weight block, the first delay block, a first complex adder, a second delay block, a second complex adder, a fourth delay block, a first complex multiplier, a second complex multiplier and a Doppler phase meter, characterized in that the output of the clock generator is connected to the clock inputs of the delay lines, 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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