RU2641644C1 - Noise filter - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: noise filter comprises the first and the second delay units, a weighting coefficient unit, the first and second complex multipliers, a weight unit, a complex adder, a complex conjugation unit, a switching unit, an accuracy unit, a switching unit and a two-channel switch and a synchronization pulse generator, which are interconnected in a certain way and carry out a coherent processing of the reference counts.

EFFECT: increased efficiency of extraction of moving target signals.

11 dwg

Description

The invention relates to radar technology and can be used in coherent-pulse radar systems to isolate the signals of moving targets against the background of passive interference during group tuning of the carrier frequency of the probe pulses.

Known radar device for detecting a moving target [1], containing sequentially included delay blocks, a complex number multiplier and a subtractor. However, this device has a low signal extraction efficiency for a moving target.

Another known device is the correlation auto-compensator [2], which contains a number of delay units, two multipliers, an adder and a unit for estimating the parameters of the correlated noise. The disadvantage of this device is the poor suppression of the edges of the extended interference due to the large time constant of the adaptive feedback circuit.

Closest to the present invention, a digital device for suppressing passive interference [3], selected as a prototype, contains two delay blocks, a block of weight coefficients, two complex multipliers, a weight block and a complex adder. However, this device due to the transient process upon receipt of the edge of the passive interference has a low efficiency of signal extraction of moving targets.

The problem to be solved in the invention is to increase the efficiency of rejecting passive interference and isolating signals of moving targets when processing a group of pulses against a background of passive interference with an a priori unknown Doppler speed.

To solve this problem, an interference suppression filter containing the first and second delay units, a weighting unit, the first and second complex multipliers, a weighting unit and a complex adder, introduced a complex conjugation unit, a switching unit, an accuracy unit, a switching unit, a two-channel switch and a clock generator .

Additional blocks introduced into the proposed device are known. Thus, the first delay unit, the first complex multiplier, the weight unit, and the complex adder connected together are used for rejecting passive interference, but their application together with the switching unit and two-channel switch is not known for more accurate interference compensation. The links between the weighting unit and the switching unit and the weight unit, the accuracy unit and the second complex multiplier, the second delay unit, the two-channel switch, the second complex multiplier and the switching unit, as well as the connections between the clock generator and the rest of the noise suppression filter blocks, which provide the optimal and consistent processing of a group of pulses, which, combined with more accurate noise compensation, increases the efficiency of signal extraction for moving targets during carrier frequency tuning against a background of passive interference with an a priori unknown Doppler speed.

Comparison with technical solutions known from published sources of information shows that the claimed solution has novelty and has an inventive step.

The claimed solution is technical in nature, feasible, reproducible and, therefore, is industrially applicable.

In FIG. 1 is a block diagram of an interference suppression filter; in FIG. 2 - delay unit; in FIG. 3 - block complex conjugation; in FIG. 4 - complex multiplier; in FIG. 5 - weight block; in FIG. 6 - complex adder; in FIG. 7 - switching unit; in FIG. 8 - precision block; in FIG. 9 - drive; in FIG. 10 - unit calculation module; in FIG. 11 - two-channel switch.

The interference suppression filter (Fig. 1) contains the first delay unit 1, the weighting unit 2, the first complex multiplier 3, the weight unit 4, the complex adder 5, the second complex multiplier 6, the switching unit 7, the second delay unit 8, the complex conjugation unit 9 , a switching unit 10, an accuracy unit 11, a two-channel switch 12, and a sync generator 13.

Blocks 1, 8 delay (Fig. 2) contain two random access memory 14; block 9 complex interface (Fig. 3) contains an inverter 15; complex multiplier 3, 6 (Fig. 4) contains two channels (I, II), each of which contains multipliers 16, 17 and the adder 18; the weight unit 4 (Fig. 5) contains two multipliers 19; complex adder 5 (Fig. 6) contains two adders 20; block 10 switching (Fig. 7) contains a counter 21, a decoder 22, blocks 23 matches and the adder 24; block 11 accuracy (Fig. 8) contains a drive 25, block 26 calculating the module and two divider 27; drive 25 (Fig. 9) contains two channels (I, II), consisting of n delay elements 28 for the interval t _d and n adders 29; unit 26 computing module (Fig. 10) contains two multipliers 30, adder 31 and block 32 extract the square root; two-channel switch 12 (Fig. 11) contains two switches 33.

The interference suppression filter operates as follows.

A group of coherent radio pulses, initially radiated with the same carrier frequency and consisting of a signal from a moving target and passive interference significantly exceeding the signal, is fed to the input of a receiving device, in which it is amplified, is transferred to the video frequency in quadrature phase detectors, and then subjected to analog-to-digital conversion (corresponding blocks in Fig. 1 are not shown).

обеих квадратурных проекций, следующие через период повторения Т, в каждом элементе разрешения по дальности (кольце дальности) каждого периода повторения образуют последовательность комплексных чиселDigital codes

of both quadrature projections following through the repetition period T, in each range resolution element (range ring) of each repetition period form a sequence of complex numbers

,

,

- номер текущего кольца дальности,

- доплеровский сдвиг за период повторения фазы (обычно помехи, ввиду ее значительного превышения над сигналом), равный

, здесь

- доплеровская частота помехи.where k is the number of the current period,

- number of the current range ring,

- Doppler shift during the phase repetition period (usually interference, due to its significant excess over the signal), equal

, here

- Doppler interference frequency.

Digital readings in the inventive device (Fig. 1) are supplied to the inputs of the first delay unit 1 (Fig. 2) and to the inputs of the weight unit 4 connected to them (Fig. 5). Each of the delay blocks 1, 8 (Fig. 2) consists of parallel-connected random access memory (RAM) 14. Moreover, each RAM 14 serves to store the values of the samples from the range rings of each quadrature channel for one period.

In block 9 of complex conjugation using an inverter 15 (Fig. 3), the sign of the imaginary projections of the delayed samples is inverted. In the complex multiplier 3, the multiplication of the corresponding complex numbers occurs, realized by operations with the projections of these numbers in accordance with FIG. 4. Formed values

с n+1 смежных элементов разрешения по дальности

строба, кроме элемента с номером n/2+1, для чего выходные величины элемента 28 задержки с номером n/2 поступают только на последующий элемент 28 задержки (фиг. 9). На выходах накопителя 25 (фиг. 9) образуются величиныenter the accuracy block 11 (Fig. 8), in which the drive 25 (Fig. 9), using the delay elements 28 and the adders 29, sums the works sliding along the range in each repetition period

with n + 1 adjacent range resolution elements

the gate, except for the element with the number n / 2 + 1, for which the output values of the delay element 28 with the number n / 2 are supplied only to the subsequent delay element 28 (Fig. 9). At the outputs of the drive 25 (Fig. 9) values are formed

- оценка сдвига фазы помехи за период повторения, усредненная по n смежным элементам разрешения по дальности.Where

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

, поступающие на первые входы комплексного перемножителя 6. Точность определения величины

определяется числом накапливаемых отсчетов n.In the block 26 for calculating the module (Fig. 10), the values ⎟Y _k определяются are determined, and then at the outputs of the dividers 27 (Fig. 8),

entering the first inputs of the complex multiplier 6. Accuracy of determining the value

determined by the number of accumulated samples n.

In the weight block 4 (Fig. 5), the incoming samples are weighed by the weighting factors g _k , which are stored in the weighting unit 2. The number of weight coefficients g _k is determined by the implemented filter order m, associated with the number of pulses in the group, equal to m + 1. In particular, when m = 1, the weighting coefficients g ₀ = -g ₁ = 1; when m = 2-g ₀ = g ₂ = 1, g ₁ = -2; with m = 3-g ₀ = -g ₃ = 1, g ₂ = -g ₃ = -3. The weights are switched in each repetition period by the switching unit 10 (Fig. 7), which provides the processing of a group of pulses (samples) with the same initial carrier frequency.

The pulse from the radar synchronizer (not shown in Fig. 1), corresponding to the radiation of the probe pulse in each period, is fed to the first control input (1) of the filter (Fig. 1), which is the first control input (1) of the switching unit 10 (Fig. 7 ), and then to the counting input of the counter 21 (Fig. 7). The counter readings corresponding to the pulse number in the group in the decoder 22 are converted into a single signal at the output pulse of the decoder 22 corresponding to the pulse number. This signal opens the coincidence cascade 23 connected to it, through which the corresponding weight coefficient passes through the adder 24 to the output of the switching unit 10 . Thus, each period and, therefore, each impulse in the group has its own weight coefficient.

весовыми суммами отсчетов всех предыдущих импульсов группы. В конечном счете, в результате весовой обработки отсчетов m+1 периодов образуется величинаThe samples weighted in the weight unit 4 are summed in the complex adder 5 with the delays delayed in the second block 8 for the repetition period T, passed through the two-channel switch 12 and multiplied in the second complex multiplier 6 by the amount

weighted sums of samples of all previous pulses of the group. Ultimately, as a result of weight processing of samples of m + 1 periods, the value

.

.

обеспечивает синфазность суммируемых отсчетов, а их взвешивание коэффициентами g_k - подавление (компенсацию) слагаемых отсчетов помехи. Сигнал от движущейся цели из-за сохранения доплеровских сдвигов фазы не подавляется.Two-dimensional rotation of delayed samples at an angle

provides the common mode of the summed samples, and their weighing by the coefficients g _k - suppression (compensation) of the summands of the interference samples. The signal from a moving target due to the conservation of Doppler phase shifts is not suppressed.

The delay time of the phase shifts introduced in the second complex multiplier 6 ensures their correspondence to the middle element of the training sample, excluded in the drive 25 (Fig. 9) in accordance with expression (1).

After the processing of data of m + 1 periods and the next tuning of the carrier frequency to the second control inputs (2) of the device (Fig. 1) and the switching unit 10 (Fig. 7) and the control input of the switching unit 7, a pulse arrives that resets the counter 21, and in block 7 switching switches the relaxation generator (multivibrator). At the command of the switching unit 7, the two-channel switch 12 switches the second delay unit 8 to the filter output, and during the repetition period T, the results of the notch V are read. The data of the first period of the next group are received and the data of the first period are processed.

The interference suppression filter is synchronized by applying to all the blocks of the claimed device a sequence of synchronizing pulses from the sync generator 13 (Fig. 1), which is controlled together with the radar synchronizer pulses (1) of the radar synchronizer pulses (1) (Fig. 1), followed by interval T. Period the repetition of the synchronizing pulses is equal to the time sampling interval t _d selected from the condition of the required range resolution.

The technical result achieved is as follows.

Uncompensated residuals of noise in the transition mode, traditionally masking the signal from the target, do not arrive at the output of the device. In the proposed device, the output receives only compensated residual noise in the steady state, which eliminates the effect of the "edge" of the noise and increases the efficiency of signal extraction of moving targets.

Thus, the interference suppression filter increases the efficiency of compensating for passive interference and isolating the signals of moving targets against passive interference with an a priori unknown Doppler speed.

Information sources

1. Patent No. 63-49193 (Japan), IPC G01S 13/52. Radar device for detecting a moving target / K.K. Toshiba. Publ. 10/03/1988. - Inventions of the countries of the world. - 1989. - Issue 109. - No. 15. - S. 52.

2. Radio-electronic systems: fundamentals of construction and theory. Reference book / Ya.D. Shirman, S.T. Baghdasaryan, A.S. Malyarenko, D.I. Lekhovitsky [et al.]; edited by Y.D. Shirman. - 2nd ed., Revised. and add. - M .: Radio engineering, 2007; from. 439, fig. 25.22.

3. A.S. USSR 743208, IPC G01S 7/36. Digital device for suppressing passive interference / D.I. Popov. - No. 2540079/09; declared 11/03/1977; publ. 06/25/1980, Bull. Number 23. - 4 p.

Claims (1)

An interference suppression filter comprising a first delay block, a weight coefficient block, a first complex multiplier, a weight block, a complex adder, a second complex multiplier and a second delay block, wherein the inputs of the first delay block are connected to the first inputs of the first complex multiplier and the first inputs of the weight block, the outputs of which are connected to the first inputs of the complex adder, the second inputs of which are connected to the outputs of the second complex multiplier, characterized in that the complex interface, a switching unit, an accuracy unit, a switching unit, a two-channel switch and a clock generator, while the outputs of the first delay unit are connected to the inputs of the complex interface unit, the outputs of which are connected to the second inputs of the first complex multiplier, the outputs of the first complex multiplier are connected to the inputs of the precision unit, the outputs of which are connected to the first inputs of the second complex multiplier, the outputs of the weighting unit are connected to the main inputs of the switching unit, the output is it is connected to the second input of the weighing unit, the first control input of the switching unit is connected to the first control input of the interference suppression filter, the outputs of the complex adder are connected to the inputs of the second delay unit, the outputs of which are connected to the main inputs of the two-channel switch, the first outputs of the two-channel switch are connected to the second inputs of the second complex multiplier, and the control input with the output of the switching unit, the second control input of the switching unit and the control input of the switching unit with connected to the second control input of the interference suppression filter, the control input of the sync generator is connected to the first control input of the noise suppression filter, and the output of the sync generator is connected to the sync inputs of the first delay block, weight coefficient block, first complex multiplier, weight block, complex adder, second complex multiplier, second delay unit, complex interface unit, switching unit, accuracy unit, switching unit and two-channel switch, the main input being E interference suppression filter are connected inputs of the first delay unit and the weighting unit, and outputs - second outputs of a two-channel switch.

Images