RU2660803C1 - Filter of noise notching - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention relates to radar technique and can be used to isolate signals of moving targets against background of passive interference during group rearrangement of carrier frequency of probing pulses. Result is achieved by the fact that interference rejection filter comprises doppler phase meter of interference, block combiner, complex combiner, complex multiplier, first delay unit, sync generator, interference correlation meter, weight calculator, second delay unit, switching unit, switching unit and two-channel switch, interconnected so as to coherently process original samples.

EFFECT: increasing efficiency of signal extraction of moving targets against background of passive interference with priori unknown correlation properties.

1 cl, 9 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 a 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 a Doppler phase noise meter, a weight unit, a complex adder, a complex multiplier, a delay unit and a synchronizer. 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 rejection of passive interference and separation of signals of moving targets when processing a group of pulses against a background of passive interference with a priori unknown correlation properties.

To solve this problem, an interference rejection filter containing a Doppler phase noise meter, a weight unit, a complex adder, a complex multiplier, a first delay unit and a clock generator, introduces an interference correlation coefficient meter, a weight calculator, a second delay unit, a switching unit, a switching unit and two-channel switch connected in a certain way.

The essence of the invention as a technical solution is characterized by a combination of essential features set forth in the claims and providing a solution to the problem by optimal and consistent processing of a group of 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 of moving targets during group tuning of the carrier frequency of the probe pulses.

In FIG. 1 shows a block diagram of a noise rejection filter; in FIG. 2 - meter Doppler phase interference; in FIG. 3 - weight unit; in FIG. 4 - complex adder; in FIG. 5 - complex multiplier; in FIG. 6 - delay unit; in FIG. 7 - drive; in FIG. 8 - meter correlation coefficient interference; in FIG. 9 - switching unit.

The interference rejection filter (Fig. 1) contains a Doppler phase interference meter 1, a weight unit 2, a complex adder 3, a complex multiplier 4, a first delay unit 5, a clock 6, a noise correlation coefficient meter 7, a weighting computer 8, a second delay unit 9 , a switching unit 10, a switching unit 11, and a two-channel switch 12.

The meter 1 of the Doppler phase of interference (Fig. 2) contains a delay unit 13, a complex conjugation unit 14, a complex multiplier 15, two drives 16, a module calculation unit 17 and two divider 18; the weight unit 2 (Fig. 3) contains two multipliers 19; complex adder 3 (Fig. 4) contains two adders 20; complex multiplier 4 (Fig. 5) contains two channels (I, II), each of which contains multipliers 21, 22 and the adder 23; blocks 5, 9 and 13 delay (Fig. 6) contain two random access memory 24; drives 16, 29 (Fig. 7) contain n delay elements 25 for the interval t _d and n adders 26; the meter 7 of the correlation coefficient of interference (Fig. 8) contains two multipliers 27, an adder 28, a drive 29 and a divider 30; block 10 switching (Fig. 9) contains a counter 31, a decoder 32, blocks 33 matches and the adder 34.

The interference rejection filter can be implemented 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 T, 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 connected inputs of the meter 1 of the Doppler phase noise (Fig. 2), the second delay unit 9 (Fig. 6) and the meter 7 of the interference correlation coefficient (Fig. 8). Random access memory (RAM) 24 (Fig. 6) of delay units 5, 13 are used to store samples for one period T, and RAM 24 of the second delay unit 9 is used for the interval τ.

In block 14 of the complex conjugation of the meter 1 of the Doppler phase of the noise, the sign of the imaginary projections of the delayed samples is inverted. In the complex multiplier 15, the multiplication of the corresponding complex numbers occurs, which is realized by operations with the projections of these numbers in accordance with FIG. 5 and leading to the formation of quantities

и

с n+1 смежных элементов разрешения по дальности

строба, кроме элемента с номером n/2+1, для чего выходные величины элемента 25 задержки с номером n/2 поступают только на последующий элемент 25 задержки (фиг. 7). В результате накопления образуются величиныIn the drives 16 (Fig. 7), using the delay elements 25 and the adders 26, summation of the projections Re

and

with n + 1 adjacent range resolution elements

strobe, except for the element with the number n / 2 + 1, for which the output values of the delay element 25 with the number n / 2 are supplied only to the subsequent delay element 25 (Fig. 7). As a result of accumulation, 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.

, а затем на выходах делителей 18 (фиг. 2) - величины

, поступающие на первые входы комплексного перемножителя 4. Точность определения величины

определяется числом накапливаемых отсчетов n.In block 17, the calculation of the module determines the values

, and then at the outputs of the dividers 18 (Fig. 2) - values

entering the first inputs of the complex multiplier 4. Accuracy of determining the value

determined by the number of accumulated samples n.

и величиной ⎜Y_k⎜ от измерителя 1 доплеровской фазы помехи определяется оценка коэффициента корреляции помехиIn the meter 7 of the correlation coefficient of interference in accordance with its structural diagram (Fig. 8) and the incoming input samples

and ⎜Y _k ⎜ from the meter 1 of the Doppler phase of the interference determines the estimate of the correlation coefficient of the interference

поступает в вычислитель 8 весовых коэффициентов. Количество вычисляемых по оценке

весовых коэффициентов

определяется реализуемым порядком фильтра режекции помех m, связанным с числом импульсов в группе, равным m+1. В частности, при m=1 весовые коэффициенты

,

; при

,

; при

,

.Rating

enters the calculator 8 weighting factors. The number calculated

weighting factors

is determined by the implemented order of the interference rejection filter m associated with the number of pulses in the group equal to m + 1. In particular, for m = 1 weights

,

; at

,

; at

,

.

. Весовые коэффициенты переключаются в каждом периоде повторения блоком 10 переключения (фиг. 9), который обеспечивает обработку группы импульсов (отсчетов) с одинаковой исходной несущей частотой.In the weight block 2 (Fig. 3), the incoming samples are weighed by weight coefficients

. The weights are switched in each repetition period by the switching unit 10 (Fig. 9), which provides 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, which is the first control input (1) of the switching unit 10, and then to the counting input of the counter 31 ( Fig. 9). The counter readings corresponding to the pulse number in the group in the decoder 32 are converted into a single signal at the corresponding pulse number of the output of the decoder 32. This signal opens the coincidence cascade 33 connected to it, through which the corresponding weight coefficient passes through the adder 34 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 адаптивной весовой обработки отсчетов m+1 периодов образуется величинаSamples weighted in weight block 2 are summed in the complex adder 3 with delays in the delay unit 5 for the repetition period T, passed through the two-channel switch 12 and multiplied in the complex multiplier 4 by the amount

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

обеспечивает необходимую для режекции помехи синфазность суммируемых отсчетов, а их взвешивание коэффициентами

- наилучшее подавление (режекцию) отсчетов помехи с коэффициентом корреляции

. Отсчеты сигнала от движущейся цели из-за сохранения доплеровских сдвигов фазы не подавляются.Two-dimensional rotation of delayed samples at an angle

provides the necessary for rejection interference common mode phase of the summed samples, and their weighing by coefficients

- the best suppression (notch) of interference samples with a correlation coefficient

. The signal samples from a moving target due to the conservation of Doppler phase shifts are not suppressed.

In the second delay block 9, the samples are delayed by the interval τ equal to the time delay of the estimates with respect to the middle element of the training sample, excluded in the drives 16 and 29 (Fig. 7) in accordance with expressions (1) and (2). The value of τ is determined by the expression

τ = t + nt _{to d} / 2,

where t _at is the calculation time of the estimation of the phase of the interference, n is the number of elements of the training sample, t _d is the interval (period) of time sampling.

и

. Тогда при режектировании отсчетов помехи с элемента разрешения, содержащего сигнал, исключается возможность ослабления или подавления сигнала за счет его влияния на используемые оценки.In this case, adaptive processing is carried out for the middle element excluded from the training set and not affecting the resulting estimates

and

. Then, when rejecting interference samples from a resolution element containing a signal, the possibility of attenuation or suppression of the signal due to its influence on the estimates used is excluded.

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. 9) and the control input of the switching unit 11, a pulse arrives that resets the counter 31, and in the block 11 switching switches the relaxation generator (multivibrator). At the command of the switching unit 11, the two-channel switch 12 switches the delay unit 5 to the filter output, and during the repetition period T, the results of the notch V are read. The data of the next group are received and the data are processed.

дискретизации t_д, выбираемому из условия требуемой разрешающей способности по дальности.The synchronization of the interference rejection filter is carried out by applying to all the blocks of the claimed device a sequence of synchronizing pulses from the synchro generator 6 (Fig. 1), controlled together with the radar synchronizer synchronization pulses (1) block 10 (not shown in Fig. 1), following interval T. Period repetition of synchronizing pulses is equal to the interval

discretization t _d selected from the conditions of the required resolution in range.

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 rejection filter increases the efficiency of suppressing passive interference and extracting signals from moving targets against 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. 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. / Ed. By Y.D. Shirman. - 2nd ed., Revised. and add. - M .: Radio engineering, 2007; from. 439, fig. 25.22.

3. A.S. 743208 USSR, 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)

A noise rejection filter comprising a Doppler phase noise meter, a weight unit, a complex adder, a complex multiplier, a first delay unit and a synchronizer, while the first outputs of the Doppler phase noise meter are connected to the first inputs of the complex multiplier, the outputs of the weight unit are connected to the first inputs of the complex adder, the second inputs of which are connected to the outputs of the complex multiplier, the control input of the clock is connected to the first control input of the interference rejection filter, and the output a generator - with the synchro inputs of the Doppler phase noise meter, weight block, complex adder, complex multiplier and the first delay block, characterized in that the noise correlation coefficient meter, weight coefficient calculator, second delay block, switching block, switching block and two-channel switch are introduced, when the first inputs of the interference correlation coefficient meter are connected to the inputs of the Doppler phase noise meter and to the inputs of the second delay unit, the second input of the the interference correlation coefficient is connected to the second output of the Doppler phase noise meter, the output of the second delay unit is connected to the first inputs of the weight block, the output of the noise correlation coefficient meter is connected to the input of the weight coefficient calculator, the outputs of which are connected to the main inputs of the switching block, the output of which is connected to the second input weight unit, the first control input of the switching unit is connected to the first control input of the interference rejection filter, the outputs of the complex adder are connected to the moves of the first delay unit, the outputs of which are connected to the main inputs of the two-channel switch, the first outputs of which are connected to the second inputs of the complex multiplier, and the control input is connected to the output of the switching unit, the second control input of the switching unit and the control input of the switching unit are connected to the second control input of the notch filter interference, the output of the clock is connected to the sync inputs of the meter correlation coefficient of interference, the calculator of the weight coefficients, the second delay unit, block re switching, switching unit and two-channel switch, the main inputs of the interference rejection filter are the connected inputs of the Doppler phase noise meter, the inputs of the second delay unit and the first inputs of the interference correlation coefficient meter, and the outputs are the second outputs of the two-channel switch.

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