RU2291459C2 - System of protection of impulse radar stations from active noise interference - Google Patents

Abstract

FIELD: the invention refers to radiolocation particularly to the modes of protection impulse radars from active noise interferences with application of automatic equalization arrangements.

SUBSTANCE: considered impulse radar stations which use in quality of an antenna system an antenna array with electronic scanning of a beam that is with electronics scanning of the diagram of the antenna direction having digital phase changers, a beam synthesizer system of the primary receiving channel, a beam synthesizer of compensating receiving channels and a multi channel automatic compensator which may be realized either by a hardware or by a program mode. Impulse radars' protection system from active noise interferences has an antenna array, digital phase changers, a beam synthesizer of the primary channel, a beam synthesizer of compensating receiving channels, a calculator realizing genetic or any other algorithm of zero phase synthesis, and a multi channel automatic compensator. At that the first output of the antenna array is connected to digital phase changers, and it's second output - with a beam synthesizer of compensating receiving channels, the output of the digital phase changers is connected with the input of the beam synthesizer of the primary receiving channel, whose output is connected with the input of the calculator and the first input of the multi channel of the automatic compensator, the output of the calculator is connected with the second input of the phase changers, and the output of the beam synthesizer of the compensating receiving channels is connected with the second input of the multi channel auto compensator, whose output is the output of the whole impulse radars' protection system.

EFFECT: increases coefficient of suppression of active noise interferences in impulse radars with multi channel automatic compensators.

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Description

The invention relates to radar, in particular to the protection of radar stations (radar) from active noise interference (ACP) using automatic compensation devices.

We consider pulsed radars in which an antenna array (AR) with electron beam scanning is used as an antenna system, i.e. electronic scanning of the antenna radiation pattern (BOTTOM), using digital phase shifters located in each dipole channel of the AR, containing a beam-forming system (DOS) of the main receiving channel, DOS of the compensation receiving channels and auto-compensator (AK), which can be implemented in hardware or software. At the same time, auto-compensators can be of any type: heterodyne or quadrature, in analog or digital version, operating at a high frequency or intermediate, with correlation feedbacks or (for digital execution) with direct calculation of weighting coefficients in accordance with the Wiener-Hopf formula

where W _opt - vector adaptive weights (vector weights);

R _nn is the covariance matrix of interference in the compensation channels;

B - column correlation vector of the main and compensation receiving channels, (Radio-electronic systems. Fundamentals of construction and theory. Handbook. / Ed. By Prof. Ya.D.Shirman. M .: ZAO MAKVIS, 1998, p.704 -708).

It is known that all types of auto-compensators have one common drawback - a limited suppression coefficient (K _supp. ) Of the order of 25 dB. The restriction of the suppression coefficient is associated with insurmountable (as practice has shown) difficulties in obtaining the amplitude-frequency and phase identity of the main and compensation receiving channels, which determines the value of the correlation coefficient (ρ), and therefore the suppression coefficient, which depends on the value of the correlation coefficient. For example, for a single-channel auto-compensator, this dependence is expressed by the formula:

Limiting the suppression ratio is especially undesirable when the interference level has a large dynamic range. After the autocompensation device while limiting the suppression, a rather high level of unsuppressed noise remains, which can significantly reduce the radar detection range. In addition, with a large level of active noise interference in heterodyne or quadrature type auto-compensators having correlation feedback, instability arises, which also reduces the auto-compensator suppression coefficient.

There are various ways to improve auto-compensation systems with an extended dynamic frequency range.

Multichannel auto-compensator (IAC) with improved dynamic range is presented in US patent No. 3938154 "Advanced system for suppressing side lobes", IPC N 04 V 7/00, NKI 343-100 LE, application No. 499374 from 08.16.1974, published on 02.10.1974. 1976 The patented system uses serial connection of tracking rings. The advantage of the circuit is the existence of such a situation in which in each tracking ring one interference “acts”. This ensures the stability of the MAC, and the suppression efficiency can be increased by increasing the steps of iteration.

In US patent No. 4086592 "Device for suppressing side lobes", IPC G 01 S 9/42, H 04 B 1/12, NKI 343-100 LE, application No. 818180 from 07/22/1977, published 04/25/1978, independence of the device from the power of the interference signal is ensured by the fact that the compensator is built in an open circuit. The compensator circuit is implemented on the basis of digital technology.

U.S. Patent No. 4119963 "Coherent Sidelobe Suppression Device for Pulse Radar", IPC G 01 S 9/233, NCI 343-17.2 PC, Application No. 782930 dated 03/30/1977, published on 10/10/1978 (Netherlands priority No. 7603559 dated 04/06/1976), an increase in the dynamic range of the interference is ensured by the introduction of blocks with amplitude characteristic y = x ^α at the main and compensation inputs of the auto-compensator, for example, logarithmic amplifiers. However, although the use of logarithmic amplifiers leads to an expansion of the dynamic range at high noise levels, due to decorrelation of noise by nonlinear devices in the main and compensation receiving channels, it is not always possible to obtain good noise suppression. It is especially difficult to get good suppression if the interference in the main and compensation channels of different levels.

The main disadvantage of all the above auto-compensation devices is the insufficient suppression of active noise interference at their high level.

The technical result of the invention is to increase the suppression coefficient of ACP in pulsed radars with multi-channel auto-compensators.

To achieve this result, a computing device is introduced into the pulsed radar with an antenna array, the electron beam scanning of which is carried out by controlling digital phase shifters located in each dipole channel of the AR, having a DOS of the main receiving channel, a DOS of the compensation receiving channels and a multi-channel auto-compensator implemented in software or hardware Implementing a Genetic Algorithm (GA) (Holland JH Genetic algorithms, Sei. Amer. pp. 66-72, July 1992. "Phase-Only A daptive Nulling with a Genetic Algorithm" IEEE Transactions on Antennas and Pro pagation. Vol.45, No6, June 1997) or any other phase synthesis algorithm for zeros similar to it, for example, one of the following sources of information: Baird C.A. and Rassweiler "Adaptive sidelobe nulling using digitally controlled Phase - shifters" IEEE Transactions on Antennas and Propagation. Vol.AP-24. pp. 638-649, 1976; or Shor R.A. "Nulling at Symmetrie pattern location with phase - only weight control." IEEE Transactions on Antennas and Propagation. Vol.AP-32. pp. 530-533, 1989.

Using the genetic algorithm, the control of the digital phase shifters used for electronic scanning of the bottom of the radar is performed only on the lower bits of the codes. In this case, preliminary dips are formed in the side lobes of the bottom with a minimal effect on the shape of the main lobe (Fig.6). These dips are further deepened with the help of a multi-channel auto-compensator, which provides the required interference suppression after the implementation of the genetic algorithm.

Figure 1 presents a block diagram of the invention.

Figure 2 - operations in accordance with the genetic algorithm.

Figure 3 is a view of the matrix M _x NP and the vector of output powers.

Figure 4 is a view of a ranked matrix.

Figure 5 - the operation of forming new weights.

Figure 6 - radiation pattern, the original and after auto-compensation.

Figure 7 - temporal levels of noise implementation in the main receiving channel of the radar.

In figure 1, the following notation is used:

1 - antenna array (AR);

2 - digital phase shifters;

3 - DOS of the main receiving channel;

4 - DOS compensation receiving channels;

5 - computing device that implements the genetic algorithm (GA), then - computing device;

6 - multi-channel auto-compensator.

The proposed system for protecting pulsed radars from the ACP consists of an antenna array 1, controlled digital phase shifters 2, a DOS of the main receiving channel 3, a DOS of the compensation receiving channels 4, a computing device 5 that implements a genetic or any other zero phase synthesis algorithm, and a multi-channel auto-compensator 6 implemented software using the above computing device 5 or hardware. The first output of the antenna array 1 is connected to the digital phase shifters 2, its second output to the DOS of the receiving compensation channels 4. The output of digital phase shifters 2 is connected to the DOS input of the main receiving channel 3, and its output to the input of computing device 5 and the first input of the multi-channel auto-compensator 6 The output of the computing device 5 is connected to the second input of the digital phase shifters 2. The output of the beam-forming system of the compensation receiving channels 4 is connected to the second input of the multi-channel auto-compensator 6, the output to This is the output of the entire protection system.

The inventive system of protection against ACP works as follows. The active noise interference signals received by the antenna array 1 are fed to digital phase shifters 2 and to the DOS of the compensation receiving channels 4. From digital phase shifters 2, the signals are fed to the DOS of the main receiving channel 3, from which, digitized and amplified, are sent to computing device 5 and to the first input of a multi-channel auto-compensator 6.

In the computing device 5, during the tuning period, weight coefficients are generated, which are stored for the clock period, and from its first output, they are transmitted to the lower bits of the control codes of the digital phase shifters 2 (input 2, control input) in order to create preliminary dips in the bottom side lobes in the direction of action ACP. From digital phase shifters 2, a signal with preliminary dips in the side lobes, i.e. with weakened noise, it again goes to the DOS of the main receiving channel 3, and from its output, to the input of the computing device 5 and to the first input of the multi-channel auto-compensator 6, the second input of which receives signals from the DOS of the compensation receiving channels 4 for further auto-compensation. In the multi-channel auto-compensator, the preliminary dips in the side lobes of the DND are deepened, and the overall suppression of the ACP (data from the simulation results) becomes a guaranteed value of 35-40 dB (Fig. 7).

The genetic algorithm works as follows. The first operation of the algorithm is the formation in the computing device 5 of the matrix M _x NP from random “0” and “1” constituting the control codes of the digital phase shifters (FIG. 2). Next, the digital phase shifters 2 are sequentially installed in accordance with the random codes of each row of the matrix and the corresponding measurement of the output power of the ACP signals received from the DOS of the main receiving channel 3. In the computing device 5, the output power vector is compiled from the measurement results (Fig. 3), which is ranked according to the increasing output power of interference, and in accordance with this is compiled a ranked matrix of output powers (figure 4). The next step (figure 5) in accordance with the genetic algorithm is to discard half of those lines that correspond to the maximum output power (figure 3). Then, as the "parents", two lines are randomly selected to create two code lines as a result of exchanging part of the codes, the volume of part of the codes is randomly selected, etc. before the formation of a new "offspring" (lines) in exchange of the discarded old. After that, the process is repeated again.

The main criterion for ending the process is the minimum output power of the interference signal at the output of the DOS of the main receiving channel.

A multi-channel auto-compensator can be implemented in software or hardware. As an example, consider a multi-channel auto-compensator, implemented in software and working according to the algorithm of direct calculation of the vector of weight coefficients in accordance with the Wiener-Hopf formula. The signals received by the compensation channels are then multiplied by this weighting factor. The vector of weights is determined by the formula (1), which in expanded form can be represented as

It should be noted that using only the phase synthesis algorithm of zero, GA, or any other, without the use of a multi-channel auto-compensator, as the simulation showed, does not give a stable result of suppressing the ACP and is random in nature, especially when there are several interference in the same interference situation. The spread of the suppression values can be different, but on average the genetic algorithm guarantees suppression of interference by 10-15 dB.

In addition, it is known that any auto-compensators, due to the finiteness of their time constant, work poorly or practically do not work with unsteady interference. In the proposed system for the protection of pulsed radars from an ACW, the use of a genetic algorithm allows you to suppress such interference, since the criterion for the operation of GA, regardless of the type of interference signal, is the minimum output power of this signal at the output of the DOS of the main receiving channel.

Claims (1)

A system for protecting pulsed radar stations from active noise interference, consisting of a series-connected antenna array, digital phase shifters, a beam-forming system of the main receiving channel, and a computing device that implements a genetic or any other zero phase synthesis algorithm to form preliminary dips in the side lobes of the antenna radiation pattern with a minimum influence on the shape of the main lobe, the output of which is connected to the second input of the digital phase shifter And beamforming system of compensation of reception channels, the input of which is connected to the second output of the antenna array and a multi-channel automatic compensator, first and second inputs of which are respectively connected to the outputs of beam systems of the main and compensation channels, and the output is the output of the entire protection system.

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