RU2305850C2 - One-channel amplitude multi-frequency direction-finder of active noise interference - Google Patents

Abstract

FIELD: radiolocation, possible use for determining angular coordinates of active noise jammers and for estimating frequency distribution of power of active noise interference in working frequency range of direction-finder.

SUBSTANCE: one-channel amplitude multi-frequency direction finder of active noise interference contains antenna, receiving device, analog-digital converter, detector, azimuth packet memory block, azimuth packet restoration block, integrator, signal amplitude memory block, comparison block and computing block for determining azimuth position of active noise jammer, and also threshold level generation block, all interconnected in a certain way.

EFFECT: increased precision when measuring angular coordinates of active noise jammers due to adjustment to frequency with maximal interference/noise ratio.

Description

The invention relates to radar and is used to determine the angular coordinates of the directors of noise active interference (PSAP) and to evaluate the frequency distribution of the power of noise active interference (SHAP) in the operating frequency range of the direction finder, based on which the optimal direction finding frequency is selected.

There are various multichannel and single-channel devices [1-4] used to determine the angular coordinates of the PSAH.

Multichannel amplitude direction finders [1, 2], providing unambiguity of the bearing and the minimum specified level of false alarms, contain several receiving channels, one of which, with a highly directional radiation pattern (LH) of the antenna, is the main one, and the rest, with weakly directional LH antennas, are additional . The disadvantages of multichannel direction finders include a large amount of equipment and the complexity of their construction.

A single-channel amplitude direction finder [3] contains a receiving device, a threshold device, and a threshold level control device, which includes a drive and an integrator, with the help of which a threshold voltage is formed that prevents the reception of signals along the side lobes of the antenna beam.

The threshold level in this direction finder is formed by the peak voltage enveloping the received signals, for which there is a drive in the threshold level control circuit. With a threshold level, the signals received through the review are compared.

The disadvantage of this analogue is the high level of false bearings.

There are other options for constructing a single-channel amplitude direction finder of active jammers, where the threshold level is formed by averaging the amplitudes of the noise received in a certain angular interval [4]. The noise amplitude adopted in the same angular interval is compared with the threshold level, which completely eliminates the influence of signal level changes in neighboring surveys on the probability of bearing error.

The closest technical solution adopted for the prototype is an amplitude direction finder of active jammers [4], which contains a series-connected antenna, receiver, detector, integrator, memory unit for signal amplitudes, a comparison unit, a computing unit, and also an averaging unit, input which is connected to the output of the integrator, and the output to the second input of the comparison unit.

The disadvantages of this scheme include the fact that the PSAF direction finder operates at one operating frequency, which, in the general case, does not coincide with the frequency of the maximum interference power level, which leads to a decrease in the noise / noise ratio at the direction finder input and, accordingly, to a decrease potential accuracy of coordinate measurement.

The technical result of the invention is to increase the accuracy of measuring the angular coordinates of the PSAA by adjusting it to a frequency with a maximum noise / noise ratio.

This is achieved by the fact that in the structural diagram of the amplitude direction finder of active interference directors, taken as a prototype and containing a series-connected antenna, receiver, detector, integrator, signal amplitude memory unit, a comparison unit and a computing unit for determining the azimuthal position of the supplier of active noise interference ( in the prototype, a counting and decisive block), as well as a threshold level formation block (in the prototype, a gain averaging block), the input of which is connected to the integrator output, and the output to the second input b In the comparison box, between the detector and the integrator, the azimuthal packet memory unit and the azimuthal packet recovery unit are connected in series, in addition, the receiving frequency switching control unit and the frequency generation unit, the output of which is connected to the second input of the receiver, the spectrum estimation unit, are connected in series, whose input is connected to the detector output, and the output to the second input of the azimuthal packet memory block.

Figure 1 presents the structural diagram of the amplitude direction finder PSHAP prototype;

figure 2 is a structural diagram of the proposed amplitude single-channel multi-frequency direction finder noise active interference;

figure 3 is a view of the azimuthal packet with multi-frequency direction finding;

figure 4 - processing of the azimuthal packet with multi-frequency direction finding;

figure 5 - amplitude-frequency characteristic of the ShAP (maximum amplitude-frequency characteristic (AFC) in the center of the operating frequency band of the direction finder);

figure 6 - amplitude-frequency characteristic of the ShAP (maximum frequency response at the edge of the operating frequency band of the direction finder).

Figure 1 and 2 adopted the following notation:

1 - antenna;

2 - receiving device;

3 - detector;

4 - integrator;

5 - a block of memory amplitudes of the signals;

6 - threshold level generating unit (gain averaging unit);

7 - block comparison;

8 is a counting block for determining the azimuthal position of the supplier of active noise interference (counting block);

9 - block forming frequencies;

10 - control unit switching the receiving frequencies;

11 - memory block of the azimuthal packet;

12 is a block for spectrum evaluation;

13 - block recovery of the azimuthal packet.

The amplitude single-channel multi-frequency direction finding device for noise active interference contains a series-connected antenna 1, receiver 2, detector 3, memory block of the azimuth packet 11, the recovery block of the azimuth packet 13, the integrator 4, the memory block of the amplitudes of the signals 5, the comparison unit 7 and the computing unit for determining the azimuthal position of the supplier of active noise interference 8, as well as the threshold level generating unit 6, the input of which is connected to the output of the integrator 4, and the output to the second input of the comparison unit 7, by been consistent connected to the control unit switching the receiving frequency 10 and the block forming frequency 9 whose output is connected to the second input of the receiving device 2, and a unit for estimating the spectrum 12, whose input is connected to the output of the detector 3, and an output - to a second input of the storage unit azimuthal package 11.

The inventive device operates as follows. From antenna 1, the signal is fed to a receiving device 2 tuned to the frequency set by the frequency shaping unit 9. Using the frequency shaping unit 9 and the control unit for switching the receiving frequencies 10, the frequency of receiver 2 is periodically tuned (clock-wise) according to the operating frequency range of the PSAP amplitude direction finder. Operating frequencies range evenly. From the receiving device 2, the signal is fed to the detector 3, and the amplitudes obtained from it are recorded in the memory block of the azimuthal packet 11. At the same time, from the detector 3, the information is transmitted to the spectrum estimation unit 12, in which the spectral characteristics of the ShAP are evaluated and the direction finding frequency is selected with the maximum ratio interference / noise. Due to the periodic (beat) change in the direction finding frequency, the resulting azimuthal packet will be cut (Fig. 3), because samples corresponding to different frequencies will vary in magnitude depending on the spectral characteristics of the ShAP. To avoid the appearance of additional errors in the determination of the angular coordinates of the PSAA, further processing is carried out according to the readings of one (selected) frequency. Such processing leads to the fact that the azimuthal packet is thinned out by the number of operating frequencies used in direction finding (Fig. 4 - curve 1).

The amplitudes of the selected frequency are read from the memory block of the azimuthal packet 11 and fed to the recovery block of the azimuthal packet 13, because without additional processing of the azimuthal packet, for example, interpolation of thinned samples, the accuracy of determining the azimuth of the PSA decreases. Next, the interpolated azimuthal packet arrives at integrator 4, where the azimuthal packet is restored. Then, the amplitude of the reconstructed azimuthal packet (Fig. 4, curve 2) is stored on each clock cycle in the signal amplitude memory 5. At the same time, the azimuthal packet arrives at the threshold level formation unit 6, in which a threshold level is formed over time T equal to the average interference level for period T, increased so that the specified probability of a false bearing is not exceeded due to random emissions of the radiation pattern (figure 4 - curve 3). Then, in the comparison block 7, each value stored in the block 5 is compared with a threshold level, and when the threshold is exceeded, a sign of the bearing is generated at the output of the comparison block 7 (Fig. 4 — curve 4). An output is generated at the output of the counting-decisive block 8, the width of which is equal to the width of the beam at the level of intersection with its threshold level. The center of the pulse corresponds to the azimuthal position of the PSAA.

The efficiency of the amplitude single-channel multi-frequency direction finding is the higher, the greater the unevenness of the estimated spectrum of the ShAP (Figs. 5, 6).

According to the proposed scheme for constructing an amplitude single-channel multi-frequency direction finder of noise active interference, mathematical modeling was carried out. In the simulation, azimuth scanning was performed in increments of 0.2 degrees. After choosing the optimal direction finding frequency, the azimuthal packet is thinned out by the number of direction finding frequencies N, respectively, the scanning step increases N times. The determination of the azimuth was carried out in two different ways: by the method of searching for the center of the azimuthal packet (PCAA) without interpolating the received samples and the PCAA method by interpolating the received samples. The interpolation was carried out in accordance with the Kotelnikov theorem [5]. The azimuth of the PSA was measured at a frequency corresponding to the maximum noise / noise ratio. The results of azimuth measurements averaged over 5 realizations, with a bandwidth of a ShAP of 20 MHz, a frequency band of a direction finder of 25 MHz (maximum AFC frequency response of a ShAP in the center of a band of frequencies of a direction finder) and a different number of scanning frequencies are presented in Table 1.

Table 1 Number of scan frequencies Error of azimuth measurement (PCAP, noninterp.), Deg. Error in azimuth measurement (PCA, interp.), Deg. one 0.1 0.1 3 0.2 0.1 6 0.8 0.1 9 1.4 0.4 12 1.4 0.9

Table 1 shows that with an increase in the number of scan frequencies, the accuracy of determining the azimuth for non-interpolation methods noticeably deteriorates, while for the interpolation method, with the optimal choice of the number of scan frequencies, the accuracy is much higher.

Based on the analysis of the results of mathematical modeling, we can conclude that the optimal number of scan frequencies when using the multi-frequency direction finding method is 3-6 frequencies.

An analysis of the accuracy characteristics of azimuth measurement by multi-frequency direction finding at 3-6 scan frequencies and interpolation of the received samples showed that this method provides azimuth measurement with an error of the order of 0.1 deg at a scan step in azimuth of 0.2 deg.

The choice of the optimal frequency for the PSAF bearing (interference bandwidth is about 20-50 MHz) allows you to get a gain in noise / noise of the order of 1-20 dB (depending on the relative position of the ShAP frequency band and the operating frequency range of the direction finder (Figs. 5, 6 )).

Thus, in the amplitude single-channel multi-frequency direction-finding detector of active noise using the frequency forming unit 9 and the receiving frequency switching control unit 10, the direction finder operates at several frequencies, using the memory block of the azimuth packet 11, the spectrum estimator 12, and the azimuth packet recovery block 13 Evaluation of the frequency distribution of the ShAP power in the operating frequency range of the direction finder, selection of optimal direction finding frequencies and restoration of the azimuth packet.

The mathematical modeling showed that the use of interpolation of the received samples can improve the accuracy of measuring the angular coordinates of the PSAA. After evaluating the frequency distribution of the ShAP power and adjusting the direction finder to the optimal direction finding frequency, the amplitude single-channel multi-frequency direction-finder of noise active interference makes it possible to obtain a gain in noise / noise of the order of 1-20 dB, which leads to a corresponding increase in the accuracy of measuring the angular coordinates of the PSA.

List of used information sources

1. US patent No. 3747100, published 1973, IPC G01S 3/06, "Device for determining the main lobe of the radiation pattern."

2. UK patent No. 1236501, published 1971, IPC G01S 3/06, "direction finder".

3. Shirman Y.D. Theoretical Foundations of Radar M .: Soviet Radio, 1970

4. RF patent No. 2074403, published 1997, IPC G01S 3/06, “Amplitude direction finder for active jammers” NNIIRT.

5. Baskakov S.I. Radio circuits and signals. M.: High School 2000

Claims (1)

An amplitude single-channel multi-frequency direction finding device for noise active interference, comprising an antenna, a receiving device and a detector connected in series, as well as an integrator, a signal amplitude memory unit, a threshold level generating unit, and a computing unit for determining the azimuthal position of the active noise interference director connected in series, and a threshold formation unit, the input of which is connected to the integrator output, and the output to the second input of the comparison unit, characterized in that between the detector and the a serially connected azimuthal packet memory unit and an azimuthal packet recovery unit are introduced by a radiator; in addition, serially connected receiving frequency switching control unit and a frequency generating unit, the output of which is connected to the second input of the receiving device, and a spectrum estimation unit, the input of which is connected to the output of the detector, are introduced , and the output is with the second input of the azimuthal packet memory block.

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