RU187857U1 - DEVICE FOR SELECTION OF AUTONOMOUS FALSE AIR TARGETS WHEN USING A WIDE BAND SENSING SIGNAL - Google Patents

Abstract

The proposed device relates to the field of radio engineering and can be used to recognize radar targets in radar systems that use broadband signals as probing, providing high resolution of individual scattering elements of a spatially distributed target.

The problem the proposed utility model is aimed at solving is a particular problem of radar recognition - selection of true targets against the background of false ones.

This device under the conditions that have a place in practice, allows to achieve the following technical result: to minimize the conditional probability of issuing, as a target designation, information about a false target.

The technical result in the proposed device is achieved by introducing two channels for calculating the differences in the initial phases of the radio pulses of the complex range portrait and the unit for generating the inter-period difference of the initial phases, which allows us to generate sufficient statistics to solve the two-alternative recognition of two classes of targets - spatially distributed objects and targets with zero transverse separation local scattering centers. 3 ill.

Description

The invention relates to the field of radio engineering and can be used in radar systems for recognition of radar targets using a broadband signal as a probe, providing high resolution of individual scattering elements of a spatially distributed target.

A device for recognizing targets in a two-frequency way [1], consisting of a pulse modulator (IM), a 1st frequency multiplier, a 2nd power amplifier (PA), a receiver of frequency signals nƒ, a series-connected receiver of frequency signals ƒ, a second frequency multiplier , phase detector and indicator, sequentially connected master oscillator (ZG), 1st PA, adder, antenna switch (AP) and antenna. In this case, the 1st output of the IM is connected to the 2nd input of the 1st PA, and the second to the 2nd input of the 2nd PA, the 1st input of which is connected to the output of the 1st frequency multiplier, the input of which is connected to the output MH. The output of the 2nd PA is connected to the 2nd input of the adder, and the AP output is connected simultaneously with the input of the frequency signal receiver ƒ and the input of the frequency signal receiver nƒ, the output of which is connected to the 2nd input of the phase detector.

This device allows you to select air targets against the background of reflections from local objects and recognize targets of different sizes among themselves. The operation of the device is based on measuring phase shifts of signals reflected by air targets at two multiple frequencies. Due to the use of multiple frequencies, information on the phase shifts of signals due to reflections from targets is separated from phase shifts occurring due to changes in the distance to the target or the angle of its bearing.

However, the proposed device cannot recognize targets with high probability, since the magnitude of the phase shift when reflected from the target is determined not only by the geometric size of the target, but also by its angle, material of manufacture, the use of a specific type of suspension equipment, etc. In addition, this device allows you to recognize targets of only two sizes, to which the wavelengths of signals of two probing frequencies are rigidly tied, since the device uses the areas of resonance and Rayleigh scattering.

It is also known a device that allows you to evaluate the transverse dimensions of radar objects [2], in which the result is achieved by the fact that the antenna system of a single-position radar in the direction of the radar target sequentially generates two radiation patterns with different widths. By measuring the amplitudes of the responses to the signals received by the antenna, the average value of the amplitudes of the responses and the normalized difference of these amplitudes are calculated. The average value of the response amplitudes is compared with the calculated normalized difference of these amplitudes and the transverse size of the radar target is determined. The response of the spatial filter (linear antenna) to a signal scattered by a complex radar target depends on the angular size of the pulse volume in which it is located. The pulse volume in the angular plane (azimuthal or elevation) is determined by the resolution interval in accordance with the expression:

where θα _0.5 is the effective width of the main lobe of the radiation pattern of the radar antenna in the angular plane; R - range to the radar target.

The width of the antenna pattern and the distance to the radar target in the case of laying the track of the detected target are known values, therefore, the angular size of the pulse volume is a known value. The ratio of the linear size of the target (L _α ) in the angular plane to the angular size of the pulse volume determines the value of the ratio of the relative extent of the target

If K _α tends to zero, then the target is a point radar target in the corresponding angular coordinate. For 0 <K _α <1, the target is group concentrated, and for K _α ≥1, it is group distributed.

It should be noted that the formation of radiation patterns of different widths is possible by changing the signal frequency or the size of the antenna apertures. Frequency change is implemented using multi-frequency signals. The mismatch body of a multi-frequency signal (with gaps in the spectrum) is multi-peak, like the mismatch body of a packet of coherent pulses.

Therefore, to reproduce the characteristics of the target in a long-range portrait, it is desirable that the interval between the peaks does not exceed the reciprocal of the duration of the least extended DP, then the gaps in the spectrum are filled. A significant drawback of multi-frequency signals is the violation of coherence due to turbine modulation and other factors, manifested due to the low pulse repetition rate and long signal duration [3].

It is also necessary to note the impossibility of implementing selection of moving targets when using multi-frequency signals. The problem lies in the dependence of the phase of the reflected signal not only on the values of the carrier frequency and radial velocity, but also on the peculiarities of the geometric dimensions of the target glider. Due to the interference of waves reflected from individual scattering elements of the target, the phase of the echo signal changes from pulse to pulse according to a random law determined by the design features of the target airframe and the target angle.

The task to which the proposed utility model is directed is the selection of true radar targets against the background of spurious signals generated by the repeater from one point in space. The proposed device differs from the considered analogue in the calculation of the inter-period difference of the initial phases Δ ₂ ϕ _{1, k} (where k is the order of the local maxima of the long-range portrait of the target) between the same-name pairs of radio pulses of complex long-range portraits obtained in a short time interval when using a broadband LFM radio pulse as a probe signal . The obtained value Δ ₂ ϕ _{1, k} can serve as decisive statistics in solving the problem of selecting true targets against false ones, in accordance with the expression [4]:

where Δ ₂ ϕ _1k is the inter-period difference of the initial phases of the first and k-th radio pulses of the long-range portrait;

L _1k is the observed distance between the scattering elements of the target (the distance between the brilliant points on the target in the picture plane);

ΔΘ is the angle by which the angle of the target changes when it moves over the time interval between two adjacent soundings;

λ is the radar wavelength.

The device is intended for the simultaneous selection of several true targets against false ones regardless of their type in a single-position surveillance radar and minimizes the conditional probability of issuing, as a target designation, information about a false target.

The block diagram of the developed device for the selection of autonomous false air targets when using a broadband probe signal is shown in FIG. one.

The device consists of a counter of the number of calls to the recognized target 1, a logical control device 2, a block for generating inter-period differences of the initial phases S, two identical channels for calculating the difference of the initial phases Q1, Q2, and threshold device 12. The channels for calculating the differences of the initial phases include: keys 3, 5, 8; shaper of counting pulses 4; pulse counter amplitude portrait 6; shift register 5; subtracting devices 9. The block for generating inter-period differences of the initial phases S consists of subtracting devices 10 and a circuit for selecting the maximum value 11. The input information of the device for selecting autonomous false air targets is the output signals of the amplitude detector (AD) and the phase detector (PD) of the radio receiving device (RPRU) .

The reference signal of the range tracking gate through the counter 1 of the number of calls to the recognized target and the control logic 2 controls the operation of the keys 3 of the channels for calculating the differences of the initial phases. When the target is first accessed (i = 1), the signals coming from the output of the HELL to the input of the first channel for calculating the differences of the initial phases Q1 of the selection device pass through key 3. Next, the output signals of the amplitude detector HELL in the form of a sequence of pulses of the long-range portrait of the target are fed to the pulse shaper of account 4 Video counting pulses corresponding to the local maximums of the RLDP control the key 5, the shift register, and go to the pulse counter of the amplitude portrait 6. The output signals of the PD of the radar receiver through the key 5 in the form of values of the initial phases of the radio pulses of a complex radar range portrait as data are fed to the shift register RG (7), all outputs of which are connected to the first inputs of the keys 8. The output of the shift register from its first output through the first key 8 is fed to the second inputs of the subtracting devices 9 . The first inputs of the subtracting devices 9 receive the output signals of the shift register RG from its 2nd and subsequent outputs through keys 8, the control signals to the second inputs of which are received from the output of the pulse counter amp a portrait portrait. The number of RG data cells is selected based on the maximum possible number of scattering local centers of the true radar target, in accordance with the range resolution. At the outputs of the subtracting devices 9, differences of the initial phases of the radio pulses of the integrated radar detector are formed relative to its last pulse.

Upon repeated access to the target (i ≠ 1), the signals from the output of the receiver’s amplitude detector, fed to the input of the second channel for calculating the differences of the initial phases Q2, are fed through its key 3 to the inputs of the counting pulse generator, key 5 and the shift register of this channel. In this case, the key 3 is controlled by the inverse output signal of the logical control device. According to a similar algorithm described for the first channel for calculating the differences of the initial phases Q1, the differences of the initial phases of the radio pulses of the integrated radar detector are calculated relative to the last pulse of the portrait upon repeated sensing. In the second sounding, the first channel for calculating the differences of the initial phases Q1 does not work.

The output of two channels of calculating the differences in the initial phases of a plurality of values of the initial phase difference between the RI complex RLDP supplied to the first and second inputs of the subtractor block 10 forming cheresperiodnoy initial phase difference S. The output of the subtracting device 10 is formed a plurality cheresperiodnyh initial phase difference Δ φ _{2 1, k} between the eponymous radio pulses of complex range portraits obtained with adjacent soundings of a radar target. From the totality of the set of inter-period differences of the initial phases in the maximum selection block 11, the maximum value Δ ₂ ϕ _{1, j} is selected. The selected value Δ ₂ ϕ _{1, j} is fed to the input of the threshold device 12, the second input of which receives the threshold voltage ξ ₀ .

In the threshold device, the selected value is compared with the threshold and a decision is made on whether the radar target belongs to a given class of targets with a non-zero transverse dimension or the opposite.

Histograms of the distribution of the recognition recognition flag for targets with different transverse dimensions: models of the Boing-747 aircraft and a system of four corner reflectors are shown in FIG. 2 and FIG. 3.

Thus, the proposed device allows you to obtain sufficient statistics to solve a particular problem of radar recognition - selection of true radar targets against the background of false radar with broadband sounding and can be made on a known element base and well-known industrial means.

BIBLIOGRAPHY

1. Nebabin V.G., Sergeev V.V. Methods and techniques of radar recognition. - M .: Radio and communications, 1984, S. 75, FIG. 3.19.

2. Patent RU 2150714 Method for measuring the transverse dimensions of radar objects in real-time radar Authors: Bondarev L.A. (RU), Vasilchenko O.V. (RU), A. Gureev (RU), Chagrin A.S. (RU), Patent holder: Military University of Military Air Defense of the Armed Forces of the Russian Federation (RU), Date of filing: 05.17.1999. Application publication date: 10.06.2000 Bull. No. 16.

3. Vishin G.M. Multi-frequency radar. M .: Military Publishing, 1973.- 89 p.

4. Nikiforov S.N., Marintsev Yu.N., Koryagin M.G. The method of selection of an autonomous false air target based on phase relationships of echo signals during sounding by broadband radio pulses // Bulletin of aerospace defense No. 4 (12). Section: The use of forces and means of aerospace defense. 2016 - S. 30-35.

Claims (1)

A device for selecting autonomous false air targets when using a broadband probe signal, characterized in that it includes a counter of the number of calls to the recognized target, a control logic device, a unit for generating inter-period differences of the initial phases, consisting of subtracting devices and a maximum selection circuit, a threshold device and two identical a channel for calculating the differences of the initial phases, each of which consists of keys 3, 5 and 8, a shaper of counting pulses, a pulse counter amplitude a portrait, a shift register and a subtractor; at the same time, the counter pulse of the tracking system for tracking the radar range is fed to the counter input of the number of calls to the recognized target, the counter output is connected to the input of the logical control device, the first input of the two channels for calculating the differences of the initial phases is the output of the amplitude detector of the radar receiver connected to the first key inputs 3, the key output is connected to the input of the counter pulse shaper, the output of which is connected to the shift register control input, to the first key input 5 and the counter input pulses of the amplitude portrait; the second input of the key 5 is the second input of the channels for calculating the differences of the initial phases and is connected to the output of the phase detector of the radar receiver, the third inputs of the channels for calculating the differences of the initial phases are the second inputs of the keys 3, and the second input of the key 3 of the first channel for calculating the differences of the initial phases is connected to the direct output logical control device, and the second key input of the second channel for calculating the differences of the initial phases is connected to the inverse output of the logical control device, the output of the keys it is connected to the shift register data input, the outputs of which are connected to the first inputs of the keys 8, the second inputs of which are connected to the corresponding outputs of the pulse counter of the amplitude portrait, while the output of the first key 8 is connected to the second input of the subtracting devices, the first inputs of which are connected to the outputs of the second and subsequent keys 8, the outputs of the channels for calculating the differences of the initial phases are the outputs of the subtraction devices, and the outputs of the channels are connected respectively to the first and second inputs of the subtracting devices of the form block tion cheresperiodnyh initial phase difference, and outputs them - to the inputs maxima computation circuit, the output of which is connected to the first input of the threshold device, the second input of which the threshold voltage.

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