RU2237906C2 - Method for protection of radar with phased antenna array against passive jamming and device for its realization - Google Patents

Abstract

FIELD: radio detection and finding, applicable in radars with a phased antenna array operating in the conditions of natural and intentionally distributed in space passive jamming.

SUBSTANCE: the method consists in the fact that two similar sounding impulse signals are radiated in succession in time, the first of the received reflected signals is delayed by the time equal to the period of repetition of impulses, the values proportional to the difference of the received signals are compared with the threshold, should it be exceed, a signal on the presence of a target is formed, after the first sounding the angular position of the beam of the phased antenna array is shifted by the value of the ray spacing at scanning relative to the direction at the first sounding, after reception of both reflected signals the value of the ratio of the difference modulus of the amplitudes of the envelopes of the received signals to their sum is determined, which is compared with the threshold. The radar has an antenna, antenna switch, pulse amplifier, radio-frequency oscillator, delay line, comparison unit and a permanent storage, as well as a pulse generator, clock-pulse generator, control unit of the antenna directivity pattern, receiver, envelope detector, the first and second analog-to-digital converters and a digital computer of the difference-sum ratio.

EFFECT: enhanced efficiency of detection by a radar with a phased antenna array of small-sized fixed and slowly moving targets, reduced time for antijamming protection.

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Description

The invention relates to the field of radar and can be used in radar stations (radar) with a phased array (PAR), operating in conditions of natural and intentional distributed in space passive interference (PP) (meteorological events, dipole and aerosol reflectors).

There is a method of protecting radar from the PP, using the principle of selection of moving targets (SDC) based on the Doppler effect. It uses the differences in the speed of the target and the source of passive interference. ("Theoretical Foundations of Radar", under the editorship of V.E.Dudevich, M .: Sov. Radio, 1978, pp. 464-484). The method consists in emitting in one direction a sequence of probe pulses, delaying the received signals by a time equal to the pulse repetition period, and in subtracting the received signals of adjacent periods.

The disadvantage of this method is the suppression, along with reflections from distributed in the space of PP reflections from stationary stationary or slowly moving radar objects (low-speed remotely piloted aircraft, hovering and slowly moving helicopters, drifting balloons, etc.), and therefore such almost no targets are found. In addition, the use of SDS requires significant time costs and, due to the shortage of pulses, can provide protection against IF only in the part of the radar coverage area.

The closest technical solutions (prototype to the method and device) is the method and device (SDC), which are described in the "Guide to radar", ed. M. Skolnik, vol. 3, M .: Sov. Radio 1979, pp. 281-284.

A known method of protecting the radar from the PP consists in emitting in the same direction two consecutive identical sounding pulses in time, delaying the first of the received signals for a time equal to the pulse repetition period, and comparing the value functionally dependent on both received signals (the difference of the received signals), threshold above which a signal is generated about the presence of the target.

The known device (radar with SDD, figure 1) contains an antenna 1 interconnected with an antenna switch 2, the input of which is connected to the output of the pulse amplifier 3, and the output is connected to the first input of the phase detector 4, a high-frequency generator 5, the output of which is connected to the pulse input the amplifier 3 and the second input of the phase detector 4, the delay line 6, the input of which is connected to the output of the phase detector 4, the adder 7, the first input of which is connected to the output of the phase detector 4, and the second input to the output of the delay line 6, the comparison device 8, the first in od coupled to an output of the adder 7, the second input - to the output DZU 9, and the output is the output of the radar.

A disadvantage of the known method and device is the suppression along with reflections from distributed PP reflections from pointless stationary or slowly moving radar objects, as well as significant time costs for noise protection.

The aim of the invention is, therefore, to increase the detection efficiency of radar with phased array small-sized stationary and slowly moving targets, as well as reducing the time cost of noise protection.

This goal is achieved by the fact that in the known method of protecting a radar with a phased array from PP, which consists in emitting in the same direction two consecutive identical sounding pulses in time, delaying the first of the received signals for a time equal to the pulse repetition period, and comparing the value functionally dependent on of both received signals, with a threshold above which a signal is generated about the presence of a target, according to the invention, after the first sensing, the angular position of the HEADLIGHT beam is shifted by the value of the beam pitch when viewing about relative to the direction during the first sounding, after receiving both signals, the value of the ratio of the modulus of the difference in the amplitudes of the envelopes of the first and second received signals to their sum is determined, which is compared with the threshold.

The increase in the detection efficiency of radars with phased arrays of small-sized stationary and slowly moving targets and the reduction in time spent on noise protection will be explained as follows.

When the radar is in operation, there are situations when in the inspection area (for example, in the tracking strobe) there is only one radar object (target or distributed in the SP space). In this case, the considered method can be used.

Each discrete of the inspection area is probed twice - by a ray whose direction coincides with the angular position of the discrete, and by a slope of the ray whose direction differs from the main one by the amount of displacement in angular coordinates. With each sounding, the amplitude of the envelope of the signal X _i , i = 1, 2 is measured and the value is formed:

The value of Z is compared with a threshold value of X _p set in accordance with the required level of suppression of the PP, or with the permissible losses in the detection of a point target (TC). Exceeding the threshold means that TC is detected in this discrete.

It can be shown that if the elevation position ε and the azimuth β of the TC position are equally probable in coordinates within the beam width at the level of 0.5 in power, the probability of its omission, i.e. the probability of the event Z <Z _p is

where f (X ₁ , X ₂ ) is the joint probability density of random variables X ₁ and X ₂ (the amplitudes of the envelopes of the signals received after the first and second soundings).

Taking the approximation of the main lobe of the bottom of the bottom of the field during the first sounding in the form

G ₁ (ε, β) = exp (-B (ε ² + β ² )), (2)

where B = 2 ln 0.5Δ ε Δ β,

Δ ε, Δ β is the distance between the sensing directions (beam pitch) normalized to the beam width at a power level of 0.5 (hereinafter, Δ = Δ ε = Δ β = 1) when viewing the viewing area, the value of the S / N ratio power at the input of the receiver when the shopping center is located at a point with coordinates ε, β is determined in the form:

Q ₁ (ε, β) = q ² G $\genfrac{}{}{0ex}{}{\text{4}}{\text{1}}$ (ε, β), (3)

where q is the C / N ratio when the shopping center is located at the bottom of the bottom.

For the second sounding, the approximation of the main lobe of the DND can be defined as:

G ₂ (ε, β) = exp (-B ((ε-δ ε) ² + (β-δ β) ² )), (4)

where δ ε, δ β are the displacement values along the coordinates ε and β,

respectively, Q ₂ (ε, β) = q ² G $\genfrac{}{}{0ex}{}{\text{4}}{\text{2}}$ (ε, β). (5)

The shift of the main lobe can be carried out both in any of the coordinates, and in both coordinates simultaneously (δ ε = δ β = δ).

For a space-borne PP (we denote RC as a distributed target), expressions (3), (5) take the form (the length of the RC is more than 2Δ):

Q _i (ε, β) = 0.44q ² , i = 1.2. (6)

When a radar object is irradiated with a radar signal with a phased array with electronic scanning, the interval between the probe pulses can be provided less than the amplitude correlation interval, so the reflected signals can be considered independent (due to the initial phase) and with known amplitudes (Theoretical Basics of Radar. Ed. Ya.D. Shirman, Moscow: Sov. Radio, 1970, p. 161), while the joint probability density of random variables X ₁ and X _{2 is} written as a product

f (X ₁ , X ₂ ) = f (X ₁ ) f (X ₂ ), where

The results of the calculations carried out in accordance with expression (I), taking into account (2) - (7) for a shopping center and a retail center, are shown in FIG.

From the obtained dependencies the following follows.

When the direction of the second sounding is shifted, the suppression (non-detection) of the RC occurs to a greater extent than the TC.

An increase in the bias in the direction of the second sounding allows one to obtain a significant suppression of the RC and to ensure a high probability of detecting the TC.

It is advisable to produce the angular displacement of the PAR beam during the second sounding by an amount equal to the step of the beam moving along one or both coordinates when inspecting the zone. In this case, re-sensing can be used as the first in the next round of protection against PP, as well as for inspection of the zone. This achieves a reduction in time spent on noise immunity.

An increase in signal power leads to an improvement in the selection capabilities of the method.

To implement the proposed method in a known device (radar with SDC) containing an antenna interconnected with an antenna switch, the input of which is connected to the output of the pulse amplifier, a high-frequency generator, the output of which is connected to the input of the pulse amplifier, a delay line, a comparison device, the output of which is the output Radar and DZU, the output of which is connected to the second input of the comparison device, a pulse generator, a clock pulse generator, a DND control unit, a receiver, an envelope detector, the first and second A swarm of analog-to-digital converters and a digital computer. The output of the pulse generator is connected to the inputs of the high-frequency generator, the DND control unit, the output of which is connected to the antenna, and the clock pulse generator, the input of the receiver is connected to the output of the antenna switch, and the output is connected to the input of the envelope detector, the output of which is connected to the input of the delay line and with the information input of the first ADC, the delay line output is connected to the information input of the second ADC, the sync inputs of both ADCs are connected to the output of the clock generator, the first and second digital inputs will calculate The spruce is connected to the outputs of the corresponding ADCs, and the output is connected to the first input of the comparison device.

A comparative analysis with the prototype shows that both of the claimed technical solutions meet the criterion of "novelty." In the study of other well-known technical solutions in this technical field, the features that distinguish the claimed invention from the prototype were not identified, which allows us to consider the claimed technical solutions that meet the criterion of "significant differences".

Figure 1 shows a block diagram of a prototype;

figure 2 - dependence of the probability of skipping on the threshold value;

figure 3 is a block diagram of the inventive device radar with headlight.

The proposed radar device with HEADLIGHTS (figure 3) contains an antenna 1 interconnected with an antenna switch 2, the input of which is connected to the output of the pulse amplifier 3, a high-frequency generator 5, the output of which is connected to the input of the pulse amplifier 3, delay line 6, comparison device 8, the output of which is the output of the radar, and DZU 9, the output of which is connected to the second input of the comparison device 8, as well as a pulse generator 10, a clock pulse generator 11, a DND control unit 12, a receiver 13, an envelope detector 14, the first and second analog-to-digital new converters 15 and 16 and a digital computer 17. In this case, the output of the pulse generator 10 is connected to the input of the high-frequency generator 5, the control unit DND 12, the output of which is connected to the antenna, and the clock generator 11, the input of the receiver 13 is connected to the output of the antenna switch 2, the output is with the output of the envelope detector 14, the output of which is connected to the input of the delay line 6 and to the information input of the first ADC 15, the output of the delay line 6 is connected to the information input of the second ADC 16, the sync inputs of both ADCs are connected to the gene Ator clock 11, the first and second inputs of digital computer connected to outputs of the respective ADCs, and output - with a first input of the comparison device 8.

The proposed device can be performed on the following functional elements.

Antenna - PAR with two-dimensional electronic scanning (in azimuth and elevation) and with circular mechanical rotation (Radar Reference, edited by S. Skolnik, vol. 2, - M .: Sov. Radio, 1977).

Antenna switch - gas discharge hoist (ibid., Pp. 42-46).

The pulse amplifier is on a traveling wave lamp (Handbook on the basics of radar technology. M., 1967, pp. 353-367).

A high-frequency generator - on a multi-cavity span klystron (ibid., Pp. 289-291).

The delay line is ultrasonic (ibid., Pp. 267-270).

Pulse generator - a type of multivibrator operating in self-oscillating mode (ibid., Pp. 232-235).

A clock generator is a type of multivibrator operating in synchronization mode (ibid., Pp. 232-235).

The receiver is a superheterodyne type (ibid., Pp. 343-344).

Envelope detector - amplitude detector (ibid., Pp. 379-381).

The DND control unit is a calculator of the electromagnetic field distribution at the FAR aperture (Handbook of Radar, edited by M. Skolnik, vol. 2, - M .: Sov. Radio, 1977, p. 69-92).

Digital and logical elements can be performed on standard microcircuits (Integrated microcircuits. Handbook edited by B.V. Tarabrin, - M .: Radio and communications, 1984):

ADP - K1107PV3;

comparison device - K561CA1;

DZU - K155RU1.

Digital computer - microcomputers (Analog and digital integrated circuits. Reference manual, edited by S.V. Yakubovsky, - M .: Radio and communication, 1985).

В устройстве сравнения 8 величина Z сравнивается с порогом Z_п, хранящимся в ДЗУ 9 и при его превышении на выходе устройства сравнения формируется сигнал о точечной цели.The device operates as follows. The signal from the high-frequency generator 5 when the next trigger pulse is received from the pulse generator 10 is fed to a pulse amplifier 3, the output of which is probed by a pulse, which is fed through the antenna switch 2 to the antenna 1, in which the distribution is calculated and entered into the PAR electromagnetic field along the aperture, forming the bottom, the maximum of the main lobe of which is directed to the analyzed point of the radar field of view, and is emitted. While the envelope of the received signal 1 of antenna X ₁ , passed through the antenna switch 2, the receiver 12 and the envelope detector 14 are in the delay line 6, using the pulse generator 10, the high-frequency generator 5 and the pulse amplifier 3, a second probe pulse is generated, which is supplied through the antenna switch 2 into the antenna 1, in which, by means of the DND 12 control unit, the distribution of the electromagnetic field along the aperture, which forms the DND, the maximum of the main lobe of which is directed to the point about Zora radar that does not coincide with the direction of the first probe, and is emitted. The envelope of the second signal X ₂ received by the antenna 1, which passed the antenna switch 2, the receiver 13 and the envelope detector 14, and the bending signal from the delay line 6, are converted into digital form in the ADCs 15 and 16 simultaneously fed to a digital computer 17, where the value is determined

In the comparison device 8, the value of Z is compared with the threshold Z _p stored in the DZU 9 and when it is exceeded, a signal about a point target is generated at the output of the comparison device.

The pulse repetition rate of the pulse generator 10 is determined by the unique range of the radar R _od , i.e. f _gy = s / (2 Rode), C is the speed of light.

The pulse repetition rate of the clock generator 11 is determined by the number of discrete range N _d on the scan and the frequency f _gi and should be f _gti ≥ N _d f _gi .

Evaluation of the effectiveness of the proposed method and device, carried out by calculation, shows the presence of a positive effect, which consists in suppressing (not detecting) distributed PP and detecting a point target (figure 2).

So, for example, if the beam of the DND during the second sounding is separated in both coordinates from the beam of the DND during the first sounding by the value of the beam width at the half power level (δ = 1) and the threshold Z _p is set to 0.3, then 90% of the spatial distribution is suppressed PP (S / N = PP / W 10) and not less than 96% of point targets are detected.

Claims (2)

1. A method of protecting a radar station with a phased array (PAR) from passive interference, which consists in emitting two identical sounding pulse signals sequentially in time, delaying the first of the received reflected signals for a time equal to the pulse repetition period, compare values proportional to the difference of the received signals, with a threshold above which they form a signal about the presence of a target, characterized in that, in order to increase the detection efficiency of radars with phased array small-sized for stationary and slow-moving targets, as well as reducing the time cost of noise immunity, after the first sensing, the angular position of the headlamp beam is shifted by the step size of the beam when viewing relative to the direction during the first sensing, after receiving both reflected signals, the value of the ratio of the amplitude difference module of the envelopes of the received signals to their the amount that is compared with the threshold. 2. A radar station containing an antenna connected to an antenna switch, the input of which is connected to the output of the pulse amplifier, a high-frequency generator, the output of which is connected to the input of the pulse amplifier, a delay line, a comparison unit, the output of which is the radar output and long-term memory (DZU) the output of which is connected to the second input of the comparison unit, characterized in that a pulse generator, a clock pulse generator (GTI), an antenna radiation pattern control unit (ECU) are introduced ON), a receiver, an envelope detector, the first and second analog-to-digital converters (ADCs) and a digital difference-sum ratio calculator (CVCS), while the output of the pulse generator is connected to the inputs of a high-frequency generator, BUDNA, the output of which is connected to the antenna and GTI, the input of the receiver is connected to the output of the antenna switch, the output is to the input of the envelope detector, the output of which is connected to the input of the delay line and to the information input of the first ADC, the output of the delay line is connected to the information input of the second ADC, sync the inputs of both ADCs are connected to the outputs of the GTI, the first and second inputs of the CVACS are connected to the outputs of the corresponding ADCs, and the output is connected to the first input of the comparison unit.

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