RU1841343C - Method for creating flickering interference to radar guidance systems with continuous radiation and sinusoidal frequency modulation - Google Patents

Abstract

FIELD: radio countermeasures.

SUBSTANCE: invention relates to the field of radio countermeasures, in particular, to methods for creating relay active radio interference designed to protect manned and unmanned vehicles from the action of homing guided projectiles. The claimed method for creating flickering interference from two jammers to guidance systems with continuous emission and narrowband and frequency modulation is based on the emission of a signal of a stealing interference in speed and an interference signal with a phase advance of the frequent modulation. Interference signals are emitted alternately from each jammer in such a way that they arrive at the suppressed missile radar simultaneously, while in-phase switching the power of the interference signals.

EFFECT: technical result is to increase the efficiency of flickering interference by providing interference on both the main and side lobes of the directional pattern of the goniometric coordinator of the homing head.

1 cl, 1 dwg

Description

Scope - radio countermeasures.

Among the relay active radio interference designed to protect manned and unmanned vehicles from the action of homing guided missiles, the most universal are interferences that act directly on the goniometric coordinator of the seeker and create additional errors in measuring the angular coordinates of protected targets. The universality of "angular" interference is expressed in the fact that, regardless of the selection principles used and the type of selective devices, the impact on the terminal link of the radio path is a goniometric coordinator, and the creation of errors in the angle should lead to an increase in missile miss. From this, however, one cannot draw a conclusion about the small role of selective circuits and ignore them in the formation of "corner" noise.

First of all, it must be borne in mind that an interfering signal can affect the coordinator only if it is passed by the selection circuits. This does not exhaust the role of selection circuits in creating corner noise. It is desirable that the combination of "corner" interference and interference acting directly on the selection circuits would increase the useful effect of the "corner" interference, i.e. led to even greater angular errors of the coordinator. Here it is necessary to emphasize the fundamental expediency of such a combination of interference. The fact is that, despite the important role of goniometric channels in modern homing heads, a significant coarsening or even complete rejection of selective devices is practically possible only in a very limited number of cases. This is due not only to the requirements of high sensitivity and noise immunity of the GOS receivers, but mainly to the need to guide missiles in conditions of work on many targets.

So, for example, in a number of foreign guidance systems, the receiver bandwidth expansion mode is used if powerful noise or impulse interference is emitted. However, the passive guidance mode is possible only under certain parameters of this interference and is an emergency, as evidenced by the available materials on these systems. Working on many targets in this mode can lead to a significant decrease in the probability of hitting.

Among the "corner" interferences, which give a useful effect both on conical scanning coordinators and on monopulse coordinators, short-base flickering interferences are the most developed. Interference signals are usually emitted from two aircraft in the form of pulses with a duty cycle close to two, and with synchronous flickering interference, the operation of the jamming transmitter on one aircraft corresponds to "silence" on the other aircraft and vice versa. In a number of other interferences, flickering interferences are the most prepared for their use in order to protect high-altitude manned and unmanned vehicles that are currently being created and promising in the near future.

When generating flickering interference, it is necessary to take into account the effect of selective circuits. So, when exposed to flickering interference on the seeker, designed to receive continuous narrow-band signals with sinusoidal frequency modulation (guiding systems "Hawk", "Superhawk", "Bloodhound-2", Sparrow-3 ", etc.), one should keep in mind the possibility selection of interference signals emitted from different aircraft, according to the Doppler frequency due to the difference in the radial velocities of these aircraft.For this reason, when such interference is created, their spectrum is usually either artificially expanded by the amount of a possible difference in Doppler frequencies, or the strobe is "tugged" synchronously with the emission of interference speed from one frequency to another.However, in all applications of short baseline flickering interference it is necessary that both aircraft are within the main lobe of the seeker antenna.Otherwise, one interference signal can be energetically superior to the other, which usually leads to only tracking In addition, naturally, conditions should be provided under which both aircraft would be in the main lobe of the target illumination radar antenna, which is easier for high-altitude aircraft and missiles.

There is, however, another difficulty that prevents an increase in the length of the base when creating conventional flickering interference to continuous radar guidance systems. This difficulty lies in the fact that the lengthening of the base leads to the need to expand the spectrum of radiated interference or to increase the required strobe "pulling" time. In both cases, there are additional energy losses. The required spread of the spectrum is determined by the increase in the difference between the Doppler frequencies of the signals from each of the aircraft.

It is known [1] that the difference between Doppler frequencies from scintillating sources is equal to

,

,

where θ is the angle at which signal sources are visible from the GOS,

- скорости ракеты и цели соответственно.

are the speeds of the missile and the target, respectively.

.It can be seen from this formula that an n-fold increase in the base can lead to an increase in ΔFg times n ² times

.

So, lengthening the base by 4 times increases ΔFg by 16 times. Due to the limited energy potential of jamming stations, the existing methods for overcoming the selective circuits of the GOS are unpromising or even unsuitable in conditions of increased bases between aircraft.

For these reasons, the base value between aircraft, recommended when emitting flickering interference, is usually small (250-400 m). The small length of the base, of course, leads not only to a decrease in the possible miss of the missile, but also makes it difficult for high-speed aircraft to fly.

The essence of the proposal

The purpose of the proposed method for creating flickering interference is to increase the effectiveness of the latter by providing the impact of interference both on the main and on the side lobes of the directional diagram of the goniometric coordinator of the GOS.

The proposed method is based on the introduction of components into the jamming signal, which would ensure forced disruption of the speed tracking mode (for the reflected signal of one of the aircraft) and capture of the jamming signal emitted from another aircraft. The specified capture occurs due to the transition of the selective device of the GOS into the search mode and (or) the entry of an interference signal emitted by the second jamming transmitter into the bandwidth of the GOS receiver. Forced transfer of the GOS selector device to the speed search mode provides an increase in the sensitivity of the GOS receiver in this mode and, as a result, the capture of signals weakened due to their reception through the side lobes. Signals are dropped and captured cyclically by emitting interference of the same nature, but shifted in time, from both aircraft.

The sequence of emitted interference signals is shown in fig. 1a, 1b. During the time interval, the transmitter installed on the first aircraft radiates a speed-stealing interference signal, and then - during the interval t ₂ t ₃ - an interference signal to the coherence test circuit. With synchronous and antiphase alternation of interference signals, at the moments of radiation of the leading one from one aircraft, the interference of the coherence test from another aircraft is emitted, and vice versa.

The power of the emitted interference signals is switched in such a way (Fig. 1c, 1d) to provide both sufficient interference efficiency to the coherence test circuit and a significant increase in the energy potential during the interval of emission of the stealth interference in speed. To this end, all available power of the jammers is reduced during the interference interval to the coherence test channel.

To clarify the essence of the processes that will occur in the selective device of the GOS under the influence of such interference, we begin by considering the case characterized by the equality of the radial velocities of both aircraft. In this case, both reflected signals are in the band of the Doppler filter. One of the interference signals, emitted from aircraft A, is characterized by a slow change in frequency (the beginning of a “steer” in speed) and high power, the other, emitted from aircraft B, is characterized by lower power and a modulating frequency function shifted in phase towards the lead (interference to the test channel for coherence). Due to the energy superiority, the greatest contribution will be made by a high power signal, which will "lead" the local oscillator of the AFC system into the GOS. At some point in time of the interval under consideration, only the escaping signal will be within the band of the GOS receiver, as a result of which the angular coordinates of the aircraft A will be measured. At this point in time, aircraft A's transmitter begins to emit interference to the coherence test channel, and aircraft B's transmitter begins to radiate speed interference. Depending on the direction of the frequency search, one of the interference signals will fall into the bandwidth of the AFC system. If at first an interference signal hits the coherence test, then due to the lack of voltage of the required value at the output of the range comparator, after the coherence test, the AFC system will again switch to the search and capture the "steal" signal in frequency. With a different search direction, the signal of "leading" interference will be immediately captured. Due to the fact that the "stealth" interference in this half-cycle is emitted from aircraft B, the seeker antenna will move in the direction of tracking aircraft B.

The coincidence of the radial velocities of both aircraft to within the speed gate bandwidth is an unlikely event. In pair flight, different radial velocities are much more likely. Let us assume that the reflected signal from aircraft A was first captured and interference to the coherence test channel is turned on at the same frequency. The AFC system, due to the action of this interference, switches to the search, as a result of which either the reflected or the interference signal of another aircraft falls into the AFC band (depending on the direction of the search). In both cases, after the capture, the angular coordinates of aircraft B are measured. In the next half-cycle, on the contrary, the signals from target A are tracked.

When the difference in radial velocities exceeds the value corresponding to the bandwidth of the Doppler filter, the requirements for the signal power ratio from two aircraft are significantly weakened, as a result of which it becomes possible to increase the base between the aircraft. Indeed, when the selector switches to the search mode due to the interference (stall) signal emitted from one of the aircraft, the signal (reflected or interference) of another aircraft can be captured when the last signal exceeds a certain level in the GOS receiver (depending on the sensitivity of the receiver and AGC schemes). At the same time, it should be noted that the signals of only one aircraft are within the speed gate, which, with a high sensitivity of the receiver, determines the possibility of their capture.

- напряжения на входе приемника от каждого из самолетов,

- соответствующие напряжения на выходе УДЧ приемника. Примем также, что коэффициент усиления приемника (до схемы АПЧ) при

постоянен и равен

, а при

коэффициент усиления обратно пропорционален выходному сигналу

To determine the necessary energy characteristics of jamming transmitters, the action of the AGC of the receiver should be taken into account. In the Doppler frequency amplifier (UDCH) of the GOS receiver (before the AFC system), the signals of both aircraft are simultaneously in the passband. Let

- voltage at the input of the receiver from each of the aircraft,

- the corresponding voltage at the output of the UHF receiver. We also accept that the gain of the receiver (before the AFC circuit) at

constant and equal

, and when

the gain is inversely proportional to the output signal

напряжение

, получим

. Соотношение (1) можно преобразовать к следующему видуBecause at

voltage

, we get

. Relation (1) can be transformed into the following form

Where

на выходе приемника, равенand the coefficient μ, which determines the magnitude of the change in the ratio

at the output of the receiver, is equal to

Where

With a large signal from one of the aircraft (A>I, α<<I), relation (2) is simplified: α ≈ A⋅μ.

определяется в основном пороговым уровнем детектора АРУ.Dependence (2) is shown in fig. 2. It follows from it that at a small value of α, corresponding to a small ratio of the pore and output voltage, a can be much larger than A, i.e. weak signal will be suppressed. For AGC systems without delay

determined mainly by the threshold level of the AGC detector.

получим

дБ. Если динамический диапазон АРУ системы АПЧ меньше μ, то потеря чувствительности равна разности между μ и динамическим диапазоном АРУ. При большом диапазоне АРУ АПЧ (>μ дБ) потери чувствительности не будет, и помеховый сигнал на входе приемника должен лишь превысить пороговую мощность (10^-15 - 10^-16 Вт), что выполняется в большинстве практических случаев. При попадании обоих сигналов в допплеровский фильтр указанные потери снижает возможности увеличения базы между самолетами. Обозначим энергетические потенциалы передатчиков помех, установленных на самолетах, через П₁ и П₂. Мощность принимаемых антенной ГСН сигналов равнаTaking

we get

db. If the AGC dynamic range of the AFC system is less than μ, then the loss of sensitivity is equal to the difference between μ and the AGC dynamic range. With a large range of AGC AFC (>μ dB), there will be no loss of sensitivity, and the interference signal at the receiver input should only exceed the threshold power (10 ^-15 - 10 ^-16 W), which is done in most practical cases. When both signals hit the Doppler filter, these losses reduce the possibility of increasing the base between aircraft. Let us designate the energy potentials of the jamming transmitters installed on the aircraft through P ₁ and P ₂ . The power of the signals received by the GOS antenna is equal to

, i = 1,2.

, i = 1.2.

Hence the ratio between the signal powers at the output of the receiver is (R ₁ = R ₂ )

where P ₁ P ₂ - the power of the transmitters during the half-cycle of interference,

- КНД антенный ГСН в направлении источников помех,

- KND antenna seeker in the direction of interference sources,

- коэффициент подавления в приемнике.

is the suppression factor in the receiver.

дБ и действия АРУ приемника

необходимо увеличение перепада мощности на

дБ.From (3) it follows that the days of compensation for losses due to side-lobe reception

dB and receiver AGC actions

it is necessary to increase the power drop by

db.

The available theoretical and experimental data on antennas with a parabolic mirror and conical scanning (used in the GOS of the Hawk, Sparrow-3 missiles, etc.) indicate that the first side lobe of the radiation pattern of such antennas can be suppressed by no more than 18 -20 dB relative to the main lobe. Subsequent lobes of the radiation pattern fall off much more slowly, changing by 1-1.5 dB when moving to the adjacent side lobe. Limiting ourselves to the first side lobes, it is easy to see that even in the worst and unlikely case of identical radial velocities of the aircraft, the required power drop of the jamming transmitter during the cycle does not exceed 20-25 dB. With a difference in speeds, which ensures the selection of signals, the requirements for the difference are significantly weakened. The expansion of the equivalent radiation pattern of the GOS antenna, achieved by the proposed method, naturally leads to the possibility of increasing the base between aircraft. So, when only the first side lobes are taken into account, this leads to a fourfold lengthening of the base. Thus, the combination of these interferences when emitted from two aircraft or missiles creates a new effect of interference, incommensurable with the effect of the action of certain types of single-point interference and leading to an increase in the equivalent base between the interference carriers.

The block diagram of the modulation part of the device according to the proposed method is shown in fig. 3.

The reference oscillator 1 outputs the initial pulses for alternately switching on the stall noise and interference to the coherence test channel. The channel, in which the disruption noise is created, consists of a gated generator of slowly changing oscillations 2, which determine the "dragging" law, and a sawtooth voltage generator 4, the frequency of which is changed by means of the control stage 3 in accordance with the drift law.

типа "меандр" поступает на парафазный усилитель 6, с выхода которого противофазные напряжения подводятся к двухтактному каскаду совпадения 7. Непрерывные пилообразные колебания от генератора 8 поступают на входы обоих плеч каскада совпадений в фазе. На выходе двухтактного каскада совпадений в течение действия импульса, подаваемого от генератора опорных импульсов, возникают пилообразные колебания, полярность которых меняется синфазно с напряжением суммирование обоих типов модулирующих помеховых колебаний производится в сумматоре 5. Результирующее колебание (с амплитудой, соответствующей размаху фазовой характеристики 27 с выхода сумматора поступает на фазовый модулятор (ЛБВ), находящийся в тракте ретранслятора помеховых сигналов. Для коммутации мощности помеховых сигналов может быть использована одна из ламп ретранслятора. Для этого импульсы с генератора опорных импульсов следует подвести к управляющему электроду этой лампы.To create synchronous interference to the coherence test circuit, it is necessary to first select the oscillation that modulated (in frequency) the signal received from the ROC. The selection is made using autoheterodyne or heterodyne receivers. Selected low-frequency sinusoidal signal, phase-shifted and converted to voltage

type "meander" is supplied to the paraphase amplifier 6, from the output of which antiphase voltages are supplied to the push-pull cascade of coincidence 7. Continuous sawtooth oscillations from the generator 8 are fed to the inputs of both arms of the cascade of coincidences in phase. At the output of the push-pull cascade of coincidences during the action of the pulse supplied from the reference pulse generator, sawtooth oscillations occur, the polarity of which changes in phase with the voltage, the summation of both types of modulating interference oscillations is carried out in the adder 5. The resulting oscillation (with an amplitude corresponding to the amplitude of the phase characteristic 27 from the output The adder is fed to a phase modulator (TWT) located in the path of the repeater of interference signals.To switch the power of interference signals, one of the lamps of the repeater can be used.To do this, pulses from the reference pulse generator should be brought to the control electrode of this lamp.

Claims (1)

A method for creating flickering interference from two jammers to guidance systems with continuous emission and narrow-band frequency modulation, based on the emission of a speed-shifting jamming signal and an interference signal with a frequency modulation phase advance, characterized in that, in order to increase the base between the jammers and the amount of miss when shooting guided missiles, alternately emit the indicated interference signals from each jammer in such a way that they arrive at the input of the jammed missile radar at the same time, while in-phase switching the power of the interference signals, providing the energy advantage of the signal of the distracting interference, which is currently being monitored by the missile radar.

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