RU2210089C2 - Way to protect radar from antiradar rocket based on use of reradiation screen - Google Patents

Abstract

FIELD: passive methods of radar protection against homing weapons, specifically, against antiradar rockets equipped with passive radar homing heads. SUBSTANCE: technical result of invention lies in increased protection of radar by method of leading antiradar rocket to point of fictitious high-power radiation positioned at distance over 100.0 m away from radar with simultaneous reduction of cost of employed technical decisions. It is suggested that reradiation facility should be located at some distance exceeding fragment scattering radius from protected radar and should be so turned that beam of main radiation of radar reradiated by it hits angle of view of homing head of antiradar rocket. When fact of employment of antiradar rocket is detected it is suggested that radar antenna should turned on reradiation facility and radar should be transferred to mode of quasicontinuous radiation to diminish relative pulse duration of radiated signal. .Turn of radar in direction of reradiation facility ensures decreased level of radiation of radar in direction of antiradar rocket to level of side lobes, that is, to level of so called background radiation as high-power signals of major lobe of directivity pattern of radar will be reradiated by proposed reradiation facility in direction of antiradar rocket. Transfer of radar to mode of quasi-continuous radiation provides for reliable excess by period of pulse repetition in radar over constant of circuit controlling homing of antiradar rocket. Above-mentioned measures ensure capture of signals from reradiation facility by homing head of antiradar rocket and re-aiming of antiradar rocket on to position of reradiation facility. As result radar remains serviceable and undamaged after explosion of antiradar rocket. EFFECT: increased protection of radar. 2 dwg

Description

 The invention relates to passive methods of protecting radar stations (radar) from homing weapons, and in particular, from anti-radar missiles (PRR) equipped with passive radar homing heads (GOS).

 As one of the passive methods, the shift of the guidance point away from the suppressed radar is widely used. Such an offset can be created in known methods by using additional radiation sources (DII) and various kinds of rereflectors [1, 2].

 There is also a method of using N DII [3], made in the form of transmitters with antennas that can withstand the effects of an explosion of the warhead of the PRR. Such transmitters may be coherent and incoherent. In the case of using an incoherent source, its signals have time and frequency parameters that differ from the parameters of the probing radar signal, which makes it possible for the radar detector to select the radar signal against the background of DII signals in frequency and time parameters. The probability of targeting the GSR PRR to the radar signal, in the case of preliminary reconnaissance before launching the PRR, is approximately 1, and in the case of independent reconnaissance of the GSN during the flight, it is 1 / (1 + N). When using coherent sources, the parameters of the signals emitted by additional sources coincide with the parameters of the probing signals (RS) of the radar. In this case, the signals from all additional sources will change along with the change in the parameters of the ES of the radar, and the GOS PRR will search again for the time and frequency parameters of the emitted signals. The probability that GOS PRR will select a radar among N false sources under the above conditions is 1 / (1 + N) [1, 2, 4].

A known method of protecting the radar from anti-radar missiles [5], which consists in the fact that on board an autonomous single radar capable of operating in motion and in place, set the trigger device for missile traps. Then determine the direction of the anti-radar missile, its range and speed, deploy the launch device of the trap missile at an angle of α _cm equal to half the width of the radiation pattern of the antenna of the trap missile and launch an uncontrolled trap rocket with the distracting signal transmitter on. In this case, the repetition period of the emitted distracting signals should be less than the time constant of the anti-radar missile guidance control loop. The launch of an unguided missile trap is carried out at an angle α _cm relative to the direction of the anti-radar missile. Next, turn off the radar radiation, which is turned on after time t = D _prr / V _prr , where D _prr is the range to the anti-radar missile; V _prr - speed anti-radar missiles.

 The disadvantage of this method is that it is expensive and not reliable enough, because depending on the launch range of the PRR, the time of its detection and the parameters of the movement of the PRR, its withdrawal from the radar being covered can be from 30 to 150 m. Taking into account the fact that the radius of expansion of fragments of the warhead of the PRR is about 100 m, the above-mentioned withdrawal of the PRR does not provide reliable protection.

 The aim of the invention is to increase the reliability of radar protection by removing the PRR to a fictitious radiation point of high power, located at a distance from the radar of more than 100 m, while reducing the cost of the applied technical solutions.

 To achieve this goal, it is proposed at some distance from the defending radar, exceeding the radius of expansion of fragments of the warhead of the PRR, to place a radiation re-reflection device (UPI) and deploy it so that the main radiation of the radar re-reflected by it falls into the viewing angle of the PRR homing head. Upon detecting the fact of the use of PRR, it is proposed to deploy the radar antenna at the UPI and put the radar into quasi-continuous radiation mode to reduce the duty cycle of the emitted signal. Turning the radar in the direction of the UPI reduces the level of radar radiation in the direction of the PRR to the level of the side lobes, i.e. to the level of the so-called background radiation, while powerful signals from the main lobe of the radar pattern will be re-emitted in the direction of the PRR by the proposed UPI. The transfer of the radar into quasi-continuous radiation mode ensures the reliability of exceeding the constant control loop by pointing the PRR of the pulse repetition period in the radar.

 To accurately reflect the radar radiation in the direction of the radar in the on-board radar computer, the required elevation angle and heading azimuth of the radar are calculated based on the knowledge of its spatial position and the radar distance from the radar, as well as knowledge of the radar range and speed. UPI is deployed at the required angles according to the signals transmitted to the elevation and azimuthal UPI drives via communication lines (wired or telecode). It is also necessary to take into account that due to the difference in the distances traveled by the radar radiated by the pulse along the shortest path to the PRR and upon re-reflection from the screen, this probe pulse will arrive at the GPR PRR twice. To make an unambiguous decision in GOS of modern PRRs, the method of selection by the pulse arrival time (range gating) is used [1, 6].

 The range gate is triggered by the radar pulse itself - the target. After the set time (0.1-0.5 μs), the GSN receiver closes for a time slightly shorter than the period of the received radar pulses, that is, it blocks itself by locking the GSN receiver. Thus, the signals and pulses of other radars transmitted to the GOS input after a temporary strobe are suppressed by the surface. Therefore, without taking additional measures, the pulse reflected by the screen will be ignored by the PRR receiver, i.e., the retargeting of the GOS will not occur. The selection of pulses, as shown above, is performed on a time interval equal to (0.1-0.5 μs), relative to the position of the radar pulse of the previous radiation period. Taking into account the installation range of the screen (d = 150-200 m), it is possible to focus on the delay in the arrival time of the pulse during re-reflection from the screen by an order of magnitude (1-1.3 μs), which excludes its passage into the receiving path. This problem can be solved by using a tunable delay line in the transmitting path of the radar [7, 8]. Applying the necessary delay, starting from one of the repetition periods, it is possible to ensure the subsequent penetration of precisely reflected pulses into the receiving path of the GOS. In this case, pulses arriving at the GOS over the shortest distance will be cut off by a temporary (long-range) selector.

 These measures ensure that the homing head of the PRR signals from the UPI and retargeting the PRR to the UPI standing point. Thus, after undermining the PRR, the radar remains operational and intact. As a less efficient application of the simulated radiation center, one can propose the use of irregularities of the earth's surface: hills, structures, etc. The main radar beam can be directed to these irregularities, observing the approximate equality of the angle of incidence and reflection of radio waves. In this case, the power of the re-emitted signal in the direction of the PRR will be less, however, in this case, too, it will exceed the power of the lateral radiation of the radar. But there is a clear advantage of this method - its cheapness. The disadvantage is the mandatory presence of irregularities on the earth's surface, which is not always the case. In addition, due to the a priori unknown point of reradiation from the earth's surface, the resolution of the problem used in modern PRR selection by the time of arrival of the pulse is technically difficult to implement.

 In more detail, the essence of the proposed method can be explained as follows. At a certain distance d from the radar being covered, an UPI is installed. The proposed radiation re-reflection device (see FIG. 1) can be a screen made of a metal (metallized) network 2, which is stretched over a rectangular metal frame 1. The frame is fixed in a rigid bracket 3 connected to a stable platform 4 by a rotary azimuth connection 6. Changing the angle places of the screen are carried out by rotating joints 5 connecting the frame 1 and the bracket 3. The use of the screen in the form of a network reduces its windage, i.e. provides its steady state in the given position in any climatic conditions. To ensure good reflective properties and high-quality mirror reflection of radio waves, the cell size of network 2 should be less than half the wavelength of radar radiation.

 UPI should be located on the ground, taking into account the a priori known direction of aviation. The line connecting the radar with the UPI should be perpendicular to the possible direction of application of the PRR. This, ceteris paribus, provides the greatest withdrawal of PRR from the radar. The UPI should also be placed so that there are no local objects (hills, trees, structures) in the path of the beam of the radar antenna in the direction of the UPI that impede the direct propagation of radio waves.

So, having located the reflecting screen (UPI) at a distance d from the radar (see figure 2) it is necessary to determine its azimuth β _{e in} advance. At the time of application of the PRR 9, the protected radar is transferred to the protection mode from the PRR, which implies the rotation of the radar 7 antenna in the direction of the screen 8, the inclusion of the quasi-continuous radiation mode (if any) and the solution of the geometric problem for the correct rotation of the screen 8.

. Абсолютная же скорость ПРР известна из многих источников [1, 6, 10] и приблизительно равна 700 м/с. Введем дополнительные обозначения: D₁ - проекция дальности от РЛС 7 до ПРР 9 на горизонтальную плоскость; D₂ - проекция дальности от ПРР 9 до экрана 8 на горизонтальную плоскость; V_прр - скорость полета ПРР; α - угол с вершиной в точке расположения экрана 8 и лучами в направлении на РЛС 7 и в точку, являющуюся проекцией ПРР на плоскость горизонта (на фиг. 2 - точка О); β - азимут ПРР; γ - угол с вершиной в точке стояния РЛС 7 между направлениями на экран 8 и точку О.Initially, radar 7 needs to detect and recognize PRR using known methods. One of them is described in [9]. There are also other special PRR recognition algorithms. The following can be used as signs characterizing attacking PRRs: polarization scattering matrix of PRR; radial component of the velocity of the PRR; the length of the PRR in the direction of radiation; motion parameter of PRR, jumps of error signals in the channel of angular automation. After detection and recognition of the PRR, the defending radar determines its angular coordinates and range. We denote the distance to the PRR by D, and the elevation angle by ε. Since the PRR is induced on the radar, its velocity vector is known

. The absolute speed of PRR is known from many sources [1, 6, 10] and is approximately equal to 700 m / s. We introduce additional notation: D ₁ - the projection of the range from radar 7 to PRR 9 on the horizontal plane; D ₂ - the projection of the range from the PRR 9 to the screen 8 on a horizontal plane; V _prr - PRR flight speed; α is the angle with the vertex at the location of the screen 8 and the rays in the direction of the radar 7 and to the point that is the projection of the PRR on the horizon plane (in Fig. 2 - point O); β is the azimuth of PRR; γ is the angle with the vertex at the radar 7 standing point between the directions to the screen 8 and point O.

The task of the correct re-reflection of the radar beam 7 from the screen 8 is solved on the basis of the equality of the incidence and reflection angles and actually comes down to finding the screen elevation angle ε _e and the angle of rotation of the longitudinal axis of the screen relative to the direction on the radar ξ.

Значит для нахождения угла ξ необходимо рассчитать угол α. По теореме косинусов справедливо
D₂ ² = D₁ ² + d² - 2D₁d cosγ. (2)
Величина угла γ, определяется из выражения
γ = β_э-β.
Очевидно также, что
D₁ = D cosε. (3)
Подставляя (3) в (2), получим

С другой стороны
D₁ ² = D₂ ² + d² - 2D₂d cosα, (5)
откуда

Подставляя (4) в (6), получим

После упрощения формулы (7), выразим угол α

Тогда выражение (1) примет вид

Используя закон отражения радиоволн от однородной изотропной плоскости (экрана 8), заключаем также, что необходимый угол места экрана определяется выражением
ε_э = ε/2. (10)
Таким образом, знание координат экрана 8 и ПРР 9 позволяет достаточно просто по формулам (9) и (10) рассчитать углы поворота и наклона экрана 8. По рассчитанным значениям углов вырабатываются соответствующие сигналы управления приводами УПИ, которые поступают по линиям связи на УПИ и разворачивают экран 8 в нужное положение.Using geometric patterns, we establish that
2ξ = 180 ^° -α,
where from

Therefore, to find the angle ξ, it is necessary to calculate the angle α. By the cosine theorem,
D ₂ ² = D ₁ ² + d ² - 2D ₁ d cosγ. (2)
The value of the angle γ is determined from the expression
γ = β _e -β.
It is also clear that
D ₁ = D cosε. (3)
Substituting (3) in (2), we obtain

On the other hand
D ₁ ² = D ₂ ² + d ² - 2D ₂ d cosα, (5)
where from

Substituting (4) in (6), we obtain

After simplifying formula (7), we express the angle α

Then expression (1) will take the form

Using the law of reflection of radio waves from a homogeneous isotropic plane (screen 8), we also conclude that the required screen elevation angle is determined by the expression
ε _e = ε / 2. (10)
Thus, the knowledge of the coordinates of the screen 8 and PRR 9 makes it easy enough to use the formulas (9) and (10) to calculate the rotation and tilt angles of the screen 8. According to the calculated values of the angles, the corresponding control signals for the UPI drives are generated, which are received through the communication lines to the UPI and deploy screen 8 to the desired position.

Из (фиг.2) и выражения (10) следует

Используя (4) и (12) с учетом времени разворота РЛС в направлении на УПИ, получим

Таким образом, по предлагаемому способу, в одном из периодов повторения и в каждом последующем периоде время излучения сигналов должно быть задержано на t₃. При этом зондирующий импульс РЛС при прямолинейном распространении волн от РЛС к ПРР отстанет в каждом периоде на t₃ и будет отрезан применяемым временным стробом от проникновения в приемный тракт ГСH ПРР. В то же время задержанный на t₃, импульс, переотраженный экраном, попадая в строб селектора, будет в каждом последующем периоде восприниматься приемником ПРР, что обеспечит перенацеливание ПРР на новый источник излучения - переотражающий экран. Это произойдет тем более потому, что переотраженные УПИ импульсы будут обладать большей мощностью, по сравнению с импульсами бокового излучением РЛС.If the turn time of the antenna in the direction of the screen 8 is denoted by T _p , then expression (9) can be clarified

From (figure 2) and expression (10) follows

Using (4) and (12), taking into account the time of the turn of the radar in the direction of the UPI, we obtain

Thus, according to the proposed method, in one of the repetition periods and in each subsequent period, the signal emission time should be delayed by t ₃ . In this case, the probe radar pulse during the straight-line propagation of waves from the radar to the PRR will lag in each period by t ₃ and will be cut off by the time gate used to penetrate the receiving GSN PRR path. At the same time, the pulse delayed by t ₃ , reflected by the screen, falling into the selector gate, will be perceived in each subsequent period by the PRR receiver, which will ensure redirection of the PRR to a new radiation source - the re-reflecting screen. This will happen all the more because the pulses reflected by the UPI will have a higher power compared to the pulses of the radar’s lateral radiation.

So, the interaction of the defending radar and UPI can be briefly represented by the following sequence of actions:
1) at a certain distance from the radar being protected, exceeding the radius of expansion of fragments of the warhead of the PRR, place a radiation re-reflection device (UPI), the line connecting the radar and the UPI should be perpendicular to the expected direction of use of the PRR;
2) upon detecting the fact of using the PRR, determine its coordinates and speed, and then deploy the radar antenna in the direction of the UPI;
3) for the exact re-reflection of radar radiation in the direction of the RRS in the on-board radar transmitter, calculate the necessary elevation and elevation azimuth of the UPI based on the knowledge of its spatial position and the distance of the UPI from the radar;
4) deploy the UPI to the necessary angles according to the signals transmitted to the elevation and azimuthal UPI drives via communication lines, ensuring that the main radar beam reflected by the UPI screen falls into the field of view of the PRR homing head;
5) to delay the signal from the radar to the PRR for a time t ₃ , to ensure that the selector of the GOS selector transmits the pulses reflected by the screen and ignores the side pulses of the radar coming to the PRR along the shortest path.

Using the proposed method provides effective protection of the radar from PRR and eliminates a number of disadvantages inherent in previously known methods:
reduced material costs for the implementation of this method;
increases the effectiveness of the fight against PRR, since the method provides for an exact match of the parameters of the re-emitted signals UPI, the parameters of the radar signals;
the excess radiation power of the simulating source is provided over the radar power;
the problem associated with the presence in the GOS PRR of a temporary cutoff of received signals;
the reliability of radar protection from PRR is increased, since the removal of a fictitious radiation point always exceeds the radius of expansion of fragments of the warhead of the PRR.

USED BOOKS
1. Golovin S. A., Sizov Y. G., Skokov A. L., Khundanov L. L. Precision weapons and the fight against it. M .: Publishing house "Arms. Politics. Conversion.", 1996.

 2. Nebabin V. G., Kuznetsov I. B. Protection of the radar from PRR. // Foreign electronics. 1991, 4. S. 67-81.

 3. Patent 4698638 (USA), cl. G 01 S - 13/10.

 4. RF patent 2099734 from 12.20.97. Ivashechkin A.A., Leonov G.A. A method of protecting a group of radar stations from anti-radar missiles using additional radiation sources and a device for its implementation. Application 96103564/09. Priority 02/23/96 (analog).

5. RF patent 2153684. Uspensky S. A., Chukhleb F. S., Druzin S. V., Skokov A. L., Ponomarev A. N., Ponomarev D. A., Mitrofanov D. G. A way to protect the radar from anti-radar missiles. IPC ⁶ G 01 S 7/38. Application 99118338. Priority 08.24.99, publ. July 27, 2000 (prototype).

 6. Burov S.V., Chudnenko V.L. Anti-radar missiles. Textbook - M., Mosk. state Institute of Radio Engineering, Electronics and Automation, 1994. S.82-141.

 7. Markov G.T. Antennas Textbook for high schools. - M .: Energy, 1975 .-- 528 p.

 8. Antennas and microwave devices / Ed. DI. Voskresensky - M .: Radio and communications, 1981. - 432s.

9. RF patent 2097782. Ermolenko V.P., Mitrofanov D.G. Anti-radar missile recognition device. IPC ⁶ G 01 S 13/02. Application 96109815. Priority 05.21.96, Publ. 11/27/97

 10. Efimov E.A., Butler A.A. Air-to-surface guided missiles. Foreign Military Review, 1995. 7, 8. P. 33-40.

Claims (1)

A method of protecting a radar station from an anti-radar missile based on the use of a re-emitting screen, which consists in emitting distracting signals, the repetition period of the emitted distracting signals being chosen less than the time constant of the anti-radar missile guidance control loop, and the remaining parameters of the distracting signals being chosen identical to the signal parameters of the protected radar station characterized in that when the detection of anti-radar missiles with known with angular coordinates and range in advance at a certain distance d from the radar station to be protected, a radiation re-reflection device (UPI) is installed, the azimuth β _{e of} the position of the UPI capable of changing the angular position of the re-emitting screen by the control signals from the radar is determined in advance, the UPI is set with this with the calculation that the line connecting it to the radar is perpendicular to the expected direction of use of the anti-radar missile with known angular coordinates and range to board vom calculator radar calculated necessary rotation angles reradiated screen included in a RLE the formulas
ε _e = ε / 2, γ = | β-β _e |;

where ε _e - the angle of the re-emitting screen in the vertical plane;
ε is the elevation angle of the anti-radar missile;
ξ is the angle of rotation of the longitudinal axis of the screen relative to the direction of the radar station;
D is the distance from the radar station to the anti-radar missile;
γ is the angle with the apex at the point of standing of the radar station between the directions on the screen and on the projection of the anti-radar missile on the earth's surface;
V _PRR - anti-radar missile flight speed;
T _p - the time to turn the antenna of the radar station in the direction of the screen;
β is the azimuth of PRR,
then they generate control signals proportional to the angles ε _e and ξ, transmit them along the communication lines to the UPI and simultaneously rotate the re-emitting screen to the angles ε _e and ξ, and the radar antennas - to the re-emitting screen, then in one of the periods of radiation the probe pulse is delayed at time t ₃ calculated by the formula

where c is the propagation velocity of radio waves.

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