The radar device masking of the jet engine air intake
(57) Abstract:The invention relates to the field of radar technology, and can be used to reduce reverse radar reflections from the inlet jet engine. The technical result is to reduce the level of radar reflections from the channel inlet jet engine when irradiated by a wide range of lengths of waves. The device consists of a solid metallic grid with square cells and form, repeating the cross-sectional profile input window vent. Having docked to the outer edge of each cell of metallized sheets in the form of isosceles triangles allows to reduce by 2 to 4 dB level radar reflections from the air intake in a wide range of wavelengths. 8 Il. The invention relates to the field of radar technology, and can be used to reduce reverse radar reflections from the inlet jet engine.Experience of research in radar characteristics of such complex objects, such as aircraft, showed that the greatest contribution to its effective ilocation station, cockpit and several others. Experimentally verified that for angles in the sector nasal angles conventional aircraft from all sources of reflection engines are dominant . Therefore, in the world practice is widespread methods and devices radar camouflage air intake duct of the engine . The closest technical solution to the claimed is a method and apparatus for masking the inlet jet engine , which consists in the fact that the air intake box 1 (Fig. 1) is divided into multiple cells or channels of smaller size 2, which prevent the penetration of the incident electromagnetic waves 3 in the intake channel 4, reflecting them in the opposite direction and, practically, do not increase the resistance to air flow. A device that implements this method is a three-dimensional lattice with a square cell with the outer edge 5, is a formed metallic plates 6 width a and thickness h (h << a), with electrical contact at the nodes and form, repeating the cross-sectional profile input window vent. However, this device prevents the penetration of electromagnetic waves inside the substantial limitations when using it in practice. Thus, this device has the following disadvantages:
c a decrease in the length of the electromagnetic wave shielding intake is required to reduce the size of the grid cell to a size smaller wavelength, which, ultimately, will significantly increase the resistance of such grate air flow;
if you build a grid with cell sizes from units of wavelengths and more, its shielding properties will be completely lost, moreover, such a lattice periodic structure will be a good Omni-directional reflector with multi-leaf diagram back reflections with high levels of EPR.Based on these shortcomings of the existing device can be used effectively only under very limited conditions.The aim of the present invention is to reduce the level of radar reflections from the channel inlet jet engine when irradiated by a wide range of lengths of waves.This objective is achieved in that the outer edge of each cell of the lattice pristykovyvayas metallized sheet in the form of an isosceles triangle 7 thickness h, base equal to the edge a, and the other is a 2; h < 0,1; < 60,
where is the wavelength of the radiation.The presence of metallic triangular plates, paired with the outer edges of the cells of the lattice (triangular ends), provides:
the destruction of the periodic structure of the lattice as Omni-directional radar reflector;
smooth coordination flat front of the incident electromagnetic wave and the absorption in the structure of the lattice as in the fall of waves from the outside and passed through the bars and penetrates in the opposite direction (the effect of "besedovschi");
the possibility of suppression of surface waves generated by the outer edge of the grate and extending along the planar face of each cell in the opposite direction.Explain each of the allegations.The outer edge of the metallic plate, forming a lattice-prototype period and when , are complex reflector. The fall of waves on a periodic series of metallic plates in the device prototype will be accompanied by the diffraction of waves on the edges of the plates and the formation of the reflected wave. Due to diffraction at the edges of the plates there is a rather complex field. This field will be present in order to be in phase. Let us consider in more detail the mechanism of scattering. Let the anglei(Fig. 3) indicates the direction of the incident wave. This wave will occur if the line BD is perpendicular to the direction of propagation of the wave, is a wave front, or in other words, the fields at the points b and D are in phase. Field of the incident wave at the points A and C or AC perpendicular to the direction of propagation of the incident wave are in phase. Field at points B and D will be in phase if the difference is equal to an integer number of waves
< / BR>where a = 0,1,2,3,....
According Fig. 3
< / BR>therefore,
Obviously, growth and (in wavelengths) the number of angles that reflected from the edges of fields are added in phase, will grow. In the end, the reflected field will have a sustainable multi-leaf structure, where the maximum levels of EPR's petals will be determined in the approximation of physical optics  , by analogy with the linear lattice of different reflectors, based on the ratio of
< / BR>where k is the number of cells in the plane orthogonal to ,
h - thickness of the plates,
a - distance between the plates (the edge length of the cell),
- wave length.The presence of triangular metallic plate, p is the expansion of the structure. As a consequence, the lattice as a whole is fairly smooth transition environment settings from the metal to the free space, so the wave reflected from the boundary between decreases in amplitude. In addition, the perimeter of jagged edges flowing currents of different phase and direction, so the average level of effective excitation of edges in a plane lower than in the rectilinear edge. Accordingly decreases to 5-6 dB level of the diffraction fields associated with the edge, as for reflected waves, and waves that passed inside the channel intake .Smooth coordination flat front incident electromagnetic wave with the structure of the lattice is provided by metallic triangular tip with the angle at the vertex of less than 60o. This design provides multiple reflection of the incident waves between the sloping edges of the triangles. In Fig. 4 shows the course of the rays in the space between the triangular ends. If to characterize reflected from this design electromagnetic wave reflection coefficient power qmthe power flux-density of the reflected wave will be determined from the relation
< / BR>where n is the number of suusi material triangular ends.Practical experience shows that for this structure qmcan reach about 20 dB .Along with this, the triangular ends allow you to suppress the level of reflection of surface waves at 32 dB in directions close to the normal of the lattice .The proposed device was tested in the open measuring polygon , as evidenced by the "test report".The substance of the proposed technical solution is illustrated in Fig. 5 - 8.In Fig. 5 shows the geometry and dimensions of the experimental model of the channel inlet jet engine (hollow metal cylinder, open on one side).In Fig. 6 - scheme of dimension EPR model channel inlet jet engine device of radar camouflage.In Fig. 7 shows the dependence of the median values of ESR (0,5dB) model feed intake in 20-degree sectors from a corner location Q at wavelengths: 0,86 cm - b, 3.2 cm - c, 10.7 cm d 17 cm - e,
f - channel model of the air intake with the proposed device masking (a = 7 cm, h = 0.1 cm; = 40);
g - model of the channel inlet with device-prototype (a = 7 cm; 8 presents the integral distribution laws EPR (P()) of a channel model of the air intake in the sector location 30 degrees relative to the normal to the input box, air intake obtained for the respective wavelengths (b, c, d, e) and the above configuration (f, g, i).The analysis shown in Fig. 7 and 8 results allows to conclude that (Act tests...) that the proposed device masking channel inlet jet engine in comparison with the device of the prototype allows to reduce the median values of EPR in the sector location 30 degrees relative to the normal to the input box intake from 2.3 to 4 dB in the wavelength range from millimeters to decimeters (from 0.86 cm to 17 cm).The proposed device also provides better than the prototype radar masking channel of the air intake in the areas of location, different from normal. This ensures reduction in the median RCS values from 3 to 10 dB.Implementation of the claimed device is not difficult. It is obvious that the invention is not limited to the above example of its implementation. Based on its schema can be provided by other variants of its realization, is not beyond the scope of the subject invention. For example, it is obvious that the application of a thin layer of radar absorbing coatings or materials on the surface of the device will improve the="ptx2">The proposed device should be used in organizations as modernization of existing and development of future aircraft with low radar visibility. The radar device masking intake of an aircraft engine, which represents a repeating profile input window vent volumetric grid with square cells, with the outer edge, equal and formed of intersecting metallic sheet width and thickness h with electric contact at the nodes, wherein the outer edges of a volume grating docked metallized sheet in the form of an isosceles triangle with thickness h, with base equal to the outside edge, and opposite the base of an acute angle , while the lattice parameters of bulk and isosceles triangles are selected on the basis of ratios
a2; h<0,1<60 ,
where is the wavelength of the radiation.
FIELD: radio-electric engineering.
SUBSTANCE: cover is formed in form of layer on basis of fiber, placed between outer and inner layers of dielectric materials. Fiber layer along thickness is formed of several cloths of textile material of synthetic filaments with carbon cover with specific electrical, in which adjacent cloths are interconnected by inserts of given thickness on basis of dielectric connecting substance. Outer layer is made of rubber. Inner layer is made of dielectric connecting substance, containing granulated material, weakening reflection of electro-magnetic waves, in amount of 5-25% of total.
EFFECT: higher efficiency.
3 cl, 1 dwg
FIELD: composite materials.
SUBSTANCE: invention discloses a method for manufacturing composite material for shielding-mediated protection against electromagnetic emission and can be used in electronics, in radio engineering, and also in a series of special-destination articles. In addition, material may be used for anechoic boxes and in various assemblies of technical devices and radio apparatuses. Method comprises mixing modified graphite-containing conducting filler and polymeric binder at weight ratio (50-80):(20-50). Once ingredients combined, mixture is additionally subjected to thermal expansion in thermal shock mode at 250-310оС and then molded. Polymeric binder is selected from polyolefins, polystyrene, fluoroplastic, polyvinylchloride paste and modified graphite is product obtained by modifying graphite with concentrated sulfuric and nitric acids. Material is characterized by that, in wavelength band from 2 to 5 cm at thickness of material up to 0.1 mm, transmission coefficient is decreased from -40 to -85 dB.
EFFECT: improved performance characteristics.
6 cl, 1 tbl, 2 ex
FIELD: electromagnetic radiation protection.
SUBSTANCE: invention relates to a method of preparation and to composition of magneto-dielectric materials absorbing electromagnetic emission. Composition is prepared by combining binder with superdispersed magneto-dielectric filler, in particular composite product obtained through caking at 1150-1250°C followed by disaggregation of cake composed of magnetic particles of ferrite material (61.5-86.7 vol %) obtained by chemical precipitation of ferrite phase from aqueous solutions, the rest being layers of dielectric oxides precipitated onto surface of magnetic particles by way of nanomolecular layering from gas medium. Invention further discloses composition including 65-75 vol % of superdispersed magneto-dielectric filler along with binder prepared by above-indicated method.
EFFECT: increased choice of electromagnetic radiation-protection materials.
2 cl, 3 tbl, 12 ex
FIELD: electromagnetic radiation protection.
SUBSTANCE: invention relates to a method of preparation and to composition of materials absorbing electromagnetic emission. Composition is prepared by combining binder with ferrite, the latter containing 60-90% of ferrite material obtained according to high-temperature ceramic technology and ground to microparticle size and 10-40% of particles belonging to ferrite phase obtained by chemical precipitation from aqueous solutions onto surface of ferrite material microparticles. Ferrite is calcined in the form of isolated precipitate at 500-600°C and then disaggregated. Invention further discloses ferrite-based composition containing 9-13% binder obtained by above-indicated method.
EFFECT: increased choice of electromagnetic radiation-protection materials.
2 cl, 5 tbl, 12 ex
FIELD: shipbuilding; devices reducing probability and range of detection of ship by enemy radar systems.
SUBSTANCE: ship has metal hull and superstructure which is made from multi-layer polymer composite material. Ratio of superstructure area to hull area shall be no less than 0.54; metal members built in superstructure are coated with radio-absorbing external layer. Open cavities in hull and in superstructure are provided with detachable shields made from material reflecting the radio waves. Provision is made for forming false radar targets for receiving enemy missiles and effective protection of personnel against radiation of own radar facilities.
EFFECT: enhanced efficiency and safety.
FIELD: antennae equipment.
SUBSTANCE: device is in form of a structure composed of cardboard pipe-like elements of various length and diameter and wedge-like inserts, positioned inside pipe-like elements. Said elements are gathered in blocks in parallel to their axis, have inner diameter 66 and 200.4 mm, one slant at 17 degrees angle or two slants symmetric to element axis at angle 35 degrees, outer and inner electric-conductive layer.
EFFECT: higher efficiency, broader functional capabilities.
8 cl, 11 dwg, 1 tbl
FIELD: radiation-absorbing coatings.
SUBSTANCE: proposed radiation-absorbing coating has rubber base three-layer flexible plate made of ferrite powder, content of the latter being different in each layer. Third layer has in its composition 10 - 15 volume percent of gralene fiber. Coating also has fourth layer abutting against metal surface of piece of equipment being protected which is made of magnetically hard rubber of arch-type magnetization whose magnetic energy corresponds to maximum of energy product (BH)max = 4 - 8 kJ/m3. Coating may have metal or ceramic magnets in fourth layer. Process for manufacturing radiation-absorbing coating includes production of each layer of plate, joining of three first layers by co-curing, magnetization of fourth layer, and installation of metal or ceramic magnets therein; fourth layer is magnetized by way of arch-type saturation whereupon this layer is attached to plate assembled of three first layers with aid of adhesive.
EFFECT: facilitated installation on and removal from machine armor, improved radiation absorbing properties within wide frequency band.
3 cl, 4 dwg, 1 tbl
FIELD: materials transmitting or trapping electromagnetic beams of definite wavelength and bandwidth for research and industrial applications.
SUBSTANCE: proposed method for producing membranes capable of passing or trapping electromagnetic radiation of definite wavelength λ and bandwidth Δλ to obtain frequency-selective membranes with any composite pattern on any insulating substrate and in any quantity includes coating insulating substrate with low-resistance paste of desired pattern. Used as low-resistance paste is low-viscosity stabilized conducting compound of ultra-dispersed powders, polymeric binder having steady electric conductivity and average particle size of 10 - 600 nm, organic solvent, and surface-active materials, proportion of ingredients being as follows, parts by mass: ultra-dispersed conducting powder, 60 - 90; polymeric binders, 39 - 7; organic solvent, 100 - 400; and surface-active materials, 1 - 3. This compound is applied by means of printer or plotter according to desired program to produce desired pattern whose layer thickness is not smaller than that of skin layer for final procedure, it is dried out.
EFFECT: enlarged functional capabilities.
1 cl, 2 tbl
FIELD: protection from electromagnetic emission.
SUBSTANCE: mesh of electric-conductive material is positioned on dielectric transparent film with applied transparent electric-conductive layer, made either of indium, or of tin, or of indium/tin alloy with thickness, approximately equal to 0,1 of skin layer, and the very mesh is applied with thickness not exceeding skin-layer by printer or plotter using electric-conductive compound, consisting of ultra-dispersive electric-conductive powder with stable electric conductivity and average size of particles 10,0-600,0 nm, polymer linking component, organic solvent and surfactant with certain ratio of components.
EFFECT: forming of transparent screens, screening properties of which do not depend on falling angle of electromagnetic emission, also light and simple to manufacture.
FIELD: reduced probability of weapon and other war materiel location by radar.
SUBSTANCE: controllable layer is made in the form of thin film of evaporated graphite and disposed between first and second insulating layers; first bidimensional-periodic lattice made of evaporated metal strips is disposed on external side of first insulating layer; second bidimensional-periodic lattice made of evaporated metal strips is disposed between second and third insulating layers; other side of third layer carries reflecting screen; conductivity B1 of first bidimensional-periodic lattice and thickness d1 of first insulating layer ensuring minimal level of echo signal in desired frequency band are chosen from mathematical expressions given in description of invention. Thicknesses of second and third insulating layers d2 and d3 of second and third insulating layers, respectively' as well as refractive indices of first, second, and third insulating layers n1, n2 n3, respectively, are chosen from expressions given in description of invention.
EFFECT: reduced cost of coating.
1 cl, 5 dwg