An airborne conformal low RCS radome

Abstract

The present invention provides an airborne conformal low RCS radome, in which a conformal wave-transmitting medium substrate coated with an absorbing material is covered on a conformal aluminum alloy frame, epoxy glue is applied on the low table of the conformal aluminum alloy frame, and the conformal wave-transmitting medium substrate and the conformal aluminum alloy frame are bonded together, and the edge chamfer of the conformal wave-transmitting medium substrate and the step chamfer of the conformal aluminum alloy frame form a V-shaped groove, and the V-shaped groove is filled with tear-resistant silicone rubber, thereby forming a conformal low RCS radome. The present invention allows the scattered waves generated at the discontinuity to be absorbed by the absorbing material to achieve the purpose of low RCS. The surface of the present invention has no protrusions, steps, or depressions except for the mounting holes, thereby avoiding scattered waves generated by structural discontinuities. The use of tear-resistant silicone rubber to fill the gaps can improve the fatigue resistance of the surface coating and enhance the crack resistance of the radome surface.

Description

Technical Field

[0001] The invention relates to the field of radar, in particular to an airborne radome, and the invention relates to low radar cross section (RCS) antenna technology. Background Art

[0002] In modern warfare, stealth is one of the key factors for aircraft to improve their survivability and penetration capabilities, and it is also an important condition for ensuring that they can be discovered and attacked before the enemy. Stealth technology, also known as low-detectable technology or target characteristic control technology, refers to the use of comprehensive means to make it difficult for the enemy to detect or shorten the detection distance of its detectors. The stealth technology that people often talk about now generally refers to radar stealth technology, which mainly achieves stealth through clever design of structure and appearance or coating with absorbing materials to reduce the signal characteristics of detected radar waves. RCS (Radar cross section) is a parameter to measure the stealth performance of a target, with a dimension of square meters or dBsm (dBm 2 ).

[0003] Airborne stealth antennas are a type of antenna installed on the surface of the skin of stealth aircraft. It not only meets the corresponding radiation performance, but also has low RCS performance. Generally, large aircraft have as many as a dozen to dozens of airborne antennas. The superposition of scattered waves from multiple antennas will cause the stealth performance of the entire aircraft to deteriorate seriously. Therefore, the RCS value of each antenna needs to be lower than -35dBsm to -40dBsm to meet the stealth requirements of the entire aircraft. Common airborne L-band antennas are mostly microstrip antennas, cavity antennas, etc. The RCS value of this type of antenna is about -30dBsm; the RCS value of airborne knife antennas, rod antennas, etc. is about -25dBsm. The stealth performance of the above antennas cannot meet the requirements of stealth aircraft.

[0004] Airborne stealth antennas mainly use two technical means to reduce the RCS value: one is to load a stealth radome, which controls the scattering direction of detection radar waves or absorbs radar waves; the other is to design a low RCS antenna radiator to control the scattering of detection radar waves by the antenna itself or directly absorb radar waves. Since the antenna radiator needs a certain shape to meet the radiation performance and cannot be excessively designed with a low RCS, the radome, as a component directly irradiated by the radar detection wave, can more directly act on the radar detection wave to produce a low RCS effect and avoid the limitation of the radiation performance on the shape of the antenna radiator. Therefore, a low RCS radome has a multiplier effect on airborne stealth antennas. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the present invention provides an airborne conformal low RCS radome. The present invention proposes a low RCS radome that can be widely used in airborne antennas, and the radome also has the characteristics of simple structure and high and low temperature resistance.

[0006] The technical solution adopted by the present invention to solve the technical problem is:

[0007] An airborne conformal low RCS radome comprises a conformal aluminum alloy frame, a conformal wave-transmitting dielectric substrate, an absorbing material and tear-resistant silicone rubber; the conformal wave-transmitting dielectric substrate coated with the absorbing material is covered on the conformal aluminum alloy frame, the size of the conformal wave-transmitting dielectric substrate completely covers the central cavity and step width of the conformal aluminum alloy frame, epoxy glue is applied on the low table of the conformal aluminum alloy frame, the conformal wave-transmitting dielectric substrate and the conformal aluminum alloy frame are bonded together, and rivets are passed through rivet holes to rivet the conformal wave-transmitting dielectric substrate and the conformal aluminum alloy frame The edge chamfers of the conformal wave-transmitting medium substrate and the step chamfers of the conformal aluminum alloy frame form a V-shaped groove, the V-shaped groove is filled with tear-resistant silicone rubber, the surface of the tear-resistant silicone rubber is coated with absorbing material to ensure that the V-shaped groove is filled full and flat, thereby forming a conformal low RCS radome; the conformal low RCS radome is loaded onto the airborne array antenna, and each radiating unit of the array antenna is just under the convex block of the conformal wave-transmitting medium substrate, and each convex block serves as a wave-transmitting window of the unit antenna to realize antenna radiation, and the radome has stealth performance.

[0008] The conformal aluminum alloy frame is in the shape of a diamond frame with a central hollow, the outer curved surface of the frame is conformal to the curved surface of the aircraft skin, and the diagonal size of the outer edge of the frame is 10%-30% larger than the diagonal size of the conformal wave-transmitting medium substrate, and the thickness is 2 times-5 times that of the conformal wave-transmitting medium substrate; the diagonal size of the central hollow of the frame is 10%-30% smaller than the diagonal size of the conformal wave-transmitting medium substrate; the cross section of the conformal aluminum alloy frame is a step, and the table surface of the outer edge is higher than the table surface of the inner edge, and the width of the lower table surface is 10mm- The height difference between the high table and the low table is equal to the thickness of the conformal wave-transmitting medium substrate coated with the wave-absorbing material. The connection between the high table and the low table is a chamfered angle, and the height of the chamfered angle is the same as the height of the step. Rivet holes are evenly distributed around the step on the low table, and the center of the rivet holes is 2mm-10mm away from the inner edge of the high table.

[0009] The conformal aluminum alloy frame is an aviation aluminum alloy material such as magnesium aluminum alloy or aluminum-lithium alloy.

[0010] The conformal wave-transmitting medium substrate is a rigid wave-transmitting material, and is made of epoxy glass fiber cloth or polycarbonate material; if it is epoxy glass fiber cloth, it is molded by a hot-pressing process; if it is polycarbonate, it is molded by a precision milling machine.

[0011] The conformal wave-transmitting medium substrate is in the shape of a plate with a thickness of 0.5 mm to 5 mm and uniform thickness. The outer curved surface of the conformal wave-transmitting medium substrate is conformal to the curved surface of the aircraft skin. The edge of the conformal wave-transmitting medium substrate is a chamfered angle, the height of the chamfered angle is the same as the step height of the conformal aluminum alloy frame, the outer contour of the conformal wave-transmitting medium substrate is a rhombus, and the acute inner angle of the rhombus is between 50° and 80°; a convex block is provided at the intersection of the diagonal lines of the rhombus of the conformal wave-transmitting medium substrate, the height of the convex block is 0.2 mm to 2 mm, the outer curved surface of the convex block is conformal to the curved surface of the aircraft skin, the outer contour of the convex block is a rhombus, a triangle or a polygon, and the acute inner angle of the convex block is the same as and parallel to that of the conformal wave-transmitting medium substrate, and the area of ​​the convex block is 10% to 80% smaller than that of the conformal wave-transmitting medium substrate.

[0012] The absorbing material is a coated absorbing material, which is uniformly coated on the surface of a conformal wave-transmitting medium substrate having a bump on one side thereof, and the conformal wave-transmitting medium substrate area outside the bump is coated with the absorbing material, and the thickness of the absorbing material is the same as the height of the bump.

[0013] The acute angle direction of the protrusion is consistent with the acute angle direction of the rhombus of the conformal wave-transmitting medium substrate.

[0014] The beneficial effects of the present invention are:

[0015] (1) Low RCS. Electromagnetic wave scattering mainly occurs in discontinuous areas, including discontinuous structures and discontinuous materials. Discontinuous structures mainly include steps, gaps, protrusions, depressions, etc. Discontinuous materials mainly refer to the connection between different materials, such as the connection between metal and non-metal, the connection between different non-metallic materials, etc. The present invention adopts a method of covering the discontinuity with absorbing materials so that the scattered waves generated at the discontinuity are absorbed by the absorbing materials, thereby achieving the purpose of low RCS. The absorbing material is filled in the connection between the conformal aluminum alloy frame and the conformal wave-transmitting medium substrate, absorbing the scattered waves caused by the material discontinuity; the absorbing material is coated on the surface of the side with the protrusion of the conformal wave-transmitting medium substrate, absorbing the scattered waves caused by the discontinuity of the protrusion; the surface of the antenna cover of the present invention has no protrusions, steps, or depressions except for the mounting holes, thereby avoiding the scattered waves generated by the structural discontinuity.

[0016] (2) Resistance to high and low temperature environments. Since the thermal expansion coefficients of the conformal wave-transmitting medium substrate and the conformal aluminum alloy frame are different in high and low temperature environments, repeated high and low temperature changes will cause fatigue tearing of the coatings such as the absorbing materials on the surface of the radome, resulting in cracks in the radome. The present invention uses tear-resistant silicone rubber to fill the gaps, which can improve the fatigue strength of the surface coating and enhance the crack resistance of the radome surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the appearance diagram of the airborne conformal low RCS radome of the present invention.

[0018] Figure 2 It is the appearance diagram of the aluminum alloy frame of the present invention.

[0019] Figure 3 It is an appearance diagram of a wave-transmitting medium substrate of the present invention that is not coated with a wave-absorbing material.

[0020] Figure 4 It is a cross-sectional view of a wave-transmitting medium substrate coated with a wave-absorbing material according to the present invention.

[0021] Figure 5 yes Figure 1 Enlarged view of a partial cross section.

[0022] Figure 6 This is a schematic diagram of Example 2.

[0023] Figure 7 This is a schematic diagram of Example 3.

[0024] Figure 8 This is a schematic diagram of Example 4.

[0025] Fig. 9 It is a comparison chart of RCS test curves of Examples 1, 2, 3, 4 and the reference radome.

[0026] Among them, 1-conformal aluminum alloy frame, 2-conformal wave-transmitting medium substrate, 3-absorbing material, 4-tear-resistant silicone rubber. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0028] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments of the specification. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0029] An airborne conformal low RCS radome comprises a conformal aluminum alloy frame, a conformal wave-transmitting dielectric substrate, an absorbing material and tear-resistant silicone rubber; the conformal wave-transmitting dielectric substrate coated with the absorbing material is covered on the conformal aluminum alloy frame, the size of the conformal wave-transmitting dielectric substrate completely covers the central cavity and step width of the conformal aluminum alloy frame, epoxy glue is applied on the low table of the conformal aluminum alloy frame, the conformal wave-transmitting dielectric substrate and the conformal aluminum alloy frame are bonded together, and rivets are passed through rivet holes to rivet the conformal wave-transmitting dielectric substrate and the conformal aluminum alloy frame The edge chamfers of the conformal wave-transmitting medium substrate and the step chamfers of the conformal aluminum alloy frame form a V-shaped groove, the V-shaped groove is filled with tear-resistant silicone rubber, the surface of the tear-resistant silicone rubber is coated with absorbing material to ensure that the V-shaped groove is filled full and flat, thereby forming a conformal low RCS radome; the conformal low RCS radome is loaded onto the airborne array antenna, and each radiating unit of the array antenna is just under the convex block of the conformal wave-transmitting medium substrate, and each convex block serves as a wave-transmitting window of the unit antenna to realize antenna radiation, and the radome has stealth performance.

[0030] The conformal aluminum alloy frame is in the shape of a diamond frame with a central hollow, the outer curved surface of the frame is conformal to the curved surface of the aircraft skin, and the diagonal size of the outer edge of the frame is 10%-30% larger than the diagonal size of the conformal wave-transmitting medium substrate, and the thickness is 2 times-5 times that of the conformal wave-transmitting medium substrate; the diagonal size of the central hollow of the frame is 10%-30% smaller than the diagonal size of the conformal wave-transmitting medium substrate; the cross section of the conformal aluminum alloy frame is a step, and the table surface of the outer edge is higher than the table surface of the inner edge, and the width of the lower table surface is 10mm- The height difference between the high table and the low table is equal to the thickness of the conformal wave-transmitting medium substrate coated with the wave-absorbing material. The connection between the high table and the low table is a chamfered angle, and the height of the chamfered angle is the same as the height of the step. Rivet holes are evenly distributed around the step on the low table, and the center of the rivet holes is 2mm-10mm away from the inner edge of the high table.

[0031] The conformal aluminum alloy frame is an aviation aluminum alloy material such as magnesium aluminum alloy or aluminum-lithium alloy.

[0032] The conformal wave-transmitting medium substrate is a rigid wave-transmitting material, and is made of epoxy glass fiber cloth or polycarbonate material; if it is epoxy glass fiber cloth, it is molded by a hot-pressing process; if it is polycarbonate, it is molded by a precision milling machine.

[0033] The conformal wave-transmitting medium substrate is in the shape of a plate with a thickness of 0.5 mm to 5 mm and uniform thickness. The outer curved surface of the conformal wave-transmitting medium substrate is conformal to the curved surface of the aircraft skin. The edge of the conformal wave-transmitting medium substrate is a chamfered angle, the height of the chamfered angle is the same as the step height of the conformal aluminum alloy frame, the outer contour of the conformal wave-transmitting medium substrate is a rhombus, and the acute inner angle of the rhombus is between 50° and 80°; a convex block is provided at the intersection of the diagonal lines of the rhombus of the conformal wave-transmitting medium substrate, the height of the convex block is 0.2 mm to 2 mm, the outer curved surface of the convex block is conformal to the curved surface of the aircraft skin, the outer contour of the convex block is a rhombus, a triangle or a polygon, and the acute inner angle of the convex block is the same as and parallel to that of the conformal wave-transmitting medium substrate, and the area of ​​the convex block is 10% to 80% smaller than that of the conformal wave-transmitting medium substrate.

[0034] The absorbing material is a coated absorbing material, which is uniformly coated on the surface of a conformal wave-transmitting medium substrate having a bump on one side thereof, and the conformal wave-transmitting medium substrate area outside the bump is coated with the absorbing material, and the thickness of the absorbing material is the same as the height of the bump.

[0035] The acute angle direction of the protrusion is consistent with the acute angle direction of the rhombus of the conformal wave-transmitting medium substrate.

[0036] Embodiment 1:

[0037] This embodiment includes a conformal aluminum alloy frame (1), a conformal wave-transmitting medium substrate (2), a wave-absorbing material (3), and tear-resistant silicone rubber (4).

[0038] like Figure 1 and Figure 2 As shown, the conformal aluminum alloy frame (1) has an outer curved surface that conforms to the aircraft, and has a rhombus-shaped outer profile. The diagonal lengths of the rhombus are 240 mm and 169 mm respectively, and the acute inner angle of the rhombus is 72°. The 16 countersunk holes on the edge of the rhombus are the connection holes between the antenna cover and the aircraft skin. The center of the conformal aluminum alloy frame (1) is a rhombus-shaped cavity. There is a step between the edge of the rhombus-shaped cavity and the line connecting the centers of the 16 countersunk holes. The step height is 2 mm, the step width is 20 mm, and the step edge is chamfered, with a chamfer height of 2 mm. There are 8 rivet holes near the chamfered edge of the step.

[0039] like Figure 3 As shown, the conformal wave-transmitting medium substrate (2) is epoxy glass fiber cloth, which is molded by hot-pressing process, and has a thickness of 1 mm and is uniform. The outer contour of the conformal wave-transmitting medium substrate (2) is a rhombus, and the diagonal lengths of the rhombus are 177 mm and 125 mm respectively. There are 4 rhombus-shaped protrusions at the intersection of the rhombus diagonals of the conformal wave-transmitting medium substrate (2), and the diagonal lengths of each protrusion are: 49.5 mm and 35 mm respectively.

[0040] like Figure 4As shown, the absorbing material (3) is evenly coated on the surface of the conformal wave-transmitting medium substrate (2) on the side with the bump, and the rest of the surface area is coated except for the raised surface of the bump. The thickness of the absorbing material is the same as the height of the bump, both of which are 1 mm.

[0041] like Figure 5 As shown, the edge of the conformal wave-transmitting medium substrate (2) is chamfered. The V-shaped groove formed by the chamfer of the conformal wave-transmitting medium substrate (2) and the step chamfer of the conformal aluminum alloy frame (1) is coated with tear-resistant silicone rubber (4). The surface of the tear-resistant silicone rubber (4) is coated with the absorbing material (3) to ensure that the V-shaped groove is filled fully and smoothly.

[0042] like Figure 1 As shown, the antenna cover of the present invention is loaded onto a 4-unit microstrip antenna array, and the electromagnetic waves radiated by each microstrip antenna unit are radiated through the 4 bumps on the antenna cover, avoiding the influence of the absorbing material on the radiated electromagnetic waves, and satisfying the radiation performance of the antenna. At the same time, the antenna cover of the present invention reduces and absorbs the scattered waves caused by various discontinuities, reducing the RCS value of the antenna.

[0043] like Figure 5 As shown, the radome of the present invention fills the gaps between different materials with tear-resistant silicone rubber (4), which can reduce fatigue tearing of the absorbing material caused by repeated high and low temperature environment changes and prevent cracks in the radome.

[0044] Embodiment 2:

[0045] The structure of this embodiment is the same as that of embodiment 1, with the following adjustments:

[0046] like Figure 6 As shown, the numbers of the diamond-shaped protrusions on the surface of one side of the conformal wave-transparent dielectric substrate (2) are 1, 3 and 2 respectively.

[0047] Embodiment 3:

[0048] The structure of this embodiment is the same as that of embodiment 1, with the following adjustments:

[0049] like Figure 7 As shown, the shapes of the protrusions on one side surface of the conformal wave-transmitting medium substrate (2) are respectively triangular, hexagonal and sawtooth.

[0050] Embodiment 4:

[0051] The structure of this embodiment is the same as that of Embodiment 1, with the following adjustments:

[0052] like Figure 8 As shown, the conformal aluminum alloy frame (1) and the conformal wave-transmitting medium substrate (2) simultaneously change their shapes into triangle, hexagon and sawtooth.

[0053] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent transformation of the content of the present invention, or direct / indirect application of the present invention in specific equipment or other related technical fields, are included in the patent protection scope of the present invention.

[0054] The following is a further description of the technical effects of the present invention in combination with the test results:

[0055] 1. Test conditions and contents:

[0056] A conventional epoxy glass fiber cloth flat antenna cover was used as a reference antenna cover. Example 1 and the reference antenna cover were respectively loaded onto a 4-unit microstrip antenna array to form two antennas. The RCS values ​​of the two antennas were tested in a compact microwave darkroom, with a test frequency of 4 GHz-18 GHz, a frequency interval of 1 GHz, an incident wave direction of the negative direction of the X axis, and an incident wave polarization of the Y axis.

[0057] 2. Test results:

[0058] Reference Fig. 9 , the horizontal axis is frequency, the vertical axis is RCS value, under the same array antenna condition, the RCS value of the radomes of Example 1, Example 2, Example 3 and Example 4 is reduced by 2dB-20dB compared with the reference radome.

Claims

1. An airborne conformal low RCS radome, comprising a conformal aluminum alloy frame, a conformal wave-transmitting dielectric substrate, an absorbing material and tear-resistant silicone rubber, characterized in that: In the airborne conformal low RCS radome; a conformal wave-transmitting dielectric substrate coated with an absorbing material is covered on a conformal aluminum alloy frame, the size of the conformal wave-transmitting dielectric substrate completely covers the central cavity and step width of the conformal aluminum alloy frame, epoxy glue is applied on the low table of the conformal aluminum alloy frame, the conformal wave-transmitting dielectric substrate and the conformal aluminum alloy frame are bonded together, and rivets are passed through the rivet holes to rivet the conformal wave-transmitting dielectric substrate and the conformal aluminum alloy frame together, the edge chamfer of the conformal wave-transmitting dielectric substrate and the step chamfer of the conformal aluminum alloy frame form a V-shaped groove, the V-shaped groove is filled with tear-resistant silicone rubber, the surface of the tear-resistant silicone rubber is coated with an absorbing material and the V-shaped groove is ensured to be filled full and flat, thereby forming a conformal low RCS radome; the conformal low RCS radome is loaded onto the airborne array antenna, each radiating unit of the array antenna is just below the convex block of the conformal wave-transmitting dielectric substrate, each convex block serves as a wave-transmitting window of the unit antenna to realize antenna radiation, and the radome has a stealth performance; The conformal aluminum alloy frame is in the shape of a diamond frame with a central hollow, the outer curved surface of the frame is conformal to the curved surface of the aircraft skin, and the diagonal size of the outer edge of the frame is 10%-30% larger than the diagonal size of the conformal wave-transmitting medium substrate, and the thickness is 2 times-5 times that of the conformal wave-transmitting medium substrate; the diagonal size of the central hollow of the frame is 10%-30% smaller than the diagonal size of the conformal wave-transmitting medium substrate; the cross section of the conformal aluminum alloy frame is a step, and the table surface of the outer edge is higher than the table surface of the inner edge, and the width of the lower table surface is 10mm- 35mm, on the high table 5mm-25mm away from the outer edge of the conformal aluminum alloy frame, there are several countersunk holes evenly distributed along the outer edge of the conformal aluminum alloy frame, and the screws are connected to the aircraft skin through the countersunk holes; the height difference between the high table and the low table is equal to the thickness of the conformal wave-transmitting medium substrate coated with the absorbing material, and the connection between the high table and the low table is a chamfer, the height of the chamfer is the same as the height of the step, and there are rivet holes evenly distributed along the steps on the low table, and the center of the rivet hole is 2mm-10mm away from the inner edge of the high table; The absorbing material is a coated absorbing material, which is uniformly coated on the surface of a conformal wave-transmitting medium substrate having a bump on one side thereof, and the conformal wave-transmitting medium substrate area outside the bump is coated with the absorbing material, and the thickness of the absorbing material is the same as the height of the bump.

2. The airborne conformal low RCS radome according to claim 1, characterized in that: The conformal aluminum alloy frame is an aviation aluminum alloy material such as magnesium aluminum alloy or aluminum-lithium alloy.

3. The airborne conformal low RCS radome according to claim 1, characterized in that: The conformal wave-transmitting medium substrate is a rigid wave-transmitting material, and is made of epoxy glass fiber cloth or polycarbonate material; if it is epoxy glass fiber cloth, it is molded by a hot-pressing process; if it is polycarbonate, it is molded by a precision milling machine.

4. The airborne conformal low RCS radome according to claim 1, characterized in that: The conformal wave-transmitting medium substrate is in the shape of a plate with a thickness of 0.5 mm to 5 mm and uniform thickness. The outer curved surface of the conformal wave-transmitting medium substrate is conformal to the curved surface of the aircraft skin. The edge of the conformal wave-transmitting medium substrate is a chamfered angle, the height of the chamfered angle is the same as the step height of the conformal aluminum alloy frame, the outer contour of the conformal wave-transmitting medium substrate is a rhombus, and the acute inner angle of the rhombus is between 50° and 80°; a convex block is provided at the intersection of the diagonal lines of the rhombus of the conformal wave-transmitting medium substrate, the height of the convex block is 0.2 mm to 2 mm, the outer curved surface of the convex block is conformal to the curved surface of the aircraft skin, the outer contour of the convex block is a rhombus, a triangle or a polygon, and the acute inner angle of the convex block is the same as and parallel to that of the conformal wave-transmitting medium substrate, and the area of ​​the convex block is 10% to 80% smaller than that of the conformal wave-transmitting medium substrate.

5. The airborne conformal low RCS radome according to claim 1, characterized in that: The acute angle direction of the protrusion is consistent with the acute angle direction of the rhombus of the conformal wave-transmitting medium substrate.

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