A high-transmittance and low-RCS radar seeker radome

Abstract

The invention discloses a high-transmittance and low-RCS radar seeker radome, belonging to the field of aircraft radome and electromagnetic window radar stealth technology. The frequency selective surface unit is composed of a 45° rotated cross ring gap and a zigzag square ring gap located on a metal patch, and there is no metal in the gap part. Among them, the zigzag square ring gap is formed by a square ring gap with four right-angle vertices and four sides with concave center points, and the concave part is composed of a rectangular gap. The zigzag square ring gap surrounds the 45° rotated cross ring gap, and the geometric centers of the two coincide, are coplanar, and are not connected to each other. The bandpass frequency selective surface structure of the wave-transmitting stealth zone adopts a zone-based design, and the difference between the maximum incident angle d1 and the minimum incident angle d2 of the radar antenna beam relative to the dielectric cover body in each zone is ≤20°. The junction between the wave-transmitting stealth zone and the dielectric cover body and the shielding stealth zone adopts a serrated design, and when the sawtooth boundary does not meet the periodic spacing of a frequency selective surface unit, the frequency selective surface pattern is not prepared.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft radomes and electromagnetic window radar stealth, and in particular relates to a high-transmittance and low-RCS radar seeker radome. Background Art

[0002] The radar seeker radome is an important component of the terminal guidance radar of the aircraft. It is usually located in the front part of the aircraft. It can protect the radar antenna system from the influence of temperature, wind, sand, humidity, salt spray and other environmental factors on the radar antenna system. In addition to protecting the radar antenna to work normally in harsh environments, the radar seeker radome is also an aerodynamic / structural / wave-transparent / stealth multifunctional integrated component that needs to meet the environmental adaptability requirements brought about by aerodynamic force, aerodynamic heat, etc. during flight, as well as related electromagnetic function requirements.

[0003] With the improvement of radar working system, the continuous improvement of detection distance and the widespread application of wide-band anti-interference technologies, higher and higher requirements are put forward for the wave transmission characteristics of radar seeker radome. In addition, the radar seeker cabin is one of the main forward scattering sources of the aircraft, and its scattering source is mainly contributed by the radar antenna, radar components and metal connectors in the cabin. Since the radar antenna is an active target, it must maintain normal electromagnetic wave transmission and reception in its own working frequency band and cannot be blocked or covered. Conventional stealth measures (such as shaping technology, antenna bias technology, absorbing structure / material technology, etc.) cannot be simply applied in radar antenna stealth. Therefore, its scattering mechanism is more complicated than that of ordinary scatterers. The frequency selective surface (FSS) stealth radome is usually used, which is the main technical approach to reduce the radar cross section (RCS) of the seeker cabin.

[0004] At present, relevant research has been carried out in the field of stealth radar radomes at home and abroad. In the paper "Integrated Curved Conformal Frequency Selective Surface Radome", Fuzhou University analyzed the wave transmittance and aiming error of the curved frequency selective surface radome at different scanning angles, and proposed a curved frequency selective surface radome processing scheme based on the linkage of a multi-degree-of-freedom laser robot and a rotating table. In the paper "Research on the Electromagnetic Properties of Radomes and Curved FSS Radomes", Nanjing University of Aeronautics and Astronautics proposed a curved FSS rapid modeling method, and studied the influence of different bending degrees on the electrical properties of FSS. In the paper "Research on Processing Methods of Non-Developable Frequency Selective Surfaces", Dalian University of Technology focused on analyzing the processing methods and error optimization methods of laser curved FSS structures. In the patent "An Adaptive Rapid Design Method for Curved Frequency Selective Surface Radome, 201911142192.9", it is proposed to conduct adaptive rapid modeling of curved frequency selective surface radomes based on the target radome shape, the incident angle distribution of the wave on the radome surface, and the optimal wave transmission function of the frequency selective surface unit. The above-mentioned papers and patents have studied the design, processing and testing of frequency selective surface antenna covers, but the research objects and contents are all frequency selective surface units or simple array structure arrangements. It is difficult to achieve a balanced design of high wave transmission and low RCS in specific practical process applications.

[0005] In view of the above problems, the present invention provides a high-transmittance and low-RCS radar seeker radome, which combines the bottlenecks of the frequency selective surface radome such as poor angle stability and limited out-of-band suppression, as well as the characteristics of the radar seeker radome such as a large aspect ratio and a wide range of incident angles, to perform a balanced design of high transmittance and low RCS of the frequency selective surface radome. Summary of the invention

[0006] The object of the present invention is to provide a high-transmittance and low RCS radar seeker radome to solve the problem of comprehensive design of the radome under the constraints of high-transmittance and high-stealth performance.

[0007] The present invention adopts the following technical solution:

[0008] A high-transmittance and low RCS radar seeker radome includes: a dielectric cover body and a stealth functional layer, wherein the stealth functional layer is divided into two areas: a wave-transmitting stealth area and a shielding stealth area. The wave-transmitting stealth area is a bandpass frequency selective surface structure, and the shielding stealth area is a metal structure. The boundaries between the wave-transmitting stealth area and the dielectric cover body and the shielding stealth area are designed in a serrated shape.

[0009] 1) The antenna cover has no stealth functional layer in the vertical height range of 0mm to h1 from the vertex along the axial direction, and the arc length L1 of the dielectric cover corresponding to the position h1 satisfies: L1≤λ1, where λ1 is the free space wavelength corresponding to the lowest frequency of the threat frequency band, and L1 is the curve obtained by the intersection of the plane perpendicular to the axial direction of the antenna cover at the position h1 and the outer surface of the dielectric cover.

[0010] 2) The antenna cover is designed as a sawtooth structure at the boundary of the bandpass frequency selection surface structure of the wave-transmitting stealth zone from the vertex along the axial direction to the vertical height range of h1 to h2. The number of sawteeth is m1, the sawtooth angle α1 is between 30° and 150°, and the sawteeth are evenly distributed around the axial direction. Among them, the arc length L2 of the dielectric cover corresponding to the position h2 satisfies: L1<L2≤λ2, where λ2 is 2.5 times the free space wavelength corresponding to the lowest frequency of the threat frequency band, and L2 is the curve obtained by the intersection of the plane perpendicular to the axial direction of the antenna cover at the position h2 and the outer surface of the dielectric cover.

[0011] 3) The antenna cover extends from the bottom end surface axially upward to the vertical height range h3, and the boundary between the wave-transmitting stealth area and the shielding stealth area is a sawtooth splicing design. The number of sawteeth at the boundary of the bandpass frequency selective surface structure of the wave-transmitting stealth area is m2, and the sawtooth angle α2 is between 30° and 150°, and the sawteeth are evenly distributed around the axial direction. Among them, h3≤the distance h4 from the radar antenna aperture to the bottom end surface of the dielectric cover.

[0012] 4) The bandpass frequency selective surface structure of the wave-transmitting stealth zone adopts a zone-divided design. According to the different incident angles of the radar antenna beam pointing relative to the dielectric cover, the bandpass frequency selective surface structure is divided into x zones along the axial direction perpendicular to the dielectric cover, and adjacent zones are continuous but non-overlapping.

[0013] The bandpass frequency selective surface structure in each of the above partitions is the same, and frequency selective surface units of different types or of the same type but different sizes can be used between different partitions to meet the variation range of the radar antenna beam pointing relative to the incident angle of the dielectric cover between different partitions.

[0014] When the partitions are too dense, the design complexity will increase, and when the partitions are too sparse, the performance improvement will not be obvious. According to design experience, the partitioning basis is: the difference between the maximum incident angle d1 and the minimum incident angle d2 of the radar antenna beam pointing relative to the dielectric cover in each partition is ≤20°.

[0015] 5) At the sawtooth boundary of the bandpass frequency selective surface structure in the wave-transmitting stealth zone, when the sawtooth boundary position does not meet the periodic spacing of a frequency selective surface unit, the frequency selective surface unit structure is not prepared at this position to avoid it being truncated at the sawtooth boundary.

[0016] 6) In the bandpass frequency selective surface structure of the wave-transmitting stealth zone, each frequency selective surface unit includes a 45° rotated cross-annular slot structure located on the metal patch, and a square annular slot structure with four corners and four sides whose centers are concave. The above two slot structures are not connected to each other and work in dual frequency bands, and f2 is 1.8 to 2.2 times of f1.

[0017] Beneficial effects of the present invention:

[0018] 1) The radome of the present invention does not include a bandpass frequency selective surface structure in the vertical height range of 0mm to h1 from the vertex along the axial direction, which can improve the radome's wave transmittance under large incident angles. At the same time, based on the difference between the maximum incident angle d1 and the minimum incident angle d2 of the radar antenna beam relative to the dielectric cover body of ≤20°, the bandpass frequency selective surface structure of the wave-transmitting stealth zone is designed in different regions to improve the stability of the radome's wave transmittance under different incident angles.

[0019] 2) The present invention adopts a serrated design at the junction of the wave-transmitting stealth zone and the dielectric cover body, and at the junction of the wave-transmitting stealth zone and the shielding stealth zone in the area of ​​height h1 to h2 axially downward from the vertex of the antenna cover and in the area of ​​vertical height range h3 axially upward from the bottom end surface of the antenna cover, so as to reduce scattering caused by discontinuity at the dielectric interface and improve the overall stealth performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the structure of a high-transmittance, low-RCS radar seeker radome in an embodiment of the present invention;

[0021] Figure 2 Schematic diagram of the design of the bandpass frequency selective surface of the wave-transmitting stealth zone in an embodiment of the present invention;

[0022] Figure 3 A top view of the radome structure of a high-transmittance, low-RCS radar seeker in an embodiment of the present invention;

[0023] Figure 4 Schematic diagram of the sawtooth boundary of the bandpass frequency selection surface in the wave-transmitting stealth zone in an embodiment of the present invention.

[0024] Figure 5 Schematic diagram of the structure of a bandpass frequency selective surface unit in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0026] See also Figure 1 to Figure 5As shown, an embodiment of the present invention provides a high-transmittance and low-RCS radar seeker radome structure, including a fiber-reinforced ceramic-based dielectric cover body 1, a stealth functional layer wave-transmitting stealth area 21, a stealth functional layer shielding stealth area 22, a metal connection end frame 3, a compartment 4, and a radar antenna 5.

[0027] Preferably, in this embodiment, the dielectric cover body 1 is a rotating body, the beam scanning angle of the radar antenna 5 is within the range of ±45° in azimuth and ±45° in elevation, the distance from the radar antenna mouth to the bottom end surface of the dielectric cover body is 130mm, and the threat frequency band range is 2GHz to 12GHz.

[0028] The vertical height area of ​​0mm to 20mm from the top of the dielectric cover body along the axial downward direction is the exposed dielectric cover body 1, which does not include the stealth functional layer wave-transmitting stealth area 21, that is, does not include the bandpass frequency selective surface structure, so as to improve the wave transmittance near the top of the dielectric cover body. Among them, the arc length of the dielectric cover body corresponding to the vertical height position of 20mm is 78.5mm≤150mm (the free space wavelength corresponding to 2GHz is 150mm).

[0029] The bandpass frequency selection surface structure boundary of the stealth functional layer wave-transparent stealth zone 21 is designed to be sawtooth-shaped in the vertical height region 20mm to 35mm axially downward from the top of the dielectric cover. Among them, the arc length of the dielectric cover corresponding to the 35mm vertical height position is 204.5mm≤375mm (2.5 times the free space wavelength corresponding to 2GHz). Preferably, in this embodiment, the bandpass frequency selection surface of the stealth functional layer wave-transparent stealth zone 21 is designed with three sawtooth structures evenly distributed around the axial direction of the dielectric cover in the vertical height region 20mm to 35mm axially downward from the top of the dielectric cover. For details, see Figure 3 and Figure 4 .

[0030] From the bottom end surface of the dielectric cover body axially upward to the vertical height area of ​​60mm, the stealth functional layer wave-transmitting stealth area 21 and the stealth functional layer shielding stealth area 22 adopt a serrated splicing design. As a preference, in this embodiment, the serrations at the boundary of the bandpass frequency selective surface structure of the wave-transmitting stealth area 21 are designed to be 9, evenly distributed around the dielectric cover body axially. Among them, the stealth functional layer shielding stealth area 22 is a metal layer structure.

[0031] The bandpass frequency selective surface structure of the wave-transmitting stealth zone 21 of the stealth functional layer adopts a zone-divided design. According to the different incident angles of the transmitting beam of the radar antenna 5 relative to the dielectric cover, the bandpass frequency selective surface structure is divided into four zones, namely 211, 212, 213, and 214, along the direction perpendicular to the axis of the dielectric cover.

[0032] In the wave-transmitting stealth areas 211, 212, 213, and 214 of the stealth functional layer, the differences between the maximum and minimum values ​​of the incident angle of the radar antenna 5 transmitting beam relative to the dielectric cover are 8°, 10°, 20°, and 15°, respectively, meeting the design basis that the difference between the maximum value d1 and the minimum value d2 of the incident angle of the radar antenna beam relative to the dielectric cover is ≤20°.

[0033] According to the maximum value of the incident angle in the above four different partitions, the same type of frequency selective surface structure with different sizes is used to perform simulation optimization design in each partition. In this embodiment, the frequency selective surface unit adopts a 45° rotated cross ring gap structure located on the metal patch, and a square ring gap structure with four corners and four sides concave in the center, and works in dual frequency bands.

[0034] In the partition 211, a=2.90 mm, b=2.70 mm, c=2.33 mm, d=0.30 mm, e=0.68 mm, f=0.55 mm, g=0.25 mm, w1=0.10 mm, w2=0.13 mm;

[0035] In the partition 212, a=2.86 mm, b=2.66 mm, c=2.29 mm, d=0.30 mm, e=0.66 mm, f=0.54 mm, g=0.25 mm, w1=0.10 mm, w2=0.13 mm;

[0036] In the partition 213, a=2.80 mm, b=2.60 mm, c=2.25 mm, d=0.29 mm, e=0.65 mm, f=0.53 mm, g=0.24 mm, w1=0.10 mm, w2=0.13 mm;

[0037] In the partition 214, a=2.74 mm, b=2.55 mm, c=2.20 mm, d=0.28 mm, e=0.64 mm, f=0.52 mm, g=0.24 mm, w1=0.09 mm, w2=0.12 mm;

[0038] In the above four different partitions, the frequency selective surface unit structure is arranged in an array according to the periodic spacing of the partition. When the periodic spacing of a frequency selective surface unit is not met at the junction of adjacent partitions and inside each partition, the frequency selective surface unit structure is not arranged at this position.

[0039] Preferably, in this embodiment, the wave-transmitting stealth area 21 of the stealth functional layer is prepared on the outer surface of the ceramic-based dielectric cover 1 by a metal slurry spraying process, and then a frequency selective surface pattern is prepared by a laser scribing process. At the sawtooth boundary of the bandpass frequency selective surface structure in the wave-transmitting stealth area, when the sawtooth boundary position does not meet the periodic spacing of a frequency selective surface unit, the frequency selective surface unit structure is not prepared at this position to avoid being cut off at the sawtooth boundary. The stealth functional layer shielding stealth area 22 is directly metallized by a metal slurry spraying process, and is connected to the rear metal end frame 3 through a conductive adhesive for conductive continuity.

Claims

1. A high-transmittance, low-RCS radar seeker radome, characterized in that: include: The dielectric cover and the stealth functional layer are divided into two regions: a wave-transmitting stealth region and a shielding stealth region. The wave-transmitting stealth region is a bandpass frequency selective surface structure, and the shielding stealth region is a metal structure. The boundaries between the wave-transmitting stealth region and the dielectric cover and the shielding stealth region are designed in a serrated shape. The radome has no stealth function layer in the vertical height range of 0mm to h1 from the vertex along the axial direction downward, and the arc length L1 of the dielectric cover corresponding to the position h1 satisfies: L1≤λ1, where λ1 is the free space wavelength corresponding to the lowest frequency of the threat frequency band, and L1 is the curve obtained by the intersection of the plane perpendicular to the axial direction of the radome at the position h1 and the outer surface of the dielectric cover; The antenna cover has a vertical height range of h1 to h2 from the vertex along the axial direction downward, and the boundary of the bandpass frequency selection surface structure of the wave-transmitting stealth zone is designed to be a sawtooth structure, the number of sawteeth is m1, the sawtooth angle α1 is between 30° and 150°, and the sawteeth are evenly distributed around the axial direction; wherein, the arc length L2 of the dielectric cover body corresponding to the position h2 satisfies: L1<L2≤λ2, wherein λ2 is 2.5 times the free space wavelength corresponding to the lowest frequency of the threat frequency band, and L2 is the curve obtained by the intersection of the plane perpendicular to the axial direction of the antenna cover at the position h2 and the outer surface of the dielectric cover.

2. The high-transmittance and low-RCS radar seeker radome according to claim 1, characterized in that: The antenna cover has a vertical height range of h3 from the bottom end surface along the axial direction upward, and the boundary between the wave-transmitting stealth zone and the shielding stealth zone is a serrated splicing design. The number of serrations at the boundary of the bandpass frequency selection surface structure of the wave-transmitting stealth zone is m2, the serration angle α2 is between 30° and 150°, and the serrations are evenly distributed around the axial direction; wherein, h3 is smaller than the distance h4 from the radar antenna aperture to the bottom end surface of the dielectric cover body.

3. The high-transmittance and low-RCS radar seeker radome according to claim 1 or 2, characterized in that: The bandpass frequency selective surface structure of the wave-transmitting stealth zone adopts a zone-divided design. According to the different incident angles of the radar antenna beam relative to the dielectric cover, the bandpass frequency selective surface structure is divided into x zones along the axial direction perpendicular to the dielectric cover. In each zone, the difference between the maximum incident angle d1 and the minimum incident angle d2 of the radar antenna beam relative to the dielectric cover is ≤20°.

4. The high-transmittance and low-RCS radar seeker radome according to claim 3, characterized in that: At the sawtooth boundary of the bandpass frequency selective surface structure in the wave-transmitting stealth zone, when the boundary position does not meet the periodic spacing of a frequency selective surface unit, the frequency selective surface unit is not arranged at this position to avoid it being truncated at the sawtooth boundary.

5. The high-transmittance and low-RCS radar seeker radome according to claim 4, characterized in that: The frequency selective surface unit is composed of a 45° rotated cross ring gap and a zigzag square ring gap located on a metal patch, and there is no metal in the gap position; wherein the zigzag square ring gap is formed by a square ring gap with four right-angle vertices and four side center points concave, and the concave part is composed of a rectangular gap; the zigzag square ring gap surrounds the 45° rotated cross ring gap, and the geometric centers of the two coincide, are coplanar, and are not connected to each other.

6. The high-transmittance and low-RCS radar seeker radome according to claim 5, characterized in that: The FSS unit structures are arranged in an array according to the periodic spacing of the partitions in which they are located. When the periodic spacing of a FSS unit is not satisfied at the junction of adjacent partitions and inside each partition, the FSS unit structure is not arranged at this position.

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