Wave-absorbing and diffuse-scattering mixed ultra-wideband RCS (radar cross section) reduction metasurface with wave-transparent window

Abstract

The invention discloses an ultra-wideband RCS (radar cross section) reduction metasurface with mixed wave absorption and diffuse scattering and a wave-transparent window, and belongs to the technical field of electromagnetic metamaterials. The metasurface adopts a four-layer cascade structure and comprises a first layer of polarization conversion structure, a second layer of 2.5 D lossy structure, a third layer of Jerusalem cross-shaped lossy structure and a fourth layer of frequency selective surface structure. By loading a lumped resistor at a specific position and adopting a metal through hole interconnection technology, dual functions of radar cross section reduction in a 1-20GHz ultra-wideband and low insertion loss wave transmission in a 8-12GHz frequency band are realized. The structure of each layer adopts a highly symmetrical design and has the characteristic of polarization insensitivity, and meanwhile, by optimizing interlayer air gaps and dielectric material selection, the structure compactness is realized on the premise of ensuring the performance. The method has important application value in the aspect of integration of stealth equipment and a communication system.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic metamaterials technology, specifically relating to an ultrawideband RCS-reducing metasurface with a wave-transmitting window that combines wave absorption and diffuse scattering. Background Technology

[0002] With the rapid development of radar detection technology, especially the widespread application of ultra-wideband radar and multi-base station radar systems, the stealth requirements of modern military equipment are increasing. The core of radar stealth technology lies in reducing the target's RCS, making it difficult for radar to detect and identify. Traditional stealth technologies typically employ two approaches: shape stealth and material stealth, but these have limitations such as narrow bandwidth, limited functionality, and large thickness.

[0003] The emergence of metamaterials and metasurfaces has brought revolutionary progress to stealth technology. They can flexibly control electromagnetic waves through subwavelength-scale artificial structural units, achieving multiple functions such as wave absorption, wave transmission, and polarization conversion, and have become an effective means of designing multifunctional stealth radomes.

[0004] While significant progress has been made in the research of ultra-wideband stealth radomes, current technologies still face the following common challenges: 1. Balancing Bandwidth and Functionality: Many designs, such as Xing Zhiyu's research on antenna analysis and stealth technology based on electromagnetic metasurfaces at the University of Electronic Science and Technology of China, and Sun Ying's research on wideband, high-performance stealth radar radomes at the same time, struggle to simultaneously achieve efficient RCS reduction and low insertion loss transmission within ultra-wideband, especially covering multiple bands like L-Ka. Expanding the bandwidth often means increasing structural complexity or thickness.

[0005] 2. Miniaturization and Thinning: As illustrated in the simulation design of an ultra-wideband stealth radome based on metasurfaces by Xiong Jie and Yang Baoping in *Modern Electronics Technology*, 2023, Issue 23, military applications impose strict limitations on the size and weight of radomes. While some designs have made progress in unit size and overall thickness, achieving the optimal balance between ultra-wideband performance and miniaturization remains a challenge.

[0006] 3. Multifunctional Integration: Modern military platforms expect radomes to not only be stealthy but also support multiple functions such as communication and radar, requiring them to possess characteristics such as polarization independence and large-angle stability. Current technologies still have room for improvement in multifunctional integration.

[0007] 4. Structural complexity and engineering feasibility: For example, CN115395222B, a stealth antenna radome with intermediate frequency transmission, two-sided hybrid polarization conversion and wave absorption, has too many layers, irregular structure, and use of lumped components, which will increase the design and manufacturing difficulty and cost, and may affect environmental adaptability and reliability.

[0008] Therefore, there is an urgent need in this field for a novel metasurface design that can comprehensively solve the above problems, namely, to achieve significant RCS reduction of <-10dB in the ultra-wideband range such as 1-20GHz, while maintaining high efficiency in wave transmission and low insertion loss in specific communication bands such as 8-12GHz, and to have a stealth radome that is polarization insensitive, relatively compact in structure and has good engineering feasibility. Summary of the Invention

[0009] This invention provides an ultrawideband RCS-reduced metasurface with a wave-transmitting window that combines hybrid absorption and diffuse scattering. It has a multi-layer structure, with each layer realizing polarization conversion, low-frequency absorption, high-frequency absorption, and band-passing functions. Overall, the reflection is less than -10 dB in the 1–20 GHz frequency band and the insertion loss is less than 1.5 dB in the 8–12 GHz frequency band, exhibiting polarization insensitivity.

[0010] To achieve the above objectives, the present invention provides the following technical solution: A hybrid absorption and diffuse scattering ultrawideband RCS-reducing metasurface with a wave-transmitting window, the metasurface having a multi-layer cascaded structure comprising, from top to bottom: a first layer, a second layer, a third layer, and a fourth layer; with air gaps between each layer.

[0011] Preferably, the first layer structure includes a first dielectric substrate, a bidirectional metal zigzag arrow disposed thereon, and a lumped resistor welded to the arrow; the dielectric constant of the first dielectric substrate is 2.2, and the loss tangent is 0.0009.

[0012] Preferably, the package size of the lumped resistor is 0201, the resistance value is the same, and the bidirectional zigzag arrow is arranged at a 45° angle.

[0013] Preferably, the second layer structure includes a second dielectric substrate, a front metal bend line, a back metal bend line, a metal through-hole connecting the front and back sides, and a lumped resistor soldered to the front and back sides; the dielectric constant of the second dielectric substrate is 2.2, and the loss tangent is 0.0015.

[0014] Preferably, the package size of the lumped resistor is 0402, and the resistance value is the same.

[0015] Preferably, the third layer structure includes a third dielectric substrate, a front metal zigzag Jerusalem cross, a back metal zigzag Jerusalem cross, and a lumped resistor welded to the center of the cross; the dielectric constant of the third dielectric substrate is 2.2, and the loss tangent is 0.0009.

[0016] Preferably, the package size of the lumped resistor is 0402.

[0017] Preferably, the fourth layer structure includes a fourth dielectric substrate, a fifth dielectric substrate, a square metal patch disposed on the front side of the fourth dielectric substrate, a cross metal patch disposed between the two dielectric substrates, and a square metal patch disposed on the back side of the fifth dielectric substrate; the dielectric constant of the fourth and fifth dielectric substrates is 3.55.

[0018] Preferably, the units 0 and 1 of the first layer structure are arranged in a checkerboard pattern to form a 1-bit encoded metasurface array.

[0019] Preferably, the metasurface has a co-polarization reflection amplitude of less than -10 dB in the 1–20 GHz band and an insertion loss of less than 1.5 dB in the 8–12 GHz band.

[0020] This invention employs a multi-layered collaborative working mechanism using four metasurface structures with different functions. Each layer is responsible for the electromagnetic response in a different frequency band, achieving ultra-wideband RCS reduction in the 1-20GHz range. It utilizes a hybrid absorption and diffuse scattering mechanism: combining absorption-type and coded metasurface technologies, it dissipates electromagnetic wave energy through resistance and achieves diffuse scattering through phase cancellation, significantly improving the RCS reduction effect. A well-designed FSS layer forms a highly efficient transmission window in the 8-12GHz frequency band, with an insertion loss of less than 1.5dB, meeting communication requirements. The highly symmetrical design of each layer structure gives the metasurface polarization insensitivity, adapting to electromagnetic waves with different polarization modes. Finally, the compact design optimizes the thickness of each layer and the selection of materials, reducing the overall structural thickness while ensuring performance. The principle is as follows: Frequency band division principle: Layer 1: Responsible for polarization conversion and RCS reduction in the 4-5.8GHz frequency band; The second layer: responsible for absorbing waves in the 1-3GHz low-frequency band; The third layer: responsible for absorbing waves in the 13-20GHz high-frequency band; The fourth layer: provides an 8-12 GHz transmission window and a reflective background for other layers.

[0021] Electromagnetic energy conversion principle: Electromagnetic energy is converted into heat energy dissipation through lumped resistance, electromagnetic wave diffuse scattering is achieved through coded metasurfaces, and electromagnetic wave transmission in specific frequency bands is achieved through resonant structures.

[0022] Impedance matching principle: Wideband impedance matching is achieved through multilayer dielectric substrate and metal structure design, and the thickness and dielectric constant of each layer are optimized to reduce electromagnetic wave reflection.

[0023] Compared with the prior art, the beneficial effects of the present invention are: 1. The present invention has a co-polarization reflection amplitude of less than -10dB in an ultra-wide frequency range of 1-20GHz, completely covering L / S / C / X / Ku and part of the Ka band, and has a good stealth effect in the ultra-wide frequency range, far exceeding the existing broadband frequency selective absorbing structure.

[0024] 2. This invention has an insertion loss of less than 1.5dB in the frequency range of 8-12GHz, and has a wide range of applications for RCS reduction of antenna systems operating in the 8-12GHz frequency band.

[0025] 3. The ultrawideband RCS-reduced metasurface with a transparent window of the present invention has highly symmetrical structure in each layer. Therefore, the absorption, polarization conversion characteristics and transmission characteristics of this design do not change with the change of polarization, and it has polarization insensitivity. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the unit structure of the ultrawideband RCS-reduced metasurface according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the first layer structure of the ultrawideband RCS-reduced metasurface according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the second layer structure of the ultrawideband RCS-reduced metasurface according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the third layer structure of the ultrawideband RCS-reduced metasurface according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the fourth layer structure of the ultrawideband RCS-reduced metasurface according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the coding array after assembling the second layer structure of the ultra-wideband RCS reduced metasurface according to an embodiment of the present invention; Figure 7 The ultrawideband RCS of this invention reduces the reflection and transmission amplitude of the metasurface under vertical polarization. Figure 8 The ultrawideband RCS of this invention reduces the reflection and transmission amplitudes of the metasurface under horizontal polarization; Figure 9 The RCS reduction value of the ultrawideband RCS reduction metasurface under vertical polarization in this embodiment of the invention; Figure 10 The RCS reduction value of the ultrawideband RCS reduction metasurface under horizontal polarization is provided in this embodiment of the invention.

[0027] In the diagram, 13 - first layer dielectric substrate, 23 - second layer dielectric substrate, 33 - third layer dielectric substrate, 43 - fourth layer dielectric substrate, 44 - fifth layer dielectric substrate, 11 - first layer structure lumped resistor, 12 - bidirectional zigzag arrow, 21 - second layer structure lumped resistor, 22 - zigzag line on the front of the dielectric substrate, 24 - metal via, 25 - zigzag line on the back of the dielectric substrate, 31 - Jerusalem cross on the front of the dielectric substrate, 32 - Jerusalem cross on the back of the dielectric substrate, 34 - third layer lumped resistor, 41 - upper metal patch, 42 - middle layer metal cross, 45 - lower metal patch. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1, combined with Figure 1 As shown, the present invention is an ultrawideband RCS-reduced metasurface with a wave-transmitting window that combines wave absorption and diffuse scattering. The metasurface is mainly composed of a first layer structure (1) polarization conversion metasurface, a second layer structure (2) 2.5D lossy layer, a third layer structure (3) Jerusalem cross-shaped lossy layer and a fourth layer structure (4) second-order bandpass FSS.

[0030] Combination Figure 2 As shown, it includes a first dielectric substrate (13), a bidirectional zigzag arrow (12) at a 45° angle, and a lumped resistor (11) with a package size of 0201 soldered at the arrow.

[0031] Combination Figure 3 As shown in the figure, this is a 2.5D lossy layer structure. It includes a second dielectric substrate (23) soldered to the back of the substrate, four lumped resistors (21) with identical 0402 packages, a metal bend line (22) on the front of the second dielectric substrate (23), a metal via (24), and a metal bend line (25) on the back of the second dielectric substrate (23). The metal bend line (22) on the front of the second dielectric substrate (23) is connected to the metal bend line (25) on the back through the metal via (24).

[0032] Combination Figure 4As shown, the third layer structure (3) consists of 3×3 small units. Each small unit structure includes a third layer dielectric board (33), a metal zigzag Jerusalem cross (31) printed on the front side and a metal zigzag Jerusalem cross (32) printed on the back side of the third layer dielectric board (33), and a lumped resistor (34) with a package of 0402 soldered to the center of the zigzag Jerusalem cross (31, 32) on the front and back sides. In order to facilitate soldering of the lumped resistor and avoid cross coupling, the metal zigzag Jerusalem cross and the lumped resistor are respectively placed on the front and back sides of the third layer dielectric board (33).

[0033] Combination Figure 5 As shown, the fourth layer structure (4) consists of 3×3 small units, including the fourth layer substrate (43), the fifth layer substrate (44), the metal square patch (41) printed on the front of the fourth layer substrate (43), the metal cross patch (42) between the fourth layer substrate (43) and the fifth layer substrate (44), and the metal square patch (45) on the back of the fifth layer substrate (44).

[0034] Combination Figure 6 As shown in the figure, the metasurface units are arranged in a 20×20 array, where the unit 0 of the first layer structure (1) and the mirror symmetric unit 1 form a 10×10 array, that is, a checkerboard arrangement of 0101, which constitutes a 1-bit coded metasurface for RCS reduction in this frequency band.

[0035] Combination Figure 7 As shown in the figure, the reflection and transmission amplitudes under metasurface TE polarization are as follows: in the frequency range of 1.1-20GHz, the co-polarization reflection amplitude is below -10dB, and in the transmission window range of 8-12GHz, the insertion loss is less than 1.5dB.

[0036] Combination Figure 8 As shown in the figure, the reflection and transmission amplitudes under metasurface TE polarization are as follows: in the frequency range of 1.1-20GHz, the co-polarization reflection amplitude is below -10dB, and in the transmission window range of 8-12GHz, the insertion loss is less than 1.5dB.

[0037] Example 2: A hybrid absorption and diffuse scattering ultrawideband RCS-reducing metasurface with a wave-transmitting window, used for a military broadband stealth communication radome. It is essentially the same as the system in Example 1, except for the structural parameters: Overall dimensions: 300mm × 300mm; First dielectric substrate: 0.508mm thick, Rogers RT5880 material; Second layer dielectric substrate: 0.508mm thick, F4B material; Third layer dielectric substrate: 0.254mm thick, Rogers RT5880 material; Fourth and fifth layer dielectric substrates: 1.524mm thick, Rogers RO4003C material; Air gap between layers: 1.0 mm.

[0038] The performance of Example 2 is as follows: RCS reduced bandwidth: 1-20GHz (reflection <-10dB); Wavelength transmission window: 8-12GHz (insertion loss <1.5dB); Polarization characteristics: Polarization insensitive (TE / TM polarization performance is consistent); Angular stability: Performance variation within ±45° is less than 3dB.

[0039] Example 3: A hybrid absorption and diffuse scattering ultrawideband RCS-reduced metasurface with a wave-transmitting window, applied to a stealth communication system for civilian unmanned aerial vehicles (UAVs). This example is designed for a civilian UAV platform, focusing on optimizing weight and cost. It is essentially the same as the system in Example 1, except for the structural parameters: Overall dimensions: 150mm × 150mm; First layer dielectric substrate: 0.4mm thick, low-cost FR-4 material; Second layer dielectric substrate: 0.4mm thick, FR-4 material; Third layer dielectric substrate: 0.2mm thick, FR-4 material; Fourth and fifth layer dielectric substrates: 1.0mm thick, FR-4 material; Air gap between layers: 0.8mm.

[0040] Performance indicators of Example 3: RCS reduced bandwidth: 2-18GHz (reflection <-8dB); Wavelength transmission window: 9-11 GHz (insertion loss < 2.0 dB); Weight: 40% lighter than the military version; Cost: 60% lower than the military version.

[0041] Example 4: A hybrid absorption and diffuse scattering ultrawideband RCS-reducing metasurface with a wave-transmitting window, applied to a shipborne multi-functional stealth radome. This example is designed for shipborne environments, emphasizing environmental adaptability and multi-band performance. It is essentially the same as the system in Example 1, except for the structural parameters: Overall dimensions: 500mm × 500mm; Special treatment: An anti-corrosion coating is added to the surface; Structural reinforcement: The addition of reinforcing ribs improves wind resistance; Sealed design: The fully sealed structure is suitable for marine environments.

[0042] Performance indicators of Example 4: RCS reduced bandwidth: 1-20GHz (reflection <-10dB); Transmission window: 8-12GHz (insertion loss <1.5dB) and also supports secondary transmission windows of 4-6GHz; Environmental adaptability: Meets the requirements for shipboard salt spray, humid heat, and vibration environments; Service life: Designed life is greater than 15 years.

[0043] Example 5: A hybrid absorption and diffuse scattering ultrawideband RCS-reduced metasurface with a wave-transmitting window, applied to an airborne conformal stealth radome. This example employs a conformal design to adapt to the curved surface of the aircraft skin. Its basic structure is similar to the system in Example 1, except for the structural parameters. Conformal design: The radius of curvature is consistent with the fuselage; Flexible connection: Flexible connection materials are used between layers; Lightweight design: Utilizes a honeycomb sandwich structure; Aerodynamic optimization: The outer surface meets aerodynamic shape requirements.

[0044] The performance of Example 5 is as follows: RCS reduced bandwidth: 2-18GHz (reflection <-10dB); Wavelength transmission window: 8-12GHz (insertion loss <2.0dB); Aerodynamic performance: The impact on aircraft aerodynamic characteristics is less than 2%; Weight: Surface density less than 3 kg / m².

[0045] The present invention is compared with existing technologies CN 115395222B and CN 116487883A and traditional materials as shown in Table 1 below: Table 1

[0046] As can be seen from the comparison results in Table 1, the present invention outperforms the prior art in several key performance indicators: 1. Widest bandwidth: Covering 1-20GHz, fully covering L / S / C / X / Ku and part of the Ka band; 2. Optimal performance: Reflection attenuation <-10dB, transmission insertion loss <1.5dB, both of which are the best among the compared technologies; 3. Thinnest thickness: A thickness of approximately λ / 6 achieves a compact structure while ensuring performance; 4. Most comprehensive functions: Simultaneously performs multiple functions including wave absorption, wave transmission, and polarization conversion; 5. Most adaptable: Insensitive to polarization and has large-angle stability.

[0047] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A hybrid wave-absorbing and diffusely scattering ultra- wideband RCS-reducing metasurface with a wave-transparent window, characterized in that, The super surface is a multilayer cascade structure, including from top to bottom: a first layer structure (1), a second layer structure (2), a third layer structure (3), and a fourth layer structure (4); and air gaps are arranged between each layer structure.

2. The ultra-wideband RCS-reducing metasurface with wave-transparent window of mixed wave-absorbing and diffuse scattering according to claim 1, characterized in that, The first layer structure (1) includes a first layer dielectric plate (13), a bidirectional metal meander arrow (12) arranged on the first layer dielectric plate (13), and a lumped resistor (11) welded at the arrow; the dielectric constant of the first layer dielectric plate (13) is 2.2, and the loss tangent is 0.0009.

3. The hybrid wave-absorbing and diffusive super-wideband RCS-reducing metasurface with a wave-transparent window according to claim 2, characterized in that, The packaging size of the lumped resistor (11) is 0201, the resistance values are the same, and the bidirectional meander arrow (12) is arranged at an angle of 45°.

4. The hybrid wave-absorbing and diffusive super wideband RCS-reducing metasurface with wave-transparent windows of claim 1, wherein, The second layer structure (2) includes a second layer dielectric plate (23), a front metal meander line (22), a back metal meander line (25), a metal via (24) connecting the front and back, and a lumped resistor (21) welded on the front and back; the dielectric constant of the second layer dielectric plate (23) is 2.2, and the loss tangent is 0.0015.

5. The hybrid wave-absorbing and diffusive super-wideband RCS-reducing metasurface with a wave-transparent window according to claim 4, wherein, The packaging size of the lumped resistor (21) is 0402, and the resistance values are the same.

6. The hybrid wave-absorbing and diffusive super-wideband RCS-reducing metasurface with a wave-transparent window of claim 1, wherein, The third layer structure (3) includes a third layer dielectric plate (33), a front metal meander Jerusalem cross (31), a back metal meander Jerusalem cross (32), and a lumped resistor (34) welded at the center of the cross; the dielectric constant of the third layer dielectric plate (33) is 2.2, and the loss tangent is 0.0009.

7. The hybrid wave-absorbing and diffusive scattering ultra-wideband RCS-reducing metasurface with a wave-transparent window of claim 6, wherein, The packaging size of the lumped resistor (34) is 0402.

8. The hybrid wave-absorbing and diffusive super-wideband RCS-reducing metasurface with a wave-transparent window of claim 1, wherein, The fourth layer structure (4) includes a fourth layer dielectric plate (43), a fifth layer dielectric plate (44), a metal square patch (41) arranged on the front of the fourth layer dielectric plate, a metal cross patch (42) arranged between the two dielectric plates, and a metal square patch (45) arranged on the back of the fifth layer dielectric plate; the dielectric constant of the fourth and fifth layer dielectric plates is 3.

55.

9. The hybrid wave-absorbing and diffusive super-wideband RCS-reducing metasurface with a wave-transparent window of claim 1, wherein, The unit 0 and the unit 1 of the first layer structure (1) are arranged in a chessboard pattern to form a 1-bit encoding super surface array.

10. The hybrid wave-absorbing and diffusive super-wideband RCS-reducing metasurface with a wave-transparent window of claim 1, wherein, The co-polarization reflection amplitude of the super surface in the 1-20 GHz frequency band is less than -10 dB, and the insertion loss in the 8-12 GHz frequency band is less than 1.5 dB.

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