Radar Cross Section Reduction Research Articles

Simplistic metasurface design approach for incident angle and polarization insensitive rcs reduction

This paper proposes the design of a metasurface for polarization and incident angle-insensitive RCS reduction applications. An ellipse-shaped unit cell is utilized as a polarization converter, which is then arranged to form a checkerboard surface. While a single layer checkerboard structure gives a wideband RCS reduction, a double layer structure yields polarization and incident angle independent operation. The two layers have unit cells rotated 450 to each other. Experimental results demonstrate an RCS reduction bandwidth of around 90%. Further the RCS reduction remains stable with polarization and incident angle variation.

A Flexible and Optical Transparent Metasurface Absorber with Broadband RCS Reduction Characteristics

Metasurface absorbers (MSAs) are of significant importance in a wide range of applications, such as in the field of stealth technology. Nevertheless, conventional designs demonstrate limited flexible characteristics and a lack of transparency, hence constraining their suitability for certain radar stealth applications. This study introduces a novel MSA operating in the broad microwave range, which exhibits both optical transparency and flexibility. The structure consists of a flexible substrate made of polyvinyl chloride (PVC), along with a resistive film composed of indium tin oxide (ITO). The proposed structure exhibits the ability to effectively absorb over 90% of the energy carried by incident electromagnetic (EM) waves across the frequency range of 9.85–41.76 GHz within an angular range of 0° to 60°. In addition, to assess the efficacy of the absorption performance, an examination of the radar cross-section (RCS) characteristics is conducted. The results indicate a reduction of over 10 dB across the aforementioned broad frequency spectrum, regardless of the central angle.

Multi-heterogeneous interfaces boost dielectric polarization in PBA-derived Co/MnO@NC ternary composites for electromagnetic wave absorption

The elaborate construction of multi-component composites has been deemed as a promising strategy to enhance dielectric polarization response capability in the preparation of highly efficient microwave absorbers. However, the rational design and integration of homogeneous composites with diverse components continues to pose a great challenge. Herein, we propose a straightforward self-assembly-carbonization strategy for fabricating Co/MnO@NC ternary composites derived from CoMn-Prussian Blue Analogous precursors, featuring enriched heterogeneous interfaces and balanced magneto-electric coupling synergy. The ternary composites effectively introduce diverse dissipation mechanisms, including interfacial polarization behavior originated from the constructed heterogeneous interfaces, dipole polarization relaxation triggered by atomic defects, and optimized magnetic loss ability from well-dispersed metallic Co species. Benefiting from these advantages, the Co/MnO@NC composites demonstrate superior electromagnetic wave absorption performances, with a minimum reflection loss value of −61.37 dB at the thickness of 3.5 mm and effective frequency absorption bandwidth of 6.32 GHz, covering the full Ku-band. Furthermore, power loss density and radar cross-section simulations validate that the Co/MnO@NC ternary composites possess exceptional microwave signal attenuation abilities, with a maximum radar cross-section reduction value of up to 27.98 dBm2 at 0°. Such outstanding absorption properties exceed those of most currently reported ternary composites and exhibit significant potential to replace conventional ferromagnetic-based absorbers. This work offers a straightforward strategy to fabricate ternary composites with excellent electromagnetic wave attenuation properties and sheds novel insights into the dissipation mechanisms.

A Wideband Polarization-Insensitive Bistatic Radar Cross-Section Reduction Design Based on Hybrid Spherical Phase-Chessboard Metasurfaces

A wideband polarization-insensitive bistatic radar cross-section (RCS) reduction design under linear and circular polarization incidence is proposed based on spherical-chessboard metasurfaces. A new metasurface element with wideband characteristics was designed, including a double split-ring structure, single-layer media, and metal board. In the proposed RCS-reduction design, the Pancharatnam–Berry (P-B) phase theory is applied with the designed metasurface element to realize phase distribution mimicking the low-scattering sphere, and thus realizing RCS reduction. In addition, the chessboard configuration is combined with spherical phase distribution to further improve the performance of monostatic and bistatic RCS reduction. Finally, the proposed RCS reduction design can not only realize wideband RCS reduction but also exhibit polarization-insensitive characteristics. It realized 10 dB monostatic and bistatic RCS reduction in a frequency band ranging from 8.5 to 21 GHz (84.8% relative bandwidth) under linear polarization (LP) and circular polarization (CP) incidence. The straightforward and efficient design method of the hybrid spherical chessboard can effectively avoid the complex and time-consuming optimization process in RCS-reduction design.

Transparent antenna with RCS tunability based on graphene and metasurface in S band

In this paper, we propose a graphene-based radar cross section (RCS) tunable antenna that utilizes metal mesh and graphene, both of which are optically transparent. The graphene sandwich structure is introduced to replace traditional components like diodes, micro-electro-mechanical systems (MEMS), and varactors, acting as an electromagnetic wave controller and significantly simplifying the device's complexity. By applying different voltages, the electrical properties of graphene are altered, enabling the regulation of reflection, transmission, and absorption of electromagnetic waves. This not only modifies the antenna's pattern but also achieves a substantial reduction in out-of-band RCS. The radiation and scattering mechanism of the antenna is carefully elaborated. The numerical and experimental results match well, which validates the effectiveness of the proposed method. The optical transmittance of the device is 27.9% at 550 nm, and the out-of-band RCS reduction is 10.01 dB at 3.83 GHz. The transparent, RCS tunable antenna proposed has significant potential applications in optical and microwave stealth technology.

Design of a multilayer absorber for ultra‐wideband radar cross section reduction

AbstractThis study proposes an ultra‐wideband multilayer absorber by combining frequency selective surface (FSS) and absorbing material. The structure is composed by three layers which are FSS loaded with resistors, absorbing material at the bottom and each layer is separated by air. The FSS in bottom has good absorption performance at high frequency while the upper layer is used to achieve low‐band absorption. To extend the absorption band to the low frequency, it further add a layer of absorbing material at the bottom. Equivalent circuit is employed to analyze the principle of the designed absorber. The simulation results show that an ultra‐wide absorption band from 0.61 to 12.33 GHz with a fractional bandwidth of 181% is realized for both TE and TM waves under the normal incidence. Furthermore, the thickness of the structure is only 0.07λL, where λL represents the wavelength of the minimum operating frequency. The designed absorber is fabricated and measured, and the measurement is in good agreement with the simulation.

Broadband RCS Reduction, Antenna Miniaturization, and Bandwidth Enhancement by Combining Reactive Impedance Surface and Polarization Conversion Metasurface

Broadband RCS Reduction, Antenna Miniaturization, and Bandwidth Enhancement by Combining Reactive Impedance Surface and Polarization Conversion Metasurface

Enhanced electromagnetic wave absorption of bacterial cellulose/ reduced graphene oxide aerogel by eco-friendly in-situ construction

Electromagnetic wave absorption materials (EWAMs) have become an effective means to address electromagnetic (EM) radiation and enhance stealth technology, among which aerogels are valued for their lightweight nature and excellent designability. This study utilized environmentally friendly preparation and in-situ reduction techniques to fabricate bacterial cellulose (BC) / reduced graphene oxide (RGO) aerogels, achieving tailored EM wave loss capabilities by controlling the reduction time of ascorbic acid. Benefitting from the effects of freeze-casting, BC winding, hydrogen bond, and RGO layers coupling, the aerogel maintains their original structure after reduction and exhibits satisfactory EM wave absorption. The minimum reflection loss (RLmin) is −38.52 dB, with an effective absorption bandwidth (EAB) of 6.68 GHz and a maximum radar cross section (RCS) reduction of 44.69 dBsm. Additionally, the aerogel’s lightweight (a low density of 9.03 mg/cm3) and outstanding thermal insulation properties enable it to adapt to complex conditions. Thus, the study provides a novel approach for the construction of industrialized and sustainable RGO-based EWAMs.

An ultralight, eco-friendly 3D porous carbon aerogel derived from cotton nano-cellulose for infrared stealth and microwave absorption

As multi-band military detection technology advances in the field of information warfare, stealth materials that are only applied for single frequency bands have extremely poor effectiveness in avoiding detection interference. Thus, it is urgent to develop stealth materials with compatible performance in multiple bands, especially infrared-radar compatible stealth materials. However, integrating infrared-radar compatiblity into one particular material remains a significant challenge. Inspired by the methods of structure design and component selection, this research provided a cotton nano-cellulose-based carbon aerogel with three-dimensional (3D) macro-mesoporous interface space for high-performance infrared-radar compatibility. When the density is only 0.005 ± 0.002 g cm−3, the infrared emissivity exhibits as low as 0.56 in 3–5 μm band and 0.52 in 8–14 μm band, the minimum reflection loss (RLmin) attains −19.8 dB, and the maximum effective microwave absorption bandwidth (EAB) covers 4.64 GHz. Additionally, computer simulation technology (CST) can be used to simulate the optimum radar cross section (RCS) reduction value of 15.86 dB m2, indicating that the aerogel has great potential in reducing the probability of being detected by radar detectors. Therefore, the lightweight porous carbon aerogels not only employ renewable and eco-friendly biomass materials, but also show great significance for high-performance infrared-radar compatibility, which is in favor of protecting human security all over the world.

Multifunctional bacterial cellulose‑derived carbon hybrid aerogel for ultrabroad microwave absorption and thermal insulation

Carbon aerogel has gained intense attention as one of the most promising microwave absorption materials. It can overcome severe electromagnetic pollution, thanks to its 3D macroscopic structure and superb conductive loss capacity. However, there is still a big challenge to endow multifunctionality to carbon aerogel while maintaining its good electromagnetic wave absorption (EWA) so as to adapt wide practical application. Herein, a novel carbon-based aerogel consisting of Cu and TiO2 nanoparticles dispersed on carbon nanofiber framework was derived from carbonized bacterial cellulose (CBC) decorated with its mother bacteria via freeze-drying, in situ growth and carbonization strategies. The synthesized carbon-based CBC/Cu/TiO2 aerogel achieved an excellent EWA performance with a broad effective absorption bandwidth (EAB) of 8.32 GHz. It is attributed to the synergistic loss mechanism from multiple scattering, conductive network loss, interfacial polarization loss and dipolar polarization relaxation. Meanwhile, the obtained aerogel also shows an excellent thermal insulation with a 3-mm-thick sample generating a temperature gradient of over 42 °C at 85 °C and a maximum radar cross-section (RCS) reduction of 23.88 dB m2 owing to the cellular structure and synergistic effects of multi-components. Therefore, this study proposes a feasible design approach for creating lightweight, effective, and multifunctional CBC-based EWA materials, which offer a new platform to develop ultrabroad electromagnetic wave absorber under the guidance of RCS simulation.

An AMC-based low-RCS conformal phased array design

Abstract In this article, an integrated radiation and scattering performance array conformed with the cylinder is presented. Wideband RCS reduction can be achieved and the radiating performance is maintained without loading any other structures. Two different antenna units with similar radiation performances and different reflection phases are designed to form a 6 × 6 conformal array. To verify the simulation results, a prototype of a 6 × 6 units integrated conformal array was fabricated and measured. The experimental results show that the proposed conformal array has better scanning performance above ±40° in the range of 8.2–11.3 GHz. In addition, the monostatic RCS reduction of the proposed array is more than 5 dB covering the working band of the array antenna with a maximum reduction value of 24.2 dB. The measured results agree well with the simulation results.

Facile and scalable preparation of gradient multilayer nanocomposite structure with preeminent microwave absorption and radar cross section reduction capability

The pressing need for the enhancement of stealth materials that are harmonious with state-of-the-art military equipment is critical, as it plays a pivotal role in bolstering the survivability and operational capabilities of advanced military technology. This research offers a straightforward approach for fabricating a gradient triple-layer absorber utilizing a Cu2O/h-BN nanocomposite and FeCoNi magnetic compounds, characterized by reduced thickness, designed for X-band wave spectrum attenuation purposes. The primary objective of this study is to examine the electromagnetic wave absorption characteristics of single-layer samples and subsequently develop a triple-layer gradient sample with distinct electromagnetic wave stealth features based on the findings. Optimal performance was observed in the gradient sample, where Cu2O/h-BN nanocomposite with 20 and 10 wt% was incorporated as a matching layer with thicknesses of 0.5 and 0.5 mm, respectively, and FeCoNi with 20 wt% was employed as an absorbing layer with a 0.4 mm thickness, surpassing the performance of the other samples. The optimal sample achieves a dissipation loss of −45.6 dB and a bandwidth of 2.9 GHz, all while maintaining a total thickness of just 1.4 mm. Facilitating multiple heterogeneous interfaces among layers, substances, and the synergistic interaction between constituent elements and layers’ thickness and arrangement enable this gradient configuration to demonstrate exceptional performance in radar stealth compatibility.

Novel cable‐like tin@carbon whiskers derived from the Ti2SnC MAX phase for ultra‐wideband electromagnetic wave absorption

AbstractOne‐dimensional (1D) metals are well known for their exceptional conductivity and their ease of formation of interconnected networks that facilitate electron migration, making them promising candidates for electromagnetic (EM) attenuation. However, the impedance mismatch from high conductivity and their singular mode of energy loss hinder effective EM wave dissipation. Construction of cable structures not only optimizes impedance matching but also introduces a multitude of heterojunctions, increasing attenuation modes and potentially enhancing EM wave absorption (EMA) performance. Herein, we showcase the scalable synthesis of tin (Sn) whiskers from a Ti2SnC MAX phase precursor, followed by creation of a 1D tin@carbon (Sn@C) cable structure through polymerization of PDA on their surface and annealing in argon. The EMA capabilities of Sn@C significantly surpass those of uncoated Sn whiskers, with an effective absorption bandwidth reaching 7.4 GHz. Remarkably, its maximum radar cross section reduction value of 27.85 dB m2 indicates its exceptional stealth capabilities. The enhanced EMA performance is first attributed to optimized impedance matching, and furthermore, the Sn@C cable structures have rich SnO2/C and Sn/SnO2 heterointerfaces and the associated defects, which increase interfacial and defect‐induced polarization losses, as visually demonstrated by off‐axis electron holography. The development of the Sn@C cable structure represents a notable advancement in broadening the scope of materials with potential applications in stealth technology, and this study also contributes to the understanding of how heterojunctions can improve EMA performance.

Graphene-Based Tunable Polarization Conversion Metasurface for Array Antenna Radar Cross-Section Reduction.

A graphene-based tunable polarization conversion metasurface (PCM) was designed and analyzed for the purpose of reducing the radar cross-section (RCS) of array antennas. The metasurface comprises periodic shuttle-shaped metal patches, square-patterned graphene, and inclined grating-patterned graphene. By adjusting the Fermi energy levels of the upper (μ1) and lower (μ2) graphene layers, different states were achieved. In State 1, with μ1 = 0 eV and μ2 = 0.5 eV, the polarization conversion ratio (PCR) exceeded 0.9 in the bandwidths of 1.65-2.19 THz and 2.29-2.45 THz. In State 2, with μ1 = μ2 = 0.5 eV, the PCR was greater than 0.9 in the 1.23-1.85 THz and 2.24-2.60 THz bands. In State 3, with μ1 = μ2 = 1 eV, the PCR exceeded 0.9 in the 2.56-2.75 THz and 3.73-4.05 THz bands. By integrating the PCM with the array antenna, tunable RCS reduction was obtained without affecting the basic radiation functionality of the antenna. In State 1, RCS reduction was greater than 10 dB in the 1.60-2.43 THz and 3.63-3.72 THz frequency ranges. In State 2, the RCS reduction exceeded 10 dB in the 2.07-2.53 THz, 2.78-2.98 THz, and 3.70-3.81 THz bands. In State 3, RCS reduction was greater than 10 dB in the 1.32-1.43 THz, 2.51-2.76 THz, and 3.76-4.13 THz frequency ranges. This polarization conversion metasurface shows significant potential for applications in switchable and tunable antenna RCS reduction.

A switchable PCM-based integrated structure with alternative radiation and stealth functions

In this work, based on the switchable polarization conversion metasurface (SPCM), the dual functions of high gain right-handed circularly polarized (RHCP) radiation and wideband 10 dB radar cross section (RCS) reduction stealth are achieved in one structure. As the key component to achieve good radiation and low RCS, the proposed SPCM unit consists of the asymmetrical Jerusalem Cross top layer and switchable metal plate bottom layer separated by an air space. Then the SPCMs are arranged in a chessboard configuration and placed above a patch array antenna with the sequentially rotated feeding network. When p-i-n diodes are on, low RCS is implemented by 180° (±37°) reflection phase differences between two neighboring SPCM cells. When p-i-ns are off, the chessboard SPCM provides a transmission window for highly directional RHCP wave radiation.

Cusp Phased Metasurfaces for Wideband RCS Reduction Under Broad Angles of Incidence

Cusp Phased Metasurfaces for Wideband RCS Reduction Under Broad Angles of Incidence

A Hybrid Mechanism Water-Based Metasurface for Antenna RCS Reduction

A Hybrid Mechanism Water-Based Metasurface for Antenna RCS Reduction

Ultra-Wide-Band and Polarization-Insensitive Metamaterial Absorber With Resistive Ink Sheet for RCS Reduction Applications

Ultra-Wide-Band and Polarization-Insensitive Metamaterial Absorber With Resistive Ink Sheet for RCS Reduction Applications

Facile synthesis of hierarchical Fe–S co-doped carbon-based composites with superior microwave absorption

Difficulty of multi-component coupling and hierarchical pore structure preparation make it challenging to manufacture highly efficient microwave absorption materials (MAMs). Herein, hierarchical porous carbon composites anchored with various types of iron sulfides are successfully fabricated using a simply feasible heating-induced self-assembly approach. Controllable electromagnetic parameters and impedance matching features of FexSy/AC (amorphous carbon) composites are obtained by varying carbonization temperature. Besides, AC and FexSy provide dielectric and magnetic losses, while defect-rich AC can effectively disperse FexSy nanoparticles, exhibiting high sintering resistance and high-density interfaces, which contributes to polarization losses. Moreover, the unique hierarchical porous structure not only offers better impedance matching, but also enhances microwave loss. The thorough investigation indicates that FexSy/AC nanocomposites exhibit outstanding microwave absorption performance by the joint effect of unique hierarchical porous structure and coupling loss of multi-components. The optimal sample (FSC-700) shows a strongest reflection loss value of up to −78.96 dB with a matching thickness of 2.85 mm, an effective absorption bandwidth (EAB, RL<−10 dB) of 6.98 GHz (11.02–18.0 GHz, spanning Ku-band), and a radar cross section (RCS) reduction value of 21.75 dBm2. In addition, the EAB can reach 13.8 GHz with the simulated thickness varies from 1.0 to 5.5 mm, covering 86 % of the measured frequency range. The in-depth research of the multi-component system with hierarchical porous structure offers an innovative and practical method for high-performance MAMs.

Resistive ink based polarization and incident angle independent wideband absorber for RCS reduction at KU and K band

In this paper, a thin, single layered, wideband, polarization-insensitive, frequency selective surface absorber for radar cross section reduction (RCS) at KU and K bands has been studied analytically and experimentally. The lossy resistive patterns on unit cell is printed using resistive ink and arranged periodically over a low-cost metal-backed FR-4 dielectric substrate. Through appropriate design and optimization, the proposed absorber demonstrates above 90 % absorption for broadband ranging from 15 GHz to 26.6 GHz, with multi-absorption peaks at 15.7, 18.5, and 22.9 GHz. The structure shows a high absorptivity of 96.8 % in the KU band and 95.7 %, and 99.3 % in the K band at the above mentioned frequencies. A fractional bandwidth of 55.8 % has been obtained at the expense of a thickness of 0.0835 λ1 (λ1 being the wavelength associated with the lower absorbing frequency). The absorption mechanism has been described with the help of surface current distribution, induced electric field, and equivalent circuit. Further, for both TE and TM waves, analysis of various polarization angles and oblique incidence angles have been investigated. It shows polarization insensitivity to normal incidence and a stable response up to 60° for oblique incidence to TM wave. The proposed absorber’s novelty comes through its thin, single-layered structure with wide band response at the KU and K frequency bands via a unique resistive ink pattern on a low cost FR-4. A prototype of the absorber has been fabricated and measured results have been validated with simulated results. A proposed single layered, wideband, thin, polarization, and angular stable absorber using resistive ink is commercially viable for RCS reduction applications at the KU and K band.