Radar Cross Section Research Articles

Integrated construction of 0D/1D/2D NiMn-LDH@CNT/MXene with multidimensionally hierarchical architecture towards boosting electromagnetic wave absorption

Constructing MXene-based absorbers with multicomponent and multidimensional hierarchical architecture is crucial but it still remains a formidable challenge to address the serious electromagnetic radiation pollution issue. Herein, a multidimensional 0D/1D/2D NiMn-LDH@CNT/MXene (NCM) hierarchical architecture composed of 0D NiMn-LDH anchored on 1D CNT and then assembled with 2D MXene is rationally constructed for electromagnetic waves (EMW) absorption. The EMW absorption performance of the resultant NCM significantly enhances thanks to the coupling effects of multicomponent and multidimensions. The balanced impedance matching, enriched EMW attenuation behaviors and plentiful polarization loss combine to facilitate EMW absorption. The NCM3 realizes an impressive reflection loss as low as −55.7 dB (2.49 mm) and a wide effective absorption bandwidth (EAB) of 5.1 GHz (12.9–18.0 GHz) with a thin matching thickness of 1.51 mm. Moreover, the regulation of matching thickness could enable the EAB to almost cover the entire frequency range. Simulated radar cross section strongly verifies the practical application potential of NCM. This work provides a valuable guidance for the design and construction of EMW absorption materials with hierarchical architecture.

Fabrication of MXene-encapsulated Co@C nanoparticles for efficient microwave absorption in the X-band

Two-dimensional MXene has structural advantages in electromagnetic wave scattering due to its layered structure, but MXene materials can lead to impedance mismatch problems due to their high dielectric constants, so it is still a challenge to design highly efficient wave-absorbing materials based on MXene with low reflection loss, thin thickness, and wide absorption frequency. In this study, composite wave-absorbing materials were fabricated from Co–Co PBA precursors and MXene using liquid nitrogen flash freezing and freeze-drying techniques. By treating MXene and the PBA precursor at a high temperature of 750 °C, a rich heterogeneous interface was formed between Co@C and MXene (CCM7), and the impedance matching was optimized to improve the reflection loss capability. The optimized sample has an effective absorption bandwidth of 4.1 GHz at 2.5 mm covering the entire X-band with a minimum reflection loss of −61.42 dB. It is also demonstrated that CCM7 is satisfactory for Radar Cross-Section of flat panels and unmanned aerial vehicles by CST calculations, and this work provides a fresh perspective on the use of effective MXene composites for microwave absorption.

The working principles of canard wings and its aerodynamic advantages and effects on aircraft

Canard wings have gradually become more and more popular since the advent of the supersonic jet era, and research on the subject has become more detailed in order to be able to manoeuvre this pair of small wings more perfectly and effectively. This paper mainly studies the aerodynamic principle of the canard wings and the impact of its aerodynamic advantages on the efficacy and stealth performance of the aircraft under different aerodynamic stability and makes a comparative analysis with the horizontal tail. Through literature analysis and review as well as a small number of comparative analyses, this paper concludes that although canard wings can provide many aerodynamic advantages, they also have their limitations. Canards can only be effectively coupled when they are close to the main wing and longitudinally higher than or equal to the height of the main wings. The radar cross-section (RCS) characteristic of the canard wings will increase with the angle of its deflection.

Sulfidation and reassembly strategy enables yolk-shell metal sulfide/alloy nanoparticles @carbon with efficient electromagnetic wave absorption

Constructing hybrid metal-organic frameworks (MOFs) demonstrates significant potential to improve electromagnetic wave (EMW) absorption performance by leveraging synergistic effects between composition and structure, addressing challenges in tuning electromagnetic parameters of single-composition MOFs. This study proposes a sophisticated strategy involving sulfidation-interface growth-reassembly: sulfide nanoparticles form by sulfidating the core (CoFe-MIL-88A), and then ZIF-67 guests grow and reassemble on the sulfided host MOF, resulting in a layered EMW absorption material. The composite material integrates synergistic effects, which include high conductive loss and defect/interface/dipole polarization induced by N and S atom doping. The CFSNC composite material outperforms previously published values, achieving a minimum reflection loss (RLmin) of −65.96 dB and an effective absorption bandwidth (EAB) of 6.15 GHz with a thickness of merely 2 mm. Simulation calculations of the real far-field radar cross-section (RCS) further validate its practical application potential. This work introduces novel ideas and methods for designing and preparing high-performance EMW absorption materials, offering both theoretical insights and practical applications.

Analysis of rain effects on China-France oceanography satellite scatterometer backscatter measurements

ABSTRACT The rotating fan beam scanning observation mechanism of China-France oceanography satellite (CFOSAT) scatterometer provides more comprehensive ocean measurements. However, its data quality is often impacted by rain contamination. In this study, we analysed the effect of rain on CFOSAT SCATterometer (CSCAT) backscatter measurements by collocating CSCAT data, the Integrated Multi-satellitE Retrievals (IMERG) rain data, and the wind reanalysis from European Centre for Medium-Range Weather Forecasts (ECMWF). The research findings indicate that, rain exhibits an intensification effect on backscatter at low wind speeds, but this effect gradually diminishes with increasing wind speeds, eventually transitioning to an attenuation effect at a wind speed between 10–20 m·s−1. At extremely high wind speeds above 20 m·s−1, the rain initially increases and then decreases CSCAT normalized radar cross section (σ 0) as the rain rate increases. The sensitivity of CSCAT σ 0 to rain rate decreases as the incidence angle increases. Its sensitivity to wind speed decreases as the rain rate increases. The azimuthal modulation becomes more pronounced with higher wind speeds and smaller incidence angles. However, rain weakens the asymmetry and anisotropy. Furthermore, the HH polarization exhibits a more pronounced susceptibility to rain compared to the VV polarization.

Synergistic effects of nitrogen/oxygen co-doping in 3D mesoporous carbon nanospheres for enhanced microwave absorption

Mesoporous carbon nanospheres have attracted significant attention in the microwave absorption (MA) field due to the broad benefits provided by their mesoporous structure. This study presents a facile hard template strategy to construct distinctive 3D N/O co-doped mesoporous carbon nanospheres (NOCS). The high surface area, abundant mesopores, and high nitrogen (N) doping levels, with proper defects on the surface provide multiple sites to absorb electromagnetic waves (EMW). Mesoporous carbon nanospheres achieve significant reflection loss (RL) of −48.19 dB and extensive effective absorption bandwidth (EAB) up to 5.52 GHz. Moreover, computer simulation technology (CST) demonstrated that all simulated Radar cross-section (RCS) values were below 20 dB m2. Thus, this work holds significant promise for effective microwave absorbers using mesoporous carbon nanospheres.

Regulating the phase composition and microstructure of Fe3Si/SiC nanofiber composites to enhance electromagnetic wave absorption

The rational introduction of multi-components to fabricate electromagnetic wave absorbing (EMA) materials with synergistic conductive/dielectric/magnetic losses promises lightweighting and excellent EMA performance, but it remains a challenge. In this work, multicomponent Fe3Si/SiC nanofibre composites with network structure were constructed by electrostatic spinning method and in-situ carbothermal reduction strategy. Design of microstructures and multicomponent modulation by controlling the carbothermal reduction temperature. As a result, the presence of a large number of non-homogeneous interfaces, three-dimensional (3D) conductive network structures and defect structures in Fe3Si/SiC nanofibre composites induces a combination of multiple loss mechanisms that significantly improve the EMA performance. When the filling amount of Fe3Si/SiC in the paraffin transmission matrix is 20 wt%, the maximum effective absorption bandwidth (EABmax) of the fabricated material reaches 5.84 GHz with a thin thickness of 2.02 mm. Moreover, the minimum reflection loss (RLmin) value at 10.96 GHz is as low as −67.57 dB. Meanwhile, the radar cross-section (RCS) simulation verifies that the F-4 peak RCS is reduced to −30.37 dB in the range of −60°<θ < 60°. It indicates that the Fe3Si/SiC nanofiber composites have a good radar-wave dissipation capability in practical applications. In summary, the comprehensive performance of lightweight multicomponent Fe3Si/SiC nanofiber composites can meet the new application requirements and is expected to become an emerging multifunctional wave-absorbing material suitable for harsh environments.

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.

Robust adaptive beamforming for cylindrical uniform conformal arrays based on low-rank covariance matrix reconstruction

Recently, conformal arrays have attracted considerable interest because such arrays can provide reduced radar cross-section and increased angle coverage. In this article, we devise a robust adaptive beamforming (RAB) approach using cylindrical uniform conformal array (CUCA). Firstly, we derive the minimum variance distortionless response (MVDR) beamformer for the CUCA by utilizing the noise subspace of interference covariance matrix (ICM) and steering vector (SV) of the signal-of-interest (SOI). Subsequently, the ICM is reconstructed by estimating the noise-free covariance matrix of the CUCA outputs and the interference projection matrix. Specifically, the noise-free covariance matrix can be regarded as multiple low-rank covariance matrices, and each low-rank matrix is reconstructed by formulating a nuclear norm minimization (NNM) problem. With the reconstructed covariance matrix, the 2-D DOAs of sources are determined by employing 2-D MUSIC spectrum to form the interference projection matrix. In addition, the SOI SV is estimated by solving a quadratically constrained quadratic programming (QCQP) problem. Numerical results demonstrate that the proposed approach is obviously superior to the existing RAB techniques.

Microwave absorption performance of La1.5Sr0.5NiO4/SrFe12O19 composites with thin matching thickness

The global focus on electromagnetic interference and pollution is undeniable. To counter these challenges, high-performance microwave-absorbing materials (MAMs), typically composed of dielectric and magnetic components, offer effective solutions by ensuring favorable impedance matching. Leveraging these MAMs has proven beneficial across various sectors, including 5G technology, information security, energy harvesting, diminished radar cross-section, and advancements in military applications. We successfully synthesized composites of La1.5Sr0.5NiO4 (LSNO) and SrFe12O19 (SrM) composites through ball milling and heat treatment. With the escalation of SrM weight percentage in the composites, noticeable alteration in structural, morphological, and static magnetic characteristics was ensured.Moreover, the amalgamation of these components bolstered the EM properties, consequently yielding exceptional microwave absorption capabilities in the composites. The composites with 40, 60, and 80 wt% of SrM (named S4, S6, and S8) exhibited excellent microwave absorption performance with an absorption rate of over 99.9 % for a thin thickness. The S4 and S8 composites attained reflection loss (RL) values of −34.75 dB and −36.93 dB, with 2.0 and 1.6 mm thicknesses, respectively. Meanwhile, the S6 composite achieved an RL value of −44.24 dB with a thickness of 1.9 mm. These composites' outstanding microwave absorption performance can be attributed to their significant magnetic loss, remarkable dielectric loss, and synergistic effects.

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.

Aerodynamic optimization of double S-duct caret intake by self-adapting non-dominated sorting genetic algorithm

The caret intake could not only provide compressed airflow to the aircraft engine stably but also should have applicable radar stealth performance. Radar stealth means that the echo intensity of the intake should be low when detected by radar, which could be measured by radar cross section (RCS). The airflow distribution of the double S-duct caret intake was numerically optimized to improve aerodynamic performance, with radar stealth performance as constraints. Self-adaptive genetic algorithm and Kriging model were used to improve the optimization efficiency. There could be multiple boundary-layer separations in the S-duct caret intake, resulting in obvious total pressure distortion at the outlet and secondary flow. To suppress these adverse airflow phenomena, the optimization of the double S-duct intake was defined as a problem with two targets and multiple constraints. By defining the probabilities of selection and variation as functions of the iteration number and the fitness, the self-adapting non-dominated sorting genetic algorithm can be applicable for such a problem. Using the Kriging model, which was proven to have satisfactory accuracy in predicting performance parameters, an optimized intake with both excellent aerodynamic and stealth performance was obtained, with a 30% reduction in DC60 value and a 47% reduction in SC60 value compared to the intake before optimization.

Theory of classical and modified spaceborne synthetic aperture radar imaging

This paper presents a novel method for spaceborne synthetic aperture radar (SAR) imaging, achieved through the statistical solution of the inverse optimization problem of image reconstruction, specifically focusing on radar cross-section (RCS). The proposed method improves upon traditional techniques by incorporating signal decorrelation, implemented via inverse filtering. A comparative analysis is provided between the modified method and the classical aperture synthesis approach, both of which are grounded in the optimization problem solution within the theory of the maximum likelihood method.

Unlocking versatile capabilities: Mixed-valence decavanadate aerogels for boosting radar, infrared, and thermal stealth

Multifunctional compatible stealth materials have emerged as the focal point of contemporary protection technology research and vanadium-based nanomaterials play a pivotal role in the development of advanced stealth materials. Here, a compatible stealth aerogel is successfully synthesized by employing mixed-valence decavanadate as the vanadium oxide (VOx) molecular model. Ultralight {VⅣVV9}/MXene aerogel (0.0429 g cm–3) exhibits exceptional radar stealth performance with a minimal reflection loss (RLmin) of −57.74 dB (99.9998% EMW absorption) and a significantly superior radar cross section reduction value of 26.77 dB m2. The aerogel's exceptional properties, including a low infrared (IR) emissivity (0.479) and a low thermal conductivity of (32.30 mW m–1 K–1), are crucial for enabling compatibility with IR and thermal stealth technologies. The presence of a mixed-valence polyoxovanadate cluster leads to an increase in the Schottky barrier and enhances magnetic properties, consequently boosting interfacial polarization and contributing to magnetic losses during electromagnetic wave (EMW) absorption. Consequently, altering the number of valence electrons significantly enhances the compatible stealth capabilities. These findings contribute significantly to our comprehension of how microstructure impacts EMW absorption processes and provide a basis for further research into the development of VOx-based compatible stealth materials.

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.

Lightweight Fe3O4/Fe/C/rGO multifunctional aerogel for efficient microwave absorption, electromagnetic interference shielding, hydrophobicity and thermal insulation

Effective integration of multiple functions into microwave absorbing materials is a future development direction, but still remains a significant challenge. This work fabricated a lightweight, multifunctional aerogel through electrostatic self-assembly, freeze-drying and in-situ pyrolysis process, achieving an in-situ composite of magnetic/dielectric components. The regulated pyrolysis temperature achieves a good balance between abundant nanopores and heterogeneous interfaces, enriched defects, and conductivity. This balance induced a synergy of dielectric loss, magnetic loss, and conduction loss at low frequencies, improving the impedance matching. The aerogel obtains a minimum reflection loss (RLmin) of −65.17 dB in the low-frequency range and a maximum effective absorption bandwidth (EABmax) of 5.76 GHz. The radar cross section (RCS) simulation confirmed its good stealth performance. In addition, an increase in aerogel loading enhanced its electrical conductivity, resulting in a higher electromagnetic interference (EMI) shielding effectiveness (SE) of 81.83 dB, the specific shielding effectiveness (SSE) up to 359.28 dB·cm3/g and the absolute shielding effectiveness (SSEt) up to 1596.82 dB·cm2/g. Beyond microwave absorption and shielding, this aerogel also exhibited good hydrophobicity and thermal insulation. This study provides a new perspective for the development of materials with microwave absorption properties in low-frequency bands and multifunctional properties for broader applications in military, communication, aerospace, and other fields.

Investigation on mechanical properties and stealth characteristics of a novel gradient-stitched composite structure

Based on the far field function of electric field, a new glass carbon fiber gradient-stitched structure is proposed and designed in the paper. In the frequency range of 8–28 GHz, the electric field distribution of transverse electric and magnetic field (TEM) waves incident obliquely on the surface of the structure by optimizing the glass fiber fabric units. It is confirmed that the surface has the function of suppressing electromagnetic wave reflection. The electrical performance simulation and testing results of the structure show that the radar cross section (RCS) is reduced by 90% in the frequency range of 12.3–26.5 GHz. In addition, a multi-scale analysis model is established to quickly predict the tensile modulus and strength of the composite material. The strength and modulus reached 26.9 GPa and 403 MPa, respectively. The simulating and testing results of mechanical properties are in good agreement.

Pomb@Co3O4-based composites for ultra-wideband microwave absorption: A multi-scale perspective from micro-, meso- and meta-structure

Microwave absorbing materials (MAMs) are used to prevent electromagnetic pollution and enhance equipment stealth. However, their limited absorption intensity and narrow effective bandwidth restrict their applicability. MAMs with a single absorption mechanism, whether dielectric or magnetic, often exhibit poor impedance matching. This paper introduces a new multiscale approach—encompassing microstructures, mesostructures and macrostructures—for designing high-performance MAMs. At the microscopic–mesoscopic level, Pomb materials derived from pomegranate peel are combined with magnetic nanoparticles (Co3O4) using a hydrothermal method. The microwave absorption properties of these composite materials were examined by varying the proportion of Pomb materials in the absorber. The effective absorption bandwidth (EAB) reached 5.5 GHz for a thickness of 2.3 mm. At the macroscopic level, a metastructure based on Pomb@Co3O4 (0.1 g) was designed to achieve ultrabroadband absorption with an EAB of 15.56 GHz, a range of 2.24–18 GHz and a total thickness of 15 mm. Additionally, the radar cross-section value of Pomb@Co3O4 (0.1 g) is below − 10 dB m2 across the angle range of − 60° to 60°, with a maximum scattering intensity of only − 7.6 dB m2. This multiscale structure design offers a promising direction for future research and development in MAMs.

Air-microwave simultaneously induced carbon fiber surface oxidation and magnetism adjustment by CoOx nanoparticles rapid assembly for interface enhancement and electromagnetic wave absorption of its composites

It is a significant challenge to develop a fast carbon fiber (CF) surface modification method, especially for the high strength electromagnetic wave (EMW) absorption materials. Herein, magnetic CoOx nanoparticles are successfully synthesized and uniformly assembled on CF surface with high oxygen-containing groups by rapid ambient microwave carbon thermal shock (MCTS). The presence of oxygen defect sites on CF surface promotes CoOx nanoparticles nucleation. The number of oxygen defects and the types of magnetic nanoparticles on the CF surface effectively adjust the surface chemical activity and the electromagnetic properties of CF, which is conducive to improving the EMW absorption performance and interface compatibility of the CoOx nanoparticles modified CF reinforced polyamide 6 (CO@CF/PA6) composites. Compared with CO@CF-0 s/PA6, the tensile strength and modulus of CO@CF-3.5 s/PA6 composite are increased by 18.1 % and 18.6 %, respectively. It also displays a minimum reflection loss value (−59.9 dB) at a thinner thickness of 1.9 mm while the maximum effective absorption bandwidth reaches 5.02 GHz with a thickness of 1.8 mm. Its radar cross-section values exhibit less than −10 dBm2 at all tested detection angles. This rapid MCTS shows great potential for large-scale production of CF modification with low-cost, efficient and environmentally friendly process.

The Effect of the Wall Thickness of the Material Loaded Cavity On the RCS Reduction

In this paper, the effect of a parallel plate waveguide's wall thickness on radar cross-section reduction (RCS) is rigorously analyzed for H-polarization by using the Wiener-Hopf Technique, when the waveguide region is loaded with dielectric material and terminated with a perfect electric conductor (PEC) plate. Transfer matrices are incorporated into the analysis to account for the effect of different material layers through continuity relations. The Fourier transforms of the diffracted field and the boundary conditions yield a modified scalar Wiener-Hopf equation of the second kind (MWHE-2). The classical procedure to solve the MWHE-2 is applied and the approximate expression of the diffracted far field is obtained. Numerical results are given by comparing with the results available in the literature for the case of the wall thickness of the cavity not being considered.