Radar Cross Section Reduction Research Articles

A restrictive design strategy of diffuse metasurfaces based on fibonacci sequences for RCS reduction

The rapid and efficient design strategy represents a highly intriguing research domain within the realm of metasurfaces. It necessitates minimizing the data load in coding metasurface design, facilitating the development of a precise approach to designing metasurfaces with specific characteristics. In this paper, we proposed a restrictive design strategy of metasurface for coding phase distributions based on the Fibonacci sequences, which is efficient to optimize designated radar cross section (RCS) reduction according to application requirements. Through the given restrictive strategy, the encoding range of the metasurfaces is reduced from the entire metasurfaces to the initial phase units in the corners, greatly reducing the total amount of data in the optimization database. In order to verify the availability of the strategy, RCS reduction metasurfaces with variable phase sequences in microwave region are analyzed. For broadband and wide-angle RCS reduction, the optimized Fibonacci discrete phase gradient (FDPG) metasurface is obtained by adjusting the phase sequences. Both the simulation and measured results show that the optimized FDPG metasurfaces by the proposed designing strategy have the RCS reduction of −10 dB in the frequency ranges of 6 GHz to 18 GHz under wide incidence angles from 0° to 30°. The simulated and measured results are good consistent over the whole frequency ranges and angle regions. This method combines mathematical sequences with physics organically, making it an important field in metasurfaces research and it is expected to play an important role in future studies.

Broadband low-scattering and high-efficiency transmission radome by combining phase gradient metasurface and FSS

In this paper, a novel method to achieve high-efficiency transmission radome with broadband low radar cross section (RCS) is proposed by combining phase gradient metasurfaces (PGMs) and frequency selective surface (FSS). The PGMs-FSS is an ultra-thin single-layered structure composed of a modified Jerusalem resonator backed with an FSS. The FSS works as a high-pass filter for transmitting the in-band signals and reflecting the out-of-band signals, and the PGMs works for reducing the RCS. The insertion loss is less than −1 dB within the passband of 15.95 GHz–17.7 GHz. Moreover, the particle swarm optimization (PSO) algorithm is used to extend the RCS reduction bandwidth as well as in-band high transmission. A prototype with a thickness of 0.08 λl (λl is the wavelength of the low frequency) is designed, fabricated, and measured. The results demonstrate that an over 10 dB RCS reduction is obtained from 7.95 GHz to 18.12 GHz, i.e., the relative bandwidth reaches 78.02%. The proposed method of combining PGM-FSS can be used in designing radomes of stealth platforms for the requirements of broadband RCS reduction as well as high-efficiency signal transmission.

Multifunctional Ultrathin Metasurface with a Low Radar Cross Section and Variable Infrared Emissivity.

The development of stealth devices that are compatible with both infrared (IR) and radar systems remains a significant challenge, as the material properties required for effective IR and radar stealth are often contradictory. In this work, based on an IR electrochromic device (IR-ECD), concepts of metamaterial manipulating electromagnetic waves are applied to develop a multifunctional ultrathin metasurface with a low radar cross section (RCS) and variable infrared emissivity. This paper presents a linear-to-linear polarization conversion metasurface (PCM) designed by hollowing the IR-ECD. In this way, the IR-ECD based on polyaniline (PANI) can also modulate the reflection waves in the microwave band without affecting its features in the infrared region. Thus, the proposed metasurface integrates both microwave stealth and variable infrared emissivity through a single layer. The measured results show that a 10 dB RCS reduction is achieved in the band of 8.46-9.5 GHz, and the infrared emissivity can be adjusted from 0.870 to 0.513 in the infrared stealth band of 8-14 μm. Due to the ultrathin thickness (only 0.081λ0 at 9 GHz), low RCS in the X-band, and variable infrared emissivity, the designed multifunctional stealth metasurface has promising applications on military platforms with various surrounding environments.

Design, optimization, and comparative analysis of wide-band polarization conversion along with dual coding sequences for RCS reduction

In this paper, a wideband polarization conversion metasurface is designed. Additionally, coding and chessboard metasurfaces are specifically tailored for radar cross-section reduction (RCS). Initially, a compact unit cell demonstrating exceptional polarization conversion performance is introduced, achieving a polarization conversion ratio (PCR) exceeding 90%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\%$$\\end{document} across frequencies ranging from 7.9 to 22.7 GHz. The PCR remains effective even when oblique incidence angles of up to 30∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ$$\\end{document} are utilized across this frequency band. Roger RT5880, with a thickness of 0.254 mm, serves as the substrate. An airgap is introduced between the substrate and the ground plane to enhance the polarization conversion bandwidth. This unit cell serves as the fundamental building block for subsequent metasurface configurations. To assess the scalability and effectiveness, a 36 ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document} 36 unit array is assembled, confirming efficient polarization conversion capabilities extending to larger structures. Moreover, a 1-bit coding unit “0” and “1” are formed by the Pancharatnam-Berry phase based on the same-sized meta-atom with 90∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ$$\\end{document} orientations. The robustness and practicality of the design are demonstrated by creating 12 ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document} 12 lattices and evaluating their RCS reduction potential under two distinct scenarios: a chessboard pattern and a coding-based scheme. Notably, its results indicate substantial RCS reduction across a broad frequency spectrum (7.9 to 22.7 GHz) for both configurations. This study demonstrates the wide-ranging applicability of metasurface design, making it a valuable contribution to the fields of microwave engineering, polarization control, and radar stealth technology. Owing to its simplicity, bandwidth, and versatility, this approach offers innovative solutions for diverse real-world applications.

A broadband reconfigurable rasorber radome based on AFSR for RCS reduction

AbstractIn this paper, a broadband reconfigurable active frequency selective rasorber is proposed, which can be used as a radome for antenna radar cross section (RCS) reduction. By tuning the active components, the radome can achieve in‐band RCS reduction and reconfigurable absorptive/transmissive states. In the absorptive state, the max bandwidth with an absorption rate greater than 90% spanning from 1.62 to 5.37 GHz; in the absorptive/transmissive state, 2.2 GHz is the transmissive frequency with the insertion loss of 93% while absorbing in 0.94–2.06 GHz and 2.63–6.5 GHz, which demonstrate impressive characteristics of broadband and a high absorption rate. Additionally, the radome can maintain performance at ±35° angular incidence and is insensitive to incident wave polarization. Furthermore, it features a lightweight and low‐profile design, with a cell electrical size of just 0.078λ × 0.078λ × 0.066λ. The prototype test shows a noteworthy correlation with simulation. This study has wider applications in the electromagnetic stealth of communication antennas and aircraft, as well as in the control of electromagnetic pollution signals in space.

Rational design of hollow bimetallic sulfide@carbon with abundant heterogeneous interfaces and conductive network synergies for efficient microwave absorption

Developing composites with rational structural design and multicomponent synergistic effects is regarded as a promising strategy for achieving excellent impedance matching and high intensity attenuation performance. Herein, a hierarchical and multifunctional hollow porous Co3S4@NiCo2S4@BPC composite with integrated strong microwave absorption (MA) and self-cleaning properties was designed. The resultant composite exhibits remarkable EMW absorption behavior with a minimum reflection loss (RLmin) of −68.1 dB at 2.3 mm. The multicomponent synergy achieves a satisfactory heterogeneous structure, invoking intense interfacial polarization. Additionally, the residual functional groups and lattice defects induced by S doping further enhance the microwave attenuation. Meanwhile, the hierarchical hollow porous structure facilitates the impedance matching between the absorber and air. Notably, the composite has ideal radar cross-section (RCS) reduction and excellent hydrophobicity, demonstrating its outstanding MA properties as well as the potential applications in complex environment. Therefore, this work provides a novel strategy for the rational design of high-performance absorbers.

Design and Fabrication of a Metasurface for Bandwidth Enhancement of RCS Reduction Based on Scattering Cancellation

Design and Fabrication of a Metasurface for Bandwidth Enhancement of RCS Reduction Based on Scattering Cancellation

Simultaneous manipulation of constituent and structure toward MOFs-derived hollow Co3O4/Co/NC@MXene microspheres via pyrolysis strategy for high-performance microwave absorption

The development of microwave absorbing materials with high performance is one of the effective strategies to solve the increasingly serious electromagnetic pollution problem, and has received the attention of researchers. Herein, the structure and composition manipulation of Ti3C2Tx MXene and MOFs derivatives are investigated. It is found that the TiO2 produced by oxidation of Ti3C2Tx MXene, as a low dielectric material, can effectively solve the impedance mismatch caused by the high conductivity of Ti3C2Tx MXene. Additionally, MOFs derivatives with excellent dielectric-magnetic properties are often obtained by high temperature pyrolysis, which also aids in the oxidation of Ti3C2Tx MXene. Here, we successfully synthesized ZIF-67 nanoparticles on the surface of a three-dimensional spherical skeleton supported by Ti3C2TX MXene nanosheets through template method and electrostatic self-assembly, and obtained Co3O4/Co/NC@MXene microspheres with an obvious hollow structure after one-step pyrolysis. This magnetic carbon heterostructure could effectively optimize the impedance matching and achieve efficient microwave absorption. The HCCM-800 sample had a minimum reflection loss value of −71.60 dB with thickness of 2.25 mm and a maximum effective absorption bandwidth achieved 5.14 GHz at 1.85 mm. Meanwhile, the radar cross section (RCS) simulation revealed that the HCCM-800 sample’s RCS reduction value could reach 20.2 dBm2 at 0° incidence angle. It is believed that this research will pave the way for further vigorous development in the field of microwave absorption.

Antenna array-based metasurface for multi-scenario wide-angle polarization-insensitive radar cross section reduction

In this paper a novel antenna array-based metasurface design method for wide-angle and polarization-insensitive radar cross section (RCS) reduction has been proposed, which can be applied to a variety of RCS reduction scenarios. The proposed metasurface subarray design employs a dual-element antenna array in which the two ports of each element are connected through a Wilkinson power divider, and meanwhile, two power dividers are connected through a microstrip line with a lumped resistor. The use of dual-polarized wide-beam antennas enables the metasurface array to respond to arbitrarily polarized as well as wide-angle obliquely incident electromagnetic waves. A portion of the electromagnetic waves received will be absorbed by the lumped resistor and converted into heat, while the remaining portion will be canceled in the space, achieving the low RCS characteristic. The proof-of-concept experiments have been conducted in several application scenarios for RCS reduction, including a metasurface array integrated with a microstrip antenna, a densely distributed dual-element metasurface array, and a randomly distributed dual-element metasurface array. Simulated and measured results confirm that the proposed method opens up a new avenue for more flexible and versatile RCS reduction devices and systems.

A low-profile coding metasurface for broadband radar cross section reduction via beam diffusion and absorption

A low-profile coding metasurface based on beam diffusion and absorption is proposed, which can be applied for broadband Radar Cross section (RCS) reduction. Through inserting resistors into the polarization conversion element, the proposed unit cell can convert a portion of the electromagnetic wave to ohmic loss as well as retain polarization conversion. Subsequently, the power loss and surface current were used to explain the mechanism of absorption and polarization conversion, and the arrangement of the elements was optimized using a simulated annealing algorithm. Furthermore, both the simulated and measured results have shown that the RCS reduction is greater than 10 dB at 6.7–19.3 GHz (the relative bandwidth is 96.9%), and the metasurface still maintains great characteristics at 45° incidence. Thanks to the proposed metasurface offer advantages such as fewer resistors, a wider bandwidth for RCS reduction, an ultra-thin profile (0.066 λL, where λL represents the longest wavelength), a stable incident angle, and a more uniform scattering of energy, it can be used in electromagnetic stealth for large targets.

Electromagnetic wave absorption performance and rheological behavior of rubber composites with low mass filling rate carbon nanofiber aerogel

With the development of electronic information science and technology, electromagnetic information security and electromagnetic pollution become more and more serious. Electromagnetic wave absorption (EMWA) rubber based on the absorbent of carbon with low density and good corrosion resistance is a kind of good EMWA materials for solving electromagnetic information security and electromagnetic pollution. In this article, three-dimensional network structure carbon nanofiber aerogels (3DNSCAs) are prepared by vacuum annealing of three-dimensional network structure agarose/zinc acetate obtained by freeze-drying of agarose/zinc acetate gel. The EMWA rubber composites with 2.2% (in mass) 3DNSCAs have almost the same density as silicone rubber (PDMS), and the dispersity of 3DNSCAs in PDMS is studied by rheological analysis. The effective absorption bandwidth (EAB, frequency for reflection loss <–10 dB) of the 2 mm thick PDMS/C-800 is 4 GHz, and the minimum value of reflection loss (RLmin) is −52 dB with the thickness of 3.5 mm. The PDMS/C-1000 with the thickness of 3.5 mm has an EAB up to 4.8 GHz. Radar cross section (RCS) reduction of PDMS/C-800 can achieve 20 dB⋅m2 at the frequency of 6 GHz.

Broadband RCS reduction metasurface based on vortex singularities generated by Spin-to-Orbital angular momentum conversion

A broadband radar cross-section (RCS) reduction employed by the vortex metasurface is proposed. The underlying physics is associated with the Pancharatnam-Berry geometrical phases involved in spin-to-orbital angular momentum conversion. The proposed metasurface generates spin-controlled vortex waves with different topological charges. The vortex singularity implements specular extremely low RCS reduction. The prototypes are fabricated and measured to verify the wideband performance of the RCS reduction. The simulated results illustrate that −10 dB broadband RCS reduction from 9 GHz to 22.5 GHz and the RCS reduction has peak values −37.2 dB, −40.8 dB, and −42.5 dB at 9.8 GHz, 13.1 GHz, and 20.8 GHz, respectively. The measurement results illustrate that −10 dB RCS reduction over 9.1–18 GHz is realized, and the RCS reduction peak −53 dB at 10.1 GHz. The measured electric field intensities and phase distribution of the vortex metasurface also be displayed. Due to the limitation of experimental conditions, no test was done in the range greater than 18 GHz. Far-field results achieve good agreement between simulations and experiments, and the near-field measurements are a subtle difference in the experimental results. This work reveals the potential advantages of vortex waves in the fields of multifunctional electromagnetic stealth, beamforming for communication systems, etc.

Optimization of wideband RCS reduction via controlled phase and amplitude in metasurface design

Optimization of wideband RCS reduction via controlled phase and amplitude in metasurface design

Absorption-transmission-diffusion-type radar cross section reduction metasurfaces based on frequency selective absorber and polarization conversion chessboard structure

Absorption-transmission-diffusion-type radar cross section (RCS) reduction metasurfaces based on the frequency selective absorber and the polarization conversion chessboard structure are proposed in this paper. The RCS reduction metasurfaces consist of three parts, i.e. the top layer realized by a cross-shaped meander line loaded with lumped resistors for low-frequency absorption and high-frequency transmission, the mid-layer constructed by angular ring vias frequency selective surface (FSS) sandwiched with two square patches FSS for broadband transmission in mid-frequency zone, and the bottom layer employed chessboard metasurfaces composed of dual-arrow type polarization conversion units for scattering cancellation in high frequency zone. The physical mechanisms of the RCS reduction metasurfaces with multifunctional electromagnetic controlling including wave absorption, bandpass transmission, polarization reversal, and phase cancellation are also discussed and analyzed. Simulation and experimental results demonstrate a reflection of lower than −10 dB for normal incident linearly polarized waves over a frequency range of 2.5 GHz–18 GHz, with a relative bandwidth of 151.22%; transmission passband properties with insertion loss better to −3 dB in the frequency range of 5.62 GHz–11.0 GHz, with a relative bandwidth of 64.74%. Due to the resonance-coupling-resonance principle, the broadband transmission with low insertion loss was obtained. The RCS properties of the proposed multi-functional metasurfaces were further analyzed by numerical simulation and experimental measurement, and the results showed that RCS reduction of over 10 dB was achieved for normal incident different polarized waves at the frequency range of 2.5 GHz to 17 GHz. Even in the case of normal incidence, there was a deviation between the reflection characteristics and RCS reduction. The RCS reduction metasurfaces are expected to be employed in applications where multi mechanism collaborative control of electromagnetic waves is of extreme importance.

An efficient parameter-retrieval-based surrogate-assisted optimization of on-platform honeycomb absorbing structures

An electromagnetic parameter-retrieval-based surrogate-assisted optimization (PSAO) algorithm is presented to reduce radar cross section (RCS) by optimizing the on-platform honeycomb absorbing structures. To facilitate the optimization process, the honeycomb structure is transformed to an anisotropic homogeneous slab, and the effective parameters of the slab are extracted by the retrieval algorithm. A multi-fidelity model is employed to reduce the computing-time consumption, in which a Gaussian process (GP) regression model is used as the substitute for the coarse model. The GP model establishes a relationship between the geometry of the honeycomb structure and the RCS response of the target coated with the equivalent slab. Finally, the optimization result of the fine model is achieved through a space mapping strategy. The accuracy of the parameter extraction algorithm is verified by analyzing the honeycomb absorbing structure. Subsequently, the proposed optimization method is applied to a metal plate and a metal cylinder, resulting in a 10 dB reduction of RCS in broadband and wide-angle scenarios. This demonstrates the applicability of the proposed PSAO algorithm to both planar and conformal on-platform honeycomb absorbing structures. Furthermore, an NACA0015 foil is analyzed, showing an average RCS reduction of 10 dB and a minimum RCS reduction of 5 dB in the X-band. These results indicate that the PSAO approach can effectively apply to complicated targets. Additionally, the proposed method exhibits significant advantages in terms of computational accuracy and efficiency compared to the traditional genetic algorithm.

In-Band RCS Reduction of Circularly Polarized Microstrip Antenna Array Based on a Novel Feed Network

In-Band RCS Reduction of Circularly Polarized Microstrip Antenna Array Based on a Novel Feed Network

A Tightly Coupled Dipole Array with Diverse Element Reflection Phases for RCS Reduction

A Tightly Coupled Dipole Array with Diverse Element Reflection Phases for RCS Reduction

Transparent and Ultra-Thin Flexible Checkerboard Metasurface for Radar-Infrared Bi-Stealth.

This paper proposed a single-layer checkerboard metasurface with simultaneous wideband radar cross-section (RCS) reduction characteristics and low infrared (IR) emissivity. The metasurface consists of an indium tin oxide (ITO)-patterned film, a polyethylene terephthalate (PET) substrate and an ITO backplane from the top downwards, with a total ultra-thin thickness of 1.6 mm. This design also allows the metasurface to have good optical transparency and flexibility. Based on phase cancellation and absorption, the metasurface can achieve a wideband RCS reduction of 10 dB from 10.6 to 19.4 GHz under normal incidence. When the metasurface is slightly cylindrically curved, an RCS reduction of approximately 10 dB can still be achieved from 11 to 19 GHz. The polarization and angular stability of the metasurface have also been verified. The filling rate of the top ITO-patterned film is 0.81, which makes the metasurface have a low theoretical IR emissivity of 0.24. Both simulation and experimental results have verified the excellent characteristics of the proposed checkerboard metasurface, demonstrating its great potential application in radar-IR bi-stealth.

Single-layer multifunctional metasurface for laser-infrared-microwave compatible stealth.

This paper presents a novel approach for achieving a multifunctional metasurface capable of multiband compatible stealth. The metasurface is designed with a single-layer metallic structure that integrates functions of radar cross-section (RCS) reduction, laser stealth, and infrared shielding simultaneously. The reduction of RCS is achieved by developing two sub-cells that employ the interference cancellation principle, leading to a 10 dB decrease in RCS across a broad frequency range of 13-21 GHz. The laser stealth capability is attained by implementing a chessboard phase distribution in the array, also based on the interference cancellation principle, efficiently cancelling the specular reflection at the laser wavelength of 1.06 µm. The significant difference in wavelength between microwaves and lasers ensures that their operational characteristics do not interfere with each other. Additionally, the metasurface exhibits an infrared shielding property with an extremely low emissivity (less than 0.03) in the infrared atmosphere window of 3-5 µm and 8-14 µm, enabling the infrared stealth capability. The proposed metasurface demonstrates exceptional performance and has an extremely thin single-layer structure, indicating that it has a promising potential for future applications in multiband compatible stealth.

Achieving RCS reduction via scattering and absorption mechanisms using a chessboard structured composite

Based on the concept of periodic structural unit, a chessboard structured composite composed of quartz fiber and carbon fiber is proposed in this study for reducing radar cross section (RCS). An automated manufacture technique – stitching was applied in the unit construction, showing the great potential on mass production and low cost. The design of RCS reduction adopts the cooperative mechanisms of absorption and scattering. The results show that the RCS reduction of chessboard structured composite is below −10dB in the range of 8.9–15.1 GHz, and the peak value of the RCS reduction can reach −23dB. By simulating the different unit parameters of chessboard regions, the optimal parameters are obtained. Region 0 and region 1 present different energy distributions and a phase difference of 180° ± 78°, which is an important reason for the scattering mechanism of chessboard structured composite. To further explore the mechanisms of scattering and absorption, the electric field, magnetic field and power loss of the two regions at the absorption peak are simulated. According to the absorption energy distribution, it can be inferred that impedance matching plays an important role in the absorption mechanism. Moreover, the oblique incidence test and simulation prove the good angular stability of chessboard structured composite. The good mechanical properties of chessboard structured composite demonstrate the great potential of structure-function integration. Furthermore, the mass production capacity of the proposed composite gives the broad prospects in practical engineering application.