Radar Cross Section Reduction Research Articles

Bamboo-Based Carbon/Co/CoO Heterojunction Structures Based on a Multi-Layer Periodic Matrix Array Can Be Used for Efficient Electromagnetic Attenuation

With the popularization of wireless communication, radar, and electronic devices, the hidden harm of electromagnetic radiation is becoming increasingly serious. The design of green biomass carbon-based interface heterojunctions based on lightweight porous materials can effectively protect against electromagnetic radiation hazards. In this work, we constructed an anisotropic heterojunction interface with magnetic and dielectric coupling based on a honeycomb-like periodic matrix multi-layer array repeating unit. The removal of lignin components from bamboo through oxidation enriches the impregnation pores and uniform adsorption sites of the magnetic medium. Further, in situ pyrolysis promotes the formation of a large number of electric dipoles at the interface between the magnetic medium and dielectric coupling inside the periodic cell carbon skeleton, enhancing interface polarization and relaxation. Local carrier traps and uneven electromagnetic density enhance dielectric and hysteresis losses, resulting in excellent impedance matching. Therefore, the obtained bamboo-based carbon multiphase composite absorbent has satisfactory electromagnetic loss characteristics. At a thickness of 1.55 mm, the effective absorption bandwidth reaches 5.1 GHz, and the minimum reflection loss (RL) value reaches −54.7 dB. In addition, the far-field radar simulation results show that the sample has an excellent RCS (radar cross-section) reduction of 33.3 dB·m2. This work provides new directions for the diversified development of green biomass and the optimization of the design of magnetic and dielectric coupling in periodic array structures.

Broadband 3-bit coding metasurface antenna with integrated radiation and scattering performance

This paper presents the design of an integrated metasurface antenna, which combines a central radiating patch with a quadru-arc (QAS) structure. The metasurface antenna simultaneously achieves high-gain radiation and complex scattering functionality. The modulation of the radiation function is primarily achieved through phase manipulation of the power division feed network, while modulation of the X-polarization scattering function is mainly accomplished by adjusting the arc of the QAS. The effectiveness of this design is verified by designing two metasurface antennas with distinct functionalities. The feed network phases are arranged in a checkerboard pattern in the first approach, resulting in four-beam radiation with a gain of 16 dBi per beam. Additionally, the scattering component utilizes eight scattering structures with a phase difference of 45 degrees to form a 3-bit coding, enabling vortex beam scattering. The second configuration arranges the feed network in phase with the deflected beam, resulting in a deflected beam radiation pattern characterized by a gain of 22.3 dBi. The scattering function is optimized using a simulated annealing-genetic algorithm for phase alignment, resulting in the achievement of RCS reduction across a wide bandwidth range of 8-24 GHz. The proposed metasurface antenna is ultimately fabricated and subjected to rigorous measurements.

Gradient metasurface covered with water-based channels for reconfigurable RCS reduction

A gradient metasurface covered with water-based channels (GMWC) is proposed for RCS (radar cross section) reduction reconfiguration. The amplitude and phase response of the metasurface unit covered by the water-based channel (WC) is altered, which results in a change in the monostatic scattering of the GMWC. Under the normal incidence of X-polarized plane waves, the RCS reduction of GMWC shows different levels when different water channels are activated. The simulated results show that the average RCS reduction of GMWC increases from 5 dB to 20 dB in 5 dB steps in the 6 GHz to 8.2 GHz frequency band under four different reconstruction states (10000;01000;00100;00001). Besides, GMWC has an average RCS reduction of 10 dB within UWB (4–18 GHz) under state 10000. Finally, GMWC is fabricated and measured, and the measured results are in agreement with the simulated results. The RCS reduction reconfiguration characteristic of GMWC has potential application in target camouflage.

Anisotropic hypocycloid inspired 3-bit digital coding metasurface for radar cross section reduction

Abstract Recently, researchers have realized various exotic electromagnetic (EM) control devices using the coded metasurfaces, sparking a broad investigation into the phase or amplitude-based encoding method, as well as their combination, in the field of metasurface design. In this paper, to evaluate the influence of random mutual coupling between the adjacent element on the scattering performance of metasurface, and also to minimize the backward radar cross section (RCS) of metal plate targets, a novel encoding approach combining the reflection phase and element-form has been proposed. During the implementation process, an anisotropic hypocycloid inspired 3-bit digital coding metasurface was designed. It consists of 9 different element-forms, with each capable of providing 7 phase states. Simulation results demonstrate that the random mutual coupling introduced by the proposed elements does not significantly affect the RCS performance of the metasurface. With a good polarization insensitivity property for both linearly and circularly polarized waves, the designed 3-bit digital coding metasurface can achieve more than 20 dB RCS reduction at 10 GHz, while simultaneously transmitting additional information by encoding the element forms. The good consistency between theoretical simulation and sample testing unequivocally validates the precision of the design, this paper may serve as a useful reference for expanding the design methods of metasurfaces.

A Hybrid Mechanism Metasurface Based on Absorption and Phase Cancellation for Ultra‐Wideband RCS Reduction

AbstractThis paper proposes a hybrid mechanism based on phase cancellation and absorption to design a metasurface with ultra‐wideband 10 dB radar cross‐section (RCS) reduction from 6 to 64.7 GHz (171%). At high frequencies of 15–64.7 GHz, 10 dB RCS reduction is achieved by a phase cancellation mechanism, which is realized by arranging a perfect electric conductor (PEC) to form an arrayed structure with varying heights. At low frequencies of 6–15 GHz, 10 dB RCS reduction is achieved by the absorption mechanism, which is realized by designing a rotationally symmetric dual‐pattern absorber. The coupled mode theory (CMT) is used to explain the absorption mechanism. Additionally, it is found that a 180° phase difference is obtained by two different patterns to enhance RCS reduction in the high‐frequency band of 28–35 GHz. Finally, the phase cancellation and absorption mechanisms are combined to achieve an ultra‐wideband 10 dB RCS reduction from 6 to 64.7 GHz, which is realized by integrating the absorber into the arrayed structure to form the ultra‐wideband RCS reduction metasurface. The designed metasurface has a compact size (subwavelength), and a thin profile with 0.105λL.

Wide-angle low-scattering transmitarray antenna based on transmit-reflect selective metasurface

Abstract A high-gain transmitarray antenna with low radar cross section (RCS) properties is presented in this paper. Compared with conventional high-profile multilayer designs, we introduce a transmit-reflect selective metasurface integrated with high-gain transmission and random scattering functions, achieving a reduced thickness of 0.13 λ 0 (where λ 0 is the wavelength at the center frequency). For the meta-atom design, we combine geometric rotation and dimension optimization to realize 1-bit independent transmit and reflection phase modulation, respectively. Moreover, in metasurface coding strategy, we employ an initial phase optimization method and a simulated annealing algorithm to determine the optimal coding matrices. The experimental results demonstrate high-performance radiation characterized by the peak gain of 23.6 dB, maximum aperture efficiency of 28.5%, and 3 dB gain bandwidth of 18.4%. For x-polarization, measured 10 dB RCS reduction bandwidth under transverse magnetic (TM) 0°-45° and transverse electric (TE) 0°-20° incidence are 9.02–11.36 GHz. For y-polarization, 10 dB RCS reduction bandwidth under TM 0–60° and TE 0–30° incidence is 8.82–10.96 GHz.

3D printed PEEK/CF nanocomposites metamaterial for enhanced resonances toward microwave absorption and compatible camouflage

The stealth materials for future weapons and equipment need to operate within the radar working band, be lightweight, easy to process, and compatible with infrared stealth. Integrating all these characteristics poses a significant challenge. This work utilizes poly (ether-ether-ketone)/carbon fibers (PEEK/CF) composite materials and employed reverse-guided manufacturing through simulation design. Incorporating a grid structure within the pyramid metamaterial enables electromagnetic wave reflecting multiple times in various directions. By optimizing the important interaction between dielectric properties of the materials structures，the Pyramid Grid Filled Metamaterial enables broadband electromagnetic wave absorption (<-10 dB, 8–18 GHz), weak angular dependence (5- 45o incidence), polarization insensitivity, radar cross section (RCS) reduction (reduction over 10 dB between θ = −60° and 60°), and infrared camouflage performance. The PGF metamaterial of 180◊180 mm2, weighs only 103.1 g at a thickness of 9 mm. This work paves a way for the design the radar infrared compatible composite metamaterials.

Design of Optically Transparent Coded Metamaterial Based on an Indium Tin Oxide Film Using Deep Learning for Radar Cross-Section Reduction

Design of Optically Transparent Coded Metamaterial Based on an Indium Tin Oxide Film Using Deep Learning for Radar Cross-Section Reduction

Biomimetic Multi-Interface Design of Raspberry-like Absorbent: Gd-doped FeNi3@Covalent Organic Framework Derivatives for Efficient Electromagnetic Attenuation.

Structural design and interface regulation are useful strategies for achieving strong electromagnetic wave absorption (EMWA) and broad effective absorption bandwidth (EAB). Herein, a monomer-mediated strategy is employed to control the growth of covalent organic framework (COF) wrapping flower-shaped Gd-doped FeNi3 (GFN), and a novel raspberry-like absorbent based on biomimetic design is fabricated by thermal catalysis. Further, a unique dielectric-magnetic synergistic system is constructed by utilizing the COF-derived nitrogen-doped porous carbon (NPC) as the shell and anisotropic GFN as the core. The electromagnetic parameters of the GFN@NPC composites can be tuned by adjusting the proportions of GFN and NPC. Off-axis electron holography results further clarify the interface polarization and microscale magnetic interactions affecting the EMW loss mechanism. As a result, the GFN@NPC samples exhibit broad EMWA performance. The EAB values of all GFN@NPC composites reach up to 6.0 GHz, with the GFN@NPC-2 sample showing a minimum reflection loss (RLmin) of -69.6 dB at 1.68 mm. In addition, GFN@NPC-2 achieves a maximum radar cross-section (RCS) reduction of 29.75 dB·m2. A multi-layer gradient structure is also constructed using metamaterial simulation to achieve an ultra-wide EAB of 12.24 GHz. Overall, this work provides a novel bio-inspired design strategy to develop high-performance EMWA materials.

Broadband low radar cross section frequency selective surface radome based on phase cancellation and spatial filtering

AbstractThis letter introduces a novel design approach for broadband radar cross section (RCS) reduction of frequency selective surface (FSS) radomes. The approach integrates the principles of phase cancellation and spatial filtering together through a hybrid design method. The phase cancellation is obtained through the checkerboard arrangement of units, and the spatial filtering characteristics is achieved by the slot etched on the ground plane. Experimental and simulation results demonstrate that etching slots on the ground plane maintains broadband in‐phase reflection and bandpass characteristics, thereby extending the bandwidth of RCS reduction through a combination of two operation bands. Theoretical analysis of the working mechanism is also provided using equivalent circuit models. In comparison to the conventional radomes, the proposed FSS radome achieves significant bandwidth improvement for RCS reduction, indicating that it has promising prospects in future low‐RCS radome applications.

A novel broadband low backscattering antenna array based on integration of absorptive and coding metasurface

AbstractThis paper presents a low‐scattering 1 × 2 patch array antenna combining resistive and coding metasurfaces (MSs) for the reduction of wideband‐backscatter. An artificial magnetic conductor technology is used to validate the proposed technique, which is fundamentally based on scattering, phase cancellation, and absorptive property of the MS. By integration of coding MS elements and an absorbent unit cell, three different array blocks are utilized to significantly reduce the monostatic and bistatic backscattered energy level from 6.5 to 16.5 GHz, as well as overall reduction from 5 to 22 GHz. Under the incidence of plane waves, various reflection phases have been observed. The diffusion of the scattering energy from the surface can be achieved by carefully choosing the phase distributions for the reflected waves. Additionally, the bistatic backscattered energy level of the prototype is realized at various frequency points. This technique is validated using artificial magnetic conductors, which uniquely combine the effects of scattering, phase cancellation, and absorption in the MS's hybrid unit cells. Further, antenna array parameters are optimized for frequency, polarization, and angular diversity, S‐parameters, radiating efficiency, reducing radar cross section (RCS) in the wideband range and ensuring robust performance. The experimental results were substantiated by simulations of the reference and proposed prototypes suggesting that the proposed prototype can be a good candidate for applications that require a low monostatic and bistatic RCS platform.

An ultra-broadband low profile modified chessboard metasurface with improved backscattering reduction

Building upon the concepts of polarization conversion and the mechanism of destructive interference, a single-layered ultra-broadband metasurface for radar cross-section (RCS) or backscattering reduction is proposed in this work. A diffusion-assisted checkerboard metasurface with re-tailored unit cells at the center leads to a significant improvement in the stealth characteristics. For this, a low profile and less complex unit cell is proposed, comprising a long metallic strip along the diagonal and two thin horizontal stubs at the edges. This unique arrangement exhibits more than 90% polarization conversion efficiency from 13.2 to 38.2 GHz. Modifying the geometry of central elements in a conventional checkerboard metasurface achieves a minimum of 15 dB RCS reduction from 10 to 38 GHz. Also, as we ascend the frequency spectrum, the beams are scattered in unintended directions with reduced signal strength. Notably, there is no beam in the boresight direction, as opposed to the conventional chessboard configurations. For off-normal incidences, the metasurface exhibits good angular stability, and a minimum of 10 dB backscattering reduction is maintained up to an incidence angle variation of 60°. The final optimized fabricated prototype exhibits measurement results that agree with the simulation results for normal and wide-angle incidences.

A Broadband RCS Reduction Metasurface With Dual Transmission Windows

A Broadband RCS Reduction Metasurface With Dual Transmission Windows

Metasurface with two-dimensional gradient-index phase distribution constructed by rotation ellipse elements for backward RCS reduction

ABSTRACT In this letter, the realization of minimizing the scattering of the Ku band is investigated by designing a two-dimensional gradient-index metasurface to control the propagation of the incident waves. Through the gradient phase design, the maximum RCS reduction was observed at 14 GHz, the x-polarized plane wave exhibits an RCS reduction of 15.43 dB, while the y-polarized plane wave shows an RCS reduction of 13.13 dB compared to the same size of PEC. The proposed metasurface with low backward RCS shows the capability to scatter the incident plane wave in different directions at both normal and oblique incidence. According to equation 2, by calculating the variable phase distribution of large-scale arrays at different frequencies, the maximum reduction of RCS can be obtained at any frequencies. Therefore, this work effectively designs and suggests the research of low RCS metasurface at different frequencies.

Pixelated slot-based dual-broadband tunable graphene metasurface absorber design through excitation of coupled modes in terahertz regime

This work presents a dual-broadband metasurface absorber (DBMSA) design inspired by the pixel-based slot patterning of the top graphene sheet (Gpat). Complimentary design procedure using slots ensures an inbuilt DC connection among graphene patterns, which makes tuning of chemical potential μc highly practical. A DBMSA provides an absorptivity (Af) ≥ 90 % from 4.46 to 5.6 THz (22.66 %) in the lower band and from 7.52 to 8.68 THz (14.32 %) in the upper band. At the same time, variation in μc (Top) from 0.5 to 1 eV leads to the coverage of an ultra-wideband (UWB) terahertz (THz) spectrum from 3.62 to 9.1 THz with Af≥ 90 % due to the overlapping of bands. The absorber is polarization-insensitive due to the symmetricity in the design of the unit cell and provides stable Af for incidence angle ≤ 60° under both transverse magnetic and electric polarization. The DBMSA is compact and ultra-thin, having periodicity and thickness of λ0/6.72 and λ0/26.9, respectively. The developed ECM model closely predicts the working principle of the metasurface. In conclusion, the proposed DBMSA can be used for several applications in the THz gap regime, such as THz shielding, radar cross-section (RCS) reduction, sensing, imaging, etc.

Designing Electronic Structures of Multiscale Helical Converters for Tailored Ultrabroad Electromagnetic Absorption

HighlightsThe energy conversion mechanism is thoroughly analyzed, with a detailed quantitative characterization of the dissipation capacities of polarization, conduction, and magnetic loss.Inspired by DNA transcription, atom and geometry configurations co-modulating multi-scale helical converters achieve the RLmin of −63.13 dB at 1.29 mm, and the maximum RCS reduction value reach 36.4 dB m2.Orbital coupling, spin and cross polarization synergize to realize a 6.08 GHz EAB, further expanding to ultrabroad electromagnetic wave absorption of 12.16 GHz through metamaterial design.

Detection and Anti-Detection with Microwave-Infrared Compatible Camouflage Using Asymmetric Composite Metasurface.

Detection and anti-detection with multispectral camouflage are of pivotal importance, while suffer from significant challenges due to the inherent contradiction between detection and anti-detection and conflict microwave and infrared (IR) stealth mechanisms. Here, a strategy is proposed to asymmetrically control transmitted microwave wavefront under radar-IR bi-stealth scheme using composite metasurface. It is engineered composed of infrared stealth layer (IRSL), microwave absorbing layer (MAL), and asymmetric microwave transmissive structure (AMTS) with polarization conversion from top to bottom. Therein, IR emissivity, microwave reflectivity, and transmissivity are simultaneously modulated by elaborately designing the filling ratio of ITO square patches on IRSL, which ensures both efficient microwave transmission and IR camouflage. Furthermore, full-polarized backward microwave stealth is achieved on MAL by transmitting and absorbing microwaves under x- and y- polarization, respectively, while forward wavefront is controlled by precise curvature phase compensation on AMTS according to ray-tracing technology. For verification, a proof-of-concept metadevice is numerically and experimentally characterized. Both results coincide well, demonstrating spiral detective wavefront manipulation under y-polarized forward wave excitation while effective reduction of radar cross section within 8-18GHz and low IR emissivity (<0.3) for backward detection. This strategy provides a new paradigm for integration of detection and anti-detection with multispectral camouflage.

Multi-dimensional, multi-interface Fe3C/carbon sheets/carbon tubes nanoarchitecture towards high-performance microwave absorption

The serious problem of electromagnetic (EM) interference brings growing demand for developing high-performance electromagnetic shielding materials. In this study, three-dimensional (3D) Fe3C/carbon/carbon tubes (Fe3C/C/CT) absorber with multi-heterointerface was prepared by a facile self-propagating followed by chemical vapor deposition (CVD) strategy. Initially, Fe3O4 nanoparticles were anchored onto carbon nanosheets through the self-propagating process. After different etching times with diluted acid, CTs with diverse dimensions and quantities were catalyzed by the modified Fe3O4 catalysts during the CVD approach and grown from the carbon sheets. Such a special nanoarchitecture, which consists of carbon sheets and carbon tubes, acts as the source of dielectric loss. Meanwhile, Fe3C nanoparticles provide magnetic loss, and the abundant interfaces facilitate synergistic electromagnetic loss. Moreover, large numbers of heterointerfaces from the unique multidimensional nanoarchitecture significantly enhance the impedance matching and produce abundant dipole polarization. Ultimately, with etching time of 30 min, the Fe3C/C/CT-30 achieves excellent electromagnetic wave (EMW) absorption property with a minimum reflection loss of −46.4 dB at 10.56 GHz with a thickness of 3.0 mm. When the thickness is 3.57 mm, the effective absorption bandwidth (EAB) can extend up to 4.48 GHz. Moreover, the practical application of the absorbers was evaluated using radar cross-section (RCS) simulation, indicating that Fe3C/C/CT-30 achieves a maximum RCS reduction value of 58 dBm2. The multi-dimensional and multi-heterointerface absorber presented in this work might offer valuable insights for optimizing electromagnetic absorbers.

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 systematic review of design and performance enhancement techniques for the reduction of radar cross section in multiple input multiple output antennas

multiple-input multiple-output technology has emerged as a pivotal solution for addressing the capacity constraints of high-speed broadband wireless networks. By employing multiple antennas at both the transmitter and receiver, multiple-input multiple-output significantly enhances wireless communication efficiency. This paper presents a comprehensive review of multiple-input multiple-output antenna design strategies tailored for fifth-generation (5 G) networks and beyond. Specifically, it critically examines methodologies aimed at mitigating radar cross section in multiple-input multiple-output antennas, a crucial aspect of antenna engineering, especially in scenarios requiring reduced detectability. Various design and performance enhancement techniques proposed in the literature for RCS reduction in multiple-input multiple-output antennas are systematically analyzed, focusing on aspects such as antenna geometry and materials methods. Synthesizing these findings provides valuable insights into the current state of research, highlighting advancements, challenges, and future directions in developing efficient multiple-input multiple-output antennas with minimized radar cross section. This review contributes to antenna technology by aiding researchers and practitioners in informed decision-making regarding radar cross section reduction techniques for multiple-input multiple-output systems, and it identifies innovative approaches pertinent to multiple-input multiple-output applications. Finally, key considerations in multiple-input multiple-output antenna design are addressed, proposing potential directions for future research and development initiatives.